Recovering

The rate at which the catalyst is lost or degrades has a major influence on the design. If degradation is rapid, the catalyst needs to be regenerated or replaced on a continuous basis. In addition to the cost implications, there are also environmental implications, since the lost or degraded catalyst represents waste. While it is often possible to recover useful materials from degraded catalyst and to recycle those materials in the manufacture of new catalyst, this still inevitably creates waste, since the recovery of material can never be complete. 

When used to separate solid-solid mixtures, the material is ground to a particle size small enough to liberate particles of the chemical species to be recovered. The mixture of solid particles is then dispersed in the flotation medium, which is usually water. Gas bubbles become attached to the solid particles, thereby allowing them to float to the surface of the liquid. The solid partices are collected from the surface by an overflow weir or mechanical scraper. The separation of the solid particles depends on the different species having different surface properties such that one species is preferentially attached to the bubbles. A number of chemicals are added to the flotation medium to meet the various requirements of the flotation process ... 

Single-stage evaporators tend only to be used when the capacity needed is small. It is more usual to employ multistage systems which recover and reuse the latent heat of the vaporized material. Three... 

The shaded areas in Fig. 6.24, known as pockets, represent areas of additional process-to-process heat transfer. Remember that the profile of the grand composite curve represents residual heating and cooling demands after recovering heat within the shifted temperature intervals in the problem table algorithm. In these pockets in Fig. 6.24, a local surplus of heat in the process is used at temperature differences in excess of AT ,in to satisfy a local deficit. ... 

Additional separation and recycling. Once the possibilities for recycling streams directly, feed purification, and eliminating the use of extraneous materials for separation that cannot be recycled efiiciently have been exhausted, attention is turned to the fourth option, the degree of material recovery from the waste streams that are left. One very important point which should not be forgotten is that once the waste stream is rejected, any valuable material turns into a liability as an effluent material. The level of recovery in such situations needs careful consideration. It may be economical to carry out additional separation of the valuable material with a view to recycling that additional recovered material, particularly when the cost of downstream effluent treatment is taken into consideration. 

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... 

If air is used as stripping agent, further treatment of the stripped material will be necessary. The gas might be fed to an incinerator or some attempt made to recover material by use of adsorption. 

Z. Evaporation. If the wastewater is in low volume and the waste material involatile, then evaporation can be used to concentrate the waste. The relatively pure evaporated water might still require biological treatment after condensation. The concentrated waste can then be recycled or sent for further treatment or disposal. The cost of such operations can be prohibitively expensive unless the heat available in the evaporated water can be recovered. 

By comparison, Fig. 13.36 shows an exothermic reactor integrated below the pinch. Although heat is being recovered, it is being recovered into part of the process which is a heat source. The hot utility requirement cannot be reduced because the process above the pinch needs at least Q//m-,n to satisfy its enthalpy imbalance. 

Theoretically, in contrast with fixed investment, this money is not lost but can be recovered when the process is closed down. 

Ultimately, the process might be permanently shut down or given a major revamp. This marks the end of the project, H. If the process is shut down, working capital is recovered, and there may be salvage value, which would create a final cash inflow at the end of the project. 

In theory, the catalyst can be recovered chemically unchanged at the end of the reaction, although it may be changed physically. 

C, b.p. 81"C. Manufactured by the reduction of benzene with hydrogen in the presence of a nickel catalyst and recovered from natural gase.s. It is inflammable. Used as an intermediate in the preparation of nylon [6] and [66] via caprolactam and as a solvent for oils, fats and waxes, and also as a paint remover. For stereochemistry of cyclohexane see conformation. U.S. production 1980 1 megatonne. 

C, b.p. 156 C. The most important of the terpene hydrocarbons. It is found in most essential oils derived from the Coniferae, and is the main constituent of turpentine oil. Contains two asymmetric carbon atoms. The (- -)-form is easily obtained in a pure state by fractionation of Greek turpentine oil, of which it constitutes 95%. Pinene may be separated from turpentine oil in the form of its crystalline nitrosochloride, CioHigClNO, from which the ( + )-form may be recovered by boiling with aniline in alcoholic solution. When heated under pressure at 250-270 C, a-pinene is converted into dipentene. It can be reduced by hydrogen in the presence of a catalyst to form... 

Ultrasonic absorption is used in the investigation of fast reactions in solution. If a system is at equilibrium and the equilibrium is disturbed in a very short time (of the order of 10"seconds) then it takes a finite time for the system to recover its equilibrium condition. This is called a relaxation process. When a system in solution is caused to relax using ultrasonics, the relaxation lime of the equilibrium can be related to the attenuation of the sound wave. Relaxation times of 10" to 10 seconds have been measured using this method and the rates of formation of many mono-, di-and tripositive metal complexes with a range of anions have been determined. 

Figure 1.1 illustrates the diversity of products derived from petroleum classified according to their distillation ranges and number of carbon atoms. From one crude to another, the proportions of the recovered fractions vary widely. A good illustration is the gasoline fraction (one of the most economically attractive) a crude from Qatar gives about 37 per cent by volume whereas a Boscan crude oil only yields 4.5%. 

One distinguishes preparatory distillations that are designed to separate the fractions for subsequent analysis from non-preparatory analytical distillations that are performed to characterize the feed itself. For example, the distillation curve that gives the recovered volume or weight as a function of the distillation temperature characterizes the volatility of the sample. 

Sample size is 100 ml and distillation conditions are specified according to the type of sample. Temperature and volume of condensate are taken simultaneously and the test results are calculated and reported as boiling temperature as a function of the volume recovered as shown in Table 2.1. 

The procedure most commonly employed (NF M 07-047 or ASTM D 2274) Is to age the diesel fuel for 16 hours while bubbling oxygen into it at 95°C. The gums and sediment obtained are recovered by filtration and weighed. There is no official French specification regarding oxidation stability however, in their own specifications, manufacturers have set a maximum value of 1.5 mg/100 ml. 

This process thus enables gasoline production to be increased if the propylene can not be used for petrochemical manufacture. It recovers ethylene economically from fuel-gas. 

The sulfur vapor is condensed and recovered in the liquid or solid form. 

As decommissioning approaches, enhanced recovery e.g. chemical flooding processes are often considered as a means of recovering a proportion of the hydrocarbons that remain after primary production. The economic viability of such techniques is very sensitive to the oil price, and whilst some are used in onshore developments they can rarely be justified offshore at current oil prices. 

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