Reactors, chemical mixed

Baldyga, J. and Bourne, J.R., 1992. Interactions between mixing on various scales in stirred tank reactors. Chemical Engineering Science, 47, 1839-1848. 

Zahradnik, J. and M. Fialova, The effect of bubbling regime on gas and liquid phase mixing in bubble column reactors. Chemical Engineering Science, 1996. 51(10) p. 2491-2500. 

Process intensification refers to a chemical process using significantly smaller equipment. Examples include novel reactors, intense mixing devices, heat and mass transfer devices that provide high surface area per unit of volume, devices... 

Sewers can be long tubular reactors as well as conduits to carry troubles from place to place. They can receive all kinds of fluids. If you work in an older large chemical plant that handles a variety of chemicals, ask around about previous problems. You may learn how some combination of unlikely fluids, such as equipment cleaning chemicals mixed with one of the raw materials or scrubber effluents, has resulted in some sort of upset. 

It may be seen that components of the model discussed thus far are generally applicable to any two phase ideal back-mixed reactor. Chemical kinetics and phase equilibrium are the two components which make the model unique. 

Perfectly mixed reactors are the key element for conducting chemical processes and in simulation of complex flow systems. Other synonyms are mixed reactor, back mix reactor, an ideal stirred reactor and the CFSTR (constant flow stirred tank reactor). As the name implies, it is a reactor in which the contents are well stirred and uniform throughout. Thus, the exit stream from this reactor has the same composition as the fluid within the reactor. 

Roth J.A., Design of completely mixed ozonation reactors . Chemical Oxidation — Technologies for the Nineties, pp. 114-129. (1991)... 

Bourne, J.R. (1997). Mixing in Single-Phase Chemical Reactors, In Mixing in the Process Industries, 2nd ed. (Harnby, N., Edwards, M.F., and Nienow, A.W., eds.), pp. 184-199, Butterworth-Heinemann, Oxford. 

Oxide fuels have demonstrated very satisfactory high-temperature, dimensional, and radiation stability and chemical compatibility with cladding metals and coolant in light-water reactor service. Under the much more severe conditions in a fast reactor, however, even inert UO2 begins to respond to its environment in a manner that is often detrimental to fuel performance. Uranium dioxide is almost exclusively used in light-water-moderated reactors (LWR). Mixed oxides of uranium and plutonium are used in liquid-metal fast breeder reactors (LMFBR). 

Chakraborty, S. and V. Balakotaiah, Low-dimensional models for describing mixing effects in laminar flow tubular reactors. Chemical Engineering Science, 2002, 57 2545-2564. 

Bouaifi, M., and Roustan, M. (2001), Power consumption, mixing time and homogenisation energy in dual-impeller agitated gas-liquid reactors, Chemical Engineering and Processing, 40(2) 87-95. 

The plant audit examines what the existing plant currently does. The audit should include all physical aspects of the reactor, including mixing and heat transfer capabilities, feed rate and position of feed addition. It is necessary to have a fundamental understanding of the reactor to determine where and how the reaction occurs. If the intention is to run a new chemical reaction scheme in existing equipment, as is the case in many fine and speciality chemicals processes, the equipment should be audited as if it were already running the new process. It may be necessary to go back to the original process plant contractors to obtain full data. 

For the scale up of a chemical reactor, inadequate mixing may result in spatial variations in, for example, reactant composition or temperature. An electrochemical reactor (cell) is a chemical reactor where the reduction and oxidation reactions are spatially separated on cathodes and anodes. The flow of ionic current through the electrolyte results in an electric field through the electrolyte. Since charged species move in response to an electrical field [1-3] and since the potential difference across the double layer impacts reaction rate, electrical field effects can significantly impact current distribution. Thus, in contrast to a chemical reactor, perfect mixing to eliminate all concentration fields does not necessarily result in uniform reaction rates. 

The required concentration of Li70H is varied to minimize the formation of tritium. A chemical mixing tank is provided to introduce the solution to the suction of the makeup pumps as required to maintain the proper concentration of Li70H in the reactor coolant system. 

The solution is poured into the chemical mixing tank and is then flushed to the suction manifold of the makeup pumps with demineralised water. A flow orifice is provided on the demineralised water inlet pipe to allow chemicals to be flushed into the reactor coolant system at acceptable concentrations. 

Since the membrane conducts oxygen ions, in the great majority of the cases through a mechanism involving anion vacancy diffusion, an equivalent counterflux of electrons should take place for charge neutrality membrane materials should be mked conductors. Perovskite-type mixed-conducting materials are considered suitable candidates for use in dense membrane reactor chemical looping processes, since they fulfill most of the required characteristics. 

Fig. 1 shows the ideal scheme for the design and scale up of a commercial reactor from laboratory experiments. In the industrial reactor, chemical reactions are most of the time strongly coupled with physical processes such as mixing, heat and mass transfer, hydrodynamics of the reacting mixture. The purpose of the different steps in Fig. 1 is to try to uncouple these processes in order to study them separately in appropriate devices. 

Because the highest possible interfacial area is desired for the heterogeneous reaction mixture, advances have also been made in the techniques used for mixing the two reaction phases. Several jet impingement reactors have been developed that are especially suited for nitration reactions (14). The process boosts reaction rates and yields. It also reduces the formation of by-products such as mono-, di-, and trinitrophenol by 50%. First Chemical (Pascagoula, Mississippi) uses this process at its plant. Another technique is to atomize the reactant layers by pressure injection through an orifice nozzle into a reaction chamber (15). The technique uses pressures of typically 0.21—0.93 MPa (30—135 psi) and consistendy produces droplets less than 1 p.m in size. The process is economical to build and operate, is safe, and leads to a substantially pure product. 

Nuclear wastes are classified according to the level of radioactivity. Low level wastes (LLW) from reactors arise primarily from the cooling water, either because of leakage from fuel or activation of impurities by neutron absorption. Most LLW will be disposed of in near-surface faciHties at various locations around the United States. Mixed wastes are those having both a ha2ardous and a radioactive component. Transuranic (TRU) waste containing plutonium comes from chemical processes related to nuclear weapons production. These are to be placed in underground salt deposits in New Mexico (see... 

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