To ensure a boiler runs properly over the course of its lifetime, treating the water that circulates within the system is mandatory. If the water is not treated properly, the boiler will begin to have problems within the first year, and its useful life will be significantly shortened.
Problems Generated by
Untreated water, even water coming from a municipal water utility, can contain dissolved solids, which form scale on the heat transfer surfaces as the water is heated. The main disadvantage of this deposited scale is that it drastically reduces the heat transfer capability of the boiler, which leads to overheating, tube failure and efficiency loss. Scale also reduces the flow area, which increases the pressure drop in boiler tubes and piping, resulting in low steam volume and potential equipment failure.
Benefits of Feedwater Treatment
Feedwater Treatment Equipment
Perhaps the most important piece of water treatment equipment is a water softener, which ensures good boiler water quality. Water softeners use a process called ion exchange to remove calcium and magnesium from the water. The hardness minerals are replaced with a highly soluble sodium or potassium ion that will not cause scale buildup, helping a boiler maintain efficiency throughout its life.
By preventing scale buildup, a water softener also reduces a boiler’s fuel consumption. A 1/16” thick layer of hardness scale can reduce heat transfer by about 12 percent, which is directly proportional to the increased amount of fuel required to compensate for the loss. The recommended hardness of boiler feedwater is less than 1 ppm, so a water softener is required for nearly all boilers.
If the boiler feedwater contains a high level of bicarbonate alkalinity and sulfates, a dealkalizer is recommended. Alkalinity is a measure of the capacity of water to neutralize strong acids such as carbonic acid, which is carbon dioxide dissolved in water. A dealkalizer keeps boiler and process equipment scale-free and also reduces corrosive condensate. This prevents scaling and reduces potential steel corrosion within the steam system.
Another piece of equipment commonly used for boiler water treatment is a deaerator or heated feedwater tank, which reduces oxygen and carbon dioxide to minute levels. The deaerator uses a mechanical scrubbing method to eliminate the harmful gases from a feedwater supply. It removes almost all harmful gases, with the remainder being removed by chemical means. For smaller facilities, a heated feedwater tank provides similar results and is more cost effective. A stainless steel tank is recommended to ensure long life.
A chemical feed system is typically required to remove the last 5 – 10 percent of impurities from boiler feedwater. Working with a chemical water treatment company makes the last stage of treating boiler feedwater easy to manage.
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This Boiler Information Tip was provided by Cleaver-Brooks