Modeling, Characteristic Analysis, and Optimization of Ideal Internal Thermally Coupled Air Separation Columns

Abstract

Cryogenic air separation is currently the most widely used but energy-intensive technology for producing large quantities of oxygen and nitrogen, where cryogenic distillation consumes about 75% of the whole air separation field; however, its thermodynamic efficiency is very low. A novel structure of a full tower ideal internal thermally coupled air separation column (ITCASC) is therefore first proposed in this paper. A rigorous mathematic model and parameter analysis are then presented. Research results show that the proposed ITCASC process can yield high-purity products of both oxygen and nitrogen simultaneously and especially has a strong driving force of heat transfer, which reveals the larger energy-saving potential in the ITCASC process. Furthermore, an optimization model of the operation parameters is presented, where both the actual energysaving potential and the ideal energy-saving potential of ITCASC are investigated. Comparative studies against the conventional cryogenic air separation column (CASC) are carried out in detail. Research results show that the proposed ITCASC process has a larger extraction rate and better energy efficiency, where the nitrogen extraction rate increases 177.94% and the unit energy consumption decreases 40% compared to the CASC process with the same product purity requirements, revealing the advantages and promising application prospect of the proposed ITCASC process.

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

“…The pressure of the HPC decreased to 0.395 MPa. Chang et al [33] and Chang and Liu [34] investigated the modeling, characteristic analysis and optimization of a fully coupled heat-integrated air separation column (HIASC), where the ideal pressure dropped to 0.39 MPa. Fig.…”

“…Fig. 2 shows a schematic diagram of the fully coupled HIASC, which has been described in more detail elsewhere [33].…”

“…The HPC pressure of a CASC is generally between 0.53 and 0.57 MPa [6,33,35] and the HPC pressure of a HIASC can ideally drop to 0.39 MPa. In this paper, an improved HIASC structure is applied in order to reduce the HPC pressure and the energy consumption.…”

“…The characteristic analysis of the structure is performed. Compared with the CASC and the fully coupled HIASC [33], the temperature distribution and the energy consumption are investigated. Furthermore, an optimization model of the heat transfer coefficient (UA) is proposed.…”

Generalized generic model control of high‐purity internal thermally coupled distillation column based on nonlinear wave theory

“…In order to provide the necessary thermal driving force for the heat transfer, the rectifying section is operated at a higher pressure than the stripping section. [5][6][7][8][9][10][11][12] Recently, a work by Cabrera-Ruiz et al 13 has shown that when one includes the compressing energy the savings are significantly affected, and in some cases hybrid structures which combine HIDiC (heat-integrated distillation column) and conventional columns have been proved to have higher economic potential than that totally using HIDiC in the separation of ternary mixtures, which reveals that the use of HIDiC should be carefully investigated for certain mixtures before real applications.…”