Experimental Study Of Mini-Riser Cold Model

As a kind of high efficient gas-solid contact reactor, circulating fluidized bed(CFB)has been widely used in oil refining and chemical industries. Fluid catalytic cracking unit which use riser as a reactor is also occupied the balance of power. But with oil resources increasingly heavy qualitative and inferior optimization, refining enterprise also faces the challenge of raw material diversity. Current evaluation of materials cracking performance, catalysts and the reactor structure and new technology development is mostly in mini-riser reactor, so as to have good comparability of data with industrial one. It is necessary in-depth study in small ascending tube gas-solid flow state in order to establish the connection between mini-riser and industrial one.A CFB with two different diameters (12mm and 16mm) was built in the State Key Laboratory of Heavy Oil Processing in China University of Petroleum. The riser is 3050mm high and the two different diameters can be switched easily. The gas-solid flow states of type 2XTL-5 and ZDT-1 were detected. The radial and the axial distributions of local solids hold up and particle velocities in the mini-riser cold model with different structure were intensively investigated.The structure parameter has important influences on the gas-solid distribution. On one hand, with the decreasing of the diameter the wall effect will be intensification, on the other hand, with pipe diameter increases to more than three times the side wall slide will be enhanced. Both of them decrease the particle radial uniformity of distribution. Pre-lifting structure can improve particle radial distribution after catalyst entrance, formed a buffer space and weaken the feeding of fluctuation between incoming nozzle zone.Mini-Riser cold model circulating fluidized bed riser experimental device in the simulation ZDT-1 type and 2XTL-5 type of riser's superficial gas velocity and particle circulation rate, shows that in the same cross-section height, the solids holdup in 2XTL-5 type is much higher than that in the ZDT-1 type, otherwise, the particle velocity is much lower than that in the later type. The radial profile of particle velocity and solids holdup in the riser of ZDT-1 is more uniform than them in the riser of 2XTL-5 between Dimensionless riser height 0.14 to 0.67.