采用NO₂-N₂O₄体系脱除粒度为~6 mm煤中的硫。实验结果表明，液固比增大和延长氧化时间有利于脱硫、脱灰，但是脱硫后的煤粒度减小，质量和挥发分增加，粘结性丧失。进一步推测了NO₂-N₂O₄体系的脱硫机理。NO₂-N₂O₄体系氧化不具有选择性，存在副反应。

A NO₂-N₂O₄ system is employed to remove sulfur in clean coal with a particle size of about 6 mm.First,a certain weight of coal has reacted with a certain volume of NO₂-N₂O₄ system for several minutes,then NO₂ escapes from coal in several hours and finally the oxidized coal is washed by water,and sampled.The test results show that both the increasing liquid-solid ratio and prolonging oxidation time are favorable for removal of sulfur and ash,but the particle size of desulfurized coal reduces but the weight and volatile matter increase,and coal loses its caking property.The desulfurization mechanism is surmised as that N₂O₄ diffuses into coal pores more easily and oxidizes coal.Some of N₂O₄ decompose thermally into NO₂,which escapes from coal with oxidation products.However,the oxidation by NO₂-N₂O₄ system is not selective.