Process flow sheet, information

Flow-sheet models are used at all stages in the life cycle of a process plant during process development, for process design and retrofits, and for plant operations. Input to the model consists of information normally contained in the process flow sheet. Output from the model is a complete representation of the performance of the plant, including the composition, flow, and properties of all intermediate and product streams and the performance of the process units. 

Often, the walkthrough and analysis of the process flow sheets lead to an early identification of P2 and waste-reduction opportunities. By studying the process flow sheets and information gathered from the walkthrough, and by conducting brainstorming sessions with team members, the team will be able to identify sources... 

Step 5.4 Record Information on Process Flow Sheets. The input data collected for the material balance can be recorded on the process flow diagram, and in tabular form on a spreadsheet. 

The total stream and individual component flows do not normally need to be shown to a high precision on the process flow-sheet at most one decimal place is all that is usually justified by the accuracy of the flow-sheet calculations, and is sufficient. The flows should, however, balance to within the precision shown. If a stream or component flow is so small that it is less than the precision used for the larger flows, it can be shown to a greater number of places, if its accuracy justifies this and the information is required. Imprecise small flows are best shown as TRACE . If the composition of a trace component is specified as a process constraint, as, say, for an effluent stream or product quality specification, it can be shown in parts per million, ppm. 

The P and I diagram will resemble the process flow-sheet, but the process information is not shown. The same equipment identification numbers should be used on both diagrams. 

In the descriptions of the various technologies, several assumptions and omissions to the process flow sheets have been made in order to help understanding of the principal issues and to improve the clarity of the descriptive. If a particular technology or approach is of interest to the reader then the process licensor should be approached for the latest updates and information. 

Usually, a process flow sheet is given which includes much important design information for the complete process. This basic resource document is the key referenee for the overall material balance for the process, and includes mass flow rates and complete chemical compositions for every stream in the process network. Other data usually included in the process flow sheet are temperature and pressure for every process stream, important physical and thermodynamic properties for each stream, identification numbers and abbreviations for each equipment component, and identification and information for every addition and removal of energy or work for the process. 

The first step is to collect pertinent information to the process, including a process flow sheet, produet information and completion of a typical questionnaire, as shown in Table 2. 

Design a 250,000 Ib/yr Lindane (99 per cent 7 isomer of benzene hexachloride) plant based on process information given in the current literature [e.g., see Chem. Eng. Progr., 52 281 (1956) Chem, Week, 78 54 (1956) Ind. Eng. CAem., 48(10) 41A (1956)], Develop the process flow. sheets, equipment specifications, and plant layout. Examine the economics of producing Lindane including (1) fixed and capital cost estimates by one or more of the methods outlined in Chap. 6, (2) profitability analysis showing return on investment and pay-out time, (3) break-even point analysis of the project, (4) economic estimates for a plant producing 500,000 Ib/yr and 750,000 Ib/yr. 

For example, a process flow sheet can easily be constructed in Excel as follows in the sheet Elow sheet draw a flow sheet by using the drawing toolbar. Any information concem-ing process conditions can be inserted in cells near the desired point of the flow sheet Eor each piece of information there need to be three cells, one for the variable name, one for the variable value, and one for the variable units. That is, to insert a stream flow rate, select a cell near the icon of the stream arrow and insert the symbolic name of the stream flow rate, i.e., F =, in a neighboring cell insert the formula = F to get the value from the Process sheet, and in another cell, nearby, insert the units, i.e., kg/s. You can add any information you like. Any changes in data are updated immediately. 

While the descriptions provided in these efforts are informative, they do not reflect reality in totality as the process flow sheets on which these estimates are based, start with highly optimistic descriptions of various operations. The eneigy flow diagram for... 

Having decided on the basic arrangement of the system components, the next step is the detailed layout of the system. For this purpose, the second type of flow diagram is used, the process flow sheet, which describes the process using defined design marks for apparatus, armatures, and flow lines. This type of diagram contains the following basic information ... 

The process flow sheet presented in Figure 32.10 provides the minimum information that should be given. Very often, additional information is implemented in the form of a rectangle with four different values, for example, pressure, enthalpy, mass flow, and temperature. The orientation, together with the units used, should also be shown in the diagram. As an example, the conflguration with the highest... 

Figure 32.12 Process flow sheet of an SOFC power plant with additional information.

A scope or budget authorization, the next level of economic evaluation, requires a more defined process definition, detailed process flow sheets, and prefinal equipment design (discussed in a later section). The information required is usually obtained fiom pilot plant, marketing, and other studies. The scope authorization estimate could cost upwards of 80,000 for a 5 million facility with a probable error exceeding 20%. 

In a new case in Hysys, add the components ethane and water, and select the appropriate fluid package (NRTL). Enter the simulation environment and mix the two streams as shown in Figure 1.39. The Workbook is used to display the stream summary table below the process flow sheet. Click on Workbook in the toolbar once the workbook appears, click on Setup in the Workbook menu, and then click on Add to add the required variables from the list of variables. Once all information required is added to the workbook, right click anywhere in the PFD area and select Add Workbook Table. 

The first step is to have a complete and detailed description of the system, process, or procedure under consideration. This must include physical properties of the materials, operating temperatures and pressures, detailed flow sheets, instmment diagrams of the process, materials of constmction, other detailed design specifications, and so forth. The more detailed and up-to-date this information is, the better the result of the analysis. 

The first step in the procedure is to define the purpose, objectives, and scope of the study. The more precisely this is done, the more focused and relevant the committee discussions can be. The next step is to collect all relevant information on the process under consideration. This includes flow diagrams, process equipment specifications, nominal flows, etc. The procedure is highly dependent on the reflabiUty of this information. Efforts expended here are worthwhile. Many committees use the flow sheet as the central stmcture to organize thek discussions. 

During process development, a model can be developed as soon as a conceptual flow sheet has been formulated. This model can be updated as more information about the process is obtained. Even at an early stage in the project, the model can be used to assess the preliminary economics of the process and the effect of technological changes on these economics. The model can aid in interpreting pilot-plant data and allows the study of many process alternatives. 

A hierarchical design procedure for process synthesis can be used in conjunction with a flow-sheeting program to analyze, evaluate, and optimize the options (60). The emphasis is on starting with the simplest possible models that will give answers to a particular question quickly so that the questions to be asked at the next decision level can be formulated. At each stage, it is necessary to ensure that the level of detail in the model is sufficient to give rehable information. 

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