立式连续干发酵装置的设计与产气特性

该研究设计的立式连续干发酵装置的几点特色包括搅拌升温调节罐、多点分布式进料、立式连续干发酵反应器和熟料回流混合过程,形成一种高固体浓度有机废弃物制取生物燃气的工艺方法及其发酵系统,可实现沼气工程的快速启动、厌氧发酵罐内无需搅拌、且节能,节水,减少沼液沼渣的排放量,保护环境,降低成本。采用上述设计的反应器进行发酵试验,研究熟料回流对产气特性的影响得出,应用回流的各组挥发性脂肪酸(volatile fatty acids,VFA)都有所降低,且回流比为1:7的VFA含量最低,氨氮没有累积,C/N接近25,产气效果最好。回流比1:9组,VFA含量累积最高,同时出现氨氮抑制产气的现象,所以得出熟料回流量过多,厌氧发酵系统就会受到抑制,且熟料回流对沼气中甲烷含量没有显著影响。

Design and biogas production characteristics of vertical continuous dry fermentation equipment

Abstract: The wet anaerobic fermentation technology generates a large amount of biogas slurry. Biogas slurry treatment is the bottleneck of anaerobic fermentation technology development. In addition, according to past experience and theoretical calculation, maintaining an adequate liquid anaerobic fermentation temperature consumes about 30% of the system capacity. In winter, it even reaches 45% in the northern cold regions. This limits the anaerobic fermentation technology development greatly in northern cold region. The dry anaerobic fermentation technology, on the other hand, does not produce biogas slurry, and its residue is easy to be processed into the organic fertilizer. The level of the moisture content of China municipal waste is especially suitable for dry anaerobic digestion. However, the dry fermentation technology is relatively new, and the system control is more difficult than liquid fermentation. From that perspective, research on development of anaerobic dry fermentation devices is the key for the success of the technology. The features of designed vertical continuous dry fermentation equipment include stir heat up adjustment tank, multipoint distribution feed, vertical anaerobic fermentation tank and slurry reflux mixing process. Altogether, the fermentation system can process high volume of solid organic waste and produce biogas. The vertical continuous dry fermentation equipment mainly included the stir heat up regulating tank, feed pump, vertical anaerobic fermentation tank and discharge pump. A reflux inlet and fresh organic waste material inlet at the top of stir heat up regulating tank were set up, the bottom of stir heat up regulating tank was connected to the vertical anaerobic fermentation tank through the feed pump. An air outlet at the top of fermentation tank was set up which was connected to the gas pipeline. The discharge port on the bottom, the biogas slurry and residue that outflowed from discharge port was divided into two paths by discharging pump and first adjust the control valve. One path was connected to reflux inlet of stir heat up regulating tank, the other was the residue export connected to the discharge piping. We expected that such design could realize a quick start for biogas generation without stirring and heating in anaerobic reactor, and without adding water consumption during the process. We also expected that such device could save energy, reduce the volume of biogas slurry residue, protect the environment, and reduce the cost. The top of the vertical anaerobic fermentation tank using multipoint feeding distribution way facilitated more uniform distribution of fermentation raw materials. The internal temperature in the fermentation tank without stirring and heating device was maintained by continuous in and out of the hot materials. We used the reactor to conduct fermentation experiment to study the effect of slurry reflux and gas characteristics by comparing with a control group. The VFA (volatile fatty acid) content of application reflux was reduced, and the VFA content was minimum by reflux ratio of 1:7. When C/N ratio was close to 25:1, there was no ammonia nitrogen accumulation and gas production was the best. The high reflux ratio of 1:8-1:9 appeared to have a certain extent accumulation of VFA content. The flux ratio at 1:9 was the highest for generating biogas slurry quantity, and the VFA accumulation phenomenon was the most obvious, which reached 7822.4 mg/L. At the same time, high ammonia concentration inhibited biogas production. In conclusion, with a high clinker backflow, the anaerobic fermentation system would be suppressed. The slurry reflux had no significant influence in methane content.