I. Analisis Perubahan Tekanan Discharge Kompresor

Peningkatan tekanan pada discharge kompresor menyebabkan kenaikan temperature pada stream inlet kondenser. Hal ini dikarenakan kenaikan tekanan pada discharge mengakibatkan kenaikan jumlah massa refrigerant yang harus dikompresikan oleh kompresor seluruh system. Dengan kata lain beban kerja kompresor menjadi bertambah besar sehingga temperature discharge kompresor meningkat. Selanjutnya kenaikan temperature pada discharge kompresor menyebabkan kenaikan temperature inlet pada condenser. Naiknya temperature pada condenser akhirnya mempengaruhi temperature pada evaporator yang kemundian juga naik. Berubahnya nilai temperature evaporator mengakibatkan perubahan terhadap besarnya kalor yang diserap oleh evaporator dari condenser. Kapasitas refrigerasi merupakan fungsi dari aliran masa dan efek refrigerasi. Tetapi kenaikan besarnya kapasitas refrigerasi ternyata lebih dipengaruhi oleh laju aliran massa.

Diagram diatas adalah ilustrasi dari perbandingan perbedaan tekanan dengan asumsi pressure drop neglected, fase refrigerant yang keluar dari condenser telah berfase cair. Jika digambarkan pada PH diagram dapat terlihat jika semakin rendah nilai tekanan maka efek refrigerasi semakin besar. Beberapa plotting pada beberapa siklus refrigerasi pada PH diagram menunjukkan beberapa hal diantaranya semakin rendahnya tekanan maka efek refrigerasi (A) yang dapat dihasilkan pun semakin besar; temperature discharge, condenser dan suction pun mengalami penurunan. Sedangkan untuk kerja kompresor (B) dapat terlihat bahwa semakin rendah tekanannya semakin besar nilai kerja kompresor yang dibutuhkan. Dengan menurunnya tekanan maka garis A akan semakin panjang atau efek refrigerasi semakin besar naming diikuti dengan garis B yang semakin melebat ke kanan atau kerja kompresor yang semakin besar. Sehingga, dapat dikatakan bahwa semakin tingginya nilai tekanan discharge pada kompresor menyebabkan besarnya duty kompresor yang semakin naik. Besarnya duty kompresor tersebut berpengaruh terhadap power yang harus di supply untuk dapat melakukan siklus refrigerasi dalam pendinginan dan pencairan gas alam. Semakin besarnya tekanan tapi menghasilkan produk dengan jumlah yang sama menyebabkan proses berjalan tidak efisien. Dimana input dan output yang didapatkan tidak sebanding. Sebaliknya jika tekanan pada discharge kompresor terlalu kecil akan menyebabkan temperature cross. Dimana refrigerant yang seharusnya temperaturenya lebih rendah menjadi lebih tinggi sehingga tidak bisa melakukan fungsinya sebagai pendingin. Sehingga diperlukan beberapa kali percobaan input data tekanan discharge kompresor untuk mendapatkan efisiensi yang tinggi dan tidak terjadi temperature cross untuk menentukan tekanan yang beroperasi secara optimum dalam proses pendinginan dan pencairan gas alam melalui simulasi hysys.

II. Analisa COP

COP merupakan fungsi dari kapasitas refrigerasi dan kerja kompresor. Sedangkan kerja kompresor sendiri dipengaruhi oleh tekanan discharge kompresor. Semakin besar tekanan discharge kompresor maka kerja kompresor akan semakin besar. Semakin besar kerja kompresor maka nilai COP akan semakin kecil. Jika definisi COP adalah efek pendinginan yang termanfaatkan dibandingkan terhadap kerja yang harus kita berikan, maka sudah pasti kita berharap COP yang dipunyai dari sistem kita adalah sebesar-besarnya. Diketahuinya nilai COP dapat menjadi suatu pertimbangan bagi konsumen untuk mengoperasikan alat yang ada. Apabila ingin melakukan penghematan daya listrik sebaiknya mengoperasikan pada keadaan COP tertinggi tetapi bila yang diinginkan adalah nilai temperature evaporasi untuk menjaga suatu produk maka sebaiknya dioperasikan pada tekanan rendah yang dapat mencapai nilai temperature evaporasi paling rendah. Untuk lebih lengkapnya download hysys analisis

Small scale LNG developments

With a little over a year to go before the tightening of maritime emission controls in northern Europe and North America, the momentum behind LNG as a marine fuel is going from strength to strength.

There is a multitude of prospective market participants at each part of the LNG marine supply chain. While many still have a way to go to firm up their market positions, some Scandinavian companies are building on their first mover status and setting a blueprint for the wider industry.

While there will always be some geographic specificities, the challenges these companies are overcoming will be echoed across all emerging LNG bunker markets.

LNG bunker developments are happening. Deals are being done. The pace of development will be gradual but the wave is building and the signs for a large market are there.

Europe blazes small scale LNG trail

From the multiple islands off the coast of Japan to the vast land mass across North America, there is increasing interest in the opportunities from emerging small scale LNG supply chains.

Whereas niche small scale LNG demand has been present in various isolated scenarios for some time, the forthcoming maritime emission regulations in northern Europe and North America are driving an anticipated step-change in the global small scale outlook.

The worldwide potential for LNG as a marine fuel could potentially reach more than 30 milion tpa by 2025, according to Paris-based integrated energy supplier GDF SUEZ, placing this specific aggregated 'small scale' segment on a par with the combined amount of LNG imported by China and India last year.

While bullish forecasts of the size of the market come with a series of disclaimers, not least due to the predominant 'wait-and-see' attitude of most prospective market participants, the opportunities for infrastructure investors and traders are both numerous and fraught with risks.

Tightening legislative controls of sulfur content in marine fuels in Europe and North America to 0.1% from 1% from the start of 2015 are setting the scene for LNG as a marine fuel to compete directly with refined fuel oil bunkers.

Additionally, a 0.5% sulfur limit - set to be rolled out globally by 2020 - means this demand is unlikely to be confined to these regions.

Low natural gas hub prices in Europe and North America compared with global LNG levels, coupled with high fuel oil prices, help counterparties on both sides of the negotiating table for LNG bunkering gain sufficient margins to close deals. It is in these regions that LNG as marine fuel are starting to take off.

The small but growing pool of LNG bunker projects in North America and northern Europe are seen as a blueprint for others. However, in Europe, like elsewhere, a series of challenges are being dealt with to varying degrees of success.

Economies of scale

One of the challenges involves adapting facilities and cost structures designed to cater solely for conventional LNG trade to the small scale trade.

The €750 000 (US$ 1.01 million) fixed cost of a berthing slot at Zeebrugge, for instance, is the same regardless of the vessel size.

This could be justifiable when a company is importing or re-exporting a conventional cargo, but with a 7500 m³ vessel it becomes cost prohibitive.

While Zeebrugge and Gate have proved the technical possibilities to berth small scale vessels, the terminals are improving the cost involved by specifically designing break-bulk facilities for the small scale trade.

In October, Zeebrugge started construction of a second jetty to accommodate ships as small as 2000 m³ from 2015 onwards. Zeebrugge capacity holder GDF SUEZ has been awarded with the additional berthing and long-term storage capacity associated with the new jetty, which it intends to use to reload small LNG carriers, such as LNG feeders and LNG bunkering vessels.

Insufficient firm commitments thus far, however, have prevented the Gate LNG terminal from sanctioning its planned break-bulk infrastructure.

Gate, nonetheless, has both imported and re-exported small scale volumes in September using its existing conventional-sized jetty and will continue to do so until a new small scale jetty is sanctioned.

Current berthing slots at Gate are more competitive than at Zeebrugge, according to market sources, underscoring the success of AGA Gas in securing two small scale LNG supply contracts from Gate LNG capacity holders. The first was with Dutch utility Eneco announced over the summer, beginning with a three-cargo string in September.

The second, which is in the final stages of negotiations, would see AGA Gas start receiving more volumes from Gate starting from 1 July 2014 from another capacity holder. Bank of America Merrill Lynch has previously said it has a supply agreement with a Scandinavian buyer starting in 2014 for which it has sourced Gate LNG volumes and sub-chartered a small scale LNG vessel.

The second supply agreement from Gate was concluded at a 100% TTF hub index price formula, ICIS understands, similar to the Eneco arrangement and comes in addition to a previous oil indexed small scale agreement that AGA Gas has with Norwegian small scale supplier Skangass.

The fixed premium to TTF would cover storage, berthing slots and LNG mark-up and is thought to be greater than US$ 2 - 3/ million Btu in total. The mark-up involved in any re-exports from Gate has to cover the initial purchase costs of the LNG into Gate, which can already be at above the hub price, a trading source added.

Written by Ludovic Aldersley, Global LNG Markets Deputy Editor, ICIS.
Edited by Callum O'Reilly
Published on 15/11/2013
Source : http://www.lngindustry.com/news/special-reports/articles/Small_scale_LNG_developments_446.aspx#.U3RJTLEqt2F

Small scale LNG developments (part two)

Demand clusters needed

The opening up of Gate to small scale business does not just reflect demand to source LNG from Gate, it has also allowed Skangass the opportunity to use the terminal as a supplementary storage base for its own liquefaction volumes from Risavika.

Skangass delivered five cargoes on board the 16 000 m³ Coral Energy between July and October, according to Gate LNG. The company has a number of regional customers and is set to increase its delivery schedule with the start-up of its fully owned receiving terminal in Lyeskil, western Sweden, in 2014 where it has sold 200 000 tpy - or two thirds of its Risavika production - to local refiner Preem. A source said the extra storage space at Gate would enable Skangass to accommodate its peak deliveries. Skangass has also been looking at buying volumes not just from Gate, but also from the Snohvit plant.

While another Swedish import project in Gothenburg is also progressing towards its final investment decision (FID), political momentum is strengthening behind a string of three to five small scale projects in Finland.

The storage capacities of the Finnish receiving terminals are understood to range from 10 000 m³ to 370 000 m³, although there would be scope for expansions as more gas-intensive activity develops. With the demand for small scale LNG often due to a lack of pipeline infrastructure, the receiving terminals need to be adjacent to a company that can take the baseload boil-off capacity while the rest of the LNG is re-packaged and sold elsewhere.

“Logistically it has to be quite a tight operation,” one terminal owner said.

Different demand clusters are needed throughout the supply chain to ensure sufficient offtake at every step along the process.

While Scandinavian demand is slowly taking shape, there are still missing parts of the supply chain, with a lack of investment in feeder vessels as a particular cause for concern. At US$ 20 million, feeder vessels are seen as expensive, and without a basket of customers to make use of the vessel, it becomes difficult to justify that investment, sources said.

Stop-gap trucking measures

With 40 vessels under construction to take LNG as a fuel, but hardly any feeder vessels to provide those bunkers, trucks are considered as capable of filling part of the void, but not for all vessel types, according to shipping consultant David Bull.

Although trucks are currently used to load LNG bunkers onto small vessels, the most efficient way of providing bunkers to large vessels such as ferries or containerships is via a ship-to-ship transfer. The transfer time is commercially important as ferries in particular need quick turnarounds in port. Truck-to-ship transfers can be conducted at a versatile number of locations, but if more than five truck loads are needed to fill a vessel, the manoeuvre starts to lose its commercial viability, Bull said.

Part of the break-bulk ambitions of the Gate LNG terminal include truck-loading services, with requests for proposals due in the first quarter of 2014. Zeebrugge already offers the service and expects to load around 500 trucks this year, an increase from 300 in 2012 and 65 in the previous year, according to terminal operator Fluxys.

In a bid to secure yet more trucking business - given it is still a long way from its 4000/year or 15/day capacity - the operator has now decided to offer a more flexible service in an auction for 2014 and 2015 truck capacity ending on 7 November. Whereas trucks were previously only able to load from 09:00-17:00 hours local time on weekdays, the company said the service from next year will be available 24/7.

GDF SUEZ has a 12-year agreement with Shell Gasnor to supply it with 7.5TWh (500,000 tonnes per annum) from Zeebrugge on board trucks that started in January 2013. In most of Europe, trucks cannot legally carry more than 24 t, or approximately 55 m³, at a time.

Global appetite

There are signs that the critical minimum of investment in the supply chain will not be ready in Europe by 2015 to warrant the 4.3 million tpy base-case projection to 2020 of an EU-funded study last year.

Speaking at a recent conference in Rotterdam, Andrew Clifton of the Society for Gas as a Marine Fuel, indicated a standardised set of rules and regulations on the subject known as the IGF code will now not come into force before July 2017 at the earliest.

He added the interim guidelines are not mandatory and that “many major issues” are yet to be agreed on, reiterating earlier concerns on the discrepancies in the timelines of regulators.

Outside of Europe, Singapore in particular is keen to rapidly develop its attributes as an LNG hub and has started work on assessing how to best offer LNG bunkering.

Most LNG bunkers will only be used inside ECAs until global regulations tighten, but buyers such as the United Arab Shipping Co. (UASC) that are aiming to deploy LNG ready vessels from Asia to Europe from late 2014, would be interested in taking LNG bunkers before entering ECAs. UASC has placed a US$ 2 billion order for 10 large 'LNG-ready' containerships, which when in LNG bunker mode would likely consume much more than any current ship on the water, according to Bull.

Written by Ludovic Aldersley, Global LNG Markets Deputy Editor, ICIS.
Edited by Callum O'Reilly
Published on 18/11/2013
Source : http://www.lngindustry.com/news/special-reports/articles/Small_scale_LNG_developments_part_two_447.aspx#.U3RJS7Eqt2F