Diffusion in calcium oxide/calcium sulfate pellets

Technical Report · Thu Oct 01 04:00:00 EDT 1981

DOI:https://doi.org/10.2172/5741489· OSTI ID:5741489

Chang, K. L.

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., IA (USA)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 5741489
• Report Number(s): IS-T-981; ON: DE82005450
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM OXIDES
CALCIUM SULFATES
CHALCOGENIDES
CHEMICAL REACTIONS
DATA
DIFFUSION
ELEMENTS
EXPERIMENTAL DATA
FABRICATION
HIGH TEMPERATURE
INFORMATION
MOLDING
NONMETALS
NUMERICAL DATA
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PELLETIZING
PELLETS
POROSITY
PRESSURE DEPENDENCE
SULFATES
SULFUR COMPOUNDS
SULFUR DIOXIDE
SULFUR OXIDES
TEMPERATURE EFFECTS