Loop reactor advantages

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). 

In the first step the chlorine from the tail gas and chlorine feed reacts with the caustic in the jet-loop reactor. The advantage of the jet-loop reactor is that it also acts as a suction device for the gas stream. The residence time of the liquid in step one is dependent on the capacity of the hypochlorite production and liquid level in the tank and varies between 1 and 4 h. A heat exchanger in the loop controls the temperatures in steps one and two. The amount of caustic in the feed-tank of step two is the back-up for failure of chlorine liquefaction. 

When an internal loop reactor is built underground, we refer to this as a deep shaft. Volumes can be up to thousands of in m. generally is much larger than T, usually of the order of 10 T, but for the deep shaft up to 100 T. In this case it is especially advantageous to use multiple feedstock inlets. 

A novel bioreactor, especially designed to work with two liquid phases, is the liquid-impelled loop reactor (Figme 11.10), in which the advantages of air lifts and... 

The advantage of the jet-loop reactor for kinetic measurements is demonstrated in the investigation of the synthesis of methanol from hydrogen and carbon monoxide at pressures of 2 - 8 MPa and temperatures of 225 - 265°C. A copper catalyst in the form of cylindrical pellets, with both diameter and length of 5 mm, was used. 

The third example (Fig. 4.3-27) is a loop reactor with internal recycle, developed by G. Lull. This reactor can advantageously be used to study kinetics of heterogenous catalytic reactions at pressures up to 40 MPa and temperatures to 500°C. The internal recycle... 

The granulate-filled sandwich structure described in Section II.B permits continuously operated loop systems to be developed as replacements for batch processes. Loop reactors so equipped also exhibit advantages by comparison to conventional fixed-bed reactors better exploitation of the catalytically active component due to smaller granulate size, lower pressure drop, and better gas-liquid mass transfer. 

The development of the Borstar PE process, by Borealis, is a relatively recent development in multi-reactor processes. The foundation of this process is the utilization of supercritical propane as diluent in the slurry loop reactor.438 Operating the slurry loop in a supercritical condition provides several advantages over the tradition diluent (isobutane). The solubility of PE drops markedly at the supercritical point of propane, allowing the process to operate... 

As the mixing of the two phases proved to be an important parameter for the reaction rate during experiments, it was concluded that the reactor should be mechanically stirred rather than a loop reactor. Mixir of the solvent phase and the organic phase wiQ ensure advantageous butene conversion. 

Aside from process comparisons, the main contrast between the systems is that of size, weight, and cost, especially for pressurized systems. Construction of batch reactors for use with ethylene at pressures of 1000 psi (70 atm) and upward has to be massive. The simple construction of the Loop process just pumps and pipework blends itself to use at high pressures. Apart from cost and weight, the small volume of the Loop reactor has obvious safety advantages. Despite these attractions, the Loop reactor system has so far been used successfully only for low-pressure systems such as poly(vinyl acetate) homopolymer for adhesives and copolymers for paint. Large-scale production of ethylene-vinyl acetate copolymers has yet to be demonstrated. 

In the following sections, a brief overview of the areas of application and advantages of the venturi loop reactor is presented. 

ADVANTAGES OF THE VENTURI LOOP REACTOR A DETAILED COMPARISON... 

There is considerable information available in the hterature on the design of ejectors (steam jet ejectors, water jet pumps, air injectors, etc.) supported by extensive experimental data. Most of this information deals with its use as an evacuator and the focus is on ejector optimization for maximizing the gas pumping efficiency. The major advantage of the venturi loop reactor is its relatively very high mass transfer coefficient due to the excellent gas-liquid contact achieved in the ejector section. Therefore, the ejector section needs careful consideration to achieve this aim. The major mass transfer parameter is the volumetric liquid side mass transfer coefficient, k a. The variables that decide k a are (i) the effective gas-hquid interfacial area, a, that is related to the gas holdup, e. The gas induction rate and the shear field generated in the ejector determine the vine of and, consequently, the value of a. (ii) the trae liquid side mass transfer coefficient, k. The mass ratio of the secondary to primary fluid in turn decides both k and a. For the venturi loop reactor the volumetric induction efficiency parameter is more relevant. This definition has a built in energy... 

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