Frontiers of Chemical Science and Engineering >
Exergy analysis of multi-stage crude distillation units
Received date: 03 Apr 2013
Accepted date: 26 Jun 2013
Published date: 05 Dec 2013
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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.
Key words: exergy; exergy loss; crude oil distillation; multi-stage; energy saving
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
nergy rate, kW | |
pecific exergy, kJ·kg-1 | |
xergy rate, kW | |
pecific enthalpy, kJ·kg-1 | |
nthalpy rate, kW | |
rreversibility or exergy loss rate, kW | |
ass flow rate, kg·s-1 | |
pecific entropy, kJ·kg-1·K-1 | |
ntropy rate, kW·K-1 | |
emperature, K | |
roportional coefficient | |
Subscripts | |
0 | nvironment condition |
In | nlet stream |
out | utlet stream |
cold | old stream |
hot | ot stream |
Qd | eat demand |
Qs | eat supply |
Qrev | ssuming the heat transfer processes in heat exchangers are reversible |
Qϕ | SSUMING 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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