Effect Of Some Natural Minerals On Transformation Behavior Of Sulfur And Its Mechanism During Pyrolysis Of Coal And Biomass

In this paper, Longma coal, wheat straw and sawdust from Linfen in Shanxi Province were selected for experiment. The Influence of tourmalines, Na-bentonite and medical stone on sulfur behavior during pyrolysis of Longma coal and biomass were investigated in fixed-bed reactor. Moreover, the thermogravimetric analysis, XRD diffraction, scanning electron microscopy (SEM) and energy spectrum (SEM-EDX) analysis, the infrared spectroscopic (IR) analysis and pyrolysis dynamics were done in order to know further the mechanism of the influence of the added natural minerals on the transformation behavior of sulfur during the pyrolysis of coal and biomass. The main conclusions are as follows:1. The effect of natural minerals on the transformation behavior of sulfur during coal pyrolysis(1) The total sulfur retention and the organic sulfur retention increased during coal pyrolysis when adding tourmaline, Na-bentonite and medical stone. However, the sulfate sulfurretention decreased significantly when adding tourmaline,Na-bentonite and medical stone. Adding Inner Mongolia tourmalineand medical stone was benefit for sulfur to turn into hydrogensulfide and at the same tine adding medical stone was also good forthe sulfur in coal to convert into carbonyl sulfide.(2) During Longma coal pyrolysis, with increasing the residencetime, the total sulfur retention and the organic sulfur retentionfirstly decreased and then increased; while sulfide sulfur retentionalmost had no change. When increasing the residence time, thetotal sulfur retention and the organic sulfur retention decreasedobviously when adding Hebei tourmaline; while the total sulfurretention, the sulfate sulfur retention and the pyritic sulfur retentionchanged slightly when adding Inner Mongolia tourmaline,Na-bentonite and medical stone.(3) Compared with the content of hydrogen sulfide frompyrolysis when adding medical stone, the content of hydrogensulfide increased when adding the medical stone loading CoMo(CoMoP/M) and the medical stone loading sulfuric acid (SO42-/M)during coal pyrolysis.2. The effect of natural minerals on the transformation behaviorof sulfur during the co-pyrolysis of coal and biomass (1) During co-pyrolysis of coal and biomass, with increasing theblending ratio of wheat straw and sawdust, the total sulfurretention decreased firstly and then increased when thetemperature is850℃and the retention time is30min. When theratio of wheat straw or sawdust was less than40%, adding medicalstone could make the total sulfur retention decrease; while whenthe ratio of wheat straw or sawdust was higher than40%, addingmedical stone made the total sulfur retention increase. Whenadding medical stone, with increasing the ratio of wheat straw orsawdust, the inorganic sulfur retention deceased while the organicsulfur retention increased significantly. Adding medical stone wasalso good for the sulfur to turn into hydrogen sulfide duringco-pyrolysis of coal and biomass.(2) The total sulfur retention decreased when the temperatureincreasing during co-pyrolysis of coal and biomass with the ratio ofcoal and wheat straw or sawdust is4:1. Adding Hebei tourmalinehad no obvious influence on the total sulfur retention, while addingmedical stone could reduce the total sulfur retention at hightemperature (>550℃). Moreover, adding Hebei tourmaline ormedical stone made the inorganic sulfur retention changeirregularly.3. The mechanism of effects of natural minerals on the transformation behavior of sulfur during coal pyrolysisFrom the results of analysis of XRD diffraction, scanning electronmicroscopy (SEM) and energy spectrum (SEM-EDX) analysis, theinfrared spectroscopic (IR) and pyrolysis dynamics analysis, onecould know that adding natural minerals had no obvious effect onthe absorption ability, surface topography and the structure of thefunctional group of the solid residual. Moreover, combining with theresults of influence of simple minerals SiO2、Al2O3、Fe2O3、CaO、KCl、Na2CO3on the total sulfur retention, one can infer that the reasonwhy natural minerals have obvious influence on the transformationbehavior of sulfur during coal pyrolysis is due to the constituent andthe physical adsorption of the natural minerals.