Wood drying Kiln: the efficiency of steam

Reduce water carry-over problems and save energy


Key points
Reduces blowdown rate

-80%

Eliminates carry-over problems
Saves energy

-1 000 000

BTU/day

Improves the overall process
The customer:
A leader in the production of OSB and lumber marketing in Canada. This plant specializes in the drying of softwood.
Background

The operation of a steam boiler in the wood drying industry poses several challenges. Surge demands for steam promotes water carry-over, which drastically reduces drying performance due to the loss of steam energy. In addition to this, carry-over also makes the boiler behave erratically due to of water level fluctuations, pipe ‘sloughing’ problems, hot water losses, and difficulties controlling the treatment program.

At the drying plant, there were few alternatives other than lowering boiler water conductivity to reduce water carry-over as much as possible. This already very inefficient method involved increasing the blowdown rate and, consequently, resulted in a costly loss of energy and treated water.


"The boiler’s power capacity is now working at 105%."



Solution

The conductivity maintained in the boiler water is connected to the concentration cycle attained before performing deconcentration blowdowns. Blowdowns are intended to eliminate the dissolved solids accumulated in water that promote water carry-over in steam. These solids come from makeup water, but also from treatment products used to protect equipment against corrosion and scaling. These products usually contain minerals and directly affect water conductivity.

The Aquafilm program was introduced and replaced conventional treatment methods to control water carry-over problems and reduce blowdown rates. Aquafilm was recommended due to its low contribution to boiler water conductivity as the treatment relies on the use of volatile organic ingredients.


Condition of the boiler tubes after using Aquafilm for 6 months.



Results

During the evaluation period with the conventional treatment method (phase 1), water carry-over was excessively high with peaks of more than 3000 μmhos/cm to the condensate. Even after significantly increasing the blowdown rate (phase 2), as illustrated by the drop in boiler water chloride concentration, episodic conductivity drifts in the condensate could be observed. As soon as Aquafilm was implemented (phase 3), condensate conductivity dropped to a stable average of 9 μmhos/cm. The gradual increase of the concentration cycles thereafter had no impact on steam quality.

Operation improvement: control carry-over

Boiler cycles

Condensate conductivity
Boiler operating at 105% rated steam capacity

Conclusion

Introducing Aquafilm technology has solved the recurring problem of water carry-over in steam, which had a drastic effect on the efficiency of the drying process. The use of volatile organic ingredients is clearly more advantageous than other conventional methods. Aquafilm improves the efficiency of operations, reduces blowdown rates, increases energy savings, and promotes treatment program stability.