Payback dogs VOC recycling

Oscar Spieler, technical director at Frontline, says that it is not commercially viable for an independent tanker operator to retrofit a VOC vapour recovery system to his ships since the cost is currently unrecoverable. Frontline has tested a prototype VOC recycling system, developed in cooperation with compatriot Norwegian company Venturie, on its Suezmax tanker Front Granite (see The Motor Ship, October 2001). Although the low-tech system has been a success from a technical point of view, commercial returns to justify the shipowner’s investment in the system have not been delivered.

Speaking to The Motor Ship, Spieler says the only beneficiaries from using the system, apart from the environment, are the shippers, i.e. the major oil companies and traders, since the loss to their cargoes during transportation is minimised. He says, the extra cargo delivered is not currently reflected in the charter rate received by Frontline. As a result it has put the installation of a second VOC recycling system onboard Front Duchess on hold.

Instead, Spieler says that Frontline has improved operational procedures onboard Frontline tankers, in line with the Intertanko developed VOCON procedures (see page 23), to reduce VOC emissions by using equipment that is already available onboard as standard. While adherence to these procedures reduces VOC emissions it does not eliminate them completely, unlike the Venturie system.

Since Frontline’s prototype Venturie installation, a second system has been installed on the Vela International owned VLCC Polaris Star. On installing this system, Vela stated that its entire fleet of 20 crude-oil tankers would be equipped with the Venturie cargo system by 2005. However a spokesman for Vela now reveals that the project is still under discussion with Venturie. Vela is a subsidiary of Saudi Aramco, the Saudi state-owned oil company, so in transporting cargoes for its parent company there is potential gain for it through the delivery of more cargo.

Venturie is currently targeting leading tanker companies including ConocoPhillips Marine, BP Shipping and STASCO; oil companies that definitely have potential gain through the delivery of more cargo. For such companies that own the cargo they ship, Venturie’s claims that the initial investment will in most cases pay for itself in less than two years (based on official figures for VOC emissions from different crude oil qualities during offshore transport) will be appealing.

The Venturie cargo system (VCS) circumvents the need to expel any vapours by injecting them directly back into the cargo tanks. That reduces pressure in the tanks while allowing the vapours to be naturally absorbed by the oil. A patented gas condenser collects the vapours from the existing venting system and allows the tank to be maintained at a more constant pressure.

The VCS does not interfere with existing security features, so all safety valves etc., located in the riser and venting system, are left unaltered. Since the inert gas is not absorbed in the VOC recovery process and nothing is lost through venting, the VCS also eliminates the need for inert gas topping

during transit.

Aside from the benefit of zero atmospheric emissions, the system also retains valuable ‘light end’ hydrocarbons and ensures the integrity of the cargo during offloading operations. Crew time is also saved and their exposure to vapour emissions is greatly reduced since there is no need to ventilate tanks into the atmosphere.

Installation work can be carried out during a vessel’s scheduled routine dry-dock maintenance at almost any yard. No special tools are required and with its compact design and total weight of less than 2,500kg, including piping, the VCS is also easy to transport to the desired installation location. The system cost is roughly $400,000 for supply and installation.