Problem Of Gas Absorption Research Articles

Gas Absorption in Slurries of Fine Particles: SO2−Mg(OH)2−MgSO3 System

The problem of gas absorption with reaction, in a slurry containing fine particles, is important in the development of processes for the removal of acidic pollutants such as sulfur dioxide. Typically, lime and lime stone slurries can be used for removal of sulfur dioxide. However, magnesium hydroxide slurries may yield a higher scrubbing capacity as a result of the more soluble reaction product, magnesium sulfite, compared to the corresponding calcium salt. In this study, absorption experiments were carried out in a stirred cell and the resulting data is analyzed using the model proposed by Mehra [Chem. Eng. Sci. 1996, 51, 461−477]. The proposed theory incorporates the process of particle dissolution and the consequent change in particle size near the gas−liquid interface, using Higbie's model of mass transfer with chemical reaction. A population balance approach is used to track the particle size distribution.

Modeling of sulphonation of tridecylbenzene in a falling film reactor

The problem of gas absorption into a falling film reactor was studied in the case of an instantaneous reaction. A diffusion–convection–reaction model was developed taking momentum, mass and heat transfer effects into account. The performance of the model was examined for sulphonation of tridecylbenzene. The resultant equations were solved using a finite difference backward implicit scheme. The results indicated an increase in the axial temperature of the liquid film for a short distance from the reactor top and the predicted conversion was in close agreement with the experimental results.

Gas Absorption with Instantaneous Irreversible Chemical Reaction in a Slurry Containing Sparingly Soluble Fine Reactant Particles

The problem of gas absorption followed by instantaneous irreversible chemical reaction in a slurry containing sparingly soluble fine reactant particles is considered. Models are developed for an infinitely deep quiescent liquid and, using the film theory, for an agitated liquid when the reactant particle dissolution in the liquid film next to the gas−liquid interface is nonnegligible. Simple analytical expressions for the rate of gas absorption are derived under the assumption of slow particle dissolution, and conditions are given for applicability of the models. A numerical example for the system SO2−Ca(OH)2 in water is discussed.

Absorption with instantaneous reaction in a droplet with sparingly soluble fines

AbstractThe problem of gas absorption followed by an instantaneous irreversible chemical reaction in a rigid droplet containing sparingly soluble fine reactant particles is discussed. A model was developed for the general case when the reactant particle dissolution near the gas–liquid interface is nonnegligible. Solids dissolution is treated taking into account the average spacing between the suspended particles. A simple analytical expression for the rate of gas absorption is derived under the assumption of slow particle dissolution, and conditions are given for applicability of the model. A numerical example, relevant for the spray‐dry desulfurization process, for the system SO2‐Ca(OH)2 in water is discussed.

The characteristic time to achieve interfacial phase equilibrium in cloud drops

The problem of gas absorption in a cloud drop for the case of a single isolated drop as well as for the case of a drop within a cloud is considered. Expressions for the characteristic times for achieving phase equilibrium between the gas-phase and liquid-phase pollutant concentrations at the air-water interface for the two cases are derived. According to the work reported herein, for highly soluble gases, the characteristic time for the case of an isolated drop as well as for the case of a drop within a cloud is directly proportional to the drop radius and inversely proportional to the accommodation coefficient of a gas. Furthermore, in the first case, the characteristic time is directly proportional to the solubility of the gas, while in the second case, it is independent of the solubility but inversely proportional to the liquid water content of the cloud. This problem has been considered previously, however, the expression in the literature is based on the concentration at the interface of a semi-infinite liquid body and is not valid for a cloud drop. The findings in this paper disagree with those obtained from the expressions derived in the literature. In addition, for highly soluble gases, the expression in the literature predicts unrealistically large characteristic times for establishment of interfacial equilibrium. The reaction characteristic times for reactions of SO 2, H 2O 2 and O 3 leading to the formation of SO 4 2− within cloud drops are calculated and compared to the characteristic times, predicted by the expressions derived here, for establishment of interfacial equilibrium for these gases. The comparison shows that the establishment of interfacial equilibrium is a rapid process for all cases considered, and does not limit the chemical reactions leading to the formation of SO 4 2− within cloud drops.

Gas absorption with exothermic bimolecular reaction in a thin liquid film: Fast reactions

AbstractA problem of gas absorption with a fast nonisothermal bimolecular reaction in a thin liquid film has been analysed. Approximate analytical solutions for the interfacial temperature rise and enhancement factor have been derived incorporating the influence of depletion of liquid reactant concentration at the interface. The effects of heat generation, heat dissipation and reaction rate parameters on enhancement factor and interfacial temperature rise have been discussed. For a certain range of parameters, multiple steady state solutions of enhancement factor and interfacial temperature rise are observed. Another interesting observation is that as the value of a dimensionless parameter ϕ increases, the enhancement factor approaches its instantaneous asymptote which is the same as that for the isothermal case in an instantaneous regime. The analysis presented here is simple and avoids complex numerical computations and it is likely to be useful in design applications.

GAS ABSORPTION WITH CHEMICAL REACTION INVOLVING A VOLATILE LIQUID REACTANT: PENETRATION THEORY SOLUTION

A penetration theory analysis is presented for the problem of gas absorption, with chemical reaction involving a volatile liquid reactant. Model equations are derived and solution techniques are presented. It is shown that as long as the diffusivities of two reactants are equal, the enhancement factors predicted by film and penetration theories only mildly differ. Except for slow and instantaneous reaction regimes, the liquid reactant volatility can be markedly detrimental to enhancement of absorption rate by chemical reaction.

Rate of gas absorption into a slurry accompanied by instantaneous reaction

The problem of gas absorption into a slurry is theoretically treated by classifying it into six cases according to the concentration profiles of the absorbed gas and the dissolved solid in the liquid phase. For each case, a mathematical model for the rate of gas absorption with the necessary condition is given based on the film concept. A numerical example is given to illustrate the treatment of a practical problem.

Solution of the problem of gas absorption in falling films of non-Newtonian fluids by orthogonal collocation technique

Solution of the problem of gas absorption in falling films of non-Newtonian fluids by orthogonal collocation technique

Gas absorption in falling non-Newtonian films

The problem ofgas absorption in films of non-Newtonian fluids falling over flat and spherical surfaces is studied. The resulting Sturm-Liouville problem is solved by series expansion on a digital computer. Numerical results for the eigenvalues, eigenfunctions, expansion coefficients and average expansion coefficients are reported for power-law fluids.