Integrated Gasification Combined-Cycle Systems

This combination of gas and steam turbines accounts for the name combined cycle. Gasification combined-cycle systems are among the cleanest and most efficient of the emerging clean coal technologies. Sulfur species, nitrogen species, and particulate matter are removed before the fuel is burned in the gas turbine. Thus, there is a much lower volume of gas to be treated than in a postcombustion scrubber. 

The gas stream must have extremely low levels of impurities not only to avoid pollution but to protect turbine components from chipping or corroding. As in the case of clean combustion, much of the sulfur-containing gas can be captured by a sorbent injected into the gasifier. 

High levels of nitrogen removal are also possible. Some of the coal-nitrogen is converted to ammonia which can be almost totally removed by commercially available processes. Nitrogen oxide formation can be held to allowable levels by staging the combustion process at the turbine or by adding moisture to hold down flame temperature. 

The theoretical advantage an IGCC plant has over a conventional coal plant is in the higher system efficiency of the combined cycle, a concept originally developed for natural gas-fired plants and used in many such plants for meeting intermediate and peak loads. 

While the overall combined cycle is more efficient than conventional pulverized coal plants, energy losses do occur in the transformation of coal into a gaseous fuel, mostly due to the heat input needed for gasification. As a result of the added gasification process needed for combined-cycle systems using coal, the IGCC process is less efficient than the same combined power generation cycle run on a fuel that does not require pretreatment such as natural gas or fuel oils. 

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The integrated gasification combined cycle (IGCC) system has two main components, a... 

K.R. Craig and M.K. Mann, Cost and performance analysis of biomass integrated gasification combined-cycle (BIGCC) power systems, NREL/TP-430-2I657, 1996... 

For large-scale biomass conversion 400-1000 MW, ) the biomass Integrated Gasification Combined Cycle (BIGCC) is a well-known concept [4], Coii ared with combustion the system has some clear advantages ... 

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