Adsorption separation performance of different absorbents for biogas decarbonization upgrading

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1 46 9 ( ) Vol.46 No Journal of Central South University (Science and Technology) Sep DOI: /j.issn ( ) 5A 13X CO 2 /CH 4 CO 2 /CH 4 13X (4.5 kpa) (300 ) 13X CO mmol/g CO 2 /CH A CO 2 13X 40% X511 O A (2015) Adsorption separation performance of different absorbents for biogas decarbonization upgrading WANG Zhixiang, YI Honghong, TANG Xiaolong, ZHAO Shunzheng, ZUO Yanran, GAO Fengyu, ZHANG Bowen (School of Civil and Environmental Engineering, University of Science and Technology Beijing, Beijing , China) Abstract: Dynamic adsorption experiments were carried out using coconut shell activated carbon, with 5A and 13X molecular sieves as adsorbents and gas mixtures with different CO 2 /CH 4 volume ratios as methane simulation. Vacuum (4.5 kpa) desorption and thermal desorption (300 ) on fully adsorbed 13X molecular sieve were carried out. The results show that the breakthrough adsorption amount of CO 2 on 13X molecular sieve is 3.21 mmol/g, and the separation factor of CO 2 /CH 4 gas mixtures is up to 10, significantly higher than those of the 5A molecular sieve and coconut shell activated carbon at room temperature and pressure. The breakthrough time becomes smaller, which accompanies the decrease of CO 2 partial pressure, and the decrease rate of adsorption amount is larger than that of partial pressure. The adsorption separation performance of vacuum desorption regeneration of 13X molecular sieve can only be restored to about 40% of the original one, while thermal desorption regeneration can achieve better results. Key words: activated carbon; molecular sieve; adsorption; breakthrough curve; regeneration (Foundation item) ( ) ( ) (Project( ) supported by the Program for New Century Excellent Talents in Chinese University; Project( ) supported by the Fundamental Research Funds for the Central Universities) yhhtxl@126.com

2 3536 ( ) 46 [1] CH 4 55%~65% CO 2 30%~ 40% CO 2 CH 4 CO 2 CH 4 [2 3] [4] [4 5] [6 7] 5A 13X A X [8] CO 2 /CH 4 5%( ) 5%( ) 5%( ) Remy [9] Li-KFI 4 MPa 303 K CO mmol/g Na-KFI 18 Shang [10] CO 2 /CH 4 (KCHA) 273 K 100 kpa 93 CO 2 /CH 4 5A 13X (CH 4 CO 2 V(CH 4 ):V(CO 2 )=3:2) ~380 μm 5A 13X ( 3~ 5 mm 250~380 μm) h 12 h 300 CH 4 CO 2 N 2 ( % % %) 1.2 (TCD) (GC 4000A ) (D08 4E ) (SHB A) (AL204) (101 3AB ) (SX G07123) (AL204) (NS 1) (NS YB05C) ( ) Fig. 1 Flow chart of experimental setup for dynamic adsorption measurements (fix bed) 10 mm 200 mm CH 4 CO 2 ( ) (TCD) (GC) ( 5%) [11]

3 [8] (α ) ( x α ij = ( x A A / xb) / x ) x A x B i j CO 2 CH CH 4 CO 2 3:2 1 g 5A 13X ml/min V(CH 4 )/V(CO 2 )=3:2 1 CH 4, 13X 2 CH 4, 5A 3 CH 4, YAC 4 CO 2, 13X 5 CO 2, 5A 6 CO 2, YAC 2 CO 2 /CH 4 (YAC) 5A 13X Fig. 2 Breakthrough curves of CH 4 /CO 2 gas mixture on coconut shell activated carbon, 5A molecular sieve and 13X molecular sieve 2 3 CO 2 0 CO 2 CH 4 3 CH 4 100% (YAC) 5A 13X CO 2 CH 4 5A B i j 13X YAC 5A 3 CO CO 2 Table 1 Breakthrough adsorption amount of CO 2 and separation factors of gas mixture on different adsorbents /(mmol g 1 ) YAC A X X CO 2 CO 2 /CH 4 5A 13X CO 2 /CH 4 2 1) 2~3 nm 1 nm CO 2 CH nm 0.38 nm [12 13] CO 2 CO 2 CH 4 [14] 5A 13X 5A 0.4~0.5 nm 13X 0.9~1.0 nm CO 2 CH 4 2) CO 2 CH 4 CO 2 CO 2 [15] CO 2 CO 2 /CH X CH 4 CO 2 3:2 9:1 1 g CO 2 /CH 4 13X CH 4 CO 2 CO 2 CO 2 13X

4 3538 ( ) ml/min 1 CH 4 V(CH 4 ):V(CO 2 )=3:2 2 CH 4 V(CH 4 ):V(CO 2 )=9:1 3 CO 2 V(CH 4 ):V(CO 2 )=3:2 4 CO 2 V(CH 4 ):V(CO 2 )=9:1 3 CO 2 /CH 4 13X Fig. 3 Breakthrough curves of CO 2 /CH 4 gas mixture on 13X molecular sieve 1 CH 4 13X 2 CH 4 13X-TD 3 CH 4 13X-VD 4 CO 2 13X 5 CO 2 13X-TD 6 CO 2 13X-VD 4 CO 2 /CH 4 13X Fig. 4 Breakthrough curves of CO 2 /CH 4 gas mixture on Vacuum desorption 13X and Thermal desorption 13X CO 2 [16 17] [18] X 2 1 g 13X CH 4 CO 2 12 ml/min 3:2 4.5 kpa 13X 13X-VD 13X 5 /min h 13X-TD CH 4 CO 2 3:2 1 g (4.5 kpa) 13X 13X-VD (300 ) 13X 13X-TD X 13X [10, 19] 13X CO 2 CH 4 CO 2 CH 4 CO 2 CH kpa 13X CO 2 CH CO 2 CH 4 CO 2 CH 4 3 1) 3 CO 2 CO 2 /CH 4 13X 5A YAC 13X CO mmol/g CO 2 /CH ) CO 2 CO 2 3) (4.5 kpa) (300 ) 2 (300 ) 13X

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