The Influence Law Of Microstructure And Pyrolysis On Lignite Spontaneous Combustion Research

Coal spontaneous combustion is a very serious disaster in coal mining and the security of coal storage and transportation. Lignite with high moisture and high self-ignition trend influences the safety of lignite storage and transportation as well as the efficiency in industrial application. In order to deepen understanding of the mechanism of coal spontaneous combustion and solve the problem of lignite spontaneous combustion, we study the coal chemical and physical structure and the changing rule of the coal spontaneous combustion reactivity based on the microstructure of coal. At the same time, we explore the relevance between coal upgrade condition and lignite microstructure, hoping to prevent coal spontaneous combustion by controlling the upgrade condition.This research mainly study the functional groups of lignite, using characterization method like infrared spectrum, chemical titration, He-TPD test, BET and TG-DTA analysis, to analyse the effect of pyrolysis on the types and content of functional groups, the pore structure of coal and their influence on coal oxidation reactivity.(1) The major functional groups of lignite are hydroxyl, carbonyl and carboxyl, epoxy bond, ester group and and alkyl such as methyl. Among them, hydroxyl and alkyl have a larger content than carboxyl and ester. The specific surface area of lignite is small, pore diameters are mostly larger than20nm. The thermogravimetric analysis shows that coal combustion mainly has three stages:low temperature oxidation and groups dissociation stage, coal skeleton combustion stage and the graphite structure oxidation reaction stage. The initial reaction temperature of lignite low temperature is low, the content of the graphite structure in lignite is small.(2) The tubular furnace is used to simulate thermal upgrade of lignite, analyzing the changing rule of the coal structure and oxidation reactivity concluded that with the increase of processing temperature, active group of lignite reduce gradually, as well as coal oxidation reaction activity. The samples treated below600℃self-ignition activity reduced little, have a high spontaneous combustion trend. After treatment temperature of800℃, the spontaneous combustion activity of coal decline significantly.(3) Pre-oxidation treat the anthracite with different oxidant, results indicated that oxidant treatment can change the surface functional groups of coal in different degrees. Hydrogen peroxide and sodium hypochlorite treatment have little effect on the activity of oxidation reaction, while the nitric acid treated anthracite has a high low-temperature oxidation reaction activity. According to the variation of coal surface groups, we can infer that oxygen-containing groups in anthracite such as carboxyl significantly improve the low-temperature oxidation activity of coal. The alkyl does not have an obvious effect on low-temperature oxidation activity of coal, but has a certain influence on the coal oxidation reaction heat.