Cost of recovery

Solution Casting. The production of unsupported film and sheet by solution casting has generally passed from favor and is used only for special polymers not amenable to melt processes. The use of solvents was generally very hazardous because of their flammabiUty or toxic nature. The cost of recovery and disposal of solvents became prohibitive for many lower price film appHcations. The nature of the drying operations leads to problems with solvent migration and retention that are not problems with melt-processed polymers. 

Absorption. Oil absorption is another process used for recovery of LPG and natural gas Hquids from natural gas. Recovery is enhanced by loweriag the absorption temperature to —45°C and by keeping the molecular weight of the absorption oil down to 100. Heat used to separate the product from the absorption oil contributes to the cost of recovery. Therefore, this process has become less competitive as the cost of energy has iacreased. A simplified flow diagram of a typical oil-absorption process is shown ia Figure 2. 

Economic Aspects. To be useful the raw materials must be recoverable at a cost not greater than the cost of similar terrestrial materials. These costs must include transportation to the point of sale. Comparative costs of recovery are strongly influenced by secondary environmental or imputed costs, such as legal costs or compensatory levies. 

Lithocholic add costs 2 or 3 times more than cholesterol. Thus, although the yields are slightly lower with cholesterol, it is cheaper to use it Furthermore, cholesterol is more widely available and in greater quantities than lithocholic add. These two factors tend to favour the use of cholesterol. Lithocholic add does have the advantages, however, of being more water soluble and is, therefore, more easily supplied to cultures in aqueous media. The costs of recovery of die desired product from the reaction brew are also commercially important. The point we are making in this in-text activity is that in selecting a substrate we need to consider more than simply the conversion effidency and the cost of the substrate. 

By manipulating the genetic machinery of the cell, it is possible to cause most cellular systems to produce virtually any biochemical material. Unfortunately, the growth of cellular systems (particularly in tissue cultures) is constrained by end-product inhibition and repression hence, it is difficult to produce end products in high concentration. Furthermore, cells are always grown in aqueous solution, so biochemicals produced by cellular routes must have intrinsically high value in order for the cost of recovery from dilute aqueous solution to be minimized. Thus, most biochemicals of commercial interest... 

The cost of recovery will be reduced if the streams are located conveniently close. The amount of energy that can be recovered will depend on the temperature, flow, heat capacity, and temperature change possible, in each stream. A reasonable temperature driving force must be maintained to keep the exchanger area to a practical size. The most efficient exchanger will be the one in which the shell and tube flows are truly countercurrent. Multiple tube pass exchangers are usually used for practical reasons. With multiple tube passes the flow will be part counter-current and part co-current and temperature crosses can occur, which will reduce the efficiency of heat recovery (see Chapter 12). 

Cost of recovery 2.2 + 1.8/J1-xa, /kmol of A The problem is to find the feed rate na0 and the fractional conversion xa for the maximum profit rate. 

One critical issue is the evaluation alternative. In the case of methanolysis, the alternatives are to make DMT and EG by depolymerization or secure materials from traditional petrochemical sources. For hydrolysis, the alternatives are TPA and EG by depolymerization or from traditional sources. For both technologies, the amount of copolymerizing isophthalate and/or 1,4-cyclohexane dimethanol is likely to be too little to justify the cost of recovery. For the various forms of glycolysis and the methanolysis/BHET hybrid, the alternative is the BHET and BHET-like materials made by the combination of a terephthalate and isophthalate plus EG and various glycols. Market prices exist for TPA and EG. BHET is not an item of commerce, and so the value must be imputed from the market price for TPA (the modern terephthaloyl) and EG, plus a conversion cost. 

There is no current commercial biologic process for the production of succinic acid. In past laboratory systems, when succinic acid has been produced by fermentation, lime is added to the fermentation medium to neutralize the acid, yielding calcium succinate (2). The calcium succinate salt then precipitates out of the solution. Subsequently, sulfuric acid is added to the salt to produce the free soluble succinic acid and solid calcium sulfate (gypsum). The acid is then purified with several washings over a sorbent to remove impurities. The disposal of the solid waste is both a directly economic and an environmental concern, as is the cost of the raw materials. Some key process-related problems have been identified as follows (1) the separation of dilute product streams and the related costs of recovery, (2) the elimination of the salt waste from the current purification process, and (3) the reduction of inhibition to the product succinic acid on the fermentation itself. Acetic acid is also a byproduct of the fermentation of glucose by Anaerobiospirillium succiniciproducens almost 1 mol of acetate will be produced for every 2 mol of succinate (3). Under certain cultivation conditions by a mutant Escherichia coli, lesser amounts of acetate can be produced (4,5). This byproduct will also need to be separated. 

The higher values correspond to the situation of high oil price and import parity pricing for propane. The lower end expresses the situation where propane is priced on a cost of recovery basis from large gas plants in the Middle East. These figures clearly indicate the competitive advantage of the latter operations. 

The cost of recovery will be reduced if the streams are located conveniently close. 

Although the dilute sources of carbon dioxide make up the greatest volume of available feed stock, the cost of recovery can be a significant component of the overall cost of a reaction process using such CO2. As membrane separation processes are further developed, they may become the most cost effective route for recovery and utilization of point source generated carbon dioxide. 

Cost of recovery of the precious metal from the spent catalyst. 

Nakatsuka and Ase (1995) found backwash most effective if the backwash pressure is more than double the operating pressure. An increase in crossflow velocity also lead to higher flux, but at the cost of higher energy consumption. Hagmeyer et al. (1996) optimised the backwash interval to 30 sec every 30 minutes. Efficiency could be further increased with the duration and frequency, but at the cost of recovery. 

In making a case on specification matters, the solvent recoverer needs to be able to predict, possibly before samples are available for test, the cost of recovery of a solvent to any required standard, since it is only by so doing that the true economics of, say, reducing water content may be calculated for the whole circuit of production and recovery. This is now possible in most cases. The properties of most binary solvent mixtures are known or can be estimated with reasonable accuracy. More complex mixtures often resolve themselves into binaries in the crucial areas and, for many ternaries, the information is in the literature. It is therefore possible for the solvent recoverer to play a part in the decisionmaking process rather than be presented with a solvent mixture that is impossible to recover but cannot be altered. 

One can expect to achieve, in selling recovered solvent, 70-80% of the virgin solvent price. The cost of recovery, not including transport, will typically lie in the range 150-300/Te so that the cheaper solvents will have a negative value loaded on transport at the solvent user s works. 

Until recently 96% of all discarded electrical and electronic equipment in Europe was landfilled. This amounted to about 14 kg of equipment per inhabitant every year, and the practice is now to be banned. All post-consumer electrical and electronic products will have to be collected and subjected to specific disposal procedures. The WEEE Directive (2002/96/EC) (February 2003) requires the manufacturers of electrical and electronic equipment appliances to bear the cost of recovery and recycling. It is intended to ensure the recovery of 300,000 tonnes of electrical and electronic plastics waste material per year by 2006, the date by which each member state should be collecting 4 kg per inhabitant by separate collection procedures. 

The best contemporary method of solvent recovery is its adsorption on active carbon [13,14], In a properly designed equipment the cost of recovery should not exceed 5-20% of the solvent cost. The method is particularly suitable for mixtures with low concentration of a solvent. The operational costs depend on the solvent, process conditions, size and construction of the equipment and the degree of recovery [15, 16]. 

The cost (actually a negative cost) of recovery of condensed and decanted solvent was taken to be the commercial value of the solvent produced per hour from either lip vent exhausts or vented from purging of the work chamber in an enclosed vapor degreaser. This cost was the mass recovered by the activated carbon, expressed on an overall hourly basis, times the following purchase prices 0.60 /lb (toluene), 3.50 (n-propyl bromide), 0.80 (perchloroethylene), 0.34 (methylene chloride), 0.61 (trichloroethylene), and 25.00 (CFC-113). The latter price is hypothetical. 

Mechanical recovery is the most commonly used oil spill response technique. This technique physically removes oil from the water surface, even in the presence of ice [35]. Unlike other cleanup techniques, mechanical recovery can be efficiently applied to treat emulsified oils as well as oils of variable viscosities. A weakness of mechanical cleanup is the recovery rate. It may be very time consuming and expensive when employed on a large scale, and require a large amount of personnel and equipment, and every additional hour of cleanup time can significantly increase the cost of recovery. A more efficient recovery device can thus reduce the cost significantly and reduce the risk of oil reaching the shoreline [31, 36]. 

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