Reactive gaseous mixtures, combustion

Compared to pure oxygen, chlorine is even more reactive. The self-ignition temperature of gaseous mixtures of organic vapours with chlorine is much lower than that of their mixtures with oxygen. Natural light can split the chlorine molecule to produce reactive chlorine radicals. Many reactions of chlorine take place near the ambient temperature. The combustion of iron in chlorine can be initiated at temperatures slighly above 100°C. 

Far from being difficult to explain, the appearance of a shock is hard to prevent in view of the chemically reactive nature of the medium in which the wave is advancing. Heat released in the combustion makes the gaseous products expand,and they push against the unburned mixture ahead of the wave front. Thus they set up a pressure wave of velocity (pr), called a precompression or "precursor wave, which has been observed in schlieren photographs and streak camera records. The flame now advances into a mixture, still unburnt but "processed by precompression and heating which increases the reactivity, in a third region between the other two ... 

Cooling air is preheated by lime in the cooling zone and is withdrawn, dedusted and re-injected via the combustion chambers. A feature of the kiln is that the temperature of the lower combustion chambers can be varied to control the reactivity of the lime over a wide range. The kiln can be fired with solid, liquid and gaseous fuels (or a mixture) and the net heat usage is about 1000 kcal/kg. It can accept stone with a minimum size of 20 mm up to a maximum size of 150 mm. Further details are available in references [16.19-16.23]. 

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