The Influence Of Horizontal Gas Boiler's Furnace Thermal Boundary Region On The Combustion Characteristic Of Low Caloric Value Gases

In general,low caloric value gas refers to coal mine gas with low concentration,blast furnace gas,low caloric value exhaust produced by chemical plants and off-gas produced in petroleum processing.Because it is difficult to ignite low caloric value gas and it is easy for them to be extinguished,they are regarded as exhaust gas and are discharged directly,which not only pollutes the environment,but also is a waste of energy.In order to improve the stability of the combustion of low calorific value gases so as to achieve the efficient and clean use of low calorific gases,this thesis specified all key factors influencing the combustion stability of low caloric value gas on the basis of summarizing and analyzing the research development of low caloric value gases in home and abroad.And then,it further determines its researching objects and research thought.This thesis develops from following aspects:(1)It summarizes the low calorific value gas combustion technologies and their principles.Focusing on the thermal boundary properties such as horizontal gas boiler's furnace,burner's structure and thermal dissipation and considering porous medium combustion technology and bluff body combustion technology,this thesis has carried out optimization research on the using of low caloric value gases of this type of boiler combustion system.(2)In order to analyze combustion and emissions characteristics of low calorific value gases after the optimization of horizontal gas boiler's combustion system,we carried out numerical modeling on low calorific value gases with different concentrations in different furnace thermal boundary conditions.Besides,we make comparisons between temperature,velocity and concentration fields of modeling computation.The result are as follows.There is a strong re-flux at blunt body burner's outlet at 0 to 50 mm and using entrainment high temperature flue gas to heat up low calorific value gases is helpful to the combustion stability of low calorific value gases.We also make comprehensive comparisons of the combustion characteristics and product characteristics of low calorific value gases in different furnace thermal boundary conditions and make sure that when using bluff body burners,porous medium heat retainer is located at the place of X=350mm in furnace and the temperature inside boilers is pretty high and at this time furnace outlet has lowest methane content and highest combustion efficiency.(3)It carried out combustion experiments on this type of boiler.These experiments test the temperature distribution inside the furnace of horizontal gas boiler and obtain the temperature distribution in different furnace thermal boundary conditions.When it compares the result of modeling computation and actual experiment result,we found they are anastomotic and verify the accuracy of numerical results from the experimental point of view.