Pinch Analysis

Developed in the past twenty years, the systematic determination for the optimal heat exchanger network, commonly called pinch analysis, provides a starting point for heat exchange design. For the above described process, there are three streams, save the reboilers and condensers, that require either heating or cooling to achieve the end desired status. Below is the initial analysis for the streams, utilizing the CENG 301 data for the heat capacities and the steps outlined in Douglas.

Here it is obvious that there is far more heat to be removed than streams to be heated. This leads one to attempt to find more heat sinks in order to save on utilities. One area initially left out of the picture is the two reboilers for the separation units. Since streams in the reboiler do not undergo a temperature difference, but instead go through a phase change, the chart representation and cascade diagram do very little good if the reboilers are to be used in the analysis. Also, if implemented correctly, the utilities can be eliminated from these reboilers, as in the base case each uses over $100,000 per year in steam.

Therefore, pinch analysis has allowed for the recognition of basic system facts and the need for more heat sinks. However, due to the lack of pinch analyses to effectively use phase changes in the overall study, it demands the use of other methods to find the optimized operation.