Batch and Continuous Processing

In both batch and continuous processes, it may be necessary to clean equipment to prevent contamination of new product. Materials used for equipment cleaning often cannot be recycled, leading to waste. 

Manufacturing processes have been improved by use of on-line computer control and statistical process control leading to more uniform final products. Production methods now include inverse (water-in-oil) suspension polymerization, inverse emulsion polymerization, and continuous aqueous solution polymerization on moving belts. Conventional azo, peroxy, redox, and gamma-ray initiators are used in batch and continuous processes. Recent patents describe processes for preparing transparent and stable microlatexes by inverse microemulsion polymerization. New methods have also been described for reducing residual acrylamide monomer in finished products. 

Tetiyl. 2,4,6-Trinitrophenylmethylm tramine (tetryl) was used ia pressed form, mostly as a booster explosive and as a base charge ia detonators and blasting caps because of its sensitivity to initiation by primary explosives and its relatively high energy content. Properties are presented ia Table 11 (173). Batch and continuous processes for the production of tetryl have been developed. Tetryl is no longer used ia the United States and has been replaced by RDX (174-178). 

Processes for Triacetate. There are both batch and continuous process for triacetate. Many of the considerations and support faciUties for producing acetate apply to triacetate however, no acetyl hydrolysis is required. In the batch triacetate sulfuric acid process, however, a sulfate hydrolysis step (or desulfonation) is necessary. This is carried out by slow addition of a dilute aqueous acetic acid solution containing sodium or magnesium acetate (44,45) or triethanolamine (46) to neutrali2e the Hberated sulfuric acid. The cellulose triacetate product has a combined acetic acid content of 61.5%. 

The flow diagram for the viscose process is given in Figure 2. The sequence of reactions necessary to convert cellulose into its xanthate and dissolve it in soda used to be performed batchwise. Fully continuous processes, or mixtures of batch and continuous process stages, are more appropriate for high volume regular viscose staple production. 

Nylon-6 is the polyamide formed by the ring-opening polymerization of S-caprolactam. The polymerization of S-caprolactam can be initiated by acids, bases, or water. Hydrolytic polymerization initiated by water is often used in industry. The polymerization is carried out commercially in both batch and continuous processes by heating the monomer in the presence of 5—10% water to temperatures of 250—280°C for periods of 12 to more than 24 h. The chemistry of the polymerization is shown by the following reaction sequence. 

Solution Polymerization. In this process an inert solvent is added to the reaction mass. The solvent adds its heat capacity and reduces the viscosity, faciUtating convective heat transfer. The solvent can also be refluxed to remove heat. On the other hand, the solvent wastes reactor space and reduces both rate and molecular weight as compared to bulk polymerisation. Additional technology is needed to separate the polymer product and to recover and store the solvent. Both batch and continuous processes are used. 

Both batch and continuous processes employ excess sulfur and operate at 85—110°C. Trace amounts of polysulftdes produce a yellow color which iadicates that all the ammonium sulfite has been consumed. Ammonium bisulfite is added to convert the last polysulfide to thiosulfate and the excess ammonia to ammonium sulfite. Concentrations of at least 70% (NH 2S2 3 obtained without evaporation. Excess sulfur is removed by filtration and color is improved with activated carbon treatment or sodium siUcate (66). Upon cooling the aqueous concentrated solution, ammonium thiosulfate crystallines. 

Both batch and continuous processes are suitable for commercial chlorination. The progress of the chlorination is convenientiy followed by specific gravity measurements. 

Other types of cokemaking technology include both batch and continuous processes, and processes that use electrical induction as the heat-transfer mechanism. Processes under development are further described in Reference 16. 

Ethyl acetate is made industrially by both batch and continuous processes (361,362). Glacial acetic acid is commonly the starting material, and any water formed during the esterification has to be removed. Sulfuric acid may be added periodically to the reactor to replace the acid lost in side reactions. 

Chemical engineers usually make detailed evaluations of costs rather than evaluations for profits or sales. However, the latter can be analyzed in a similar manner to costs by using the equations shown in Table 9-38. For this puraose, the sign convention will be reversed because an increase in sales or profits would be considered favorable, whereas an increase in cost would be considered unfavorable. The equations can be apphed to both batch and continuous processes. 

CE is generally more suited to analytical separations than to preparative-scale separations. However, given the success of CE methods for chiral separations, it seems reasonable to explore the utility of preparative electrophoretic methods to chiral separations. Thus, the purpose of this work is to highlight some of the developments in the application of preparative electrophoresis to chiral separations. Both batch and continuous processes will be examined. 

As discussed in Sections 14.2 and 14.3, a critical difference between batch and continuous processes lies in equipment utilization. The complexity (or simplicity) of synthesis and isolation is a critical factor in determining whether a whole process is viable for switching from B2C. Given that it takes an average of eight synthetic steps to produce an API from raw materials [51], it is clear that the average API manufacturing process is probably too complex in its current form. Reduction in the number of process steps for a continuous process will, to a first approximation, reduce the plant costs pro rata. 

Another illustration for the distinction between batch and continuous process is depicted in Fig. 1.2. The discreteness of tasks that characterise a batch process is evident in Fig. 1.2a. The use of storage becomes necessary when the completion of... 

In order to handle batch operations effectively, the time dimension cannot be ignored. This is due to the fact that almost all operations within the batch process environment are time dependent. Figure 4.4 shows comparison between batch and continuous processes on the exploration of water reuse opportunities. In continuous operations, only the concentration constraints determines the feasibility of water reuse from one process to another. This implies that if the outlet water concentration from process A is less than the maximum allowed inlet water concentration to process B, then water from process A could be reused in process B. On the other hand, if water from one process, say process B, is at a concentration higher than the maximum allowed in another process, say process A, the water reuse opportunity from process B to process A is nullified. 

Comparison of Batch, Semi-Batch, and Continuous Processes. 97... 

Mockus, L. and Reklaitis, G.V. (1999a) Continuous-time representation approach to batch and continuous process scheduling. 1. MINLP formulation. Ind. Eng. Chem. Res., 38, 197-203. 

Lee, K Park, H. and Lee, I. (2001) A novel nonuniform discrete time formulation for short-term scheduling of batch and continuous processes. Ind. Eng. Chem. Res., 40, 4902—4911. 

Batch and continuous processes may also be compared by examining their governing mass-balance relations. As an elaboration of equation 1.5-1, a general mass balance may be written with respect to a control volume as ... 

PBT can be made by using both batch and continuous processes. Early commercial processes were DMT-based batch processes that involved two distinct... 

As mentioned earlier, both batch and continuous processes can be used to make PBT. Some manufacturers also incorporate solid-state or solid-phase polymerization (SSP or SPP, respectively) processes to increase molecular weight. 

As Mullin 3-1 points out, this equation can be used for comparing batch and continuous processing since Vw and nFVL represent the wash liquor requirements for both cases. 

Asphalt feedstock (flux) is contacted with hot air at 200-280°C (400-550°F) to obtain desirable asphalt product. Both batch and continuous processes are in operation at present, but the batch process is more prevalent because of its versatihty. Nonrecoverable catalytic compounds include copper sulfate, zinc chloride, ferric chloride, aluminum chloride, phosphorus pentoxide, and others. The catalyst does not normally contaminate the process water effluent. 

Betz G, Junker Biirgin P, Leuenberger H. Batch and continuous processing in the production of pharmaceutical granules. Pharmaceutical Dev Technol 2003 8(3) 289-297. 

Figure 3. Theoretical recoveries for batch and continuous processing modes (membrane rejection — 90%).

---