Autoclave stirred tank

Polyethylene is the simplest addition polymer, and we will briefly describe its polymerization process. Polyethylene, as discussed previously. Is made by opening the double bond in the ethylene molecule, and chemically bonding the monomers together in a reactor. That reactor can involve an autoclave (stirred tank) process or a tubular process. It can be done at low pressure (about 300 psi) or at pressures as high as 50,000 psi. Temperatures are controlled at some elevated level such as 125 to 250°C, but the temperature needed is very specific to the type of polymer structure desired. 

As discussed above, it was clear that ethylene/1-butene copolymers possessed significantly improved mechanical properties compared to ethylene homopolymer products, so that a commercial particle-form reactor design was needed that could provide polyethylene copolymers over a range of Flow Index values with sustained operability over extended periods of time without reactor shut down. Adding 1 -butene to the polymerization process made the autoclave stirred tank reactor even more difficult to operate, as reactor wall fouling problems persisted and in some cases polymer particle morphology was reduced due to some polymer components becoming soluble in the n-pentane. 

An independent development of a high pressure polymerization technology has led to the use of molten polymer as a medium for catalytic ethylene polymerization. Some reactors previously used for free-radical ethylene polymerization at a high pressure (see Olefin polymers, low density polyethylene) have been converted to accommodate catalytic polymerization, both stirred-tank and tubular autoclaves operating at 30—200 MPa (4,500—30,000 psig) and 170—350°C (57,83,84). CdF Chimie uses a three-zone high pressure autoclave at zone temperatures of 215, 250, and 260°C (85). Residence times in all these reactors are short, typically less than one minute. 

FT synthesis was carried out in a 0.3 L autoclave-type slurry continuous stirred tank reactor under pressurized conditions. The catalyst was reduced with hydrogen... 

Stimuli-responsive materials, shape-memory polymers as, 22 355-356 Stirling cycle, 8 43 Stirred autoclave, 14 89, 92t Stirred autoclave reactor, 20 216 Stirred batch RO unit, 21 644 Stirred mills, 16 615 Stirred tank bioreactors, 1 737-740 oxygen transfer driving force, 1 734 Stirred tank electrochemical reactor (STER), 9 660-662... 

Discontinuous (batch) processes are carried out in pressure vessels (autoclaves) where DMC is maintained as liquid by autogenous pressure. Instead, CF reactions at atmospheric pressure require that both DMC and the reagent(s) in the vapor phase come into contact with a catalytic bed a constraint that has spurred the development of new applications and alternative reaction engineering, namely, GL-PTC and the continuously fed stirred-tank reactor (CSTR). 

A bnlk polymerization reactor can be as simple as a tube into which the reactants are fed and from which the polymer mixture emerges at the end it can be more of a traditional, continnons stirred-tank reactor (CSTR), or even a high-pressure autoclave-type reactor (see Figure 3.21). A bulk polymerization process need not be continuous, but it should not be confnsed with a batch reaction. There can be batch bnlk polymerizations jnst as there are continnons bulk polymerizations processes. 

A number of processes have been developed to obtain products of different physical properties. The nature of the product is affected by the addition of diluents or other additives before carrying out the polymerization. Autoclaves or stirred-tank reactors, and tubular reactors, or their combinations have been developed for the industrial production of high-pressure polyethylene.206,440 Pressures up to 3500 atm and temperatures near 300°C are typically applied. 

The stirred-tank reactor or stirred autoclave is continuously operated when rapid changes in concentration do not allow samples to be taken from the reactor for analysis. In the stirred-tank reactor complete uniformity of concentration and temperature throughout the reactor is assumed. The exit stream from the reactor has the same composition as the fluid within the reactor (Fig. 3.3-1). The rate of reaction can be evaluated from the material balance... 

The autoclave reactors used today in the high-pressure polymerization of ethylene are single stirred-tank reactors, cascades of stirred autoclaves, and multi-chamber autoclaves. 

Single stirred-tank reactors were run in the first industrial scale processes to manufacture LDPE. Today they are used only for plants having lower capacities. The design of a single autoclave is shown in Fig. 5.1-6. It consists of a thick-walled forged-, or two-layer shrunk mantle. The ratio of inside length to inner diameter is typically in the range of one to two, and the volume is 1 - 2 m3. 

The ultrafine iron oxide catalyst run was conducted in a 300 mL autoclave operated as a continuous stirred tank reactor (CSTR) using a configuration similar to that reported previously.12 The catalyst (10 g) was slurried with a C30 oil (ethyl), pretreated with CO (Liquid Carbonic,... 

S3] A process for the oligomerization of ethylene for the production of linear a-olefins had to be developed in stirred tank reactor assuming isothermal conditions and was executed in the kinetic regime. The latter was assured by increasing the rotational speed of the impeller until the rate of reaction did not increase further. The autoclave reactor was heated by an external blanket and supplied with cooling water circulation through an internal coil. 

Fluidized bed o Continuous stirred tank (Double) Loop Rotating ring disc Ui Stirred tank cascade g n> Stirred tank + tower Tower or tower cascade 1 Extruder Mixer + conveyor CPFR 1 u -P M H tJ Xi -p 2 rQ o Batch stirred tank + autoclave with gate paddle nuscer c Batch stirred tank + filter press BR u Batch stirred tank J Polymerization reactions... 

High pressure batch stirred tank reactor. Substrates (equimolar solution of oleic acid and oleyl alcohol) were filled into thermostated autoclave and mixed. Enzyme preparation was added and finally CO2 was pumped with a high pressure pump up to desired pressure. Reactor volume was 0.5 L (Pmax = 450 bar, Tmax = 200°C) (Figure 1). 

Reactors used in ethylene polymerizations range from simple autoclaves and steel piping to continuous stirred tank reactors (CSTR) and vertical fluidized beds. Since the 1990s, a trend has emerged wherein combinations of processes are used with transition metal catalysts. These combinations allow manufacturers to produce polyethylene with bimodal or broadened molecular weight distributions (see section 7.6). 

The most commonly used high pressure reactor is the stirred autoclave, also referred to as a stirred tank reactor (STR). These reactors are commercially available in sizes ranging from 50 ml to 500 gallons. A typical small scale reactor... 

Also, polymerization reactions are carried out in a variety of reactors including agitated batch reactors, continuous stirred tank reactors (CSTR), multizone autoclaves, loop reactors, tubular reactors, fluidized bed reactors, and a combination of these reactors. 

Batch, semibatch, and continuous stirred tank reactors residence time 600 to 15,000 s (10 min to 4 h) heat of reaction primarily exothermic reaction rate slow to moderate. High-pressure autoclaves <100 L. Unique to semibatch phases liquid, gas-liquid, liquid-liquid, gas-liquid catalytic solid. Use where a batch operation is appropriate (Section 16.11.6.24), but one reactant (e.g., gas) needs to be added continuously or if the initial reaction rate is very high. Selectivity is best for parallel reactions. For more details, see CSTR, Section 16.11.6.26. 

The reactor schematic is shown in Figure 1. Continuous stirred tank reactor (CSTR) experiments were conducted in a 50 mL Microclave from Autoclave Engineers, rated to 344 bar and 616 K. Catalyst particles were suspended in the reaction mixture by an impeller operating at 1200 RPM. Fixed-bed reactor experiments were conducted in a 1 I.D. stainless steel tubular reactor from Autoclave Engineers, rated to 1110 bar at 700 K. The catalyst bed was supported on both ends with glass wool (Alltech) and stainless steel mesh screens, which... 

The experimental work reported here deals with optimum reaction conditions for the liquefaction of the major biomass component, cellulose, in an aqueous system. While lignin in wood may change the results qualitatively, we do not expect that transfer of our conclusions to a wood-based system will invalidate these results. However, there are some differences and our results should be used as indicators rather than quantitative measures of performance in other systems. For instance, at Albany, the reactor is a stirred tank, and consequently some of the oil has a longer residence time, while some proceeds through rapidly. This causes some difference between results at Albany and our experiments, which were performed in small autoclaves. Here we simply apply the results of our work generally to biomass liquefaction systems, with Albany as an example, without attempting to claim a 1 1 correspondence. In any event, laboratory work in support of the Albany pilot plant is proceeding separately at our laboratory (4-10). while the research reported here is basic in nature (41 -43). 

Hansenula polymorpha and Saccharomyces cerevisiae were cultivated on synthetic medium with 1% glucose in fed-batch and continuous mode, respectively, in the absence of antifoam agents. For the nutrient preparation, sterilization and storage, 300-, 600-, 1000- and 5000-1 stirred tank vessels were used. The nutrient salt medium was steriUzed without glucose. The glucose solution was autoclaved separately and was added to the cold, sterilized nutrient medium. The flotation column was operated in continuous mode. 

The Slurry Polymerization Process with Super-Active Ziegler-Type Catalyst Systems From the 2 L Glass Autoclave to the 200 m Stirred Tank Reactor... 

How many of these polyolefin production plants have been installed since the beginning of this industry One way to develop the answer to this question, which we do not pursue in depth here, is to follow the technology licensors. For example, we know that ICI were active in licensing LDPE and that by 1977, they had 23 licensees, and a total installed capacity of 812,000 tons. However, their founding technology was based on the stirred tank reactor (autoclave), and this could not be scaled up in the same way that tubular reactors, developed by others, could. By 1980, ICI had lost the first producer advantage , had not led the way in technology development, and in 1982, exited the PE business. 

The stirred tank with a jacket for heating or cooling (also called autoclave or digester) is the workhorse of the pharmaceutical, fine-chemicals, mineral and paper industries. It is used as a reactor, mixer, decanter, heater and cooler. The bubble and slurry-bubble columns too are akin to the STR. It is used as a batch reactor or semi- or fed-batch reactor for those reactions requiring a large residence time, as the tubular reactor would be too long and unwieldy. The STR is bulky, and the yield and selectivity could be low. 

The main issue in condensation polymerization is the retention of equivalent concentrations of both contra-functional groups (COOH and NH2), because an excess of either one eventually decreases the chain length significantly. Hence it is customary to react both monomers in a first stage forming a Nylon salt (hexa-methylene diammonium adipate) as an aqueous solution which is conveniently stored or transported. Polymerization is carried out in a stirred tank (autoclave), either batchwise or continuously, at pressures up to 20 atmospheres and temperature of 200 C to 275 C. 

Batch, semibatch and continuous stirred tank reactors Residence time 600-15 000 s (10 min to 4 h) heat of reaction primarily exothermic reaction rate slow to moderate. High pressure autoclaves < 100 L. 

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