Contrast Analysis Of Concurrent And Countercurrent Heating Methods Of Fixed-type Hot Recycling Rotating Drum

Asphalt mixture plant heat mixing and regeneration equipment generally uses downstream heating.In recent years,with the deepening of heat regeneration technology research,countercurrent plant heat mixing and regeneration equipment has appeared on the market.Due to the difference in the structure and heating method of the downstream and upstream thermal regeneration equipment,there are obvious differences in the production capacity,quality and energy consumption of the obtained asphalt pavement recycled material(RAP).Therefore,it is very necessary to study the use of forward and reverse flow heating processes in the regeneration drying cylinder to optimize the structure of the thermal regeneration equipment,reduce environmental pollution and improve energy utilization.The thesis compares and analyzes the heating mechanism of the co-current and counter-flow regenerative drying drums.Through the kinematic analysis of the asphalt pavement reclaimed material(RAP)particles,the residence time of RAP in the drum,the speed of the drum,and the installation inclination angle are obtained.The relationship between flue gas flow rate and length-to-diameter ratio,among which flue gas flow rate has the greatest influence on the difference between the residence time of concurrent heating and countercurrent heating.The discrete element software EDEM was used to simulate and analyze the distribution and motion state of RAP particles in the regenerative drum.Based on the law of conservation of heat,a one-dimensional heat transfer model of the regenerative drum was established.The heat transfer coefficient,heat transfer area and mathematical model were used to determine the values of the relevant parameters based on the material properties of the RAP,and quantitatively describe the heating trend of RAP under different heating mechanisms.Taking the heat-mixing regeneration equipment of a company as the research object,MATLAB is used to simulate the heat transfer mathematical model,and the simulation results are verified by actual production tests.The results show that: under the same fuel consumption conditions,the use of countercurrent heating can increase the RAP discharge temperature relative to downstream heating by 23.8°C,which effectively improves the overall thermal efficiency of the regenerative drying drum and is conducive to energy saving and consumption reduction.In general,the regenerative drying cylinder adopts the countercurrent heating method,and its heating effect is significantly better than the downstream heating.