The effect of potassium bromide and sodium carbonate on coal char combustion reactivity.

Journal Article · Mon Dec 01 04:00:00 EST 2003 · Proposed for presentation at the 30th International Symposium on Combustion held June 25-30, 2004 in Chicago, IL.

OSTI ID:970725

Molina, Alejandro; Shaddix, Christopher R; Blevins, Linda Gail; Murphy, Jeffrey J

The addition of halogens, particularly iodine, to the gas during coal char oxidation has been used in previous studies to quench gas-phase chemistry, thereby allowing one to separate the effects of homogeneous and heterogeneous reactions. Halogen addition suppresses the gas-phase radicals to near-equilibrium levels. A similar effect can be expected from other compounds with high efficiency as fire suppressants, such as alkali metals. The effectiveness of the use of additives in distinguishing homogeneous and heterogeneous reactions during char oxidation relies on the assumption that radicals are suppressed while heterogeneous reactions occurring on the char surface are not affected. The present work tests this assumption for potassium bromide (KBr) and sodium carbonate (Na{sub 2}CO{sub 3}) reacting with a pulverized eastern bituminous coal char during oxidation. An increase in CO and a slight reduction in particle temperature were observed with the addition of KBr, consistent with known effects of halogens on gas-phase chemistry. An increase in particle size was also observed with the KBr addition. This observation and the results of model calculations suggest that there is significant incorporation of liquid KBr on the char surface under the conditions examined. With Na{sub 2}CO{sub 3} addition, the particle temperature did not change, the particle size showed a slight decrease, and CO production increased. Although the mechanisms for Na interaction with radicals at combustion conditions are not well established, char oxidation modeling suggests that a decrease in OH concentration in the particle boundary layer is the cause for the observed increase in CO production. It is concluded that Na{sub 2}CO{sub 3} has clear advantages over KBr for inhibiting gas-phase chemistry without affecting char oxidation for the conditions investigated here.

• Research Organization: Sandia National Laboratories
• Sponsoring Organization: USDOE
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 970725
• Report Number(s): SAND2004-8017J
• Journal Information: Proposed for presentation at the 30th International Symposium on Combustion held June 25-30, 2004 in Chicago, IL., Journal Name: Proposed for presentation at the 30th International Symposium on Combustion held June 25-30, 2004 in Chicago, IL.
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
ADDITIVES
ALKALI METALS
BITUMINOUS COAL
BOUNDARY LAYERS
CHARS
CHEMISTRY
COMBUSTION
EFFICIENCY
HALOGENS
IODINE
OXIDATION
PARTICLE SIZE
POTASSIUM BROMIDES
PRODUCTION
RADICALS
SODIUM CARBONATES