The kinetics of the reductive decomposition of calcium sulfate with carbon monoxide

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:7268432

Oh, J S

The kinetics were investigated using thermogravimetric equipment under various conditions of temperature (1050-1200 C) and gas composition (0-7% carbon monoxide, 0-10% sulfur dioxide, and 10-50% carbon dioxide). Pellets reacted at selected conditions were withdrawn from the reaction system at various stages of the reaction and analyzed by X-ray powder diffraction, scanning electron microscopy with electron microprobe, and BET surface area analysis. In contrast to previous views of the reaction, the reductive decomposition of calcium sulfate was found to involve two separate reactions: (1) the reduction of calcium sulfate to calcium oxide and (2) the sulfidation of calcium oxide to calcium sulfide. When the reducing potential was lower than 0.25, sulfidation did not appear to occur until the sulfate was almost completely converted to the oxide. The reduction of sulfate was found to take place simultaneously throughout a pellet, indicating negligible resistance to intra-pellet diffusion. On the other hand, sulfidation of the oxide seemed to follow a shrinking unreacted-core model. A mathematical model based on the Erofeev equation was developed to represent both the nucleation kinetics and the intrinsic gas-solid reaction kinetics. The rate of reduction was found to be first order with respect to carbon monoxide concentration and to have an activation energy of 479 kJ/mole. For the sulfidation of the oxide, a shrinking unreacted-core model of chemical reaction control was used to analyze the experimental data. The reaction was found to be first order with respect to carbon monoxide concentration, with an activation energy of 174 kJ/mole.

• Research Organization: Iowa State Univ. of Science and Technology, Ames, IA (USA)
• OSTI ID: 7268432
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102* -- Chemical & Spectral Procedures
ACTIVATION ENERGY
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM OXIDES
CALCIUM SULFATES
CALCIUM SULFIDES
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COHERENT SCATTERING
DECOMPOSITION
DIFFRACTION
ELECTRON MICROPROBE ANALYSIS
ELECTRON MICROSCOPY
ENERGY
EQUATIONS
GRAVIMETRIC ANALYSIS
KINETIC EQUATIONS
KINETICS
MATHEMATICAL MODELS
MICROANALYSIS
MICROSCOPY
OXIDES
OXYGEN COMPOUNDS
QUANTITATIVE CHEMICAL ANALYSIS
REACTION KINETICS
REDUCTION
SCANNING ELECTRON MICROSCOPY
SCATTERING
SULFATES
SULFIDATION
SULFIDES
SULFUR COMPOUNDS
SULFUR DIOXIDE
SULFUR OXIDES
SURFACE AREA
SURFACE PROPERTIES
THERMAL ANALYSIS
THERMAL GRAVIMETRIC ANALYSIS
VERY HIGH TEMPERATURE
X-RAY DIFFRACTION