Natural Gas Liquids

Natural Gas Liquids Recovery

Processing of natural gas to recover NGL is typically required to meet pipeline hydrocarbon dewpoint specifications and often enables the recovery and separation of a higher value product. Costain offers optimised process designs for NGL recovery plants utilising Joule-Thomson refrigeration, cryogenic turbo-expanders and/or mechanical refrigeration. Processes offer high thermodynamic efficiency, using available refrigeration more effectively, to achieve economic deep recovery of NGL.

 

Costain's patented technology applies features such as refluxing heat exchangers, multiple turbo-expanders, high pressure wash columns and residue gas recycle to deliver propane and ethane recoveries in excess of 95%.  Process schemes can be tailored to offer optimum levels of NGL liquid recovery against project specific criteria.

 

Costain's technologies and advanced process design techniques can equally be applied to revamp and debottlenecking projects to cater for changes in feed conditions or to increase liquids recovery.

Natural Gas Liquids Fractionation


Natural gas liquid recovery plants normally produce a mixed NGL product which is typically further fractionated into ethane, commercial propane, butane and condensate products. Propane may be needed as a separate product or as a mixed LPG product with butane and flexibility is often required to vary composition. NGL product requirements are highly dependent on market factors and geographical location.

Costain has considerable experience in the design of fractionation systems, including highly integrated column systems used in its cryogenic processes, developed using sophisticated process modeling and thermodynamic analysis techniques. In addition to identifying the best separation sequence and optimising the fractionation system, Costain can identify potential high efficiency schemes to reduce utility consumption.

Costain also has experience in using the latest high capacity column tray, random packing and structured packing designs to reduce column diameter, improve energy efficiency or to debottleneck existing columns. 

Natural Gas Liquids from Liquid Natural Gas


A wide range of liquefied natural gas (LNG) compositions are produced worldwide and countries such as the UK and US, with distribution networks requiring low Wobbe Index gas, may require gas quality adjustment at LNG receiving terminals to meet entry specifications. Recovery of high value NGL products at the receiving terminal can help meet gas specifications and is a viable alternative to nitrogen ballasting. NGL recovery may also be attractive in emerging LNG importing countries with high domestic LPG demand such as India and China.

Costain has developed effective processes for the high recovery of NGLs from LNG. Extraction units recovering LPG or ethane can be integrated into the re-gasification process on new or existing terminals without the need for additional refrigeration or compression equipment.

Costain has evaluated NGL extraction processes for a number of terminals, with assessment of potential performance over a range of LNG compositions, considering temperature variation with send-out rate and the impact of boil-off gas re-condensation.

Integration

Experience and capability in both natural gas liquefaction and cryogenic nitrogen rejection enables Costain to propose efficient processes with integrated NGL extraction.

Such integration can enable significant reduction in requirements for compression power and consolidation of heat exchange equipment, reducing both capital and operating costs. Optimisation techniques include the use of thermodynamic analysis to provide realistic power targets, allowing accurate benchmarking of process schemes to ensure cost-effective recovery levels.

Operability is an important consideration and Costain is able to draw on considerable experience in both design and operation of highly integrated cryogenic processes.

NGL Treating

 

 

To meet NGL product specifications, removal of contaminants is typically required. Costain has experience in the design and supply of systems for:

•  - Separation of carbon dioxide from ethane or LPG product



•  - Stripping of hydrogen sulphide (H₂S) from condensate using steam or fuel gas and subsequent treating using licensed technologies for mercaptan removal



•  - Removal of sulphur compounds (e.g. COS) from NGL products, for example using metal oxides or regenerable molecular sieve.

 

 

 

 

 

 

 

 

 

 

 

 

 

  NGL and Olefins Recovery from Refinery and Petrochemical Offgas

 

 

Costain’s capability and experience in natural gas processing for recovery of NGL components is complemented by a long track record in the design of cryogenic units for the recovery of both NGLs and olefins from refinery and petrochemical offgas streams.

In many cases valuable saturated and unsaturated hydrocarbons, including ethylene, propylene and butylenes would otherwise be burnt and recovery can provide valuable additional products or feed stocks.

Costain is able to provide services from concept design through to supply of modular plant for new build and retrofit projects.