Senior Design Project Final Report

This report presents a completed feasibility study for the production of hydrogen gas from fermentation of a combined influent of wastewater sludge and food waste in ananaerobic digester. The development of the process topology as well as the calculations performed on it is based on several empirical reaction kinetic equations. The choice ofprocess is directly linked to the stages of fermentation and the conditions that govern them. Normally, if the fermentation process goes to completion the main product is methane gas.It is produced via the uptake of hydrogen gas and volatile fatty acids by a consortium of methanogenic bacteria and archaea. However, fermentation of organic matter is a sequential process and methanogenesis represents only the final stage. The objective is to stop the final stage of the process from happening to have hydrogen gas and organic acids as final products. This is achieved by operating the reactor at low Hydraulic Retention Time’s (HRTs) of two days or less, as compared to twenty days for the normal process, and by actively removing hydrogen from the reactor. Both actions enhance the transformation of higher organic acids and alcohols into acetic acid and thus increase the yield of hydrogen. The purification of the hydrogen is achieved with a palladium-silver membrane before further compression and storage. Each of the operation units are described together with its process design. The utility cost for the project is estimated at $47,900 per year. The process flow diagram (PFD) introduces the detailed layout of the plant with the streams properly labeled with massflow rate, temperature, and pressure specifications.Presently, the designed plant produces hydrogen at a rate of 0.05767 lb/min which is sold at $12 per lb as 99.99% pure,compressed hydrogen. Through the Capcost program, the project cost is estimated at $2,200,000.