Equipment cost as a function

Cost Indices In some cases, the cost of a piece of equipment is available from a previous study, and it is desirable to evaluate its present cost. Because of inflation and other economic changes, it is necessary to correlate equipment cost as a function of time. In this regard, cost indices are useful tools. A cost index is an indicator of how equipment cost varies over time. The ratio of cost indices at two different times provides an estimate for the extent of equipment-cost inflation between these two times. Hence,... 

Figure 8. Equipment cost as a function of work/heat ratio for various hot water supply temperatures.

Figure 5.24 shows a graph indicating the equipment costs as a function of capacity for sodium sulfate crystallizers and ammonium sulfate crystallizers of the FC and the DTB type. 

One method proposed for estimating the cost of fuel cell power plants is to calculate distributive (bulk) costs as a function of the equipment cost using established factors based on conventional generating technologies. When applied in such a way as to compensate for the differences associated with a fuel cell plant, this approach can yield reasonable results. NETL has elected, based on the international prominence of the Association for the Advancement of Cost Engineering (AACE), to utilize this approach in estimating the costs for fuel cell/turbine power plant systems currently under study. 

Installation labor cost as a function of equipment size shows wide variations when scaled from previous installation estimates. Table 7 shows exponents varying from 0.0 to 1.56 for a few selected pieces of equipment. 

Figure 6 shows the layout of the piping system. Equipment and installation costs (including welding) were obtained from manufacturer1s data and from estimating guides for several nominal pipe diameters. These estimates were then fitted to obtain a formula for the installed pipe cost as a function of nominal pipe diameter, Zp(DR). 

Fig. 6.1-4 Overall factor for the direct plant costs as a function of the average value of the machines and pieces of equipment (Prinzing 19S5].

In the design of a fine chemicals plant equally important to the choice and positioning of the equipment is the selection of its size, especially the volume of the reaction vessels. Volumes of reactors vary quite widely, namely between 1,000 and 10,000 L, or ia rare cases 16,000 L. The cost of a production train ready for operation iacreases as a function of the 0.7 power. The personnel requirement iacreases at an even lower rate. Thus a large plant usiag large equipment would be expected to be more economical to mn than a small one. 

Published Cost Correla.tions. Purchased cost of an equipment item, ie, fob at seller s site or other base point, is correlated as a function of one or more equipment—size parameters. A size parameter is some elementary measure of the size or capacity, such as the heat-transfer area for a heat exchanger (see HeaT-EXCHANGETECHNOLOGy). Historically the cost—size correlations were graphical log—log plots, but the use of arbitrary equation forms for correlation has become quite common. If cost—size equations are used in computer databases, some limit logic must be included so that the equation is not used outside of the appHcable size range. 

The factorial method of cost estimation is often attributed to Lang (1948). The fixed capital cost of the project is given as a function of the total purchase equipment cost by the equation ... 

The contribution of each of these items to the total capital cost is calculated by multiplying the total purchased equipment by an appropriate factor. As with the basic Lang factor , these factors are best derived from historical cost data for similar processes. Typical values for the factors are given in several references, Happle and Jordan (1975) and Garrett (1989). Guthrie (1974), splits the costs into the material and labour portions and gives separate factors for each. In a booklet published by the Institution of Chemical Engineers, IChemE (1988), the factors are shown as a function of plant size and complexity. 

In addition to the direct cost of the purchase and installation of equipment, the capital cost of a project will include the indirect costs listed below. These can be estimated as a function of the direct costs. 

In real life, other problems involving discrete variables may not be so nicely posed. For example, if cost is a function of the number of discrete pieces of equipment, such as compressors, the optimization procedure cannot ignore the integer character of the cost function because usually only a small number of pieces of equipment are involved. You cannot install 1.54 compressors, and rounding off to 1 or 2 compressors may be quite unsatisfactory. This subject will be discussed in more detail in Chapter 9. 

Charts, correlations, and tables in the sources cited earlier relate capital costs to various parameters characteristic of the equipment to be evaluated. Table B.2 lists typical parameters used to correlate equipment costs for common types of process equipment. Figure B.3 is an example of such correlations for the cost of heat exchangers as a function of exchanger area. These forms of cost curves generally appear as nearly straight lines on log-log plots, indicating a power-law relationship between capital cost and capacity, with exponents typically ranging from 0.5 to 0.8. 

The types of equipment used, which range from stirred tanks and mixer-settlers to centrifugal contactors and various types of columns, affect both capital and operating costs [9]. In the decision to build a plant, the choice of the most suitable contactor for the specific situation is most important. In some systems, because of the chemistry and mass transfer rates involved, several alternative designs of contacting equipment are available. In the selection of a contactor, one must consider the capacity and stage requirements solvent type and residence time phase flow ratio physical properties direction of mass transfer phase dispersion and coalescence holdup kinetics equilibrium presence of solids overall performance and maintenance as a function of contactor complexity. This may appear very complicated, but with some experience, the choice is relatively simple. 

The ideal high-throughput analytical technique would be efficient in terms of required resources and would be scalable to accommodate an arbitrarily large number of samples. In addition, this scalability would be such that the dependence of the cost of the equipment to perform the experiments would scale in a less than linear manner as a function of the number of samples that could be studied. The only way to accomplish this is to have one or more aspects of the experimental setup utilize an array-based approach. Array detectors are massively multiplexed versions of single-element detectors composed of a rectangular grid of small detectors. The most commonly encountered examples are CCD cameras, which are used to acquire ultraviolet, visible and near-infrared (IR) photons in a parallel manner. Other examples include IR focal plane arrays (FPAs) for the collection of IR photons and channel electron multipliers for the collection of electrons. 

The total costs of the electrodialytic water dissociation with bipolar membranes are the sum of fixed charges associated with the amortization of the plant investment costs and of the operating costs which include energy and maintenance costs and all pre- and post-treatment procedures. The total costs are a function of the membrane properties, of the feed-solution composition, the required acid and base concentrations, and several process and equipment design parameters such as stack construction and operating current density. 

Smaller reactor size reduces the cost, improves control, and isolates process variables, however, effects of catalyst aging/deac-tivation as a function of time are not similarly reduced. These effects can be accelerated in the laboratory environment by increased temperature, water partial pressure, contaminant gas partial pressure, and various contaminant metals. As with scaled down equipment, these efforts are not without problems, however, when some catalyst lifetimes are measured in years, this is the only viable solution to meaningful catalyst research and development. This type of testing, coupled with characterization, has resulted in FCC catalysts with less resistance to coking and thus longer service life. 

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