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Abstract

Feed gas for Shell’s Gas to Liquids (GTL) project in Qatar is supplied from the North Field. Before this sour gas can be processed in the GTL plant it has to be rigorously treated to meet the stringent contaminant specifications for a modern GTL process.

The feed gas contains a wide range of contaminants, including H2S, CO2, several mercaptan species and COS. Treating this gas to specification requires a series of treating processes. These processes have to be selected and integrated to provide a treating complex that is not only cost effective, but also will remove contaminants in an environmental friendly way.

Sustained development has been one of the key elements in the process selection of the Pearl GTL treating units, and this can be clearly seen from the final line-up that has been selected. For the main acid gas removal unit a selective amine process has been chosen. By removing mercaptans in a molecular sieve process, rather than by using a physical solvent the co-absorption of hydrocarbons has been minimized. This improves hydrocarbon efficiency and thus reduces CO2 emissions from burning these hydrocarbons in the sulfur recovery unit is. All sulfur containing streams from the treating units are routed to the sulfur recovery unit, which has been fitted with a special burner arrangement and an integrated tail gas treating unit to maximize the sulfur recovery efficiency over a wide range of feed gas compositions.

The paper provides details on the process selection process taken by Shell Global Solutions, showing the process options that were available and the environmental benefits that were achieved.

Introduction

The Pearl GTL project will be located in Ras Laffan, Qatar and will consist of two trains, which together will produce 140,000 barrels of middle distillates and base oils from natural gas using Shell GTL technology. In addition the plant will produce significant quantities of condensate and LPG. The Pearl GTL project has completed the FEED design phase. Start-up of the project is targeted for late 2009.