Question

This is a chemical egineer question. from Elementary Principles of Chemical processes 4th edition. FBR 4.60

Under the futureGen 2.0 project (http://www.futuregenalliance.org/) sponsored by the U.S. Department of energy, a novel proccess 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 pure oxygen (O2); the heat released produces steam, which is then used for heating and to drive turbines that generate electricity. An excess of O2 is 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 50kg/s and oxygen is fed in 8.33% excess. For the purposes of this analysis, the chemical formula of coal can be approximated as C5H8O2.

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 remaing unknown flow rates and mole fraction. 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 of 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.

Answer 1

The chemical formula for coal -CHgO2 The rate of coal is 50 Molar mas s of coal =5x12+8x1+2x16=100 mol kg 50 Molar flow rate of Coal - S500 100 mol The reaction for combustionof coal is as follows: 582 mole coal requires 6 moles of O2 Oxygen provided is 8.33% extra. So, molar flow rate of oxygen - 500 x s 1mol CH.O 3250 mol mo Thus, the molar flow rate of is 3250 Moles of Co2-5xm oles of C.H,O,-5x500 -2500 Moles of H2O= 4x moles of CH80,-4x500 mo = 2000 Moles of O2 remained 3250 mo. | 6 × 500 = 250 mol s Since CO2 during sequestration accumul ates in soils can suppress respiration in the root zone or result in soil aci dification, which would be harmful to plants Catastrophic releases even unlikey, can kill vegetati on and animal s PROS The amount of heat released will be more when pure Inerts like nitrogen sometimes reacts with fuel gases and produce unwanted products So, this can beprevented uisng pure oxygen CONS The combustion reaction can become uncontrollable Additional cost in producing enriched oxygen from air