A New Method to Evaluate Hydrogen Sulfide Removal from Biogas

Abstract

Hydrogen sulfide in biogas fuel increases the speed at which the system utilizing the biogas corrodes. This corrosion may be prevented by separating and removing hydrogen sulfide from the biogas. There are multiple technologies available to remove hydrogen sulfide (such as the gas-gas membrane tested in this thesis); however, evaluating the effectiveness of hydrogen sulfide removal in an inexpensive manner is difficult to do. A device was constructed capable of a virtually simultaneous high precision volumetric flow and concentration measurements on moving biogas. The volumetric flow was measured by sampling the pressure from the center of two different points along a rigid tube and correlating pressure sensor voltage to the maximum velocity measured with a velocity probe. The hydrogen sulfide and methane concentrations were measured using chemical gas sensors. A mass balance was completed around a reverse selective membrane system with the calculated difference between flows based on known input and measured output concentrations coming within 15% of each other. Though the volumetric flow measurements were in doubt, this device was able to determine that using a 20 cm2 polyamide membrane under low pressures suitable for a digester (2 PSI) will increase methane concentration in biogas from 60% to 62% but is not effective at removing 1000 ppm of hydrogen sulfide. This device was primarily designed for determining the feasibility of adapting a membrane system to a farm scale biogas generation process.