Reactor Design and Results

Some reactors are designed specifically to withstand an explosion (14). The multitube fixed-bed reactors typically have ca 2.5-cm inside-diameter tubes, and heat from the highly exothermic oxidation reaction is removed by a circulating molten salt. This salt is a eutectic mixture of sodium and potassium nitrate and nitrite. Care must be taken in reactor design and operation because fires can result if the salt comes in contact with organic materials at the reactor operating temperature (15). Reactors containing over 20,000 tubes with a 45,000-ton annual production capacity have been constmcted. 

The combination of highly exothermic reactions with a sharp increase in viscosity as conversion proceeds controls reactor design and operational conditions in full-scale operations. The art of sulfonation is to maintain the optimal reaction temperature and reaction time, resulting in products with small amounts of byproducts and good color. 

Methane can be oxidatively coupled to ethylene with very high yield using the novel gas recycle electrocatalytic or catalytic reactor separator. The ethylene yield is up to 85% for batch operation and up to 50% for continuous flow operation. These promising results, which stem from the novel reactor design and from the adsorptive properties of the molecular sieve material, can be rationalized in terms of a simple macroscopic kinetic model. Such simplified models may be useful for scale up purposes. For practical applications it would be desirable to reduce the recycle ratio p to lower values (e.g. 5-8). This requires a single-pass C2 yield of the order of 15-20%. The Sr-doped La203... 

Abstract This chapter embodies two sections. In the first section a survey of the state of the art of azo-dye conversion by means of bacteria is presented, with a focus on reactor design and operational issues. The relevance of thorough characterization of reaction kinetics and yields is discussed. The second section is focused on recent results regarding the conversion of an azo-dye by means of bacterial biofilm in an internal loop airlift reactor. Experimental results are analyzed in the light of a comprehensive reactor model. Key issues, research needs and priorities regarding bioprocess development for azo-dye conversion are discussed. 

Computer software allows the solution of more complex problems that require numerical, as opposed to analytical, techniques. Thus, a student can explore situations that more closely approximate real reactor designs and operating conditions. This includes studying the sensitivity of a calculated result to changing operating conditions. 

The transfer hydrogenation methods described above are sufficient to carry out laboratory-scale studies, but it is unlikely that a direct scale-up of these processes would result in identical yields and selectivities. This is because the reaction mixtures are biphasic liquid, gas. The gas which is distilled off is acetone from the IPA system, and carbon dioxide from the TEAF system. The rate of gas disengagement is related to the superficial surface area. As the process is scaled-up, or the height of the liquid increases, the ratio of surface area to volume decreases. In order to improve de-gassing, parameters such as stirring rates, reactor design and temperature are important, and these will be discussed along with other factors found important in process scale-up. 

There is an increasing awareness that the commonly employed textbook knowledge and heuristics (9) is insufficient for the systematic development of high-performance reactor designs. The result is a lack of innovation, quality, and efficiency in many industrial designs. Researchers from various perspectives are... 

In the case of an exothermic reaction the energy generated needs to be efficiently removed otherwise a runaway reaction could occur with potentially disastrous consequences. The catalyst itself may also be sensitive to even small increases in reaction temperature which may shorten its lifetime or result in a loss in reaction selectivity. The energy generated in an exothermic reaction may be recovered, often as steam, and used as a cost credit that energy has to be efficiently removed from the reaction section of the plant, again with impact on reactor design and cost. 

L.M. Quick and S. Kamitomai, Catalytic combustion reactor design and test results. Proc. 2nd Int. Workshop Catalytic Combustion 18-20 Apnl, Tokyo (H. Arai, ed.). Catalysis Society of Japan, Tokyo, 1994, p. 132. 

Basie of design Extrapolation of subpilot reactor conditions and results Keactor charge consisting of 2,038 g of organic phase and 285 g of the aqueous phase permitted the absorption of 20 liters/hr (59 g/hr) of chlorine at a reaction temperature of 70 C with 99 per Cent conversion of the chlorine... 

The resulting models may be used in various applications, including chemical reaction equilibria, which is important to chemical reactor design, and phase equilibria, which arises in distillation, solvent extraction, and crystallization. But in addition to such traditional applications, thermodynamic models may also be used to help solve many other engineering problems, such as those involving surface and interfacial phenomena, supercritical extraction, hazardous waste removal, polymer and composite material development, and biological processing. 

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