Dynamic modeling and collocation-based model reduction of cryogenic air separation units

High purity distillation columns and multi‐stream heat exchangers (MSHXs) are critical units in cryogenic air separation plants. This article focuses on modeling approaches for the primary section of a super‐staged argon plant. A full‐order stage‐wise model for distillation columns in air separation...

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Bibliographic Details
Published in:AIChE journal 2016-05, Vol.62 (5), p.1602-1615
Main Authors: Cao, Yanan, Swartz, Christopher L. E., Flores-Cerrillo, Jesus, Ma, Jingran
Format: Article
Language:English
Subjects:
Air separation
Chemical engineering
collocation method
Columns (process)
Computer simulation
cryogenic air separation
distillation
Dynamics
Heat exchangers
Mathematical models
modeling
Modelling
moving boundary
multi-stream heat exchanger with phase change
Phase change
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Summary:High purity distillation columns and multi‐stream heat exchangers (MSHXs) are critical units in cryogenic air separation plants. This article focuses on modeling approaches for the primary section of a super‐staged argon plant. A full‐order stage‐wise model for distillation columns in air separation units (ASUs) that considers key process phenomena is presented, followed by a reduced‐order model using a collocation approach. The extent of model reduction that can be achieved without losing significant prediction accuracy is demonstrated. A novel moving boundary model is proposed to handle MSHXs with phase change. Simulation results demonstrate the capability of the proposed model for tracking the phase change occurrence along the length of the heat exchanger. Dynamic simulation studies of the integrated plant show that the thermal integration between the feed and product streams captured in the primary heat exchanger is critical to accurately capture the behavior of ASUs. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1602–1615, 2016
ISSN:0001-1541
1547-5905
DOI:10.1002/aic.15164