Soot blower blowing medium selection

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Soot blowers are auxiliary equipment, which is necessary for safe, economical and long-term operation of boilers. According to the different fuels are used by the boiler, the ash generated on the heated surface can be different. Due to different types of ash, such as slagging, staining, dry ash, etc., different types of soot blowing media can be selected to meet the requirements. These are industrial water (water temperature 20 ° C ~ 60 ° C), superheated steam, saturated steam, compressed air and so on. See the table below for details:

 

Under normal circumstances, industrial water is not used to remove ash. When burning low-quality coal, especially high-alkaline lignite, it will cause serious coking and form large coking, and then use industrial water to remove coke. When the fuel has a large moisture or a high sulfur content, compressed air soot blowing should be preferred, especially in the low temperature flue area to prevent the formation of “cement-like scaling”.

 

Soot blowing part Smoke temperature range °C Degree of ash accumulation
Extremely serious Serious Medium to light
Hearth

 

Water above 1000 °C Water, saturated steam, superheated steam, air Saturated steam, superheated steam, air Superheated steam, air
Screen, superheater

 

600-1000°C Superheated steam, saturated steam, air Superheated steam, air Superheated steam, air
Economizer 300-600°C superheated steam, air superheated steam, air superheated steam, air
Air preheater 150-300°C superheated steam, air superheated steam, air superheated steam, air

 

Pressure and soot blowing energy of the soot blowing medium:

The soot blower sweeps the dry ash by using the energy of the jet to separate the dry ash, which is carried away by the flue gas after blowing. The role of the soot blower in blowing the coke slag is very complicated. It has both thermodynamic quenching and quenching, as well as the use of mechanical energy of the jet to produce crashing, peeling, smashing, blowing, etc. Therefore, the blowing effect of the soot blowing medium is related to the nozzle diameter, pressure, arrangement, and the soot blowing distance.

 

The pressure of the hydraulic soot blowing medium is generally around 10-13 kg / cm2, and the preferably nozzle diameter is Φ4-Φ6 mm. The starting pressure and the nozzle diameter must be strictly controlled. Generally, the hydraulic soot blowing medium is used in high temperature furnace where the ash accumulation is serious.

The pressure of saturated steam soot blowing medium is generally around 8-12 kg / cm2. Because steam contains a certain humidity, it is generally used for blowing the high temperature furnace and high temperature convection tube.

The superheated steam soot blowing medium has a certain degree of superheat and has high kinetic energy. The applicable range is wide. As long as the pressure and temperature parameters are controlled, all the heating surfaces can be basically applied. It is generally recommended that the blowing pressure is around 10-16 kg/cm2, the temperature range is 280~320 °C, and the large unit can reach 20 kg/cm2.

Compressed air blow media has less energy storage than superheated steam, so compressed air is not as effective as superheated steam and saturated steam, but the air soot blowing medium can be applied to the air preheater of the tail flue. There will be no “cement-like scaling” on the heat transfer components. When compressed air is used as the blow medium, the pressure is generally around 12 kg / cm2 and the maximum is 14 kg /cm2.

The selection of the soot blower medium should be determined by specific conditions of the on-site boiler. The firstshould be effective, the secondshould be economical, and the third is the choice should be comprehensively whichmeans according to the structure of the boiler, the combustion method, and the fuel composition, etc. Sometimes air and steam can be used in combination; industrial water and steam can also be used in combination; thus, the specific choice been made must through carefully considerations.