ABSTRACT

Two solids which can form or deposit in gas transmission lines, gas hydrates and diamondoids, were investigated.

A high pressure apparatus has been designed which enables the rates of hydrate formation from ice to be determined under dynamic gas conditions. The rate of hydrate formation was found to increase with gas flow rate at gas temperatures slightly above the ice point, but this effect was diminished at lower temperatures.

Vapor pressure curves for two diamondoids, adamantane and diamantane, were determined between 25 C and 300 C. Solubilities of these diamondoids were also determined in various organic liquid solvents and dense CO2.

Analytical solutions to the rate of hydrate or diamondoid removal from pipelines containing significant hydrate or diamondoid deposits were also derived.

INTRODUCTION

Discoveries of natural gas in harsh environments have found that solids such as diamondoids, waxes, and hydrates can deposit during production of natural gas. The formation of these solids in natural gas pipelines can be a severe problem. The kinetics of solid deposition and dissolution in natural gas systems are important to the design of processes for prevention of solids deposition and/or removal of solids already deposited.

Gas Hydrates

Gas hydrates belong to the family of non-stoichiometric inclusion compounds called clathrates. They are formed by the encagement of gas molecules (guest) in the interstices of a hydrogen bonded water (host) molecules. Unlike ice, gas hydrates can exist above the ice point (0°C) if conditions permit.

The rates of gas hydrate formation and dissociation under static gas conditions has been studied(1–7). Heat transfer characteristics of gas hydrate dissociation has also been investigated(8,9). in this study measurements of the rate of hydrate formation under static and dynamic gas conditions were performed to determine the effect of flowing gas on the rate of hydrate formation.

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