Study On The Influence Of Inherent Minerals On Nitrogen Transformation In The Process Of High Alkali Coal Thermal Utilization

Zhundong coalfield has huge reserves of coal resources,some of which is called high alkali coal because the alkali metal content exceeds 0.4%.In the process of heat utilization,the inherent minerals such as alkali metals in coal can be used as catalysts to change the reactivity of coal and affect its thermal reaction process and NO_x emissions.In order to achieve the clean and efficient utilization of high alkali coal,a thermogravimetric-differential scanning calorimeter,an infrared analyzer and a quadrupole mass spectrometer?TG-DTG-FTIR-MS?were used for pyrolysis experiments,and the pyrolysis-gas chromatography-mass spectrometer?PY-GC-MS?and X-ray photoelectron spectroscopy?XPS?test methods were used to qualitatively analyze the effects of inherent minerals in coal on coal pyrolysis and nitrogen conversion.The results show that water-soluble Na inhibits the pulverized coal reaction,reduces the output of the main pyrolysis gas,and promotes the conversion of semi-char nitrogen to tar nitrogen.Ammonium acetate soluble Na and Ca promoted the pyrolysis reaction of coal powder,increased the formation of main pyrolysis gas,and promoted the conversion of tar nitrogen to gaseous nitrogen.The soluble minerals of hydrochloric acid have little effect on the activity of pyrolysis reaction,promote the formation of main pyrolysis gas,and inhibit the conversion of semi-coke nitrogen to tar nitrogen.The pyrolysis experiment was carried out in a tube furnace,and the precipitation of pyrolysis of NH₃ and HCN was analyzed by UV spectrophotometry.The influence of intrinsic minerals on the precipitation of coal pyrolysis of NH₃ and HCN was analyzed from a quantitative perspective.The results show that the main product of pyrolysis of gaseous nitrogen is NH₃,which is much higher than HCN.Water-soluble Na promoted the formation of NH₃,but inhibited the formation of HCN.The soluble Na and Ca of ammonium acetate promoted the formation of NH₃,but had little effect on the formation of HCN.The soluble minerals of hydrochloric acid had little effect on the precipitation of gaseous nitrogen.The combustion experiment was carried out under different pretreatment conditions and different O₂ concentrations by TG-DTG-FTIR-MS.The results show that the presence of water-soluble Na,ammonium acetate soluble Na,Ca and hydrochloric acid soluble minerals during coal combustion inhibits the combustion of coal powder.Water-soluble sodium and ammonium acetate soluble Na and Ca can reduce the precipitation of NO_x.With the increase of oxygen concentration,the amount of NO precipitated increased,while the amount of NO₂precipitated decreased first and then increased.When the concentration of O₂ was 20%,the total amount of NO_x emissions was the least.