木糖高温厌氧发酵产氢的影响因素及两相产氢-产甲烷的能量转化效率

Effects on hydrogen production from thermophilic anaerobic fermentation of xylose and energy conversion efficiency of two-phase hydrogen-methane production

通过批次实验,考查了木糖高温(55℃)厌氧发酵中初始pH(5.0~10.0)和初始底物浓度(2.5~15 g·L^(-1))对产氢效率、液相产物以及木糖降解率的影响;并进行了两相产氢-产甲烷实验,对比单相产甲烷与两相产氢-产甲烷能量转化效率。结果表明:在初始pH=5.0或初始底物浓度为2.5 g·L^(-1)时无氢气产生,最大产氢率1.31 mol H2·(mol木糖)-1在pH=7.0,底物浓度7.5 g·L^(-1)时获得,同时木糖降解率和累积产氢量分别为97.48%和328.4 mL;其主要代谢副产物为丁酸和乙酸,属于丁酸型发酵。厌氧产氢后末端产物甲烷产率为274.9 mL CH_4·(g COD)-1,两相系统能量转化效率达到63.98%,高于单相产甲烷系统的49.39%。

The effects of the initial pH（ 5. 0—10. 0） and substrate concentration（ 2. 5—15. 0 g·L^-1） on the hydrogen yield,distribution of liquid by-products,and xylose degradation efficiency of anaerobic fermentation were investigated at 55 ℃ by batch tests. Methane-production tests were also conducted to contrast the energy conversion efficiency of single-phase methane production and two-phase hydrogen-methane production. No hydrogen production was observed at an initial pH of 5. 0 or substrate concentration of 2. 5 g·L^-1. The largest hydrogen yield,1. 31 mol H_2·（ mol-xyloseconsunmed）- 1,was obtained at an initial pH of 7. 0 and substrate concentration of 7. 5 g · L^-1. Meanwhile,the xylose degradation efficiency and cumulative hydrogen production were97. 48% and 328. 4 mL,respectively. The main metabolic by-products were butyric acid and acetic acid,corresponding to a butyric-acid-type fermentation. The methane yield was 274. 9 mL CH_4·（ g COD）- 1based on the end products after hydrogen fermentation. The overall energy conversion efficiency of the two-phase process could reach 63. 98%,exceeding that of the single-phase methane-producing system（ 49. 39%）.