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When the fuel coal is fed into the furnace through the coal feeding hopper, it reacts chemically with the gasifying agents (air and water vapor) blown into the furnace from below. This results in the formation of five layers along the height of the material layer, from bottom to top: the ash layer, the oxidation layer, the reduction layer, the dry burning layer, and the drying layer. The injected gasifying agent first passes through the slag layer, where it is preheated. As it rises into the high-temperature fuel layer, the following reactions occur between carbon and oxygen: 2C + O = 2CO + Q, 2CO + O2 = 2CO2 + O, C + O = CO2 + Q. All of these reactions are exothermic, resulting in very high temperatures; this layer is known as the oxygen layer. The hot gas generated in the oxygen layer continues to rise, coming into contact with the fuel in the upper layers, thereby triggering a reduction reaction. The reactions in the main reduction layer are mainly: CO2 + C = 2CO – Q, C + H2O = CO2 + 2H2 – Q, and C + H2O = CO + H2 – Q. In the secondary reduction layer, carbon monoxide and excess water vapor react to form CO2 and H2: CO + H2O = CO2 + H2 + Q. Additionally, a side reaction that produces methane occurs as well: C + 2H2 = CH4 + Q. The hot gases generated in the reduction layer rise further upward, heating the coal layers above, thereby creating a dry distillation and drying zone. The volatile organic compounds resulting from carbonization are evaporated due to the physical heat generated by the rising hot gases. The moisture in the drying layer is also dried using this heat; after that, it is processed by a dust remover and made available for use in the working furnace.