Reactor-Heat Exchanger Assembly

Figure 17.19. Reactors for the oxidation of sulfur dioxide (a) Feed-product heat exchange, (b) External heat exchanger and internal tube and thimble, (c) Multibed reactor, cooling with charge gas in a spiral jacket, (d) Tube and thimble for feed against product and for heat transfer medium, (e) BASF-Knietsch, with autothermal packed tubes and external exchanger, (f) Sper reactor with internal heat transfer surface, (g) Zieren-Chemiebau reactor assembly and the temperature profile (Winnacker- Weingartner, Chemische Technologie, Carl Hanser Verlag, Munich, 1950-1954).

One of the problems in commercial plant design for direct oxidation of ethylene to ethylene oxide is the removal of reaction heat at reaction temperature. A form of reactor similar to that used for phthalic anhydride manufacture is characteristic, with catalyst enclosed in long narrow tubes, many of which are mounted together with suitable headers to form a reactor assembly. Heat is removed and the temperature controlled by means of a suitable fluid, such as oil, circulating around the outside of the catalyst tubes and then to an outside heat exchanger for removal of heat. 

Six-control rod subassemblies made of 90% enriched B4C were used in JOYO MK-II and were located symmetrically in the third row. In 1994, one control rod was moved to the fifth row to provide a position for irradiation test assemblies with on-line instrumentation. Since then, the control rod subassemblies have been loaded asymmetrically. The JOYO cooling system has two primary sodium loops, two secondary loops and an auxiliary cooling system. The cooling system uses approximately 200 tons of sodium. In the MK-II core, sodium enters the core at 370°C at a flow rate of 1 100 tons/h/loop and exits the reactor vessel at 500°C. The maximum outlet temperature of a fuel subassembly is about 570 C. An intermediate heat exchanger (IHX) separates radioactive sodium in the primary system from non-radioactive... 

The post analysis results from a plant wide dynamics code MIMIR-N2 are in excellent agreement with the experimental data as shown in Fig. 12. Various key parameters are clarified to improve the calculation accuracy through the study. In the short-term analysis, the evaluation of thermo-hydraulic behavior in the core is largely affected by the inter-assembly heat transfer effect, the pump flow coast characteristics and coolant flow distribution. For the long-term analysis, it is important to assess precisely the buoyant head effect in the IHX, the heat exchange effects in the lower plenum of the IHX and others. The experimental result is also applied to the assessment of natural convection characteristics in the MONJU reactor. 

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