Liquid reactor material

A process is described [224] in which an exothermic reaction takes place in a semi-batch reactor at elevated temperatures and under pressure. The solid and liquid raw materials are both toxic and flammable. Spontaneous ignition is possible when the reaction mass is exposed to air. Therefore, the system must be totally enclosed and confined in order to contain safely any emissions arising from the loss of reactor control, and to prevent secondary combustion reactions upon discharge of the materials to the atmosphere. Further, procedures and equipment are necessary for the safe collection and disposal of solid, liquid, and gaseous emission products. 

Regarding this new edition first of all I should say that in spirit it follows the earlier ones, and I try to keep things simple. In fact, I have removed material from here and there that I felt more properly belonged in advanced books. But I have added a number of new topics—biochemical systems, reactors with fluidized solids, gas/liquid reactors, and more on nonideal flow. The reason for this is my feeling that students should at least be introduced to these subjects so that they will have an idea of how to approach problems in these important areas. 

In general, for a trickle-bed reactor, a material balance is required for each of the components present, taken over each of the gas and liquid phases. In the example, however, pure hydrogen will be used and the volatility of the other components will be assumed to be sufficiently low that they do not enter the vapour phase. This means that the material balance on the gas phase can be omitted. It also means that there will be no gas-fllm resistance to gas-liquid mass transfer. In the liquid phase, material balances are required for (i) the hydrogen (reactant A), and (ii) the thiophene (reactant B). The amounts of each of the reactants consumed will be linked by the stoichiometric equation ... 

J.H. Park and G. Dragel, Development of Aluminide Coatings on Vanadium-Base Alloys in Liquid Lithium, Eusion Reactor Materials Semiannual Progress Report for the Period Ending, DOE/ER-0313/13, 1993, pp.405-410. 

Figure 116. Ammonia production based on heavy fuel oil (l.inde flow scheme with Texaco gasification) a) Air separation unit h) Soot extraction c) C02 absorption d) Methanol/H,() distillation e) Stripper f) Mol regenerator g) Refrigerant h) Dryer i) liquid N2 scrubber j) Syngas compressor k) Nil, reactor Material Balance...

Figure E5.8 is a hypothetical process used for demonstration by Diamond Shamrock Co. of their flowsheeting code PROVES. Makeup gas is compressed, combined with recycle gas, and fed, together with liquid raw material, into a three-phase, suspended bed catalytic reactor. The reactor is cooled by recirculating liquid through a heat reclamation steam generator. Reaction products are condensed and the pressure of the exit stream reduced in two stages. The gas from the first-stage separator is recirculated, whereas the liquid from the second-stage separator is fed into a distillation column. Pure product is withdrawn from the bottom of the column. The distillate is a by-product that is pumped to another plant.

Chang and Rochelle (16) measured SO2 absorption at 25°C in a continuous stirred reactor with an unbroken gas/liquid interface. They varied Ps02 pH> and concentrations of acetic acid and adipic acid in 0.3 M NaCl. Because SO2 absorption was quantified by liquid-phase material balance, there were no experiments with greater than 1 mM total dissolved sulfite. 

The discussion in this paper appties to wide classes of phase transformations that occur by a nucleation and growth mechanism. Examples of such transformations indude many common transformations, such as boiling and freezing of a liquid and condensation of a vapor, as well as some much less well known transformations, such as oxidation of a metal surface and formation of voids in nudear reactor materials. There are some types of phase transformations, such as spinoidal decomposition, that occur as soon as they are thermodynamically allowed and do not require nudeation. 

Spray towers/column Usually treated as a gas-liquid reactor. Liquid is sprayed counter currently to gas flow. Used for corrosive and liquids containing substantial amount of solid materials. Higher energy usage and capital investment... 

Gas absorption and any associated chemical reaction is always accompanied by the simultaneous release of heat of solution and heat of reaction. The micro-scale phenomena taking place close to the interface therefore involve the generation and diffusion of heat as well as the diffusion and reaction of material species. In developing a fundamental appreciation of simultaneous mass and heat transfer in gas-liquid reactions it is important for the heat effects to be incorporated into the analysis of diffusion and reaction because the rates and pathways of chemical reactions are usually enormously sensitive to temperature. In particular, for the case of gas-liquid reactor performance, if the heat effects are such that the mass transfer with reaction zone adjacent to the interface is at a temperature significantly different from the bulk, the yield and the selectivity performance will be erroneously interpreted if reaction is assumed to take place at the bulk liquid temperature. In consequence, the basic conceptual design of a commercial gas-liquid reactor could incorporate fallacious reasoning leading to inefficient operation at sub-optimal yield. 

There are probably more c s-liquid reactors operating worldwide in the chemical industry than reactors of any other type. Since chemical transformations are the very backbone of chemical manufacture, it follows that gas-liquid reactors merit continued attention and research in the effort to improve product quality and raw material utilisation. 

However the general performance characteristics of a backmixed gas-liquid reactor element, determined without a priori assumptions, and governed by the coupling of the diffusion reaction equations to the gas and liquid phase material balances, has not been reported in the literature. VHiilst the treatment is simplified by the analytical expressions of the type in Eqn (80), it would appear that the complexity of the trial and error solutions for the interface concentrations and... 

The general performance features of the backmixed gas-liquid reactor element requires the incorporation of the above expressions into the usual gas and liquid material balance relationships and this remains to be undertaken. Also, the elucidation of optimal gas-liquid element configurations as envisaged in Fig. 6, so that gas-liquid reactor designs can give good yield performance, appears to require considerable further effort. 

Following on the work of Teramoto, Hoffman, Sharma and Luss (28) have performed an analysis of the adiabatic gas-liquid reactor operating in continuous backmixed flow of the liquid phase for this consecutive (1,1) - (1,1) reaction. They used data relative to the system chlorine/n-decane with a selectivity ratio of k /kp = 1. 1 The boundary conditions were formulated in terms of overall material balances on the gas and liquid phases, so that for component A, the boundary condition at the film-bulk junction is given by... 

Table HI lists the neutron absoiption cross sections for many of the metals described above, as well as their cross section relative to the typical reactor material, zirconium. Materials with a very large cross section relative to zirconium would result in a reduction in the thermal utilization factor f and hence a reduction in Nff. Consequently, Ta, W, V, Mo and Ni based alloys would be impractical choices for a reactor core. From this literature survey, it appears that Fecralloy would provide the greatest promise as a containment material for liquid lead. In addition Tantiron may be an alternate choice. More extensive studies on the applicability of inhibitors such as Ti should be undertaken to determine their affect on the corrosion resistance of these materials. 

Weeks, J. R. and Klamut, C. J., "Liquid Metal Corrosion Mechanisms, Corrosion of Reactor Materials, Vol. I, International Atomic Energy Agency, pp. 106-132. 

J.K. Fink, J.J. Heilberger, R. Kumar, and R.A. Blomquist. 1977. Interaction of refractories and reactor materials with sodium. Nuclear Technol., 35 656-662. W.R. Kanne. 1973. Corrosion of metals by liquid bismuth-tellurium solutions. 

The equilibrium conversion can be increased by employing one reactant in excess (or removing the water formed, or both). b. Inerts concentration. Sometimes, an inert material is present in the reactor. This might be a solvent in a liquid-phase reaction or an inert gas in a gas-phase reaction. Consider the reaction system... 

The liquid used for the direct heat transfer should be chosen such that it can be separated easily from the reactor product and so recycled with the minimum expense. Use of extraneous materials, i.e., materials that do not already exist in the process, should be avoided because it is often difficult to separate and recycle them with high efficiency. Extraneous material not recycled becomes an effluent problem. As we shall discuss later, the best way to deal with effluent problems is not to create them in the first place. 

The use of an unnecessarily hot utility or heating medium should be avoided. This may have been a major factor that led to the runaway reaction at Seveso in Italy in 1976, which released toxic material over a wide area. The reactor was liquid phase and operated in a stirred tank (Fig. 9.3). It was left containing an uncompleted batch at around 160 C, well below the temperature at which a runaway reaction could start. The temperature required for a runaway reaction was around 230 C. ... 

In early designs, the reaction heat typically was removed by cooling water. Crude dichloroethane was withdrawn from the reactor as a liquid, acid-washed to remove ferric chloride, then neutralized with dilute caustic, and purified by distillation. The material used for separation of the ferric chloride can be recycled up to a point, but a purge must be done. This creates waste streams contaminated with chlorinated hydrocarbons which must be treated prior to disposal. 

The reactor effluent might require cooling by direct heat transfer because the reaction needs to be stopped quickly, or a conventional exchanger would foul, or the reactor products are too hot or corrosive to pass to a conventional heat exchanger. The reactor product is mixed with a liquid that can be recycled, cooled product, or an inert material such as water. The liquid vaporizes partially or totally and cools the reactor effluent. Here, the reactor Teed is a cold stream, and the vapor and any liquid from the quench are hot streams. 

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