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A diesel purifier starts to work at an exhaust temperature of around 120°C, thereafter its efficiency rises very quickly.  At 230 °C, it removes over 80% of carbons; at 300°C, over 90% of carbon monoxide and over 80% of hydrocarbons, until at 350° C efficiency levels out, with the Purifier eliminating over 90% of both pollutants.
As a forklift shifts heavier loads, the more pollution it produces.  With a Purifier fitted, the greater the load, the more pollution is reduced.  For example, at 1400 rev/min and full load, a typical diesel-powered fork-lift truck produces nearly 3000ppm of carbon monoxide; the Purifier reduces this to around 270ppm - a reduction of over 90%.

The benefits of such Purifiers are therefore:
High reduction of carbon monoxide to reduce problems of dizziness and headaches which affects the concentration of the operator.
Effective conversion of hydrocarbons and aldehydes.  This translates to less eye and throat irritation.  The diesel odours are virtually eliminated.

 

It should be noted that a Purifier has a limited lifespan of between 5000 and 8000 hours. This lifespan will be influenced by:

  • The performance of the engine

  • The quality of the diesel used

  • Airflow rate

  • Sulphur content of engine oil used

The Purifiers convert CO to CO₂, through a chemical reaction with the precious metal coating on the honeycomb monolith. This coating will with time be worn off, hence the need for a replacement unit.

The Design

Whatever shapes the purifier take, the design principles are essentially the same.  Each purifier consists substantially of a high-quality grade stainless steel case containing a ceramic honeycomb.

Purifiers are available in more than 400 different configurations to suit virtually every fork-lift truck and bus on the market.
Whatever shapes the purifier take, the design principles are essentially the same.  Each purifier consists substantially of a high-quality grade stainless steel case containing a ceramic honeycomb.

This honeycomb supports a platinum-based catalyst that reacts with pollutants to form carbon dioxide and water as follows:

  • (Carbon Monoxide) 2CO + O₂ → 2CO₂ converted to harmless

  • (Aldehydes) HCHO + O₂ → CO 2 + H₂O converted to harmless

  • (Hydrocarbons) 4HC +SO₂ → 4CO₂ + 2 H₂O converted to harmless

 
High-technology research and development goes into each purifier model.  For the optimum conversion of gases to occur, the maximum surface area of the catalyst has to come into contact with the maximum volume of exhaust gas.  Yet the gas must not be blocked by the catalyst support in any significant way, otherwise engine efficiency will be impaired, hence the honeycomb design, which creates a turbulent gas-flow to force the maximum amount of gas into contact with the catalyst. 
The cross-section of each cell in the honeycomb is made to particularly fine tolerances. The time path and optimum cell size (to allow the emissions to flow freely) and catalyst surface area (to allow the gas to react easily) are all crucial aspects of the purifier design.

Each model is made to particularly heavy-duty specifications, and is resistant to vibration.  The purifiers are also compact, to fit into small engine compartments and should not interfere with normal engine maintenance.