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1

Generation of H2 on board LNG vessels for consumption in the propulsion system

Fernández Ignacio Arias, Gómez Manuel Romero, Gómez Javier Romero, López-González Luis M.

Polish Maritime Research

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2020

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nr 1

83--95

EN

At present, LNG vessels without reliquefaction plants consume the BOG (boil-off gas) in their engines and the excess is burned in the gas combustion unit without recovering any of its energy content. Excess BOG energy could be captured to produce H2, a fuel with high energy density and zero emissions, through the installation of a reforming plant. Such H2 production would, in turn, require on-board storage for its subsequent consumption in the propulsion plant when navigating in areas with stringent anti-pollution regulations, thus reducing CO2 and SOX emissions. This paper presents a review of the different H2 storage systems and the methods of burning it in propulsion engines, to demonstrate the energetic viability thereof on board LNG vessels. Following the analysis, it is identified that a pressurised and cooled H2 storage system is the best suited to an LNG vessel due to its simplicity and the fact that it does not pose a safety hazard. There are a number of methods for consuming the H2 generated in the DF engines that comprise the propulsion plant, but the use of a mixture of 70% CH4-30% H2 is the most suitable as it does not require any modifications to the injection system. Installation of an on-board reforming plant and H2 storage system generates sufficient H2 to allow for almost 3 days’ autonomy with a mixture of 70%CH4-30%H2. This reduces the engine consumption of CH4 by 11.38%, thus demonstrating that the system is not only energy-efficient, but lends greater versatility to the vessel.

2

Chosen problems of transport and vessel’s fuelling by liquefied natural gas

Herdzik J.

Journal of KONES

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2018

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Vol. 25, No. 2

157--162

EN

It was presented the possibilities and ways of methane transport by sea. They are still searched new better possibilities of methane transport especially when the gas mining is at the sea. The advantages of using methane as marine fuel are discussed because it seems to be ecological and cheaper one. The lack of LNG bunkering network for vessels is the biggest problem to share methane as a marine fuel. Only a few ports inside the Baltic Sea area give such possibility. Of course, the network is under construction but the development goes too slowly to fulfil the International Maritime Organization (IMO) requirements on 2020 year. A challenge is to prevent failure during cargo operations, loading hose failure, pipe rupture, manifold leak, tank overflowing, or rupture etc. The risk of failure is increased due to very low temperature of liquid methane and the quick temperature change of all elements of cargo system during operations. The aim of the work was to show the indicated problems of vessel’s fuelling by LNG. It was discussed the methane slip during cargo operations and fuelling. The misfires during burning processes into the engines are the biggest problem due to very narrow window of methane self-ignition. It happens the misfiring or knocking cycles. It disturbs the correct work of the engine, resulting in quick engine malfunction or damage.

3

Selected problems of transport in port towns – tri-city as an example

Budzyński M., Ryś D., Kustra W.

Polish Maritime Research

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2017

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S 1

16--24

EN

Port towns are strategic places from the point of view of transport systems. They form integration junctions for various transport branches , apart from the traditional - road and railway ones , also for water( sea) transport which is active there. Moreover, air transport comes also into consideration , whose efficient functioning must be connected with good accessibility, that concerns sea transport as well. Efficient and safe servicing the ports is crucial for their functioning. Problems associated with the overloading of lorries, which leads to degradation of road surface structure , observed in Gdynia, are discussed as an example in this paper. Problems of road traffic safety (RTS) are presented in this paper on the example of Gdańsk. The two issues : the road traffic safety and road surface degradation constitute only some transport problems of port towns , but they are very important, from the point of view of their specificity, for integration junctions of all the transport branches for people and goods. However, in discussing selected aspects of transport in port towns it is necessary to refer to the managing of integrated transport system with taking into account its traffic safety aspects.

4

Calculation of boil-off gas (BOG) generation OF KC-1 membrane LNG tank with high density rigid polyurethane foam by numerical analysis

Jeong H., Shim W. J.

Polish Maritime Research

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2017

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nr 1

100--114

EN

Recently, a new type of LNG tank named “KC-1 membrane LNG tank” has been developed by Korean Gas Corporation (KOGAS), and Samsung Heavy Industries (SHI) is currently building KC-1 membrane type LNG carriers. Unlike other LNG tanks, the KC-1 membrane LNG tank has a single-insulation structure rather than a double-insulation structure. For a given tank’s boundary condition, heat transfer analysis is performed from the external to the internal environment of the LNG tank by numerical simulation for three tanks. In each tank, the main thermally resistant layer of insulation is assembled with a High density rigid Polyurethane Foam (H-PUF), which is blown with one of three different types of hydrofluorocarbons—namely—HFC-365mfc, 245fa, and 245fa-e (enhanced). Advantage of such blowing agents is that it has a lower Ozone Depletion Potential (ODP) than HCFC-141b or carbon dioxide ( ) that has been used in the past as well as having low thermal conductivity. A Reduced Order Model is utilized to a 3-dimensional section of the insulation to calculate equivalent thermal conductivity. The equivalent thermal conductivity of the insulation is then applied to the rest of LNG tank, reducing the size of tank simulation domain as well as computation time. Tank’s two external and internal boundary conditions used are those defined by the International Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC) and the United States Coast Guard (USCG) conditions. Boil-off Rate (BOR) of the tank that has the insulation with H-PUF blown with HFC-245fa resulted in 0.0927 %/day and 0.0745 %/day for IGC and USCG conditions, respectively.

5

On board LNG reliquefaction technology: a comparative study

Gómez J., Gómez M., Garcia R., Catoira A.

Polish Maritime Research

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2014

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nr 1

77-88

EN

Reliquefaction technologies are being currently applied on board liquefied natural gas (LNG) carriers on the basis of economic criteria and energy efficiency. A variety of reliquefaction techniques have been developed so far during the last decade. Nevertheless, technology enhancement continues being a research area of interest. In this article the different technologies applied to the reliquefaction of the boil-off gas (BOG) on LNG carriers have been described, analysed and discussed, contributing to highlight the process and operation characteristics as well as selection plant criteria. Finally, a comparison of the different reliquefaction plants, considering their capacities and efficiencies as well as other technical data of interest has been carried out.

6

Selected problems of boil-off gas utilization on LNG carriers

Michalski R., Głomski P.

Journal of Polish CIMAC

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2011

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Vol. 6, no 1

141-148

EN

Heat inflow to a cargo of liquefied natural gas (LNG) from the surroundings causes generation of vapours called boil-off gas (BOG) and thus an increase of a vapour pressure in cargo tanks. The paper discusses selected issues related to handling of boil-off gas on LNG carriers. Presented are general conditions permitting vapour pressure increase during the voyage, conditions enabling its venting and burning in gas combustion units (GCU, thermal oxidizers). Particular attention is given to BOG utilization as a fuel in steam or gas turbines or reciprocating engines. Presented are general comments on selection criteria for choosing a solution of LNG carrier propulsion system. Attention is drawn to an increase of possibilities of heat recovery from exhaust gas from Diesel engines and gas turbines. This is due to a lowering of exhaust gas dew point temperature thus deeper cooling of the exhaust gas in exhaust gas boilers is possible. This enables production of larger quantities of steam which can be directed to auxiliary steam turbine and as a result increasing the efficiency of the ship’s energy system. The paper also addresses the specifics of fuel installation operation on ships utilizing LNG vapours as a fuel.

7

Problems with determination of evaporation rate and properties of boil-off gas on board LNG carriers

Głomski P., Michalski R.

Journal of Polish CIMAC

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2011

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Vol. 6, no 1

133-140

EN

The paper discusses selected issues related to the problems of determining boil-off (evaporation) rate (BOR) of liquefied natural gas (LNG) on board LNG carriers. Review of available literature describing theoretical models of LNG boiling-off phenomenon during maritime transport is presented. Given are examples of simulation results of LNG evaporation process based on theoretical analysis. Also presented are methods of determining boil-off rate based on the results of observations of the concerned phenomenon on board selected ships. The paper draws attention to theoretical differences in a daily boil-off gas (BOG) quantity resulting from the adopted method of determining BOR. Namely, in some publications BOR values refer to the loaded quantity of LNG (or even to the ship’s cargo carrying capacity), and in the rest to the current quantity on board. The paper outlines resulting theoretical differences in quantity of cargo remaining on board. Addressed are also issues related with variable, in the course of the voyage, BOG (and thus LNG) composition determining its heating value, which is of particular importance in the case of its use as a fuel for ship’s engines.

8

Charakterystyka zagrożeń związanych z transportowaniem i magazynowaniem skroplonego gazu ziemnego - LNG

Sedlaczek R.

Wiertnictwo, Nafta, Gaz

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2010

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T. 27, z. 3

601-615

PL

Rosnące zapotrzebowanie na gaz ziemny w skali światowej (około 2% rocznie) oraz trudności w jego odbiorze z miejsc występowania siecią rurociągów przesyłowych do odbiorcy przyczyniły się do rozwoju technologii LNG. Technologia ta wykorzystuje wyjątkowo korzystne własności gazu ziemnego w postaci skroplonej. Gaz ten ulega skropleniu w temperaturze -162 stopni Celsjusza przy ciśnieniu atmosferycznym, a zmianie stanu skupienia towarzyszy 600-krotne zmniejszenie objętości właściwej. Dzięki temu możliwy i opłacalny staje się transport tego paliwa drogą morską na wielkie odległości (ponad 3 tys. km). Podstawowym warunkiem, który musi spełnić technologia transportu gazu ziemnego w postaci skroplonej, jest oczywiście bezpieczeństwo dla ludzi i środowiska. Te same własności ciekłego gazu, które czynią go tak korzystnym w transporcie, sprawiają, że stosowanie technologii LNG niesie za sobą pewne potencjalne zagrożenia. W pracy przedstawiony został problem odparowania metanu w terminalach LNG. Wyszczególnione zostały główne przyczyny tego procesu, a także zaprezentowany został przykład liczbowy ilustrujący wielkości "wyparu" dla terminala odbiorczego o założonych parametrach. W dalszej części scharakteryzowane zostały zagrożenie pożarowo wybuchowe oraz zjawiska "Rapid phase transition" i "Rollover", z którymi możemy mieć do czynienia w sytuacjach awaryjnych podczas transportowania i magazynowania LNG.

EN

Due to the rising worldwide demand for natural gas (about 2%/year), and large distances between potential producers and consumers, LNG technology has been growing rapidly in recent years. LNG technology bases on favourable properties of natural gas in the liquid form. Natural gas condenses into liquid at temperature of approximately -162 degrees of Celsius at atmospheric pressure. Liquefaction reduces its volume by approximately 600 times, making it more economical to transport through the ocean (distances over 3000 km). The most important requirement for LNG technology is to provide safety for people and the environment. The properties of LNG, that make it so profitable, make it potentially hazardous at the same time. In this paper the LNG boil off gas generation for receiving terminals has been presented. The sources of boil-off gas have been discussed, and a numeric example, which illustrates the BOG generation for the specific set of assumptions, has been provided. In further part of the article fire and explosion hazardous, the rapid phase transition (RPT) and the rollover phenomena, which can occur during transporting and storing LNG, have been discussed.

9

Analysis of possibilities of the application of dual fuel engines as a main propulsion on LNG gas carriers

Giernalczyk M.

Journal of KONES

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2008

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Vol. 15, No. 4

147-155

EN

Gas carried on LNG carriers is liquefaction gas at ambient pressure and temperature minus 163 C degree is subject to boil - off and cause increase in pressure. This phenomenon makes danger of explosion. The simplest possibility to circumvent the foresail event is to release - liquefied gas to atmosphere. However, the mentioned way causes losses of cargo and air pollution. Method that is more rational is to use boil - offfuel gas as propulsion energy in dual fuel engines. This paper describes exploitation costing of main propulsion on LNG carriers trying to find out the best solution. There are presented fuel gas supply systems as well various types of engines driven by fuel gas. Moreover, author presents further design development of main propulsions of LNG carriers. In the case of cryogenic tankers intensive interest in their purchase is observed. In orders portfolio for the next several years the ships with steam turbine power plant dominate. Is this related with the large exploitation experiences: with possibility of combustion of both vaporized gas (BOF) and heavy fuel in the boilers and with the possibilities of steam utilization to heating means, including liquid fuel gasification. The possibility of the exploitation of a new kind gas ship called LNGRV (RV- regasification vessel) is poised since, which in the large distance from the shore carries out LNG gasification and through several days' forces gas to the undersea pipeline. However steam turbine propulsion is characterized by lowest efficiency, among of thermal engines. Whereas thermal efficiency of COGES system is presently higher considering growing power of steam turbines in the system jointed thermodynamically with gas turbines.

PL

Przewożony statkami naturalny gaz w postaci skroplonej, przy ciśnieniu atmosferycznym i temperaturze - 163oC, na skutek niedoskonałej izolacji ulega odparowaniu, powodując wzrost ciśnienia i stwarzając tym samym zagrożenie eksplozji. Celem uniknięcia zagrożenia wypadku, najprostszym sposobem obniżenia ciśnienia w zbiorniku jest usunięcie do atmosfery odparowanej części gazu, jednak wiąże się to ze znacznymi stratami oraz jest sprzeczne z wymogami ochrony środowiska. Innym, bardziej racjonalnym sposobem jest wykorzystanie tego gazu jako energii w silnikach napędu głównego, którymi mogą być dwupaliwowe silniki tłokowe. Niniejsza praca jest próbą analizy różnych rozwiązań, obejmujących silniki średnio- i wolnoobrotowe, zmierzającą do wyboru najbardziej dogodnego pod względem ekonomicznym. Zawiera opisy instalacji paliwowych obsługujących różne typy silników napędu głównego w tym zasilanych gazem, ponadto przedstawia oferty różnych producentów tych silników. Autor pokazuje tendencje rozwojowe dotyczące projektowania nowoczesnych gazowców typy LNG. W przypadku zbiornikowców kriogenicznych obserwuje się wzmożone zainteresowanie ich zakupem. W portfelu zamówień na najbliższe lata dominują statki z napędem turbiną parową. Jest to związane z dużymi doświadczeniami eksploatacyjnymi: możliwością spalania zarówno odparowanego gazu (BOF) jak i paliwa ciężkiego w kotłach oraz możliwościami wykorzystania pary do celów grzewczych, w tym regazyfikacji. Rozważana jest bowiem możliwość eksploatacji nowego rodzaju gazowca nazywanego LNGRV (ang. RV - regasification vessel), który w dużej odległości od brzegu dokonuje regazyfikacji LNG i przez kilkanaście dni wtłacza gaz do podmorskiego rurociągu. Jednak napęd turbiną parową charakteryzuje się najniższą, spośród silników cieplnych sprawnością. Natomiast sprawność cieplna systemu COGES jest obecnie wyższa ze względu na rosnącą moc turbin parowych w układzie skojarzonym termodynamicznie z turbinami gazowymi.