Study On The Thermal Properties Of Humic Acid Extraction And Pyrolysis Reaction

Xinjiang is rich in coal resources,with a total predicted resource of 2.19 trillion tons,accounting for about 40.6%of the total predicted coal resources in the country,mainly including low rank coal such as long flame coal,non-sticky coal and weak sticky coal.At present,Xinjiang’s coal resources are mainly used for power generation,gasification,blue carbon production and so on,with large waste of resources and low production added value..Therefore,local use of Xinjiang’s low rank coal to produce products with high added value and easy storage and transportation has a very good market prospects and development space,and is also the basis for scientific development of Xinjiang’s coal resources.In this paper,Naomaohu lignite in Hami area of Xinjiang is taken as the research object.Humic acid in coal is extracted by H₂O₂ oxidation alkali extraction method and Alkali-H₂O₂ oxidation method,and the structure of humic acid is characterized.Different oxidation methods and the key factors affecting the oxidation process,such as coal/H₂O₂ solid-liquid ratio,oxidation time and oxidation temperature,are investigated respectively This paper analyzes the yield of humic acid,structural characteristics,optimization of oxidation methods and conditions,and explores how to improve the yield of the product to achieve the purpose of efficient utilization of lignite resources.At the same time,the extracted humic acid,raw coal and coal oxidation residue were pyrolyzed in the range of 450-650℃,and the characteristics of the pyrolyzed products were preliminarily explored.The product yield,structure characterization and pyrolysis analysis under different oxidation methods and conditions are as follows:（1）In the process of humic acid extraction from Hami Lignite by H₂O₂ oxidation alkali extraction,under the optimum conditions of coal/30%H₂O₂（W/V）ratio of 1/5,reaction time of 6 hours and oxidation temperature of 60℃,the humic acid and black humic acid can not be extracted completely,and the yield of humic acid is low,the highest yield is only 4.45%,among which Brown humic acid is only 4.45%The highest yield was 1.46%,and the highest yield of black rot acid was 2.99%.（2）In the process of extracting humic acid from Hami Lignite by hydrogen peroxide oxidation in alkaline environment,the optimum conditions of extracting humic acid from coal were determined as follows:coal/30%H₂O₂（W/V）ratio 1/3,reaction time 6 hours,oxidation temperature 60℃,at this time,the highest yield of humic acid was 59.78%,of which the yield of brown humic acid was 18.19%,the yield of black humic acid was 41.59%.（3）According to theanalysis of humic acid product structure,the humic acid product obtained by oxidation of Hami lignite contains aromatic structure and carbon carbon double bond structure,mainly 1-4ring aromatic structure,but less highly conjugated aromatic structure.Among them,there are a lot of aromatic bond types in the products of fulvic acid,with a strong absorption peak at the wavelength of 410nm,mainly four ring aromatic structure,and a small number of three ring and five ring aromatic structure;there are more carbon carbon double bond structures in the products of fulvic acid,with a strong absorption at the wavelength of 325 nm,and a small number of shoulder peaks within the wavelength of 340-400 nm,mainly two ring aromatic structure,and a small number of shoulder peaks at the same time one ring and three ring aromatic structure.（4）In the analysis of humic acid,raw coal and coal oxidized residue,it is concluded that the conversion rate of tar in pyrolysis products can be improved by the initial oxidative depolymerization of raw coal and extraction of humic acid,which is less molecular weight,and the humic acid is easier to pyrolysis than raw coal and coal oxidation residue.The highest yield of tar is 22.26%and 12.73%at 500℃and 14.13%and11.74%at 600℃.The above research shows that Alkali-H₂O₂ oxidation method is a very good method to extract humic acid,which can fully oxidize the coal;after the humic acid pyrolysis,the tar yield increases,that is,the raw coal is oxidized to a small molecular weight material and then pyrolyzed,which can significantly improve the tar yield.