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Solid fired boilers should regularly be checked for clinker and the same should be removed. Clinker may reduce the boiler operating efficiencies.

Clinkers have been a recurring problem in all solid-fired boilers for long. Clinkers, also known as slag, and in coal fired boilers consist of the noncombustible elements and minerals found in coal that melt and fuse together as lumpy ashes from coal combustion.

Clinkers resemble volcanic ash and lava. They occur in the high-temperature furnace area of the boiler. The most common cause of clinker in a boiler is inferior fuel sources. Low-quality coal, such as lignite, contains a higher concentration of water and minerals including pyrite, iron, calcium, sodium and potassium. When heated to the extreme temperatures needed for boiler operations, these compounds break down and interact with the boiler interior, the air, released moisture and with each other. The resulting debris then either sticks to the walls of the boiler or falls to the floor where it is covered by another boiler operation by-product, ash.

Sometimes poorly maintained or operated equipment is the cause of clinker formation. If the boiler's air-to-fuel ratio is not correct, the coal will not burn properly. Coal is pulverized before it is burned, and if it is not done correctly, even the best coal will not burn thoroughly, promoting clinker.

Large clinkers accumulation on the combustion grate can hinder air passage and increase operational and maintenance costs. Thus it is recommended to check the boiler internal surfaces regularly for clinker and verify the controllable elements such as operating practices to minimize its occurrence.

Illustration:

Clinker formed in Boiler