Equipment Sizing and Costing

Example 3 Equipment Sizing and Costing Oil at 490,000 Ib/h is to be heated from 100 to 170°F with 145,000 Ib/h of kerosene initially at 390 F from another section of a plant. The oil enters at 20 psig and the kerosene at 25 psig. The physical properties are 

Estimate the cost of an all-carbon-steel exchanger in late 2004. Assume a counterflow shell-and-tube exchanger. 

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Now if we imagine a reforming system at equilibrium, and increase the pressure (the applied stress), then the reaction will try to proceed in a direction that will reduce the pressure (stress). Because a reduction in the number of molecules in a system will reduce the stress, an elevated pressure will tend to inhibit the reforming reaction. (Note reforming systems often operate at moderate pressures, for operation at pressure will reduce the equipment size and cost. To compensate for this elevated pressure, the designer may be required to raise the temperature.)... 

In the past, coal or heavy hydrocarbon feedstock ammonia plants were not economically competitive with plants where the feedstocks were light hydrocarbons (natural gas to naphtha). Because of changing economics, however, plants that can handle heavy hydrocarbon feedstock are now attracting increasing attention- In addition, the continuous development and improvement of partial oxidation processes at higher pressure have allowed reductions in equipment size and cost. Therefore, the alternate feedback ammonia plants based on a partial oxidation process may become economically competitive in the near future. 

Table 2.2 gives equipment sizes and cost data for several alternative designs. Molecular weights are assumed for simplicity to be 50 lb/mole and density is 50 lb/ft3. An aspect ratio Cdiameter/length) of 0.5 is used. 

Subprograms and data banks for equipment sizing and costing. Process simulation programs enable the designer to consider alternative processing schemes. 

Other modules take care of equipment sizing and cost estimation, perform numerical calculations, handle recycle calculation (described in more detail below), optimize, and serve as controllers (executives) for the whole set of modules so that they function in the proper sequence. Figure 5.11 illustrates the information flow in a fiowsheeting package composed of modules. 

ChemCAD steady-state process simularo, including equipment sizing and costing... 

Understand the role of process simulators in process creation and be prepared to lean about their roles in equipment sizing and costing, profitability analysis, optimizatira, and dynamic simulation in the chapters that follow. 

Equipment Sizing and Costing Using ASPEN PLUS to Initiate Evaluation... 

To estimate equipment sizes and costs using Aspen IPE for a process simulated with ASPEN PLUS, it is necessary to prepare the simulation results for use with Aspen IPE. While this is accomplished in a similar manner for most of the major process simulators, these notes focus on the steps to prepare ASPEN PLUS simulations. For the steps when using the other process simulators, the reader should refer to the Aspen IPE User s Guide (press the Help button in Aspen IPE). 

In this section, the use of Aspen IPE for equipment sizing and costing is illustrated for a depropanizer and for the monochlorobenzene separation process. 

In this section, equipment sizes and costs are estimated for the monochlorobenzene (MCB) separation process, which is discussed in Section 4.4 of the textbook and in the multimedia portion of the CD-ROM (ASPEN Principles of Flowsheet Simulation Interpretation of Input and Output —> Sample Problem) that contains these course notes. Beginning with the file, MCB.bkp, which is available on the CD-ROM, additional mixture properties are added and the DISTL subroutine, used to model the D1 distillation column, is replaced with the RADFRAC subroutine. The reflux ratio computed using the RADFRAC subroutine is 3.35, as compared with 4.29 computed using the approximate DISTL subroutine. Also, the stream flow rates differ slightly (< 1%). Both of the files, MCB-IPE.bkp and MCB-IPE.rep, are on the CD-ROM. 

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