Numerical Analysis And Structural Design Of Flow And Heat Transfer Process Of Small Horizontal Drying Coal-fired Hot Blast Stove

Based on the energy structure characteristics of China's rich coal,less oil and lean natural gas,and the expensive price of oil and natural gas,the use of coal-fired hot blast stoves to dry agricultural products can not only save costs,but also exist wider sources of fuel.However,at present,coal-fired hot blast stoves have problems such as insufficient combustion,low thermal efficiency,and severe pollutant emissions.Therefore,how to improve the structure of existing coal-fired hot blast stoves to make them burn efficiently and reduce emissions is of great significance for protecting the environment.Aiming at the problems mentioned above in hot blast stove,in this paper,a small horizontal coal-fired hot blast stove with the multi-downward flue gas flow path construction and hot air without pollution is developed.It aims to efficiently burn coal fuel,reduce pollutant emissions,and achieve energy-saving,environmentally friendly,and low-cost drying of agricultural products.In this paper,the combustion of the hot-blast stove combustion chamber is simulated by the FLUENT software.At the same time,the experimental platform is built and the rationality of the numerical simulation calculation is verified by experiments.Finally,the structure of the hot-blast stove combustion chamber is improved by numerical simulation.?1?Small coal-fired hot blast stove system is designed and the experimental prototype is built.Firstly,the working principle and basic composition of the hot blast stove are studied.Then the design and selection of the hot blast stove equipment are carried out,including the fuel combustion system,the air heat exchange system and the desulfurization and dust removal system.The fuel combustion system is designed as the multi-downward flue gas flow path construction,the air heat exchange system is designed as a finned shell-and-tube heat exchanger,and the desulfurization and dust removal system uses a wet desulfurization dust collector.The experimental prototype is built.?2?The combustion chamber of a coal-fired hot blast stove is numerically simulated and verified.In this paper,the FLUENT software is used to simulate the combustion condition in the combustion chamber of a coal-fired hot blast stove.The geometric model of the hot blast stove combustion chamber is established,and the calculation model meshes.The turbulence model,component model,discrete phase model,radiative heat transfer model and particle phase combustion model are used to simulate the combustion process of coal in the combustion chamber of the hot blast stove.Through the analysis of temperature contours,velocity contours,component concentration distribution contours,pressure contours and particle concentration contours,it is concluded that the combustion high temperature zone lies between the bottom of the grate and the top of the second baffle,and the temperature of the third combustor decreases continuously.The turbulence intensity of the air flow in the first combustor and the second combustor is relatively high,and the flue gas flow in the third combustor is relatively gentle.Most of the particulate matter is mainly concentrated in the bottom area of the grate.As the airflow flows around the baffle,the concentration of particulate matter is gradually reduced.The whole combustion chamber operates under negative pressure.The temperature verification experiment is carried out on the numerical simulation,and the simulation results are basically consistent with the experimental values.The relative errors of experiment and simulation are within 10%,which proves the reliability of the numerical simulation results,and provides a solid reference for the later research and improvement of the structure of hot blast stove.?3?The structure of the combustion chamber of the coal-fired hot blast stove is improved.The combustion chamber structure of the coal-fired hot blast stove is improved by changing the length of the third baffle and increasing the secondary air vent.The improved combustion chamber of hot blast stove is simulated by FLUENT software.The temperature field in the furnace,the concentration of the particles in the furnace,and the average mass fraction of the combustible gas?CO+H₂+CH₄?in the furnace are studied.By comparing with the results obtained in the previous section,the conclusion is drawn:Shortening the length of the third baffle by 30mm can obtain the maximum temperature of the furnace outlet.Increasing the length of the third baffle by 40mm can more effectively reduce the discharge of particulate matter at the exit of the furnace.Increasing the secondary air vent can effectively reduce the average mass fraction at the furnace outlet?CO+H₂+CH₄?.By comparing and analyzing various factors,the length of the third baffle in the hot-blast stove combustion chamber is 280mm.