Heat integration grand composite curve

The most fundamental concepts in Pinch analysis are Composite and Grand Composite Curves. Composite Curves (Fig. 10.1-left) visualises the flow of heat between the hot and cold process streams selected for heat integration. A composite curve is obtained by plotting the cumulative enthalpy of streams, cold or hot, against temperature. The relative position of the composite curves depends on the minimum temperature difference between cold and hot streams. This sets also the Pinch position as the place where the heat transfer between the hot and cold streams is the most constrained. 

Although the composite curves can be used to set energy targets, they are not a suitable tool for the selection of utilities. The grand composite curve is a more appropriate tool for understanding the interface between the process and the utility system. It is also, as is shown in later chapters, a useful tool for study of the interaction between heat-integrated reactors and separators and the rest of the process. 

Use of the Grand Composite Curve for Heat Integration of Reactors... 

Establish the heat integration potential of simple columns. Introduce heat recovery between reboilers, intermediate reboilers, condensers, intermediate condensers, and other process streams. Shift the distillation column pressures to allow integration, where possible, using the grand composite curve to assess the heat integration potential. 

The appropriate placement of distillation columns when heat integrated is not across the pinch. The grand composite curve can be used as a quantitative tool to assess integration opportunities. 

Figure 16.38 shows a heat pump appropriately integrated against a process. Figure 16.38a shows the overall balance. Figure 16.38b illustrates how the grand composite curve can be used to size the heat pump. How the heat pump performs determines its coefficient of performance. The coefficient of performance for a heat pump can generally be defined as the useful energy delivered to the process divided by the power expended to produce this useful energy. From Figure 16.38a ...

Using the grand composite curve, the loads and temperatures of the cooling and heating duties and hence the COPhp of integrated heat pumps can be readily assessed. 

USE OF THE GRAND COMPOSITE CURVE FOR HEAT INTEGRATION OF REACTORS... 

Consider now a few examples of the use of this simple representation. A grand composite curve is shown in Figure 21.2a. The distillation column reboiler and condenser duties are shown separately and are matched against it. The reboiler and condenser duties are on opposite sides of the heat recovery pinch and the column does not fit. In Figure 21.2b, although the reboiler and condenser duties are both above the pinch, the heat duties prevent a fit. Part of the duties can be accommodated, and if heat integrated,... 

The appropriate placement of distillation columns when heat integrated is not across the heat recovery pinch. The grand composite curve can be used as a quantitative tool to assess integration opportunities. The scope for integrating conventional distillation columns into an overall process is often limited. Practical constraints often prevent integration of columns with the rest of the process. If the... 

Refrigeration cycles offer many opportunities for heat integration with the process. These can be explored using the grand composite curve. 

Figu re 6.11 Composite curves (a) and grand composite curve (b) after the heat integration of the benzene recycle column. 

The counter-current heat flow of the streams selected for integration may be represented by means of Composite Curves (CC). Another diagram. Grand Composite Curve (GCC) allows the visualisation of the excess heat between hot and cold streams, against temperature intervals. This feature helps the selection and placement of utilities, as well as the identification of the potential process/process matches. 

The methodology for column heat integration is explained by Figure 13.8, which can be applied for new and retrofit designs. Let us explain the methodology step-by-step as below. The T-H plot is the column grand composite curve (CGCC), which is discussed in Chapter 11. 

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