Slurry reactor Design Issues

Multiple phases exist in slurry reactors. The solid phase is typically a catalyst. The liquid phase is a reactant or product. There can also be a gas phase, usually one of the reactants. The design issues involve separating the phases and recycling catalyst and reactant back to the reactor. 

The slurry phase reactor provides much better and more flexible temperature control compared to the Arge reactor. It can operate at higher temperatures and with more active catalyst without formation of coke or catalyst breakup. The key operating issues are catalyst/liquid separation and catalyst attrition. Sasol has apparently resolved these design issues successfully. 

A number of industrial reactors involve contact between a fluid (either a gas or a liquid) and solids. In these reactors, the fluid phase contacts the solid catalyst which may be either stationary (in a fixed bed) or in motion (particles in a fluidized bed, moving bed, or a slurry). The solids may be a catalyst or a reactant (product). Catalyst and reactor selection and design largely depend upon issues related to heat transfer, pressure drop and contacting of the phases. In many cases, continuous regeneration or periodic replacement of deteriorated or deactivated catalyst may be needed. 

The first United States patent that described the vertical pipe-loop slurry polymerization reactor illustrated in Figure 5.11 was issued to Donald D. Norwood on April 26,1966, as U.S. Patent 3,248,179 and assigned to Phillips Petroleum Company. Earlier applications filed in 1959 were abandoned, thus explaining the relatively late issue date on the Norwood patent. Although Donald Norwood was the only name on the first United States patent issued to Phillips Petroleum, Philips Petroleum credits three process engineers, D. D. Norwood, S. J. Marwil and R G. Rohling, for the design of the vertical loop reactor [24]. 

U.S. Patent 3,152,872 issued to J.S. Scoggin and Harvey S. Kimble on October 13, 1964, and assigned to Phillips Petroleum Company, provides a detailed description of the separation system used to isolate the solid polyethylene granular particles from the liquid diluent used in the vertical pipe-loop reactor. The contributions of Scoggin and Kimble were important in the design and start-up of the first commercial loop reactor in Pasadena, Texas, in 1961. It should be noted that the first vertical loop reactor used n-pentane as the slurry solvent, which was later changed to isopentane and then to isobutane in about 1970. 

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