Smart LNG regasification

[jbmr]

Hello,

Having been recently involved in a few LNG regasification projects I noticed that most of the recent LNG regasification terminals seem to derive the energy for LNG regasification from cooling down seawater or burning gas. When you consider the amount of energy involved in LNG liquefaction this is a bit of a pity, especially if you consider that more efficient processes exist for instance:

1- Using "free" warm water from a power plant or other industrial facility to supply the energy for vaporisation
2- Using a Rankine cycle to warm up LNG AND generate power

I would be interested in hearing from recent applications involving any of the previously mentionned technologies (in particular the second one) and why Rankine cycle are not more widely used.
I would also be interested in examples of integration of LNG terminals with other industries (CO2 production, Liq N2 production etc...)

 

[dcasto]

his company advertises a lot about recovering energy.

http://www.ormat.com/our-businesses/recovered-energy/applications/

Way back in the 70's I worked at a place where they used Tubine driven pumps to boost the pressure to 1000 psig, then the cryogenic liquid was vaporized in the exhaust.

 

[rmw]

I just had this conversation with a young colleague. The problem is the capital cost. Unless you site a LNG plant adjacent to an existing power plant it is a tremendous investment to build a power plant just to get some warm water to liquify LNG. LNG plants tend to be sited based on suitability for access by oceangoing vessels, not heat sources. Much cheaper to buy a burner than build a power plant to burn the same fuel to get some heat.

I think I know the plant that Dcasto refers to and if it is the one I am thinking of, I noticed that at the time of expansion they didn't repeat their initial design.

It is all economics. Al Gore may want to save the planet, but the bankers own it. ROI rules.

rmw

 

[jbmr]

Thank you for your input. You are probably right rmw but I can't help thinking it is a real shame to burn gas to degrade a potentially valuable cold source... I guess the ROI equation will eventually change with the price of energy going up...

 

[dcasto]

I doubt the ROI will change as energy goes up. If there is no demand for the cooling, then there is no value and nothing will be done.

I once proposed we run a coil through the exhaust on an engine to make warm water for coffee and pipe it around the plant, what a waste of hot exhaust and not enough coffee drinkers.

 

[rmw]

Dang, and I thought all the good ideas had been thought up.

rmw

 

[Samiran]

I don't think it is the capital cost that has not boosted the use of this technology, it is probably that the technolgy has not matured enough for this application & also requirement of a threshold capacity to make this viable. I had a discussion with Ormat on this. It is only recently more research is being made to make use of cold energy to generate power in LNG Terminals when LNG Terminals are being operated from 1960s. Think about it..you probably would use 1% of the sendout gas to heat up and vaporize LNG and that is almost a quarter million dollar per LNG cargo unloaded. If you're unloading 100 cargoes a year, you lose 25 MM USD - a huge sum of money. Of course the cheaper way is to use sea water (where it is not too cold)but you still need power to run the pumps. I personally feel it makes absolute sense to use this cold energy to generate power AND regas LNG as well simultaneously. Incidentally, Ormat is currently executing its first project in Spain for an LNG Terminal. We will need to see how that project comes up.

 

[SWang]

Which are the contractors in these LNG terminal design and construction?

 

[TexasPE]

What is a real shame is that the Interstate Natural gas pipeline companies are not working with the GoM based gas processing straddle plant operators to use the cooling from vaporizing LNG as a substitute for propane precooling in their NGL extraction process.

 

[davefitz]

One of the smarter ways to regasify LNG is to integrate a C3+ stripper facility at the regas terminal- one can directly make use of the cryogenic temperatures of the offloaded LNG to enable removal of the heavy fraction . By stripping the heavies ( C3, C4 <C5, etc) one can condition the regas stream to have a HHV and wobbe index that is similar to that of domestic US natural gas. The stream of NGL's fromthe removed heavy fraction can be shipped to markets that need the butane, propane, etc.

There is another smarter way to regas the LNG applies at sites that adjust the wobbe index by addition of inerts, such as N2 and CO2. Conventional ways of producing N2 are quire expensive and energy ineficient- cryogenic distillation or PSA pressure swing absorption. One unconventional way to produce an inert stream is to fire a boiler with LNG fuel gas, operate it at very low O2 levels ( and at a positive draft), to produce an exhaust gas that is nearly completely composed of H2O, N2, and CO2. The H2O can be removed by condensing heat exchangers and/or desiccants, andthe remaining N2 and CO2 can be cooled to low temperatures prior to compression by passing thru a HX that is also warming up the cryogenic LNG. At the right combination of T and P, one can alsostripout most of the CO2, if that is needed for pipeline corrosion concerns.

Still another means of making use of the -273 F LNG stream is to use this stream to cool the inlet air flow to a cryogenic gas distillation facility; the N2 is used for LNG conditoning / wobbe adjustment, while the O2 is sold to hospitals or welders gas.

 

[MortenA]

If you include c2+ in the LNG - then its not LNG. Its more like CNG. This is a feasible way and could possibly be the largest energy saving in the "process chain". But it will not work with any existing facilities!

The two other idear are quite good too - but perhaps not requiring energy to this scale!

Best regards

Morten

 

[davefitz]

MortenA;

There are patented processes the also remove the C2, as well as the C3+ , at the regas terminal, and some are being implemented at new regas sites as we speak. Unless there is a local consumer that can absorb the C2 via pipeline, there is supposedly a shortage of seaworthy tankers that can ship the C2. But, not my area of expertise.

 

[meierdani]

The LNG cold exergy recovery in LNG regas terminal is a pretty frequent topic in recent years, and you do find some examples that have been put in service,i.g. in Negishi LNG terminal of Tokyo Gas ( i v been there and investigate the subject for a couple of days), totally they have got 40% of cold exergy been recovered(23.8% for power generation, and 14.8% for air separation and CO2 production). Currently 39.3% of total power consumption of Nigishi terminal came from LNG cold energy. Another example is from Kita Kyushu LNG terminal of Japan, which is a small one and get the cargo mainly from Bontang of Badak. Totally they have 60% cold energy been reused (9400KW totally, Rankine cycle through intermediate media- 4050kw, and 5350 kw from LNG vaporization expansion).
Therefore, I guess to answer your question in a sentence, I don't see there is any technical difficulties in reusing the LNG 'cold energy', but I am afraid the cost would be a main issue. I personally tend to believe the condition of downstream market for the 'by-product' such as LN2, LO2 or LAr and CO2 and overall effects including both environmental one and effects to local community would be considered at the same time to decide the final design. Unfortunately, these factors are in generally belong to different sectors (most common case all over the world), which means a more overall consideration would probably merely be an illusion.