Maximum energy recovery pinch

In practice, the integer number of shells is evaluated from Eq. (7.18) for each side of the pinch. This maintains consistency between achieving maximum energy recovery and the corresponding minimum number of units target Nu- ixs- In summary, the number of shells target can be calculated from the basic stream data and an assumed value of Xp (or equivalently,... 

Example 16.1 The process stream data for a heat recovery network problem are given in Table 16.1. A problem table analysis on these data reveals that the minimum hot utility requirement for the process is 15 MW and the minimum cold utility requirement is 26 MW for a minimum allowable temperature diflFerence of 20°C. The analysis also reveals that the pinch is located at a temperature of 120°C for hot streams and 100°C for cold streams. Design a heat exchanger network for maximum energy recovery in the minimum number of units. 

The pinch design method developed earlier followed several rules and guidelines to allow design for minimum utility (or maximum energy recovery) in the minimum number of units. Occasionally, it appears not to be possible to create the appropriate matches because one or other of the design criteria cannot be satisfied. 

Figure 16.23a shows the complete design, achieving maximum energy recovery in one more unit than the target minimum due to the inability to tick off streams below the pinch. 

Determine the pinch temperatures and the minimum utility requirements for the streams set out in the table below, for a minimum temperature difference between the streams of 20°C. Devise a heat exchanger network to achieve the maximum energy recovery. 

To design the network for maximum energy recovery start at the pinch and match streams following the rules on stream heat capacities for matches adjacent to the pinch. Where a match is made transfer the maximum amount of heat. 

Figure 23.42 shows an existing system that is set for maximum energy recovery, in which a new main is introduced away from the site pinch. The new main allows an increase in the steam generation and a change from steam use at a higher pressure to the new pressure. This has the... 

Given the stream data provided in Table 6.3, identify the energy targets and pinch temperatures. Design a HEN that achieves the maximum energy recovery. 

It is not trivial to determine the best modification options that could feature minimal capital cost and the smallest effect on existing infrastructure and thus achieve maximum energy savings. The search for such options could be very time consuming for a complex heat recovery system. The incentives to find practical yet optimal modifications have been discussed by many other researchers and practitioners. The network pinch method developed by Zhu and Asante (1999) has been proven successful for practical applications, which will be discussed in detail in this chapter. 

The second method involves a predictive method that determines VLE and liquid-liquid equihbrium (LLE), which are important for designing evaporators and condensers. Another method is a powerful tool for parameter determination and optimization by Levenberg and Marquardt [28]. This method can be used to develop complex models for process engineering purposes which require an adaptation of parameters to experimental results. The final analysis method deals with the pinch-point method developed by Linnhoff etal. [29]. This technique aims to identify the maximum possible heat recovery and the minimum energy requirement of a thermal or chemical process [30-32]. The apphcation of this method to fuel cell systems is explained in the final part of this section. 

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