TYPE OF IMPURITIES INTO BOILER FEED WATER

Heii Askpowerplant users how are you? I hope you all are good today we discussed a very important topic related to boiler feed water chemistry in power plant .this topic is TYPE OF IMPURITIES INTO BOILER FEED WATER. if any impurities of boiler feed water which is discussed into this article exceed beyond the limit it cause the boiler corrosion or boiler chocking etc. so boiler feed water treatment is very crucial thing in terms of boiler operation so before boiler feed water treatment we should know about what type of impurities available into the boiler feed water .

The natural water contains solid, liquid and gaseous impurities and therefore, therefore this water cannot use for the generation of steam in boilers. The impurities present in the water should be removed before its use in steam generation. The necessity for reducing the corrosive nature and quality of dissolved and suspended solids in feed water has become increasingly important with the advent of high pressure, critical and supercritical boilers.

TYPE OF IMPURITIES INTO BOILER FEED WATER

The impurities present in the boiler feed water are classified as given below

–Undissolved and suspended solids materials
–Dissolved salts and minerals
–Dissolved Gases
— Other material (as oil, acid) either in mixed or unmixed forms.

A ) Undissolved and suspended solids materials

a) Turbidity and sediment

Turbidity in the water is suspended insoluble matter including coarse particle’s (mud, sediment, sand, etc.) That settled rapidly on standing. Amounts range from almost zero in most groundwater and 60,000 ppm in muddy and turbulent river water. The turbidity of feed water should not be exceeding 5 ppm. These materials can be removed by settling, coagulation, and filtration. Their presence is undesirable because heating or evaporation produces hard stony scale deposits on the heating surface and clog fluid system both are objectionable as they cause damage to the boiler system.

A standard amount of measurement of hardness is taken as being the amount of calcium carbonate ( caco3) in the Water and is referred to in part per million (ppm) or grain per gallon ( grains/gallon *17.1=ppm )

b) Sodium and Phosphate salts

These are extremely soluble in water and do not deposits unless highly concentrated. Their presence is troublesome as they are alkaline in nature and accelerate the boiler corrosion

C) Chlorides

Majority of the chlorides causes increased corrosive action of water.

d) Iron
Most common soluble iron in water is ferrous bicarbonate. The water containing ferrous bicarbonate deposits becomes yellowish and reddish sediment of ferric hydroxide if exposed to air. Majority of group surface water contains less than 5 ppm but even 0.3 ppm can create trouble in the feed water system by soft scale formation and accelerating the corrosion.

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e) Manganese

It also occurs in similar form as iron and it is also equally troublesome.

f) Silica

Most natural water contains silica ranging from 1 to 100 ppm. Its presence is highly objectionable as it forms a very hard scale in boilers and forms insoluble deposits on turbine blades. In modern high-pressure boilers, its presence is reduced as low as 10-50ppb.

READ MORE ARTICLES RELATED TO BOILER FEED WATER TREATMENT BELOW LINKS:

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Boiler Water analysis and its importance

WATER IMPURITIES AND THEIR CLASSIFICATION

Water impurities and their harmful effects on boiler

Filtration process in water treatment

Sedimentation Process in water treatment

WORKING PRINCIPAL OF MIX BED DEIONISER IN D.M PLANT

g) Microbiological growth

Various growths occur in surface water (lake and river). The micro-organisms are including diatoms, molds, bacterial slimes, algae, manganese & sulfate-reducing bacteria, and many others. These can cause the coating on the heat exchanger and clog the flow passages and reduce the heat transfer rate.

h) Color

Surface waters from Swamy areas become highly colored due to decaying vegetation. Color of feed water is objectionable as it causes foaming in boilers and may interfere with treatment processes. It is generally removed by chlorination or adsorption by active carbon.

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joginder chauhan

Hi, all power engineers. I am Joginder Chauhan. I am the founder of the website www.askpowerplant.com. I am also a power plant engineer with over ten years of experience in the power sector. During this period, I learned about different power technologies like AFBC, CFBC, TRAVELLING GRATE, PULSATING GREAT, PF BOILER, WHRS, and many more. My motive for this site is to share my power sector knowledge with every person who belongs to this field; on this website, I share information related to boiler operation, boiler maintenance, turbine operation & maintenance, boiler & turbine question answers, D.M plant, and all topic related to power plant sector please join this website for latest updation regarding power plant ………..thanks ( JOGINDER CHAUHAN )

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