Reactor jacketed

Batch distillation equipment can range from a free-standing column with a reboiler, condenser, receiver, and vacuum system, to the use of a jacketed reactor with a condenser. Distillation often involves the generation of combustible vapors in the process equipment. This necessitates the containment of the vapor within the equipment, and the exclusion of air from the equipment, to prevent the formation of combustible mixtures that could lead to fire or explosion. 

Although fluidized sand or alumina can also be used in the jacket of these somewhat larger reactors, the size makes the jacket design a problem in itself, hence these reactors are seldom used. An advantage of the jacketed reactor is that several—usually four—parallel tubes can be placed in the same jacket. These must be operated at the same temperature, but otherwise all four tubes can have different conditions if needed. This type of arrangement saves time and space in long-lasting catalyst life studies. Jacketed tubular reactors come close, but still cannot reproduce industrial conditions as needed for reliable scale-up. Thermosiphon reactors can be used on all but the most exothermic and fast reactions. 

When batch hydrolysis is being employed a weighed excess amount of water is placed in a glass-lined jacketed reactor. Dichlorodimethylsilane is run in... 

Preparation. On a coml scale the nitration of naphthalene is carried out in two steps using a cylindrical jacketed reactor 1.6 x lm with a conical bottom. It is fitted with a discharge pipe 8cm in diameter and a stirrer which can be rotated at 85—90rpm. The jacket can be heated with steam or cooled with cold w. The cover is provided with an opening for the addn of naphthalene and a vent for the removal of gaseous prods... 

Hexanediol (0.5 mol/L), dimethyl fumarate (0.5 mol/L), toluene and Novozyme (33.3 g/L) are introduced in a thermostatted double-jacketted reactor fitted with a short thermostatted distillation column and a nitrogen inlet. The temperature is set at 60°C and a nitrogen flow (0.2 L/min) is bubbled into reaction medium. Methanol and toluene are collected in a flask and die volume of the solution is held constant by addition of toluene. After reaction (15 days) the catalyst is removed by filtration and the solvent is evaporated under reduced... 

The remaining reactors are of similar design as shown in Fig. 22. These are bottom fed, completely filled vessels. There is a central upward pumping screw surrounded by a draft tube through which coolant circulates. The reactant syrup descends in the annular space between the draft tube and the jacketed reactor wall. In this annular space is a circular rank of manifolded vertical tubes with circulating coolant... 

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. 

Induction heated general purpose plant only Water-jacketted reactor only... 

Figure 3. Example of Graphical Output from Analysis Mode. Reaction progress for water-jacketted reactor, with Cascade coupled temperature controllers, both in self-tuning mode.

Figure 5.4-3. Stirred-tank jacketed reactor. Figure 5.4-4. Typical agitators.

A standard AE (DIN) stirred-tank jacketed reactor is shown in Fig. 7.2-1. It is equipped with several nozzles for loading and discharging the materials, and measuring probes that can also act as baffles, a manhole with sight glass, and a stirrer with driving system. 

This discontinuous process is based on a heat-jacketed reactor equipped with an agitator, an inlet for purging nitrogen and the addition of an oil, and a cooler. A cold trap condenses and separates the oil from the gas for re-use in the reactor. 

In most jacketed reactors or steam-heated reboilers the volume occupied by the steam is quite small compared to the volumetric flow rate of the steam vapor. Therefore the dymamic response of the jacket is usually very fast, and simple algebraic mass and energy balances can often be used. Steam flow rate is set equal to condensate flow rate, which is calculated by iteratively solving the heat-transfer relationship (Q = UA AT) and the valve flow equation for the pressure in the jacket and the condensate flow rate. 

One of the classical problems in scaling-up a jacketed reactor is the decrease in the ratio of heat-transfer area to reactor volume as size is increased. This has a profound effect on the controllability of the system. Table 11.1 gives some results that quantify the effects for reactors varying from 5 gallons (typical pilot-plant size) to 5CKX) gallons. Table 11.2 gives parameter values that are held constant as the reactor is scaled up. 

The process begins in a prepolymerizer, which is a water-jacketed reactor with a mixer in it. See Figure 23—12.) The styrene is partially polymerized by adding the peroxide initiator and heating to 240—250°F for about four hours. About 30% of the styrene polymerizes and the reactor contents become syrupy goo. Thats about as far as the prepolymer step can go—30% conversion— because the mixing and heat transfer gets very inefficient as the goo gets thicker, and the polymerization becomes hard to control. 

If the coolant flow rate is sufficiently high in a jacketed reactor or if boiling liquid is used as the heat transfer fluid, then is constant, as we have assumed implicitly in the previous discussion. 

A major goal in wall cooling is to spread out the hot zone and prevent very high peak temperatures. High peak temperatures cause poor reaction selectivity, cause carbon formation, deactivate catalysts, and cause corrosion problems in the reactor walls. CocuJTent flows spread out the hot zone and cause lower peak temperatures, but many additional design features must be considered in designing jacketed reactors. 

Temperature profiles in jacketed reactors can be examined rather simply by writing the energy balance on the coolant and on the reactor. In analogy with the energy-balance equation in the PFTR... 

The student should recognize these problems with the jacketed reactor as similar to those encountered in analysis of heat exchangers. The only difference in chemical reactors is that now we have considerable heat generation by chemical reaction on one side of the heat exchanger. The equipment used for these reactors in fact looks very similar to heat exchangers, but pressures, temperatures, and catalysts must be chosen very carefully, and materials of constmction are frequently more difficult to deal with in the reactive environment... 

The reactor configuration might look as shown in Figure 6-15 for the jacketed reactor and with an internal cooling cod. ff is not constant, we have to solve an energy balance on the coolant along with the mass and energy balance on the reactor, where now the coolant has inlet temperature T o and outlet temperature and the coolant flows with volumetric flow rate ii(. and has contact area A, with the reactor. 

The jacketed reactor may be assumed to have mixed flow (either by stirring the jacket or by mixing through natural convection) so the jacket also obeys the CSTR equation. Therefore, for the jacketed reactor with a single reaction we write the three equations... 

A typical reaction calorimeter consists of a jacketed reactor, addition device, temperature transducer(s) and calibration heaters. There are a number of devices within Dow ranging from the commercially available Mettler RC-1 (1-2 L volume) to smaller, in-house reactors (10-50 ml). While each of these devices has their unique attributes (e.g., in-situ spectrometry, quick turn-around, ability to reflux, etc.), all of the calorimeters will produce a signal of heat flow vs. time. The heat flow is usually produced in response to the addition of a reagent or an increase in temperature. Volume of gas or pressure generated may also be measured. 

Open-Loop versus Closed-Loop Dynamics It is common in industry to manipulate coolant in a jacketed reactor in order to control conditions in the reactor itself. A simplified schematic diagram of such a reactor control system is shown in Fig. 8-2. Assume that the reactor temperature is adjusted by a controller that increases the coolant flow in proportion to the difference between the desired reactor temperature and the temperature that is measured. The proportionality constant is Kc. If a small change in the temperature of the inlet stream occurs, then... 

The third item is other ways to increase heat transfer area. They include circulating reactor liquid through an external heat exchanger or autorefrigeration. The dynamics of both of these alternatives will be studied in Chapter 3. As earlier mentioned, for a jacketed reactor, the heat transfer area can be increased by using larger aspect ratios. 

For enzyme uptake studies, 0.1 g of substrate (corn flour or carboxym-ethylcellulose) and 24 mL of buffer were added to a 40-mL jacketed reactor. The temperature was maintained at 52 2°C using a water bath. A 1.5-mL "blank" sample was collected from the reaction mixture and added to 3 mL of the dinitrosalicylic acid (DNS) reagent. Then 500 pL of the soluble enzyme was added to the reactor to initiate the reaction. Samples were collected every 3 min, and the DNS assay (4) was performed for all the samples. One unit of enzyme releases 1 pmol of reducing groups/min, the absorbance of which can be measured at 540 nm. Thus, the amount of activity transferred to the support can be determined from the sugar pro-... 

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