Flowsheets examples

Figure 3.16. Flowsheet, Example 3.7, Compositions are weight percent. (Adapted from E. S. Henley and H. Beiber. Chemicai Engineering Calcuiations, McGraw-Hill Book Co., New York, O 1959.]...

FIGURE 8.8 (a) Flowsheet example and (b) basic block diagram for the flowsheet. 

The introduction of an extraneous component as a heat carrier aflfects the recycle structure of the flowsheet. Figure 4.6a presents an example of the recycle structure for just such a process. 

Example 6.1 The flowsheet for a low-temperature distillation process is shown in Fig. 6.19. Calculate the minimum hot and cold utility requirements and the location of the pinch assuming AT, m = 5°C. 

The choice of the appropriate azeotropic distillation method and the resulting flowsheet for the separation of a particular mixture are strong functions of the separation objective. For example, it may be desirable to recover all constituents of the original feed mixture as pure components, or only some as pure components and some as azeotropic mixtures suitable for recycle. Not every objective may be obtainable by azeotropic distillation for a given mixture and portfolio of candidate entrainers. 

The flowsheet for the recommended test system appears on the next page in Figure 4.2.1. Parts mentioned in the bill of materials below the flowsheet are examples for success l models. Other good parts can also be used. 

Since safety considerations are so important in any facility design, Chapter 14 has been devoted to safety analysis and safety system design. (Volume 1, Chapter 13 discusses the need to communicate about a facility design by means of flowsheets and presents general comments and several examples of project management. )... 

A separate table such as the example in Table 15-2 is prepared for each line designation. Each valve is assigned a designation on the flowsheets and explained in this table. The pipe, valves, and fittings table can sp( acceptable valves by manufacturer and model number, by a generic description, or by a combination of the two as shown in the example. It should be pointed out that Tables 15-1 and 15-2 are examples from American Petroleum Institute Recommended Practice (API RP) 14E and are illustrative only. There are almost as many different formats for pipe, valve, and fip "" tables as there are companies, and these examples are in no manner ty or recommended. Often, for. simphcity, valve types are not described i pipe, valve, and fittings specifications but on separate sheets for each. ... 

From the basic process-containing flowsheet other engineering specialties develop their own details. For example, the instrument engineer often takes the requirements of the process and prepares a completely detailed flowsheet which defines every action of the instruments, control valves, switches, alarm horns, signal lights, etc. This is his detailed working tool. 

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. 

The various items are usually numbered by type and in process flow order as set forth on the flowsheets. For example ... 

The process engineer identifies heat exchange equipment in a process by the operation or function it serves at a particular location in the flow cycle. For example, the bottom vaporizer on a product finishing distillation column is usually termed Finishing Column ReboUer E-16, or Reboiler E-16 the overhead vapor condenser on this column is termed Condenser E-17 etc. The usual operations involved in developing a process flowsheet are described in Table 10-11, or Chapter 1, Volume 1. 

FIGURE 8.2 Example of a flowsheet generated by computer-aided process synthesis, as would be seen on the screen of a computer terminal. The column on the left side of the figure shows options available in the particular design program being run. Courtesy, Peter Piela, Carnegie-Mel Ion University. 

The flowsheet shown in the introduction and that used in connection with a simulation (Section 1.4) provide insights into the pervasiveness of errors at the source, random errors are experienced as an inherent feature of every measurement process. The standard deviation is commonly substituted for a more detailed description of the error distribution (see also Section 1.2), as this suffices in most cases. Systematic errors due to interference or faulty interpretation cannot be detected by statistical methods alone control experiments are necessary. One or more such primary results must usually be inserted into a more or less complex system of equations to obtain the final result (for examples, see Refs. 23, 91-94, 104, 105, 142. The question that imposes itself at this point is how reliable is the final result Two different mechanisms of action must be discussed ... 

Present the MSPS graphically to the user (by highlighting the pipes on the flowsheet, for example). Ask the user to specify any pipes that he or she prefers to keep open. Mark all such pipes as unsatisfactory. If there are no unsatisfactory pipes, return the current SPS as the ASPS. 

In this example the flowsheet of the EDTA process has been modified by removing the following valves vlO, vll, vl3, and v20. The result of the modifications is shown in Fig. 17. 

The second example that is used to illustrate the design methodologies is a modification to the EDTA problem as follows. The structure of the flowsheet is exactly the same as the one presented in Section IV. The only change to the problem is the statement that sulfuric acid and formaldehyde should not be allowed to come into contact with each other. 

By way of an example, one may consider the case of hydrometallurgical reactors. Leaching is the most important of the different unit operations, and is prominently placed and assigned due emphasis in a typical hydrometallurgical process flowsheet. A representative list of the various types of reactors used for agitation leaching is given in Table 1.21. 

The electrostatic separation method is the exclusive choice in some specific situations, for example in the cases of rutile and ilmenite deposits. These deposits generally contain minerals of similar specific gravities and similar surface properties so that processes such as flotation are unsuitable for concentration. The major application of electrostatic separation is in the processing of beach sands and alluvial deposits containing titanium minerals. Almost all the beach sand plants in the world use electrostatic separation to separate rutile and ilmenite from zircon and monazite. In this context the flowsheet given later (see Figure 2.35 A) may be referred to. Electrostatic separation is also used with regard to a number of other minerals. Some reported commercial separations include those of cassiterite from scheelite, wolframite from quartz, cassiterite from columbite, feldspar from quartz and mica, and diamond from heavy associated minerals. Electrostatic separation is also used in industrial waste recovery. 

This section on flowsheets basically aims to provide some illustrative examples of the use of the various mineral processing unit operations that have been described. A general flowsheet involving almost all the unit operations pertinent to mineral processing is shown in Figure 2.32. The others refer specifically to beach sands, lead-zinc concentration, molybdenum, and the rare earths. 

Commercial-scale application of solvents coming under the category of neutral reagents is largely found as applied to the nuclear industry materials, as in example, for the separation and refining of uranium, plutonium, thorium, zirconium, and niobium. A process flowsheet for extracting niobium and tantalum from various resources is shown in Figure 5.23. It will... 

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 that attempts to predict how the process would behave if it were constructed (Figure 1.2b). Having created a model of the process, the flowrates, compositions, temperatures and pressures of the feeds can be assumed. The simulation model then predicts the flowrates, compositions, temperatures, and pressures of the products. It also allows the individual items of equipment in the process to be sized and predicts, for example, how much raw material is being used or how much energy is being consumed. The performance of the design can then be evaluated. There are many facets to the evaluation of performance. Good economic performance is an obvious first criterion, but it is certainly not the only one. 

The flowsheets shown in Figure 1.4 feature the same reactor design. It could be useful to explore the changes in reactor design. For example, the size of the reactor could be increased to increase the amount of FEED that reacts5. 

The calculation in this example can be conveniently carried out in spreadsheet software. However, many implementations are available in commercial flowsheet simulation software. 

Reactor heat carrier. As pointed out in Chapter 7, if adiabatic operation is not possible and it is not possible to control temperature by indirect heat transfer, then an inert material can be introduced to the reactor to increase its heat capacity flowrate (i.e. product of mass flowrate and specific heat capacity). This will reduce temperature rise for exothermic reactions or reduce temperature decrease for endothermic reactions. The introduction of an extraneous component as a heat carrier effects the recycle structure of the flowsheet. Figure 13.6a shows an example of the recycle structure for just such a process. 

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