摘要
本文以玉米秸和麦秸为原料,设定30℃、35℃、40℃三个中温温度梯度和48℃、51℃、54℃、57℃四个高温温度梯度,进行静态厌氧消化产气潜力和特性研究,并确定合适的温度作为秸秆动态厌氧消化运行温度。然后对适宜温度下动态运行的发酵装置和运行工艺控制条件进行了研究,并实现相应的最高池容产气率。主要结论如下:
(1) 35～40℃为秸秆中温静态厌氧发酵的合适温度范围。35℃下玉米秸和麦秸原料TS产气率分别为0.492 m~3·kg~(-1)和0.499 m~3·kg~(-1);40℃下分别为0.515 m~3·kg~(-1)和0.517 m~3·kg~(-1)。秸秆高温静态厌氧消化合适的温度范围为51～54℃。51℃下玉米秸和麦秸原料TS产气率分别为0.572 m~3·kg~(-1)和0.576 m~3·kg~(-1);54℃下分别为0.528 m~3·kg~(-1)和0.530 m~3·kg~(-1)。
(2)秸秆中温动态厌氧发酵合适的发酵温度首选40℃,在SRT 17～18d,发酵温度40℃下,理想状态的池容产气率2.3～2.4m~3·m~(-3)·d~(-1),原料TS产气率0.41m~3·kg~(-1);高温动态厌氧发酵合适的发酵温度为51～54℃。在原料滞留期17～20d,发酵温度51℃下,理想状态的池容产气率2.3～2.7 m~3·m~(-3)·d~(-1),原料TS产气率0.46 m~3·kg~(-1);在原料滞留期14～15d,发酵温度54℃下,理想状态的池容产气率2.8～3.0 m~3·m~(-3)·d~(-1),原料TS产气率0.42 m~3·kg~(-1)。
(3)秸秆动态厌氧反应器内物料呈“上部秸秆浮渣-下部发酵液”两相分布,设计底部进料反应器在上部出料;顶部进料反应器在下部出料,出料口在原料浮渣和发酵液接触面附近。
(4)对于顶部进料反应器,适当搅拌可以显著增加产气量,平均池容产气率比不搅拌反应器提高了65%。
(5)相对于底部进料,顶部进料方式并没有表现出运行优势,在施加搅拌下,其池容产气率仅提高了2%,并且表现出出渣困难。建议秸秆动态厌氧发酵采用“底部进料-上部出料”方式,无需搅拌。
(6)在原料滞留期17d左右,秸秆高温(52±1℃)和中温(39±1℃)动态厌氧消化运行的最高有机负荷均为4.71kgTS/(m3·d)左右,最高池容产气率分别为1.92 m~3·m~(-3)·d~(-1)和1.63 m~3·m~(-3)·d~(-1),原料TS产气率分别为0.41 m~3·kg~(-1)和0.35 m~3·kg~(-1)。高温厌氧消化的最高池容产气率和相应原料产气率比中温提高了17%。从升温保温的代价进行考察,认为大型秸秆沼气工程经济可行的发酵温度首选40℃。
Based on corn and wheat straw for materials, setting 30℃, 35℃and 40℃three medium temperature gradient and 48℃, 54℃, 51℃and 57℃four high temperature gradient, we studied the anaerobic digestion biogas potential and characteristics, and determined the appropriate temperature as dynamic anaerobic digestion operating temperature. Then on appropriate temperature, we studied the fermentation reactors and control conditions of dynamic fermentation, and pursued the supreme gas yield of per unit digester volume. Main conclusions are as follows:
(1) The best fit temperature range of medium temperature static anaerobic fermentation is 35～40℃. The biogas yield of corn and wheat straw at 35℃are 0.492m~3·kg~(-1) and 0.499m~3·kg~(-1) respectively; 0.515m~3·kg~(-1) and 0.517m~3·kg~(-1) respectively at 40℃. The best fit temperature range of high temperature static anaerobic fermentation is 51～54℃. The biogas yield of corn and wheat straw at 51℃are 0.572m~3·kg~(-1) and 0.576m~3·kg~(-1) respectively; 0.528m~3·kg~(-1) and 0.530m~3·kg~(-1) respectively at 54℃.
(2) The proper fermentation temperature of medium temperature dynamic anaerobic fermentation is 40℃. Under 40℃, SRT17～18d, gas yield of per unit digester volume of the ideal state is 2.3～2.4m~3·m~(-3)·d~(-1), biogas yield is 0.41 m~3·kg~(-1). The proper fermentation temperature of high temperature dynamic anaerobic fermentation is 51～54℃. Under 51℃, SRT17～20d, gas yield of per unit digester volume of the ideal state is 2.3～2.7 m~3·m~(-3)·d~(-1), biogas yield is 0.46 m~3·kg~(-1). Under 54℃, SRT14～15d, gas yield of per unit digester volume of the ideal state is 2.8～3.0 m~3·m~(-3)·d~(-1), biogas yield is 0.42 m~3·kg~(-1).
(3) Dynamic anaerobic reactors present "upper straw-lower liquid sludge" distribution, thus we design a top mouth for the bottom material feeding reactor and a low mouth for the top feeding reactor.
(4) For top feeding reactor, appropriate stiring can significantly increase the biogas production, the average gas yield of per unit digester volume improved 65%.
(5) Relative to the bottom feeding reactor, top material feeding reactor showed no operation advantagement. We suggest that straw dynamic anaerobic fermentation can use "bottom feeding-upper discharging" pattern without stirring.
(6) Under SRT17d, the highest organic load of high temperature (52±1℃) and medium temperature (39±1℃) dynamic anaerobic digestion is 4.71 kgTS/(m3·d), supreme gas yield of per unit digester volume are 1.92m~3·m~(-3)·d~(-1) and 1.63m~3·m~(-3)·d~(-1) respectively, biogas yield are 0.41 m~3·kg~(-1) and 0.35 m~3·kg~(-1) respectively. Gas yield of per unit digester volume and biogas yield of the high temperature anaerobic digestion increased 17%. Considering the cost of heating, we suggest that the feasible fermentation temperature of large straw biogas project is 40℃.
引文
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