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    基于LaFeO3的废塑料分级热解–化学链气化制富氢合成气及机理

    Hydrogen-Rich Syngas Production and Mechanism via Staged Pyrolysis-Chemical Looping Gasification of Waste Plastics Based on LaFeO3

    • 摘要: 在面向“双碳”目标的废弃物资源化利用进程中,废塑料气化合成气因其富碳氢特性与负碳潜力成为新兴技术焦点。相比于传统焚烧或填埋导致碳资源耗散与二次污染,气化技术将聚烯烃类废弃物定向转化为高纯度合成气,具备低污染、经济效益高、灵活性强等优势,为废弃物高值化利用与绿氢联产提供了关键路径,在实现资源循环和减少环境污染方面有着显著效应。针对常规气化产物气品质不高、催化剂易失活等问题,提出了废塑料分级热解–化学链气化(Staged Chemical Looping Gasification,SCLG)工艺,采用溶胶凝胶法合成的典型钙钛矿LaFeO3载氧体,在固定床反应系统上开展了聚丙烯气化试验研究,考察热解温度、气化温度、LaFeO3(OC)与聚丙烯(PP)质量比对LaFeO3载氧体气化性能的影响机理。该工艺将原料和载氧体分离,能有效避免传统一段式气化工艺中催化剂易被固体残渣、焦炭和焦油污染问题,此外分级反应充分发挥了载氧体的部分氧化能力和还原金属的催化裂解能力,有效提高了合成气的产率和品质。结果表明:热解温度对气化效果的影响较小,而适当提升气化温度效果显著,合适的m(OC):m(PP)能较好地平衡氧化重整和催化裂解两步反应,具备较好的气化效果。在600 ℃热解温度、850 ℃气化温度以及m(OC):m(PP)为1∶1的反应条件下具有最佳的气化效果,此时合成气产率为143 mmol/g,碳转化率达82%,CO选择性为80%,并具有较好的循环稳定性。为废塑料资源化及高效稳定气化技术的规模化发展提供了指导。

       

      Abstract: In the process of waste resource utilization for the goal of “double carbon”, waste plastic gasification syngas has become the focus of emerging technologies due to its rich hydrocarbon characteristics and negative carbon potential. Compared with the carbon resource dissipation and secondary pollution caused by traditional incineration or landfill, gasification technology converts polyolefin waste into high-purity syngas, which has the advantages of low pollution, high economic benefits and strong flexibility. It provides a key path for high-value utilization of waste and green hydrogen co-production, and has a significant effect in realizing resource recycling and reducing environmental pollution.To address challenges such as inadequate syngas quality and catalyst deactivation in conventional gasification processes, a staged chemical looping gasification (SCLG) process is proposed. A typical perovskite-type LaFeO3 oxygen carrier, synthesized via the sol-gel method, is employed in gasification experiments using polypropylene in a fixed-bed reaction system. The influence of pyrolysis temperature, gasification temperature, and the mass ratio of LaFeO3(OC) to polypropylene (PP) on the gasification performance of the LaFeO3 oxygen carrier is systematically investigated. In this process, the feedstock and oxygen carrier are physically separated, thereby effectively avoiding issues of catalyst contamination by solid residues, char, and tar that are commonly encountered in single-stage gasification. Furthermore, the staged reaction mechanism fully utilizes the partial oxidation capacity of the oxygen carrier and the catalytic cracking ability of the reduced metal, leading to a notable improvement in both the yield and quality of syngas. Results indicate that the pyrolysis temperature exerts limited influence on gasification performance, whereas appropriately elevated gasification temperatures are found to significantly enhance the process. An optimal m(OC)∶m(PP) ratio is identified to effectively balance the two-step reactions of oxidative reforming and catalytic cracking, resulting in improved gasification outcomes. Under conditions of a pyrolysis temperature of 600 ℃, a gasification temperature of 850 ℃, and an m(OC)∶m(PP) ratio of 1∶1, the optimal gasification performance is achieved: a syngas yield of 143 mmol/g, a carbon conversion rate of 82%, CO selectivity of 80%, and satisfactory cycling stability are obtained. Guidance is provided for the scaling of efficient and stable gasification technology and the resource utilization of waste plastics.

       

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