Coal Gasification Technology and Syngas ProductionRuben Reyes ChE379

Purpose/OutlineGasification technologyDifferent types of gasifiersProducts from gasificationSyngas production, Gasifiers used for IGCC power plantsConclusion

Coal Gasification TechnologiesBasic Overview of gasificationCoal or other fuelsOxidation carefully controlledH2, CO2, CH4, other products H2 can be purified Ash/slag leftovers3 types of gasifiersMoving bedFluid BedEntrained Flow Underground Coal GasificationVertical wells and pathway creationControlled retraction injection point

Above ground gasificationMoving bed reactor (Lurgi dry ash and BGL - slagging)Counter-current flow of coal and oxidizing blastBlast composed of air and hot syngas, so low oxygen consumptionOperates on reactive carbon sources Good heat transfer heats the carbon source creating methane and tarPost production cleaning and scrubbing requires greater energy use

BGL gasifier (fixed bed, slagging)Figure 1: BGL Gasifier

Above Ground GasificationFluid-bed reactor (Winkler, HTW, CFB dry ash; KRW, U-Gas Agglomerating)Air fluidizes a bed and carbon containing particles addedProper mixing of fuel and oxidant provide good mass transfer and heat transferFine particle will escape with syngas and needs to be cleaned Very good heat/mass transfer so partially reacted carbon may settle with ashSlagging will reduce fluidization, so temp remains below softening point for ash

Winkler Gasifier (Fluid bed, dry ash)Figure 2: Winkler Gasifier

Above Ground GasificationEntrained flow reactors (Shell, Texaco, E-gas, Noell, KT - Slagging)Carbon source is made of very fine particles in a liquid or slurry for very good mass transferVery little residence timeCo-current flow with oxygen where high temperatures can be reachedLow heat transfer means hot exiting gas with no methane or tar, but more oxygen required.High temperature and very small carbon sources make it an ideal process for coal gasification.High temperatures without charringNo agglomeration because of fine particle size preparationTexaco Gasifier (entrained flow, slagging)Figure 1: Texaco Gasifier

Underground Coal GasificationVertical wells, soviet technologyH2 and O2 are injected and ignited to create syngas, CO2 and methaneCoal deposits do not allow for transport of the gases from the injection well to recovery well very easilyClosely spaced wells and reverse combustion methods are employed to create a cavity between wellsThis process works, but requires many wells to be constructedFigure 5: Current UGC

Underground Coal GasificationControlled retraction injection point from oil technology (CRIP)The oil industrys horizontal drilling for production and injection wells to deliver and absorb syngas continuouslyOnly one injection well, the ignition continues through the inseam as the injection wells are retreated. The product is collected in a product wellConcerns about ground water inhibit the use of UCG.

Figure 6: CRIP UGC

Syngas production and energy industryCO2 removalUsed for oil reclamationCan be injected back in groundCombined cycleCombustion turbineHeat used for generating steamFuel cell uses

ConclusionsThere are many ways that carbon containing compounds may be gasifiedCoal gasification occurs best in entrained flow reactors such as the Texaco gasifierThe coal will not heat up as much and will not create methane and tar.The requirement for fine particles into the gasifier prevents agglomerationUnderground coal gasification technology is present and used today but with certain challengesWater contamination Impact on environment and landPotential benefits are many Syngas used in combined cycle energy productionHydrogen fuel cell use for energy production and transportation purposesMethane and hydrogen have applications in the chemical industry where they can be used.Not mentioned, gasification is first step in coal liquefaction process.Coal gasification could reduce dependence on foreign oilCO2 sequestration

ReferencesGasification reference shelf - images and photos. (n.d.). National Energy Technology Laboratory.Retrieved November 20, 2007, from http://www.netl.doe.gov/technologies/coalpower/gasification/pubs/photo.html Gasification Technology and R&D. (n.d.). U.S. Department of energy. Retrieved November 20, 2007,from http://www.fossil.energy.gov/programs/powersystems/gasification/index.html Higman, C., & Van Der Burgt, M. (n.d.). Gasification. Elsevier. Retrieved November 20, 2007, fromGoogle Book Search database: http://books.google.com.ezproxy.lib.utexas.edu/books?id=ZUlRaUrX8IUC&printsec=frontcover&dq=gasification&sig=Sxb9s5qmKK03xe9INbsiuoJwwX8#PPP1,M1 Underground Coal Gasification. (n.d.). World Coal Institute. Retrieved November 20, 2007, from WorldCoal Institute Web site: http://www.worldcoal.org/pages/content/index