CN113528206B - Desulfurization system and method - Google Patents
Desulfurization system and method Download PDFInfo
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- CN113528206B CN113528206B CN202010284257.XA CN202010284257A CN113528206B CN 113528206 B CN113528206 B CN 113528206B CN 202010284257 A CN202010284257 A CN 202010284257A CN 113528206 B CN113528206 B CN 113528206B
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
- C10L3/10—Working-up natural gas or synthetic natural gas
- C10L3/101—Removal of contaminants
- C10L3/102—Removal of contaminants of acid contaminants
- C10L3/103—Sulfur containing contaminants
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/40—Capture or disposal of greenhouse gases of CO2
Abstract
The invention discloses a desulfurization system and a desulfurization method, and belongs to the technical field of desulfurization. In the desulfurization system, the acid gas absorption unit comprises a desulfurization absorption tower, a purification gas separator connected with an outlet at the top of the desulfurization absorption tower, and a first barren liquor circulating pump connected with an inlet at the upper part of the desulfurization absorption tower. The flash evaporation unit comprises a first heat exchanger, a flash evaporation three-way valve, a primary flash evaporation assembly, a secondary flash evaporation assembly and a first diverter valve which are connected in sequence; the first flow dividing valve is communicated with an inlet of the purification gas separator through a pipeline, and the first heat exchanger is communicated with a bottom outlet of the desulfurization absorption tower. The solvent regeneration unit comprises a second heat exchanger, a solvent regeneration tower, a first cooler, a gas-liquid separator and a reflux pump. The secondary flash evaporation component, the second heat exchanger and the solvent regeneration tower are connected in sequence; the solvent regeneration tower, the second heat exchanger and the first barren solution circulating pump are connected in sequence; the solvent regeneration tower, the first cooler, the gas-liquid separator, the reflux pump and the solvent regeneration tower are connected in sequence; the gas-liquid separator is connected with the acid gas enrichment unit.
Description
Technical Field
The invention relates to the technical field of desulfurization, in particular to a desulfurization system and a desulfurization method.
Background
The raw natural gas produced from a formation typically contains significant amounts of carbon dioxide and sulfur-containing compounds, such as hydrogen sulfide, organic sulfur (mercaptans, carbonyl sulfide, etc.). According to the current natural gas standard GB17820-2018, the content of hydrogen sulfide in the product natural gas is required to be less than or equal to 6mg/m 3 The total sulfur content is less than or equal to 20mg/m 3 . Therefore, it is necessary to subject the raw natural gas to desulfurization treatment.
The organic sulfur content in most raw material natural gas is less than or equal to 100mg/m 3 In view of the situation, at present, a physical-chemical solvent method is mostly adopted to remove organic sulfur in raw natural gas, so that the total sulfur content in purified gas meets the standard. The desulfurization solvent and the active components used in the solvent method can simultaneously remove organic sulfur and carbon dioxide in the raw material natural gas.
In the process of implementing the invention, the inventor finds that at least the following problems exist in the prior art:
when the prior art uses a desulfurization solvent for desulfurization, although the total sulfur content in the purified gas can be ensured to reach the standard, the problem of overhigh co-absorption rate of carbon dioxide often exists, the absorption process has no selectivity, the concentration of hydrogen sulfide in the formed acid gas is reduced, and the yield loss of the product natural gas is caused.
Disclosure of Invention
In view of the above, the present invention provides a desulfurization system and method, which can solve the above technical problems.
Specifically, the method comprises the following technical scheme:
in one aspect, a desulfurization system is provided, comprising: the acid gas absorption unit, the flash evaporation unit, the solvent regeneration unit and the acid gas enrichment unit are connected in sequence;
wherein the acid gas absorption unit comprises: the device comprises a desulfurization absorption tower, a purification gas separator connected with an outlet at the top of the desulfurization absorption tower through a pipeline, and a first barren solution circulating pump connected with an inlet at the upper part of the desulfurization absorption tower through a pipeline;
the flash unit comprises: the first heat exchanger, the flash evaporation three-way valve, the first-stage flash evaporation assembly, the second-stage flash evaporation assembly and the first flow dividing valve are sequentially connected through pipelines, wherein a first outlet of the first flow dividing valve is communicated with an inlet of the purified gas separator through a pipeline, and the first heat exchanger is communicated with a bottom outlet of the desulfurization absorption tower through a pipeline;
the solvent regeneration unit includes: the system comprises a second heat exchanger, a solvent regeneration tower, a first cooler, a gas-liquid separator and a reflux pump;
the liquid outlet of the secondary flash evaporation assembly, the second heat exchanger and the first upper inlet of the solvent regeneration tower are connected in sequence;
the bottom outlet of the solvent regeneration tower, the second heat exchanger and the first barren liquor circulating pump are sequentially connected;
the top outlet of the solvent regeneration tower, the first cooler, the gas-liquid separator, the reflux pump and the second upper inlet of the solvent regeneration tower are sequentially connected;
and a gas outlet of the gas-liquid separator is connected with the acid gas enrichment unit.
In one possible design, the acid gas enrichment unit includes: the system comprises an acid gas absorption tower, a third heat exchanger, an acid gas regeneration tower, a rich solution booster pump, a second barren solution circulating pump, a semi-rich solution circulating pump and a barren solution cooler;
the lower inlet of the acid gas absorption tower is connected with the gas outlet of the gas-liquid separator through a pipeline;
the bottom outlet of the acid gas absorption tower, the third heat exchanger, the rich liquid booster pump and the upper inlet of the acid gas regeneration tower are connected in sequence;
the bottom outlet of the acid gas regeneration tower, the third heat exchanger, the second barren solution circulating pump, the barren solution cooler and the middle inlet of the acid gas absorption tower are sequentially connected;
and the lower outlet of the acid gas absorption tower, the semi-rich liquid circulating pump and the upper inlet of the acid gas absorption tower are sequentially connected.
In one possible design, the desulfurization system further includes: the first outlet of the second flow dividing valve is connected with the purified gas separator through a pipeline;
and the inlet of the second flow dividing valve is communicated with the top outlet of the acid gas absorption tower.
In one possible design, the desulfurization system further includes: a sour gas three-way valve;
the inlet of the acid gas three-way valve is connected with the gas outlet of the gas-liquid separator, one of the two outlet ends is connected with the rear-end sulfur recovery unit, and the other outlet end is connected with the gas inlet at the bottom of the acid gas absorption tower.
In one possible design, the primary flash assembly includes: the device comprises a primary flash tank and a primary rectifying column connected with a top outlet of the primary flash tank.
In one possible design, the secondary flash assembly includes: the secondary flash tank is communicated with the bottom outlet of the primary flash tank, and the secondary rectifying column is connected with the top outlet of the secondary flash tank;
wherein a gas outlet of the secondary rectification column is communicated with an inlet of the first splitter valve;
the inlet of the flash three-way valve is connected with the tube pass outlet of the first heat exchanger, one outlet of the flash three-way valve is connected with the inlet of the primary flash tank, and the other outlet of the flash three-way valve is connected with the inlet of the secondary flash tank.
In one possible design, a filtration assembly is provided on the line between the second heat exchanger and the solvent regenerator.
In one possible design, the lower parts of the solvent regeneration tower and the acid gas regeneration tower are respectively provided with a first reboiler and a second reboiler.
In one possible design, the desulfurization system further includes: and the second cooler is arranged between the first barren solution circulating pump and the upper inlet of the desulfurization absorption tower.
In another aspect, a desulfurization method is provided, wherein the desulfurization method employs the desulfurization system.
In one possible design, the method includes:
acid gas absorption by an acid gas absorption unit: feeding raw natural gas from a lower inlet of a desulfurization absorption tower, feeding a desulfurization solvent from an upper inlet of the desulfurization absorption tower by using a first barren solution circulating pump, in the desulfurization absorption tower, reversely contacting the raw natural gas with the desulfurization solvent, performing desulfurization treatment by using the desulfurization solvent, discharging formed rich liquid from a bottom outlet of the desulfurization absorption tower, and allowing formed purified gas to enter a purification gas separator from a top outlet of the desulfurization absorption tower for gas-liquid separation;
performing multistage flash by using a flash unit: the rich solution enters a first heat exchanger, exchanges heat with the lean solution from the solvent regeneration tower and is heated, and then sequentially enters a primary flash evaporation assembly and a secondary flash evaporation assembly for flash evaporation to form secondary flash evaporation gas with the main component of carbon dioxide, and the secondary flash evaporation gas returns to the purified gas through the control of the flow rate of a first flow dividing valve so as to compensate the loss of product gas caused by the excessive absorption of the carbon dioxide by the desulfurization solvent in the purified gas;
and (3) utilizing a solvent regeneration unit to regenerate the desulfurization solvent: the rich solution obtained after the flash evaporation of the secondary flash evaporation component enters a solvent regeneration tower for regeneration after heat exchange through a second heat exchanger, so that the acid gas is desorbed, the formed barren solution is discharged into the second heat exchanger from the bottom outlet of the solvent regeneration tower to exchange heat with the rich solution after the flash evaporation of the secondary flash evaporation component, and then is recycled to the desulfurization absorption tower for reuse through a first barren solution circulating pump;
acid gas enrichment is carried out by using an acid gas enrichment unit: and after the crude acid gas formed after the acid gas is desorbed is cooled to a set temperature through a first cooler from a top outlet of the solvent regeneration tower, gas-liquid separation is carried out through a gas-liquid separator, the liquid obtained through the separation is returned to the solvent regeneration tower through a reflux pump for reuse, and the crude acid gas obtained through the separation enters an acid gas enrichment unit for concentration.
In one possible design, the crude acid gas enters an acid gas absorption tower, reversely contacts with the desulfurization barren solution to carry out primary desulfurization treatment, and continuously goes upward to reversely contact with the desulfurization semi-rich solution entering from an inlet at the upper part of the acid gas absorption tower to carry out secondary desulfurization treatment; discharging the residual gas as enriched tail gas from the top of the acid gas absorption tower;
after exchanging heat of part of rich solution formed at the bottom of the acid gas absorption tower through a third heat exchanger, the rich solution enters an acid gas regeneration tower through a rich solution booster pump so as to regenerate acid gas, and the regenerated acid gas enters a rear-end sulfur recovery unit;
the regenerated desulfurization barren solution formed in the acid gas regeneration tower is led out from the tower bottom, exchanges heat with rich solution formed at the tower bottom of the acid gas absorption tower through a third heat exchanger, is cooled to a set temperature through a barren solution cooler, and is pumped into the acid gas absorption tower by a second barren solution circulating pump for recycling;
and a semi-rich liquid circulating pump for desulfurization formed at the bottom of the acid gas absorption tower is introduced into the upper part of the tower so as to improve the removal depth of hydrogen sulfide in the enriched tail gas.
The technical scheme provided by the embodiment of the invention at least has the following beneficial effects:
the desulfurization system provided by the embodiment of the invention can be used for selectively desulfurizing the raw material natural gas, and can effectively solve the problem of overhigh removal of carbon dioxide on the premise of meeting the requirement of meeting the standard of the total sulfur content in the purified gas. When in application, the method can comprise the following steps:
(a) Acid gas absorption by an acid gas absorption unit: the method comprises the steps of feeding raw natural gas containing carbon dioxide, hydrogen sulfide and organic sulfur from a lower inlet of a desulfurization absorption tower, feeding a desulfurization solvent from an upper inlet of the desulfurization absorption tower by using a first barren liquor circulating pump, wherein the raw natural gas is in reverse contact with the desulfurization solvent, absorbing all hydrogen sulfide in the raw natural gas and most organic sulfur and carbon dioxide by using the desulfurization solvent, forming a rich solution and discharging the rich solution from a bottom outlet of the desulfurization absorption tower, and enabling formed purified gas to enter a purification gas separator from a top outlet of the desulfurization absorption tower for re-separation so as to separate liquid carried in the purified gas.
(b) Performing multistage flashing by using a flashing unit: the rich solution is subjected to heat exchange with the lean solution at the bottom of the regeneration tower through a second heat exchanger, the rich solution is heated and then sequentially enters a first-stage flash evaporation assembly and a second-stage flash evaporation assembly for flash evaporation, wherein most of hydrocarbons and a small amount of carbon dioxide absorbed in the rich solution are evaporated through the first-stage flash evaporation assembly by controlling flash evaporation pressure, and a small amount of hydrocarbons and a large amount of carbon dioxide remained in the rich solution are continuously evaporated through the second-stage flash evaporation assembly. Because the first flow dividing valve is connected with the second-stage flash evaporation assembly, the flow of the second-stage flash evaporation gas is controlled to return to the purified gas through the first flow dividing valve so as to compensate the product gas amount lost due to excessive removal of carbon dioxide by the desulfurization solvent.
(c) And (3) utilizing a solvent regeneration unit to regenerate the desulfurization solvent: the rich solution after the flash evaporation of the secondary flash evaporation component enters a solvent regeneration tower for regeneration after heat exchange through a second heat exchanger, so that the acid gas in the rich solution is desorbed to form a lean solution, and the aim of regenerating the desulfurization solvent is fulfilled. And the regenerated desulfurization solvent, namely the barren solution is discharged into a second heat exchanger from an outlet at the bottom of the solvent regeneration tower to exchange heat with the pregnant solution after flash evaporation of the secondary flash evaporation assembly, and then the barren solution is pressurized by a first barren solution circulating pump and then is pumped into a desulfurization absorption tower to be circularly absorbed.
(d) Acid gas enrichment is carried out by using an acid gas enrichment unit: and after the crude acid gas is cooled to a set temperature through a first cooler from a top outlet of the solvent regeneration tower, gas-liquid separation is carried out through a gas-liquid separator, the liquid obtained through separation is returned to the solvent regeneration tower for reuse through a reflux pump, and the crude acid gas obtained through separation enters an acid gas enrichment unit for concentration so as to improve the concentration of hydrogen sulfide in the acid gas. In addition, the content of carbon dioxide can be reduced, and the concentrated acid gas enters a rear-end sulfur recovery unit.
Therefore, the desulfurization system provided by the embodiment of the invention can be used for carrying out desulfurization treatment on the raw material natural gas, removing hydrogen sulfide and organic sulfur in the raw material natural gas and further enabling the total sulfur content in the purified gas to meet the standard. Meanwhile, the secondary flash evaporation gas containing a large amount of carbon dioxide is back-mixed into the purified gas by the flash evaporation unit and is output, so that the removal loss of the product natural gas can be reduced, and the high-selectivity desulfurization treatment is realized.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a desulfurization system provided in an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an acid gas enrichment unit according to an embodiment of the present invention.
The reference numerals denote:
1-a desulfurization absorption tower, 2 a purification gas separator, 3-a first barren solution circulating pump,
4-the first heat exchanger is arranged in the heat exchanger,
5-first-stage flash evaporation assembly, 51-first-stage flash evaporation tank, 52-first-stage rectifying column,
6-a secondary flash evaporation component, 61-a secondary flash evaporation tank, 62-a secondary rectifying column,
7-a first flow dividing valve, 8-a second heat exchanger, 9-a solvent regeneration tower, 10-a first cooler,
11-a gas-liquid separator, 12-a reflux pump, 13-an acid gas absorption tower, 14-a third heat exchanger,
15-acid gas regeneration tower, 16-rich liquor booster pump, 17-second lean liquor circulating pump, 18-semi-rich liquor circulating pump,
19-a lean liquor cooler, 20-a second diverter valve,
211-a flash evaporation three-way valve, 212-a regeneration tower bottom three-way valve, 213-an acid gas three-way valve,
22-filtration module, 23-first reboiler,
24-second reboiler, 25-second cooler.
Detailed Description
In order to make the technical solutions and advantages of the present invention clearer, the following will describe embodiments of the present invention in further detail with reference to the accompanying drawings.
In one aspect, an embodiment of the present invention provides a desulfurization system, as shown in fig. 1, including: the acid gas absorption unit, the flash evaporation unit, the solvent regeneration unit and the acid gas enrichment unit are connected in sequence.
Wherein, the sour gas absorption unit includes: the device comprises a desulfurization absorption tower 1, a purification gas separator 2 connected with an outlet at the top of the desulfurization absorption tower 1 through a pipeline, and a first barren liquor circulating pump 3 connected with an inlet at the upper part of the desulfurization absorption tower 1 through a pipeline.
The flash unit comprises: the first heat exchanger 4, the flash evaporation three-way valve 211, the first-stage flash evaporation assembly 5, the second-stage flash evaporation assembly 6 and the first flow dividing valve 7 are sequentially connected through pipelines, wherein a first outlet of the first flow dividing valve 7 is communicated with an inlet of the purification gas separator 2 through a pipeline, a tube pass inlet of the first heat exchanger 4 is connected with the bottom of the desulfurization absorption tower 1 through a pipeline, and a shell pass inlet and outlet are connected with the regeneration tower bottom three-way valve 212 and the first lean solution circulating pump 3.
The solvent regeneration unit includes: a second heat exchanger 8, a solvent regeneration tower 9, a first cooler 10, a gas-liquid separator 11 and a reflux pump 12.
Wherein, the liquid outlet of the secondary flash evaporation component 6, the second heat exchanger 8 and the first upper inlet of the solvent regeneration tower 9 are connected in sequence; the bottom outlet of the solvent regeneration tower 9, the second heat exchanger 8 and the first barren solution circulating pump 3 are connected in sequence.
The top outlet of the solvent regeneration tower 9, the first cooler 10, the gas-liquid separator 11, the reflux pump 12 and the second upper inlet of the solvent regeneration tower 9 are connected in sequence; and a gas outlet of the gas-liquid separator 11 is connected with the acid gas enrichment unit.
The working principle of the desulfurization system provided by the embodiment of the invention is as follows:
the desulfurization system provided by the embodiment of the invention can be used for selectively desulfurizing the raw material natural gas, and can effectively solve the two problems of low acid gas concentration and high product gas loss caused by excessive removal of carbon dioxide on the premise of meeting the requirement that the total sulfur content in the purified gas reaches the standard. When in application, the method can comprise the following steps:
(a) Acid gas absorption by an acid gas absorption unit: raw material natural gas containing carbon dioxide, hydrogen sulfide and organic sulfur is fed from a lower inlet of a desulfurization absorption tower 1, a desulfurization solvent is fed from an upper inlet of the desulfurization absorption tower 1 by a first barren solution circulating pump 3, in the desulfurization absorption tower 1, the raw material natural gas is in reverse contact with the desulfurization solvent, the desulfurization solvent is used for absorbing all the hydrogen sulfide and most of the organic sulfur and carbon dioxide in the raw material natural gas, a formed rich solution is discharged from a bottom outlet of the desulfurization absorption tower 1, and formed purified gas enters a purification gas separator 2 from a top outlet of the desulfurization absorption tower 1 to be subjected to gas-liquid separation so as to separate liquid carried in the purified gas.
(b) Performing multistage flash by using a flash unit: after the rich liquid is preheated to a set temperature through the first heat exchanger 4, the rich liquid sequentially enters the first-stage flash evaporation assembly 5 and the second-stage flash evaporation assembly 6 to be flashed under the control of the flash evaporation three-way valve 211, wherein most of hydrocarbons and a small amount of carbon dioxide absorbed in the rich liquid are evaporated by the first-stage flash evaporation assembly 5 by controlling the flash evaporation pressure, and a small amount of hydrocarbons and a large amount of carbon dioxide remained in the rich liquid are continuously evaporated by the second-stage flash evaporation assembly 6. Because first diverter valve 7 is connected with second grade flash distillation subassembly 6, the second grade flash distillation gas passes through first diverter valve 7 control flow and returns to in the purified gas to compensate the product gas loss that causes because of excessive desorption carbon dioxide in the purified gas.
(c) And (3) utilizing a solvent regeneration unit to regenerate the desulfurization solvent: the rich solution after the flash evaporation of the secondary flash evaporation component 6 enters a solvent regeneration tower 9 for regeneration after heat exchange through a second heat exchanger 8, so that the acid gas in the rich solution is desorbed to form a lean solution, and the aim of regenerating the desulfurization solvent is fulfilled. The regenerated desulfurization solvent, namely the barren solution, is discharged into the second heat exchanger 8 from the bottom outlet of the solvent regeneration tower 9 to exchange heat with the pregnant solution after flashing by the secondary flashing component 6, and then is recycled to the desulfurization absorption tower 1 by the first barren solution circulating pump 3 for reuse.
(d) Acid gas enrichment is carried out by using an acid gas enrichment unit: the crude acid gas is cooled to a set temperature through a first cooler 10 from a top outlet of a solvent regeneration tower 9, gas-liquid separation is carried out through a gas-liquid separator 11, liquid obtained through separation is returned to the solvent regeneration tower 9 through a reflux pump 12 for recycling, and the crude acid gas obtained through separation enters an acid gas enrichment unit for concentration so as to improve the concentration of hydrogen sulfide in the acid gas. In addition, the content of carbon dioxide can be reduced, and the concentrated acid gas enters a rear-end sulfur recovery unit.
Therefore, the desulfurization system provided by the embodiment of the invention can be used for desulfurizing the raw natural gas, so that hydrogen sulfide and organic sulfur in the raw natural gas are removed, and the total sulfur content in the purified gas meets the standard. Meanwhile, the secondary flash steam containing a large amount of carbon dioxide is returned to the purified gas by the flash evaporation unit for output, so that the removal loss of the product natural gas can be reduced, and the high-selectivity desulfurization treatment is realized.
The flash evaporation unit provided by the embodiment of the invention can be understood as a heat exchange multistage flash evaporation unit, and comprises: first heat exchanger 4, flash distillation three-way valve 211, one-level flash evaporation subassembly 5, second grade flash evaporation subassembly 6 and first reposition of redundant personnel valve 7, the shell side entry of first heat exchanger 4 and regeneration tower bottom three-way valve 212 one of them exit linkage, the shell side export links to each other with the entry of first barren liquor circulating pump 3, the tube side entry links to each other with the barren liquor export of desulfurization absorption tower 1 bottom, the tube side export then is connected to the entry of the flash evaporation three-way valve 211 on one-level flash evaporation subassembly 5 upper reaches.
The first splitter valve 7 splitter valve has a first outlet for back-mixing the secondary flash gas containing a significant amount of carbon dioxide into the purge gas and a second outlet for transporting part of the secondary flash gas to the tail gas treatment unit and venting. The split ratio is controlled according to the content of carbon dioxide in the product natural gas, so that the product gas amount is improved to the maximum extent under the condition that the content of the carbon dioxide is not over standard (the content of the carbon dioxide in the product gas is less than or equal to 3 percent).
The absorption pressure of the desulfurization absorption tower 1 can be 4-8 MPa, the desulfurization absorption tower can adopt a tower plate and filler composite structure, the lower half section of the tower is of a plate structure, the number of plates is not lower than 18 layers, the height of an overflow weir is not lower than 120mm, the upper half section of the tower is of a filler tower structure, the height of the filler is not lower than 10m, and multi-point feeding is required to meet different gas quality requirements.
The desulfurization absorption tower 1 creatively adopts a composite structure of the filler and the plate tower, thereby not only avoiding the defect of insufficient contact time of the plate tower, but also reducing the risk of easy blockage of the filler tower. The lower half section of the absorption tower adopts a plate structure, so that impurities carried in the raw material natural gas can be washed away while providing a gas-liquid absorption reaction contact place, and the impurities are prevented from entering the upper half section to block the filler; the upper half section of the absorption tower adopts a filler structure, so that the gas-liquid contact time can be effectively prolonged, the flooding rate is reduced, and the organic sulfur removal rate is improved. The absorption tower with the innovative design has the advantages of both a plate tower and a packed tower, and is particularly suitable for removing organic sulfur.
The purification gas separator 2 is mainly used for separating water and desulfurization solvent such as amine liquid entrained in the purified gas. The gas-liquid separator 11 includes a gas outlet at the top and a liquid outlet at the bottom.
Further, as shown in fig. 2, the acid gas enrichment unit comprises: an acid gas absorption tower 13, a third heat exchanger 14, an acid gas regeneration tower 15, a rich liquid booster pump 16, a second lean liquid circulating pump 17, a semi-rich liquid circulating pump 18 and a lean liquid cooler 19.
Wherein, the lower inlet of the acid gas absorption tower 13 is connected with the gas outlet of the gas-liquid separator 11 through a pipeline;
the bottom outlet of the acid gas absorption tower 13, the third heat exchanger 14, the rich liquid booster pump 16 and the upper inlet of the acid gas regeneration tower 15 are connected in sequence;
the bottom outlet of the acid gas regeneration tower 15, the third heat exchanger 14, the second lean solution circulating pump 17, the lean solution cooler 19 and the middle inlet of the acid gas absorption tower 13 are sequentially connected;
the lower outlet of the acid gas absorption tower 13, the semi-rich liquid circulating pump 18 and the upper inlet of the acid gas absorption tower 13 are connected in sequence.
When the method is applied, the crude acid gas enters the acid gas absorption tower 13 and reversely contacts with the desulfurization barren solution entering from the inlet at the middle part of the acid gas absorption tower, after most of hydrogen sulfide and part of carbon dioxide in the crude acid gas are absorbed by the desulfurization barren solution, the crude acid gas continuously moves upwards and reversely contacts with the desulfurization semi-rich solution entering from the inlet at the upper part of the acid gas absorption tower 13, and the hydrogen sulfide in the crude acid gas is further removed. The remaining gas is discharged as an enriched tail gas from the top of the acid gas absorption tower 13. Meanwhile, part of the rich solution formed at the bottom of the acid gas absorption tower 13 exchanges heat through a third heat exchanger 14, enters an acid gas regeneration tower 15 through a rich solution booster pump 16 to regenerate the acid gas therein, and the regenerated acid gas enters a rear-end sulfur recovery unit through a top outlet of the acid gas regeneration tower 15. The regenerated desulfurized lean solution formed in the acid gas regeneration tower 15 is led out from the tower bottom, exchanges heat with the rich solution through the third heat exchanger 14, is cooled to a set temperature through the lean solution cooler 19, and is pumped into the acid gas absorption tower 13 through the second lean solution circulating pump 17 for recycling.
Further, another part of the rich liquid formed at the bottom of the acid gas absorption tower 13 is conveyed to the upper part of the tower through a semi-rich liquid circulating pump 18, so as to improve the removal depth of the hydrogen sulfide in the enriched tail gas and simultaneously facilitate the reduction of the absorption rate of the carbon dioxide. It will be appreciated that the semi-rich circulation pump 18 is arranged to be substantially different from conventional acid gas enrichment systems.
Further, the desulfurization system provided by the embodiment of the present invention further includes: a second flow dividing valve 20, wherein a first outlet of the second flow dividing valve 20 is connected with the purified gas separator 2 through a pipeline; the inlet of the second separation valve is communicated with the top outlet of the acid gas absorption tower 13.
The enriched tail gas discharged from the top of the acid gas absorption tower 13 is divided by using the second flow dividing valve 20, and the enriched tail gas can be introduced into the purification gas separator 2 as product natural gas on the premise that the product gas does not exceed the standard, or the enriched tail gas enters a tail gas treatment unit for treatment and then is discharged.
It can be understood that the tail gas involved in the embodiment of the present invention mainly contains nitrogen and carbon dioxide. The tail gas treatment unit is mainly used for removing sulfur-containing compounds such as sulfur dioxide and hydrogen sulfide, and cannot be directly discharged into the atmosphere.
Further, the desulfurization system provided by the embodiment of the present invention further includes: and an inlet of the acid gas three-way valve 213 is connected with a gas outlet of the gas-liquid separator 11, one of the two outlet ends is connected with the rear-end sulfur recovery unit, and the other outlet end is connected with a gas inlet at the bottom of the acid gas absorption tower 13.
Through setting up sour gas three-way valve 213 to whether the control desulfurization process needs to adopt sour gas enrichment unit, when not needing, can make sour gas directly get into rear end sulphur recovery unit. Therefore, through the acid gas three-way valve 213, the acid gas enrichment unit can be skipped to recover the traditional amine desulphurization process, and the flexibility of the desulphurization process is improved.
Furthermore, a flash three-way valve 211 is also arranged between the bottom outlet of the desulfurization absorption tower 1 and the inlet of the flash evaporation assembly, the inlet end of the flash three-way valve is connected with the bottom of the desulfurization absorption tower 1, one outlet end of the flash three-way valve is connected with the inlet of the first-level flash evaporation tank, and the other outlet end of the flash three-way valve is connected with the inlet of the second-level flash evaporation tank, so that the step of the second-level flash evaporation can be skipped to recover to the traditional amine desulfurization process, and the flexibility of the desulfurization process is improved.
Similarly, the lean solution outlet at the bottom of the regeneration tower is also provided with a regeneration tower bottom three-way valve 212, the inlet of the regeneration tower bottom three-way valve is connected with the lean solution outlet at the bottom of the regeneration tower, the two outlet ends of the regeneration tower bottom three-way valve are respectively connected with a second heat exchanger and a second heat exchanger, and by switching the three-way valves, heat exchange before flash evaporation can be selected to improve flash evaporation efficiency or heat exchange before regeneration of the traditional process is recovered, so that the flexibility of the desulfurization process is further improved.
In the embodiment of the present invention, the primary flash evaporation assembly 5 includes: a primary flash tank 51, and a primary rectification column 61 connected to the top outlet of the primary flash tank 51.
Most of hydrocarbons and a small amount of carbon dioxide absorbed in the rich solution are evaporated through the primary flash tank 51, and the primary flash gas is desulfurized through the primary rectifying column 61, so that the formed primary flash gas can be used as plant fuel gas.
Wherein for the primary rectification column 61 a small lean stream (e.g. 1/50 of the volume flow of the flash gas at standard conditions) can be used to remove a small amount of hydrogen sulphide contained in the primary flash gas, since the primary flash gas has two removals, one being returned to the purge, requiring that the purge hydrogen sulphide after back-mixing does not exceed 6mg/m 3 . The other part is to enter a tail gas treatment unit or be used as fuel gas of a factory, and the total sulfur is required to be not more than 100ppm and can meet the requirements.
In the embodiment of the present invention, the secondary flash evaporation assembly 6 includes: a secondary flash tank 61 communicated with a bottom outlet of the primary flash tank 51; and a secondary rectification column 62 connected to the top outlet of the secondary flash tank 61;
wherein the gas outlet of the secondary rectification column 62 is communicated with the inlet of the first splitter valve 7.
An inlet of the flash three-way valve 211 is connected with a tube pass outlet of the first heat exchanger 4, one outlet of the flash three-way valve 211 is connected with an inlet of the first-stage flash tank 51, and the other outlet is connected with an inlet of the second-stage flash tank 61 and used for switching between single-stage flash and multi-stage flash.
And (3) continuously distilling out a small part of hydrocarbons and most of carbon dioxide remained in the rich liquid through a secondary flash tank 61, and further desulfurizing the secondary flash gas through a secondary rectifying column 62 to improve the concentration of the carbon dioxide in the secondary flash gas.
It will be appreciated that the carbon dioxide content of the rich liquor is much higher than the organic sulphur content, so that in the secondary flash the carbon dioxide will flash out more easily, while the organic sulphur remains in the rich liquor. According to the embodiment of the invention, the hydrocarbons and the carbon dioxide are respectively flashed out through the pressure difference of two-stage flashing and the equilibrium constant difference of different gases.
For example, the primary flash evaporation pressure is 0.6 to 0.8MPa, the secondary flash evaporation pressure is 0.2 to 0.3MPa, and the flash evaporation pressure is set to ensure that the primary flash evaporation gas mainly contains hydrocarbons and the secondary flash evaporation gas mainly contains carbon dioxide.
The desulfurization solvent used in the first-stage rectification column 61 and the second-stage rectification column 62 is the same as that used in the desulfurization absorption tower 1.
The embodiment of the invention utilizes the gas-liquid separator 11 to carry out gas-liquid separation on the crude acid gas so as to obtain acid water and dry crude acid gas. Acid water is pumped into the acid gas regeneration tower 15 through the reflux pump 12 to supplement water consumed by secondary steam, and crude acid gas enters the sulfur recovery unit after entering the acid gas enrichment unit for enrichment or directly enters the sulfur recovery unit without enrichment.
Further, in the embodiment of the present invention, a filtering assembly 22 is disposed on the pipeline between the second heat exchanger 8 and the solvent regeneration tower 9 to filter the rich liquid flashed by the secondary flash evaporation assembly 6, so as to remove impurities or oil contamination therein. The filter assembly 22 may include a plurality of filters, such as three filters, arranged in series, and the filters may be mechanical filters or carbon filters.
Specifically, the lower portions of the solvent regeneration tower 9 and the acid gas regeneration tower 15 are provided with a first reboiler 23 and a second reboiler 24, respectively.
By using the first reboiler 23 and the second reboiler 24, the solution can be heated to generate secondary steam to extract the rich solution in the regeneration tower to regenerate the acid gas absorbed by the rich solution, thereby realizing the solvent regeneration.
In the embodiment of the invention, the acid gas absorption tower 13 adopts a plate tower structure, the absorption pressure is 60-90 KPa, the number of tower plates is 20, and absorption barren solution can enter from the tower plates of 8-12 layers; the bottom of the tower is provided with a semi-rich liquid circulating pump 18 which is used for conveying the rich liquid at the bottom of the tower to the top of the tower, so that the hydrogen sulfide in the gas flow is thoroughly removed. The absorption liquid used in the acid gas absorption tower 13 may be an aqueous solution of organic amine, wherein the organic amine includes, but is not limited to: one or more of methyldiethanolamine, triethanolamine, hydroxyethyl ethylenediamine and tert-butylamine ethoxy ethanol.
Further, a second cooler 25 may be provided on a line between the first lean solution circulation pump 3 and the upper inlet of the desulfurization absorbing tower 1 for reducing the temperature of the lean solution from about 90 ℃ to less than 40 ℃ for recycling. Wherein the second cooler 25 includes but is not limited to: air coolers and/or water coolers.
The desulfurization system provided by the embodiment of the invention has flexible process switching design, and is realized by arranging the control valve at a key position:
the flash three-way valve 211 is used for switching between single-stage flash evaporation and multi-stage flash evaporation; the regeneration tower bottom three-way valve 212 is used for switching normal-temperature flash evaporation and preheating flash evaporation; the acid gas switching valve 213 is used to select whether to adopt an acid gas enrichment unit; the first and second diverter valves 7 and 20 are used to control the amount of carbon dioxide back-mixed into the purified gas, and the process flow can be reduced to a conventional amine desulfurization process by adjusting the control valves.
In another aspect, embodiments of the present invention further provide a desulfurization method, where the desulfurization method applies any one of the desulfurization systems mentioned above.
Specifically, the method comprises the following steps:
acid gas absorption by an acid gas absorption unit: raw material natural gas is fed from the lower inlet of the desulfurization absorption tower 1, a desulfurization solvent is fed from the upper inlet of the desulfurization absorption tower 1 by using the first barren solution circulating pump 3, in the desulfurization absorption tower 1, the raw material natural gas is in reverse contact with the desulfurization solvent, desulfurization treatment is performed by using the desulfurization solvent, formed rich liquid is discharged from the bottom outlet of the desulfurization absorption tower 1, and formed purified gas enters the gas purification and separation device 2 from the top outlet of the desulfurization absorption tower 1 to be subjected to gas-liquid separation.
Performing multistage flash by using a flash unit: the rich solution exchanges heat with the lean solution from the solvent regeneration tower 9 through the first heat exchanger 4, the lean solution is heated to a set temperature and then sequentially enters the first-stage flash evaporation assembly 5 and the second-stage flash evaporation assembly 6 to be subjected to flash evaporation, second-stage flash evaporation gas with the main component of carbon dioxide is formed, and the flow of the second-stage flash evaporation gas is controlled through the first diversion valve 7 to return to the purified gas so as to compensate the loss of product gas caused by excessive absorption of the carbon dioxide by the desulfurization solvent in the purified gas.
And (3) utilizing a solvent regeneration unit to regenerate the desulfurization solvent: the rich solution obtained after the flash evaporation of the secondary flash evaporation component 6 enters the solvent regeneration tower 9 for regeneration after heat exchange through the second heat exchanger 8, so that the acid gas is desorbed, the formed regenerated barren solution is discharged into the second heat exchanger 8 from the bottom outlet of the solvent regeneration tower 9 to exchange heat with the rich solution after the flash evaporation of the secondary flash evaporation component 6, and then is circulated to the desulfurization absorption tower 1 again through the first barren solution circulating pump 3 for reuse;
acid gas enrichment is carried out by using an acid gas enrichment unit: and after the crude acid gas formed after the desorption of the acid gas is cooled to a set temperature by a first cooler 10 from an outlet at the top of the solvent regeneration tower 9, gas-liquid separation is carried out by a gas-liquid separator 11, the liquid obtained by the separation is returned to the solvent regeneration tower 9 by a reflux pump 12 for recycling, and the crude acid gas obtained by the separation enters an acid gas enrichment unit for concentration.
Further, the method also comprises an acid gas enrichment step: the crude acid gas enters the acid gas absorption tower 13, and is in reverse contact with the desulfurization barren solution (i.e., absorption liquid) to perform primary desulfurization treatment, and then continues to go upward to be in reverse contact with the desulfurization semi-rich solution entering from the upper inlet of the acid gas absorption tower 13 to perform secondary desulfurization treatment (i.e., deep desulfurization treatment).
The remaining gas is discharged as an enriched tail gas from the top of the acid gas absorption tower 13.
After heat exchange is carried out on part of rich liquid formed at the bottom of the acid gas absorption tower 13 through a third heat exchanger 14, the rich liquid enters an acid gas regeneration tower 15 through a rich liquid booster pump 16 so as to regenerate the acid gas, and the regenerated acid gas (also called enriched acid gas) enters a rear-end sulfur recovery unit.
The regenerated desulfurization barren solution formed in the acid gas regeneration tower 15 is led out from the tower bottom, exchanges heat with the rich solution formed at the tower bottom of the acid gas absorption tower 13 through the third heat exchanger 14, is cooled to a set temperature through the barren solution cooler 19, and enters the acid gas absorption tower 13 through the second barren solution circulating pump 17 for recycling.
And a semi-rich liquid circulating pump 18 for desulfurization formed at the bottom of the acid gas absorption tower 13 is introduced into the upper part of the tower and used as a semi-rich liquid for desulfurization so as to improve the removal depth of hydrogen sulfide in the enriched tail gas.
In the embodiment of the present invention, the semi-rich liquid refers to an absorption liquid at the bottom of the acid gas absorption tower 13, such as an amine liquid, which absorbs some hydrogen sulfide and carbon dioxide, and thus has a weak absorption capacity for carbon dioxide. The semi-rich liquid is pumped to the acid gas absorption tower 13, so that hydrogen sulfide in the enriched tail gas is absorbed as clean as possible, and carbon dioxide is absorbed as little as possible. According to the embodiment of the invention, the barren solution is pumped into the acid gas absorption tower 13 from the middle section, and then the semi-rich solution is used for ensuring that the hydrogen sulfide does not exceed the standard, so that the absorption amount of carbon dioxide can be effectively reduced, and the concentration of the hydrogen sulfide in the acid gas can be improved.
In the desulfurization system and the desulfurization method provided by the embodiment of the invention, the organic sulfur removal rate of the used desulfurization solvent is more than or equal to 90%. The solvent includes but is not limited to physical solvent, chemical solvent and physical chemical solvent, besides the main component of the solvent, also includes but is not limited to activator, inhibitor, foam inhibitor and so on. For example, lean amine liquids may be used as the desulfurization solvent to ensure a sufficiently high sulfur removal rate. Aiming at the two types of desulfurization solvents, the removal rate of carbon dioxide can be reduced and the concentration of acid gas can be improved while the higher organic sulfur removal rate is ensured. The acid gas load of the physical and chemical solvent is not more than 0.55mol/mol (calculated by alkaline substances); the acid gas load of the physical solvent is not more than 0.8mol/mol (based on the physical solvent); the acid gas load of the chemical solvent is not more than 0.8mol/mol (based on alkaline substances).
In the desulfurization absorption tower 1, the reverse contact of the raw material natural gas and the desulfurization solvent can be carried out under a pressure of 5.0 to 7.0 MPa.
After the rich solution obtained by the flash evaporation of the secondary flash evaporation component 6 is subjected to heat exchange by the second heat exchanger 8, the temperature of the rich solution can reach 80-90 ℃, and when the rich solution enters the solvent regeneration tower 9 for regeneration, the regeneration pressure can be 110-120KPa.
The lean solution formed after desorption of the acid gas has a temperature of about 120 c, for example, 125 c, when it is drawn from the bottom of the solvent regenerator 9, and is heat-exchanged with the rich solution by the second heat exchanger 8, so that the temperature can be lowered to about 90 c.
Further, a second cooler 25 may be provided on a line between the first lean solution circulation pump 3 and the upper inlet of the desulfurization absorbing tower 1 for reducing the temperature of the lean solution from about 90 ℃ to less than 40 ℃ for recycling. Wherein the second cooler 25 includes, but is not limited to: air coolers and/or water coolers.
The inventive example also provides a specific example of the desulfurization of feed natural gas using the desulfurization method of the present invention and using a conventional amine process, wherein the compositions of the feed natural gas and the respective intermediate gases are shown in table 1.
TABLE 1
| Material(s) | H 2 Content of S% | CO 2 Content% | CH 4 Content% | Organic sulfur content mg/m 3 | Flow rate kmol/h |
| Raw material gas | 1.56 | 4.35 | 94.09 | 120 | 1000 |
| First stage flash gas | 0.007 | 211.212 | 72.21 | 8.5 | 5.13 |
| Secondary flash gas | 0.02 | 78.56 | 20.212 | 2.3 | 22.94 |
| Crude sour gas | 38.65 | 60.10 | 1.25 | 21163 | 40.1 |
| Acid gas enrichment | 54.42 | 44.17 | 1.41 | 21105 | 213.3 |
| Enriched tail gas | 1.17 | 91.81 | 7.02 | 1106 | 17.10 |
| Purified gas (invention) | 2.2mg/m 3 | 1.91 | 98.09 | 8.5 | 954.2 |
| Purified gas (conventional process) | 1.5mg/m 3 | 0.06 | 99.94 | 6.8 | 937.6 |
As can be seen from table 1, in the conventional amine-method organic sulfur removal process, since the desulfurization solution is difficult to selectively remove carbon dioxide and organic sulfur, carbon dioxide is almost completely removed even when the organic sulfur removal rate is high, and only 0.06% of carbon dioxide remains in the purified gas when the carbon dioxide content in the raw natural gas is 4.35%.
By adopting the method provided by the embodiment of the invention, the content of carbon dioxide in the purified gas is increased to 1.91 percent due to the back mixing of the secondary flash steam, and the selectivity is greatly improved. For a medium scale natural gas purification plant with a throughput of 400 ten thousand Fahrenheit/day, about 7.5 million Fahrenheit removal losses are reduced per day. The content of hydrogen sulfide in the acid gas generated by the common process is 38.65%, and after the method provided by the embodiment of the invention is adopted, the hydrogen sulfide concentration in the acid gas is greatly improved to 54.42% through two times of concentration by multi-stage flash evaporation and acid gas enrichment, the quality of the acid gas is obviously improved, and the removal rate of organic sulfur is still more than 90%. Therefore, the desulfurization system and the desulfurization method provided by the embodiment of the invention have great advantages compared with the traditional amine method organic sulfur removal process.
The above description is only for the convenience of understanding the technical solutions of the present invention by those skilled in the art, and is not intended to limit the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (12)
1. A desulfurization system for use in the desulfurization of natural gas, the desulfurization system comprising: the acid gas absorption unit, the flash evaporation unit, the solvent regeneration unit and the acid gas enrichment unit are sequentially connected;
wherein the acid gas absorption unit comprises: the device comprises a desulfurization absorption tower, a purification gas separator connected with an outlet at the top of the desulfurization absorption tower through a pipeline, and a first barren solution circulating pump connected with an inlet at the upper part of the desulfurization absorption tower through a pipeline;
the flash unit comprises: the first heat exchanger, the flash evaporation three-way valve, the first-stage flash evaporation assembly, the second-stage flash evaporation assembly and the first flow dividing valve are sequentially connected through pipelines, wherein a first outlet of the first flow dividing valve is communicated with an inlet of the purification and gas separator through a pipeline, the first heat exchanger is communicated with a bottom outlet of the desulfurization absorption tower through a pipeline, rich liquid passes through the first heat exchanger, exchanges heat with lean liquid from the solvent regeneration tower to be heated, then sequentially enters the first-stage flash evaporation assembly and the second-stage flash evaporation assembly to be subjected to flash evaporation to form second-stage flash evaporation gas with carbon dioxide as a main component, and the flow of the second-stage flash evaporation gas is controlled by the first flow dividing valve to return to purified gas;
the solvent regeneration unit includes: the system comprises a second heat exchanger, a solvent regeneration tower, a first cooler, a gas-liquid separator and a reflux pump;
the liquid outlet of the secondary flash evaporation assembly, the second heat exchanger and the first upper inlet of the solvent regeneration tower are connected in sequence;
the bottom outlet of the solvent regeneration tower, the second heat exchanger and the first barren solution circulating pump are connected in sequence;
the top outlet of the solvent regeneration tower, the first cooler, the gas-liquid separator, the reflux pump and the second upper inlet of the solvent regeneration tower are sequentially connected;
and a gas outlet of the gas-liquid separator is connected with the acid gas enrichment unit.
2. The desulfurization system of claim 1, wherein the acid gas enrichment unit comprises: the system comprises an acid gas absorption tower, a third heat exchanger, an acid gas regeneration tower, a rich solution booster pump, a second barren solution circulating pump, a semi-rich solution circulating pump and a barren solution cooler;
the lower inlet of the acid gas absorption tower is connected with the gas outlet of the gas-liquid separator through a pipeline;
the bottom outlet of the acid gas absorption tower, the third heat exchanger, the rich liquid booster pump and the upper inlet of the acid gas regeneration tower are sequentially connected;
the bottom outlet of the acid gas regeneration tower, the third heat exchanger, the second barren solution circulating pump, the barren solution cooler and the middle inlet of the acid gas absorption tower are sequentially connected;
and the lower outlet of the acid gas absorption tower, the semi-rich liquid circulating pump and the upper inlet of the acid gas absorption tower are sequentially connected.
3. The desulfurization system of claim 2, further comprising: the first outlet of the second flow dividing valve is connected with the purified gas separator through a pipeline;
and the inlet of the second flow dividing valve is communicated with the top outlet of the acid gas absorption tower.
4. The desulfurization system of claim 2, further comprising: a sour gas three-way valve;
the inlet of the acid gas three-way valve is connected with the gas outlet of the gas-liquid separator, one of the two outlet ends is connected with the rear-end sulfur recovery unit, and the other outlet end is connected with the gas inlet at the bottom of the acid gas absorption tower.
5. The desulfurization system of claim 1, wherein said primary flash assembly comprises: the device comprises a first-stage flash tank and a first-stage rectifying column connected with an outlet at the top of the first-stage flash tank.
6. The desulfurization system of claim 5, wherein the secondary flash assembly comprises: the secondary flash tank is communicated with the bottom outlet of the primary flash tank, and the secondary rectifying column is connected with the top outlet of the secondary flash tank;
wherein a gas outlet of the secondary rectification column is communicated with an inlet of the first splitter valve;
the inlet of the flash three-way valve is connected with the tube pass outlet of the first heat exchanger, one outlet of the flash three-way valve is connected with the inlet of the primary flash tank, and the other outlet of the flash three-way valve is connected with the inlet of the secondary flash tank.
7. The desulfurization system of claim 1, wherein a filtration assembly is disposed on a line between the second heat exchanger and the solvent regeneration column.
8. The desulfurization system according to claim 2, wherein the lower portions of the solvent regeneration column and the acid gas regeneration column are provided with a first reboiler and a second reboiler, respectively.
9. The desulfurization system of claim 1, further comprising: and the second cooler is arranged between the first barren solution circulating pump and the upper inlet of the desulfurization absorption tower.
10. A desulfurization method using the desulfurization system according to any one of claims 1 to 9.
11. The desulfurization method according to claim 10, characterized in that the method comprises:
acid gas absorption by an acid gas absorption unit: feeding raw natural gas from a lower inlet of a desulfurization absorption tower, feeding a desulfurization solvent from an upper inlet of the desulfurization absorption tower by using a first barren solution circulating pump, in the desulfurization absorption tower, reversely contacting the raw natural gas with the desulfurization solvent, performing desulfurization treatment by using the desulfurization solvent, discharging formed rich liquid from a bottom outlet of the desulfurization absorption tower, and allowing formed purified gas to enter a purification gas separator from a top outlet of the desulfurization absorption tower for gas-liquid separation;
performing multistage flash by using a flash unit: the rich solution enters a first heat exchanger, exchanges heat with the lean solution from the solvent regeneration tower and is heated, and then sequentially enters a primary flash evaporation assembly and a secondary flash evaporation assembly for flash evaporation to form secondary flash evaporation gas with the main component of carbon dioxide, and the secondary flash evaporation gas returns to the purified gas through the control of the flow rate of a first flow dividing valve so as to compensate the loss of product gas caused by the excessive absorption of the carbon dioxide by the desulfurization solvent in the purified gas;
and (3) utilizing a solvent regeneration unit to regenerate the desulfurization solvent: the rich solution obtained after the flash evaporation of the secondary flash evaporation component enters the solvent regeneration tower for regeneration after heat exchange through the second heat exchanger, so that the acid gas is desorbed, the formed barren solution is discharged into the second heat exchanger from the bottom outlet of the solvent regeneration tower to exchange heat with the rich solution subjected to flash evaporation of the secondary flash evaporation component, and then is recycled to the desulfurization absorption tower for reuse through the first barren solution circulating pump;
acid gas enrichment is carried out by using an acid gas enrichment unit: and after the crude acid gas formed after the acid gas is desorbed is cooled to a set temperature through a first cooler from a top outlet of the solvent regeneration tower, gas-liquid separation is carried out through a gas-liquid separator, the liquid obtained through the separation is returned to the solvent regeneration tower through a reflux pump for reuse, and the crude acid gas obtained through the separation enters an acid gas enrichment unit for concentration.
12. The desulfurization method according to claim 11, characterized in that the method comprises:
the crude acid gas enters an acid gas absorption tower, reversely contacts with the desulfurization barren solution to carry out primary desulfurization treatment, and continuously goes upward to reversely contact with the desulfurization semi-rich solution entering from an inlet at the upper part of the acid gas absorption tower to carry out secondary desulfurization treatment; discharging the residual gas as enriched tail gas from the top of the acid gas absorption tower;
after exchanging heat of part of rich solution formed at the bottom of the acid gas absorption tower through a third heat exchanger, the rich solution enters an acid gas regeneration tower through a rich solution booster pump so as to regenerate acid gas, and the regenerated acid gas enters a rear-end sulfur recovery unit;
the regenerated desulfurization barren solution formed in the acid gas regeneration tower is led out from the tower bottom, exchanges heat with rich solution formed at the tower bottom of the acid gas absorption tower through a third heat exchanger, is cooled to a set temperature through a barren solution cooler, and is pumped into the acid gas absorption tower by a second barren solution circulating pump for recycling;
and a semi-rich liquid circulating pump for desulfurization formed at the bottom of the acid gas absorption tower enters the upper part of the tower so as to improve the removal depth of hydrogen sulfide in the enriched tail gas.
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