Full calculations of plant efficiency

In Chapter 4 calculations were made on the overall efficiency of CBT plants with turbine cooling, the fraction of cooling air (tp) being assumed arbitrarily. In this chapter, we outline more realistic calculations, with the cooling air fraction i/r being estimated from heat transfer analysis and experiments. 

There are several papers in the literature which give details of cycle calculations, and include details of how the cooling flow quantity may be estimated and used. Here we describe one such approach used by the author and his colleagues. Initially, we summarise how i/rcan be obtained (fuller details are given in Appendix A). We then illustrate how this information is used in calculations, once again using a computer code in which real gas effects are included. 

Subsequently, we refer briefly to other comparable studies, including the calculations of exergy losses and rational efficiency. Finally, we show the real gas exergy calculations for two practical plants—[CBT]i and [CBTX]i. 

The method devised by Holland and Thake [ 1 ] for estimating the cooling air (vv, ), as a fraction of mainstream entry flow to a blade row (vvg), i.e. tp = wjw, was described by Horlock et al. [2] and is reproduced in Appendix A Fig. A. 1 shows diagrammatically the notation employed there and the same symbols are defined and used below. 

Consider first a convectively cooled blade row (Fig. A.la). It is. shown in Appendix A that the mass flow of cooling air (vv. ) required for a mass flow of mainstream gas (Wg), entering at temperature Tg, is given by 

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Chapter 5. Full calculations of plant efficiency A new temperature difference ratio is written as... 

Average dust concentration downstream of the filter unit was measured to be well below 5 mg/Nm. Measured filtration efficiency at 190 C and 9 cm/s corresponds to a filter efficiency above 99.83%, verified in a full-scale pilot plant. Calculated average... 

On Figure 14.1, results of researches of separating ability of a rotoklon depending on conditional speed of gas v, calculated on full section of the device are introduced. Comparison of considered devices by means of criterion relative technical and economic efficiency 0 is spent. The cited data has illustrative character and shows possibilities of application of criteria of technical and economic efficiency 0 for comparison purposes gascleaning plant devices. 

Heat and mass balance equations are used in all aspects of process modelling however, what is key to this model is an understanding of the electrolytic process behind the cell. For example, the model must be able to predict current efficiency and k-factor if it is to predict electricity consumption. Most of these electrolytic parameters are calculated using empirical relationships derived from experimental data both from test cells and the full-scale plant. Considering k-factor, this is primarily a function of brine strength and temperature. Figure 20.5 illustrates the experimentally derived function used in the model. 

The above equation was used for scale-up calculations and design of both the pilot plant and full-scale Electropulse Column. A total of 18 experimental runs for uranium(VI) electrolytic reduction was performed on the 20-cm diameter pilot-scale column. (10) As shown in Figure 4, the predicted reduction efficiency calculated from equation (4) correlated well with the experimental values obtained during these runs. The same good correlation between the predicted and experimental R(u) values was achieved later during cold uranium tests in the full-scale unit (Figure 4). The accuracy of correlation was within the range of 6%. 

Figure 4. Comparison of experimental U reduction efficiencies with those calculated (predicted) from the derived equation (%) pilot plant column, ( ) full-size...

Column 4 represents costs based on plant modifications enabling polarization and intercompartmental leakage to be eliminated, and full capacity and desalting to be achieved. The modifications would have involved additional work to the extent of 142,900. This cost has been added to the original costs in calculating amortization. No allowance has been made for credit for redundant equipment, or for the fact that these modifications if originally incorporated would actually have reduced the capital costs. Replacement and service costs are based on conservative values, as shown in the notes to the table. A mean coulomb efficiency of 75% throughout the plant has been allowed for, with membranes discarded... 

A certain ratio of partial vapor pressures of the more-permeable component at the permeate and at the feed side is usually fixed and maintained in the laboratory experiment. When calculating the performance of a real plant in the above-described manner this ratio has to be kept even for the last increment of the membrane area, otherwise a transfer of the laboratory data to the full-scale plant will lead to large errors. By an additional efficiency factor corrections for any differences between the more ideal conditions in the laboratory experiment and the more realistic conditions in an industrial plant may be introduced. 

At Fukushima Daiichi Unit 1, an anticipated 920 MW of energy would be transferred to the sea every hour while the plant was operating at full-power (given fliat it would produce 460 MW of electric power, at a level of one third efficiency (Van Wylen and Sonntag, 1973), twice the energy would be rejected versus the electricity produced). If we assume that a 90 °F sea water temperature is the maximum that can be allowed for marines life safety, it is easy to calculate the minimum pumping power required for this process. It turns out that at full power operation, the Fukushima Daiichi sea water pumps would need to move about 220,000 gal/min to sufficiently cool the turbine exhaust steam. 

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