Solubilltles of N20, C2H4, and C2H2 and dlffuslvlty of N20 In various aqueous solutions of amines (MEA, DEA, TEA, MIPA, DIPA, and EDA) were measured at 25 OC and I atm of pressure. For these present systems, solubllity and dlffuslvlty data could not be correlated by suitable correlations. The best ways to estimate solubility and dlffusivily of C02 in aqueous solutions of amines may be log (a/a,)co, = log (~/Q,)N,o and (D/D,)co, = ( D/Dw)N,O, respectively, using the Corresponding data for N20.Aqueous solutions of amines are widely used in gas-liquid contact operations for the removal of acidic gases. The solubility and the diffusivity of the acidic gas in these solutions are fundamental physicochemical properties necessitated in the design of gas-liquid contactors. These properties, however, cannot be conventionally measured because of the presence of chemical reaction and, hence, must be estimated by the corresponding data for nonreacting gases. For the time being, no correlation has been developed on the solubility and the diffusivity of gases in amine solutions. I t is rather essential to systematically accumulate data on solubility and diffusivity.The previous paper (2) reported that the solubility of CO, in aqueous amine (monoethanolamine, diethanolamine, triethanolamine, or ethylenediamine) solution may be reliably estimated from the corresponding values of N20 by log (~/ c u , )~, = log ( O I / C U~)~,~. Such a correlation is considered to be applicable to estimate the diffusivity of CO,.In view of these facts, the solubility of N20, C2H4, or C2H, in aqueous solutions of amines was measured by a volumetric method and the diffusivity of N20 by means of a laminar liquid-jet apparatus. Experimental SectionAqueous solutions of amines (monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), mono(isopropy1 alcoho1)amine (MIPA), di(isopropy1 alcoho1)amine (DIPA), and ethylenediamine (EDA)) were prepared from distilled water and reagent grade amines of guranteed purity. The solution was degassed by refluxing it for a sufficient length of time before being used in the solubility experiment. The composition of the solution was determined by volumetric titration.For gases, N,O, C, H, , and C, H2 were supplied from commercial cylinders with minimum purities 99.8, 99.6, and 99.9 %, respectively, and confirmed by analyzing by gas chromatography.The gas solubilities were measured by a volumetric technique. Systems studied were N20-MIPA and -DIPA, C2H4-MIPA and -DIPA, and C2H2-MEA, -DEA, -TEA, -MIPA, -DIPA, and -EDA. The apparatus and operating method were essentially the same as those employed in our previous study (2). Briefiy, the principle of the apparatus used is that a measured volume of solute gas is brought in contact with a measured quantity of gas-free liquid, equilibrium is established by agitation, and the remaining volume of gas (undissolved) is measured. The change in the gas volume gives the amount dissolved in the liquid. Further details of
The absorption rate of lean SO2 and/or NO2 into aqueous slurries of fine Ca(OH)2 or Mg(OH)2particles was measured using a stirred vessel with a plain gas-liquid interface at 25°C and 1 atm. The absorption process of lean SO2 into Ca(OH)2 slurries was found to be almost gas-film controlled under the partial pressures considered here. On the other hand, for SO2-Mg(OH)2slurry system, the diffusion of the reactant across the liquid film was significant and the absorption rate was increased with solid concentration. The observed enhancement factors were compared with the theoretical prediction according to the previously proposed model to estimate the dimensionless parameter concerning solid dissolution. For NO2-slurry system, the reaction between NO2and the aqueous slurry may satisfactorily be considered the reaction between NO2and water. The hydrolysis was found to be second-order in NO2and the secondorder rate constant was derived as 5.0X107//molà"sec.The absorption rate of NO2 with coexistence of SO2into aqueous slurries of Mg(OH)2greatly exceeded that of NO2alone into clear solutions with the same sulfite concentrations, which may be due to the solid-surface reaction in a region from the interface to the reaction plane. Introducti onThe elementary processes involved in chemical absorption into slurry are (i) diffusion of solute gas in the liquid film, (ii) chemical reaction and (iii) dissolution of solid (one of the reactants of Ca(OH)24)5) and absorption of SO2 into aqueous slurries of Mg(OH)23) using a stirred-tank absorber with a plain gas-liquid interface. But in our previous work3>5), the gas-phase composition of solute gases was restricted to percentorder of magnitude. The concentration of SO2 in the flue gases emitted from stationary combustion sources is generally less than several thousand ppm by volume. Therefore, it is necessary to discuss the absorption mechanism of lean SO2 by aqueous slurries.The present work was undertaken to check the applicability of the proposed model to the chemical absorption of such lean solute gas as is encountered in flue gases. To this end, absorption of SO2 by aqueous slurries of Ca(OH)2 and Mg(OH)2 was carried out using a stirred vessel with a plain gas-liquid interface.An aqueous Mg(OH)2 slurry has an advantage of yielding high scrubbing capacity for the removal of SO2 as a result of the presence of more soluble reaction product, MgSO3, than the corresponding Casalt. Dissolved MgSO3 in a slurry solution is also favorable for the absorption of NO2. In considering this, the simultaneous absorption of lean SO2 and NO2 into aqueous slurries of Mg(OH)2 was in
Experiments were carried out over a wide range of contact time for the absorption of carbon dioxide into aqueous amine solutions. It was suggested from the experimental results with a laminar liquid-jet, a wetted wall column and a quiescent liquid absorber that the present absorption processes should be analyzed by a gas absorption with the consecutive reaction of the form of A + 2B 4 R and A +R ? ! + ' Products. The values of rate constants for the second-order first reaction step (kI) €or the diethanolamine and triethanolamine were estimated as 1340 and 16.8 l/mol-sec, respectively. The value of rate constant for the second reaction step was found to be constant irrespective of the liquid reactant.number of experimental investigations on chem-A ical absorption have been vigorously done with
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