Exothermic oxidation reactions

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. 

The exothermic oxidation reaction is carried out ia the gas phase at temperatures of 1200°C or higher. Relevant thermodynamic data are given ia Table 11. ... 

Table 11. Energy Changes in the Exothermic Oxidation Reaction ...

The most recent major expln in a US TNT plant occurred in May 1974 at the Radford Army Ammunition Plant. The accident completely destroyed one of the three continuous nitration lines at the plant. According to the AMC News, Sept 1974, the investigation board reported that an operator inadvertently introduced a 5 to 6-foot rubber hose to clean out unwanted material that had collected in a transfer line leading to the nitrator, when the hose was pulled from his hands into the nitrator. This resulted in a rapid temp rise and subsequent explosion. The hose was commonly used in this manner . The material causing the blockage in the transfer line was believed to be an oxidation product of TNT, 2,2 -dicarboxy-3,3, 5,5,-tetra-nitroazoxybenzene, also referred to as White Compound. The introduction of the rubber hose caused a rapid, exothermic oxidation reaction between the hose material and the mixed acid present. The heat generated by this reaction caused a local acceleration of the normal nitration/oxidation reactions which occur in the nitrator until a critical temp was reached, at which point rapid oxidation of DNT/TNT proceeded as a runaway reaction, igniting the material present in the vessel. 

Figure 20, a magnitude schematic view of zone 1 in Fig. 19, depicts this effect. These exothermic oxidative reactions in zone 1 can release sufficient heat to expel partially combusted products, pyrolysis products, and fuel and oxidizer fragments into the gas phase, where they can intermix and burn completely. The maximum flame temperature will then be reached in the luminous zone, where the largest portion of the heat is released. However, a relatively... 

The reverse flow reactor (RFR) concept was originally patented by Cottrell in 1938 [64] in the United States and further developed and appHed to different purposes by several researchers, for example, Matros and coworkers [65]. This technology has found its application also in the field of catalytic oxidation [66]. The incinerator containing two sets of regenerative-type heat exchangers and at least two catalyst honeycombs uses flow reversal to recover the heat produced in exothermal oxidation reactions [67]. A regenerative heat exchanger can typically achieve a heat... 

Input energy requirements for the process are significantly reduced since the energy released by the exothermic oxidation reactions serves as a driving force for the endothermic dehydrogenation reaction. 

Thermal integration is an important aspect of the system. Figure 3a depicts a fuel cell coupled to a catalytic POX reformer. This reformer thermally matches very well with the 800°C SOFC technologies being developed. However, both the reformer and fuel cell involve exothermic oxidation reactions, and heat is in... 

For heat pumps based on the exothermic oxidation reactions taking place in mine-waste tips, the longevity of the operation will be limited by the mass of reactant (sulphide or organic caibon/coal) within the waste. However, if the principles above are applied and the reaction rates within the waste deduced, the longevity of the exothermic reactants can be estimated (see, e.g., Stroinberg Banwart 1994, 1999). In practice, however, many mine-waste tips are... 

Combustion Any type of exothermic oxidation reaction, including, but not limited to, burning, deflagration, and detonation. 

In addition to mass integration, the reforming process, Eqs. (1) and (2), which overall is endothermic, is energetically coupled to the exothermic oxidation reactions, Eqs. (3) and (4). Thus, the heat required for the generation of hydrogen is provided. 

This can be thought of as an exothermic oxidation reaction combined with an endothermic steam-reforming reaction. 

The ratio of steam to oxygen (air) in the gasifier controls the peak temperature in the combustion zone. If a nonslagging operation is desired, sufficient steam is added to offset exothermic oxidation reactions with endothermic steam-carbon reactions to stay safely below the ash-fusion temperature. Slagging gasifiers operate at a higher temperature, and ash is removed in a molten state and then quenched in a water bath. 

Fire, combustion, deflagration, and detonation are all terms used to describe exothermic oxidation reactions. They are distinguishable from each other by their reaction velocities. 

The occurrence of consecutive reactions, leading to combustion, which lower the selectivity to MA when the alkane conversion, is increased. At n-butane conversions, up to 60-70%, the extent of the consecutive reaction to give combustion products is not substantial, but the decrease in selectivity becomes dramatic when the conversion exceeds 70-80%. This observation has been attributed to the development of local catalyst overheating associated with the highly exothermic oxidation reactions and to the poor heat-transfer properties of the catalytic material. This problem is obviously more important in fixed-bed rather than mixed (fluidized) reactors, in which the heat transfer is faster. 

A prerequisite of the ignition of a polymeric material is that the rate of heat accumulation due to the exothermal oxidation reaction (heat generation) is higher than the rate of heat dissipation to the environment (heat removal). 

Theoretical research into the problem of combustion propagation on the surface of condensed fuels involving heterogeneous oxidation has been reported It has been found that the combustion velocity depends on thermal effects, kinetic parameters of the exothermic oxidation reaction on the surface, and on the rate of... 

The use of a membrane reactor for shifting equilibrium controlled dehydrogenation reactions results in increased conversion, lower reaction temperatures and fewer byproducts. Results will be presented on a palladium membrane reactor system for dehydrogenation of 1-butene to butadiene, with oxidation of permeating hydrogen to water on the permeation side. The heat released by the exothermic oxidation reaction is utilized for the endothermic dehydrogenation reaction. 

Because the PPR is operated as an adiabatic reactor, the strongly exothermic oxidation reaction (iii) causes a temperature wave traveling through the bed, giving rise to a peak outlet temperature in the initial period of the acceptance cycle, as. shown in Fig. 26. In this figure, the temperature profile predicted by a mathematical model developed at the Shell laboratory in Amsterdam is compared with the profile measured in an industrial reactor to be described later. During the initial oxidation period, the copper is not yet active for reaction with sulfur oxides, so there is a slip of sulfur in the initial period, as can be seen in Fig. 27. It can be inferred that the sulfur dioxide concentration profile of the effluent of the industrial reactor is in close agreement with the profile predicted on the basis of a kinetic model developed at the Shell laboratory in Amsterdam. 

Bollyn, M. van den Bergh, A. Wright, A., Accelerated Scale-up. Reaction Calorimetry and Reactor Simulation—Combined Techniques Accelerate Scale-Up of a Highly Exothermic Oxidation Reaction. Chemical Plants and Processing 1996, 1,3. 

Periodic flow reversal inducing forced unsteady-state conditions [339]. The flow to the reactor is continuously reversed before the steady state is attained. A dual hot-spot temperature profile, characterized by a considerably lower temperature than in the single hot spot that would develop in the traditional flow configuration, forms in exothermic oxidation reactions. An increase in selectivity and better reactor control (lower risk of runaway) is possible over fixed-bed reactor operations, but compared... 

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