Plug flow polymer tubular reactor

EQUATIONS FOR A PLUG FLOW POLYMER TUBULAR REACTOR WITH BRANCHING KINETICS... 

For viscous solutions, the assumptions of plug flow are not strictly valid. If the velocity profile is not flat, polymer solution near the tube wall will move more slowly than that near the center of the tube. Since the slow-moving polymer near the wall remains in the reactor longer, it will polymerize to a higher conversion (or extent of reaction) than the bulk material. This higher conversion will then compound the viscosity problem. Studies on the effect of this deviation from plug flow in tubular polymerization have to be carried out by Hamer and Ray [4,5]. 

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 ...

Another method to increase the number of polymer particles produced in the first stage reactor with initiator and emulsifier concentrations fixed is to employ a plug flow type reactor such as a tubular reactor for the first stage. The minimum residence time of a plug flow reactor 6 necessary to produce the same number of polymer particles as in E batch reactor is tc. Thus, from Eq.(31) We have ... 

Tubular and columnar apparatus (apparatus length-to-diameter ratio L/d > 100) including screw equipment relate to plug-flow reactors type [7,8]. Plug-flow reactors are applied for many of gas-phase reactions realized in production quantities, in particular for ethylene polymerization under high pressure conditions [9], and for some liquid-phase reactions, for example polystyrene synthesis in columns and other rubbers and plastics productions. Near 10% of polymer and 30% of fibers manufacture are produced in apparatus of such types [10]. 

There are different tubular and column plug flow reactors as well as screw reactors [1]. Plug flow reactors are used for various gas-phase reactions occuring within industrial-scale production, particularly for the reactions of nitrogen oxide oxidation, ethylene chloration, and high-pressure ethylene polymerisation. They are also used for some liquid-phase and gas-liquid reactions, e.g., styrene polymer production in a column, plastic and rubber production, synthesis of ammonia and methanol, and sulfation of olefins [2]. 

Consider first the case of two tubular reactors in series, making high-impact polypropylene. Reactor 1 produces isotactic polypropylene, while random ethylene-propylene copolymer is made in Reactor 2. Assuming that both reactors are ideal plug-flow reactors, the residence time of all the polymer particles in each reactor is exactly the same. Consequently, if the distribution of active sites in the... 

Sohition. As demonstrated in Example 3, the chain length depends on how long a chain is allowed to grow. In a batch reactor and an ideal plug-flow reactor, all chains react for the same length of tim hence, the product will be essentially monodisperse. In a CSTR and a laminar-flow tubular reactor, the residence time of chains in the reactor varies, causing a spread in the distribution. Keep in mind, however, that ideal pluf flow is a practical impossiblity, particularly with highly viscous polymer solutions. Compare these conclusions with those of Chapter X, Example 13. 

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