75T 5.3MPa fluidized bed boiler firing-up

This post was last edited by gjn1970 on 2011-7-4 09:54. Cooking is usually done at the later stage of drying. 1. Furnace cooking conditions: 1) The moisture content of the refractory brick mortar sample in the later stage of furnace drying is less than 7% ； 2) The chemical dosing, sampling pipelines, and machinery have all been installed and tested successfully ； 3) All chemicals for chemical water treatment and boiler cleaning have been prepared ； 4) All driving equipment of the boiler (including the lighting facilities in the plant) are in normal operation ； 5) All operators for the boiler, chemical analysis, and other sections have arrived at their posts. 2. Furnace boiling process: 1) After the furnace has been dried properly, use blowdown to lower the water level to 150 mm below the center line ； 2) The solution prepared by mixing NaOH and NaPO4 is pumped into the boiler using a dosing pump ； 3) Open the feedwater bypass valve to supply water into the furnace, maintain the water level at 130 mm above the center line, stop the water supply, close the feedwater bypass valve, open the recirculation valve, and proceed with boiler blowing. For sub-high-pressure boilers operating at a pressure of 5.3 MPa, the boiler cleaning process is generally carried out in three phases, with different pressures at each phase: Phase 1: 1) Recheck the auxiliary equipment of the boiler as well as all other devices to ensure they are in operational condition; start up the coal feeder, exhaust fan, supply fan, etc., and adjust the air flow appropriately. 2) Prepare fuel in the boiler for ignition and pressure building; once the pressure reaches 0.1 MPa, open the superheater drain valve and flush one of the nearby level gauges. 3) Raise the pressure slowly to 0.4 MPa again; the installation personnel are required to conduct a thorough inspection of all pipes and valves and tighten the bolts. The boiler should then be operated at 0.4 MPa for 8–12 hours, with a steam discharge rate of 10% of the rated evaporation capacity. Sampling for analysis is carried out every 4 hours, and the analysis results are communicated to the operators. 4) Determine the amount of wastewater to be discharged and the timing of such discharge based on the site conditions; during discharge, closely monitor the water level to maintain stability, prevent disruption in the water circulation, and keep accurate records of the water level. 5) During the first phase of boiler startup, it is required that the water level be maintained at +130 mm. Operators must take readings from instruments such as those showing flue gas temperature, flue gas pressure, temperature, water level, and expansion values every hour. Phase 2: 1) Raise the pressure slowly again to 2.5 MPa, and then flush each instrument pipeline. The boiler is boiled at a pressure of 2.5 MPa for 10–12 hours, with the steam discharge amount being around 5% of the rated evaporation capacity. 2) The duty operator should strictly control the water level at +160 mm, and check the upper and lower level gauges every 2 hours, making proper records. 3) The laboratory technician shall test the boiler water every 2 hours; the alkalinity of the boiler water must not be lower than 45 mgN/L, otherwise chemical additives should be added. At the same time, based on experience, discharge should be carried out once on a regular basis; during this process, the water level must be strictly controlled to ensure minimal fluctuations, and records of the discharge should be kept. 4) Operate at a pressure of 2.5 MPa, test the output of each fan as well as the total air pressure, and keep records. Meanwhile, the operators are required to adjust and monitor the steam pressure, water level, and flue gas temperature; if necessary, the superheater drain can be used for adjustment. Phase 3: 1) Slowly increase the pressure to 3.2 MPa for stable combustion, maintain the water level at +160 mm and the steam temperature between 380°C and 400°C; operate at this pressure for 12 to 24 hours. 2) Open the feedwater bypass valve to control its flow rate, and then carry out water replacement by continuously feeding and discharging water. 3) According to the laboratory technician’s instructions, appropriately open the drain valve, and assign a dedicated person to monitor the drum water level while maintaining timely communication. 4) The laboratory technician shall take samples for analysis every hour and keep detailed records. When the alkalinity of the boiler water is within the specified range (usually ≤18 mgN/L), water replacement can be stopped and the boiler boiling process can be concluded. 3. Precautions for boiler descaling: 1) The water level in the boiler should be at a low level before adding chemicals; during descaling, the highest level in the steam drum should be maintained, but it is strictly prohibited for the chemicals to enter the superheater. 2) During boiler boiling, the time for each blowdown should generally not exceed half a minute to prevent disruption of the water circulation. 3) At the end of the middle stage of furnace firing, the mortar should be analyzed; generally, by the end of Phase I, the moisture content of the mortar sample should have dropped to 4–5%, and by the end of Phase II, it should be 2%. 5% or less; if this level is not achieved, the cooking time can be appropriately extended to ensure that the moisture content of the mortar meets the required standards. 4) Operators and laboratory technicians must follow the specifications strictly and keep detailed records. 4. After boiler cleaning: 1) Once the cleaning is complete and the boiler has been shut down with water drained, the drum should be opened to thoroughly clean any deposits and residues attached to its interior. 2) The laboratory technicians and commissioning staff of the power plant should, together with the personnel from the installation company, inspect the inner wall of the steam drum. It is required that the inner wall be free of rust and oil stains, and that a protective layer of sodium phosphate be present on it.

This post was last edited by zgj2405 on 2011-7-4 at 18:30. The information provided is not comprehensive enough; if you need professional written materials, feel free to contact me.