Continuous-membrane column performance

The performance of the continuous membrane column was characterized earlier (28) in a manner analogous to the transfer unit concept for packed columns. The expressions developed for NMU (difficulty of separation) and HMU (efficiency) were... 

A continuous cross-flow filtration process has been utilized to investigate the effectiveness in the separation of nano sized (3-5 nm) iron-based catalyst particles from simulated Fischer-Tropsch (FT) catalyst/wax slurry in a pilot-scale slurry bubble column reactor (SBCR). A prototype stainless steel cross-flow filtration module (nominal pore opening of 0.1 pm) was used. A series of cross-flow filtration experiments were initiated to study the effect of mono-olefins and aliphatic alcohol on the filtration flux and membrane performance. 1-hexadecene and 1-dodecanol were doped into activated iron catalyst slurry (with Polywax 500 and 655 as simulated FT wax) to evaluate the effect of their presence on filtration performance. The 1-hexadecene concentrations were varied from 5 to 25 wt% and 1-dodecanol concentrations were varied from 6 to 17 wt% to simulate a range of FT reactor slurries reported in literature. The addition of 1-dodecanol was found to decrease the permeation rate, while the addition of 1-hexadecene was found to have an insignificant or no effect on the permeation rate. 

Figure 19.6. Gas permeation equipment and performance, (a) Cutaway of a Monsanto Prism hollow fiber module for gas separation by permeation, (b) Flowsketch of a continuous column membrane gas separator, (c) Composition profiles of a mixture of C02 and Oz in a column 5 m long operated at total reflux [Thorman and Hwang in ( Turbak, Ed.), Synthetic Membranes II, American Chemical Society, Washington DC, 1981, pp. 259-279],...

Sometimes reaction rates can be enhanced by using multifunctional reactors, i.e., reactors in which more than one function (or operation) can be performed. Examples of reactors with such multifunctional capability, or combo reactors, are distillation column reactors in which one of the products of a reversible reaction is continuously removed by distillation thus driving the reaction forward extractive reaction biphasing membrane reactors in which separation is accomplished by using a reactor with membrane walls and simulated moving-bed (SMB) reactors in which reaction is combined with adsorption. Typical industrial applications of multifunctional reactors are esterification of acetic acid to methyl acetate in a distillation column reactor, synthesis of methyl-fer-butyl ether (MTBE) in a similar reactor, vitamin K synthesis in a membrane reactor, oxidative coupling of methane to produce ethane and ethylene in a similar reactor, and esterification of acetic acid to ethyl acetate in an SMB reactor. These specialized reactors are increasingly used in industry, mainly because of the obvious reduction in the number of equipment. These reactors are considered by Eair in Chapter 12. 

Equipment used to produce biotech products should be qualified for design, installation, operation, and performance [15]. The aging and continued performance of re-used process materials such as column resins is an important consideration during the validation of a biotech process. Demonstration of microbial control during processing is also a critical component of process validation, particularly in difficult to clean equipment such as alBnity columns or ultrafiltration membranes. Finally, consistent and reasonable step yield of individual unit operations can be verified during consistency and commercial product manufacturing. 

The continuous production of COS was found to be feasible with combination of a column reactor packed with immobilized chitosanase and UF membrane system, and this system was developed by Jeon and Kim (2000b), named as dual reactor system (Figure 5.2). In this system, production of COSs may be performed in two steps. In the first step, chitosan is partially hydrolyzed by the immobilized chitosanase prepacked in the column reactor and the product is supplied to the UF membrane system for the production of COS. As expected, the viscosity of partially hydrolyzed chitosan was low thereby it does not create fouling problems under controlled conditions, and continuous production of COSs was achieved. This method ensures a greater productivity per unit enzyme, ability to control molecular weight distribution and more efficient continuous production process compared to those of conventional methods. Therefore, this method is commonly used to produce different molecular size COSs to study their bioactivities. 

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