Environmental Factors in Process Design

The selection of reaction pathways to reduce byproduct toxicity is a key consideration when a design team creates specific problems from a primitive problem, and during preliminary 

To reduce the possibilities for accidents and spills, with their adverse environmental consequences, processes are often designed to reduce the number of transient operations, clean-up periods, and catalyst regeneration cycles. In other words, emphasis is on the design of a process that is easily controlled at or near a nominal steady state, with reliable controllers and effective fault-detection sensors. 

Environmental objectives are normally not well defined because economic objective functions normally involve profitability measures, whereas the value of reduced pollution is not easily quantified by economic measures. As a consequence, design teams often formulate mixed objective functions that attempt to express environmental improvements in financial terms. In other cases, the team may settle for the optimization of an economic objective function, subject to bounds on the concentrations of the solutes in the waste streams. It is important to assess whether the constraints are hard (not allowed to be violated) or soft (capable of being violated under unusual circumstances). Emphasis must be placed on the formulation of each constraint and the extent to which it must be honored. 

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