Study On The Effect Of Pretreatment On Micro-structure And Thermal-chemical Performance Of Shengli Lignite

The Shengli Lignite is abundant in China. The chemical reaction performances are difference as its large water content, high volatile, low calorific. Different methods were used to investigate the structure and thermal chemical performance of Shengli Lignite, which was conducive to understand the nature of lignite in depth. This paper selected Shengli lignite as object to study, and the lignite samples were pretreated by solvent(Acetone, Tetrahydrofuran, NMP/CS2) swelling, hydrothermal solvent(NMP and NMP/CS2) extraction, alkali(Sodium hydroxide) treatment which were characterized by Industry Analysis, FT-IR, BET, SEM and Oxygen adsorption performance. It are investigated the pyrolysis and combustion of the coal samples, and the focused on the thermochemical reaction performance of the alkali treatment coal.Experment results show that, it is largest of Shengli Lignite’s swelling degree in the tetrahydrofuran solvent, middle in the NMP/CS2 mixed solvent and minimum in the acetone solvent. For the acid, oxidation and alkali pretreatment of Shengli Lignite, among them, the swelling degree of the acid treatment and oxidation treatment increased, but the swelling degree of the alkali treatment decreased. It is low temperature oxygen adsorption test for the pretreatment tetrahydrofuran swelling of coal samples,the results show that its low temperature oxidation activity significantly lower than the Shengli Lignite. So the swelling coal samples have a poor performance of oxidation and were not easy to spontaneous combustion.Compared to the Shengli Lignite, the combustion performance of hydrothermal solvent extraction of coal samples are different, its main combustion peak is moved to the high temperature region, indicating its combustion performance became poor. We can conclude from the pyrolysis characteristic parameter values that maximum weight loss rate of SR150℃NMP/CS2 is higher than other samples. While the maximum weight loss temperature of SR150℃NMP/CS2 is slightly lower than other samples. So this coal sample possess better pyrolysis performance.Comparing the Shengli Lignite to its alkali- treatment samples, the main combustion peak of alkali-treatment samples were all moved to high temperature region. The alkali concentration of 0.5mol/L and 1mol/L coal samples appeared apparent combustion hysteresis after 550℃,indicating that the combustion performance of alkali-treatment samples became poor,and the combustion performance became worse as the increasing of alkali concentration. The main products were H2 and CO2 during the gasification of alkali treatment. The maximum of generation rate of the alkali-treatment samples put forward about 20℃ comparing to the Shengli Lignite.The starting temperature of alkali-treatment samples put forward about 60℃. From the above all, we can conclude that the alkali-treatment improved the stream-gasification performance of lignite.