Stirred beds

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 principle, PE gas phase plants are so-called swing units which are able to produce both HDPE, MDPE and LLDPE, even if cost-wise it is better to avoid frequent switches between the PE grades with different densities. The gas phase process is the most commonly used technology for the production of LLDPE with 1-butene or 1-hexene as a comonomer. Fluidised bed gas phase process technology is licensed by Univation (Unipol) and BP (Innovene), stirred bed gas phase technology by Basell (Lupotech G). 

Reactor type Tubular or autoclave Autoclave CSTR Loop or CSTR Fluidized or stirred bed... 

Apparatus and Procedure - The experiments with the solid feedstocks and the initial experiments on liquid samples were carried out in the apparatus shown in Figure 1A. The vapors from a stainless steel, stirred-bed carbonizer/vaporizer at 873°K were cracked at atmospheric pressure in a tube reactor heated in a platinum-wound furnace. The reactor was 30 mm ID and had a 100 mm long hot zone within 20°K of the maximum reactor temperature. Solid feedstocks were introduced at about 1 g min. from a vibratory table through a water-cooled port. Liquids were injected at the same point from a mechanically driven syringe at 0.1-0.8 ml min. The amount fed was determined by weighing the feeders. 

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.

Particles of polypropylene are continuously formed at low pressure in the reactor (1) in the presence of catalyst. Evaporated monomer is partially condensed and recycled. The liquid monomer with fresh propylene is sprayed onto the stirred powder bed to provide evaporative cooling. The powder is passed through a gas-lock system (2) to a second reactor (3). This acts in a similar manner to the first, except that ethylene as well as propylene is fed to the system for impact co-polymer production. The horizontal reactor makes the powder residence time distribution approach that of plug-flow. The stirred bed is well suited to handling some high ethylene co-polymers that may not flow or fluidize well. 

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

BP Chemical Polypropylene Propylene Gas-phase horizontal stirred bed 8 2000... 

At least five industrial-scale biomass gasifiers were available commercially from U.S. manufacturers in the 1990s. A two-stage stirred-bed gasifier is available from Producers Rice Mill Energy. The company built three gasifiers of 11 to 18 t/day capacity in Malaysia for rice hull feedstocks. Sur-Lite Corporation built small-scale, fluid-bed gasifiers of up to 10 GJ/h capacity for cotton-gin... 

ABSTRACT A novel reactor configuration has been developed in our laboratory which addresses the heat transfer limitations usually encountered in vacuum pyrolysis technology. In order to scale-up this reactor to an industrial scale, a systematic study on the heat transfer, the chemical reactions and the movement of the bed of particles inside the reactor has been carried out over the last ten years. Two different configurations of moving and stirred bed pilot units have been used to scale-up a continuous feed vacuum pyrolysis reactor, in accordance with the principle of similarity. A dynamic model for the reactor scale-up was developed, which includes heat transfer, chemical kinetics and particle flow mechanisms. Based on the results of the experimental and theoretical studies, an industrial vacuum pyrolysis reactor, 14.6 m long and 2.2 m in diameter, has been constructed and operated. The operation of the pyrolysis reactor has been successful, with the reactor capacity reaching the predicted feed rate of 3000 kg/h on a biomass feedstock anhydrous basis. 

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. 

Schliinder, . U. (1984) Heat transfer to packed and stirred beds from immersed bodies. Chem. Eng. Process., Vol. 18, pp. 31-53. 

Solution-polymerized SBR is made by termination-free, anionic/live polymerization initiated by alkyl lithium compounds. Other lithium compounds are suitable (such as aryl, alkaryl, aralkyl, tolyl, xylyl lithium, and ot/p-naphtyl lithium as well as their blends), but alkyl lithium compounds are the most commonly used in industry. The absence of a spontaneous termination step enables the synthesis of polymers possessing a very narrow molecular weight distribution and less branching. Carbon dioxide, water, oxygen, ethanol, mercaptans, and primary/secondary amines interfere with the activity of alkyl lithium catalysts, so the polymerization must be carried out in clean, near-anhydrous conditions. Stirred bed or agitated stainless steel reactors are widely used commercially. 

Low Btu gas requires cleanup before it can be burned in a turbine. Several cleanup devices have been used on the output stream of the stirred bed gasifier at the Morgantown Energy Technology Center. 

Fig. 1. Comparison of typical solid-state fermentation (SSF) and submerged liquid fermentation (SLF) systems. A stirred-bed SSF bioreactor of the design of Durand and Chereau [2] is compared with a typical stirred SLF bioreactor. For each bioreactor an expanded view of the microscale is also shown, in order to highlight differences between the micro-structure of the two systems. The relative scales make it clear that mixing is possible on much smaller scales in SLF than in SSF, since in SSF mixing cannot take place at scales smaller than the particle size. Note that particle sizes in SSF are commonly larger than 1 mm...

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