Recirculating exhaust gas through a low-pressure path
The iCER is designed to cool and recirculate part of the exhaust gas through a low-pressure path during operation in gas mode. Compared to a high-pressure path, the main benefit is the ability to use the full turbocharger capacity. It is possible to recirculate exhaust gas up to a maximum rate of 50% mass flow. This is handled through a system adjacent to the engine that circulates part of the exhaust gas after the turbine through a Cascade Exhaust gas Cooler (CEC) to the compressor inlet. The exhaust gas and the fresh air are mixed before entering the compressor wheel of the turbocharger.
Arrangement and process flow of CEC, circulation water and drain
The image above shows a simplified process flow diagram of the iCER system. The cooling process reduces the temperature of the exhaust gas to below its dew point of ~40°C. Below the dew point water starts to condense out of the exhaust gas which leads to excess water in the system. This helps to avoid an increase of acidity in the recirculated water.
The water for cooling the exhaust gas is recirculated fresh water stored in a circulation tank. The recirculated fresh water used in the CEC is cooled by sea water via a plate heat exchanger.