Thermal stability of acidic sulfates in kraft recovery boilers

Journal Article · Sun May 01 00:00:00 EDT 1994 · Tappi Journal; (United States)

OSTI ID:7294214

Tran, H ^[1]; Poon, W; Barham, D ^[2]

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1. Pulp and Paper Centre, McGill, Quebec (Canada)
2. Univ. of Toronto, Ontario (Canada). Dept. of Chemical Engineering and Applied Chemistry

Acidic sulfates, such as NaHSO[sub 4] and Na[sub 2]S[sub 2]O[sub 7], are suspected in sticky deposit formation and tube corrosion in the generating bank and economizer regions of kraft recovery boilers. Their stability was examined in air, moist conditions, and in the presence of Na[sub 2]CO[sub 3] at various temperatures. The results showed that, in air, NaHSO[sub 4] melts and decomposes to solid Na[sub 2]S[sub 2]O[sub 7] and water vapor at about 180 C. Na[sub 2]S[sub 2]O[sub 7] is relatively stable up to its melting point of 380 C. Molten Na[sub 2]S[sub 2]O[sub 7] partially decomposes to solid Na[sub 2]SO[sub 4], which reacts with the remaining Na[sub 2]S[sub 2]O[sub 7] to form a newly identified compound, 3Na[sub 2]S[sub 2]O[sub 7][center dot]2Na[sub 2]SO[sub 4]; this compound melts at 570 C. Solid Na[sub 2]S[sub 2]O[sub 7] and its complex compounds react rapidly with H[sub 2]O vapor at 300 C to re-form liquid NaHSO[sub 4], which can be corrosive for the generating bank tubes during boiler operation. These acidic sulfates can coexist with Na[sub 2]CO[sub 3] below their respective melting points. They are hygroscopic, absorbing water from moist air to form sulfuric acid, which may cause tube wastage during boiler outages.

• OSTI ID: 7294214
• Journal Information: Tappi Journal; (United States), Vol. 77:5; ISSN 0734-1415
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
REFUSE-FUELED BOILERS
CORROSION
FOULING
SODIUM SULFATES
STABILITY
DEPOSITION
HEAT EXCHANGERS
MELTING POINTS
PAPER INDUSTRY
SODIUM CARBONATES
ALKALI METAL COMPOUNDS
BOILERS
CARBON COMPOUNDS
CARBONATES
CHEMICAL REACTIONS
INDUSTRY
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SODIUM COMPOUNDS
SULFATES
SULFUR COMPOUNDS
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
WOOD PRODUCTS INDUSTRY
092000* - Biomass Fuels- Combustion- (1990-)
320305 - Energy Conservation
Consumption
& Utilization- Industrial & Agricultural Processes- Industrial Waste Management