How do you treat Boiler feed water?
A boiler feed water treatment system is a collection of technologies that address your unique boiler feed water treatment requirements.
The kind and amount of boiler-feed water treatment system are determined by the operating pressure. The feed-water requirements become considerably stricter as the boiler pressure increases. The maximum permitted hardness of boiler feed water operating at pressures of 0-10, 10-15, 15-30, and greater than 30kg/cm2 is 80, 40, 10, and 2 ppm, respectively. As a result, the softening treatment process must be carefully selected based on the needed circumstances. For boiler water treatment, a mix of water treatment procedures is sometimes used.
A well-designed and effective boiler feed water treatment system should be able to:
1: Before entering the boiler, efficiently treat the boiler feed water and eliminate any dangerous pollutants.
2: Encourage the use of internal boiler chemistry control.
3: Make the best use of steam condensate.
4: Prevent return-line corrosion.
5: Avoid plant outages and boiler breakdowns.
6: Extend the life of your equipment.
Basic processes followed in the treatment of boiler feed water
A: Membrane processeslike reverse osmosis and nanofiltration: Reverse osmosis (RO) and nanofiltration (NF) are frequently utilized later in the boiler feed water treatment system process to remove the majority of the dangerous pollutants that might foul and clog the RO/NF membranes.
They both push pressured water through semipermeable membranes, trapping pollutants such as bacteria, salts, organics, silica, and hardness while allowing concentrated, purified water to pass through. These filtering devices, which are not usually necessary in boiler feed water treatment, are primarily utilized with high-pressure boilers where the concentration of suspended and dissolved particles must be exceedingly low.
B: Coagulation/chemical precipitation: After removing all big items from the initial water supply, different chemicals are introduced to a reaction tank to remove bulk suspended particles and other impurities. This procedure begins with a series of mixing reactors, usually one or two that add specialized chemicals to remove all of the smaller particles in the water by combining them into heavier particles that settle out. Aluminium-based coagulates, such as alum and poly-aluminium chloride, are the most often utilized. A modest pH change may also help coagulate the particles.
C: Filtration and ultrafiltration: The following stage is often used to remove any suspended particles such as silt, turbidity, and some forms of organic waste. This is frequently advantageous early in the process since removing suspended particles upstream can help prevent membranes and ion exchange resins from fouling later in the pretreatment process. Depending on the type of filtration utilized, suspended particles as small as one millimetre can be eliminated.
D: Ion exchange/softening: When pre-treating boiler feed water, a softening resin can be used if there is significant hardness complexed with bicarbonates, sulphates, chlorides, or nitrates.This approach employs a strong acid cation exchange mechanism, in which resin is charged with a sodium ion, and when the hardness passes through, it has a stronger affinity for calcium, magnesium, and iron, allowing it to grasp that molecule and release the sodium molecule into the water.
Some boiler feed water treatment systems will use dealkalization after softening to lower alkalinity/pH, an impurity in boiler feed water that can cause foaming, corrosion, and embrittlement. A powerful anion exchange resin is used in sodium chloride dealkalization to substitute bicarbonate, sulfate, and nitrate with chloride anions. Although it does not completely remove alkalinity, it does remove the bulk of it in a simple and cost-effective manner.
E: Deaeration/degasification: Any condensate returned to the system at this stage in the boiler feed water treatment process will mix with the treated makeup water and enter the deaeration or degasification process. When gases like oxygen and carbon dioxide adhere to boiler equipment and pipes, they generate oxides and cause rust.
As a result, eliminating these gases to acceptable levels (almost 100 percent) might be critical to the boiler system's service life and safety. Deaeration devices exist in a variety of layouts depending on the manufacturer, but for degasification or oxygen scavengers, you may utilize a tray- or spray-type deaerator.
After thoroughly purifying the boiler feed water, it is sent into the boiler, where it is heated and utilized to produce steam. In the facility, pure steam is consumed, steam and condensate are lost, and condensate return is pumped back into the process to meet up with the pre-treated makeup water and cycle through pretreatment once again.
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