Precautions For Coal Fired Boiler Transformation


Precautions For Coal Fired Boiler Transformation
The long-standing problems of coal-fired boilers, such as large-scale pollutants, small monomer capacity, emissions close to the ground, and mismatch between main and auxiliary machines, have been magnified again. Undoubtedly, the transformation of coal-fired boilers will become the focus of urban air pollution control in the next step.

Precautions For Coal Fired Boiler Transformation

First: Basic Principle of Changing Coal-fired Boiler into oil (gas) boiler
1. The reformed coal-fired boiler must have the following conditions:
① The pressure parts of the original boiler are basically intact and have the value of continuous use;

② The water gas system, air supply system, and induced draft system of the original boiler shall be basically intact.

2. The reformed boiler shall achieve the following objectives:
① Keep the original boiler-rated parameters (such as steam pressure, steam temperature, return water temperature, etc.) unchanged;

② Maintain or improve the output and efficiency of the original boiler.

3. Through the transformation, the purpose of eliminating smoke and dust is achieved, and the requirements of environmental protection are met.

4. The boiler transformation scheme must be simple, easy, low investment, quick effect, and short construction period. Therefore, the smaller the scope of boiler transformation, the better. It can be realized only through boiler transformation and combustion devices. The transformation part does not exceed the basic structure scope of the boiler body.

Second: Problems to be paid attention to when changing coal-fired boiler into oil (gas) boiler
1. To change to the mechanized stratified combustion of oil (gas) boilers, the front, and rear arches should be removed first, and the bottom heating surface should be added to replace the grate to prevent the grate from overheating and burning out.

2. For the small-sized boiler that changes coal burning to oil (gas) fired boiler, that is, from the original negative pressure combustion to the present micro positive pressure combustion, attention must be paid to the furnace wall structure and sealing.

3. The type selection and arrangement of burners are closely related to the furnace form so that the flame in the furnace is better filled and no air flow dead corner is formed; Avoid flame interference between adjacent burners; Keep the flame at the center of the furnace under low load to prevent the flame center from deviating from the symmetrical center of the furnace; The unburned gas mixture shall not contact the heating surface to avoid incomplete combustion; High-temperature flame shall not scour the heating surface at high speed, and avoid overheating the pipe wall due to excessive heat intensity of the heating surface. The arrangement of the burner shall also consider the arrangement of the gas pipeline and the reasonable arrangement and use of the pipeline.

4. The flue gas velocity of the convective heating surface of the oil-gas fired boiler is not limited by the fly ash wear condition, and the flue gas velocity can be appropriately increased to increase the heat transfer coefficient of the convective heating surface; For the boiler with superheated gas, the heating area shall not be increased. Attention shall be paid to the capacity of the steam water separator in the furnace to ensure the steam quality, especially for the boiler with superheated gas.

5. In order to prevent high-temperature corrosion, coal is changed into fuel oil, because the fuel oil contains metal elements such as sodium and vanadium. After combustion, the melting point of oxide eutectic crystal is very low, generally around 600 ℃ or even lower. After sublimation at high temperatures in the furnace, this kind of oxide condenses on the heating surface at relatively low temperatures to form corrosive high-temperature ash deposits, and the faster the corrosion rate is. Therefore, during the transformation, special coatings such as ceramics and silicon carbide should be coated on the surface of the heating surface that is prone to high-temperature corrosion, and materials with good high-temperature corrosion resistance can also be selected to improve their high-temperature corrosion resistance.

6. To prevent the explosion in the boiler, when the coal is changed into oil (gas) boiler when the oil droplets (gas) with poor atomization or incomplete combustion are collected by hot gas in the furnace or tail, explosion-proof doors shall be installed at appropriate positions of the boiler due to the danger of fire and explosion, and ignition program control and flameout protection devices shall be added to the automatic control to ensure the safe operation of the boiler.