How do Chemical Oxygen Scavengers Help Control Condensate System Corrosion?
As previously mentioned mechanical equipment (de-aerator) is often used to reduce feed-water oxygen. The best designed and operated de-aerators can reduce oxygen to as low as 0.007 parts per million or less. Most de-aerators or feed-water heaters are less effective. Since very samll amounts of oxygen, however, can cause boiler corrosion and corrosion in steam condensate system, chemical treatment is therefor, needed to assure complete oxygen removal. Sodium sulphate is the chemical most commonly used for this purpose. Greatly improved oxygen removal is obtained, hoev-er, when the sulphate is catalyzed. Catalyzed sodium sulphate can reduce oxygen content of water (at room temperature) from the saturation point to zero in less than 30 seconds. Without a catalyst it takes up to 10 minutes under the same conditionis to reduce the oxygen content by only about 30 per cent. Fast reac-tions are important since oxygen should be removed before the water enters the boiler. Otherwise some oxygen w
