Lng Facility With Integrated Ngl Recovery For Enhanced Liquid Recovery And Product Flexibility

PATENT
Lng Facility With Integrated Ngl Recovery For Enhanced Liquid Recovery And Product Flexibility
United States Patent Application 20120042690 Kind Code:A1
Inventors:
Qualls, Wesley (Katy, TX, US)
Ransbarger, Weldon L. (Houston, TX, US)
Huang, Shawn S. (Spring, TX, US)
Yao, Jame (Sugar Land, TX, US)
Elliot, Doug (Houston, TX, US)
Chen, Jong Juh (Sugar Land, TX, US)
Lee, Rong-jwyn (Sugar Land, TX, US)
Application Number: 13/282936
Publication Date: 02/23/2012
Assignee: ConocoPhillips Company (Houston, TX, US)
Abstract:
Process for efficiently operating a natural gas liquefaction system with integrated heavies removal/natural gas liquids recovery to produce liquefied natural gas (LNG) and/or natural gas liquids (NGL) products with varying characteristics, such as, for example higher heating value (HHV) and/or propane content. Resulting LNG and/or NGL products are capable of meeting the significantly different specifications of two or more markets.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a method and apparatus for liquefying natural gas. In another aspect, the invention concerns an improved liquefied natural gas (LNG) facility capable of efficiently supplying LNG products meeting significantly different product specifications.
2. Description of the Prior Art
The cryogenic liquefaction of natural gas is routinely practiced as a means of converting natural gas into a more convenient form for transportation and/or storage. Generally, liquefaction of natural gas reduces its volume by about 600-fold, thereby resulting in a liquefied product that can be readily stored and transported at near atmospheric pressure.
Natural gas is frequently transported by pipeline from the supply source to a distant market. It is desirable to operate the pipeline under a substantially constant and high load factor, but often the deliverability or capacity of the pipeline will exceed demand while at other times the demand will exceed the deliverability of the pipeline. In order to shave off the peaks where demand exceeds supply or the valleys where supply exceeds demand, it is desirable to store the excess gas in such a manner that it can be delivered as the market dictates. Such practice allows future demand peaks to be met with material from storage. One practical means for doing this is to convert the gas to a liquefied state for storage and to then vaporize the liquid as demand requires.
The liquefaction of natural gas is of even greater importance when transporting gas from a supply source that is separated by great distances from the candidate market, and a pipeline either is not available or is impractical. This is particularly true where transport must be made by ocean-going vessels. Ship transportation of natural gas in the gaseous state is generally not practical because appreciable pressurization is required to significantly reduce the specific volume of the gas, and such pressurization requires the use of more expensive storage containers.
In view of the foregoing, it would be advantageous to store and transport natural gas in the liquid state at approximately atmospheric pressure. In order to store and transport natural gas in the liquid state, the natural gas is cooled to B240° F. to B260° F. where the liquefied natural gas (LNG) possesses a near-atmospheric vapor pressure.
Numerous systems exist in the prior art for the liquefaction of natural gas in which the gas is liquefied by sequentially passing the gas at an elevated pressure through a plurality of cooling stages whereupon the gas is cooled to successively lower temperatures until the liquefaction temperature is reached. Cooling is generally accomplished by indirect heat exchange with one or more refrigerants such as propane, propylene, ethane, ethylene, methane, nitrogen, carbon dioxide, or combinations of the preceding refrigerants (e.g., mixed refrigerant systems). A liquefaction methodology that may be particularly applicable to one or more embodiments of the present invention employs an open methane cycle for the final refrigeration cycle wherein a pressurized LNG-bearing stream is flashed and the flash vapors are subsequently employed as cooling agents, recompressed, cooled, combined with the processed natural gas feed stream, and liquefied, thereby producing the pressurized LNG-bearing stream.
In the past, LNG facilities have been designed and operated to provide LNG to a single market in a certain region of the world. As global demand for LNG increases, it would be advantageous for a single LNG facility to be able to supply LNG to multiple markets in different regions of the world. However, natural gas specifications vary greatly throughout the world. Typically, such natural gas specifications include criteria such as higher heating value (HHV), Wobbe index, methane content, ethane content, C3+ content, and inerts content. For example, different world markets demand an LNG product having an HHV anywhere between 950 and 1160 BTU/SCF. Existing LNG facilities are optimized to meet a certain set of specifications for a single market. Thus, changing the operating parameters of an LNG facility in an effort to make LNG that would meet the non-design specifications of a different market creates significant operating inefficiencies in the facility. These operating inefficiencies associated with producing LNG for non-design specifications generally makes it economically unfeasible to serve more than one market with a single LNG facility.
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Supersonic separation in onshore natural gas dew point plant

Journal of Natural Gas Science and Engineering, Volume 6, May 2012, Pages 43–49
Supersonic separation in onshore natural gas dew point plant
Priscilla B. Machadoa, , Juliana G.M. Monteiroa, , Jose L. Medeirosa, , Hugh D. Epsomb, , Ofelia Q.F. Araujoa, ,
a Escola de Química, Universidade Federal do Rio de Janeiro, Avenida Horácio Macedo, 2030-Ilha do Fundão, Rio de Janeiro-RJ 21941-909, Brazil
b Twister BV, Einsteinlaan 10, 2289 CC RIJSWIJK, The Netherlands
Abstract
Conditioning of natural gas (NG) for sales requires meeting water- and hydrocarbon-dew points (WDP and HCDP, respectively) while assuring high heating value (HHV) specifications achievable through minimal extraction of C₅₊ components (NGL).
Authors compare technically and economically a supersonic separator technology – Twister^®, which can promote simultaneously WDP, HCDP and enhanced NGL extraction – to a conventional gas treating technology, consisting of an onshore natural gas dew pointing plant with TEG Dehydration unit coupled to a Joule-Thomson/Low Temperature Separation unit (TEG + JT/LTS).
Full Text Source (Subscription or Fee): http://www.sciencedirect.com/science/article/pii/S1875510012000273

A Comparative Study of Natural Gas Liquids Recovery Methods

Distributed Generation and Alternative Energy Journal, Volume 27, Number 2 / Spring 2012, Pages: 42 - 55
A Comparative Study of Natural Gas Liquids Recovery Methods
Chad Olsen ^A1, Theodore A. Kozman ^A2, Jim Lee ^A3, Kirkrai Yuvamitra ^A4
A1  University of Louisiana at Lafayette
^A2 Engineering and Technology Management and Mechanical Engineering, University of Louisiana Lafayette
^A3 Louisiana Industrial Assessment Center, University of Louisiana Lafayette and Associate
^A4 Department of Mechanical Engineering, University of Louisiana at Lafayette
Abstract:
Reducing the hydrocarbon dew point of natural gas has been an issue for pipeline transportation since large intrastate, interstate, and international pipelines were developed. The problems surrounding the processing and transportation of large quantities of natural gas are numerous and interconnected.
Authors review major natural gas liquids recovery methods including refrigeration methods, chemical methods, physical methods, and combined heat and power (CHP) systems. The advantages and the disadvantages of each method are discussed.
Full Text Source (Subscription or Fee): http://fairmontpress.metapress.com/app/home/contribution.asp?referrer=parent&backto=issue,4,6;journal,1,6;linkingpublicationresults,1:122072,1