Optimising Liquefied Natural Gas Production with an Intelligent Valve Strategy Figure 1: Valve Applications in a Typical Liquefaction Plant
Lean amine pump recycle
Flow control Gas-to-flare
Joule Thompson letdown
Lean amine pump recycle main Flow control
Liquified natural gas process
Joule Thompson letdown
Boil of gas compressor anti-surge
Export pressure flow regulator
Level control
Gas-to-flare blowdown
Import Choke
pressure regulator
Compressor anti-surge
Level control
Production Figure 2: Cross Section of a Typical Valve Slug catcher Processing Liquefaction Transport
dust, acid gases, helium, water and heavy hydrocarbons. They can be extremely harmful, so preventing emissions is vital.
The engineering contractor and the plant operator should work closely to determine which valves require a higher level of attention during design and manufacture. Typically these are the valves associated with the compressors, such as anti-surge (see Figure 4), hot gas bypass or Joule Thompson.
When commissioning LNG valves it is important to select a provider that understands the unique challenges at different stages of the process and has the ability to apply the correct technology. A bespoke, intelligent specification enables more precision in the design of valves, leading to better operability in the field. The best providers will also be able to draw on past experience, suggesting innovative ways to overcome difficulties and ensure peak performance. Relatively straightforward measures, such as modifying trim design, can have a significant impact. If the trim arrangement is not correctly specified it can open up the potential for leakage and poor process control, whereas modifying it in line with the operating conditions will reduce the risk of problems such as cavitation and flashing.
After Installation
dealing with inconsistent hazardous fluid compositions at extremely high pressures). Sweetening involves the removal of components that may cause problems downstream or during transportation – such as
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Typically, LNG valves are supplied with a two-year warranty; however, conducting a detailed pre-commissioning site survey, then cross- checking the eventual installation, can underpin an extended warranty of up to four years. This provides peace of mind and can help reduce the total lifetime cost of each valve. It also demonstrates confidence on the supplier’s part in terms of the quality and durability of the valves, as well as the high standard of the specification, design and manufacture.
HYDROCARBON WORLD – VOLUME 6 ISSUE 2 Flow
Depressurising gas-to-flare
Rich amine letdown
Compressor anti-surge
Propane pre-cooling
Compressor anti-surge
Propane pre-cooling
Hot gas bypass
stripper H2S
stripper CO2
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