V.A. Juvekar

Absorption of CO2 in a suspension of lime

The kinetics of absorption of lean CO2 in a suspension of lime was studied in 5 and 20 cm i.d. bubble columns and a 12.5 cm i.d. mechanically aginated contactor. The absorption of CO2 is accompanied by a fast pseudo first order reaction. The rate of absorption in a batch of a suspension of lime remains essentially constant up to a level of carbonation of about 90 per cent and thereafter it decreases, due to the resistance associated with the dissolution of solids. The published data in the literature and the reported mechanism have been reanalyzed.

Fast reactions in slurry reactors: Catalyst particle size smaller than film thickness: Oxidation of aqueous sodium sulphide solutions with activated carbon particles as catalyst at elevated temperatures

Abstract Catalyst particles, smaller than the diffusion film thickness, in slurry reactors, can enhance the specific rate of absorption substantially over that in the presence of coarser particles, even when the reaction is sufficiently fast to occur in the film in the absence of catalyst particles. This is illustrated with a study of the kinetics of absorption of oxygen in aqueous solutions of sodium sulphide. This study was carried out in stirred contactors with plane interface of 14.5 and 7.5 cm i.d. at temperatures of 80° to 150°C and a total pressure of 1.5 to 9.5 atm, with or without fine activated carbon particles (average particle size 1.7 and 4.33 microns; 0.01 to 2.0% w/w loading) as a catalyst. Some experiments were also conducted with coarse carbon particles (average particle size 85 microns and particle size > 20 μm). Under certain conditions, in the absence of activated carbon, the absorption is accompanied by fast pseudo first order reaction in the film. In a number of cases with fine carbon particles, the specific rate of absorption increased by a factor of 2 to 11 and in some cases this factor was as high as 14. A simple theory has been developed which indicates that, under certain conditions, at higher catalyst loading, the specific rate of absorption will be inversely proportional to the particle size.

Modified Shrinking Core Model for Reversible Sorption on Ion-Exchange Resins

Abstract A modified shrinking core model is proposed to correlate dynamics of acid sorption on weak base ion-exchange resins in free base form. The model considers reversibility of the sorption process which is ignored in the conventional shrinking core model. The model is easy to apply and is shown to yield results which are in agreement with a computationally intensive rigorous model. The model is successfully verified using the experimental data on sorption of strong acids (HCl and HNO3) on weak base resins (Dowex WGR-2 and Amberlite IRA-93).

Criteria for supersaturation during simultaneous absorption-desorption

This paper extends the recent analysis of Shah, Pangarkar and Sharma[1] on the criteria for supersaturation during simultaneous absorption-desorption. Firstly two important chemical systems are considered. Subsequently, the role of the gas phase mass transfer resistance on the supersaturation criteria for both physical and several chemical systems are examined. Finally, the effects of heat liberation at the gas—liquid interface onto the supersaturation criteria for the physical systems are briefly evaluated. The results indicate that the necessary condition for the supersaturation is DD/DA < 1 even when gas phase resistance and thermal effects are important. Here DC and DA are the liquid phase diffusivities of the desorbing and absorbing components.

Simultaneous absorption of two gases accompanied by a complex chemical reaction: approximate solutions☆

Abstract Approximate solutions to the problem of simultaneous absorption of two gases in a liquid accompanied by a complex chemical reaction have been presented based on the film theory. Two approximate profiles, a nonlinear exponential profile and a trigonometric profile, for the concentration of each of the gaseous species in the film have been used in analysing the problem. The complex scheme considered is: For the exponential case two approximations have been considered: [1] in which the higher order terms are included, and [2] in which the higher order terms are neglected. The results obtained using the two profiles have been compared with numerical solutions for the film theory in the range of from 1 to 3. The results show that both the approximations yield solutions close to the numerical, in particular case [1] of the exponential approximation. Some special cases have then been considered followed by a discussion of an industrially important system: simultaneous absorption of ethylene and chlorine in water to give ethylene chlorohydrin.