Coal gasification IGCC power plant

Coal gasification units offer unique flexibility in that the syngas can also be chemically converted to liquid fuels for use in transportation (coal liquefaction). Alternatively the hydrogen can be refined from the synthesis gas to produce hydrogen fuel. An integrated combined cycle (IGCC) power plant could be used for electric power production during peak demand times and then shifted to liquid fuel production at nonpeak demand times. 

Valero, A., Uson, S. (2006). Oxy-co-gasification of coal and biomass in an integrated gasification combined cycle (IGCC) power plant. Energy, 31, 1643—1655. 

The air emissions from coal gasification plants u e quite low. In fact, it is possible to design an IGCC power plant whose air emissions are as low as those firom a natural gas combined-cycle power plant. Specific provisions of the Qean Air Act Amendments (CAAA) of 1990 favor coal gasification over direct coal combustion. These provisions include maximum SO2 emissions or "caps" reductions and offsets for SO2/NOX, restriction on trace component hazardous air pollutants, and incentives for coal gasification repowering of existing power plants. 

An IGCC plant generally produces fewer water effluents than a conventional coal-fired power plant does. The amount of process water blowdown is about the same for both gasification and direct coal combustion. However, the steam cycle in IGCC power plants produces much smaller amounts of wastewater blowdown because less than 40% of the total power generated comes from the steam cycle. 

It has also been proposed to convert conventional direct coal combustion power plants to oxygen combustion to reduce the CO2 recovery cost. However, this would require over twice the oxygen needed for coal gasification and would result in lower thermal efficiency than IGCC power plants with CO2 recovery in a new plant or in repowered plants. 

In addition to the coal properties, the reasonable and unified boundary conditions need to be defined in order to evaluate and compare processes. The first section of Table 5.11 presents process-related variables. The gasification pressure was set to 30 bar, a typical value for integrated gasification combined cycle (IGCC) power plants as well as some chemical syntheses (e.g., Fischer-Tropsch) [60,65]. In the case of slagging entrained-flow gasification, the gasification temperature was set at >100 K above the ash fluid temperature for the reasons discussed in Section 4.5.2. A typical value is between -1-100 and -1-150 K [61]. The thermal capacity of the modeled reactors was set to a thermal input of 500 MW on the basis of the LHV as a suitable size for a state-of-the-art reactor. 

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