Calcium sulfite hemihydrate dissolution and crystallization
Experiments were conducted to measure the dissolution and crystallization rate of calcium sulfite hemihydrate in aqueous solutions typical of flue gas desulfurization processes. A stagnant mass transfer model integrated with solution equilibrium was developed to predict CaSO/sub 3/.1/2H/sub 2/O dissolution rates as a function of pH, temperature, solution composition,and particle size. The crystal growth rate was found to be a strong function of relative supersaturation and strongly inhibited by dissolved sulfate. The growth rate per unit BET surface area, R' (mole/cm/sup 2/-min), is given by: 9.7 x 10/sup -4/ exp(-10250/RT) x (RS/sub CaSO/sub 3// - 1)/sup 2/ x RS/sub CaSO/sub 4// - 1, where RS/sub CaSO/sub 3// and RS/sub CaSO/sub 4// are the relative saturations with respect to calcium sulfate (CaSO/sub 3/.1/2H/sub 2/O) and gypsum (CaSO/sub 4/.2H/sub 2/O) respective. Scanning electron microscopy and infrared 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-formed columnar, hexagonal crystals.
- Research Organization:
- Texas Univ., Austin (USA)
- OSTI ID:
- 6444622
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALINE EARTH METALS
AQUEOUS SOLUTIONS
CALCIUM
CRYSTAL GROWTH
CRYSTALLIZATION
DATA
DISPERSIONS
DISSOLUTION
ELECTRON MICROSCOPY
ELEMENTS
EXPERIMENTAL DATA
HYDRATES
INFORMATION
INFRARED SPECTRA
MASS TRANSFER
METALS
MICROSCOPY
MIXTURES
NUMERICAL DATA
OXYGEN COMPOUNDS
PARTICLE SIZE
PH VALUE
PHASE TRANSFORMATIONS
SCANNING ELECTRON MICROSCOPY
SIZE
SOLUTIONS
SPECTRA
SULFITES
SULFUR COMPOUNDS
TEMPERATURE DEPENDENCE