Coal Gasification Technology and Syngas Production Ruben Reyes

Coal Gasification Technology and Syngas Production Ruben Reyes Ch. E 379

Purpose/Outline • Gasification technology – Different types of gasifiers – Products from gasification • Syngas production, Gasifiers used for IGCC power plants • Conclusion

Coal Gasification Technologies – Basic Overview of gasification • • • Coal or other fuels Oxidation carefully controlled H 2, CO 2, CH 4, other products H 2 can be purified Ash/slag leftovers – 3 types of gasifiers • Moving bed • Fluid Bed • Entrained Flow – Underground Coal Gasification • Vertical wells and pathway creation • Controlled retraction injection point

Above ground gasification • Moving bed reactor (Lurgi – dry ash and BGL - slagging) BGL gasifier (fixed bed, slagging) – Counter-current flow of coal and oxidizing blast – Blast composed of air and hot syngas, so low oxygen consumption – Operates on reactive carbon sources – Good heat transfer heats the carbon source creating methane and tar – Post production cleaning and scrubbing requires greater energy use Figure 1: BGL Gasifier

Above Ground Gasification • Fluid-bed reactor (Winkler, HTW, CFB – dry ash; KRW, UGas – Agglomerating) Winkler Gasifier (Fluid bed, dry ash) – Air fluidizes a bed and carbon containing particles added – Proper mixing of fuel and oxidant provide good mass transfer and heat transfer – Fine particle will escape with syngas and needs to be cleaned – Very good heat/mass transfer so partially reacted carbon may settle with ash – Slagging will reduce fluidization, so temp remains below softening point for ash Figure 2: Winkler Gasifier

Above Ground Gasification • Entrained flow reactors (Shell, Texaco, E-gas, Noell, KT - Slagging) Texaco Gasifier (entrained flow, slagging) – Carbon source is made of very fine particles in a liquid or slurry for very good mass transfer – Very little residence time – Co-current flow with oxygen where high temperatures can be reached – Low 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 charring • No agglomeration because of fine particle size preparation Figure 1: Texaco Gasifier

Underground Coal Gasification • Vertical wells, soviet technology – H 2 and O 2 are injected and ignited to create syngas, CO 2 and methane – Coal deposits do not allow for transport of the gases from the injection well to recovery well very easily – Closely spaced wells and reverse combustion methods are employed to create a cavity between wells – This process works, but requires many wells to be constructed Figure 5: Current UGC

Underground Coal Gasification • Controlled retraction injection point from oil technology (CRIP) – The oil industry’s horizontal drilling for production and injection wells to deliver and absorb syngas continuously – Only one injection well, the ignition continues through the inseam as the injection wells are retreated. – The product is collected in a product well – Concerns about ground water inhibit the use of UCG. Figure 6: CRIP UGC

Syngas production and energy industry • CO 2 removal – Used for oil reclamation – Can be injected back in ground • Combined cycle – Combustion turbine – Heat used for generating steam • Fuel cell uses

Conclusions • • There are many ways that carbon containing compounds may be gasified Coal gasification occurs best in entrained flow reactors such as the Texaco gasifier – The coal will not heat up as much and will not create methane and tar. – The requirement for fine particles into the gasifier prevents agglomeration • Underground coal gasification technology is present and used today but with certain challenges – Water contamination – Impact on environment and land • Potential benefits are many – Syngas used in combined cycle energy production – Hydrogen fuel cell use for energy production and transportation purposes – Methane 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 oil – CO 2 sequestration

References • • Gasification 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. htm l 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. htm l Higman, C. , & Van Der Burgt, M. (n. d. ). Gasification. Elsevier. Retrieved November 20, 2007, from Google Book Search database: http: //books. google. com. ezproxy. lib. utexas. edu/ books? id=ZUl. Ra. Ur. X 8 IU C&printsec=frontcover&dq=gasification&sig=Sxb 9 s 5 qm. KK 03 xe 9 INbsiuo. Jw w. X 8#PPP 1, M 1 Underground Coal Gasification. (n. d. ). World Coal Institute. Retrieved November 20, 2007, from World Coal Institute Web site: http: //www. worldcoal. org/pages/content/index