Cyclical batch, control

Of these, the flexible batch is by far the most difficult to automate and requires a far more sophisticated control system than either the cyclical batch or the multigrade batch facihty. 

Since elution is basically a batch technique, continuous production requires cyclic batch operation under automatic control. This is achieved, first, by using repetitive automatic... 

Figure 19.7. Cyclic batch elution chromatography obtaining high product purity and high throughput by using incomplete resolution (overlapping bands) and recycling the mixed fraction (mf) to the feedstock (a) Control of band separation and cut points determines fractional impurities t mij mr and Ami /mr2-<4l)> (b) Chromatogram for separation of pure ds- and trans- 1,3-pentadiene. Components 1, isoprene 2, trans- 1,3-pentadiene 3, cis-l,3-pentadiene 4, cyclo-pentadiene. Component 1 is eluted at almost the same time as component 4 of the...

Cyclic nature of Implement mechanical integrity program batch process (e.g.,, Design equipment for easy replacement start/stop, thermal cycling). Possibil- Consider demand of cycling while designing ity of mechanical equipment and controls wear and tear. Possible loss of containment. ... 

Sorensen (1999) has suggested a cyclic operation policy for batch distillation with repeated filling and dumping of the reflux drum. This configuration achieves the maximum attainable separation and requires minimal control. Furthermore, such a column can be operated very safely. 

The process control system should be designed to maintain the plant under safe conditions of temperature, pressure, flow rates, levels, and compositions. In most continuous plants the process control system will attempt to maintain the process within reasonable bounds of a steady-state condition. In batch or cyclic processes, the... 

The ratio of cyclic to linear oligomers, as well as the chain length of the linear siloxanes, is controlled by the conditions of hydrolysis, such as the ratio of chlorosilane to water, temperature, contact time, and solvents (60,61). Commercially, hydrolysis of dimethyldichlorosilane is performed by either batch or a continuous process (62). In the typical industrial operation, the dimethyldichlorosilane is mixed with 22% azeotropic aqueous hydrochloric acid in a continuous reactor. The mixture of hydrolysate and 32% concentrated acid is separated in a decanter. After separation, the anhydrous hydrogen chloride is converted to methyl chloride, which is then reused in the direct process. The hydrolysate is washed for removal of residual acid, neutralized, dried, and filtered (63). The typical yield of cyclic oligomers is between 35 and 50%. The mixture of cyclic oligomers consists mainly of tetramer and pentamer. Only a small amount of cyclic trimer is formed. 

The manufacture of silicone polymers via anionic polymerization is widely used in the silicone industry. The anionic polymerization of cyclic siloxanes can be conducted in a single-batch reactor or in a continuously stirred reactor (94,95). The viscosity of the polymer and type of end groups are easily controlled by the amount of added water or triorganosilyl chain-terminating groups. 

Most PTC reactions are carried out on an industrial scale in the batch mode in mixer-settler arrangements. In view of the reactor design in the liquid-solid-liquid PT-catalyzed reaction, Ragaini and coworkers [147-149] reported the use of fixed-bed reactors with a recycling pump or with a recycling pump and an ultrasonic mixer, and emphasized the importance of effluent recycle concept. Schlunt and Chau [150] reported the use of a cyclic slurry reactor, which allowed the immiscible reactants to contact the catalyst sites in controlled sequential steps. However, for triphase reactions in liquid-liquid systems where... 

Batch, cyclic, and continuous processes are shown schematically in Figure 9.3. Batch and cyclic processes are usually divided into a closed system (or simply a system) and surroundings continuous processes are divided into an open system (or control volume) and surroundings. 

Batch time comparisons are provided for the separation of one zeotropic and two heteroazeotropic systems. We consider batch time as a direct indication of energy consumption since the boilup is constant for all columns. The columns are operated as closed systems. In the multivessel a ternary mixture is separated simultaneously in one such close operation and the final products are accumulated in the vessels (Wittgens et al, 1996). In the cyclic column the products are separated one at each time and for a ternary mixture a sequence of two such closed operations is needed. An indirect level control strategy based on temperature feedback control is implemented as proposed by Skogestad et al (1997). 

The fed-batch technique of cultivation is limited by fermenter volume because the volume of fermentation broth increases after each substrate addition. This disadvantage can be avoided by application a cyclic feeding strategy [9-11] which allows one to control the synchrony of individual cell development [9] by the limiting substrate concentration. The preliminary simulation results on a computer show that this type of environmental control of continuous production of exocellular hydrolytic enzymes based on our model is very promising. 

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