KR101977426B1 - Method and apparatus for circulating a glycol stream containing a concentration of divalent cations, and method of producing a natural gas product stream - Google Patents

Abstract

The process stream containing the natural gas is carried along with the glycol-containing stream through the pipeline to a downstream location, and at a downstream location it is separated into at least an aqueous phase and a natural gas phase. The glycol is recovered from the aqueous phase to form a stream of recovered glycol. The stream of recovered glycol comprises at least a first portion and a second portion. The first portion of the recovered glycol is subjected to a chemical divalent cation removal step whereby the divalent cation is removed from the first portion of the glycol undergoing the chemical divalent cation removal step. The second portion of the recovered glycol did not undergo a chemical divalent cation removal step.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method and apparatus for circulating a glycol stream having a divalent cation concentration and a method for producing a natural gas product stream, and a method for producing a natural gas product stream. BACKGROUND OF THE INVENTION < RTI ID =

The present invention relates to a method and apparatus for recycling a glycol stream having a divalent cation concentration. In another aspect, the present invention is directed to a method of making a natural gas product stream.

The production pipeline from off-shore (mineral) hydrocarbon reservoirs to the ground or floating topside facility for processing the mixture to recover the desired hydrocarbon product, is composed of hydrocarbons including natural gas, water, and dissolved salts Glycol recycling is often used in connection with the transport of the mixture. Due to the changing physical conditions during the transfer of the pipeline, there is a problem that the fluid is formed in the fluid mixture of the pipeline and the line is clogged. One solution that is heavily applied to the hydrate formation problem is to add relatively low water content glycols (referred to as dilute glycols) to the subsea level < RTI ID = 0.0 > And then extracting the glycol as a so-called rich glycol from the process fluid at the topside facility. Abundant glycols have a higher water content than dilute glycols. The glycol often chosen for this purpose is monoethylene glycol (MEG), in which case the dilute glycol is referred to as lean MEG and the abundant glycol is referred to as abundant MEG.

From the operating cost and environmental standpoint, the glycol stream must be recycled. To this end, abundant MEGs are typically regenerated to form lean MEGs and then reused as hydration inhibitors in the production line. The abundant MEG usually contains a balance of hydrocarbons, high water levels, corrosion products, product chemicals, and mixtures of dissolved inorganic salts.

One of the major challenges associated with the maintenance of MEG loops is the presence of salts that can raise problems in glycol recycle loops such as injection points, production pipelines, and scaling of topside processing equipment. Thus, salt management is an important factor in glycol recirculation systems. In particular the two, such as Ca ^{2 +} cations are particularly important, since the solubility of salts formed from these divalent cations is due to the first, such as NaCl or KC1 is relatively low compared to the salts.

WO 2011/028131 discloses an apparatus and method for recovering MEG after using MEG as a hydration inhibitor in a gas and oil production line. The process fluid from the production line is separated to produce an aqueous fraction and a hydrocarbon fraction of abundant MEG. Divalent cations are precipitated from the aqueous fraction of abundant MEG by injecting chemicals such as NaOH or K ₂ CO ₃ or other materials to achieve sufficient alkalinity and heating of the aqueous fraction. The solid particles are removed from the aqueous fraction of abundant MEG by purging the liquid with a purging gas, and the foam formed on the surface of the aqueous fraction is removed. Subsequently, the MEG is regenerated to recover fractions of the lean MEG.

A disadvantage of the method disclosed in WO 2011/028131 is that it requires a relatively large amount of chemicals.

In a first aspect, the present invention provides a method of circulating a glycol stream having a concentration of divalent cations,

Conveying a process stream containing natural gas through a pipeline from an upstream location to a downstream location;

- injecting a glycol-containing stream into said pipeline at an injection point and carrying said glycol-containing stream with said process stream through said pipeline to said downstream location;

- separating said process stream with said glycol-containing stream into at least an aqueous phase and a natural gas phase in said downstream location, said aqueous phase containing at least a portion of a glycol derived from said glycol-containing stream, Separating the process stream with at least a portion of the natural gas from the process stream with the glycol containing stream into at least an aqueous phase and a natural gas phase;

Recovering the glycol from the aqueous phase to form a stream of recovered glycol wherein the step of recovering the glycol from the aqueous phase comprises the step of recovering the glycol from the aqueous phase, ; And

- transporting the recovered glycol stream to the injection point and adding the recovered glycol stream to the injected glycol containing stream,

Wherein the stream of recovered glycol comprises at least a first portion and a second portion and wherein the first portion of the recovered glycol is subjected to a chemical divalent cation removal step whereby the divalent cation is subjected to the chemical divalent cation removal step The second portion of the recovered glycol is not subjected to the chemical divalent cation removal step.

In another aspect, the present invention provides an apparatus for circulating a glycol stream having a concentration of divalent cations,

- a pipeline extending from said upstream position to said downstream position for conveying a process stream containing natural gas from an upstream position to a downstream position;

An injection point for injecting the glycol-containing stream into the pipeline and into the process stream;

An inlet separation system arranged in said downstream position to receive said process stream with said glycol containing stream and to separate said process stream with said glycol containing stream into at least an aqueous phase and a natural gas phase, The natural gas phase containing at least a portion of the natural gas from the process stream;

- a collection system inlet in fluid communication with the inlet separation system, the collection system being arranged to receive the aqueous phase through the recovery system inlet and to recover the glycol from the aqueous phase to form a stream of recovered glycol, A glycol recovery system further comprising a recovery system outlet for withdrawing a stream of glycol and comprising a chemical divalent cation removal unit arranged in a first path between the recovery system inlet and the recovery system outlet; And

And a glycol injection line fluidly connecting the withdrawal system outlet to the injection point and arranged to transport the withdrawn stream of glycol from the glycol recovery system to the injection point,

Wherein the glycol recovery system further comprises a second path between the withdrawal system inlet and the withdrawal system outlet and wherein the second flow path includes a first portion and a second portion of the recovered glycol stream, Wherein the first portion of the recovered glycol is passed through the chemical divalent cation removal unit such that the divalent cation is removed from the first portion of the glycol that has passed through the chemical divalent cation removal unit And the second portion of the recovered glycol does not pass through the chemical divalent cation removal unit.

In another aspect, the present invention provides a method of making a natural gas product stream,

Conveying a process stream containing natural gas through a pipeline from an upstream location to a downstream location;

Injecting a glycol-containing stream into said pipeline at an injection point and carrying said glycol-containing stream through said pipeline to said downstream location;

- separating the process stream with the glycol-containing stream into at least an aqueous phase and a natural gas phase in the downstream location, the aqueous phase containing at least a portion of the glycol derived from the glycol-containing stream, Separating the process stream with at least a portion of the natural gas from the process stream with the glycol containing stream into at least an aqueous phase and a natural gas phase;

Simultaneously recovering the glycol from the aqueous phase to form a stream of recovered glycol and further treating the natural gas phase to produce a natural gas product stream; And

Transporting the recovered glycol stream to the injection point and adding the recovered glycol stream to the injected glycol containing stream,

Wherein the step of recovering the glycol from the aqueous phase comprises a chemical divalent cation removal step wherein the stream of recovered glycol comprises at least a first portion and a second portion and wherein the first portion of the recovered glycol comprises Through the chemical divalent cation removal step, a divalent cation is removed from a first portion of the glycol undergoing the chemical divalent cation removal step, and the second portion of the recovered glycol is a glycol having a divalent cation concentration It does not undergo a chemical divalent cation removal step to circulate the stream.

Hereinafter, the present invention will be further described by way of example and with reference to the accompanying non-limiting drawings.

Figure 1 schematically illustrates a method and apparatus for circulating a glycol stream, including a glycol recovery system, in a method and apparatus for producing a natural gas product stream.
Figure 2 schematically illustrates a reference case of a glycol recovery system that does not comply with the present invention.
Figures 3-7 schematically illustrate various embodiments of a glycol recovery system, each of which may be used in embodiments of the present invention.

For purposes of this description, unless indicated otherwise, a single reference numeral will be assigned to the line as well as the stream carried by that line. Like numbers refer to like parts, streams or lines. While the invention is described herein with reference to one or more specific combinations of features and implementations, many of its features and implementations may be independently implemented in other embodiments, or in combination, equally or similarly It will be readily understood that it is functionally independent of other features and implementations.

This disclosure relates to the circulation of a glycol stream, which comprises injecting a glycol-containing stream into a pipeline at an upstream location, wherein the glycol-containing stream is conveyed through the pipeline to a downstream location with the process stream Injecting; Recovering the glycol at a downstream location; And re-transporting the stream of recovered glycol for regeneration to an upstream location. In the methods and apparatus described herein, only the first portion of the recovered glycol is subjected to a chemical divalent cation removal step, whereby the divalent cation is chemically removed from the portion of the glycol that is merely passing through the chemical divalent cation removal step. The second portion of the recovered glycol did not undergo the chemical divalent cation removal step, preferably any chemical divalent cation removal step, after its most recent injection into the pipeline.

As a result, the chemical consumption in the divalent cation removal step is less, and less amount of chemical is required to be injected. In addition, the equipment associated with performing the chemical divalent cation removal step can be kept smaller.

The chemical divalent cation removal step may be a wet chemical divalent cation removal step. This wet chemical divalent cation removal step allows the injection of the chemical into the glycol through the chemical divalent cation removal unit. Furthermore, handling of solid adsorbents can be avoided.

The concentration of divalent cations in the recovered glycol is higher than when all the recovered glycols undergo a chemical divalent cation removal step. However, as long as the amount of divalent cations removed is at least equal to the amount of divalent cations entering through the non-recycle portion of the process stream, the divalent cation load in the pipeline can be maintained below the preselected value have.

In a preferred mode of operation, the relative amount of glycol in the first portion is selected relative to the total amount of glycol recovered so that the concentration of divalent cations that have reached the pipeline at the downstream location is maintained below the preselected value. This can be accomplished typically by controlling the flow rate of the first portion of the glycol delivered to the chemical divalent cation removal step and the split ratio of the total flow rate of the glycol delivered to the stream of glycol recovered through the downstream location.

For the purposes of the present description, the term " recovered glycol ", which has been received at the downstream location from the pipeline, has once passed through the glycol recovery system and has been received at the downstream location from the pipeline, It is used for rare glycols that have not been re-injected. Although the recovered glycol stream does not preclude the inclusion of newly added glycols from other glycol sources, such glycols are not considered to be recovered glycols.

The chemical divalent cation removal unit typically comprises a chemical component injection system fluidly connected to a source of chemical components that is capable of reacting with a divalent cation.

Examples of divalent cations include Fe ^{2 +} , Ca ^{2 +} , Mg ^{2 +} , Ba ^{2 +} , and Sr ^{2 +} . In addition to these examples, other cations are also present. Ca < ^{2 +} > is considered to be most appropriate in the context of the present invention, since it is the most abundant divalent cation in normal formation water.

Returning now to Figure 1, there is shown an apparatus for circulating a glycol stream having a divalent cation concentration according to the present invention.

The pipeline 10 extends from the upstream position A to the downstream position B to convey the process stream 11 containing the natural gas from the upstream position A to the downstream position B. The pipeline has an upstream end 12 at an upstream location A and a downstream end 14 at a downstream location B. Typically, the pipeline 10 is in fluid communication with the hydrocarbon production chamber 5 via its upstream end 12.

An injection point 20 is provided at the upstream position A for injecting the glycol-containing stream into the pipeline 10 and the process stream 11 carried therein. In Figure 1, the injection point 20 is shown schematically in the pipeline 10 between the upstream end 12 and the downstream end 14, but this is not a requirement of the present invention. It may be located upstream of the upstream end 12, such as at the junction 15 between the hydrocarbon production chamber 5 and the upstream end 12 of the pipeline 10.

The upstream location (A) is often located at sea, but this is not a major requirement of the present invention. However, in many practical applications, glycol injection is preferred when transporting process streams containing natural gas and water through an underwater pipeline from an offshore location. The downstream position (B) can often be on shore as such, or at sea in a hydrocarbon processing platform such as a floating production, storage and unloading unit. There is typically a transfer zone C between the upstream position A and the downstream position B where essentially the process stream 11 is transported from the upstream position A to the downstream position B. On the other hand, the stream of the recovered glycol 50 is transported from the downstream position B to the upstream position A through the transporting zone C.

An inlet separation system (30) is provided at the downstream position (B). The pipeline 10 is connected to the inlet separator 30 through its downstream end 14. The inlet separation system 30 is arranged to receive the process stream with the injected glycol containing stream and to separate the process stream with the glycol containing stream into at least the aqueous phase 40 and the natural gas phase 60. The aqueous phase (40) contains at least a portion of the glycol derived from the glycol-containing stream. The natural gas phase need not consist solely of natural gas and contain at least a portion of the natural gas from the process stream.

An inlet separation system is known to those of ordinary skill in the art. As a non-limiting example, the inlet separation system 30 of FIG. 1 includes a high pressure separator 31 in the form of a three-phase separator, and a low pressure separator 37. High pressure separator 31 is fluidly connected to hydrocarbon condensate discharge line 32, high pressure aqueous phase discharge line 33, and high pressure gaseous discharge line 34. The low pressure separator is connected to the high pressure aqueous phase discharge line 33 via the selective heater 35 and the pressure reducing valve 36, respectively. In the low pressure separator 37, the high pressure aqueous phase 33 is separated into an aqueous phase and a low pressure gas phase, and a low pressure condensate, each of which is discharged from the low pressure separator 37. To this end, the low pressure separator is connected to a low pressure condensate top discharge line 38, a low pressure gaseous discharge line 39 and a low pressure aqueous phase discharge line 40.

The aqueous phase (40) from the inlet separation system (30) is withdrawn from the low pressure separator (37). One or both of the high pressure gaseous discharge line 34 and the low pressure gaseous discharge line 39 may be connected to the natural gas phase line 60 for conveying the natural gas phase to the natural gas processing system 200 as shown in dashed lines. For example, a pressure regulator selected from a pressure reducing valve, an expansion turbine, and a compressor may be inserted as needed to regulate the pressure in the high pressure gas phase and / or the low pressure gas phase to obtain the target natural gas processing pressure. Preferably, the high pressure gaseous discharge line 34 is connected to the natural gas phase line 60 because it optimally utilizes the pressure already available in the pipeline 10.

The high pressure separator 37 may typically be operated at a pressure of 40 to 100 bara, such as about 70 bara, and the low pressure separator may typically operate at 10 to 40 bara, e.g., about 25 bara. These pressures are examples and do not limit the present invention.

Also in the downstream position B, a glycol recovery system 100 is provided. The glycol recovery system 100 includes a recovery system inlet 105 in fluid communication with the inlet separation system 30. The glycol recovery system 100 is arranged to receive the aqueous phase 40 through the recovery system inlet 105 and also to recover the glycol from the aqueous phase 40 to form a stream of recovered glycol 50. The recovery system 100 further includes a withdrawal system outlet 107 for withdrawing the stream of recovered glycol 50. The glycol recovery system 100 includes a chemical divalent cation removal unit 130 arranged in a first flow path 110 extending from the recovery system inlet 105 to the recovery system outlet 107 via a divalent cation removal unit 130 ). The possible arrangement of the divalent cation removal unit 130 in the glycol recovery system 100 will be discussed in more detail below.

The apparatus described so far with reference to Fig. 1 comprises: from a starting point of the upstream position A to a downstream position B reaching as an enriched glycol stream via the transfer zone C; Through a regeneration process in which the rich glycol stream is regenerated to form a lean glycol stream; And then circulating the glycol stream in the form of a lean glycol stream from the downstream position B back to the beginning of the upstream position A via the transfer zone C. [

If desired, glycol storage means (not shown) may be provided in the glycol circulation loop. Typically, an enriched glycol storage tank may be provided to temporarily store the aqueous phase 40 at a downstream location B upstream of the glycol recovery system 100. In addition, a dilute glycol storage tank may be provided to temporarily store a stream of recovered glycol 50 at downstream location B prior to conveying the recovered glycol stream at upstream location A.

In operation, the natural gas containing process stream 11 is conveyed from the hydrocarbon production chamber 5 via the connection 15 through the pipeline 10 from the upstream position A to the downstream position B. The glycol-containing stream is injected into the pipeline 10 at the injection point 20 and carried with the process stream 11 through the pipeline 10 to the downstream position B. At the downstream location, the process stream 11, along with the glycol-containing stream, is separated into at least the aqueous phase 40 and the natural gas phase 60. The aqueous phase (40) contains at least a portion of the glycol derived from the glycol-containing stream. The natural gas phase (60) contains at least a portion of the natural gas from the process stream (11).

The glycol is recovered from aqueous phase 40 to form a stream of recovered glycol 50 and the recovery of glycol from aqueous phase 40 is carried out in a chemical divalent cation removal step carried out in chemical divalent cation removal unit 130 .

The recovered glycol 50 is carried in a glycol injection line which fluidly connects the withdrawal system outlet 107 at the downstream position B with the injection point 20 at the upstream position A. [ The glycol injection line is arranged to transport the withdrawn stream of glycol 50 from the glycol recovery system 100 to the injection point 20. Thus, the stream of recovered glycol 50 is transported to the injection point 20 and added to the injected glycol-containing stream.

A natural gas processing system 200 in fluid communication with the inlet separation system 100 is provided. The natural gas processing system 200 is adapted to receive the natural gas phase 60 through the processing system inlet 205 and to further process the incoming natural gas phase 60 to form the natural gas product stream 70 . Thus, the natural gas processing system 200 further includes a processing system outlet 207 for discharging the natural gas product stream 70.

Various types of natural gas processing systems are known to those of ordinary skill in the art, and the particular choice of the appropriate type depends on demand and requirements. For example, the natural gas processing system 200 may include a dew pointing unit, a dewatering unit, an acid gas removal unit, a mercury removal unit, a natural gas liquid extraction unit, a cooling unit, a liquefaction unit, a nitrogen removal unit, Unit may include one or more gas processing units in the natural gas processing flow passage 202 extending between the processing system inlet 205 and the processing system outlet 207. [

Turning now to Figures 2-7, some examples of glycol recovery systems that can be used as the glycol recovery system 100 in Figure 1 are shown. All systems include a chemical divalent cation removal unit 130 arranged in a first flow path 110 between the recovery system inlet 105 and the recovery system outlet 107. The chemical divalent cation removal unit 130 includes a chemical component injection system 132 fluidly connected to a source 133 of chemical components. The chemical component is preferably capable of reacting with a divalent cation to form a solid phase reaction product. When a chemical moiety is injected into the first portion of the glycol through the chemical divalent cation removal step 130, the chemical moiety can react with at least a portion of the divalent cations present in the first moiety of the glycol.

The reacted divalent cations may be removed from the chemical divalent cation removal unit 130 in the form of a slurry stream 136. To this end, the chemical divalent cation removal unit 130 may comprise means for separating the slurry from the liquid bulk 138, preferably a glycol centrifuge (not shown). The liquid bulk 138 is also exhausted from the chemical divalent cation removal unit 130 containing an aqueous phase, including the glycol, from which the slurry stream 136 has been removed. The liquid bulk 138 is then also conveyed through the glycol recovery system 100 towards the withdrawal system outlet 107. The slurry stream 136 may be pumped off for further processing and / or disposal.

Suitably, the chemical component is an alkali component. In such a case, the glycol recovery system 100 preferably includes an acid injection system 162 for injecting acid into the glycol 50 recovered to neutralize the alkalinity caused by the injection of the alkaline component. The acid injection system 162 is fluidly connected to the acid source 163. The acid suitable for this purpose is HCl, but other acids may also be used freely and selectively.

The alkali component may be selected from the group consisting of, for example, alkaline hydroxides (for example, potassium hydroxide and sodium hydroxide) and alkaline carbonates (for example, potassium carbonate), and combinations thereof. Hydroxides may be selected if there is sufficient CO ₂ in the chemical divalent cation removal unit 130 (typically introduced via the aqueous phase 40) in the aqueous phase 40 as the hydroxide reacts to form the carbonate. If there is an insufficient amount of CO ₂ in the chemical divalent cation removal unit 130 to form the carbonate, an alkaline carbonate may be preferred.

Suitably, the alkali component is injected at an alkali injection rate sufficient to ensure that the pH inside the chemical cation removal unit 130 is sufficiently high for divalent cations to form precipitates. Generally, this requires a pH value within the chemical cation removal unit 130 of at least about 8.0, more typically at least about 8.9. When all the divalent cations are precipitated, it is not necessary to further increase the alkali injection rate. Generally, pH values above 10.0 are unnecessary and wasteful for alkaline components.

Figure 2 relates to a reference case not according to the invention. In addition to the chemical divalent cation removal unit 130, the reference case includes a regenerator 140 and an optional reclamation unit 150.

The regenerator 140 is arranged to separate water from the glycol in the regeneration step. This regenerator 140 may be arranged in the glycol recovery system 100 between the chemical divalent cation removal unit 130 and the recovery system outlet 107 as shown in the embodiment of FIG. 2, And downstream of the cation removal step.

As known to one of ordinary skill in the art, the central element in this regenerator 140 is typically a glycol distillation column. Water evaporates from the glycol-containing aqueous phase 40 and water vapor with very low concentrations (e.g., less than 1,000 ppm by weight) of glycol is discharged as an overhead stream from the glycol distillation column. The water vapor is typically condensed in a reflux condenser and fed to the reflux drum. Any unconcentrated vapor 142 may be moved to a flare or discarded in any other suitable manner. Some of the condensed liquid is fed back to the top of the glycol distillation column as a reflux stream (typically assisted by the reflux pump); The remainder exits the regenerator 140 as a resulting water stream 144 and is further processed. A small hydrocarbon condensate stream 146 may also be withdrawn from the reflux drum and discarded. The dilute glycol is discharged from the bottom of the glycol distillation column, some of which is reboiled and sent back to the glycol distillation column as stripping vapor. The remainder of the dilute glycol may be discharged from the regenerator 140 in the form of a regenerated glycol stream 148. The above-described types and other types of regenerators are well known to those of ordinary skill in the art, and further explanation is not required in connection with the present disclosure.

The optional reuse unit 150 is typically a distillation reclamation unit and serves to perform a reuse step of reusing the glycol from the salt by chemical rather than distillation. Here too, the monovalent, highly soluble salt is removed from the glycol.

Reuse units for this purpose are well known to those of ordinary skill in the art. Typically, the glycol is flash separated from the flash separator by reducing the pressure to preferably sub-atmospheric pressure. Salt-free dilute glycols are typically flushed off the flash separator as an overhead stream that is subsequently condensed for further use. The stream of non-salt lean glycol exits the reuse unit via line 158. A mixture of crystallized salts and glycol flows out from the bottom of the flash separator. After removing the crystalline salt from the mixture (typically using centrifugation techniques), the glycol is heated and recycled back to the flash separator either as a separate stream or along with the glycol feed stream. A recycle pump may be used to assist in recycling. The salt is removed from the process through the salt line 152 for further processing and disposal.

A defoaming agent may be used upstream of the regenerator 140 and / or the optional rehearing unit 150 to prevent foaming in the regenerator and selective reheating unit. It is expected that these defoamers may only be needed occasionally during certain upset situations.

The optional reuse unit 150 may be provided between the recovery system inlet 105 and the regenerator 140, if provided, or between the regenerator and the recovery system outlet 107, as shown in the embodiment of FIG. 2, As shown in FIG. In the reference case of Fig. 2, it is not necessary for the entire glycol to pass through the reusing unit 150. Fig. For example, only slipstream 151 of 10-50% of the regenerated glycol stream 148 passes through the reuse unit 150 and the remainder bypasses the reuse unit 150 via the reuse unit bypass line 155 do. The percentage entering the slipstream is determined by how much salt needs to be removed to maintain the desired target content of salt in the recovered glycol stream 50. This slip stream arrangement may also be applied to embodiments in which the optional recycling unit 150 is disposed in the glycol recovery system 100 between the recovery system inlet 105 and the regenerator 140. Alternatively, the optional reac- tion unit 150 may be arranged so that all of the glycol recovered in the recovered glycol stream passes through the reuse unit 150, similar to the regenerator 140. [

The optional reuse unit 150, if provided, is preferably provided between the chemical divalent cation removal unit 130 and the recovery system outlet 107, as shown in the embodiment of FIG. 2, And downstream of the cation removal step. The reuse unit 150 also removes most of the alkalinity from the glycol due to its distillation nature, so that the reuse unit 150 can be removed in the chemical divalent cation removal step and / or in the glycol recovery system 100 downstream of the unit 130, , The remainder of the added alkali component is removed with a salt. In the embodiment using acid component injection, an additional advantage is that the chemical consumption in the form of acid consumption is advantageously reduced at the same time.

In the reference case of FIG. 2, there is no available second flow path from the withdrawal system inlet 105 to the withdrawal system outlet 107 via the recovery system 100, bypassing the chemical divalent cation removal unit 130, It can be seen that all of the recovered glycol 50 must pass through the chemical divalent cation elimination unit 130. Likewise, all of the recovered glycol 50 must pass through the regenerator 140. However, since there is an available reuse unit bypass line 155, it is possible that not all of the recovered glycol 50 passes through the reuse unit 150.

Turning now to Figures 3-7, various embodiments that may be utilized in the present invention are shown. In this embodiment, the regenerator 140 and the optional reuse unit 150, and the selective acid injection system 162 may be provided as described above with reference to FIG. A chemical divalent cation removal unit 130 is also provided with the chemical component injection system 132 and the source 133. However, an essential difference between the embodiment according to the present invention and the reference case is the presence of a second flow path extending between the withdrawal system inlet 105 and the withdrawal system outlet 107, the second flow path being a chemical divalent cation removal Bypasses the unit 130. In the figures, the second flow path follows the desalination bypass line 125. The first flow path does not pass through the desalination bypass line 125 but instead follows a desalinization slip stream 111 that is guided through at least the chemical divalent cation removal unit 130.

As such, the stream of recovered glycol 50 is separated from the first portion of the recovered glycol that has passed through the minimal, chemical divalent cation removal unit 130 and the first portion of the recovered glycol that has not passed through the chemical divalent cation removal unit 130 As shown in FIG. In fact, the second part moving through the desalination bypass line 125 did not pass through any chemical desalination device and / or step.

Only the first portion of the glycol is split and passes through the chemical divalent cation removal unit 130 in the form of a desalting slipstream 111. As a result, the consumption rate of the chemical in the chemical divalent cation removal unit 130 is lower and much less chemical flow is required through the chemical component injection system 132. [ Furthermore, optional other equipment associated with the chemical cation removal unit 130, and any chemical source removal source, such as any source of supply for the chemical component (s) used in the chemical divalent cation removal unit 130, Can be made smaller due to the lower flow rate.

As shown in FIG. 3, the division of the first part of the glycol is controlled by the controller 108. The controller 108 compares the total flow rate of the glycol delivered to the stream of glycol 50 recovered via the glycol recovery system (e.g., in line 40) To control the relative flow rate of the first portion of the first fluid. The controller cooperates with a flow control valve 109, for example, arranged in a desalination slipstream line 111 to control the relative flow rate of the first part of the glycol delivered to the chemical divalent cation removal unit 130 It is possible.

The relative flow rate may be controlled in response to the concentration of the divalent cations reaching the pipeline 10 at the downstream location (B). The relative flow rate of the glycol in the first portion compared to the total flow rate of the recovered glycol is controlled such that the concentration of divalent cations reaching the pipeline 10 at the downstream location B is maintained at a selected value below the preselected value . In doing so, in principle, steady state operation can be achieved so that any additional load of divalent cations entering the pipeline 10, in addition to the divalent cations injected with the glycol-containing stream, Lt; / RTI >

A preselected value may be preselected to remove scaling in the player 140. [ Generally, scaling is prevented if the concentration of each divalent cation in the rich glycol passing through the regenerator is below the saturation level in the operating conditions (including pH value, pressure, temperature, etc.) experienced by the regenerator 140. It may be determined by any method that is well within the ordinary skill in the art, including by experimental or computational methods.

The saturation level itself may be affected by controlling the pH value of the aqueous phase 40. The pH value of the aqueous phase 40 may be controlled by controlling the injection rate of the selective acid in response to the pH value. Preferably, the target pH value is set low enough to achieve the desired saturation level. Suitably, the target pH value is in the range of 5.5 to 6.9. Thus, an infusion rate controller is provided and may be coupled to a pH sensor capable of generating a pH signal indicative of the pH value of the aqueous phase 40 and to a flow control valve in the acid injection system 162 (not shown) ). The pH value may be set from a signal generated by a suitable sensor in any suitable stream, but any location downstream of the pipeline 10 and upstream of the regenerator 140 is preferred.

Thus, the acidity (pH value) of the feed stream to the regenerator 140 is preferably controlled to help prevent scaling in the regenerator as a result of higher concentrations of divalent cations circulating with the glycol.

The relative amount of glycol in the first portion compared to the total flow of glycol 50 recovered so that the concentration of divalent cations supplied to the regenerator 140 (and / or the regeneration step) is maintained at a selected value below the preselected maximum value If the regenerator 140 is provided by controlling the flow rate, scaling can be prevented more directly.

The controller 108 and its operation as described with reference to Fig. 3 may also be applied to other embodiments including the embodiment shown in Figs. 4-7.

It can be seen that the regenerator 140 is arranged such that both the first and second portions of the stream of glycol 50 recovered at the glycol recovery system outlet 107 pass through the regenerator 140 and / or the regeneration step.

On the other hand, the selective reuse unit 150 may be in one or both of the first flow path and the second flow path. In an advantageous embodiment, all (or most) of the first part of the recovered glycol passed through the chemical divalent cation removal step and / or unit 130 has passed the reuse step (e.g., FIGS. 3 and 4). As such, the reuse step also removes alkaline chemicals from the glycol present in the liquid bulk 138, so that the amount of selective acid injection (if applied) can be reduced. Thus, if the entire portion of the glycol does not need to pass the reuse step for salt removal, rather than allowing the first part or a portion of the first part to bypass the reuse step, the second part of the recovered glycol is re- It is a better choice to be able to circumvent.

As shown in the embodiment of Figs. 3 and 4, the selective reuse unit 150 is provided in the first flow path, not in the second flow path. In this arrangement, the first portion of the recovered glycol 50 (the portion through which the chemical divalent cation removal unit and / or the step passes) also passes through the optional reuse unit 150 and / or step (chemical divalent cation The second portion of the recovered glycol stream 50 (not passing through the removal unit and / or step) did not pass through the optional reuse unit 150 and / or step. This permits maximum removal of the alkali component added to the chemical demetallization unit 130 and at the same time allows for minimization of the required size of the optional recapture unit 150. [ For comparison, in the embodiment of Figures 5-7, the glycol may pass through or bypass the reuse unit 150 regardless of whether it has passed through the chemical divalent cation removal unit 130 or not.

In the embodiment of Figures 4 and 6 the regenerator is arranged in the recovery system 100 between the recovery system inlet 105 and the chemical divalent cation removal unit 130 such that the chemical divalent cation removal step is carried out in a glycol recovery system Lt; RTI ID = 0.0 > 100 < / RTI > Here, the flow rate required to pass through the chemical divalent cation removal unit 130 is much lower because the stream undergoing the chemical divalent cation removal step has a relatively low water content compared to the aqueous phase containing the rich glycol Because the branch is based on the regenerated glycol taken from the regenerated glycol stream 148. As a result, the associated equipment can be much smaller.

Moreover, the probability of mercury contamination in precipitated solids is smaller if the chemical divalent cation removal step is carried out downstream of the regeneration step in the glycol recovery system. This facilitates further disposal of the precipitated solids.

A comparative example will now be provided to further illustrate the invention by comparing exemplary calcium loads in the various streams of the embodiments of FIGS. 3 and 4 as compared to the reference case of FIG. For example, it is assumed that 30 kg / hr of Ca < ^{2 +} > is added to the aqueous phase 40 due to the mineral load in the process stream 11 produced from the hydrocarbon production column 5. Most of which are within 4,500 barrels per day of the number of strata produced. The flow rate (kg / hr) of Ca ^& lt ^{; 2 +} & gt ^; in the various streams identified by the reference numerals used above is reproduced in Table 1.

In the reference case, 33% of the glycol passed through the reuse unit 150 and 67% passed through the reuse unit bypass line 155. In the embodiment of the present invention, the relative flow rate of the glycol in the first portion 111 was 27.5%, and 72.5% was moved through the desalination bypass line 125. It is assumed that the regenerator 140 does not affect the Ca flow. A value of 27.5% was selected to ensure that the calcium flow rate in the pipeline 10 was maintained at a selected value of 109 kg / hr.

In the standard case, the injection rate of the chemical 2 is a removal unit (130) 238 ㎏ / hr of KOH was required to achieve the total target removal of 30 ㎏ / hr of Ca ^{2 +,} with only approximately in the embodiment of Figure 4 102 kg / hr was required. On removal of chemical divalent cations, the alkalinity remained the same in each case at a pH value of 9.0. The pH value of the recovered glycol stream 50 was lowered (to the value of 6.3) by the addition of HCl as acid to control the pH value of the aqueous stream 40 for a target value of pH = 6.2. The basic case required an HCl injection rate of 86 kg / hr, whereas only 12 kg / hr was required in the case of FIGS. 3 and 4. Therefore, the present invention is particularly advantageous in that, if all or most of the first portion of the recovered glycol 50 has passed the optional reclamation step and / or the unit 150 and also reduces acid consumption (if selective acid infusion is applied) And serves to reduce the acid injection rate.

The above-described methods and apparatus can be used in a method for producing a natural gas product stream. These methods include:

- conveying the process stream (11) containing natural gas through the pipeline (10) from the upstream position (A) to the downstream position (B);

- injecting the glycol-containing stream into the pipeline (10) at the injection point (20) and conveying the glycol-containing stream through the pipeline to the downstream position (B);

- separating the process stream (11) with the glycol-containing stream into at least the aqueous phase (40) and the natural gas phase (60) at the downstream location (B).

Simultaneously with the recovery of the glycol from the aqueous phase 40 to form a stream of recovered glycol 50 as described above, the natural gas phase 60 is further processed to produce a natural gas product stream 70. As described above, the stream of recovered glycol 50 is transported to the injection point 20 and added to the glycol-containing stream being injected.

The further treatment of the natural gas phase 60 may be carried out by one or more gas treatment steps selected from the group consisting of dew pointing, dehydration, acid gas removal, mercury removal, extraction of natural gas liquid, cooling, liquefaction, nitrogen removal, To at least a fraction of the fluid (60).

If the natural gas treatment system 200 includes at least a liquefier unit in its natural gas treatment channel 202 and / or the further treatment of the natural gas phase 60 comprises at least a liquefaction step, the natural gas product stream may be cryogenic (Typically less than about -160 ° C at near atmospheric conditions, typically below 1.2 bara) or in the form of a liquefied natural gas stream that may be transported in bulk form by tankers.

The natural gas treatment system 200, together with a glycol recovery system and optionally an inlet separation system, may all be provided on a single floating platform, for example a floating vessel comprising one or more storage tanks. One or more storage tanks may be provided downstream of the natural gas treatment system 200 and may be arranged to receive and store the natural gas product stream until the natural gas product stream can be unloaded.

In the above-described method and apparatus, any embodiment that allows for smaller equipment is particularly advantageous if the downstream position B is in the sea, since the marine space for the processing equipment is relatively insufficient and generates high additional costs to be.

It will be understood by those of ordinary skill in the art that the present invention may be carried out in many different ways without departing from the scope of the appended claims.

Claims (21)

As a method for circulating a glycol stream having a divalent cation concentration,
Conveying a process stream containing natural gas through a pipeline from an upstream location to a downstream location;
- injecting a glycol-containing stream into said pipeline at an injection point and carrying said glycol-containing stream with said process stream through said pipeline to said downstream location;
- separating said process stream with said glycol-containing stream into at least an aqueous phase and a natural gas phase in said downstream location, said aqueous phase containing at least a portion of a glycol derived from said glycol-containing stream, Separating the process stream with at least a portion of the natural gas from the process stream with the glycol containing stream into at least an aqueous phase and a natural gas phase;
Recovering the glycol from the aqueous phase to form a stream of recovered glycol wherein the step of recovering the glycol from the aqueous phase comprises the step of recovering the glycol from the aqueous phase, ; And
- transporting the recovered glycol stream to the injection point and adding the recovered glycol stream to the injected glycol containing stream,
Wherein the stream of recovered glycol comprises at least a first portion and a second portion and wherein the first portion of the recovered glycol undergoes a chemical divalent cation removal step whereby the divalent cation undergoes the chemical divalent cation removal step Wherein the second portion of the recovered glycol is removed from the first portion of the glycol and the second portion of the recovered glycol does not undergo the chemical divalent cation removal step. The method according to claim 1,
The chemical divalent cation removal step comprises injecting a chemical component into the first portion of the glycol and reacting the chemical component with at least a portion of the divalent cations contained in the first portion of the glycol Wherein the glycol stream has a concentration of divalent cations. 3. The method of claim 2,
Wherein the chemical component is an alkaline component, the glycol stream having a divalent cation concentration. 4. The method according to any one of claims 1 to 3,
The relative flow rate of the glycol in the first part is always selected, compared to the total flow rate of the recovered glycol so that the concentration of the divalent cations reaching the pipeline at the downstream position is kept below the preselected value, A method for circulating a glycol stream having a cation concentration. 4. The method according to any one of claims 1 to 3,
Wherein the step of recovering the glycol from the aqueous phase further comprises a regeneration step in which water is separated from the glycol such that both the first portion and the second portion of the recovered glycol stream go through the regeneration step , Wherein the glycol stream having a concentration of divalent cations is circulated. 6. The method of claim 5,
Wherein the regeneration step in a single selective pass recovering glycol from the aqueous phase is downstream of the chemical divalent cation removal step, wherein the glycol stream having a concentration of divalent cations is cycled. 6. The method of claim 5,
Wherein the chemical divalent cation removal step recycles a glycol stream having a concentration of divalent cations downstream of the regeneration step, in a monoselective path for recovering glycol from the aqueous phase. 4. The method according to any one of claims 1 to 3,
Wherein the process for recovering the glycol from the aqueous phase further comprises a reclamation step comprising distillation. 9. The method of claim 8,
Wherein the reusing step is downstream of the chemical divalent cation removal step in a single selective path for withdrawing glycol from the aqueous phase, wherein the glycol stream has a concentration of divalent cations. 9. The method of claim 8,
Wherein all of the first portion of the recovered glycol goes through the reuse step, wherein the glycol stream has a concentration of divalent cations. 4. The method according to any one of claims 1 to 3,
Further comprising the step of injecting an acid into the recovered glycol. 4. The method according to any one of claims 1 to 3,
Wherein the natural gas phase during the circulation of the glycol stream is selected from the group consisting of dew pointing, dehydration, acid gas removal, mercury removal, extraction of natural gas liquid, cooling, liquefaction, nitrogen removal, Of the glycol stream having a concentration of divalent cations, wherein the glycol stream is further treated to a gas treatment step to produce a natural gas product stream. An apparatus for circulating a glycol stream having a divalent cation concentration,
- a pipeline extending from said upstream position to said downstream position for conveying a process stream containing natural gas from an upstream position to a downstream position;
An injection point for injecting the glycol-containing stream into the pipeline and into the process stream;
An inlet separation system arranged in said downstream position to receive said process stream with said glycol containing stream and to separate said process stream with said glycol containing stream into at least an aqueous phase and a natural gas phase, The natural gas phase containing at least a portion of the natural gas from the process stream;
- a collection system inlet in fluid communication with the inlet separation system, the collection system being arranged to receive the aqueous phase through the recovery system inlet and to recover the glycol from the aqueous phase to form a stream of recovered glycol, A glycol recovery system further comprising a recovery system outlet for withdrawing a stream of glycol and comprising a chemical divalent cation removal unit arranged in a first path between the recovery system inlet and the recovery system outlet; And
And a glycol injection line fluidly connecting the withdrawal system outlet to the injection point and arranged to transport the withdrawn stream of glycol from the glycol recovery system to the injection point,
Wherein the glycol recovery system further comprises a second path between the withdrawal system inlet and the withdrawal system outlet and wherein the second flow path includes a first portion and a second portion of the recovered glycol stream, Wherein the first portion of the recovered glycol is passed through the chemical divalent cation removal unit such that the divalent cation is removed from the first portion of the glycol passing through the chemical divalent cation removal unit And wherein the second portion of the recovered glycol does not pass through the chemical divalent cation removal unit, wherein the second portion of the recovered glycol does not pass through the chemical divalent cation removal unit. 14. The method of claim 13,
Wherein the concentration of the divalent cation reaching the pipeline at the downstream position is greater than the total amount of glycol delivered to the stream of glycol recovered through the glycol recovery system, Further comprising a controller arranged to control the flow rate of the first portion of the glycol. The method according to claim 13 or 14,
An apparatus for circulating a glycol stream having a divalent cation concentration, further comprising an acid component injection system. A method of making a natural gas product stream,
Conveying a process stream containing natural gas through a pipeline from an upstream location to a downstream location;
Injecting a glycol-containing stream into said pipeline at an injection point and carrying said glycol-containing stream through said pipeline to said downstream location;
- separating the process stream with the glycol-containing stream into at least an aqueous phase and a natural gas phase in the downstream location, the aqueous phase containing at least a portion of the glycol derived from the glycol-containing stream, Separating the process stream with at least a portion of the natural gas from the process stream with the glycol containing stream into at least an aqueous phase and a natural gas phase;
Simultaneously recovering the glycol from the aqueous phase to form a stream of recovered glycol and further treating the natural gas phase to produce a natural gas product stream; And
Transporting the recovered glycol stream to the injection point and adding the recovered glycol stream to the injected glycol containing stream,
Wherein the step of recovering the glycol from the aqueous phase comprises a chemical divalent cation removal step wherein the stream of recovered glycol comprises at least a first portion and a second portion and wherein the first portion of the recovered glycol comprises Through the chemical divalent cation removal step, a divalent cation is removed from a first portion of the glycol undergoing the chemical divalent cation removal step, and the second portion of the recovered glycol is a glycol having a divalent cation concentration Wherein the stream of the natural gas product stream is not subjected to a chemical divalent cation removal step to circulate the stream. 17. The method of claim 16,
Wherein the further processing step of the natural gas phase further comprises at least one gas treatment step selected from the group consisting of dew pointing, dehydration, acid gas removal, mercury removal, extraction of natural gas liquid, cooling, liquefaction, nitrogen removal, To at least a fraction of the gaseous phase. 9. The method of claim 8,
Wherein the distillation is a distillation under sub-atmospheric pressure, wherein a glycol stream having a concentration of divalent cations is circulated. 11. The method of claim 10,
Wherein the second portion of the recovered glycol circulates a glycol stream having a concentration of divalent cations that has not undergone the reuse step. 12. The method of claim 11,
A method for circulating a glycol stream having a concentration of divalent cations, wherein the rate of injection is controlled in response to a pH value of the aqueous phase. 16. The method of claim 15,
And an acid infusion rate controller coupled to a pH sensor capable of generating a pH signal indicative of the pH value of the aqueous phase and coupled to an acid infusion rate control valve.

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