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Gas Dehydration Design with Glycol Solutions

Natural gas contains many contaminants, one of them is water. When the gas is transmitted to the surface from processing and finally pipeline transmission, its pressure and temperature reduced naturally in the well string. This reduce the capacity of natural gas to hold water vapor and free water is condensed. The water vapor must be reduced to meet sales gas requirement, which is usually around 2-7 lb/MMscf.

For many years, glycol solutions have been used for natural gas drying. Early glycol dehydration units utilized diethylene glycol (DEG). Triethylene glycol (TEG) came into use around 1950 primarily because its higher boiling point thus gives better separation of water and greater dew point depression without causing thermal decomposition of the glycol. Tetraethylene glycol (T4EG) has been used in some specialized cases, but in majority, triethylene glycol is used.

In this post, I want to share preliminary design of gas dehydration unit using glycol solutions. Calculation and formulae used in this post can be accessed through this link. Read More

Natural Gas Dehydration using Desiccant and Sizing (Bonus Free Spreadsheet)

In this post, I want to share you about natural gas dehydration using desiccant using adsorption principle and how to size it.

In common commercial use, desiccant can be classified into three categories, which are gels (alumina or silica gels), alumina, and molecular sieves.

When used for natural gas dehydration, silica gel will give outlet dewpoints of approximately -70o to -80oF. As for alumina, outlet dewpoint is appoximately -100oF. Molecular sieves produced the lowest water dewpoints, as low as -150oF. For gas going into cryogenic processing, the only adsorbent that can obtain the required dehydration is a molecular sieve.

Table below shows characteristics of several type of desiccants [1]. Read More