适宜初始温度提高秸秆光合细菌制氢效果

Appropriate initial temperature improving hydrogen production effect by using photosynthetic-bacteria with straws

秸秆微粉的光合细菌制氢过程是放热反应,引起的热效应会直接影响产氢效果。为了实现高效低能耗产氢,该文采用秸秆微化粉碎与酶水解预处理相结合的方法,利用自制的秸秆微粉光合细菌制氢反应热测试系统,进行了不同初始温度对秸秆微粉酶解光合细菌制氢反应热的影响试验研究,结果表明:当初始温度为30℃时,最大反应热约为7.1 kJ,最大产热速率约为1.01 kJ/h,反应末期累计反应热约为32.9 kJ,累计产氢量约为745.9 mL,光合细菌制氢反应最充分,产氢效果最好;累计产氢量和底物能量转化率可用累计反应热的二次多项式来表示,光能转化率可用累计反应热的三次多项式来表示。该研究结论可为揭示秸秆微粉酶解光合细菌制氢过程的热量释放变化规律,从生物反应热角度优化工艺参数和预测光合细菌制氢效果提供参考依据。

In photosynthetic-bacteria hydrogen production with enzyme-hydrolyzed fine straws, the growth and reproduction of photosynthetic bacteria will occur in an appropriate temperature range, and the resulting heat effect will have direct influence on hydrogen production due to exothermic processes in the hydrogen production reaction of photosynthetic bacteria with organic acid. Therefore, the research on effects of initial temperature on the reaction heat in the photosynthetic-bacteria hydrogen production with enzyme-hydrolyzed fine straws, is helpful to figure out the heat release rule in such photosynthetic-bacteria hydrogen production, and thus, to provide proper control to the initial temperature to meet the purpose of efficient hydrogen production. In this paper, with the combination method of micro-grinding and enzyme hydrolysis of straws, blank control tests for reaction liquid were performed with photosynthetic hydrogen-production flora of F1, F5, F7, F11, L6, S7 and S9 screened out after flora enrichment, separation, and cultivation, by using a self-developed testing system for reaction heat in the photosynthetic-bacteria hydrogen production with fine straws. The tests were made with the conditions of fine maize straws of 53-61 μm, substrate concentration of 30 mg/mL, initial pH value of 7.0, illumination intensity of 2 000 lx, inoculation and non-inoculation of 20% photosynthetic mixed bacteria flora which was on the logarithmic growth phase, and at the initial temperatures of 25, 30 and 35℃, identifying the relations between reaction heat and reaction time at the three initial temperatures, variation characteristics of the heat production rate, variation characteristics of the cumulative reaction heat, and the relations between the cumulative reaction heat and the cumulative hydrogen production, optical energy conversion rate and substrate energy conversion rate; optimizing process parameters in the photosynthetic-bacteria hydrogen production reaction; and presenting the relations model of the cumulative reaction heat and the cumulative hydrogen production, optical energy conversion rate and substrate conversion rate. Research results showed that, different initial temperatures had significant influence on the result of photosynthetic-bacteria hydrogen production with fine maize straws. In case of initial temperature of 30℃, maximum reaction heat of approximately 7.1 kJ, maximum heat production rate of approximately 1.01 kJ/h, cumulative reaction heat of approximately 32.9 kJ at the end of reaction, and cumulative hydrogen production of approximately 745.9 mL, the photosynthetic-bacteria hydrogen production reaction was conducted to its most extent and yielded the best result. Although initial temperatures were different, the variations of reaction heat and cumulative heat reaction were basically the same, this was to say, their maximum heat production rate occurred at the reaction time of 8 h and their minimum heat production rate occurred at the reaction time of 12 h; With the increase of the cumulative reaction heat, the cumulative hydrogen production and the substrate energy conversion rate would increase, which could be expressed with a quadratic polynomial; with the increase of the cumulative reaction heat, the optical energy conversion rate would increase and decrease, which could be expressed with a cubic polynomial. These research results provide reference basis to reveal the heat release rule in the photosynthetic-bacteria hydrogen production with enzyme-hydrolyzed fine straws, and to optimize process parameters and predict the photosynthetic-bacteria hydrogen production result from the perspective of biologic reaction heat.