The two most significant pollutants produced by humans (anthropogenic) are NOx emissions and particulates. Information on NOx emissions can be found here.
Q. What are particulate matter emissions?
A. These are solid and liquid particles which are small enough to be suspended in the air (aerosol), and will be inhaled. They are produced by:-
Q. What is Particulate Matter (PM)?
A. Particulate Matter is the name given to these solid and/or liquid particles, and they are defined by their size. If particles are more than 100 microns (a tenth of a millimetre) in size, they won’t stay suspended in the air. Two grades of PM are regulated:-
Q. How are particulates formed in a diesel engine?
A. Air is compressed in the cylinder of diesel engines, and finely atomised fuel is injected into the cylinder. The fuel burns, but the fuel-rich regions don't burn completely, producing soot particles and partly-burnt fuel. As the exhaust cools, the partially-burnt fuel is adsorbed onto the soot particles, producing a toxic mixture.
Q. Why are more particulates formed in a diesel engine than in a petrol/gasoline engine?
A.Fuel burn is less even in a diesel engines than in a petrol/gasoline engine.
Q. How are particulates removed from diesel exhausts?
A. Modern commercial vehicle have particulate filters in their exhaust systems, which mechanically trap the soot particles. These are mainly ceramic, but some are woven metal. In most cases the filters can be regenerated by increasing the exhaust temperature, which burns off the carbon.
Q. Why are particulates harmful?
A. Small particles can penetrate deep into the lungs and cause respiratory problems. Nano-particles can even enter the bloodstream. It is worth noting that tobacco smoke produces particulates in the most harmful range.
Q. How do you remove particulates from industrial processes?
A. A wide range of equipment is available depending on the size range and quantity of particles produced. These include cyclones, electrostatic precipitators, wet scrubbers and fabric filters.
Omnagen can advise on measuring and mitigating particulate emissions. Contact details are here.
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