TABLE OF CONTENTS An organic pollutant is to be removed from a wastewater stream. The flowrate of the waste stream is 20 kg/s and its inlet composition of toluene is 330 ppmw. It is desired to reduce the toluene composition in water to 30 ppmw. Three external MSAs are considered: air ( S 1) for stripping, activated carbon ( S 2) for adsorption, and a solvent extractant ( S 3). The data for the candidate MSAs are given in Table 4-5. The equilibrium data for the transfer of the pollutant from the waste stream to the j th MSA is given by
where y 1 and x j are the mass fractions of the toluene in the wastewater and the j th MSA, respectively.
| Stream | Upper bound on flowrate (kg/s) | Supply composition (ppmw) | Target composition (ppmw) | m j | ? j (ppmw) | C j ($/kg MSA) |
|---|---|---|---|---|---|---|
| S 1 | ? | 0 | 9000 | 0.015 | 5000 | 3.1x10 ?3 |
| S 2 | ? | 70 | 8000 | 0.001 | 15,000 | 0.08 |
| S 3 | ? | 50 | 2100 | 0.002 | 10,000 | 0.06 |
Use the pinch diagram to determine the minimum operating cost of the MEN.
SOLUTION
Based on the given data and equation (4.54), we can calculate 
to be 0.344, 10.088, and 29.268 $/kg of pollutant removed for air, activated carbon, and extractant, respectively. Since air is the...
