Raw material recovery

Raw material recovery can be achieved through solvent extraction, steam-stripping, and distillation operations. Dilute streams can be concentrated in evaporators and then recovered. Recently, with the advent of membrane technology, reverse osmosis (RO) and ultrafiltration (UF) can be used to recover and concentrate active ingredients [14]. 

Much more complex substances than water should be considered for recycling. These would include the reuse of solvents, cleaning compounds, and. in some instances, using traditional waste components as sources of raw materials. Recovery of valuable materials from wastes may prove less expensive than procuring the same substance from a supplier. 

H. Bockhom, A. Homung, and U. Homnng, Stepwise pyrolysis for raw material recovery from plastic waste, J. Anal. Appl. Pyrolysis, 46, 1, (1998). 

H. Bockhorn, A. Homung and U. Homung, Stepwise Pyrolysis for Raw Material Recovery from Plastic Waste, J. Anal. Appl. Pyrol, 46, 1-13 (1998). 

Other materials in waste that is thermally processed also were studied by pyrolytic techniques, typically with the purpose of regenerating the monomers or of obtaining other useful small molecules. For example, pyrolytic studies were performed for the evaluation of the possibilities for re-utilization of nylon carpet waste [7], the recycling of thermoset polymeric composites [8], the recovery of methyl methacrylate from poly(methyl methacrylate) waste [9], as well as for other raw material recovery from pyrolysis of plastic waste [10]. The results of incineration of various other types of waste also were studied at model scale [11, 12). These studies were applied to specific waste materials associated with the manufacturing process or to municipal solid waste [13-15)... 

Stahlberg, R., Feuerriegel, U., and Runyon, D. J., Thermoselect-energy and raw materials recovery process foundation for the continuous conversion of wastes, in Proceedings of the 1995 International Incineration Conference, Bellevue, WA, May, 1995, 535. 

Traditional fermentation generally involves many process steps which are inefficient and uneconomical in terms of utilization of raw materials,recovery of product, and energy consumption. Continuous cross-flow membrane micro-filtration and ultrafiltration, when correctly introduced, have been shown to improve this process significantly. 

As part of the discussion on the use of textile construction membranes, it should be made clear what happens at end-of-Ufe for materials used so far for building construction. Thermoplastic membrane components like PVC can be processed after each utilization period under certain conditions and be supplied for reuse in the raw material cycle. Leading European manufacturers of PVC/PES membranes and roofing sheets have united in order to recycle post-consumer waste, disused membranes and PVC materials (ref. Vinyl) in most modem plants with approved thermo-physical procedures. The output of this recycling process is then used for new products. An important factor in the operation of these and other environmental raw-material recovery procedures is logistics, which includes the materials being carefully prepared and sorted prior to delivery. The processing plants are potentially able to achieve a turnover of more than one ton per hour (ref. recovinyl). 

Figure 21.1. Schematic diagram of raw material recovery from waste cellophane. [Adapted from Monk D W,...

The above described process is an in-process recovery of raw materials, which are used for production of a final product. Such processes are developed in industry to make technology more efficient or to reduce waste. In fabric coaling, the edge trimming produces 6 to 10% of all wastes. Recovery of raw materials is essential for the coated fabric industry. This initiated munerous attempts in developing plasticizer (among other raw materials) recovery systems based on the solvent extraction or the steam distillation processes. Two reasons hinder the use of these processes economy and quality of the plasticizer. Production usually involves several different plasticizers, which are difficult and costly to separate. ... 

Reduce the carbon footprint associated with the production of building materials, and reduce the energy consmned in conventional raw materials recovery (clay, clay sand, feldspar, etc.) ... 

Though MOM deprivation product 2.2.21 was accidentally obtained, it was still useful to test two key reactions for total synthesis Wessely oxidative dearomatization reaction and intramolecular Diels-Alder reaction (Fig. 2.20). A pair of diethyl phthalate derivative 2.2.22 with the ratio of 2 1 and 95 % yield could be obtained from phenol 2.2.21 in acetic acid solvent with the presence of lead tetraacetate at room temperature after 5 min. Then, we tried intennolecular Diels-Alder reaction. Unfoitunately, both substrate 2.2.22 and dimethyl acetylene dicarboxylate were not producing Diels-Alder product 2.2.23 under toluene refluxing or sealing mbe heating conditions, only gave the results of raw material recovery. 

Figure 10.7 shows the basic tradeoff to be considered as additional feed and product materials are recovered from waste streams and recycled. As the fractional recovery increases, the cost of the separation and recycle increases. On the dther hand, the cost of the lost materials decreases. It should be noted that the raw materials cost is a net cost, which means that the cost of lost materials should be adjusted to either... 

Figure 10.7 shows that the tradeoff between separation and net raw materials cost gives an economically optimal recovery. It is possible that significant changes in the degree of recovery can have a significant effect on costs other than those shown in Fig. 10.7 (e.g., reactor costs). If this is the case, then these also must be included in the tradeoffs. 

Figure 10.7 Effluent treatment costs should be included with raw materials costs when traded off against separation costs to obtain the optimal recovery. (From Smith and Petela, Chem. Eng., 513 24, 1991 reproduced by permission of the Institution of Chemical Engineers.)...

Commercial production of acetic acid has been revolutionized in the decade 1978—1988. Butane—naphtha Hquid-phase catalytic oxidation has declined precipitously as methanol [67-56-1] or methyl acetate [79-20-9] carbonylation has become the technology of choice in the world market. By-product acetic acid recovery in other hydrocarbon oxidations, eg, in xylene oxidation to terephthaUc acid and propylene conversion to acryflc acid, has also grown. Production from synthesis gas is increasing and the development of alternative raw materials is under serious consideration following widespread dislocations in the cost of raw material (see Chemurgy). 

The procedure is technically feasible, but high recovery of unconverted raw materials is required for the route to be practical. Its development depends on the improvement of catalysts and separation methods and on the avaHabiUty of low cost acetic acid and formaldehyde. Both raw materials are dependent on ample supply of low cost methanol. 

Generally, for most fermentation processes to yield a good quality product at a competitive price, at least six key criteria must be met. (/) Fermentation is a capital intensive business and investment must be minimised. (2) The raw materials should be as cheap as possible. (J) Only the highest yielding strains should be used. (4) Recovery and purification should be as rapid and as simple as possible. (5) Automation should be employed to minimise labor usage. (6) The process must be designed to minimise waste production and efftciendy use all utilities (26,27). 

Alternative Processes. Because of the large quantity of phosphate rock reserves available worldwide, recovery of the fluoride values from this raw material source has frequently been studied. Strategies involve recovering the fluoride from wet-process phosphoric acid plants as fluosiUcic acid [16961-83-4] H2SiFg, and then processing this acid to form hydrogen fluoride. 

Proof of the existence of benzene in the light oil derived from coal tar (8) first estabHshed coal tar and coal as chemical raw materials (see Eeedstocks, COAL chemicals). Soon thereafter the separation of coal-tar light oil into substantially pure fractions produced a number of the aromatic components now known to be present in significant quantities in petroleum-derived Hquid fuels. Indeed, these separation procedures were for the recovery of benzene—toluene—xylene (BTX) and related substances, ie, benzol or motor benzol, from coke-oven operations (8) (see BTX processing). 

For environmental reasons, the entire process is handled by enclosed equipment. Lead recoveries of 96% can be obtained from the raw materials, and sulfur dioxide gas released in the process is used to produce sulfuric acid. Four plants are in operation as of 1994. Three are in Russia and one is in Italy. 

Condensable Hquids also are recovered from high pressure gas reservoirs by retrograde condensation. In this process, the high pressure fluid from the reservoir produces a Hquid phase on isothermal expansion. As the pressure decreases isotherm ally the quantity of the Hquid phase increases to a maximum and then decreases to disappearance. In the production of natural gas Hquids from these high pressure wells, the well fluids are expanded to produce the optimum amount of Hquid. The Hquid phase then is separated from the gas for further processing. The gas phase is used as a raw material for one of the other recovery processes, as fuel, or is recompressed and returned to the formation. 

Table 1 gives the average metal content of the earth s cmst, ore deposits, and concentrates. With the exceptions of the recovery of magnesium from seawater and alkaU metals from brines, and the solution mining and dump or heap leaching of some copper, gold, and uranium (see Uranium and uranium compounds), most ores are processed through mills. Concentrates are the raw materials for the extraction of primary metals. 

MPa (15—20 atm), 300—400 kg benzene per kg catalyst per h, and a benzene ethylene feed ratio of about 30. ZSM-5 inhibits formation of polyalkjlated benzenes produced with nonshape-selective catalysts. With both ethylene sources, raw material efficiency exceeds 99%, and heat recovery efficiency is high (see Xylenes and ethylbenzene). 

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. 

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