Gasification process
Syngas produced from coal, petroleum coke or heavy liquids can be used directly to produce electric power or can be converted to hydrogen, CO2, petrochemical feedstocks, methanol, substitute natural gas, transportation fuels and chemicals. The reliability, capital costs and environmental results of the four major gasification technologies have been extensively documented, and gasification-knowledgeable lenders consider them to be fully commercial.
Gasification byproducts are benign, consisting of 99%+ pure elemental sulfur plus an inert and non-leaching vitreous slag that has been approved for use in road construction or as landfill cover. Unlike PC plants, no fly ash is generated, so not only are incremental treatment and disposal costs avoided, there is the potential to sell the gasification byproducts at a profit. SOx and NOx levels well within New Source Emissions Standards can be achieved for coals containing up to 7% sulfur.
Using multiple gasification trains, the next generation of plants in the 500MW to 800MW range will be capable of achieving availabilities 90% or better.
Current plant designs are capable of achieving over 40% efficiency, with heat rates in the 8,400 to 8,900 MMBTU/KWh range, depending on configuration. Future efficiency gains from advanced turbine designs and more efficient oxygen production are expected to further widen the efficiency gap in favor of gasification over more traditional clean coal technologies such as CFB and supercritical PC. A detailed comparison shows that because of its higher efficiency, lower operating costs and market for byproducts, IGCC will actually dispatch ahead of supercritical and CFB coal-fired technology.
Carbon from all coal-producing plants will soon be regulated. By capturing CO2 at the source rather than after it has gone up the stack, gasification can capture CO2 at fraction of the cost of even the most advanced conventional PC technology, and mercury can be removed at 1/10 the cost. This will be increasingly important with the recent overturning of the EPA's cap and trade plan for regulating mercury emissions, which is shortly expected to subject individual plants to specific emissions limits.