Design And Simulation Of The Heating System Of The Intensive Curing Barn Using Biomass Briquette Fuel

At present,the traditional bulk curing barn is mainly heated by coal-fired hot blast stove,the energy density of the heat supply medium is low,the heat loss of the system is large,and there are problems such as low heat supply efficiency and serious environmental pollution.In this paper,a centralized heating system with biomass briquette fuel as boiler fuel and high energy-density heat-conducting oil as heat medium was designed,which provided a theoretical guidance for realizing the replacement of coal for tobacco leaf baking process.Firstly,the components,calorific value and combustion characteristics of biomass briquette fuel were studied by experimental methods.It was found that biomass briquette fuel had the characteristics of high moisture,high volatile content,low ash,low sulfur and low calorific value.It had good combustion characteristics,which was performed by ignition temperature was low,flammability,combustion stability,volatile devolatilization characteristics,burnout characteristics and comprehensive combustion characteristics were good.The combustion process mainly included three stages,namely,a dry dehydration stage,a volatile devolatilization and combustion stage,and a coke combustion and burnout stage,wherein the average activation energies of the second and third stages were 191.18kJ/mol and 315.86kJ/mol,respectively,the average activation energy for all combustion stages was 242.02 kJ/molThen,according to the fuel characteristics and the requirements of the tobacco leaf baking process,this paper designed a heat-conducting oil furnace using biomass briquette fuel and a heating chamber heat exchanger group,the design plan was determined by the calibration calculation.The heat-conducting oil furnace had a reasonable heating surface layout,the positive and negative balance efficiency error was 0.03%,the heat transfer coefficient of the plate-fin heat exchanger was 8.88 W/(m~2°C),and the heat transfer error was 1.28%,which met the design requirements.Finally,the heating performance of the bulk curing barn heating system was studied by the combination of thermal test and numerical simulation.Through the analysis of the numerical simulation results of the heat-conducting oil furnace,the furnace structure was optimized by changing position of the secondary air and adding the rear arch,which improved the furnace temperature,increased the residence time of the flue gas and the combustion efficiency.The numerical simulation results of the heat transfer process in the heating chamber of the baking room showed that the different oil supply temperature had no obvious influence on the velocity distribution of the heating chamber air.As the oil temperature increased,the temperature distribution of the air tended to be uneven,the temperature rise of air and the convective heat transfer coefficient of the air side were increased.Controlling the oil supply temperature between 150°C and 160°C is beneficial to improve the economics of tobacco leaf baking.