An air separation unit (ASU) represents the largest overall energy consumption (about 15–20%) in a steel production facility. Therefore, improving the operating efficiency of an ASU is an effective way to achieve energy savings and emission reductions. The exergy calculation program for an air separation process is developed, and the detailed exergy calculations and analysis for an actual ASU with capacity of 40,000 Nm3/h in service at Tangshan Tangsteel Gas Co. Ltd. are performed. The results show that the molar exergy contained in oxygen is the largest among all gaseous products, liquid argon contains the largest molar exergy among all liquid products, and liquid products of the same type have larger exergy values than their gaseous equivalents. In a same condition scenario (same environmental condition, same air feed mass flow at rated load operation of the expander), increasing liquids production is an effective way to enhance the process efficiency, especially by increasing liquid argon production at the rated load operation of the expander. The object efficiency of the process from the cleaning unit to production in an actual 40,000 m3/h ASU is 46.84%, while the simple efficiency of the cold box of the ASU is 64.31%. The largest amount of exergy loss is caused by the air compressor (AC), the packed-type air cooling tower (PACT), and the molecular sieve (MS) purifier. The cryogenic ASU itself is well operated from an exergetic viewpoint. On the basis of exergy analysis conducted, this study provides a reference for the improvement of the ASU analyzed and provides a reference for ASUs in general.
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July 2015
Research-Article
Exergy Analysis for Air Separation Process Under Off-Design Conditions
Li Yao,
Li Yao
School of Metallurgical and
Ecological Engineering,
Ecological Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
;Tangshan Tangsteel Gas Co. Ltd.
,Tangshan 063016
, China
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Lige Tong,
Lige Tong
1
School of Mechanical Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
;Beijing Engineering Research Center for
Energy Saving and Environmental Protection,
e-mail: ligetongcn@163.com
Energy Saving and Environmental Protection,
University of Science and Technology Beijing
,Beijing 100083
, China
e-mail: ligetongcn@163.com
1Corresponding author.
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Aijing Zhang,
Aijing Zhang
School of Mechanical Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
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Yunfei Xie,
Yunfei Xie
School of Mechanical Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
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Jianbiao Shen,
Jianbiao Shen
School of Mechanical Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
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Huazhi Li,
Huazhi Li
School of Mechanical Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
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Li Wang,
Li Wang
School of Mechanical Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
;Beijing Engineering Research Center for
Energy Saving and Environmental Protection,
Energy Saving and Environmental Protection,
University of Science and Technology Beijing
,Beijing 100083
, China
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Shiqi Li
Shiqi Li
School of Metallurgical and
Ecological Engineering,
Ecological Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
Search for other works by this author on:
Li Yao
School of Metallurgical and
Ecological Engineering,
Ecological Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
;Tangshan Tangsteel Gas Co. Ltd.
,Tangshan 063016
, China
Lige Tong
School of Mechanical Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
;Beijing Engineering Research Center for
Energy Saving and Environmental Protection,
e-mail: ligetongcn@163.com
Energy Saving and Environmental Protection,
University of Science and Technology Beijing
,Beijing 100083
, China
e-mail: ligetongcn@163.com
Aijing Zhang
School of Mechanical Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
Yunfei Xie
School of Mechanical Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
Jianbiao Shen
School of Mechanical Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
Huazhi Li
School of Mechanical Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
Li Wang
School of Mechanical Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
;Beijing Engineering Research Center for
Energy Saving and Environmental Protection,
Energy Saving and Environmental Protection,
University of Science and Technology Beijing
,Beijing 100083
, China
Shiqi Li
School of Metallurgical and
Ecological Engineering,
Ecological Engineering,
University of Science and Technology Beijing
,Beijing 100083
, China
1Corresponding author.
Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received February 27, 2014; final manuscript received February 15, 2015; published online April 8, 2015. Assoc. Editor: Abel Hernandez-Guerrero.
J. Energy Resour. Technol. Jul 2015, 137(4): 042003 (5 pages)
Published Online: July 1, 2015
Article history
Received:
February 27, 2014
Revision Received:
February 15, 2015
Online:
April 8, 2015
Citation
Yao, L., Tong, L., Zhang, A., Xie, Y., Shen, J., Li, H., Wang, L., and Li, S. (July 1, 2015). "Exergy Analysis for Air Separation Process Under Off-Design Conditions." ASME. J. Energy Resour. Technol. July 2015; 137(4): 042003. https://doi.org/10.1115/1.4029911
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