Characteristics of start-up and use of oil fired boilers
Characteristics of start-up and use of oil fired boilers
1、 Oil fired boiler boiling:
Newly installed, overhauled, or long-term decommissioned fuel boilers must undergo boiling out before formal start-up. Boiling can be done separately or together with the oven in the later stages. Its purpose is to remove rust, oil stains, and other contaminants from the boiler’s evaporative heating surface, reduce corrosion on the heating surface, and improve the quality of boiler water and steam.
2、 Fuel fired boiler ignition and pressure boosting:
Generally, after adding water to a fuel fired boiler, it can be ignited and pressurized: for a boiler that needs to be baked and boiled, after the boiling is completed, it needs to be drained and cleaned before adding water again, and then ignited and pressurized. After ignition, as the combustion process proceeds, the heat transfer process between the flue gas and the heating surface also begins. The water added to the boiler is continuously heated until it reaches saturation temperature, and steam is produced.
After a gas boiler generates steam, it starts to increase pressure. At the same time, the saturation temperature of the furnace water continues to rise. Due to the increase in boiler water temperature, the metal wall temperature of the steam drum and evaporation heating surface also increases, and attention should be paid to thermal expansion and thermal stress issues. Due to the thick wall thickness of the steam drum, the main issue during heating is thermal stress, while also considering its overall thermal expansion. For heating surface pipes, due to their long length and thin wall thickness, the main issue during heating is overall thermal expansion, while also paying attention to their thermal stress. When the axial expansion of the pipe is limited, the thermal stress will increase to a large value. During the process of temperature rise and pressure rise, there is a temperature difference along the wall thickness and between the upper and lower walls of the steam drum (horizontal drum), that is, the temperature of the inner wall is higher than that of the outer wall, and the temperature of the upper wall is higher than that of the lower wall.
In order to prevent excessive thermal stress in oil fired boilers, the pressure boosting process of the boiler must be carried out slowly. During the ignition and pressure boosting process, the steam parameters, water level, and working conditions of various components of the boiler are constantly changing. In order to prevent abnormal situations and accidents, it is necessary to closely monitor the changes in various instrument indications, adjust and control process parameters such as pressure, temperature, and water level within the allowable range, and also assess the reliability and accuracy of various instruments, valves, and other control facilities. In addition, attention should also be paid to observing each cooked surface to ensure even temperature changes in the cold and hot exchange of each part, and to prevent local overheating and equipment damage.
3、 Heating and steam merging of oil fired boilers:
The so-called oil fired boiler heating refers to the use of steam to slowly heat pipes, valves, flanges and other components, causing their temperature to slowly rise, avoiding sudden steam supply to cold or lower temperature pipes, in order to prevent damage to pipes, valves and other components due to excessive thermal stress. At the same time, drive out the condensate in the pipeline to prevent water hammer during steam supply.
The warm-up time of cold steam pipelines is generally not less than 2 hours; The heating time for hot steam pipelines is generally 0.5 to 1 hour. When warming up the pipes, it is necessary to check whether the expansion of the steam pipeline is good and whether the supports and hangers are normal. If there is any abnormal phenomenon, the heating of the pipes should be stopped to identify the cause and eliminate the fault.
Parallel steam, also known as parallel boiler or parallel boiler, refers to the operation of a boiler that supplies steam to a shared steam main. Before merging, the combustion should be weakened, and all drain valves on the steam pipeline should be opened to fully drain to prevent impact; Flush the water level gauge and maintain the water level below the normal water level line; Make the steam pressure of the start-up fuel boiler slightly lower than the steam pressure inside the steam main pipe (low-pressure boiler is 0.02-0.05MPa lower; medium pressure boiler is 0.1-0.2MPa lower); Then slowly open the main steam valve and isolation valve to connect the started boiler with the steam main.