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Flexible LNG

Hydrocarbon Engineering,


In today’s economically challenging environment, creative solutions are paramount to business success. Second-hand plants are being sold at a fraction of their new capital cost; often saving companies as much as 40 - 50% compared a new plant.  In addition to saving capital, used plants present a time saving.  Generally, plants such as LNG facilities can be operated in-place or relocated from their present sites and be ready for operation within 18 months or less.  Most facilities are available with technical support from the engineers who previously operated these plants.

LNG peak shaving facilities are typically used for storing surplus natural gas to meet the sudden consumption requirements of extreme cold weather or heat waves.

Alternative uses for the LNG plant include:

  • Liquefying associated gas, reducing emissions and allowing oil fields to pump more oil.
  • Reliably build LNG inventory for use in peak demand and emergency situations. In these situations, the LNG is vaporised at a high rate and injected back into the natural gas pipeline supply grid.
  • It can liquefy the boil-off gases from cryogenic storage tanks, leaving larger liquefaction lines to idle.
  • Delivery to industrial sites with no natural gas pipeline.
  • It can also liquefy gas for vehicle fueling stations.

The following describes a used LNG peak shaving plant offered by International Process Plants (IPP) USA.  The LNG peak shaving plant is part of a larger natural gas transmission and storage system.

This facility can liquefy up to 2400 Nm³/hr of natural gas, which results in 4 m³/hr of LNG (600:1 ratio of gas to liquid). The entire facility was significantly upgraded from 2003 to 2008 with the goal of safely operating another 20 years. The €20 MM upgrade included:

  • Two submersible, retractable pumps.
  • Two high-pressure pumps.
  • New instruments and Siemens PCS-7 DCS for the entire plant.
  • New Linde cold box.
  • New boil-off gas (BOG) compressor.
  • Replacement of all process valves with stainless steel valves.
  • Various optimisation improvements.
  •  

LNG storage tank and equipment

The tank is 37 m dia. x 32 m tall with a capacity of 22 700 m³ or 14 million Nm³ of gas at the design pressure of 68 mbar. The tank is designed to API 620 Q code specifications and is surrounded by earthen embankments capable of containing the entire liquid contents of the tank.

Some natural gas boils off the tank over time. Instead of re-liquefying this gas, it is instead used to regenerate the five PSA beds in the conditioning section of the plant. After cleaning the PSA beds, the gas is compressed with the new BOG compressor and sent back to the pipeline.

Two submersible and retractable pumps are used for pumping LNG from the tank. They are two-stage centrifugal pumps rated for 80 m³/hr @ -162°C and 6 bar.  They have a 140 mm impeller and pump casing constructed of aluminum alloy, as well as a 10 kW motor with a Siemens Micro Master variable frequency drive. There is a Bentley Nevada Model 3500 vibration monitoring system installed on these pumps. The internal pump column is 333 mm dia. x 30 m tall.

Other major equipment includes: 8-stage Ingersoll Rand reciprocating compressor with 2800 kW motor, two 81.5 CBM/Hr Bingham centrifugal high pressure pumps, three 10 000 gallon double-wall liquid nitrogen tanks, three 5000 CBM/hr liquid nitrogen pumps, two 50 000 CBM/hr (gas flow) LNG vaporisers with natural gas burners, 875 CBM/hr Burckhardt boil-off reciprocating gas compressor, and new Electronic Instruments and Siemens PCS-7 control system.

Summary

According to a recent report, approximately 100 LNG terminals, in 17 countries, are scheduled for operation by the year 2020.  An LNG facility with complete engineering and existing equipment will allow a company to produce in a shorter timeframe and quickly compete in the marketplace.

Written by Cheryl Sergewick, International Process Plants. For more information, please click here.

Read the article online at: https://www.hydrocarbonengineering.com/special-reports/04022013/lng_peak_shaving_plant_benefits_001/


 

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