Migration And Transformation Of Thiophene Sulfur During High Temperature Pyrolysis Of Medium High Sulfur Coking Coal

With the gradual depletion of high quality low-sulfur coking coal resources,metallurgical coke production enterprises are paying more and more attention to medium and high-sulfur coal with relatively low prices.A large amount of sulfur in medium and high sulfur coal is converted into thiophene sulfur which is difficult to remove during pyrolysis and exists in the solid phase product of pyrolysis,resulting in high sulfur content in the finished coke,which is difficult to meet the needs of blast furnace production.This is the main reason for limiting its application in metallurgical coke production.In this paper,the migration and transformation process of sulfur in the pyrolysis process of medium and high sulfur coal is studied,and the migration and transformation law of stable organic sulfur in coal,especially thiophene sulfur,is revealed,which is of great significance to promote the clean utilization of coal,reduce the production cost of blast furnace and expand the raw material of metallurgical coke.In this paper,the typical low,medium and high sulfur coking coals were taken as the research objects.The changes of physical and chemical properties and the migration and transformation of sulfur during coal pyrolysis under different pyrolysis atmospheres（nitrogen,water vapor,CO₂ and coke oven gas）and pyrolysis temperatures（500°C～1100°C）were explored.The main results are as follows:（1）The migration law of sulfur in coal is related to pyrolysis temperature.Before900°C,a large amount of inorganic sulfur and some unstable organic sulfur decomposed.When the pyrolysis temperature reaches 900°C～1000°C,other forms of sulfur will be converted to thiophene sulfur,and the content of thiophene sulfur will increase.When the pyrolysis temperature is higher than 1100°C,part of thiophene sulfur is decomposed.（2）The effect of water vapor on the migration of sulfur in coal is affected by its concentration and temperature.A large amount of water vapor（40%～60%）will lead to a decrease in the physical and chemical properties of low-sulfur coal.When the final pyrolysis temperature is 900°C,the pore expansion effect of a small amount of water vapor（20%）is beneficial to the desulfurization of the bulk sample.Continued heating will hinder the release of sulfur-containing gas from high organic sulfur coal and hinder the decomposition of thiophene sulfur.At 1100°C,the introduction of a small amount of water vapor（20%）can effectively remove sulfur from high-inorganic sulfur coal and promote the precipitation of sulfur in the gas phase.（3）The effect of CO₂ on sulfur migration is mainly reflected in high temperature conditions.When the final pyrolysis temperature is 1100°C,a small amount of CO₂（10%）is beneficial to the development of the pore structure of block high organic sulfur coal and promotes the decomposition of thiophene sulfur.More CO₂（15%）is only conducive to the removal of sulfur in high inorganic sulfur coal,which is not conducive to the removal of thiophene sulfur.（4）Coke oven gas can effectively promote the decomposition of organic sulfur in medium and high-sulfur coal in the form of H₂S and SO₂.Coke oven gas can promote the sulfur in high inorganic sulfur coal to escape in advance in the form of COS,and has no significant effect on high organic sulfur coal.Coke oven gas can promote the decomposition of thiophene.