外力挤压对秸秆厌氧发酵产沼气的影响

Effect of Extrinsic Extruding Pressure on Biogas Production of Agricultural Straw

针对秸秆静态厌氧消化中存在秸秆间互相挤压造成秸秆紧实度大幅增加的现象,文章研究了接种物绝对充足与接种物不足两种条件下在不同外力挤压下秸秆厌氧消化产沼气特性,对发酵过程中的产气情况、发酵液理化特性以及秸秆物质损失等进行了分析。结果表明:在接种物绝对充足条件下,当秸秆容重为0.03~0.10 t·m^-3时,秸秆产气均在合理的范围内,单位干物质产气量和平均甲烷体积分数分别为148.21~183.08 mL·g^-1和47.53%~52.37%。当秸秆容重提高至0.20 t·m^-3时,秸秆产气受到明显抑制,秸秆单位干物质产气量和产气中平均甲烷体积分数分别仅为11.71 mL·g^-1和20.66%,远低于其他处理。在接种物不足条件下,没有外力挤压作用的处理日产气量为先增加后缓慢降低的正常状态,单位干物质产气量为301.26 mL·g^-1;有外力挤压作用的处理在实验第5天至第17天期间产气受到明显抑制,经两次人工调节系统pH值后,于实验第17天后产气才逐渐恢复,实验结束时单位干物质产气量为136.18~181.46 mL·g^-1。此外,外力挤压造成秸秆产气峰值出现时间延迟、产气峰值和产气速率降低、秸秆物质损失减少。以上结果可以看出,无论是在接种物充足还是不足条件下,物料间的挤压均不利于物料厌氧消化产沼气,工程中应尽量避免秸秆间互相挤压的现象。

In view of the phenomenon of substantial increase in compactness of straw due to the squeezing between straws in the static anaerobic digestion,the characteristics of biogas production in straw anaerobic digestion under different extrinsic extruding conditions with inoculum absolutely sufficient and insufficient condition,respectively,were studied in laboratory,and the gas production,physicochemical properties of fermentation broth and material loss of straw,were analyzed in this paper.The results showed that,under the condition of absolutely sufficient inoculants,when the bulk density of straw was 0.03~0.10 t·m^-3,the gas production of straw was all within a reasonable range,the gas production per unit dry matter and the average methane content were 148.21~183.08 mL·g^-1 and 47.53%~52.37%,respectively.When the bulk density of straw increased to 0.20 t·m^-3,the gas production of straw was significantly inhibited,the gas production per unit dry matter of straw and the average methane content were only 11.71 mL·g^-1 and 20.66%,which were far lower than other treatments.Under the condition of insufficient inoculants and without the external extruding pressure,the daily gas output increased first and then decreased slowly,the gas production per unit dry matter was 301.26 mL·g^-1.For the condition of insufficient inoculants with the extrinsic extruding pressure,the gas production was significantly inhibited from the 5th day to the 17th day,after two artificial adjustments of system pH,gas production gradually recovered from the 17th day,the gas production per unit dry matter was 136.18~181.46 mL·g^-1 at the end of the experiment.In addition,the extrinsic extruding pressure caused time delay of peak gas production,decreasing peak gas production,gas production rate,and material loss rate.It can be seen from the above results that the extruding between materials is not conducive to the anaerobic digestion and biogas production under both condition of sufficient or insufficient inoculants,and the phenomenon of mutual extrusion between straw should be avoided as far as possible in the project.