The kinetics of crystal growth of calcium sulfate dihydrate
TL;DR: In this paper, the authors studied the crystallization of calcium sulfate dihydrate on the addition of seed crystals to stable supersaturated solutions at various temperatures between 15 and 45 °C.
About: This article is published in Journal of Crystal Growth.The article was published on 1970-03-01. It has received 176 citations till now. The article focuses on the topics: Seed crystal & Supersaturation.
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TL;DR: In this paper, a physical model for the description of fouling, caused by sedimentation and crystallization, is presented, in order to verify the theoretical considerations, experiments were carried out on a test rig, which could also be used for field experiments.
Abstract: Fouling and/or scaling of heat transfer surfaces causes serious problems in industry. Prevention of fouling is therefore essential for technical (considerable deterioration of heat transfer) and also economic reasons (increased costs). In order to provide successful countermeasures, it is, however, necessary to obtain more detailed information on the physical, chemical and biological processes which produce fouling. Based on the already known fouling mechanisms, it is shown that a satisfactory prediction of fouling behaviour of heat exchangers is not yet possible. This contribution presents a physical model for the description of fouling, caused by sedimentation and crystallization. It is assumed that, during fouling, deposition and removal processes overlap. In order to verify the theoretical considerations, experiments were carried out on a test rig, which could also be used for field experiments. Aqueous CaSO4 solutions served as experimental liquids. A comparison of experimental and calculated fouling factors shows a satisfactory agreement.
211 citations
TL;DR: The rate of crystal growth of Mn3O4 (hausmannite) and βMnOOH (feitknechtite) in aerated aqueous manganous perchlorate systems, near 0.01 M in total manganese, was determined at pH levels ranging from 7.00 to 9.00 and at temperatures from 0.5 to 37.4°C as mentioned in this paper.
175 citations
TL;DR: The growth of calcium oxalate monohydrate crystals in stirred suspensions has been studied by following the changes in ionic conductivity in supersaturated solutions containing both stoichiometric and non-stochastic concentrations of lattice ions at various temperatures in the range 15-45 °C as discussed by the authors.
171 citations
TL;DR: In this paper, the utility of a laboratory diagnostic approach was investigated for a systematic evaluation of the impact of operating conditions, membrane type, and antiscalant effectiveness on membrane mineral salt scale formation.
167 citations
01 Jun 1988
TL;DR: In this article, the authors studied the kinectics of scale formation on heat exchanger surfaces from aqueous solutions by a highly reproducible technique and found that scale formation takes place directly on the surface of the heat exchange without any bulk or spontaneous precipitation in the reaction cell.
Abstract: The kinectics of calcium sulfate dihydrate (CaSO4 · 2H2O, gypsum) scale formation on heat exchanger surfaces from aqueous solutions has been studied by a highly reproducible technique. It has been found that gypsum scale formation takes place directly on the surface of the heat exchanger without any bulk or spontaneous precipitation in the reaction cell. The kinetic data also indicate that the rate of scale formation is a function of surface area and the metallurgy of the heat exchanger. A variety of polymeric and nonpolymeric scale inhibitors such as polyacrylates (mol wt 900–250,000), acrylate-based copolymers, polyphosphates (pyro-, tripoly-, and hexametaphosphates), and phosphonates [aminotri(methylenephosphonic acid), 1-hyroxyethylidine 1,1-diphosphonic acid, and 2-phosphonobutane 1,2,4-tricarboxylic acid] have been examined for their effects on the rate of scale formation. The results indicate that the amount of gypsum scale formed on heat exchanger surface is strongly affected by changing the functional group, molecular weight, and concentration of the inhibitor. In addition, amount of gypsum scale formed suggests an optimum effectiveness with molecular of ∼ 2000 for the polyacrylates studied in the molecular weight range 900–250,000. Scanning electron microscopic investigations of the gypsum crystals grown in the presence of polyacrylates show that structures of these crystals are highly modified. A mechanism based upon surface adsorption of inhibitors on the growing gypsum crystals is discussed. The order, in terms of decreasing effectiveness on the rate of gypsum growth, of various scale inhibitors studied is polyacrylic acid (mol wt ∼ 2,000) ⪢ hexametaphosphate > phosphonates.
167 citations
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