Study On Pyrolysis Of High-sulfur Petroleum Coke And Its Isothermal Co-gasification With Coal/Biomass

Petroleum coke is a by-product of crude oil refining,and gasification technology is an important way to realize its large-scale utilization,but the low reactivity of petroleum coke is a key bottleneck need to overcome urgently.Co-gasification of coal,biomass,etc.with petroleum coke can effectively improve its gasification reactivity,which is the focus of current research.However,the existing studies mainly focus on the gasification of semi-coke,lacking in-depth understanding of the laws of petroleum coke pyrolysis,thus leading to insufficient understanding of the synergistic mechanism of petroleum coke-coal/biomass co-gasification.In view of this,this work selects high-sulfur petroleum coke which is difficult to use,and systematically studies the influence of different pyrolysis conditions on the physicochemical properties and gasification reactivity of semi-coke,explores the synergistic mechanism of isothermal co-gasification of petroleum coke with lignite/straw,investigate the isothermal co-gasification mechanism of petroleum coke and coal/biomass,and the influence of the composition and thermochemical behavior of power plant coal/biomass ash on petroleum coke gasification was also revealed.First,the effect of slow pyrolysis on the structure and sulfur release of petroleum coke was investigated by thermogravimetric-mass spectrometry.It is found that the petroleum coke will undergo an obvious secondary cracking reaction when the temperature is higher than 1000°C,and the degree of carbon ordering will gradually increase in four stages,accompanied by the softening,plasticization,solidification and graphitization of the semi-coke,respectively.During the pyrolysis process,the release of sulfur includes two slow stages（<500℃and 900-1100℃）and two fast stages（500-900℃and>1100℃）;the final release rate of sulfur（the final temperature is 1375℃）decreased with the increase of heating rate.When the heating rate increased from 10K/min to 50K/min,the sulfur release rate decreased from 41%to 25%.Secondly,the influence of different pyrolysis conditions（temperature,time,pyrolysis rate,etc.）on the structure and gasification reactivity of petroleum coke was systematically studied.The results show that increasing the pyrolysis temperature and prolonging the pyrolysis time will increase the degree of graphitization of carbon;when the temperature is less than 1200℃,the transformation of amorphous carbon to incomplete carbon is dominant,and the degree of graphitization of carbon increases slowly,while When the temperature>1200℃,the transformation of incomplete carbon to graphitized carbon dominates,and the degree of carbon graphitization increases rapidly.In different temperature ranges,the effect of pyrolysis temperature on semi-coke gasification reactivity is different;at 1300°C and CO₂ atmosphere,the time required to complete the isothermal gasification of petroleum coke is about 1/2 of the time required for temperature-programmed pyrolysis-isothermal gasification.Thirdly,the synergistic reaction law of isothermal co-gasification of petroleum coke and lignite/straw was studied.It is found that the reactivity of petroleum coke-straw co-gasification is better than that of petroleum coke-lignite,and the synergy in the co-gasification process mainly occurs after the lignite/straw is completely gasified into ash.For the co-gasification of petroleum coke and lignite,the catalytic effect of acid-dissolved Ca in the coal is significant in CO2 atmosphere;for the co-gasification of petroleum coke and straw,when the proportion of straw is 50%,the molten ash in the late stage of gasification（Carbon conversion>0.6）will wrap the carbonaceous particles,thereby slowing down the gasification reaction.Finally,the influence mechanism of coal/biomass ash on the isothermal gasification behavior of petroleum coke was explored.The results show that under the studied temperature conditions（1000℃,H₂O atmosphere）,the type and content of alkaline minerals in the ash are the main factors affecting its catalytic effect when the ash ratio is low（<20wt%）;when the ash ratio is high（50 wt%）,the catalytic effect is affected by both ash melting characteristics and active mineral content.