Variable Performance Of Biomass Boilers For Clean Heating In Rural Areas And Control System Research

In the rural areas of northern China,the use of biomass energy is an effective way to achieve clean heating and cope with the goal of"carbon peaking and carbon neutrality".However,the overall technical level of biomass heating boilers is not high at present,especially when operating under variable operating conditions,they are faced with poor fuel adaptability,unstable combustion,low efficiency and high NO_x emission.It has become a technical bottleneck restricting the large-scale application of biomass energy.Under the support of the project"Comprehensive Demonstration of Clean utilization Technology of Resources,Low nitrogen combustion and clean heating Technology and Demonstration of biomass Mixed Materials in North China and Northeast Villages and Towns under the National Key Research and Development Plan"（2020YFD1100302）,combined with the clean heating demonstration project in villages and towns,this paper carried out a study on the variable working condition performance and control system of low nitrogen biomass boilers for rural clean heating.After studying the variation rule of parameters such as heating performance and flue gas NO_x emission of material boiler under variable load condition,the regulation strategy of biomass boiler combustion condition and rural building heat load dynamic matching was proposed,and the intelligent control system of biomass boiler under variable load condition was developed.The combustion emission and efficiency of biomass boiler are improved,which has good theoretical and practical value.The main work completed in this paper is as follows:1)According to the winter heating needs of the demonstration project,the 500 kW biomass low nitrogen combustion heating boiler was developed,and some basic parameters such as the boiler feeding volume,air distribution volume,furnace body size and so on were determined,as well as the basic structure of the boiler system,and the prototype production was completed.Applied to the biomass boiler coupled air source heat pump and ground source heat pump built in Miaopuan Community,Linyi County,Dezhou City to construct a multi-source complementary collaborative heating system.2)Combined with the demonstration project,the biomass boiler operation test study under variable（low）load condition was carried out.The variation law of effluent temperature,NO_x emission,CO and SO₂ emission of biomass boiler along with parameters such as feed amount and air-fuel ratio was discussed to find the best operating parameters under low load conditions.The research shows that the thermal efficiency of the biomass boiler is up to 84.6%in the best operating condition,87.5%in the operating condition where the thermal efficiency is over 70%,25%in the operating condition where the thermal efficiency is over 80%,and the heat transfer performance of the boiler is good.3)On the basis of the study of variable operating conditions,fuzzy control algorithm is applied to the boiler control system,the automatic control strategy of boiler variable load operation is proposed,and the hardware design and software design of intelligent control system for biomass low nitrogen combustion boiler are completed,as well as the development of monitoring system for biomass low nitrogen combustion boiler.Hardware design includes combustion control system hardware structure design,hardware wiring design and electrical control cabinet layout design;Software design includes PLC program design,man-machine interface design,and remote debugging function design.The boiler monitoring system includes remote data collection system and pollutant emission monitoring system,realizing the purpose of on-line monitoring of the boiler operating data and air pollutant emission in biomass heating demonstration project.4)The boiler intelligent control system developed was applied to the 500 kW,60 kW,20 kW biomass heating boilers developed in cooperation with enterprises for different demonstration projects,and completed the tripartite detection of pollutant emission and thermal performance of the improved biomass boiler,and achieved good results.Among them,the NO_x emission of the 20 kW biomass low-nitrogen combustion boiler is 184mg/m³,which is reduced by 52.82%compared with the traditional biomass household boiler.The NO_x emission of 60 kW biomass low nitrogen combustion boiler is 138 mg/m³,a decrease of 64.62%;the NO_x emission of 500 kW biomass low nitrogen combustion boiler is 99 mg/m³,a decrease of 74.62%.In this paper,through the experimental research and theoretical analysis of the biomass boiler flue gas emission characteristics and heating characteristics of clean heating demonstration project,the variable operating condition control system of biomass heating boiler is developed,which improves the combustion emission and combustion efficiency of biomass boiler,and has good theoretical and practical value.