ENVR 192

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 amount 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 evaporation, 3) the total amount of water consumption for power production in scenario I is about 0.471 gallons/kWh, 4) the amount 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 prepare the feed coal slurry, 6) the total amount of water required for hydrogen production is about 3.331 gallons per lb H₂ in scenario III and 7) water consumption for power generation and hydrogen production increases by ~31-36% if the process wastewater (including cooling tower blow-down water) is not treated and recycled.