Flowsheet equipment

Feasibility (factored) 30% Process Flowsheets, Equipment Size, Regional Location... 

Concept identification 10 2. Concept generation produce Conceptual design, flowsheet Equipment costs using flowrate 0... 

Design several alternative steady-state processes flowsheet, equipment sizes, operating conditions and utilities. 

Once the flowsheet structure has been defined, a simulation of the process can be carried out. A simulation is a mathematical model of the process which attempts to predict how the process would behave if it was constructed (see Fig. 1.1b). Having created a model of the process, we assume the flow rates, compositions, temperatures, and pressures of the feeds. The simulation model then predicts the flow rates, compositions, temperatures, and pressures of the products. It also allows the individual items of equipment in the process to be sized and predicts how much raw material is being used, how much energy is being consumed, etc. The performance of the design can then be evaluated. 

An initial guess for the reactor conversion is very difficult to make. A high conversion increases the concentration of monoethanolamine and increases the rates of the secondary reactions. As we shall see later, a low conversion has the effect of decreasing the reactor capital cost but increasing the capital cost of many other items of equipment in the flowsheet. Thus an initial value of 50 percent conversion is probably as good as a guess as can be made at this stage. 

Clearly, the time chart shown in Fig. 4.14 indicates that individual items of equipment have a poor utilization i.e., they are in use for only a small fraction of the batch cycle time. To improve the equipment utilization, overlap batches as shown in the time-event chart in Fig. 4.15. Here, more than one batch, at difierent processing stages, resides in the process at any given time. Clearly, it is not possible to recycle directly from the separators to the reactor, since the reactor is fed at a time different from that at which the separation is carried out. A storage tank is needed to hold the recycle material. This material is then used to provide part of the feed for the next batch. The final flowsheet for batch operation is shown in Fig. 4.16. Equipment utilization might be improved further by various methods which are considered in Chap. 8 when economic tradeoffs are discussed. 

Power requirements for spiral plants are low, consisting primarily of pumping energy and possibly a thickener or other pulp-handling equipment associated with the flowsheet. 

FIG. 25-17 Schematic flowsheet illustrating the individual elements of an open, single-layer hiofilter system. Particulate filtration and/or temperature adjustment is often combined with the equipment to adjust gas humidity content. 

Preliminary Process Flowsheet. This will show major equipment and lines, preliminary equipment details (vessel diameter, number of trays, pump flow and driver horsepower, etc.), major instrumentation, and, it is hoped, have a material balance at the bottom of each drawing with flows keyed to a numbering system on the diagram. The process flowsheets should cover both the process and utility sides of the plant. 

Figure 12-2. Flowsheet and floor plan of hazardous equipment. (Source Shabica [2].)...

The result of process synthesis is a flowsheet which represents the configuration of the various pieces of equipment and their interconnection. Next, it is necessary to analyze the performance of this flowsheet. 

The path diagram provides the big picture for mass flow from a species viewpoint. This is a fundamentally different vision from the equipment-oriented description of a process (the flowsheet), in which the big picture is lost. The path diagram can also be used to determine the effect on the rest of the diagram of manipulating any node. In addition, as will be shown later, it provides a systematic way for identifying where to remove the pollutants and to what extent they should be removed. 

The initial aim of the procedure is to generate a reasonable base case design that can be used for preliminary economic evaluation of the process. This can subsequently be optimized and/or compared with any process alternatives that are identified. The complete process is always considered at each decision level, but additional fine detail is added to the structure of the flowsheet at any stage. Established heuristics and equipment selection procedures are used together with new process synthesis insights to guide each flowsheet decision. 

Designs and/or specifies items of equipment required to define the process flowsheet or flow system specifies corrosion resistant materials of construction. 

Chemical engineering performance design for specific items of equipment required for a flowsheet, and mechanical interpretation of this to a practical and reasonable specification. Here the process requirements are converted into hardware details to accomplish the process end results at each step in the product production process. 

Used to present the heat and material balance of a process. This may be in broad block form with specific key points delineated, or in more detailed form identifying essentially every flow, temperature and pressure for each basic piece of process equipment or processing step. This may and usually does include auxiliary services to the process, such as steam, water, air, fuel gas, refrigeration, circulating oil, etc. This type of sheet is not necessarily distributed to the same groups as would receive and need the piping flowsheet described next, because it may contain detailed confidential process data. 

Figure 1-17 [2] can be used as a guide in establishing relative sizes of equipment as represented on a flowsheet. This chart is based on approximate relative proportions pictured by the mind s eye [2]. For example, the 10-foot diameter x 33-foot high tank would scale to 1.5 inches high. By using the height-developed scale factor, the diameter would be (1.5"/33 ) (10 ) = 0.45" or say 0.5" diameter on the flowsheet. 

For some purposes the addition of equipment specification and performance data on the flowsheets adjacent to the item is of value. In many cases though, this additional information makes the sheets difficult to read. The... 

The two types of lines on a flowsheet are (1) those representing outlines and details of equipment, instruments, etc., and (2) those representing pipe carrying process or utility liquids, solids, or vapors and electrical or instrument connections. The latter must be distinguished among tliemselves as suggested by Figure 1-21. 

Some equipment code systems number all items on first process flowsheet with 100 series, as C-101, C-102, P-106 to represent compressors number 101 and 102 in different services and pump 106 as the sixth pump on the sheet. The second sheet uses the 200 series, etc. This has some engineering convenience but is not always clear from the process view. 

From an examination of the process flowsheet the man-hours total 685 for the significant equipment. Items such as steam traps and miscellaneous small time-items can be omitted from the total. Includes 75 man-hours for pipeline sizing. 

In some cases, they may be anticipated by a knowledge of the status of the process data prior to the start of engineering acthity. The larger projects are somewhat easier to group than the smaller ones. Process engineering is not always handled as completely for the small jobs. This is to say that flowsheets may be simplified, detailed equipment and line schedules may not be required, and the over-all project can be completely visualized at the outset, which is not the case with large projects. 

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