Reactor Jacket temperature

Figure 1. Typical reactor temperature profile for continuous addition polymerization a plug-flow tubular reactor. Kinetic parameters for the initiator 1 = 10 ppm Ea = 32.921 kcal/mol In = 26.492 In sec f = 0.5. Reactor parameter [(4hT r)/ (DpCp)] = 5148.2. [(Cp) = heat capacity of the reaction mixture (p) = density of the reaction mixture (h) = overall heat-transfer coefficient (Tf) = reactor jacket temperature (r) = reactor residence time (D) = reactor diameter].

The ability to manipulate reactor temperature profile in the polymerization tubular reactor is very important since it directly relates to conversion and resin product properties. This is often done by using different initiators at various concentrations and at different reactor jacket temperature. The reactor temperature response in terms of the difference between the jacket temperature and the peak temperature (0=Tp-Tj) is plotted in Figure 2 as a function of the jacket temperature for various inlet initiator concentrations. The temperature response not only depends on the jacket temperature but also, for certain combinations of the variables, it is very sensitive to the jacket temperature. 

Figure 6, Ejfect of solvent concentration on the molecular weight-conversion rehtionships of a tubular-addition polymerization reactor of fix size using a specified initiator type. Each point along the curves represents an optimum initiator feed concentrationr-reactor jacket temperature combination, (kinetic parameters of the initiator Ea = 24,948 Kcal/mol In k/ = 26,494 In sec f = 0.5)...

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 ...

T = temperature p = density AH = heat of reaction h = heat-transfer coefficient D = reactor diameter Cp = heat capacity Rp = polymerization rate Tj = reactor jacket temperature P = pressure... 

The process shown at the bottom of Figure 2.21 gives the conditions for this design. The reactant concentration in the first reactor is even higher (2.18 kmol/m3), so the reaction rate is large despite the smaller volume. This produces a required heat transfer rate that is still quite large (1.16 x 106 J/s) relative to the smaller heat transfer area (27.5 m2). The result is a very large AT in the first reactor (jacket temperature is 300 K), which is 89% of the total available ... 

The required reactor-jacket temperature difference on scale-up, with a constant Lewis number, is... 

Poljmerization was initiated by addition of an aqueous potassium persulfate solution to the reactor. The emulsion temperature was maintained near 40°C by control of a combination of three variables (f) reactor jacket temperature, (2) agitator speed, and (3) catalyst addition rate. The progress of polymerization (86) was... 

Using the process parameters reported by Engell and Klatt [22], the steady-state behavior of the reactor may be investigated as a function of the feedrate U], The reactor jacket temperature, 2, is fixed at 130"C and X o is fixed at 5.1 mol/L. 

Temperature Oscillation Calorimetry A more elegant way to estimate online the overall heat transfer coefficient without any additional measurement was developed by Carloff [ 11] by the technique known as temperature oscillation calorimetry, TOC. In this approach, the unknown product UA is computed from the analysis of the sine-shaped oscillations, which are superposed on either the reactor temperature or jacket temperature. The objective is to decouple the slow dynamic of the chemical heat production from the fast dynamic variable heat transfer during the reaction. The oscillations can be achieved either by adding a calibration heater to the system or by adding a sine signal to the set point of either T or Ty Figure 7.2 shows the evolution of the reactor and jacket temperatures in a reaction calorimeter where a sine wave temperature modulation was superimposed on the reactor jacket temperature. 

The maximum attainable production was sought that did not cause thermal runaway. By gradually increasing the temperature of the water, boiling under pressure in the reactor jacket, the condition was found for the incipient onset of thermal instability. Runaway set in at 485.2 to 485.5 K for the 12 m reactor and at 435.0 to 435.5 K for the shorter, 1.2 m reactor. The smaller reactor reached its maximum operation limit at 50 K lower than the larger reactor. The large reactor produced 33 times more methanol, instead of the 10 times more expected from the sizes. This... 

Recirculation of non-boiling liquids can be achieved by bubbling inert gas through the liquid in the reactor jacket. This is less practical for fluids with significant vapor pressure, because the jacket still must be under pressure, and a large condenser must be installed to condense the liquid from the vapor-saturated gas at the jacket temperature. It is more useful with molten metals and salts. For the design details of the reactor tube s inside, the same considerations apply as for a thermosiphon-controlled reactor. 

A Microsoft Excel spreadsheet (Example 7-ll.xls) was developed for predicting the jacket temperature required for either heating up or cooling down reactants in a batch reactor. 

Experiments were performed in tlie SIMULAR calorimeter using the power compensation method of calorimetry (note that it can also be used in the heat flow mode). In this case, the jacket temperature was held at conditions, which always maintain a temperature difference ( 20°C) below the reactor solution. A calibration heater was used to... 

An exception to the above are fatty acid methyl esters, which, due to the reaction mechanism involving molecular rearrangements with excess S03, have to be sulfonated at a slightly higher mole ratio of S03 to methyl esters (namely, 1.15-1.20/L). Outside the reaction tubes, in the reactor jacket, cooling water is circulated to control the liquid-film temperature and removing the reaction heat. 

The reaction heat is removed by the vacuum evaporation of dilution water. The resulting water vapors allow complete degassing and stripping of any trace of undesired low boiling by products (i.e., 1,4-dioxane for ethoxy sulfates). The product temperature is accurately controlled with the vacuum level kept in the reactor and by the temperature control in the reactor jacket. The automatic control of the different process parameters, i.e., flow rate of reagents, vacuum degree, temperature of thermostatting water, also allows for accurate control of the product concentration. 

Temperature control is primarily obtained via the sensible heat of the cooled feed stream with the remaining heat of reaction being removed by the reactor jacket. 

Effects of Initiator Parameters. Initiator types can best be characterized by the frequency factor (k ) and the activation energy (E ), and the effect of these parameters on the molecular weight-conversion relationship is shown in Figures 7 and 8. The curves shown are the result of choosing the jacket temperature-inlet initiator concentration combination which maximizes the reactor conversion for each initiator type investigated. 

Figure 9, Effect of the initiator activation energy on the molecular weight distribution of an addition polymer produced in a tubular reactor constant frequency factor and at widely different values of initiator—jacket temperature combination (the conversion is optimized In k/ = 26.492...

The computer simulation study of the operation of the tubular free radical polymerization reactor has shown that the conversion and the product properties are sensitive to the operating parameters such as initiator type, jacket temperature, and heat transfer for a reactor of fixed size. The molecular weight-conversion contour map is particularly significant and it is used in this paper as a basis for a comparison of the reactor performances. 

There exists an optimum jacket temperature for maximizing conversion at a given average molecular weight product. The study further suggests that an unstable operating region exists where wide conversion fluctuations result from attempts to increase the reactor conversion by minor adjustments in initiator amount or jacket temperature. 

In order to investigate the kinetics, heat of reaction and other aspects of the system, the RCl reaction calorimeter was employed. This system allows to perform the reaction in a 2 liters glass reactor, while controlling the reactor and jacket temperatures. Following the reaction, the heat released at any time period can be determined. The operation and application of this system has been discussed in numerous publications (refs. 5,6). 

Example 5.5 Ingredients are quickly charged to a jacketed batch reactor at an initial temperature of 25°C. The jacket temperature is 80°C. A pseudo-first-order reaction occurs. Determine the reaction temperature and the fraction unreacted as a function of time. The following data are available ... 

Solution There are several theoretical ways of stabilizing the reactor, but temperature control is the normal choice. The reactor in Example 5.7 was adiabatic. Some form of heat exchange must be added. Possibilities are to control the inlet temperature, to control the pressure in the vapor space thereby allowing reflux of styrene monomer at the desired temperature, or to control the jacket or external heat exchanger temperature. The following example regulates the jacket temperature. Refer to Example 5.7. The component balance on styrene is unchanged from Equation (5.29) ... 

Use the inlet temperature rather than the jacket temperature to control the reactor in Example 14.8. 

Reactor volume (L) Product yield (%) Jacket temperature (°C)... 

With dt = 0.025 m study the effect of varying inlet temperature (Tq = 600, 640, 660 K, with constant jacket temperature. Note the hot spot effect in the reactor temperature profile. 

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