| Our country being of the largest consumption amount of coal; as low rank coal is the ideal chemical-used resource, represented in shaanbei region of Shaan-Ning-Meng area is rich in low rank coal resources, and low-middle temperature pyrolysis and liquefaction of coal have been with considerable scale in the area. Considering to the development of coal utilization and clean coal technology, grading utilization of coal through pyrolysis has become the urgent way to speed up upgrading the coal chemical industry. Pyrolysis of coal is the initial and primary procedure of all the processes of coal utilization such as combustion, gasification and liquefaction of coal, for coal in low-medium temperature, there are crucial theoretical and practical significance in researching the pyrolysis of coal at low-middle temperature.JJ coal and FG coal were used in the research, and Co-Mo/Al2O3, Ni-Mo/AL2O3 catalysts were prepared by the method of equal volume dipping. Equipments of TG-FTIR and Powder-Particle Fluided bed (PPFB) were used to research the impacts of the factors such as reaction gases (inert gas & mixing hydrogen gas), catalysts (MCM-41, Co-Mo/Al2O3 and Ni-Mo/Al2O3) on the behavior of pyro lysis of coal, the characteristics of gases(CO, CO2, CH4, CnHm, NH3, etc.) released from pyrolysis of coal and the components distribution of tar. Summarizing the main contents as follows:(1) Due to the difference of two coals in their properties and microcosmic structure, the difference of their pyrolysis behavior existed. Polycondensation reaction happened mainly during the second degassing phase of the pyrolysis of FG coal, but cracking reaction occurred while the polycondensation reaction happened during the pyrolysis of JJ coal, and one apparent weight loss peak appeared. Compared to pyrolysis under N2, the stable reactions of free radicals of hydropyro lysis of coal were promoted, and the pyrolysis conversion of coal were enhanced. The hydropyro lysis conversion of coal arised while catalysed by the MCM-41, Co(Ni)-Mo/Al2O3, and the catalysis on the secondary reaction are significantly. (2) One large FTIR absorbance peak of CO2 appeared during the second degassing phase of the pyro lysis of JJ coal for cracking reaction occurred in the meantime. In addition to this, the patterns of main gases (CH4, CO and CO2, CnHm and NH3, etc.) released from two coals were similar. The relative amount of CO became larger under hydrogen because the reverse reaction of Water Gas Shift Reaction happened. When catalysts were used, decarboxyl reaction to generate CO2 was promoted by MCM-41 of pyrolysis of coals; and under hydrogen, the hydrocraking of cross-band, side chains of sromatics and aliphatics CnHm were promoted while hydropyrolysis catalysed by MCM-41 and Co(Ni)-Mo/Al2O3; beyond that, the nitrogen removal reaction was promoted too.(3) Components of tar from pyrolysis of coal in PPFB contained lightweight aromatics (BTX, etc.), phenols (PCX, etc.), naphthalenes, heterocyclic compounds, aliphatics (including chain aliphatics and cycloaliphatics), polycyclic aromatic compounds (PAC), etc.. As the pyrolysis temperature arised from 600℃to 750℃, the relative contents of lightweight aromatics, naphthalenes, heterocyclic compounds, aliphatics and PAC increased, while phenols decreased. Under hydrogen, the qulity of tar became lighte, for the relative contents of BTX, PCX increased; hydro-stability of PAC was enhanced, and the weight aromatics with high value-added such as indenes, fluorenes and phenanthrenes increased, hydro-substituted products such as H-indene generated, and the relative content of naphthalene reduced. The hydro-cracking and hydro-stability were promoted in pyrolysis and hydropyrolysis of coal catalysed by Co(Ni)-Mo/Al2O3, as a result of which, the yield of the light aromatics, naphthalenes with better stability and stable bands enhanced, and the relative content of aliphatics decreased.
|
PDF Full Text Request