Reflux condensers, with batch processing

Process Unit or Batch Unit A process unit is a collection of processing equipment that can, at least at certain times, be operated in a manner completely independent from the remainder of the plant. A process unit normally provides a specific function in the production of a batch of product . For example, a process unit might be a reactor complete with all associated equipment (jacket, recirculation pump, reflux condenser, and so on). However, each feed preparation tank is usually a separate process unit. With this separation, preparation of the feed for the next batch can be started as soon as the feed tank is emptied for the current batch. 

The general charac teristics of the main types of reac tors—batch and continuous—are clear. Batch processes are suited to small production rates, to long reaction times, or to reactions where they may have superior selectivity, as in some polymerizations. They are conducted in tanks with stirring of the contents bv internal impellers, gas bubbles, or pumparound. Temperature controf is with internal surfaces or jackets, reflux condensers, or pumparound through an exchanger. 

Because hydrolytic reactions are reversible, they are seldom carried out in batch wise processes [26,28,36,70]. The reactor is usually a double jacket cylindrical flask fitted with a reflux condenser, magnetic stirrer, and thermometer connected with an ultrathermostat. The catalyst is added to the reaction mixture when the desired temperature has been reached [71,72]. A nitrogen atmosphere is used when the reactants are sensitive to atmospheric oxygen [36]. Dynamic methods require more complicated, but they have been widely used in preparative work as well as in kinetic studies of hydrolysis [72-74]. The reaction usually consists of a column packed with a layer of the resin and carrying a continuous flow of the reaction mixture. The equilibrium can... 

A 500 cc flask equipped with a mechanical stirrer, reflux condenser and a soda-lime tube was filled with 230 cc of absolute xylene, 27.5 g of 1-methyl-3-bromomethylpiperidine, 53.3 g of phenothiazine and 14.2 g of finely powdered sodium amide, and the solution was heated under reflux for 6 hours. After cooling water was added and the batch was extracted with ether. As the hydrochloric acid salt of the obtained phenothiazine derivative is difficultly soluble in water, the further processing was carried out by way of the acetate. The etheric solution was extracted several times in a separating funnel with dilute acetic acid. The combined aqueous extracts were basified, extracted with ether, dried with potassium carbonate and, after removal of the ether, distilled in vacuo. 

For both batch and semibatch processes, the reactor kettle is often provided with heating or cooling as needed by external sources such as cooling water, tempered water, steam, oil, or electric or reflux condensers. The reaction vessel may also be put under vacuum to remove undesired volatile material. In many cases, the removal of volatiles is not simply a requirement to achieve regulatory requirements, but rather to drive the reaction to completion. For example, in condensation polymerization... 

According to components bubble point (table 2), the distillation involves the separation of the methanol and the resultant reactants (for the most part water) from the reaction mixture. Propylene glycol and by-products are then recovered from the boiler. The overhead batch distillation column consists of a packed column of 50 cm in length and 10 cm in diameter. A condenser equipped with a complex controlled reflux device completes this process. A heat transfer fluid supply reactor jacket with a temperature varying from 10 to 170°C according to the operating steps. 

The activated Ba(OH)2 was used as a basic catalyst for the Claisen-Schmidt (CS) condensation of a variety of ketones and aromatic aldehydes (288). The reactions were performed in ethanol as solvent at reflux temperature. Excellent yields of the condensation products were obtained (80-100%) within 1 h in a batch reactor. Reaction rates and yields were generally higher than those reported for alkali metal hydroxides as catalysts. Neither the Cannizaro reaction nor self-aldol condensation of the ketone was observed, a result that was attributed to the catalyst s being more nucleophilic than basic. Thus, better selectivity to the condensation product was observed than in homogeneous catalysis under similar conditions. It was found that the reaction takes place on the catalyst surface, and when the reactants were small ketones, the rate-determining step was found to be the surface reaction, whereas with sterically hindered ketones the adsorption process was rate determining. 

A batch distillation plant consists of a still or reboiler, a column with several trays, and provisions for reflux and for product collection. Figure 13.10(c) is a typical equipment arrangement with controls. The process is applied most often to the separation of mixtures of several components at production rates that are too small for a continuous plant of several columns equipped with individual reboilers, condensers, pumps, and control equipment. 

Figure 12-41. Process B Batch reaction with reactants added during the reaction. Little flammable and hazardous material are present at any time. A reflux (or knockback) condenser is used to provide additional heat transfer. (Source S. M. Englund, Inherently Safer Plants Practical Applications, Process Safety Progress, Vol. 14, No. 1, pp. 63-70, AlChE, 1995.)...

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