Water consumption in an IGCC plant for cogeneration of hydrogen and power - Abstract

Water usage in coal gasification and other proposed coal-based systems for power and fuels generation is increasingly becoming an important national issue due to the limited availability of water resources and the growing demand for water in the domestic, agricultural and industrial sectors. In this study, CHEMCAD process simulation software was employed to evaluate water demand in an IGCC plant (550MWe gross) equipped with a CO2 capture unit for co-generation of hydrogen and power. Three process scenarios were considered based on the levels of hydrogen and power generated as final products: 1) combust all of the hydrogen to generate power, 2) combust only a portion of the hydrogen so that 50% of the total hydrogen generated is available and 3) similar to scenario II, but with 85% hydrogen availability. The results from the process simulation studies provided the following conclusions: 1) scenario I had the highest total water demand mainly because a large amt. of cooling water is needed to condense steam, 2) about 64% of water consumed in scenario I is used for cooling tower make-up and lost to evapn., 3) the total amt. of water consumption for power prodn. in scenario I is about 0.471 gal/kWh, 4) the amt. of process water consumed in different stages, except water used in fuel gas humidification, is comparable for the three scenarios but the water demand for cooling tower make-up is different, 5) the highest process water demand is for the water-gas shift reactors followed by water used to prep. the feed coal slurry, 6) the total amt. of water required for hydrogen prodn. is about 3.331 gal per lb H2 in scenario III and 7) water consumption for power generation and hydrogen prodn. increases by ∼31-36% if the process wastewater (including cooling tower blow-down water) is not treated and recycled. on SciFinder(R)]