Cost comparison method

The cost comparison method determines the costs of one or two investment projects and compares them. 

In an economic comparison of these three common abatement systems, a 1991 EPA study (58) indicates extended absorption to be the most cost-effective method for NO removal, with selective reduction only matching its performance for small-capacity plants of about 200—250 t/d. Nonselective abatement systems were indicated to be the least cost-effective method of abatement. The results of any comparison depend on the cost of capital versus variable operating costs. A low capital cost for SCR is offset by the ammonia required to remove the NO. Higher tail gas NO... 

This method is based on cost comparison between bit records and the current bit run. 

Table 1 presents a cost comparison between phytodegradation and pump-and-treat methods. Tables 2, 3, and 4 compare cost estimates for phytoremediation with estimates for other treatment technologies. Because these values are often based on bench- or pilot-scale data, the information should be viewed with caution. 

TABLE 1 Cost Comparison between Phytodegradation Using Hybrid Poplar Trees and a Conventional Pump-and-Treat Method (3 Wells and Reverse Osmosis System)... 

TABLE 1 Cost Comparison of Biological Tkeatment Methods... 

Since 1990 there has been an enormous amount of comparison between DFT and alternative methods based on the molecular wave function. The bottom line from all of this work is that, as a rule, DFT is the most cost-effective method to achieve a given level of accuracy, sometimes by a very wide margin. There are, however, significant exceptions to this rule, deriving either from inadequacies in modern functionals or intrinsic limitations in the KS approach for determining the density. This section describes some of these cases. 

Purchasing specifications include not only performance data, materials, structural details, plot plan considerations, guarantees, etc., but also methods of bid evaluation, applicable unit costs, energy costs and amortization period. A good group of specifications will permit a true cost comparison of competitive towers on an installed, as well as on an operating, basis. Table 6.3 summarizes the normal specifications that should be considered. 

We will base our simulations on a simple Hiickel molecular orbital (HMO) picture of Ceo. This approach may not embody the rigour inherent in more sophisticated methods of calculation, such as DFT, but is capable of demonstrating the underlying physical principles without incurring the additional computational cost of methods such as DFT. Where appropriate, we will make comparisons with other theoretical results in the literature, most notably DFT, in order to note similarities or discrepancies. 

On an industrial scale, resolution of racemates is still in many cases the preferred way of producing enantiomerically pure compounds. If chiral-pool compounds are not available as optically active starting materials, a cost comparison of asymmetric and resolution processes often attributes advantages to the latter. Among the top 15 optically active pharmaceutical drugs and their intermediates, a chemical asymmetric process could be established only in the case of naproxen. For all others, diastereomeric and biocatalytic resolution are the methods, apart from fermentation, of creating optically pure compounds. 

In addition, to the direct cost comparison between SMETs and traditional methods the benefits of obtaining additional information on water quality need to be considered. 

Submerged fermentation procedures are used almost exclusively today. A few surface fermentation processes (on liquids or solids) are still used. Cost comparisons of labor, air compression, infection, etc., can be made, but modem batch fed, highly instrumented and computerized submerged methods predominate. Submerged methods are also the predominant culture propagation technique. The general principle is to have the fewest possible... 

Equipment Cost Comparisons, Several methods have been proposed for approximating costs of equipment of different size or capacity when the cost of a given unit is known. Williams offers the general "six-tenths factor. If the cost of a given unit is known at one capacity and 1 R. Williams, Jr., Chem. Eng., 64(12) 124 (1947). 

With a question like this, a little empirical work is worth a mountain of speculation. In her comparison of methods of cost estimation in health care effectiveness in the field of perinatal care, Mugford found that there was little evidence that unit costs derived from simpler methods were very different from those derived from more costly research methods, including clinical trials (Mugford, 1996). General approaches to modelling costs appeared to have been more influential. 

The third process, financial control of the project, is again based on the cost accounts. The basic control method is an ongoing comparison between actual and planned cost accumulation. Methods such as the earned value technique develop ratio measures that help the controller to analyze the schedule and cost deviations over time and employ control limits as triggers for corrective action. The control is usually performed at the WP cost account level. 

Table 21.4.1. Cost comparison of textile cleaning methods...

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