Abstract: In order to prevent the safety accident occurrence in the thermal drying process of municipal sludge, the burning and explosion properties of sludge in the state of accumulation and dispersion were analyzed by using relevant instruments. And combined with the technique and equipment of the sludge heat drying workshop, the safety risks in the thermal drying process of the sludge are researched systematically. The results showed that no self-heating occurs when sludge was stored at 140 ℃ for 24 hours, but when the temperature increased to 170 ℃ sludge releases heat, and spontaneous combustion occurs between 200 ℃and 220 ℃. Which means that when the internal temperature of the layer drying process system is greater than 170 ℃, the possibility of sludge exotherm and spontaneous combustion is high, while the safety risk of storing dry sludge at room temperature is low. When the sludge dust and air form a mixture dust, explosion will occur, and the explosion pressure will increase as the sludge particle size becomes smaller, which indicates that there is a danger of sludge dust explosion inside the sludge dust collector. When the sludge is dried, ammonia gas, hydrogen sulfide and methane will be produced, so that there is a danger of gas combustion or explosion in the closed drying system. These results can provide safe technical support for the design of intrinsically safe sludge drying equipment and the development of sludge drying technology. At the same time, it has guiding significance and reference value for the safety of municipal sludge drying.

Key words: safe production, sludge, thermal drying, dust explosion