Study On Deep Desulfurization Of High-sulfur Petroleum Coke

Petroleum coke was widely used in electrolytic aluminum industry,cement industry,electricity industry,steel industry,etc.,due to its high carbon content(>85 wt%),low volatility(<12 wt%),low ash(<0.5 wt%)and high calorific value industry.However,the high sulfur content in petroleum coke and the content of high metallic impurities(mainly Ni and V)greatly limit the applications of petroleum coke.In this paper,the desulfurization methods of alkali-catalyzed calcination,wet chemical oxidation and alkali-catalyzed calcination combined with ultrasonic oxidation were developed,and the appropriate desulfurization agents for petroleum coke were selected to optimize desulfurization process.In addition,the chemical structure,thermal stability,microstructure,microcrystalline structure and other properties of petroleum coke before and after desulfurization were studied.The main conclusions are as follows:(1)The optimum conditions during alkali catalytic calcination process were as follows:calcination temperature of 700?,reaction time of 120 min,added Na2CO3 amount of 25%,particle size of 80 ?m.And the maximum desulfurization rate of high-sulfur petroleum coke could reach 89.3%under the above conditions.In addition,the characterization results show that the characteristic absorption peaks of petroleum coke after calcination at 863 cm-1 and 744 cm-1 are obviously weakened or almost disappeared by FT-IR analysis,indicating that calcination desulfurization under H2 atmosphere exhibits a significant desulfurization effect for high-sulfur petroleum coke.The thermal stability of petroleum coke after calcination was better by TG analysis,and the degree of orientation of aromatic flake and the crystallinity of petroleum coke was increased by XRD analysis.(2)The desulfurization treatment for high-sulfur petroleum coke by using commonly used oxidants such as H2O2,HNO3 and KMnO4,and the results showed that KMnO4 exhibited the best desulfurization effect on petroleum coke,and the desulfurization rate could reach 70.2%.The desulfurization effect of HNO3 was second,and the desulfurization rate could reach 40%,While H2O2 showed the worst desulfurization effect,and desulfurization rate of only reached 20%.The desulfurization rate of petroleum coke reached the maximum value of 95%under such conditions of oxidation temperature of 80?,KMnO4 solution concentration of 15 wt%,liquid-solid ratio of 20 mL/g,reaction time of 120 min and particle size of 80 ?m.During such deep desulfurization of petroleum coke,organic sulfur in sulfoxide sulfur and thiophenic sulfur are completely removed,and the desulfurization efficiencies of sulfoxide sulfur and thiophene sulfur are 96.8%and 93.9%,respectively.(3)Two-stage desulfurization treatment of petroleum coke with sulfur content of 7.57%was carried out by the combination methods of alkali catalysis and ultrasonic assisted oxidation.Fourier Transform Infrared Spectroscopy(FT-IR),Scanning Electron Microscopy(SEM),X-ray Diffraction(XRD)and other characterization methods were combined to analyze the chemical structure,surface morphology,microcrystalline structure of petroleum coke before and after desulfurization.The desulfurization rate of petroleum coke reached the maximum value of 67.2%through alkali catalyzed calcination under such conditions of reaction temperature of 900 0C,added Na2CO3 amount of 25%,holding time of 2 h,particle size of 80 ?m and heating rate of 1?/min;and the total desulfurization rate further reached 93.5%through ultrasonic assisted oxidation under such conditions of oxidation temperature of 80 ?,HNO3 concentration of 65 wt%,reaction time of 12 h,particle size of 80 ?m and liquid-solid ratio of 20 mL/g.More definitely,the removal rates of thiophenic sulfur and sulfoxide exhibited 73.4%and 59.8%during the alkali-catalyzed calcination,and the total removal rates of thiophenic sulfur and sulfoxide did 93.6%and 93.3%after subsequent ultrasonic assisted oxidation,respectively.