Reactor jackets, pilot plant reactors

In specifying the number of jacket zones and the aspect ratio for a full-scale reactor, there is a limitation on the temperature adjustment time. This implies that it must be of the same duration as experienced in the pilot plant reactor. Combining Equations 13-89 and 13-97 yields... 

Sulfur dioxide is oxidized to sulfur trioxide in a small pilot-plant reactor. SO2 and 100% excess air are fed to the reactor at 450 C. The reaction proceeds to a 65% SO conversion, and the products emerge from the reactor at 550°C The production rate of SO3 is 1.00 x 10 kg/min. The reactor is surrounded by a water jacket into which water at 25 C is fed. 

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. 

Assuming the same aspect ratio (L/D = 2), the diameter is 10 times larger (2.29 m), which gives a heat transfer area that is only 100 times larger (32.95 m2). If the overall heat transfer coefficient is the same as in the pilot plant (we will come back to this issue in Chapter 2), the required temperature differential between the reactor and jacket increases by a factor of 10 (jacket temperature is 304 K instead of 330 K). The flowrate of makeup cooling water (19.54 kg/s) increases by a factor of 4000. 

The jacket of a pilot plant batch reactor is divided into three zones. Using the data in Example 13-2, determine the outlet temperature, the heat removed, and the cooling time for both pilot and full-scale batch reactors. 

For the safety reason, new pilot plants are often equipped with inert cooling/heating fluids in reactor jackets and condensers. Aromatic compounds and mixtures thereof and silicones are widely used as heat exchange fluids. The range of operating temperatures desired generally dictates the choice of heat exchange fluid. Aromatic heat... 

FROM PILOT PLANT TO MANUFACTURING EFFECT OF SCALE-UP ON OPERATION OF JACKETED REACTORS... 

Temperature control for laboratory reactors is typically easy because of high heat transfer area-reactor volume ratios, which do not require large driving forces (temperature differences) for heat transfer from the reactor to the jacket. Pilot- and full-scale reactors, however, often have a limited heat transfer capability. A process development engineer will usually have a choice of reactors when moving from the laboratory to the pilot plant. Kinetic and heat of reaction parameters obtained from the laboratory reactor, in conjunction with information on the heat transfer characteristics of each pilot plant vessel, can be used to select the proper pilot plant reactor. 

Similarly, when moving from the pilot plant to manufacturing, a process engineer will either choose an existing vessel or specify the design criteria for a new reactor. A necessary condition for operation with a specified reactor temperature profile is that the required jacket temperature is feasible. We have therefore chosen to focus on heat transfer-related issues in scale-up. Clearly there are other scale-up issues, such as mixing sensitive reactions. See Paul [1] for several examples of mixing scale-up in the pharmaceutical industry. 

Based on initial heat flow calorimetry studies, a process development engineer must choose the appropriate reactor vessels for pilot plant studies. A pilot plant typically has vessels that range from 80 to 5000 L, some constructed of alloy and others that are glass lined. In addition some vessels may have half-pipe coils for heat transfer, while others have jackets with agitation nozzles. A process drawing for a typical glass-lined vessel is shown in Figure 4. In Sections 3.1.4.1 and 3.1.4.2 we review fundamental heat transfer relationships in order to predict overall heat transfer coefficients. In Section 3.1.4.3 we review experimental techniques to estimate heat transfer coefficients in process vessels. 

FIGURE 8 Temperature profiles (jacket inlet, jacket outlet, and reactor) for a pilot plant reactor. (From ref. 19.)... 

B. Wayne Bequette, Rensselaer Polytechnic Institute, Troy, New York, From Pilot Plant to Manufacturing Effect of Scale-Up on Operation of Jacketed Reactors... 

The laboratory introduced synthesis gas into the pilot plant in early December 1947. Operations were relatively trouble-free, and the unit was shut down voluntarily on February 11,1948, in order to replace the upper reactor section and its two coolers with two sections of 4-inch pipe, jacketed with a cooling oil. Inspection of the reactor sections removed revealed that they were in excellent condition. All cooler tubes were clear and there was practically no catalyst accumulated on the reactor walls. The only case of accumulation worthy of mention was several small nodules of very hard catalyst which appeared in the venturi-shaped section at the bottom of the upper 4-inch section of the reactor. Slight evidence of corrosion was... 

A condensed version of the ERDL alkylation pilot plant flow plan is shown in Figure 4. Olefin and isobutane feed streams are separately pumped to the unit from large feed storage vessels with Lapp Pulsafeeder diaphragm pumps and metered with turbine flow meters. The streams are then combined, caustic scrubbed, water washed and dried with molecular sieves before being sent to the reactor. The combined feed stream is then injected into the acid-hydrocarbon emulsion in the stirred reactor vessel. In order to maintain a constant temperature environment both reactor and settler are coolant jacketed. 

A phenolic resin was being produced in a 5.9 m reactor by the reaction between phenol and formaldehyde using a sodium hydroxide catalyst. The vessel was fitted with a stirrer, a temperature probe, a steam heating/water cooling Jacket and cooling coils. The resin was being formulated in this reactor for the first time after pilot plant laboratory trials in a 2.27 m reactor. 

Hence, this paper focuses on the slave-loop control and presents a detailed case study where the impact of the slave-loop is illustrated by the temperature control of a pilot plant presented in Section 2. The tendency model of the jacket of the reactor is given in Section 3, while in Section 4 this model is utilized in a model-based control algorithm. Based on the real-time control results presented also in this section, some conclusions will be drawn in Section 5. 

The conversion of 2 to 3 was optimized at full scale in the VRT reactor. In addition to confirming the productivity, safety, product quality, and economic benefit of the process, the robustness of the process was also demonstrated. Finally, this pilot study provided the basis for a full-scale commercial manufacturing design specification. Having fixed the optimum residence time, the process was then transferred into a plant Fixed Residence Time (FRT) cyanation reactor which employed a fixed length of jacketed static mixer for commercial manufacture. This FRT was capable of producing 300 metric tonnes per year of 3, with the same purified step yield of 80% that was achieved in the laboratory capillary reactor. 

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