Need for Water Treatment and Problems Due to Water

8/10/2019 Need for Water Treatment and Problems Due to Water

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Water related problems in boiler operation and theirsolutions

By

Thermax Ltd, Chemical Division, Pune 411 0!

1."ntroduction

The safety, reliability & efficiency of the boilers depends largely on properconditioning of the feed water.

Water contains dissolved gases and solids. This water is not suitable for boiler and

needs a complete external as well as internal treatment before use. The objective ofthe internal treatment program is to ensure

a) #$%&T' !y eliminating scaling and deposition in boilers which may cause

overheating of tubes leading to accidents.

b) (&L"$B"L"T' by reducing unscheduled shut downs and failures and avoidproduction losses.

c) L)*+&( L"%& !y reducing corrosion of boiler metal, which reduce metal

thic"ness and also cause failures.

d) &%%"C"&*C' To maintain pea" efficiency by "eeping boiler internals free of any

deposits.

!y preventing # scaling ,corrosion and carryover the above objective can be met.

$or the conditioning of feedwater various internal treatment programs are in use.

% brief view of various conditioning programs systems is given in this paper which

will enable boiler user to select right program.

*eed or -ater treatment

a. mpurities in water

'ature mpurity

1 (oluble # onic ations alcium, *agnesium, +otassium,(odium, %mmonium, ron *anganese etc

%nions !icarbonates, carbonates, 'itrates,

hlorides, silica etc.

nsoluble # 'onionic (uspended matter, Turbidity, silt,colloidal silica

- aseous /xygen, arbondioxide, chlorine

0 /thers olor, /il, /rganics


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b. (ignificance of the impurities

"mpurity Problem caused

+aseous

1 issolved /xygen +itting corrosion arbondioxide 2niform corrosion in condensate

)thers

- /il3/rganics arryover

#oluble . "onic

0 alcium3*agnesium (caling

4 (odium3+otassium orrosion

5 hlorides3(ulfates orrosion

6 arbonates3!icarbonates (caling,$oaming

7 8ydroxides (caling,$oaming

9 (ilica (caling, eposition

"nsoluble / *onionic

1: (uspended solids3(ilt $ouling

11 olloidal (ilica (caling,deposition

c. ;xternal treatment # To remove the impurities in water

-. *eed or "nternal treatment

IMPURITIES

INSOLUBLE

SOLUBLE

SETTLING

FILTERATION

CLARIFICATION

GASEOUS

CHORINEOXYGEN

DEAREATOR ACTOVATED CAR

SOFTENING DEMINERALISATION

DEALKALISER


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;xternal treatment is done by use of e


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/ /

'a/ + / + /'a

/ /

'a 'a

B

>emar"s

ommonly used in formulations.

. helant # based treatment program

The chelant reacts with the alcium,*agnesium, ron and forms soluble complexes,which can be discharged during the blowdown.

;T% & 'T% are the common chelants used in the helant based treatment programs

-OOC - CH2 CH2COO-

N CH2 CH2 N

-OOC - CH2 CH2COO-

>emar"s

'ot very commonly used.

%longwith the antiscalants # /xygen scavengers have to be used to scavenge the

oxygen in the feedwater to prevent attac" of oxygen on boiler metallurgy.

)xyen scaveners

a. (odium (ulfite = 'a(/-

'a(/- C D / 'a(/0

(emars


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- 'ot used in 8igh pressure boilers as it brea"s down to form hydrogen

sulfide.

- t adds to the total dissolved solids

b. 8ydraEine = '80

'80 C / 'C 8/

(emars

- +referred /xygen scavenger in 8igh pressure boilers.

- (luggish in reacting with oxygen as compared to (odium sulfite

- /rganic in nature hence does not add to T( & end products are

'itrogen & water.- Fow flash point & carcinogenic in nature to be handled with care.

/ther /xygen scavengers # not commonly used

- ;8%

- arbohydraEide

- (odium erythorbate

- 8ydroemar"s


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- 2sed in formulations

- The molecular weight and the anionic charge decide the correct selection of

polymer to function as dispersant.- +olymers should be thermally stable to function as dispersants.

P2 Boosters in Boiler -ater conditionin

The most common +8 booster used is caustic.8owever, use of caustic is not done in

medium or high pressure boilers as if the monitoring is not done properly it may leadto caustic embrittlement.

/ther p8 boosters

- %mmonia

- *orpholine

- *ono cylohexyl amine.

3)D&(* T(&*D

emineralised water along with condensate return is commonly used for boiler feed

in many medium & high pressure boilers. The scarcity of water, increase in cost ofwater and fuel , now the trend is to go for all organic treatment for boiler feed water

conditioning.

With the advent of polymer technology it is possible to prepare specific polyamine sfor boiler water conditioning.

#election o the Proram

The treatment programs available for water conditioning are described above. The

selection of the program is decided by following customer specific re


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The table below gives guidelines for selection of treatment program based onpretreatment method chosen and boiler pressure

+ressure

Gg3cm

+retreatment used onditioning program recommended

oil type (oftener 3 * helant # polymer= scavenger!elow : (oftener +olymer=phosphate=scavenger=chelant

* $ilming amine # scavenger

: = 0: (oftener +olymer=phosphate=scavenger=chelant

* $ilming amine # scavenger

%bove 0: *3;%;>%T/> $ilming amine

*ote

The treatment programs may have merits & demerits. The success of the treatment

programs lies in correct selection, monitoring and controlling the program.

THERMAX CHEMICAL DIVISION ASSISTS IN SELECTING RIGHT WATER

TREATMNT FOR YOUR PROBLEMS INBOILER WATER MANAGEENT.

HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH


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Need for Water Treatment and Problems Due to Water

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