A rigorous surface renewal model for transient gas absorption with first-order chemical reaction in a stirred liquid. (15th March 2023)

• Record Type: Journal Article
• Authors: Huang, Hengshuo; Chatterjee, Siddharth G.
• Is Part Of: Chemical engineering science. Volume 268(2023)
• Publication Date: 2023-03-15
• Subjects: Gas absorption -- Diffusion -- First-order reaction -- Mass transfer -- Surface renewal model -- Unsteady state; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2022.118393
• Languages: English
• ISSNs: 0009-2509

Abstract

Graphical abstract: Highlights: A rigorous surface renewal model is developed for unsteady-state gas absorption with first-order chemical reaction. Model accounts for both the rate of gas absorption and that of dissolved-gas transfer to the bulk liquid. The two rates show an inverse behavior during the initial moments of absorption after which they level out. A hybrid model for performing unsteady-state gas absorption calculations is proposed. Abstract: This work presents a rigorous surface renewal model for unsteady-state gas absorption in a stirred batch cell in which the dissolved gas undergoes a first-order chemical reaction with a liquid-phase reagent for the cases of zero and finite gas-phase mass-transfer resistance, with the concentration of dissolved gas in the bulk liquid being a function of time. For oxygen absorption in water containing a reagent (e.g., sodium sulfite), the model predicts that the rates of absorption and dissolved-gas transfer to the bulk liquid have an inverse behavior during the initial moments of absorption after which they level out as steady state is approached, with the former being higher than the latter due to the consumption of dissolved gas by the reaction occurring in the surface elements. In general, predictions of the dissolved oxygen concentration made with the rigorous model compare quite well with those of a much simpler pseudo steady-state model. However, the rigorous surface renewal model gives a finer grained picture of the phenomenon of absorption, i.e., of the rates of absorption and dissolved-gas transfer, especially during the initial moments of absorption. A hybrid model, which uses both the pseudo steady-state and rigorous surface renewal models, is proposed for performing unsteady-state gas absorption calculations.