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ALTERNATIVE FUELS Lecture 6 Fuel Tech-ll.pptx

  1. Introduction  Gasification is a process that converts carbonaceous material, Such as fossil fuels and biomass in to a mixture of mostly hydrogen and carbon monoxide( called Synthesis gas & Syngas)  The syngas can be burned as a fuel or processed to produced chemical and other fuels
  2. coal gasification is still in development, it is also supposed to be a very perspective technology. Be a very perspective technology. applied to many branches of industry such as chemistry, metallurgy and energy production, provided that different requirements about its parameters will be fulfilled. Many characteristics of product gas are strongly connected with its composition. Therefore, problem of optimization of CG technology becomes an especially important issue. In context of using syngas for particular aims, earlier mentioned optimization could be understood as a choice of the best scope of input parameters and appropriate proceeding of process.
  3. Underground Coal Gasification  Underground coal gasification (UCG) is an industrial process, which enables coal to be converted into product gas.UCG is an in-situ gasification process carried out in non-mined coal seams using injection of oxidants, and bringing the product gas to surface through production wells drilled from the surface.  The process converts coal into a gaseous form (syngas) through the same chemical reactions that occur in surface gasifiers.  The economics of UCG look promising as capital expenses should be considerably less than surface gasification essentials.
  4. Process Description  Different stages for UCG: Step 1: Find the coal Step 2: Drill the boreholes Step 3: Link the boreholes Step 4: Ignite the coal Step 5: Inject O2 and steam Step 6: Extract the syngas
  5. Condition suitable for UCG  Coal seam should not have major geological disturbances • The roof and floor of the seam should have low permeability so that leakage is minimized. • Seam should be preferably free from water. Water should be drained off before process. • Coals of low quality is preferred. Using sub-bituminous coal has advantages of having greater permeability & its tendency to sink and spell when heated aids to providing the ‘packed bed’. • Any seam thickness can be gassified. Thickness of 6m is preferable. • Reserve should be high and it should be nearer to customer.
  6. Factor Affecting UCG
  7. Technology Involved in UCG  Opening up coal seam for gasification • Drilling pattern • Linkage between boreholes • Linking operation • Gasification process • Subsidence • Extraction process at the surface (not that mining people’s job)
  8. Benefits of UCG  Un-economical seams (low quality/ greater depth with thin seam) can be made useful.  It provides an indigenous gas/energy source.  Flexibility in commercial use, less Nitrogen and sulphur oxides.  Potential method of exploitation of reserves which are not amenable to conventional mining.  Elimination of hard and often unhealthy jobs of men in u/g  Impact on the environment is far less. The fertile soil is conserved. No dumps or waste heaps.  Possibility of recovering coal with high sulphur and ash.  Much less time for construction work of UCG station.  The gas is a potential chemical feed stock  Ash is left in u/g and less tipping dirt is produced  Labour intensity is low.
  9. Potential use for UCG
  10. Disadvantages  The extraction of reserve is less than deep mining (energy balance is also less favourable)  Capital input is greater than deep mining  Gas produced is dirty, has a low calorific value and is variable in quality.  The cost of making SNG will be higher than importing liquid natural gas  The gas is costly to pipe much over 16km and to store  There will be noise from drilling  New skills are to be taught.
  11. Surface Coal Gasification  Developed in 1800s to produce town gas and city lighting  Renewed interest due to rise in oil prices, depleting oil &gas reserves and IGCC technology  Coal is exposed to hot steam and controlled amounts of air or oxygen under high temperatures (250°-900°C) and pressures.  Produces Syngas, hydrocarbons, water vapours, anhydrous ammonia and phenols. The gas comprises of N2, CO2, CO, H2, CH4, O2, etc•  Environmental friendly  Reduced greenhouse gases e.g. CO2 can be captured easily and at lower costs
  12. Advantages  One of the most abundant energy sources  it can be burned directly, transformed into liquid, gas, or feedstock  Inexpensive compared to other energy sources  Good for recreational use (charcoal for barbequing, drawing)  Can be used to produce ultra-clean fuel  Can lower overall amount of greenhouse gases ( liquification or gasification)  Leading source of electricity today  Reduces dependence on foreign oil  By-product of burning (ash) can be used for concrete and roadways
  13. Disadvantages  Source of pollution emits waste, SO2 , Nitrogen Oxide, ash  Coal mining mars the landscape  Liquidification , gasification require large amounts of water  Physical transport is difficult  Technology to process to liquid or gas is not fully developed  Solid is more difficult to burn than liquid or gases  Not renewable in this millennium  High water content reduces heating value  Dirty industry—leads to health problems  Dirty coal creates more pollution and emissions
  14. END