Ceramic Diesel Particulate Filters: Advanced Emission Purification for Cleaner Urban Air

Governing bodies around the world are introducing increasingly stringent emission regulations. This has led to a push to develop ever more efficient filters, especially for diesel exhaust systems.
Ceramics in exhaust systems offer a highly effective way to purify vehicle emissions, improving air quality and making urban environments cleaner places to live. Ceramic Diesel Particulate Filters (DPF) are particularly effective, with some removing nearly 100% of soot from the exhaust emissions.
Today, DPF systems are being fitted as standard on many diesel vehicles, especially large trucks, coaches and heavy machinery. To work on the road, they are designed to be highly durable and easy to maintain.

Types of Ceramic Used in Diesel Exhaust Systems

Ceramic isn’t the only material used in exhaust filters. Paper and metal fibres can also be used to filter diesel particles. However, ceramic filters keep costs low, are easy to mass produce, are extremely durable, and provide fine filtration of particles. The following types of ceramic have become commonplace in DPF systems:

Cordierite

Cordierite is the most common ceramic used in wall-flow filters. Wall-flow filters force gas to flow directly through the filter, unlike flow-through filters such as catalytic converters.
Cordierite is an ideal material for DPFs as it filters out a very high percentage of particles and is fairly cheap.
The only downside of using cordierite ceramic is that it can melt if the filter is being regenerated – a maintenance process that involves burning off filtrate material to clean it. The risk of damaging the ceramic is especially high if there has been a large accumulation of soot and particles. Therefore cordierite filters often need a catalyst to lower the regeneration temperature.
The structure of the filter is similar to the honeycomb core of a catalytic converter, but the DPF has plugged channels, meaning the gas is forced through the wall and the filtrate is collected on the inlet face.

Silicon Carbide

Silicon carbide is a ceramic that is also used in wall-flow filters. Silicon carbide filters aren’t as popular as cordierite ones, for the simple reason that they are more expensive. The reason for the added cost is that they are not thermally stable, so cement has to separate the filter cores to protect them from heat expansion.
Silicon carbide DPFs work on the same principle as the cordierite filters. The efficiency of these types of filter can be as high as 95%. Silicon carbide also has a high melting point of 2700oC.