Thermal Stability Study Of Biogas CHP System In Huazhuang

In order to uncover the causes for the low fermentation temperature of large and medium biogas project in cold season,the paper studies the stability of Huazhuang biogas cogeneration system to find that the heat loss from biogas slurry discharge is the main factor affecting the stability of the system.According to the principle of "energy grade and matched the temperature and pressure of stream sources and consumers",a biogas cogeneration coupled heat pump system has been built to utilize heat pump providing a large number of low-grade thermal energy to preheat the feed to enhance the heat supply to improve the system stability.Comparing and analyzing the stability of system before and after the optimization which could be found that the complement of energy can reduce the influence of heat loss of the material and improving the stability of the large and medium-sized biogas project.The heat loss is the major factor to affect of the large and medium-sized biogas project.so the research of this paper can provide the basis for the future optimization of biogas project design.The main contents and results of this paper are as follows:(1)In this paper,the biogas cogeneration system of Huazhuang Holstein Cow Breeding Demonstration Center has been taken as research object.By analyzing the 9 years data of the system,the main heat loss of the system is dissipated from the fermentation tower,gas storage tower and discharge,The heat loss of the fermentation tower in the cold season accounted for 13.0% ~ 19.2% of the total heat loss,the heat loss of the tower was 4.1% ~ 9.9%,and the heat loss was 70.9% ~ 82.9%.Analyzing of the data from November 2015 to January 2016 which could been known that the average temperature of fermentation tower in cold season was 23.6?,average gas production of 2# fermentation tower was 226m3/d,the heat loss of fermentation tower is low for the reason that the fermentation tower with relative good insulation measures while the heat loss caused by the discharge has the main impact on the stability of the system,and it is also the main reason that the operation status of Huazhuang biogas cogeneration system can not meet the design requirements.(2)The optimization of the stability problem caused by the discharge of Huazhuang biogas cogeneration system is carried out.The heat treatment of the acidification tank is carried out and the biogas cog eneration coupled heat pump system is constructed.The heat recovery system is provided by the absorption heat pump system.Water in the acidification tank on the feed preheating,both to achieve the system of energy and realize the energy stage-utilization,compared to the system before and after optimization of stability,the optimal fermentation temperature can be achieved 35? medium temperature fermentation requirements in the cold season and the gas production of a single tower is about 523.6m3/d which can effectively solve the influence of the heat loss on the stability of the fermentation system.(3)The power generation efficiency of Huazhuang biogas cogeneration system is about 33%,and the efficiency of cogeneration is only 50.3% ~ 67.4%.By constructing the biogas cogeneration coupled heat pump system to ensure the stable operation of the system and the cogeneration efficiency of up to 91.8%,absorption heat pump system using exhaust gas with 627? of internal combustion engine as a driving heat source,the heating coefficient of heat pump is 2.12,the system can provide 7111.82MJ/d of heat to meet heat demand of each fermentation tower with 4743.31MJ/d to satify the 35? fermentation which is far better than the heat supply of 2508.92MJ/d,the optimized system not only can achieve stable operation,but also effectively ensure its economy.The biogas residue back to the field can earn 219,000 yuan,power internet earn 284,700 yuan,saving coal costs 38,000 yuan,reduce the sewage charges 294,000 yuan,for the biogas cogeneration system to lay the material basis for the promotion and application.In order to solve the problem of the stability of Huazhuang biogas cogeneration system,and a biogas cogeneration coupled heat pump system is constructed accord ing to its main problems.The stability of the system is optimized and analyzed.Thermal performance and economic analysis have been done,the research has a certain reference value to the future optimization of biogas project.