BHARAT HEAVY ELECTRICALS LIMITEDPOWER SECTOR – WESTERN REGION RECOMMENDED PROCEDURE FOR ALKALI BOIL OUT OF 2 X 165 TPH AFBC BOILERS AT JSL, RAIGARH A) INTRODUCTION: The alkali boil out of a boiler is carried out in order to clean the internal surfaces of the water-touched parts from oil, grease, rust, silica and other adhered impurities B) SCOPE: The scope of cleaning during this operation includes a portion of feed line, entire evaporative system of boiler and economizer. C) TECHNIQUE: For carrying out the alkali boil out, 1000 ppm of Trisodium Phosphate and ppm of Disodium Phosphate are used as cleaning agents. The alkali boil out is carried out in one stage at drum pressure of 40 Kg/cm². D) PREPARATIONS: 1. Pre-boiler system should be flushed with alkali solution and 2 nos. BFP should be made ready for regular operation from control room. 2. All the drum internals including the secondary steam separators are erected in position as per drawings. 3. Boiler should be made ready in all respects for regular operation upto drum pressure of 40 Kg/cm². For carrying out alkali boil out, external combustor will be utilized for raising bed material temperature of 1 st compartment. Further parameters will be raised by coal firing in 1 st compartment. 4. HP/LP Dozing system should be made ready for dozing of chemicals during boil out activity. 5. Boiler drum level g/g should be commissioned with lighting arrangement. 6. Feed water and CBD sampling lines should be ready for taking samples. 7. Required chemicals should be checked for quality and quantity. Arrangements for mixing of chemicals with DM water at drum level should be made. Lab facilities should be ensured for testing of samples. 1 further dozing should be done through phosphate dozing pumps. Make up the drum level and again light up the boiler to raise pressure to 40 Kg/cm² for next two hours. Alkali boil out is declared completed after oil content in sample collected shows less than 5 ppm or till 8 blow are completed. Hand gloves. 10. 2. Expansion readings should be recorded at 10. Put out the coal firing and issue below down through low point drains by opening each drain valve for one minute duration. Face Masks and Aprons) should be made available. 6. First aid box and safety appliances (Gum boots. CBD sample should be analysed for phosphate and oil level content. 20 & 40 Kg/cm² drum pressure and uniformity must be ensured. drain sample to be analysed for phosphate and oil content. Boiler drum pressure will be maintained for 2 hrs. boiler parameters should be slowly raised upto drum pressure of 40 Kg/cm². Ensure that the drum level does not fall below visibility limits. Required quantity of chemicals should be mixed in a separate 200-liter drum and dozed slowly in boiler through manhole door. E) PROCESS: 1. 2 . The blow down activity is repeated every two hours as per above procedure. whichever is later. 5. Expansion trams should be installed to monitor the movement of pressure parts.BHARAT HEAVY ELECTRICALS LIMITED POWER SECTOR – WESTERN REGION 8. 11. If phosphate content drops below half the initial value. After every blow down. 3. Supply of adequate quantity of DM water should be ensured before start of operation. Expansion constraints should be identified and removed. 4. A minimum of 12 hours boil out is a must. Drum manhole door should be opened and water should be filled upto feet below manhole door bottom level. For proper digestion of chemicals. After closing manhole door. 9. Permanent lighting and communication facilities should be ensured at all working locations. Boiler is boxed-up and allowed for natural cooling. Then drain the boiler and analyse drain sample for phosphate. raising level upto normal. open the drum vents.BHARAT HEAVY ELECTRICALS LIMITED POWER SECTOR – WESTERN REGION 7. 3 . Hot drain the boiler when drum temperature is about 90 deg c. After completion of alkali boil out.0 Kg/cm². Thereafter. boiler is released for acid cleaning operation. drum manhole doors should be opened and checked for any loose debris and the same should be cleaned. 8. Fill the boiler upto minimum level of drum and back flush the superheater into the drum. When drum pressure reaches 2. After completion of alkali boil out. Repeat this activity till phosphate content drops below 25 ppm. High purity of steam depends on the cleanliness of the waterside of the boiler. apart from imparting cleanliness of waterside surfaces. Ammonium Bi Fluoride is added to the cleaning solution.0 and Hydrazine content not less than 200 ppm. Chemical cleaning. RAIGARH A) INTRODUCTION: Modern power stations demand high purity of steam in order to prevent fouling of the turbine and safe operation of the power plant. D) PREPARATIONS: 1. The above layer is reinforced further by the process of second stage passivation. These include rust due to atmospheric corrosion and formation of oxides of iron due to the heat treatment at shop.BHARAT HEAVY ELECTRICALS LIMITED POWER SECTOR – WESTERN REGION PROCEDURE FOR ACID CLEANING OF 2 X 165 TPH AFBC BOILERS AT JSL. In the final phase of cleaning the freshly pickled surfaces are protected from corrosion by a passivated layer of magnetic formed chemically by the addition of Hydrazine and ammonia. Boiler components during manufacture in shop from raw material to final shape and during erection at site undergo both physical and chemical changes. To intensify the action of Hydrochloric Acid and to dissolve siliceous impurities. 4 . Alkali boil out of water-touched parts should be completed as per procedure. at a later stage. at a drum pressure of 40 Kg/cm². To lessen the action of acid on parent metal suitable inhibitor is added to the picking solution. During pickling the superheater connecting tubes will be plugged suitability from inside the drum and remain filled and pressurized with Ammoniated Hydrazine water confirming to pH 10. C) TECHNIQUE: Chemical cleaning of the boiler will be carried out by a pickling solution of 4% inhibited Hydrochloric Acid by circulation method. leaves behind a thin uniform protective layer of magnetic oxides of iron (called magnetite). B) SCOPE: The scope of cleaning includes a portion of the feed line complete evaporative system of the boiler. Fire fighting arrangement. first aid and safety appliances should be kept ready before start of the process. circulating pumps (3 nos. 7. Steam should be made available at the rate of 10 TPH at 10 Kg/cm². 5 . 11. For neutralization of acid. Sufficient storage of DM water must also be ensured before start of process. of 150 M3/Hr. Service water facility should be arranged near tank area for the purpose of getting water bath in case of contact with chemicals. The scheme of connecting the boiler and pipelines including provisional equipment is attached (the provisional equipments are designed to achieve circulation of chemicals in WW/Eco tubes and consist of dissolving tank. 10. 9. Arrangements should be made for nitrogen capping during the process of pickling. gauge glasses. circulating water pumps must be trial run and system should be ensured leak proof. it’s preferable to dig an earthen pit of 200 M3. 8. Isolate all the instrument tapping. Representative water wall tube sample should be hung inside the drum as well as dissolving tank. Necessary temporary drain lines and raw water lines should be laid accordingly. 12. 250°C at inlet of dissolving tank.BHARAT HEAVY ELECTRICALS LIMITED POWER SECTOR – WESTERN REGION 2. 3. Required number of nitrogen cylinders should be made available before start of pickling process. Remove all the drum internals. Lab facilities including services of chemist must be ensured for analyzing the samples as per the requirement of the process. Inhibitor should be tested before use for its efficiency. Arrangements should be made for continuous supply of DM water and heating steam to the dissolving tank (as required for the process) with valves and fittings as per scheme. Fixing of down comer orifice 13. 5. 6. connecting pipes and valves. Arrangement should be made for pumping out of neutralized solution into the plant drain canals. 4. Before charging chemicals. 12 Kg/cm²). BHARAT HEAVY ELECTRICALS LIMITED POWER SECTOR – WESTERN REGION 14. ix) Stop circulation once three consecutive samples show almost same values of acid and iron concentration or if the circulation is done for maximum of 4 hours (total acid contact time to be less than 6 hours). M. Simultaneously charge calculated quantity of ammonium bifluoride into the mixing tank by several increments. This sample is to be collected at intervals of 10 minutes. vii) Total quantity of acid required to achieve acid concentration of 4% in the circulating solution is to be added in one hour. Water Rinse 6 . PROCESS: a) Acid Pickling: i) Fill the entire system with DM water. at the pump discharge and return line and analyse for acid strength and iron concentration. Maintain 3 to 5 Kg/cm² pressure in the drum. Continue circulating for four hours for the purpose of hot flushing and drain the system completely. iii) Admit steam into the mixing tank and raise the temperature of circulating water to 60°C as measured in return line. ii) Ensure that water flows from the drum vents to the collecting tank and to the mixing tank. with the pumps running to achieve through mixing. vi) Add required quantity of 30-32% Hydraulic acid in a controlled manner so that acid concentration as measured in the sample from pump discharge does not exceed 6%. iv) Take fresh DM water into the tank and establish circulation as per steps i + ii and raise the temperature of water to 60°C. x) Drain the system under N2 blanking b) D. Establish circulation in the system by running circulating pumps. viii) Collect sample from circulating solution. SH drain & fill connections from LPD header should be disconnected/isolated. v) Cut off steam and add required quantity of inhibitor. at an interval of 15 minutes. f) Passivation The objective of passivation is to prevent corrosion since the cleaned surfaces are more susceptible for corrosion at a very fast rate.BHARAT HEAVY ELECTRICALS LIMITED POWER SECTOR – WESTERN REGION i) On completion of draining of acidic solution.2% W/v citric acid monohydrate. d) D. Water Rinse i) On completion of draining rinse the system with plain DM water. raise the temperature to 85-90°C after establishing circulation. 7 .M. iii) Hot drain the system under atmospheric air by keeping the drum vents open. M. c) Citric Acid Rinse i) On completion of draining. e) Neutralization i) Fill the system with plain D. drain the system under nitrogen cover when the values stabilize. fill the system with DM water and establish circulation. ii) Raise the temperature to 55°C and add 0.5 to 4. The corrosion is prevented by providing a thin of magnetite (first stage). fill the system with plain D.2% Trisodium phosphate Na3 PO4 12H2O and maintain circulation for 6 hours. water. which gets strengthened in the subsequent firing of the boiler (second stage). iii) Add liquid ammonia to raise the pH of the solution to 3. iii) Drain the system under nitrogen blanket. water and establish circulation. ii) Add required quantity of 0. ii) Collect samples from pump discharge and return line and analyse for acid and iron concentration. M.0 and circulate for 2 hours.1% Disodium phosphate Na2 HP04 7H2O and 0. ii) One or two rinsing operations are to be done till the iron content drops down to 50 ppm and acidity is absent. iii) All the draining operations are to be done under nitrogen blanket. iv) Collect samples and analyse for pH and iron content. PH of DM water is raised to 9. raising the pH to 9. The boiler is kept in service for 24 hours maintaining the hydrazine concentration not less than 20-25 ppm in feed water. the boiler is boxed up and allowed for natural cooling. all vents are opened and at about 90°C drum temperature. Water samples are taken from feed line to find out hydrazine concentration and pH value. upon completion of hydraulic test at working pressure. to get a concentration of 200 ppm are charged in the operating level in drum and lighted up. the solution is drained hot from the system and left aerated by natural draft. ii) Inspection of preparatory work for second stage passivation The drum is inspected thoroughly and all loose debris cleaned manually. The second stage passivation marks the end of the chemical cleaning process. The hydrazine concentration is maintained at 200 ppm through out the operation. ammonia liquor. At the end of the process. The solution is left to circulate for about 20 hours at a temperature of 85 – 90°C. After 20 hours. The steam pressure in drum is gradually raised to 40 Kg/cm² and maintained at that value. SH connections to be normalized . The boiler should be prepared for regular operation.5 by adding ammonia and hydrazine is changed to get a connection of 200 ppm. Thereafter boiler is released for steam blowing operations.All the provisional equipments are dismantled and original fittings and mounting are installed back. The temperature of water is raised and maintained at 85°C by external steam heating. Bottom headers hand hole pipe connections are removed and the headers are cleaned with water. At 2 Kg/cm² drum pressure. 8 .BHARAT HEAVY ELECTRICALS LIMITED POWER SECTOR – WESTERN REGION i) First Stage Passivation The system is filled with DM water and adjusted for circulation. the water in the system is drained and the system is left aerated.5 and hydrazine. iii) Second Stage Passivation The chemicals viz. The super heater plugs and down comer orifice plates are removed and drum internals are refitted. 0 2 S te a m 1 6 8 . 9 x 6 . 3 5 P 3 2 3 .1 x 6 .0 2 x x x x .3 9 114 114 114 114 DC BHEL.3 .3 x 6 .3 . 3 5 D is s o lv in g ta n k Vent c o lle c t o r s 1 1 4 .3 .3 x 7 . PSW R HQ . R A IG A R H S C H E M E F O R A C ID C L E A N IN G F O R 2 X 1 6 5 T P H B O IL E R N e u tr a lis in g p it 3 2 3 .FW 006 FW 005 ECO T o D H -II W W I/L H D R W W O /L H D R 2 1 9 .0 2 6 .0 2 D M 1 1 4 .1 1 B o ile r D r u m 6 .0 2 6 .3 5 LEG END P e r m a n e n t lin e T e m p o r a r y lin e P P r e s s u r e in d ic a to r T e m p e r a tu r e in d ic a t o r T C ir c u la t io n p u m p S a m p lin g p o in t S R e g u la tin g v a lv e RT DC P S S NB 40 P 2 1 9 . 3 5 NB 40 RT N 2 F illin g T T S S NB 40 NB 40 P P P R O J E C T : J S L .3 x 6 .0 2 6 . 9 x 6 .NAG PUR BHARAT HEAVY ELECTRICALS LIMITED POWER SECTOR – WESTERN REGION . 1 x 6 . 2 m3 each. Citric Acid (IS: 5464: 1970) 300 Kg. RAIGARH (FOR ONE BOILER ONLY) SL.BHARAT HEAVY ELECTRICALS LIMITED POWER SECTOR – WESTERN REGION SPECIFICATION OF CHEMICAL AND QUALITY FOR ALKALI BOIL OUT AND ACID CLEANING ACTIVITIES OF 2 X 126 TPH AFBC BOILERS AT JSL. IS: 1747: 1972) 9. 10 . Coronil: 213 Special 5. Disodium Phosphate Na2HpO47H2O 250 Kg. 120 Nos. 8. Hydrated Lime 15 Tons 11. Ammonium Bifluoride 600 Kg 10. Ammonia: 25% 120 Liters. 2. Nitrogen Cylinders (6. 7. Beaching Powder 3 Tons 150 Liters. NAME OF CHEMICAL QUALITY 1. 6. Hydrochloric Acid: 30% (IS: 265: 1976) 20 Tons 4. Hydrazine Hydrate: 80% 400 Liters. 3. NO. Trisodium Phosphate Na3PO412H2O (IS: 573: 1973) 500 Kg.