Investigation Of Flow Field Of Catalyst Sealing And Bed In Ⅱ-type Radial Flow Reactors Of Momentum Exchange Controlling Without Controlling Pressure Drop

The radial flow reactor is a highly-efficient reactor for energy saving and is particularly suitable for gas-solid catalytic reaction, which is widely used in chemical industry and petrochemical industry. The industrial radial flow reactors are usually reactors of momentum exchange controlling, such as ethylbenzene dehydrogenation reactor in vacuum, ammonia oxidation reactor in atmospheric pressure, catalytic reformation reactor in medium pressure, continual catalytic reformation reactor and toluene disproportionation reactor in low pressure. The II-type flow radial reactor is the optimum selection of the radial reactor of momentum exchange controlling and has the advantages of simple structure, low pressure drop and uniform distribution of fluids.In this thesis, the flow fields in the catalyst sealing and the bed ofΠ-type axial-radial flow reactor, and in the each layer ofΠ-type multi-layered radial flow reactor without controlling pressure drop were studied in several large-scale cold experimental plants. The effects of flow type, catalyst sealing height, restricted zone and pressure distribution in main channels on flow field were investigated. The principles of scale-up of the radial reactor were discussed and scale-up models ofΠ-type radial reactor without controlling pressure drop were proposed.The investigations can be expressed as follows:The two-dimensional flow model was used to simulate and analyze the flow properties of the fluid in the catalyst sealing and the bed ofΠ-type axial-radial flow reactor with the boundary conditions obtained through experiments in aΦ3mx7m cold experimental plant. The results demonstrated that the radial flow velocity in the bed ofΠ-type radial reactor without controlling pressure drop was uniform along the axial direction.Pressure profiles in the flow channels and layers in aΦ3mx5m cold model ofΠ-type three-layer radial flow reactor were measured and the flow properties of three-layer radial reactor were investigated. The results showed that in the centrifugal and centripetal flow reactors, the uniformity of the radial flow velocity in the bed was strongly affected by the uniformity of the pressure differences between the distributing channel and collecting channel along the axial direction, whereas the uniformity of the radial flow velocity in the bed was greatly influenced by the uniformity of the pressure distribution of the bed along the radial direction. Moreover, the layer next to the channel in which the pressure gradient varied significantly along the flow direction had the worse uniformity of flow distribution while the layer next to the channel in which the pressure gradient varied slightly had the better uniformity.The effects of catalyst sealing height, flow type and restricted zone on the residence time and axial velocity of the fluid in the catalyst sealing were also studied. At small catalyst sealing height, there was more outflow flowing through the top of the catalyst sealing. The axial velocity of the top of the catalyst sealing was maldistribution along radial direction, the velocity in the inner was two times of that in the outer, and the residence time of the fluid in the catalyst sealing was smaller than that in the main catalyst bed. At big catalyst sealing height, there was little outflow flowing. The axial velocity was uniformity, but the residence time was two times of that in the main catalyst bed. There was more outflow flowing through the top of the catalyst sealing in centripetal flow than in centrifugal flow at small catalyst sealing height, but there was the same outflow flowing at big catalyst sealing height. Restricted zone could finely change the residence time distribution of the catalyst sealing. When the limiting ratio was 25%, the smallest residence time in the catalyst sealing increased by 30%.The mathematical model to describe the hydrodynamic behavior ofΠ-type radial reactor without controlling pressure drop was developed. And the momentum recovery coefficients were obtained in the large-scale cold experimental plants. The model and parameters were used for scale-up of the reactor.Design of aΠ-type axial-radial reactor without controlling pressure drop for ethyl-benzene dehydrogenation of 500 kt/a was proposed. The reactor with the advantages of simple structure and uniform flow distribution could be used in the new ethyl-benzene dehydrogenation technology.