3 Alkaline Boil-Out Chemical Cleaning Procedure

Document Number:

AE&E CZ s.r.o. Prepared:

Approved:

Jan Gänsdorfer

Jan Gänsdorfer

Date:

Date:

30.10.2009

30.10.2009

PX-PPKZ-0935331 Document status:

Customer’s Number:

Platný

Revision:

0

Page:

1/11

Ambarli Reg. No.: 28.5010 Order No.: Project Stage:

Alkaline Boil-out, chemical cleaning Procedure Preliminary

Content 1

Purpose of chemical cleaning ......................................................................... ................................................................................. ........ 2 1.1 Boiler Basic data:.............................................................................................. 2 1.2 Boiler internal volumes ................................................................. ..................................................................................... .................... 2

2

Alkaline cleaning procedure ................................................................ .................................................................................... .................... 3 2.1 Basic conditions to be fulfilled prior to alkaline cleaning .................................. 3 2.2 The scope of cleaning .................................................................. ...................................................................................... .................... 3 2.3 Cleaning procedure ...................................................................... .......................................................................................... .................... 4 2.4 Criteria for evaluation of alkaline cleaning........................................................ cleaning........................................................ 6 2.5 Boiler post- chemical cleaning operation.......................................................... 6

3

Acid chemical cleaning ........................................................................ ............................................................................................ .................... 7 3.1 Basic conditions to be fulfilled prior to acidic cleaning ..................................... 7 3.2 The scope of cleaning .................................................................. ...................................................................................... .................... 7 3.3 Performance of the cleaning............................................................................. 7 3.4 Criteria for evaluation of acidic cleaning......................................................... cleaning......................................................... 11 3.5 Boiler post- cleaning operation ................................................................. ....................................................................... ...... 11

BOILER_P-#72476-v1-Alkaline_Boil-out__chemical_cleaning_Procedure

Document Number:

Ambarli

PX-PPKZ-0935331

Alkaline Boil-out, chemical cleaning Procedure Registration number:

1

Customer’s Number:

Revision:

28.5010

0

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Purpose of chemical cleaning Chemical cleaning ensures special proces for removing grease and other mechanical impurities from internal surfaces of HRSG pressure systems. Chemical cleaning is proposed in 2 options – alkaline cleaning and acid chemical cleaning. The correct option shall be chosen based on inspection of internal pressure parts of the boilers during boiler erection. In compliance with VGB R 513 acid chemical cleaning should be performed if the amount of deposits exceeds 100 g/m 2 . Nevertheless because of the boiler construction (horizontal evaporator tubes with natural circulation) and its higher sensitivity of the boiler internal surfaces purity there is strongly recommended to apply an acid chemical cleaning procedure. During designing, preparation and execution of boiler chemical cleaning recommendation of the VGB R 513 guideline shall be followed.

1.1

Boiler Basic data: HP Part Outlet steam mass flow

78,1 kg/s

Outlet steam temperature

540°C

Outlet steam pressure

115 bar(g)

IP Part Outlet steam mass flow

13,2 kg/s


326 °C


31 bar(g)

LP Part Outlet steam mass flow

8 kg/s


195 °C


4 bar(g)

RH Steam

1.2

Outlet steam mass flow

90,13 kg/s


540 °C


31 bar(g)

Boiler internal volumes

Boiler pressure part

HP

Item

Volume (m3)

Superheater inc.steam pipe

20.67

Evaporator inc.downcomer and riesers

45.10

Economiser inc.feed water pipe

43.06

Drum – steam part

19.26


Ambarli Alkaline Boil-out, chemical cleaning Procedure Registration number:

RH IP

28.5010

Revision:

0

21.77

HP part - TOTAL

149.86

Superheater inc.steam pipes

50.16


8.25

Page:

3/11

32.21

Economiser inc.feed water pipe

4.63

Drum – steam part

7.99

Drum – water part

9.45

IP part - TOTAL

62.53


27.83


55.20

Economiser (CPH) inc.feed water pipe

55.49

Feed water tank – steam part

20.00

Feed water tank – water part

78.30

LP part - TOTAL

236.82 489.37

Boiler Total 2

PX-PPKZ-0935331 Customer’s Number:

Drum – water part


LP

Document Number:

Alkaline cleaning procedure Alkaline cleaning of evaporator and ECO systems shall be performed in compliance with VGB R 513, art.4.5.1. „strong alkaline boil out“. Alkaline cleaning stall be done during plant hot test after GT start up when flue gas heat can be utilized for heating of alkaline cleaning solution.

2.1

Basic conditions to be fulfilled prior to alkaline cleaning •

Pressure test of the boiler has been done

•

Boiler drum has been manually cleaned

•

Condensators has been already flushed and is at disposal

•

Condensate pumps are in disposal

•

Make Up water is at disposal

•

2.2

Sampling of LP, IP and HP saturated steam and LP IP and HP boiler water is in operation

•

Temporaries are installed and respective chemicals are ready to use

•

GT is prepared for idle run test

The scope of cleaning

The following pressure parts of boiler will be cleaned:

HP system: BOILER_P-#72476-v1-Alkaline_Boil-out__chemical_cleaning_Procedure


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Economizer Evaporator Drums till the operational levels Internal volumes per 1 boiler: 110 m3

IP system: Economizer Evaporator Drums till the operational levels Internal volumes per 1 boiler: 47,5 m3

LP system: Condensate heater Evaporator FW tank till the normal levet Internal volumes per 1 boiler: 47,5 m3

2.3

Cleaning procedure

Alkaline cleaning will be done in the following steps:

2.3.1

Flushing of the boiler

The task is to remove mechanical impurities from. Feed(Make Up) water will be used for this purpose. During test of Condensate pumps it will be flushed the condensate piping into the condensate heater, condensate heater up to the LP boiler drum. All drains from the evaporator stall be opened. Feed water pumps stall be operated at max. permissible flow ( it is necessary to check pump pressure-flow diagram ). Main feeding valve shall be fully opened until max. level in the boiler drums is reached. Then feed water flow will be controlled through coupling speed (or feed water outlet valve, if necessary).After short flushing, when the amount of impurities in the discharged water is visually checked, condensate pump is put out of operation, boiler is fully discharged and flushed once again by the same procedure. In case that discharged water still contains large visible impurities this procedure has to be repeated. With the same manner will be flushed the IP and HP boiler systems. Waste water from flushing: Removing of waste water from flushing does not represent any problem. Waste water normally contains 50 -100 mg/l of solids, that can be settled in the cooling or neutralization pit and water can be pumped into sewerage. Neverthless this procedure has to be consulted with chemical service of the client. BOILER_P-#72476-v1-Alkaline_Boil-out__chemical_cleaning_Procedure


2.3.2

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Application of the alkaline chemical solution

Boiler will be filled with the make up water and then cleaning solution will be pumped into the condensate heater, IP and HP economizers. GT will be started and pressure in the boiler drums will be increased acc. to start up curves up to approx 20 bar(g) in the HP drum, 8 bar(g) in the IP drum and 3 bar in the FW tank. During the boiler heating by pass line shall be slightly opened. The flue gas temperature upstream of the first superheater should not be higher than 500 oC. Boiler shall be operated at this pressure for 2 hrs and it is necessary to prevent carry over into the superheater - conductivity of the saturated steam is checked. After 2 hrs pressure in the boiler shall be decreased with max. allowable speed up to 2-4 bar(g). This procedure (heating and cooling) shall be 2x repeated and in the end clearing solution stall be discharged at max. allowable speed into the neautralization pit. Boiler will be then flushed incl all vents and drains from the top of the boiler up to the lowest point of the boiler. The whole clearing with alkaline solution stall be repeated once again.

2.3.3

Wastes from alkaline cleaning

It is supposed to collect cleaning solution in the neutralization pit of the boiler. The solutions will be neutralized using hydrochloric acid until pH about 7 is reached. Then discharge solution shall be diluted and cooled down using raw water until permissible values from the point of temperature and composition for discharge into sewerage are reached. Neutralized solutions stall be discharged in co-operation with chemical service of the client to comply with local prescriptions. 2.3.4

Chemicals for alkaline cleaning

The following chemicals are fed per m3 NaOH 100%

1 kg

Na3PO4x12H2O

0,5 kg

Non foaming wetting agent

0,01 l

HCl 32

for passivation of the cleaning solution



2.3.5

Engineering aspects

2.3.5.1

Temporary Equipments

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The main parts are temporary dosing pumps , dissolving tank, effluent neutralizing tank, connecting pipings made from carbon steel or rubber hoses, valves. 2.3.5.2

Dosing of chemicals

Cleaning solution will be prepared in the temporary dissolving tank having approx.1 m3 volume and pumped using temporary dosing pump into the boiler in front of condensate heater, IP and HP economizers. Cleaning solution shall be pumped into the boiler filled with feed water up to minimal boiler level pumps are out of operation ). When handling with chemicals safety prescriptions has to be strictly kept mainly when working with sodium hydroxide. 2.3.5.3

Feeding of the boiler

Boiler feeding has to be controlled in such a way that level in the boiler drums is maintained sligtly above the lowest permissible level.

2.4

Criteria for evaluation of alkaline cleaning

Chemical cleaning can be declared as satisfactory and completed when: •

•

•

•

•

2.5

Chemical cleaning procedure has been done as prescribed Sufficient amount of chemicals has been dosed into boiler ( pH of the cleaning solution has to be approx. 12,5) Neutralization of waste water has been done as mutually agreed prior chemical cleaning commencement Inspection of both drums has been performed and final mechanical cleaning has been done in case that it was necessary Inspection sockets on headers has been cutted and the surface of headers has been found generally clean, large impurities,if any, has to be removed manually.

Boiler post- chemical cleaning operation

Steam blowing is preferred to be done consecutively in few days after chemical cleaning In case that that boiler hot test cannot follow i tis necessary to carry out proper boiler lay up procedure. Intermittent blowdown should be often done ( at every boiler shutdown ) and continuous blowndown has to be largely open during first weeks of operation.



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Acid chemical cleaning Acid chemical clearing will be used when deposits on pressure part sof the boiler are higher than 100 g/m2. Acid cleaning usually allows to prepare better quality of boiler internal surfaces comparing to alkaline cleaning. It is advisable to carry out acidic cleaning by specialized company having practical knowledge of this activity and securing thus that all safety measures are kept. This company has to possess respective approval of authorities. It can be used variety of different acids for cleaning but preferable is the usage of hydrofluoric acid that has the best cleaning ability for removing of iron oxides. Acidic cleaning has to be done during cold commissioning phase max. 2 weeks prior start of the hot testing of the boiler. Selection of the best cleaning process depends on local conditions –e.g. if there is not low pressure steam for heating of cleaning solutions then the only procedure that can be applied is acid cleaning using hydrofluoric acid. In case that there is source for heating of cleaning solutions then other acids can be used e.g. citric acid.

3.1

Basic conditions to be fulfilled prior to acidic cleaning •

Pressure test of the boiler has been done

•

Boiler drums has been manually cleaned

•

Condensate tank has been already flushed and is at disposal

•

Make up water is at disposal

•

Sampling of LP, IP and HP boiler water are in operation

•

•

3.2

Temporary equipments are installed and respective chemicals are ready to use Safety precautions are fulfilled

The scope of cleaning

Option 1 – Static method The following pressure parts of LP and HP will be cleaned: Economizer, Evaporator

Option 2 – Forced circulation method The following pressure parts of LP and HP will be cleaned: Economizer, Evaporator, Drum, Superheater, main steam piping 3.3

Performance of the cleaning

3.3.1

Option 1

3.3.1.1

Initial flushing

The whole pressure part of the boiler will be flushed with water to remove loose dirt, sand, dust etc. BOILER_P-#72476-v1-Alkaline_Boil-out__chemical_cleaning_Procedure


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Two flushings are supposed to be done in dependance to cleanliness of discharged water. During the first flushing tightness of the whole system will be checked. Flushing phase will be completed when discharged water is clean and free from rough impurities. Then only evaporator and ECO will be drained, superheater will kept full of water to prevent ingress of the cleaning solution into the superheater 3.3.1.2

Degreasing

Removing of eventual oily or greasy substances from internal surfaces of evaporator and economizer will be done by means of non –foaming degreasing agent Alkon Special, which is effective also at lower temperatures. Solution of 0,5 kg/m3 will be prepared in the dissolving tank, then twice pumped into the system and drained back to the dissolving tank. This phase will approx. 4 hrs. Degreasing solution will be then discharged from the boiler into the effluent neutralizing storage tank. 3.3.1.3

Pickling

Oxides layer will be removed by the following mixture of chemicals: 1,5 %hydrofluoric acid + 0,2% corrosion inhibitor Rhodine A The mixture will be prepared in the dissolving tank and pumped into the system. Cleaning solution will be exchanged several times between dissolving tank and the cleaned system to ensure homogenous mixture and precise laboratory analysis. Temperature: circa 20 deg C. Duration: until steady iron and acid concentration in the cleaning solution is achieved . It is supposed that pickling phase will be completed in 4-6 hrs. Then the pickling solution will be discharged into effluent neutralizing tank. 3.3.1.4

Final rinse

Boiler will be then filled with water and flushed several times. This phase will be finished when iron concentration in the discharged water is less than 50 mg Fe/l. Discharged water from flushings will be neutralized similarly to a/m step. 3.3.1.5

Neutralization, temporary passivation

This stage will be performed as follows: Mixture of 0,3% citric acid and 0,1% of inhibitor Rhodine A will be prepared in the dissolving tank and pumped into the boiler. After 1 hour the solution will be discharged back to the dissolving tank. Ammonia will be then added to increase pH to 8,5 –9 and then sodium nitrite in concentration 0,5 g/l will be added. Boiler will be filled with this mixture and after 2 hours the solution will be drained into the effluent neutralizing tank . Then the boiler drums will be opened and remaining not-dissolved impurities, if any, will be cleaned mechanically.



3.3.1.6

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Wastes from acidic cleaning

All waste solutions will be collected in the effluent neutralizing tank for neutralization and treatment. Mixing of the waste solutions and its neutralization will be secured by pressure air. Waste solutions from flushings- there is no need for special treatment. Discharged water will be collected in the neutralization tank and set back water pumped into local sewage system Waste solution from degreasing- active carbon will be added to the discharged water in order to adsorb organic matters present in the solution and then drained into local sewage system. Waste solution from pickling and flushing after pickling- discharged water will be neutralized using lime to precipitate calcium fluoride,iron oxides and adjust pH of the solution. Active carbon will be also added to decrease content of organic matters. After laboratory control set back water can be discharged into the sewerage ( Dilution of this set back water using raw water will be done, if necessary ). Solid waste will be transported in authorized storege area or on other agreed place Waste solution from passivation- discharged water will be oxidized using chlorinated lime with addition of active carbon. 3.3.2

Option 2

3.3.2.1

Flushing

The aim of this cleaning phase is the same as specified in option 1. Both LP and HD system will be filled with water and tightness test of the whole system using temporary pumps will be done. Water in both systems will be circulated for circa 15 min. and then, during continuous drain and refill, the whole system will be flushed. In case that there is not enough of demineralized water the system can be drained and flushing can continue when enough water is at disposal. Flushing phase will be completed when discharged water is clean and free from rough mechanical impurities. 3.3.2.2

Degreasing

The aim of the process is the same as specified in option 1. Degreasing of both systems will be done using 0,5 % solution of proper detergent e.g. Dubaryl DCX at 70 °C. Both systems will be filled with water and ,during circulation and system heating-up, detergent will be added. Cleaning solution will be circulated for 8 hours. When decreasing phase is complete cleaning solution will be discharged into the effluent neutralizing storage tank.. 3.3.2.3

Pickling

The system will be filled up with water and then inhibitor (RODINE 31 A) will be dosed into the system through dissolving tank to reach concentration of 0,2 %in the cleaning system. The solution will be consequently homogenized by means of 1 hr circulation through both systems. BOILER_P-#72476-v1-Alkaline_Boil-out__chemical_cleaning_Procedure


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Similarly hydrofluoric acid will be consequently dosed through dissolving tank to reach concentration 1% in the cleaning system. Pickling solution will be circulated and cleaning procudure will proceed at 50 - 60 °C for approx. 2-3 hrs. Samples will be taken and analysed in 1hour intervals. The acid and iron concentrations will be determined. The pickling phase is finished when steady iron and acid concentrations in the cleaning solution are achieved . Used pickling solution will be then drained into the neutralisation tank . 3.3.2.4

Final rinse

Boiler will be then filled with water and flushed several times. This phase will be finished when iron concentration in the discharged water is less than 50 mg Fe/l. 3.3.2.5

Neutralisation, temporary passivation

This stage will be performed as follows: The system will be filled up with water and then the inhibitor (RODINE 31 A) will be dosed into the system through dissolving tank to reach concentration of 0,1 %in the cleaning system. The solution will be homogenized by means of 1 hr circulation through both systems. Citric-acid will be then dosed through dissolving tank to reach concentration 0,3% in the cleaning system. Concentration of dissolved iron will be checked in 0,5 hr intervals and cleaning proper will proceed till the value uf dissolved iron is stabilized. Ammonia will be then added to increase pH to 8,5 –9. Consequently passivation phase will commence by adding of hydrogen peroxide. Passivating solution will be circulated for 4 hrs at temperature circa 50°C. At the end of passivation phase solution will be drained into the effluent neutralizing tank. Boiler drums will be then opened and remaining not-dissolved impurities, if any, will be removed mechanically. 3.3.2.6

Wastes from acidic cleaning

All waste solutions will be collected in the effluent neutralizing tank for neutralization and treatment. Mixing of the waste solutions and its neutralization will be secured by pressure air. Waste solutions from flushings- there is no need for special treatment. Discharged water will be collected in the neutralization tank and set back water pumped into local sewage system Waste solution from degreasing- active carbon will be added to the discharged water in order to adsorb organic matters present in the solution and then drained into local sewage system. Waste solution from pickling and flushing after pickling- discharged water will be neutralized using lime to precipitate calcium fluoride, iron oxides and adjust pH of the solution. Active carbon will be also added to decrease content of organic matters. After laboratory control set back water can be discharged into the sewerage ( Dilution of this set back water using raw water will be done, if necessary ). Solid waste will be transported in authorized storage area or on other agreed place BOILER_P-#72476-v1-Alkaline_Boil-out__chemical_cleaning_Procedure


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Waste solution from passivation- discharged water will be oxidized using chlorinated lime with addition of active carbon. 3.3.3

Engineering aspects

3.3.3.1

Temporary Equipments

The main parts are temporary process pumps, dissolving tank, effluent neutralizing tank , injector for dosing of liquid chemicals or the suitable dosing pump, connecting pipings made from carbon steel or rubber hoses, valves. In the option No. 2 (circulating method) shall be the temporary piping connected so that circulation from both sides (form side of ECO and form the main steam line) will be possible. Therefore an suitable temporary bypass of the drum shall be installed. Demineralized water supply line will be fire hose, as well as effluents discharge from neutralizing tank. 3.3.3.2

Preparation of cleaning solutions

All cleaning solutions will be prepared in the dissolving/neutralizing tank, liquid chemicals will be dosed by means of injector.

3.4

Criteria for evaluation of acidic cleaning

Chemical cleaning can be declared as satisfactory and completed when: •

•

•

•

•

3.5

Chemical cleaning procedure has been done as prescribed Neutralization of waste water has been done as mutually agreed prior chemical cleaning commencement Inspection of both drums has been performed and final mechanical cleaning has been done in case that it was necessary Inspection sockets on headers has been cutted and the surface of headers has been found generally clean, large impurities, if any, has to be removed manually. Testing tube samples do not exhibit remaining oxide layer higher than 20 g/m2

Boiler post- cleaning operation

Passivation of the pressure parts of the boiler is only temporary one and ensures boiler protection for approx. 2 weeks. Natural protective magnetite layer will be formed during “hot” operation and therefore it is recommended to start boiler immediately after removing of temporaries. If this is not possible proper lay up of already clean boiler has to be applied.


3 Alkaline Boil-Out Chemical Cleaning Procedure

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