Engine exhaust gas contains partially burnt fuel and lubricating oil and ash. These particulates can form deposits on boiler Tubes. Especially during prolonged low load operation, which reduces exhaust gas velocity, it may lead to higher soot deposition. It may be due to burning poor quality fuel, poor combustion due to defective injector or inefficient fuel purification. These deposits on the tubes may get heated and rise above self ignition temperature. Soot deposits may be ignited by glowing carbon particulates in the exhaust gases. The ignition temperature of the soot is usually less than 400 C, however if the deposits stick, it could fall below 200 C. Soot fires can occur after the engine has shut down, therefore it is important to maintain water circulation after shut down.
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