| The existing coal slurry combustion technology generally has such problems as difficulty in ignition,low burnout rate,unreasonable combustion organization,and can not ensure stable operation.The coal powder double cone burner developed by the China Coal Research Institute is an advanced technology system for coal combustion and utilization.It is verified by engineering practice that the double cone inverse injection burner has the characteristics such as small ignition power,short starting and stopping time,high thermal efficiency,stable combustion and wide load regulation.It is of great significance to study the adaptability of the combustion mechanism and the combustion process of coal slurry to the development of coal slurry dual cone reverse burner.In this paper,a reverse jet device for pneumatic atomization is set up in the pulverized coal double cone reverse jet burner.The reverse jet combustion structure of water and pulverized coal is realized in this paper,and a test platform to verify the numerical simulation results is obtained.Based on the description of different mathematical models of combustion reactions,eddy dissipation models and finite rate models are established respectively.The simulated data are verified by the experimental data.The results show that the finite rate model contains both the reaction faster than the mixing rate and the reaction that is slower than the mixing rate,while the reaction faster than the mixing rate is consistent in the calculation of the fluid mechanical reaction flow,and the reaction history is changed and the calculation results are not in conformity with the actual results.This conclusion is verified in the finite rate model of oxygen enriched combustion simulation.The results of the improved eddy dissipation numerical model are basically consistent with the actual test conditions in the temperature,pressure and NO_X of the burner,so the numerical data are of reference value.So far,a numerical simulation platform for coal slurry combustion process has been established.The combustion process of coal slurry in a double cone burner is studied from the point of view of fluid dynamics and combustion structure.The difference between pulverized coal and coal slurry combustion is compared,and the feasibility of using the coal slurry in a double cone burner is verified.The main conclusions are as follows:the coal slurry torch is stronger than the pulverized coal in the double cone burner,and the NOX emission is reduced by about 20%.The core temperature of coal slurry flame decreased by 201 degrees and appeared early.The decay rate was fast.Both the overtemperature and overpressure of the conical end cover of the burner were observed under the condition of coal slurry combustion.The reasons for this phenomenon include water atomization and volume expansion of water vapor,increasing initial velocity and lagging of coal slurry ignition process.During the experiment,the bluff body was arranged in the burner to reduce the temperature of the end cover.In view of the above phenomena,the development of coal slurry dual cone inverse burner should consider reducing the cooling strength of double cone,increasing axial distance and adding bluff body.Based on the test and calculation results obtained,the pulverized coal double cone burner is optimized.The technical measures include:the diameter of the burner outlet is reduced from 500mm to 450mm,the angle of the front cone is increased from 7 to 9,the swirling flow strength is increased by 20%,and the preheating temperature of the combustion air is increased from 20 to 150.The calculation model is established and calculated.The results show that the temperature in the burner increases by 120 degrees,the combustion process is effectively strengthened,and the front cone pressure is reduced.Therefore,the adoption of technical means can effectively solve the problem of coal slurry combustion organization. |
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