Rich stream

A differential countercurrent contactor operating with a dilute solution of the consolute component C and immiscible components A and B is shown in Figure 8. Under these conditions, the superficial velocities of the A-rich and B-rich streams can be assumed not to vary significantly with position in the contactor, and are taken to be and Ug, respectively. The concentration of C in the A-rich stream is and that in the B-rich stream is C-. ... 

Gaseous Effluents. Twenty percent of the carbon disulfide used in xanthation is converted into hydrogen sulfide (or equivalents) by the regeneration reactions. Ninety to 95% of this hydrogen sulfide is recoverable by scmbbers that yield sodium hydrogen sulfide for the tanning or pulp industries, or for conversion back to sulfur. Up to 60% of the carbon disulfide is recyclable by condensation from rich streams, but costly carbon-bed... 

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

Once again, because of the unified approach of this text to all mass-exchange operations it i.s important to emphasize that the symbols G and L will be used to designate the flowrates of the rich stream and the MSA, respectively and not necessarily flowrates of gas and liquid. 

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. 

Figure 3.3 Representation of mass exchanged by two rich streams.

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. 

In order to synthesize an optimal MEN for intercepting the off-gas condensate, we constnict the pinch diagram as shown in Fig. 4.9. Since the three MSA s lie completely to the left of the rich stream, they are all thermodynamically feasible. Hence, we choose the one with the least cost ( /kg NH3 removed) namely the resin. The annual operating cost for removing ammonia using the resin is ... 

Immediately above the pinch, the number of rich streams is equal to the number of the MSAs, thus the feasibility criterion given by Eq. (5.8a) is satisfied. The second feasibility criterion (Eq. 5.12a) can be checked through Fig. 5.7. By comparing the values of with G, for each potential pinch match, one can readily deduce that it is feasible to match Si with either R or R2 immediately above the pinch. Nonetheless, while it is possible to match S2 with R2, it is infeasible to pair S2 with R] immediately above the pinch. Therefore, one can match Si with Ri and S2 with R2 as rich-end pinch exchangers. 

Stream Data for the COG-Sweeteaing Problem Rich Stream MSAs... 

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.. 

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