First principles dynamic modeling and multivariable control of a cryogenic distillation process

Abstract

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. AbstractIn order to investigate the feasibility of constrained multivariable control of a heat-integrated cryogenic distillation process, a rigorous first principles dynamic model was developed and tested against a limited number of experiments. It was found that the process variables showed a large amount of interaction, which is responsible for the difficulties with the presently used, PID-based, control scheme, especially in load-following situations, which are common in air separation plants such as for instance integrated coal gasification combined cycle plants. Contrary to what is suggested in the literature, it was found that vapor hold-up in low-temperature, high-pressure columns does not play a significant role in the process dynamics. Despite large throughput changes and non-linear process behavior, multivariable model predictive control using a linearized model for average operating conditions, could work well provided all process flows have sufficient range. Due to the strong interactive nature of the process variables, process changes have to be made slowly, since otherwise manipulated variables easily saturate and process output targets cannot be maintained.

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

“…10,[12][13][14] An alternative way of modeling distillation columns in ASUs follows the conventional full-order stage-wise model (FOSM) approach. 2,3,7,15 FOSMs usually consist of material and energy balances, tray hydraulics, thermodynamic correlations, pressure drop profiles, and other physical properties. FOSMs can either be steady state or dynamic.…”

“…3,15 The reader can refer to our previous work for details on the full equation set. 17 The vapor pressure drop is a function of the vapor velocity and the liquid head at the tray above 43 P n 2P n11 5af ðq v n ; y n ; V n Þ1bf ðq…”

“…As shown in Figure 11, a customized grid was developed. Due to the sharp temperature profile of the hot air stream around the TP section (stages [11][12][13][14][15] and toward the end point of the SC section (above stage 40), we kept the model for these sections in a stage-wise manner (CPs at the exact stage location). There are negligible differences between predictions with the partially collocated and the full stage-wise model.…”

Heat integrated distillation operation

“…Roffel et al [110] proposed a heat integrated cryogenic distillation column (HICDiC) that is constructed with two smaller columns, keeping one above another, within a single distillation shell. The lower part of the distillation tower is the high-pressure column and the upper part the low-pressure column.…”

Modeling, Characteristic Analysis and Optimization of an Improved Heat‐Integrated Air Separation Column

“…1. The difference in boiling points due to the pressure difference becomes the driving force for the transfer of energy in the integrated reboiler-condenser [5]. A large pressure difference is required between the HPC and LPC for the exchange of vaporization heat with condensation heat.…”