Molten salt interactions in coal processing. Final technical report. [In sodium carbonate, sodium carbonate/sodium sulfate mixtures and sodium chloride melts using oxidizing (air, oxygen and carbon dioxide) or inert (argon and nitrogen) sparge]

Technical Report · Fri Dec 30 04:00:00 EST 1983

OSTI ID:5524898

Dunks, G B; Stelman, D

The oxidation of spectroscopic-grade graphite in sodium carbonate, sodium carbonate/sodium sulfate mixtures, and sodium chloride melts using oxidizing (air, oxygen, and carbon dioxide) or inert (argon and nitrogen) sparge was investigated between 900 and 1050/sup 0/C. The oxidation rate increased with increasing graphite surface area, increasing melt temperature, and increasing oxygen concentration. The rate, at 900/sup 0/C using air sparge, was faster in pure sodium carbonate than in pure sodium sulfate with the maximum rate observed in mixed melts. At 950/sup 0/C, the oxidation rate was virtually equal in the two pure melts; at >982/sup 0/C, the rate was faster in pure sodium sulfate. In melts containing sodium sulfate, the rate-determining step was apparently the same for reactions conducted in oxidizing and inert atmospheres, with sodium sulfate acting as a catalyst in the former and a reagent in the latter. The overall oxidation rate using air sparge in sodium chloride melt was the slowest of the melts studied; however, the oxygen and temperature dependences suggested that the rate-limiting step was the same as in sodium carbonate melt. Electrochemical evidence for the formation of metallic sodium suggested that a first step in the oxidation process was the reduction of sodium ion by graphite. The positive centers thus generated in the graphite matrix apparently reacted with oxyanions in the melt to produce carbon monoxide and/or carbon dioxide. The oxidation rate of a graphite electrode using carbon dioxide-containing sparge gas was increased by applying positive potentials and decreased by applying negative potentials, which supports such an ionic mechanism. The initial rates of graphite oxidation using nitrogen or carbon dioxide sparge were approximately equal and were 6.5 times slower than the rate using air in sodium carbonate melt. 51 figures, 9 tables.

• Research Organization: Rockwell International Corp., Canoga Park, CA (USA). Energy Systems Group
• DOE Contract Number: AT03-76ER70030
• OSTI ID: 5524898
• Report Number(s): ESG-DOE-13419; ON: DE84004745
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010404 -- Coal
Lignite
& Peat-- Gasification
010600* -- Coal
Lignite
& Peat-- Properties & Composition
36 MATERIALS SCIENCE
360603 -- Materials-- Properties
AIR
ALKALI METAL COMPOUNDS
CARBON
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBONATES
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
COMPARATIVE EVALUATIONS
DATA
ELEMENTAL MINERALS
ELEMENTS
EXPERIMENTAL DATA
FLUIDS
GASES
GRAPHITE
HALIDES
HALOGEN COMPOUNDS
INFORMATION
KINETICS
MINERALS
NONMETALS
NUMERICAL DATA
OXIDATION
OXIDES
OXYGEN
OXYGEN COMPOUNDS
REACTION KINETICS
SODIUM CARBONATES
SODIUM CHLORIDES
SODIUM COMPOUNDS
SODIUM SULFATES
SULFATES
SULFUR COMPOUNDS
TEMPERATURE DEPENDENCE
VERY HIGH TEMPERATURE