LAB EXPERIMENT 05
Mill water treatment
PERFORMANCE/OBJECTIVES
Study of feed water treatment in a mill.TOOLS Water treatment
plantTHEORY Water is generally in forms soft water and hard water.
And for boiler purpose we have need soft water rather than hard
water. All natural waters contain varying amounts of suspended and
dissolved solids as well as dissolved gases (O2, CO2) The type and
amount of impurities in fresh water vary with the source (lake,
river, well) Impurities in water are of importance when water is to
be used for steam generation. For higher-pressure boilers, feed
water must be pre-treated to remove impurities
Impurities in water and effects on boiler:
REMOVING IMPURITIES FROM BOILER FEED WATER:Feed water is
filtered to remove suspended matter and if the suspended solids are
very fine, a flocculation step may be needed to enable effective
filtration
Filtration Filtration is the essential first step before the
chemical treatment. Filtration minimizes suspended solid
impurities. If rust, sand (silica) etc. is not filtered out; they
lead to severe scale formation.Chemical precipitation
Chemical precipitation is a process in which chemical added
reacts with dissolved minerals in the water to produce a relatively
insoluble reaction product. Precipitation methods are used in
reducing dissolved hardness, alkalinity, and silica. The most
common example is lime-soda treatment
Ion Exchange
Passing water through a simple cation exchange softener all the
Calcium and Magnesium ions are removed and replaced with Sodium
ions.Deaeration of water Dissolved oxygen in water is a major cause
of boiler system corrosion. It should be removed before the water
is put in the boiler. Membrane Contactors: Fabricated with
hydrophobic hollow, fiber micro porous membrane. They are installed
to control corrosion in boiler. By removing gases such as oxygen
and Carbon dioxide the amount of corrosion is reduced. These
devices do not require chemicals to operate so operating costs are
less
Reverse Osmosis In combination with other advanced technologies,
RO is being used to treat brackish water, industrial wastewater for
Boiler feedwater pretreatment.
RESULTS/ OBSERVATION:
Hence we learned what water treatment should be given before
putting it in to the boiler to avoid loss to the boiler
efficiency.
Name: _____________________________________________ ID No.
____________________
Score:________________ Signature of the lab tutor_______________
Date:_________________
12
