03 - 3 Pinch Technology In recent years a new technology...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
3 Pinch Technology In recent years a new technology for minimising the energy requirements of process plants has been developed: this has been named Pinch Technology or Process Integration by its major proponent, Linnhoff (Linnhoff and Senior, 1983; Linnhoff and Turner 1981). Fkcess plants, such as oil refineries or major chemical manufacturing plants, require that heating and cooling of the feed stock take place as the processes occur. Obviously it would be beneficial to use the energy from a stream which requires cooling to heat another which requires heating; in this way the energy that has to be supplied from a high temperature source (or utility) is reduced, and the energy that has to be rejected to a low temperature sink (or utility) is also minimised. Both of these external transfers incur a cost in running the plant. Pinch technology is an approach which provides a mechanism for automating the design process, and minimising the external heat transfers. Pinch situations also occur in power generation plant; for example, in a combined cycle gas turbine (CCGT) plant (see Fig 3.1) energy has to be transferred from the gas turbine exhaust to the working fluid in the steam turbine. A T-s diagram of a CCGT plant is Fig. 3.1 Schematic of CCGT
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
48 Pinch technology shown in Fig 3.2, where the heat transfer region is shown: the pinch is the closest approach in temperature between the two lines. It is defined as the minimum temperature difference between the two streams for effective heat transfer, and is due to the difference in the properties of the working fluids during the heat transfer process (namely, the exhaust gas from the gas turbine cools down as a single phase but the water changes phase when it is heated) - this limits the amount of energy that can be taken from the hot fluid. The heat transfer processes are shown on a temperature-enthalpy transfer diagram in Fig 3.3, where the pinch is obvious. Entropy, S Fig. 3.2 T-s diagram of CCGT fluid Pinch pint / Steam I Q=AH I Enthalpy Fig. 3.3 H - T diagram of CCGT Perhaps the easiest way of gaining an understanding of pinch techniques is to consider some simple examples.
Background image of page 2
A heat transfer network without a pinch problem 49 3.1 A heat transfer network without a pinch problem This example has a total of seven streams, three hot and four cold, and it is required to use the heating and cooling potential of the streams to minimise the heat transfer from high temperature utilities, and the heat transfer to low temperature utilities. The parameters for the streams involved in the processes are given in Table 3.1. The supply temperature, T,, is the initial temperature of the stream, and the target temperature, TT, is the target final temperature that must be achieved by heat transfer. The heat flow capacity, mC, is the product of the mass flow and the specific heat of the particular stream, and the heat load is the amount of energy that is transferred to or from the streams.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 17

03 - 3 Pinch Technology In recent years a new technology...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online