The Material Recycle Pinch Diagram

The material recycle pinch diagram is a graphical procedure for targeting the minimum amount of fresh feed usage and waste discharge as well as the maximum possible recycle 

Process number Mass load of contaminant (kg/h) Inlet concentration (ppm) Outlet concentration (ppm) Water flow (10 kg/h) 

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Generate the Material Recycle Pinch Diagram containing source composite curve and sink composite curve. 

Figure 6.A.4 The regions above and below the pinch point on the material recycle pinch diagram.

Figure 4.3 The materials recycle pinch diagram for direct recycle problems [14].

Figure 6.8 The shifted material recycle pinch diagram for Table 6.2.

The source composite curve in Figure 6.A.1 has not been shifted. To determine the minimum amount of fresh feed usage and waste discharge as well as the maximum amount of recycle, the user has to move the source composite curve horizontally until the sink composite curve touches the source at the pinch point and the remainder of the source composite curve exists entirely to the right of the sink composite curve (that is, curves cannot overlap). Pinch point is the point where the load of recycled sources matches with that of the sinks [18]. Figure 6.8 shows the shifted material recycle pinch diagram. 

Figure 6.A. 1 The non-shifted material recycle pinch diagram.

As an illustration of a class of problems in mass integration, let us consider the direct recycle problem. The objective of this problem is to determine the optimal allocation of sources to sinks without the addition of new equipment. Each source is characterized by a flowrate and composition. For each sink there are constraints on the acceptable feed, which are given in terms of lower and upper bounds on flowrate and composition. One approach to solving this problem is through the use of the material recovery/recycle pinch diagram developed by El-Halwagi et al. [14]. Fig. 4.3 is a representation of this graphical tool. First, flowrate and composition data are collected for all the recyclable streams (referred to as sources) and units (referred to as sinks) that can accept the recycle to reduce the consumption of the fresh resources. The flowrate and composition of impurities are used to calculate the load of impurities in each source as follows ... 

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