Acid Cleaning Ppt

7/31/2019 Acid Cleaning Ppt

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OBJECTIVE THE OBJECTIVE OF THIS PROCEDURE IS TO CLEAN THE

INTERNAL SURFACE OF STEAM GENERATINGPORTION AND HEATING SURFACE(ECONOMISER)

USING SPECIFIED CHEMICALS.BY CARRYING OUT AN

EFFECTIVE ALKALI BOIL-0UT GREASE AND ANY

OTHER PROTECTIVE COATING APPPLIED ON THEINNER SURFACES OF PRESSURE PARTS ARE

REMOVED.THEN IT IS SUBJECTED TO ACID CLEANING

FOR THE REMOVAL PATCHY MILL SCALE AND

RUST.FINALLY THE ACID PICKLED SURFACE IS

PASSIVATED FOR THE FORMATION OF UNIFORM AND

COHERENT MAGNETITE LAYER


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STATE OF PLANT THE FLAP OF NRV PROVIDED IN

ECONOMIZER FILLING LINE IS REMOVED TOFACILITAE FAST FILING AND DRANING.

ALL THE AUXILLARIES ARE MADE READYAND AVAILABLE FOR BOILER LIGHT UP.THIS

INCLUDES AUXILLARY STEAM,CHEMICALDOZING PUMPS,TANKS CC PUMPS,FANS OILPUMP ETC.

NITROGEN CAPING SYSTEM AT SUITABLELOCATION FOR EASE OF PPERATION.

PROPER NEUTRALIZATIN ARRANGEMENT TONEUTRALIZE EFFLUENT BEFORE DISPOSAL


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FOR ABO ONLY PRIMARY SEPARATOR ARE ERECTEDIN UPPER DRUM AND BAFFLE PLATE IN LOWERDRUM.SECONDARY SEPARATORS AND DRYER NOT

ERECTED IN THE UPPER DRUM AND ORIFICE NOTERECTED IN LOWER DRUM.FOR ACID CLEANINGPRIMARY SEPARATOR IS ALSO REMOVED.

BOILER TUBE COUPONS ARE TO BE PLACED AT TWOENDS INSIDE BOILER UPPER AND LOWER DRUMS TOEFFECTIVENESS OF CLEANING.


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MINIMUM REQUIREMENT

ONE SET ID,FD FAN,ONE SAPH ALONG WITH OIL

CARRY OVER PROBE,SOOT BLOWING SYSTEM,FIRE

DETECTION SYSTEM,ROTOR STOPPAGE ALARMAND

AIR MOTOR,LDO,SCANNER FAN,HP DOSING AND LP

DOSING SYSTEM,ALL BCW PUMP,BAH,COMPLETION

OF ATT FOR URNACE.

PROVISION FOR FREE EXPANSION OF BOILER AND

EXPANSION MARKER.BLOW DOWN SYSTEM.

PERSONAL SAFETY EQUIPMENTS.

PURGE WATER FOR CC PUMP.

READINESS OF TWO ESP PASS IN ALL RESPECT.

EYE WASH BOTTLE AND EYE SHOWER.


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CHEMICAL USEDSL NO ACID

Blr water

Concentr

ation in

%Quantity

required Used forProcess SL NO ACIDBlr water

Concentr

ation in

%

Hydrochl

oric acid

(HCL) 5 % + 1 % 70 tons Acidpickling

& soaking

Hydrochl

oric acid

(HCL) 5 % + 1 %Rodine 0.20 % 800 lts Rodine 0.20 %Ammoniu

m

Bifloride 0.25 % 1000 kgAmmoniu

m

Bifloride 0.25 %

Ammonia

ted Citric

Acid0.2 % 800 kg Ammoniated citric

acid rinseAmmonia

ted Citric

Acid0.2 %

Di/Trisod

ium

phosphat

e

0.1 % &

0.2 % in

the boiler800 &

1500 kgs

Neutraliz

ation

processDi/Trisod

ium

phosphat

e

0.1 % &

0.2 % in

the boiler


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STEPS FOR ABO

Prepare chemical water in chemical

preparation tank of 60 m3 DM water

through boiler fill pump ,add TSP 60 kg ,add

DSP 30 kg ,start heating through steam from

aux PRDS and run chemical pumps onrecirculation till a temp of 50 deg is

achieved.

Check the chemical solution concentrationof 500 ppm of DSP and 1000 ppm of TSP is

achieved.


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Fill the boiler through bottom ring header drain, eco linedrain ,eco inlet header drain, BCW suction lines ,( BCWdischarge valve closed ) by chemical dosing pump till

the minimum level of tank as marked at view glass oftank .

Raise the drum pressure up to 40 ksc in steps of 10kscand take expansion readings,maintain it at 40 ksc , takeboiler expansion reading, hold 40 ksc for 4 hrs.Collectwater samples from CBD sample point for analysis ofalkalinity ,phosphate content ,dissolved silica and oil

content


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Kill the fire in the boiler ,give blow down of 1 minutethrough bottom ring header drain to

IBD(front).Ensure drum level does not go out ofvision in gauge glass.(DWLG at drum)

Raise the drum level through MDBFP, Repeat the

operation of raising the drum pressure to 40 ksc,then hold it for 2 hrs.give blow down through bottomring header drain to water wall drain header, for 1minute after killing fire

Repeat the same procedure and give blow downthrough ECO line drains & ECO inlet header drain


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During this process if phosphateconcentration drops to half of the initial value,

dose additional chemicals through phosphatedosing system to achieve originalconcentration.The boil out is declared complete when the oil

contained in analyzed sample is less than 5PPM or minimum eight blow downs (in samesequence) are completed whichever is latter.

Box up the boiler keeping BCW pumps inservice. Allow the boiler to go under naturalcooling ( ID suction & FD discharge open.).


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Fill the boiler with hot 80 deg DM water throughchemical feeding pump upto lowest port of drum.

Back flush the S/H with DM water containing200ppm hydrazine and PH raised to 10 withammonia till it overflows into drum. Collect thesample from the sampling points of S/H Headerand low point drains for testing.

Drain the boiler through IBD.

Continue the filling & draining for rinsing till thephosphate contain in sample is less than 2 ppm.


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Steps for acid cleaning

MOCK TRIAL:

Mock trial is to be conducted one day in

advance so as to check the healthiness of

various pumps, valves and other connected

system. Boiler filling in 1 hr (approx) and

draining in 1 hr(approx) are to be achieved.

Boiler filling with DM water & lighting up the

boiler to raise the temp. to 80 0c before going

for acid injection.


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Filling of Boiler along with Acid injection(Picking/Soaking)Fill the boiler with 60-70 0C water from the 250

mm temporary header through water walls lowpoint drain hdr. / Eco filling line/ BCW pumpsunction manifold)Once the boiler drum level is at the bottom port

stop filling through BCW suction manifoldContinue filling through other sources.

Fill the boiler up to the drum level is 100 mm

above center line.

Start Boiler Water Circulating (BCW) pumpB

,center pump.


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Take sample at every 10 min interval.Continue this process till the iron content is inequilibrium for 3 consecutive sample .Start draining the boiler under N2 capping to theneutralization PitDM water rinse, after Acid pickling/Soaking is

completed: Refill the boiler with DM water at 60-70 0C.Fill up to 50 % of the gauge glass .Then startback flushing of the SH through the LTSH drain

till the water level is raised in the drum up to 8-9ports. Continue this operation till the sampleresult pH is upto 4.0


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Ammoniated Citric Acid rinse after DM waterrinse: Start injection of citric acid solutionprepared at temporary DM filling pump discharge

through the acid injection pump & regulation valveat the acid pump dischargeAdjust the pH at thefilling point around 3.5-4.0. Collect sample from BCW pump discharge

header after stopping the pump & analyze foracid strength & iron concentration .Continue this operation till 3 consecutivesamples read the acid % & iron content are

steady .This operation shall be minimum 4 hrs &maximum 5 hrs duration .


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Demineralised water rinse: Continue the boilerfilling & draining operation till the sample at pointB is having IRON < 25 ppm

Neutralisation of the boiler system:To removeacid pockets and neutralized acid.

Fill the boiler with TSP AND DSP Solun. Light upthe boiler & raise the pressure to 10 ksc .Hold the pressure for about 6 hrs. After 6 hrs killthe fire .

Allow the boiler to cool naturally .Drain the boiler after metal temperature of < 90 0Cis achievedBoiler is drained with drum vents open to

atmosphere & no N2 capping is used .


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Passivation of Boiler :TO MAKE A LAYER OFMAGNETITE COATING ON PICKLED SURFACEFill the boiler with DM water & inject the preparedblended solution so that the final water having 200ppm of N2H4 & pH of 10 is feed to the boiler .Lightup the boiler at slow rate .

Raise the drum pressure to 40 ksc & hold it for 24hrsAfter 24 hrs shut down the boiler & allow it to cooldown slowly .

Neutralisation of boiler effluentsAs soon as the acid is drained to the neutralizing pitcaustic soda is added to neutralize .As soon as the citric acid is drained to the

neutralizing pit caustic soda is added to neutralize .


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Acid Cleaning Ppt

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