RESEARCH ARTICLE

Exergy analysis of multi-stage crude distillation units

  • Xingang LI 1,2 ,
  • Canwei LIN 1 ,
  • Lei WANG 3 ,
  • Hong LI , 1,2
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  • 1. School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
  • 2. National Engineering Research Center of Distillation Technology, Tianjin 300072, China
  • 3. Yunnan Jiehua Clean Energy Development Co., Ltd., Kunming 650224, China

Received date: 03 Apr 2013

Accepted date: 26 Jun 2013

Published date: 05 Dec 2013

Copyright

2014 Higher Education Press and Springer-Verlag Berlin Heidelberg

Abstract

This paper aims to investigate the multi-stage effect on crude distillation units (CDUs) in thermodynamics. In this regard, we proposed three-, four-, five-, and six-stage CDU processes with all variables constrained to be almost the same except for the number of stages. We also analyzed the energy and exergy to assess the energy consumed by each process. Because additional distillation units would share the processing load and thus prevent products with low boiling points from overheating, the heat demand of the CDUs decreases with increasing stages and thus reduces the heat supply. Exergy loss is considered as a key parameter to assess these processes. When the exergy losses in heat exchangers are disregarded, the three- and four-stage CDUs have lower exergy losses than the five- and six-stage CDUs. When the overall exergy losses are considered, the optimum number of stages of CDUs depends on the exergy efficiency of heat integration.

Cite this article

Xingang LI , Canwei LIN , Lei WANG , Hong LI . Exergy analysis of multi-stage crude distillation units[J]. Frontiers of Chemical Science and Engineering, 2013 , 7(4) : 437 -446 . DOI: 10.1007/s11705-013-1349-y

Acknowledgements

This research was supported financially by the National Basic Research Program of China (No. 2009CB219905), the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT0936) and Top Talents Program of Yunnan Province, China (No. 2011HA010).
Nomenclature
E ˙nergy rate, kW
expecific exergy, kJ·kg-1
E ˙xxergy rate, kW
hpecific enthalpy, kJ·kg-1
H ˙nthalpy rate, kW
I ˙rreversibility or exergy loss rate, kW
m ˙ass flow rate, kg·s-1
specific entropy, kJ·kg-1·K-1
S ˙ntropy rate, kW·K-1
Temperature, K
φroportional coefficient
Subscripts
0nvironment condition
Innlet stream
oututlet stream
coldold stream
hotot stream
Qdeat demand
Qseat supply
Qrevssuming the heat transfer processes in heat exchangers are reversible
QϕSSUMING the value of exergy loss is proportional to the amount of exergy provided by the hot streams in heat exchangers with a constant proportional coefficient
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