Multiple-stage process

Patterns of cyclic carbopalladation. As discussed above, the fundamentally stoichiometric and living nature of carbopalladation imposes various difficulties to be overcome. Carbopalladation can, in principle, be either a single-stage process or double- or multiple-stage processes. Double-and multiple-stage carbopalladation reactions have often been called either domino or cascade carbopalladation reactions. In some cases, two-stage carbopalladation reactions have also been called tandem carbopalladation reactions. None of these three words is a chemical term, and choice between them is a matter of taste. In this chapter, the term cascade will be used for both double- and multiple-stage carbopalladation processes. 

Now consider a multiple-stage process with countercurrent flow of the raffinate and extract phases. Fig. 2B. Countercurrent is the most efficient multistage configuration. One can write a mass balance around the nth stage, as indicated by envelope 1, using the following units for a continuous flowing process ... 

Non-genotoxic carcinogens are not able to change the DNA. A permanent irritation or inflammation of cells can provoke an increased cell proliferation, which can result in a multiple-stage process leading to a tumor. 

The microstructured extraction devices are attractive for process intensification, since they allow precisely controlled and rapid extraction and the small dimensions permit their flexible use in multiple-stage processes including the repetition of reaction and extraction operations. These advantages are effective for reaction... 

Graphical determination of the number of trays. A plot of the operating-line equation (10.6-2) as y versus x will give a curved line. If x and y are very dilute, the denominators 1 — X and 1 — y will be close to 1.0, and the line will be approximately straight, with a slope L/V. The number of theoretical trays are determined by simply stepping off the number of trays, as done in Fig. 10.3-3 for a countercurrent multiple-stage process. 

There are two t)q)es of processes. One is called a single stage process, while another is termed a two or multiple stage process. The single stage... 

Various polymer morphologies with different molecular structures and molecular weights can be achieved with a multiple-stage process. It is possible to control the morphology of the system with layers, lobes or isolated domains of specific composition. 

Cyclohexane. The LPO of cyclohexane [110-82-7] suppUes much of the raw materials needed for nylon-6 and nylon-6,6 production. Cyclohexanol (A) and cyclohexanone (K) maybe produced selectively by using alow conversion process with multiple stages (228—232). The reasons for low conversion and multiple stages (an approach to plug-flow operation) are apparent from Eigure 2. Several catalysts have been reported. The selectivity to A as well as the overall process efficiency can be improved by using boric acid (2,232,233). K/A mixtures are usually oxidized by nitric acid in a second step to adipic acid (233) (see Cyclohexanol and cyclohexanone). 

Solvent Extraction. With solvent extraction, organics are separated from a waste by mixing the waste with a solvent capable of dissolving or extracting the organics. The extraction process can have multiple stages and be operated where the solvent and waste pass concurrently or countercurrenfly. 

Exothermic processes, with cooling through heat transfer surfaces or cold shots. In use are sheU-and-tube reactors with smaU-diameter tubes, or towers with internal recirculation of gases, or multiple stages with intercoohng. Chlorination of methane and other hydrocarbons results in a mixture of products whose relative amounts... 

Figure 7-4. The Scientific Design Co. process for producing ethylene glycols from ethylene oxide (1) feed tank, (2) reactor, (3,4,5) multiple stage evaporators, 4 operates at lower pressure than 3, while 5 operates under vacuum, evaporated water is recycled to feed tank, (6) light ends stripper, (7,8) vacuum distillation columns.

In comparison to batch processing, this process operates at the final concentration with associated low fluxes. The use of multiple stages where the retentate outlet from one stage feeds the next allows successive systems to operate at different fluxes and will improve membrane productivities. 

It is possible to employ either multiple individual tanks in series or units containing multiple stages within a single shell (see Figure 8.2). Multiple tanks are more expensive, but provide more flexibility in use, since they are more readily altered if process requirements change. In order to minimize pump requirements and maintenance, one often chooses to allow for gravity flow between stages. When the reactants are of limited miscibility, but differ... 

The desulfurization process can be carried out either, in a dedicated reactor, or within a simple storage vessel, or during transportation (in pipelines) or intermediate processing vessels. Nutrients addition, pH, and aeration are adjusted as necessary. Multiple stages can be added to the reaction to enhance the sulfur removal process and decrease the reaction time below the probable 300 h required. The produced sulfates are removed by the addition of agents such as alkaline calcium, magnesium, aluminum, barium, and metal compounds such as oxides, hydroxides, and carbonates. 

Semicontinuous production processes can be described in a similar way as batch production processes by adding a duration information to a material flow. This makes it possible to handle the overlapping of independent process orders over multiple stages in campaign planning and semicontinuous production planning. 

It is proposed to reduce the concentration of acetaldehyde in aqueous solution from 50 per cent to 5 per cent by mass, by extraction with solvent S at 293 K. If a countercurrent multiple-contact process is adopted and 0.025 kg/s of the solution is treated with an equal quantity of solvent, determine the number of theoretical stages required and the mass flowrate and concentration of the extract from the first stage. 

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