Boiling plan after major boiler overhaul

Boiler blowdown operation procedures: I. Preparations before blowdown: 1. All systems required for blowdown (such as blowdown, drain, sampling, and chemical dosing) have been installed and verified to be in good working condition. 2. The thermal and electrical instruments required for boiler operation, as well as the remote control facilities, have all been installed and calibrated. 3. The coal conveying and ash removal systems can meet the requirements. 4. The temporary dosing and sampling equipment has been installed and is ready for use at any time. 5. Sufficient chemicals are available for furnace boiling, and their purity is tested and analyzed. 6. All equipment required for adding chemicals during boiler boiling has been placed in the designated locations, and all other necessary materials are also available. 7. Once the furnace drying is complete and successful, cooking in the furnace can begin, and the furnace walls can be continued to be dried. II. Precautions for personnel responsible for preparing the chemicals during furnace boiling: 1. Crushing, transporting, preparing the solution, and adding chemicals to the furnace must be carried out under the supervision of a qualified person. 2. Personnel responsible for preparing medications must be equipped with rubber clothing or aprons, rubber gloves, rubber shoes, protective glasses, and masks, among other items. 3. Shattering caustic soda must be carried out at a specially designated location, with one’s face turned to the side to prevent skin burns. 4. When adding chemicals, the drum pressure must be reduced to zero or the water level kept at its lowest level. III. Boiler cleaning procedure: For components such as the drum, water wall, and economizer, chemical treatment is carried out in three stages using the alkali cleaning method in accordance with relevant regulations. The specific process is as follows: 1. Chemical addition and boiler cleaning in the first stage (using a temporary chemical dosing tank and dosing pump): 1) Amount of chemical to be added: 100 Kg of 100% pure sodium hydroxide (NaOH) is used to prepare an alkaline solution with a concentration of 20%. 2) Boiling: Light the fire and increase the pressure to 0.3–0.4 MPa; carry out screw tightening and the installation of handhole covers during this period. After 12 hours, at a pressure of 0.3–0.4 MPa, drain water through the drain valves (make sure the water level is restored to its maximum level before draining). While draining, open the drain valves of each header in sequence to ensure even drainage; the amount of water drained should be 10% of the total volume of water in the boiler. 2. Second-phase chemical dosing and boiler boiling: 1) Dosage amount: 80 Kg of NaOH with 100% purity is used to prepare a 20% alkaline solution, while 100 Kg of trisodium phosphate (Na3PO4·12H2O) is used to create a mixed solution. 2) Boiler boiling: Raise the pressure to 1.0–1.5 MPa; after boiling for 8 hours, reduce the pressure to 0.3–0.4 MPa to drain water, with the amount of water drained still being 10% of the total volume in the boiler. (The water level should be raised to its maximum level before draining water), and then raise it back to the maximum level. 3. Phase 3: Chemical addition and boiler boiling: 1) Amount of chemical to be added: Prepare 150 Kg of trisodium phosphate (Na3PO4·12H2O) into a solution with a concentration of 10%. 2) Boiler sterilization: Raise the pressure to 2.5 MPa and conduct sterilization for 8 hours. After the third phase of boiler heating is complete, the water is replaced. This replacement is carried out through the lower header of the boiler and continuous blowdown, until the quality of the boiler water meets the standards for trial operation. IV. Precautions during the boiler cleaning process: 1. Demineralized water should be used for make-up water during the boiler cleaning process. 2. The pressure increase rate of the boiler is as follows: Pressure range | Pressure increase rate | Total time 0–0.4 MPa | 0.1 MPa/30 min | 120 min 0.4–1.5 MPa | 0.1 MPa/14 min | 160 min 1.5–2.5 MPa | 0.1 MPa/4 min | 40 min 3. When the steam pressure reaches 0.05–0.1 MPa, close all air valves. 4. During furnace heating, the expansion readings of various components at working pressures of 0.5, 1.0, 1.5, 2.0, and 2.5 Mpa should be recorded, along with whether they meet the specified values. 5. During the boiler firing process, samples should be taken from the drum and the lower water wall headers in order to monitor and analyze changes in the alkalinity and phosphate levels of the boiler water. Generally, sampling is carried out as follows: 1) Testing begins one hour after the first stage of boiler firing, and then every 2 hours after pressure is applied. 2) Once before and once after wastewater discharge. 3) Once per hour after water change. 6. The alkalinity of the boiler water in all its parts should be uniform; during boiler firing, the alkalinity of the boiler water must not be lower than 50 mmol/L, otherwise chemical additives should be added. 7. The blowdown time at each point during the boiler heating process shall not exceed 30 seconds to prevent disruption of the water circulation. 8. When the boiler is in operation, usually only one drum level gauge is used, with the others kept as spares, so that the drum level is maintained at a high level. 9. During boiler heating, the medicinal solution is not allowed to enter the superheater. 10. After cooking is complete, change the water and rinse the hydrophobic valve and drain valve that were in contact with the chemical solution. 11. During boiler operation, the exhaust valve of the superheater outlet header should be opened to cool the superheater. 12. After the boiler is cooked, all the manholes and access holes in the steam drum, the lower water wall header, and the economizer header should be opened in order to clean the interior of the boiler, and it is necessary to check whether the blowdown valves are blocked or stuck. 13. After heating the furnace, check the cleanliness of the inner walls of the steam drum and header. 1) The inner surface is free of oil stains and rust, as well as any residual iron oxide particles or welding slag. 2) The inner surface has no secondary rust formation, and a protective film is formed. 3) A temporary high/low water level signal should be added during boiler boiling.

Boiler firing reference document: GB50273-2009 \"Code for Construction and Acceptance of Boiler Installation Projects\", Section 9.3 Boiler firing； Appendix B of TSG G5003-2008 \"Rules for Chemical Cleaning of Boilers\": Chemical cleaning processes for industrial boilers and their requirements. Appendix E of GBT34355-2017 \"Rules for Chemical Cleaning of Steam and Hot Water Boilers\": Chemical cleaning processes for industrial boilers and their requirements