Stirred-bed reactor

Gas-phase polymerization of propylene was pioneered by BASF, who developed the Novolen process which uses stirred-bed reactors (Fig. 8) (125). Unreacted monomer is condensed and recycled to the polymerizer, providing additional removal of the heat of reaction. As in the early Hquid-phase systems, post-reactor treatment of the polymer is required to remove catalyst residues (126). The high content of atactic polymer in the final product limits its usefiilness in many markets. 

Catalytic measurements were carried out in a stirred-bed reactor of stainless steel. The details of the reactor and experimental procedures have been described elsewhere [4]. 

Novolen A process for making polypropylene in the gas-phase, using a vertical stirred-bed reactor. Developed by BASF and engineered by Uhde. Eight plants had been licensed as of 1985. A metallocene-catalyzed version was introduced in 1996. The name is used also for the product. 

Finally, Rong and coworkers discuss the roll of surface oxygen on the MCS process75. Rong employed a lab-scale stirred bed reactor and then applied XPS to analyze the silicon samples before and after the reaction. The reactivity of silicon depended on the initial thickness of the native oxide on the silicon. After the reaction the surfaces of all of the samples were mostly covered with Si02. There was no observed correlation between the surface and bulk O content. XPS analysis showed the presence of Al, Ca and Ti impurities in some samples. Titanium on the surface appeared to increase the reactivity, whereas Ca decreased the selectivity of Di formation. Addition of ZnO to the silicon before CuCl improved reactivity and also decreased the induction period of the reaction. XPS studies of samples prepared in this manner exhibited a lower Zn surface concentration compared to the samples where CuCl, Si and ZnO were mixed together. 

In Scheme 18 a gas-phase stirred bed reactor for BD polymerization is shown. A 0.25 L semi-batch reactor was used by Ni et al. for studies on the influence... 

Scheme 18 Gas-phase stirred bed reactor for BD polymerization TC = temperature control, PC = pressure control, HT = monomer tank, VG = vacuum gauge, C = catalyst injection column, MS = molecular sieves column, H = heat exchanger [388], reprinted with permission of John Wiley Sons, Inc.

The horizontal stirred-bed reactor (1) is unique in the industry in that it approaches plug-flow type of performance, which contributes... 

In a properly designed industrial scale reactor, feedstock conversion is achieved at a certain throughput capacity. In order to scale-up the reactor, heat and mass transport phenomena must be studied. This includes heat transfer phenomena, feedstock conversion kinetics and the movement of particles inside the reactor. In this work, both experimental and theoretical studies were carried out to investigate these phenomena. Two different configurations of moving and stirred bed reactors, the batch scale rotative and a continuous feed Process Development Unit (PDU), have been used to generate the data in accordance with the principle of similarity. A dynamic model to scale-up the reactor was then tested. 

In a moving and stirred bed reactor, the most inqrortant parameters representing the feedstock flowing behavior are the residence time the velocity of feedstock movement and the feedstock bed thickness in the reactor The "Single Blade Volume Output" model proposed in this work is based on the assumption that at the outlet of the reactor, the amount of feedstock accumulating in front of each agitation blade is determined by the value of Abusing a power expression,... 

Two different configurations of moving and stirred bed reactors, the batch scale rotative and PDU reactors, have been used for the tests in accordance with the principle of similarity. 

Roy, C., D. Blanchette and B. de Caumia. Horizontal Moving and Stirred Bed Reactor. Canadian Patent Claim Number 2,196,841. US Patent Number 8,811,172. International Patent Number 98,902,153.0. 

Figure 4. Continuous stirred bed reactor for gas phase olefin polymerization.

Dowlex DSM Compact process Mitsui CX-process Novolen process Innovene process (horizontal stirred bed reactor)... 

Three main types of gas-phase reactors are used in the industry fluidized-bed, vertical stirred-bed and horizontal stirred-bed reactors. 

Treatment of these silicon charges with methyl chloride gave a product mixture of monosilanes (CHsSiCls, (CH3)2SiCl2 (main product), (CH3)3SiCl) as well as disilanes Si2(CH3)jcCl6 i). These synthesis experiments were carried out in a stirred-bed reactor. 

The stirred bed reactor is one method which has been employed on a fairly large scale for agitating a solid reacting with a gas. At the same time it allows the solid to flow from one end of the reactor to the other, and a counter-current system can be used if required. 

Fig. 5.2. Stirred bed reactor (From C. D. Harrington and A. E. Ruehle, Uranium Production Technology, copyright 1959, D. Van Nostrand, Princeton, New...

A bank of four horizontal stirred beds is used, one above another, of the screw conveyor type. The top one is for calcination in air to remove traces of nitric acid, water and carbonaceous products, the middle two for hydrofluorination and the lower one mainly for partial sintering and den-sification of the product in hydrogen fluoride. Each stirred bed reactor is 20 ft long and 16 in. internal diameter, the lower ones made of inconel and the upper one of stainless-steel. The powder flows from a hopper at the top, via a seal hopper between the calcination and hydrofluorination sections, to another hopper and feeding system at the bottom, as shown in Fig. 5.8. Air and anhydrous hydrogen fluoride pass in counter-current flow to the solids in the appropriate reactors, the efBuent gases being conducted to suitable filters and dust collectors. 

Olefin polymerization through heterogeneous catalysis is one of the most important processes to produce polyolefin resins. In this process, small catalyst particles are continuously fed into reactors operated under controlled temperature, pressure, and chemical composition. Gas-phase olefin polymerization can be carried out in fluidized bed reactors and in vertical and horizontal stirred bed reactors. To compete with other process types and maintain a high level of efficiency, the monomer mixture must be operated close to its dew... 

Industrial-scale SSP is carried out in moving packed bed, fluidized bed, and stirred bed reactors Mallon and Ray have published a brief discussion of idealized models of these reactors [75]. Fluidized beds have a serious drawback because of the high consumption of gas needed to keep the bed in a fluidized state, and residence time distribution is unfavorable to high conversions. Stirred beds in series are a possible solution, depending on economic details. 

Gas-phase reactors for olefin polymerization are divided into two classes fluidized-bed reactors and stirred-bed reactors. The stirred-bed reactors can be further classified into vertical and horizontal. 

The narrower residence time distribution of horizontal stirred-bed reactors leads to higher yields per pass, formation of less off-specification material, and more uniform impact copolymers and reactors blends. 

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