| As the second largest oil resource consuming country in the world,the petroleum industry of China is developing rapidly,and a large amount of oily sludge is produced inevitably.Oily sludge is a highly hazardous solid waste that has been included in the National "Dangerous Waste List" and must be disposed reasonably.The contents of water and oil in the refinery oily sludge are high and exist in the form of emulsification.Demulsification is an effective way to greatly reduce the amount of oily sludge,and effectively recover the oil resources with high economic value from oily sludge.As a mature and widely used demulsification technology,centrifugation can achieve oil-water separation rapidly to a certain extent.However,the demulsification efficiency of centrifugation is low,so a suitable pre-demulsification method before centrifugation is necessary to strengthen the demulsification efficiency.Due to the unique advantages of microwave demulsification,this paper proposes a demulsification method that pre-demulsified by microwave at first,then dehydrated by centrifugation for refinery oily sludge,and mainly carried out experimental research on the three aspects of the microwave demulsification characteristics,mechanism and analysis of demulsification products of oily sludge.The specific research content and main conclusions are as follows:Based on the analysis of the physical and chemical properties of oily sludge,a series of centrifugal demulsification property experiments were carried out.The emulsification type and basic physical and chemical characteristics parameters of the refinery oily sludge used in this paper were tested,and it was found that the type of oily sludge used was water-in-oil,which is more difficult for demulsification.The thermogravimetric characteristic of the oily sludge were analyzed.The results showed that the demulsification temperature of the oily sludge should be controlled below 77?.The characteristics of centrifugal dehydration of oily sludge were explored,and it was found that as the centrifugal speed,time and temperature increased,demulsification efficiency of oily sludge increased at first,then almost unchanged.Compared with the centrifugation time,the centrifugal speed has a greater influence on the centrifugal dewatering effect of oily sludge.The process and characteristics of microwave demulsification of oily sludge were studied.It was found that microwave heating can significantly reduce the Zeta potential of oily sludge,and the Zeta potential gradually decreased with the increased power.The effects of temperature,power and stirring time on the microwave demulsification efficiency of oily sludge were explored and the significance of each factor was analyzed through orthogonal experiments.The demulsification efficiency of oily sludge increased at first,then decreased with the increase of microwave heating temperature and power,while it increased at first,then almost unchanged with the increase of stirring time.The order of influence was:temperature>power>stirring time.The demulsification process of the oily sludge heated by microwave irradiation and water bath were compared from different angles,the results showed that compared with conventional heating,due to the combined effect of thermal and non-thermal effects,microwave heating not only significantly improves the demulsification efficiency of sludge(25.4%),but also can reduce the demulsification temperature(>40?),the demulsification time(>95%),and the centrifugal speed(-36.7%).The effects of different additives on the microwave demulsification of oily sludge were explored and the overall demulsification efficiency of oily sludge was compared.It was found that the pyrolysis residue of oily sludge is clean and low consumption,and can effectively enhance the microwave demulsification effect of the oily sludge.The composition and content of the demulsification products in each layer of oily sludge under different demulsification conditions were analyzed.The results showed that the demulsified oily sludge is divided into three layers.The upper is mainly composed of oil,the middle is mainly water,and the lower is mainly moisture and solid.Among them,the mass ratio of the centrifugal phase products in the middle is the highest(>50%),the lower is the second,and the upper is the smallest.The composition of the oil in the centrifugal phase products of each layer was analyzed,and it was found that the main components of the three-layer centrifugal oil phase are gasoline,diesel and heavy oil,respectively.The oil in the media can be separated and recovered by standing and the recovery rate of oil is 38.3%under the best demulsification condition,and 91.02%of the recovered oil products is diesel component,of which the content of each ingredient all meet the national refined oil standard,and have the potential for application.Based on the systematic research of the demulsification of oily sludge,a technical route for the demulsification of oily sludge is proposed.According to the analysis results of demulsification products,the two-stage demulsification process that 0.5%pyrolysis residue is used to assist the primary microwave demulsification and centrifugal dehydration,then conventional heating demulsification and centrifugal dehydration was carried out.The overall dehydration rate is up to 77.2%under this process.At the same time,the energy consumption of different demulsification processes were calculated and the energy consumption of direct pyrolysis and pyrolysis after demulsification were compared.It was found that the energy consumption of the two-stage demulsification process is at a low level among many similar demulsification processes and has better economy.Compared with the direct pyrolysis,the total energy consumption of oily sludge which was pyrolysised after demulsification was reduced by about 56.1%.It can be seen that demulsification is of great significance for the utilization of oil sludge. |
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