Navigator Gas is engaged in a series of projects to enhance the efficiency and environmental performance of its fleet of large ethylene and ethane carriers
Navigator Gas operates globally in the LPG, petrochemical gas and ammonia trades, with a fleet of 38 semi-pressurised/fully refrigerated (semi-ref) gas carriers. Active in both the spot and time charter sectors, the fleet’s time is about evenly split between the two.
The company has recently added the transport of ethane to its strong presence in the ethylene trades. While ethylene is a key building block in the manufacture of petrochemicals, ethane is an optimum feedstock in the production of ethylene. The surging output of shale gas in the US is rich in ethane.
Navigator Gas brought economies of scale to ethylene transport 20 years ago when it introduced the largest semi-ref gas carriers ever built. The company’s recently introduced ethane carriers are, similarly, among today’s largest semi-ref ships.
One of the company’s ethane-capable ships, the 35,000 m3 Navigator Aurora, has recently had its dual-fuel main engine converted to enable the burning of ethane. The vessel is fixed on a long-term time charter to Borealis for the carriage of ethane from the Mariner East terminal near Philadelphia on the US east coast to the chemical company’s ethylene cracker at Stenungsund in Sweden for use as a feedstock.
Based in London, the Navigator Gas commercial team is headed by chief commercial officer Oeyvind Lindeman, while chartering manager James Parrett leads a team of four charterers. Navigator Gas also works with selected brokers and directly with buyers, suppliers and trading houses, chartering in tonnage as and when required.
Technical management of the Navigator fleet has traditionally been undertaken by carefully selected ship management companies and the ship operator has enjoyed long-term relationships with both Northern Marine Management (NMM) in Glasgow and Thome Shipmanagement in Singapore. The overall goal, however, has always been to bring technical and crew management in-house.
In 2016 Navigator Galaxy became the first vessel to be managed in-house, switching from NMM to Navigator Gas Shipmanagement, headed by the company’s fleet and technical director Paul Flaherty. The programme to internalise ship management has been rolled out across the fleet over the past two years and Navigator Gas Shipmanagement currently manages 10 of the fleet’s 38 vessels in-house. The process will be continued over the next two to three years, until company management is responsible for the bulk of the fleet.
Ethylene gas cooler
The ethylene gas cooler allows warm cargo to be cooled on loading
A recent Navigator Gas innovation is the ethylene gas cooler, a technology which allows ethylene-capable vessels to chill the cargo before it enters the cargo tanks. The concept enables more relatively warm cargo to be loaded at a higher rate.
Navigator Gas has also fitted purge condensers to many vessels. Purge condensers allow cargo vapour to be recovered from the stream of incondensable gases, including nitrogen, vented from cargo tanks. Invariably, a quantity of cargo is carried along with the vented gases and the purge condenser can re-liquefy the cargo element and redirect it back to the cargo tanks. Cargo emissions and losses are reduced as a result.
The main engines on the company’s G-class gas carriers have been modified to embrace ‘eco-nozzles’. These devices improve ignition quality, reducing fuel consumption, emissions and maintenance loads as a result.
The company has also invested in the Hans Jensen lubrication systems on its Planet- and Zodiac-class vessels. This kit significantly reduces the quantity of cylinder lubricating oil used. Navigator Gas reports that the technology pays for itself in around two years on the ships provided with such systems.
Navigator Gas has taken steps to be compliant with the ballast water management regulations and has fitted two different ultraviolet-type treatment systems on its ships, from Alfa Laval and Trojan. This is a rolling programme and 20 retrofits are planned over the next three years.
However, the future selection of ballast water treatment equipment will also be determined by which systems have been fully approved by the US Coast Guard. This is a critical factor as most Navigator Gas vessels load cargoes at US ports.
Although no Navigator Gas ship has been fitted with an exhaust gas scrubber as yet, the company does not rule out the possibility. Navigator Gas takes the long-term view on the 0.5% global sulphur cap that will be introduced in January 2020. The aim is to specify gas-burning engines for all newbuildings, and there is also the possibility of converting existing ships to enable them to burn ethane.
In addition to the immediate task of transporting ethylene and ethane, Navigator Gas is moving up the logistics supply chain and expanding its terminal operations.
The Navigator Enterprise partnership, a 50/50 joint venture with Enterprise Products Partners (EPP), is building a 1M tonnes per annum (mta) ethylene export terminal on the Houston Ship Channel in Texas. The facility, which will comprise a chiller train, a 30,000-tonne storage tank and a dedicated marine jetty, will be able to load vessels with fully refrigerated ethylene at 1,000 tonnes per hour for shipment to Europe and Asia.
The new Navigator Enterprise terminal is due for completion in late 2019. According to Navigator Gas, the company is currently investigating the possibility of developing similar terminal projects.
Achieving sulphur cap goal with ethane fuel
Navigator Gas has successfully converted the LNG-burning, dual-fuel main engine on its 35,000 m3 ethylene/ethane/LPG carrier Navigator Aurora to run on ethane. Carried out while the ship was berthed alongside at Frederikshavn in Denmark, the project was undertaken in tandem with, among others, charterer Borealis, engine manufacturer MAN Energy Solutions and gas carrier cargo system supplier TGE Marine.
Navigator Gas and Borealis took the decision to convert the 2016-built vessel’s main engine after a successful ethane fuel trial on the MAN test bed engine at Kawasaki in Japan in July 2017. The parties agreed that if it was possible to utilise cargo carried by the vessel as a fuel source, the initiative would enable them to comply with the new 0.5% global sulphur cap to be introduced in January 2020, utilising a guaranteed supply of cost-effective fuel that meets the required emissions reduction requirements.
“This project represents a significant investment by both Navigator Gas and Borealis and clearly demonstrates a strong commitment to environmental protection and the reduction of greenhouse gas emissions"
As a result of the conversion, Navigator Aurora’s MAN B&W 6S50 ME-C8.2-GI dual-fuel main engine, with its ability to run on natural gas, has now been re-categorised as a 6S50ME-C-GIE ethane-burning, dual-fuel engine.
Following the conversion, Navigator Gas director of fleet and technical operations Paul Flaherty said: “This project represents a significant investment by both Navigator Gas and Borealis and clearly demonstrates a strong commitment to environmental protection and the reduction of greenhouse gas emissions. The retrofit modification complies with all current and expected global emissions requirements.”
Paul Flaherty (Navigator Gas): “This project demonstrates a strong commitment to environmental protection”
The project involved two key stages: the first required parent engine testing at Kawasaki to prove that burning ethane in the MAN gas-injection (GI) engine was possible. The trials were successful and showed that suitable, clean-burning power was available at a fuel gas injection pressure of just over 300 bar.
The second stage involved the detailed planning of the modifications across several different equipment suppliers, as well as obtaining approvals from the vessel’s class society and its Liberian flag administration.
Once these hurdles were cleared, the conversion work was carried out over a period of 15 days and was completed on 20 July 2018. On the occasion Navigator Gas fleet manager Mark Macey said, “The success of the ME-GIE conversion project is the culmination of four years of close co-operation between Navigator Gas, Borealis, ABS, ABS Consulting, TGE, MAN Energy Solutions, Northern Marine and the Liberian administration. The contributions of all parties concerned resulted in the successful completion of this historic conversion.”