Research On Swelling Pretreatment To Enhance Microwave Pyrolysis Characteristics Of Waste Tires

Rencently,the automobile industry has developed rapidly,and the amount of waste tires has increased year by year,which has caused serious environmental pollution and ecological damage.The recycling of waste tires is a very potential approach,but there are problems such as low efficiency,easy coking and high energy consumption during the conventional pyrolysis of waste tires.Based on the unique advantages that swelling can destroy the rubber molecular bond of waste tires and enhance the heat and mass transfer process to improve the thermal efficiency,combined with the characteristics of microwave selective volume heating,a method of microwave induced pyrolysis of waste tires which modified by swelling was proposed in this paper to explore the pyrolysis characteristics of waste tires.The swelling of waste tires,microwave pyrolysis process and the distribution of pyrolysis products were studied.First,an experimental study on the swelling characteristics of waste tires was carried out to explore the change characteristics of different factors on the swelling of waste tires.It is found that the swelling of waste tires by coal tar is effective.At the same time,the higher the temperature and the smaller the tire particle size,the better the swelling of rubber.The swelling effect of waste tires is best when the temperature is 40℃ and the particle size is 1×1cm,and the swelling degree is 1.67.In addition,it is found that microwave has a strong promoting effect on swelling.Under the action of microwave field,swelling saturation is reached at about 1.5h of microwave time,which is far lower than 60h under conventional swelling conditions,and the swelling rate is faster,which fully proves microwave can promote the swelling process.On this basis,the experimental study on the pyrolysis process of waste tire before and after swelling was carried out to explore the change rule of the pyrolysis products of waste tire with the pyrolysis time before and after swelling.First,the kinetic analysis before and after swelling was carried out,and the average apparent activation energy of waste tire pyrolysis after pure tire pyrolysis and swelling pretreatment was 60.39 kJ/mol and 43.78kJ/mol,respectively.After swelling,the activation energy of waste tire was lower and it was easier to pyrolysis.In terms of the pyrolysis three-phase yield,it was found that with the increase of pyrolysis time,the pyrolysis gas yield gradually increased.At 10min～20min,the pyrolysis oil yield increased from 36.88%to 47.13%,and the yield of pyrolysis carbon decreased from 53.36%to 39.32%.At the initial stage of pyrolysis,more small molecule gases are generated during pyrolysis.After swelling,the pyrolysis gas of waste tires is more productive and more small molecule substances are produced.The proportion of small molecule oil in the pyrolysis oil increases,and the proportion of macromolecule oil decreases.When the time increases to 30 minutes,the macromolecular gas in the pyrolysis gas cracks,the reducing atmosphere causes the increase of CO,and the polymerization of small molecular substances in the pyrolysis oil leads to the increase of macromolecular substances.After swelling,the pyrolysis degree of waste tire is deeper,and the proportion of macromolecular oil in the pyrolysis oil is higher.The pyrolysis degree of pyrolytic carbon gradually deepens with time.After swelling,the pyrolysis carbon of waste tires produces more pores,which is more conducive to subsequent treatment applications.In addition,a comparison between microwave pyrolysis and conventional pyrolysis was carried out,and it was found that the final weight loss rate of microwave pyrolysis was 56%,which was 27.3%higher than that of conventional pyrolysis,reflecting the advantages of microwave pyrolysis of waste tires.Finally,the influence of swelling on the distribution of pyrolysis products was studied.It is found that the highest pyrolysis oil yield is 48.25%at 720W,and the pyrolysis oil yield of waste tires after swelling is 67.18%,which is greatly improved.After swelling,the pyrolysis of waste tires produces more small molecules than before swelling.The proportion of macromolecular oils such as naphthalene in the pyrolysis oil increases.The volatile content of pyrolysis charcoal is 28.65%lower than that before swelling.The fixed carbon content increased,and the content of H element decreased significantly,and the C/H ratio is about 33.32%higher than before swelling,indicating that the pyrolysis of waste tires after swelling is more complete.In addition,the synergistic effect between coal tar and waste tire is explored,and it is found that the experimental value of pyrolysis oil yield of waste tire after swelling by coal tar pretreatment was 3.84,6.02 and 5.78 percentage points higher than the theoretical value of co-pyrolysis oil of coal tar and waste tire under the same proportion under different power,and the maximum value reached at 720W.Through the experiments of the influence of different swelling degrees on the yield of pyrolysis oil,it is found that when the microwave power is 720W and the swelling degree is about 1.4,the pyrolysis oil yield of waste tire was the highest,which was about 14.57%higher than that of pure waste tire.