Liquefied Natural Gas is a chain, not a process. Gas has to be cleaned, cooled, stored, shipped, and warmed back to a gaseous state under conditions that would damage most industrial equipment. Each link in the chain uses specialised technology, and each link has its own cost, efficiency, and emissions profile. This hub links to deeper explanations of each stage.
The LNG chain at a glance
The full LNG chain has five operational stages:
- Upstream production. Natural gas is produced from conventional reservoirs, unconventional plays (shale, tight gas, coal-bed methane), or as associated gas from oil production. Field compression, dehydration, and initial impurity removal happen here.
- Pre-treatment and liquefaction. At the export plant, gas is stripped of CO₂, H₂S, water, mercury, and heavier hydrocarbons that would freeze at cryogenic temperatures. The clean feed is then cooled in a multi-stage refrigeration "train" to roughly −162 °C and stored as a liquid at near-atmospheric pressure.
- Storage and loading. LNG is held in insulated tanks — typically full-containment double-walled storage with 9% nickel-steel inner tanks — until a carrier arrives. Loading arms transfer LNG from the tank to the ship while handling boil-off gas (BOG) carefully.
- Shipping. Purpose-built cryogenic carriers move LNG across oceans. The two main containment philosophies are Moss spherical tanks and membrane systems (GTT Mark III and No96). Propulsion has shifted from steam turbines toward more efficient dual-fuel diesel-electric, two-stroke engines using BOG as fuel, and (in the Q-Max generation) slow-speed engines with onboard reliquefaction.
- Regasification and distribution. At the import terminal, LNG is warmed back to gas using seawater, ambient air, or submerged combustion vapourisers, then injected into pipeline networks. Floating storage and regasification units (FSRUs) perform the same function on a ship, allowing faster deployment in smaller markets.
Deep-dives on each stage
Liquefaction
Pre-treatment, C3MR and mixed-refrigerant cycles, heat-exchanger design, and the "train" as the basic unit of capacity.
14 min readLNG carriers
Moss spherical and membrane containment, Q-Flex and Q-Max classes, propulsion options, and boil-off management at sea.
12 min readRegasification
Shore-based vapourisers, FSRUs, send-out metering, and the integration between an LNG terminal and the national pipeline network.
14 min readCarbon capture at LNG plants
Why liquefaction plants are natural CCS candidates, where the CO₂ comes from, and how capture has been integrated at facilities such as Gorgon and in Qatar's North Field expansion.
11 min readWhy cryogenics drives the whole design
At −162 °C, ordinary carbon steel becomes brittle and ordinary seawater behaves like an almost infinite heat reservoir. Every piece of equipment in the chain is designed around that temperature: the materials (9% nickel steel, stainless steel, aluminium alloys), the insulation (perlite, vacuum, polyurethane foam), the loading arms, the pump seals, and the choice of refrigerants. A single material misstep — for example, a trace of mercury reaching an aluminium heat exchanger — can destroy equipment and shut down a train for months, which is why pre-treatment standards are strict and continuous monitoring is the norm.
Cryogenics also shapes efficiency. Liquefaction consumes roughly 8–10% of the feed gas's energy; shipping adds another 0.10–0.15% of cargo per day as boil-off, part of which is recovered by burning as fuel. Electrification of compression, waste-heat recovery, and slow-speed two-stroke marine engines have all aimed to reduce that inherent energy penalty.
Where technology is evolving
- Larger trains. The industry has moved from 1–3 MTPA trains (1970s–1990s) toward 5–8 MTPA mega-trains, capturing scale economies at the cost of longer lead times.
- Modular and small-scale. At the other end, factory-built modular liquefaction (FLNG and onshore small-scale) serves stranded reserves and smaller markets where a mega-train would be too large.
- Electric drives. Electric compression reduces direct CO₂ emissions at the facility, shifting the carbon intensity to the power mix behind the plug.
- Low-methane-slip ships. Newer marine engines have reduced unburnt methane release, addressing one of the main criticisms of LNG as a bunker fuel.
- CCS integration. Integrating carbon capture with the acid-gas removal unit at a liquefaction plant is technically straightforward but depends on CO₂ storage infrastructure nearby.