Under the FutureGen 2.0 project (http://www.futuregenalliance.org/) sponsored by the U.S. Department of Energy, a novel process is used to convert coal into electricity with minimal greenhouse gas (CO2) emissions to the atmosphere. In the process, coal is combusted in a boiler with pureO2; the heat released produces steam, which is then used for heating and to drive turbines that generate electricity. An excess ofO2is supplied to the boiler to convert all the coal into a flue gas consisting of carbon dioxide, steam, and any unreacted oxygen. The mass flow rate of coal to the boiler is 50 kg/s, andO2is fed in 8.33% excess. For the purposes of this analysis, the chemical formula of coal can be approximated asC5H8O2.
- (a)Draw and label the flowchart and carry out the degree-of-freedom analysis using balances on atomic species.
- (b)Determine the molar flow of oxygen supplied to the boiler.
- (c)Solve for the remaining unknown flow rates and mole fractions. Determine the molar composition of the flue gas on a dry basis.
- (d)A feature that makes the FutureGen power plant unique is the intent to capture the CO2 generated, compress it, and pump it into deep geological formations in which it will be permanently stored. List at least two safety or environmental issues that should be considered in the construction and operation of this plant.
- (e)List at least two pros and two cons of using pure O2 versus air.