Product recovery

The recovery of lactic acid fi om the fermentation medium is a major cost item for the entire process (Vick Roy 1985 Datta 

The first step in the conventional recovery processes is heating the fermentation beer to 80—100 °C and increasing the pH to 10 to kill the bacteria, coagulate proteins, and maintain calcium lactate s solubility in the beer. The crude calcium lactate solution is then filtered, decolorized with activated carbon, and concentrated by evaporation. Lactic acid is recovered by addition of sulfuric acid and then further purified by one of the following routes (O Fig. 1.11)  

Filtration, carbon treatment, and concentration of lactic acid 

Organic Add and Solvent Production Acetic, Lactic, Gluconic, Succinic, and Polyhydroxyalkanoic Acids 

Formation of lactate esters and fractionation (pharmaceutical quality) 

Besides MA, maleic acid, fumaric acid, carbon monoxide, carbon dioxide, and water are the major by-products of the oxidation of benzene. Ben-zoquinone, as may be noted, is proposed as an intermediate during MA 

In MA from the C4-hydrocarbon process, the nature of by-products is quite different. Among these are the lower monoacids (e.g., acetic, acrylic, crotonic), the corresponding aldehydes,etc. Some of these are produced in amounts too small to make an economic recovery possible. In either situation (benzene or C4), nitrogen, water, and the oxides of carbon are vented to the air after the recovery of products and hydrocarbons. If a significant amount of hydrocarbon is unreacted, it may be recycled if practical. If this is not possible, any of the available emission control technologies, especially for benzene-based processes, may be considered.  

The major difference between various commercial processes is observed in the recovery of maleic anhydride from the effluent stream of the reactor. Commonly employed methods fall into one of the following categories  

In practice, as we shall see later, the last category is usually employed as a secondary recovery in processes employing benzene as a feed.  

The effluent stream contains a low concentration of MA in the gas phase (1.5% by weight). Part of this is recovered as a solid by cooling the effluent as in the Ruhroll process. The Scientific Design (SD) process, on the other hand, collects MA as a molten liquid by cooling the stream above the dew point of water. This prevents formation of any significant concentration of maleic acid produced by hydrolysis which may potentially isomerize to fumaric acid. (See Chapter 1.) The molten MA is collected as such in the Scientific Design process.Alternatively, the molten MA can be collected on ceramic supports as claimed by Monsanto. 

It would seem a rather pointless exercise planning the installation of a preparative HPLC system without considering the process to recover the product from the chromatographic eluent. There is no simple answer to the question since it will 

When lyophilising from trays in a shelf freeze dryer try transferring the solution to Gortex 

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Manufacturing approaches for selected bioproducts of the new biotechnology impact product recovery and purification. The most prevalent bioseparations method is chromatography (qv). Thus the practical tools used to initiate scaleup of process Hquid chromatographic separations starting from a minimum amount of laboratory data are given. 

Recovery nd Purifica.tion. The production of EH Lilly s human insulin requires 31 principal processing steps of which 27 are associated with product recovery and purification (13). The production process for human insulin, based on a fermentation which yields proinsulin, provides an instmctive case study on the range of unit operations which must be considered in the recovery and purification of a recombinant product from a bacterial fermentation. Whereas the exact sequence has not been pubUshed, the principle steps in the purification scheme are outlined in Figure la. 

Fig. 1. (a) Process flow sheet for human insulin production, recovery, and purification (12) (b) corresponding steps in recovery of biosynthetic human... 

A membrane filter which can uniformly remove all viral agents regardless of the size of the viral agent is not available. Part of the difficulty is that the efficient recovery of the biological product diminishes as the size difference between the vims and biological product lessens. Thus a balance needs to be met where vims removal and product recovery are optimized. 

The derivatives are hydroxyethyl and hydroxypropyl cellulose. AH four derivatives find numerous appHcations and there are other reactants that can be added to ceUulose, including the mixed addition of reactants lea ding to adducts of commercial significance. In the commercial production of mixed ethers there are economic factors to consider that include the efficiency of adduct additions (ca 40%), waste product disposal, and the method of product recovery and drying on a commercial scale. The products produced by equation 2 require heat and produce NaCl, a corrosive by-product, with each mole of adduct added. These products are produced by a paste process and require corrosion-resistant production units. The oxirane additions (eq. 3) are exothermic, and with the explosive nature of the oxiranes, require a dispersion diluent in their synthesis (see Cellulose ethers). 

The purpose of such scmbbing operations may be any of the following gas purification (eg, removal of air pollutants from exhaust gases or contaminants from gases that will be further processed), product recovery, or production of solutions of gases for various purposes. Several examples of appHed absorption processes are shown in Table 1. 

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). 

Increasing efforts to heterogenize homogeneous catalysts for LPO are apparent (2,206—209). Significant advantages in product recovery, catalyst use, and catalyst recovery are recognized. In some instances, however, the active catalyst is reported to be material dissolved from the sotid catalyst (210). 

Refinery hydrogen requirement is met either by direct manufacture or indirect by-product recovery. Manufacture is typically by steam methane... 

Sales demand for acetophenone is largely satisfied through distikative by-product recovery from residues produced in the Hock process for phenol (qv) manufacture. Acetophenone is produced in the Hock process by decomposition of cumene hydroperoxide. A more selective synthesis of acetophenone, by cleavage of cumene hydroperoxide over a cupric catalyst, has been patented (341). Acetophenone can also be produced by oxidizing the methylphenylcarbinol intermediate which is formed in styrene (qv) production processes using ethylbenzene oxidation, such as the ARCO and Halcon process and older technologies (342,343). 

The low (ca 2%) yield of NO, the tendency to revert to N2 and O2 if the product stream is not quenched rapidly, the consumption of large (ca 60,000 kWh/1N2 fixed) amounts of electricity, and the concomitant expense to sustain the arc all led to the demise of this process. The related Wisconsin process for oxidising N2 at high temperatures in a pebble-bed furnace was developed in the 1950s (13). Although a plant that produced over 40 t/d of nitric acid was built, the product recovery costs were not economically competitive. 

Vapor-phase catalytic oxidation of dutene is a mote direct route to the dianhydtide. Hbls in Europe apparently uses this route, which eliminates the need for a separate dehydration step and for handling of any oxidants or solvents. Continuous operation is faciHtated, corrosion is minimized, and product recovery is simplified. The vapor-phase oxidation of dutene is similar to that of o-xylene to phthaHc anhydtide, and phthaHc anhydtide units can be... 

Crude Tar and Tar Products. Where the tar distillery is sited close to the carboni2ing plant, the cmde tar is transferred directly from the tar—liquor separating vessels on the by-product recovery unit to the storage tanks. Otherwise, it is shipped in rail or road tankers or by barge. Cmde tar is stored in mild-steel tanks maintained at 40—50°C by steam coils. 

Vanadium Vanadium product recovery process recovered... 

Charcoal was an important industrial raw material in the United States for iron ore reduction until it was replaced by coal in the early 1880s. Charcoal production increased, however, because of the demand for the by-products acetic acid, methanol, and acetone. In 1920, nearly 100 by-product recovery plants were in operation in the United States, but the last plant ceased operation in 1969. 

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%. 

By-Product Recovery. The anode slime contains gold, silver, platinum, palladium, selenium, and teUurium. The sulfur, selenium, and teUurium in the slimes combine with copper and sUver to give precipitates (30). Some arsenic, antimony, and bismuth can also enter the slime, depending on the concentrations in the electrolyte. Other elements that may precipitate in the electrolytic ceUs are lead and tin, which form lead sulfate and Sn(0H)2S04. 

Fig. 5. Hydrogen puritication process with by-product recovery.

Product Recovery. Comparison of the electrochemical cell to a chemical reactor shows the electrochemical cell to have two general features that impact product recovery. CeU product is usuaUy Uquid, can be aqueous, and is likely to contain electrolyte. In addition, there is a second product from the counter electrode, even if this is only a gas. Electrolyte conservation and purity are usual requirements. Because product separation from the starting material may be difficult, use of reaction to completion is desirable ceUs would be mn batch or plug flow. The water balance over the whole flow sheet needs to be considered, especiaUy for divided ceUs where membranes transport a number of moles of water per Earaday. At the inception of a proposed electroorganic process, the product recovery and refining should be included in the evaluation to determine tme viabUity. Thus early ceU work needs to be carried out with the preferred electrolyte/solvent and conversion. The economic aspects of product recovery strategies have been discussed (89). Some process flow sheets are also available (61). 

It is clear from Table 7 that the undivided cell has considerable power usage savings over the divided cell operation. Also, there are no membrane costs, and cell fabrication is much cheaper. In addition, it was possible to simplify the product recovery in the undivided cell process. 

Evaporation. In most chemical industry evaporation systems, the objective is product recovery, although occasionally the objective is concentration of an organic waste from an aqueous solution, to facihtate incineration. Similar equipment is used extensively for desalination of salt or brackish water (see also Water, supply and desalination). 

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