Absorber simulation and design using a nonequilibrium stage model

Krishnamurthy, R.; Taylor, Ross

doi:10.1002/cjce.5450640114

Cited by 28 publications

(10 citation statements)

References 12 publications

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“…The vaporization rate of water at the bottom of the column is >60% larger than the interfacial mass transfer rate of CO 2 and over two times larger than that for H 2 S. However, at the top of the column, the condensation rate of water accounts for only 25% of the total mass transfer rate. Heat effects similar to those presented in Figure 4 have been reported for nonreactive systems by Raal and Khurana 44 and Krishnamurthy and Taylor 1 .…”

Section: Modeling Of Packed Columns Interfacial Mass Transfer Rates H...supporting

confidence: 85%

“…Many researchers − have recognized the importance of using a fundamental rate-based approach for modeling the heat and mass transfer processes present in separation systems. However, the use of the fundamentals of rate-based modeling in reactive separation processes, like reactive absorption or reactive distillation, is a relatively recent development .…”

Section: Introductionmentioning

confidence: 99%

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Rate-Based Modeling of Reactive Absorption of CO₂ and H₂S into Aqueous Methyldiethanolamine

Pacheco

Rochelle

1998

Ind. Eng. Chem. Res.

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A general framework was developed to model the transport processes that take place during reactive absorption when both rate- and equilibrium-controlled reactions occur in the liquid phase. This framework was applied to the selective absorption of H2S from fuel gas containing CO2 using aqueous methyldiethanolamine. A rate-based distillation column module was used for the column integration. The Maxwell−Stefan and enhancement factor theories were utilized. In packed columns, CO2 absorption is controlled by diffusion with fast chemical reactions; in trayed columns it is controlled primarily by physical absorption. Gas−film resistance is never significant for CO2 absorption. For H2S absorption, gas− and liquid−film resistances are important, and diffusion of bisulfide controls the liquid−film resistance. Heat effects produce temperature bulges that can cause equilibrium “pinches” at the maximum temperature. This phenomenon gives an optimum packing height for the H2S removal. Trayed columns are more selective than packed columns for H2S removal, primarily because of the larger number of liquid-film mass transfer units.

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Section: Modeling Of Packed Columns Interfacial Mass Transfer Rates H...supporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Rate-Based Modeling of Reactive Absorption of CO₂ and H₂S into Aqueous Methyldiethanolamine

Pacheco

Rochelle

1998

Ind. Eng. Chem. Res.

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“…On the basis of previous studies of tray absorbers, 3,4 we expect significant variations in the transient gas flow rate and pressure in packed absorbers in response to large changes in the feed gas concentration. The literature contains several examples of steadystate operation of concentrated packed absorbers [7][8][9][10] and undesirable behavior in dilute absorbers during transients; 11,12 however, we found no prior studies reporting the effect of concentrated feed gases on transient behavior.…”

Section: Introductionmentioning

confidence: 89%

“…Krishnamurthy and Taylor 10 provide a review of the developments in the modeling of packed columns. A majority of published models are steady-state models intended primarily for design.…”

Section: Introductionmentioning

confidence: 99%

Transient Pressure and Flow Predictions for Concentrated Packed Absorbers Using a Dynamic Nonequilibrium Model

Gunaseelan

Wankat

2002

Ind. Eng. Chem. Res.

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A dynamic, nonisothermal, nonequilibrium model is developed to predict detailed transient behavior during startup and transition to standby for concentrated random-packed absorbers. The model accounts for solvent evaporation and transient hydraulic behavior and is used to simulate the aqueous absorption of gaseous HCl. During startup, the simulations show a large decrease in the gas flow rate followed by a recovery due to high rates of solvent evaporation. The model predicts a spike in the solute composition in the gas during the startup transient. At low mass-transfer rates, this spike can cause unacceptable solute levels in the vent. During the transition to standby operation (where feed gas is replaced with carrier gas), there is an appreciable increase in the gas flow rate and pressure in the column. The peak transient gas flow rates are about 3 times greater than the feed rate, and the peak pressure drops are about 20 times greater than those at flooding. These spikes may be too brief to flood the column, but mechanical damage is possible. The transient also shows solute being desorbed from the bottom part of the column and re-absorbed in the upper part of the column, which causes a burp of solute in the vent gas. In less concentrated columns, the burp can result in unacceptable solute levels in the vent. These problems can be addressed by initially reducing the carrier gas flow rate. The model also applies to the use of scrubbers for the control of toxic vent emissions.

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“…The mass‐transfer coefficients for the gas and liquid films were estimated as follows:

\frac{k_{g_{k}} R T}{{a D}_{g_{k}}} = 5.32 {(R e)}^{0.7} {(S c)}^{1 / 3} {({a d}_{p})}^{- 2}

k_{L} {(\frac{μ_{L}^{2}}{{normalρ}_{L}^{2} g_{i}})}^{1 / 3} / D_{{C O}_{2}} = 0.015 true(normalR normale true) {(S c)}^{1 / 3} I

where

I = \frac{{(\frac{μ_{normalL}^{2}}{ρ_{L}^{2} g_{i}})}^{1 / 3} {(\frac{k_{O H} C_{O H}}{D_{L, K}})}^{1 / 2}}{\tanh true({true(\frac{μ_{L}^{2}}{ρ_{L}^{2} g_{i}} true)}^{1 / 3} {true(\frac{k_{O H} C_{O H}}{D_{L, K}} true)}^{1 / 2} true)}

…”

Section: Plant Absorber Modelmentioning

confidence: 99%

Greenhouse gas removal from industrial effluents: The role of inorganic additives

Gomes

Ahmadi

2018

Can J Chem Eng

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This work is focused on the investigation of the effects of inorganic additives for carbon dioxide absorption in a liquid solvent containing potassium carbonate. Incorporating the kinetics of the main reaction steps, we considered the interactions between the governing transport mechanisms for determining the effects of gas and liquid outlet temperatures and lean carbonate compositions on outlet carbon dioxide concentration. We estimated the mass transfer coefficient using the surface renewal formalism. Based on the rate-determining steps for the reaction and mass transfer, we developed mathematical models comprising sets of nonlinear differential and algebraic equations, which were solved using the software we developed. Plant data from an industrial unit were used for validating the model, which was subsequently employed for evaluating species concentration profiles, flow rates, temperature, and pressure in the absorber. The effects of the types of promoters, pressure, temperature, and concentration profiles of the promoters were estimated to evaluate the performance of the absorber.

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Absorber simulation and design using a nonequilibrium stage model

Cited by 28 publications

References 12 publications

Rate-Based Modeling of Reactive Absorption of CO₂ and H₂S into Aqueous Methyldiethanolamine

Rate-Based Modeling of Reactive Absorption of CO₂ and H₂S into Aqueous Methyldiethanolamine

Transient Pressure and Flow Predictions for Concentrated Packed Absorbers Using a Dynamic Nonequilibrium Model

Greenhouse gas removal from industrial effluents: The role of inorganic additives

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Absorber simulation and design using a nonequilibrium stage model

Cited by 28 publications

References 12 publications

Rate-Based Modeling of Reactive Absorption of CO2 and H2S into Aqueous Methyldiethanolamine

Rate-Based Modeling of Reactive Absorption of CO2 and H2S into Aqueous Methyldiethanolamine

Transient Pressure and Flow Predictions for Concentrated Packed Absorbers Using a Dynamic Nonequilibrium Model

Greenhouse gas removal from industrial effluents: The role of inorganic additives

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Product

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Rate-Based Modeling of Reactive Absorption of CO₂ and H₂S into Aqueous Methyldiethanolamine

Rate-Based Modeling of Reactive Absorption of CO₂ and H₂S into Aqueous Methyldiethanolamine