Studies of the Major Factors Affecting Magnesium Limestone Dissolution

Meserole, F.B.; R, Glover; Stewart, David A.

doi:10.1021/bk-1982-0188.ch005

Cited by 4 publications

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“…It was found that the presence of citric acid significantly reduces crystal growth rate and particle size, and produces spiny crystals; nitrilotris methylene triphosphoric acid (NMTP) on the other hand produces disc crystals. Meserole et al, [18] found that solution composition influenced the calcium sulfite crystal size and habit. Calcium sulfite precipitated in the presence of high sulfate concentration was rod shaped or globular with some foliated growth patterns, whereas that precipitated in the presence of high chloride concentration or in dilute solutions was lamellar or acicular in habit.…”

Section: Introductionmentioning

confidence: 99%

Calcium sulfite hemihydrate: Crystal growth rate and crystal habit

Tseng

Rochelle

1986

Environ. Prog.

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The crystal growth rate of CaS03 * V2H20 was measured by a pH-stat method in aqueous solution with pH 3.5 to 6.5, 1 to 25 mM dissolved sulfite, 0.01 to 0.3 M Ca", and 0 to 25 mM sulfate. The growth rate was a strong function of relative supersaturation and was strongly inhibited by dissolved sulfate. The growth rate per unit BET surface area, R' (moldcm2-min), is given by: 9.7 X low4 exp (-1025WRT) x (RScaso,-1)2 X RSCaSo4-l, where RSCaSO3 and RSCaSO4 are the relative saturations with respect to calcium sulfite and gypsum, respectively. Scanning electron microscopy and IR spectroscopy demonstrated that solids generated in the presence of dissolved sulfate contained solid solution sulfate and crystallized as agglomerates of very thin platelets. In the absence of solid or dissolved sulfate the solids were agglomerates of well-informed columnar, hexagonal crystals.

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Section: Introductionmentioning

confidence: 99%

Calcium sulfite hemihydrate: Crystal growth rate and crystal habit

Tseng

Rochelle

1986

Environ. Prog.

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Dissolution rate of calcium sulfite hemihydrate in flue gas desulfurization processes

Teseng

Rochelle

1986

Environ. Prog.

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The rate of calcium sulfite dissolution in slurry scrubbers and hold tanks for flue gas desulfurization affects SOz absorption, limestone utilization and sulfite oxidation. The dissolution rates of calcium sulfite were measured by the pH-state method. A mass transfer model was developed assuming that calcium sulfite particles behave as spheres in an infinite stagnant solution. The model combined with the Bechtel-modified Radian solution equilibrium program successfully predicts calcium sulfite dissolution rates at pH 3.5 -5.5, 23 and 55 "C, 0.001 -0.3 M Ca" and 2 -25 mM dissolved sulfite. The effects of sulfate content in solids and liquids and particle sizdshape were also studied. At conditions typical of flue gas desulfurization processes calcium sulfite dissolution was controlled by mass transfer, not surface reaction kinetics. Dissolution was fast at low pH and slowed near the equilibrium pH determined by dissolved Ca" and SO; concentrations in the aqueous solutions, K,, of the CaSO, V2Hz0 solids, and temperature. The presence of dissolved Mg+ increased the equilibrium pH and enhanced the disolution rate. The presence of dissolved sulfate reduced the dissolution rate and the equilibrium pH. The effect of sulfate was not adequately described by the mass transfer model. Philip C. Tseng and Gary T. Rochelle, Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712 INTRODUCTIONThe objective of this work is to measure and model the dissolution rate of calcium sulfite in flue gas desulfurization processes which absorb SO, by a slurry of lime or limestone with simultaneous calcium sulfite/sulfate crystallization. Calcium sulfite dissolution can be important in these processes because it affects the solution composition and chemical equilibria in the scrubbing solution, and therefore affects SOz absorption, sulfite oxidation, and limestone dissolution [ I ] . Rates of both SO, absorption and limestone dissolution are usually determined by mass transfer with equilibrium acidhase reactions in the solution [2,3,4,5,6,7,8] The reported solubility (mg/l) of CaSO, . 1/2Hz0 in water is 43 (18"C, [20]) and 46.3 (30"C, [2I;>. Lowell et al.[22] reported in the Radian solution equilibrium program a measured thermodynamic solubility product of CaSO, . [24] give an expression of CaSO, . 1/2H,O solubility as a function of temperature:Log KP = 838.3/T -9.7572 (2)Discrepancies in these results may have resulted from the difficulties in controlling the dissolved sulfate concentration and the variation in solid sulfate content of the CaSO, .1/2H,O samples used in these experiments.In this paper, the dissolution rates of CaSO, . 1/2H20 at conditions typical of flue gas desulfurization processes were measured using the pH-stat method introduced by Chan [I61 and Prada [25]. A model was developed by using mass transfer with equilibrium aciabase reactions similar to Chan and Rochelle's work for CaCO, dissolution [I]. This work is a part of an effort for overall scrubber modeling which includes rate models f...

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A continuous and mechanistic representation of calcite reaction-controlled kinetics in dilute solutions at 25�C and 1 atm total pressure

Arakaki

Mucci

1995

Aquat Geochem

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Studies of the Major Factors Affecting Magnesium Limestone Dissolution

Cited by 4 publications

References 0 publications

Calcium sulfite hemihydrate: Crystal growth rate and crystal habit

Calcium sulfite hemihydrate: Crystal growth rate and crystal habit

Dissolution rate of calcium sulfite hemihydrate in flue gas desulfurization processes

A continuous and mechanistic representation of calcite reaction-controlled kinetics in dilute solutions at 25�C and 1 atm total pressure

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