Optimization and Upgrading of Biogas from Brewery Waste for Boiler
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Date
2019-05
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Addis Ababa University
Abstract
Rises in fuel prices and the continued pollution to the environment calls for a search to find cost effective and environmentally cautious methods of finding alternative fuels especially for industrial purposes while Ethiopia is spending around 2,000,000,000 birr/year for HFO. The treatment can be costly for the owners but a method such as anaerobic digestion can be used to treat the waste , minimize environmental pollution due to the use of fossil fuel at the same time minimize the financial cost. .This study focuses on optimization and upgrading of biogas from brewery waste and for boiler.. This research emphasizes on production of biogas from brewery waste and cow dung focusing on the optimization of process parameters such as temperature, HRT and TS for the maximal biogas production.
Optimization of those variables was carried out by General factorial Design Expert software. Firstly, the characteristics of each of the two items were investigated in detail comparatively. The results obtained can be summarized as follows: Biogas volume and composition from brewery waste was 0.5L, 35% using 10 day, 35 ℃, 8%Ts and compared to Cow dung that yielded 3.9L, 70% using 10 day, 35 ℃, 8%Ts. Therefore, to increase the amount of methane composition and yield brewery waste and cow dung were mixed based on the recommendation from literature Total solid of 4%, 8% and 12%, Temperature at 25℃, 35 ℃, 50℃ and hydraulic retention time at 10, 15, and 20 days. From the experiment, all three parameters had significant effects on biogas volume and composition. The optimum conditions for maximizing the biogas yield and composition were 10 day, 35 ℃, 8%Ts a in which maximum biogas yield of 0.3 lit /gm. Out of which 60% is methane that is upgraded. The methane was upgraded to 81.4% methane using 25% caustic water absorption process.
During upgrading the carbon dioxide content reduced below 22% and hydrogen sulphide was negligible during the production step. The upgraded methane gave calorific value of 6967.84Kcal/m3which has energy generating potential of 8.1kwh/m3. While this waste has a potential to generate 15,240.636 kwh/day of energy which could cover 16.6% of HFO consumption it can generate energy equal to12, 954.54 kwh/day and save 6,591,764.508 birr/year of its budget. In addition, there is a benefit for the environment and human health.
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Keywords
Anaerobic digestion, Biogas, Methane, Brewery waste, cow dung, Heavy fuel oil