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Appendix

D CanmetENERGY

C a n a d i a n C l e a n P o w e r C o a l i t i o n : A p p e n d i x d D01

CCPC/CanmeteNerGY Phase III

Final report of CanmeteNerGY deliverables

Prepared by:

Dr. Robin Hughes

Research Engineer

CanmetENERGY

Executive Summary In 2009 CanmetENERGY executed a Task Shared Agreement to provide 'Technical Support to CCPC's Phase III Project for the Development of a Clean Coal, Zero Emission Power Plant'. At this time the Canadian Clean Power Coalition (CCPC) was a non-profit organization with the mandate to research, develop and demonstrate commercially viable clean coal technologies to reduce greenhouse gas and other emissions of concern. The CCPC had been given authority to represent the interests of its industrial (Basin Electric Power Co-operative, EPCOR (now Capital Power Corporation), the Electric Power Research Institute (EPRI), SaskPower Corporation, TansAlta Corporation, and Nova Scotia Power Corporation) and governmental partners (Alberta & Saskatchewan) in any undertakings. Subsequent to the execution of this agreement Sherritt International joined the CCPC. This report is a compilation of the deliverables generated by CanmetENERGY as outlined in Schedule #1 of the Task Shared Agreement up to March 31, 2011 - the end date of CanmetENERGY's projects supporting the Agreement. The projects included:

1. Near Zero-Emissions Coal Gasification 2. CO2 Capture from Syngas and Flue Gas Using Solid Sorbents 3. High Efficiency, Low Emission Advanced Clean Coal Technology

The objectives of these projects were to:

1. Reduce the technical risks and take advantage of the opportunities in deploying coal-fired entrained flow slagging gasification technology in Canada. The major risks for coal gasifier operators are technical (meeting production targets, maintaining gasifier availability in a predictable manner, and safe operations) and financial (proving to financial institutions that the project is feasible and profitable) in order to obtain attractive financing terms and conditions. Gasification technology suppliers believe that the costs of hydrogen production can be reduced by up to twenty per cent (20%) in the mid term through the industrial application of current R&D programs. CanmetENERGY’s work program will support the design and commissioning of commercial facilities, such as the EPCOR IGCC power generating station with CO2 capture, and the Dodds-Roundhill hydrogen production facility and will provide information required for optimizing the operation of these facilities on an on-going basis. 2. Develop advanced CO2 separation processes using solid sorbents with reduced energy and efficiency penalties when compared to competing technologies.

C a n a d i a n C l e a n P o w e r C o a l i t i o n : A p p e n d i x dD02

The abstracts of the Deliverables form the body of this report. The actual deliverables are provided as appendices. The deliverables are identified using a 2 part identifier of the format H.NN. H is one of: 1. Gasification Journal Publications, 2. Gasification Reports, 3. Gasification Conference Proceedings, 4. Ca Looping Journal Publications, 5. Ca Looping Conference Proceedings. The activities that were to be undertaken are provided below with commentary and cross-references to the Deliverables: 1. Determine gasification characteristics of Canadian coals & pet coke; pure, beneficiated and blended; slurried and dry feedstocks:

a. Physical and chemical properties (ultimate, proximate, porosity). b. Mineral composition and variation (Scanning electron microscopy w/ EDX). c. Reactivity and syngas composition (Pressurized thermogravimetric analysis,

entrained flow slagging gasifier pilot plant). d. Effect of ash composition on slagging properties (High temperature viscometer

(max 1700°C), entrained flow slagging gasifier pilot plant, modeling). e. Speciation and emission of trace elements including heavy metals such as Hg

(entrained flow slagging gasifier pilot plant). f. Slurryability (Fann viscometer). g. Provide training opportunities to CCPC participants as and when requested, in the

operation of a pilot-scale, high pressure, high temperature gasifier and its ancillaries.

The gasification characteristics outlined above have been determined for fuels including Genesee coal raw and hydrothermally processed, Coal Valley coal both raw and washed, Boundary Dam lignite raw and hydrothermally processed, and Suncor petroleum coke. Documents 1.1,2.4, 2.5, and 3.2 provide information regarding physical and chemical properties, mineral composition and variation, reactivity, and slurryability. Documents 1.2, 1.4, 2.2, 2.6, and 3.2 provide information regarding the effect of ash composition on slagging properties. Document 2.8 provides results of a study on mercury capture in from syngas on activated carbon and Ca based sorbents. CCPC participants did not request training opportunities in the operation of the gasifier, and so no deliverable is available for this activity.

2. Develop and test gasifier component designs and materials: a. Evaluate heat transfer, corrosion and slag adhesion of materials for injectors and

cooling walls (entrained flow slagging gasifier pilot plant, high temperature oven; max 1700°C).

Limited information on this activity is available in documents 1.1 and 1.3. Additional information will be available in the completed PhD theses of Marc Duchesne expected in Q1 2012.

3. Investigate methods for improving gasification power plant efficiency firing high ash coals:

a. Develop and test a high pressure, dense phase, dry coal pneumatic conveying system (cold model setup, and gasifier pilot plant).

b. Warm / Hot gas cleaning (entrained flow slagging gasifier pilot plant). c. Coal Beneficiation (entrained flow slagging gasifier pilot plant if sufficient fuel

available).


Process flow diagrams and design calculations for dense phase conveying and hot gas clean-up (particulate) at pilot scale have been completed. The CanmetENERGY pilot plant test rig for dense phase conveying and for hot gas filtration is at 90% completion. Document 2.3 provides a technology brief for gasification technology for the year April 2009 to March 2010. No deliverables for this activity are provided here. Results of gasification tests for coal beneficiation are provided in documents 2.4 and 2.5

4. Create application specific process simulations:

a. Determine efficiency and environmental performance of systems for hydrogen, steam and power.

b. Emphasis on breakthrough technologies.

Document 2.1 provides a report of CanmetENERGY's process simulation for IGCC for a series of Canadian fuels. CanmetENERGY effort in this area was also directed towards supporting CCPC tasks including the Jacobs Advanced Gasification Technology Study and the EPRI Integrated Gasification Combined Cycle Technology Roadmap.

5. Create computational fluid dynamics models of gasifier injectors, reactors and quench systems for technology scale-up and for process improvement:

a. Heterogeneous and homogenous reactions. b. Slag deposition.

Documents 3.1 and 3.3 provide information on computational fluid dynamics for coal gasification and model validation efforts. Document 2.7 is a complete data package that will allow validation of computational fluid dynamics models being created by academia, government R&D organizations and industry for entrained flow gasifiers. This data package will be used by the Massachusetts Institute of Technology, University of Utah (large eddy simulations) and the US DOE NETL for the development of high quality gasifier reactor and quench system models.

6. Develop and test regenerable solid CO2 sorbents:

a. High temperature (500 – 700 °C) sorbents such as CaO and moderate temperature (<400 °C) sorbents such as hydrotalcite and zeolites.

b. Dual fluidized bed combustion & gasification pilot plant, pressurized thermogravimetric analysis, porosymmetry, scanning electron microscopy with EDX.

Documents 4.1 through 4.37 and 5.1 through 5.4 provide the results of CanmetENERGY's deliverables for Ca looping combustion and oxy-fuel CFBC. Oxy-fuel CFBC is both a suitable standalone CO2 capture technology for low quality fuels and performs the regeneration step in Ca looping. Document 4.6 is a review of solid looping cycles in general. Documents 4.27 and 4.37 are review articles on Ca looping. All three are recommended reading as introductions to this technology. For additional information regarding calcium looping for the purpose of hydrogen production specifically refer to documents 4.18 and 4.25.


Table of Contents

1 GASIFICATION JOURNAL PUBLICATIONS _____________________________________ D08

1.1 Entrained-FlowGasifierFuelBlendingStudiesatPilotScale _____________________________ D08

1.2 ArtificialNeuralNetworkModeltoPredictSlagViscosityOveraBroadRangeof TemperaturesandSlagCompositions ________________________________________________ D08

1.3 CharacterizationofSlagGeneratedinaPilot-scaleEntrained-flowGasifier __________________ D09

1.4 PhaseChangesandViscosityBehaviourofSlagFromCoalandPetroleumCokeBlends _______ D09

2 GASIFICATION REPORTS _____________________________________________________ D10

2.1 ApplicationofIGCCTechnologyinCanada:ComputerSimulationofIGCCina Canadian Context _______________________________________________________________ D10

2.2 ApplicationsofFactSageintheAnalysisofGasifierSlagging ____________________________ D11

2.3 ApplicationofIGCCTechnologyinCanada:PhaseXIII–TechnologyBrief _________________ D11

2.4 BeneficiatedFuelStudyPart1:FuelCharacterization ___________________________________ D12

2.5 BeneficiatedFuelStudyPart2:FuelCharacterizationandGasification _____________________ D12

2.6 BriefReportforCCPConSlagViscosityWork ________________________________________ D12

2.7 DataPackageforSlurry-FedEntrainedFlowGasifierCFDModelValidation: WashedCoalValleyCoal _________________________________________________________ D13

2.8 PerformanceofCaO-basedSorbentsforRemovalofTraceMetalContaminant(Hg) fromSyntheticCoalGasificationSyngas _____________________________________________ D13

3 GASIFICATION CONFERENCE PUBLICATIONS _________________________________ D14

3.1 SimulationofEntrainedFlowCoalGasification _______________________________________ D14

3.2 OptimizationofCanadianPetroleumCoke,CoalandFluxingAgentBlendsViaSlag ViscosityMeasurementsandModels ________________________________________________ D14

3.3 EntrainedFlowSlaggingSlurryGasificationandtheDevelopmentofComputational FluidDynamicsModelsatCanmentENERGY ________________________________________ D15

4 CALCIUM LOOPING JOURNAL PUBLICATIONS ________________________________ D16

4.1 DeterminationofIntrinsicRateconstantsoftheCaO–CO2Reaction _______________________ D16

4.2 ADiscrete-Pore-Size-Distribution-BasedGas–SolidModelanditsApplicationtothe CaO+CO2Reaction _____________________________________________________________ D16


4.3 CarbonationofFlyAshinOxy-fuelCFBCombustion __________________________________ D16

4.4 SequentialSO2/CO2CaptureEnhancedbySteamReactivationofaCaO-BasedSorbent _______ D17

4.5 SonochemicalTreatmentofFBCAsh:AStudyoftheReactionMechanismandPerformance ofSyntheticSorbents ____________________________________________________________ D17

4.6 SolidLoopingCycles:ANewTechnologyforCoalConversion ___________________________ D18

4.7 InvestigationofAttemptstoImproveCyclicCO2CapturebySorbentHydration andModification ________________________________________________________________ D18

4.8 ParametricStudyontheCO2CaptureCapacityofCaO-BasedSorbentsinLoopingCycles _____ D18

4.9 ThermalActivationofCaO-BasedSorbentandSelf-ReactivationduringCO2Capture LoopingCycles _________________________________________________________________ D19

4.10 SulphationandCarbonationPropertiesofHydratedSorbentsfromaFluidizedBedCO2 LoopingCycleReactor ___________________________________________________________ D19

4.11 SteamHydrationofSorbentsfromaDualFluidizedBedCO2LoopingCycleReactor _________ D20

4.12 Ca-basedSorbentLoopingCombustionforCO2CaptureinPilot-ScaleDualFluidizedBeds ____ D21

4.13 CO2LoopingCyclePerformanceofaHigh-PurityLimestoneafterThermal Activation/Doping _______________________________________________________________ D21

4.14 ChangesinLimestoneSorbentMorphologyDuringCaO-CaCO3LoopingatPilotScale _______ D22

4.15 SinteringandReactivityofCaCO3-BasedSorbentsforInSituCO2CaptureinFluidized BedsunderRealisticCalcinationConditions __________________________________________ D22

4.16 ImprovementofCaO-BasedSorbentPerformanceforCO2LoopingCycles _________________ D23

4.17 CO2LoopingCyclesWithCaO-BasedSorbentPretreatedinCO2atHighTemperature ________ D23

4.18 CO2captureFromSyngasviaCyclicCarbonation/CalcinationforaNaturallyOccurring Limestone:ModellingandBench-ScaleTesting _______________________________________ D23

4.19 Long-TermCalcination/CarbonationCyclingandThermalPretreatmentforCO2Capture byLimestoneandDolomite _______________________________________________________ D24

4.20 SO2RetentionbyCaO-BasedSorbentSpentinCO2LoopingCycles _______________________ D24

4.21 CaO-BasedPelletsSupportedbyCalciumAluminateCementsforHigh-Temperature CO2Capture ___________________________________________________________________ D25

4.22 ScreeningofBindersforPelletizationofCaO-BasedSorbentsforCO2Capture ______________ D26

4.23 TheLong-TermBehaviorofCaO-BasedPelletsSupportedbyCalciumAluminate CementsinaLongSeriesofCO2CaptureCycles ______________________________________ D26


4.24 EffectofPartialCarbonationontheCyclicCaOCarbonationReaction _____________________ D27

4.25 CO2CapturefromSimulatedSyngasviaCyclicCarbonation/CalcinationforaNaturally OccurringLimestone:Pilot-PlantTesting _____________________________________________ D27

4.26 AStudyontheActivityofCaO-BasedSorbentsforCapturingCO2 in Clean EnergyProcesses________________________________________________________________ D28

4.27 TheCalciumLoopingCycleforLarge-scaleCO2Capture _______________________________ D28

4.28 CompetitionofSulphationandCarbonationReactionsduringLoopingCyclesforCO2 CapturebyCaO-BasedSorbents ___________________________________________________ D29

4.29 SulfationPerformanceofCaO-BasedPelletsSupportedbyCalciumAluminateCements DesignedforHigh-TemperatureCO2Capture _________________________________________ D29

4.30 EmissionsofSO2andNOXduringOxy-FuelCFBCombustionTestsinaMini-Circulating FluidizedBedCombustionReactor _________________________________________________ D30

4.31 MorphologicalChangesofLimestoneSorbentParticlesduringCarbonation/Calcination LoopingCyclesinaThermogravimetricAnalyzer(TGA)andReactivationwithSteam ________ D30

4.32 CO2CarryingBehaviorofCalciumAluminatePelletsunderHigh-Temperature/High-CO2 ConcentrationCalcinationConditions _______________________________________________ D31

4.33 CarbonationofCaO-BasedSorbentsEnhancedbySteamAddition ________________________ D31

4.34 SinteringandFormationofaNonporousCarbonateShellattheSurfaceofCaO-Based SorbentParticlesduringCO2-CaptureCycles _________________________________________ D32

4.35 EnhancementofIndirectSulphationofLimestonebySteamAddition ______________________ D33

4.36 ReactivationandRemakingofCalciumAluminatePelletsforCO2Capture __________________ D33

4.37 CaLoopingTechnology:CurrentStatus,DevelopmentsandFutureDirections _______________ D34

5 CA LOOPING CONFERENCE PUBLICATIONS ___________________________________ D35

5.1 CharacterizationofAshesfromOxy-FuelCombustioninaPilot-ScaleCirculating FluidizedBed __________________________________________________________________ D35

5.2 RoleoftheWater-GasShiftReactioninCO2CaptureFromGasificationSyngas UsingLimestones _______________________________________________________________ D35

5.3 HydrationandPelletizationofCaCO3-DerivedSorbentsforIn-SituCO2Capture _____________ D36

5.4 EffectofOperatingConditionsonSO2andNOXEmissionsinOxy-FuelMini-CFB CombustionTests _______________________________________________________________ D36


1 GAS IFICATIO N J O URNAL PUB LICATIONS

1.1 ENTRAINED-FLOW GASIFIER FUEL BLENDING STUDIES AT PILOT SCALE

Cousins, A., McCalden, D.J., Hughes, R.W., Lu, D.Y. and Anthony, E.J., “Entrained-flow Gasifier Fuel Blending Studies at Pilot Scale”, Canadian Journal of Chemical Engineering, 86, 335-346, 2008. For the foreseeable future, coal and petroleum-based materials, such as petroleum Coke, residuals, and high-sulphur fuel oil, are being adopted as the feedstocks of choice for gasification projects. Of particular interest from a Canadian perspective is Coke generated from the thermal cracking of the oil sands in Western Canada. Oil sand Coke contains high sulphur (5–6%), and also typically has a low volatile content, and lower reactivity than most coals. Experimental runs have recently been conducted on the pilot-scale entrained-flow gasifier at CETC-Ottawa, blending oil sand Coke with sub-bituminous and lignite coals, to try and enhance the gasification potential of these materials. Blending Genesee sub-bituminous coal with the delayed oil sands Coke was found to alleviate problems encountered with slag plugging the reactor when running with Genesee coal alone. Blends of Genesee sub-bituminous and Boundary Dam lignite coals with Coke achieved higher carbon conversions and cold gas efficiencies than runs completed with the Coke by itself. While using CO2 as the conveying gas into the gasifier was not found to significantly affect the conversion obtained, steam addition was found to have a marked effect on CO and H2 concentrations in the syngas. 1.2 ARTIFICIAL NEURAL NETWORK MODEL TO PREDICT SLAG VISCOSITY OVER A BROAD

RANGE OF TEMPERATURES AND SLAG COMPOSITIONS

Duschene, M., Hughes, R., Lu, D., Macchi, A., and Anthony, E.J. “Artificial neural network model to predict slag viscosity over a broad range of temperatures and slag compositions”, Fuel Processing Technology, 91, 831-836, 2010. Threshold slag viscosity heuristics are often used for the initial assessment of coal gasification projects. Slag viscosity predictions are also required for advanced combustion and gasification models. Due to unsatisfactory performance of theoretical equations, an artificial neural network model was developed to predict slag viscosity over a broad range of temperatures and slag compositions. This model outperforms other slag viscosity models, resulting in an average error factor of 5.05 which is lower than the best obtained with other available models. Genesee coal ash viscosity predictions were made to investigate the effect of adding Canadian limestone and dolomite. The results indicate that magnesium in the fluxing agent provides a greater viscosity reduction than calcium for the threshold slag tapping temperature range.


1.3 CHARACTERIZATION OF SLAG GENERATED IN A PILOT-SCALE ENTRAINED-FLOW GASIFIER

Cousins, A., Hughes, R., McCalden, D., Lu, D., and Anthony, E.J. "Characterization of Slag Generated in a Pilot-scale Entrained-flow Gasifier", submitted for publication

A series of gasification tests have been completed using the pilot scale entrained flow slagging gasifier at CanmetENERGY using Canadian coals, oil sands coke, and blends of these fuels to determine if the produced slags are non-hazardous in nature. Solid wastes generated during these tests soot and slag samples) were analyzed for their carbon content, crystallinity, and toxic constituent leaching tendency in an attempt to provide more insight into the possibility of disposal or by-product use of gasifier produced solid waste. In addition tests were performed with blends of these fuels to determine slag composition. The gasification tests were performed at conditions representative of commercial gasifiers using a dry fuel feed configuration. The char and slag samples were found to be inert with regards to their leaching potential, and so disposal of these streams should not be an issue. Slag samples also had low carbon contents, making them acceptable for use in such areas as aggregates and road bases. Cross sections of a core sample drilled through the gasifier wall showed the degree of penetration of the slag into the refractory, and the dissolution of refractory material into the slag. As a result, when considering the disposal of these materials, thought should also be given to the properties of the refractory lining used inside the gasifier.

1.4 PHASE CHANGES AND VISCOSITY BEHAVIOUR OF SLAG FROM COAL AND PETROLEUM COKE BLENDS

Marc A. Duchesne, Alexander Y. Ilyushechkin, Robin Hughes, Dennis Lu, David McCalden, Arturo Macchi, Edward J. Anthony The slagging behaviour of petroleum coke and coal blends must be known to determine suitable blending requirements for entrained-flow slagging gasification. In the present study, the viscosities of Australian and Canadian coal ashes, petroleum coke ashes and blends of these were measured in the temperature range of 1150-1600ºC. The effect of limestone or dolomite addition on viscosity was also tested for one coal ash and a coal ash/petroleum coke blend. In addition, pure vanadium oxide (a major component of petroleum coke) was added to two coal ashes in an attempt to single out vanadium’s effect. Results show that limestone and dolomite are effective viscosity reducers. Also, increasing the amount of petroleum coke ash or vanadium oxide tends to reduce the viscosity of the blends at higher temperatures. However, it can decrease the temperature of critical viscosity which will increase viscosity at lower temperatures. FactSage phase equilibrium predictions and quenched sample analysis via SEM and EPMA were used to link solids formation to changes in the viscosity-temperature relation. The presence of vanadium stimulates solids precipitation, which increases viscosity dramatically at lower temperatures. Finally, predictions from several slag viscosity models were compared to measured values. The viscosity model which provided the most accurate predictions was utilized for optimization of fluxing agent addition and blend ratios.


2 GAS IFICATIO N REPO RTS

2.1 APPLICATION OF IGCC TECHNOLOGY IN CANADA: COMPUTER SIMULATION OF IGCC IN A CANADIAN CONTEXT

Lu, D., Hughes, R., “Application of IGCC Technology in Canada: Computer Simulation of IGCC in a Canadian Context”, Report to Environment Canada, December 2009.

This report summarizes process simulation of IGCC systems operating with Canadian feedstocks. The results of the following tasks are reported:

1. Develop and validate an IGCC process model with PRO/II simulation software based on the following configuration and assumptions from the DOE/NETL report entitled “Cost and Performance Baseline for Fossil Energy Plants”: • Oxygen-blown, coal-fuelled, slagging Shell gasification operated with radiant

syngas cooler and quench via syngas recycle. • Sulfinol sulphur recovery system • Illinois #6 bituminous coal. • Syngas nitrogen dilution used to the maximum extent possible without

generating additional N2 for the sole purpose of dilution, syngas humidification and dilution steam addition to achieve approximately 120 Btu/scf syngas LHV resulting in 15 ppm NOx emission.

• Claus unit for sulphur recovery • Tail gas treating unit with tail gas recycle for 99.8% overall sulphur recovery

to achieve a SOx emission of 4 ppm. • Activated carbon bed applied to achieve 95% Hg removal • Water scrubbing installed to achieve PM emissions of ~0.003 g/MJ.

The cost and performance baseline report is being used for validation as it has been prepared in a rigorous fashion by a respected EPC (engineering procurement contractor) with experience in the area of IGCC.

2. Compare the performance and emissions of various Canadian feedstocks using a Shell gasifier-based IGCC design based upon the best publicly available information for the following configuration:

• Oxygen-blown fossil fuel-fired Shell gasifier-based IGCC system with radiant and convective high-temperature syngas cooling and amine sulphur recovery system for Canadian coals, and coal and petroleum coke blends.

3. Characterize the performance and emissions of these systems to provide insight into the potential benefits and optimizations in the future simulations with these technologies.


2.2 APPLICATIONS OF FACTSAGE IN THE ANALYSIS OF GASIFIER SLAGGING

Duchesne, M., “Applications of FactSage in the Analysis of Gasifier Slagging”, Report to Ecole Polytechnique, 2009. FactSage is a powerful tool when it comes to the prediction of slag thermodynamic properties and equilibrium states. To demonstrate its relevance in the field of fossil fuel gasification, three applications are discussed with emphasis on slagging behaviour. For the first application, phase diagrams were created to display slag liquidus temperatures as a function of composition. With these diagrams, suggestions could be made as to the amount of iron additive and limestone fluxant required for gasification of hydrocracker residue. For the second application, viscosity predictions were calculated and displayed within FactSage interfaces. With these predictions, a temperature and blend ratio of two fuels was recommended to produce slag with a viscosity below 25 Pa•s. Also, amounts of limestone addition were recommended for another fuel to keep slag viscosity below 25 Pa•s at various temperatures. For the third application, a sophisticated slag viscosity calculation tool was created with the ability to automate mass viscosity predictions with twelve different models. Since two of these models are FactSage-dependent, the tool was designed to access FactSage, perform automated FactSage calculations and extract information pertaining to slag viscosity predictions. Finally, key issues regarding future integration of FactSage in slagging behaviour predictions are discussed. 2.3 APPLICATION OF IGCC TECHNOLOGY IN CANADA: PHASE XIII – TECHNOLOGY BRIEF

Granatstein, D., Anthony, EJ, “Application of IGCC Technology in Canada: Phase XIII – Technology Brief”, Report to Environment Canada, March 2010. This technology brief for the period April 2009 to March 2010 summarizes gasification technology activities in Canada, the USA, and other countries. A number of ‘papers of interest’ are summarized as well.


2.4 BENEFICIATED FUEL STUDY PART 1: FUEL CHARACTERIZATION

Coville, K., Champagne, S,. Hughes, R., Lu., D. “Beneficiated Fuel Study Part 1: Fuel Characterization”, Report to Sherritt International June 2010. To meet the world’s increasing energy demands in an environmentally conscious manor, it will be necessary to make efficient use of the world’s coal supply. In order to do this, the optimal feedstock to be fed as a slurry to a gasification process must be determined. Bench scale experiments were conducted at CanmetEnergy, Ottawa, to evaluate raw and beneficiated coal slurries and to determine which type of coal would be optimal for use in gasification and IGCC. The results showed that neither beneficiation process changed the sulphur content of the coals. The hydrothermally processed Boundary Dam Lignite was found to have similar reactivity, higher ash fusion temperatures, and better slurryability than its untreated form. Furthermore, dried hydrothermally processed Boundary Dam Lignite had even better slurryability. The washed Coal Valley coal was found to have higher reactivity, lower ash fusion temperatures, significantly lower ash content and slightly worse slurryability than its raw form. However, mixtures of petroleum coke with beneficiated Coal Valley coal had the ability to maintain good slurryability up to 55% solids, which was not possible with either type of pure coal slurry. The blended slurry with 75% petroleum coke and 25% beneficiated Coal Valley coal showed the best slurryability of all petroleum coke and Coal Valley slurries that were tested.

2.5 BENEFICIATED FUEL STUDY PART 2: FUEL CHARACTERIZATION AND GASIFICATION

Hughes, R., " Beneficiated Fuel Study Part 2: Fuel Characterization and Gasification", Report to Sherritt International April 2011. This 2nd part of the Beneficiated Fuel Study provides additional fuel characteristics for the previously reported fuels and also provides data for Genesee hydrothermally processed coal. A number of the fuels were gasified in the CanmetENERGY entrained flow gasifier and here we present the operating parameters and test results. Analysis results of the products of gasification, i.e. syngas, soot, and slag, are presented. The potential benefits and disadvantages of the beneficiation techniques employed are discussed for use with integrated gasification combined cycle power production.

2.6 BRIEF REPORT FOR CCPC ON SLAG VISCOSITY WORK

Duchesne, M., Hughes, R., “Brief Report for CCPC on Slag Viscosity Work”, Report to CCPC, March 2011. Nineteen slag temperature-viscosity curves are presented for Genesee, Coal Valley, Suncor petroleum coke, an imported petroleum coke, blends of these fuels, and with fluxants added.


2.7 DATA PACKAGE FOR SLURRY-FED ENTRAINED FLOW GASIFIER CFD MODEL VALIDATION: WASHED COAL VALLEY COAL

Chui, E., Majeski, A., Hughes, R., Lu, D., McCalden, Runstedtler, A., Anthony, EJ. "Data Package for Slurry-Fed Entrained Flow Gasifier CFD Model Validation: Washed Coal Valley Coal", Report to CCPC, April 2011. Advanced gasification technology with carbon sequestration and storage can capture and permanently store 90 percent or more of CO2 emissions from power production and hydrogen production facilities using fossil fuels as feedstock. This can nearly eliminate coal related greenhouse gas emissions and pollution from industries using this technology thus improving North America’s environment, health, and economic strength. The ability to reliably measure and predict process parameters and the composition and properties of process streams inside gasifiers is urgently needed to improve understanding of the fundamentals of coal gasification and gasifier reactor operation. This improved understanding, through the combination of real-time monitoring/analysis of key operating parameters and critical components and Computational Fluid Dynamics (CFD) modeling, will lead to optimized performance and extended gasifier component life. CFD modeling provides a platform for understanding gasification fundamentals and reaction kinetics, and evaluating process efficiency and performance for a variety of feedstocks, applications, and technology options with CO2 capture. The present work is targeted at the development of gasification technology by providing fundamental data for gasification CFD model validation and gasifier operation based on in-situ measurement of gases and solids directly from a slurry-fed slagging gasifier reactor. This document provides a data package for CFD model validation that includes detailed fuel characteristics, gasifier reactor and burner geometry, burner spray characteristics, quench vessel geometry and quench spray characteristics, syngas composition before and after quench, and solid product characteristics.

2.8 PERFORMANCE OF CAO-BASED SORBENTS FOR REMOVAL OF TRACE METAL CONTAMINANT (HG) FROM SYNTHETIC COAL GASIFICATION SYNGAS

Lu, D., Champagne, S., Assaker, R., Hughes, R., “Performance of CaO-based Sorbents for Removal of Trace Metal Contaminant (Hg) from Synthetic Coal Gasification Syngas”, Report to Environment Canada, 2011. CanmetENERGY has studied different types of CaO-based sorbents for their capacity to adsorb mercury from gasification syngas at elevated temperatures. A fixed bed reactor approach was used to test sorbent capacities at various conditions. To prevent mercury from amalgamating with stainless steel tubing, all stainless steel tubing prior to entering the sorbent bed was coated with a silicon coating, SilcoNert™ 2000, a recommended treatment for metal components when analyzing for mercury. When varying only the temperature for calcined limestone in syngas, the initial mercury capture rate for the 450°C trial was much greater than the 650°C trial. Compared to a pure activated carbon, the doped (3% NaCl) and non-doped dolomite and limestone had a lower mercury capture rate. All of the CaO-based sorbents tested in the temperature window between 450°C and 650°C captured between 35% and 50% of the mercury in the syngas.


3 GASIFICATION CONFERENCE PUBLICATIONS

3.1 SIMULATION OF ENTRAINED FLOW COAL GASIFICATION

Chui, E., Majeski, A., Lu, D., Hughes, R., Gao, H., McCalden, D., Anthony, E.J., “Simulation of Entrained Flow Coal Gasification”, Energy Procedia 1, 503-509, 2009. Integrated gasification combined cycle (IGCC) with carbon capture and storage (CCS) is a viable greenhouse gas control technology in using coal for power and/or hydrogen generation. This work describes the development of a pilot-scale pressurized entrained flow coal gasification facility and the parallel computational fluid dynamics (CFD) based simulation capability for the purpose of advancing commercial coal gasification technology. The gasification simulation approach, its present predictive performance and the potential areas for further improvement are presented.

3.2 OPTIMIZATION OF CANADIAN PETROLEUM COKE, COAL AND FLUXING AGENT BLENDS VIA SLAG VISCOSITY MEASUREMENTS AND MODELS

Duchesne, M., Ilyushechkin, A., Macchi, A., Anthony, E.J. “Optimization of Canadian Petroleum Coke, Coal and Fluxing Agent Blends via Slag Viscosity Measurements and Models”, International Pittsburgh Coal Conference, Istanbul, Turkey., 2010. The slagging behavior of petroleum coke must be known to determine suitable feedstock blends for entrained-flow slagging gasification. To increase the amount of slag formed and maintain a low viscosity, petroleum coke may be blended with coal and/or a fluxing agent such as limestone or dolomite. Viscosity measurements were performed for various blends of artificial Genesee coal ash, Suncor petroleum coke ash, limestone and dolomite in a neutral gas atmosphere. Adding petcoke to the coal provided a moderate reduction in viscosity, while limestone and dolomite additions were very effective for viscosity reduction. FactSage phase equilibrium predictions and quenched sample analysis via SEM and EPMA were used to link solids formation to changes in the viscosity-temperature relation. Slag blends without limestone or dolomite showed glassytype behaviour, while those with limestone or dolomite showed crystalline-type behaviour. Predictions from several slag viscosity models were compared to measured values. The viscosity model which provided the most accurate predictions was utilized for optimization of fluxing agent addition to various petcoke and coal blends.


3.3 ENTRAINED FLOW SLAGGING SLURRY GASIFICATION AND THE DEVELOPMENT OF COMPUTATIONAL FLUID DYNAMICS MODELS AT CANMENTENERGY

Hughes, R., Lu., D., Majeski, A., Corber, A., Anthony, E.J. “Entrained Flow Slagging Slurry Gasification and the Development of Computational Fluid Dynamics Models at CanmetENERGY”, International Pittsburgh Coal Conference, Istanbul, Turkey., 2010. The development of computational fluid dynamics (CFD) models representing entrained flow slagging slurry gasification has proven difficult due to limited information being available in the open literature regarding gasifier geometry, burner spray characterization, and local gas and char conditions. This paper describes efforts made by Canadian national laboratories CanmetENERGY and the National Research Council, to provide the data required for developing and validating gasification CFD models. The CanmetENERGY two tonne per day (slurry feed rate) pilot-scale gasifier has been modified to allow local gas and char conditions to be sampled from within the gasifier and from the syngas exiting the quench vessel during gasifier operation. A series of Canadian and U.S. solid feedstocks have been gasified and a subset of the results of these gasification tests is presented here. The National Research Council’s Institute for Aerospace Research spray characterization laboratory is determining droplet size and velocity characteristics for the CanmetENERGY slurry gasifier burner spray at elevated pressure and temperature. Gasifier geometry, burner spray characterization, local gas and char conditions, fuel characteristics, and slag viscosity measurements have been used in the development of CanmetENERGY CFD models representing the system. The data is being forwarded to our industrial, academic, and government research partners in Canada and the U.S.


4 CALCIUM LO O PING J O URNAL PUB LICATIO NS

4.1 DETERMINATION OF INTRINSIC RATE CONSTANTS OF THE CAO–CO2 REACTION

Sun, P., Grace, J.R., Lim, C.J. and Anthony, E.J. “Determination of Intrinsic Rate Constants of the CaO-CO2 Reaction”, Chemical Engineering Science, 63, 47-56, 2008. The rate constant of the CaO–CO2 reaction was studied for two sorbents using an atmospheric thermogravimetric analyzer (ATGA) and a pressurized thermogravimetric analyzer (PTGA). A grain model was used to determine the rate-controlling steps. The intrinsic rate was found to have a variable order with respect to CO2 partial pressure, with a first-order reaction changing to zero-order dependence when the CO2 partial pressure exceeded ~ 10 kPa. No further rate enhancement was observed under pressurized conditions, which was explained by a two-step Langmuir mechanism. The activation energies were 29 ± 4 and 24 ± 6kJ/mol for the limestone and dolomite tested.

4.2 A DISCRETE-PORE-SIZE-DISTRIBUTION-BASED GAS–SOLID MODEL AND ITS APPLICATION TO THE CAO + CO2 REACTION

Sun, P., Grace, J.R., Lim, C.J. and Anthony, E.J. “A Discrete-Pore Size-Distribution-based Gas-Solid Model and Its Application to the CaO + CO2 Reaction”, Chemical Engineering Science, 63, 57-70, 2008. Experimental data obtained in both atmospheric and pressurized thermogravimetric reactors indicate that carbonation is insensitive to the CO2 partial pressure in terms of final conversion and apparent carbonation rate. A new gas–solid model is formulated to describe the entire experimental carbonation history, with measured rate constant and pore size distribution data as input. The effective diffusivity in the product layer is the only fitting parameter, dependent on the evolution of the pores. The model is able to predict atmospheric and pressurized thermogravimetric reactor carbonation data with fitted activation energies of 215 and 187 kJ/mol for the limestone and dolomite tested.

4.3 CARBONATION OF FLY ASH IN OXY-FUEL CFB COMBUSTION

Wang, G., Jia, L., Tan, Y. and Anthony, E.J. “Carbonation of Fly Ash in Oxy Fuel CFB Combustion”, Fuel.87, 1108-1114, 2008. Oxy-fuel combustion of fossil fuel is one of the most promising methods to produce a stream of concentrated CO2 ready for sequestration. Oxy-fuel FBC (fluidized bed combustion) can use limestone as a sorbent for in situ capture of sulphur dioxide. Limestone will not calcine to CaO under typical oxy-fuel circulating FBC (CFBC) operating temperatures because of the high CO2 partial pressures. However, for some fuels, such as anthracites and petroleum cokes, the typical combustion temperature is above 900 °C. At CO2 concentrations of 80–85% (typical of oxy-fuel CFBC conditions with flue gas recycle) limestone still calcines, but when the ash cools to the calcination temperature, carbonation of fly ash deposited on cool surfaces may occur. This phenomenon has the potential to cause fouling of the heat transfer surfaces in the back end of the boiler, and to create serious operational difficulties. In this study, fly ash generated in a utility CFBC boiler was carbonated in a thermogravimetric analyzer (TGA) under conditions expected in an oxy-fuel CFBC. The temperature range investigated was from 250 to 800 °C with CO2 concentration set at 80% and H2O concentrations at 0%, 8% and 15%, and the rate and the extent of the carbonation reaction were determined. Both temperature and H2O concentrations played important


roles in determining the reaction rate and extent of carbonation. The results also showed that, in different temperature ranges, the carbonation of fly ash displayed different characteristics: in the range 400 °C < T 6 800 °C, the higher the temperature the higher the CaO to carbonate conversion ratio. The presence of H2O in the gas phase always resulted in higher CaO conversion ratio than that obtainable without H2O. For T 6 400 °C, no fly ash carbonation occurred without the presence of H2O in the gas phase. However, on water vapour addition, carbonation was observed, even at 250 °C. For T 6 300 °C, small amounts of Ca(OH)2 were found in the final product alongside CaCO3. Here, the carbonation mechanism is discussed and the apparent activation energy for the overall reaction determined.

4.4 SEQUENTIAL SO2/CO2 CAPTURE ENHANCED BY STEAM REACTIVATION OF A CAO-BASED SORBENT

Manovic, V. and Anthony, E.J. “Sequential SO2/CO2 capture enhanced by steam reactivation of a CaO-based sorbent”, Fuel 87, 1564-15733, 2008. The steam hydration reactivation characteristics of three limestone samples after multiple CO2 looping cycles are presented here. The CO2 cycles were performed in a tube furnace (TF) and the resulting samples were hydrated by steam in a pressure reactor (PR). The reactivation was performed with spent samples after carbonation and calcination stages. The reactivation tests were done with a saturated steam pressure at 200 °C and also at atmospheric pressure and 100 °C. The characteristics of the reactivation samples were examined using BET and BJH pore characterization (for the original and spent samples, and samples reactivated under different conditions) and also by means of a thermogravimetric analyzer (TGA). The levels of hydration achieved by the reactivated samples were determined as well as the conversions during sulphation and multiple carbonation cycles. It was found that the presence of a CaCO3 layer strongly hinders sorbent hydration and adversely affects the properties of the reactivated sorbent with regard to its behavior in sulphation and multiple carbonation cycles. Here, hydration of calcined samples under pressure is the most effective method to produce superior sulphur sorbents. However, reactivation of calcined samples under atmospheric conditions also produces sorbents with significantly better properties in comparison to those of the original sorbents. These results show that separate CO2 capture and SO2 retention in fluidized bed systems enhanced by steam reactivation is promising even for atmospheric conditions if the material for hydration is taken from the calciner. 4.5 SONOCHEMICAL TREATMENT OF FBC ASH: A STUDY OF THE REACTION MECHANISM

AND PERFORMANCE OF SYNTHETIC SORBENTS

Rao, A., Anthony, E.J. and Manovic, V. “Sonochemical Treatment of FBC Ash: A Study of the Reaction Mechanism and Performance of Synthetic Sorbents”, Fuel, 87, 1927-1933, 2008. This work explores the reaction mechanisms for the sonochemical-enhanced carbonation of fluidized bed combustion (FBC) ash. Ashes from Nova Scotia Power’s 165 MWe circulating fluidized bed combustor (CFBC) as well as synthetic ash prepared directly from limestone have been used. Acetone tests were carried out using pure acetone as well as acetone/water mixtures (4:1 ratio). Tests with acetone demonstrated that, without previous hydration of the ash, significant carbonation is not achieved. Experiments were also conducted to determine the role of hydration temperature on the carbonation of FBC ash. X-ray diffraction (XRD) analysis of synthetic ash after sonication has also been carried out. Analysis of the data obtained revealed that the process is well described by a series reaction mechanism. Initial hydration temperature does not appear to


significantly impact the carbonation of FBC ash. Synthetic ash does not behave like FBC ash due apparently to its extreme susceptibility to the size reduction capability of ultrasonics.

4.6 SOLID LOOPING CYCLES: A NEW TECHNOLOGY FOR COAL CONVERSION

Anthony, E.J. “Solid Looping Cycles: A New Technology for Coal Conversion”, special anniversary edition of Industrial and Engineering Chemistry Research, 47, 1747-1754, 2008. This article examines both oxygen looping cycles (otherwise known as chemical looping combustion), and lime-based CO2 looping cycles, where calcined limestone is used for in situ CO2 capture. There has been a rapid rise in the amount of research carried out recently, and both technologies are likely to see practical application in the near future. However, these technologies urgently require demonstration at the large pilot plant level - in the case of chemical looping cycles for use with high-pressure syngas of the type likely to be produced by current coal gasification technologies and in the case of CO2 looping cycles both for combustion and gasification applications with coal. Both approaches have potential for application in schemes for H2 production, but these have not been considered here, although such applications will also inevitably follow in the medium to long term.

4.7 INVESTIGATION OF ATTEMPTS TO IMPROVE CYCLIC CO2 CAPTURE BY SORBENT HYDRATION AND MODIFICATION

Sun, P., Grace, J.R., Lim, C.J. and Anthony, E.J. “Investigation of Attempts to Improve Cyclic CO2 Capture by Sorbent Hydration and Modifications”, Industrial and Engineering Chemistry Research, 47, 2024-2032, 2008. A three-part experimental program was carried out to investigate possible methods to improve sorbent reversibility during cyclic calcination/carbonation using one limestone and one dolomite. In the first part, the different roles of steam and water are discussed and investigated. Steam addition during carbonation and calcination did not help to significantly achieve good reversibility. Hydration, especially with low-temperature steam and liquid water, is promising to help improve sorbent reversibility by regenerating favorable pore size distributions; however, a carbonate layer inhibited hydration. Preliminary tests were also conducted on possible agents that might improve CO2 capture efficiency and sorbent cyclic performance. An ~1:1 molar ratio of CaO to Al2O3 showed promising results on a free-lime basis. A series of other tests did not give promising results, but provided information relevant to developing synthetic CO2 sorbents. It was also found that CO can regenerate CaO from CaSO4 formed during co-capture of SO2 and CO2, but the rate of reduction is too slow to be of practical interest. 4.8 PARAMETRIC STUDY ON THE CO2 CAPTURE CAPACITY OF CAO-BASED SORBENTS IN

LOOPING CYCLES

Manovic, V. and Anthony, E.J. "A Parametric Study on CO2 Capture Capacity of CaO-based Sorbents in Looping Cycles", Energy and Fuels, 22, 1851-1857, 2008. An experimental parametric study on the CO2 capture activity of four limestone-derived CaO-based sorbents has been performed. Experiments were done in a thermogravimetric analyzer (TGA) at temperatures ranging from 650 to 850 °C. Three particle-size fractions of Kelly Rock limestone and powders obtained by their grinding were also tested, while the influence of carbonation and calcination durations was


examined at 750 and 850 °C. Calcination is typically performed in an atmosphere of N2 and carbonation in 50% CO2 (N2 balance), and the influence of the effective CO2 concentration surrounding reacting particles was examined by changing the sample mass in some experiments. The results indicated that increasing the calcination/carbonation temperature had a negative influence on the sorbent activity, while the influence of particle size was small, although larger particles have higher activity. This was unexpected, but it can be explained by the higher content of impurities in the smaller particles. Grinding enhances sorbent activity, and this appears to be more than simply due to increased external surface area of the sorbent particles in the powdered samples. Prolonged carbonation time has a negative effect on the sorbent performance. The formation and decomposition of CaCO3 as well as its presence on the sorbent surface at higher temperatures appear to be key factors in the loss of surface area (i.e., decrease in sorbent activity). However, it is shown that the prolonged exposure to calcination conditions employed in this work (inert atmosphere) has a slightly beneficial effect on sorbent behavior as a function of the number of calcination/carbonation cycles. Experiments with larger sample masses typically resulted in better conversions. Analysis of scanning electron microscope (SEM) images of spent sorbent particles obtained from different reactor types indicated that thermal stresses are the main cause for sorbent particle fracture and attrition.

4.9 THERMAL ACTIVATION OF CAO-BASED SORBENT AND SELF-REACTIVATION DURING CO2 CAPTURE LOOPING CYCLES

Manovic, V. and Anthony, E.J., “Thermal Activation of CaO-based Sorbent and Self-Reactivation during CO2 Capture Looping Cycles”, Environmental Science and Technology, 42, 4170-4174, 2008. In this study, the thermal activation of different types of CaO based sorbents was examined. pretreatments were performed at different temperatures (800-1300 °C) and different durations (6-48 h) using four Canadian limestones. Sieved fractions of the limestones, powders obtained by grinding, and hydroxides produced following multiple carbonation/calcination cycles achieved in a tube furnace were examined. Pretreated samples were evaluated using two types of thermogravimetric reactors/ analyzers. The most important result was that thermal pretreatment could improve sorbent performance. In comparison to the original, pretreated sorbents showed better conversions over a longer series of CO2 cycles. Moreover, in some cases, sorbent activity actually increased with cycle number, and this effect was especially pronounced for powdered samples preheated at 1000 °C. In these experiments, the increase of conversion with cycle number (designated as self-reactivation) after 30 cycles produced samples that were ~50% carbonated for the four sorbents examined here, and there appeared to be the potential for additional increase. These results were explained with the newly proposed pore-skeleton model. This model suggests, in addition to changes in the porous structure of the sorbent, that changes in the pore-skeleton produced during pretreatment strongly influence subsequent carbonation/ calcination cycles.

4.10 SULPHATION AND CARBONATION PROPERTIES OF HYDRATED SORBENTS FROM A FLUIDIZED BED CO2 LOOPING CYCLE REACTOR

Manovic, V., Lu, D. and Anthony, E.J., “Sulphation and Carbonation Properties of Hydrated Sorbents from a Fluidized Bed CO2 Looping Cycle Reactor”, Fuel, 87, 2923-2931, 2008.


Sulphation and carbonation have been performed on hydrated spent residues from a 75 kWth dual fluidized bed combustion (FBC) pilot plant operating as a CO2 looping cycle unit. The sulphation and carbonation tests were done in an atmospheric pressure thermogravimetric analyzer (TGA), with the sulphation performed using synthetic flue gas (0.45% SO2, 3% O2, 15% CO2 and N2 balance). Additional tests were carried out in a tube furnace (TF) with a higher SO2 concentration (1%) and conversions were determined by quantitative X-ray diffraction (QXRD) analyses. The morphology of the sulphated samples from the TF was examined by scanning electron microscopy (SEM). Sulphation tests were performed at 850 °C for 150 min and carbonation tests at 750 °C, 10 cycles for 15 min (7.5 min calcination + 7.5 min carbonation). Sulphation conversions obtained for the hydrated samples depended on sample type: in the TGA, they were ~75–85% (higher values were obtained for samples from the carbonator); and in the TF, values around 90% and 70% for sample from carbonator and calciner, respectively, were achieved, in comparison to the 40% conversion seen with the original sample. The SEM analyses showed significant residual porosity that can increase total conversion with longer sulphation time. The carbonation tests showed a smaller influence of the sample type and typical conversions after 10 cycles were 50% – about 10% higher than that for the original sample. The influence of hydration duration, in the range of 15–60 min, is not apparent, indicating that samples are ready for use for either SO2 retention, or further CO2 capture after at most 15 min using saturated steam. The present results show that, upon hydration, spent residues from FBC CO2 capture cycles are good sorbents for both SO2 retention and additional CO2 capture.

4.11 STEAM HYDRATION OF SORBENTS FROM A DUAL FLUIDIZED BED CO2 LOOPING CYCLE REACTOR

Manovic, V., Lu, D. and Anthony, E.J., “Steam Hydration of Sorbents from a Dual Fluidized Bed CO2 Looping Cycle Reactor”, Fuel 87, 3344-3352, 2008. Results are presented on steam hydration of spent residues obtained from a 75 kWth dual fluidized bed combustion (FBC) pilot plant unit operating in a CO2 looping cycle mode. The samples were collected from the unit under various conditions, which included electrical heating of the reactor, as well as firing with coal, and biomass under oxy-fuel combustion conditions. In addition, different operating times, i.e., number of cycles (25 min–455 min/1–25 cycles) were examined, with the carbonator operating at temperatures of 600–700 °C and the calciner at 850–900 °C. The samples collected came from the calciner, carbonator and cyclone. Steam hydration itself was done under atmospheric pressure in saturated steam at 100 °C for periods of 15, 30 and 60 min. The original limestone sample, as well as the spent samples from the pilot plant and the hydrated samples were examined to determine their hydration and carbonation levels, as well as their unreacted CaO content using TGA and XRD analysis. In addition, samples were characterized for pore distribution (nitrogen adsorption/desorption: BET and BJH), skeleton characterization, with density by He pycnometry and particle surface area morphology (SEM/EDX), as well as changes in sample volume during hydration (sample swelling). The results obtained showed successful hydration (typically only ~10% unreacted CaO) even for hydration periods as short as 15 min, and very favorable sample properties. Their pore surface area, pore volume distribution and swelling during hydration are promising with regard to their use in additional CO2 capture cycles or SO2 retention. However, their predisposition to fracture is the main disadvantage observed with these samples. This may result in difficulties in terms of their handling in FBC systems, due to intensified attrition and consequent elutriation from the reactor.


4.12 CA-BASED SORBENT LOOPING COMBUSTION FOR CO2 CAPTURE IN PILOT-SCALE DUAL FLUIDIZED BEDS

Lu, D., Hughes, R.W. and Anthony, E.J., “Ca-based Sorbent Looping Combustion for CO2 Capture in Pilot Scale Dual Fluidized Beds”, Fuel Processing Technology, 89, 1386-1395, 2008. To demonstrate process feasibility of in situ CO2 capture from combustion of fossil fuels using Ca-based sorbent looping technology, a flexible atmospheric dual fluidized bed combustion system has been constructed. Both reactors have an ID of 100 mm and can be operated at up to 1000 °C at atmospheric pressure. This paper presents preliminary results for a variety of operating conditions, including sorbent looping rate, flue gas stream volume, CaO/CO2 ratio and combustion mode for supplying heat to the sorbent regenerator, including oxy-fuel combustion of biomass and coal with flue gas recirculation to achieve high-concentration CO2 in the off-gas. It is the authors' belief that this study is the first demonstration of this technology using a pilot-scale dual fluidized bed system, with continuous sorbent looping for in situ CO2 capture, albeit at atmospheric pressure. A multi-cycle test was conducted and a high CO2 capture efficiency (>90%) was achieved for the first several cycles, which decreased to a still acceptable level (>75%) even after more than 25 cycles. The cyclic sorbent was sampled on-line and showed general agreement with the features observed using a lab-scale thermogravimetric analysis (TGA) apparatus. CO2 capture efficiency decreased with increasing number of sorbent looping cycles as expected, and sorbent attrition was found to be another significant factor to be limiting sorbent performance. 4.13 CO2 LOOPING CYCLE PERFORMANCE OF A HIGH-PURITY LIMESTONE AFTER THERMAL

ACTIVATION/DOPING

Manovic, V., Anthony, E.J. Abanades, C.J, and Grasa, G., “CO2 Looping Cycle Performance of a High-Purity Limestone after Thermal Activation/Doping", Energy and Fuels, 22, 3258-3264, 2008. The influence of thermal pretreatment on the performance of a high-purity limestone (La Blanca) during CO2 capture cycles is investigated in this paper. This limestone was chosen for more detailed investigation because, in earlier research, it failed to show any favorable effect as a result of thermal pretreatment. Here, the original sample, with a particle size of 0.4-0.6 mm, and ground samples were thermally pretreated at 1000-1200 °C, for 6-24 h, and then subjected to several carbonation/calcination cycles in a thermogravimetric analyzer (TGA). This work shows that thermal pretreatment failed to produce a significant self-reactivation effect during CO2 cycles, despite the use of a wide range of conditions during pretreatment (grinding, temperature, and pretreatment duration) as well as during cycling (CO2 concentration and duration of the carbonation stage). Additional doping experiments showed that both high Na content and lack of Al in La Blanca limestone cause poor self-reactivation performance after thermal pretreatment. Scanning electron microscope-energy-dispersive X-ray (SEM-EDX) analyses also confirmed more pronounced sintering and loss of activity, which we believe are caused by the relatively high Na content. However, stabilization of sorbent particle morphology by Al can allow this limestone to show self-reactivation performance and higher conversions over a longer series of CO2 cycles.


4.14 CHANGES IN LIMESTONE SORBENT MORPHOLOGY DURING CAO-CACO3 LOOPING AT PILOT SCALE

Hughes, R., Macchi, A., Lu, Y., Anthony, E.J., “Changes in Limestone Sorbent Morphology during CaO-CaCO3 Looping at Pilot Scale”, Chemical Engineering Technology 32, No. 3, 425-434, 2009. A pilot-scale dual fluidized bed combustion system was used for CO2 capture using limestone sorbent with CaO-CaCO3 looping. The sorbent was regenerated at high temperature using an air- or oxygen-fired fluidized bed calciner with flue gas recycle firing hardwood pellets. Two limestones were evaluated for CaOCaCO3 looping. Changes in the sorbent morphology during the tests were identified by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). Changes in pore size distribution and sorbent surface area that occurred during reaction were determined by N2 BET porosymmetry. Thermogravimetric analysis (TGA) was used to determine the activity of the sorbent after processing in the dual fluidized bed combustion system. It was found that oxygen fired calcination with high CO2 partial pressure reduced the effectiveness of the two limestone sorbents for CO2 capture when compared to material calcined under oxygen-enhanced air combustion. A shell 1–2 lm thick, with reduced porosity, was formed around the sorbent particle and is believed to be responsible for reduced conversion of CaO to CaCO3. It is believed that ash deposition contributes to the formation of the shell. 4.15 SINTERING AND REACTIVITY OF CACO3-BASED SORBENTS FOR IN SITU CO2 CAPTURE

IN FLUIDIZED BEDS UNDER REALISTIC CALCINATION CONDITIONS

Lu, D., Hughes, R., Anthony, E.J. and Manovic, V., “Sintering and Reactivity of CaCO3-based Sorbents for In-situ CO2 capture in Fluidized Beds under Realistic Calcination Conditions”, Journal of Environmental Engineering, 135, 404-410, 2009. Sintering during calcination/carbonation may introduce substantial economic penalties for a CO2 looping cycle using limestone/dolomite-derived sorbents. Here, cyclic carbonation and calcination reactions were investigated for CO2 capture under fluidized bed combustion (FBC) conditions. The cyclic carbonation characteristics of CaCO3-derived sorbents were compared at various calcination temperatures (700–925°C) and different gas stream compositions: pure N2 and a realistic calciner environment where high concentrations of CO2 >80–90% (and the presence of SO2) are expected. The conditions during carbonation employed here were 700°C and 15% CO2 in N2 and 0.18% or 0.50% SO2 in selected tests, i.e., typically expected for a carbonator. Up to 20 calcination/carbonation cycles were conducted using a thermogravimetric analyzer (TGA) apparatus. Three Canadian limestones were tested: Kelly Rock, Havelock, and Cadomin, using a prescreened particle size range of 400–650 micron. In addition, calcined Kelly Rock and Cadomin samples were hydrated by steam and examined. Sorbent reactivity was reduced whenever SO2 was introduced to either the calcining or carbonation streams. The multi-cyclic capture capacity of CaO for CO2 was substantially reduced at high concentrations of CO2 during the sorbent regeneration process and carbonation conversion of the Kelly Rock sample obtained after 20 cycles was only 10.5%. Hydrated sorbents performed better for CO2 capture, but also showed significant deterioration following calcination in high CO2 gas streams. This indicates that high CO2 and SO2 levels in the gas stream lead to lower CaO conversion because of enhanced sintering and irreversible formation of CaSO4. Such effects can be reduced by separating sulphation and carbonation and by introducing steam to avoid extremely high CO2 atmospheres, albeit at a higher cost and/or increased engineering complexity.


4.16 IMPROVEMENT OF CAO-BASED SORBENT PERFORMANCE FOR CO2 LOOPING CYCLES

Manovic, V. and Anthony, E.J., “Improvement of CaO-Based Sorbent Performance for CO2 Looping Cycles”, Thermal Science, 13, 89-104, 2009. This paper presents research on CO2 capture by lime-based looping cycles. This is a new and promising technology that may help in mitigation of global warming and climate change caused primarily by the use of fossil fuels. The intensity of the anticipated changes urgently requires solutions such as the developing technologies for CO2 capture, especially those based on CaO looping cycles. This technology is at the pi lot plant demonstration stage and there are still significant challenges that require solutions. The technology is based on a dual fluidized bed reactor which contains a carbonator – a unit for CO2 capture, and a calciner – a unit for CaO regeneration. The major technology components are well known from other technologies and easily applicable. However, even though CaO is a very good candidate as a solid CO2 carrier, its performance in a practical system still has significant limitations. Thus, research on CaO performance is critical and this paper discusses some of the more important problems and potential solutions that are being examined at CETC-O.

4.17 CO2 LOOPING CYCLES WITH CAO-BASED SORBENT PRETREATED IN CO2 AT HIGH TEMPERATURE

Manovic, V., Anthony, E.J., Loncarevic, D., “CO2 Looping Cycles with CaO Based Sorbents Pretreated in CO2 at High Temperature”, Chemical Engineering Science, 64, 3236-3245, 2009. In this study, pretreatment o f CaO-based sorbent in a CO2 atmosphere at high temperature is investigated for its effect on CO2 capture. Three limestones from three widely different geographical locations are used for the tests: Kelly Rock (Canada), La Blanca (Spain), and Katowice (Poland).The particle sizes used are typically as employed in fluidized bed conversion systems. Pretreatment was done in a tube furnace at different temperatures and for different durations. The pretreated samples are characterized by nitrogen physisorption tests, scanning electron microscopy (SEM), and carbonation/calcination conversion measurements in a thermogravimetric analyzer (TGA).The results obtained showed significant decrease of sorbent surface area after pretreatment and the presence of smooth CaO grains was typical of the sorbent particle surface morphology. The pore surface area of pretreated sorbent samples increased after CO2 cycling, with a peak in pore volume distributions at 50nm, and SEM images showed there appearance of smaller CaO grains. In the case of Kelly Rock and Katowice samples, this led to an increase in CO2 capture activity, up to 45% after 20 cycles. After that, conversions decreased but still remained 5–10% above those for the original (no pretreatment) samples. This beneficial effect means that particles of larger size, typical of fluidized bed combustion (FBC) systems, can be suitably pretreated for use in longer series of CO2 capture cycles. An additional expected advantage of pretreating sorbent in this manner is reduced elutriation at any given FBC condition. Attempts to pretreat La Blanca failed, as they did when using N2, and it is believed that this is explained by the high Na content of this limestone.

4.18 CO2 CAPTURE FROM SYNGAS VIA CYCLIC CARBONATION/CALCINATION FOR A NATURALLY OCCURRING LIMESTONE: MODELLING AND BENCH-SCALE TESTING

Lu, D., Symonds, R., Macchi, A., Hughes, R., and Anthony, E.J., “CO2 Capture from Syngas via Cyclic Carbonation/Calcination for a Naturally Occurring Limestone (I): Modeling and Bench-Scale Tests”, Chemical Engineering Science, 64, 3536-3543, 2009.


The intrinsic rate constants of the CaO–CO2 reaction, in the presence of syngas, were studied using a grain model for a naturally occurring calcium oxide-based sorbent using a thermogravimetric analyzer. Over temperatures ranging from 580 to 700 ◦C, it was observed that the presence of CO and H2 (with steam) during carbonation caused a significant increase in the initial rate of carbonation, which has been attributed to the CaO surface sites catalyzing the water–gas shift reaction, increasing the local CO2 concentration. The water– gas shift reaction was assumed to be responsible for the increase in activation energy from 29.7 to 60.3kJ/mol for limestone based on the formation of intermediate complexes. Changes in microporosity due to particle sintering during calcination have been credited with the rapid initial decrease in cyclic CaO maximum conversion for limestone particles, whereas the presence of steam during carbonation has been shown to improve the long-term maximum conversion in comparison to previous studies without steam present.

4.19 LONG-TERM CALCINATION/CARBONATION CYCLING AND THERMAL PRETREATMENT FOR CO2 CAPTURE BY LIMESTONE AND DOLOMITE

Chen, Z., Song, H.S., Portillo, M., Lim, C.J., Grace, J.R. and Anthony, E.J., “Long-term Calcination/Carbonation Cycling and Thermal Pretreatment for CO2 Capture by Limestone and Dolomite”, Energy and Fuels 23, 1437–1444, 2009. Capturing carbon dioxide is vital for the future of climate-friendly combustion, gasification, and steam-reforming processes. Dry processes utilizing simple sorbents have great potential in this regard. Long-term calcination/carbonation cycling was carried out in an atmospheric-pressure thermogravimetric reactor. Although dolomite gave better capture than limestone for a limited number of cycles, the advantage declined over many cycles. Under some circumstances, decreasing the carbonation temperature increased the rate of reaction because of the interaction between equilibrium and kinetic factors. Limestone and dolomite, after being pretreated thermally at high temperatures (1000 or 1100 °C), showed a substantial increase in calcium utilization over many calcination/carbonation cycles. Lengthening the pretreatment interval resulted in greater improvement. However, attrition was significantly greater for the pretreated sorbents. Greatly extending the duration of carbonation during one cycle was found to be capable of restoring the CO2 capture ability of sorbents to their original behavior, offering a possible means of countering the long-term degradation of calcium sorbents for dry capture of carbon dioxide.

4.20 SO2 RETENTION BY CAO-BASED SORBENT SPENT IN CO2 LOOPING CYCLES

Manovic, V., Anthony, E.J. and Loncarevic, D. “SO2 Retention by CaO based Sorbent Spent in CO2 Looping Cycles”, Industrial & Engineering Chemistry Research 48, 6627–6632. 2009. CaO-based looping cycles are promising processes for CO2 capture from both syngas and flue gas. The technology is based on cyclical carbonation of CaO and regeneration of CaCO3 in a dual fluidized-bed reactor to produce a pure CO2 stream suitable for sequestration. The main limitation of natural sorbents is the loss of carrying capacity with increasing number of reaction cycles, resulting in the need for extra sorbent, and subsequent spent sorbent waste. Use of spent sorbent from CO2 looping cycles for SO2 capture is investigated in this study. Three limestones were investigated: Kelly Rock (Canada), La Blanca (Spain), and Katowice (Poland, Upper Silesia). Carbonation/calcination cycles were performed in a tube furnace with both the original limestones and samples thermally pretreated for different times (i.e., sintered). The spent sorbent samples were sulfated in a thermogravimetric analyzer (TGA). The changes in


the resulting sorbent pore structure were then investigated using mercury porosymmetry. It has been shown that the sulphation rates of both thermally pretreated and spent sorbent samples are lower in comparison with those of the original samples. However, final conversions of both spent and pretreated sorbents after longer sulphation time were comparable or higher than those observed for the original sorbents under comparable conditions. Maximum sulphation levels strongly depend on sorbent porosity and pore surface area. The shrinkage of sorbent particles during calcination/ carbonation cycling resulted in a loss of sorbent porosity on the order of ≤48%, which corresponds to maximum sulphation levels of ~55% for spent Kelly Rock and Katowice. This is ~10% higher than that seen with the original samples after 15 h of sulphation. By contrast, La Blanca limestone had more pronounced particle shrinkage during pretreatment and cycling, leading to porosities lower than 35%, which resulted in sulphation conversion of spent samples <30%, which is significantly lower than that for the original sample (45%). These results showed that spent sorbent samples from CO2 looping cycles can be used as sorbents for SO2 retention in cases where significant porosity loss does not occur during CO2 reaction cycles. The higher conversions of spent samples are explained by a shift in pore size distribution toward larger pores that reduce the reaction rate and pore plugging near the particle’s outer surface, with formation of either unreacted core or unreacted network patterns. In the case of spent Kelly Rock and Katowice samples, sorbent particles are practically uniformly sulfated, achieving final conversions that are determined by the total pore volume available for the bulky CaSO4 product.

4.21 CAO-BASED PELLETS SUPPORTED BY CALCIUM ALUMINATE CEMENTS FOR HIGH-TEMPERATURE CO2 CAPTURE

Manovic, V., and Anthony, E.J., “CaO-Based Pellets Supported by Calcium Aluminate Cements for High Temperature CO2 Capture”, Environmental Science and Technology, 43, 7117-7122, 2009. The development of highly efficient CaO-based pellet sorbents, using inexpensive raw materials (limestones) or the spent sorbent from CO2 capture cycles, and commercially available calcium aluminate cements (CA-14, CA-25, Secar 51, and Secar 80), is described here. The pellets were prepared using untreated powdered limestones or their corresponding hydrated limes and were tested for their CO2 capture carrying capacities for 30 carbonation/calcination cycles in a thermogravimetric analyzer (TGA). Their morphology was also investigated by scanning electron microscopy (SEM) and their compositions before and after carbonation/calcination cycles were determined by X-ray diffraction (XRD). Pellets prepared in this manner showed superior behavior during CO2 capture cycles compared to natural sorbents, with the highest conversions being >50% after 30 cycles. This improved performance was attributed to the resulting substructure of the sorbent particles, i.e., a porous structure with nanoparticles incorporated. During carbonation/calcination cycles mayenite (Ca12Al14O33) was formed, which is believed to be responsible for the favorable performance of synthetic CaO-based sorbents doped with alumina compounds. An added advantage of the pellets produced here is their superior strength, offering the possibility of using them in fluidized bed combustion (FBC) systems with minimal sorbent loss due to attrition.


4.22 SCREENING OF BINDERS FOR PELLETIZATION OF CAO-BASED SORBENTS FOR CO2 CAPTURE

Manovic, V., and Anthony, E.J., “Screening of Binders for Pelletization of CaO-Based Sorbents for CO2 Captures”, Energy and Fuels, 23, 4797–4804, 2009. CaO-based CO2 looping cycle technology is a promising method for separation of CO2 from flue gas and syngas at high temperatures. The process of CO2 capture is expected to take place in fluidized-bed combustion (FBC) systems, which implies significant attrition and elutriation of the solid sorbent. Hence, both reactivation of spent sorbent and preparation of modified CaO-based sorbent may be required to maximize the performance of the sorbent. One of the more promising methods to achieve reactivation, namely, hydration, seems to produce very fragile particles, which are unlikely to be suitable for FBC applications. Thus, it is expected that pelletization of the obtained powder may be required. In this paper, we present initial results on the screening of suitable binders for pelletization. Two types of bentonite (Na- and Ca-bentonite) and four types of commercial calcium aluminate cements (CA-14, CA-25, Secar 51, and Secar 80) were investigated here, with a primary focus of maintaining a high CO2-capture capacity over 30-35 cycles. The tests were carried out using a thermogravimetric analyzer (TGA), and the results showed that the presence of bentonites led to faster decay in activity as a result of the formation of calcium-silica compounds with low melting points, which leads to enhanced sintering. This is confirmed by scanning electron microscopy (SEM) and also X-ray diffraction (XRD), which showed the presence of spurrite [Ca5(SiO4)2CO3] as the dominant compound in the pellet after this series of cycles. Better results were obtained with no binder, i.e., by hydration of lime, where Ca(OH)2 plays the role of the binder. Promising results were obtained also with calcium aluminate cements, where no effect of sintering because of the presence of these binders was noticed. Thus, on the basis of this study, the use of calcium aluminate cements for pelletization of CaO-based sorbent is recommended.

4.23 THE LONG-TERM BEHAVIOR OF CAO-BASED PELLETS SUPPORTED BY CALCIUM ALUMINATE CEMENTS IN A LONG SERIES OF CO2 CAPTURE CYCLES

Manovic, V. and Anthony, E.J., “The Long-term Behavior of CaO based Pellets Supported by Calcium Aluminate Cements in Long Series of CO2 Capture Cycles” Industrial and Engineering Chemistry Research 48, 8906-8912, 2009. A series of carbonation/calcination tests consisting of 1000 cycles was performed with CaO-based pellets prepared using hydrated lime and calcium aluminate cement. The change in CO2 carrying capacity of the sorbent was investigated in a thermogravimetric analyzer (TGA) apparatus and the morphology of residues after those cycles in the TGA was examined by scanning electron microscopy (SEM). Larger quantities of sorbent pellets underwent 300 carbonation/calcination cycles in a tube furnace (TF), and their properties were examined by nitrogen physisorption tests (BET and BJH). The crushing strength of the pellets before and after the CO2 cycles was determined by means of a custom-made strength testing apparatus. The results showed high CO2 carrying capacity in long series of cycles with an extremely high residual activity of the order of 28%. This superior performance is a result of favorable morphology due to the existence of large numbers of nano-sized pores suitable for carbonation. This morphology is relatively stable during cycles due to the presence of mayenite (Ca12Al14O33) in the CaO structure. However, the crushing tests showed that pellets lost strength after 300 carbonation/calcination cycles, and this appears to be due to the cracks formed in the


pellets. This effect was not observed in smaller particles suitable for use in fluidized bed (FBC) systems.

4.24 EFFECT OF PARTIAL CARBONATION ON THE CYCLIC CAO CARBONATION REACTION

Grasa, G., Abanades, C. and Anthony, E.J., “The Effect of Partial Carbonation on the Cyclic CaO Carbonation Reaction”, Industrial and Engineering Chemistry Research. 48, 9090-9096, 2009. CaO particles from the calcination of natural limestones can be used as regenerable solid sorbents in some CO2 capture systems. Their decay curves in terms of CO2 capture capacity have been extensively studied in the literature, always in experiments allowing particles to reach their maximum carbonation conversion for a given cycle. However, at the expected operating conditions in a CO2 capture system using the carbonation reaction, a relevant fraction of the CaO particles will not have time to fully convert in the carbonator reactor. This work investigates if there is any effect on the decay curves when CaO is only partially converted in each cycle. Experiments have been conducted in a thermobalance arranged to interrupt the carbonation reaction in each cycle before the end of the fast reaction period typical in the CaO-CO2 reaction. It is shown that, after the necessary normalization of results, the effective capacity of the sorbent to absorb CO2 during particle lifetime in the capture system slightly increases and CaO particles partially converted behave “younger” than particles fully converted after every calcination. This has beneficial implications for the design of carbonation/calcination loops. 4.25 CO2 CAPTURE FROM SIMULATED SYNGAS VIA CYCLIC CARBONATION/CALCINATION

FOR A NATURALLY OCCURRING LIMESTONE: PILOT-PLANT TESTING

Symonds, R., Lu, D., Hughes, R., Anthony, E.J., and Macchi, A., “CO2 Capture from Simulated Syngas via Cyclic Carbonation/Calcination for a Naturally Occurring Limestone: Pilot Plant Testing”, Industrial and Engineering Chemistry Research, 48, 8431–8440, 2009. Experiments were performed using a dual fluidized bed reactor system, operated in a batch mode, in order to investigate the effects of steam and simulated syngas on CO2 capture and sorbent conversion efficiency for a naturally occurring Polish calcitic limestone. In addition, the effect of high partial pressures of CO2 on the calcination process was examined using either oxygen-enriched air or oxy-fuel combustion in the calciner. As expected, calcination under oxy-fuel conditions resulted in decreased carbonation conversion due primarily to particle sintering and pore pluggage. On average there was a decrease in carbonation conversion of approximately 36.5 and 33.4% for carbonation with steam and steam/simulated syngas, respectively, compared to similar experiments using oxygen-enriched air. However, during the carbonation of the limestone with steam present in the feed gas, it was observed that the high CO2 capture efficiency period was significantly extended compared to carbonation with only CO2 present. This resulted in increased CaO conversion from approximately 16.1 to 29.7% for the initial carbonation cycle. A further increase in carbonation conversion, from 29.7 to 46.9%, was also observed when simulated syngas conditions (CO, H2) were used in the carbonator. Analysis of the outlet gases also confirmed that the calcined limestone catalyzes the water gas shift reaction, which we believe results in enhanced CO2 concentration levels at the grain surfaces of the sorbent.


4.26 A STUDY ON THE ACTIVITY OF CAO-BASED SORBENTS FOR CAPTURING CO2 IN CLEAN ENERGY PROCESSES

Wang, J., Manovic, V., Wu, Y. and Anthony, E.J., “A Study on the Activity of CaO-based Sorbents for Capturing CO2 in Clean Energy Processes”, Applied Energy, 87, 1453-1457, 2010. CaO-based regenerative sorbents for CO2 capture in power generation and H2 production are receiving growing attention. A major challenge for this technology is the decay of sorbent activity with increasing number of the sorption/regeneration cycles. Evaluation of long-term sorbent activity currently requires substantial experimental work. In this study, the dependence of the activity on the number of sorption/ regeneration cycles is examined, and the apparent dependence on the number of cycles is related to the duration of sorbent regeneration. By relating the decay in activity of the sorbent to its decrease in surface area due to sintering, interesting insights can be drawn. A method for determination of the long-term activity has been proposed, which can greatly reduce the experimental work for sorbent development and process evaluation.

4.27 THE CALCIUM LOOPING CYCLE FOR LARGE-SCALE CO2 CAPTURE

Blamey, J., Anthony, E.J., Wang, J. and Fennell, P., “The Calcium Looping Cycle for Large-Scale CO2 Capture”, Progress in Energy and Combustion Science, 36, 260-279, 2010. The reversible reaction between CaO and CO2 is an extremely promising method of removing CO2 from the exhaust of a power station, generating a pure stream of CO2 ready for geological sequestration. The technology has attracted a great deal of attention recently, owing to a number of its advantages: the relatively small efficiency penalty which it imposes upon a power station (estimated at 6–8 percentage points, including compression of the CO2); its potential use in large-scale circulating fluidized beds (a mature technology, as opposed to the vastly up scaled solvent scrubbing towers which would be required for amine scrubbing); its excellent opportunity for integration with cement manufacture (potentially decarbonising both industries) and its extremely cheap sorbent (crushed limestone). Unfortunately, sorbent (CaO) derived from natural limestone markedly decreases in its reactivity over a number of cycles of reaction with CO2. Much current and promising research involves the investigation of a number of different methods to either reduce the rate of decay in reactivity, to boost the long-term reactivity of the sorbent or to reactivate the sorbent. Technologies investigated include thermal pretreatment or chemical doping of natural sorbents and the production of artificial sorbents. Attrition of the limestone can be a problem during repeated cycling in, e.g. a circulating fluidized bed, and some of the strategies to enhance the long-term capacity of the limestone to take up CO2 can increase attrition. Strategies to counteract attrition, such as pelletization of highly reactive materials, have succeeded in reducing, though not eliminating, this problem. Each of these topics is reviewed in detail here, as are potential competing reactions with sulphurous compounds and the large-scale integration of the calcium looping cycle with both a power station and a cement works, including a number of assessments of the economics of the cycle. A number of pilot plants demonstrating the technology have been constructed around the world. No major problems have been encountered thus far, and so calcium looping technology is currently moving to the demonstration scale in a number of locations.


4.28 COMPETITION OF SULPHATION AND CARBONATION REACTIONS DURING LOOPING

CYCLES FOR CO2 CAPTURE BY CAO-BASED SORBENTS

Manovic, V. and Anthony, E.J., “Competition of Sulphation and Carbonation Reactions during Looping Cycles for CO2 Capture by CaO-Based Sorbents”, Journal of Physical Chemistry A., 114, 3997-4002. 2010. Two types of sorbents are investigated here (natural limestone and highly reactive calcium aluminate pellets) to elucidate their reactivity in terms of sulphation and carbonation and determine the resulting effect on looping cycles for CO2 capture. The sorbents are tested in a thermogravimetric analyzer (TGA) apparatus using typical synthetic flue gas mixtures containing 15% CO2 and various concentrations of SO2. The sulphation and carbonation conversions were determined during sulphation/carbonation/calcination cycles. The sorbent morphology and its changes were determined by means of a scanning electron microscope (SEM). The results showed that sulphation, that is, the formation of CaSO4 at the sorbent surface, is a cumulative process with increasing numbers of reaction cycles, which hinders sorbent ability to capture CO2. In the case of high sorbent reactivity, as determined by its morphology, the unfavorable effect of sulphation is more pronounced. Unfortunately, any increase in the temperature in the carbonation stage accelerates sulphation more than carbonation as a result of higher activation energy for the sulphation reaction. The SEM analyses showed that although sulphation and carbonation occur during cycles involving calcination, an unreacted core/partially sulphated shell sorbent particle pattern is formed. The main outcomes of this research indicate that special attention should be paid to the sulphation when more reactive and more expensive, synthetic CaO-based sorbents are used for CO2 capture looping cycles. Desulphurization of flue gas before CO2 capture appears to be essential because CO2 looping cycles are so strongly affected by the presence of SO2.

4.29 SULFATION PERFORMANCE OF CAO-BASED PELLETS SUPPORTED BY CALCIUM ALUMINATE CEMENTS DESIGNED FOR HIGH-TEMPERATURE CO2 CAPTURE

Manovic, V., and Anthony, E.J., “Sulphation Performance of CaO-based Pellets Supported by Calcium Aluminate Cements Designed for High-Temperature CO2 Capture”, Energy & Fuels, 24, 1414-1420, 2010. CaO-based sorbents supported by calcium aluminate cements were originally prepared as sorbents for CO2 capture in looping cycles. However, their high affinity for CO2 at high temperatures suggests that they will readily react with any SO2 present in flue gases to be decarbonated. Thus, the sulphation performance of these pellets was investigated in this study using a synthetic flue gas in a thermogravimetric analyzer (TGA). The results obtained showed that after 6 h in gas containing 0.5% SO2 at 900 °C the pellets prepared from hydrated lime and cement were >90% sulfated. They showed the highest sulphation affinity among the sorbents tested here. Namely, Cadomin limestone was <30% sulfated and the corresponding hydrated lime <70%. The pellets prepared from limestone powder and cement had significantly lower sulphation (~65%) in comparison to that for pellets obtained from hydrated lime and cement. The scanning electron microscope (SEM) images of sulfated samples clearly showed the presence of a sulfated shell at the surface of original limestone particles, while the calcium aluminate pellets had porous morphology even after almost 100% sulphation. The X-ray diffraction (XRD) analyses showed that mayenite (Ca12Al14O33), which is responsible for the goodCO2 capture performance of these pellets, was not present after sulphation. Pellets


after 30 carbonation/calcination cycles displayed significantly reduced affinity for SO2, with sulphation conversions at ~15%, but they easily recovered this capacity with ~80% sulphation levels after hydration. These results clearly show that, for the pellets to perform well, the presence of SO2 must be avoided during looping cycles at least during sorbent regeneration at high temperatures. 4.30 EMISSIONS OF SO2 AND NOX DURING OXY-FUEL CFB COMBUSTION TESTS IN A MINI-

CIRCULATING FLUIDIZED BED COMBUSTION REACTOR

Jia, L., Tan, Y. and Anthony, E.J., “Emissions of SO2 and NOx during Oxy-fuel CFB Combustion Tests in a Mini-CFBC”, Energy and Fuels, 24, 910–915. 2010. Anthropogenic CO2 production is primarily driven by fossil fuel combustion, and the current energy demand situation gives no indication that this will change in the near future. In consequence, it is increasingly necessary to find ways to reduce these emissions when fossil fuel is used. CO2 capture and storage (CCS) appears to be among the most promising approaches. All of the CCS technologies involve producing a nearly pure stream of CO2, either by concentrating it in some manner from the flue gases or by using pure oxygen as the combustion gas. The latter option, oxy-fuel combustion, has now been well studied for pulverized coal combustion, but to date has received relatively little attention in the case of oxy-fuel circulating fluidized bed combustion (CFBC). Recently, oxy-fuel FBC has been examined in a 100 kW pilot plant operating with flue gas recycle at CanmetEnergy. The results strongly support the view that this technology offers all of the advantages of air-fired FBC, with one possible exception. Emissions such as CO or NOx are lower or comparable to those of air firing. It is possible to switch from air firing to oxy firing easily, with oxygen concentrations as high as 60-70%, and flue gas recycle levels of 50-60%. Only sulphation is poorer, which is not in good agreement with other studies, and the reasons for this discrepancy need further exploration. However, longer tests have confirmed these findings with two coals and a petroleum coke. It also appears that changing from direct to indirect sulphation with the petroleum coke improves the sulphation, although a similar effect could not be confirmed with coal from these results.

4.31 MORPHOLOGICAL CHANGES OF LIMESTONE SORBENT PARTICLES DURING CARBONATION/CALCINATION LOOPING CYCLES IN A THERMOGRAVIMETRIC

ANALYZER (TGA) AND REACTIVATION WITH STEAM

Wu, Y., Blamey, J., Anthony, E.J., and Fennell, P., “Morphological Changes of Limestone Sorbent Particles during Carbonation/Calcination Cycles in TGA and Reactivation with Steam”, Energy and Fuels, 24, 2768-2776, 2010. Carbonation and calcination looping cycles were carried out on four limestones in a thermogravimetric analyzer (TGA). TheCO2 carrying capacity of a limestone particle decays very quickly in the first 10 cycles, reducing to about 20% of its original uptake capacity after 10 cycles for the four limestones studied in this work, and it decreases further to 6-12% after 50 cycles. A new steam reactivation method was applied on the spent sorbent to recover the loss of reactivity. The steam reactivation of multi-cycled samples was conducted at atmospheric pressure. Steam reactivation for 5 min at 130 °C of particles that had undergone 10 cycles resulted in an immediate increase (by 45-60% points) in carrying capacity. The morphological changes of limestone particles during the cycling and steam reactivation were studied using both an optical microscope and scanning electron microscopy (SEM). The diameters of limestone particles shrank by


about 2-7% after 10 carbonation/calcination cycles, and the particle diameters swelled significantly (12-22% increase) after steam reactivation. These size changes are important for studies of attrition and mathematical modeling of carbonation.

4.32 CO2 CARRYING BEHAVIOR OF CALCIUM ALUMINATE PELLETS UNDER HIGH-TEMPERATURE/ HIGH-CO2 CONCENTRATION CALCINATION CONDITIONS

Manovic, V., and Anthony, E.J., “The CO2 Carrying Capacity Behavior of Calcium Aluminate Pellets under High-Temperture/High-CO2 Concentration Calcination Conditions”, Ind. Eng. Chem. Res., 49, 6916–6922, 2010. Sintering and a resulting loss of activity during calcination/carbonation can introduce substantial economic penalties for a CO2 looping cycle using CaO-based sorbents. In a real system, sorbent regeneration must be done at a high temperature to produce an almost pure CO2 stream, and this will increase both sintering and loss of sorbent activity. The influence of severe calcination conditions on the CO2 carrying behavior of calcium aluminate pellets is investigated here. Up to 30 calcination/carbonation cycles were performed using a thermogravimetric analyzer apparatus. The maximum temperature during the calcination stage in pure CO2 was 950 °C, using different heating/cooling rates between two carbonation stages (700 °C, 20% CO2). For comparison, cycles were also done using N2 during the calcination stages. In addition, the original Cadomin limestone, used for pelletization, was also examined in its original form and the results obtained were compared with those for the aluminate pellets. As expected, high temperature during calcination strongly reduced CO2 carrying capacities of both sorbents. However, aluminate pellets showed better resistance to these severe conditions. The conversion profiles obtained are significantly different to those obtained under milder conditions, with significant increased activity during the slower, diffusion-controlled, carbonation stage. Moreover, scanning electron microscopy analysis of samples after prolonged carbonation showed that pore filling occurred at the sorbent particle surfaces preventing diffusion of CO2 toward the particle interior.

4.33 CARBONATION OF CAO-BASED SORBENTS ENHANCED BY STEAM ADDITION

Manovic, V. and Anthony, E.J., “Carbonation of CaO-Based Sorbents Enhanced by Steam Addition”, Industrial and Engineering Chemistry Research, 49, 9105-9010, 2010. The carbonation reaction has recently been intensively investigated as a means of CO2 capture from gas mixtures such as flue gas produced during fossil fuel combustion. Unfortunately, this gas-solid reaction is limited due to formation of the solid product (CaCO3) at the reacting surface and sintering, all of which reduce the carrying capacity of the sorbent. In this work the enhancement of carbonation conversion by means of steam addition to the carbonating gas was studied. Seven limestones of different origin and composition as well as one synthetic sorbent (calcium aluminate pellets) were tested. A thermogravimetric analyzer (TGA) was employed for the carbonation tests at different temperatures (350-800 °C) in a gas mixture containing typically 20% CO2 and 10 or 20% H2O(g). The samples tested were calcined under an N2 (800 °C) or CO2 (950 °C) atmosphere to explore the influence of different levels of sample sintering, and the results obtained were compared with those seen for carbonation in dry (no steam) gas mixtures. The morphology of samples after carbonation under different conditions was examined by a scanning electron microscope (SEM). It was found that carbonation is enhanced by steam, but this is more pronounced at lower temperatures and for more sintered samples. With increasing temperature and carbonation time, the enhancement of


carbonation becomes negligible because the conversion reaches a “maximum” value (~75-80% for samples calcined in N2) even without steam. Carbonation of samples calcined in CO2 is enhanced at different levels depending on the sorbent tested. The shape of carbonation profiles and morphology of carbonated samples show that steam enhances solid state diffusion and, consequently, conversion during carbonation. 4.34 SINTERING AND FORMATION OF A NONPOROUS CARBONATE SHELL AT THE SURFACE

OF CAO-BASED SORBENT PARTICLES DURING CO2-CAPTURE CYCLES

Manovic, V. and Anthony, E.J., “Sintering and Formation of a Nonporous Shell at the Surface of CaO-Based Sorbent Particles during CO2-Capture Cycles”, Energy and Fuels, 24, 5790-5796, 2010. The existence and formation of a carbonate shell at the surface of the particles of CaO-based sorbents is investigated in this paper. Two sorbents were tested: natural Kelly Rock (KR) limestone and synthetic pellets (KR-CA-14) prepared from the same limestone and calcium aluminate cement (CA-14).Various different series of calcination/carbonation cycles were carried out in a thermogravimetric analyzer (TGA) apparatus, and the sorbent samples produced after those cycles were analyzed with a scanning electron microscope (SEM). It is shown that sintering during cycles is more pronounced at the surface of sorbent particles, which results in the formation of nonporous areas or even a totally nonporous shell that surrounds a partially reacted CaO core. However, the dependency of shell formation upon cycle number is difficult to elucidate by SEM because increasing cycle numbers achieve lower conversion levels, which reduce the chance of shell formation. Prolonged carbonation after a series of cycles showed that there is a limit in maximum conversion levels, which cannot be solely explained by product layer formation at the interior sorbent surface area. The SEM images of samples after prolonged carbonation periods clearly show the presence of more sintered areas at the outer particle surface and/or carbonate shell/partially reacted particle pattern. This is explained by the phenomenon of more pronounced sintering at the sorbent particle surface than seen in the particle interior because of surface tension and more pronounced loss of pore volume near the exterior of the particle. The formation of a carbonate shell at the particle surface is a different phenomenon from that of the formation of a product layer at the pore surface area and also limits diffusion during carbonation.


4.35 ENHANCEMENT OF INDIRECT SULPHATION OF LIMESTONE BY STEAM ADDITION

Stewart, M.C., Manovic, V., Anthony, E.J. and Macchi, A., “Enhancement of Indirect Sulphation of Limestone by Steam Addition”, Environ. Sci. and Technology, 44, 8781–8786, 2010. The effect of water (H2O(g)) on in situ SO2 capture using limestone injection under (FBC) conditions was studied using a thermobalance and tube furnace. The indirect sulphation reaction was found to be greatly enhanced in the presence of H2O(g). Stoichiometric conversion of samples occurred when sulphated with a synthetic flue gas containing 15% H2O(g) in under 10 h, which is equivalent to a 45% increase in conversion as compared to sulphation without H2O(g). Using gas pycnometry and nitrogen adsorption methods, it was shown that limestone samples sulphated in the presence of H2O(g) undergo increased particle densification without any significant changes to pore area or volume. The microstructural changes and observed increase in conversion were attributed to enhanced solid-state diffusion in CaO/CaSO4 in the presence of H2O(g). Given steam has been shown to have such a strong influence on sulphation, whereas it had been previously regarded as inert, may prompt a revisiting of the classically accepted sulphation models and phenomena. These findings also suggest that steam injection may be used to enhance sulfur capture performance in fluidized beds firing low-moisture fuels such as petroleum coke. 4.36 REACTIVATION AND REMAKING OF CALCIUM ALUMINATE PELLETS FOR CO2 CAPTURE

Manovic, V., and Anthony, E.J., “Reactivation and Remaking of Calcium Aluminate Pellets for CO2 Capture”, Fuel 90, 233-239, 2011. CaO-based pellets supported with aluminate cements show superior performance in carbonation/calcination cycles for high-temperature CO2 capture. However, like other CaO-based sorbents, their CO2 carrying activity is reduced after increasing numbers of cycles under high-temperature, high-CO2 concentration conditions. In this work the feasibility of their reactivation by steam or water and remaking (reshaping) was investigated. The pellets, prepared from three limestones, Cadomin and Havelock (Canada) and Katowice (Poland, Upper Silesia), were tested in a thermogravimetric analyzer (TGA). The cycles were performed under realistic CO2 capture conditions, which included calcination in 100% CO2 at temperatures up to 950 °C. Typically, after 30 cycles, samples were hydrated for 5 min with saturated steam at 100 °C in a laboratory steam reactor (SR). Moreover, larger amounts of pellets were cycled in a tube furnace (TF), hydrated with water and reshaped, and tested to determine their CO2 capture activity in the TGA. It was found that, after the hydration stage, pellets recovered their activity, and more interestingly, pellets that had experienced a longer series of cycles responded more favorably to reactivation. Moreover, it was found that conversion of pellets increased after about 70 cycles (23%), reaching 33% by about cycle 210, with no reactivation step. Scanning electron microscope (SEM) analyses showed that the morphology of the low-porosity shell formed at the pellet surface during cycles, which limits conversion, was eliminated after a short period (5 min) of steam hydration. The nitrogen physisorption analyses (BET, BJH) of reshaped spent pellets from cycles in the TF confirmed that sorbent surface area and pore size distribution were similar to those of the original pellets. The main alumina compound in remade pellets as determined by XRD was mayenite (Ca12Al14O33). These results showed that, with periodic hydration/ remaking steps, pellets can be used for extended times in CO2 looping cycles, regardless of capture/regeneration conditions.


4.37 CA LOOPING TECHNOLOGY: CURRENT STATUS, DEVELOPMENTS AND FUTURE DIRECTIONS

Anthony, E.J., “Ca Looping: Current Status and Future Directions”, Greenhouse Gases, Science and Technology, accepted 2011. Calcium looping technology is a promising new technique for high-temperature scrubbing of CO2 from flue gas and syngases. Current economic projections suggest it might be able to capture CO2 at costs of ~$20/ton of avoided CO2. Nonetheless there are questions about the long-term behaviour of natural sorbents in such systems, and there is substantial R&D being done on this technology worldwide to answer questions about whether the performance of natural sorbents can be improved, or whether it would be better to use synthetic ones. The current period is particularly interesting as the first pilot plants and demonstration units capable of operating continuously are now coming on stream, and if successful these will lead to large scale industrial demonstrations of the technology in the next 10 to 15 years.


5 CA LO O PING CO NFERENCE PUB LICATIO NS

5.1 CHARACTERIZATION OF ASHES FROM OXY-FUEL COMBUSTION IN A PILOT-SCALE

CIRCULATING FLUIDIZED BED

Wu, Y., Jia, L., Tan, Y.. and Anthony, E.J., “Characterization of Ashes from Oxy-Fuel Combustion in a Pilot-Scale Circulating Fluidized Bed”, Proceedings of the 9th International Conference on Circulating Fluidized Beds, Hamburg, Germany, May 13-16, 2008. Since 2005 CETC-Ottawa has carried out oxy-fuel combustion experiments on its modified mini-CFBC facility with different combinations of fuels and limestones. Limestone was premixed with the fuel and fed to the CFBC for SO2 capture and the bed ash (BA) and fly ash (FA) produced from the oxy-fuel combustion were collected and characterized. The methods used included X-ray fluorescence (XRF), X-ray diffraction (XRD), carbon analysis, thermogravimetric analysis (TGA), and surface analysis, to obtain their physical and chemical properties. The main purpose of the work is to characterize ashes from oxy-fuel CFBC firing, and identify significant differences, if any, from ashes generated from air fired CFBCs. The results indicate that the char carbon content in the FA is much higher than that in the BA. If sulphur capture in the combustor is via direct sulphation, the CaCO3 content in both BA and FA are also relatively high. The Brunauer-Emmett-Teller (BET) surface area and the pore volume in the FA are much greater than that in the BA and in the FA smaller size pores predominate.

5.2 ROLE OF THE WATER-GAS SHIFT REACTION IN CO2 CAPTURE FROM GASIFICATION SYNGAS USING LIMESTONES

Lu, D.L, Symonds, R.T., Hughes, R.W. and Anthony, E.J., “Role of the Water Gas Shift Reaction in CO2 Capture from Gasification Syngas using Limestones”, Proceedings of the 20th International Conference on Fluidized Bed Combustion, pp. 540-548, Xi’an, China, May 2009. The work in this paper aims at determining the effect of gasification syngas on the carbonation reaction and conversion for several naturally occurring calcium-based sorbents. Experiments were performed via the use of a thermogravimetric analyzer (TGA) and it was observed that the presence of CO and H2 caused an increase in initial rate of approximately 70.6%. The increase in reaction rate was attributed to the sorbent surface sites catalyzing the water-gas shift reaction; as well, the shift reaction was assumed to be responsible for the increase in activation energy for limestone based on the formation of intermediate complexes. A pilot-scale dual fluidized bed reactor system was applied to further investigate the effect of the shift reaction on CO2 capture and sorbent conversion for two limestones (Katowicz and Cadomin limestone). During carbonation with steam present in the feed gas, it was observed that the high CO2 capture period was significantly extended as compared to carbonation with only CO2 present. Based on the outlet gas analysis, it was confirmed that the sorbent particles were in fact catalyzing the water-gas shift reaction, increasing the overall sorbent conversion to approximately 46.9% for the first cycle. In terms of sorbent regeneration, the oxy-fuel combustion conditions employed (high CO2 and O2 atmosphere), resulted in enhanced sorbent sintering, thus producing the negative effect on carbonation conversion.


5.3 HYDRATION AND PELLETIZATION OF CACO3-DERIVED SORBENTS FOR IN-SITU CO2 CAPTURE

Lu, D., Hughes, R.W., Reid, T. and Anthony, E.J., “Hydration and Pelletization of CaCO3-Derived Sorbents for In-Situ CO2 Capture”, Proceedings of the 20th International Conference on Fluidized Bed Combustion, pp. 569-575, Xi’an, China, May 2009. Steam hydration and pelletization of limestone were investigated using a thermogravimetric analyzer (TGA) to improve the sorbent utilization for in-situ CO2 capture under typical fluidized bed combustion (FBC) operating conditions. Steam hydration of CaO improves carbonation capacity but the hydrated sorbent is very fragile, which will be a problem for FBC applications. Similar sorbent improvements in terms of maintaining/enhancing reactivity were observed by sorbent fine grinding and pelletization, which appears to be a method of using hydrated sorbent in fluidized bed applications. 5.4 EFFECT OF OPERATING CONDITIONS ON SO2 AND NOX EMISSIONS IN OXY-FUEL MINI-

CFB COMBUSTION TESTS

Jia, L, Tan, Y. and Anthony, E.J. “Effect of Operating Conditions on SO2 and NOx Emissions in Oxy-Fuel Mini-CFB Combustion Tests”, Proceedings of the 20th International Conference on Fluidized Bed Combustion, pp. 936-940, Xi’an, China, May 2009.

Anthropogenic CO2 production is caused primarily by fossil fuel combustion. In consequence, it is increasingly necessary to find ways to reduce these emissions when fossil fuel is used. CO2 capture and storage (CCS) appears to be among the most promising. All of the CCS technologies involve producing a pure stream of CO2 either by concentrating it from the flue gases, or by using pure oxygen as the combustion gas. The latter option, oxy-fuel combustion, has now been well studied for pulverized coal combustion, but has received relatively little attention to date in the case of oxy-fuel circulating fluidized bed combustion. Recently, oxy-fuel CFBC has been examined in a 100 kW pilot plant operating with flue gas recycle at CanmetEnergy. The results strongly support the view that this technology offers all of the advantages of air-fired FBC, with one possible exception. Emissions such as CO or NOx are lower or comparable to air firing. It is possible to switch from air-firing to oxy-firing mode easily, with oxygen concentrations as high as 60-70%, and flue gas recycle levels of 50-60%. Only sulphur capture is poorer. However, this result is not in good agreement with other studies, and the reasons for this discrepancy need further exploration. Here, longer tests have confirmed previous findings from CanmetEnergy with two coals and a petroleum coke. It also appears that changing from direct to indirect sulphation with the petroleum coke improves sulphur capture efficiency, although a similar effect could not be confirmed with coal from these results
