Cheng Shan, Gao Xiangpeng, Cao Liwen, Wang Quanbin, Qiao Yu
State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei 430074, China.
School of Energy and Power Engineering, Key Laboratory of Renewable Energy Electric-Technology of Hunan Province, Changsha University of Science & Technology, 960, 2nd Section, Wanjiali RD (S), Changsha, Hunan 410114, China.
ACS Omega. 2020 Dec 17;5(51):33445-33454. doi: 10.1021/acsomega.0c05426. eCollection 2020 Dec 29.
Self-sustaining smoldering combustion is a promising technology for treating sewage sludge from wastewater treatment plants because of its low energy inputs. Proper use or disposal of the resulting ashes requires thorough characterization of their properties, including the content of total organic carbon (TOC). Here, we develop a two-step method for quantifying TOC in the raw ashes from sewage sludge smoldering combustion. The first step is to thermally treat the raw ashes at 500 °C in N for 1 h, followed by ultimate analysis of both the raw ashes and the thermally treated ashes. This enables the quantification of carbon released during thermal treatment. The second step is nonisothermal thermogravimetric analysis (TGA) of the thermally treated ashes, in which the samples are heated to 900 °C at 10 °C/min in air. The weight losses at 310-500 °C are confirmed to be caused by organic carbon oxidation, allowing us to determine the contents of carbon retained in the thermally treated ashes. The sums of these two portions of carbon represent the contents of TOC in the raw ashes, which are ∼0.85-6.52 wt % (dry basis), depending on their locations and particle sizes. The two-step (thermal treatment-TGA) method is validated via a method that includes acid washing of the thermally treated ashes, ultimate analysis of the acid-washed ashes, and TOC analysis of the leachates. The two-step method is simple and accurate and, importantly, provides thorough information on the thermal behavior of the raw and thermally treated ashes.
自持阴燃燃烧是一种很有前景的处理污水处理厂污泥的技术，因为其能量输入较低。妥善使用或处置产生的灰烬需要全面表征其性质，包括总有机碳（TOC）含量。在此，我们开发了一种两步法来定量污水污泥阴燃燃烧产生的原始灰烬中的TOC。第一步是在氮气中将原始灰烬于500℃热处理1小时，然后对原始灰烬和热处理后的灰烬进行元素分析。这能够定量热处理过程中释放的碳。第二步是对热处理后的灰烬进行非等温热重分析（TGA），其中样品在空气中以10℃/分钟的速率加热至900℃。确认在310 - 500℃的重量损失是由有机碳氧化引起的，从而使我们能够确定保留在热处理后灰烬中的碳含量。这两部分碳的总和代表原始灰烬中TOC的含量，其范围为约0.85 - 6.52 wt%（干基），具体取决于它们的位置和粒径。通过一种包括对热处理后的灰烬进行酸洗、对酸洗后的灰烬进行元素分析以及对浸出液进行TOC分析的方法，验证了两步法（热处理 - TGA）。该两步法简单准确，重要的是，它提供了有关原始和热处理后灰烬热行为的全面信息。
