CN114907894A - Method for removing methanol from natural gas - Google Patents
Method for removing methanol from natural gas Download PDFInfo
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- CN114907894A CN114907894A CN202210658949.5A CN202210658949A CN114907894A CN 114907894 A CN114907894 A CN 114907894A CN 202210658949 A CN202210658949 A CN 202210658949A CN 114907894 A CN114907894 A CN 114907894A
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 title claims abstract description 322
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 110
- 239000003345 natural gas Substances 0.000 title claims abstract description 55
- 238000000034 method Methods 0.000 title claims abstract description 49
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 35
- 239000007789 gas Substances 0.000 claims abstract description 29
- 239000000243 solution Substances 0.000 claims abstract description 27
- 239000007864 aqueous solution Substances 0.000 claims abstract description 26
- 239000002994 raw material Substances 0.000 claims abstract description 23
- 238000010521 absorption reaction Methods 0.000 claims abstract description 22
- 239000002253 acid Substances 0.000 claims abstract description 13
- 238000000926 separation method Methods 0.000 claims abstract description 13
- 230000018044 dehydration Effects 0.000 claims abstract description 5
- 238000006297 dehydration reaction Methods 0.000 claims abstract description 5
- 239000002808 molecular sieve Substances 0.000 claims abstract description 4
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims abstract description 4
- 238000001179 sorption measurement Methods 0.000 claims abstract description 4
- 230000008929 regeneration Effects 0.000 claims description 24
- 238000011069 regeneration method Methods 0.000 claims description 24
- 239000007788 liquid Substances 0.000 claims description 13
- 238000010438 heat treatment Methods 0.000 claims description 11
- 238000001816 cooling Methods 0.000 claims description 8
- 238000007599 discharging Methods 0.000 claims description 6
- 238000002485 combustion reaction Methods 0.000 claims description 4
- 238000005086 pumping Methods 0.000 claims description 3
- 238000004064 recycling Methods 0.000 claims description 3
- -1 methyl-dimethyl-ammonium-ethyl-ammonium-acetate Chemical compound 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract description 10
- 238000007710 freezing Methods 0.000 abstract description 5
- 230000008014 freezing Effects 0.000 abstract description 5
- 238000004364 calculation method Methods 0.000 description 6
- 238000005516 engineering process Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 238000012856 packing Methods 0.000 description 4
- 238000005261 decarburization Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000004088 simulation Methods 0.000 description 3
- 239000006096 absorbing agent Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004821 distillation Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000011049 filling Methods 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 239000002912 waste gas Substances 0.000 description 2
- 239000002351 wastewater Substances 0.000 description 2
- UJJCKYKIYPQYIE-UHFFFAOYSA-N 2-ethoxytridecane Chemical compound CCCCCCCCCCCC(C)OCC UJJCKYKIYPQYIE-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- GBMDVOWEEQVZKZ-UHFFFAOYSA-N methanol;hydrate Chemical compound O.OC GBMDVOWEEQVZKZ-UHFFFAOYSA-N 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000011112 process operation Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000012808 vapor phase Substances 0.000 description 1
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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
-
- 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
- C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
- C10L2290/54—Specific separation steps for separating fractions, components or impurities during preparation or upgrading of a fuel
- C10L2290/541—Absorption of impurities during preparation or upgrading of a fuel
-
- 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
- C10L2290/00—Fuel preparation or upgrading, processes or apparatus therefore, comprising specific process steps or apparatus units
- C10L2290/54—Specific separation steps for separating fractions, components or impurities during preparation or upgrading of a fuel
- C10L2290/542—Adsorption of impurities during preparation or upgrading of a fuel
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2
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- Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention discloses a method for removing methanol from natural gas, which comprises the steps of feeding raw natural gas containing methanol into an absorption tower, and chemically absorbing acid gas CO in the raw natural gas by using MDEA (methyl-dimethyl-EA) aqueous solution 2 Meanwhile, the methanol in the raw material natural gas is dissolved and absorbed by water, and the natural gas without acid gas and methanol enters a molecular sieve adsorption dehydration system from the top of the absorption tower. The invention removes CO from the acid gas of the raw material natural gas containing methanol 2 The methanol-containing water solution from the separation tank is subjected to methanol removal, the process is mature, the adaptability is strong, the device is particularly suitable for working conditions that the content of methanol in raw natural gas is high and the fluctuation range is large, the methanol in the raw natural gas can be effectively removed, pure water for dissolving MDEA is recycled, the LNG cold box is prevented from being blocked due to methanol freezing, and the stability and the reliability of production are improved.
Description
Technical Field
The invention relates to the technical field of natural gas manufacturing, in particular to a method for natural gas dealcoholization.
Background
In order to prevent the natural gas from forming freezing blockage during dehydration due to the high water freezing point in winter, methanol is added to reduce the water freezing point, so that a small amount of saturated methanol steam is brought into the raw natural gas. If the methanol in the raw material natural gas is not removed, when the methanol dissolved in the MDEA aqueous solution reaches a saturated state, the methanol enters the LNG cold box along with the raw material natural gas, and the methanol freezes at the temperature of-97.8 ℃, so that a narrow channel of a plate-fin heat exchanger of the cold box is blocked, and the normal production operation is influenced.
In the existing natural gas liquefaction process, methanol is basically not considered, methanol removing processes and devices are lacked, few methanol removing devices are provided, the raw material natural gas is directly subjected to methanol removal in a water scrubber mode on a main process route, the pressure of the main process route is high, the pressure needs to be increased to 5MPa, the flow is large, the requirement on equipment is high, and the investment is large; and few of the gas stripping tower processes are adopted, the system is complex, the equipment is more, the separation effect is not ideal, the tail gas is not well treated, and the environmental protection requirement is difficult to achieve.
Disclosure of Invention
Aiming at the problems in the related art, the invention provides a method for removing methanol from natural gas, which aims to overcome the technical problems of high equipment requirement and large investment in the prior related art.
In order to achieve the purpose, the invention adopts the following technical scheme: the invention provides a natural gas methanol removal method, which comprises the following steps of 1, feeding raw natural gas containing methanol into an absorption tower, and chemically absorbing acid gas CO in the raw natural gas through MDEA (methyl-dimethyl-ethyl-EA) aqueous solution 2 Simultaneously, the methanol in the raw material natural gas is dissolved and absorbed by water, and the natural gas without acid gas and methanol enters a molecular sieve adsorption dehydration system from the top of an absorption tower;
step 2, the bottom of the absorption tower contains CO 2 The MDEA aqueous solution of the methanol enters a regeneration tower after being decompressed and flashed, the MDEA aqueous solution is heated by a reboiler for regeneration, the qualified MDEA aqueous solution flows out of the bottom of the regeneration tower, and the gas flowing out of the top of the regeneration tower enters CO after being cooled by air 2 The separation tank is used for separating the waste water from the waste water,
step 3, for CO 2 The aqueous solution containing methanol at the bottom of the separation tank is rectified and separated by a double rectifying tower, the methanol vapor separated from the top of the second rectifying tower is fed to a flare tower for combustion, and qualified dilute MDEA aqueous solution flows out of the bottoms of the first rectifying tower and the second rectifying tower and returns to the system for reuse.
In a possible design, in the step 2, the diameter of each of the first rectifying tower and the second rectifying tower is less than 300mm, and the first rectifying tower and the second rectifying tower are atmospheric towers.
In one possible design, in step 1, a methanol-containing feed natural gas is fed to the absorber column at a pressure of 5 MPa.
In one possible design, the concentration of the MDEA aqueous solution is 40 weight%.
In one possible design, in step 2, the bottom of the absorber column contains CO 2 The aqueous solution of methanol MDEA was reduced to 0.9 MPa.
In one possible design, in step 2, regeneration is carried out by heating to 121 ℃ via a reboiler.
In one possible design, step 3 is specifically a dilute solution of MDEA containing methanol from CO 2 And discharging from the bottom of the separator, pumping the discharged liquid into a first rectifying tower, heating the liquid by a reboiler, cooling the rectified water vapor containing methanol and MDEA into liquid by air, then feeding the liquid into a second rectifying tower, heating the liquid by the reboiler again, discharging the rectified methanol and a small amount of water vapor from the top of the second rectifying tower to a torch tower to be combusted, and recycling the dilute solution containing a small amount of MDEA.
In a possible design, in step 3, the water vapor containing methanol and MDEA rectified out enters the second rectifying tower after being air-cooled into liquid, and is heated to 105 ℃ again by the reboiler.
In one possible design, step 3, a dilute methanol-containing MDEA solution is removed from CO 2 The bottom of the separator was discharged and pumped into the first rectification column and heated to 105 ℃ by a reboiler.
In a possible design, in step 2, the gas flowing out of the top of the regeneration tower enters CO after being air-cooled to 42 DEG C 2 And (5) separating the tank.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention removes CO from the acid gas of the raw material natural gas containing methanol 2 The methanol-containing water solution from the separating tank is subjected to methanol removal, the process is mature, the adaptability is strong, and the method is particularly suitable for the raw material natural gasThe working condition that the content of the medium methanol is high and the fluctuation range is large can effectively remove the methanol in the raw material natural gas, recover the pure water used for dissolving the MDEA, avoid the LNG cold box from being frozen and blocked due to the methanol, and improve the stability and the reliability of production.
2. The invention aims at the special condition that the raw material natural gas contains methanol, fully combines the industrial production reality, utilizes the condition that the prior device adopts the methanol removing technology on a non-main production line, the methanol removing unit can operate independently of the main process route, adopts the skid-mounted structure and the unique process of the double rectifying towers with normal pressure, filling, no condenser and the reboiler type, can be installed and overhauled under the condition that the main production line does not stop production, and has low manufacturing cost and convenient operation. The process device adopts an air cooling technology, can completely remove methanol and recover pure water, and the removed methanol is sent to a torch tower for combustion, thereby being energy-saving and environment-friendly.
3. The method has the advantages of low investment and low power consumption, adopts the air cooling technology, and saves energy and protects the environment because the waste gas is burnt in a torch tower.
4. The invention adopts the normal pressure double-tower heating rectification process, the equipment is simple, and the separation effect is good.
5. The invention adopts a skid-mounted structure, has small occupied area and convenient and flexible operation.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, 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 process flow diagram of a process for natural gas demethanization according to the present invention;
FIG. 2 is a process flow diagram of an absorption column according to the present invention;
FIG. 3 is a process flow diagram of a regenerator column of the present invention;
FIG. 4 is a process flow diagram of the present invention for heated double distillation of desalted water containing methanol.
Detailed Description
For further explanation of the various embodiments, the drawings which form a part of the disclosure and which are incorporated in and constitute a part of this specification, illustrate embodiments and, together with the description, serve to explain the principles of operation of the embodiments, and to enable one skilled in the art to understand the embodiments and advantages of the disclosure for reference and without scale, wherein elements are not shown in the drawings and like reference numerals are used to refer to like elements generally.
As shown in fig. 1-4, embodiments of the present invention disclose a method for natural gas demethanization, comprising the steps of: raw material natural gas containing methanol (0.1 mol%) enters an absorption tower at the pressure of 5MPa, and acid gas CO in the raw material natural gas is chemically absorbed by MDEA (40 weight%) aqueous solution 2 Simultaneously, the methanol in the raw material natural gas is dissolved and absorbed by water, the natural gas without acid gas and methanol enters a molecular sieve adsorption dehydration system from the top of the absorption tower, and the bottom of the absorption tower contains CO 2 The MDEA aqueous solution of the methanol is decompressed to 0.9MPa, flashed and enters a regeneration tower, the MDEA aqueous solution is heated to 121 ℃ by a reboiler for regeneration, qualified MDEA aqueous solution flows out of the bottom of the regeneration tower, and vapor phase components flowing out of the top of the regeneration tower mainly comprise water vapor and CO 2 Methanol and MDEA gas are cooled to 42 ℃ by air and then enter CO 2 Separation tank, CO 2 The discharged CO at the top of the separation tank is mainly 2 The gas flows out from the bottom and mainly comprises an aqueous solution containing methanol and MDEA. To CO 2 The aqueous solution containing methanol at the bottom of the separation tank adopts double rectifying towers to carry out rectification separation, methanol water vapor which is removed at the top of the second rectifying tower is sent to a torch tower to be combusted, so that the environmental protection and no pollution are ensured, and the qualified dilute MDEA aqueous solution which flows out from the bottoms of the first rectifying tower and the second rectifying tower returns to the system to be reused, thereby reducing the loss of pure water.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention removes CO from the acid gas of the raw material natural gas containing methanol 2 The methanol-containing water solution from the separating tank is subjected to methanol removal, the process is mature, the adaptability is strong, and the method is particularly suitable for the original processThe working condition that the methanol content in the material natural gas is high and the fluctuation range is large can effectively remove the methanol in the raw material natural gas, recover the pure water used for dissolving the MDEA, avoid the LNG cold box from being blocked due to methanol freezing, and improve the stability and the reliability of production.
2. The invention aims at the special condition that the raw material natural gas contains methanol, fully combines the industrial production reality, utilizes the condition that the prior device adopts the methanol removing technology on a non-main production line, and the methanol removing unit can operate independently of the main process route. The process device adopts an air cooling technology, can completely remove methanol and recover pure water, and the removed methanol is sent to a torch tower for combustion, thereby being energy-saving and environment-friendly.
3. The method has the advantages of less investment and low power consumption, adopts the air cooling technology, and saves energy and protects environment because the waste gas is burnt in the torch tower.
4. The invention adopts the normal pressure double-tower heating rectification process, the equipment is simple, and the separation effect is good.
5. The invention adopts a skid-mounted structure, has small occupied area and convenient and flexible operation.
As shown in fig. 1, specifically, the method includes the following steps:
1) the method comprises the steps of utilizing an existing absorption tower and a regeneration tower unit, and dissolving and absorbing methanol in natural gas in the absorption tower through water in MDEA (methyl dodecyl ethyl ether EA) aqueous solution; in the regeneration tower, the CO is absorbed 2 Heating the MDEA rich solution containing acidic gas and dissolved methanol to 121 deg.C by reboiler, and adding CO 2 When acid gas, methanol vapor and water vapor are decomposed and separated out, the temperature is reduced by an air cooler, and then CO is added 2 Separation by a separator, CO 2 And the acid gas is discharged to the atmosphere.
2) Methanol-containing MDEA dilute solution from CO 2 Discharging from the bottom of the separator, pumping into a first rectifying tower, heating to 105 deg.C by reboiler, air cooling the rectified water vapor containing methanol and MDEA to obtain liquid, feeding into a second rectifying tower, and heating to 10 deg.C by reboilerAnd (4) discharging the methanol and a small amount of water vapor which are rectified again from the top of the second rectifying tower to a flare tower to be burnt, and recycling a small amount of dilute solution containing MDEA.
3. The main technological parameters are as follows:
1) after the treatment of the absorption tower, the content of methanol in the deacidified gas natural gas is 0ppm, and the content of methanol in the MDEA barren solution is 3.9 ppm.
2) Methanol in the torch tower carries away a small amount of water vapor, and the water loss is about 0.7m per day 3 。
3) The first rectifying tower and the second rectifying tower are both in a type of filling, no condenser and a reboiler, and the heat required by the reboiler is 186 kW.
4) The diameters of the first rectifying tower and the second rectifying tower are both less than phi 300mm, the first rectifying tower and the second rectifying tower are normal pressure towers, and the main materials are stainless steel.
Several common demethanol processes compare their benefits to the process of the present invention:
the methanol removing effect of the process method is verified as follows:
1. firstly, checking the absorption amount of methanol in the absorption tower
The raw material gas flow rate is 20833Nm3/h, the methanol content in the raw material gas is 2000ppm, namely 0.11 mol%, which is equivalent to 33.09 kg/h.
Assuming that all the methanol enters the MDEA solution, the concentration of MDEA is 40%, the content of CO2 in raw material gas is 3.0 mol% according to the design amount, and the flow rates of lean solution and rich solution are 25000kg/h according to the design flow rate.
The MDEA solution of the simulated absorption tower (phi 1000x26550, the height of a packing is 14m, and the theoretical plate number is 24) absorbs CO2 and methanol as shown in FIG. 2;
the results of the decarburization absorption tower simulation calculation are shown in the following table:
therefore, the MDEA solution of the existing absorption tower can completely absorb the methanol in the raw material gas. The pH of the rich solution was 8.5.
2. And secondly, checking the distillate quantity of the methanol from the regeneration tower:
as shown in fig. 3, a simulation calculation was performed for the MDEA regenerator (no condenser, reboiler, regenerator Φ 1000x27543, 18m high packing, equivalent to theoretical plate number 31).
The simulation calculation result of the decarburization regeneration tower is as follows:
therefore, the existing regeneration tower can completely distill out the methanol in the rich solution, and the methanol content in the barren solution is less than 10ppm, which meets the requirement. The pH of the barren solution was 10.1.
As shown in FIG. 4, the raw material gas composition (containing 2000ppm of methanol) was subjected to CO regeneration after the decarburization regeneration tower 2 The technological parameters (temperature, flow and components) of the desalted water containing methanol in the separator are rectified to remove methanol, and the rectifying tower is at normal pressure.
Through preliminary design and calculation, the scheme of adopting one rectifying tower still has the problem of emission, and the following main calculation results of the scheme of adopting the double rectifying towers are as follows:
1) equipment parameters: the pump flow is 1.3m3/h, and the design pressure is 0.4 MPa.G; the heat exchanger is plate type, the heat exchange area is 65m2, and the pressure is normal; the diameter of the rectifying tower is phi 305mm, the height of the packing is 13.2m (equivalent to 23 trays), and the pressure is normal; the diameter of the rectifying tower is 152mm, the height of the packing is 10.8m (equivalent to 19 tower plates), and the pressure is normal. The heat of the air cooler 4 is-138 kW, and the heat of the air cooler 6 is-10.5 kW.
2) Heat balance: the heat requirement of the reboiler of the rectification column is 120000kcal/h, namely 139.56 kW. The heat required by the reboiler of the re-rectifying tower is 35000kcal/h, namely 41 kW.
3) Material balance: the MDEA solution which is sent to a recovery pump after the rectifying tower contains 3.58ppm of methanol, which meets the requirement. The methanol content of the rectified MDEA solution is 0.17ppm, and the MDEA solution can be recycled. The steam flow of the removed methanol is 60.7kg/h, wherein the water accounts for 46.2 wt%, the methanol accounts for 53.8 wt%, the MDEA accounts for 0.63ppm, and the loss of the MDEA is very low. Thus, without air cooling, the methanol steam could be burned in a flare, or discharged as sewage, with about 1.5 tons of emissions per day with 0.7 tons of desalted water lost.
4) According to the calculation, when the content of the methanol in the raw material gas is reduced, the water discharge amount, the MDEA loss and the heat consumption are correspondingly reduced. When the rectifying tower is additionally provided with the condenser, the heat and the water discharge are increased, and the elasticity of the process operation is reduced due to the requirement of the reflux ratio, so that the operation control is not facilitated.
Therefore, the heating double-tower distillation scheme has satisfactory and feasible methanol removal effect.
While, for purposes of simplicity of explanation, the methodologies are shown and described as a series of acts, it is to be understood and appreciated that the methodologies are not limited by the order of acts, as some acts may, in accordance with one or more embodiments, occur in different orders and/or concurrently with other acts from that shown and described herein or not shown and described herein, as would be understood by one skilled in the art.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A method for natural gas demethanization comprising the steps of,
step 1, feeding raw natural gas containing methanol into an absorption tower, and chemically absorbing acid gas CO in the raw natural gas through MDEA (methyl-dimethyl-ammonium-ethyl-ammonium-acetate) aqueous solution 2 Simultaneously, the methanol in the raw material natural gas is dissolved and absorbed by water, and the natural gas without acid gas and methanol enters a molecular sieve adsorption dehydration system from the top of the absorption tower;
step 2, the bottom of the absorption tower contains CO 2 The MDEA aqueous solution of the methanol enters a regeneration tower after being decompressed and flashed, the MDEA aqueous solution is heated by a reboiler for regeneration, the qualified MDEA aqueous solution flows out of the bottom of the regeneration tower, and the gas flowing out of the top of the regeneration tower enters CO after being cooled by air 2 A separation tank;
step 3, for CO 2 The aqueous solution containing methanol at the bottom of the separation tank is rectified and separated by adopting a double rectifying tower, the methanol vapor removed from the top of the second rectifying tower is sent to a torch tower for combustion, and the qualified dilute MDEA aqueous solution flows out from the bottoms of the first rectifying tower and the second rectifying tower and returns to the system for reuse.
2. The method for natural gas demethanization of claim 1, wherein in the step 2, the first rectifying tower and the second rectifying tower have a diameter less than Φ 300mm and are atmospheric towers.
3. The method for natural gas demethanization according to claim 1 or 2, wherein, in the step 1, the raw natural gas containing methanol is fed into the absorption column at a pressure of 5 MPa.
4. The process for natural gas demethanization of claim 3, wherein the concentration of the aqueous MDEA solution is 40 weight%.
5. The process for natural gas demethanization of any one of claims 1, 2 or 4, wherein in step 2, the MDEA aqueous solution containing CO2 and methanol at the bottom of the absorption column is depressurized to 0.9 MPa.
6. The process for natural gas demethanization of any one of claims 1, 2 or 4, wherein in step 2, the MDEA aqueous solution entering the regeneration column after flashing is heated to 121 ℃ through a reboiler for regeneration.
7. The method for natural gas demethanization of any one of claims 1, 2, or 4, wherein step 3 is specifically, the methanol containing MDEA dilute solution is separated from CO 2 And discharging from the bottom of the separator, pumping the discharged liquid into a first rectifying tower, heating the liquid by a reboiler, cooling the rectified water vapor containing methanol and MDEA into liquid by air, then feeding the liquid into a second rectifying tower, heating the liquid by the reboiler again, discharging the rectified methanol and a small amount of water vapor from the top of the second rectifying tower to a torch tower to be combusted, and recycling the dilute solution containing a small amount of MDEA.
8. The method for natural gas demethanization of claim 7, wherein in the step 3, the rectified water vapor containing methanol and MDEA is cooled by air to be liquid, and then enters the second rectifying tower, and is heated to 105 ℃ again by the reboiler.
9. The method for natural gas demethanization of claim 7, wherein in step 3, the methanol containing MDEA dilute solution is separated from CO 2 The bottom of the separator was discharged and pumped into the first rectification column and heated to 105 ℃ by a reboiler.
10. The method for natural gas demethanol as claimed in any one of claims 1, 2 or 4, wherein in step 2, the gas flowing out of the top of the regeneration tower enters CO after being air cooled to 42 ℃ 2 And (5) separating the tank.
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| CN202210658949.5A CN114907894A (en) | 2022-06-09 | 2022-06-09 | Method for removing methanol from natural gas |
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
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