Optimization recovery from waste streams

Optimization problems in process design are usually concerned with maximizing or minimizing an objective function. The objective function might typically be to maximize economic potential or minimize cost. For example, consider the recovery of heat from a hot waste stream. A heat exchanger could be installed to recover the waste heat. The heat recovery is illustrated in Figure 3.1a as a plot of temperature versus enthalpy. There is heat available in the hot stream to be recovered to preheat the cold stream. But how much heat should be recovered Expressions can be written for the recovered heat as ... 

After several runs of the electrolysis process, the active metal fission products such as alkali, alkaline earth and rare earth metals are accumulated in the molten salt. The accumulated fission products must be removed from the molten salt because they will affect the recovery efficiency of U and TRU. Periodically, the molten salt is removed from the electrolysis cell, purified using the salt purification process and recycled to the electrolysis cell. However, the molten salt always contains U and TRU with the fission products because the electrolysis is used to recover pure U and TRU without fission products. Therefore, fission products removed from the molten salt are always accompanied by some amount of U and TRU. It is necessary to optimize between the loss of U and TRU and the quantity of fission products removed because an increased removal of the fission products results in an increased contamination by the TRU in the waste stream. 

Leemann, M., Eigenberger, G., and Strathmann, H. (1996). Vapor permeation for the recovery of organic solvents from waste air streams Separation capacities and process optimization. J. Membr. Sci. 113, 313. 

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