Publication costs assisted by Atomic Energy of Canada LimitedThe surface tension of H2S-saturated water has been measured at pressures up to 3.0 MPa and at temperatures within the range 25-130 °C. Monolayer coverage of the surface of the aqueous solution by H2S occurred at about one-half the saturation pressure, P8, of liquid H2S at a given temperature. Multilayer condensation increased significantly as P8 was approached. Interfacial tensions between liquid H2S and aqueous H2S solutions were measured between 30 and 40 °C. These data were used to show that the spreading coefficients, S2, for liquid H2S on water were positive and that liquid H2S spread on the aqueous phase. The standard thermodynamic properties for the adsorption of H2S on water were calculated at the zero-coverage limit between 25 and 130 °C. The unusually high adsorption coefficient for H2S on water was found to be due to a large, positive entropy of adsorption.Publication costs assisted by the National Science Foundation Measurements of the three interfacial tensions, ß, ß , and , in the three-liquid-phase, quaternary system benzene-ethanol-water-ammonium sulfate, at 21 °C, are reported. It is found that Antonoff s rule, = ß + ,37, holds to within the precision of the measurements through the whole of the three-phase region, from one critical end point to the other. The theoretical implications of this result are discussed. It is found also that the variation of ß with , 7 through the three-phase region is in qualitative accord with that predicted by theory.
Control of supersaturation in a 1-L continuous cooling KCI crystallizer was investigated. The supersaturation was determined from on-line measurements of the density and temperature of clear liquor samples. A cascade control scheme was used to control the supersaturation through the manipulation of the co-saturated feed temperature set-point while maintaining the crystallizer temperature at 303.2 K. Experimental results showed that due to the suppression of spontaneous nuclearion, a decrease in the measured supersaturation resulted in a 23 % increase in the mean crystal sue and a 12% decrease in the amount of NaCl impurity in the KCI crystals.. On a 6tudi6 le contr6le de la sursaturation dans un cristalliseur de KCI h refroidissement continu de 1 L. La sursaturation a 6tt5 d6terminb 21 partir de mesures continues de la masse volumique et de la temp6rature des kchantillons de liqueur Claire. On a utilis6 un schkma de contr8le en cascade pour rkguler la sursaturation par la manipulation du point de consigne de temp6rature d'alimentation cosaturk, tandis que la temp6rature du cristalliseur 6tait maintenue A 303,Z K. Les fisultats exp6rimentaux montrent que, du fait de la suppression de la nuclbtion spontade, une diminution de la sursaturation mesurk entraine une diminution de 23% de la taille moyenne des cristaux et une diminution de 12% de l'impuret6 du NaCl dans les cristaux de KCI. rystallization is an important separation process in the C chemical industry, with widespreaduse in the production and purification of bulk chemicals, fermizers, pharmaoeuticals, etc. Despite the varied applications of crystallization, the successful design and operation of industrial crystallizers are based largely on experience as opposed to being based on theoretical principles. Previous work on the on-line control of crystal product quality has primarily dealt with control of the crystal size distribution (CSD). Feedback control of the nuclei density (Rovang and Randolph, 1980; Randolph et al., 1981; Randolph and Low, 1982; Randolph et al., 1987), or of the lines suspension density (Rohani, 1986; Rohani and Lee, 1987; Rohani and Paine, 1991), and manipulation of the h e s dissolution rate have shown some success in the control of CSD in continuous crystallizers. Various control strategies used in industrial crystallizers are discussed by Rohani CrystallizationKineticsofPUassi~chloride'',Ind. Eng.Chem. Res. 28, 844-850 (1989).
his paper concerns coupled heat and mass transfer in granular potash when it is stored and handled as a bulk material. Potash T fertilizer, comprised mostly of sylvite (KCI), with small mass fractions of halite (NaCI) and carnallite (KMgC13.6H,0), is highly soluble in water. When exposed in humid air, the potash particles will adsorb moisture. Subsequently, when the relative humidity (RH) drops, moisture will be released from the granular particles by drying process. If this occurs a t moisture contents greater than 0.3%, the small potash particles will cake to form larger particles or clumps, which impedes the handling and flow of this granular material and is especially unfavourable for uniform distribution by most agricultural machines. Pyne et al. (1996) studied the interaction between water vapour and granular potash fertilizers. They used an isothermal heat conduction calorimeter to measure the rate of water vapour uptake by potash as a function of water vapour pressure over a potash sample. Their results show that there are two transition reactions for moisture uptake with increasing relative humidity, one occurring at about 0.60 RH where significant moisture accumulations begin, and the other at about 0.84 RH. In a recent work, Hansen et al. (1998) used the same method to investigate the effect of anitcaking agents on the thermodynamics and kinetics of water sorption by potash fertilizers. Caking research is reported by Walker et al. (1998) for mixed granular nitrogen, phosphorus and potassium (NPK) fertilizers. Their research indicates that the caking process is dominated by free water through capillary adhesion and crystal bridging processes.Moisture-potash interactions depend on the surface composition of the particles. Potash is primarily composed of potassium chloride (KCI), but it contains internal and surface impurities. Internally, crystal particles of potassium chloride may trap some sodium and magnesium which will form sodium chloride (NaCI) and carnallite (KMgCI3.6H,O) microcrystalk inside potassium chloride crystals. Processing potash to remove impurities results in higher concentrations of impurities on the surface of every particle, since either flotation or recrystallation is completed in a brine which is a mixed solution of KCI, NaCI, and MgCI,, with very small amounts of organic materials in it. The potash particles produced from these flotation or recrystallation processes are subjected to a centrifugal de-brining process. There is typically 2% -4% residual brine on the particle surfaces after surface de-brining. In the subsequent drying process, the residual brine forms mixed crystals, comprised of Sylvite (KCI), Halite (NaCI) and Carnallite (KMgC13.6H,0), with small local compostitonal variations on the surface of each particle. Some of these impurities (i.e. NaCl and KMgC13.6H,0) may be covered by trace amounts of organic materials. Thus, only a part of the above water *Author to whom correspondence may be addressed. E-mail address: shiwen@ ualberta.ca Potash is a widely used granu...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.