Boiler Feedwater Systems use water to supply, or in this case “feed”, a boiler so it can generate steam or hot water. For some industry needs the feedwater is stored, pre-heated and conditioned in a feedwater tank before it goes into the boiler via a feedwater pump. That’s what we are talking about today.
Feedwater is most often a combination of return water and fresh water purified in 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 from the boiler it contains liquid droplets and gases. The water that remains at the bottom of the boiler picks up any leftover foreign matter so these impurities need to be emptied from the boiler into drains.
To avoid problems in the boiler system, the feedwater should be properly conditioned. The water needs to be high quality since untreated water and its impurities can cause significant problems to the system like those below:
Corrosion
Corrosive “leftovers” are usually removed with a deaerator. Deaerators are nothing new. They’ve been used in power plants and water tube type boilers because they remove undissolved oxygen and raise the temperature of the feedwater. Operating costs can be reduced by recovering flash steam when returned by high temperature condensate. Since feedwater temperatures are also raised, less boiler fuel is required to convert feedwater to useable steam. Boiler tubes, condensate lines, and process piping have a much longer life when the pitting action of untreated water is eliminated. Feedwater needs to be alkalized to a pH of 9 or higher to reduce oxidation and to support the forming of a stable layer of magnetite on the waterside surface of the boiler. This will protect the material underneath from further corrosion.
Scale and Sludge
Feedwater conditioning is critical. Without proper conditioning during operation, heat from the burner can release oxygen in raw feedwater in the form of bubbles that can attach to boiler tubes and the sides of the boiler drum shell. These bubbles can cause scale, corrosion and sludge to form. Any scale and sludge need to be cleaned out on a regular basis because when deposits are left behind they reduce heat transfer in the boiler, reduce the flow rate and eventually they will cause blockage in the boiler tubes. Any non-volatile salts and minerals that remain once the feedwater is evaporated have to be removed because by this point they would be concentrated and require excessive “blow-down” (draining) to avoid solid crystals from forming. Minerals that form scale can be even worse. This is the whole reason for adding demineralized water to replace feedwater losses.
Sufficient Water
Another important factor is keeping enough water in the boiler. Otherwise the boiler system can shutdown due to the low water condition. This makes it exceedingly important to size a feedwater system so it will be able to maintain a proper water level in the boiler at all times. A properly sized feedwater system will have a tank that is capable of feeding the boiler and pumps to deliver water at the correct rate and pressure.
Carbis Fluid Handling, LLC specializes in Boiler Feedwater Systems and can design a system to fit your particular business applications. We also carry chemical dosing systems for boiler feedwater treatment. These systems can make workflow more efficient by accurately metering corrosion inhibitors, pH control, the use of oxygen scavengers, and more thereby keeping your boiler system running smoothly for a long time. Contact Carbis Fluid Handling, LLC today, and see how a Boiler Feedwater System can make things more efficient and cost-effective for your company.
