Procedures for starting and stopping industrial boilers: Master them for safety
Steam Boiler - The Most Advanced Technology in Industrial Boilers
In various industries, a boiler is an essential device used to generate high-pressure steam for various purposes such as manufacturing, processing, transportation, etc. However, a boiler is also a device that poses many accident risks if not operated safely.
Therefore, mastering the start-up and shutdown process of industrial boilers is a mandatory requirement for all boiler operators. So, what is this process? Let's find out in the following article.
1. Industrial Boiler Start-up
Industrial Boiler Start-up Process
The industrial boiler start-up process includes the following steps:
- Fully open the water valves on the water supply line into the water tank and boiler.
- Fully open the air vent valve on the boiler body.
- Fully close the main steam valve on the boiler body.
- Operations on the control panel: Choose "Pump 1" or "Pump 2". Select automatic mode for water pump operation.
- Start the fuel supply system to feed fuel into the boiler. Activate the conveyor belt at a speed of 8Hz for 2 minutes.
- Use combustible material or diesel oil to ignite the fire. Use a torch to ignite the boiler.
- Observe the combustion chamber and distribute fuel evenly.
- Start the exhaust fan at 10-12Hz.
- Start the blow fan at 5-6Hz, gradually increasing to 10Hz if the combustion process is intense.
- Adjust the fuel supply rate according to the combustion level, observe the flame in the combustion chamber. Increase the combustion chamber temperature to 900⁰C.
- Close the air vent valve when the boiler pressure is in the range of 0.5-1 barG.
- When the boiler pressure is in the range of 2-3 barG, fully open the main steam valve. Note to purge the pipelines before fully opening.
- When the steam parameters meet the requirements, the boiler has been successfully started, proceed to supply steam to the plant. Note to purge the pipelines before fully opening the valve.
- Inform the plant that the start-up process is complete, ready to serve production. End the start-up process.
Clean the combustion chamber before igniting the boiler
2. Industrial Boiler Shutdown
Industrial Boiler Shutdown Process
The industrial boiler shutdown process includes the following steps:
- Stop the fuel supply, after ensuring no fuel remains in the fuel hopper and transport equipment, stop the fuel supply devices. Set the switch to the "Off" position.
- Record the operating parameters of the boiler in the operation log.
- When the combustion chamber temperature drops below 700⁰C, turn off the second-stage fan, fuel injection fan, and recirculation fan.
- When the combustion chamber temperature drops below 500⁰C, confirm that the fuel has burned out. Turn off the first-stage air fan and reduce the frequency of the exhaust fan to reduce negative pressure in the combustion chamber.
- When the combustion chamber temperature drops below 350⁰C, turn off the smoke fan.
- Turn off auxiliary equipment, ash discharge equipment, and smoke treatment equipment.
- Keep the boiler water supply pump in automatic mode and monitor the water level; never turn off the boiler water supply pump.
- When the steam pressure drops below 50% of the working pressure, manually raise the water pump with a warning level for full water, then stop the pump.
- Close the main steam valve after pumping enough water to ensure water circulation in the boiler for the next start-up. Note: Do not pump water and close the valve simultaneously.
- Turn off the electrical system. End the normal boiler shutdown process.
3. Notes During Operation
The following points must be accurately followed during boiler operation:
- Ensure compliance with water supply requirements for the boiler. Any deviation in water quality can lead to serious problems in operation due to the accumulation of impurities...
- Never allow the water level in the steam tube to go unnoticed.
- The fan/pump motor should be sized to meet the load (at working temperature) to avoid overloading the motor.
- Do not operate the boiler below 50% load, as this will lead to non-existence of boiling and cause other issues in operation.
- The steam layer temperature should never exceed 900oC.
Use a small rake to evenly spread fuel across the grate, ensuring even combustion in the combustion chamber
- Operators must strictly follow the procedures and regulations issued during boiler operation. All necessary technical parameters and operating conditions of the boiler must be recorded in the operation log to provide a basis for accurate economic and technical evaluations, optimizing boiler operation, and finding technical solutions to ensure the long life of the boiler.
- Adjust the fuel supply rate according to the boiler load, avoiding excessive pressure that may cause automatic shutdown or temperature drop leading to boiler shutdown. Maintain the combustion chamber temperature in the range of 800 - 850oC. Limit burning the boiler below 50% capacity to prevent deposits of products on the surface of fire tubes, water heating elements, and exhaust gas pathways, resulting in a reduction in the heat transfer coefficient of the boiler.
- Adjust the push fan pressure to maintain the fuel boiling layer, always maintain the combustion chamber pressure at -2 to -5 mm water column.
- If the combustion chamber temperature increases excessively, the fuel supply rate can be reduced.
- If the combustion chamber temperature rapidly drops below 700oC, reduce the pressure of the forced draft fan and the induced draft fan (while maintaining an even boiling layer), reduce the fuel supply rate to a low level, and closely observe the flame. If the fire chamber still has a dark red color with a greenish tint from the fuel fire, maintain the current state of the combustion chamber until the temperature rises slowly and repeat the process outlined in the ignition phase until the combustion chamber temperature reaches 800oC, then return to normal boiler operation.
- In each shift, operators must check all equipment in the boiler operating area to timely detect any abnormal activities, such as strange noises, localized excessive heat, valve leaks, flange leaks, or unusual vibrations. Pay special attention to checking the alarms and safety devices of the boiler.