Features & Benefits
- Recognized and listed by the U.S. Mine Safety and Health Administration (MSHA)
- Passive Diesel Particulate Filter (DPF) system that is ideal for mining application
- Great at reducing deadly emissions, such as Carbon Monoxide (CO), Hydrocarbons (HC) and Particulate Matter (PM). Visible smoke is completely eliminated by the filter
- This technology is pivotal in assisting retrofit compliance with the newly adopted MSHA rules regarding diesel particulate matter (DPM) emissions in underground mines
- Available in two options: Cordierite or Silicone Carbide
- Compact design with thermal insulation
- Optional computerized controller with 3 customizable alarms and data logging capabilities
- System maintenance intervals of 2000 to 6000 hours
- Stainless steel housing, custom fit available
S-Series – Technology
Nett® S-Series diesel filters utilise cordierite or silicon carbide wall-flow monoliths to trap the soot produced by heavy-duty diesel engines. The cylindrical filter element consists of many square parallel channels running in the axial direction, separated by thin porous walls, as shown below.
The channels are open at one end and plugged at the other, which forces the particle laden exhaust gases to flow through the walls. Gas is able to escape through the pores in the wall material. Particulates, however, are too large to escape and are trapped in the filter walls and in the inlet channels. A proprietary noble metal catalyst is coated onto the inside surface of the filter monolith. The catalyst lowers the soot combustion temperature allowing the filter to regenerate. The accumulated soot is oxidised in the filter during regular operation of the engine. For about 25-30% of the engine operating time, the exhaust temperatures must be at least 275-300°C (530-575°F) for proper filter regeneration when ULSD (ultra-low sulfur diesel) fuel is used.
The exact temperature requirements change with engine technology, with installations on older, dirty engines requiring higher exhaust temperatures for regeneration. For example, filters installed on older off-highway engines with high DPM emissions (e.g., >= 0.30 g/bhp-hr) may require temperatures of 325-400°C (615-750°F). The regeneration also depends on other factors, such as the vehicle duty cycle, filter sizing and type of diesel fuel used. ULSD fuel (S < 15 ppm wt.) is now widely available and should be used whenever possible with any diesel particulate filter.
Nett® diesel particulate filters are available with either cordierite or silicon carbide (SiC) substrates. Cordierite substrates perform satisfactory in most heavy-duty applications with high exhaust temperatures. However, in low-temperature applications which may experience “uncontrolled regenerations”, cordierite is more susceptible for damage from high temperatures, such as melting. Silicon carbide has higher maximum operating temperature limits and better durability in high temperature applications. Disadvantages of SiC include higher weight and higher cost.
S-Series – Performance
The soot filtration efficiency of the Nett® S-Series catalytic diesel filter increases with the soot loading in the unit. Even at low soot loads the filter efficiency exceeds 90% (blue line in Figure below). The visible smoke is completely eliminated by the filter, resulting in a dramatic improvement of smoke opacity readings.
Typical exhaust gas pressure drop on a properly regenerating filter is between 5 and 10 kPa (20-40″ H2O). There is a relationship between the exhaust gas temperature and the filter pressure drop. Applications with higher exhaust temperatures regenerate better, accumulate less soot in the filter, and experience lower pressure drop. The filter pressure drop is also influenced by the engine-out DPM emissions. Dirty engines with high soot emissions require that more DPM is captured and oxidized in the filter, resulting in higher average soot loading and pressure drop. For this reason, filters are likely to work at a higher pressure drop when installed on high polluting engines.
Gas Phase Performance
Due to the presence of the oxidation catalyst, reductions in Carbon Monoxide (CO) and Hydrocarbon (HC) emissions are also observed in the filter. The gas phase performance of the Nett® S-Series filters is similar to that of a standard diesel oxidation catalyst, as illustrated in the figure below.