Learn about boiler feed water:
Boiler feedwater requires, in addition to the usual criteria for feed water, a special higher quality criterion for water hardness. This requirement is to prevent as much as possible deposition, scale build-up that corrodes the system, reduces heat transfer capacity and can cause bad consequences for the system.
Steam power is widely used in many industries with the general principle that heat is converted to steam and thus insoluble and water-soluble residues are retained in the boiler.
Boiler feed water must therefore meet high quality criteria for hardness.
Under the action of heat, the process of water evaporation occurs and along with that process, the chemicals in the water change according to their own physical processes, many substances are produced and many substances are decomposed leading to the formation of water. Insoluble residues stick or deposit, interfering with heat transfer and transport in the equipment. Each type of residue has specific physical and chemical properties in terms of color, hardness, adhesion to metal surfaces..
Chemical components that deposit and stick in the boiler:
- Residues of alkaline earth metal compounds are mainly calcium and magnesium such as CaCO3, CaSO4 ….and are named according to the maximum composition such as carbonate, sulfate, phosphate…
- Residues of iron compounds such as: Fe2O3, FeSiO3 ….
- Residues of copper compounds and silicate residues.
How are scaling and corrosion in boilers classified?
Boiler sludge is classified as follows:
– The protective layer of iron oxide is much needed: dark brown to black, very thin (<< 0.1 mm), solid like a laminated scale, this deposit does not increase the temperature of the heat exchanger wall surface
– Unwanted porous scale: gray or light brownish color made up of contaminants in the water (mainly hard bite, or siliceous deposits), this deposit always increases the temperature of the exchange wall surface. heat exchanger
– Porous sediment layer: light brown to reddish brown in color, is the product of the iron corrosion process, formed mainly by the amount of iron present in the boiler feed water – boiler. This layer of sediment is almost unavoidable in the boiler – boiler system
– Local blistering or peeling like scale due to corrosion caused by oxygen during kiln shutdown.
Unwanted scale will increase the temperature of the furnace wall. This temperature rise depends on the thickness, composition and porosity of the deposit layer and can lead to overheating of the material, loss of strength, damage or explosion of the boiler-boiler.
Corrosion process in boiler – boiler is mainly electrochemical corrosion. This is a reaction between a metallic material and the environment that results in the material or component being destroyed earlier than its normal life.
Boiler water treatment:
Water treatment inside boiler:
That is, the treatment process by quantitatively adding moving chemicals to feed water and boiler – boiler water to create sludge in the boiler – boiler. This method of treatment is applicable only to boilers – boilers with low heat transfer efficiency.
Hardness and silicate deposits can be significantly reduced if a sufficient amount of Na3PO4 is added in proportion to the initial hardness of the feed water. The carbonate and non-carbonate hardness reacts with phosphate and produces calcium and magnesium phosphate deposits, which mostly exist suspended in the boiler water – boiler. During operation, the residue needs to be removed through a sufficiently large blowdown. After the operation, it is necessary to remove all the deposits deposited in the boiler – the boiler through additional blowdown.
Water treatment outside boiler:
Using water softener to retain the hardness on the exchange resin and change the hardness by sodium, it is better improved if adding RO purified water filter or demineralization device.
KS – Boiler specializes in manufacturing, installing and maintaining industrial boilers:
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