Research On Flow Characteristics And Reaction Behaviour In Quick-contact Cyclone Reactor

Fluid catalytic cracking process is one of the most important technologies to processheavy oil. Due to heavier and worse raw oil, traditional catalytic cracking units face enormouschallenges. Some disadvantages of riser reactor are increasingly obvious, such as longreaction time, severe coking, and poor product quality. In order to optimize productcomposition, it is necessary to develop new catalytic cracking reactor to realize high severitycondition. In this paper, numerical simulation, experimental study and theoretical analysis areadopted to study the new quick-contact cyclone reactor. Internal two-phase flow, particles’residence time distribution, and gas-solid heat transfer are comprehensively researched.Moreover, the reaction gradient field in flow gradient field is investigated.Firstly, Computational fluid dynamics is used to study turbulent flow characteristics andmigration rules in cyclone reactor, so that rotation intensity, pressure gradient filed andparticles’ trajectories could be obtained. It could be found that gas flow and solid particlesmix under low-vlocity shear flow in mixer, which provides the prerequisite for catalyticreaction. Gas-solid mixing flow enters into the runners of guided vanes uniformly, followedby rotation and acceleration. So strong rotation flow is formed in separator, and solid particlesmigrate to the wall quickly to realize the gas-solid rapid separation.Secondly, gas-solid quick-contact time and heat transfer are studied in cyclone reactor, sothat particles’ residence time and temperature fileds are mainly analyzed. The conclusionscould be obtained that most of the particles’residence time curves are single-peak distribution,that is, solid particles reach the dust mouth in short and consistent time. The quick-contacttme doesn’t affect gas-solid mixing obviously. Through the temperature field, heat transferprocesses are quickly performed between gas flow and solid particles, especially for the inletof mixer, gas temperature changes in larger gradient.On this basis, internal flow and heat transfer are further studied under different structureparameters (inlet location, vane-guided location, vane-guided angles, vane-guided numbers),different operation parameters (catalyst oil ratio, operation temperature, entering way, particlesize). The results show that structure parameters and operation parameters have influences inflow field and temperature field in different degrees. At the same time, the interaction ofvarious parameters can not be ignored.Finally, this paper uses optimized structure parameters to simulate catalytic crackingreaction process in cyclone reactor. Through comparisons of product mass fraction in cyclonereactor and riser, it could be drawn the conclusions that although the final conversion is lower in cyclone reactor, but for product selectivity, cyclone reactor has the advantage of improvingproduct structure and decreasing coking. Furthermore, combined with the rotary flowcharacteristic, matching relationships of flow gradient field and reaction gradient field areestablished.These above studies lay the foundation for in-depth study of catalytic cracking reaction,and also provid theoretical basis for the research and development of new quick-contactreactor.