Energy savings, maximizing

In unit operations control, the individual column variables are treated only as constraints and so long as the values of these constraints are within acceptable limits, the column is controlled (optimized) to maximize production rate, profitability, etc. Economics of individual fractionators may continually change throughout the life of the plant, because energy savings can be important at one particular time, whereas product recovery can be more important at other times. 

The unfoamed mixture should be as concentrated as possible, consistent with mix stability, In order to minimize wet add-on and to maximize energy savings. 

From the above consideration, it is clear that the maximal surface area of the honeycomb-like electrodes can be attained by the careful selection of parameters of the PO regimes. This is followed by the decrease in the quantity of evolved hydrogen and, hence, by the improvement of the structural stability of the honeycomb-like electrodes. Simultaneously, analysis of the specific energy consumption shows that energy saving is achieved in the production of the honeycomblike electrodes by the shortening of deposition pulse and by the decrease in the quantity of evolved hydrogen [23, 49]. 

Energy savings—the maximal scope for energy savings in absorbed duty could be 47 (81.8 — 34.8) MMBtu/h or fired duty of 55 MMBtu/h assuming a heater efficiency of 85%. 

For optimum efficiency of usage, steam should be employed at its highest energy level, consistent with each particular application need. And, as noted above, additional fuel costs to supply steam at higher rather than lower pressures are small compared with the delivered energy benefits. Ultimately, therefore, higher pressures produce overall financial savings and maximize efficiencies. 

Heat energy can be saved by using the hot bottom product to preheat the feed in an economizer (Figure 2.89c). In order to maximize the amount of heat recovered, a VPC is used as the cascade master of the feed temperature controller. The goal of optimization is to keep the bypassed flow at a minimum. Therefore, the VPC is usually set at about 10% of the valve opening. 

For the current operation in Figure 19.1 with the boiler fuel of 337 MMBtu/h at 6/MMBtu, import power of 9.4 MW at 70/MWh and BFW of 40 klb/h at 2.5/klb, the total energy cost is 24.3 MM/year versus that of 21.3 MM/year for the maximal operation in Figure 19.6. Thus, the maximal efficient mode saves 3 MM/year of energy cost compared with the current operation. The fundamental reason behind this can be explained with the concept of PEE introduced previously. 

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