秸秆与游离发酵液接触比例对产沼气特性的影响

摘要

Effects of contact ratio of straw and free fermentation liquid on characteristics of anaerobic fermentation were investigated by batch experiment at (37±1)℃. The fermentation liquid (i.e., total solid was 10%) was used as the reflux daily. The solid and liquid phases of the fermentation materials were separated by arranging porous filter plates at different heights of the reactor bottom, which led to the contact ratios of straw and fermentation liquid were 100% (T1)、50% (T2)and 0% (T3), respectively, during the experiment. Results of biogas yield showed that there was no distinct differences of biogas yield and VS content between the three treatments. This indicated that reduction of contact ratio of straw and fermentation liquid had no impact on biogas yield. Reflux of fermentation liquid for the emerged straw could achieve the same effect of mass transfer as the submerged one. This result provides scientific basis for improving the effective fermentation concentration during the anaerobic digestion of straw. The experiment also found that the contact ratio of fermentation liquid to straw was negatively related with the reaction time. This contact ratio became stable after 6-day anaerobic digestion latter, indicating that the actual free fermentation liquid decreased within the whole system. The major reason is that the straw after 6-day fermentation achieved saturation condition (i.e., 16.42% solid content of straw) and had the effects of adsorption and interception. Thus it is suspicious that the method of devotion to the rate of high solid content and the feasibility of adopts the reflux of fermentation liquid could be benefit to straw anaerobic digestion operation. Other experiment should be conducted to study the effects of water adsorption character, filling height and degree of compaction on the change of water retention property. Furthermore, the analysis of solid content of material is necessary to provide support for the parameter optimization during the dry digestion of straws.%在中温(37±1)℃条件下,以破碎麦秸为原料,采用批次进料和消化液每天回流方式(发酵固含率为10%),通过在反应器底部设置不同高度的多孔滤板使秸秆与游离发酵液接触比例分别为100%(T1)、50%(T2)和0%(T3),研究秸秆与游离发酵液接触比例对产沼气特性的影响.结果表明：从产气特征和发酵前后VS变化来看,各处理均无明显差异,表明减少秸秆与游离发酵液的接触比例,对秸秆产沼气效果无影响,即通过渗滤液每天回流方式,未浸没于游离发酵液中的秸秆可以达到与浸没秸秆相同的传质效果,此结果为秸秆厌氧发酵工程中提高秸秆有效发酵浓度提供了理论依据.此外,试验还发现,T3处理中消化液与秸秆接触比例随发酵进程呈逐渐降低趋势,并于发酵第6d基本稳定,表明发酵系统中实际的游离发酵液量逐渐减少,分析认为秸秆物料对消化液有吸收和截持作用,发酵第6d 后已达秸秆物料吸持水饱和状态(秸秆物料含固率为16.42%).