Research On Solid-solid Heat Transfer In Circulating Fluidized Bed

Because the thermal capacity of solid particles is larger than that of gas and the particles ofGeldart A have good fluid property, energy source of the new petroleum refining process willhave very broadly perspectives of application if the residual heat of FCC can be taken out bysolid-solid heat transfer in circulating fluidized bed,.The study was carried out with heat transfer system of homemade circulating fluidized bed.The inner and the outer circulating systems were studied separately by using three kinds of FCCcatalyst as circulating materials. The influence of catalyst inventories, aeration air quantity andmain air quantity on circulating catalyst rate was studied too. The results of experiments showthat the proper catalyst inventories and the aeration air quantity can enhance the operationstability of equipments. Lastly the conditions which were ascertained are as follows: fluidizationvelocity of inner tube 2.4m/s, fluidization velocity of outer tube 2.5m/s;aeration air quantity ofinner tube 0.22m/s, aeration air quantity of outer tube 0.19m/s;catalyst inventories of inner tube5000g, catalyst inventories of outer tube 5000g;catalyst circulating rate of inner tube 43kg/h ,catalyst circulating rate of outer tube 35kg/h.The efficiency of heat transfer system was studied by simulating the situation of practicalproduction in heat transfer experiments. The influence of suspension density, fluidizationvelocity, beds temperature, diameter of catalyst particles and material properties on heat transfercoefficients was studied with the proper conditions. The results of experiments show that thesuspension density and the heat transfer coefficients decrease with catalyst circulating rateincreasing;the heat transfer coefficients increase with bed temperature increasing, thefluidization velocity and the particles diameter decreasing;the good efficiency of heat transfercan be obtained by using solid particles with the larger thermal capacity.Firstly the heat transfer process of system was simplified, the physical model was built byusing the instability theory of particle floc. Then the equation of process operation was resolvedand the mathematic model of heat transfer process was given by Laplace equation. Lastly theparameter of model was regressed and the equation of heat transfer coefficients of the solid-solidheat transfer system was put forward according to experiment results. The forecast value and theexperiment value of heat transfer coefficients were compared. It is satisfied with the needs ofengineering design that the error is less than 15%.