Flowsheets for processes

Figure 2.35 (A) Flowsheet for heavy mineral processing in Thailand. (B) Flowsheet for processing bastnasite from mountain pass, California.

Figure 3. Conceptual flowsheet for processing aluminum residues...

Another advantage is that a prereformer may be preferred in flowsheets for processing heavier feedstocks. The prereformer converts heavier hydrocarbons to methane before they are fed to the steam reformer. This allows the steam reformer to be designed for methane service. The prereforming catalysts are very sensitive to poisons. Therefore a good feed purification section is essential.70... 

Fig. 19.20. Flowsheet for processing soybeans by aqueous extraction processing (Source Lawhon etal., 1981).

Flowsheets for processes are sometimes generated without following the hierarchy of properties described previously. As an example, Siirola [20] proposed a reactive-distiUation solution to make methyl acetate. Unit operations that combine the property differences present abrupt departures from common methodologies. With the advent of various pieces of equipment, such as differential side-stream feed reactors (i.e., semicontinuously fed batch reactors), continuous evaporator-reactors (e.g., wiped-film evaporators), and reactive distillation columns, one can consider these unit operations in the development of conceptual designs. As an example, Doherty and Malone [21] have presented systematic methods for reactive distillation design. 

Copper refinery bleed streams contain various amounts of nickel mixed with copper, iron, arsenic and other impurities. Separation of the impurities is achieved by pH adjustment to precipitate the impurities. A nickel carbonate intermediate product can be produced to feed the EMEW circuit and control pH during electrowinning. A schematic diagram showing a basic flowsheet for processing crude nickel sulfate from copper refinery bleed is provided in Figure 2. In cases where the bleed from the copper refinery is processed directly by an acid purification unit [10, 11], the return of acid to the refinery is accomplished and the cost of neutralization is significantly reduced. 

Because of the great variety of aqueous waste streams and differences in process flow arrangements in different plants, there is no standard flowsheet for processing aqueous wastes from the PUREX process. Figure 14.15 depicts the principal steps in one possible scheme for concentrating the wastes and recovering water and nitric acid from them. Low-level, low-acid, low-salt wastes are neutralized, if necessary, and concentrated in a simple flash or vapor-compression evaporator to produce LLW concentrates and waste sufficiently decontaminated for return to process. 

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. 

Figure 4.16 Final flowsheet for the production of butadiene sulfone in a batch 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. 

Fig. 1. A typical process flowsheet for acrolein manufacture. A, Fixed-bed or fluid-bed reactor B, quench cooler C, absorber D, stripper E and F,...

Process. synthesis. Concept development, construction of flowsheets for new processes, and redesign or modification of existing process flowsheets. 

Figure 3.24 shows the process flowsheet for an ethylene/ethylbenzene plant, Gas oil is cracked with steam in a pyrolysis furnace to form ethylene, low BTU gases, hexane, heptane, and heavier hydrocarbons. The ethylene is then reacted with benzene to form ethylbenzene (Stanley and El-Halwagi, 1995). Two wastewater streams are formed R ... 

Flfiure 3.24 Process flowsheet for an ethylene/ethylbenzene plant. 

Prepare/supervise preparation of draft of process flowsheets for review by others. 

The flowsheet also describes the process to management as well as those concerned tvith preparing economic studies for process evaluation. 

Many s)mbols are pictorial which is helpful in representing process as well as control and mechanical operations. In general, experience indicates that the better the representation including relative locating of connections, key controls and even utility connections, and service systems, the more useful will be the flowsheets for detailed project engineering and plant design. 

Figure 1-20B. Commonly used instruments for process instrumentation flowsheets. Adapted by permission, ISA Std. ANSI Y32.20—1975, ISA S5.1—1973, Instrumentation Symbols and Identification," Latest edition, 1984.

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

Figure 3 shows a flowsheet for plutonium processing at Rocky Flats. Impure plutonium metal is sent through a molten salt extraction (MSE) process to remove americium. The purified plutonium metal is sent to the foundry. Plutonium metal that does not meet foundry requirements is processed further, either through an aqueous or electrorefining process. The waste chloride salt from MSE is dissolved then the actinides are precipitated with carbonate and redissolved in 7f1 HN03 and finally, the plutonium is recovered by an anion exchange process. 

The above information was used to develop conceptual flowsheets for the extraction of all of the actinides (U, Np, Pu, Am, and Cm) from high-level liquid waste from PUREX processing using 0.4 M 0fuel using 0.8 M DHDECMP in DEB. In both flowsheets, no oxidation state of Pu is necessary since the III, IV, and VI state extract into the organic phase. 

Conceptual Flowsheet for the Extraction of Actinides from HLLW. Figure 5 shows a conceptual flowsheet for the extraction of all the actinides (U, Np, Pu, Am, and Cm) from HLLW using 0.4 M 0< >D[IB]CMP0 in DEB. The CMPO compound was selected for this process because of the high D m values attainable with a small concentration of extractant and because of the absence of macro-concentrations of uranyl ion. Distribution ratios relevant to the flowsheet are shown in previous tables, IV, V, VI, and VII and figures 1 and 2. One of the key features of the flowsheet is that plutonium is extracted from the feed solution and stripped from the organic phase without the addition of any nitric acid or use of ferrous sulfamate. However, oxalic acid is added to complex Zr and Mo (see Table IV). The presence of oxalic acid reduces any Np(VI) to Np(IV) (15). The presence of ferrous ion, which is... 

The flowsheet in Figure 6 is somewhat analogous to that proposed and tested by Mclsaac, Baker, Krupa, LaPointe, Meikrantz, and Schroeder C3) for processing HLLW from LWR using DHDECMP. The major differences are the larger phase ratios in the extraction... 

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