Research On Droplet Evaporation,Heat Transfer And Hydrodynamics Characteristics In FCC Riser Reactor

FCC riser reactor is the core device of the catalytic cracking,in which exists complicated heat and mass transfer,flow and cracking reaction of feed jets,medium gas and catalyst particles.Traditional studies were confined to the dynamic characteristics between oil and solid catalyst,however,the droplets evaporation,heat transfer and flow characteristics is still lack of full understanding,thus this research has a good prospective and value.The analysis of inject feed operating parameters provide guidance for feeding operation parameter optimization and configuration,and enhance the efficiency of catalytic cracking reaction and the product yield.Based on convective heat transfer theory and liquid-solid contact heat transfer theory,coupled with kinetic model to theoretically establish the droplet evaporation and movement equations,then used Matlab software to get the discrete solution.The results show that the oil droplet went through three different stages,namely,transient heating,unbalanced evaporation and balanced evaporation;Initial diameter,jet velocity and temperature influence much of the droplet evaporation rate and the movement trajectory;The best initial droplet diameter was determined by the jet velocity and initial temperature.Numerically simulate FCC riser reactor based on the Euler-Lagrange DPM model using Fluent software.The oil droplet evaporation,heat transfer and flow dynamic characteristics were studied and the influences of several key operating parameters were carefully analyzed to determine the optimal condition.The results are as follows,Oil jet velocity,spray cone angle,feed temperature can promote feed oil spray evaporation rate,heat transfer and mixing characteristics within certain range,however,too large values of these three factors produce negative effects on evaporation and flow characteristics,the optimal values of oil jet velocity,spray cone angle,feed temperature are 40 m/s,120 °and 350? respectively;Smaller oildroplet size is beneficial to improve evaporation,heat transfer and flow characteristics,thus,the droplet diameter are best to be smaller than 105 microns;Feeding by single nozzle results in poor oil evaporation,heat transfer and flow condition,while multiple symmetrical feed nozzle installation can greatly increase the efficiency of the heat transfer and flow characteristics;Increasing the feed nozzle angle promotes oil evaporation,heat transfer and flow conditions,but too large installation angle causes too long existence of oil within riser and excessive cracking phenomenon,the optimal installation angle is 60°.