Karim Khursheed, Hoffmann Rebecca, Klasson Thomas, Al-Dahhan M H
Chemical Reaction Engineering Laboratory (CREL), Department of Chemical Engineering, Washington University, St. Louis, MO 63130, USA.
Bioresour Technol. 2005 Nov;96(16):1771-81. doi: 10.1016/j.biortech.2005.01.020. Epub 2005 Apr 2.
We studied the effect of mode of mixing (biogas recirculation, impeller mixing, and slurry recirculation) and waste strength on the performance of laboratory scale digesters. The digesters were fed with 5% and 10% manure slurry, at a constant energy supply per unit volume (8 W/m3). The experiments were conducted in eight laboratory scale digesters, each having a working volume of 3.73 L, at a controlled temperature of 35+/-2 degrees C. Hydraulic retention time (HRT) was kept constant at 16.2 days, resulting in a total solids (TS) loading rate of 3.08 g/Ld and 6.2 g/Ld for 5% and 10% 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 with a methane yield of 0.26-0.31 L CH4/g volatile solids (VS) loaded. This was possibly because of the low solids concentration in the case of 5% manure slurry, where mixing created by the naturally produced gas might be sufficient to provide adequate mixing. However, the effect of mixing and the mode of mixing became prominent in the case of the digesters fed with thicker manure slurry (10%). Digesters fed with 10% manure slurry and mixed by slurry recirculation, impeller, and biogas recirculation produced approximately 29%, 22% and 15% more biogas than unmixed digester, respectively. Deposition of solids inside the digesters was not observed in the case of 5% manure slurry, but it became significant in the case of 10% manure slurry. Therefore, mixing issue becomes more critical with thicker manure slurry.
我们研究了混合方式（沼气再循环、叶轮搅拌和料浆再循环）以及废物强度对实验室规模沼气池性能的影响。沼气池以5%和10%的粪肥浆进料，单位体积能量供应恒定（8瓦/立方米）。实验在八个实验室规模的沼气池内进行，每个沼气池的工作体积为3.73升，控制温度为35±2摄氏度。水力停留时间（HRT）保持恒定在16.2天，5%和10%粪肥浆进料的总固体（TS）负荷率分别为3.08克/升·天和6.2克/升·天。结果表明，当以5%的粪肥浆进料时，未搅拌和搅拌后的沼气池表现相当相似，产沼气速率为0.84 - 0.94升/升·天，甲烷产量为0.26 - 0.31升CH₄/克挥发性固体（VS）负荷。这可能是因为在5%粪肥浆的情况下固体浓度较低，自然产生的气体所形成的混合可能足以提供充分的搅拌。然而，在以较浓粪肥浆（10%）进料的沼气池情况下，搅拌的效果和搅拌方式变得显著。以10%粪肥浆进料并通过料浆再循环、叶轮和沼气再循环搅拌的沼气池分别比未搅拌的沼气池多产生约29%、22%和15%的沼气。在5%粪肥浆的情况下未观察到沼气池内有固体沉积，但在10%粪肥浆的情况下这变得很明显。因此，对于较浓的粪肥浆，搅拌问题变得更为关键。
