Experimental Study On Microwave Pyrolysis Characteristics Of Oil Sludge From Oil Refinery

With the development of industry,the demand of crude oil is increasing day by day.The composition of oil sludge is complex and harmful,but at the same time it contains a large number of available resources.The pyrolysis treatment of oil sludge and the realization of resource utilization represent the development direction of oil sludge treatment,and it is also the hot spot of oil sludge treatment research at home and abroad.Using the unique heating mechanism of microwave,the oil sludge was treated by demulsification and pyrolysis.The effects of different factors on demulsification and dehydration of oil sludge under microwave heating were studied.In addition,the characteristics of oil sludge during microwave pyrolysis and the effects of different factors on the product distribution characteristics of oil sludge during microwave pyrolysis were studied.Firstly,the demulsification experiment of oily sludge under microwave heating was carried out to explore the influence of different factors on the dewatering rate of oily sludge under microwave heating.Under the same conditions,compared with the conventional heating method,the dewatering rate of oil sludge after microwave heating was significantly increased,with an average increase of 7.08%.With the increase of microwave irradiation time,the dehydration rate rises rapidly,reaching the highest when the microwave irradiation time is 90s,and the dehydration rate is 50.31%.With the continuous increase of microwave irradiation time,the dehydration rate presents a downward trend.When the microwave power is 100W,the demulsification rate is 44.51%.With the increase of microwave intensity,the dehydration rate presents an increasing trend,reaching the highest when the microwave power is 500W,and the dehydration rate is 49.77%.With the continuous increase of microwave power,the demulsification rate showed a decreasing trend.For the pyrolysis residue of oil sludge and biomass coke(peanut shell),the dehydration rate was the highest under the condition of 60s microwave time and 300W microwave power,which was 56.50%and 52.11%,respectively.Compared with the optimal condition when using microwave alone,the dehydration rate increased by 6.19%and 1.8%,respectively.For silicon carbide and activated carbon,the dehydration rate is the highest when the microwave irradiation time is 40s and the microwave power is 300W,which is 53%and 51.60%,respectively.Compared with the optimal condition when using microwave alone,the dehydration rate is 2.69%and 1.29%respectively.For dehydration effect,sludge pyrolysis residue>biomass coke(peanut shell)>silicon carbide>activated carbon.Based on the research on the demulsification characteristics of oil sludge,the microwave pyrolysis experiment of oil sludge was carried out to explore the dynamic change characteristics of pyrolysis yield and products over time.As the pyrolysis time increases,the yield of pyrolysis gas and pyrolysis oil gradually increases.When the pyrolysis time increases from 5min to 10min,the pyrolysis products change significantly.The content of pyrolysis carbon decreases from 22%to 13%,and the content of pyrolysis gas increases from 8.3%to 14.4%.According to the change law of pyrolysis gas,pyrolysis can be divided into four stages:the precipitation of water molecules and small molecules of volatile substances in oil sludge,the increase of pyrolysis oil content,the increase of the proportion of small molecules of pyrolysis oil products,and the decrease of the proportion of large molecules of oil.Pyrolysis gas production increased rapidly,which H2,CH4,C2H4 proportion bigger,as the secondary reaction,and proportion of CH4 fell slightly,the proportion of CO,CO2 slightly rise;After the pyrolysis time of 10min,the content of small molecule oil decreased and the content of polycyclic aromatic compounds in the pyrolysis oil increased.The main cracking reaction has been completed and the yield of each component has not changed significantly.The influence of different factors on the yield and composition of pyrolysis products was explored.When the microwave heating power increased from 300W to 700W,the content of pyrolysis carbon kept decreasing,the yield of pyrolysis oil increased from 66%to 74%,and the content of pyrolysis gas kept increasing.With the increase of microwave power,the degree of pyrolysis further deepened.When microwave power from 700W to 900W,pyrolysis gas production rate increased from 16.6%to 17.8%,with the increase of power,in the pyrolysis gas CH4,H2 content increasing;The proportion of small molecular substances in pyrolysis oil increases.With the increase of microwave heating power,the ratio of polycyclic aromatic compounds in pyrolysis oil increases.When the carrier gas velocity increased from 100mL/min to 200mL/min,the yield of pyrolysis oil and pyrolysis gas increased significantly.When the carrer gas velocity increased from 200mL/min to 300mL/min,the yield of pyrolysis products changed little.When activated carbon content from 5%to 10%,the yield of pyrolysis oil,pyrolysis gas in constant ascension,increased by 3.3%and 2.1%,respectively,when activated carbon content is increased from 10%to 15%,the content of pyrolysis oil fell by 1.2%,the content of pyrolysis gas increased by 2.4%,with activated carbon levels continue to rise,the pyrolysis oil,pyrolytic carbon content continues to decline,pyrolysis gas content increased;After adding activated carbon,the CH4,H2 content in pyrolysis gas with increased with the increase of adding amount of activated carbon,C2H4,CO content after rising with the increase of carbon content to fall;After the addition of solid residue,the content of liquid phase products increased by about 1%when the addition ratio increased from 0%to 10%.After increasing from 10%to 20%,the liquid phase product content decreased by 2%.At the same time,the content of the gas phase product increased by about 2%,after joining biochar,CH4,CO content is more noticeable change,when the adding amount of biomass tar from 5%to 20%,the content of CH4 increased by 10%;In terms of the quality of pyrolysis oil,the effect of adding activated carbon is the best,followed by that of solid residue and biomass coke.In this paper,by studying the changes of the process characteristics of the three phase products of oil sludge demulsification pretreatment and oil sludge pyrolysis,as well as the factors affecting microwave pyrolysis,the characteristics of microwave pyrolysis process and the changes of the products are revealed,so as to provide basis and design guidance for the subsequent pyrolysis process and promote the technological progress of oil sludge resource utilization.