National Research Council of Italy, Institute of Atmospheric Pollution Research, via Salaria 29,300, 00015 Monterotondo, Italy.
National Research Council of Italy, Institute of Atmospheric Pollution Research, via Salaria 29,300, 00015 Monterotondo, Italy.
J Environ Manage. 2018 Jul 1;217:288-296. doi: 10.1016/j.jenvman.2018.03.113. Epub 2018 Apr 5.
This study investigates the conversion of sewage sludge from wastewater treatment plants (WWTP) into biomethane for automotive fuel or grid injection. A prototype plant was monitored in Northern Italy, based on vacuum swing adsorption (VSA) on synthetic zeolite 13×: this biogas upgrading method is similar to pressure swing adsorption (PSA) and commonly used for other kinds of biomass. Measurements of biogas inlet, biomethane outlet and off-gas were performed including CH, CO, CO, H, O, N, HCl, HF, NH, HS and volatile organic compounds (VOCs). Critical levels were observed in the biogas for of HS and HCl, whose concentrations were 1570 and 26.8 mg m, respectively. On the other hand, the concentration of halogenated VOCs (including tetrachloroethylene and traces of perfluoroalkilated substances, PFAS) and mercaptans were relatively low. A simultaneous and reversible adsorption on 13× zeolite was achieved for HS and CO, and carbon filters played a minor role in desulfurisation. The presence of HCl is due to clarifying agents, and its removal is necessary in order to meet the required biomethane characteristics: an additional carbon-supported basic adsorbent was successfully used to remove this contaminant. This study also highlights the interference of CO towards HCl if sampling is performed in compliance with the new EU standard for biomethane. High total volatile silicon (TVS) was confirmed in sewage sludge biogas, with a major contribution of siloxane D5: the suitability of this compound as an indicator of total siloxanes is discussed. Results demonstrate that volatile methyl siloxanes (VMS) do not represent a critical issue for the VSA upgrading methodology.
本研究探讨了将污水处理厂（WWTP）的污泥转化为生物甲烷，用于汽车燃料或电网注入。该原型工厂位于意大利北部，基于合成沸石 13×的真空变压吸附（VSA）进行监测：这种沼气升级方法类似于变压吸附（PSA），常用于其他类型的生物质。对沼气入口、生物甲烷出口和废气进行了测量，包括 CH、CO、CO、H、O、N、HCl、HF、NH、HS 和挥发性有机化合物（VOCs）。在沼气中观察到 HS 和 HCl 的浓度达到了临界水平，分别为 1570 和 26.8 mg/m³。另一方面，卤代 VOCs（包括四氯乙烯和痕量全氟烷基化物质 PFAS）和硫醇的浓度相对较低。HS 和 CO 可在 13×沸石上同时实现可逆吸附，而碳过滤器在脱硫方面作用较小。HCl 的存在是由于澄清剂，为了满足所需的生物甲烷特性，必须去除 HCl：成功使用了一种额外的载碳碱性吸附剂来去除这种污染物。本研究还强调了如果按照新的欧盟生物甲烷标准进行采样，CO 对 HCl 的干扰。在污水污泥沼气中确认了高总挥发性硅（TVS），其中硅氧烷 D5 的贡献较大：讨论了该化合物作为总硅氧烷指标的适用性。结果表明，挥发性甲基硅氧烷（VMS）对于 VSA 升级方法不是一个关键问题。
