Spontaneous combustion propensity refers to the high oxidation activity of coal at room temperature, which is an intrinsic characteristic of coal.
It depends on the substance and conditions of coal formation and represents the ability of coal to interact with oxygen.
Intact coal can only be oxidized on its surface, which generates less heat and is not easy to accumulate, so it will not spontaneously ignite.
On the contrary, when coal is compressed, the molecular structure of coal changes and oxygen free radicals increase.
In addition, the greater the degree of coal fragmentation, the greater the oxidation surface area, the easier it is to spontaneous combustion.
To sum up, the premise of coal spontaneous combustion is that the coal with spontaneous combustion tendency is in a broken state.
Spontaneous combustion is a complex chain free radical oxidation reaction.
Therefore, only continuous oxygen supply can make the spontaneous combustion process continue downward.
When the conditions are suitable, the heat generated in the process of coal oxidation accumulates continuously, and the temperature of coal increases continuously, so that the reaction continues and accelerates.
That is, the heat generated by oxidation is greater than the heat lost, until the heat accumulation of broken coal reaches its ignition point, spontaneous combustion can occur.