Separation technologies/processes economics

Many, but not all, reactor configurations are discussed. Process design, catalyst manufacture, thermodynamics, design of experiments (qv), and process economics, as well as separations, the technologies of which often are appHcable to reactor technology, are discussed elsewhere in the Eniyclopedia (see Catalysis Separation Thermodynamics). 

As documented in Chapter 5, zeolites are very powerful adsorbents used to separate many products from industrial process steams. In many cases, adsorption is the only separation tool when other conventional separation techniques such as distillation, extraction, membranes, crystallization and absorption are not applicable. For example, adsorption is the only process that can separate a mixture of C10-C14 olefins from a mixture of C10-C14 hydrocarbons. It has also been found that in certain processes, adsorption has many technological and economical advantages over conventional processes. This was seen, for example, when the separation of m-xylene from other Cg-aromatics by the HF-BF3 extraction process was replaced by adsorption using the UOP MX Sorbex process. Although zeolite separations have many advantages, there are some disadvantages such as complexity in the separation chemistry and the need to recover and recycle desorbents. 

We have at our disposal a large number of parameters known both from reference literature or experience. We should define a unique response or optimization parameter, and in case this does not work we should make an attempt with a general response. Since extraction refers to processes of separating phases, they are defined by several parameters-technologically, thermodynamically, economically, statistically, etc. Important and essential properties of the separation process are degree of separation of the required component, economy per finished product and quality of product. Growth of any of these parameters brings about a fall in others. 

Continuous counter-current separation by SMB chromatography improves process economics. Nevertheless, more improved processes have been developed recently. They are all based on the standard SMB technology but operated under variable process conditions to reduce the costs of column hardware and stationary phase as well as for fresh eluent and eluent work-up. 

R. Spillman, Economics of gas separation membrane processes, in R.D. Noble and S.A. Stern, (Eds.), Membrane Separation Technology. Elsevier, Amsterdam, 1995, Chap. 13, pp. 589-667. 

---