Natural gas is derived from subterranean formations and, as it occurs in nature, normally contains contaminates, the most common of which is water. Removing entrained water from natural gas substantially decreases the problems of transportation, processing, and ultimate use of the natural gas, such as for purposes of providing heat for homes, heating water, and for multiple industrial applications. Natural gas is one of nature's best sources of energy. Water causes many problems in the transportation and processing of natural gas, including the formation of hydrates and water contributes immeasurably to corrosion in pipelines and in processing equipment.
For these reasons, it is common in the natural gas industry to employ process vessels, systems, and methods for removing water, along with other contaminates, from the natural gas stream that is produced from a subterranean formation. This basic concept is referred to generally as “dehydration” which can be accomplished in multiple ways. One of the methods of dehydration that is particularly effective in producing very dry gas is the use of a desiccant in the form of deliquescing salts. Deliquescence is a process wherein a solid chemical, such as a salt, is dissolved gradually and becomes liquid by attracting and absorbing moisture from gas passing in contact with it. Gas dehydration by the process of deliquescence is well known and frequently used in industry, particularly in applications where a very dry gas is required. Free water entrained in natural gas can be removed in a variety of ways, such as by a hydrocyclone. However, by the process of deliquescence, soluble water can be removed to effectively reduce the dew point.
In the typical application of deliquescence as a dehydration process, a bed of deliquescing salts is provided within a dehydration vessel through which the wet gas passes. As the wet gas contacts the deliquescing salts, water is absorbed from the gas stream. In the process, the salts are dissolved forming a liquid salt solution (brine) that passes downwardly into a lower portion of the vessel. Dry gas having passed through the bed of deliquescing salts is then discharged through a dry gas outlet. The dissolved deliquescing salts (brine) that collect as a liquid are typically in a highly concentrated form. A problem that has been encountered with using deliquescence as a dehydration method is that brine accumulated in the process has a strong tendency to recrystallize—that is, to form solids that are difficult to remove from a treating vessel.
The essence of the invention herein is a method of reducing the recrystallization of the brine and that improves the gas dehydration process by accomplishing these three functions: 1) the brine solution absorbs additional water from the wet gas stream when they contact with sufficient turbulence, theoretically, the brine solution can absorb up to 30% more water; 2) when this water is absorbed from the wet inlet gas stream, the brine solution is no longer saturated and is less likely to crystallize due to process temperature changes; and 3) by using the concentrated brine solution to promote additional water absorption from the wet gas stream, the amount of deliquescing salt required will be reduced by as much as 30%.