Recirculated loop reactor

Continuous polymerization systems offer the possibiUty of several advantages including better heat transfer and cooling capacity, reduction in downtime, more uniform products, and less raw material handling (59,60). In some continuous emulsion homopolymerization processes, materials are added continuously to a first ketde and partially polymerized, then passed into a second reactor where, with additional initiator, the reaction is concluded. Continuous emulsion copolymerizations of vinyl acetate with ethylene have been described (61—64). Recirculating loop reactors which have high heat-transfer rates have found use for the manufacture of latexes for paint appHcations (59). 

Several types of tubular reactors have been reported. Recirculation loop reactors have a pump which continuously circulates the reacting dispersion through a tube loop with raw materials being introduced at one location and product latex removed at another. Material passing through the pump is remixed with each pass. If the circulation rate is significantly higher than the feed and effluent rates, which is usually the case, the residence time distribution approaches that of a well-mixed CSTR, Hence this reactor cannot be used to produce latexes with narrow PSDs. 

The reaction is initiated with nickel carbonyl. The feeds are adjusted to give the bulk of the carbonyl from carbon monoxide. The reaction takes place continuously in an agitated reactor with a Hquid recirculation loop. The reaction is mn at about atmospheric pressure and at about 40°C with an acetylene carbon monoxide mole ratio of 1.1 1 in the presence of 20% excess alcohol. The reactor effluent is washed with nickel chloride brine to remove excess alcohol and nickel salts and the brine—alcohol mixture is stripped to recover alcohol for recycle. The stripped brine is again used as extractant, but with a bleed stream returned to the nickel carbonyl conversion unit. The neutralized cmde monomer is purified by a series of continuous, low pressure distillations. 

Another version of a fluidized-bed reactor has been introduced by Vogelbusch (Austria). This reactor has an internal recirculation loop set up by means of a high flow impeller. The system utilises porous glass beads for immobilizing the cells. However, glass beads may not work with all types of cells. 

Loop Reactors For some gas-hquid-solid processes, a recirculating loop can be an effective reactor. These involve a relatively high horsepower pumping system and various kinds of nozzles, baffles, and turbulence generators in the loop system. These have power levels... 

Adding a recirculating loop to the transport reactor, a well-mixed condition is achieved provided the recirculation rate is large with... 

BWRs do not operate with dissolved boron like a PWR but use pure, demineralized water with a continuous water quality control system. The reactivity is controlled by the large number of control rods (>100) containing burnable neutron poisons, and by varying the flow rate through the reactor for normal, fine control. Two recirculation loops using variable speed recirculation pumps inject water into the jet pumps inside of the reactor vessel to increase the flow rate by several times over that in the recirculation loops. The steam bubble formation reduces the moderator density and... 

Column reactors can contain a draft tube - possibly filled with a packing characterized by low pressure drop - or be coupled with a loop tube, to make the gas recirculating within the reaction zone (see Fig. 5.4-9). In recent years, the Buss loop reactor has found many applications in two- and three-phase processes About 200 Buss loop systems are now in operation worldwide, also in fine chemicals plants. This is due to the high mass-transfer rate between the gas and the liquid phase. The Buss loop reactor can be operated semibatch-wise or continuously. As a semibach reactor it is mostly used for catalytic hydrogenations. 

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. 

Loop reactors continuous flow reactors in which all or part of the product stream is recirculated to the reactor, either directly or mixed with a reactant supply stream. 

Table 26.1 shows the effects of the two main design variables. Specifically, the results of the batch simulations for the same system as described above are given for different in-loop reactor (catalyst) volumes, recirculation rates. As would be expected increasing the catalyst volume decreases the hypochlorite concentration at all points and times through the process. Increasing the recirculation rate also appears to have a... 

This process has a classical on-line instrumentation gathering measurements of liquid flow rates (at the input of the reactor and in the recirculation loop), temperature and pH in the reactor and biogas flow rate and composition i.e., CO2, CH4 and H2 content in the biogas) [30]. In addition, the following sensors were installed over the years a TOC analyzer, a titrimetric sensor [3] and a FT-IR spectrometer [29]. Since 1998, this instrumentation provides us with the following on-line measurements in the liquid phase every... 

For the case of impossible 3-D reactor or vessel sampling, this upward-flowing pipeline sampler should be implemented with the reactor in a recirculation loop configuration, as shown in Figure 3.20. The only new requirement is a low-power pump, to be operated full-time for all systems where this is feasible. 

The self-mixing up-streaming recirculation loop ranks as the prime example of the SUO lot transformation in which a 3-D lot (reactor) has been turned into an easy to sample 1-D configuration (pipeline). 

The operation of an LC-Finer is best described by means of a process flow schematic (Figure 2). The LC-Finer reactor maintains the catalyst (typically American Cyanamid 1442B cobalt molybdenum 1/32 inch extrudate or Shell 324 nickel molybdenum 1/32 inch extrudate) in constant motion, suspended by the recirculation of copious volumes of liquid. This recirculation results in a 35-50% bed expansion and the reactor operates at a uniform temperature with essentially no pressure drop. In a commercial unit there is a recycle of hydrogen rich gas along with a distillate liquid stream which is combined with the fresh SRC. The PDU differs from the commercial unit design in that there is no recycle gas or liquid streams. The bed expansion is maintained with an external recirculation loop. It should be noted that the PDU fractionator separates the liquid product into a light oil (L.O.) and a heavy oil (H.O.). The combination of these two oil streams is designated as total liquid product (TLP). 

The obtained results have shown that the configuration where the recirculation tank was irradiated and the catalyst was used in suspension appeared to be the most interesting for industrial applications [73]. Moreover, it was observed that the degradation rate was higher when an immersed lamp was used compared to a system with an external lamp [81]. Therefore, actually the studies in progress are realized in the system described elsewhere [39] consisting of a Pyrex annular photoreactor with a 125-W medium-pressure Hg lamp axially positioned inside the reactor. The separation module containing the flat-sheet membrane was connected to the photoreactor in a recirculation loop. 

Many plants have been designed and operated on a batch system with various stirring systems and recirculation loops since the early 1950s but the latest thinking for bulk production is probably the plants that Davy Process Technology has developed for alkoxylation. At least 10 plants of its design have been put into beneficial operation since they were first introduced in 1990 and are based on the Buss Loop Reactor technology. 

Description The Spherizone process is Basell s new proprietary gas-loop reactor technology based on a Multi-Zone Circulating Reactor (MZCR) concept. Inside the reactor (1) the growing polymeric granule is continuously recirculating between two interrelated zones, where two distinct and different fluodynamic regimes are realized. 

Fortunately we can readily solve many of the problems associated with a direct supply of cooling water. For example, in Fig. 4.15 we have provided a water recirculation loop to maintain a large constant flow of water through the jacket. Fresh cooling water is added to the loop to maintain the desired reactor temperature. This arrangement keeps... 

The second issue for cooled tubular reactors is how to introduce the coolant. One option is to provide a large flowrate of nearly constant temperature, as in a recirculation loop for a jacketed CSTR. Another option is to use a moderate coolant flowrate in countercurrent operation as in a regular heat exchanger. A third choice is to introduce the coolant cocurrently with the reacting fluids (Borio et al., 1989). This option has some definite benefits for control as shown by Bucala et al. (1992). One of the reasons cocurrent flow is advantageous is that it does not introduce thermal feedback through the coolant. It is always good to avoid positive feedback since it creates nonmonotonic exit temperature responses and the possibility for open-loop unstable steady states. 

Application To produce aqueous formaldehyde (AF) or urea formaldehyde precondensate (UFC) from methanol using Haldor Tbpspe A/S FK-Series iron/molybdenum-oxide catalysts. Description The process is carried out in a recirculation loop at low pressure (0 to 6 psig) (1 to 1.5 bar abs). Vaporized methanol is mixed with air and recycle gas that were boosted by the blower (1). The mixture may be preheated to about 480°F (250°C) in the optional heat exchanger (2) or it may be sent directly to the reactor (3). In the reactor, methanol and oxygen react in the catalyst-filled tubes to make formaldehyde. Reaction heat is removed by an oil heat transfer medium (HTM). The reacted gas exits the reactor at approximately 540°F (290°C) and is cooled in the LP steam boiler (4) to 260°F (130°C) before entering the absorber (5). In the absorber, the formaldehyde is absorbed in water or urea solution. Heat is removed by one or two cooling circuits (6, 7). From the lower circuit (6)... 

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