7 MATERIAL BALANCES REACTIONS CH EN 170 STEADYSTATE

7. MATERIAL BALANCES: REACTIONS CH EN 170

STEADY-STATE SPECIES BALANCE WITH ONE OR MORE REACTIONS For chemical species A: Rate of A flowing in. Rate of A formed in system. Rate of A flowing out. Rate of A consumed by system. Can be written in terms of mass or moles. Rate of accumulation of A.

SS SPECIES BALANCE WITH REACTION(S) Mass: Mole:

MASS AND MOLE FORMATION/CONSUMPTION RATES

STOICHIOMETRY We can use the stoichiometry of chemical reactions to find ratios between rates of molar formation/consumption.

EXAMPLE: MOLE BALANCES WITH A REACTION Methane is burned in air. List mole balances for each species present. Things you need to know: A burning hydrocarbon produces carbon dioxide and water. Air is nitrogen and oxygen. in out air

EXAMPLE: MOLE BALANCES WITH A REACTION Express all the other rates of consumption and formation in terms of the consumption of methane.

EXAMPLE: MATERIALS BALANCE WITH REACTION A fuel cell has reaction 2 H 2+O 2 -> 2 H 2 O. where O 2 comes from air (21 mol% O 2, 79 mol% N 2). H 2 flows into the cell at rate 27 gmol/min. Air is a separate stream. Amount of O 2 is 50% more than stoichiometric amount to react with H 2. Conversion of H 2 is 85%. Assume single exit stream. What is flow rate of each species in that stream?