Batch vs. continuous processes

If the volume/economics situation justifies continuous production versus batch production then the process development chemist has a whole new array of techniques available to minimise waste production at source, i.e. in the operation of the process. Recovery and recycle of solvents or raw materials as integral parts of the continuous process lead to greater efficiencies than most batch processes, make costs of production lower, and hence enhance the competitive position of the product in the market 

Esterification processes, particularly trans-esterification, provide good examples of such modifications leading to enhanced process performance and waste minimisation. The following generalised process flow diagrams will illustrate the point adequately. 

As an example, consider the transesterification of a simple methyl ester, MeOCOR , exchanging the methyl for a more complex alcohol, R OH, in the presence of a metal alcoholate catalyst, M(OX) [10]. 

The equilibrium is driven to the right by removal of methanol. An excess of the methyl ester is also required to ensure optimum conversion of the more complex, and probably more expensive, alcohol R OH. 

If the process is modified to include the formation of an intermediate, reactive ester by reaction of the methyl ester with the metal alcoholate in stoichiometric proportions, methanol can easily be removed before further reaction of the reactive ester with the desired alcohol. This latter reaction takes place at high yields with substantial absence of impurities [11]. Of course, effective use and recycle of the metal is essential to provide cost effective manufacture. 

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Should energy efficiency also be analyzed in terms of batch vs continuous processes ... 

Batch vs Continuous Reactors. Usually, continuous reactors yield much lower energy use because of increased opportunities for heat interchange. Sometimes the savings are even greater in downstream separation units than in the reaction step itself Especially for batch reactors, any use of refrigeration to remove heat should be critically reviewed. Batch processes often evolve Httle from the laboratory-scale glassware setups where refrigeration is a convenience. 

Process Flowsheet Batch vs. Continuous operation Detailed unit operations selection Control and operation philosophy Information above plus process engineering design principles and experience... 

In this subsection, specific operating parameters will be discussed. These includes nutrient media for use during desulfurization process, toxicity of solvent to various biocat-alytic strains, effect of oil/water ratio on biocatalyst as well as desulfurization rates and subsequent separations, biocatalyst density during desulfurization, and finally, the alternative to operate the desulfurization process in batch vs. continuous mode. 

Desired scale of operation, and type (batch vs. continuous). Ease of process scale-up and scale-down, as well as range of granule property control at one scale... 

The use of automated process controls and processing equipment is more likely to be utilized in an excipient plant than in a finished dosage form manufacturing plant Use of automated equipment is appropriate when adequate inspection, calibration, and maintenance procedures are utilized. Production equipment and operations will vary depending on the type of excipient being produced, the scale of production, and the type of operation (i.e., batch vs continuous). 

If computer-integrated resin handling systems are considered, one must compare their operating procedures with one s process requirements. These process requirements describe the flow of resin and product through the system, which determines the system s electronic architecture. Pertinent considerations include batch vs. continuous operations, the type and number of conveying lines, resin storage and distribution, quality control means and procedures, inventory control, the type and quantity of process parameter sensors, the type and quantity of controlled devices, modes (automatic, semiautomatic, manual, and/or shutdown modes), process information, process management controls, and centralized vs. local operation (Fig. 9-1). 

This strong text organizes separation processes as batch vs continuous and as staged vs differential. It sensibly includes coupled separation and chemical reaction. Supported by strong examples and problems, this non-conven-tional organization reinforces the more conventional picture of unit operations. ... 

Batch vs. Continuous. Some nitrile rubber producers use a batch process. The batch process has the advantage of making small amounts of many different products, thus enabling the producer to tailor-make polymers for relatively low-volume specialty applications. Obviously, however, the disadvantage is the relatively high changeover costs. On the other hand, some nitrile rubber producers use a continuous process. This process is relatively low cost but limits the number of products that can be economically produced since minimum run quantities are relatively large. 

Protein purity, yield and quality are easily affected by processing conditions (e.g. temperature, time, flour to solvent ratio, condition and protein solubility of the starting material, type of equipment and process used, g forces used for centrifugation, laboratory vs. pilot scale extraction, batch vs. continuous extraction, etc.). 

Solvent extraction is a separation process by which solutes are transferred from a solid or liquid mixture into a solvent. Oilseed extraction refers to preferential dissolution of oil by contacting oilseeds with a liquid solvent. Solvent extraction is the most efficient technique to recover oil from oilseeds. The process efficiency depends on the oilseed preparation prior to extraction, temperature, mode of operation (batch vs. continuous and co-current vs. countercurrent operations), equipment design and, most importantly, solvent type. Residual oil in the meal is expected to be less than 1% after commercial solvent extraction. 

NG. Batch-wise production of NG is described in Vol 6, G99-102, and continuous methods such as the Schmid t-Meissner and Biazzi processes are discussed in Vol 3, C501 — 505. The Swedish injector process and the Hercules tubular nitrator will be described below, but before doing this we will discuss certain aspects of glycerin nitration that are common to both batch and continuous methods, and then contrast the main features of the batch process vs the continuous process... 

Continuous vs. Batch Processing. It is the usual rule in process design to choose continuous processing in preference to batch processing based purely on economic reasons. By operation on a continuous 24 hr/ day basis, smaller-size, less expensive processing equipment is used. Process operation is steady state and easier to control by automatic instrumentation than is batch operation. Thus, capital investment, fixed charges, and labor requirements are minimized. However, batch processing is not a completely obsolete method in the chemical industry. It is feasible in such cases as ... 

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