Siloxanes in Biogas: Approaches of Sampling Procedure and GC-MS Method Determination

A new approach of siloxane sampling based on impinger, micro-impinger, adsorption on active carbon, and direct TedlarBag methods followed by gas chromatography-mass spectrometry (GC-MS) was developed for the analysis of three linear (L2–L4) and four cyclic (D3–D5) volatile methyl siloxanes (VMSs). Three kinds of organic liquid-medium characterized by different polarities, namely acetone, methanol, and d-decane as siloxanes trap were arranged in the experiment which is widely discussed below. Thus, the GC-MS equipped with SUPELCOWAX-10 capillary column was employed to perform monitoring of VMS content in the analyzed biogas samples originating from landfill, wastewater treatment plants, and agriculture biogas plants. In all samples that have undergone the analysis, cyclic and linear VMSs were found in quantities exceeding 107.9 and 3.8 mg/m³, respectively. Significant differences between siloxanes concentrations depending on biogas origin were observed. Moreover, the high range of linearity (0.1 to 70.06 mg/m³), low LoD (0.01 mg/m³), low LoQ (0.04 mg/m³), and high recovery (244.1%) indicate that the procedure and can be applied in sensitive analyses of silica biogas contaminants. In addition to the above, the impinger method of sampling performed better than active-carbon Tube and TedlarBag, particularly for quantifying low concentrations of siloxanes. Overall, the evaluation of sampling methods for biogas collection simplified the analytical procedure by reducing the procedural steps, avoiding the use of solvents, as well as demonstrated its applicability for the testing of biogas quality.     

稀土化合物对褐煤产甲烷接种物驯化的影响

为了提高褐煤转化为生物燃气得率、扩大煤制天然气煤种资源,从活性污泥出发,利用褐煤作为碳源,驯化能分解褐煤的接种物,通过添加不同浓度的稀土化合物对接种物进行选择性培养,分析接种物驯化过程中碱度、COD浓度、辅酶F420质量摩尔浓度和产气量的变化。研究结果表明:在50℃培养温度下,每天进料量为250目褐煤1 g,接种物驯化30 d,添加0.25 g·L^-1 CeCl3,在第21 d辅酶F420质量摩尔浓度达到最高1.400×10^-3 mmol·g^-1,累积产气量250.33 mL,COD去除率达81.56%,碱度增加了49.72%;添加0.25 g·L^-1 LaCl3,在第27 d辅酶F420质量摩尔浓度的最高值1.479×10^-3 mmol·g^-1,累积产气量248.53 mL,碱度增加了52.68%,均高于不添加稀土化合物的空白对照组,揭示添加稀土化合物驯化接种物有助于富集厌氧微生物,尤其是产甲烷菌,接种物活性污泥的TS,VS值在驯化后均增加,说明接种物活性污泥经过驯化后有助于降解褐煤产甲烷。