Mass transfer with complex chemical reactions in gas–liquid systems: two-step reversible reactions with unit stoichiometric and kinetic orders

Bhat, RD Vas; Kuipers, J.A.M.; Versteeg, Geert

doi:10.1016/s1385-8947(99)00104-7

Cited by 43 publications

(27 citation statements)

References 25 publications

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“…Reaction kinetics are supposed to be first order relative to the concentrations, as written below (Vas Bhat et al, 2000;Cents et al, 2005) :…”

Section: Modellingmentioning

confidence: 99%

“…Hence, the molecular diffusion is the only mass transfer mechanism. Far from the interface (bulk), it is assumed that the concentrations of all the species are in the chemical equilibrium state.In the liquid phase, the CO 2 takes part to the following chemical reactions (Haut, 2004;Rhem et al, 1963) :Reaction kinetics are supposed to be first order relative to the concentrations, as written below (Vas Bhat et al, 2000;Cents et al, 2005) :Coupling between Mass Transfer and Chemical Reactions during the Absorption of CO2 in a NaHCO3-Na2CO3 Brine : Experimental and Theoretical Study C. Wylock, P. Colinet, T. r 1 and r 2 are respectively the reaction rates of reaction (1) and reaction (2). Reaction (1) consumes CO 2 provided by the gaseous phase and subsequently changes the chemical balance of the reaction (2).…”

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confidence: 99%

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Coupling between Mass Transfer and Chemical Reactions during the Absorption of CO2 in a NaHCO3-Na2CO3 Brine : Experimental and Theoretical Study

Wylock¹,

Colinet²,

Cartage³

et al. 2008

International Journal of Chemical Reactor Engineering

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A key step of the refined sodium bicarbonate (BIR ) production by the Solvay process consists in the gas-liquid mass transfer of carbonic gas CO 2 from a gaseous mixture of CO 2 and air to a sodium carbonate Na 2 CO 3 and bicarbonate NaHCO 3 brine. This transfer takes place in 20-m high and 2.5-m wide bubble columns (the BIR columns). This large size induces a large contact time between gas and liquid, in order to increase the amount of transferred CO 2 . Nevertheless, the gas phase leaving the columns contains an important quantity of CO 2 (only half of the CO 2 is transferred). It causes a huge CO 2 emission to the atmosphere (the equivalent of 150 Smart driving at 100 km/h, for a single column). More, the CO 2 is produced by lime calcination. This process requires a large amount of energy. It represents the major part of the energy consumption to produce BIR. In the past decades, several optimizations of the BIR process were performed by an empiric approach. There are today some limits to this approach for applications requiring high levels of purity and a well-defined granulometry. Moreover, the ecologic pressure becomes more and more constraining for the greenhouse effect gas emission. Accordingly, Solvay is seeking for a more fundamental approach. Currently, several studies are realized in the chemical engineering department at the ULB. The final goal is to create a complete model of a BIR bubble column, taking into account all the phenomena taking place in it. This model will be used in order to optimize the CO 2 transfer rate in the column. As a direct consequence of this optimization, the CO 2 emission and the energy consumption of the BIR production will hopefully be reduced.The objective of the work presented in this paper is to develop a model of the mean CO 2 flux density, expressed by unit of time and interfacial area, in a BIR bubble column, that will be integrated in the future complete model of a BIR column. No solid phase is considered in this paper.The CO 2 transfer rate from a bubble of gas to the brine is controlled by the physico-chemical phenomena occurring in the thin layer of liquid near the interface. After the CO 2 absorption in this liquid layer, the CO 2 is transferred by diffusion and is involved in several chemical reactions. These reactions modify (accelerate) the gas-liquid mass transfer rate.The liquid phase flow around the bubbles, rising up in the columns, influences the mass transfer rate too. The scale of this phenomenon is different from the physico-chemical phenomena. A multiscale approach is then followed.A mathematical modelling of the coupling between mass transfer and chemical reaction is first developed. The equations of the model are solved numerically, using COMSOL Multiphysics. In order to validate experimentally this model, a Mach-Zehnder interferometer is set up. The scale-up of this model to a bubble, in a second time, is carried out by completing the model of the coupling with a representation of the liquid phase flow around a bubble. It is called the bubble-li...

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“…Reaction kinetics are supposed to be first order relative to the concentrations, as written below (Vas Bhat et al, 2000;Cents et al, 2005) :…”

Section: Modellingmentioning

confidence: 99%

mentioning

confidence: 99%

Coupling between Mass Transfer and Chemical Reactions during the Absorption of CO2 in a NaHCO3-Na2CO3 Brine : Experimental and Theoretical Study

Wylock¹,

Colinet²,

Cartage³

et al. 2008

International Journal of Chemical Reactor Engineering

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“…K 1 and K 2 are the chemical equilibrium constants of the reaction (2) and (3), respectively. Their values are referenced in the literature (Vas Bhat et al, 2000).…”

Section: Reactions In Liquid Phasementioning

confidence: 99%

“…The CO 2 solubility coefficient, h, the CO 2 diffusion coefficient, D CO 2 , and the kinetic constant of the reaction (2), k 11 , are calculated as functions of the temperature and the concentrations in the i th compartment using the correlations referenced by Vas Bhat et al (2000). The model shows a great sensitivity to these parameters.…”

Section: Modeling Parametersmentioning

confidence: 99%

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Compartmental Modeling of an Industrial Column

Wylock¹,

Larcy²,

Cartage³

et al. 2009

Chemical Product and Process Modeling

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). It leads to the necessity to set a complex system to recycle the CO 2 downstream the columns. Nevertheless, an important amount of CO 2 is emitted to the atmosphere. Furthermore, the CO 2 is produced by lime calcination. This process requires a large amount of energy. It represents the major part of the energy consumption of the entire process.Accordingly, Solvay is seeking a more fundamental approach. The objective of this work is the development of an operational BIR column model, taking into account all the phenomena taking place in it, using a compartmental modeling approach. Notice that the goal of this paper is not to provide a final validated model. That will be realized in a further work, based upon the results of this work.The structure of the model is developed in section 2.1 following the approach proposed by Haut et al. (2004). This structure is based on the analysis of experimental measurements realized on an industrial column located in Dombasle (France) by Hirschauer (2001). This model will be used to understand the complex interactions between the different phenomena taking place in the columns and to optimize the NaHCO 3 crystal quality and the CO 2 transfer rate in the columns.The gaseous phase is modeled in section 2.2 using the approach developed by Haut and Cartage (2005). The bubble-liquid CO 2 transfer rate is quantified by an expression validated for the BIR columns by Wylock et al. (2008a) and presented in section 2.3. The solid phase is modeled by a classical Population Balance Equation (PBE) (Randolph and Larson, 1971). The concentrations of the dissolved species are calculated using balance equations as presented in section 2.4.All the parameters appearing in the model can be estimated, at least roughly. They are estimated from data or correlations found in the literature, from theoretical and experimental studies or from the analysis of the measurements performed by Hirschauer (2001) on a column located in Dombasle.Using the estimated parameters, a classical operating point of a column located in Dombasle is simulated. The results of this simulation are in good agreement with experimental measurements.Moreover, a parametric sensitivity analysis of the model is performed. This analysis allows identifying which parameters have a strong influence on the model behaviour, in order to direct further studies that have to be realized to improve the model.Finally, some modeling perspectives are proposed.

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Claus¹

2020

Catalysis From a to Z

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Mass transfer with complex chemical reactions in gas–liquid systems: two-step reversible reactions with unit stoichiometric and kinetic orders

Cited by 43 publications

References 25 publications

Coupling between Mass Transfer and Chemical Reactions during the Absorption of CO2 in a NaHCO3-Na2CO3 Brine : Experimental and Theoretical Study

Coupling between Mass Transfer and Chemical Reactions during the Absorption of CO2 in a NaHCO3-Na2CO3 Brine : Experimental and Theoretical Study

Compartmental Modeling of an Industrial Column

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