Thermally Extruding Of Oily Sludge And Biomass For Co-producing Of Pellet Fuel And Purified Oil

Oily sludge is a typical waste produced from petrochemical industry and a kind of hazardous waste.Because the stable three-phase system(water-oil-solid)of oily sludge is difficult to be destroyed,oily sludge has not been effectively treated.The hazardous s of oily sludge mainly come from the oil components.By recovering oil,the harmlessness and resource utilization of oily sludge can be accomplished.However,the high-water content and high stability are two major limiting factors for the traditional treatments of oily sludge.In this paper,a method of thermally extruding of oily sludge and biomass is proposed.Biomass is added to the oily sludge,which acts as a rigid frame construction builder in the material forming process,to improve its porosity,structural rigidity and the compressive strength of the material.The material realized solid-liquid separation under the combined action of heat and pressure,obtain the pellet fuel and purified oil at the same time,and realize the high degree of resource utilization of oily sludge and biomass.The influence of the mixture ratio of oily sludge and biomass,the molding pressure and the temperature on forming process were studied.The relaxed pellet density,hardness,specific energy consumption,energy density,absorbed moisture content and particle combustion process of pellet were analyzed to explore its potential as fuel.At the same time,the SARA,GC-MS and FTIR of the crude oil and recovered oil were analyzed,and mechanism of the thermally extruding of oily sludge and biomass was elucidded.The research conclusions are listed as follows:(1)The content of moisture,oil,and solid of the oily sludge are 51.05±2.21%,28.00±1.07%,and 20.95±0.26%,respectively.The calorific value of oily sludge is 12.64±0.42MJ/kg,and the HHV of biomass is 19.35±0.16 MJ/kg.Molding is an energy-intensive process,which means the higher the energy density of the particles,the more beneficial it is for thermal conversion and applications.Compared with the calorific value of the original material,the calorific values of pellets were greatly improved,and the energy intensity is obvious,indicating that the energy density is realized by the co-molding of oily sludge and biomass,which is conducive to the application thermal conversion of pellets.(2)In the oily sludge-biomass co-molding process,oil serves as a lubricant to reduce the friction between particles and the mold,so as to reduce the specific energy consumption.Which can protect the equipment and mold,reduce the cost of equipment maintenance,and is beneficial to improve the molding efficiency.Resin,Asphaltene and other components in the oily sludge play a bonding role in the pellets.In addition,elastic deformation occurs during the process of pellets destruction,which requires a larger force to continue acting on the pellets to destroy the pellets.According to the study of co-molding experiments under different conditions in this paper,when the mixing ratio is 1:1,the molding pressure is 50 MPa,and the temperature is 150°C,the hardness,breaking energy consumption and the maximum of breaking force are the largest.And the pellet is the most stable,which is conducive to the storage and transportation of the pellets.The HHV of pellets are greatly increased and the energy intensity is obvious,which is suitable for the utilization of fuel.(3)In this paper,the actual combustion process of pellets was studied.The isothermal combustion process of pellets can be divided into heating and drying stage,volatile matter release and flame formation stage,coke and ash stage.In the volatiles release stage,the flame above the pellet gradually increases and becomes brighter,then gradually shrinks and goes out.The duration of drying stage of different pellets is almost the same,but the duration of flame is quite different.The higher the content of oily sludge,the longer the flame duration of pellet combustion,the higher the flame temperature,the greater the thermal radiation,which is conducive to the use of the pellets as fuel.The concentration of Zn,Cu and Hg in combustion residue is seriously out of standard,and stabilization treatment is required.In summary,the pellets produced by thermally extruding of oily sludge and biomass have great potential as fuel.(4)The composition of the crude oil and coupling oil was studied.It was found that the main reaction occurred during the hot pressing process is physical reaction.About 5.88% of Saturates hydrocarbon and Aromatic hydrocarbon in the oil phase were volatilized by heat.About 13.10% of the oil phase was separated from the particles caused by pressure.Compared with the crude oil,the Asphaltene content decreased obviously and the Resin content increased significantly.At the same time,about 9.02% of the oil was trapped in the particles due to the adhesion and adsorption of oil relative to solid components and biomass skeleton,in which the Resin and Asphaltene accounted for the majority.In all,it is feasible to co-producing of pellet fuel and purified oil by thermally extruding of oily sludge and biomass,which can achieve the utilization and harmlessness of oily sludge at the same time.The pellets can be utilized through thermal conversion,and the coupled oil can be further improved and utilized.