Аннотация
The current paper presents experimental investigations as well as
numerical simulations on the influence of water and humidity on the
self-ignition of combustible bulk materials. It is well known, that
bulk materials may undergo self-ignition if stored under specific
conditions. In some cases, large amounts of these materials are exposed
to a humid surrounding, e.g. dried coal in a moist atmosphere. Due
to the effects of condensation and adsorption of water, additional
heat is generated and transported into the bulk material. If the
pile is stored slightly below its self-ignition temperature, the
bulk material can become supercritical and an ignition occurs. Experiments
were carried out for German lignite coal sampled in two different
particle size fractions. They showed, that subcritical deposits turned
to supercritical behaviour if the relative humidity in the surrounding
was suddenly increased or water was poured on the surface of the
sample. Besides the experiments, a numerical model was established
to describe the effects of self-heating until ignition of the deposit,
including the transportation of moisture. Simulations with this model
led to satisfying results when compared to the experiments.
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