Combustion properties of kraft black liquor solids were studied using a
laminar entrained flow reactor. The tendency of black liquors to release fume
(compounds containing Na⁺, K⁺, Cl⁻, SO₄²⁻, SO₃²⁻, S₂0₃²⁻ and C0₃²⁻) during
combustion were observed at 1000°C. Black liquor solids with a size fraction of
63 to 100 μm were burned in a mixture of 4% 0₂ and 96% N₂ at a residence time of
0.67 seconds. Combustion properties of one black liquor (liquor #3) were studied
by varying the solids feed rate from 0.47 to 1.08 g/min (liquor feed rate study).
Combustion properties of five North American and Finnish black liquors were
studied at a target solids feed rate of 0.73 g/min (liquor to liquor study).
Black liquor fuming was observed to be a decreasing function of solids feed
rate and an increasing function of excess oxygen. The appearance of char residues
varied from black and porous at high solids feed rates to white and dense at low
solids feed rates. Combustion may have been enhanced at low solids feed rates by
liquor swelling due to a combination of heat and mass transfer effects and limited at
high solids feed rates by inter-particle and bulk gas mass transfer limitations.
For the liquor to liquor study, black liquors were observed to release fume
differently. Chars produced during this study varied in appearance, indicating that
the black liquors had unique combustion properties. Variations in temperature and
mass transfer effects resulting from liquor swelling properties were likely responsible
for the variability in liquor fuming behavior. The liquors that contained the most
NaCl and had the highest anionic equivalents as C0₃²⁻ (or other chemical species)
produced the most fume. Sodium vaporization varied from 25.2% to 33.7%:
Liquors #2 and #5 vaporized the most sodium and also had the lowest
concentrations of measured anions in their char residues.
Potassium and chloride enrichment factors for the five liquors were slightly
lower than those of common industrial boilers. Liquor #3 had a concentration of Cl⁻
that was (roughly) an order of magnitude higher than the other liquors studied;
however, it also had the lowest chloride enrichment factor. / Graduation date: 2002
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29075 |
| Date | 08 June 2001 |
| Creators | Train, Ron |
| Contributors | Frederick, W. James |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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