Abstract:

Domestic large-scale biogas projects mostly use the fermentation technology at psychrophilic or mesophilic temperature, which results in low biogas production rate and large fermentor volume. And high cost for investment is the main obstacle for the advancement of biogas projects. On the other hand, straw as a common low-grade biomass in rural areas is burned at random, causing serious air pollution. Therefore, in this work, thermochemistry coupled with thermophilic fermentation was proposed to accelerate manure processing rate and promote the efficient usage of straw by burning straw to maintain the temperature for thermophilic fermentation process transformed from mesophilic fermentation. Feasibility of this coupling process was analyzed. By increasing temperature step-wisely from 30℃ to 55℃, volumetric gas production rate of pig farm biogas would increase from 1.43m³·m^-3·d^-1 to 3.40 m³·m^-3·d^-1, and digester volume could be reduced from 1200 m³ to 500 m³. In order to maintain fermentation temperature(55℃), 339 tons of straw would be consumed every year to burn straw instead of biogas for heating.

Key words: anaerobic, biomass, biogas project, thermophilic fermentation, thermochemistry, methane

摘要：

我国规模化养殖场沼气工程普遍采用常温和中温发酵技术, 产气速率低导致发酵罐体积大和投资高, 是制约其快速发展的关键因素。另一方面, 秸秆作为农村常见低劣生物质常常被随意焚烧而导致严重的空气污染。为此, 本文提出将畜禽粪便高温发酵与秸秆热化学燃烧耦合的新思路, 通过秸秆燃烧为高温发酵过程提供热量, 将常温和中温发酵转变为高温发酵过程, 提高畜禽粪便厌氧发酵的处理速率, 同时避免秸秆的浪费。对耦合新工艺的计算结果表明, 对于万头猪场沼气工程, 发酵温度从30℃提高到55℃, 容积产气率由1.43 m³·m^-3·d^-1提高至3.40 m³·m^-3·d^-1, 发酵罐体积从1200 m³减小到500 m³;为维持高温发酵(55℃)所需热量, 年利用秸秆339 t。

关键词: 厌氧, 生物质, 沼气工程, 高温发酵, 热化学, 甲烷