Department of Chemical Engineering, National Institute of Technology, Durgapur-713209, West Bengal, India.
Environmental Engineering Group, CSIR-Central Mechanical Engineering Research Institute, Durgapur-713209, West Bengal, India.
J Environ Manage. 2019 Jun 1;239:395-406. doi: 10.1016/j.jenvman.2019.03.067. Epub 2019 Mar 28.
Continuous generation of plastic waste has prompted substantial research efforts in its utilization as a feedstock for energy generation. Pyrolysis has emerged as one of the best waste management technique for energy extraction from the plastic waste. The objective of this work is to investigate the effect of operating temperature on the liquid product yields in the pyrolysis process by non-isothermal heating. Non-catalytic thermal pyrolysis of waste polyethylene (PE) [high density polyethylene (HDPE)], waste polypropene (PP), waste polystyrene (PS), waste polyethylene terephthalate (PET) and mixed plastic waste (MPW) was carried out in a non-sweeping atmosphere in a semi-batch reactor at four different temperatures 450, 500, 550, and 600 °C. The minimum degradation temperature of the mixed and individual plastics was obtained using a thermogravimetric apparatus (TGA) at a heating rate of 20C/min. The TGA results show that all plastics degrade in a single step and the degradation temperatures of PS > PET > PP > HDPE, while mixed plastic degradation indicates two distinct degradation steps. Further, a waste polymer shows a lower degradation temperature than the virgin polymer. The degradation of HDPE is found to produce the maximum oil yield with minimum solid residue. The degradation of PET results in the highest amount of solid and benzoic acid as crystals and gas with no oil. Degradation of mixed plastic causes oil yield in the intermediate range of pyrolysis of individual plastic wastes. Overall, 500 °C is observed to be an optimum temperature for the recovery of low-density pyrolytic oil with the highest liquid yield. The degradation of PE and PP is found to be caused by random chain scission followed by inter and intramolecular hydrogen transfer. The degradation of PS occurs by side elimination or end chain scission followed by β-scission mechanism. The degradation of mix plastics results from random chain scission followed by β-scission mechanism. The effect of temperature on oil and gas recovery as well as recovery time was also assessed.
不断产生的塑料废物促使人们大量研究如何将其用作原料来发电。热解作为一种最佳的废物管理技术，可从塑料废物中提取能量。本工作的目的是通过非等温加热研究操作温度对塑料废物热解过程中液体产物产率的影响。在非吹扫气氛中，在半分批式反应器中，在 450、500、550 和 600°C 的四个不同温度下，对废聚乙烯（PE）[高密度聚乙烯（HDPE）]、废聚丙烯（PP）、废聚苯乙烯（PS）、废聚对苯二甲酸乙二醇酯（PET）和混合塑料废物（MPW）进行非催化热解。使用热重分析仪（TGA）在 20°C/min 的加热速率下获得混合和单独塑料的最小降解温度。TGA 结果表明，所有塑料均在一步中降解，且 PS>PET>PP>HDPE 的降解温度升高，而混合塑料降解则表明有两个不同的降解阶段。此外，废聚合物的降解温度低于原始聚合物。HDPE 的降解产生了最大量的油和最小量的固体残渣。PET 的降解导致最高量的固体和苯甲酸晶体以及无油气体。混合塑料的降解导致单独塑料热解的中间范围内的油产率。总体而言，观察到 500°C 是回收低密度热解油的最佳温度，其液体产率最高。PE 和 PP 的降解被发现是由随机链断裂引起的，然后是分子内和分子间的氢转移。PS 的降解是通过侧消除或末端链断裂引起的β-断裂机制。混合塑料的降解是由随机链断裂引起的，然后是β-断裂机制。还评估了温度对油和气回收以及回收时间的影响。
