Wärtsilä has unveiled a new system at the Marintec conference in Shanghai aimed at lowering tanker emissions of volatile organic compounds (VOCs) during laden voyages.
The group says its Voyage Emissions Reduction (VER) offers two options for shipowners looking to minimise losses through VOC evaporation -- a reabsorption model and a fuel model.
The fuel model of the VER is a patent-pending design that utilises VOCs as fuel for tanker vessels, and Wärtsilä VOC product line general manager Hans Jakob Buvarp told Tanker Shipping and Trade that the system's biggest innovation was in combining VOCs and LNG to power vessels.
"The actual innovation here is to use the uncondensed VOC in combination with LNG as fuel for engines," Mr Buvarp said.
"Wärtsilä have made extensive research and testing of mixing of LVOC and LNG for both 2-stroke and 4-stroke engines. The mixing unit is quite sophisticated in order to maintain fuel gas flow to the engine at the correct pressure and with the correct methane number."
The reabsorption model of the VER – by which VOCs are recirculated into a vessel’s cargo tanks – eliminates an average cargo loss of 270 tons per week on a 320,000 dwt VLCC, and requires less energy that other, similar systems, according to Mr Buvarp.
"Our information is that the competitors use in excess of 100 kw. This can also easily be verified as the competitors are using a DN 300 cargo pump to pump the oil. Pumping of oil using this size of pump will require more energy than compressing VOC as we do in our system."
Wärtsilä describes the reabsorption VER model as an easy-to-install system that ‘plugs in’ to a vessel’s existing infrastructure, while configuration of the fuel model is dependent on several aspects of an individual ship's design.
In terms of overall VOC emissions reduction, Mr Buvarp said initial calculations were in the range of 70-80% for the reabsorption system, depending on the type of crude being transported.
"This is supported by simulations done in our design tools. We are currently testing to VER installations on two newbuilds and will use this opportunity to finally verify our calculations.
"For the fuel version ... the reduction rate will be depending on how much VOC we are able to mix into the LNG fuel and also to a certain degree the compressor capacity."
Prices for the VER systems are being kept under wraps for the time being – and, again vary by ship design on the fuel model – however Wärtsilä Marine Solutions Vice President Timo Koponen said its VER systems could pay for themselves in a short period of time with the cost savings they offered owners.
“The VER system [eliminates] cargo waste and [lowers] tanker fuel costs, thus enabling a payback time that can be less than one year,” Mr Koponen said.