Pinch analysis

T0 is the absolute temperature of the environment. For a given heat load, energy loss is directly related to the value of ATmin. When the temperature levels move into the cryogenic region in a process, ATmin must decrease as the square of the temperature level to maintain the same rate of lost work. 

Each temperature is a fixed value on the vertical axis, and enthalpy change rates are relative quantities. We estimate the enthalpy changes rather than absolute enthalpies, and the horizontal location of a composite line on the diagram is arbitrarily fixed. The location of ATmm on the composite diagram is where the hot and cold curves most closely approach each other in temperature in a vertical direction. We move one of the two curves horizontally until the distance of the closest vertical approach matches the selected ATmin. The overshoot of the hot composite curve represents the minimum cold utility (qc mm) required, and the overshoot of the cold composite curve represents the minimum hot utility (gh mm) required for the process. 

Pinch analysis can optimize the combined heat and mass exchanger network and chemical reactor systems with heat exchangers. 

2 Heat Exchanger Network Synthesis and Pinch Analysis 

More sophisticated techniques can solve problems with multiphase shell-and-tube exchangers, phase changes of process streams, and varying overall heat transfer coefficients. We may analyze a heat exchanger network as a single heat 

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As can be seen from Fig, 3.7, the pinch decomposes the synthesis problem into two regions a rich end and a lean end. The rich end comprises all streams or parts of streams richer than the pinch composition. Similarly, the lean end includes all the streams or parts of streams leaner than the pinch composition. Above the pinch, exchange between the rich and the lean process streams takes place. External MSAs are not required. Using an external MSA above the pinch will incur a penalty of eliminating an equivalent amount of process lean streams from service. On the other hand, below the pinch, both the process and the external lean streams should be used. Furthermore, Fig. 3.7 indicates that if any mass is transferred across the pinch, the composite lean stream will move upward and, consequently, external MSAs in excess of the minimum requirement will be used. Therefore, to minimize the cost of external MSAs, mass should not be transferred across the pinch. It is worth pointing out that these observations are valid only for the class of MEN problems covered in this chapter. When the assumptions employed in this chapter are relaxed, more general conclusions can be made. For instance, it will be shown later that the pinch analysis can still be undertaken even when there are no process MSAs in the plant. The pinch characteristics will be generalized in Chapters Five and Six. 

Linnhoef, B. Chem. Eng. Prog. 90 (Aug. 1994) 32. Use pinch analysis to knock down capital costs and emissions. 

LINNHOFF, B. (1993) Trans IChemE 71, Part A, 503. Pinch Analysis — a state-of-the-art overview. 

Wang YP and Smith R (1995) Time Pinch Analysis, Trans IChemE, A73 905. 

Wang, Y.P., Smith, R., 1995. Time pinch analysis. Trans. IChemE, 73a 905-914. 

Other established attempts on heat integration of batch plants are based on the concept of pinch analysis (Linnhoff et al., 1979 Umeda et al., 1979), which was initially developed for continuous processes at steady-state. As such, these methods assume a pseudo-continuous behaviour in batch operations either by averaging time over a fixed time horizon of interest (Linnhoff et al., 1988) or assuming fixed production schedule within which opportunities for heat integration are explored (Kemp and MacDonald, 1987, 1988 Obeng and Ashton, 1988 Kemp and Deakin, 1989). These methods cannot be applied in situations where the optimum schedule has to be determined simultaneously with the heat exchanger network that minimises external energy use. 

Fig. 12.12 Water reuse network resulting from pinch analysis (first sequence) (Majozi et al., 2006)...

Pinane, 3 231 24 487 cis-Pinane, 24 495 Pinanols, 24 477, 495 Pinch, making stream matches at, 13 199-200. See also Pinch point Pinch analysis, 10 163 20 735-737 applications of, 20 763 total site, 20 751... 

Pinch analysis, targets of, 13 217 Pinch design. See also Pinch Design Method... 

Total reflection X-ray fluorescence spectrometry, 26 435-437 Total sideband suppression (TOSS) technique, 23 741 Total site pinch analysis, 20 751 Total solids flux, in thickener design and scale-up, 22 58... 

Baetens, D., Water pinch analysis minimisation of water and wastewater in the process industry, Chapter 11 in Water recycling and resource recovery in industry Analysis, technologies and implementation, Edited by P.Lens et al., IWA publishing, 2002, ISBN 1 84339 005 1. 

Prof David C W. Hui Chemical Engineering, HKUST Pinch analysis, system optimization... 

Most of the existing HEN synthesis methods rely on either heuristic rules (for example, pinch analysis method [2]) or mathematical programming (for example, simultaneous optimization approach [3-6]). And further, to some typical objectives considered in the HEN synthesis such as utility consumption, total number of matches, and total exchanger area, the flexibility of the HENs for feasible operation under possible variation of source-stream temperatures and/or heat-capacity flow rates has been emphasized in some recent articles [6-10]. For HEN synthesis, the analysis of this flexibility, defined as the size of the region of feasible operation in the space of desired or undesired deviations of pa-... 

Integration of heat and power Mass integration to prevent waste Pinch analysis, source sink diagrams... 

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