Experimental Study On Sodium Release During Thermal Reaction Of High Ash Coal In Shanxi

It is an important foundation for the efficient and rational development of Shanxi modern coal chemical industry to use the“two high”coal of Shanxi.Commonly used control means include washing and flux,while sodium-based fluxes have the most desirable effect.In this paper,the No.15 and NO.9 coal mine of Sihe,Fenghuangshan No.9 coal mine of Jincheng District in Shanxi Province were selected as research objects.Na₂SO₄,Na₂CO₃,NaCl and NaOH fluxes were added to explore the influence of different flux types,addition amounts,atmosphere and temperature to sodium release.Enriching the ash chemistry of coal and providing guidance for the efficient and stable operation of high-ash and high-melting coal in Shanxi for the entrained flow gasifier.Firstly,the occurrence of sodium in coal with different fluxes in different temperature is simulated by thermodynamics equilibrium software.The result shows that the sodium under pyrolysis,gasification and combustion conditions would eventually release at a fully high temperature.Different atmospheres will significantly affect the morphological changes of sodium,mainly affecting the transformation characteristic temperature,release rate and final form of sodium element.The conversion of sodium is close to 100%under pyrolysis conditions while about 80%under gasification and combustion conditions.The addition amount of flux cannot significantly change the occurrence mode of sodium-containing minerals.Except for Al and Si,S,Ti and Fe in coal will be easier to react with sodium.Secondly,a fixed bed experiment was designed to study the effect of flux form and addition on sodium release.Under pyrolysis atmosphere,temperature had the most significant effect on sodium release rate.While when temperature is over 1000°C,the rate increase is not obvious.Different kinds of flux have certain influence on the release rate of sodium,the release rate of Na₂CO₃,and NaCl flux is between 35⁴0%,and the sample with Na₂SO₄ flux is between 30³5%.The NaOH sample release rate is approximately 20%.Higher S/A will inhibit the release of Na,and high S+A will also have a significant inhibitory effect on sodium release.The fluidized bed experiment was designed to study the factors affecting the sodium release rate,the change of reaction atmosphere had a significant effect on the release rate.The instantaneous concentration of Na in the combustion atmosphere was significantly higher than that of pyrolysis and gasification.Finally,combined with TGA and XRD analysis,the decomposition of pyrite takes place in 460°C is,the decomposition of calcite takes place around in 740°C,and the weight loss peak at 580°C means the decomposition of kaolinite,and the peak at 825°C stands for the decomposition of Muscovite.According to the mineral composition of coal samples,there is almost no mineral decomposition weight loss phenomenon after 1000°C.Combined with thermodynamic calculations,it is known that typical Shanxi high-ash anthracite hardly releases Si and Al under pyrolysis conditions;Na is released at high temperature as Na;but Cl element can significantly affect the release of Na,and Na will release as NaCl will before1200°C.With the temperature rises further Na is released as Na elemental form,the coal sample will react with Al in a carbon-thermal reaction.The test results of ash fusion temperature show that SH15 coal sample has the lowest ash melting point,SH9 coal sample has the highest ash melting point,and coal ash content has obvious influence on ash melting point.The most suitable addition amounts for the Na₂SO₄ flux fluxing effect were 2.5%,2%,and 1%,respectively,and for Na₂CO₃ fluxes,the most suitable addition amounts were 1%,3%,and 2%,respectively.