Mixer for removing impurities from gases and liquids

A vessel for mixing a fluid with a reagent as the fluid flows through the vessel includes a vessel wall that encloses an interior volume. The vessel includes a first end, a second end spaced, and an axis that extends from the first end to the second end. The axis is configured to intersect and form an angle with a reference plane. The vessel also includes a fluid inlet proximate the first end through which the fluid enters the interior volume, a fluid outlet proximate the second end through which the fluid exits the interior volume, a port through which the reagent enters the interior volume, and at least one packing material positioned within the interior volume between the fluid inlet and the fluid outlet. The packing material randomly distributes the fluid and the reagent as the fluid flows through the vessel from the fluid inlet towards the fluid outlet.

BACKGROUND

The present invention relates to vessels for mixing a fluid with a reagent, catalyst or other chemical.

Typically, when natural gas or other hydrocarbons are produced from a well, the gas and hydrocarbons must undergo some initial treatment to make it suitable for transportation in pipelines and other methods of conveyance. This treatment may include the removal of water, brine, and/or other impurities that may be produced concurrently with the natural gas and hydrocarbons.

For example, it is not uncommon for natural gas to include anywhere from trace amounts to high concentrations of hydrogen sulfide gas (H2S) or other impurities. In the case of H2S, it is inflammable, toxic to people, and corrosive to many metals. Because of its corrosive effects on metals, most pipeline operators establish maximum concentrations of H2S that are permissible in any feed stock introduced into their pipelines. Thus, any excess H2S must be removed from natural gas before it can be transported via these pipelines.

Typically, and in the case of H2S, stripping agents or strippers are mixed with the natural gas produced from a well. This mixing typically occurs in a stripping tower, typically a vertical tower. The natural gas is introduced at the bottom and allowed to travel upward while the stripping agent is introduced near the top of the tower and allowed to travel downward. The natural gas and the stripping agent interact in the tower, thereby lowering the concentration of H2S within the natural gas that exits near the top of the tower. Optionally, mechanical agitators may be included as part of the tower to affect the reaction of the natural gas with the stripping agent.

These vertical towers, however, require a large footprint and typically are fixed installations. Thus, they are expensive to manufacture and maintain. This cost, in turn, tends to be prohibitive for those wells that produce relatively smaller amounts of natural gas. Further, energy to power mixers and agitators may be limited at a well site.

Thus, there is need for a relatively lower cost mixing vessel that reduces or eliminates the need for an electrical source of power and relies upon passively created pressure gradients and “static” mixing (i.e., without the use of powered pumps or mixers). Further, there is a need for a mixer that has a smaller footprint than others known in the art. In particularly, there is a need for mixers that can be mounted to a pallet and transported to a well site for use singly or in series with other similar mixers.

BRIEF SUMMARY

A vessel for mixing a fluid with a reagent as the fluid flows through the vessel includes a vessel wall having an outer surface and an inner surface spaced apart from the outer surface, thereby enclosing an interior volume. The vessel includes a first end, a second end spaced apart from the first end, and an axis that extends from the first end to the second end. The axis is configured to intersect and form an angle with a reference plane, wherein the angle is between zero degrees and 20 degrees. The vessel also includes a fluid inlet proximate the first end through which the fluid enters the interior volume, a fluid outlet proximate the second end through which the fluid exits the interior volume, a port through which the reagent enters the interior volume, and at least one packing material positioned within the interior volume between the fluid inlet and the fluid outlet, the packing material configured to randomly distribute the fluid and the reagent as the fluid flows through the vessel from the fluid inlet towards the fluid outlet.

In another embodiment, a vessel for mixing a fluid with a reagent as the fluid flows through the vessel includes a vessel wall having an outer surface and an inner surface spaced apart from the outer surface. The vessel wall is configured to enclose an interior volume. The vessel includes a first end positioned a first height above a reference plane, a second end spaced apart from the first end, the second end being positioned a second height above the reference plane, and an axis that extends from the first end to the second end. A fluid inlet is proximate the first end through which the fluid enters the interior volume and a fluid outlet is proximate the second end through which the fluid exits the interior volume. At least one reagent enters the interior volume through a port. A first packing material and at least a second packing material are positioned within the interior volume between the fluid inlet and the fluid outlet. Each of the first packing material and the second packing material have a first end having a packing material inlet and a second end spaced apart from the first end, the second end having a packing material outlet. The packing material outlet of the at least second packing material is positioned asymmetrically relative to the packing material outlet of the first packing material.

In an embodiment of a method of using the disclosed vessels includes mixing a natural gas that includes an impurity at a first concentration with a stripping agent that reacts with the impurity so as to reduce the first concentration of the impurity within the natural gas to a second concentration. The mixing occurs within a vessel having a first end and a second end spaced apart from the first end. The method includes introducing the natural gas into an interior volume of the vessel through a fluid inlet proximate the first end of the vessel, introducing the stripping agent into the interior volume of the vessel through a port, and passing the natural gas and the stripping agent into a first packing material via a first packing material inlet and out of the first packing material via a first packing material outlet. The method further includes passing the natural gas and the stripping agent into at least a second packing material via a second packing material inlet and out of the second packing material via a second packing material outlet oriented asymmetrically relative to the first packing material outlet. The method then removes the natural gas from the interior volume via a fluid outlet port positioned downstream of the second packing material. In some embodiments, the method comprises creating a pressure gradient within the natural gas between the first end and the second end of the vessel.

Various embodiments of the present inventions are set forth in the attached figures and in the Detailed Description as provided herein and as embodied by the claims. It should be understood, however, that this Summary does not contain all of the aspects and embodiments of the one or more present inventions, is not meant to be limiting or restrictive in any manner, and that the invention(s) as disclosed herein is/are and will be understood by those of ordinary skill in the art to encompass obvious improvements and modifications thereto.

Additional advantages of the present invention will become readily apparent from the following discussion, particularly when taken together with the accompanying drawings.

DETAILED DESCRIPTION

Illustrated inFIGS. 1-7is a vessel10for mixing a fluid with a reagent as the fluid flows through the vessel. The vessel is suitable for mixing any type of fluid, either liquid or gas, with one or more reagents, catalysts, fluids (liquid or gas), or solids.

As just one non-limiting example, the fluid may be a mixture of produced fluids from an oil or gas well. As is known, produced fluid from an oil or gas well typically includes fluids in a gaseous phase, a liquid phase, and sometimes both. The produced fluid often includes hydrocarbons with hydrocarbon chains of varying length. In addition, the produced fluid may contain water and, perhaps, other impurities such as hydrogen sulfide (H2S).

The vessel10includes a vessel wall12having an outer surface14and an inner surface16spaced apart from the outer surface14. The vessel wall12is configured to enclose an interior volume18. The vessel wall12may be made of most known materials, and typically is formed of a metal that is non-reactive or minimally reactive with any fluids and reagents within the interior volume, or is otherwise provided with special treatments and/or coatings to protect the metal. For example, the inner surface16of the vessel wall12optionally includes a coating that provides protection to the vessel wall10from the fluid and any reagent present within the interior volume18. The vessel10also includes a first end20and a second end22spaced apart from the first end20.

Optionally, the vessel wall12may be jacketed with elements (not illustrated) that either heat or cool the outer surface of the vessel wall12. The heating or cooling elements may be used to more precisely control the temperature and, consequently, any temperature dependent reactions, within the interior volume18of the vessel10.

The vessel10optionally includes one or more legs that support and, in some instances, are coupled to the outer surface14of the vessel wall12. As illustrated, the vessel10includes a first leg23proximate the first end20and a second leg24spaced apart from the first leg23and, in this instance, proximate the second end22. Each leg23,24, optionally includes a cradle21to support the vessel10. The cradle21may be coupled to the outer surface14of the vessel wall12via brackets, as illustrated. The height H1of the first leg23is less than the height H2of the second leg24as measured from a reference plane28. In most instances, the reference plane28is the ground, a concrete pad, or other typically level surface, such as a frame, upon which the vessel is mounted. Consequently, the first end20of the vessel10is positioned a first height25above the reference plane28and the second end22is positioned a second height27above the reference plane28, as illustrated inFIG. 3. Of course, one will understand that the opposite can be true (i.e., H1is greater than H2), or that the heights of the legs23,24can be the same. The legs23,24are illustrated as triangular bar stock, but can be of any shape and made of any material.

An axis26(FIGS. 3 and 7) extends from the first end20to the second end22. The axis26is configured to intersect and form an angle30with the reference plane28. The angle30is between zero degrees inclusive and 20 degrees, inclusive. More preferentially, the angle30is between 5 degrees inclusive, and 15 degrees, inclusive, and yet still more preferentially, the angle30is between 8 degrees inclusive, and 12 degrees, inclusive. Positioning the vessel10at an angle30creates a pressure gradient within the interior volume18of the vessel10without the use of mixers, agitators, pumps, or other mechanical systems. Further, the angle30and the consequent pressure gradient is a function of the rate at which the fluid and reagent interact. In other words, the angle30can be optimized as a function of the mass-balance equation between the fluid and the reagent.

It is noted that while the pressure gradient primarily is created passively as described above, the vessel10may include pumps, agitators, and mixers (not illustrated) to create and/or maintain a pressure gradient and to further enhance the mixing of the fluid and the reagent as described below.

The vessel10, as illustrated, is an elongated cylinder, with a length along the axis26much greater than its width or diameter between the top and the bottom of the vessel. Of course, the vessel10can include other dimensions and shapes, including spherical, square, rectangular, and others.

The vessel10includes fluid inlet32proximate the first end20through which the fluid enters the interior volume18. Optionally, the vessel10includes an auxiliary fluid inlet33also typically proximate the first end20and through which the fluid or another fluid or reagent may enter the interior volume18. Optionally, a diffuser31is coupled to at least one of the fluid inlet32and the auxiliary fluid inlet33. The diffuser31diffuses the fluid passing through the fluid inlet32, for example, over a greater area and more randomly than would otherwise occur without the diffuser31. Once passing through the vessel10, the treated fluid exits the interior volume18through a fluid outlet34proximate the second end22.

The vessel10also optionally includes at least one of a pressure relief valve40typically positioned proximate the second end22to relieve excess pressure during atypical circumstances, and a fluid drain42typically positioned proximate the first end20to empty the vessel10for maintenance and before transporting the vessel10.

A port36permits the reagent to enter the interior volume18. Typically, the port36is positioned proximate the first end20, but it may be positioned elsewhere along the vessel10.

The vessel10includes at least one of a fluid level detector,38, which can include at least one of a fluid level sensor and a viewing port configured to provide a user with a level of the fluid within the vessel10. A fluid level sensor may be of any type known in the art, while a viewing port may include an observation window through which a user may optically view the level of the fluid.

Within the vessel10, at least one packing material50(FIGS. 9 and 10) is positioned within the interior volume18between the fluid inlet32and the fluid outlet34. In some embodiments, the vessel10includes a first packing material50and at least a second packing material50. The packing material50is configured to randomly distribute the fluid and the reagent as the fluid flows through the vessel10from the fluid inlet32towards the fluid outlet34. The packing material50includes a first end52with a packing material inlet53and a second end54with a packing material outlet55spaced apart from the first end52as defined by the flow of fluid through the packing material50from the first end52to the second end54. At least the packing material outlet55may be of any shape and orientation, include perforated screens or plates in which the perforations or openings are randomly positioned or concentrated in one portion or area of the outlet.

Optionally, the packing material outlet55of the at least second packing material50is positioned asymmetrically relative to the packing material outlet55of the first packing material50. Positioning the outlets asymmetrically aids in redistribution the fluid and reagent about the interior volume18, which better ensures mixing between the fluid and the reagent and reduces the risk of channeling of the flow of the fluid and/or reagent in such a way that reduces, and possibly prevents, mixing of the fluid and reagent.

The packing material50may be formed, typically, from a material that is minimally or non-reactive with the fluid and the reagent. For example, the packing material50may be of various types of plastics, non-reactive metals (e.g., stainless steel), ceramics, and other materials. Further, the packing material50may be of any shape, including spheres, oblong, and irregular shapes, provided that it assists in distributing the fluid and the reagent randomly within the interior volume18as the fluid and reagent travel between the fluid inlet32and the fluid outlet34. Just a few, non-limiting examples of the packing material include at least one of a Pall ring as illustrated inFIGS. 9 and 10, Bialecki ring, Raschig ring, Intalox saddle, and Berl saddle, and any combinations of these packing materials as well as others.

Optionally, the vessel10includes a retention device,60, that retains or maintains at least one of a position and an orientation of the packing materials50within the interior volume18. For example the retention device60, may be a wire, mesh, or perforated basket. As illustrated, the retention device60is cylindrical in shape to conform partly to the interior volume18of the vessel10. Optionally, the retention device60includes a key that interacts with a complementary feature within or on the inner surface16of the vessel wall12to maintain the position and/or orientation of the retention device60. Similarly, an optional cross-member61coupled to the interior surface16of the vessel wall12may act to at least position and/or orient at least one of the retention devices60within the interior volume18.

The retention device optionally includes at least an outlet plate62with at least one opening64, as best illustrated inFIGS. 5 and 8. The outlet plate62may be integrally formed with the retention device60or may be a separate component coupled to the retention device60. The opening64is asymmetric relative to the overall shape of the outlet plate62.

As illustrated inFIGS. 5 and 8, the opening64is in the shape similar to that of a half-circle offset from the center line of the outlet plate62. Alternatively, the opening64may be of any shape and orientation, including perforated screens or plates in which the perforations or openings are randomly positioned or concentrated in one portion or area of the outlet plate62. InFIGS. 5 and 8, the openings64are orientated such that each opening64is asymmetric to the opening64of the adjacent retention device60and packing material55. As illustrated, the openings64are each rotated 90 degrees relative to the opening64of at least one of the preceding and succeeding outlet plates62. Other configurations to asymmetrically orient the openings64are of course possible, including rotating adjacent openings64either more or less than 90 degrees.

The opening64provides the same function as the packing material outlet55, discussed above, in that the opening64asymmetrically aids in redistributing the fluid and the reagent about the interior volume18, which better ensures mixing between the fluid and the reagent and reduces the risk of channeling of the flow of the fluid and/or reagent in such a way that reduces, and possibly prevents, adequate mixing of the fluid and reagent.

The outlet plate62may be used in addition to the packing material outlet55discussed above or as an alternative to the packing material outlet55. In some instances, the outlet plate62may be coupled directly to or be incorporated into the packing material50. Thus, in such an embodiment, the outlet plate62and the opening64actually comprise the packing material outlet55.

The vessel10optionally includes a seal70, such as a sealing ring. Typically, the seal or sealing ring70is positioned between at least one of adjacent retention devices60and packing materials50. The sealing ring70helps to ensure the fluid and reagent flows through at least one of the packing material50and the retention device60. The sealing ring70may be formed of metals—typically those that are non-reactive with the fluid and the reagent—elastomers, and other materials known to provide a seal.

With the structure of the vessel10explained, a non-limiting example of a method of mixing a fluid and a stripping agent or reagent are now discussed. While the method discussed is within the context of natural gas, particular natural gas as produced from a well, as the fluid treated within the vessel, it is understood that other fluids and treatments may be used with the vessel.

The method disclosed is for mixing a natural gas that includes an impurity at a first concentration with a stripping agent or reagent that reacts with the impurity so as to reduce the first concentration of the impurity within the natural gas to a second concentration. For example, the natural gas may include hydrogen sulfide, H2S, which typically must be removed or reduced sufficiently in concentration within the natural gas to permit the natural gas to be handled more safely and to be transported within pipelines or other methods of conveyance without the restrictions or special accommodations that the presence of H2S ordinarily requires. The mixing occurs within a vessel10as described above.

The natural gas, or the fluid, is introduced into the interior volume18of the vessel10through a fluid inlet32proximate the first end20of the vessel10. The stripping agent, such as an H2S stripping agent or scavenger, is introduced into the interior volume18of the vessel10through a port36.

The natural gas and the stripping agent passes into a first packing material50via a first packing material inlet52and out of the first packing material50via a first packing material outlet54. The natural gas and the stripping agent then passes into at least a second packing material50via a second packing material inlet52and out of the second packing material50via a second packing material outlet54oriented asymmetrically relative to the first packing material outlet54. Optionally, the packing material50is retained within a retention device60as described above.

The natural gas and the stripping agent move through the interior volume18of the vessel10under the action of a pressure gradient created between the first end20and the second end22of the vessel10. The pressure gradient may be created by positioning the first end20of the vessel10a first height25above the reference plane28and positioning the second end22of the vessel10a second height27above the reference plane28. Alternatively, the pressure gradient may be created by causing an axis26that extends from the first end20to the second end22of the vessel10to intersect and form an angle30with the reference plane28, wherein the angle30is between zero degrees and 20 degrees.

The natural gas with a reduced concentration of the impurity is then removed from the interior volume18of the vessel10via a fluid outlet port34positioned downstream of the second packing material50.

The present invention, in various embodiments, includes providing devices and processes in the absence of items not depicted and/or described herein or in various embodiments hereof, including in the absence of such items as may have been used in previous devices or processes, e.g., for improving performance, achieving ease and/or reducing cost of implementation.