Economizer recirculation for low-load stability in heat recovery

Details Economizer recirculation for low-load stability in heat recovery Economizer recirculation for low-load stability in heat recovery

1985-06-20

1986-04-15

Favors, Edward G.

Liquid heaters and vaporizers

Feed heaters

Boiler circuit

122406R, 122452, 122456, 122477, F22D 100

Patent

active

045820279

ABSTRACT:
A recirculation apparatus is employed to recirculate a portion of the feedwater in a vertical-tube economizer to reduce the likelihood of reverse flow and steaming at startup and/or low load. A recirculation valve, opened at low load, directs part of the water from the economizer outlet back to the inlet of the boiler feed pump via a deaerator. The recirculated water not only increases the pumping head across the economizer tube planes, but also reduces the temperature rise of the increased water flow rate passing through the economizer tubes which now enters the economizer tube bank at an elevated temperature. The reduced temperature rise in a given single pass through a tube plane consequently reduces the buoyant force which opposes the pumping head in downflowing tube planes. Additionally, the amount of water being recirculated at these light load conditions results in a total boiler feed pump flow which is well within the capacity of a given pump size without consideration of the present invention. Furthermore, a simple control system could be employed whereby the recirculation valve is opened or closed dependent upon the level of gas turbine loading compared to a predetermined stability threshold load level.

REFERENCES:
patent: 2594471 (1952-04-01), Marshall
patent: 2702026 (1955-02-01), Dalin
patent: 3349755 (1967-10-01), Miller
patent: 4206802 (1980-06-01), Reed et al.

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