Reactors recirculation reactor

The BWR water chemistry parameters are given in Table 4 (19). Originally, no additives were made to feedwater—condensate or the primary water. The radiolytic decomposition of the fluid produced varying concentrations of O2 in the reactor vessel, ranging from about 200 ppb O2 in the reactor recirculation water to about 20 ppm O2 in the steam. Stoichiometric amounts of hydrogen were also produced, ie, 2 mL for each mL of O2. Feedwater O2 was about 30 ppb, hence the radiolytic decomposition of the water was a primary factor in determining the behavior of materials in the primary system and feedwater systems. 

Reactors with a packed bed of catalyst are identical to those for gas-liquid reactions filled with inert packing. Trickle-bed reactors are probably the most commonly used reactors with a fixed bed of catalyst. A draft-tube reactor (loop reactor) can contain a catalytic packing (see Fig. 5.4-9) inside the central tube. Stmctured catalysts similar to structural packings in distillation and absorption columns or in static mixers, which are characterized by a low pressure drop, can also be inserted into the draft tube. Recently, a monolithic reactor (Fig. 5.4-11) has been developed, which is an alternative to the trickle-bed reactor. The monolith catalyst has the shape of a block with straight narrow channels on the walls of which catalytic species are deposited. The already extremely low pressure drop by friction is compensated by gravity forces. Consequently, the pressure in the gas phase is constant over the whole height of the reactor. If needed, the gas can be recirculated internally without the necessity of using an external pump. 

The H-Cocd Process, based on H-Oil technology, was developed by Hydrocarbon Research, Inc. (HRI). The heart of the process was a three-phase, ebullated-bed reactor in which catalyst pellets were fluidized by the upward flow of slurry and gas through the reactor. The reactor contained an internal tube for recirculating the reaction mixture to the bottom of the catalyst bed. Catalyst activity in the reactor was maintained by the withdrawal of small quantities of spent catalyst and the addition of fresh catalyst. The addition of a catalyst to the reactor is the main feature which distinguishes the H-Coal Process from the typical process. 

With a reaction-limited deposition process, the film should have uniform thickness as long as the partial pressures ofreactants do not vary with position. In a tubular reactor, the conversion of reactants must be kept small or the film thickness will depend on the location of the sohd in the reactor, with upstream regions having a greater deposition rate. It is therefore common to use a gas recirculation reactor (a recycle PFTR) so that the composition of the reactants is independent of position in the reactor to assure uniform film thickness. 

A thorough comparative study of the reactivity of O-, OJ, and Oj toward alkanes and alkenes on MgO has been carried out by Lunsford and co-workers (see Sections V and VI in Ref. 1 and Section VI in this article). In these stoichiometric studies, a known concentration of oxygen species on the surface was reacted with a known amount of hydrocarbon in a recirculation reactor and the products were analyzed. In all cases, a 1 1 stoichiometry was observed. 

Lyubarski et al. [192] studied the oxidation of tolualdehyde, phthalic anhydride and maleic anhydride, separately and in mixtures, using a recirculation reactor with a high temperature V2Os catalyst at 400—460° C. o-Tolualdehyde (and o-xylene) were found to stabilize phthalic anhydride, even with a 10 1 excess of the latter. Phthalic anhydride, in turn, appeared to inhibit the maleic anhydride oxidation. Consequently, the tolualdehyde oxidation seemingly follows a parallel scheme... 

Notes All water cooled exchangers operate with water in at 75°F and out at 100°F. All pumps are centrifugal except the complex transfer, and the sulfonation reactor feed, which are both piston type the neutralization reactor recirculation pump and the transfer pumps are gear pumps. 

Hydrogen oxidation on Pt catalyst in adiabatic recirculating reactor Horak and Jirafcek (45) X X... 

It is interesting to note that the cis-trans ratios obtained by Ghorbel and coworkers (312) on 1-butene isomerization were mostly unaffected by the chemisorption of the different poisons and corresponded to the thermodynamically determined ratio. The same result was obtained by Knozinger and Aounallah (377), when 1-butene was isomerized in a recirculating reactor at 120°C on tj-A1203 (activated at 500°C) that was partially poisoned by pyridine. In micro-catalytic pulse experiments, on the other hand, one observes kinetically determined primary product distributions with cis-trans ratios of about 2 (370). Different types of active sites appear, therefore, to be involved in the doublebond shift and in the cis-trans isomerization, the latter remaining unaffected by pyridine chemisorption. 

The most applied CSTRs are recirculation reactors in heterogeneous catalysis and well stirred vessels in slurry or liquid-phase systems. Injection of a (5-pulse of a tracer should give an exponentially decaying output concentration ... 

In recirculation reactors, a recirculation ratio Rc (ratio of the total flow returned to the inlet and the total outlet flow) larger than 20 is frequently recommended [11, 16]. This criterion is not complete as is apparent from the literature [17-19]. One can demand that the rate over the catalyst bed may not change more than 5%, thus for an nth order isothermal reaction,... 

Key Features of an Internal Recirculation Reactor [After Shah, 1979]... 

It is necessary to consider the mass balances over the electrochemical cell and the reservoir to describe the temporal evolution of COD in the batch recirculation reactor system given in Fig. 1.5. Considering that the volume of the electrochemical reactor Ve (m3) is much smaller than the reservoir volume Vr (m3), we can obtain from the mass balance on COD for the electrochemical cell the following relation ... 

In recent years these problems have been largely overcome with the development of gas-phase continuous back-mixed reactors like the Berty reactor. This reactor recirculates the gas... 

Fig. 8.1 Types of ideal chemical reactors (Levenspiel, 1996). The batch recirculation reactor system consists of a vessel of total volume V and a reactor of a specified volume Vr, CSTR continuously stirred tank reactor.

On the other hand, the treatment of M in a batch recirculation reactor system will generate a completely different concentration profile (Fig. 8-2, situation B). Small fractions of fluid are continuously removed from the batch tank and pumped through the photoreactor module (PR). Here, the same amount of OH... 

The kinetics must be obtained in a reactor that should be as simple as possible with a well-characterized geometry in such a way that the obtained parameters are point value results of position and time. The laboratory device shovm in Figures 4 and 5 is a continuous flow, well-mixed, recirculating reactor. The details are described in Table 2. The reader interested in... 

A specific t)q)e of recirculating reactor is the commercial indoor-air treatment device. The device is characterized by a small operating volume (a few lifers af mosf), which is several orders of magnitude smaller than the reservoir (a room, vehicle, or aircraft, for example). The reactor itself can be eifher free standing or part of a larger system, usually an air-conditioning system, and is supposed to be able to take care of continuous emission of... 

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