Instructions for operating a fluidized bed boiler

1. Purpose

Operating Instructions for Steam Boiler

  • Help users understand the operation process of the equipment.
  • Assist users in starting and stopping the device.
  • Provide guidelines for users to maintain common requirements.
  • Help users accurately identify any defects whenever they occur and assist users in handling them correctly.

2. Important Notes

Check Water Supply before Starting Steam Boiler

The following points must be followed accurately when operating the steam boiler:

  • Ensure the requirements of the water supply are met when supplying to the boiler. Any deviation in the quality of water can lead to serious issues during operation, possibly due to sedimentation and impurities.
  • Never allow the water level in the water tube to be unobserved.
  • The fan/pump motor should be appropriately sized to meet the load (at working temperature) to avoid overloading the motor.
  • Do not operate the boiler below 50% load, as it will lead to non-existent boiling and other operational issues.
  • The steam layer temperature should never exceed 900°C.

3. Preparing to Ignite the Boiler

Clean Combustion Chamber before Starting Steam Boiler

  1. Clean the air injection nozzles in the combustion chamber thoroughly.
  2. Clean the combustion chamber and the air vent box through the bottom door.
  3. Prepare the fuel.
  4. Prepare crushed coal: 7-10 kg.
  5. Prepare Diesel oil: 20 liters.
  6. Start the ID fan and FD fan. Adjust the damper to maintain a combustion chamber pressure of -2 to -5 mm water column. Mark the damper position for the checked boiling state. Finally, close the air valves of the ID and FD fans.
  7. Ignite the combustion chamber, maintaining an even coal bed over the entire surface.
  8. Observe the combustion chamber and use a small shovel to move unburned fuel to where it has burned, ensuring even combustion throughout the combustion chamber with a bright red flame.
  9. Start the pusher fan and slowly open the air damper of the pusher fan depending on the fuel combustion level. At this point, the fuel will burn vigorously, and the flame will become brighter as the combustion chamber temperature increases gradually. This is a critical stage, requiring continuous monitoring of the fuel flame color. When the fuel burns vigorously with a bright red flame, it's ready.
  10. If the flame becomes dark red, and the combustion chamber temperature tends to decrease, reduce the pusher fan air (about 5-10 mm water column) and continue to monitor the combustion chamber state. If the temperature continues to decrease, reduce the air; if the temperature stabilizes, stop reducing the air and then gradually increase if needed.
  11. During the slow, red flame combustion with the coal bed, heat is gradually applied to the fuel, causing the combustion chamber temperature to increase steadily. Slow combustion depends on several key factors: the quality and moisture content of the coal, the initial temperature of the environment, and most importantly, the operation of the furnace by the operator.
  12. Continue monitoring the fuel combustion. If the fuel burns evenly, gradually adjust the air damper of the pusher fan (FD) and the suction fan (ID) accordingly to increase the combustion bed to the boiling state. During this stage, pay attention to:
  13. Gradually increase the air damper to achieve strong fuel combustion and rapid combustion chamber temperature increase. Adjust the air damper quickly if needed, and vice versa.
  14. Excessive adjustment of the pusher fan and suction fan air dampers compared to the combustion chamber state can lead to cooling of the combustion chamber, causing the furnace to shut down.
  15. Maintain the boiling state as described above, and the two temperature probes must have a good boiling layer for accurate temperature measurement in the combustion chamber. Ensure even fuel combustion and gradually increase the combustion chamber temperature to the fuel ignition temperature. During this stage, if the combustion chamber temperature does not rise or rises too slowly, reduce the air to match; if the temperature rises too quickly, increase the air accordingly.
  16. Monitor the combustion chamber temperature to gradually adjust the pusher fan pressure and adjust the suction fan air damper accordingly to maintain a combustion chamber pressure of -2 to -5 mm water column. Simultaneously, during the gradual increase in the fuel supply rate, increase the combustion chamber temperature. At this point, the fuel has reached a completely boiling state, and the furnace starts stable burning. When the combustion chamber temperature reaches 700-720°C, the process of controlling the air valves to maintain the stable boiling layer of the fuel ends. From this stage, only adjust the fuel supply rate to control the combustion chamber temperature within the range of 800-
  17. When steam escapes through the steam release valve (safety valve), allowing steam to completely expel air from the steam chamber, close the steam release valve. Observe the pressure gauge, and when the boiler pressure reaches the operating pressure, open the main steam valve to supply steam for production.

4. Operating Instructions

Preparing Fuel for Steam Boiler Group

When starting up, follow these steps:

  1. Check the water level in the boiler.
  2. Check the soft water tank to ensure it is full.
  3. Select pump 1 or 2 for operation.
  4. Open the air release valve. Turn on the water supply switch. The feed pump will start, and the water level in the boiler will begin to rise. The feed pump indicator light will turn on. Once the feed pump reaches its working level, it will stop, and the indicator light will turn off.
  5. Close the main steam valve.
  6. Close the smoke dampers of ID and FD fans to the minimum position.
  7. Check and ensure that all other equipment is in good working condition.
  8. Turn the control handle to the feed position. If the water level is low, the alarm will sound. Turn the control handle to the water supply position until the water level is sufficient.
  9. Gradually open the ID and FD fan air dampers to increase the combustion process. Opening the air damper too much can cool the boiling layer. Monitor gas pressure and steam layer temperature.
  10. Supply fuel if necessary to maintain the steam layer temperature.
  11. To operate normally, the steam layer temperature will be adjusted within the range of 800 to 8500C, and the pressure in the combustion chamber will be around -2 to -5 mm water column. However, these parameters will depend on the load conditions and fuel quality.
  12. Under stable conditions, pay attention to the governor, air damper position, air pressure, and steam layer temperature corresponding to different loads.

5. Boiler Maintenance during Operation

Maintaining Operation of Steam Boiler Group

  • Operators must strictly follow the procedures and regulations issued during the boiler operation. All necessary technical parameters and the operational status of the boiler must be recorded in the operation logbook to provide a basis for correct economic and technical assessments, optimizing the boiler operation, and finding technical solutions to ensure the long-term durability of the boiler.
  • Adjust the fuel supply rate according to the boiler's load level, avoiding excessive pressure buildup that can lead to automatic shutdown or temperature drop causing a shutdown. Maintain the combustion chamber temperature in the range of 800 to 8500C. Limit operating the boiler below 50% capacity to prevent deposits on the surfaces of the fire tubes, water heating surfaces, and flue gas pathways, which could reduce the boiler's heat transfer coefficient.
  • Adjust the pusher fan pressure to maintain the fuel's boiling layer, always keeping the combustion chamber pressure at -2 to -5 mm water column.
  • If the combustion chamber temperature rises excessively, you may need to reduce the fuel supply rate.
  • If the combustion chamber temperature drops rapidly below 7000C, reduce the pusher fan and suction fan air pressure (while maintaining an even boiling layer throughout). Reduce the fuel supply rate to a low level and closely observe the flame. If the flame remains dark red with occasional blue flashes of fuel flames, maintain the current combustion chamber status until the temperature increases slowly and repeats the process outlined in the fuel group ignition stage until the combustion chamber temperature reaches 8000C, then return to normal boiler operation.
  • During the operator's shift, check all devices in the boiler operating area thoroughly to promptly detect any abnormal activities, such as strange noises, excessive localized heating, valve leaks, and abnormal vibrations. Pay special attention to check the boiler's alarm and safety devices.

6. Boiler Shutdown

Stopping Fuel Supply when Shutting Down the Steam Boiler Group

Keep the boiler in normal operation and proceed with the following steps:

  1. Stop the fuel supply.
  2. Wait for the combustion chamber temperature to drop below 4000C, then turn off the pusher fan and suction fan. Open the fire-viewing doors completely, open all the air dampers of the suction fan to allow the boiler to cool naturally with natural convection. Turn on the water supply pump.
  3. Close the main steam valve, then slowly and gently open the air release valve (auxiliary steam valve) to reduce the boiler pressure and leave the air release valve in the open position to avoid creating a vacuum in the boiler drum when the water in the boiler cools down.
  4. Let the fuel burn out and allow the boiler to cool naturally for about 2 hours until it can no longer produce steam. At this point, the feed pump is still on, so if the boiler water level drops below the average level, the feed pump will automatically supply water to the boiler.
  5. To completely cool down the combustion chamber, perform a bottom blowdown of the boiler, blowdown the gage glasses, and blowdown the pressure gauges. Continue the bottom blowdown and blowdown of the gage glasses until the total dissolved solids in the boiler water are less than 3500 ppm. During bottom blowdown, if the boiler water level falls below the average level, the feed pump will automatically supply water to the boiler. However, close monitoring is essential to ensure that the boiler water level remains visible in the gage glasses throughout the bottom blowdown process, and it should be at the working level once the blowdown is completed. Then disconnect the main disconnect switch from the electrical panel.
  6. When the boiler water has cooled to approximately ambient temperature, tightly close all boiler valves, including the main steam valve, auxiliary steam valve, feedwater valve, and various blowdown valves.
  7. Place the entire water supply system, including pumps, tanks, valves, pipes, etc., in the off state.
  8. Thoroughly clean all parts of the boiler and auxiliary equipment. Complete the boiler operation process.

7. Some Features During Boiler Operation

Boiler Combustion Flame

a. Control of Air and Smoke

  • At low temperatures, air and smoke with high density can increase the load on the suction fan when opening the air damper. Therefore, when the combustion chamber temperature is still low, do not operate the suction fan with the air damper fully open, and gradually open the air damper to ensure fan safety. The amount of air required for combustion is directly proportional to the fuel mass and combustion. The rated load of electric motors is calculated for the full load mode of the boiler at its operating temperature of 750 ¸ 8500C.
  • The forced draft fan supplies air for fuel combustion. Its air damper is adjusted to match the fuel input to the combustion chamber to maintain optimal combustion chamber temperature.
  • The induced draft fan is adjusted only to maintain the combustion chamber pressure within the range of -2 ¸ -5 mm water column.

b. Fuel Control

  • The amount of fuel supplied to the furnace is controlled by adjusting the fuel supply rate to match the load level of the boiler and distribute it evenly throughout the combustion chamber.
  • When changing the fuel supply rate within a wide range, adjust the induced draft fan and forced draft fan dampers appropriately to maintain the optimal state of the combustion chamber.

c. Smoke Temperature Control

  • The smoke temperature indicator and control help determine the current temperature of the smoke flow and stop the boiler when the smoke temperature exceeds the set limit (within the range of 280¸3000C) to ensure boiler safety (stop all fans and fuel supply),
  • An excessively high smoke temperature can result from water shortage or intense combustion in the chamber, uncontrolled high chamber temperature. Therefore, when the smoke temperature rises too high, the boiler must be stopped to identify and rectify the cause before resuming operation.

d. Combustion Chamber Temperature Control

  • The combustion chamber temperature is indicated and controlled by a temperature control system. It shows the current temperature of the firebox, triggers alarms, and stops the fuel supply system when the chamber temperature is too high or too low compared to the set temperature. In this case, the fans continue running, and the boiling layer is maintained so that the operator can gradually return the boiler to normal operation.
  • To ensure accurate chamber temperature control, it is essential to maintain a well-boiling state, especially in the vicinity of the two temperature sensors. Additionally, ensure good contact at the wire connection points and avoid disconnecting wires from the temperature control system during sensor maintenance while the boiler is in operation.

e. Steam Pressure Switch

  • The steam pressure switch stops the boiler when the pressure exceeds the set limit and automatically restarts the boiler when the pressure drops below the lower set value.

8. Operating Notes

For proper preparation and real-time operation, inspect the following points around the boiler regularly:

  • Regularly check the soft water supply. If the supply water is hard, it should be regenerated immediately.
  • No excessive noise from the fan motors or any other moving parts.
  • No leakage from any valves or connections.
  • No overheating of any boiler parts.
  • The feedwater pump operates in an on-off state, ensuring proper level control, and it must maintain the appropriate water flow.
  • The exhaust gas from the flue is normal.
  • No electrical arcing or communication loss in the electrical circuits.
  • All control and safety devices are functioning correctly.
  • Stable steam pressure and water level must be maintained within the required range.
  • No excessive fuel combustion in the combustion chamber.
  • Regularly perform boiler blowdown. The frequency depends on the quality of the water used in the boiler.
  • Blowdown the level control switch and the water pipe each shift to remove possible sediment.
  • Drain a small amount of water from the tank each shift to remove potential sediment.
  • Record the exhaust gas temperature.
  • Maintain the optimal boiling layer temperature.
  • Maintain negative pressure in the combustion chamber within the range of -20 ¸ -50 Pa. Adjust by changing the ID fan speed.
  • Ensure that the flue gas exit temperature is within the required range for the load. If it is high, check for fouling of heat transfer surfaces or smoke path obstructions.
  • Check and maintain the current flow in the PA fan, FD fan, ID fan, pumps, etc., within the specified limits and record them in their logs.
  • Ensure that there is no air leakage in the flue gas outlet.
  • Ensure the correct fuel size. There should be no foreign objects like metal pieces or stones in the fuel, and the fuel supply equipment should not malfunction during operation.
  • Check the uniformity of the boiling layer.
  • Check and ensure that smoke or fly ash discharge in the boiler house is limited.
  • Ensure that all boiler operations are accurately recorded in the operation log, including chemicals, blowdowns, etc.

Steam Boiler Operation Guide


  • The boiler must be immediately shut down for emergency repair if there is a malfunction of the pressure-bearing parts of the boiler that poses a serious safety risk.
  • When the operating license of the boiler expires (according to the permit of the labor safety technical inspection), the boiler operation must be stopped for inspection, repair, and re-inspection to continue use.
  • Repairs, both minor and major, to the boiler must be carried out by individuals and entities recognized by the state and must comply with the current safety technical regulations of the boiler.
  • In case of unresolved issues or malfunctions, contact the boiler supplier.
  • All incidents and their resolutions must be recorded in the operation log.
  • Any changes to the structure and operating principles of the boiler must be approved by the boiler supplier. If a facility makes unauthorized changes, all responsibility lies with that facility.