Abstract

This paper describes the formulation and basis of the microcomputer, program, HYDRATE. BAS, which calculations hydrate formation conditions of natural gases. The program is based on the Carson and Katz program is based on the Carson and Katz method for hydrate predictions. It is designed for pressures in the range 100 to 2000 psia (700 to 1400 kPa), and temperatures between 32 and 80 degrees F (0 and 26 degrees C). Comparisons with published experimental data indicate average pressure deviations of +/- 30 psi (200 kPa) and temperature deviations, is of +/- 2 degrees F (1 degrees C). The program is written in BASIC, for Osborne 1*, IBM PC** and compatibles. PC** and compatibles.

Introduction

Hydrates are solid crystalline inclusion-compounds (clathrates) which contain two components, referred to as host and guest. Free water molecules form a metastable crystal lattice, which is stabilized by light gas molecules (C1 through C4 paraffins, carbon dioxide, and hydrogen sulfide) occupying the crystal cavities.

* Osborne 1 is a trademark of Osborne Computer Corporation

** IBM PC is a trademark of International Business Machines, Inc.

Molecules larger than butanes cannot fit into the cavities and thus do not form hydrates.

Hydrates cause problems by plugging pipelines, valves, and other process pipelines, valves, and other process equipment. Proper design, therefore, includes, predicting the conditions under which predicting the conditions under which hydrates may form. Several methods are available for predicting potential hydrate forming conditions:

  • experimental

  • graphical

  • graphical-analytical

  • analytical

Early hydrate prediction methods are based on graphical techniques. Carson and Katz produced the first reliable hydrate produced the first reliable hydrate prediction method based on gas composition. prediction method based on gas composition. Campbell describes both graphical and graphical-analytical methods. The analytical technique developed by Parrish and Prausnitz depends on the mechanisms of statistical thermodynamics, and is probably the most widespread method in use probably the most widespread method in use today.

Hydrate packages that are available on the market today are based on the Ng-Robinson modifications of the Parrish-Prausnitz technique. Normally the programs run on a timesharing/mainframe system. Recently, this method has also become able for microcomputers.

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