Hydrogen oxygen explosion

A certain amount of water is always formed when oxide or hydroxide catalysts are used. If additional catalyst has to be added or the previous batch regenerated by oxygen, the hydrogen in the vessel must, of course, be previously removed by evacuation and before hydrogen is readmitted the vessel must be re-evacuated to avoid a hydrogen-oxygen explosion. 

You may get the idea that all chemical reactions go to completion when you watch a hydrogen-oxygen explosion or watch a piece of wood burn in the fireplace. Chemicals do not always react to form products with the complete conversion of reactants, however. Whenever the point is reached at which the forward reaction is proceeding at the same rate as the reverse reaction, equilibrium is established and the amounts of reactants and products remain unchanged. But because equilibrium is a dynamic condition, the forward and reverse reactions are still happening so that each reactant or product is replaced as soon as it is consumed. 

Later, much more detailed predictions of safe operation in micro reactors in the explosive regime with the example of the hydrogen/oxygen reaction could be given [9,82,117,118], It was predicted that micro-channel processing under given conditions can be considered as intrinsically safe. 

GP 11] [R 19] Based on an analysis of the thermal and kinetic explosion limits, inherent safety is ascribed to hydrogen/oxygen mixtures in the explosive regime when guided through channels of sub-millimeter dimensions under ambient-pressure conditions [9], This was confirmed by experiments in a quartz micro reactor [9],... 

Figure 3.51 Schematic flow scheme of a micro-reactor system used for burning hydrogen and oxygen at large throuputs. A mixer is applied for reducing the volume of the explosive hydrogen/ oxygen mixture in advance to the reaction [115],...

Remember the explosive mixture limits are wide and different from other fuels even very rich hydrogen-air or hydrogen-oxygen mixtures can burn violently. 

Mixtures are potentially highly explosive, approaching the energy of hydrogen-oxygen systems. 

Explosive limits for this combination have been studied from 1 to 20 bar at 50°C. Hydrogen, Oxygen... 

Many of the early contributions to the understanding of hydrogen-oxygen oxidation mechanisms developed from the study of explosion limits. Many extensive treatises were written on the subject of the hydrogen-oxygen reaction and, in particular, much attention was given to the effect of walls on radical destruction (a chain termination step) [2], Such effects are not important in the combustion processes of most interest here however, Appendix C details a complex modem mechanism based on earlier thorough reviews [3,4],... 

Figure 3.2 depicts the explosion limits of a stoichiometric mixture of hydrogen and oxygen. Explosion limits can be found for many different mixture ratios. The point X on Fig. 3.2 marks the conditions (773 K latm) described at the very beginning of this chapter in Fig. 3.1. It now becomes obvious that either increasing or decreasing the pressure at constant temperature can cause an explosion.

Belles prediction of the limits of detonability takes the following course. He deals with the hydrogen-oxygen case. Initially, the chemical kinetic conditions for branched-chain explosion in this system are defined in terms of the temperature, pressure, and mixture composition. The standard shock wave equations are used to express, for a given mixture, the temperature and pressure of the shocked gas before reaction is established (condition 1 ). The shock Mach number (M) is determined from the detonation velocity. These results are then combined with the explosion condition in terms of M and the mixture composition in order to specify the critical shock strengths for explosion. The mixtures are then examined to determine whether they can support the shock strength necessary for explosion. Some cannot, and these define the limit. 

The set of reactions that determine the explosion condition of the hydrogen-oxygen system is essentially... 

This equation suggests that if a given hydrogen-oxygen mixture, which could have a characteristic value of/dependent on the mixture composition, is raised to a temperature and pressure that satisfy the equation, then the mixture will be explosive. 

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