Abstract:At present, the dry anaerobic fermentation technique is still not applied widely among biogas plants in China. Especially, there are few reports on dry fermentation techniques employed in biogas plants. Aimed to this situation, a design method of horizontal plugflow dry anaerobic fermentation equipment was developed, which employed a screw convey for continuous inlet and a vacuum device for outlet. Based on this method, a pilot scale equipment was developed with an effective volume of 180L. The equipment consisted of screw convey, dry anaerobic fermentation reactor, vacuum pump for discharge, gas purification reactor and solidliquid separation device. All the above devices were online controlled with a computer. The pilot equipment was started up using mixture of cow dung and corn straw with a mixing ratio of 3∶1 (dry matter ratio), the inoculums accounted a proportion of 30% in inlet raw materials and the initial total solid content was 20%. The whole startup (103d) could be divided into three stages. During stage I, the reactor was operated at room temperature, the average biogas producing rate for the reactor was 0.17m3/(m3·d). After 68 d of running, the reactor temperature was raised to 38℃, and then the average biogas producing rate was risen to 0.25m3/(m3·d), with a decrease of methane content. Meanwhile, the pH value was decreased significantly. After 70d of running, the inoculation was increased to 50% by adding biogas slurry. After that the biogas production rate of the reactor was increased rapidly and reached the highest point of 0.58m3/(m3·d). The average biogas production rate was around 0.48m3/(m3·d), and methane content was stable at about 56%. At the end of the start-up, the dry matter degradation rate of raw materials reached more than 48%. The performance of the reactor during start-up suggested that the equipment could run normally, which meet the design requirement.
