Premium
The dynamics of a packed gas absorber by frequency response analysis
Author(s) -
Gray Robert I.,
Prados John W.
Publication year - 1963
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690090215
Subject(s) - carbon dioxide , inlet , chemistry , steady state (chemistry) , mechanics , raschig ring , thermal diffusivity , mixing (physics) , frequency response , packed bed , flow (mathematics) , thermodynamics , analytical chemistry (journal) , phase (matter) , materials science , chromatography , physics , mechanical engineering , electrical engineering , organic chemistry , quantum mechanics , engineering
Abstract The unsteady state behavior of a packed‐column gas absorber was investigated by comparing the results of experimental frequency response tests with theoretical frequency responses determined for several postulated flow models. Carbon dioxide was absorbed in water from air‐carbon dioxide mixtures in a 6‐in. I.D. Pyrex pipe, packed to a depth of 5.12 ft. with 5/8‐in. ceramic Raschig rings. A sinusoidal variation in inlet gas‐phase carbon dioxide concentration was produced by a specially designed linear valve, driven at frequencies of 0.1 to 15 cycles/min. Inlet and outlet gas‐phase concentration sinusoids were measured continuously with specially designed high‐speed thermal conductivity cells. Liquid flows from 0 to 222 lb. moles/hr.‐sq. ft. and gas flows from 1 to 20 lb. moles/hr.‐sq. ft. were investigated. Separate frequency response tests on inlet and outlet mock‐ups permitted determination of the frequency response of the packing section alone. Results were expressed graphically as Bode plots. Theoretical frequency response curves were calculated based on three different flow models: no axial mixing, axial mixing described by a series of perfectly mixed cells, and axial mixing described by an effective longitudinal diffusivity. Neither of the three models gave completely satisfactory agreement with the experimental magnitude‐ratio curves above about 1 cycle/min., although the slug flow model appeared somewhat better than the others. The theoretical phase‐shift curves were almost indistinguishable for the three models and agreed well with the experimental curves.