APPLICATION REPORT
Power Plant Coal Silos
Industry: Power Plant, Midwest US
Problem: In a large 3300 megawatt power generation plant, 28 - 1000 ton coal pulverizer feeder silos were in an advanced stage of deterioration due to aggressive rusting of the ASTM 242 weathering steel. Engineers at the power plant had attempted to sand blast the steel surface and apply epoxies but as soon as it was sandblasted it immediately formed a coat of rust and the epoxies would not adhere to the surface. After this attempt failed they felt they would have to remove and replace all 28 coal silos. Estimated labor and material cost was between $500,000 and $750,000 per silo. Engineers were desperately seeking a more cost-effective solution to restore the silos to normal operating conditions.
Solution: Power plant engineers restored (rather than replaced) the silos by lining the sloping portions of the coal silos with Phoscrete Concrete, one inch thick.
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Phoscrete Liner was placed on the sloping portion
of the silos and 1 foot up the vertical walls. |
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Savings Using Phoscrete: Labor and material cost averaged less than $ 50,000 per silo, saving at least $500,000 per silo x 28 = $14 million.
Products Applied: Phoscrete 601
Method of Installation: Gunning
Equipment Used: Allentown double chamber gunnite machine with 1200 ft of line, 1200 cfm compressor.
Scope of Work: Wash down inside of silo with a prep coat of Liquid Activator to remove coal particles and combat rust. Allow to dry. Feed Phoscrete 601 dry aggregate and pre-measured Liquid Activator through the double chamber gunnite machine and line the inside of the silo one inch (1”) thick with Phoscrete. Wait one (1) hour and return to service. Repeat 27x.
Installation Date: September 1990
Phoscrete Stopped the Rusting on the A 242 Weathering Steel. The phosphoric acid component of Phoscrete converts iron oxides (rust) into metal phosphates (bonding agent). The Phoscrete Liner formed a strong chemical bond to the steel and protects the silos from future corrosion and deterioration.
Phoscrete is Abrasion Resistant. Because of the high alumina content, Phoscrete delivered superior resistance to abrasive wear and erosion due to the large amount of coal processed through the silos.
Follow Up: The 28 Phoscrete-lined coal mill silos have been in service more than eighteen years and processed nearly 200 Million tons of coal.
In October 2008, Power Plant Engineers reported that the Phoscrete Liners in all 28 silos show very little wear and they expect that the silos will easily handle an additional 200 Million tons of coal.
Based on the success of the Phoscrete Liners in the coal silos, Phoscrete was used at one of their other plants to restore the service life of a 600 ton coal bunker.