| Summary: | 碩士 === 崑山科技大學 === 環境工程研究所 === 98 === Livestock raising is usually recognized as of first importance for the global warming because of its greenhouse gas emission. In Taiwan, pig farming dominates the livestock raising. Biogas rich in methane was produced after anaerobic treatment of piggery wastewater. But it suffers from high level of hydrogen sulfide for the application of biogas.
In Taiwan, hydrogen sulfide is removed from biogas by wet scrubbing or biological treatment, but both of them suffer from large space taken and high capital cost. In this study, a recycled material, iron ring, was taken as adsorbent for the removal of hydrogen sulfide from biogas. Under different flow rates, adsorption capacities were determined until the concentration of hydrogen sulfide in off gas build up to 300 ppm which is the maximum level allowed in natural gas. When the flow rates were controlled at 1.02, 0.76 and 0.52 bed volumes (BV)/min, the adsorption capacities were 40, 78 and 100 BVs per kilogram of iron ring, respectively; equivalent to 0.20, 0.37 and 0.28 g hydrogen sulfide per kilogram of iron ring, respectively; and equivalent to 1.05, 1.91 and 1.43 g hydrogen sulfide per square meter surface area of iron ring, respectively. Above results showed that adsorption capacity decreases with the increasing of flow rate because of mass transfer limitation.
In addition, adsorption capacity was determined when the iron rings were completely exhausted by hydrogen sulfide under the flow rate of 0.52 BV/min and an influent hydrogen sulfide concentration of 6,093 ppm. It is 2,898 BVs and 6.2 g hydrogen sulfide per kilogram and 32.1 g hydrogen sulfide per square meter surface area of iron ring.
In addition to iron ring, a commercial adsorbent, iron oxide, for the removal of hydrogen sulfide was tested also. Hydrogen sulfide can be removed completely until 3,467 BVs of biogas go through the column for each kilogram of iron oxide. It shows that the adsorption capacity of commercial iron oxide is greatly higher than that of recycled iron ring. But the gas flow was hindered seriously because of the moisture content of biogas makes the iron oxide granules bind together, this problem needs to be solved for a better application of iron oxide.
|
|---|
