Gas-phase Reactors

Chemical Kinetics, Tank and Tubular Reactor Fundamentals, Residence Time Distributions, Multiphase Reaction Systems, Basic Reactor Types, Batch Reactor Dynamics, Semi-batch Reactors, Control and Stability of Nonisotheimal Reactors. Complex Reactions with Feeding Strategies, Liquid Phase Tubular Reactors, Gas Phase Tubular Reactors, Axial Dispersion, Unsteady State Tubular Reactor Models... 

A more recent review by Fahidy (FI) concerns the chemical engineering approach to electrochemical processes, such as fluidized-bed reactors, bipolar particulate reactors, pulsed electrochemical reactors, gas-phase electrochemical reactors, electrocrystallization and electrodissolution, and the enhancement of heat and mass transfer in electric fields. In this review, the author also discusses dimensionless mass-transfer equations applied in cell design. Such equations are reviewed in greater detail in Section VI. 

In a fixed bed reactor, gas phase reactions are generally carried out using a stationary bed of solid catalyst. In a typical reactor, suitable screens support the bed of catalyst particles, through which the gas phase flows. Gaseous reactants adsorb on the catalyst surface, reactions occur on this surface and reaction products desorb back to the gas phase. Two major types of fixed bed reactor are the conventional axial flow fixed bed reactor and the radial flow fixed bed reactor. These types are shown... 

Figure 4 presents the results of one such study. Petcoke carbon conversion was plotted versus reactor gas-phase residence time calculated for the trial runs, and a trend line was extrapolated to 100% conversion. From this graph, it was... 

Inertizing the gas phase by flushing the reactor gas phase with an inert gas such as Nitrogen, C02, HC1. 

To keep the reactor gas phase below the L.F.L. in chlorine (method 1) is the safer method where only proper temperature control is necessary. 

To keep the reactor gas phase above the U.F.L. in chlorine (method 2) may not be quite safe. On start-up the temperature must be set to the process normal value ensuring enough fuel vapour pressure before chlorine injection. If a condensor is used where the fuel vapour pressure is depleted, the gas flow composition may enter the flammable range. Glass condensors are better not used or protected from light. 

If chlorine does not evolve in the gas phase in normal process conditions, an inert gas flush in the reactor gas phase is recommended (see below). If a chlorine flow evolves from the liquid reaction mixture unreacted, enough inert gas flush must be provided in the reactor gas phase to lower the chlorine concentration below the minimum oxidizer concentration (MOC) of the fuel flammable range. 

If HC1 is released in the gas phase, this gas contributes to the reactor gas phase blanketing. However one should take into account rapid changes in the process conditions, if the wanted chlorination reaction stops due to catalyst depletion or reactant consumption. More unreacted chlorine can be released in the gas phase, the HC1 production can disappear. Therefore monitoring of the gas phase chlorine concentration using a chlorine analyser is recommended. 

Application The Borstar polypropylene (PP) process can produce homopolymers, random copolymers, heterophasic copolymers, and very high-rubber-content heterophasic copolymers. It is a modular process consisting of a loop reactor/gas-phase reactor combination. 

Here V is the reactor gas-phase volume, v the volumetric flow rate to and leaving the reactor, and the concentration defined by the subscript out applied throughout the reactor since it is well mixed. 

Figure 11.12 Reactor performance-pressure drop trade-off index (Eq. (11.35)) for different structured reactors. Gas phase, physical properties air (STP, standard temperature and pressure).

Figure 6.13 Mass transfer effectiveness for different microstructured reactors. Gas-phase, physical properties of air at 20 °C, 0.1 MPa.

Figure 3.16 Flow diagram of the polypropylene vertical reactor gas phase process [15, Ullmaim, 2001]...

This process uses a horizontally stirred reactor instead of the vertical helical agitator of the process described in Section 3.2.5.3.2. The condensed recycled monomers are sprayed into the top of the reactor provide cooling, while uncondensed monomers and hydrogen injected into the base maintain the gas composition. Figure 3.17 also includes a deactivation and purge step (b) similar to the previously described processes (Spheripol, Hypol, vertical reactor gas phase). All these processes, including the horizontal reactor gas phase, use 4 generation catalysts. 

Slurry reactors, rather than gas-phase reactors, are used in the majority of laboratory studies of catsJytic olefin polymerization. Results from slurry reactors are frequently used to predict the activity of catalysts for gas-phase reactors. Gas-phase processes are... 

For the production of standard high-impact block copolymers, similar differences were found in overall economics between processes as found with homopolymers gas-phase and bulk slurry processes with three or more continuous reaction stages in series. Such processes are significantly more costly than our standard two-reactor, gas-phase and bulk slurry processes, but the products they produce are very high performance and cannot yet be matched in a two-stage reaction system. The products command significantly higher prices, and these complex slurry processes are, therefore, expected to remain in use (at least in Japan and Western Europe) beyond the 1993 timeframe. 

A. Single Reactor Gas Phase Innovene Process BP (BP Chemicals) with INSITE (Dow Catalysts) Technology... 

Autoclave reactors Tubular Reactors Gas Phase Slurry Solution... 

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