Utility consumption

Example 6.2 A process is to be divided into two operationally independent areas of integrity, area A and area B. The stream data for the two areas are given in Table 6.6." Calculate the penalty in utility consumption to maintain the two areas of integrity for = 20°C. 

Solution To identify the penalty, first calculate the utility consumption of the two areas separate from each other, as shown in Fig. 6.22a. Next, combine all the streams from both areas and again calculate the utility consumption (see Fig. 6.226). Figure 6.23a shows the problem table cascade for area A, the cascade for area B is shown in Fig. 6.236, and that for areas A and B combined is shown in Fig. 6.23c. 

With areas A and B separate, the total hot utility consumption is (1400 +... 

Figura 12.1 The plus/minua principle guides process changes to reduce utility consumption. (From Smith and Linnhoff, ChERD, 66 195, 1988 reproduced by permission of the Institution of Chemical Engineers.)...

By contrast. Fig. 13.46 shows an endothermic reactor integrated below the pinch. The reactor imports Qreact from part of the process that needs to reject heat. Thus integration of the reactor serves to reduce the cold utility consumption by Qreact- There is an overall reduction in hot utility because, without integration, the process and reactor would require (Qumin + Qreact) from the utility. 

If botb reboiler and condenser are integrated with the process, this can make the column difficult to start up and control. However, when the integration is considered more closely, it becomes clear that both the reboiler and condenser do not need td be integrated. Above the pinch the reboiler can be serviced directly from hot utility with the condenser integrated above the pinch. In this case the overall utility consumption will be the same as that shown in Fig. 14.16. Below the pinch the condenser can be serviced directly by cold utility with the reboiler integrated below the pinch. Now tlje overall utility consumption will be the same as that shown in Fig. 14.1c. 

The overall yield of the process is at least 87 mol %, and 2.3 mol of methanol per mole of final product are needed, an excess of 15% over the 2.0 theoretical amount. The methanol can be recycled from the manufacture of poly(ethylene terephthalate). Reported utilities consumptions per kilogram of product are 1.2 kg of 1400-kPa steam, 420 kj of boiler fuel, and 0.5 kWh of electricity (72). 

Vendor shall advise in his quotation under a section labeled "Utilities", all utility consumption required for the system. 

This means that the value chosen for ATmm will determine the size of the heat exchangers in a network. Reducing ATmm will increase the heat recovery, decreasing the utility consumption and cost, but at the expense of an increase in the exchanger size and capital cost. 

With Areas A and B separate, the total hot utility consumption is (1400 + 0) = 1400 kW and the total cold utility consumption is (0+ 1350) = 1350 kW. With Areas A and B combined, the total utility consumption is 950 kW of hot utility and 900 kW of cold utility. 

Calculate the penalty in utility consumption to maintain the two areas of integrity for ATmin = 20°C. 

Thus the hot and cold utility consumption both need to be increased by 1.6 MW to restore the Arm to the original 10°C. In fact there is no justification to restore the Arm back to the original 10°C. The amount of additional energy shifted along the utility path is a degree of freedom that should be set by cost optimization. However, the example illustrates how the degrees of freedom can be manipulated in network optimization. 

Figure 18.34a shows the network evolved to reduce the utility consumption to the point where the temperature... 

Distillation not across the pinch. Here the situation is somewhat different. Figure 21.1b shows a distillation column entirely above the pinch. The distillation column takes heat Qreb from the process and returns Qcond at a temperature above the pinch. The hot utility consumption changes by (Qreb - Qcond)- The cold... 

The case study was solved using the uneven discretization of time formulation presented in this chapter. The mathematical model for the scenario without heat integration (standalone mode) involved 88 binary variables and gave an objective value of 1060 rcu. This value corresponds to the production of 14 t of product and external utility consumption of 12 energy units of steam and 20 energy units... 

Metabolic poisoning (O2 utilization/consumption, glycolysis, gluconeogenesis) Compensatory factors... 

Selectivity is a relative term that means a desorbent must have balanced strength or selectivity for the adsorbent relative to the desired feed normal paraffins. A desorbent that is more strongly held by the adsorbent than the feed normal paraffins will be difficult for the desired feed normal paraffins to displace from the adsorbent This results in poor adsorbent utihzation due to a loss in selective volume. At the same time, a desorbent carmot be too weakly attracted to the selective volume (relative to the feed normal paraffins) or excessive desorbent circulation is needed to displace the feed component from the adsorbent. In this situation, excessively high desorbent rates are needed to recover feed normal paraffins from the adsorbent These high desorbent flush rates result in non-economical process conditions due to excessively high utility consumption in post-Sorbex product fractionation. 

Utility Consumption Rate Unit Cost in Dollars Total Cost... 

Vannuccini, S. (2004). Overview of fish production, utilization, consumption and trade. FAO fishery information, data and statistic unit report, ftp //ftp.fao.org/fi/stat/overview/ 2001 / commodit/2001fisheryoverview.pdf. 

THE VENDOR SHALL GUARANTEETHE MECHANICAL OPERATION OF THE EGUPMENT AND SYSTEM PROVIDED FOR A MINIMUM OF ONE YEAR AFTER START-UP. HLR EXPECTS PROCESS GUARANTEES ON THE SPECIFIED DISTILLATION RATES. CONDENSER PmFORMANCE.AM> MAXIMUM PRESSURE DROPS. ENTRAINMENT, AIR LEAKAGE RATES AND UTILITY CONSUMPTIONS SHALL BE SPECIFIED. ALLPROOUCT AND PROCESS SPECIFICATIONS WHICH THE VENDOR CANNOT GUARANTEE SHALL BE ENUMERATED. 

Research on the synthesis of economically optimal heat exchanger networks (HENs) has been performed for over 15 years (Nishida et al., 1981). As a result of this research, two general conclusions have emerged (1) the optimum network generally features minimum or close to minimum utility consumption, and (2) the optimum network generally has a mini-... 

---