Preparative batch operations

These devices are replacing the older tank and spiral-conveyor devices. Better provisions for speed and ease of fill and discharge (without powered rotation) minimize downtime to make this batch-operated device attractive. Heat-transfer coefficients ranging from 28 to 200 W/(m °C) [5 to 35 Btu/(h fF °F)] are obtained. However, if caking on the heat-transfer walls is serious, then values may drop to 5.5 or 11 W/(m °C) [1 or 2 Btu/(h fH °F)], constituting a misapplication. The double cone is available in a fairly wide range of sizes and construction materials. The users are the fine-chemical, pharmaceutical, and biological-preparation industries. 

In batch operation there will be periods when product is being produced, followed by nonproductive periods when the product is discharged and the equipment prepared for the next batch. The rate of production will be determined by the total batch time, productive... 

Continuous operation provides high rates of production with more constant product quality. There are no downtimes during normal operation. Reactant preparation and product treatment also have to run continuously. This requires careful flow control. Continuous operation can involve a single stirred tank, a series of stirred tanks or a tubular-type of reactor. The latter two instances give concentration profiles similar to those of batch operation, whereas in a single stirred tank, the reaction conditions are at the lowest reactant concentration, corresponding to effluent conditions. 

The slowest step, which determines the speed of the entire analysis, is the sample decomposition step. Digestion of organic materials has generally taken the longest time of all sample types. Although it is true that most of these procedures could be made very efficient in batch operations, efforts to reduce preparation time by modification of procedures could prove invaluable to a routine laboratory(59). Some examples of this as applied to the analysis of bovine liver(60) and orange juice(61) can be found. 

The anthraquinone vat dyes provide, in certain instances, the ultimate in fastness properties although the shades are often rather dull. The products are, however, frequently difficult to prepare commercially, requiring multistage small-batch operations and are thus less economically viable than related dye classes. Thus, they are used almost exclusively in high quality outlets of long life expectancy. An example of historic interest is the dye formed by condensation of two molecules of 1-aminoanthraquinone and one of cyanuric chloride (9) which was discovered in 1921 (Cl Vat Orange 18). The significance of the reactive... 

Process steps include feed preparation, extraction, s >aration, and extxact finishing. Process parameters must be determirad for each raw material to achieve the optimum yield and quality of extract. The plant design must take into account hi pressure operation, food processing concerns, and repeated batch operation on lew bulk density solids. 

In the pharmaceutical industry most solid compounds are crystallized in batch operations, i.e., the crystalline product is isolated at the end of the operating cycle. Many bulk chemicals, such as table sugar, are prepared through continuous processes, in which the product is collected throughout the crystallization cycle. Batch crystallization produces a narrower range of particle size and may afford better control for the efficient crystallization of molecules from complex mixture [14]. 

A relatively pure form of natural gypsum (Terra Alba) consisting of 98.6% CaSO ZHjO was used for this study. The gypsum was ground to pass a 150-p.m (No. 100) sieve and calcined in a laboratory kettle designed for both continuous and batch operation. In this manner, three 15-kg lots of stucco were prepared by continuous calcination, and three 5-kg lots of stucco were calcined by the batch process. To two lots of the latter, either calcium chloride or surfactants were added. 

In continuous operations this can be done easily. In batch operations however, often filtration equipment cannot efficiently operate with extremely thin cakes. The long discharge times required to remove residual product in preparation for the next cycle, etc., make operation at a product s optimal... 

The most widely used methods by far employ coherent or granular gels. The former are most commonly polyacrylamide or agarose and the latter is usually Sephadex. Gels have been used in the preparative applications of each of the three common electrophoretic modes, isoelectric focusing (lEF), isotachophoresis (ITP) and zone electrophoresis (ZE). Regardless of the mode utilized, the procedure is most often a batch operation and employs either a cylindrical flat bed or annular separation chamber. Isotachophoresis has been applied to preparative scale fractionations in both polyacrylamide (.3) and Sephadex... 

When cyclohexyl chloride is the desired product for use in the preparation of cyclohexylamine or for condensations according to the Friedel and Crafts reaction, it appears advantageous to chlorinate in the presence of light and to use at least a 10 1 molar ratio of cyclohexane to chlorine in a cyclic process. The products of reaction are continuously withdrawn from the reaction chamber to a still (Fig. 6-6) where the unconverted cyclohexane is distilled off, condensed, and returned to the chlorinator which is provided with an encased battery of electric lights. The chlorinator, which is maintained at 65-65°C, is preferably made of lead, nickel, or Monel metaJ in order to provide better resistance against the corrosive action of the reaction products. A 5deld of about 94 per cent cyclohexyl chloride is thus obtained in batch operations when about half of the chlorine theoretically required to convert all the cyclohexane to cyclohexyl chloride has been reacted. 

The Biazzi Process. For many years, the process for preparing nitroglycerine has been carried out in small batch operations, and the procedure has varied only slightly. In recent years, a modem continuous process, developed by Mario Biazzi of Switzerland, has b n gradually replacing the older manufacturing methods. The apparatus (Fig. 12-12) consists of a nitrator, a separator, and three mechanically stirred washers. The entire... 

Assuming that the annual production requirement has been established, one of the first problems faced in process design is to choose a process cycle so that material and energy balances on a time basis can be worked out and all of the necessary flow sheets prepared. Questions related to a 24-hr or 8 hr/day operation and production by sequential batch operation or on a steady-state continuous basis must be resolved. 

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