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- The process to convert natural gas into LNG is based on three steps, gas treatment, gas compression and refrigeration.
- Since the natural gas contains many non-methane gas and impurities and water which can freeze and damage equipment during the compression phase, it must be treated to remove condentates or NGLs.
- Then the purified methane concentrated at 99% goes to the compressors trains to be transformed from gas into liquid
The liquefaction is completed by cryogenic refrigeration with propane condensers at -162°C.
- Depending on the licenses, the phases of compression and refrigeration can be combined in different ways to optimize efficiency or reliability.
- These compressors may be driven by turbines, they are called mechanical trains, or by large electrical motors leading to call them electrical trains.
- In both cases the regulation of these compressors is critical because of their sizes in respect with the whole LNG plant and their source of supply in energy (gas,steam or electricity) as well as in natural gas feedstock.
- Therefore the process also requires very strict safety measures and precautions during all liquefaction stages, due to the highly vulnerable and flammable nature of the gas involved.
For these reasons, all the LNG plants use normally two trains of compressors running in parallel.
- This design request more capital expenditure but it provides better balanced production and eliminate risks of shutdown in case of unplanned service operations required.
The Company, it’s Consultants and Strategic Partners possess more than one hundred man-years of experience in the Engineering, Procurement and Construction Management over the entire LNG Supply Chain and the use of LNG to produce electricity.
The Company, it’s Consultants and Strategic Partners are developing a micro-economic strategy to bring LNG onshore, in developing Nations lacking a terminal, gasification facility and the pipeline infrastructure to deliver the gas to the electrical production facilities.
This process will be outlined below and will be compared to the more conventional methods of liquifiction and gasification. As we go through the elements of the LNG Supply Chain we will outline the steps required to implement this type of LNG Supply Chain.The whole process of LNG Development is referred to as the LNG Supply Chain and consists of field development, liquefaction, shipping and receiving terminal and is illustrated in the Drawing below.
The line drawing show below is a pictorial representation of the various avenues which can bring Natural Gas from the field where it originated to the final consumer of the products. The drawing also shows the relationship between Upstream, mid-stream and downstream of the natural gas supply chain. This supply chain has the LNG Supply Chain as one of it’s subsets.
Natural Gas Supply Chain
1.1. LNG Field Development:
Natural gas accounts for about one quarter of all energy consumed in the United States. Approximately 14 percent of U.S. natural gas consumption is for electricity generation. Natural gas also serves as the raw material to make paint, plastics, fertilizer, steel, fabrics, glass and numerous other products. Natural gas is vital to the U.S. economy and is becoming a major factor in the Global Energy market.
Natural gas is commercially extracted from oil fields and natural gas fields. Gas extracted from oil wells is called casinghead gas or associated gas. The natural gas industry is extracting gas from increasingly more challenging resource types: sour gas, tight gas, shale gas and coalbed methane.
PHOTO OF NATURAL GAS PRODUCTION PLATFORM IN CARIBBEAN WATER
In the early stages of the installation of generating capacity in the Sovereign Nations of Ghana, the liquefaction and loading facility in Trinidad will be used to acquire LNG. The power plants in the Philippines will be powered by LNG acquired in Indonesia or in Australia.
The LNG Train
The LNG Train refers to the compressor and refrigeration trains used in industrial process to convert natural gas into Liquefied Natural Gas, called LNG.
Liquefied natural gas (LNG) is an obvious way to transport gas where pipelines are not available. The traditional way to distribute LNG is to use dedicated ships that are as large as possible. These large ships transport LNG from major liquefaction facilities located in a handful of places around the world to the LNG import facilities. Since many ships are not designed to transport partial loads, these import facilities need to have tanks large enough to receive the full cargo from an LNG ship. While this large-scale approach keeps transportation costs down, the problem is that it creates limitations. Firstly, the receiving terminals need to be relatively large. A receiving terminal of say, 160,000 cubic meters, requires a very significant investment. For a power plant having a 100 MW of capacity, this 160,000 m3 would represent about half a year’s consumption, which is far too much for an efficient use of capital. The most common solution to this problem has been to build LNG import terminals only at locations where the gas consumption is large enough, thus completely ruling out smaller disconnected locations, such as islands or small countries.
Small Scale Transportation
The transportation of LNG on a smaller scale is already happening in several places around the world, most typically using trucks. LNG trucks are essentially vehicles having a pressurized LNG tank.
PHOTO OF AN LNG TANKER TRUCK
These are offered by many manufacturers, and come in different sizes. In some countries even multi-unit trailers are used. Unfortunately, this solves only regional and not overseas transport requirements. Another method is to use dedicated LNG containers. This makes it possible to use the same container for both marine and road transport. The disadvantage is the relatively small capacity possible, which only makes sense for smaller power plants. Using smaller vessels to transport LNG is not yet common, but it is already happening. Norway has been one of the early users of small vessels for the distribution of LNG, since the geography of the country is attractive for marine transportation, even in quantities as small as 1000 m3. The Caribbean, on the other hand, needs slightly larger scale transportation capacity. Vessels of around 10,000 m3 are ideal for many locations, but such vessels are not yet shuttling back and forth from island to island. There needs to be LNG sources that make LNG available for smaller vessels, and in order for this to happen, their business model needs to take smaller scale vessels into account. By trying to load smaller vessels from the same loading bays as the larger ones, valuable dock time would be utilized for a smaller volume sale. LNG export terminals need, therefore, to have additional loading bays dedicated for these smaller vessels.
An analogy could be trains and trucks. Trains are more cost efficient for cargo transportation, but that does not mean that trucks are not needed, or that they are cost prohibitive. Both are essential for a functioning transportation system. In the same way, LNG needs to be transported using both cost efficient large vessels, as well as flexible 10,000 m3 smallscale vessels that reach more places.
Hub and spoke concept
A natural solution for improving the efficiency of transporting LNG on a smaller scale is to use a hub. The hub can be a new, or even an existing LNG terminal. It can be land-based or floating. Smaller vessels could make ‘milk runs’ to several locations, or back and forth trips to a single location, which would keep the distances relatively short. The trips of the smaller vessels are the spokes, hence the name ‘hub and spoke’ for this distribution model. At present this distribution model is not yet applied in the Caribbean. Nevertheless, due to the imminent widespread demand
for gas, it would be surprising if this concept does not materialize within the next few years. On the other hand, as several new LNG export terminals have been announced in the region, including several terminals in the Gulf of Mexico and one in Colombia, some of the export terminals themselves may become regional small-scale LNG distribution hubs.
LNG is transported in specially designed ships to re-gasification facilities. These ships are double-hulled and have capacities from 25,000 to 138,000 m3 or more. The ships are fitted with a special cargo containment system inside the inner hull to maintain the LNG at atmospheric pressure and in it’s liquid state. The majority of the LNG ships in the fleet are of the Moss Design.
NOTE: Moss Design: This design is owned by the Norwegian company Moss Maritime and it is a spherical tank. Most Moss type vessels have 4 or 5 tanks. The outside of the tank has a thick layer of foam insulation that is either fitted in panels or in more modern designs wound round the tank. Over this insulation is a thin layer of “tinfoil” which allows the insulation to be kept dry with a nitrogen atmosphere.
PHOTOGRAPH OF MOSS DESIGN LNG TANKER AT SEA
PHOTOGRAPH OF MOSS DESIGN LNG TANKER IN PORT
1.4. RECEIVING TERMINAL
Near the end of the supply chain is the receiving terminal. The key components of the proposed LNG terminal, including marine jetty facilities for unloading LNG, special tanks for LNG storage, process equipment for the re-gasification of LNG, utilities and other infrastructure, are depicted in the process overview in the following diagram.
PROCESS OVERVIEW OF LNG GASIFICATION
PHOTOGRAPH OF LNG RECEIVING TERMINAL
In order to expedite the process of empowering Ghana and other Arican Nations the Company will establish a different process on the receiving end of the LNG Supply Chain.
The Company will purchase a used Jack-up rig (shown in the photograph below)