Advanced economizers were installed two years ago as part of major upgrade of eight boilers in a district heating plant operated by Toronto-based Enwave Energy Corp.
Each gas-fired boiler is 14 by 45 by 12' and weighs about 65 tons. Each watertube boiler has a steam-generating capacity of 100,000 lb/hr at 390°F (199°C) and 200 psig. The combustion temperature of the flame inside the firebox on these boilers is approximately 2,200°F (1,204°C), and the flue gas leaving the boilers ? which heats the economizers ? is 450 to 550°F (232 to 288°C).
Early tests of the first two boilers showed a 79 to 96 percent increase in combustion efficiency. This boosted the boiler output from 100,000 to 120,000 lb of steam per hour and saved 11.5 billion BTUs per boiler, when operated for a full 170-day heating season. The exhaust temperature from the boilers was reduced from 550 to 95°F (288 to 35°C) without precooling, and the unsightly plume from the plant’s 300’ stack completely disappeared.
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