Karim Khursheed, Hoffmann Rebecca, Thomas Klasson K, Al-Dahhan M H
Chemical Reaction Engineering Laboratory (CREL), Department of Chemical Engineering, Washington University, St. Louis, MO 63130, USA.
Water Res. 2005 Sep;39(15):3597-606. doi: 10.1016/j.watres.2005.06.019.
Laboratory-scale digesters were operated to study the effect of mixing (via biogas recirculation, impeller mixing, and slurry recirculation) on biogas production. Three sets of experiments were performed using cow manure slurry feed with either 50, 100, or 150 g/L total solids (TS) concentrations (referred in the text as 5%, 10%, and 15% manure slurry). The experiments were conducted at a controlled temperature of 35 degrees C and a hydraulic retention time of 16.2 days, resulting in TS loadings of 3.1, 6.2, and 9.3g/Ld for 5%, 10%, and 15% manure slurry feeds, respectively. Results showed that the unmixed and mixed digesters performed quite similarly when fed with 5% manure slurry and produced biogas at a rate of 0.84-0.94 L/Ld. The methane yield was found to be 0.26-0.28 L CH4/g volatile solids loaded. However, the effect of mixing and the mode of mixing became important when the digesters were fed thick manure slurry feeds (10% and 15%). Digesters fed with 10% and 15% manure slurry and equipped with external mixing produced about 10-30% more biogas than the unmixed digester. While the mixed digesters produced more biogas than unmixed digesters, digester mixing during start-up was not beneficial, as it resulted in lower pH, performance instability and prolonged start-up time. Mixing using biogas recirculation system was found not to be effective in the case of 15% manure slurry feed under the experimental conditions studied.
在实验室规模的消化器中进行操作，以研究混合方式（通过沼气再循环、叶轮搅拌和料浆再循环）对沼气产量的影响。使用总固体（TS）浓度为50、100或150 g/L的牛粪料浆进行了三组实验（文中称为5%、10%和15%的牛粪料浆）。实验在35摄氏度的受控温度和16.2天的水力停留时间下进行，5%、10%和15%牛粪料浆进料的TS负荷分别为3.1、6.2和9.3 g/L·d。结果表明，当进料为5%的牛粪料浆时，未混合和混合的消化器表现相当相似，产气速率为0.84 - 0.94 L/L·d。发现甲烷产量为0.26 - 0.28 L CH₄/g挥发性固体负荷。然而，当消化器进料为浓稠的牛粪料浆（10%和15%）时，混合的影响和混合方式变得很重要。进料为10%和15%牛粪料浆且配备外部混合装置的消化器比未混合的消化器产生的沼气多约10 - 30%。虽然混合消化器比未混合消化器产生更多的沼气，但在启动期间进行消化器混合并无益处，因为这会导致pH值降低、性能不稳定和启动时间延长在所研究的实验条件下，发现对于15%牛粪料浆进料，使用沼气再循环系统进行混合是无效的。
