Capacity ratio method

The cost of more complex equipment items, as reactors, furnaces, dryers, or filters can be estimated for preliminary design by means of a global quotation called the capacity ratio method. The cost is expressed by a power-law correlation as ... 

A second order-of-magnitude approach is the ratio method, based on the assumption that capital investment can be correlated with plant capacity in a manner similar to that used for equipment. This gives... 

The ratio method is also particularly useful for quick estimates over a range of capacities after a calculated estimate for one size has been made (10). The calculated estimate can be separated into groups C, C2,. .., according to individual equipment exponents n, n2,. Then an overall plant capacity exponent n can be calculated from... 

Exponential Methods Rapid capital-cost estimates can be made by using capacity-ratio exponents based on existing cost data of a company or drawn from pubhshed correlations. 

The ratio method is a simple technique whereby known capital cost data for an existing chemical plant are adjusted to provide a cost estimate for the desired plant capacity. This method is also able to update figures to account for inflationary effects of past years. Finally the capital cost figure is adjusted for exchange rate differences between countries. The method is centred around the use of key cost estimation indices such as the CE Plant Cost Index and the Marshall and Stevens (M S) Index. 

Cost-curve estimates. There is a power exponent-ratio method of estimating corrections for the major deficiency in Table 8.3, previously illustrated by reflecting the significant effect of size or capacity on cost. These exponent-ratios indicate that costs of similar process units or plants are related to capacity by an equation of the following form ... 

METHOD E POWER FACTOR APPLIED TO PLANT-CAPACITY RATIO. This method for study or order-of-magnitude estimates relates the fixed-capital investment of a new process plant to the fixed-capital investment of similar previously constructed plants by an exponential power ratio. That is, for certain similar process plant configurations, the fixed-capital investment of the new facility is equal to the fixed-capital investment of the constructed facility C multiplied by the ratio R, defined as the capacity of the new facility divided by the capacity of the old, raised to a power x. This power has been found to average between 0.6 and 0.7 for many process facilities. Table 19 gives the capacity power factor (x) for various kinds of processing plants. 

Estimate by the turnover-ratio method the fixed-capital investment required for a proposed sulfuric acid plant (battery limit) which has a capacity of 140,000 tons of 100 percent sulfuric acid per year (contact-catalytic process) using the data from Table 19 for 1990 with sulfuric acid cost at 72 per ton. The plant may be considered as operating full time. Repeat using the cost-capacity-exponent method with data from Table 19. 

The adiabatic expansion method is not the best method of determining the heat capacity ratio. Much better methods are based on measurements of the velocity of sound in gases. One such method, described in Part B of this experiment, consists of measuring the wavelength of sound of an accurately known frequency by measuring the distance between nodes in a sonic resonance set up in a Kundt s tube. Methods also exist for determining the heat capacities directly, although the measurements are not easy. 

The ratio method. When a sample is subjected to a linear temperature increase, the rate of heat flow into the sample is proportional to its instantaneous heat capacity. Regarding this rate of heat flow as a function of temperature, and comparing it with that for a standard sample under the same conditions, we can obtain the heat capacity as a function of temperature. The procedure has been described in detail by O Neil (1966). The principle of this method is shown schematically in Figure 4.5. 

Figure 4.5. Heat capacity determination by the ratio method.

The method described in Problem 7.20 is that of Clement-Desormes for determining y, the heat capacity ratio. In an experiment, a gas is confined initially under = 151.2 kPa pressure. The ambient pressure, p2 = 100.8 kPa, and the final pressure after temperature equilibration is pa = 116.3 kPa. Calculate y for this gas. Assume the gas is ideal. 

GRT particles have an ability to adsorb hydrocarbons. However, their adsorption capacity is low in comparison with adsorbent materials currently in use. To improve its adsorption capacity various methods for manufacturing of adsorbents and their various uses were proposed, as discussed in this section. An oil absorptive material of lower cost can be obtained by graft copolymerization through blending of various proportions of GRT of particle size of 100 mesh with 4-tert-butylstyrene (tBS), as a monomer in the presence of divinylbenzene, as a crosslinker, and benzoylperoxide, as an initiator (Wu and Zhou, 2009). Oil absorbency of the grafted blends reached a maximum of 24.0 g/g at a feed ratio GRT/tBS of 60/40 and a divinylbenzene concentration of 1 wt.%. 

For example, this method reveals a high correlation coefficient between measured capacity ratios and the sum of theoretically calculated molecular interaction energy and molecular property values, opening the possibility for quantitative analysis of chromatographic retention mechanisms. 

Retention time in gas chromatography is related to a combination of retention and volatility, similar to solubility in liquid chromatography. Predicting volatility is as difficult as predicting solubility. Volatility has been explained as the enthalpy of vaporization (Avap f), and a method for predicting volatility has been proposed." If the A apH values are available, it may be possible to predict retention time. Unknown A apH values have been calculated from the relationship between the van der Waals volume and reference AyapH values. The values are summarized with the corresponding reference values in Table 1 of the Appendix (p. 278). Values of A apH have also been related to capacity ratios. The correlation coefficients were 0.896 and 0.852 ( = 48) for DBl and CPSilS columns, respectively, which appear to be acceptable correlation coefficients, except that the relationship for allq l alcohols deviated from those of other compounds as seen Figure 4.4. 

The correlation between those capacity ratios that were measured, those predicted by the former method using NlogP, " and those predicted by this new method using MIFS2, at pH 8.49 are summarized in Figure 6.18. The measured and predicted capacity ratios of phenolic compounds are given in Table 10 of the Appendix (p. 303). 

The retention time of phenolic compounds in reversed-phase liquid chromatography was predicted via molecular interaction energy values calculated using the MM2 program. The precision of the capacity ratios predicted by this new method was equivalent to a former method in which the retention time was predicted by log P calculated using the MOPAC program. Furthermore, the prediction of capacity ratios of phenolic compounds in reversed-phase... 

Thus, knowing the particle characteristics, R and e, and the slope of the linear isotherm, we can readily determine the effective diffusivity D. This method can be conveniently carried out with a simple linear plot, without recourse to any numerical optimization procedures (provided, of course, that the capacity ratio B is known beforehand). 

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