So it takes a lot of effovt for preventing coal spontaneous combustion in per year in coal mine methods are grout nitrogen flooding and even pressure fire-extinguished to prevent coal spontaneous combustion.

• 为此,煤矿每年都要花很大气力防止煤炭自燃,采取了灌浆、氮、压灭火等阻止煤炭自燃的措施。