Functional Mechanisms Of Inorganic Sodium On Combustion Characteristics Of Zhundong Coal During Combustion

The application of Zhundong(ZD)coal has got a wide range of attention because of its huge reservation.Combustion characteristics of ZD coal are remarkably affected by the high sodium content of their parent ZD coal.Besides,sodium has a low temperature melt point,which can cause serious economic and safety problems,such as fouling,slagging,and bed agglomeration.Therefore,the effects of inorganic sodium on the utilization of ZD coal should be explored.This thesis investigated the mode of occurrence of sodium in ZD coal and its migration characteristics during pyrolysis and combustion by using Inductively Coupled Plasma Mass Spectrometry(ICP-MS).The total content of sodium decreased with the increase of pyrolysis temperature.Most part of inorganic sodium transformed into organic sodium between the temperature of 0-600 ?,and 90% of total content of sodium were released when the pyrolysis temperature was beyond 800?.During ZD coal combustion,80% of total sodium were released during 0-600 ?,while the content of Ca and Fe were relatively stable.Acid washing and inorganic sodium impregnation methods were used to deal with ZD coal samples.Effect of inorganic sodium on pyrolysis reactivity and yields of pyrolysis gas product were analyzed by TG-MS.Experimental results reflected that inorganic sodium can inhibit the pyrolysis reactivity and gas products,but with the increase of inorganic sodium,the inhibited effect was mitigated.Effect of homogeneous and heterogeneous inorganic sodium on char reactivity and structure during ZD coal pyrolysis were analyzed by FTIR(Fourier Transform Infrared Spectroscopy),Raman spectroscopy,BET specific surface area analyzer and SEM,in a single and double fixed bed reactor.Experimental results showed both homogeneous and heterogeneous inorganic sodium can accelerate the decomposition of O-contained functional group the inhibit the polycondensation,but they also blocked the pore structure of ZD chars,which is detrimental to physical structure.Finally,this work built a novel high heating rate combustion system,which was heated by high temperature plasma,and the effect of inorganic sodium on the combustion characteristics of ZD coal were investigated.According to the experimental results,the mechanism of inorganic sodium in the combustion process was obtained: 1)The reduction of the volatile chain length during the ignition process and the blockage of pore structure of the ZD coal,thus increasing the ignition temperature and the ignition time;2)With the proceeding of combustion,the incorporation of inorganic sodium in the redox and catalytic cracking reactions increases the concentration of free radicals,thereby increasing the burning rate of the ZD coal and reducing the burnout time of the ZD coal.