CBEMS 45A: Chemical Processing and Material Balances HOMEWORK 8

Due: Wed., 11-27-13 (by 5 PM)

1. Problem 6.9 (Hint: Table B.4)

2. Problem 6.27

3. Contemporary Issues Developing countries have little access to oil and gas for fuel to produce electricity

and heat their homes. Natural gas can be produced from a readily available natural resource: cow manure. Indeed, the production and sale of natural gas biogas has become a business for some individuals. This problem explores the production of methane from cow dung in a simple reactor called a digester. No inoculum is required because the dung has the methanogenic bacteria in it already in the cow. The bacteria produce methane in the cow bowel and continue to produce it in the digester. Some media is added to the dung in the digester reactor to maintain moisture and provide some additional nutrients to facilitate the methane production. A 30L digester bioreactor is charged with media and 3.75L of cow dung. The reactor produces 5L of biogas per one liter of cow dung at a pressure of 1 atm and a temperature of 27oC. The biogas leaving the digester is saturated with water. On a dry basis, this gas contains 80 mol% methane and 20 mol% carbon dioxide. The gas is then fed to a furnace with 7 mols of dry air and undergoes complete combustion and complete conversion. Determine the composition of the resulting gas. Assume ideal gases.

HW-8CBEMS45A HW08 Solutions p1CBEMS45A HW08 Solutions p2CBEMS45A HW08 Solutions p3