Moderate retrofitting

Existing area of each exchanger in with additional area (shown by +) and reduction in area (shown by ) in brackets 

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Figure 7.10 Comparison of Pareto fronts for moderating retrofitting at various generations with population size of 500 crosses, circles, pluses and diamonds are the solutions at 100, 250, 500 and 1000 generations, respectively. The solution selected for discussion is in the oval.

Figure 7.11 HEN after moderate retrofitting according to the selected solution in figure 7.10.

R-401B (22/152a/124) MP66 AlliedSignal DuPont CFC-12 R-500 Blend (moderate glide) Alkylbenzene or polyol ester Alkylbenzene or polyol ester or in some cases mineral oiF Transport Refrigeration retrofits Retrofits including air conditioners dehumidifiers Close to CFC-12. Use where evap. temperature below -10 F. 

Under such conditions, the focus of retrofitting and revamping existing units will be optimizing middle-distillate production. Consequently, to meet higher quality requirements for middle distillates, E.U. refiners are projected to invest in hydrocracking capacity. Such investments may include standalone units and moderate conversion of units upstream of the FCC.15 Refiners will also raise hydrotreating capability. 

Gasification 55 moderate High temperature processes and natural gas substitution. Retrofit potential for oil and gas boilers. 

The rest of this chapter is structured as follows. The next section describes HENs and the structural representation used in this study for HEN retrofitting. Section 7.3 discusses the improvement techniques that can be used to retrofit HENs. Section 7.4 describes the methodology to retrofit HENs, which includes MOO, HEN model and exchanger reassignment strategy (ERS). The case study solved by the methodology is described in Section 7.5. Section 7.6 discusses the results obtained for simple, moderate and complex retrofitting. Finally, conclusions of this study are presented in Section 7.7. 

In the following sub-sections, MOO results for simple, moderate and complex retrofitting of HEN in the case study are presented and discussed. The objectives used in MOO are cost of retrofit and utility cost, and the approach temperature on each heat exchanger in HEN... 

Figure 7.14 Comparison of Pareto fronts for simple, moderating and complex retrofitting of HEN in the case study diamonds and pluses are the solutions for simple retrofitting with 15% and 30% area addition, respectively and circles and triangles are the solutions for moderate and complex retrofitting, respectively.

A minimum approach temperature of 15 °C is used for optimizing simple, moderate and complex HEN retrofitting in the case study in this chapter. Study the effect of changing the minimum approach temperature from 15 °C to 10 °C, 20 °C and 30 °C for simple, moderate and/or complex retrofitting. Note that this requires meth-ods/programs similar to those described in this chapter. 

PetroChina announced a commercial alkene alkylation process (Scheme 2.8) using composite ionic hquids, [(C2)3NH]C1-A1C13 (X(AlCl3) = 0.67) mixed with CuCl to tune the acidity of the ionic hquid for process optimization [131]. In 2006, this process was retrofitted into an existing 65 000 ton per year sulfuric acid alkylation unit in China [132]. The process operates at ambient temperature and moderate pressure, with increased yields and greater process unit capacity (40%... 

The gap size between adjacent structures or between adjoining structural units can turn out to be too small in an actual earthquake in which plastic displacements of the soil and of the structure develop, as it is customary to design the structure, and thus also the gap size, for a moderate earthquake, assuming elastic behaviour. The problem of insufficient gap size can also arise when retrofitting nuclear power plants for increased seismic requirements can occur. 

Figure 6 quantifies the performance of the additional FVD for increasing levels of the seismic input, i.e., PGA = 0.10 g (low intensity), flg = 0.25 g (moderate earthquake), and = 0.40 g (strong motion). It is evident that in all the three cases, the FVD allows mitigating the seismic response. Due to the highly nonlinear behavior of the selected device, however (i.e., the small velocity exponent a = 0.3), this retrofitting technique is more efficient in case of low intensity, that is, the lower the PGA, the higher the... 

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