Economics of design

Operating costs vary widely from plant to plant because of numerous factors such as  

Type of plant— modern or obsolete, simple or elaborate. 

Feedstock quality—gravity, octane number of gasoline, etc. 

Complete costs can seldom be assembled at a particular date, and hence cost indexes such as those of Table 23-1 must be. employed. Indexes are especially useful if they are kept up to date in readily available publications. The ENR (Engineering News Record) index of constrq6tion costs has been used since 1913 and it is published each month. Likewise the Nelson Refinery Construction Cost Index is published in the first issue each month of The Oil and Gas Journal. Refinery wages and the productivity of refinery labor can be obtained (or computed) from informa -tion in the monthly magazine entitled Survey of Current Business (U.S. Department of Commerce) or from quarterly issues (January, April, July, and October) of The Oil and Gas Jouranl (Itemized Cost Indexes). There is no truly satisfactory way to state an operating cost index because the value of fuel varies widely from plant to plant, and the fuel cost Nelson, W. L.,. . . How it is Computed, Oil Gas J., Oct. 1, 1956, p. 110. 

Year ENR construc- tion Nelson refinery construction Refin- ery wages Productivity (bbl per man) Operating cost  

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Anderson, E. D. and E. W. Haxbart, Economics of Design of Heat Exchangers, presented at Ninth Annual Pet. Mech. Eng. Conf, ASME, Sept. 1954, Los Angeles, CA. 

The obvious question arises When is a model of a process good enough This is not a trivial question, and it can only be answered fiiUy when the detailed economics of design and practicality are taken into account. Here, we have simply illustrated the hierarchy of one simple process, and how to find the limits of validity of each more complicated model in the hierarchy. In the final analysis, the user must decide when tractability is more important than precision. 

Overall project profitability. The economics of the overall project should be evaluated at different stages during the. design to access whether the project is viable and whether major changes are needed. 

Since the discovery of living cationic systems, cationic polymerization has progressed to a new stage where the synthesis of designed materials is now possible. The rapid advances in this field will lead to useful new polymeric materials and processes that will greatiy increase the economic impact of cationic initiation. 

The selection of a particular type of reduction depends on technical feasibiUty and the economics of the process as well as on physicochemical considerations. In particular, the reducing agent should be inexpensive relative to the value of the metal to be reduced. The product of the reaction, RX, should be easily separated from the metal, easily contained, and safely recycled or disposed of. Furthermore, the physical conditions for the reaction should be such that a suitable reactor can be designed and operated economically. 

The business climate of the 1990s is different from the past. Factors such as increased competition, a global marketplace, rapid technical shifts, and greatly compressed product life cycles constantly open new opportunities for plastics in general and reinforced plastics in particular. Reinforced plastics have become widely accepted for particular appHcations because they offer a combination of design, performance, and economic benefits to the user. These materials have had a proven record of success since the 1940s. 

Effects of Rate Conditions. It is essential for commercial a-quartz crystals to have usable perfection growth at a high rate and at pressure and temperature conditions that allow economical equipment design. The dependence of rate on the process parameters has been studied (8,14) and may be summarized as follows. Growth rate depends on crystallographic direction the (0001) is one of the fastest directions. Because AS is approximately linear with AT, the growth rate is linear with AT. Growth rate has an Arrhenius equation dependence on the temperature in the crystallization zone ... 

High Water Velocities. The abiUty of high water velocities to minimize fouling depends on the nature of the foulant. Clay and silt deposits are more effectively removed by high water velocities than aluminum and iron deposits, which are more tacky and form interlocking networks with other precipitates. Operation at high water velocities is not always a viable solution to clay and silt deposition because of design limitations, economic considerations, and the potential for erosion corrosion. 

Extensive design and optimization studies have been carried out for this sequence (108). The principal optimization variables, ie, the design variables that have the largest impact on the economics of the process, are the redux ratio in the azeo-column the position of the tie-line for the mixture in the decanter, determined by the temperature and overall composition of the mixture in the decanter the position of the decanter composition on the decanter tie-line (see Reference 104 for a discussion of the importance of these variables) and the distillate composition from the entrainer recovery column. 

An appropriate procedure for executing the design of an absorber-stripper system is to set up a carefully selected series of design cases and then evaluate the investment costs, the operating costs, and the operability of each case. Some of the economic factors that need to be considered in selec ting the optimum absorber-stripper design are discussed later in the subsec tion Economic Design of Absorption Systems. ... 

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