Heat reactor-design

Reactor design will be Improved, but only on the base of existed Heating Reactor design, in order to minimize R D work. (The Heating Reactor Sections, Systems and parameters are shown in Fig. 1-3 and Tab. 1.)... 

In this variant boiling is introduced in the 200MW demonstration Heating Reactor design... 

This variant is more close to the existed Heating Reactor design. Changes are very small. Radioactive water leakage is almost impossible and power productivity is enough high. 

In above variants, the first one imder the same pressine (=2.5MPa) as for the existed Heating Reactor design, tlie reactor can supply some quantity power, but the quantity is small and po er efficiency is low (see... 

Figure 1.5 A different reactor design leads not only to a different separation system but also to additional possibilities for heat integration. (From Smith and Linnhoff, Trans. IChemE, ChERD, 66 195, 1988 reproduced by permission of the Institution of Chemical Engineers.)...

The use of excess reactants, diluents, or heat carriers in the reactor design has a significant effect on the flowsheet recycle structure. Sometimes the recycling of unwanted byproduct to the reactor can inhibit its formation at the source. If this can be achieved, it improves the overall use of raw materials and eliminates effluent disposal problems. Of course, the recycling does in itself reuse some of the other costs. The general tradeoffs are discussed in Chap. 8. 

The problem with the fiowsheet shown in Fig. 10.5 is that the ferric chloride catalyst is carried from the reactor with the product. This is separated by washing. If a reactor design can be found that prevents the ferric chloride leaving the reactor, the effluent problems created by the washing and neutralization are avoided. Because the ferric chloride is nonvolatile, one way to do this would be to allow the heat of reaction to raise the reaction mixture to the boiling point and remove the product as a vapor, leaving the ferric chloride in the reactor. Unfortunately, if the reaction mixture is allowed to boil, there are two problems ... 

Indirect heat transfer with the reactor. Although indirect heat transfer with the reactor tends to bring about the most complex reactor design options, it is often preferable to the use of a heat carrier. A heat carrier creates complications elsewhere in the flowsheet. A number of options for indirect heat transfer were discussed earlier in Chap. 2. 

Evolving Reactor Design to Improve Heat Integration... 

Some reactors are designed specifically to withstand an explosion (14). The multitube fixed-bed reactors typically have ca 2.5-cm inside-diameter tubes, and heat from the highly exothermic oxidation reaction is removed by a circulating molten salt. This salt is a eutectic mixture of sodium and potassium nitrate and nitrite. Care must be taken in reactor design and operation because fires can result if the salt comes in contact with organic materials at the reactor operating temperature (15). Reactors containing over 20,000 tubes with a 45,000-ton annual production capacity have been constmcted. 

Most maleic anhydride production in the United States is based on benzene as feedstock, even though substantial Hterature exists on the use of butenes (132—134). However, the rapidly increasing demand and price for benzene (as high as 620 /t in 1986 versus 310 /t for ethylene) have made benzene (qv) less attractive and butenes a better feedstock. Not only are theoretical yields better, 1.75 kg/kg of butenes compared to 1.26 kg/kg of ben2ene, but less oxygen is required and the oxidation produces less heat, which is critical in reactor design. 

An equimolar mixture of carbon monoxide and chlorine reacts at 500 K under a slight positive pressure. The reaction is extremely exothermic (Ai/gQQp. = —109.7 kJ or —26.22 kcal), and heat removal is the limiting factor in reactor design. Phosgene (qv) is often produced on-site for use in the manufacture of toluene diisocyanate (see Amines, aromatic-diaminotoluenes Isocyanates, organic). 

The U.S. Department of Energy has funded a research program to develop the Hquid-phase methanol process (LPMEOH) (33). This process utilizes a catalyst such as copper—zinc oxide suspended in a hydrocarbon oil. The Hquid phase is used as a heat-transfer medium and allows the reaction to be conducted at higher conversions than conventional reactor designs. In addition, the use of the LPMEOH process allows the use of a coal-derived, CO-rich synthesis gas. Typical reactor conditions for this process are 3.5—6.3 MPa (35—60 atm) and 473—563 K (see Methanol). 

A number of factors limit the accuracy with which parameters for the design of commercial equipment can be determined. The parameters may depend on transport properties for heat and mass transfer that have been determined under nonreacting conditions. Inevitably, subtle differences exist between large and small scale. Experimental uncertainty is also a factor, so that under good conditions with modern equipment kinetic parameters can never be determined more precisely than 5 to 10 percent (Hofmann, in de Lasa, Chemical Reactor Design and Technology, Martinus Nijhoff, 1986, p. 72). 

Two complementai y reviews of this subject are by Shah et al. AIChE Journal, 28, 353-379 [1982]) and Deckwer (in de Lasa, ed.. Chemical Reactor Design andTechnology, Martinus Nijhoff, 1985, pp. 411-461). Useful comments are made by Doraiswamy and Sharma (Heterogeneous Reactions, Wiley, 1984). Charpentier (in Gianetto and Silveston, eds.. Multiphase Chemical Reactors, Hemisphere, 1986, pp. 104—151) emphasizes parameters of trickle bed and stirred tank reactors. Recommendations based on the literature are made for several design parameters namely, bubble diameter and velocity of rise, gas holdup, interfacial area, mass-transfer coefficients k a and /cl but not /cg, axial liquid-phase dispersion coefficient, and heat-transfer coefficient to the wall. The effect of vessel diameter on these parameters is insignificant when D > 0.15 m (0.49 ft), except for the dispersion coefficient. Application of these correlations is to (1) chlorination of toluene in the presence of FeCl,3 catalyst, (2) absorption of SO9 in aqueous potassium carbonate with arsenite catalyst, and (3) reaction of butene with sulfuric acid to butanol. 

It follows that the position of thermodynamic equilibrium will change along the reactor for those reactions in which a change of tire number of gaseous molecules occurs, and therefore that the degree of completion and heat production or absorption of the reaction will also vaty. This is why the external control of the independent container temperature and the particle size of the catalyst are important factors in reactor design. 

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