World’s First LNG-Powered Inland Waterway Tanker

For the past few years, a healthy competition has been going on to build the most innovative and eco-friendly inland waterway ship. Recently, motor tanker Amulet won a Ship of the Year award for its reduced fuel consumption. This issue’s Argonon is sure to be on the shortlist for next year’s award. Where motor tanker Amulet sought efficiency in her diesel-electric propulsion, and Vorstenbosch in economy of scale, the Argonon reduces fuel costs and emissions by using a dual fuel installation, with her main engines running on a mix of 80% LNG and 20% diesel. Argonon Shipping (member of the Deen Shipping Group) counts on a reduction of 20% in CO2 emissions, 40% in NOx emissions and over 95% in fine particles, when comparing to similar diesel-driven ships.

Fuel of the future

It is no big secret that LNG (Liquefied Natural Gas) is considered by many in the industry as the fuel of the future. The reasons are twofold:

– natural gas burns cleaner than diesel, resulting

in lower CO2 and NOx emissions and virtually

no particles,

– the cost of natural gas is both lower and more

predictable than the cost of diesel fuels.

The disadvantages are the necessity to install a cryogenic tank, which keeps the LNG liquid at a temperature of -162°C and the lack of a suitable distribution system. For the time being, Argonon will be fuelled by a truck which brings the LNG from the terminal in Zeebrugge. Plans are already well advanced for a permanent LNG bunker station in Zwijndrecht in the Netherlands, a place were much of the inland waterway traffic passes nearby on a regular basis.

Dual fuel

Argonon is a dual-fuel tanker, which means that she will normally sail on a mixture which is 80% LNG and 20% marine diesel oil (MDO). The diesel is added to the mix for its combustion under compression, thus omitting the need for spark plugs. Her dual-fuel engines also allow the tanker to sail on pure diesel, giving her an extended range, as the Argonon still has the same capacity for MDO as comparable motor tankers.

The 40 cubic metre cryogenic tank on deck has enough capacity for a roundtrip to Basel and back to Rotterdam (1,600 kilometres), but Argonon will normally operate in the ARA-triangle (Antwerp-Rotterdam-Amsterdam), supplying seagoing vessels with fuel.

The tank and the evaporator installation were supplied by Cryonorm Projects, an Alphen a/d Rijn-based company which entered the LNG market in 2003 and can cover the entire LNG supply chain. Because the LNG is stored under a pressure a 3 bar, higher temperatures, up to 152°C below zero, are allowed. After gasification, the natural gas is drawn into the cylinders of the engines by a venturi, which is placed between the air filter and the turbo blower. In the cylinder, diesel is injected into this air/LNG mixture and then compressed, resulting in the required explosion. Besides the modification to the turboblowers, Argonon’s main engines are pretty standard Caterpillar 3512 engines. Their output is 1134 kW each. Because of the 20% diesel, the engines have the torque characteristics of standard diesel engines, allowing for quick acceleration. The dual fuel has a cleaner combustion than pure diesel, resulting in less luboil consumption and longer service intervals.

Gas turbines

The LNG is kept liquid under pressure and at -162°C in a double-walled tank. To turn it into gas for consumption in the main engines, an evaporator is mounted behind the tank. The suction of gas is automatic due to the venturi-effect in the turbo blowers. The main engines will always run on diesel for the first few minutes. The thermal insulation in the tank is never perfect, and thus the liquid gas is constantly boiling. By removing this ‘boil-off ‘ from the tank, the temperature can be kept constant. On Argonon, there is a boil-off of about 50 litres of gas per hour. This gas is put to good use: it drives two 30 ekW gas turbines in the engine room, of the type Capstone microturbine, which are essentially the ship’s generators. Because they provide a constant output, while loads are continuously varying, the generators feed their power into a battery bank.

The main switchboard is fed from the battery bank through invertors. Furthermore, the heat in the exhausts from the gas turbines is used for various purposes:

– for hotwater used in the floor heating, – for preheating of the evaporator for the

LNG tank,

– for the absorption cooler of the AC.

The microturbines, which basically use an unwanted byproduct of the LNG tank, are a nice example of tri-generation: they produce electricity, hot water and air-conditioning. Argonon Shipping have calculated that the fuel bill for floor heating and airconditioning on a similar vessel would amount to € 18,000 per year. For the eight deepwell cargo pumps from Marflex, the power from the gas turbines is not sufficient. When pumping cargo, a diesel generator is used, which is mounted in the front engine room and which is also used for the electrically driven jet thruster from Veth. The front engine room also houses a harbour/emergency diesel generator and a diesel-fired thermal oil boiler for the tankheating system.

New rules

A dual-fuel installation is not new as such. Ships have been sailing for years on dual fuel, for example on the Norwegian coast. The application of dual fuel propulsion on an inland waterway vessel is however entirely new, and the regulations for seagoing dual-fuel ships were not always suitable for the particularities of inland shipping.

A new set of rules was established with the Central Commission for the Navigation of the Rhine, the Dutch Shipping Inspectorate and Lloyd’s Register.

One of the modifications is the omission of the requirement that all the gas piping should be double-walled throughout the engine room, but on very strict conditions regarding the engine room ventilation. On seagoing vessels, it is impossible to ventilate each and every corner of the engine room. On Argonon, this is exactly what they did. The engine room ventilation was designed using computational fluid dynamics calculations, which were validated on board with a smoke test. Fresh air is blown in at six different spots, and there is a central air outlet with an explosion-proof ventilator. The throughput is 30,000 m3 per hour and even with one ventilator out of service, sufficient ventilation is achieved in the entire engine room. In those spots were proper ventilation is not possible, such as an escape trunk, a gas detector was installed. Another requirement is that the combustion air for the engines is ducted from outside, instead of using the engine room air. The fire protection of the engine room and the front engine room is with FM200 extinguishing gas.

Methane slip

In dual fuel engines, there is a short moment in each cycle where both the inlet and outlet valves are open simultaneously. This causes so-called methane-slip: the seeping out of a small portion of unburned natural gas through the exhaust piping. The greenhouse effects of methane are approximately 23 times worse than those of CO2. Although there are currently no requirements concerning this methane-slip, Argonon Shipping has opted to install an oxidation catalytic converter which burns the methane. This catalytic converter is stand alone and does not need any supply of urea. For the proper functioning of the catalytic converter, a regulating valve was installed in the exhaust line to slow the exhaust gas speed by increasing the backpressure.

Safety

Contrary to what one might expect, the biggest hazard of LNG is not fire or explosions. The LNG is not flammable and in gaseous form, the air and gas mixture ratio has to be very precise to achieve combustion. In the outside air, it is virtually impossible. The biggest risk of LNG in liquid form is a leakage. If a large quantity of the liquid would spill on deck at -162°C, it would immediately make the steel very brittle, causing cracks in the deck plating. But on Argonon, the tank is very well protected. If the vessel would collide with a low bridge for example, the large bunker boom would be the first thing to be hit. Even during a fire on deck, with temperatures at 1,000°C, the inside of the tank would only heat up by 1.2°C per 24 hours. In terms of crew training, the dual fuel installation is not a big burden. A one-day training suffices to make the engineer qualified.

Other green cards

The green credentials of Argonon are not limited to her dual fuel installation. In a number of other ways, fuel savings have been achieved. The fixed- pitch propellers are placed in nozzles, which improve their efficiency. A vertically mounted hydrospoiler, type Dolphin XR-T 1700 from Van der Velden Marine Systems, is mounted on the aft side of the nozzles, converting some of the rotational energy of the propeller wakes into forward thrust. The HD220 rudders – a pair behind each propeller – have an asymmetrical profile for increased efficiency. When bunkering small coasters, which can have quite a lot of rolling and swaying motions, it is preferred to have the mooring lines slack and keep some distance of the ship. To minimize extensive bowthruster use in those cases, the Argonon is equipped with a telescopic spudpole in the bow.

To reduce the number of fuel tanks, the Argonon is built with a ‘Scheldehuid’ construction, which consists of Y-shape framing in the shell which offers improved impact resistance when comparing with traditional framing systems. This allows for the cargo tank size to be increased from 380 m3 to 1,000 m3. It was also Gerard Deen who built the first ship with this type of construction and which became the license holder for the patent owned by Damen Shipyards. Since the first ship Apollo, built in 2008, already 36 vessels have been built with the ‘Scheldehuid’ construction.

Length to beam ratio

Another distinctive feature of the Argonon is her length to beam ratio. She measures 110 metres, allowing for shorter waiting times for mooring positions than her 135 metres counterparts, but her beamy hull of 16.20 metres wide still allows for 6,000 ton of cargo tank capacity. That is an often required quantity of fuel for seagoing vessels, which prefer to be supplied by a single vessel in one go. The cargo piping has two completely segregated lines up into the tip of the bunker beam, allowing the Argonon supply two different types of fuel at the same time.

Shipyard Trico

Trico is a relatively new shipyard. It is based very near to the centre of Rotterdam at the Waalhaven. Incidentally, the first client of the shipyard was Deen Shipping, with Amphiro. Originally the yard was established by shipowners who had no patience for the waiting lists at established yards and decided to built their own ship. For Deen Shipping, Argonon is the third vessel built at Trico and a proof of confidence, as it is a very innovative vessel. As for all Trico ships, the hull was built in China and then towed on a pontoon, along with seven other hulls, to the Netherlands for outfitting.

Possible

A dual fuel installation is not the only way to meet the stringent CCR4 emission norms which will apply to new inland waterway ships from 2016. The alternative is to clean diesel engines’ exhausts with soot filters and catalytic converters, but these are also costly investments, and do not reduce the fuel consumption or CO2 emissions. The big advantage of LNG as a fuel is that it is both greener than diesel and economically viable. Argonon Shipping and Trico have now proven that it is not only sensible, but also possible, even for the strict regulatory environment of inland shipping. Depending on the use of the ship, the owners expect a return on investment of about three to six years, after which the fuel costs will be about 20% lower than for a similar diesel-powered ship, assuming the current price difference between LNG and diesel remains and will not increase in the future.

If a suitable space for the LNG tank can be found, it is also very doable to retrofit an existing ship with a dual fuel installation. With the global reserves of crude oil running out rapidly, demonstrated by its high price per barrel in spite of the global recession, natural gas is the most likely candidate for a transitional fuel until a durable alternative is found. One such alternative is LNG produced from biomass (bio-LNG), and the Argonon can sail on a bio-LNG/diesel mixture without any modifications. Her propulsion would then be CO2 neutral.

Port Personality of the Year

Gerard Deen, CEO of Deen Shipping: “The biggest difficulties to overcome for the construction of Argonon were not of a technical nature. Obtaining the necessary approvals and establishing the regulatory framework occupied the lion’s share of meeting time.” The extra cost of this pioneering work was offset with subsidies from the European Fund for Local Development. For his efforts to pave the way for LNG as a fuel in inland shipping, Gerard Deen was awarded the ‘Port Personality of the Year’ on 5 December 2011 by the Rotterdam- based Port Personality of the Year Foundation.

Bruno Bouckaert