Waste stream, composition

Waste stream composition and flow rate can be used to estimate the amount of raw materials lost as waste. The product of the amount lost to waste and the purchase price sets the incentive for pollution prevention in terms of raw material cost alone. 

Factors that influence the destruction efficiency include local temperatures and gas composition, residence time, extent of atomization of liquid wastes and dispersion of solid wastes, fluctuations in the waste stream composition and heating value, combustion aerodynamics, and turbulent... 

Zirconate pyrochlores have a low isomorphic capacity with respect tetravalent actinides. However the amount of isomorphic substitution can be increased by coupled substitution of Ca, according to the scheme 2REE = An" -i- Ca. Production of single phase ceramic can be attained only for actinide waste streams with rather simple chemical compositions. In the case of a complex waste stream composition, extra phases occur [129]. Finally, zirconate matrices require high temperatures for their synthesis. In order to prepare REE-zirconates from oxide mixtures, sintering at 1500-1600 for about 50 hours is required... 

The factors that must be taken into account in the selection of the equipment and, consequently, for efficient waste separation, are waste characteristics (particle size, waste stream composition, waste components density, moisture content, tendency for aggregation, etc.), products specifications, design parameters, and space requirements. The various types of air separators (air concentrators, Stoners) are the most widely used equipment. Heavy media separators are also used in some cases. 

Reverse osmosis employs a semipermeable membrane that allows passage of the solvent molecules, but not those of the dissolved organic and inorganic material. A pressure gradient is applied to cause separation of the solvent and solute. Any components that may damage or restrict the function of the membrane must be removed before the process is performed. Capital investment and operating costs depend on the waste stream composition. 

Chemical process []. You are a process engineer at a factory that produces chlorine soda. On the process line, a mixer is fed with 450 kg/h of a stream that contains a solution of 5 % w/w NaOH and 10 % w/w NaCl, and another stream of 550 kg/h that contains a solution of 7 % w/w NaOH and 8 % w/w NaCl. The resulting stream is fed to an evaporator in which the output stream is 20 % w/w NaOH. This stream is fed to a crystallizer/separator that produces two streams to eliminate the excess of NaCl solution. The scrap stream removes 70 % of the NaCl and contains no NaOH. The stream of product leaving the crystallizer/separator is composed of 30 % NaOH. Calculate (a) What is the performance of the process, expressed in kilograms of solution of product/kilograms of solution fed] (b) What is the composition and mass flow rate of the product stream (c) How much water evaporated in the process (d) What is the waste stream composition ... 

If the composition of the waste stream is known, then the theoretical oxygen demand can be calculated from the appropriate stoichiometric equations. As a first level of approximation, we can assume that this theoretical oxygen demand would be equal to the COD. Then, experience with domestic sewage indicates that the average ratio of COD to BOD will be on the order 1.5 to 2. The following example will help to clarify these relationships. 

The thermal degradation of mixtures of the common automotive plastics polypropylene, ABS, PVC, and polyurethane can produce low molecular weight chemicals (57). Composition of the blend affected reaction rates. Sequential thermolysis and gasification of commingled plastics found in other waste streams to produce a syngas containing primarily carbon monoxide and hydrogen has been reported (58). 

Residuals Produced The resulting effluent may contain dissolved inorganic salts at concentrations which may be unacceptable for discharge. Based on the chemical composition of the waste stream, a precipitate may be formed which may require removal and disposal. 

Segregation simply refers to avoiding the mixing of streams. In many cases, segregating waste streams at the source renders several streams environmentally acceptable and hence reduces the pollution-prevention cost. Furthermore, segregating streams with different compositions avoids unnecessary dilution of streams. This reduces the cost of removing the pollutant from the more concentrated streams. It may also provide composition levels that allow the streams to be recycled directly to process units. 

On a y-x (MeCabe-Thiele) diagram, this equation represents the operating line that extends between the points (y/", xj") and (y , x ) and has a slope of Ly/G,. Equation (2.10) has thitee unknowns, yf , Lj and xj . Let us first fix the outlet composition of the waste stream, yf". As depicted by Fig. 2.9, the maximum themetically attainable outlet composition of the MSA, xj", is in equilibrium with y ". An infinitely laige mass exchanger, however, will be needed to undertake... 

On the other hand, when x is fixed and yj" is left as an unknown, the minimum theoretically attainable inlet composition of the waste stream, yf" is in equilibrium with x " (Fig. 2.10), i.e. 

By employing a minimum allowable composition difference of j, at the lean end of the exchanger, one can identify the minimum practically feasible outlet composition of the waste stream to be y° which is given by... 

Typically, waste streams are either disposed of or forwarded to process sinks (equipment) for lecycle/reuse. In case of hnal discharge, the taiget composition of the undesirable species in each waste stream corresponds to the environmental regulations. On the other hand, if the intercepted waste stream is to be recycled to a process sink, its target composition should satisfy the constraints imposed by the process sink. 

Equation (3.5) can be used to establish a one-to-one correspondence among all composition scales for which mass exchange is feasible. Since most environmental applications involve dilute systems, one can assume that these systems behave ideally. Hence, the transfer of the pollutant is indifferent to the existence of other species in the waste stream. In other words, even if two waste streams contain species that are not identical, but share the same composition of a particular pollutant, the equilibrium composition of the pollutant in an MSA will be the same for both waste streams. Hence, a single composition scale, y, can be used to represent the concentration of the pollutant in any waste stream. Next, (3.5) can be employed to generate Ns scales for the MSAs. For a given set of corresponding composition scales y,x, X2,..., xj,..., it is thermodynamically and practically feasible to transfer the pollutant from any waste stream to any MSA. In addition, it is also feasible to transfer the pollutant from any waste stream of a composition y/ to any MSA which has a composition less than the xy obtained from (3.5b). 

On the pinch diagram, the vertical overlap between the two composite streams represents the maximum amount of the pollutant that can be transfeired from the waste streams to the process MSAs. It is referred to as the integrated mass... 

Optimizing the use of flie external MSA The pinch diagram (Fig. 3.12) demonstrates that below the pinch, the load of the waste stream has to be removed by the external MSA, S3. This renders the remainder of this example identical to Example 2.2. ThereftKc, the optimal flowrate of S3 is 0.0234 kg mol/s and the optimal outlet composition of S3 is 0.(X)85. Furthermore, the minimum total annualized cost of the benzene recovery system is 41,560/yr (see Fig. 2.13). 

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