ผลของเวลาการกวนและการเวียนตะกอนต่อการผลิตก๊าซชีวภาพจากเศษอาหารโดยระบบหมักไร้อากาศแบบแห้งในขนาดใช้งานจริง / ทวินันท์ สเลอาด = Effects of mixing time and sludge recirculation on biogas production from food waste by full-scale dry anaerobic digestion system / Tawinun Saleard
This research aims to study the effects of mixing time and sludge recirculation on biogas production from food waste by a full scale dry anaerobic digestion system. The system used in the study was a horizontal cylindrical stainless steel tank with a volume of 12 m³ and equipped with a paddle mixer. The research was divided into two experiments. The first experiment was studied about the sludge recirculation rate. The second experiment was to find the appropriate mixing time to produce biogas. The system was operated for approximately 30 days per each experiment. The result of the experiment at steady state showed an efficiencies of COD removal to be 80.93% and 82.91% at a sludge recirculation rate of 50 and 100 percent (volume by volume), respectively. The efficiencies of TS removal were 69.87% and 71.92% and for TVS removal were 82.50% and 83.85 %, respectively. The sludge recirculation rate is effective to improve efficiencies of COD, TS and TVS removal. The biogas yield was 0.69 m³/kg COD removed for a recirculation rate at 50 percent and 0.71 m3/kg COD removed for a recirculation rate at 100 percent with methane percentages content of 56.35% and 60.90%, respectively. It can be concluded that the sludge recirculation rate of 100 percent can produce the highest biogas rate in this study. The experiment of the influence of the mixing time on the biogas production with the mixing time at 30, 60 and 90 minutes per day and it was found that the efficiencies of COD removal were 85.07%, 87.35% and 83.58%, respectively. It shows that the mixing time at 60 minutes per day has the best organic removal rate. The efficiencies of TS removal were 74.85%, 76.42% and 78.29% and the efficiencies of TVS removal were 85.40%, 86.69% and 87.68 %, respectively, which shows that an increase in mixing time can enhance the effective of COD, TS and TVS removal significantly. The comparison of mixing time at 30, 60 and 90 minutes per day showed a biogas rate of 0.53, 0.69 and 0.52 m³/kgCOD removed and also production of methane at 58.4%, 61.6% and 55.9%, respectively. As a result, the mixing time of 60 minutes per day is most suitable for biogas production in this study