REPORT ON DM PLANT
NAME –SAURABH RANJAN
EMP. NO.- 900004
APCPL ET -09
There is continuous withdrawal of steam and continuous return of condensate to the boiler, losses due to blowdown and leakages have to be made up to maintain a desired water level in the boiler steam drum. For this, continuous make-up water is added to the boiler water system. Impurities in the raw water input to the plant generally consist of calcium and magnesium salts which impart hardness to the water. Hardness in the make-up water to the boiler will form deposits on the tube water surfaces which will lead to overheating and failure of the tubes. Thus, the salts have to be removed from the water, and that is ...view middle of the document...
■ Raw water contains many dissolved minerals and organic materials.
■ At high temperature certain minerals left scaling on the tube metal of the boiler and cause permanent damage.
■ Some dissolved minerals leads to corrosion of tube metals. Some leads to foaming
■ At high pressure and temperature an element, silica can be carried away with steam causing damage to turbine low pressure stage.
■ The performance and life expectancy of the station greatly depends on water chemistry compliance.
■ A Thermal Power Station needs water of varying quality for different process and hence the requirement.
Different water qualities in use at power plants
■ Boiler feed water…..Conditioned DM water.
■ Condenser cooling…..Raw water/ Clarified & post-chlorinated water
■ Other aux. cooling…..Clarified water.
■ H2 generation plant…..DM water.
■ ESP / Channel flushing…..Raw/ Clarified water.
■ Drinking water…..Filtered & post-chlorinated water.
■ DM plant operation…..Filtered water.
Steps of treatment process
■ Aeration of raw Adding chemicals for bacteria removal
■ Adding chemicals for sedimentation of suspended particles
■ Ion Exchange process
■ Water treatment process is generally made up of two sections :
■ Pretreatment section
■ Demineralisation section
1.1 Demineralization of Water Using Ion Exchange Resins – Ion Exchange
Natural water contains dissolved salts, which dissociate in water to form charged
particles called ions. These ions are usually present in relatively low concentrations. The
presence of some of these ions leads to problems for applications such as in heating
systems, steam generation etc. and hence are termed as ionic impurities. The commonly
encountered ions in water include the positively charged Cations, namely Calcium,
Magnesium and Sodium. The negatively charged anions include the alkalinity, sulfates,
chlorides and Silica.
Ion Exchange resins are well suited for removal of these impurities for the following
1. Resins have a very high capacity to remove ions in low concentrations.
2. Resins are most stable and can be readily regenerated.
3. Resins are stable over a wide range of temperatures.
4. The process is suitable for both large and small installations.
5. The process is reversible.
Ion Exchange Resins are generally insoluble polymeric materials manufactured using
suspension polymerisation using Styrene and Divinylbenzene (DVB) that carry ion
exchangeable functional groups.
These ions can be exchanged with stoichiometrically equivalent amount of ions of the
same sign. Carriers of exchangeable Cations are called Cation exchangers and that for
anions are called Anion exchangers.
Type I Type II
Ion Exchange Resins
1.2 Types of ion Exchange resins