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Pumping condensate near boiling point using traditional centrifugal pumps reduces condensate temperature and wastes useful energy. Instead, using steam operated pumps, which successfully pump condensate at high temperatures, results in savings.

Condensate forms at a temperature close to boiling point. While pumping condensate centrifugal pumps loose heat which reduces the temperature of condensate. Additionally, hot condensate damages the pump via cavitation.

A low pressure area in the pump called the ‘eye’ produces the suction effect, drawing liquid into the pump. Though the drop in pressure is small, because condensate is close to its vapor pressure, even small pressure difference causes a portion of it to flash into steam in the form of small bubbles. While traveling through the impeller passageways of the pump, these bubbles experience increasing pressure.

At a point, this pressure exceeds the vapor pressure causing the steam bubbles to implode with considerable force. The resulting damage, cavitation, damages the inner surface of the pump. In this process 10kcal/kg heat is lost, reducing the condensate temperature.

Instead, the use of steam operated pumps can result in both an avoidance of pump damage and a safe handling of boiling condensate. Additionally, because these pumps run on steam, alternative sources of energy are unneeded.

Illustration:

Energy Lost
A Per hr 2000 x 10 kcal/hr =
20000kcal/hr
B Energy from 1 ltr of Furnace oil (F.O) burnt
in the boiler
10200 Kcal/kg x0.8* =
8160
Equivalent F.O lost
C Per Hour (A/B) /0.95** 2.6 ltrs
D Litres of Furnace oil lost per Day
C x 24 hrs)
62.4 ltrs
E Litres of Furnace oil lost annually
(D x 330 days)
20.5 Kilo liters

Consider 2 TPH of condensate being pumped via a traditional centrifugal pump.

* Assuming boiler efficiency of 80%

** Assuming FO density of 0.95.