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有机固体废弃物经厌氧发酵处理后可产生生物质能源,是未来固废处理处置技术碳减排的主要发展方向之一。餐厨垃圾和城市污泥都属于有机固体废物。截至2018年,我国餐厨垃圾的年产量超过了1.0×108 t[1],餐厨垃圾中富含淀粉、脂类、蛋白质及纤维素等有机物,对其进行生物转化后再利用已成为其主要处理方式。城市污泥是城镇污水处理厂的副产物,随着污水处理率的提高,城市污泥产生量亦随之逐年递增[2]。因此,被逐渐淘汰的填埋处理方式和综合成本较高的焚烧处理处置方式,已不能满足对城市污泥处理处置的节能减排要求[3]。在碳中和背景下,将这些有机固废进行厌氧发酵以获取生物质能源,符合节能降耗及资源回收的目标[4]。
氢气是清洁能源,可利用范围很广。氢气产于厌氧发酵的初级阶段,但通常产氢效率不高。为提高产氢率,相对早期的研究集中在污泥不同方式的预处理方面[5-7]。目前,已有采用添加铁刨花促进厌氧发酵产氢的报道[8]。近年来,有关铁系物对厌氧发酵产甲烷影响的研究越来越得到关注,相关报道分别集中在零价铁或三价、二价铁方面,这主要是铁元素在系统中的多重作用导致[9-16]。截至目前,这些研究已取得较理想的效果[8,17-18]。因为甲烷是从厌氧发酵第二阶段的产氢产乙酸转化而来,因此,提高第二阶段的产氢产酸量,才能有助于提高甲烷产量。然而,上述研究仅针对厌氧产沼气方面,而对产氢的效果和机理研究较少[18-19]。此外,目前还尚无多价态铁复合材料对厌氧发酵产氢的研究报道。
为提高有机固废发酵产氢效率,基于前期研究基础[20-22],本实验利用机械加工厂的废弃铁刨花制备了一种新型复合铁材料(FE/FEO),探讨FE/FEO材料对城市污泥与餐厨垃圾混合固废的厌氧发酵产氢作用;并考察其厌氧发酵的产氢效果,分析厌氧发酵过程中各种指标的变化,并对制备的FE/FEO材料的形貌、成分进行了测试,最终对其厌氧发酵的作用进行了阐述。本研究拟为提高厌氧发酵产氢方面提供新技术和数据积累。
复合铁添加物对混合有机固废厌氧产氢的影响
Effects of iron filings additives on anaerobic hydrogen production from mixed organic solid wastes
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摘要: 将城镇污水处理厂的城市污泥与餐厨垃圾混合后,经厌氧消化处理后可产生能源气体氢气,从而达到资源化利用的目的。废铁屑是机械加工厂的固体废弃物,将其处理后可得到一种新型复合铁材料(FE/FEO)。将城市污泥和餐厨垃圾预处理后按体积比1∶1比例混合,分别等分放入2个反应器中,一个投加FE/FEO粉末作为为FE/FEO组,另一个不加FE/FEO作为对照组,考察了FE/FEO对上述混合有机固废厌氧产氢的影响。结果表明,在厌氧反应的24 h内,FE/FEO组的最大氢气体积分数为61.4%,比不加FE/FEO的对照组增加了15%;FE/FEO组的累积产氢率和最大产氢率分别为49.0和22.7 L·kg−1(以1 kg挥发性有机固体所能产生的氢气体积计),比对照组分别增加了56 %和59%。FE/FEO组的亚铁离子质量浓度在第24 h达到最大,即109.8 mg·L−1。FE/FEO组产生的挥发性有机酸为2 675 mg·L−1,比对照组提高了15%。FE/FEO粉末中不仅含有零价铁、氧化亚铁,还有针孔状α-FeOOH,其结构松散、比表面积大,可对厌氧发酵系统中的微生物菌群起到支撑骨架作用。本研究结果可为提高有机固废厌氧发酵产氢效率提供参考。Abstract: Mixed wastes of municipal sludge from urban wastewater treatment plant (WWTPs) and kitchen waste from catering industry could be utilized to produce biomass energy gas hydrogen by anaerobic digestion process. Iron scraps, solid waste from mechanical processing plants, was treated to iron-containing FE/FEO powder in this paper. After pretreatment, mixing municipal sludge mixed with the same amount of kitchen waste (by the ratio of 1∶1), and then equally divided into two reactors. FE/FEO material was added to one of the anaerobic reactors as FE/FEO group while the other one without FE/FEO as the control group. The effect of FE/FEO on the rate of yield hydrogen by anaerobic fermentation process for the mixed organic solid waste was investigated. The results showed that the maximum hydrogen volume fraction of FE/FEO group was 61.4%, which was 15% higher than that of the control group, while cumulative hydrogen yield and the maximum yield of daily hydrogen of FE/FEO group were 49. 0 and 22.7 L·kg−1 (based on the volume of hydrogen produced by 1 kg volatile organic solid) within 24 hours, respectively, which were 56% and 59% higher that of the control group, respectively. The content of Fe2+ in the FE/FEO group reached a maximum value of 109.8 mg·L−1 at the 24th hour; while the content of volatile organic acid by 2 675 mg·L−1 was 15% higher than that of the control group during 24 h. It is found that FE/FEO powder not only contains elemental Fe and ferrous oxide, but also pinhole α-FeOOH, which increases the specific surface area and plays an important role as the loose structure frame of the microbes in the anaerobic system. Therefore, the addition of FE/FEO plays a promoting role in hydrogen production by anaerobic fermentation process. The study can provide a reference for improving the hydrogen production by anaerobic fermentation process for organic solid wastes.
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Key words:
- iron scraps /
- anaerobic digestion /
- production of hydrogen /
- municipal sludge /
- food waste
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表 1 混合有机固废及其物料的理化指标
Table 1. Physical and chemical indexes of each material
供试材料 pH 含固率/% VS/(g·L−1) TS/(g·L−1) 餐厨垃圾 6.03 22.97 219.10 228.00 城市污泥 11.45 3.05 23.91 32.75 混合有机固废 9.06 4.34 31.57 39.36 -
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