12/01/2020
At Emigreen® we specialise in designing and delivering the latest emission control technology. In this article we explain how our systems work.
Exhaust gas cleaning systems reduce nitrogen oxide (NOx) emissions and particulate matter (soot) in diesel engine exhaust. Our advanced aftertreatment systems future-proof ships for emission standards compliance as international and local emission limits are continually lowered by increasingly stringent regulations.
Fact: Current International Maritime Organisation (IMO) regulations limit nitrogen oxide emissions to around 2 grams per kWh. Some projects require even lower NOx emission levels. Our systems can be configured to meet these requirements without major system changes.
Since no two engines are the same, every aftertreatment system has to be custom engineered to engine-specific settings, specifications and performance requirements. While output requirements differ, the operating principles remain the same.
Aftertreatment housings are designed to minimise exhaust noise. A well-balanced configuration achieves attenuation ratings comparable to residential grade silencers, with attenuation of approximately 35 and 45 dB(A) for combined systems.
The acoustic performance of both the housing and the silencer can be customised to meet specific requirements.
The moment the sensors detect that the engine is running, the control systems start monitoring the following engine parameters:
Fact: Once all of the engine-specific parameters have been set, the systems function fully independently and require very little attention.
Our diesel particulate filter (DPF) system traps particles in the exhaust stream and periodically incinerates the soot that builds up in the filter. Using a burner to elevate exhaust temperatures, our systems burn off the soot and reduce it to ash.
The ash that remains in the filter can be removed by the crew at regular or irregular intervals, whichever is most convenient.
The burner is activated by the engine monitoring systems whenever the engine parameters exceed predefined threshold values.
Fact: High-precision programming prevents excessive back pressure that would otherwise reduce engine efficiency.
Our SCR system starts injecting a urea and water solution (Ad Blue) into the exhaust stream when the exhaust temperature reaches the level required for a chemical reaction to occur between the urea and the nitrogen oxides (NOx) in the exhaust gasses.
Depending on the load on the engine and the temperature of the exhaust gasses, the SCR unit is programmed to inject the exact amount of urea needed to reduce NOx emissions below the required level.
Fact: Urea injection is automatically adjusted in response to NOx levels in the engine exhaust, which are monitored by the SCR controller.
The urea injection rate is automatically adjusted in response to engine NOx output at a certain load based on pre-set values. This adjustment is fine-tuned based on feedback from NOx sensors. This process is controlled by our own software.
A certain amount of air is also injected into the mixing pipe to facilitate the mixing of the urea with the exhaust gasses. The required amount of air is calculated by the SCR controller and injected through the air dosing skid included in the system.
Fact: The systems can be connected to the alarm monitoring system so the crew can monitor the systems from all control locations on board.
For certain projects in environmental sensitive area’s (such as Natura 2000-areas) extremely low NOx emissions can enable a shipowner to accumulate more points on the tender. Aerius calculations can be used for the total calculation on the NOx emission on a complete tender.
Jelle Westerhof is sales manager at Emigreen® and applies our industry-leading solutions to the projects of our clients. Feel free to reach out to Jelle for feedback on this article, for questions and for a free consultation.
