Continuous recycle reactor

Methods of achieving uniform composition copolymers from various polymerisation processes have been described. Hanson and Zimmerman (11) used a continuous recycle reactor to produce copolymers of a known and predictable homogeneous composition at relatively high percentage conversion. Hatate et al (12) studied a continuous copolymerisation in stirred tank reactors and considered the effect of micro-mixing on the copolymer... 

In contrast to other studies, oxidation carried out in this department on a Pt/7-Al203 catalyst has not uncovered any oscillatory behaviour in the temperature range of 100-185 °C. Addition of a hydrocarbon like but-l-ene, but-2-ene, or propene induces sinusoidal or relaxation type oscillations at temperatures above 150 °C. The experimental set-up used consists of a continuous recycle reactor system. The catalyst is packed in the cylindrical tubes. The gas flow rates are precisely measured with a bubble flow-meter. The reactor outlet is connected to a magnetic deflection mass spectrometer. An electronic peak select unit allows up to four mass numbers to be continuously monitored. The output data are connected to a PDP 11/45 computer for automatic and fast data logging. The data thus stored in the computer can be analysed later. The line diagram of the experimental set up is given in Figure 1. 

Figure 3.40 shows a schematic diagram of a continuous recycle reactor, CRR. With high values of F, the whole reactor (balance line 2) approximates a CSTR, working at differential conversions with rj 2 according to Equ. 3.90. Writing the balance for line 1, the equation for is... 

Bafas IC, Constantinou IE, Vayenas CG. Partial oxidation of methane to formaldehyde with 50% yield in a continuous recycle reactor separator (CRRS). Chem Eng J 2001 109—15. 

Development of the first recycle reactor was one of the consequences of a challenging situation. The ethylene oxide process had reached a high level of sophistication and excellent performance after 25 years of continuous R D. To improve results achieved by so many excellent people over so many years was a formidable task. 

In previous studies, the main tool for process improvement was the tubular reactor. This small version of an industrial reactor tube had to be operated at less severe conditions than the industrial-size reactor. Even then, isothermal conditions could never be achieved and kinetic interpretation was ambiguous. Obviously, better tools and techniques were needed for every part of the project. In particular, a better experimental reactor had to be developed that could produce more precise results at well defined conditions. By that time many home-built recycle reactors (RRs), spinning basket reactors and other laboratory continuous stirred tank reactors (CSTRs) were in use and the subject of publications. Most of these served the original author and his reaction well but few could generate the mass velocities used in actual production units. 

Continuous Model "C0NGAS". This model predicts performance of an ideal continuous wellstirred polyreactor. The model system consists of a continuous backmix reactor in which the total powder volume is held constant. There are four inlet streams 1) Makeup of pure propylene, 2) Catalyst feed, 3) Hydrogen feed, and 4) Recycle. The single effluent powder stream is directed through a perfect separator that removes all solids and polymer and then the gases are recycled to the reactor. The makeup propylene is assumed to disperse perfectly in the well-mixed powder. 

Moderate Reactor Productivity. The rhodium catalyst is continuously recycled, but the catalyst is inherently unstable at low CO partial pressures, for example in the post-reactor flash tank. Under these conditions the catalyst may lose CO and eventually form insoluble Rhl3 resulting in an unacceptable loss of expensive catalyst. This reaction is also more likely to occur at low water concentrations, hence in order to run the process satisfactorily catalyst concentrations are kept low and water concentrations relatively high. Hence through a combination of lower than optimum reaction rate (because of low catalyst concentrations) and water taking up valuable reactor volume the overall reactor utilization is less than optimum. 

In this work we present results obtained both with batch and continuous flow operation of the gas-recycle reactor-separator utilizing Ag and Ag-Sm203 electrocatalysts and Sr(lwt%) La203 catalysts, in conjunction with Linde molecular sieve 5A as the trapping material, and discuss the synergy between the catalytic and adsorption units in view of the OCM reaction network. 

Appropriate setting of two on-off valves (Fig. 1) allows the system to be operated either as a batch recycle reactor or as a continuous-flow steady-state recycle reactor. 

The performance of the Sonogashira reaction is claimed to be the first example of a homogeneously metal-catalyzed reaction conducted in a micro reactor [120], Since the reaction involves multi-phase postprocessing which is needed for the separation of products and catalysts, continuous recycling technology is of interest for an efficient production process. Micro flow systems with micro mixers are one way to realize such processing. 

Fig. 1 A continuous recycle-loop reactor for catalyst studies.

Two types of continuous membrane reactors have been applied for oligomer- or polymer-bound homogeneous catalytic conversions and recycling of the catalysts. In the so-called dead-end-filtration reactor the catalyst is compartmentalized in the reactor and is retained by the horizontally situated nanofiltration membrane. Reactants are continuously pumped into the reactor, whereas products and unreacted materials cross the membrane for further processing [57]. 

Notice that the structure of the model (16) is not restricted to bioprocesses and it can be used to describe a very large number of chemical processes as well. Examples of this class of processes are continuous reactors, recycle reactors and interconnected reactors where the matrix A t) is normally a function of the plant operating conditions (e.g., the dilution rate(s)). Now, the framework of uncertainties and the minimum knowledge on the system that are necessary to design the observers is formally described. For this purpose the following hypothesis is introduced. 

These findings differ from ordinary nth-order reactions (n > 0) where the plug flow reactor is always more efficient than the mixed flow reactor. In addition, we should note that a plug flow reactor will not operate at all with a feed of pure reactant. In such a situation the feed must be continually primed with product, an ideal opportunity for using a recycle reactor. 

Catalytic hydrogenation in supercritical carbou dioxide has been studied. The effects of temperature, pressure, and CO2 concentration on the rate of reaction are important. Hydrogenation rates of the two double bonds of an unsaturated ketone on a commercial alumina-supported palladium catalyst were measured in a continuous gra-dient-less internal-recycle reactor at different temperatures, pressures, and C02-to-feed ratios. The accurate control of the organic, carbon dioxide, and hydrogen feed flow rates and of the temperature and pressure inside the reactor provided reproducible values of the product stream compositions, which were measured on-line after separation of the gaseous components (Bertucco et al., 1997). 

Figure 13.18 Continuous recycle fermentor membrane reactor. An ultrafiltration module removes the liquid products of fermentation as a clean product. This system is being developed for production of ethanol, acetone and butanol by fermentation of food processing waste streams...

For reactions where high-pressure requirements do not allow large diameter tanks for homogeneous reaction kinetics, a loop reactor can be used. The loop is a recycle reactor made of small diameter tubes. Feed can be supplied continuously at one location in the loop and product withdrawal at another. 

The recycle reactor is used to reach an operating condition between the theoretical boundaries predicted by the continuous stirred tank reactor and the plug flow reactor. 

A new reactor concept for the study of catalyst deactivation is presented, it consists of the combination of an electrobalance and a recycle reactor. With the electrobalance, the coke content on the catalyst is measured continuously. The recycle reactor operates gradientlessly at high conversion, with on-line gas chromatographic analysis of the effluent. Thus, the catalyst activity and product selectivities may be coupled directly with the coke content and the coking rate on the catalyst. 

Frequently the kinetic description of catalyst deactivation and coke formation is complicated by instationary reaction conditions prevailing during the respective experiments. In this paper two experimental methods are presented.which enable the determination of such kinetics avoiding this problem 4 Use of a concentration controled continuously operated recycle reactor 4 Experimentation at the thermodynamic equilibrium of the main reaction to determine the coke formation kinetics at well defined operating conditions... 

The enzymatic reactor consisted of a 500 mL-continuous tank reactor BIOSTAT Q (Braun-Biotech International) coupled to the ultrafiltration membrane. The additional volume of the ultrafiltration unit and piping was around 150 mL. Three solutions were added to the reactor by means of three variable speed peristaltic pumps, containing (a) Orange II, Mn2+ and oxalic acid (b) H2O2 and (c) MnP. Another peristaltic pump was used in order to feed the effluent into the ultrafiltration unit (Fig. 10.3). The recycling feed flow ratio was maintained at 12 1, as this flow rate allowed an adequate homogeneity of the enzymatic mixture but prevented the polarization or fouling of the membrane. 

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