Pinch technology

In this section the fundamental principles of the pinch technology method for energy integration will be outlined and illustrated with reference to a simple problem. The method and its applications are described fully in a guide published by the Institution of Chemical 

The development and application of the method can be illustrated by considering the problem of integrating the utilisation of energy between 4 process streams. Two hot streams which require cooling, and two cold streams that have to be heated. The process data for the streams is set out in Table 3.3. Each stream starts from a source temperature Ts, and is to be heated or cooled to a target temperature Tt. The heat capacity of each stream is shown as CP. For streams where the specific heat capacity can be taken as constant, and there is no phase change, CP will be given by  

Stream number Type Heat capacity CP, kW/°C Ts °C T, °C Heat load kW 

The heat load shown in the table is the total heat required to heat, or cool, the stream from the source to target temperature. 

There is clearly scope for energy integration between these four streams. Two require heating and two cooling and the stream temperatures are such that heat can be transferred from the hot to the cold streams. The task is to find the best arrangement of heat exchangers to achieve the target temperatures. 

The heat transferred between the streams is shown on the diagram as A//ex, and the heat transferred from the utilities as AH cold and AHhot  

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The use of the pinch technology method in the design of heat exchanger networks has been outlined in Sections 3.17.1 to 3.17.6. The method can also be applied to the integration of other process units such as, separation column, reactors, compressors and expanders, boilers and heat pumps. The wider applications of pinch technology are discussed in the Institution of Chemical Engineers Guide, IChemE (1994) and by Linnhoff et al. (1983), and Townsend and Linnhoff (1982), (1983), (1993). 

Tjoe TN and Linnhoff B (1986) Using Pinch Technology for Process Retrofit, Chem Eng, April 47. 

Linnhoff B and Vredeveld DR (1984) Pinch Technology Has Come of Age, Chem Eng Prog, July 40. 

Majozi, T., Zhu, X.X., 2001. A novel continuous time MILP formulation for multipurpose batch plants. 1. Short-term scheduling. Ind. Eng. Chem. Res., 40(25) 5935-5949 Obeng, E.D.A., Ashton, G.J., 1988. On pinch technology based procedures for the design of batch processes. Chem. Eng. Res. Des., 6 255-259... 

Taffe, P., Pinch Technology for Batch Processes, Processing, December, pp. 20-21 (1987). 

Hydrogen Pinch Technology has been applied commercially by several companies including AspenTech, BP-Amoco, Engineers India, Exxon, ICI, Linnhoff-March, M.W. Kellogg and UOP.44-45... 

The results of thermodynamic analysis may be in line with those of economic analysis when the thermodynamic cost optimum, not the maximum thermodynamic efficiency, is considered with process specifications. Figure 5.3 shows pinch technology in terms of optimum hot and cold utilities by accounting for the investment costs and exergy cost. With an optimum approach temperature ATmin, the total cost may be optimized. 

A number of experimental chemical process synthesis procedures have been developed with a hierarchical architecture based on both the hierarchical structure of the chemical innovation process and the physical property hierarchy. Examples include PIP (Kirkwood et al, 1988) and BALTAZAR (Mahalec and Motard, 1977). This hierarchical approach is also evident in the Pinch Technology Onion Diagram (Linnhoff and Ahmad, 1983). The hierarchical approach is also the foundation for the two early textbooks on process synthesis methodology (Rudd et al, 1973 Douglas, 1988). 

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