Boiler Water Treatment (16-20).ppt

8/9/2019 Boiler Water Treatment (16-20).ppt

1/23

Water Systems: water

conditioning for Process and

Boiler use•Prajakta Desai

•Niranjani Deshpande

•Sukhada Dhone•Sanuj Dubey

•Neille !ernandes


2/23

"ntroduction

• "ndustrial water

# Process water: Water that is used for$ or

comes in contact with an end product or the

materials used in an end product%

# Boiler feed water

# Water that seres in any leel of the

manufacturing process• &ommon contaminants: &a$ 'g$ !e$ (l$

Silica$ silt$ oil


3/23

Impurity Resulting in Got rid by

Soluble )ases *+S &orrosion of boiler tubes (eration$ deaeration andchemical treatment

,+

&,

Suspended

solids

Sediment and

turbidity

Sludge and scale carryoer &larification$ filtration and

chemical treatment

&arryoer$ foaming andcorrosion,rganic matter

Dissoledcolloidal solids

,il and grease !oaming$ deposition &oagulation$ filtration

*ardness &a

- 'g

Scaling$ inhibits *.$ boiler tube

burn thru

Softening and internal treatment

Na$ (lkalinity$Na+&,/$

!oaming$ corrosion$embrittlement

"on e0change$ deioni1ation

Sulphates *ard scales if &a present Deioni1ation

&hlorides Priming$ foaming Deioni1ation

!e$ 'n 2usting$ resistence to *. (eration$ filtration$ ion e0change

Silica Scaling Deioni1ation$ lime3soda process


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.reatment 'ethods

• 40ternal .reatment

• "nternal .reatment


5/23

40ternal methods of

conditioning• &larification

• !iltration

• "on e0change• 'embrane separation


6/23

&larification

• 2emoes all types of solids - large particles # sediments$ oil$

natural org% matter$ colour etc%

• &onsists of 5 steps # screening$ coagulation3flocculation$

sedimentation$ fine filtration%

• Screening protects downstream units from large$ easily separableobjects%

• .hree types:

# !ine screening 6spacing 7 89 mm

# 'edium screening 6spacing 89 # 59 mm

# &oarse screening 6spacing ; 59 mm

• &oagulation3flocculation remoes suspended solids - colloidal

particles%


7/23

&larification 6contd%

• "mportant factors # elocity gradient$ time$ p*

• !lotation # to separate particles haing density lesser

than water%

• .hree types: # Natural

# (ided

# "nduced

• "nduced flotation facilitated through bubbling of air< +types #

# Dissoled air flotation 6D(! 6bubbles of 59 # =9 µm

# 'echanical flotation 6bubbles of 9%+ # + mm


8/23

!iltration

• Separates undissoled solids from water by means of a

filter 3 porous substance$ membrane or permeable fabric%

• .hree types of filtration:

#'icro filtration 6pore si1e 9%8 # 89 >m

# ?ltra filtration 6pore si1e 83899nm

# Nano filtration 6pore si1e 7 8 nm

• 'icro filtration # remoes bacteria< used for biological

wastewater treatment$ effluent treatment$ separation ofoil3water emulsions%

• ?ltra filtration 3 separation of suspended solids$ colloids$

bacteria$ irus%


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!iltration 6contd%

• + ultra filtration module configurations:

# Pressuri1ed system or pressure3essel configuration

# "mmersed system

• Nano filtration # water softening$ decolouring$ micro3pollutant remoal 6org% matter$ heay metals$ pesticides%

• ?ltra - nano filtration # pressure drien processes%

• Pre3treatment # protects filtration membranes<

microfiltration # pre3filter for ultra filtration and so on%


10/23

"on 40change

• 2esins 3 acidic@basic radicals with ions fi0ed on them< e0changed

with ions present in water%

• .heoretically remoes 899 A of salts< does not remoe organics$

irus or bacteria%

• + types of resins # gel type 6microporous and macroporous orloosely cross3linked type%

• / systems of resin beds:

# Strong acid cation Strong base anion

# Strong acid cation weak base anion Strong base anion # 'i0ed3bed Deioni1ation

• "on e0change plant # softens water$ remoes heay metals$

produces deminerali1ed water%


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2eerse ,smosis 62,

• By applying pressure greater than osmotic pressure$ water flows from

the higher concentration solution to lower one%

• 'ostly used for desalination< also for waste water treatment%

• (pplied pressure depends on the type and salinity of water%

• Working pressure: # 7 8C bar for tap water 67 8C99 ppm

# 8C # +C bar for brackish water 67 999 ppm

# C9 # =C bar for sea water 6/C999 # 5C999 ppm

• 2, plant preceded by pretreatment to aoid membrane fouling by

sediments$ bacteria$ metal o0ides - chlorine%

• 2, permeate water more acidic than the feed water due to dissoled

&,+% &ommon post3treatment are p* neutrali1ation and

reminerali1ation%


12/23

4lectrodioni1ation

• &ombines membrane separation and ion3

e0change to proide high efficiency

deminerali1ation process%

• 4lectric potential transports - segregates chargedaEueous species%

• 4lectric current continuously regenerates resin< no

need for periodical regeneration%

• Deioni1ation chamber 3 ion e0change resin$

packed between cationic - anionic e0change

membranes%


13/23

4lectrodioni1ation

• (dantages

# continuous operation

# eliminates use of chemicals for regeneration

# low power consumption

• Disadantages

# Not used for water with hardness ; 8

# reEuires purification pretreatment

# Pre3remoal of &,+


14/23

"nternal .reatment methods

• Deaerators:

• Dissoled non3condensibles: ,+ and &,+

• Pitting and corrosion• 'echanical deaeration: reducing solubility of gases

# "ncreased temperature # Decreased partial pressure oer the water # &ommonly used purge gas: steam # (dantages:

# No added impurities # 4asily aailable # (lso proides heat

# Pressure@Facuum operation$ GHA of total and free is remoed

• &oupled with chemical scaengers for completedeaeration


15/23

&orrosion control

• p* control # Different for different components$ different

alloys

# &S : optimum p* I H%+ to H%J at feed watertemperatures

# 'S : optimum p* I %C to 8+%= in boilers

# &u and &S : % to H%+

# 'aintained by addition of amines or smallamount of caustic soda

# (oidance of addition of ammonia


16/23

&orrosion control contd%

• ,0ygen control: during operation

# &hemical Scaengers added to feedwater and

condensates

• Sodium sulfite$ bisulfite$ hydra1ine• Kuinone$ ascorbate

# &ommon entry: between deaerator and storage

Sodium sulfite: easy to handle$ safe$ for pressures of 7 =9 bar$

solid addition to system$ decomposition to corrosie gases

*ydra1ine: no solid addition$ high pressures$ but to0ic$ handling

issues$ (mmonia liberation$ slower reaction

# &onstant sampling and monitoring


17/23

&orrosion &ontrol contd%

• &ontrol: downtime and storage # ,0ygen in3leakage and p* lowering

# Dry storage: long downtime$ month or more

• &ompletely dried• (pplied dessicants like Euicklime$ silica gel$

actiated alumina

# Wet storage: short downtime

• &leaning$ inspection and filling with deaeratedfeedwater

• (ddition of scaenger$ heat addition


18/23

Deposits

• Scaling@deposition from carryoer

• &arbonate@Phosphate control # (ddition of certain amounts of carbonate@phosphate for ensuring

precipitate in the form of salts% Preention of Sulphates

# !or remoal of hardness$ &a and 'g # Precipitation in bulk instead of at walls$ non3adherent

• ,rganic supplements: fluid sludge formation 6polymeraddition # Bottom blowdown remoes sludge

• &helant control

• &ombination of addities

• Blowdown


19/23

&ase study 3Boiler tube failure

• Failure mode :Oxygen corrosion

• Result: 3-5 shutdowns.

• Reasons 3"mproper deaeration%

3*igh leel of dissoled o0ygen%

3Leakage in recirculator pump%


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Boiler tube failure


21/23

est practices

• !aintain the e"uipment properly %

• #ontrol the composition o$ the boiler

$eed water

• Identi$y optimal chemicals $or the

pre%ention o$ biological growth

• &lectrically powered water conditioningunits


22/23

Best practices3continued

• 'retreatment o$ ma(eup water

• !aterials o$ construction

• Optimi)e the $re"uency o$ cleaningboilers.

• Recent techni"ues

- 'agnetic water treatment.


23/23

.*(NM ,?

Boiler Water Treatment (16-20).ppt

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