With emissions under the spotlight, inert gas generation has a key role to play in making shipping safer, greener and more efficient
The SOLAS rules that mandate the installation of inert gas systems on tankers were first introduced in 1980, when they applied to vessels of 100,000 dwt or greater. These rules were swiftly expanded to vessels of 20,000 dwt and greater in 1981. Skip forward to 1 January 2016 and the boundaries moved again, this time applying to all tankers of 8,000 dwt or greater with keels laid after that date. However, some commentators question whether the SOLAS amendment adequately considers the differences between oil and chemical tankers, a matter that could be worth addressing in its own right at another juncture.
The Oil Companies International Marine Forum (OCIMF) goes even further than the amendment, advising that all oil tankers to be fitted with inert gas generators (IGG), regardless of size: “Over the years many lives have been lost, or serious injuries sustained, due to incidents involving fires and explosions on non-inerted tankers transporting flammable oil cargoes,” states OCIMF.
“The installation of an inert gas system on oil tankers of all sizes that carry flammable oil cargoes is both technically and operationally feasible. The effective use of the system, allied with training and the application of correct procedures, prevents incidents involving fires and explosions in cargo tanks and will result in a significant safety performance improvement when carrying flammable oil cargoes on oil tankers.”
While these systems do indeed increase vessel safety through their use of non-flammable or toxic gases, there are important safety concerns around man-entry to spaces that have been inerted, with asphyxia a risk if safety procedures are not followed and safety equipment is not used correctly. This emphasises the importance of ensuring the human factor is covered by making sure crew properly following safety management system (SMS) directions for such operations
Furthermore, with the advent of tighter emissions controls, the wastewater generated through the scrubbing process that gas generated using IGGs undergoes could be a potential source of environmental pollution.
In 2017, an incident was reported on the Nautical Institute’s Mariners' Alerting and Reporting Scheme (MARS) that illustrates the importance of managing the human factor and that seafarers are properly briefed on SMS procedures. In this situation, a 13,000-dwt tanker was in port and about to load cargo when the shore-based loading master requested the vessel’s tanks be inerted prior to loading.
“The wastewater generated through the scrubbing process that gas generated using IGGs undergoes could be a potential source of environmental pollution”
The ship’s master consulted with the chief officer and decided not to run the IGG as recent experience had shown that it was possible that carbon residue and sediments could be introduced into the seawater being used in the cooling/cleaning phase in the scrubber, which could then be washed overboard and cause pollution.
Wärtsilä’s general manager for inert gas systems Ole Fjeld notes that there are questions around the environmental impact of emissions from inert gas generators, adding: “It’s basically an exhaust generator.”
He points out that while IMO’s 2020 regulation focuses on sulphur emissions, nitrogen oxides (NOx) are widely seen as a potential target for future emissions. As such, savvy operators are considering how to meet the potential challenges such regulation could pose.
Mr Fjeld cites examples of floating installations, such as floating production, storage and offloading vessels (FPSOs) and floating liquefied natural gas plants (FLNGs), which also make use of inert gas generators.
Such installations are covered by maritime law and by laws relating to industrial installations in certain jurisdictions. In Europe, industrial installations are required by law to use “best available techniques” to reduce emissions and limit environmental harm. This legal phrasing covers not just the technology used at an installation, but also the design, construction, maintenance, operation and decommissioning of the installation itself. An example of this is the Goliat FPSO, operated by Equinor and Eni, in the Barents Sea.
Tanker operators can learn from IGS emissions-reduction strategies used on installations such as Goliat (image: T3n60/Wikimedia Commons)
Eni’s Coral FLNG project meanwhile was the first such vessel to incorporate an emissions requirement for its IGG into its design.
And Mr Fjeld says that Wärtsilä is producing an IGG for a customer that has requested the system be run at full scale prior to installation to ensure an accurate picture is given of operational efficiency and the measurement of airborne emissions alongside those in the scrubber water.
The efficient operation of IGGs not only help the environment, they also reduce costs. Such savings can be increased by ensuring the system is providing a clean burn at the fuel combustion stage.
In order to get the most efficient burn, droplets of fuel need to be as small as possible, explains Mr Fjeld. In co-operation with DNV GL, Wärtsilä is working on a system that will enable smaller droplets to be generated.
“Additive manufacturing gives us the ability to make more complex geometry that hasn’t been possible with traditional manufacturing methods,” says Mr Fjeld. “For inert gas, it’s specifically the nozzles that atomise the diesel.”
This technology increases efficiency by ensuring more of the fuel is burned, but also reduces emissions by the same token of burning matter that would otherwise be discharged in the scrubbing process.
“It’s basically an exhaust generator, so it’s a very environmentally unfriendly machine from the outset”
Initially this system will be rolled out for FPSO applications, but further down the line it will also be made available for tanker installations following verification with DNV GL, says Mr Fjeld. “Since inert gas is a safety system we need to be very careful about new developments,” he points out.
When choosing an IGG for a newbuild tanker, Mr Fjeld advises operators to opt for one that has the same service life as the vessel itself. And of course, regular maintenance is also important, avoiding the potential adverse environmental impact of an IGG that develops faults, avoiding costly breakdowns and making them more efficient, thereby using less fuel.
And while the maintenance of IGGs can be difficult, due to the size of the installations they operate on and their complexity, there are steps owners can take to simplify the process; these include running deckhouse modules and skid-based systems that can be dropped into place in a plug-and-play manner.
2016 SOLAS amendment 220.127.116.11
For tankers of 8,000 tonnes deadweight and upwards constructed on or after 1 January 2016 when carrying cargoes described in regulation 1.6.1 or 1.6.2, the protection of the cargo tanks shall be achieved by a fixed inert gas system in accordance with the requirements of the Fire Safety Systems Code, except that the Administration may accept other equivalent systems or arrangements, as described in paragraph 5.5.4