横推流式连续干法厌氧发酵设备设计与试验

Design and Start-up Test of Horizontal Plug-flow Dry Anaerobic Fermentation Equipment

我国干法厌氧发酵技术仍然处于试验示范阶段,尤其是连续式干法厌氧发酵技术仍停留在实验室小试阶段。针对上述问题,基于螺旋输送和真空负压出料原理,研究了横推流式连续厌氧干法发酵装置设计方法,并试制1套有效容积180 L的中试设备。该平台主要由螺旋进料、干法厌氧发酵、负压出料、气体净化收集、固液分离、在线控制等单元组成。在牛粪与玉米秸秆干物质混合质量比为3∶1、接种量30%、混合原料总固形物质量分数20%的条件下,分3个阶段启动和调试中试平台,整个调试过程共持续103 d。第1阶段,反应器在室温下运行33 d,平均容积产气率为0.17 m^3/(m^3·d);第2阶段,提升反应器温度至中温38℃,反应器平均容积产气率升至0.25 m^3/(m^3·d)左右,但pH值有明显降低,且沼气中甲烷含量降低;反应器运行68 d后进入第3阶段,通过添加沼液提高接种量,之后反应器的容积产气率快速升高,最高可达0.58 m^3/(m^3·d),此阶段中试装置平均容积产气率为0.48 m^3/(m^3·d),甲烷质量分数稳定在56%左右,混合原料的干物质降解率达到48%以上。结果表明,该横推流式连续厌氧干法发酵平台可实现固体物料的连续进出料和稳定连续产气,达到了设计要求。

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 plug flow 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 solid liquid 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 start up （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 0.17m^3/（m^3·d）. After 68 d of running, the reactor temperature was raised to 38℃, and then the average biogas producing rate was risen to 0.25m^3/（m^3·d）, with a decrease of methane content. Meanwhile, the pH value was decreased significantly. After 70d 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 0.58m^3/（m^3·d）. The average biogas production rate was around 0.48m^3/（m^3·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.