Study On Mechanism Of Alkali Metal And Alkaline Earth Metals On Co-pyrolysis Of Low Rank Coal And Biomass

In this paper, lignite from Inner Mongolia east and non-stick coal and long flame coal from Ordos Area with soybean grass and rice straw from Xuzhou area were used. Firstly, the distribution of low temperature pyrolysis products of different low rank coal and biomass under different mixing ratios were determined. Then the pyrolysis parameters of long flame coal and straw were studied by thermogravimetric analysis method and dynamic model was established to obtain the kinetic parameters of the co-pyrolysis process. Then ICP-AES was applied to determine AAEMs in the samples and expounded the migration law of AAEMs in the co-pyrolysis process of low rank coal and biomass. Finally, using double temperature tube furnace pyrolysis long flame coal, straw, straw ash removal, long flame coal which added AAEMs and long flame coal and straw separately and stacking samples under different temperature got coke and tar products, which were studied by ICP-AES, FTIR, XPS, MIP, GC/MS. Draw the following conclusion:(1)With the increase of the proportion of biomass, the yield of semicoke decreased, and the yield of water, tar and gas showed an increasing trend. The largest sum of the difference between the experimental value and the theoretical value of three kinds products produced by co-pyrolysis of low rank coal and biomass was long flame coal and straw in the mixing ratio of 1:1 and the value was 6%.(2) Using long flame coal, straw, ash removed straw and long flame coal which edded AAEMs as raw materials, the samples were mixed with each other, and then thermogravimetric analysis was carried out to study the kinetic parameters. The results showed that AAEMs in rice straw has a catalytic effect, but at the same time, it is influenced by the organic component of rice straw.(3) The migration of AAEMs in the co-pyrolysis process of low rank coal and biomass is transferred through the gas and solid method. With the increased of pyrolysis temperature, the release of AAEMs gradually increased. The Na+、 K+and Mg2+ were transferred to the long flame coal tar from the release of AAEMs of rice straw pyrolysis, meanwhile, K+and Mg2+ in char of long fame coal reduced with small molecule organic matter released by thermal decomposition of rice straw.(4) With the increase of pyrolysis temperature, types and quantities of functional groups of coke decreased and aromatic structure increased. Coke pore diameter and huge pore increased, the gas produced by straw pyrolysis further increase the pore and huge pore of coal char. Factors affecting the change of functional groups in the semi coke surface of long flame coal were the AAEMs and organic molecules produced by the pyrolysis of rice straw, The addition of AAEMs, that increased the relative content of C-C,C-H and C-O, decreased the relative content of C=O,COO- and transformed sulfur compounds to organic sulfur from on the surface of semi coke. The pyrolysis of straw which increased the relative content of C-O, decreased the relative content of C=O and COO-, compared with the simple addition of AAEMs effectively further promoted the char nitrogen compounds to form more simple, inhibited the conversion of inorganic sulfur and promoted organic sulfur removal. The GC/MS analysis of tar showed that, the co-pyrolysis of rice straw and the long flame increased hydrocarbons and light compounds of the coal tar, and increased the content of aromatic compounds in tar. The volatile contained AAEMs which produced during the process of rice straw pyrolysis plays a catalytic role in the process of pyrolysis, which makes the small molecules in coal to be combined with the active molecules of straw pyrolysis to increase the light component.