Institute of Urban Agriculture, Chinese Academy of Agricultural Sciences, Chengdu, China; Thermochemical Conversion of Biomass Research Group, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
Thermochemical Conversion of Biomass Research Group, Ghent University, Coupure Links 653, 9000 Ghent, Belgium.
Sci Total Environ. 2020 Sep 20;736:139731. doi: 10.1016/j.scitotenv.2020.139731. Epub 2020 May 26.
Supercritical water oxidation (SCWO) is a technology that can oxidize various organic (wet) wastes into CO. Complete oxidation of specific organics with SCWO goes in tandem with tailored conditions, typically involving elevated operating temperatures, long residence times, high oxidizer-to-waste ratios, or a combination of those, which promote difficulties, e.g., corrosion. These challenges hamper the practical implementation of SCWO, albeit SCWO offers excellent oxidation efficiencies. This work proposes a novel process combining mild supercritical water oxidation (SCWO) with membrane filtration to enhance the oxidation of organics. The modified SCWO works at mild reaction conditions (i.e., 380 °C, 25 MPa and oxidizer equivalence ratios as low as 1.5) to potentially decrease the risks. The membrane filtration discards clean effluent and recycles the retentate (containing incomplete oxidized organics) back to the mild SCWO process for further oxidation, thereafter resulting in near-complete removal of organics. Fresh feed is continuously added, as in the conventional process, along with recycled retentate to guarantee the throughput of the modified SCWO process. A mixture of SCWO-resistant volatile fatty acids (TOC = 4000 mg·L) was studied to validate the proposed process. The proposed process in this study enhances the organic decomposition from 43.2% to 100% at mild conditions with only 10% capacity loss. CO was the dominant gas product with traces of CO and H. Carbon output in the gas products increased with recirculation and got close to the carbon input of the freshly added feed ultimately. The results indicated that the proposed process maximized the benefits of both technologies, which allows the development of a technological process for supercritical water oxidation, as well as a new stratagem for waste treatment.
超临界水氧化（SCWO）是一种可以将各种有机（湿）废物氧化为 CO 的技术。通过 SCWO 完全氧化特定有机物需要与定制条件相结合，通常涉及升高的操作温度、较长的停留时间、氧化剂与废物的高比值或这些条件的组合，这会带来一些困难，例如腐蚀。这些挑战阻碍了 SCWO 的实际实施，尽管 SCWO 提供了优异的氧化效率。本工作提出了一种将温和超临界水氧化（SCWO）与膜过滤相结合的新工艺，以增强有机物的氧化。改性 SCWO 在温和的反应条件下（即 380°C、25MPa 和氧化剂当量比低至 1.5）运行，以降低风险。膜过滤去除清洁的流出物，并将截留物（含有未完全氧化的有机物）循环回温和 SCWO 过程进行进一步氧化，从而导致有机物的近完全去除。新鲜进料像常规过程一样连续添加，同时添加循环截留物，以保证改性 SCWO 过程的吞吐量。研究了一种 SCWO 抗性挥发性脂肪酸（TOC=4000mg·L）的混合物，以验证所提出的工艺。本研究中提出的工艺在温和条件下将有机物分解率从 43.2%提高到 100%，仅损失 10%的能力。CO 是主要的气体产物，有痕量的 CO 和 H。随着循环的进行，气体产物中的碳输出增加，最终接近新添加进料的碳输入。结果表明，所提出的工艺最大限度地发挥了两种技术的优势，为超临界水氧化技术的发展以及废物处理的新策略提供了可能。
