TABLE OF CONTENTS In many cases, it is useful to determine the potential improvement in the performance of a whole process or sections of the process without actually developing the details of the solution. In this context, the concept of targeting is very useful. Targeting is aimed at benchmarking the performance of a process ahead of detailed design and without commitment to the specific details of the strategies leading to improvement. This a priori approach ensures that the process capabilities are explored without exhausting the designer s time and effort. Examples of important mass targets include minimum consumption of material utilities (solvents, water, etc.), minimum discharge of wastes, minimum purchase of fresh raw materials, minimum production of undesirable byproducts, and maximum sales of desirable products.
To illustrate the concept of overall mass targeting, let us start by considering the objective of minimizing the discharge of a waste. Later, other objectives will be discussed.
Consider the case when it is desired to determine the target for minimizing the load of a discharged species (e.g., pollutants in effluents). Three sets of data for that species are first collected: fresh usage, generation/depletion, and terminal discharge. The fresh usage (F) corresponds to the quantity of the targeted species in streams entering the process (the waste stream may have entered the process as a fresh feedstock or a material utility). Within any process, several phenomena contribute to the net balance of a species. Generation (G) refers to the net amount...
