Diffusion in calcium oxide/calcium sulfate pellets
Diffusion rates in calcium oxide pellets after partial conversion to calcium sulfate were measured. A Wicke-Kallenbach type diffusion cell operated in the pulse-response mode was used to measure effective diffusivity. Cylindrical calcium oxide pellets were formed from the powder using pelletizing pressures of 10,000, 20,000 and 30,000 psi. The pellets were reacted at 325, 500 and 600/sup 0/C with sulfur dioxide and oxygen to form calcium sulfate. The volume of calcium sulfate is 2.7 times that of calcium oxide, so partial pore closure occurs. The diffusivity was measured in the original pellet and in pellets partially reacted to several different conversion levels. The effective diffusivity decreases as conversion decreases and is roughly inversely proportional to pellet porosity squared for low conversions. However, the porosity and diffusion rate do not become zero when the reaction rate approaches zero. Pore closure is, therefore, not the mechanism which limits the ultimate conversion. A large diffusion resistance through the calcium sulfate product layer probably causes the reaction to stop before total conversion. The final conversion obtainable increases as reaction temperature increases and decreases as pelletizing pressure increases.
- Research Organization:
- Ames Lab., Ames, IA (United States)
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 5741489
- Report Number(s):
- IS-T-981; ON: DE82005450
- Resource Relation:
- Other Information: Thesis
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CALCIUM OXIDES
CHEMICAL REACTIONS
DIFFUSION
PELLETIZING
POROSITY
CALCIUM SULFATES
OXYGEN
SULFUR DIOXIDE
EXPERIMENTAL DATA
HIGH TEMPERATURE
PELLETS
PRESSURE DEPENDENCE
TEMPERATURE EFFECTS
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CHALCOGENIDES
DATA
ELEMENTS
FABRICATION
INFORMATION
MOLDING
NONMETALS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
SULFATES
SULFUR COMPOUNDS
SULFUR OXIDES
400201* - Chemical & Physicochemical Properties