Blackthorn Environmental - Exhaust Gas Purification Systems

Blackthorn designs and supplies exhaust gas purification systems for both diesel and gas engines used in a variety of applications including generators, pumps, forklift trucks, and vehicles used in the mining, tunnelling, municipal and airport sectors. We currently supply systems based on catalytic converters and diesel particulate filters, but we also test and introduce new technologies as they become available.

Catalytic converters

Catalytic converters are normally employed to oxidise toxic exhaust gases such as carbon monoxide and hydrocarbons, but in some cases they can also be used to reduce oxides of nitrogen (Nox). Blackthorn can supply catalytic converters suitable for engines from 10kW to 2MW or more, running on either diesel or gas. Products supplied can be based on either ceramic or metal substrates, and the catalytic coating can be optimised for specific exhaust temperature ranges.

We can supply catalytic converters designed to attach easily to the existing exhaust tubes or, alternatively, we can make bespoke exhaust tubes with a catalytic converter incorporated. Another option is to package the catalytic converter as a combined unit together with a silencer.

Diesel particulate filters

Diesel particulate filters are used to reduce diesel particulate matter, a soot-like material which is potentially carcinogenic and therefore tightly regulated. Filtration efficiencies of up to 99% can be achieved by a category of products known as ‘wall-flow’ filters, while another category known as ‘partial’ filters has a filtration efficiency of about 50%.

Wall-flow diesel particulate filters

In a wall-flow diesel particulate filter, all the exhaust gas is required to flow through a porous filter wall, which separates out particulates larger than the pore size. In order to prevent the filter from becoming blocked it is necessary for this collected particulate matter to be combusted at regular intervals. This combustion, which is usually known as regeneration, requires a certain minimum temperature, which in many cases can be provided by the exhaust gas itself.

However, in some cases the exhaust gas does not reach the necessary temperature with the required frequency, and in these situations an external heat source must be provided, such as electrical heating elements. Besides temperature there are many other factors critical in specifying a wall-flow filter correctly, and Blackthorn has the necessary knowledge and experience to design and supply an effective system.

Monitoring and maintaining wall-flow filters

Wall-flow filters are very reliable if correctly specified for the application, but they do have the potential to become blocked with serious implications for both the filter and the engine. Therefore it is good practice to install a system which continuously monitors exhaust backpressure and alerts the operator or mechanic if this exceeds a certain threshold. Blackthorn can design and supply this kind of monitoring system. In addition, we can periodically clean filters to remove ash and also thermally regenerate filters which have become blocked.

Partial diesel particulate filters

Partial filters have lower filtration efficiency than wall-flow filters, with the best ones achieving about 50% reduction in particulate matter; however, they have a major advantage over wall-flow filters in that they cannot become blocked. Because a partial filter is ‘failsafe’ from the point of view of engine operation, it is not necessary to carry out continuous monitoring as it would be for a wall-flow filter; therefore the costs are significantly lower.

As well as particulate matter, partial filters reduce carbon monoxide and hydrocarbons, but they are not suitable for all diesel engines, and Blackthorn will be happy to provide advice.