Polymer reactor

Choplin, L. and Villermaux, J., 1994. Viscous mixing in polymer reactors. American Institute of Chemical Engineers Symposium Series, 299, 123-129. 

Figure 7. Tubular plug-flow addition polymer reactor effect of the frequency factor (ka) of the initiator on the molecular weight-conversion relationship at constant activation energy (Ea). Each point along the curves represents an optimum initiator feed concentration-reactor jacket temperature combination and their values are all different, (Ea = 32.921 Kcal/mol In ka = 35,000 In sec ...

As is common in most polymer reactor design problems, heat transfer is one of the major process concerns. For example, if the heat transfer is primarily through the wall of a jacketed reactor, the overall heat transfer coefficient is a function of both the agitator configuration and the degree of swelling of the particles. 

The precipitation polymerization literature is reviewed with particular attention to the influence of particle formation and growth, autoaccelerating polymerization rates, and copolymer composition drift on polymer reactor design. 

N. Friis and A. E. Hamielec, Principles of Polymer Reactor Design, in Polymer Reaction Engineering Course Notes, McMaster University, Hamilton, Ontario, Canada, p.55. 

In 1967 a paper by Boyle IJ provided a more quantitative method for designing vents for polymer reactors. It was based on reaction rate, heat of reaction, and vapor pressure data. Boyle assumed that the venting of a system can be approximated by sizing to discharge the entire batch contents as a liquid. 

Web-coating polymerizations (e.g., as used for photographic film and coated abrasives) literally achieve a piston flow reaction environment. Mechanically driven screw devices used as finishing reactors for PET closely approximate piston flow. Motionless mixers can do this as well. However, polymer reactors that closely approximate piston flow are the exception. 

We are first concentrating on commercially-available instrument technologies providing in situ measurements in polymer reactors, as opposed to those requiring new instrument development or external sampling loops. 

Temperature control of a large, highly exothermic semi-batch chemical or polymer reactor can be an involved problem. The reaction may be auto-acceleratlng. Heat transfer rates can vary during the process. Random disturbances can enter the process from many sources. Changes In... 

Hamielec, A.E., Computer Applications Modeling of Polymer Reactor Systems , Proceedings - Polymer Characterization Conference, Cleveland State University. Division of Continuing Mucation, Qeveland, Ohio, April 30 - May 1, 1974. 

Fig. 37. Score plot of batch polymer reactor data (numbers indicate batch numbers).

Fig. 38. Explained variance by batches (a) and over time (b) for batch polymer reactor data.

C. Comprehensive Example 3 Diagnosis of Operating Problems in a Batch Polymer Reactor... 

Fig. 45. Top-level organization of malfunction hypotheses for an existing batch polymer reactor with a focus on Step 1 Initial Charge problems.

Flexible Control of Laboratory Polymer Reactors by Using Table-Driven Software... 

Population Balance Approach. The use of mass and energy balances alone to model polymer reactors is inadequate to describe many cases of interest. Examples are suspension and emulsion polymerizations where drop size or particle distribution may be of interest. In such cases, an accounting for the change in number of droplets or particles of a given size range is often required. This is an example of a population balance. 

Associated with the class of polymer particles n(t,i)dx in the polymer reactor is a physical property p(t,x) (e.g. diameter or area of particles of class (t,x), etc.). Then, a total property Pit) (e.g. total particle diameter in the reactor at time t) can be obtained by summing (integrating) p(t,x) over all classes of particles in the reactor vessel, viz ... 

The ETHOS MR is constituted of a multimode cavity very close to domestic oven with safety precautions. It can use standard glassware or glass (420 mL up to 2.5 bar) and polymer reactors (375 mL up to 200 °C and 30 bar) with magnetic stirring. The magnitude of microwave power available is 1 kW. The optical temperature sensor is immersed in the reaction vessel for quick response up to 250 °C. An infrared sensor is also available. A ceiling mounted is available in order to make connection with a conventional reflux system located outside the cavity or to ensure addition of reactants. 

Polymer flow issues are concerns on the part of plant operations personnel that can arise when one proposes to put an in-line NIR probe (or pair of probes) into a polymer reactor or transfer line. These concerns tend to be plant or process-specific. Plant personnel are likely to be concerned if the probe will change the pressure drop in the line, create a cold spot in the reactor or line, protrude into the flow stream, or create dead spots (e.g. recessed probes or the downstream side of protruding probes). There may also be plant- or process-specific resfricfions on where probes (or analyzers) can be located, on pipe sizes, on the use of welds, and on materials of construction. It is critical to involve plant operations personnel (including process operators) as early as possible in discussions about probe design and location. 

Miniaturizing a conventional-flow screening system (macro-scale system) to a chip-based system comprises a number of changes, such as flow rates, reagent supply, and the material. While the conventional system with the open tubular reactors is restricted to polymer reactors, the choice of materials for the chip is... 

Acrylic Polymer Reactor Accident Investigation Lessens Learned and Three Years Later, Michael Gromacki... 

Estimates of historical exposures were developed for these same plants (Blair et al., 1998 Stewart et al., 1998). Using the measurements described above (Zey McCammon, 1989 McCammon Zey, 1990 Zey Bloom, 1990), the average estimate for the polymer reactor operators TWAg exposure in the 1950s and 1960s was about 7 ppm [15 mg/m l in one plant and around 15-20 ppm [33 4 mg/ni J in the other two fibre plants. These levels fell to 3-9 ppm [6.5-19.5 mg/m ] in the 1970s. 

Many polymer reactions, for example, are highly exothermic, so the temperature control concepts outlined in this book must be applied. At the same time, controlling just the temperature in a polymer reactor may not adequately satisfy the economic objectives of the plant, since many of the desired polymer product properties (molecular weight, composition, etc.) are created within the polymerization reactor. These key properties must be controlled using other process parameters (i.e. vessel pressure in a polycondensation reactor or chain transfer agent composition in a free-radical polymerization reactor). 

The polymer industry experienced very rapid growth over the last five decades. A vast variety of products are produced for a myriad of applications. The heart of a polymer process is the reactor. Because there are many types of polymerization reactions, there a wide variety of types of polymer reactors, both batch and continuous. 

Some polymerization reactions are highly exothermic, so the problems of temperature control, which are the major emphasis of this book, are important in these systems. However, beyond the issue of temperature control, polymer reactors must produce a product with the desired properties. The final polymer product properties, such as viscosity, molecular weight distribution, particle size, and composition, are important for consistent performance of the polymer. These properties depend on more than just temperature and few can be measured online.12... 

Particles move upwards in a series of discrete fast movements ("jumps"), punctuated by periods of relative inactivity ("idle time" or "quiescent time"). It is during these idle times that the particles are able to sinter in polymer reactors, and control of the length of these periods is necessary to prevent defluidisation by sintering (Seville et al., 1998). 

The basic issues of scaleup are the same for polymer reactors as for ordinary chemical reactors. The primary problem is that the capacity for heat and mass transfer increases less rapidly than the reactor volume and throughput. The remedies are also similar, but the high viscosities characteristic of polymers... 

The subject is treated elsewhere in this Symposium, and was reviewed by Nauman (173) and Gerrens (174) a few years ago. Therefore a thorough discussion of mixing effects in polymer reactors would go beyond the scope of this paper. It is likely that signi-... 

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