Natural gas condensate processing

Abstract

Disclosed herein are methods and systems for processing natural gas streams. In particular, the subject matter disclosed herein relates to methods and systems for processing a partially condensed natural gas stream that does not include a separate heavy hydrocarbon condensate processing section. The methods and systems include separating a condensed stream from an uncondensed light hydrocarbon vapor stream, increasing the energy of the condensed stream and / or the light hydrocarbon vapor stream, and reinjecting the condensed stream into the light hydrocarbon vapor stream so that the condensate can subsequently be processed together with the light hydrocarbons. Subsequent processing includes removing free water, and controlling the temperature of the natural gas stream downstream of reinjection to remain above the dew point of the natural gas stream.

Description

[Technical Field]

[0001] The present disclosure relates to natural gas processing. In particular, embodiments disclosed herein relate to a natural gas processing method in which hydrocarbons condensed in a natural gas pipeline or during gas compression are treated before undergoing processing including free water removal, drying, mercury removal, and natural gas filtration. A system for processing natural gas condensate by reducing investment costs is also disclosed herein. [Background technology]

[0002] Heavy hydrocarbons often condense in natural gas pipelines or during gas compression. The amount of hydrocarbon condensate as well as the amount of condensed water depends on the natural gas composition, pressure, and temperature. Several scenarios can occur during gas pipeline operation. Pressure drop, heat transfer between the soil and the gas, flow, land type, and network topology are important aspects.

[0003] According to current technology, in natural gas processing plants, the condensate is processed separately from the gas stream. A separator is present to separate the gas / vapor fraction from the condensate. Additionally, if the temperature is below the water dew point, the separator is configured to further separate the heavier condensed water from the hydrocarbon condensate. The separated hydrocarbon condensate is then processed separately before being sent to a storage device or fractionation unit. The specific processing steps required depend on the product specifications.

[0004] For example, hydrocarbon condensate processing steps may include residual free water removal, drying, mercury adsorption, filtration, and condensate stripping to obtain a stabilized hydrocarbon condensate and a vapor fraction that is returned to the three-phase separator. Processing steps for the gas / vapor fraction from the separator may include compression, cooling, separation in a second separator (called a knockout drum), drying, mercury adsorption, and filtration before sending the residual gas stream to its final intended use.

[0005] Such an approach has a negative impact on the cost of the system in terms of capital expenditure costs and overall footprint, due to the large number of devices that need to be provided.

[0006] Therefore, improved methods and systems for natural gas condensate processing that address the complexity and cost problems of current art methods and systems would be beneficial and welcome in the art. More generally, it is desirable to provide methods and systems adapted to more efficiently address the problems associated with hydrocarbon condensation due to increased pressure and / or decreased temperature in systems containing natural gas streams. Summary of the Invention

[0007] In one aspect, the subject matter disclosed herein is directed to a natural gas processing method in which hydrocarbons condensed in a natural gas pipeline or during gas compression are separated from a non-condensable light hydrocarbon vapor stream as a condensed stream containing heavy hydrocarbons and certain amounts of other components, particularly water, and reinjected into the non-condensable light hydrocarbon vapor stream after the light hydrocarbon vapor stream has been compressed and / or after the condensed stream has been heated or further vaporized. In particular, the condensed stream is reinjected into the light hydrocarbon vapor stream prior to processing prior to storage or fractionation of the light hydrocarbon vapor stream. Such processing can include, for example, free water removal, drying, mercury removal, and hydrocarbon filtration. The natural gas processing method includes controlling the temperature of the natural gas stream after reinjection and, if the temperature is below the natural gas dew point, increasing the energy of the system by compressing the light hydrocarbon vapor stream and / or heating or even vaporizing the condensed stream before reinjecting it into the light hydrocarbon vapor stream.

[0008] A further aspect of the present disclosure relates to a natural gas processing system including a separator that separates a light hydrocarbon vapor stream and a condensate stream, a gas compressor adapted to compress the light hydrocarbon vapor stream and / or a heater adapted to heat the condensate stream, a pump adapted to reinject the condensate stream into the light hydrocarbon vapor stream at the suction side or the discharge side of the gas compressor, and a temperature controller configured to operate the gas compressor and / or the heater. In particular, the separator is configured to further separate heavier condensed water from the hydrocarbon condensate when the temperature is below the water dew point. The natural gas processing system further includes a heater for heating the condensate stream before reinjecting the condensate stream into the light hydrocarbon vapor stream. [Brief explanation of the drawings]

[0009] A more complete understanding of the disclosed embodiments of this invention and many of the attendant advantages thereof will be readily obtained as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings. [Figure 1] 1 is a schematic diagram of a system for processing natural gas according to an embodiment of the present disclosure. [Figure 2] 1 shows a flow chart of a method for processing natural gas according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] According to one aspect, the present subject matter is directed to methods and systems for treating a natural gas stream following condensation of a fraction of the natural gas stream as a result of pressure reduction and / or cooling of the stream.

[0011] According to another aspect, the subject matter disclosed herein relates to methods and systems for processing a partially condensed natural gas stream by separating a condensed stream from a non-condensable light hydrocarbon vapor stream, increasing the energy of the light hydrocarbon vapor or condensed stream, and reinjecting the condensed stream into the light hydrocarbon vapor stream prior to processing and subsequent storage and / or fractionation of the natural gas stream. The temperature of the natural gas stream downstream of the reinjection of the condensed stream into the light hydrocarbon vapor stream is controlled to remain above the dew point of the natural gas stream. If the temperature is below the dew point of the natural gas stream, the condensed stream is heated prior to reinjection into the light hydrocarbon vapor stream. Notably, heating the condensed stream can also include vaporizing at least a portion of the condensed stream prior to reinjection into the light hydrocarbon vapor stream.

[0012] Additionally, according to another embodiment, if the temperature of the natural gas stream downstream of the reinjection of the condensed stream into the light hydrocarbon vapor stream is more than 10°C above the natural gas dew point, the natural gas stream downstream of the reinjection point is cooled.

[0013] According to one embodiment, processing of the natural gas stream after reinjection of the condensate stream into the light hydrocarbon vapor stream and prior to storage and / or fractionation may include free water removal, drying, mercury adsorption, filtration, and condensate stripping.

[0014] Specifically, disclosed herein is a natural gas processing system that includes a two-phase or three-phase separator adapted to separate a natural gas stream into a light hydrocarbon vapor stream and a condensate stream, or into a light hydrocarbon vapor stream, a heavy hydrocarbon condensate stream, and a water stream, a gas compressor for compressing the light hydrocarbon vapor stream and / or a heater for heating the condensate stream, and a pump for reinjecting the heavy hydrocarbon condensate stream into the light hydrocarbon vapor stream. The system may also include a vaporizer for upstream vaporizing the condensate stream and reinjecting it into the light hydrocarbon vapor stream. Downstream of the reinjection point, the natural gas processing system includes a temperature control device adapted to maintain the temperature of the natural gas stream above the natural gas dew point by operating the gas compressor, the heater, and / or the vaporizer.

[0015] According to one aspect, downstream of the reinjection point, the natural gas processing system comprises a processing section upstream of the storage system or fractionation unit, which includes a knockout drum for separating residual water, and may include a dryer, an adsorber adapted to adsorb mercury eventually present in the stream, and a filter.

[0016] According to one aspect, the heated or at least partially vaporized condensate stream can be alternately reinjected into the suction or discharge side of the gas compressor. Additionally, the knockout drum of the processing section is operated below the water dew point. A cooler can be present downstream of the reinjection point to cool the natural gas stream if its temperature is above the water dew point.

[0017] According to more general aspects, disclosed herein are improved methods and systems for processing an at least partially condensed natural gas stream, which do not include a separate condensate processing section, except for optional heat exchange steps and units adapted to heat or vaporize the condensate before reinjecting it into a non-condensable natural gas fraction so that the condensate can subsequently be processed together with light hydrocarbons. In particular, the methods and systems for processing an at least partially condensed natural gas stream include separating a light hydrocarbon vapor stream and a condensed stream, increasing the energy of the light hydrocarbon vapor stream or the condensed stream, and reinjecting the condensed stream into the light hydrocarbon vapor stream prior to processing and subsequent storage and / or fractionation of a natural gas stream composed of the reinjected condensed stream and the light hydrocarbon vapor stream. Increasing the energy of the light hydrocarbon vapor can be achieved by compressing the light hydrocarbon vapor stream and reinjecting the condensed stream into the compressed light hydrocarbon vapor stream, and / or by heating or vaporizing the condensed stream.

[0018] This makes it possible to realize a natural gas processing system with reduced equipment count, site area, and investment costs.

[0019] Reference will now be made in detail to the embodiments of the present disclosure, one or more examples of which are illustrated in the Figures. Each example is provided by way of explanation of the disclosure, not as a limitation of the disclosure. Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. References throughout this specification to "one embodiment" or "an embodiment" or "some embodiments" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the disclosed subject matter. Thus, the appearances of the phrases "in one embodiment," "in an embodiment," or "in some embodiments" in various places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0020] When presenting elements of various embodiments, the articles "a," "an," "the," and "said" are intended to mean that there are one or more of the element. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0021] Referring now to the drawings, Figure 1 shows a schematic diagram of an exemplary natural gas processing system. The natural gas processing system is supplied with a natural gas feed 1, which is sent via natural gas feed line 2 to a three-phase separator 3, where the natural gas feed is separated into a light hydrocarbon vapor fraction, a heavy hydrocarbon condensate fraction, and a water fraction. The light hydrocarbon vapor stream exits separator 3 through vapor line 4 and is sent to gas compressor 5, and then through gas compressor discharge line 6 to cooler 7 and knockout drum 13. The heavy hydrocarbon condensate stream exits separator 3 through condensate line 8 and is sent to pump 9 and condensate heater 10. Downstream of condensate heater 10, the heavy hydrocarbon condensate stream is injected into gas compressor discharge line 6 upstream of cooler 7 through heated condensate line 11. Water is recovered from separator 3 through water discharge line 12.

[0022] From cooler 7, the natural gas stream, which contains both a heated heavy hydrocarbon condensate stream and a compressed light hydrocarbon vapor stream, is sent to knockout drum 13 via knockout drum feed line 21. Knockout drum 13 is operated above the natural gas dew point but below the water dew point to condense only water. The natural gas vapor stream from knockout drum 13 is sent to dryer 14 via dryer feed line 15, then to Hg adsorber 16 and filter 17, and finally to a storage or fractionation unit (not shown) via outlet line 18. Water is recycled to natural gas feed line 2 via condensate recycle line 19.

[0023] A thermometer (not shown) is used to control the temperature of the natural gas stream in knockout drum feed line 21. When the temperature is between the natural gas dew point and the water dew point, both cooler 7 and heater 10 are off. When the temperature is below the natural gas dew point, heater 10 is used to heat the heavy hydrocarbon condensate stream. When the temperature is above the water dew point, cooler 7 is used to cool the natural gas stream downstream of the reinjection point.

[0024] In some embodiments, at least a portion of the heated heavy hydrocarbon condensate from condensate heater 10 may be recovered from heated heavy hydrocarbon condensate line 11 for recirculation to natural gas supply line 2 via natural gas recycle line 20.

[0025] 2 shows a flow chart summarizing the method disclosed herein for processing an at least partially condensed natural gas stream prior to storage or fractionation. The natural gas processing method includes the following subsequent steps: - separating (30) the at least partially condensed natural gas stream into a condensate stream and a light hydrocarbon vapor stream; - increasing the energy (40) of the light hydrocarbon vapor stream and / or condensate stream; - reinjecting (50) the condensed stream into the light hydrocarbon vapor stream; - controlling (60) the temperature of the natural gas stream.

[0026] In some embodiments, increasing the energy of the light hydrocarbon vapor stream and / or the condensed stream (40) comprises heating or even at least partially vaporizing the heavy hydrocarbon condensed stream and reinjecting the condensed stream into the light hydrocarbon vapor stream, and / or compressing the light hydrocarbon vapor stream and reinjecting the condensed stream into the compressed light hydrocarbon vapor stream.

[0027] In some embodiments, the final step (60) of treating the natural gas stream includes separating at least the free water and drying. In other embodiments, downstream of the drying step, the final step (60) of treating the natural gas stream includes removing Hg and filtering.

[0028] In some embodiments, prior to reinjecting the condensed stream into the light hydrocarbon vapor stream (50) in order to maintain the temperature of the natural gas stream above the natural gas dew point, the methods disclosed herein include heating the condensed stream. In particular, heating is necessary when the ratio between the optionally compressed light hydrocarbon vapor stream and the condensed stream is too low to vaporize the entire condensate when mixed with the light hydrocarbon vapor stream.

[0029] In some embodiments, to maintain the temperature of the natural gas stream below the water dew point, the methods disclosed herein include cooling the natural gas stream after reinjecting the condensed stream into the light hydrocarbon vapor stream (50). Cooling may be required, particularly during the summer months, when ambient temperatures are high and heat exchange between the ambient and the natural gas stream may cause undesirable heating of the natural gas stream.

[0030] In some embodiments, prior to step (50) of reinjecting the condensed stream into the light hydrocarbon vapor stream, a step is provided of recovering a portion of the condensed stream and recycling it to step (30) of separating the at least partially condensed natural gas stream into a condensed stream and a light hydrocarbon vapor stream.

[0031] While aspects of the present invention have been described in terms of various specific embodiments, it will be apparent to those skilled in the art that many modifications, changes, and omissions are possible without departing from the spirit and scope of the claims. Additionally, unless otherwise specified herein, the order or sequence of any process or method steps may be varied or rearranged according to alternative embodiments.

Claims

1. 1. A method for processing a natural gas stream, wherein the natural gas stream is at least partially condensed, the method comprising: - separating (30) said at least partially condensed natural gas stream into a condensate stream and a light hydrocarbon vapor stream; - Increasing the energy (40) of the light hydrocarbon vapor stream and / or condensate stream; - reinjecting (50) the condensed stream into the light hydrocarbon vapor stream; - controlling (60) the temperature of the natural gas stream after the step (50) of reinjecting the condensed stream into the light hydrocarbon vapor stream, 1. The method of claim 1, wherein increasing the energy (40) of the light hydrocarbon vapor stream and / or the condensed stream operates according to the step (60) of controlling the temperature of the natural gas stream (6) after reinjecting the condensed stream (50) into the light hydrocarbon vapor stream above the natural gas dew point to maintain the temperature of the natural gas stream (6) after reinjecting the condensed stream (50) into the light hydrocarbon vapor stream.

2. 2. The method of processing a natural gas stream as set forth in claim 1, wherein said step (40) of increasing the energy of said light hydrocarbon vapor stream comprises compressing said light hydrocarbon vapor stream prior to step (50) of reinjecting said condensed stream into said light hydrocarbon vapor stream.

3. said step of increasing the energy (40) of said condensing stream comprising:

3. The method of claim 1 or 2, further comprising the step of pumping the condensed stream prior to the step (50) of reinjecting the condensed stream into the light hydrocarbon vapor stream.

4. Increasing the energy (40) of the condensed stream comprises:

4. The method of claim 3, further comprising the step of heating the condensed stream prior to the step (50) of reinjecting the condensed stream into the light hydrocarbon vapor stream.

5. Increasing the energy (40) of the condensed stream comprises:

5. The method of claim 4, further comprising at least partially vaporizing the natural gas in the condensed stream prior to reinjecting (50) the condensed stream into the light hydrocarbon vapor stream.

6. 6. The method of claim 4 or 5, wherein the step of heating (40) the separated stream uses waste heat from the step of compressing the vaporous hydrocarbon stream.

7. if the temperature measured in controlling the temperature of the natural gas stream (60) is greater than the water dew point after reinjecting the heavy hydrocarbon condensate stream into the compressed light hydrocarbon vapor stream (50), The method comprises: The method according to any one or more of the preceding claims, further comprising the step of cooling the natural gas stream after the step (50) of reinjecting the condensed stream into the compressed light hydrocarbon vapor stream.

8. After the step (60) of controlling the temperature of the natural gas stream, after the step (50) of reinjecting the heavy hydrocarbon condensate stream into the compressed light hydrocarbon vapor stream, the method further comprises: - separating free water from said natural gas stream, and then - drying said natural gas stream.

9. 9. The method of claim 8, further comprising recycling the separated free water to the step (30) of separating the at least partially condensed natural gas stream into a condensate stream and a light hydrocarbon vapor stream.

10. 10. The method according to claim 8 or 9, further comprising the step of: after the drying step: - removing Hg from said natural gas stream; - filtering said natural gas stream.

11. After step (30) of separating the at least partially condensed natural gas stream into a condensate stream and a light hydrocarbon vapor stream and before step (50) of reinjecting the condensate stream into the light hydrocarbon vapor stream, - recovering a portion of said condensate stream; The method according to any one or more of the preceding claims, further comprising the step (30) of separating the at least partially condensed natural gas stream into a condensate stream and a vapor natural gas stream, and recycling the recovered portion of the condensate stream.

12. After step (30) of separating the at least partially condensed natural gas stream into a condensate stream and a light hydrocarbon vapor stream and before step (50) of reinjecting the condensate stream into the light hydrocarbon vapor stream, The method according to any one or more of the preceding claims, further comprising the step of separating a water stream from the condensate stream.

13. 1. A system for treating a natural gas stream (1), said system comprising: a separator (3) adapted to separate a light hydrocarbon vapor stream (4) and a condensate stream (8); a gas compressor (5) adapted to compress the light hydrocarbon vapor stream (4) and / or a heater (10) configured to heat the condensed stream (8); a pump (9) adapted to increase the pressure of the condensate stream (8), convey the condensate stream (8), and reinject the condensate stream into the light hydrocarbon vapor stream (4) in the natural gas stream (6) through a condensate stream line (11); a cooler (7) adapted to cool the temperature of the natural gas stream (6); and a temperature control device for the natural gas stream (6) configured to operate the gas compressor (5) and / or the heater (10) and the cooler (7).

14. The system of claim 13, further comprising an evaporator configured to evaporate the condensate stream (8).

15. 15. The system according to claim 13 or 14, wherein the heater (10) is arranged downstream of the pump (9) along the condensate flow line (11).

16. The system according to any one or more of claims 13 to 15, wherein the separator (3) is a three-phase separator (3) adapted to further separate a water stream from the condensate stream.

17. 17. The system according to any one or more of claims 13 to 16, further comprising a knock-out drum (13) downstream of the cooler (7), the knock-out drum (13) adapted to separate a water condensate stream and a natural gas vapor stream.

18. 18. The system of claim 17, further comprising a dryer (14) downstream of the knock-out drum (13) adapted to dry the natural gas vapor stream from the knock-out drum (13).

19. 20. The system of claim 18, further comprising a mercury adsorber (16) downstream of the dryer (14).

20. 20. The system of claim 18 or 19, further comprising a filter (17) downstream of the dryer (14) and / or the mercury adsorber (16).

21. The system according to any one or more of claims 17 to 20, further comprising a condensate recirculation line (19) from the knock-out drum (13) to the separator (3).

22. The system according to any one or more of claims 13 to 21, further comprising a heavy hydrocarbon recycle line (20) from the condensate stream line (11) to the separator (3).

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