Versatile tankers for Atlantic ethane traffic

Innovative ships committed long-term to transatlantic shipments of US shale gas
Innovative ships committed long-term to transatlantic shipments of US shale gas
JS INEOS Insight leads the Chinese-built Dragon series of multi-gas carriers
JS INEOS Insight leads the Chinese-built Dragon series of multi-gas carriers

A new chapter has opened in liquefied gas transportation with the entry into service of Danish owner Evergas’ first Dragon design vessels: the largest, most flexible and state-of-the-art multi-gas carriers to date. David Tinsley reports.

The 27,500m3-capacity JS INEOS Insight and JS INEOS Ingenuity have given first form to the semi-refrigerated design, engineered with propulsion machinery capable of operating on ethane cargo boil-off as well LNG and diesel oil.

Copenhagen-based Evergas, wholly-owned by Greenship Gas of Singapore and parent Jaccar Holdings of Luxembourg, has a 15-year deal with INEOS to ship ethane feedstock, originating in western Pennsylvania’s shale gas deposits, to the Swiss chemical group’s refineries in Scotland and Norway.

A bold statement emphasising the value of the new energy resource to economic development is represented by the slogan ‘Shale Gas for Manufacturing’ along the hull sides of JS INEOS Insight, and by ‘Shale Gas for Chemicals’ along the flanks of JS INEOS Ingenuity.

Ethane is obtained as part of the processing of natural gas, and is mainly used as a feedstock for the production of ethylene. Two dedicated import terminals have been constructed at INEOS Olefins & Polymers’ petrochemical plants at Rafnes, in southern Norway, and at Grangemouth, on the Forth in Scotland. A huge investment project at Grangemouth has included the construction of a 60,000m3 ethane storage tank, the largest in Europe.

Beyond price advantage

INEOS’ business plans extend beyond importing the advantageously priced US feedstock to becoming a major player in UK shale gas production and fostering a British and European shale gas revolution.

The Dragon-class programme foresees a series of eight newbuilds from Sinopacific Offshore & Engineering, designed to provide a “virtual pipeline” for ethane across the Atlantic. On the strength of the INEOS shipment deal, the initial tranche of orders covering four vessels was awarded in January 2013, followed by further pairs contracted in May and November 2014.
Privately-owned SOE is China’s leader in the market for small and medium size LPG and liquefied ethylene gas (LEG) carriers. The Dragon LNG/multi-gas tankers are all being delivered from the company’s Qidong yard on the Yangtze, responsible for constructing the cargo tanks, cargo system and final completion. Hull fabrication has been subcontracted in each case to the associated company Sinopacific Shipbuilding Group, at Dayang.

Once the programme has been completed, the Dragon fleet is expected to convey over 800,000 tonnes per annum of US ethane to northern Europe. Although this will constitute the vessels’ primary and contractual task for the next decade and a half, the design offers considerable scope across the liquefied gas cargo transportation market.

The cargo section comprises two Type C bilobe tanks, each of 9,686m3 capacity, plus a smaller, conical-shaped tank forward of 8,194m3. The tank design builds on experience with ethylene transportation. Its across-the-board cargo intake capability is implicit in a minimum allowable tank temperature of -163°C, at which LNG is carried, and a maximum permissible tank pressure of 4.5 bar, suited to LPG and the full range of petrochemical gases.

Ethane will be conveyed at -89°C. Given a density of 0.545, a full load of ethane will represent a cargo deadweight of approximately 15,000 tonnes. Besides ethylene, propylene, propane, vinyl chloride monomer (VCM), butane, butylenes and butadiene, the containment system provides for a host of other liquefied cargoes, including dimethyl ether (DME), currently being researched as a future energy option.

Multi-gas cargo

Two different types or grades of cargo can be simultaneously handled, as regards loading, transportation, conditioning by reliquefaction, and discharge.

Each vessel has been supplied with a comprehensive, integrated engineering package from Wärtsilä, encompassing engines and propulsion equipment, liquefied gas fuel systems and cargo handling plant. The project constituted the first case in which areas of expertise introduced through the 2012 acquisition of the Hamworthy Group, notably gas plant, were combined with core, traditional Wärtsilä businesses to provide a complete offering under the Wärtsilä name.

The primary power installation is based on two six-cylinder Wärtsilä 50DF main engines, individually rated at 5,850kW, driving a 6.6m-diameter controllable pitch propeller through a TCH350 twin-input, single-output gearbox. The Dragon vessels were originally designed with dual-fuel LNG/diesel power, but the specification was subsequently adapted to give the ability to also burn ethane, allowing the use of cargo gas.

Classification society Bureau Veritas (BV) worked with Evergas and the Danish Maritime Authority to verify and ensure that utilising ethane would be at least as safe as required by the IGC Code and would not impair engine compliance with the Marpol Annex VI emission criteria.

BV business development manager Martial Claudepierre said: “Using ethane required extra engine room ventilation and additional gas detection, plus modifications to the main engines including a lower compression ratio, different turbocharger nozzles and derating of the engine(s) to cope with the lower knocking resistance of ethane.”

Twin-engine installation

The Wärtsilä outfit includes two shaft generators, the shaft line with its bearings and seals, an Energopac high-efficiency rudder integrated with the proprietary propeller, and two 20DF dual-fuel gensets of 2,112kW apiece. The LNG fuel tank storage is located on the after part of the weatherdeck.

The twin engine installation confers not only redundancy but also efficiency across the ship’s operating profile, allowing for navigation at economic speed on a single engine. Evergas is looking to maximise running time on ethane or LNG, rather than simply switching to gas mode when in Emission Control Area (ECA) waters. The two shaft alternators, affording a total 3,600kW output, allow for reduced use of the auxiliaries when the ship is under way, yielding significant fuel savings over time.

The cargo handling design, cargo plant, reliquefaction system for ethane, LPG and other petroleum gases, cargo pumps, boil-off gas compressors, LNG fuel system, cargo control arrangements and energy recovery system, all emanated from Wärtsilä Oil & Gas, successor to Hamworthy.

Wärtsilä said that it had been able to achieve optimal energy consumption for the entire vessel by having responsibility for engineering and supplying the complete cargo plant, gas fuel supply system and propulsion.

This is clearly demonstrated, for example, where the LNG supply system is integrated with the cargo handling system so that it can be used to cool the cargo. In so doing, less energy and power is needed to keep the cargo temperature suitably low. On a semi-refrigerated tanker of this type, a substantial amount of energy would normally be required to re-liquefy evaporating cargo.

Truly unique

Evergas chief executive officer Steffen Jacobsen is unequivocal as to the significance of the Dragon-class programme: “I’ve worked in the shipping business for 35 years and it’s fair to say that these ships represent a world first on many levels. No one has ever tried to ship ethane in these quantities and over this distance before. To do this, we had to invent completely new ways of doing things. These ships are truly unique,” he said.

Over the past several years, ethane production in the USA has been steadily increasing, from 869,000 barrels per day (bpd) in 2010, to nearly 1.1m bpd by March 2015. In addition, US ethane prices have declined relative to other fuels. The growth in production has spurred exports by pipeline to Canada and investment in the domestic US petrochemical industry. The move by INEOS Olefins & Polymers, one of Europe’s largest petrochemical companies, to ship US ethane to Europe signifies an important milestone in the development of the export trade.

INEOS Olefins & Polymers was the first European company to contract for ethane feedstock from the USA. In 2012, it contracted with Range Resources as supplier, and with Sunoco Logistics for the associated transportation capacity on the Mariner East pipeline project, to provide ethane from the Appalachian Basin to the Marcus Hook shipment facility near Philadelphia.

The Marcus Hook Industrial Complex, located along the Delaware River, was formerly a Sunoco refinery, and is an LPG, refined products and crude oil terminal as well as processing and storage complex. The Mariner East 1 and Mariner East 2 pipeline projects were implemented to deliver natural gas liquids(NGLs) from the Marcellus and Utica shale areas in western Pennsylvania, West Virginia, and eastern Ohio to Marcus Hook.

Ethane transportation from the USA is set to rapidly advance in unitary scale, and will reach a new level towards the end of 2016 with the scheduled arrival of the first of six, fully-refrigerated 87,000m3 very large ethane carrier (VLEC) newbuilds. Ordered by the Reliance Group, the tankers will supply ethane feedstock to Indian refineries. Construction of the series has been entrusted to Samsung Heavy Industries, and each of the ships will be operated and managed by Mitsui OSK Lines (MOL) of Japan.

What is ethane?

Ethane is a colourless, odourless, gaseous hydrocarbon belonging to the paraffin series; its chemical formula is C2H6. Ethane is structurally the simplest hydrocarbon that contains a single carbon-carbon bond. The second most important constituent of natural gas, it also occurs dissolved in petroleum oils and as a by-product of oil refinery operations and of the carbonisation of coal.

The industrial importance of ethane is based upon the ease with which it may be converted to ethylene (C2H4) and hydrogen by pyrolysis, or cracking, when passed through hot tubes. Like propane and, to a lesser extent, like butane, ethane is a major raw material for the huge ethylene petrochemical industry, which produces such important products as polyethylene plastic, ethylene glycol, and ethyl alcohol.

More than 90% of the ethane produced in the 1960s was burned as fuel without separation from natural gas. Ethane gas can be liquefied under pressure or at reduced temperatures and thus be separated from natural gas.

(Description courtesy of Encyclopaedia Britannica)

PRINCIPAL PARTICULARS--JS INEOS INSIGHT

Length overall

180.3m

Length b.p.

170.8m

Breadth, extreme

26.6m

Depth

14.8m

Draught, summer

9.4m

Corresp. deadweight

20,918t

Loaded displacement

32,088t

Gross tonnage

22,887t

Cargo tank capacity

27,566m3

Main engine power(MCR)

2 x 5,850kW

Service speed

16 knots

Class

BV

Class notations

BV I, +HULL, +MACH, Liquefied Gas Carrier, Type 2G, Dualfuel, Unrestricted Navigation, CPS(WBT), +VeriSTAR, HULL DFL, +AUT-UMS, +SYS-NEQ, MON-SHAFT, Clean Passport, Greenship, InWaterSurvey

Flag

Denmark

 

Table 2.

CARGO LIST--DRAGON CLASS

Cargo

Temperature (°C) at atmospheric pressure

Methane

-163

Ethylene

-104

Ethane

-89

Propylene

-48

Propane

-45

DME(Dimethyl ether)

-25

VCM(Vinyl chloride monomer)

-14

Iso-butane

-12

Butylenes

-7

Butadiene

-5

Butane

0

Other cargoes for which the ship is certificated: Methyl chloride; Acetaldehyde; Dimethyl amine; Ethyl chloride; Diethyl ether; Isoprene (monomer); Isopropyl amine; Monoethyl amine; Pentanes/pentenes; Vinyl ethyl ether.

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