aiche-2004 brief summary

BRIEF SUMMARY OF PAPERS PRESENTED AT AICHE-2004 SEMINAR:

Prepared by

K.M.Babu. 1.0 STEAM EXPLOSION IN AN AMMONIA PLANT: W. K. Taylor and J. Kelly Thomas Saskferco Products Inc, Baker Engineering & Risk Consultants, Inc.

An explosion occurred in a superheated steam line when Saskferco was starting up its ammonia plant in Saskatchewan, Canada. A steam explosion is a violent vaporization that can occur when water hits a very hot surface. The volume of expansion of water is more than 1600 times from Liquid to vapor when water slugs hit a very hot surface. A steam explosion in U.K. steel works in 1975 caused fatalities. In Saskferco’s case the explosion’s impact did not injure anyone, but they lost three days production and costs associated with incidental repairs.

Contributing factors for the explosion were:

• Overfilling the steam drum and upstream of the Steam Super Heater coil. • A faulty attemperator valve that led boiler feed water to enter the super heater. • A faulty check-valve on the steam drum.

The leaking attemperator allowed water to hit hot steel and vaporize explosively. A

slug of water blew back to the super heater, carrying the attemperator nozzle with it. Steam trapped ahead of the slug, over-pressured an internal super heater component and damaged it. The incident cost Saskferco about three days of downtime and some minor repair costs.

It is possible that one can get away with introducing water at a later, hotter stage of start-up as long as it is carried away by the steam flow. Introducing water during the initial phase of start up, when there is no steam flow, or when the plant is in a colder condition, may represent the worst case. Regardless, it is never a good thing to have water where it does not belong.

This article emphasizes the fact that both beyond High level and beyond low-level operation of Steam Drum is highly unsafe and can lead to severe damages. Sudden rush up of water slugs in a small confined or blocked heated space would lead to steam explosion which eventually might lead to damage of Equipment.

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2.0 NEW DUPLEX STAINLESS STEEL DP28WTM CONTRIBUTES TO SAFE AND RELIABLE OPERATION OF UREA PLANT: Eiki Nagashima and Yoshimi Yamadera Toyo Engineering Corporation, Sumitomo Metal Ind., Ltd. Toyo Engineering and Sumitomo jointly developed a new duplex stainless steel DP28W™ for mega urea plants and they claim it has an excellent passivating property in urea carbamate solution. Duplex SS was used for HP decomposer in 70s, but not used for HP stripper and carbamate condenser and TEC applied this material in their ACES process. Essential factors for urea plant equipment: - less passivating air requirement; lower cost; resistance to SCC; weldability; resistance

to erosion; higher strength. - Key features of DP28W™ are: • chemical composition shows excellent corrosion resistance not only in the base case

but also in the HAZ, per boiling nitric acid test (Huey test) • high mechanical strength compared to austenitic SS and conventional duplex SS • has good weldability • about 1/3 of normal passivating air required • tube thickness can be reduced by 30% when used in place of 25Cr-22Ni-2Mo. 3.0 DECISION TOOL FOR MAJOR REVAMPING OF FERTILIZER PLANTS: Rangarajan . S.V. Sampath Saudi Arabian Fertiliser Company (SAFCO), Al-Jubail, KSA This paper describes a methodology that was developed in decision making for plant revamping options. The methodology involves the following steps: 1. Selection of revamp criteria (Rc) 2. Consideration of each Rc using High, Medium and Low ratings and assignment of

numerical values 3. Evaluating revamp criteria for cost and payout in numerical terms to arrive at revamp

factor (RF) and matching it with Benefit criteria (BC) 4. Developing nomograph using RF and BC range values to produce a decision tool 5. Referring the values of each proposal from the nomograph and arriving at the

decision



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Rc includes the following -

6. Mechanical integrity 7. Process upgrading 8. Regulatory requirements 9. Marketing requirements 10. Operational convenience. SAFCO used this methodology for two proposals each on ammonia and urea plants. Based on that, methanator feed pre-heater and urea reactor revamp fell into high category where as MEA absorber revamp and flare stack for ammonia gas fell into low category, which could be done in next 2-3 years. This is primarily an empirical model, modeled with assumed relative criteria numbers for different situations. 4.0 MEGAMMONIA-THE MEGA-AMMONIA PROCESS FOR THE NEW CENTURY: William L E Davey and E. Filippi Lurgi /Ammonia Casale This paper describes the MEGAMMONIA process developed by Lurgi and Ammonia Casale. Block flow diagram of Lurgi’s MEGAMMONIA process.

ASU – Air Separation Unit

Supplied by an air separation specialist such as Air Products or Air Liquide. Alternatively, these same companies would build own and operate the ASU and sell industrial gases over the fence.

Air

Nat Gas Liquid NH3

O2

ASUN2

FuelCO, CH4, Ar

CPOx(60 bar)

CO Shift(HT Only)(55 bar)

RNWU(52 bar)

AmmoniaSynthesis(200 bar)



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CPOx – Catalytic Partial Oxidation Unit

The catalytic partial oxidation section consists of a pre-reformer and a partial oxidation reactor and waste heat boiler. There is no steam methane reformer (SMR) as in a conventional ammonia plant. A fired heater supplies the heat normally recovered from the convection section of the SMR (e.g. steam superheater). Lurgi has had clients who are leery of the CPOx operating at, 60 bar (870 psig) with gas feed. Lurgi does have one CPOx with liquid hydrocarbon feed operating at 60 bars. With gas feed they have one operating at 50 bar and several at 40 – 45 bar. As a variation, Lurgi has offered a CPOx at 40 bars with a compression stage between the CO shift and RNWU. They claim that it makes little to no difference on the efficiency.

CO Shift The CO conversion section consists of a high temperature reactor only. There is no low temperature reactor as in a conventional ammonia plant. Lurgi has found that in their process the low temperature reactor cannot be justified. The remaining unconverted CO is scrubbed in the nitrogen wash unit and used as fuel in the fired heater.

RNWU – Rectisol, Nitrogen Wash Unit The gas purification unit consists of a Rectisol unit and a nitrogen wash unit. There is no methanator as in a conventional ammonia plant. Lurgi removes the catalyst poisons (CO and CO2) rather than consume H2 converting them to CH4. Lurgi is the licensor of Rectisol. The Rectisol unit (a cold methanol absorber) removes the CO2. Lurgi has studied aMDEA with BASF for such a process and has found that the cutoff for a single absorber is around 2200 T/d. For 4000 T/d, they calculated three parallel absorbers were required. The N2 wash unit removes the remaining CO, CH4 and Ar and returns them to fuel. The plant produces enough CO2 to convert all ammonia to urea (2.3 MT per year).

Ammonia Synthesis

Despite the large production, the synthesis loop is still conventional employing magnetite catalyst. The loop is designed by Casale and uses two reactors. The first reactor has two beds with an internal interchanger. The second reactor has one bed. There is a waste heat boiler between the two reactors.

A breakdown of the capital expenses is as follows: Process Plant 61% Utilities (incl. CT) 15% Tank farm (40 kT) 7% ASU 17%



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Environmental: There are three key environmental benefits to this process scheme as follows:

1. No LTS means low or no VOC emissions (e.g. methanol). 2. No SMR means low NOx and less noise emissions. 3. Stoichiometric CO2 production means 1⁄3 less emissions to atmosphere provided

there is a sink for the CO2 such as urea. 5.0 THE REVAMPING OF FOSFERTIL CUBATAO AMMONIA PLANT, A SUCCESSFUL EXPERIENCE: S.A.DeOliveira Guirado, E. Filippi and M.Badano AmmoniaCasale,Ultrafertil This paper describes the revamping done at Ultrafertil plant in Brazil that increased production rates from 520 to 600 tpd. The revamp included following changes to existing plant. • Installation of pre-reformer (Axial-Radial flow pattern), mainly to handle fluctuations

in refinery off gas composition (used as feed gas) • Modification of primary reformer convection section. • Replacement of primary reformer burners • Reduction of S/C ratio from 3.9 to 3.5 • Reformer Tubes replaced with Manurite XM from Manoir (Old tubes were of Villares LRE9 with 140 mm OD and 16 mm thickness) (New tubes were of 141.5 mm OD and 9.5 mm thickness of Manurite XM from Manoir) • Replacement of ammonia converters with axial-radial converters The above revamp resulted in achieving an average daily production of 614 tpd and reduced energy consumption by about 10.55%. Reformer Catalytic Tubes outside wall temperatures reduced from 950. Deg.C to 880. Deg.C and Synthesis loop pressure reduced by 20 bars. Converter out let Ammonia Concentration increased from earlier 10% to 14%. Fosfertil S/A is a private Brazilian Company originally designed by Foster Wheeler in the year 1970. This plant was designed to operate on Naphtha raw material both as feed and fuel. Due to exorbitant increase in cost of Naphtha and un-availability of Natural Gas this plant started using Refinery off gases available from a nearby Refinery as Raw material. Due to frequent changes in ROG composition, the revamp of the plant with Pre-Reformer addition for alleviating the Primary Reformer operating conditions and to reduce energy consumption was contemplated.



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6.0 EXPERIENCES OF HP-NB &TI CATALYST TUBES AFTER USING OF LONG TERM AT ELEVATED TEMPERATURE: Toshikazu Shibasaki, Takaaki Mohri and Ikuo Kojima Chiyoda Corporation, ChAS Business Division This paper summarized the results of metallurgical examination of HP-Nb & Ti reformer catalyst tubes after 10 years of use and proved that metallurgical stability of this material at higher temperature service is better than that of HK-40 and IN519 materials. Creep rupture strength of HP-Nb & Ti material is higher than that of HK-40 and IN-519 materials, especially, after use at elevated temperature. The paper highlighted that HP-Nb &Ti had a maximum change of ID less than 1%, which translates into a remaining life of reformer tubes of about 50,000 hours. The Author perceives that measuring the inner diameter is a more useful method for estimating the remaining tube life. If the change is below 1%, the tube is expected to have more than 50% remaining life. 7.0 MATERIALS INVESTIGATION OF A 26-YEAR-OLD PRIMARY REFORMER EFFLUENT TRANSFER HEADER: Peter Jaras and Don Timbres Agrium Inc. This paper describes the material and mechanical investigations on different metallic and non-metallic materials of construction of a M.W. Kellogg design primary reformer outlet transfer header. The objective of the investigation was to determine in-service deterioration after 26 years in operation. The components that were investigated were: • Water jacket • Carbon steel transition can to header shell joint • Transition header shell • Welded header shell • Transition cone assembly containing dissimilar metal welds • Metallic liner • By-pass tube • Transition cone • Riser tube top • Collection header • Catalyst tube to tube top • Refractory



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The investigation conclusions were: 1. Deep corrosion pits (60% of wall thickness) in the water jacket, likely to be formed

by oxygen corrosion 2. Fusion line cracking on the steel side of the SA-516-70/Incoly 800H dissimilar metal

welds in transition cone assemblies 3. Extensive sigma formation on metallic liner components 4. No evidence of creep surface carbonization. 5. EDX analysis of weld metals suggests to use the electrodes/filler metals similar to

Inco-weld A and Inconel Filler metal 82 during fabrication. 6. Mechanical properties of refractory much reduced compared to original. Primary Reformer Transfer header completed 26 years of service and the replacement of Transfer header was planned as s safe measure, at the same time of furnace re-harp (Second re-harp) to save time and money. 8.0 OPERATING EXPERIENCE USING aMDEA® IN A COAL-BASED AMMONIA PLANT CO2 REMOVAL SYSTEM ORIGINALLY DESIGNED FOR HOT POTASSIUM CARBONATE: Mike Just, Steve Pouliot, Chris Grossmann, John A. Nichols and Satish Reddy Dakota Gasification Company, BASF Corporation Dakota Gasification Company is an US based company primarily engaged in the business of producing synthesis gas using Coal as raw material through coal gasification process. DGC purchased an old CF Braun Ammonia plant (1000 STPD) located at Fort Madison and shifted total plant to the Beulah site where they are producing synthesis gas using coal gasification technology. The Fort Madison plant was revamped to 1200 STPD after shifting to Beulah. Earlier this plant was using catacarb process (Hot potassium carbonate) for CO2 removal application. In 1996, when plant was revamped to 1200 STPD capacity CO2 removal section was also revamped to aMDEA process replacing the earlier Catacarb process (Hot Potassium Carbonate Process). The following items were thoroughly considered during the revamp: 1. Process temperatures 2. Heat exchanger and heat integration 3. CO2 loading capacity and absorption characteristics of the solvent. 4. Pump capacities 5. Tower dimensions and internals



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The author explains, it is all advantages, and the plant gained in terms of energy saving. Reduced CO2 slip from absorber and reduced equipment maintenance due to less corrosion. The CO2 slip from Absorber reduced to <100 ppm from the earlier CO2 slip value of 1000 to 2000 ppm. LP steam consumption reduced to 9 MT/Hr from the earlier value of 20 MT/Hr. After considering the increased, pumping power of aMDEA solution, still there is a net reduction in energy consumption by 30% over the base case in CO2 removal section. The energy saving is in line with the generally expected savings for an aMDEA revamp from hot potassium carbonate system. 9.0 ACHIEVE COST AND QUALITY BENEFITS BY INTEGRATING PROCESS SAFETY MANAGEMENT AND PLANT INFORMATION SYSTEMS: Georges A. Melhem and Aman A. Ahmad ioMosaic Corporation This paper describes the fundamental role of integrated information systems in facilitating and maintaining sustainable process safety management (PSM) programs. Integrating PSM and plant information management system will provide following benefits: • Plant information is accurate, kept current with plant changes and available to all

users whenever required. • Compliance with engineering standards and regulations and adherence to best

practices such as for incident reporting, plant modifications, etc. • Leverage knowledge in other plant systems for wider benefit. • Eliminate/reduce errors inherent in paper based systems, procedures and work

processes. • Accelerate and streamline plant projects. • Gain business intelligence/decision support due to knowledge stored and analyzed in

the system. The author suggested implementing the document management system (DMS), an “electronic central filing room” for the following primary functions: • Capture and store information. • Facilitate information retrieval within DMS. • Control distribution and revision of information such as P&IDs, PFDs, etc. • Streamline management of change (MOC) or modification system workflow. • Enforce MOC best practices, regulatory guidelines, and corporate methodologies. Enhance audits and reporting.



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10.0 CNOOC CHEMICALS LTD. NEW FERTILIZER PLANT: Yang Yexin and James H.Gosnell KBR, CNOOC After merger of M.W.Kellogg and CF.Braun companies this is the first grass roots plant commissioned combining the technical features of both M.W.Kellogg and CF. Braun Processes. This plant located in Hainan Province, PR of China was commissioned in September-2003 and is one of the lowest energy plants. This plant uses a typical Natural Gas containing 20.7% CO2, 16.8% N2 and 60.7% Methane and the designer has to make major adjustments in the generally offered process design to other clients. This plant was built for CNOOC and has a 1500 tpd of ammonia and 2700 tpd of urea plant using Stamicarbon technology and Yara urea granulation process. The main features of KBR purifier process are: • Process air compressor driven by a Frame 5 gas turbine • Mild operating conditions for primary reforming • About 55% excess air to the secondary reformer • BASF’s aMDEA process for CO2 removal • KBR’s cryogenic Purifier to remove inerts from the raw synthesis gas • Horizontal magnetite converter • Unitized ammonia chiller The Purifier technology enabled CNOOC without any need of CO2 removal at upstream of primary reformer even though there is a potential increase of severity in reforming operation. This process allowed methane slip to rise from primary reformer as any additional methane from it can be removed in cryogenic purifier and it compensates high severity in reformer operation. About 28% of N2 is required with the feed to make NH3. With almost 17% N2 in natural gas, this would normally require significantly lower amount of process air to secondary reformer, which transfers reforming duty to primary reformer. 17% N2 requires the primary reformer be operated at higher temperature by about 35 DegC in a conventional ammonia plant in order to maintain same H/N ratio. The normal H/N ratio at Purifier inlet is 2.0 and at CNOOC, it is designed for 1.8 to keep primary reformer exit temperature same as it would have been with H/N ratio of 2.0. However, CNOOC plant is designed for methane slip of more than 2% from secondary reformer, higher than normal Purifier process. The project was kicked off in March 2001 and performance test completed in March/April 2004. Actual cost of the project was about 89% of the budget cost.



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The Ammonia plant achieved an energy efficiency of 6.5 Gcal/MT of ammonia. Separate discussions with M/S KBR revealed that CNOOC Plant has been designed for a cooling water temperature of 32.0 Deg.C. Ammonia Plant energy 6.5Gcal/MT is exclusive of Ammonia Cooling water Pumping Energy. Generally cooling water Pumping energy remains in the order of 0.14 Gcal/MT to 0.17 Gcal/MT for a typical 1500 MTPD Ammonia Plant. 11.0 IMPROVEMENTS ON SYNTHESIS GAS COMPRESSOR FOLLOWING PIPING FAILURES: Venkat Pattabathula and Victor Garcia Agrium, Borger, TX M/s. Agrium Borger Nitrogen Operations, operates a MW Kellogg designed Ammonia Plant of 1000 STPD capacity. The plant is about 30 years old and over the years the plant capacity was increased to 1500 STPD through many de-bottleneck projects, involving process equipment. As part of one of the retrofit projects, a larger size recycle wheel (19”) was installed in place of an old smaller size recycle wheel in the synthesis gas compressor (103-J) in anticipation of upgrading the plant capacity to 1800 STPD. But due to high natural gas prices, the plant has been running at reduced rates for the last three years making it necessary to throttle the recycle suction motorized valve Sp-70. This increased the differential pressure (DP) across SP70 and energy usage of 103-J. Problem noticed: Instrument fittings tapings on the suction and discharge side of the compressor failed. Total three failures took place. Investigation of problem Analysis: A detailed failure analysis conducted revealed that the root cause of the Hp fittings failure was the harmonic vibrations. Corrective actions taken: The original compressor supplier Dresser-Rand was contacted to address the piping vibrations. Dresser-Rand sent a proposal for trimming the recycle wheel and for installing a new Duct-Resonator Array in the recycle wheel. Dress-Rand experience has shown Duct Resonator (D-R) arrays are very effective at reducing turbo machinery noise at the source.



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Finally based on Dress-Rand recommendations recycle wheel was trimmed from 19” to 18.5” size, which would still enable the operation of the plant at 1500 STPD.

A new Duct Resonator array was also designed and installed on the outlet diffuser wall side of the fan path. The entire mechanical job was done in two weeks time. Conclusion & End Results: The root cause for Synthesis gas compressor high pressure piping vibration was the size of recycle wheel, which was larger than required. This resulted into pressure pulsations that transmitted to the Synthesis gas piping. Trimming the recycle wheel and installation of Duct Resonator array have helped to reduce the piping vibrations. Recycle wheel suction valve could be opened fully and compressor energy usage was reduced due to reduced DP across Sp70 from 100 psig to 10 psig. The average reduction in noise level achieved is about 10 dB. This average reduction of 10 dB in noise level, due to DR array installation was observed in about 50 other compressor installations as verified by the Author from the supplier. 12.0 INSPECTION OF SERPENTINE PIPING COILS IN PROCESS HEATERS UTILIZING INTELLIGENT PIGS: Richard D. Roberts QUEST TruTec LP. This paper describes remotely operated autonomous inspection tool (Intelligent pig), Furnace Tube Inspection System (FTIS), that was developed by QUEST Integrated, Inc. This new technique enables inspection of both convection and radiant section coils in reformer furnace and it relies on custom designed ultrasonic (UT) technology to acquire wall thickness, diametrical dimension, and shape information like bulging, swelling, and ovality, throughout the coils. The FTIS intelligent pig is transported through the interior of the Serpentine piping coil via a column of water, which provides propulsion, and coupling for the ultrasonic transducers. The inspection data is processed and stored on board the FTIS intelligent pig using high speed digital signal processing. Features such as internal corrosion, erosion, pitting, bulging, swelling, and deformation are easily located and quantified. Custom software provides the ability to view the entire coil in both 2-Dimensioanl and 3-Dimensianl graphics.



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The author has presented two case studies of coil inspections using FTIS e.g. crude heater and vacuum heater and he has mentioned that preliminary results can be available within minutes after the data are downloaded to make quicker decisions about bringing furnace on line. 13.0 ON-STREAM & ENERGY EFFICIENCY OF INDIAN AMMONIA & UREA PLANTS –AN ANALYSIS: S. Nand and Manish Goswami Fertiliser Association of India This paper highlighted the improvements made in energy consumption in Indian ammonia and urea plants, over the past two decades. The average overall energy efficiency of ammonia plants has come down to 9.30 Gcal/MT during 2002-03 compared to the value 12.48 Gcal/MT prevailed during 1987-88. This corresponds to a reduction of 25.5%. The average energy consumption of 25% most efficient Indian ammonia plants at 8.41 Gcal/MT is lower than 8.49 Gcal/MT for the most efficient 25% ammonia plants in the world. The total weighted aver energy consumption of US gas based ammonia plants (42 Nos) is about 9.94 Gcal./MT where as for Indian ammonia gas based plants (22 Nos.) the value is 9.61 Gcal/MT. The average energy consumption of (15 Nos.) gas based Indian ammonia plants is lower at 8.51 Gcal/MT compared to the average energy consumption value of 8.77 Gcal/MT of Chinese gas based Ammonia plants (8 Nos.) 14.0 DYNAMIC BEHAVIOR OF THE WASTE HEAT BOILER FOR AMMONIA PLANT: Jiri Jekerle ALSTOM Power Energy Recovery GmbH

This paper describes the calculations of the pressure and temperature changes on the waterside of the waste heat boiler for some transient operating cases. The temperature changes on the water and gas sides determine the temperature distributions as well as the time dependent stress distribution in the pressurized parts of the waste heat boiler, which could affect lifetime of the waste heat boiler.



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The study of unsteady operating cases like start up, shutdown or quick trip conditions is an important engineering step during the planning and design of the ammonia plant equipment. The knowledge of the transient behavior of the boilers, pressure vessels and other equipment improve the understanding of possible failures and help to find the root causes to prevent them and any consequential damages. The method described in this paper is based on the mass and energy balance and volume equations for the pressure vessels and equations of specific enthalpy and specific volume of water and steam.

This method has been previously verified by comparing them with experimental data obtained from real equipment. The proper use of described simulation method makes it possible to gain an accurate and pragmatic description of the dynamic behavior of waste heat boilers. The boiler feed water pump failure example presented in this paper emphasizes the necessity to pay detailed attention to the possibility of failures occurring. The results help to improve the technical and operating reliability and efficiency of whole ammonia plant. 15.0 HOW TO BRING EXISTING AMMONIA PLANTS UP-TO-DATE: Svend Erik Nielsen and Peter Vang Christensen Haldor Topsoe A/S The paper highlighted the need and urgency of reducing the energy consumption of Ammonia plants as the global natural gas and Hydrocarbon prices are continuously increasing. Particularly this is applicable to those old vintage Plants which are operating above the world average benchmark energy value. Also pointed about various options available to increase the capacity and reduce the energy consumption. HTER (Holder Topsoe Exchange Reformer) is a proprietary and patented design of Holdor Topsoe, and its claimed advantages have been presented. The newly developed HTER if incorporated operates in parallel with the existing primary reformer and reduces the load on both process side and combustion side of the existing reformer. The Author has presented comparative figures for both pre-reformer and HTER revamped options of an existing 1500 MTPD ammonia plant to 1650 MTPD Capacity. When data presented are evaluated the energy number for pre-reformer option has been found to be on lower side by 0.1 Gcal/MT of Ammonia compared to HTER option.



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This particular HTER revamp option will suit those plants where primary reformer is a bottleneck for increasing capacity, and all other sections of the plant have margins for envisaged capacity increase. Also this option will suit to a situation where low cost steam can be imported from a coal-fired boiler available in the complex. HTER is more like a capacity addition revamp option and will not give any substantial energy saving. The IFFCO revamp options, which are under implementation, were also presented with more detailing on S-50 converters. S-50 converters will be added in series down stream to the existing converter.

In Kellogg designed IFFCO plants newly added S-50 converter would have a lower heat exchanger to pre-heat the existing converter outlet gas, which is at a lower temperature (about 325. Deg.C.).

In Haldor Topsoe designed IFFCO plants the newly added S-50 converter will be without a lower heat exchanger. In Kellogg designed IFFCO plants after S-50 converter one new MP steam boiler shall be introduced and in Topsoe designed IFFCO plants after S-50 converter one HP Steam boiler shall be introduced. As per Topsoe the expected energy saving on account of S-50 converter addition alone shall be between 0.15 Gcal/MT to 0.3 Gcal/MT depending on the plant specifics and existing loop configurations 16.0 REVAMP OF LIAOHE’S AMMONIA PLANT WITH KRES TECHNOLOGY TO REDUCE NATURAL GAS USAGE: Avinash Malhotra, Paul Kramer and Shashi Singh, KBR Shenzhen Liaohe Tongda Chemicals, Ltd. This paper describes the successful scale up of Kellogg Reforming Exchanger System (KRES) from 350 MTPD Ammonia Plant that was first time installed at Kitimat, Canada in 1994 to a 1000 MTPD Capacity at Liaohe plant in China in 2003. The KRES suited well for this plant as they were looking at reducing natural gas consumption on site due to reduced gas supply. Ammonia Plant Process Steam requirement is partly fulfilled by importing Steam from off-sites Coal fired Boiler. The Ammonia Plant revamp at Liahoe consisted of replacing the existing Primary Reformer and Secondary Reformer with a new proprietary KBR designed KRES system consisting of KRES exchanger, Auto thermal Reformer and Process Heater. Also O2 enriched Process Air is supplied to the ATR.



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KBR has improved its design features of KRES from Kitimat plant to this plant such as: • Higher operating pressure of KRES from 19 bar to 32 bar • Reduced tube size of KRES to 1” • Refractory protected tube sheet design that allows use of SS metallurgy • Optimised catalyst size & shape With the KRES, Liaohe plant reduced their natural gas usage from 10.09 to 7.17 Gcal/MT and the net energy consumption of ammonia plant reduced from 10.09 to 9.44 GCal/MT as the required steam is supplied by coal fired offsite boiler at the site. 17.0 CONSERVING ENERGY USING ANALYTICAL TECHNIQUES WHILE PROTECTING THE ENVIRONMENT: Jahangir Waheed and Aneeza Qazi Engro Chemicals, Pakistan This paper describes the energy conservation idea by using urea hydrolyser steam as reformer feed steam in ammonia plant. At Engro, ammonia plant process condensate is also fed to urea hydrolyser to remove ammonia and methanol from the condensate. When Engro made first attempt to use hydrolyser steam, they have experienced the following problems: • Poisoning of LTS catalyst from chlorides, which got into process condensate from a

leaking CW exchanger in CO2 removal section. • Deactivation of pre-reformer catalyst due to the presence of sulphates in hydrolyser

vent stream which otherwise being vented before this change. • High ammonia content in CO2 product from ammonia plant resulted in carbamate

formation and corroded Cu-Ni exchangers in urea plant. Later on, Engro procured an on-line Ion Chromatograph to measure chlorides and sulfates to ppb levels and Cu-Ni exchangers in urea plant were replaced with SS. The urea hydrolyser vent steam was again lined up to ammonia plant reformer and found no problems as Engro was closely monitoring the chloride and sulphate levels. They have also developed new operating procedures to divert urea hydrolyser steam to vent in case of any abnormalities in its quality that is analysed with Ion Chromatograph. As a result, Engro successfully saved energy and improved site environmental standards by reducing ammonia, and methanol emissions into atmosphere. The essence of the whole project lies in improved monitoring techniques and stringent monitoring standards without which it can cause damage to the process far exceeding its benefits.



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18.0 FAILURE OF SEMI-LEAN CATACARB PUMP DUE TO REVERSE FLOW INVESTIGATION AND FOLLOW-UP: David Craig Agrium

A semi-lean Catacarb solution pump in Agrium’s Redwater plant in Alberta, Canada spun backwards and caused the pump and turbine to fail catastrophically within two minutes. Agrium conducted a detailed investigation using the cause-mapping method. To help prevent similar failures, Agrium installed a new check valve with a remote-operated block valve, but no external shaft. Summary: • Reverse rotation of pumps, especially due to a high-pressure gas or vapor, can result

in a catastrophic failure of pump and driver. • Using manual block valves for emergency isolation is not an option if the manual

block valves are too large. • The use of sealant compounds should only be viewed as a temporary fix. • Management of change (or modification assessment) is required to control and review

potential issues when using leak sealant compounds. • Standardized operating procedures during normal change over, start up & shut down

of pumps have to be religiously followed and communicated to all the concerned. Consider check valves as protection against reverse flow on a pump trip but not as part of the normal operating system for starting and stopping pumps. KRIBHCO’S perspective: Similar incident happened in Ammonia-II plant during the year 1986, when 107-JC/JCT back rotated. Due to NRV failure, Process gas backed from Absorber, resulting in fire, and subsequent damage to Pump & Turbine. Machine was not available for about one year after the incident. Plant operation was managed with only 107-JA/JB. Improvements over the year 1986 prevailed situation:

• Pump discharge valves are motorized for quick positive isolation. • Check valves are inspected/Serviced during ATR and other opportunities. • Pump Change Over/Start/Stop/ operations are standardized. • AOP Start alarm contact changed to Motor from earlier L.O. Header contact to

help panel operators.



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19.0 GRANULATION PROCESS OF STAMICARBON EXCELLENT GRANULE QUALITY WITH ENVIRONMENT FRIENDLY PROCESS: P. Djavdan and J. Meessen Stamicarbon This paper describes Stamicarbon’s new fluid bed urea granulation process that was installed in Agrium’s Fort Saskatchewan plant. Agrium granulation plant has two lines of 625-mtpd capacity each, commissioned in the year 2003. This new process consumes about half of the normal usage of urea formaldehyde and has less dust formation and Stamicarbon claims it’s because of low-pressure film sprayer process with no atomizing air. This new granulation process was first applied at Grodno’s plant in Belarus. The reduced formaldehyde consumption would offer attractive savings to urea producers and the granulation plant ran for more than three months without granulator washing at Agrium plant. 20.0 INTEGRATING RISK BASED INSPECTION INTO AMMONIA STORAGE RISK MANAGEMENT PLANS: Michael J. Conley and Ken Stevens The Equity Engineering Group, Inc., PCS Nitrogen This paper discusses the application of risk assessment technology in general, and more specifically Risk Based Inspection (RBI). Studies of RBI as applied to ammonia storage and handling have been performed to analyze the hazards presented by corrosion or other ongoing degradation of equipment. The primary elements of RBI are consequence and frequency and secondary elements are inspection effectiveness and its impact on damage likelihood. The RBI results are carefully calibrated to match other risk assessment efforts focusing on other hazards. By presenting the results of all risk assessments using similar metrics, management is provided with a powerful tool to make decisions regarding application of resources to control threats to Safety, Health & Environment. Essence: Inspection is the observation of damaged states of equipment or structures. As such, it is a form of risk assessment. High risks are identified by the presence of cracks, or the discovery of metal corroded below the wastage allowance. Low risks are indicated by the absence of such conditions. Control or management of the risks is ensured by carrying out risk mitigating measures such as repair, replacement, or change of operating parameters. Such mitigating activities require management support and commitment to do all the necessary rehabilitation.



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21.0 EXPERIENCE OF USING A NON-INTRUSIVE APPROACH TO THE INSPECTION OF A 23-YEAR AMMONIA STORAGE TANK: Stanley Reid PCS Nitrogen, Trinidad This paper describes a non-intrusive approach to the inspection of a 33,000 tonne ammonia storage tank in Trinidad and it also highlights the inspection findings after the insulation was removed. The paper correlates the inspection results with the findings from an Engineering Assessment and Acoustic Emission testing. This plant has noticed seventy-six cracks on the dome of the tank at insulation clips and at long seams. A metallurgical review of the cracks identified the cause of cracking to be stress corrosion cracking by ammonium nitrate. This type of cracking is found under poorly sealed insulation when high stresses, usually caused by welds that were not stress relieved and accentuated by relatively warm temperatures. The presence of ammonium nitrate from atmosphere and its exposure to air contributed to SCC. The cracking resulted when the ammonium nitrate was dissolved in rainwater and washed through crevices in the insulation on to the metal surfaces. The engineering assessment, the AE test and the NDE performed, all showed the tank's shell and floor were in sound condition. AE test was not done on the Dome and no results were available for comparison with conventional NDE test results. 22.0 A RIGOROUS ASSESSMENT PROCEDURE FOR DEVELOPING INSPECTION PLANS FOR AMMONIA UNITS J.L. Andreani, G.M. Buchheim, M.J. Conley and K.J. Stevens Equity Engineering This paper describes a rigorous assessment procedure used to develop inspection plans for ammonia storage tanks, bullets and Horton spheres. The procedure includes a qualitative review of data, a risk based inspection (RBI), assessment of storage vessel and its associated piping and related pressure equipment, a fitness for service (FFS) evaluation of the storage vessel, an analysis of associated piping, and assessment of pressure relief capacities. This company assessed a half a dozen ammonia storage units and developed plans that emphasize non-intrusive technology to avoid SCC damage associated with warming and opening of storage vessels for inspection. They claim that risk of SCC and other safety concerns inherent with decommissioning may be far greater than risk of continued service with less frequent internal inspection while providing more in-service inspection and monitoring.



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Author also expressed the views that Inspecting for SCC could be a difficult task.

Ammonia cracks are generally shallow with a high length to depth ratio. Every inspection technique has a threshold for detectable crack size and small cracks may not be detected by any inspection technique. However based on the advancements made in the sensitivity of inspection methods, intrusive methods involving surface inspection, and a non-intrusive technology, acoustic emission (AE) testing, can be used to inspect for crack like flaws.

However, along with complexities related to the finding and sizing SCC surface

flaws, intrusive inspection introduces the additional complication of oxygen contamination.

As a non-intrusive technology, AE does not introduce the possibility of oxygen contamination, or the need for warming refrigerated Storage tanks. AE method can be used to determine the existence of cracks, which can later be sized using Ultrasonic (UT) methods. 23.0 REDUCING STRESS AND INCREASING THROUGHPUT OF REFORMER BY GOOD TUBE DESIGN: Bill Cotton and John Brightling Johnson Matthey Catalysts This paper details how to improve the performance of primary reformer by the correct catalyst selection and application of good design techniques when considering primary reformer re-tubes. Common modes of reformer tube failures are generalized and localized overheating. Reformer tubes can be inspected using destructive testing, visual inspection, acoustic emission, eddy current, radiography and laser profilometry (LOTIS). As per the Author Laser Profilometry is the most accurate method available for Reformer tube inside diameter measurement and therefore the amount of creep strain the tube has suffered. Catalyst type & size, promoters used in catalyst and catalyst loading method would have significant impact on reformer tube stresses. The catalyst size & shape should be optimized such that it gives good turbulence of process gas for better heat flux distribution and to keep metal skin temperature of tubes at the lowest possible level. Modern catalyst loading method such as UNIDENSE achieves less pressure drop variation and hence reduced tube wall temperature (TWT) variation. Two case studies of reformer re-tube projects were presented where significant improvements noticed with thin wall tubes and low DP catalyst loading technique and this has helped to reduce TWTs.



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The relative strength of HP micro Alloy tubes is 2.2 times higher than that of HK-

40 tubes. This strength improvement is due to the increased amount of Secondary carbides, which are finely distributed throughout the parent material. They prevent the movement of dislocations through the material and hence resist the movement reducing the extent of creep damage. In HK-40 only the chromium forms the Carbides whilst for the later alloys, Niobium forms secondary carbides. Titanium, zirconium, Tungsten, and cesium are all strong carbide formers and form finer carbides that last longer, providing higher strengths that are retained for longer. These higher strengths allow for a reduction in tube wall thickness when utilizing modern Alloys. 24.0 UPGRADING OF AMMONIA PLANT EMERGENCY SHUTDOWN SYSTEM: Syed Salman Bin Aslam Engro Chemicals, Pakistan This paper shares the experience of upgrading an old and obsolete pneumatic emergency shutdown system with a Triple Modular Redundant (TMR) electronic system. Addition to the already existing trips, new trips such as S/G ratio, furnace low draft, WHB steam drum low level, Furnace coils protection w. r. t BFW circulation and some CO2 removal system protections were added to the new ABB system while switching over from Pneumatic to Electronic system. Engro used the following strategy in developing a new emergency shutdown system: 1. Identification of potential hazards and appropriate classification based on

HAZOP/PHA. 2. Improvements of control system to avoid a particular event. 3. Time delays (0.5 sec) in trip security actuation. 4. Development of one-line diagram for implementation in phases. 5. Scrutinizing the process through multidisciplinary team. Additions and deletion of trips based on their own experience and industrial networking has been implemented. In 1995 Engro Chemicals had a bitter experience of dry out operation of Secondary Reformer effluent waste heat Boiler that resulted in substantial damage. This incident forced the plant management to think about more safe and advanced instrumentation so that efficient control systems could be configured for Safe handling of the Plant. Other human aspects like dependency on certain skilled personnel, response time & efficiency, judgment of individuals were also deliberated before change over to electronic control system. .



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25.0 SERIAL KILLERS IN THE PROCESS PLANT: George S. Price Plant Safety Analysts Inc. Paper was not presented during the Seminar but the Summary of the text of the Paper is as under: Many parallel sub-processes do take place within the systems during the course of operation of a large scale Process Plant. These sub-processes many times remain unnoticed, as they happen to be on a very smaller scale and without interrupting the Plant Operation. But these sub-processes may lead to major incidents and can cause loss of property and injury to the operating personnel. Examples of such Sub-Processes are: 1.0 Spillage of Oil drops from Bearing End covers, Valves Glands & Bonnets.

(If continued/ or remained unnoticed may lead to fire incidents and disrupt plant operation. Also may cause fall of people due to slippery ground/floor situations caused by Oil leaks.)

2.0 Waste cotton/ Scaffolding Material used for Cleaning & Repair of Equipment. (If not disposed/removed properly & timely may lead to a fire situation. Waste cotton fallen accidentally in Process equipment may block the flow passage in Pipes or Equipment.)

3.0 Custody of Spares & loose material used in Plant: (Ensuring proper custody of Bolts, nuts and tools while opening and boxing up of Equipment. Otherwise may cause unexpected damage to critical equipment and may lead to un-expected Downtime.)

4.0 Vacuum & Temperature Pit falls: (Common scientific principles are always to be kept in mind while handling equipment to protect them from damage arising out of Natural processes governed by simple scientific principles.) Example: Process vessels operated at higher temperatures if not designed to with stand high vacuum conditions would collapse in blocked position, if proper care is not taken when they are reaching ambient temperature. Blocked CO2 Absorber will create high vacuum when it gets cooled down to ambient temperature and if not recognized properly it might cause injuries to operating personnel. (CO2 Stripper & Deaerator are provided with Vacuum breakers and they should be confirmed for availability at regular intervals.)



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Conclusion: The sub-processes are inherent to the systems handled by different Process Plant Operators and mostly remain Plant Specific. No formal training is in place to address these sub-processes and they are generally not found in Plant Operating and training manuals. Obviously, Entrepreneurs striving for overall sustained success have to spend time and money to take care of these subconscious issues as well. 26.0 DETECTION OF HYDROGEN DAMAGE IN CARBON-½MOLYBENUM PIPEWORK AND PROCESS VESSELS: C Jones, D Keen, C Thomas and A Dowrie Materials Performance Technologies, Incitec Pivot Ltd. This paper describes recent experience with carbon, 1/2 moly steels. High temperature hydrogen attack (HTHA) has caused significant damage to piping and pressure vessels. The Damage mechanism that leads to HTHA is: Ø Dissolution of hydrogen from the Process environment. Ø Decarburisation caused by the reaction between carbon (as carbide) and dissolved

hydrogen to form methane. Ø Fissuring and cracking caused by internal methane pressure.

Non-destructive testing (primarily ultrasonic) detected the damage. Macro cracks in heat-affected zones are one form of HTHA damage that seems to occur particularly in newer, alloy-steel vessels. Pressure equipment should be rejected in accordance with API 579. The paper also proposed an engineering-based critical assessment procedure for hydrogen-damaged items.

As per the 5th edition of API941 “ Steels for Hydrogen Service at Elevated

Temperatures and Pressures in Petroleum Refineries and Petrochemical Plants”, The C-0.5 Mo Safe working line has been removed from the Nelson Curves within this code. This now means that C-0.5 Mo material usage for H2 Service at elevated temperatures and pressures is not recommended and is treated at par with normal Carbon Steel material.

The Author opined that Fitness for Service of a Vessel is decided by assessing not only the primary applied stresses such as hoop stress (Generated by internal pressure) but also require a knowledge of secondary stresses such as thermal and residual stresses. Further when HTHA has been detected and the detected level of damage restricts detection of macro cracks, then that material/Equipment would not be fit for service.



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27.0 MODELING OF AN ACCIDENTAL RELEASE OF ANHYDROUS AMMONIA AND ITS ATMOSPHERIC DISPERSION: Vasilis M. Fthenakis Brookhaven National Laboratory, Upton, NY This paper describes fundamentals of two-phase release of anhydrous ammonia from cracked or ruptured containers, the extent of aerosol rainout on the ground, subsequent evaporation, and the atmospheric dispersion of the ammonia vapor/aerosol cloud. The predictions of several models are compared with an actual case of catastrophic release caused by a recent derailment of a freight train.

An extremely large release of ammonia occurred in Minot, North Dakota on 18 January 2002 under very cold ambient conditions. Calculations based on mass balances and fluid dynamics suggest that between 20 to 30% of the released ammonia rained out near the release location due to gravitational settling and collusions with the ground. The balance of the mass was dispersed as an enormous cloud comprising aerosol and vapor. Using LPOOL evaporation model, the author calculated that about 1% of the rainout ammonia evaporated during the first few minutes. Using ALOHA /DEGADIS and SLAB, the author determined that concentrations of ammonia in excess of the ERPG-3 level of 750 ppm extended to 4.3 to 5.8 miles. 28.0 HOW TO ACHIEVE PLANNED PERFORMANCE ON YOUR NEW PROJECT: Jorge A. Camps Jacobs Consultancy Inc. This paper describes challenges involved in achieving planned performance on a new project. The projects listed by the author were: • Point Lisas Nitrogen Ltd • PCSN2, Trinidad. • Profertil in Argentina • FertiNitro in Venezuela • Farmland’s Petroleum Coke All these projects were not typical repeat exercises and each one involved one or more elements of innovation or technical project risk. Some lessons learned were: a) None of the projects failed, but each had a different measure of success. Some of

these new projects had lower than expected initial production rates for variety of reasons.



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b) Not all “new technology” resulted in production or operational difficulties.

However, all projects with one or more significant technology developments went through learning experiences that caused certain initial impairments on production.

c) Difficulties caused by certain deficiencies in fabrication or construction quality had a greater negative impact on production than new technology issues.

d) Even though infrastructure and site location topics received attention, significant issues surfaced on several projects.

e) Only three of the above 5 projects achieved long term production after the first year operation and one of these reached production target during its third year of operations. One project is implementing repair plans to achieve its long-term production target in its fifth year of operation.

Some Findings & Conclusions spelt by the Author: Where ever or whenever there is a “first-of-a-kind-situation”, Consider the potential effect and devise steps to mitigate it.

If there are multiple “firsts” or trend-setting aspects, consider whether these may feed on each other or create potential “frightening combinations”. If so, mitigate the risk or avoid them altogether. As a rule of thumb, two or more significant “firsts” may constitute a frightening combination for a major industrial project. 29.0 ADVANCED MODELING TOOLS AND TECHNIQUES FOR PRIMARY REFORMERS: Mike Davies, Barry Fisher and Bill Cotton Johnson Matthey Catalysts This paper provides a broader overview of key modeling techniques showing how each can be applied to provide valuable insight into particular aspects of reformer design and operation. PRIMARY is Johnson Matthey’s in-house reformer simulation program originally known as REFORM. Typical uses of PRIMARY include reconciliation of operating plant data, determination of tube temperature margins, estimation of catalyst activities, optimisation of catalyst loading, reformer optimisation, and reformer design. The modelling of individual parts of the reformer such as inlet header systems, burners, radiant box, tubes, outlet header, tunnels, convection section, coils and catalyst size & shape are discussed in detail.



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30.0 RECENT DEVELOPMENTS IN UREA PLANT DESIGN: Pan Orphanides, Orphanco Greece. This paper reviews the recent developments in urea technology and they include: a) Urea synthesis technology for large-scale single unit grass root plants up to 4,500 mt

using equipment such as pool condenser, and pool reactor, of Stamicarbon, Toyo’s Vertical Submerged Condenser and Casale’s Full Condenser.

b) Use of new materials such as Duplex steels (27-28% Cr min) and Safurex v/s 25/22/2 L austenitic steels for improved corrosion resistance and mechanical strength.

c) Urea granulation using new Stamicarbon FBG Process. d) Advanced feature for urea cooling with Fluidised Bed Cooler as bulk flow cooler has

relatively restricted application. For a typical 2000 MTPD Urea plant the power consumption for a Fluidized Bed Cooler is about 1.8 MW compared to the 200 KW needed by the Bulk flow cooler facility. 31.0 INSPECTION OF PRESSURE SWING ADSORPTION VESSELS AND MOLECULAR SIEVE DRYERS USING ACOUSTICAL EMISSION TESTING: Don H. Timbres, Robert Pelletier and John Blazenko Agrium Inc. This paper describes the acoustical emission inspections conducted on five pressure swing adsorption (PSA) vessels and six molecular sieve dryers at two Agrium facilities. The acoustical emission testing was followed up with an internal inspection of two PSA vessels and three molecular sieve dryers. Conclusions and observations from AE and internal inspection are as follows: 1. The AE did not pick up any small defects on one of the vessels those were found

upon internal inspection. 2. The AE did show some cracks on another vessel, but no cracks found upon internal

inspection. 3. Internal inspection of molecular sieve dryers did not indicate any evidence of

deterioration to their mechanical integrity. 4. Follow up evaluation is required in the AE test depending on the intensity level

recorded, to justify further non-destructive examination and any remedial attention.



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KRIBHCO’S Perspective: In PGR Plant two Dryers are in Operation since commissioning in the year1989. These were never visually inspected from inside till to Date. Pending a thorough full-fledged inspection, other NDT methods should be used and a non-intrusive inspection should be carried out to assess any symptoms of unwanted Damage.

Though the partial pressure of H2 in the Process gas handled by PGR Dryers is

less than the partial pressure of H2 in the make up Synthesis gas Dryers of Ammonia Plant (Where ever they are used), it would be prudent to check PGR plant Dryers without remaining complacent. 32.0 COMMON PROBLEMS ON PRIMARY REFORMERS: Bill Cotton and Peter Broadhurst Johnson Matthey Catalysts This paper discussed common reformer problems, including problems with: • Catalysts: poisons, carbon formation and hot tubes, catalyst breakage, the effect of

water, and catalyst loading • Reformer tubes: hot tubes, tube failure, generalized & localized overheating, stress

corrosion cracking of tube tops and bottoms, bowed tubes, pigtails, and risers • Radiant boxes: flue gas mal-distribution.

(Mal-distribution could be due to improper adjustment of Air dampers for individual row of Burners which might result in post burning scenario in some of the rows,)

• Burners: after-burning, excessive air, fan issues • Header designs: fuel and fuel header designs including symmetry problems • Refractory: general damage, damage to anchors and tracking behind refractory.

(Refractory anchors MOC selection should be done carefully keeping in view the most severe conditions.)

• Coffins (Also known as Tunnels): Damage to the coffins would lead in mal-distribution of flue gases resulting in higher bottom skin temperature of tubes in some banks.

• Risers Protection: On one Kellogg Reformer, the Risers suffered from significant cracking around 30% of the way down the riser caused by flame impingement due to flame deviation from the vertical. As a short term fix the upper part of the Riser was insulated. This would cause a marginal reduction in radiant box efficiency.

The Author also presented some of the advantages of UNIDENSE CATALYST LOADING, which will address some of the problems associated with Primary Reformer Operation. KRIBHCO’S Perspective: UNIDENSE loading may give some qualitative benefits. But calculating the cost advantage over conventional loading is not a simple straightforward method. Majority of the problems explained by the Author would creep in during the course of Plant Operation and cannot be attributed directly to Catalyst Loading.



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33.0 METHAMMONIA - AN ALTERNATIVE TO RELOCATING AMMONIA/UREA COMPLEXES: William Davey and Carlos Lange Lurgi This paper suggests using methanol, as feedstock to make ammonia in place of natural gas and it might be an attractive option for ammonia producers in USA and India who are planning to invest on offshore plants. The author presented the following strategies for the survival of the US nitrogen industry: 1. Do nothing and maintain status quo. That means operate plants at lower natural gas

prices and shutdown plants at higher prices. 2. Change feedstock to LNG. Most of the time, importing LNG is not cheaper than it

can be purchased from US gas grid. 3. Change to coal or petroleum coke as feedstock. Although, this route may ensure

business survival in the longer term, the capital penalty is severe, and the economic viability is doubtful.

4. Relocate ammonia production capacity to low gas cost country and ship liquid ammonia back to US. The market for direct injection of ammonia as fertiliser is falling. CO2, which is essential for the production of urea and UAN solutions, does not accompany the liquid ammonia.

5. Relocate entire fertiliser production capacity to a low gas cost country and ship urea/UAN direct to US customers. There could be an objection of US agriculture lobby to the exposure of imported fertilisers and security concerns with the import of nitrate solutions.

6. Locate low cost methanol from a low gas cost country, ship it to USA and convert it into ammonia.

The author mainly talked about this last option. A new methanol reformer can be added to existing plant and the entire hot front end of ammonia plant can be taken out of service (including shift converters). The methanol-reformed gas can be directly fed to CO2 removal unit and one can still use the existing backend of ammonia plant. The current cash cost of producing UAN from natural gas on the US Gulf Coast is $88.30. The cash cost of making one ton of UAN based on imported methanol feedstock would be $43.78 and hence, the author feels that making ammonia from methanol could be an attractive option for US fertilizer producers. *****



aiche-2004 brief summary

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