沼气增温与控制系统的设计与仿真

Design and simulation of biogas warming and control system

冬季北方寒冷地区温度偏低,难以满足大中型沼气厌氧发酵系统对于温度的要求。为了解决该问题,针对天津地区某奶牛场沼气工程,设计了一套回收发电机余热并辅助电加热为发酵罐体供热的沼气增温控制系统,且实验确定最佳控制温度为35℃。在该系统中,罐体内部均匀布置竖直型循环加热管路,从而使料液温度分布更加均匀,热响应更加迅速,6 d左右即可将发酵罐内发酵料液提升到所需最佳温度;另外,采用罐内部温度及循环水流量的反馈调节,使料液的温度波动维持在±1℃范围内,解决了在冬季由于温度过低而导致沼气产气率偏低、甚至停滞的问题;同时,采用MATLAB软件对基于F-PID及传统PID的温度控制系统进行了仿真。对比结果表明,F-PID控制器较传统PID控制器超调量减小3℃,响应时间缩短60%,表明F-PID系统具有更高的效率、稳定性及实用价值。

In the cold northern regions of China,winter temperatures are too low to meet the temperature requirement of a large biogas anaerobic fermentation system. To overcome this problem,a biogas warming control system was designed for a dairy farm biogas project in Tianjin,which was heated by the recyclable waste heat of generators and assisted by electric heating. The optimum temperature was 35 ℃,as determined by experiments.In this system,vertical circulating heating pipes were evenly equipped in the tank so that the feed temperature could increase more uniformly and rapidly; the time to reach the optimum temperature is only six days. Furthermore,because a feedback temperature and circulation water control system was applied to the tank,the range of the liquid material temperature was maintained within ± 1 ℃,which enhanced the biogas production rate and ensured the stability of the biogas production. In addition,the temperature control systems based on F-PID and conventional PID were simulated with the use of MATLAB. Comparative results showed that the overshoot value and the response time of the F-PID system were reduced 3 ℃ and 60% compared with those of the conventional PID system,which confirms that the F-PID system is more effective and reliable and has a great practical value.