Influence Of Pyrolysis Conditions On Properties Of Tobacco Stem Biochar

To tobacco stem as raw material,this study set the pyrolysis temperature（400℃,500℃,600℃,700℃）and retention time（1.5h,2.5h,2h,3h）interaction experiment as a condition of the preparation,by portable biomass carbonization mechanism for biochar,analyzed different preparation conditions of tobacco rod properties of biochar,summarizes the nature of the smoke rod biochar changing with the pyrolysis temperature and retention time,selected tobacco rod the best preparation conditions of biochar for tobacco rod resource utilization and agricultural waste provides the theory basis for preparation of high quality biochar.The main research results are as follows:（1）The pyrolysis temperature and retention time had an effect on the physical and chemical properties of the tobacco stem biochar.Biochar prepared under different preparation conditions is alkaline（9.50-10.10）,and the p H value increases with the increase of pyrolysis temperature and retention time.The maximum biochar yield was 30.86%（pyrolysis temperature 400℃,retention time 1.5h）.The average ash content of biochar is 26.40%.The volatile content decreased with the increase of pyrolysis temperature and retention time.（2）Pyrolysis temperature and retention time had an effect on the element content of tobacco stem biochar.The carbon content of tobacco stem biochar prepared under different preparation conditions increased significantly with the increase of pyrolysis temperature,ranging from551.66 to 651.68 g·kg^-1.Total nitrogen content of tobacco stem biochar ranged from 15.05 to 25.62 g·kg^-1,total phosphorus from 1.72 to 7.82g·kg^-1,and total potassium from 88.43 to 167.75 g·kg^-1.Total nitrogen content decreased with the increase of pyrolysis temperature,while total phosphorus and total potassium increased with the increase of pyrolysis temperature and retention time.The contents of alkali-hydrolyzed nitrogen,available phosphorus and available potassium in tobacco straw biochar all increased with the increase of pyrolysis temperature,and the content of available nutrients was the highest at the pyrolysis temperature of 700℃（3）Pyrolysis temperature and retention time have an effect on the surface characteristics of tobacco stem biochar.Tobacco stem biochar all has a pore-like structure,and the specific surface area and micropore area increase with the increase of pyrolysis temperature,and the average pore diameter is the opposite;under 700℃（3h）,the maximum specific surface area(50.57 m²·g^-1)and micropores(57.07 m²·g^-1)of tobacco stem biochar.In the Fourier infrared spectrum,as the pyrolysis temperature increases,the degree of aroma and stability of the biochar increase.（4）The heavy metal content of tobacco stem biochar is low.The adsorption amount of Pb²⁺and Cd²⁺by tobacco stem biochar increased with the increase of pyrolysis temperature and retention time,and the adsorption amount of Pb²⁺was greater than that of Cd²⁺.The adsorption range of Pb²⁺by tobacco stem biochar was 11.87～22.27 mg·g^-1,while that of Cd²⁺was 12.08～19.15 mg·g^-1.All in all,the preparation conditions play a decisive role in the properties of the tobacco stem biochar,and the properties of the tobacco stem biochar produced by different preparation conditions are significantly different.According to the specific requirements,the suitable preparation conditions can be selected to produce tobacco rod biochar.For example,the total potassium and available potassium contents of the tobacco stick biochar produced at the pyrolysis temperature of 600℃and the retention time of 3h are higher than other conditions,which can be used to improve the soil potassium deficiency.The total phosphorus content in the biochar produced at the pyrolysis temperature of 600℃and the retention time of 2.5h is higher than other conditions,which can be used to improve the soil phosphorus deficiency.The surface properties of the biochar produced by pyrolysis temperature of 700℃and retention time of 3h are better than other conditions,which can be used for soil pollution remediation.