ion-exchange process (softener plant) water passes through bed of natural zeolite of synthetic resin...

Ion-exchange process (softener plant)• Water passes through bed of natural zeolite of synthetic resin to

remove hardness• Calcium (Ca) and magnesium (Mg) replaced with sodium (Na) ions• Does not reduce TDS

External Water Treatment

1

Softener Plant

2

DM System

3

4

Osmosis• Solutions of differing concentrations

• Separated by a semi-permeable membrane

• Water moves to the higher concentration

External Water Treatment

5

Reversed Osmosis (RO)• Higher concentrated liquid pressurized

• Water moves in reversed direction

External Water Treatment

6

RO System

7

8

Electrodialysis

9

Electrodialysis for Water Treatment

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External Water Treatment

&

Internal Water Conditioning

11

Prevention of internal scale by forming deposits in sludge shape

Injection of chemicals•Different chemicals for different water impurities

•Conditions:

For low amounts of feed water impurities

For low pressure boilers, TDS content has higher limits

Internal treatment alone not recommended

Internal Water Conditioning

12

Scale control

Injection of chemical additives• Minerals (Na2CO3, Na3PO4, Na2HPO4,

NaH2PO4, (NaPO3)6 ,…)• Organics (Chelants, Lignins, Starches,

Tannins, …)• Minerals + Organics

Chelants (NTA, EDTA, …)

Internal Water Conditioning

13

De-aeration• Removal of various dissolved gases from

water (O2, CO2, …)

• These gases are corrosive.• De-aerator can decrease amount of dissolved

gases in water.

External Water Treatment

14

External Water Treatment

Steam

Storage Section

De-aerated Boiler Feed Water

Scrubber Section (Trays)

Boiler Feed Water

Vent

Spray Nozzles

• O2 and CO2 removed by heating feed water

• Economical treatment process

• Vacuum type can reduce O2 to 0.02 mg/L

• Pressure type can reduce O2 to 0.005 mg/L

Mechanical de-aeration

15

Removal of Dissolved Oxygen TracePitting Corrosion control

• Sodium sulphite:

Increases TDS: increased blow down

• Hydrazine

Does not increase TDS: used in high pressure boilers16

2 3 2 2 42Na SO O 2Na SO

2 4 2 2 2 2 2N H (NH NH ) O 2H O N

Mechanical (Boiler design) High level of water in drumsDeficiency on separator operationSudden increasing boiler load (reduction of pressure)

Chemical High TDSHigh alkalinityOil and organic impurities

Causes of Carry Over

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Corrosion & scale control

Acid (H+) attackAdjustment of water pH based on

manufacturer recommendation

Water Conditioning

18

Caustic embrittlement control

Adjustment of water NaNO3/NaOH ratio depending to boiler pressure (According to manufacturer recommendation)

Water Conditioning

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• Controls TDS of the boiler water

• Boiler sludge conditioning

• Blows off water and replaces it with feed water

• Conductivity measured as indication of TDS levels

Boiler Blow Down

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Benefits• Lower pretreatment costs

• Reduced maintenance downtime

• Increased boiler life

• Lower consumption of chemicals

Boiler Blow Down

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Types of blow down• Batch (Periodic)

• Manually operated valve reduces TDS• Large short-term increases in feed water• Substantial heat loss

• Continuous• Ensures constant TDS and steam purity• Heat lost can be recovered• Common in high-pressure boilers

Boiler Blow Down

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• Application of proper external treatment

• Application of accurate internal conditioning

• Amounts of used chemical

• Amounts of produced wastes/sludge

• Amounts of wasted water (blow down)

• Cost of monitoring & Control

• Economy of water treatment/conditioning

• Recirculation of used steam

Water/Chemical Economics / Optimization

23

THANKSFOR YOUR ATTENTION

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