Study On Large-scale Combustion Technology Of Coal Pyrolysis Semi-coke

Coal pyrolysis semi-coke is the main by-product of large-scale low-grade coal pyrolysis classification and quality utilization project.Its efficient,clean and large-scale utilization plays a key role in improving the overall utilization efficiency.In this paper,the quasi industrial scale pulverized coal and coke powder CO combustion experiment is carried out to explore the combustion characteristics of semi-coke CO combustion under the condition of similar industrial scale suspension combustion.The experimental results show that the q₃ value of gas-phase incomplete combustion loss is stable below 1%,and the q₄ range of solid-phase incomplete combustion loss is 0.4%?1.7%.q₄ increases with the increase of the proportion of coke in the fuel.The no content in flue gas under various working conditions is in the range of 150?350mg/Nm^3,and the SO₂ content is stable between 0.2?2.4 mg/Nm³.Compared with pulverized coal,adding a certain proportion of coke to the fuel reduces the pollutant emission to varying degrees.Finally,based on the experimental law,the technical ideas and implementation points of mixed combustion of semi-coke in large pulverized coal boiler are provided.In order to continue to explore the application of pyrolysis semi-coke as fuel instead of civil loose coal in small industrial kilns,the combustion experiment of single formed semi-coke was carried out.Firstly,compared with Fukang coal combustion at900?,it is found that the formed semi-coke has weak intensity in the initial stage of combustion,longer reaction time and worse ignition performance,but it has a good effect of low nitrogen oxide and low sulfur dioxide emission.The results show that with the increase of furnace temperature,the burnout time of formed semi-coke decreases,but the overall cycle is more than 2h,and the internal temperature of particles can rise to the furnace temperature after entering the furnace for about 10 minutes;During combustion,NOx emission is inhibited by the catalytic reduction of carbon and carbon ash,and SO₂ emission is mainly related to high-temperature sulfate decomposition.Then the experiment is carried out with semi-coke particles with approximately equal surface area and 1/3 of the original mass.It can be found that the overall combustion rate of the changed sample reaches 4 times of the previous one,the burnout cycle is greatly shortened,and the pollutant emission characteristics have not changed significantly.Therefore,in practical industrial application,it is suggested to change the shape of solid ball,increase the internal gap of particles,reduce the particle size,and adopt the combustion organization conditions of 900?and higher temperature in the combustion process.Finally,according to the experimental exploration law,the key points that need to be paid attention to in the actual industrial kiln burning formed semi-coke fuel are analyzed and summarized.Combined with the combustion experiment of formed semi-coke,the combustion reaction model of single particle formed semi-coke particles is established to explore the combustion process of formed semi-coke in more detail.Combined with thermodynamic and kinetic equations,the changes of internal temperature,mass,diameter and other parameters with time in the combustion process of formed particles are calculated.The results are in good agreement with the experimental data,it is very valuable to deeply understand the combustion process of formed semi-coke.