Blackthorn Environmental Limited is a London-based company which designs and supplies systems to purify exhaust emissions from diesel and gas engines.

Our expertise encompasses diesel particulate filters and selective catalytic reduction (SCR), while applications include power generation, pumping, marine propulsion, and non-road mobile machinery.

Diesel particulate filters for power applications

Diesel particulate filters (DPFs) capture soot, which is responsible for black smoke, although the most dangerous particles are so small they are invisible.

Particulate matter is often referred to by the size range. For example, particles under ten microns are referred to as PM10s, while those under 2.5 microns are called PM2.5s.

Flues from 30 year old 800kW stationary diesel engine, with engine running under full load.
Flues for two 400kVa standby generators at a data centre.
Wall-flow diesel particulate filter element made from silicon carbide.
Diesel particulate filter installation on a 400kVa standby generator.
DPF module with two filter elements for an 800kW engine.
SCR catalytic converter based on a substrate made from glass fibre.
SCR catalytic converter based on metal substrates.
Screen shot of SCR control panel showing a 94% reduction in NOx.
Container of ‘AUS40’, a solution of 40% urea in water, which is a popular reductant when applying SCR technology for stationary and marine applications.
Diesel oxidation catalyst incorporated in a front pipe for a containerised 250kVa genset.

When designing a diesel particulate filter it is important to think about how the accumulated diesel particulate matter is going to be removed. This process is known as ‘regeneration’.

Blackthorn can supply filters that regenerate using the exhaust heat alone, which is known as ‘passive regeneration’, and also filters where the heat necessary for regeneration is provided by another source referred to as ‘active regeneration’. In some cases, the best option may be to use disposable filter elements, which we can supply too.

Selective catalytic reduction

Selective catalytic reduction (SCR) technology is often used to reduce nitrogen oxides (NOx) in exhaust gas streams which contain a high level of oxygen such as on diesel or lean-burn gas engines.

SCR involves mixing a reductant with the exhaust gas and then passing this mixture through a catalytic converter. The reductant is usually a solution of urea such as ‘Adblue’ or ‘Diesel Emission Fluid’ (DEF). When heated, this reductant converts to ammonia gas, which reacts with the nitrogen oxides.

A well-designed SCR system reduces NOx by in excess of 90%. Therefore, they are suitable as a retrofit solution to bring stationary engines into compliance with the Medium Combustion Plant Directive (MCPD).

Medium Combustion Plant Directive

The Medium Combustion Plant Directive (MCPD) applies to combustion plants, including those involving internal combustion engines, with a thermal input in the range of 1mW-50mW.

New combustion plants are required to comply with the MCPD from December 2018, while existing plants have a cut-off date dependent on their size and whether or not they export electricity to the grid.

The MCPD regulates several types of pollutant, but its main focus is NOx. Therefore, making an internal combustion engine compliant with the regulation usually involves installing an SCR system.

Oxidation catalytic converters for lean-burn gas and diesel engines

Oxidation catalytic converters are used to oxidise carbon monoxide and hydrocarbons (often referred to as VOCs), and are suitable for use on lean-burn gas as well as diesel engines. When they are installed on diesel engines they may be referred to as diesel oxidation catalysts (DOC).

Catalytic converters comprise a structure with a high surface area, usually referred to as a ‘substrate’, on top of which a catalytic coating is deposited. The substrate may be made from a variety of materials including a ceramic known as ‘cordierite’ and also metal foil called ‘fecralloy’.

Blackthorn designs and supplies catalytic converters in a wide range of sizes up to 1200mm diameter, with a variety of coatings suitable for different fuels and temperature ranges.

Three-way catalytic converters for stoichiometric gas engines

Three-way catalytic converters earn their name due to their ability to deal with three types of pollutants: carbon monoxide, hydrocarbons, and NOx. However, they can only be used on engines where there is a very limited amount of oxygen in the exhaust gas, which are known as stoichiometric engines.

Engines fuelled by gas or petroleum may run stoichiometrically, but diesel engines never do. Blackthorn designs and provides three-way catalytic converters in a range of sizes and with substrates made from cordierite, fecralloy, or other materials.

Emissions control systems maintenance and diagnosis

Some exhaust emissions control systems require regular maintenance. This might include removing ash from diesel particulate filters or urea crystals from SCR catalytic converters.

SCR systems also require regular replacement of filters between the reductant tank and the nozzles, and sometimes replacement nozzles too. It is necessary to diagnose faults with emission control systems correctly, which in some cases can lead to improvements in system design.

Blackthorn has been active in this sector for over 20 years, so please get in touch if you need its expertise.