Process evaluation total plant cost

Step 5. Economic evaluation. Not shown in this example, but included in a process synthesis program such as PIP, are algorithms for costing and economic evaluation of the process. Process equipment is sized and priced and total plant investment is estimated. Requirements and costs for utilities and raw materials, other operating costs, and product values are estimated. These values are used to evaluate the profitability of the proposed process and can provide a sound basis for a more detailed design. 

A firm is evaluating two competing projects. The first is a new ( grass roots ) inorganic chemicals plant, while the second is the expansion of a textile fibers facility. The process engineers have estimated the projected annual revenue, total capital investment, and total annual cost (without capital recovery) for each project, as follows ... 

The annual total cost was analyzed considering 3 variables (i) total water flowrate (see Fig. 5a, b) (ii) freshwater flowrate (see Fig. 5c) and (ii) water reuse flowrate (see Fig. 5d). This evaluation was done considering the total annual cost variation respect to the total flowrate into two steps. First, an interval of water reuse possibilities was observed, according to Fig. 5a, in which the total water flowrate varies from 132.7 to 132.85 t h In this interval the total cost decreased linearly until the minimum Pinch flow rate. Below the 132.7 t h there are no viable reuse networks. In a second analysis it was observed that above 132.85 t h the total annual cost increased, as can be observed in Fig. 5b. It means that in this interval there are no possibilities of reuse and the process operation is between the minimum necessary limits for the key component mass transfer until the maximum available value to the industrial plant operation. 

The following are the major units in a chemical plant. Evaluate the bare-module cost for each unit and for the entire process. Assuming no allocated costs for utilities and related facilities, estimate the direct permanent investment, the total depreciable capital, and the total permanent investment for the process. 

Part Three includes chapters that provide instruction and examples of the design of heat exchangers, multistage and packed towers, and pumps, compressors, and expanders. In addition, Chapter 16 provides guidelines for selecting processing equipment and equations for estimating the purchase costs of a broad array of equipment items. Furthermore, Section 16.7 shows how to use the Aspen Icarus Process Evaluator (IPE), with the process simulators, to estimate purchase costs and the total permanent investment for a chemical plant. 

Recently, Contos et al. (50) and McCandless and Contos (51) have made a comprehensive assessment of the economics of the major chemical coal cleaning processes. Since pilot plant data were not available for most processes, the costs were based on preliminary conceptual designs. Taking bituminous coal from the Pittsburgh seam as a representative coal (which contained 1.93 wt% total sulfur, about 66% of which was pyritic sulfur), capital and operating costs for a feed rate of 7,200 metric ton/day plant were evaluated based on the first quarter of 1977 prices. A brief summary of their study is shown in Table 2. 

For an existing process plant, the designer has the opportunity to take measurements of the fume or plume flow rates in the field. There are two basic approaches which can be adopted. For the first approach, the fume source can be totally enclosed, and a temporary duct and fan system installed to capture the contaminant. For this approach, standard techniques can be used to measure gas flow rates, gas compositions, gas temperatures, and fume loadings. From the collected fume samples, the physical and chemical characteristics can be established using standard techniques. For most applications, this approach is not practical and not very cost effec tive. For the second approach, one of three field measurement techniques, described next, can be used to evaluate plume flow rates and source heat fl uxes. 

The overall problem, from sulfur in a raw gas through sulfur recovery and tail gas treating, has historically been addressed by a case study approach. In this approach, each plant section is optimized based upon predetermined subsystem interfaces. A preferred approach, rather, is to evaluate the entire system analytically, allowing the interfaces between the subprocesses to float, to determine the overall cost-effective,approach. In this technique, compromises are taken in each of the unit processes so that the total system operates more effectively. 

---