Production of Ash in Exhaust Systems

1. Sources of Ash-Forming Compounds

Engine Oil Additives:

• Detergents and Dispersants: These additives keep the engine clean by preventing deposits. They often contain metals such as calcium, magnesium, and zinc.
• Anti-Wear Agents: Zinc dialkyldithiophosphate (ZDDP) is a common anti-wear agent that contains zinc and phosphorus.
• Other Additives: Various other additives can include metals like barium and molybdenum.

Fuel Additives:

• Octane Boosters: Some fuel additives used to increase octane rating contain metallic compounds.
• Detergents: Added to fuel to clean the fuel system and combustion chamber, they might also contain metallic components.

2. Combustion Process

When the engine operates, both fuel and oil are burnt. Here’s how the combustion process works:

• Fuel Injection and Atomisation: Fuel is injected into the combustion chamber where it mixes with air.
• Compression and Ignition: The air-fuel mixture is compressed and ignited, leading to combustion.
• Oil Consumption: A small amount of engine oil also enters the combustion chamber, either through the cylinder walls or via the crankcase ventilation system.

3. Formation of Ash

During combustion, the metal-containing compounds from both the fuel and oil additives undergo a series of chemical reactions:

• Oxidation: Metal-containing compounds oxidise to form metal oxides.
• Combustion Residue: These metal oxides do not burn completely and remain as solid residues.
• Ash Particles: The solid residues are carried away with the exhaust gases as fine ash particles.

4. Ash Deposition in the Exhaust System

As the exhaust gases travel through the exhaust system, including components like the catalytic converter and diesel particulate filter (DPF), ash can deposit and accumulate.

• Catalytic Converter: Ash can coat the catalyst surfaces, reducing their effectiveness over time.
• Diesel Particulate Filter (DPF): In diesel engines, the DPF captures particulate matter, including soot and ash. While soot can be periodically burnt off during regeneration cycles, ash remains and accumulates, eventually requiring filter replacement or cleaning.

5. Impact on the Exhaust System

• Clogging and Pressure Drop: Accumulated ash can clog components like the DPF, leading to increased backpressure and reduced engine efficiency.
• Maintenance and Replacement: Regular maintenance is needed to manage ash buildup, including cleaning or replacing clogged filters.
• Emission Control: Excessive ash can interfere with the operation of emission control systems, potentially leading to higher emissions.

6. Mitigation Strategies

To minimise ash production and its impact:

• Use Low-Ash Oils: Formulated with fewer metallic additives to reduce ash formation.
• Optimise Fuel Additives: Using cleaner additives that minimise metallic content.
• Regular Maintenance: Ensuring timely oil changes and proper engine maintenance to reduce oil consumption.
• Regeneration and Cleaning: Implementing regular DPF regeneration cycles and periodic cleaning of exhaust components.

BAC101 Diesel Particulate Filter (DPF) Cleaner

The BAC101 DPF cleaner is designed to remove ash and other particulates from within the DPF filter through a combination of chemical action and thermal processes. Here’s how it typically works:

1. Chemical Cleaning Action

• Penetration: The BAC101 cleaner contains chemicals that penetrate the porous walls of the DPF filter where ash and other particulates accumulate.
• Chemical Reaction: These chemicals react with the ash and soot, breaking down their structure. The reaction often involves converting the solid particulates into soluble compounds or smaller particles that are easier to expel.

2. Thermal Activation

• Heating the DPF: The cleaner is usually used in conjunction with a heating process. The vehicle’s engine or an external heat source is used to raise the temperature of the DPF to a level where the chemical reactions are more effective.
• Regeneration: The elevated temperature helps in burning off the carbonaceous soot, a process known as regeneration. The BAC101 cleaner can enhance this process by lowering the temperature at which the soot combusts.

3. Flushing and Expelling Particulates

• Solubilisation: Once the ash and soot are broken down, the resulting compounds can be more easily removed from the DPF.
• Exhaust Flow: The normal exhaust flow through the DPF helps to flush out these compounds. The cleaner may produce a liquid or gaseous byproduct that helps carry away the particulates.

4. Final Cleaning Steps

• Inspection and Testing: After the cleaning process, the DPF is usually inspected to ensure that it is free of significant blockages and is functioning correctly.
• Additional Flushing: In some cases, additional flushing with water or air may be required to remove any residual chemicals or particulates.