Numerical Simulation Study On Combustion Characteristics Of 35t/h Pulverized Coal Boiler

Small and medium-sized coal-fired industrial chain boilers have serious energy waste and high pollutant emissions.Therefore,it is urgent to find a feasible alternative to energy conservation and emission reduction.The retrofit scheme of the coal-fired industrial chain boiler to Chamber burning pulverized coal boiler can effectively increase the boiler thermal efficiency and reduce pollutant emissions.Studying the efficiency and low NOx operation of this retrofit scheme has practical engineering significance and theoretical value.The research object of this paper is a 35t/h pulverized coal boiler which was retrofitted from a test chain boiler in a factory.In the process of retrofit,compared with the front and back wall cross collocation,the layout of the fr ont wall of the new type of swirl burner can reduce the difficulty of retrofit and save resources.Therefore,in the original test plan,two new swirl burners were arranged near the water wall of the front wall.First,the pulverized coa l boiler was tested under low load and the temperature data in the boiler was measured.In order to achieve stable and safe combustion in the boiler,it is necessary to analyze the combustion situation in the boiler under different loa ds of the pulverized coal boiler.To this end,this paper uses Solidworks soft ware to establish the computational domain physical model of pulverized coal boilers.Based on computational fluid dynamics(CFD)method,the combustion process of 35t/h pulverized coal test boiler under different load conditions of100%,75% and 60% was numerically simulated.Comparing the simulation r esults with the test temperature data,the error is less than 15%,indicating tha t the simulation calculation is more accurate.The results show: In the original design,due to the interaction between the swirl burners,the high temperature flame is concentrated in the center of the boiler at the intersection of the two swirl burners;At the same time,because the boiler depth is less than the j et flame length,the high temperature flame flushes the back wall at rated loa d,which is not conducive to the safe operation of the pulverized coal boiler;With the reduction of load,this situation has been improved.The NOx produ ction in the boiler is the lowest at rated load.Based on the above research,in order to match the flame length of the s wirl burner with the depth of the boiler,and to ensure safe combustion and r educe the interaction between the swirl burners,a scheme of adding a preheat ing chamber structure is adopted.Firstly,under the rated load,the combustion situation in the boiler under different air distribution ratio conditions is discu ssed.The results show: Increasing the internal secondary air ratio can increase the disturbance in the preheating chamber.Excessive internal secondary air c auses the flame center to move forward,Too little internal secondary air will make the pulverized coal fuel not be effectively mixed with the air,and it is easy to blow out.Finally,numerical simulations of the combustion process u nder three different loads are performed.The results show: The preheating cha mber structure can effectively solve the danger of burning flames against the wall.The combustion in the boiler is stable under different load conditions.T he total amount of NO produced is less affected by load changes.This paper discusses the combustion situation in the boiler under different load conditions of the original scheme.On this basis,the new structural tran sformation plan was discussed.Exploring the effect of the ratio of distribution and load on the combustion in the boiler.It provides theoretical support and reference for the transformation of coal-fired industrial chain boiler.