花庄沼气热电联产系统热稳定性研究

发布时间：2018-08-12 11:04

【摘要】：为找出寒冷季节大中型沼气工程发酵温度低的原因,本文通过对花庄沼气热电联产系统现状的稳定性研究,发现排出沼液所导致的热损是影响系统稳定性的主要因素,根据“温度对口、能量梯级利用”的原则,构建沼气热电联产耦合吸收式热泵系统,利用热泵提供大量品位较低的热能预热进料,实现系统的补能以减少进出料对系统稳定性的影响,并对比分析系统优化前后稳定性,进料的补能可以弥补出料热损的影响就能够解决大中型沼气工程稳定性问题,出料热损是影响大中型沼气工程稳定性最重要的因素,故可为今后沼气工程的设计优化提供依据,本文主要的研究内容与结果如下:(1)本文以花庄荷斯坦奶牛繁育示范中心的沼气热电联产系统为研究对象,通过对系统运行9年以来的数据进行分析,可得出系统主要热损来源于发酵塔、储气塔和出料,在寒冷季节发酵塔热损占总热损的13.0%~19.2%,储气塔热损4.1%~9.9%,而出料热损70.9%~82.9%,通过重点分析2015年11月至2016年1月的数据,可得寒冷季节发酵塔平均温度23.6℃,2#发酵塔的平均产气量226m3/d,由于发酵塔保温措施较好自身热损不大,说明出料所导致的热损对系统的稳定性影响最大,也是导致花庄沼气热电联产系统运行现状均不能达到设计要求的主要原因。(2)针对花庄沼气热电联产系统出料所导致的稳定性问题进行优化改造,通过对酸化池进行保温处理,并构建沼气热电联产耦合吸收式热泵系统,利用吸收式热泵系统提供的33.7℃循环水在酸化池内对进料预热,既实现对系统的补能又实现能量的综合梯级利用,对比系统优化前后稳定性可得,优化后发酵温度基本可实现寒冷季节35℃中温发酵的要求,且单个塔的产气量在523.6m3/d左右,通过实现对进料的预热补能,有效解决出料热损大对发酵系统稳定性的影响。(3)花庄沼气热电联产系统发电效率30%左右,热电联产效率仅为50.3%~67.4%,通过构建沼气热电联产耦合吸收式热泵系统,保证系统稳定运行的同时,由于存在热泵的补能现象,热电联产效率可达91.8%,吸收式热泵系统利用内燃机的627℃的烟气作为驱动热源,制热性能系数2.12,可向系统提供7111.82MJ/d的热量,满足每个发酵塔35℃时4743.31MJ/d的需热量,远超优化前2508.92MJ/d,优化后系统可实现稳定运行,同时也有效地保证其经济性,其中沼液沼渣还田收益21.9万元,电力上网收益28.47万元,节约煤炭费用3.8万元,减少排污费36.12万元,沼气热电联产系统的推广应用奠定物质基础。本课题创新点:针对花庄沼气热电联产系统工艺流程及结构存在的问题,定量分析系统热损及其原因,通过构建沼气热电联产耦合吸收式热泵系统,对比分析系统优化前后热稳定性,并进行相关热性能与经济性分析,对今后沼气工程优化改造具有一定的参考价值。
[Abstract]:In order to find out the reason of low fermentation temperature of large and medium-sized biogas project in cold season, this paper studies the stability of Huazhuang biogas cogeneration system and finds that the heat loss caused by discharging biogas slurry is the main factor affecting the stability of the system. Received heat pump system, using heat pump to provide a large number of low-grade thermal energy preheating feed, to achieve system supplement to reduce the impact of feed and discharge on the stability of the system, and comparative analysis of the stability of the system before and after optimization, feed supplement energy can make up for the impact of discharge heat loss can solve the stability of large and medium-sized biogas project, discharge heat loss It is the most important factor affecting the stability of large and medium-sized biogas projects, so it can provide a basis for the design and optimization of biogas projects in the future. The main research contents and results of this paper are as follows: (1) This paper takes the biogas cogeneration system of Holstein Dairy Cattle Breeding Demonstration Center in Huazhuang as the research object, and divides the data of the system for 9 years. The results show that the main heat loss of the system comes from the fermentation tower, the gas storage tower and the discharging tower. The heat loss of the fermentation tower accounts for 13.0%~19.2% of the total heat loss in the cold season, the heat loss of the gas storage tower is 4.1%~9.9%, and the heat loss of the discharging tower is 70.9%~82.9%. The output of gas is 226m3/d, and the heat loss caused by the heat preservation measures of the fermentation tower is small, which indicates that the heat loss caused by discharging has the greatest influence on the stability of the system, and is also the main reason that the operation status of the Huazhuang biogas cogeneration system can not meet the design requirements. (2) The stability of the Huazhuang biogas cogeneration system caused by discharging. Through the heat preservation treatment of the acidizing pool and the construction of the coupled absorption heat pump system of the methane heat and power generation, the feed is preheated in the acidizing pool with 33.7 C circulating water provided by the absorption heat pump system, which can not only make up the energy of the system but also realize the comprehensive cascade utilization of the energy. The stability of the system before and after optimization is compared. The results show that the optimized fermentation temperature can basically meet the requirement of 35 C medium temperature fermentation in cold season, and the gas yield of a single tower is about 523.6 m3/d. By preheating and energy supplement to the feed, the influence of large heat loss of the discharged material on the stability of fermentation system can be effectively solved. (3) The power generation efficiency of Huazhuang biogas-fired cogeneration system is about 30%, and the cogeneration efficiency is only about 50%. 50.3% ~ 67.4%. By constructing the coupled absorption heat pump system of biogas-fired cogeneration, the system can run stably. At the same time, the cogeneration efficiency can reach 91.8% due to the supplementary energy of heat pump. The absorption heat pump system uses the flue gas of 627 C of internal combustion engine as the driving heat source, and the coefficient of performance is 2.12, which can provide 7111.82 MJ/d heat to the system. The optimized system can realize stable operation and effectively ensure its economy. Among them, the returning of biogas slurry and biogas residue is 219,000 yuan, the returning of electricity is 2847,000 yuan, the coal cost is saved 38,000 yuan, the sewage discharge fee is reduced 360,200 yuan, and the biogas-heat-power coupling is also reduced. The innovation point of this subject: In view of the problems existing in the process and structure of Huazhuang biogas cogeneration system, the heat loss of the system and its causes are analyzed quantitatively. Through the construction of biogas cogeneration coupled absorption heat pump system, the thermal stability of the system before and after optimization is compared and analyzed, and the related thermal performance is carried out. And economic analysis will be of some reference value for the optimization and transformation of biogas projects in the future.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S216.4;TM611.25

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