TECHNICAL FIELD

This disclosure relates to glycol regeneration in relation to gas dehydration.

BACKGROUND

When produced from a reservoir, natural gas usually contains some water and is typically completely saturated or at the water dew point. This water can cause problems for downstream processes and equipment. For example, the water can either freeze in piping or form hydrates with carbon dioxide and hydrocarbons (such as methane hydrates). Gas dehydration units depress the hydrate formation point of the gas through water removal. One example of a gas dehydration unit is a glycol dehydration unit, in which glycols are used to dehydrate the gas. Without dehydration, a free water phase (liquid water) could also drop out of the natural gas as it is either cooled or the pressure is lowered through equipment and piping. This free water phase often contains some portions of acid gas (such as hydrogen sulfide and carbon dioxide) and can cause corrosion.

SUMMARY

This disclosure describes technologies relating to glycol regeneration in relation to gas dehydration. The subject matter described in this disclosure can be implemented in particular implementations, so as to realize one or more of the following advantages over traditional glycol dehydration processes. Glycol losses (for example, by escaping with the dehydrated gas) can be reduced. Purity of the regenerated glycol can be increased. Emissions of toxic compounds (such as sulfur dioxide) can be reduced. The amount of gas sent to the flare from the glycol dehydration process can be reduced. Operating costs associated with the glycol dehydration process can be reduced.

Certain aspects of the subject matter described can be implemented as a method. By a glycol contactor, a glycol stream is contacted with a wet gas stream including water to transfer at least a portion of the water from the wet gas stream to the glycol stream. The glycol stream entering the glycol contactor includes a mixture of triethyelen glycol and tetraethylene glycol. The glycol stream exiting the glycol contactor includes the portion of the water from the wet gas stream. The glycol stream exiting the glycol contactor is flowed to a glycol regeneration system. By the glycol regeneration system and using a solvent including iso-octane, the glycol stream is fractionated to remove the portion of the water from the glycol stream. The fractionated glycol stream is recycled to the glycol contactor.

This, and other aspects, can include one or more of the following features.

The glycol stream including the water from the wet gas stream can be received as feed at a first stripping column section of the glycol regeneration system. A first overhead stream including the iso-octane and the water can be discharged from the first stripping column section. A first bottoms stream can be discharged from the first stripping column section. The first bottoms stream can be received as feed at a second stripping column section of the glycol regeneration system. A second overhead stream can be discharged from the second stripping column section. A second bottoms stream including the triethylene glycol and tetraethylene glycol can be discharged from the second stripping column section. The second overhead stream can be received at the first stripping column section. A first portion of the iso-octane of the first overhead stream can be recycled to the first stripping column section. A second portion of the iso-octane of the first overhead stream can be recycled to the second stripping column section.

The mixture of triethylene glycol and tetraethylene glycol can include from approximately 10 weight percent (wt. %) to approximately 30 wt. % of tetraethylene glycol.

The mixture of triethylene glycol and tetraethylene glycol can include approximately 20 wt. % of tetraethylene glycol.

The second bottoms stream can be the fractionated glycol stream recycled to the glycol contactor.

The second bottoms stream can include less than 0.1 wt. % of iso-octane.

The iso-octane and the water of the first overhead stream can be separated before recycling the first and second portions of the iso-octane.

A mass ratio of the first portion to the second portion can be in a range of from approximately 1:5 to approximately 1:10.

Certain aspects of the subject matter described can be implemented as a method. A stream including one or more glycols and water is received as feed at a first stripping column section. A first overhead stream including iso-octane and the water is discharged from the first stripping column section. A first bottoms stream is discharged from the first stripping column section. The first bottoms stream is received as feed at a second stripping column section. A second overhead stream is discharged from the second stripping column section. A second bottoms stream including the one or more glycols is discharged from the second stripping column section. The second overhead stream is received at the first stripping column section. A first portion of the iso-octane of the first overhead stream is recycled to the first stripping column section. A second portion of the iso-octane of the first overhead stream is recycled to the second stripping column section.

This, and other aspects, can include one or more of the following features.

The stream can include a mixture of triethylene glycol and tetraethylene glycol.

The mixture of triethylene glycol and tetraethylene glycol can include from approximately 10 wt. % to approximately 30 wt. % of tetraethylene glycol.

The mixture of triethylene glycol and tetraethylene glycol can include approximately 20 wt. % of tetraethylene glycol.

The second bottoms stream can include less than 0.1 wt. % of iso-octane.

The iso-octane and the water of the first overhead stream can be separated before recycling the first and second portions of the iso-octane.

A mass ratio of the first portion to the second portion can be in a range of from approximately 1:5 to approximately 1:10.

Certain aspects of the subject matter described can be implemented as a gas dehydration system. The gas dehydration system includes a glycol contactor and a glycol regeneration system. The glycol contactor is configured to receive a wet gas stream including water. The glycol contactor is configured to receive a glycol stream including a mixture of triethylene glycol and tetraethylene glycol. The glycol contactor is configured to dehydrate the wet gas stream by contacting the wet gas stream with the glycol stream. The glycol stream exiting the glycol contactor includes at least a portion of the water from the wet gas stream. The glycol regeneration system is configured to remove the portion of the water from the glycol stream such that the glycol stream can be recycled to the glycol contactor. The glycol regeneration system includes a first stripping column section and a second stripping column section. The first stripping column section is configured to receive the glycol stream including water as feed. The first stripping column is configured to discharge a first overhead stream including iso-octane and the portion of the water. The first stripping column is configured to discharge a first bottoms stream. The second stripping column is configured to receive the first bottoms stream as feed. The second stripping column section is configured to discharge a second overhead stream. The second stripping column section is configured to discharge a second bottoms stream including the glycol stream free of the portion of the water. The first stripping column section is configured to receive the second overhead stream and a first portion of the iso-octane of the first overhead stream. The second stripping column is configured to receive a second portion of the iso-octane of the first overhead stream.

This, and other aspects, can include one or more of the following features.

The mixture of triethylene glycol and tetraethylene glycol can include approximately 10 wt. % to approximately 30 wt. % of tetraethylene glycol.

The mixture of triethylene glycol and tetraethylene glycol can include approximately 20 wt. % of tetraethylene glycol.

The second bottoms stream can include less than 0.1 wt. % of iso-octane.

The details of one or more implementations of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

