Abstract: The process of anaerobic fermentation of kitchen waste can be enhanced to some extent by increasing the stirring process, which improves the organic loading of anaerobic fermentation and the efficiency of biogas production. Common mechanical stirring processes can accomplish the stirring within the anaerobic digestion tanks, but they also have several drawbacks, such as high operational energy consumption, insufficient stirring, the difficulty of daily operation and maintenance, as well as the inability to break down large particles and fibrous materials. By introducing an innovative gas-liquid mixed jet stirring technology to replace the mechanical stirring process in the anaerobic digestion process, not only the aforementioned issues could be avoided, but also the mixing effect and biogas yield within the anaerobic fermentation tanks were enhanced. This technology has been successfully and stably operated in the anaerobic fermentation project of kitchen waste for over a year. In the anaerobic fermentation tanks of kitchen waste, the gas-liquid mixed jet stirring could enhance the daily biogas production of the kitchen waste slurry and increase the CH4 content in the biogas by about 9%. At the same time, it could also increase the biogas yield per ton of slurry by about 30% and improve the biogas production rate by about 18%. From the analysis results of slurry mixing degree, equipment investment, ease of installation, operation and maintenance, treatment capacity, energy saving and consumption reduction, the gas-liquid mixed jet stirring has obvious advantages in engineering application.

Key words: gas-liquid jet stirring, mechanical stirring, anaerobic digestion, kitchen waste