CONDENSATE MANAGEMENT

When steam condenses, energy is transferred to the cooler material to be heated. This accounts for only around 75% of the energy supplied in the boiler to produce the steam. The remainder, about 25%, is still held by the condensed water.

As well as having heat content, the condensate is distilled water: ideal for use as boiler feed water. An efficient installation will collect every drop of condensate it economically can, and either return it to the deaerator or boiler feed water tank, or use it in the process.

Condensate is discharged through steam traps from a higher to a lower pressure. As a result of this drop in pressure, some of the condensate will then re-evaporate, and is referred to as flash steam. The proportion that will flash off differs according to the level of pressure reduction between the ‘steam’ and ‘condensate’ sides of the system, but a figure of 10-15% by mass is typical.

About half of the energy mentioned above (i.e. 12.5% of the total energy supplied) could be lost through flash steam

Flash Steam Recovery along with condensate return is therefore an essential part of achieving an energy efficient system.

An effective condensate recovery system collects the hot condensate from the steam using equipment and returns it to the boiler feed system. It can rapidly pay for itself in reduced fuel costs alone. The graph here illustrates the heat content of steam.

e.g. For saturated steam at 7 bar g:

Total energy in steam(from Steam Tables)	= 2769 kJ/kg
Energy transferred to the product when the steam condenses	= 2048 kJ/kg
Energy left in condensed water	= 721 kJ/kg
Proportion of total energy which left the boiler house	= 721/2769 = 26 %

The advantages of recovering the condensate are as follows:-

 

•  As condensate is recovered, the energy costs are reduced.

• Water Charges

• Effluent Restrictions

• It Maximizes Boiler Output

• It is Ideal Boiler Feed Water

• Savings by Condensate Recovery