Boiler Feedwater Systems use water to “feed” a boiler in order to generate steam or hot water. Depending on the industry needs for a feedwater system can differ. What we’re addressing today is an instance when feedwater is stored, pre-heated and conditioned in a feedwater tank before it goes into the boiler by way of a feedwater pump.
What is Feedwater exactly? Usually it’s a combination of return water and fresh water purified to varying degrees. Feedwater composition depends on the purity of the make-up water and the amount of condensate returned to the boiler. When steam escapes the boiler it is made up of gases and liquid droplets. The water that remains at the boiler’s base will pick up any leftover foreign matter so these impurities need to be emptied from the boiler and drained away.
To avoid creating problems in the boiler system, the feedwater has to be properly conditioned. The water needs to be high quality because untreated water can cause big problems to the system like the issues below:
Corrosive matter is often removed with a deaerator. Deaerators are used in power plants and water tube type boilers because they do two things – remove undissolved oxygen and raise the temperature of the feedwater. Flash steam can be recovered from high temperature condensate and because feedwater temperatures are also raised, less boiler fuel is needed to convert feedwater to steam thereby producing monetary savings.
Untreated water can cause pitting in the condensate lines, boiler tubes, and process piping of the feedwater system. To preserve your system and give it a longer life, feedwater must be alkalized to a pH of 9 or higher to reduce oxidation and support the forming of a stable layer of magnetite on the waterside surface of the boiler. This layer protects the material underneath from further corrosion.
Scale and Sludge
Feedwater conditioning is critical. Without proper conditioning during operation, heat from the burner can release bubbles of oxygen into raw feedwater. Not good. These bubbles can attach to boiler tubes and the sides of the boiler drum shell and cause scale and sludge to form. Any scale and sludge has to be cleaned out on a regular basis. If deposits are left behind they can reduce heat transfer in the boiler, reduce the flow rate and will eventually cause blockage in the boiler tubes. Minerals that create scale are even worse. That’s why demineralized water is added to replace feedwater losses.
If the boiler system does not contain enough water it can shut down. This is why it’s so important to properly size a feedwater system so it will maintain the correct water level in the boiler at all times. A properly sized feedwater system has a tank that can feed the boiler and pumps that deliver water at the correct pressure and rate.
Carbis Fluid Handling specializes in Boiler Feedwater Systems. We can design and engineer a system to suit your unique needs. We also have chemical dosing systems for treating boiler feedwater. These feedwater systems create a more efficient workflow by metering corrosion inhibitors, pH control, and the use of oxygen scavengers. Contact Carbis Fluid Handling today and see how we can help make your company more efficient.