Special Report: Converting natural gas to LNGby Arabian Oil & Gas Staff on Mar 15, 2017
In the night, city lights all around the globe illuminate the sky. But some of these lights are not from cities. They are actually flares from gas wells.
In remote areas across the world, it is often way too expensive to move gas to LNG plants for processing. This means that large volumes of natural gas are stranded or flared. But what if it was possible or even easy to move the LNG plants to the gas?
That is exactly what the Dresser-Rand business, part of Siemens, is doing with its new LNGo natural gas liquefaction system that converts natural gas into valuable LNG right at the source.
Flexible, efficient and reliable
The Dresser-Rand business’ LNGo natural gas liquefaction system is a modularised, portable natural gas liquefaction plant designed to provide onsite natural gas liquefaction. The low-pressure system is sized to produce approximately 7,000 gallons (26.5 cubic metres) of liquefied natural gas (LNG) per day, while the high-pressure system is sized to produce approximately 30,000 gallons (113.5 cubic metres) per day.
Stranded wells typically found in newly developed gas fields or at the edge of the existing fields with immature gas gathering infrastructure are ideal candidates for the LNGo system. Gas reserves contained in remote areas can represent billions of dollars in unused assets. And building land-based LNG production facilities can be costly, complex and time-consuming.
The LNGo system’s versatility is an attractive feature. The micro-scale LNGo solution can be deployed in rough terrain or remote regions, eliminating the need to establish an expensive gas pipeline infrastructure or arrange for long-distance trucking of LNG from centralised plants to point of use. It can function as a decentralised solution where the requisite pipeline infrastructure is lacking, or as an onsite transformation solution to reduce or eliminate flaring of gas at, for example, oil rigs or producing gas fields. The system provides a small-footprint, low-cost alternative to pipelines and enables stakeholders to monetise stranded gas assets economically and reliably. And it can be moved to another location once the well is depleted or a pipeline infrastructure is put in place.
The system uses proven engineered product technologies from Siemens and the Dresser-Rand business. The MOS high-speed reciprocating compressor includes components designed to enhance performance. The compressor frame and cylinders are matched to provide years of smooth, reliable and efficient compression service when operated within OEM recommendations. The Guascor natural gas engine that powers the system’s generator-sets uses leading technology and produces low emissions.
In addition to enabling stakeholders to monetise stranded gas, the LNGo system eliminates environmental concerns such as flaring. Flares are typically associated gas or lower value process gas that requires gas pre-treatment. With the LNGo system, flaring is avoided or substantially reduced. The purge flow from gas conditioning is blended into the fuel supply to the power module.
The gas conditioning module removes CO2, H2O and many of the heavy hydrocarbons (C3+) from the incoming feed gas stream. Clean, dry gas ensures optimal liquefaction performance. An additional conditioning module is available for laden gas depending on the gas composition.
The system integrates complete control of all modules of the LNGo system for both the low-pressure and high-pressure systems. Remote-capable control logic is available with wireless instrumentation and transmitters and can be used wherever it is advantageous and code compliant. This helps ensure system reliability and uptime. Full turn-key installation and commissioning services are available, as well as routine operation, monitoring and maintenance contracts to ensure ongoing reliable and available operation.
A standardised product made up of packaged modules
This point-of-use production plant is a standardised product made up of packaged modules that may include power module(s), compressor module, process module and a gas conditioning module. Natural gas powers the unit (if grid power is not used) and is also used as the process refrigerant to eliminate complexity and maintenance. So, this system recycles off-gas and uses it to power the plant.
The gas conditioning module cleans and separates pre-treated gas into one product stream for the liquefaction process and one purge stream for power generation. The process module contains all liquefaction process equipment and employs four cooling phases. The compressor module provides four stages of gas compression. The power module houses the motor control centre and system controls and provides power for the entire LNGo low-pressure (LP) system.