Liquid ash corrosion, remaining life estimation and superheater/reheater replacement strategy in coal fired boilers

Conference · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5708902

Alice, J A; Janiszewski, J A

The liquid ash corrosion of superheater and reheater tubing in coal fired boilers is commonly accepted to be caused by the action of liquid sodium and potassium iron trisulfates Na/sub 3/Fe(SO/sub 4/) and K/sub 3/Fe(SO/sub 4/)/sub 3/. These species melt at temperatures between 1030/sup 0/F and 1160/sup 0/F (555-625/sup 0/C) depending on the relative amounts of sodium and potassium. Rapid tube wastage begins when the tube metal temperature reaches the trisulfate melting point. The key to improved availability in fossil boilers is to identify and replace, during a planned outage, tubes which are likely to fail before the next planned outage. The authors have developed a computerized method for estimating the remaining life of superheater/reheater tubes based on accelerated liquid ash corrosion. The scheme of analysis employs the following logic: (1) measurement of tube wastage from several removed samples, (2) estimation of tube metal temperature from I.D. scale thickness and thermocouple data, (3) estimation of trisulfate melting point from chemical analysis of the ash deposit and (4) using the computer model to calculate remaining life as a function of tube wastage rate metal temperature. The practical application of this strategy is presented for a coal fired boiler in the GPU system.

• OSTI ID: 5708902
• Report Number(s): CONF-851005-
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
014000 -- Coal
Lignite
& Peat-- Combustion
20 FOSSIL-FUELED POWER PLANTS
200104* -- Fossil-Fueled Power Plants-- Components
42 ENGINEERING
421000 -- Engineering-- Combustion Systems
ALKALI METAL COMPOUNDS
ASHES
AVAILABILITY
BOILERS
CARBONACEOUS MATERIALS
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
COAL
COMBUSTION
COMPUTER CALCULATIONS
COMPUTERIZED SIMULATION
CORROSION
CORROSION PRODUCTS
CORROSIVE EFFECTS
DIMENSIONS
ELEMENTS
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FOSSIL-FUEL POWER PLANTS
FUELS
HIGH TEMPERATURE
IRON COMPOUNDS
IRON SULFATES
LIQUID METALS
LIQUIDS
MATERIALS
MEASURING INSTRUMENTS
MELTING POINTS
METALS
OUTAGES
OXIDATION
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PIPES
POTASSIUM COMPOUNDS
POTASSIUM SULFATES
POWER PLANTS
RESIDUES
SCALING
SERVICE LIFE
SIMULATION
SODIUM COMPOUNDS
SODIUM SULFATES
SULFATES
SULFUR COMPOUNDS
SUPERHEATERS
THERMAL POWER PLANTS
THERMOCHEMICAL PROCESSES
THERMOCOUPLES
THERMODYNAMIC PROPERTIES
THICKNESS
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE