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Optimal Process Loca~t/iion for NGL Recovery in LNG Plant

IP.com Disclosure Number: IPCOM000217697D
Publication Date: 2012-May-10

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Page 01 of 19

Pa~r # I~9~~

Optimal Process Loca~t/iion for NGL Recovery in LNG Plant

Douglas A. Attaway Stanley Huang

 Heinz Kotzot Charles A. Durr

KBR

Kellogg Brown & Root, Inc.

601 Jefferson Avenue Houston, Texas 77002

Prepared for Presentation at the AIChE 2005 Spring National Meeting
LNG IV - Research & Development

Copyright © Kellogg Brown & Root, Inc.

January 2005

Unpublished

AIChE shall not be responsible for statements or opinions contained in papers or printed in its publications.


Page 02 of 19

Paper # 1897

ABSTRACT

    Natural Gas Liquid (NGL) recovery is an inherent part of most LNG production facilities. The feed gas to a LNG plant contains in most cases ethane and heavier hydrocarbons. Even if the C2+ components are not desired as a separate product, they often must be recovered to varying degrees to:

  satisfy refrigerant makeup needs
¯ prevent plugging in the liquefaction section

meet LNG specifications, primarily heating value

    The placement of the NGL recovery system within an LNG process is becoming an area of greater interest. Traditionally the removal of NGL from the feed gas has been integrated into the precooling section, which provides partial condensation for separation. However KBR recently has been involved in cases where front end NGL recovery, which is upstream of the gas cooling section, became the preferred design.

    The purpose of this paper is to compare the efficiency of front end versus integrated NGL recovery for an LNG production facility in a neutral approach to liquefaction technology. It will use a generic liquefaction process as a basis for comparison. The analysis is not based on any proprietary liquefaction process.

    The NGL recovery technique varies with the placement in the process. Front end NGL recovery will use a conventional expander plant design with full pressure recovery. Integrated NGL recovery can employ different schemes, such as condensation by refrigerant or expander technology. A series of process simulations are used to model the liquefaction process with selected NGL recovery methods at various temperature levels in the feed gas chilling train. A comparison based on specific power is applied to evaluate the options. This will address the impact of process locations on different NGL recovery methods. The results of this work will shed light on trends in this area and serve as a useful guideline for future process design.


Page 03 of 19

Paper# 1897


Optimal Process Location for NGL Recovery in LNG Plant

INTRODUCTION

    Virtually every liquefied natural gas (LNG) production facility has some form of natural gas liquids (NGL) recovery. It is normally required for preventing solidification and plugging in the cryogenic portion of the plant as well as meeting LNG product specifications and providing refrigerant make-up. In many cases it is attractive to recover and market the heavier components as separate products or provide them as feedstock to a nearby chemical plant or refinery [Ref. 4].

    The ubiquitous...