Continuous reactor systems

Continuous emulsion polymerization systems are studied to elucidate reaction mechanisms and to generate the knowledge necessary for the development of commercial continuous processes. Problems encountered with the development of continuous reactor systems and some of the ways of dealing with these problems will be discussed in this paper. Those interested in more detailed information on chemical mechanisms and theoretical models should consult the review papers by Ugelstad and Hansen (1), (kinetics and mechanisms) and by Poehlein and Dougherty (2, (continuous emulsion polymerization). 

Continuous reactor systems usually consist of stirred tanks connected in series with all the recipe ingredients fed into the first reactor and the product removed from the last reactor. 

Ideally one would like a continuous reactor system to operate indefinitely at the desired steady-state. Unfortunately, a number of factors can cause shorter runs. Formation of wall polymer and latex flocculation is one such problem. This phenomenon can reduce reactor performance (for example, loss of heat transfer), lower product quality, and shorten run time. 

Batchwise operating three-phase reactors are frequently used in the production of fine and specialty chemicals, such as ingredients in drags, perfumes and alimentary products. Large-scale chemical industry, on the other hand, is often used with continuous reactors. As we developed a parallel screening system for catalytic three-phase processes, the first decision concerned the operation mode batchwise or continuous. We decided for a continuous reactor system. Batchwise operated parallel sluny reactors are conunercially available, but it is in many cases difficult to reveal catalyst deactivation from batch experiments. In addition, investigation of the effect of catalyst particle size on the overall activity and product distribution is easier in a continuous device. 

In continuous reactor systems, all reactants are continuously fed to the reactor, and the products are continuously withdrawn. Typical continuous reactors are stirred tanks (either single or in cascades) and plug flow tubes. Continuous reactors are characterized by stationary conditions in that both heat generation and composition profiles remain constant during operation (provided that operating conditions remain unchanged ). 

SEMISEQ - Sequential-Parallel Reactions in a Semi-Continuous Reactor System... 

An ester in aqueous solution is to be saponified in a continuous reactor system. Batch exper-... 

Fig. 2.1.5 Schematic drawing of a continuous reactor system. (From Ref. 38.)...

Figure 17.24. Types of reactors for synthetic fuels [Meyers (Ed.), Handbook of Synfuels Technology, McGraw-Hill, New York, 1984], (a) ICI methanol reactor, showing internal distributors. C, D and E are cold shot nozzles, F = catalyst dropout, L = thermocouple, and O = catalyst input, (b) ICI methanol reactor with internal heat exchange and cold shots, (c) Fixed bed reactor for gasoline from coal synthesis gas dimensions 10 x 42 ft, 2000 2-in. dia tubes packed with promoted iron catalyst, production rate 5 tons/day per reactor, (d) Synthol fluidized bed continuous reactor system for gasoline from coal synthesis gas.

G, Bell, R. Todd, J.A. Blain, J.D.E. Patterson and C.E.L. Shaw, Hydrolysis of triglycerides by solid phase lipolytic enzymes of Rhizopus arrhizus in continuous reactor systems. Biotech. Bioeng.,23,1981,1703-1719. 

A bituminous coal from Utah (Table I) was used in this work. The coal oil (Table II) used was obtained from a bituminous coal by hydrogenation using zinc chloride as the catalyst in a semi-continuous reactor system. Anthracene, phenanthrene, WS9 and NIS used were pure grade chemicals of over 99% purity. H-zeolon was a synthetic mordenite cracking catalyst and was supplied by Norton Chemical Company. NIS-H-zeolon was prepared by spraying nickel on H-zeolon with a subsequent sulfiding operation. NIS-WS -SiO -A1 O. catalyst used was a commercial hydrocracking catalyst. Analyses of reactants and products were done by standard methods. 

The bottom line is that the broader application of microwave technology is worth pursuing. Any eventual commercial adoption of technology such as a microwave-irradiated continuous reactor system generating attractive economics, both in capital and operating terms, would stimulate broader interest in evaluating the technology. 

A question of considerable interest in coal hydroliquefaction chemistry is the amount and nature of "organically bound metals in the coal. One reason for this interest is the observation that when supported metal direct conversion catalysts are used in liquefaction reactors, a primary mode of deactivation is metals deposition Q, 2). In particular, recent work at the Pittsburgh Energy Technology Center (PETC) (4,5) and elsewhere (3) has indicated very high levels of titanium deposition on supported Co Mo catalysts used in the fixed bed continuous reactor system. It has been suggested that the culprits in such deposition are soluble metal species (6 9) The analyses of a Western Kentucky (Homestead) hvBb feed coal and of material deposited between the catalyst pellets in the fixed bed reactor at PETC (4) are shown in Table I. 

Economics The MTO process competes favorably with conventional liquid crackers due to lower capital investment. It is also an ideal vehicle to debottleneck existing ethylene plants and, unlike conventional steam crackers, the MTO process is a continuous reactor system with no fired heaters. 

Continuous emulsion polymerization processes are industrially important for the large-scale production of synthetic polymer latexes, and have been used particularly where the solid polymer is to be recovered by coagulating the polymer latex. St-Bu rubber latex was one of the earliest latex products manufactured using continuous emulsion polymerization processes consisting of a number of stirred-tank reactors in series (CSTRs). Since the 1940s, continuous emulsion polymerization processes have been developed for a variety of products and with different reactor configurations [328]. This is because these continuous reactor systems have several advantages, such as [329] ... 

Degradation constant k = 3.2-M/h for anaerobic batch experiment in serum bottles k = 2.4 -M/h for dechlorination in anaerobic batch or continuous bioreactor k = 2.4 -M/h in the sequential anaerobic-aerobic continuous reactor system (Armenante et al. 1999)... 

Quality variations in the polymer produced in bstch reactors are often caused by slight variations in the reactor start up procedure. Furthermore, the polymerization rate may change considerably during the batch and this may give tempetature variations that are difficult to reproduce causing batch-to-batch variations in quality. These problems would be minimized with CSTRs if the continuous reactor system could be operated for at least several weeks before wall fouling and coagulum buUd up become critical and require reactor shutdown for cleanup. If an effective start-up procedure for a continuous reactor train is not available, the costs associated with offspec material could make continuous operation uneconomical. In addition, with a continuous reactor system one loses the flexibility of batch reactors when a multiproduct operation, with its short productions runs, is involved. 

Commercial continuous reactor systems generally consist of a number of continuous stirred-tank reactors (CSTRs) connected in series. The reagents are pumped into the first reactor and the product is removed from the last. Heat is exchanged through reactor jackets and internal cooling surfaces. 

A number of factors need to he considered when developing a product that will be produced in a continuous reactor system. The initial development work on most new products is carried out in batch reactors. Bottle polymerizers are often us for this purpose because a large number of experiments can he completed quickly. These early experiments provide a product that can he tested against fundamental standards (molecular weight, particle size, rheology, etc,) and in proposed applications. PreHminary recipes evolve from such tests. 

Variation and manipulation of phenomena result in the changes in phases (L L/S), process variables (T, c, pt) and geometry (tank, column —> multichannel, small scale channel, chemically active surface). The concept of the continuous reactor system offers potential to intensify the peracetic acid process. 

Stirred tank reactor systems can also operate in a continuous mode. In this configuration, fresh medium is continually supplied to the reactor and the desired products are continuously removed in the course of production. A continuous system is referred to as a chemostat when the flow rate is set to a constant value. It is further known as a turbidostat when the flow rate is set to maintain a constant turbidity or cellular concentration.f Continuous reactor systems are commonly abbreviated as CSTR or CSTF and they refer to continuous stirred tank reactor and continuous stirred tank fermenter, respectively. 

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