The mechanism of good combustion depends on:

(i) Fuel Oil Quality:

• Residual fuel oil, commonly used in boilers, has a high viscosity. This necessitates pre-heating to improve pumpability, filtration, and atomisation. A viscotherm often helps maintain the correct pre-heat temperature and viscosity for optimal combustion. Impurities like water, sodium, vanadium, asphaltenes, sludges, and catalytic fines (aluminium and silicon) negatively impact combustion efficiency. Water causes flame fluctuations and should be removed through draining and purification. Sodium and vanadium require chemical additives to mitigate their corrosive effects as they cannot be removed by simple purification. Asphaltane presence leads to carbon deposits and should be minimized in the bunkered fuel. Finally, catalytic fines need to be removed via filtration and purification.

(ii) Fuel Temperature:

• Appropriate fuel temperature is essential for effective atomisation. This creates a larger surface area for interaction with oxygen in the combustion chamber. Lighter hydrocarbon fractions burn in the primary flame zone, essential for initiating and sustaining combustion. Heavier fractions vaporize in the secondary flame zone, completing the combustion process.

(iii) Optimum Quantity of Air:

• The correct air-to-fuel ratio is paramount. Preheated air, if possible, needs to be supplied in the appropriate proportion to the fuel. Insufficient air leads to incomplete combustion and unburnt hydrocarbons, while excess air carries away heat, reducing efficiency. Proper mixi

• Residual fuel oil contains various impurities that hinder efficient combustion and can damage boiler components. Treatment strategies focus on removing or mitigating the negative effects of these impurities:
• Water is removed through draining and purification processes.
• Sodium and Vanadium Control: These cannot be effectively removed; therefore, chemical additives are used to counteract their corrosive effects.
• Asphaltane Reduction: Low asphaltane content in the bunkered fuel oil is crucial to minimize hard carbon deposits. This relies on selecting fuel with low asphaltane levels.
• Catalytic Fines Removal: Proper filtration and purification methods remove catalytic fines.
• Viscosity Control: Pre-heating the fuel to the correct viscosity ensures efficient atomisation and combustion.

• Soot Blowing: High-pressure steam or air is injected into the boiler, dislodging soot deposits from the tubes.
• Sonic Equipment: High-frequency sound waves introduced into the boiler uptake cause vibrations that prevent soot from settling on heat transfer surfaces, keeping it suspended for easier removal.

Soot Removal Equpment Diagram: