Episode 5

REGASIFICATION

Liquid natural gas (LNG) is converted back to its gaseous state before being fed into the local grid or pipeline systems and distributed to end users. The regasification process is carried out at land-based terminals or in floating storage and regasification units (FSRUs) on board ships or barges.

FIND YOUR APPLICATION

LNG TERMINAL

FSRU

LNG TERMINAL

LNG terminals are generally located at purpose-built ports. The LNG is unloaded from ships via pipelines and stored in specially-designed cryogenic tanks at a temperature of -162⁰C to maintain its liquid state. However, there is usually minor evaporation – or boil off gas (BOG). This is captured using compressors and condensers and fed back into the LNG system.

The LNG from the tanks, together with the BOG from the compressors, is collected by a reliquefier, before being pumped at high pressure into the regasification system.

REGASIFICATION PROCESS

The LNG is converted back to a gas with heat exchangers. Seawater is used to heat either a glycol/water mixture or propane. These in turn heat and vaporize the LNG as it passes through the heat exchanger. Some LNG terminals also use turbine flue gases from their energy recovery systems as a heating medium.

Once transformed back into a gas, it is then metered, analyzed and odorized before entering the transmission system.

Lube

Oil Cooler

Lube

Oil Cooler

LNG
Vaporizer

Compressor

BOG Recondenser

LNG Storage

LNG Tanker

BOG Compressor

LNG

Lube Oil

Sea Water

GLYCOL PROCESS

LNG Vaporizer GPHE

Sea Water

Condensate/Water

Steam

Glycol

LNG

LNG Pre Heater
Shell & Tube HX

LNG Storage

Sea Water

Sea Water Filter

Condensate

Steam

Sea Water Heater
K°Bloc

Glycol Evaporator
Gasketed Plate
Heat Exchanger
LWC

LNG TERMINAL

WHITEPAPER: THE RIGHT CHOICE
FOR FSRU APPLICATIONS

Designing heat exchangers to withstand the mechanical stresses in cryogenic temperature and high pressure operations can lead to very bulky equipment. On FSRU, where space is at a premium, finding an appropriate solution can be a huge challenge.
Kelvion has developed the K°BOND to meet it by combining compactness and performance. The K°BOND comprises stainless steel plates, each chemically etched with micro-channels. These are then bonded together to create a solid core of metal, ensuring high mechanical resistance.

FLOATING STORAGE AND REGASIFICATION UNIT [FSRU]

FSRUs combine LNG storage and built-in regasification units on board vessels. They can receive and store LNG from conventional carriers and regasify as needed. FSRUs offer a number of advantages over on-shore terminals. As well as being a faster and more economic option, with a lower environmental impact, they have the flexibility to move to different locations to meet market requirements and seasonal fluctuations in demand.

Additionally, FSRUs can provide a central LNG storage hub for unloading onto smaller carriers which transport it to smaller ports or areas that are far away from gas pipeline networks.

FSRU PROPANE PROCESS

Propane is used as the heating medium in a heat exchanger to bring the temperature of LNG up from -162 ⁰C to -10 ⁰C. A second stage follows using seawater. Propane does not freeze at -162⁰C and it is also used to keep the sea water out of the direct LNG heating circuit.

The propane enters the heat exchanger at around 0 ⁰C and circulates in a closed loop. During heat exchange, the propane condenses to -5 ⁰C and is then fed into a circulating pump and heated against sea water in a second heat exchanger. This heats it back to a gas at -0 ⁰C before returning to the first stage heat exchanger.

LNG

Sea Water Heater
K°Bloc

Propane Evaporator
Gasketed Plate
Heat Exchanger
LWC

Steam

Condensate

Sea Water Filter

Sea Water

LNG Vaporizer K°Bond

LNG Pre Heater K°Bond

Sea Water

Condensate/Water

Steam

Propane

LNG

FSRU GLYCOL PROCESS

Although propane is a relatively safe form of energy, it does pose the risk of explosion as it needs to be stored under high pressure. For this reason many new FSRUs use glycol as the heating medium.

Glycol systems are enclosed and therefore cleaner. They are not exposed to dirt and particulates associated with water-based systems. Filtration is not required, saving on powering and maintaining filtration pumps. Also, because the glycol has added anti-corrosion properties, there is a further reduction in maintenance costs, ensuring long- lasting performance and efficiency.