Boiler feed water
A
boiler is a device for generating steam, which consists of two
principal parts: the furnace, which provides heat, usually by burning a
fuel, and the boiler proper, a device in which the heat changes water
into steam. The steam or hot fluid is then recirculated out of the
boiler for use in various processes in heating applications. The water circuit of a water boiler can be summarized by the following pictures: | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
The boiler receives the feed water, which consists of varying proportion of recovered condensed water (return water) and fresh water, which has been purified in varying degrees (make up water). The make-up water is usually natural water either in its raw state, or treated by some process before use. Feed-water composition
therefore depends on the quality of the make-up water and the amount of
condensate returned to the boiler. The steam, which escapes from the
boiler, frequently contains liquid droplets and gases. The water
remaining in liquid form at the bottom of the boiler picks up all the
foreign matter from the water that was converted to steam. The
impurities must be blown down by the discharge of some of the
water from the boiler to the drains. The permissible percentage of blown
down at a plant is strictly limited by running costs and initial
outlay. The tendency is to reduce this percentage to a very small
figure. | | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Proper
treatment of boiler feed water is an important part of operating and
maintaining a boiler system. As steam is produced, dissolved solids
become concentrated and form deposits inside the boiler. This leads to
poor heat transfer and reduces the efficiency of the boiler. Dissolved
gasses such as oxygen and carbon dioxide
will react with the metals in the boiler system and lead to boiler
corrosion. In order to protect the boiler from these contaminants, they
should be controlled or removed, trough external or internal treatment.
For more information check the boiler water treatment web page. In the following table you can find a list of the common boiler feed water contaminants, their effect and their possible treatment. Find extra information about the characteristics of boiler feed water.
Source: http://energyconcepts.tripod.com/energyconcepts/water_treatment.htm
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