� The net efficiency of a coal-fired powerplant can be increased to over 55%

� Gas and steam turbine process also possible in coal-fired power plants

� Coal gasification aids CO2 separation

efficiencies due to the combination of gas turbines and steamturbines. Among the combined processes, the gas and steam turbineprocesses with integrated coal gasification (IGCC – IntegratedGasification Combined Cycle) have won the most recognition. IGCC technology has already seen considerable development on thelarge scale. The research objective is to develop this further, to achieve "slim" IGCC, i.e. simplification and optimisation of thesystem technology, and improvement of cost-effectiveness. In thefuture, it will also be possible to use combined processes as additionaloptions for the extraction of chemical elements (e.g. synthetic fuels,hydrogen). In the last 30 years, the German Federal Government has sponsoredmore than 100 projects which focus on gasification technology, witha total budget of 400 million euros. The current 5th Energy ResearchProgramme also emphasises the great potential of this technology forthe "energy efficiency" strategy, as well as for "CO2 separation". Onthe European level, setting similar objectives, the Commission issponsoring low-CO2 electricity generation technologies based oncoals, including CO2 storage.

At present, lignite and black coal power plants provide abouthalf of the electricity in Germany. The other half comprisesnuclear power plants (approx. 30%) and power plants based

on natural gas and renewable energy sources. Large power plantsbased on coal will continue to be necessary in the energy mix for theforeseeable future. Due to the age of the German power plant infra-structure, and the phasing-out of nuclear power, 40,000 MW ofexisting capacity must be replaced in Germany by the year 2020 (notincluding required expansion). Thus, in energy research, there has foryears been a focus on the development of power plant concepts withhigher energy efficiency and lower environmental impact for allenergy sources, in order to make use of the opportunities which themodernisation of the power plant infrastructure represents. For the energy source coal, there are two strategies: one has theobjective of increasing the efficiency in conventional steam powerplants by means of increased temperature and pressure in the steamturbine process, and optimisation of lignite drying. The otherinvolves further development of the known combined processes forgenerating electricity from coal. These processes enable very high

Model of the world's first large-scale IGCC power plant with integratedCO2 separation and storage. The power plant will have a gross capacityof 450 MW, and should be commissioned by about the year 2014(source: RWE)

Power plants with coal gasification

Fig. 1

� Fundamentals of IGCC technology

� Conversion of fuels into gas

An IGCC power plant generally comprisesthe stages: coal treatment, gasification, gastreatment, and gas utilisation. For gasification of coals, fixed bed, fluidisedbed, and entrained flow reactors are used. Thechoice of the appropriate process dependson the fuel used, and on the desired gas util-isation, among other things. If it is envisagedthat the gas will be utilised in a gas and steamturbine process, fluidised bed and entrainedflow processes are particularly suitable, inwhich gasification occurs at high pressureof at least 25 – 30 bar. Entrained flow gasi-fication, compared to fluidised bed gasifica-tion, takes place at considerably higher tem-peratures above the ash fusion point, whichon one hand significantly improves the gasquality, but on the other hand greatly in-creases the operating costs due to higheroxygen consumption (fig. 3).The raw gas from the gasification containsa multitude of contaminants and harmfulsubstances which are undesirable in subse-quent gas utilisation, and the exact propor-tion of these substances depends on thegasification process. First, depending on the

temperature of the raw gas, cooling is nec-essary. Then, the dust contained in the gas isseparated off. Condensable ingredients suchas ammonia and hydrogen chloride can beseparated off by means of a water wash. Inthe final gas purification step, the sulphurouscomponents must be removed, usually ashydrogen sulphide (H2S). Hydrogen sul-phide can be converted to elementary sul-phur, or to sulphuric acid.

After gas treatment, the pure gas is used forelectricity generation in a gas and steam tur-bine process. The gas is burnt in a combus-tion chamber, and the hot combustion gas isreleased via a gas turbine. Subsequently, theexhaust gas still has a temperature of up to600 °C, and is used to create high pressuresteam, which is released via a steam turbine.

Fig. 3: Gasification process for coal

In order to use coal in a combined gas andsteam turbine process with between 50 and60% efficiency, it is necessary to convert thesolid fuel coal into a combustible gas. Thisprocess step is called gasification. Here,unlike in combustion, a fuel is not com-pletely converted to CO2 and H2O, butmainly to CO and H2. Both solid and liq-uid fuels are suitable as raw materials forgasification. In the gasification reactor, thefuel reacts with a gasification agent whichcontains oxygen, usually an oxygen-steammixture, pure oxygen, or air. The heatingnecessary for gasification occurs in thereactor itself. This method of operation iscalled autothermic gasification. Allother-mic gasification, in which the heat is fedinto the reactor from outside, is not imple-mented on a large scale.

� Perspectives and potentials

2 BINE projektinfo 09/06

Compared to conventional steam power plants,IGCC power plants have significantly higherefficiency and lower emissions (fig. 4). Due tothe coupling of the gas and steam turbineprocess to the generation of electricity, veryhigh efficiencies can be achieved. Modern

steam power plants based on lignite have anefficiency of 43%. The medium-term poten-tial of steam power plants is up to 50% for lig-nite power plants with predrying and 700 °Ctechnology, and > 50% for hard coals. InIGCC power plants, efficiencies of over 55%

can be achieved in the future. Compared toother advanced power plant processes, IGCCtechnology exhibits the highest efficiency, andthus the lowest specific CO2 accrual.Due to the intensive gas purification beforethe gas and steam turbine process, naturally

Fig. 2: Chemical fundamentals of coal gasification

Main components

H2 25–30 Vol.-%CO 30–60 Vol.-%CO2 5–15 Vol.-%H2O 2–30 Vol.-%CH4 0–5 Vol.-%

Harmful substances and contaminants

H2S 0.2–1 Vol.-%COS 0–0.1 Vol.-%N2 0.5–4 Vol.-%Ar 0.2–1 Vol.-%

NH3 + HCN 0–0.3 Vol.-%

Fixed bed gasification Fluidised bed gasification Entrained flow gasification

Gas Gas

Gas

Coal(3–30 mm)

Coal(1–5 mm)

Coal(0.1 mm)

Steam+O2

Steam+O2

Steam+O2

Steam+O2

Coal(0.1 mm)

Slag/ash Slag/ash Slag/ash

Oxygen SteamCoal

Gasification with carbon dioxideC + CO2 2CO

Gasification with hydrogenC + 2H2 CH4

Combustion with oxygenC + O2 CO2

Water gas shift reactionCO + H2O H2 + CO2

Gasification with steamC + H2O CO + CO + H2

Formation of methaneCO + 3H2 CH4 + H2O

Gasification with oxygenC + 1/2 O2 CO

� Key areas of research and development

BINE projektinfo 09/06 3

occurring impurities such as sulphur are already removed before com-bustion, and therefore cannot reach the exhaust gas flow. In the gas pu-rification within the IGCC process, the gas to be purified only has a rel-atively low volume flow, as it is pressurised and is not diluted withnitrogen. This significantly reduces the complexity of CO2 separation.In contrast, the exhaust gases of conventional steam power plants areat ambient pressure, and the harmful substances are highly diluted dueto the high proportion of nitrogen in the combustion air. The IGCC power plant has a more complex structure than steam pow-er plants. Thus, the investment costs are higher than for steam powerplants. Due to the higher investment costs, the resulting power produc-tion costs are also higher than those of steam power plants, but withIGCC, due to the higher efficiency, the proportion of the total costs ac-counted for by fuel costs will be lower (figs. 5 and 6).

PPs without CO2 separation PPs with CO2 separation

Reference PP

Efficiency [%]

Spec. invest. costs[€/kW]

Electricity genera- tion costs* [%]

BoA-Plus IGCC# Conv.technology

Oxyfuel IGCC#

100 100 116 250 190 180

1120 1160 1370 2620 2260 2050

43 47 52 28 37** 42

Fig. 6: IGCC power plants have the lowest investment costs andelectricity generation costs among power plants with CO2separation (example: lignite*) [RWE/as in Sept. 05]

Fig. 4: Comparison between the emissions figures of conventionalsteam power plants and those of an IGCC power plant

*

* Energy research sees 55%efficiency as feasible for IGCC,and is working towards this target

* incl. CO2 compression, liquefaction and 300 km transport** incl. predrying, i.e. approx. 4% advantage over raw coal combustion taken into account# RWE calculates the achievable efficiency of IGCC to be somewhat lower, at 52%

CO2 separation: During gas purificationin an IGCC power plant, it is straight-forward to separate not only sulphurouscomponents, but also CO2. This technologyhas proven itself for decades in gas treat-ment for chemical syntheses. Optimal inte-gration into an IGCC power plant, and thedisposal of the CO2, are central issues in cur-rent research projects. The German projectCOORIVA (CO2 Reduction via IntegratedGasification and Separation) within theCOORETEC programme (CO2 ReductionTechnologies) and the European ENCAPproject (Enhanced Capture of CO2) aremaking a significant contribution to thedevelopment and realisation of CO2-freepower plant concepts based on gasificationtechnology.

Increasing efficiency and decreas-ing costs: Although IGCC power plantswith efficiencies of over 50% could be builtalready with today's technology, a further

efficiency increase is being worked towardsintensively. Optimisation of gasificationprocesses, implementation of new gas pu-rification processes such as hot gas desul-phurisation and membrane processes, aswell as increasing gas turbine efficiency, areat the centre of the R&D activities.

In parallel, an intensive search for costreduction possibilities is taking place. Theresearch project "55%-Plus IGCC PowerPlant" has resulted in the successful devel-opment of advanced IGCC concepts withefficiencies over 55%, and electricity gener-ation costs below 40 euros/MWh. Furtherprojects involve new process concepts fordry desulphurisation, or CO2 reduction bymeans of increased gas turbine efficiency(COOREFF).

Manufacture of chemical products:On the basis of gasification technology, it isnot only possible to generate electricity, but

also to produce liquid and gaseous fuels, aswell as other chemical products (coal chem-istry). The product spectrum ranges frommotor fuel, to hydrogen, to ammonia andmethanol. As these products are todaymainly extracted from natural gas andmineral oil, an intensive search is takingplace for alternative production possibili-ties based on coal. In the European projectsDYNAMIS and HYPOGEN, hydrogenproduction in particular is being promoted.

Additional research tasks include fuelqualification for selection of suitable fuels,improvement of cost-effectiveness by meansof increasing system availability, develop-ment of synthesis gas turbines and hydro-gen turbines, as well as examination of ash/slag behaviour.

1400 140

1200 120

1000 100

800 80

600 60

Spec

ific

inve

stm

ent c

osts

in e

uros

/kW

Elec

tric

ity g

ener

atio

n co

sts

%

Steam power plant η = 40%

Steam power plant η = 45%

IGCC η = 55%

Fig. 5: Investment costs comparison (as in 2006) betweenconventional steam power plants and IGCC power plant

* Energy research sees 55% efficiency as feasible for IGCC,and is working towards this target

SO2 35NOx 2.6dust 30CO2 1,250

SO2 0.8NOx 0.8dust 0.1CO2 1,000

SO2 0.07NOx 0.35dust 0.001CO2 800

Steam power plant– past –

Steam power plant– state of the art –

IGCC power plant

Emissions in kg/MWh

PROJECT ADDRESSES▼

IGCC technology is part of the sup-port concept COORIVA. A list of theparticipating scientific institutions andcompanies is available for download atwww.bine.info Service/InfoPlus.

Project coordination• Institut für Energieverfahrenstechnik

und ChemieingenieurwesenTechnische Universität (TU) Bergakademie FreibergProf. Dr.-Ing. B. MeyerReiche ZecheD-09596 Freiberg

▼ ADDITIONAL INFORMATION

Literature• Higman, C.; Burgt, M. van der: Gasification.

Burlington, MA (USA) : Elsevier Science,2004. 391 S., ISBN 0-7506-7707-4

Internet• Projektinformation COORETEC:

http://www.cooretec.de

• http://www.iec.tu-freiberg.de

• United States: http://fossil.energy.gov

• http://www.gasification.org

Images• Figs. 1 and 6 – RWE• Figs. 2 – 5 and 7 Institut für Energie-

verfahrenstechnik und Chemieingenieur-wesen der Technischen Universität TUBergakademie Freiberg

KERS

TIN

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4 BINE projektinfo 09/06

� Outlook

� Existing IGCC power plants

Fig. 7: The five coal-based IGCC power plants currently in operation worldwide

IGCC power plant Buggenum Wabash River Tampa Puertollano Vresova

Location The Netherlands USA USA Spain Czech Republic

Year ofcommissioning 1994 1995 1996 1998 1996 (2005)*

Electrical capacity 253 MW 262 MW 250 MW 300 MW 351 (430)* MW

Fuel Black coal + Black coal + Black coal Black coal + Lignitebiomass petroleum coke petroleum coke

Gasifier type Prenflo E-Gas GE Shell Sasol-Lurgi (GSP)*

Net efficiency Hu 43% 39% 41% 42% 44% (41%)*

*2005 plant expansion

Worldwide, five IGCC power plants based on coal were commissioned between 1990and 2000. Three of those power plants are in Europe, and two in the United States.Also, in a number of refineries, there are additional IGCC power plants which areoperated with crude oil residues and which, alongside electricity, primarily producehydrogen. In Schwarze Pumpe, Germany, the Swiss Sustec Group operates a plant formethanol production from coals and waste, with an integrated gas and steam turbineprocess.

For financial reasons, the technology used in the five IGCC power plants mentionedabove has as yet failed to achieve acceptance, but fundamental experience has beengathered with regard to the process. This experience is a good basis for further devel-opment towards "slim" IGCC. New IGCC power plants are currently being planned,both in Germany and internationally. In Europe, the main driving force pushingtowards construction of such power plants is CO2 separation. In the USA, the emphasisis also on cost-effective and environmentally friendly electricity generation with IGCCtechnology. Alongside electricity generation, the manufacture of chemical products,especially fuels, is also playing an increasing role. In Germany, RWE Power AG is planning a CO2-free IGCC power plant with a netelectrical capacity of 360 MW, which should be commissioned by 2014. E.ON UK hasannounced a similar project for Great Britain for the year 2011. A CO2-free powerplant is also being planned in the USA as part of the FutureGen initiative. There are also numerous other IGCC power plants being planned in the USA, both with and with-out CO2 separation.

PROJECT ORGANISATION

■ Project FundingFederal Ministry of Economicsand Technology (BMWi)D-11019 Berlin

Project Management Organisation Jülich (PTJ)Research Centre JülichDr. Hubert HöwenerD-52425 Jülich

■ Project Number0327700A - H und Z; 0327117

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■ ISSN0937 – 8367

■ PublisherFIZ KarlsruheD-76344 Eggenstein-Leopoldshafen

■ ReprintReproduction of this text is permitted providedthe source is quoted and a complimentary copyis provided to the publisher; reproduction ofthe images contained in this newsletter requires the prior approval of the copyright owner.

■ EditorDr. Katrin Ogriseck, Uwe Milles

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