Selective dehydration of high pressure natural gas using supersonic nozzles

Karimi, Anahid (2006) Selective dehydration of high pressure natural gas using supersonic nozzles. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (5MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

The dwindling high quality crude oil reserves and increasing demand for natural gas has encouraged energy industries further towards the discovery of remote offshore reservoirs. Consequently, new technologies have to be developed to efficiently produce and transport stranded natural gas to consuming markets. Compactness of production systems is the most challenging design criteria for offshore applications. From the gas quality perspective, water vapour is the most common impurity in natural gas mixtures. At very high gas pressures within the transportation systems hydrate can easily form even at relatively higher temperatures. Therefore, gas dehydration or hydrate inhibition systems for offshore gas production/processing facilities should meet these requirements. It should also be noted that at certain pressure and composition conditions, the presence of heavy hydrocarbons (C₂⁺) in natural gas increases pipeline flow capacity and improves compression efficiencies. Supersonic separators are proposed in this thesis as a compact high-pressure processing system capable of selectively removing water from high-pressure natural gas streams without affecting the hydrocarbon content. A computer simulation linked to a thermodynamic property package is presented to predict the water removal efficiency and to compare the proposed system with conventional techniques. The simulation is first validated with a commercial computational fluid dynamics (CFD) software (Fluent) and then the effect of pressure, temperature, flow rate, friction and backpressure of the system in this method are analysed. Supersonic nozzles are also placed in different locations in a three-stage separation train on an offshore crude oil production platform to test the efficiency for the recovery of Natural Gas Liquids (NGLs) from associated gas. The recovery of NGLs can significantly improve the economy of offshore crude oil production.

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