Experimental Study On The Effect Of Coal Combustion And Slagging Characteristics Of Alkali Metal In Zhundong Lignite

Zhundong lignite in Xinjiang is of great significance to alleviate the shortage of fossil energy in China with its rich reserves.However,the high alkali metal content in coal restricts the utilization of the coal.It is of great significance to study the effect of alkali metal on the slag and combustion in the coal to accelerate the extensive application of the coal.In order to study the effect of alkali metal on slag and combustion.two pretreatment methods,water washing and acid alkali deashing were used as representative to study the effect of alkali metal removal on coal structure and combustion characteristics,and several analytical methods,including X ray diffraction(XRD),specific surface area analysis(BET),inductively coupled plasma emission spectroscopy(ICP-AES),thermogravimetric analysis,and planar laser induced fluorescence(OH-PLIF)based on two-dimensional transient measurement were used.The results show that both water washing and deashing have the ability to remove the ash and the main mineral alkali metals,and acid-base deashing can remove almost all ash contents and the alkali metal.Water washing and deashing have little effect on the microcrystal structure of coal and Although the ignition temperature and burning temperature of coal are increased-the burning rate and the stability in the middle of combustion are improved.It is observed by OH-PLIF that the total amount of OH released from water washing coal and deashing coal is more than that of the raw coal,and water washing coal and deashing coal burn faster than raw coal,but the raw coal can burn out faster.In addition,alkali coal and other minerals are added to the deashing coal to form the coal having similar content of ash to zhundong lignite,and then change the content of sodium and calcium to analyze the influence of alkali metal addition on coal slagging and contaminationa ccurately and quantitatively.The result shows that with the increase of the content of sodium in coal,the melting point of ash is generally decreasing.The reason is that the sodium in the coal ash is easy to combine with silicon,aluminum,calcium and other oxides to form nepheline and other low melting point crystals and low temperature eutectic,so as to enhance the slagging characteristics of coal ash and reduce the melting point of ash.With the decrease of calcium content and the increase of sodium content,the 4 kinds of ash melting temperatures are decreasing.