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4. Suppose that you are the engineer in the charge of the gasification section of the Acme Substitute Natural Gas Company. ASNG Co. runs fixed-bed, dry-ash gasifiers. The raw gas is cleaned, shifted, and sent to a methane synthesis unit. Every morning you receive a report from ASNG’s analytical laboratory on the characteristics of the coal that will be fed to the gasifiers during the next day’s operations. One important characteristic is the ash fusion temperature (AFT), i.e., the temperature at which the ash will begin to melt and form a liquid slag. It is vitally important to keep the bed temperature not only below the AFT, but usually ≥100°C below, to allow for a margin of safety. One day the lab report indicates that the AFT for the coal about to go to the gasifiers is substantially lower than it has been in recent weeks. (a) What instructions will you issue to the plant operators for adjusting the steam/oxygen ratio being fed to the gasifiers? (b) Why? (c) What impact will this change have on the H2/CO ratio in the product gas? (d) Why? (e) How will this change affect operation of the water-gas shift unit? (f) Why?