External cleanliness of the boiler, superheater, reheater, economiser and air heater surface has direct bearing on efficiency, capacity, and draft loss. The frequency of cleaning depends upon the quality of fuel used, load conditions, disposition of the equipment and steam temperature. Dry and saturated steam and compressed air are used for soot removal. If lancing is used, compressed air is preferred. While hand lancing a steam boiler, particular care should be taken to ensure sufficient negative furnace pressure to protect those doing the lancing operation. If water lancing is employed, direct impingement of water on tubes, headers or drums must be avoided to prevent thermal quench cracking.
It is desirable to increase the furnace draft above normal when operating soot blowers or to change over to manual operation during the blowing period. Before operating blowers, its pipeline should be thoroughly drained.
Compressed air is preferable for the cleaning operation when the units are not in service, as steam may cause external corrosion. When the rotating type of soot blowers are installed, the nozzles must be maintained in proper position relative to the tubes. If they become displaced, serious erosion of tube metal and consequent failure can result. When retractable blowers are installed, the operation should be carefully watched to prevent damage to the blowing elements in case they do not retract properly.
Portable steam lances can also cause wasting of tubes if directed upon the same location for long periods. Soot blowers should be carefully examined at the time of each internal inspection and faults if any corrected.
Mechanism of Sonic Soot Blowing
Sonic soot blowers offer a cost-effective and non-destructive means of preventing ash and particulate build-up within the power generation industry. They use high energy – low frequency sound waves that provide 360° particulate de-bonding and at a speed in excess of 344 meters per second. Because they employ non-destructive sound waves, unlike steam soot blowers they eliminate any concerns over corrosion, erosion or mechanical damage and do not produce an effluent stream.
The sonic soot blower can in some ways be compared to a musical reed instrument such as an oboe, where the ‘base tone’ is created by blowing air over a reed and then converting this ‘base tone’ into a particular high or low note, depending on how far the sound wave has to travel along inside the body of the instrument.
The sonic soot blower operates in the same manner, the ‘base tone’ being produced by passing compressed air into a wave generator which houses a titanium diaphragm causing it to oscillate rapidly.
Difference between Sonic soot blowing & Steam soot blowing