Study On Atomization And Combustion Characteristics Of Heavy Oil In Asphalt Mixing Plant

In recent years,China has vigorously carried out infrastructure construction,which requires a large amount of fossil fuels to produce asphalt mixture every year.However,there are some problems such as poor fuel combustion effect and high emission of pollution gas in the process of oil burner in asphalt mixing station.Therefore,numerical simulation method is adopted in this paper to study the atomization characteristics and heavy oil combustion characteristics of Y-type atomizing nozzle under different parameters,so as to provide guidance for the design and optimization of heavy oil burner in asphalt mixing station.The main work and conclusions are as follows:1)Simulation and analysis of two-phase flow and atomization characteristics of Y-type atomizing nozzle.A simulation model of atomizing characteristics of Y-type atomizing nozzle was established to explore the influence of structural parameters(mixing chamber length,inlet angle,inlet diameter ratio)and process parameters(fuel mass flow rate,air inlet pressure,fuel temperature)on gas-liquid two-phase flow and atomizing performance indexes in the nozzle.The results show that the increase of inlet pressure and fuel temperature is beneficial to the atomization of heavy oil,and the increase of fuel mass flow will increase the Sauter mean diameter.And the air pressure should not be lower than 0.5MPa.In terms of structural parameters,the optimal length of the mixing chamber is 15～20mm,the reasonable range of inlet Angle is 60～75°,and the diameter ratio of the inlet is between 1.0～1.1.2)Simulation of burner combustion characteristics under variable condition.The simulation model of combustion characteristics of heavy oil burner was established,and the influences of the oil/gas ratio of burner,the angle of the flame plate fan,the diameter of the flame plate,the number of the blade of the flame plate fan and the number of oil injection holes on the distribution characteristics of temperature and concentration in the drum were explored.The results show that the oil/gas ratio has an important effect on the temperature and gas component distribution in the cylinder,and the reasonable value range of the oil/gas ratio is 1.0～1.1.The change of the structure of the flame stabilizer has little effect on the temperature distribution and the flame length in the drum,but the change of the number of the blade and the diameter of the flame stabilizer will make the flame incline.The reasonable value range of the diameter of the flame stabilizer is 610～620mm,the number of the blade of the flame stabilizer is 24,and the optimal Angle of the flame stabilizer is 30.The decrease of the number of oil holes can improve the combustion effect of heavy oil,but the emission concentration of NO will increase.3)Orthogonal simulation analysis of combustion characteristics.Orthogonal simulation experiments were carried out to explore the sequence of important influences of different factors on performance indicators such as maximum combustion temperature,flame length,NO emission concentration and CO emission concentration.The results show that the number of fuel injection holes has the greatest influence on the temperature and flame surface distribution in the drum,the excess air coefficient has the greatest influence on the emission concentration of CO and NO,and the structure of the flame stabilizer plate affects the spatial distribution of combustion reaction in the drum.By comparing the simulation results of the four optimal working conditions,the optimal parameter combinations of the burner are obtained as follows: 1.44,600 mm,20,60° and 8.