Summary of Abnormal Catalyst Level in the Reduction Section of UOPⅢ Continuous Reforming (Common Catalyst Moving Bed Issues Similar to Those in Continuous Reforming)

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I previously posted a request for help on HCBBS regarding abnormal catalyst level in the reduction section of UOP III continuous reforming; the link is as follows: “Request for help regarding frequent sudden drops in the catalyst level in the reduction section of UOP third-generation continuous reforming” http://bbs.hcbbs.com/thread-616963-1-1.html. Since I am about to leave my position in continuous reforming, I am now summarizing this issue. Firstly, chemical production involves a large number of reactions that make use of catalysts, which brings up the issue of the configuration of these catalyst beds. These include fixed beds (such as hydrocracking and hydrorefining), moving beds (such as continuous reforming and S-Zorb gasoline adsorption desulfurization), and boiling beds, also known as fluidized beds (such as catalytic cracking). The continuous reforming catalyst is a spherical particle with a diameter of about 1.5 mm. The structure of the moving bed catalyst for continuous reforming is as follows: the catalyst is contained within two cylindrical sleeves, the inner and outer ones, which are made of Johnson netting. The reaction gases can pass through freely, but the catalyst cannot, as a result of this design. The catalyst moves slowly from top to bottom within the cavities of the inner and outer cylindrical sleeves, while the reaction gases pass radially through the catalyst bed. The UOP III continuous reforming reactor section consists of 1 reduction section and 4 reactors. The catalyst flows from top to bottom through the reduction section, Reactor 1, Reactor 2, Reactor 3, and Reactor 4. The connection between each pair of sections is such that the catalyst is transferred from the bottom of the circular sleeve of the previous reactor to the top of the next reactor, and this process repeats itself. These 8 material legs are arranged at equal angles, allowing the catalyst to fall down evenly and slowly; at the outlets of these legs, a nearly conical surface is formed naturally. The naturally formed nearly conical surfaces at the outlets of the 8 catalyst material legs together constitute a nearly horizontal surface. If one of the 8 catalyst legs becomes clogged, the conical surfaces that naturally form at the outlets of the two adjacent legs will increase in size, and the gap between these two conical surfaces will also widen – this is what is known as the natural angular cavity in the catalyst bed. If no other factors are present, the natural angular cavities formed by catalyst flow do not change significantly. However, in a reforming reactor, a large amount of reaction gas and oil passes radially through the catalyst bed, and the natural angular cones that are formed are susceptible to the radial forces exerted by these gases and oils; as a result, they collapse and fill those angular cavities, causing the catalyst bed to move downward rapidly. “The sudden drops in the material level in the reduction section of UOP’s third-generation continuous reforming unit can be explained by the theory mentioned above; the same principle can also be applied to similar situations in other types of moving-bed reactors. It is understood that the issue of abnormal material level in the reduction section of UOP III continuous reforming has occurred in various refineries. It is hoped that more data on this phenomenon will be collected, so as to gain a better understanding of such incidents, discuss their root causes, and ultimately raise this issue to a theoretical level for further research and resolution.