Batch continuous processing contrasted

In a batch process, the main steps operate discontinuously. In contrast with a continuous process, a batch process does not deliver its product continuously but in discrete amounts. This means that... 

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... 

In the pharmaceutical industry, and to some extent the fine chemicals industry, an important advantage of a batch reactor is traceability. The product from a particular batch will have a uniform consistency, and can be uniquely labelled and readily traced. In contrast, the product from a continuous process may change gradually over time, and it is therefore more difficult to trace a particular impurity or fault in the material. Batch reactors are, however, rarely the most efficient in terms of throughput and energy use when the reaction kinetics are fast. Batch systems are also much more labour intensive than continuous processes. 

Characteristic features of bulk versus fine chemicals manufacture are shown in Table 2.1. Fine chemicals manufacture often involves multi-step syntheses and is generally performed batch-wise in multi-purpose equipment. This contrasts with bulk chemicals manufacture, which generally involves continuous processing in dedicated plants. 

The dominant role of the batch operation over the continuous process throughout the pigment industry is somewhat in contrast to the patent literature, which includes numerous proposals for complete azo pigment manufacture by the continuous process as well as descriptions of the partial steps, such as the diazotization or the coupling reaction. 

In a subsequent experiment, the larger dendritic catalyst 6b was used under optimized eonditions, whieh was expected to result in a slower loss of activity. The results (Fig. 9b) did not show much improvement, indicating that catalyst deactivation was still a major problem. Indeed the number of turnovers (catalytic reaction events) of catalyst 6b was only 260 in the continuous process compared with the value of 3 273 determined in the batch reaction experiment in contrast, the monomeric model compound showed a number of turnovers of 6 027. 

A type of processing equipment in which the entire amount of material to be used is put into the mixer and mixed for a definite period, with multiple recirculation of material through the mixing zone, in contrast to what happens in a continuous mixer. After the mixing period the whole amount of material is removed from the mixer. In oil production or processing, the process in which emulsion is collected in a tank and then broken in a batch. This process is used as opposed to continuous or flow-line treating of emulsions. 

Another problem associated with the batch technique is poor reaction control (unsatisfactory stirring, temperature control, etc). To overcome the problems outlined above a semi-continuous polymerization technique has been introduced [27]. In this technique a mixed monomer/inifer feed is added at a sufficiently low constant rate to a well stirred, dilute BC13 charge. Due to stationary conditions maintained during the whole polymerization, well-defined telechelic products with symmetrical end groups and theoretical polydispersities could be obtained. The kinetics of the polymerization has been discussed and the DPn equation has been derived. In contrast to the batch technique, the DPn for the semi-continuous technique is simply given by the [monomer]/[inifer] ratio. Thus, very reactive or unreactive inifers, unsuitable for batch polymerization, can also be used in the semi-continuous process. 

Does the system involve RCRA hazardous chemicals If so, try to use continuous processes even if the scale is relatively small. Continuous processes generate waste at a constant rate. The composition of the waste is also constant with time and, hence, the treatment is easier. In contrast, batch processes generate wastes... 

Relative to stricfly batch bioreactors, continuous and fed batch bioreactors require more connections to process stteams through which sterility must be maintained throughout the entire period the reactor is onstream. When contamination does occur in equipment used to carry out a continuous process, it can rapidly spread to downstream units. By contrast, confinement or isolation of contaminants can be accomplished more readily in a batch reactor and its associated auxiliary facilities. 

An alternative method of producing charcoal was developed in the early 1900s by Orin Stafford, who then helped Henry Ford establish his briquette business. Called the retort method, this involves passing wood through a series of hearths or ovens. It is a continuous process wherein wood constantly enters one end of a furnace and charred material leaves the other in contrast, the traditional kiln process burns wood in discrete batches. Virtually no visible smoke is emitted from a retort, because the constant level of output can effectively be treated with emission control devices such as afterburners. 

Caprolactam for use as fibers is hydrolytically polymerized in batches as 80%-90% aqueous solutions with 0.2%-0.5% acetic acid and ethylene diamine at 250-280° C. The acetic acid acts as chain stabilizer (see above). The ethylene diamine increases the amine equivalent of PA 6 so that mixed weaves of Perlon and wool can be evenly dyed. The water is removed as steam in the polymerization progresses. Caprolactam is also polymerized continuously by what is known as the VK process (vereinfacht-A ontinuierliche, or simplified continuous, process). This process is carried out without pressure with, for example, 6-amino caproic acid or AH salt as initiator. In contrast to the production of nylon 6,6, this process can proceed continuously the melt can be directly spun from the reactor. Polyamide 6 fibers have good properties but they yellow slowly since pyrrole structures are formed at the chain ends. 

But in contrast to the batch oriented processes in this case the subprocesses are to be carried out in a continuous way conjunct with all advantages and risks mentioned in Chapter 2. The zones are not necessarily mechanically and spacially separated from each other as the following explanations will show. 

The ammonia reactor is a continuous process material constantly moves through the unit. A batch process, in contrast, is characterized by chemical or physical change without material moving in or out, except at the beginning or end of a cycle. A chemical reaction you conduct in a flask in your introductory chemistry laboratory is a batch process. Continuous processes are rarely encountered in undergraduate chemical laboratories, yet they dominate in the chemical industry. We shall explore the reasons for the preeminence of continuous processes later. 

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