Cogeneration Facility Uses Spray Nozzles to Cool Hot Spots in Boilers
 Steam Cools Hot Spots, Reduces Unscheduled Maintenance of Refractory Lining
PROBLEM: In the coal mining regions of Pennsylvania, cogeneration plants burn culm, anthracite coal's waste, in boilers to generate electricity. These large boilers produce intense heat causing erosion to the refractory material lining the boilers. The erosion affects the performance of the refractory material until eventually, heat passes through the liner to the outer steel shell, producing "hot spots" on the steel.
This cogeneration facility used a "makeshift" system of spray nozzles and lances to spray steam onto the hot spots. Typically steam isn't used as a coolant; but in this application the steam was actually cooler than the refractory and provided the necessary cooling.
However, the makeshift system distributed the steam inefficiently. The hot spots vary in width from 2" to 12" (5.1 to 30.5 cm) so it was difficult to accurately position the steam over each hot spot. Better control and positioning of the steam would provide more efficient use of the steam's cooling ability. Plus, the lances were poorly secured to catwalks around the boilers, creating not only an unsightly appearance but a potential safety hazard as well.
Because of the inefficiencies of this makeshift cooling system, "unscheduled" maintenance on the refractory lining was often necessary. This involved shutting down and cooling the boiler and repairing or replacing the worn refractory lining. The entire process could take up to three days, during which time, neither electricity - nor profit - was being produced.
SOLUTION: Spraying Systems Co. recommended the installation of two different types of spray nozzle assemblies. The spray nozzles are secured to portable lances allowing for easy movement as new hot spots are detected. The first lance is equipped with a single UniJet® blow-off nozzle which is specially designed to handle steam. The nozzle is aimed at a single hot spot for efficient cooling of small areas.
The second lance is equipped with a UniJet blow-off double swivel nozzle body. Its dual nozzles and adjustable fitting make it flexible enough to combat larger hot spots and to reposition the nozzles as needed.
The refractory lining is inspected during routine maintenance and then, after the boiler is up and running, the lances are repositioned as new hot spots become apparent. Productivity has increased while maintenance has decreased due to the efficiencies of this innovative steam spraying system.
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