CAJ | 학술논문

甲烷原位富集是通过厌氧发酵直接制取生物天然气的一项技术，该技术通过将溶解在发酵液中的 CO2持续脱除达到产出高甲烷含量沼气的目的，影响甲烷原位富集效果的关键是CO2的脱除方式。为了研究和探索适宜甲烷原位富集的脱碳方式，该文研究了空气吹脱、真空脱碳和超声波辅助空气吹脱3种脱碳方式对甲烷原位富集的影响。采用葡萄糖配制的人工废水为原料，在中温38℃条件下开展了厌氧发酵甲烷原位富集试验。结果表明，空气吹脱除碳方式下，发酵液日循环比率（daily recycle rates，DRR）为0.2和0.4 L/(L·d)时，所产沼气中甲烷平均体积分数分别达到了76.4%和78.3%，比对照组的65.4%分别提高了17%和20%；DRR为0.2 L/(L·d)空气吹脱组的累积甲烷产量与对照组相近，但DRR为0.4 L/(L·d)空气吹脱组累积甲烷产量比对照下降了15%，原因是吹脱提高了溶解氧含量并导致了抑制作用；在真空度0.1 MPa下真空脱碳组沼气甲烷体积分数比DRR为0.2 L/(L·d)的空气吹脱组下降了4.6%。超声波辅助空气吹脱试验结果表明，超声波可以加强CO2吹脱效果，在前3 min内其脱除CO2的速度比空气吹脱组提高了32%，同时经过21 min吹脱经其处理发酵液中游离态CO2的脱除量比单独空气吹脱组提高了29.8%。总之，控制空气吹脱携带溶解氧对厌氧发酵的抑制作用是甲烷原位富集工艺需重点考虑的因素，超声波对CO2空气吹脱能产生明显的促进作用，值得深入研究。
갑완원위부집시통과염양발효직접제취생물천연기적일항기술，해기술통과장용해재발효액중적 CO2지속탈제체도산출고갑완함량소기적목적，영향갑완원위부집효과적관건시CO2적탈제방식。위료연구화탐색괄의갑완원위부집적탈탄방식，해문연구료공기취탈、진공탈탄화초성파보조공기취탈3충탈탄방식대갑완원위부집적영향。채용포도당배제적인공폐수위원료，재중온38℃조건하개전료염양발효갑완원위부집시험。결과표명，공기취탈제탄방식하，발효액일순배비솔（daily recycle rates，DRR）위0.2화0.4 L/(L·d)시，소산소기중갑완평균체적분수분별체도료76.4%화78.3%，비대조조적65.4%분별제고료17%화20%；DRR위0.2 L/(L·d)공기취탈조적루적갑완산량여대조조상근，단DRR위0.4 L/(L·d)공기취탈조루적갑완산량비대조하강료15%，원인시취탈제고료용해양함량병도치료억제작용；재진공도0.1 MPa하진공탈탄조소기갑완체적분수비DRR위0.2 L/(L·d)적공기취탈조하강료4.6%。초성파보조공기취탈시험결과표명，초성파가이가강CO2취탈효과，재전3 min내기탈제CO2적속도비공기취탈조제고료32%，동시경과21 min취탈경기처리발효액중유리태CO2적탈제량비단독공기취탈조제고료29.8%。총지，공제공기취탈휴대용해양대염양발효적억제작용시갑완원위부집공예수중점고필적인소，초성파대CO2공기취탈능산생명현적촉진작용，치득심입연구。
In situ methane enrichment method can increase the methane content in biogas, which is a cost-effective technology used for producing bio-methane compared with conventional biogas upgrading technologies. During the in situ methane enrichment process, liquid stream from the anaerobic digester is circulated through a CO2-desorption unit and then returned back to the digester. The most important step in this process is CO2 desorption. In this study we evaluated the effects of different CO2 desorption techniques. Three CO2 desorption methods including air stripping, vacuum extraction and ultrasonic-auxiliary air stripping were studied through experiments. The experiments were conducted under mesophilic (38℃) anaerobic digestion by using synthetic wastewater with glucose and supplemental nutrients. The experimental apparatus included one anaerobic digester with volume of 1 500 mL and two CO2-desorption bottles with volume of 500 mL used for air stripping and vacuum extraction respectively. The results showed that the average volume fraction of methane in biogas reached 76.4%and 78.3%for the air stripping groups (aeration fluxes of 205 mL/min and daily stripping time of 30min), and increased by 17%and 20%compared to the control (65.4%) with the daily recycle rates of liquid stream (DRR) at 0.2 L/(L·d) and 0.4 L/(L·d), respectively. The cumulative methane production is similar to controlled one for the group with DRR of 0.2 L/(L·d). But the cumulative methane production decreased by 15%compared with control one for the group with DRR of 0.4 L/(L·d). In situ methane enrichment effect of the group of CO2 vacuum extraction with 0.1 MPa vacuum maintaining 5 min was slightly lower than that of the air stripping group with aeration flux at 205 mL/min, daily stripping time 20min and DDR 0.2 L/(L·d). The methane volume fraction of biogas in the first group was decreased by 4.6% compared to that of the second group. However, the difference is not significant (P>0.05). The results of experiment of ultrasonic-auxiliary air stripping, with aeration flux of 100 mL/min, daily stripping time of 21 min and ultrasonic frequency of 40 kHz, show that ultrasonic wave can accelerate CO2 air stripping, especially when the concentration of CO2 in the liquid was high. During the initial 3 min of stripping the CO2 removing rate of ultrasonic-auxiliary air stripping group was advanced by 32%compared to air stripping group. The total free CO2 removal amount from the liquid stream was increased by 29.8% compared to air stripping group during the whole stripping time of 21 min. Furthermore, ultrasonic wave has potential advantages on CO2 removing by lowering pH of liquid and increasing anaerobic digestion efficiency through decomposing many complex organic compounds. Therefore, the effect of air stripping and vacuum extraction on methane enrichment has no significance difference, but vacuum extraction has no problem of oxygen inhibition, the control of which is vital for successful running of in situ methane enrichment process of air stripping. Ultrasonic-auxiliary air stripping method has advantages for CO2 desorption due to its unique characteristics of lowering pH, degrading complex compounds and increasing CO2 removal.