TABLE OF CONTENTS Dehydration is the process by which water is removed from natural gas. This is a common method used for preventing hydrate formation. If there is no water present, then it is impossible for a hydrate to form. If there is only a small amount of water present, then the formation of hydrate is less likely.
There are other reasons for dehydrating natural gas. Removing water vapor reduces the risk of corrosion in transmission lines. Furthermore, dehydration improves the efficiency of pipelines by reducing the amount of liquid accumulating in the lines or even eliminates it completely.
There are several methods of dehydrating natural gas. The most common of these are (1) glycol dehydration (liquid desiccant), (2) molecular sieves (solid adsorbent), and (3) refrigeration. Each of these methods is reviewed in this chapter. Several other dehydration methods are less commonly used, and they are not discussed here.
A typical water specification is 112 mg of water per standard m 3 of gas (7lb/MMCF) in many jurisdictions in the United States and 64 mg/Sm 3 (4lb/MMCF) in many jurisdictions in Canada. In other jurisdictions, other specifications are employed. Furthermore, the process may dictate that a lower water content is required. For example, cryogenic processes (i.e., those operating at very low temperature) require that the gas be very dry.
It is also common to refer to the water content of a gas in terms of water dewpoint, the dewpoint being the temperature at which the water just begins...
