TABLE OF CONTENTS So far we have looked at ways of finding energy and cost targets, designing heat exchanger networks and choosing appropriate utilities for a given set of stream data, either from an existing process or from a proposed flowsheet for a new plant. But what would happen if we change the operating conditions on the plant? For example, we may wish to run a distillation column at a slightly different pressure and temperature. The streams associated with the column will also change in temperature, so the set of stream data will change. As a result, the energy and cost targets and the heat exchanger network will also be different. Indeed, can we find a way to systematically change the process conditions in order to reduce the overall energy targets?
Whether we are designing a new plant or trying to improve an existing one, there will often be a range of operating conditions that could be used. Of course, it would be possible to obtain targets for all the different possible conditions by simply repeating the problem table analysis each time. However, this trial and error method is time consuming and does not really improve our understanding of the process.
We want to know how a change in the conditions of one stream will affect the energy use of the overall plant, and to find the optimum new conditions. Pinch technology allows us to achieve this, using what is known as process change analysis.
Process change is defined as...
