Rich composite stream

Having represented the individual rich streams, we are now in a position to construct the rich composite stream. A rich composite stream represents the cumulative mass of the pollutant lost by all the rich streams. It can be readily obtained by using the diagonal nile for superposition to add up mass in the overlapped regions of streams. Hence, the rich composite stream is obtained by applying linear superposition to all the rich streams. Figure 3.4 illustrates this concept for two rich streams. 

Next, a global representation of all process lean streams is developed as a lean composite stream. First, we establish Ns/> lean composition scales (one for each process MSA) that are in one-to-one coirespondence with the rich scale according to the method outlined in Section 3.5. Next, the mass of pollutant that can be gained by each process MSA is plotted vei us the composition scale of that MSA. Hence, each i xx ess MSA is represented as an arrow extending between supply and target compositions (see Fig. 3.5 for a two-MSA example). Ihe vertical distance between the arrow head and tail is given by... 

Common synthetic-based raw materials for surfactant production include ethylene, and propylene. Crude oil consists of a complex mixture of long chain hydrocarbons and aromatic molecules. Natural gas is a mixture of short chain hydrocarbons rich in methane, ethane, propane, and butane. The exact composition of both depends on its source and how it has been processed. Ethylene and propylene are produced by thermal or catalytic cracking of natural gas or aromatic rich petroleum streams. 

This problem can be stated generally as follows given are a set of rich process streams Ri (i= 1,2,... its flow rates, G its supply inlet compositions yi"p and its target outlet compositions. Given also are a set of lean streams 5) (/-1,2,...,A(s), its maximal... 

To display the results of the Cl method graphically. Table 11.2 is used to prepare the rich composite curve, which combines curves R1 and R2 in Figure 11.6a into one composite curve. Beginning with zero mass of solute at y = 0.(XX)3, the lowest mass fraction of a rich stream, and using Table 11.2, the cumulative mass of solute removed at the interval mass fractions are... 

The destruction of sarin (GB) in the EDS using aqueous MEA (45 percent) as the treatment chemical produces an organic-rich neutralent stream, as described in Chapter 2. The postireatment of this neutralent stream is the focus of this report, but there are also other liquid waste streams that must be dealt with. The other streams result from the riusing of the EDS chamber with water after each use to remove residual MEA and soUd residues and the cleaning to remove other solid and liquid residues. These waste streams must also be prepared for ultimate disposal unless their compositions meet the feed requirements for an on-site treatment works. The diverse nature of these waste streams is illustrated in Table C-1. 

The dehydration of relatively pure carbon dioxide is of increasing interest because of its use in enhanced oil recovery (EOR) projects. These projects often require the transmission of CO2 as supercritical fluid from the production facility to the consuming locations. As with natural gas transmission, dehydration is normally required to prevent corrosion and/or hydrate formation in the transmission lines and downstream equipment. Unlike natural gas, the saturated water content of carbon dioxide increases with increased pressure at pressures above about 1,000 psia. This effect is shown in Figure 11-4 (Case et al., 1985). A much more detailed discussion of the variation of water content of C02-rich gas streams with temperature, pressure, and composition is given by Diaz et al. (1991). 

The flow directions in a PSA process are fixed by the composition of the stream. The most common configuration is for adsorption to take place up-flow. AH gases with compositions rich in adsorbate are introduced into the adsorption inlet end, and so effluent streams from the inlet end are rich in adsorbate. Similarly, adsorbate-lean streams to be used for purging or repressurizing must flow into the product end. 

Table 8. Typical Compositions of By-Product Hydrogen-Rich Stream ...

The two condensate Hquids must be used to provide reflux and distiUate streams. NormaHy, the reflux ratio, r, is chosen so that r = L jD > (j). This requires that the reflux rate be greater than the condensation rate of entrainer-rich phase and that the distiUate rate be correspondingly less than the condensation rate of entrainer-lean phase. This means that the distiUate stream consists of pure entrainer-lean phase, ie, Xj = x, and the reflux stream consists of aU the entrainer-rich phase plus the balance of the entrainer-lean phase. Thus, the overall composition of the reflux stream, Hes on the... 

Example 4 Calculation of the BP Method Use the BP method with the SRK eqiiation-of-state for K values and enthalpy departures to compute stage temperatures, interstage vapor and hqiiid flow rates and compositions, and rehoiler and condenser duties for the light-hydrocarhon distdlation-coliimn specifications shown in Fig. 13-51 with feed at 260 psia. The specifications are selected to obtain three products, a vapor distillate rich in Cri and C3, a vapor side-stream rich in n-C4, and a bottoms rich in n-C and n-Cg. 

As has been previously mentioned, the minimum TAC can be identified by iteratively varying e. Since the inlet and outlet compositions of the rich stream as well as the inlet composition of the MSA are fixed, one can vary e at the rich end of the exchanger (and consequently the outlet composition of the lean stream) to minimize the TAC of the system. In order to demonstrate this opdmization procedure, let us first select a value of e at the rich end of the exchanger equal to 1.5 X 10 and evaluate the system size and cost for this value. 

As can be seen from Fig, 3.7, the pinch decomposes the synthesis problem into two regions a rich end and a lean end. The rich end comprises all streams or parts of streams richer than the pinch composition. Similarly, the lean end includes all the streams or parts of streams leaner than the pinch composition. Above the pinch, exchange between the rich and the lean process streams takes place. External MSAs are not required. Using an external MSA above the pinch will incur a penalty of eliminating an equivalent amount of process lean streams from service. On the other hand, below the pinch, both the process and the external lean streams should be used. Furthermore, Fig. 3.7 indicates that if any mass is transferred across the pinch, the composite lean stream will move upward and, consequently, external MSAs in excess of the minimum requirement will be used. Therefore, to minimize the cost of external MSAs, mass should not be transferred across the pinch. It is worth pointing out that these observations are valid only for the class of MEN problems covered in this chapter. When the assumptions employed in this chapter are relaxed, more general conclusions can be made. For instance, it will be shown later that the pinch analysis can still be undertaken even when there are no process MSAs in the plant. The pinch characteristics will be generalized in Chapters Five and Six. 

Material balance for each rich stream around composition intervals ... 

Given a number Nr of waste (rich) streams and a number Ns of lean streams (physical and reactive MSAs), it is desired to synthesize a cost-effective network of physical and/or reactive mass exchangers which can preferentially transfer a certain undesirable species. A, from the waste streams to the MSAs whereby it may be reacted into other species. Given also are the flowrate of each waste stream, G/, its supply (inlet) composition, yf, and target (outlet) composition, yj, where i = 1,2,..., Nr. In addition, the supply and target compositions, Xj and x j, are given for each MSA, where j = 1,2, Ns. TTie flowrate of any lean stream, Ly, is unknown but is bounded by a given maximum available flowrate of that stream, i.e.. 

Now that a procedure for establishing the corresponding composition scales for the rich lean pairs of stream has been outlined, it is possible to develop the CID. The CID is ccHistructed in a manner similar to that described in Chapter Five. However, it should be noted that the conversion among the corresponding composition scales may be more laborious due to the nonlinearity of equilibrium relations. Furthermore, a lean scale, xj, represents all forms (physically dissolved and chemically combined) of the pollutant. First, a composition scale, y, for component A in... 

There are several gaseous wastes emitted from the process (see Dunn and El-Halwagi, 1993, and Homewoik Problem 8.5). In this exanqile, we focus on the gaseous waste leaving the multiple effect evaporators, R, whose primary pollutant is H2S. Stream data for this waste stream are given in Ihble 8.1. A rich-( ase minimum allowable composition difference, of 1.5 x 10 ° kmol/m is used. 

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