Introduction: The growing role of natural gas in the world energy supply is accompanied with rapid growth of transportation in liquid phase, mostly of overseas deliveries from gas fields to countries of concentrated consumption. Most of the imported gas is vaporized and distributed by pipelines. But there is a relatively high potential of gas users not connected to pipelines, which can be served with liquefied natural gas (LNG) with onshore distribution systems. This is an additional segment of market for gas traders. For ensuring access to these opportunities for short and medium future, trailer filling interfaces should be included into new projects of LNG receiving terminals. It has been proved that the size of economical throughputs by “virtual pipelines” is much higher than the currently working systems. Potential of volume of LNG, distributed directly to gas end users off pipeline can be estimated, depending on available downstream infrastructure, to 20% of the terminal throughput. However, it can be much more in countries without existing pipeline systems. The needs of isolated end users can be also covered by local liquefiers at wells or pipelines. The LNG onshore distribution includes also fueling stations for vehicles. Current number of LNG satellite and fueling stations in Europe can be estimated to more than 1000 (Turkey 600, Spain 300, Norway 70, Portugal 30, Poland 20, Russia 15 etc.). Their total throughput can be estimated to 4000 ton/day or 2 milliards m3/year, which is 4% of the capacity of the transit pipeline Russia-Germany. While the LNG onshore distribution technology has been used in USA for decades, similar wide application is in progress in Japan, China, Australia, with other countries, especially in Asia and South America, going to follow these examples.
Virtual pipeline: Instead or in parallel to a pipeline network, a system of virtual pipelines can be implemented, which can cover blank points among the pipelines, or substitute pipelines on large distances. Techniques, needed for the virtual pipeline starts at an LNG source, which can be a marine terminal, intermediate LNG storage or local liquefier storage.
Means of transport: Trailer, rail car or barge filling interface is needed with a sufficient number of connection points and possibility of future enlargement. Trailers can be filled by internal tank pressure in case that they are vacuum insulated pressure vessels. The volume of an optimized European trailer is 50 m3, but 56 m3 were delivered for Norway. In case of close to atmospheric pressure flat bottom tanks, immersed pumps are required. The pressurized LNG for filling trailers can be also withdrawn from outlet of the immersed LNG supply pumps to vaporizers.
Rail cars are specifically suitable for large volume transport on fixed routes. In Europe, the volume of an optimized rail car is 100 m3, but it can be 131 m3 in USA.
Road, rail or sea shore transport is realized with special pressure vessel vehicles, similar to those for other liquid fuels, but vacuum insulated. Holding time (no-vent) of such tanks is typically multiply longer than the time of the full and empty vessel trip. There are no losses during transport and no refrigeration is needed.Because LNG is 2.5 times lighter than water, the size of the vessels is more frequently limited by volume than by weight.
The 40 foot ISO container is a flexible solution for LNG distribution. Because of small LNG density it makes possible usage of the entire available size for the tank, still in compliance with the maximum allowable gross weight of 30 480 kg. An optimized ISO container has volume of 43,5 m3. An advantage of ISO containers is the possibility of continuous transport over road-rail-river-sea-ocean without any liquid transfer directly to the end user. Another important advantage is the possibility of using the container not only as a means of transport, but also as a temporary satellite station.Parameters of some Chart LNG technology products find in the table:
|Type of vessel||volume [m3]||pressure [bar]|
|Trailer (Fig. 1)||
|Rail car (Fig. 2)||
|ISO container 40 foot (Fig. 3)||
|Ship fuel tank (Fig. 4)||
Barge transport of LNG is well developed in insular and rugged-shore countries like Japan or Norway. Typically, barges with one to twenty thousand m3 capacity are used for shore navigation. An LNG fueled ferry Fjord 1 and LNG carrier Pioneer Knutsen with capacity of 1000 m3 LNG operate along the Norwegian sea shore.
Satellite stations: Satellite stations are built at the end user site or at a local pipeline net, serving more users. Purpose of the satellite station is to accumulate enough liquid for the maximum period between two LNG deliveries and to vaporize it to pressurized gas with maintaining the required flowrate, pressure and temperature, which typically doesn’t require any operation personal. Ambient vaporizers with no energy consumption are used, sometimes with minor electric trim heaters. Vacuum insulated tanks are widely used for this application even in sizes formerly covered by flat bottom tanks only. Their advantage is pressure vessel design, which doesn’t need pumps for the usual range of pressure gas generation, no vent or re-condensation and simple operation. The smallest satellite stations were built with tanks of21 m3volume for deliveries of 50 m3/hour. For example, the largest ever plant of such kind was built by Chart Ferox for Gasnor at Moesjen, Norway, using five683 m3tanks to total capacity of 3415 m3. The station is served with barges. With ten ambient vaporizer in polar conditions, it delivers 5000 Sm3/hour gas.
Such stations can be used for large peak shaving interventions. Their capacity 1230 ton is sufficient for feeding a pipeline system with a flowrate of 24 000 Nm3/hour for 72 hours, or to feed a power plant with electric output 100 MW for 72 hours.
Current largest contract for a satellite station in Norway consists from nine vacuum insulated tanks with unit sizes 500, 683 and 1000 m3, resulting in 6415 m3 total.
For economical feasibility of LNG distribution systems, first step is to identify the available sources of gas and liquid respectively. If there is a single source, the marine LNG receiving terminal, then the situation for an onshore distribution of LNG is very prospective, because LNG is already available while gas has to be generated by heated vaporizers consuming 2% of the gas flowrate.
The most important parameter is the price of gas pipeline to be built. In heavily populated and industrialized regions with complex underground infrastructure and atomized land ownerships the price is very high, which drives for road transport of LNG, and vice versa for low cost pipelines.
For example, considering medium costs of pipeline, the economical limit of trailer transport to the distance of 500 kmresults in 100 trailers/day. This represents a quantity of 1 milliard (109) Sm3/year (680 000 tpa).
Use of LNG for vehicle fueling:
With the growth of application of CNG in vehicle transport, current priority are regular distances and accessibility of re-fueling opportunities. Distances like 20 km in the country and 5 km in cities are considered for optimal in industrial countries. Nowhere is the pipeline system so dense, that it would offer possibilities of building CNG stations directly on motorways and highway crossings in regular distances. Economic savings on natural gas fuel are mostly lost and positive environmental effects reduced, when the vehicles have to go several km for refueling. LCNG stations are the solution. Cars don’t have to go for fueling, but LNG goes after the cars to the optimum located sites, brought in trailers to the station storage tanks. Low energy/low investment liquid compression in pumps results in lower costs. This way, LCNG stations are an effective system for completing the infrastructure of the CNG refueling chains.
LNG vehicle fueling offers additional benefits. LNG density is nearly three times higher than CNG, which offers much longer run of vehicles. This is a sufficient reason for LNG distribution even in regions with a well-developed pipeline infrastructure. LNG is used especially for fueling of heavy duty trucks and busses. Number of such vehicles operated mainly in USA and some in other countries is estimated to 5000. Three50 m3vessel LNG trailer train in Australia pulled with a dual fuel tractor with three500 literLNG tanks.
Chart LNG on board systems have been delivered widely for LNG vehicles. In Europe, especially the Polish bus manufacturer Solbus is using them for their OEM LNG bus. Also, truck manufacturers Volvo and Iveco brought their new types of heavy trucks equipped with Chart LNG systems. Gazprom organized a “blue corridor” presentation trip of LNG vehicles with Chart onboard systems, started in Warszawa in the first half of September 2012, over Paris to the Hannover fair, where the fueling will be presented with Chart Ferox mobile LNG fueling station.
Railway locomotives are also a prospective segment of application of vehicle fueling. Compressed natural gas (CNG) and liquefied natural gas (LNG) fueled locomotives and trains are currently operating in Peru, India, Thailand, Sweden and the USA. This application will presumably attract more interest after a recent (2006) recognition on the volume of US diesel locomotive annual emissions 800 000 tons nitrogen oxides and 25 000 tons of fine particulates. Switching locomotives use integrated LNG fuel tanks. Their application has important environmental benefits, as the stations are in or close to heavily populated areas. Long distance locomotives can be equipped with independent tenders sufficient to go hundreds kilometers in both directions, which makes it possible to use a single fueling site. Chart D&S manufactured tender with the capacity of 76 m3 see in the figure.
Barges, supply boats and ferries have been converted to LNG fueling in Norway. Considerable reduction of nitrous oxides were reported. Chart Ferox built re-fueling stations for ferries with the storage capacity of 2 × 500 m3 and a 1100 liters/min fueling pump.
Conclusions:The current increase of LNG production stimulates projects of onshore distribution of LNG directly to end users’ satellite stations and vehicle refueling stations. The success of these projects increases the demand on LNG. Additional market of LNG is in the range of several per cent of the total LNG sale with prospects for a continuous growth. Variety of LNG liquefaction, storage and transportation techniques of standard nature is available for support of “virtual pipeline” projects for economical and fast implementation. Another advantage of this solution is flexibility of size, location and equipment mobility according to the changes of the market.
Vaclav Chrz will be presenting Recent development of LNG onshore distribution and ship fueling at the Cryogenics stream at Gastech 2012 Exhibition’s Centres of Technical Excellence (CoTEs). To learn more, register here for this free seminar on 10 October 2012 at the ExCeL centre in London.
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