Product recovery adsorption

At the completion of adsorption, the less selectively adsorbed components have been recovered as product. However, a significant quantity of the weaMy adsorbed species are held up in the bed, especially in the void spaces. A cocurrent depressurization step reduces the bed pressure by allowing dow out of the bed cocurrendy to feed dow and thus reduces the amount of product retained in the voids (holdup), improving product recovery, and increases the concentration of the more strongly adsorbed components in the bed. The purity of the more selectively adsorbed species has been shown to depend strongly on the cocurrent depressurization step for some appHcations (66). A cocurrent depressurization step is optional because a countercurrent one always exists. Criteria have been developed to indicate when the use of both is justified (67). 

Of the four commercial processes for the purification of carbon monoxide two processes are based on the absorption of carbon monoxide by salt solutions, the third uses either low temperature condensation or fractionation, and the fourth method utilizes the adsorption of carbon monoxide on a soHd adsorbent material. AH four processes use similar techniques to remove minor impurities. Particulates are removed in cyclones or by scmbbing. Scmbbing also removes any tars or heavy hydrocarbon fractions. Acid gases are removed by absorption in monoethanolamine, hot potassium carbonate, or by other patented removal processes. The purified gas stream is then sent to a carbon monoxide recovery section for final purification and by-product recovery. 

The H2S comes out with the reactor products, goes through the product-recovery system of the FCCU, and eventually goes to a Claus plant for sulfur recovery. The metal oxide adsorbent recirculates with the spent cracking catalyst back to the regenerator for the next SO adsorption cycle. 

Product Recovery. The aHyl chloride product is recovered through the use of several fractional distillation steps. Typically, the reactor effluent is cooled and conducted into an initial fractionator to separate the HCl and propylene from the chloropropenes, dichloropropanes, dichloropropenes, and heavier compounds. The unconverted propylene is recycled after removal of HCl, which can be accompHshed by adsorption in water or fractional distillation (33,37,38) depending on its intended use. The crude aHyl chloride mixture from the initial fractionator is then subjected to a lights and heavies distillation the lighter (than aHyl chloride) compounds such as 2-chloropropene, 1-chloropropene, and 2-chloropropane being the overhead product of the first column. AHyl chloride is then separated in the second purification column as an overhead product. Product purities can exceed 99.0% and commercial-grade aHyl chloride is typicaHy sold in the United States in purities about 99.5%. 

The product is extracted from the culture fluid by adsorption onto caibon or resins rather than by solvent. This illustrates an important general point that antibiotic manufacturing processes differ from one another much more in their product recovery stages than in their fermentation stages. Figure 7.4 illustrates a typical production ronte from inoculum to bulk antibiotic. 

The USEPA surveys identified four resin adsorption systems in the pesticide industry [7]. Phenol, pesticide, and diene compounds are all effectively removed by these systems. At least one system realized a significant product recovery via regeneration and distillation. The design surface loading rates vary from 1.0 to 4.0 gpm/ft with empty bed contact times of 7.5 to 30 minutes. 

T0880 Western Product Recovery Group, Inc., Coordinate Chemical Bonding and Adsorption (CCBA) Process... 

The growing interest in various )5-lactam antibiotics, especially the cephalosporins, over the last decade has called upon improvement in their production methods via modification of either the basic process and the microbial strain or the downstream processing techniques. The product recovery may involve various methods of extraction and purification which play an important role in the overall process economics [12]. During recent years much attention has been given to the development of liquid membrane (LM) processes which usually exhibit high extraction rates and selectivity as compared to those achievable in conventional solvent extraction and adsorption processes. 

Integrated bioprocesses can be used to enhance the production of valuable metabolites from plant cell cultures. The in situ removal of product during cell cultivation facilitates the rapid recovery of volatile and unstable phytochemicals, avoids problems of cell toxicity and end-product inhibition, and enhances product secretion. In situ extraction, in situ adsorption, the utilization of cyclodextrin, and the application of aqueous two-phase systems have been proposed for the integration of cell growth and product recovery in a bioreactor. The simultaneous combination of elicitation, immobilization, permeabilization, and in situ recovery can promote this method of plant cell culture as a feasible method to produce various natural products including proteins. 

Primary recovery of the active ingredient from the solid or liquid phase to remove large quantities of unwanted waste materials, which may themselves be processed further. Suitable techniques include solvent extraction, precipitation by chemical or physical changes to the product-containing solution, and ultrafiltration or microfiltration to separate products above a particular size. Work done on combined biomass separation-primary product recovery processes such as expanded-bed adsorption are now being commercialized in the pharmaceutical industry. 

The adsorbent particles are normally used as beads, extrudates, or granules (-0.1 -0.3 cm equivalent diameters) in conventional H2 PSA processes. The particle diameters can be further reduced to increase the feed gas impurity mass transfer rates into the adsorbent at the cost of increased column pressure drop, which adversely affects the separation performance. The particle diameters, however, cannot be reduced indefinitely and adsorption kinetics can become limiting for very fast cycles48 New adsorbent configurations that offer (i) substantially less resistance to gas flow inside an adsorber and, thus, less pressure drop (ii) exhibit very fast impurity mass transfer coefficients and (iii) minimize channeling are the preferred materials for RPSA systems. At the same time, the working capacity of the material must be high and the void volume must be small in order to minimize the adsorber size and maximize the product recovery. Various materials satisfy many of the requirements fisted above, but not all of them simultaneously. 

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