System and method for eluting methanol by using molecular sieve and circulating water

Abstract

The invention discloses a system for eluting methanol by using molecular sieve and circulating water. The system comprises an adsorption system and a regeneration system, the adsorption system is used for filtering, dehydrating and demercurating raw material natural gas containing methanol to obtain cooling gas; the regeneration system is used for performing methanol removal treatment on the cooling gas. The method for removing methanol comprises the following steps: enabling methanol-containing natural gas to pass through a dust filtering separator, sequentially dehydrating, removing mercury and drying, regenerating the molecular sieve dehydrating tower which just finishes dehydration by using the formed dry gas as cooling gas to form rich regeneration gas, and carrying out secondary heat exchange heating on the cooling gas, the rich regeneration gas and heat-conducting oil, the heated regenerated gas enters a dehydrating tower to desorb water adsorbed by the molecular sieve, then is subjected to three-stage cooling together with the regenerated gas, and finally enters a water washing tower to complete separation of alcohol-containing water. The method is mature in process, high in adaptability, especially suitable for the working conditions that the methanol content in the natural gas is high and the fluctuation range is large, and capable of effectively removing methanol in the raw material natural gas and recycling alcohol-containing water.

Description

Technical Field

[0001] The invention belongs to the technical field of natural gas processing, and relates to a system for eluting methanol with a molecular sieve and circulating water, and also relates to a method for eluting methanol with a molecular sieve and circulating water. Background Art

[0002] When the raw gas contains methanol, if the molecular sieve that absorbs methanol is not selected, the raw gas will be enriched in the liquefied gas tower of the liquid hydrocarbon separation device after dehydration and enter the downstream device, resulting in excessive methanol content in the liquefied gas product, which does not meet the index requirements of the liquefied gas product. The existing natural gas dehydration process is basically based on methanol-free, lacking methanol removal technology and equipment; for natural gas containing methanol, the existing methods mostly use gas stripping tower technology, which has a complex system, many equipment, unsatisfactory separation effect, and difficult to handle tail gas, making it difficult to meet environmental protection requirements. Summary of the invention

[0003] The purpose of the present invention is to provide a system for eluting methanol using molecular sieve and circulating water, which solves the problems of high equipment requirements and large investment in the existing methanol elution technology.

[0004] The present invention also aims to provide a method for eluting methanol using molecular sieve and circulating water.

[0005] The first technical solution adopted by the present invention is a system for eluting methanol with molecular sieve and circulating water, including an adsorption system and a regeneration system; the adsorption system is used to filter, dehydrate and remove mercury from raw natural gas containing methanol through a molecular sieve dryer to obtain dry gas; the regeneration system uses dry gas to realize cyclic adsorption and regeneration of the molecular sieve to separate the alcohol-containing water in the raw natural gas.

[0006] The present invention is also characterized in that:

[0007] The adsorption system includes three stages of dust filter separators connected in series, a dehydration tower is connected in series between the first dust filter separator and the second dust filter separator, and a demercuration tower is connected in series between the second dust filter separator and the third dust filter separator; there are multiple dehydration towers, each of which is equipped with a molecular sieve dryer.

[0008] The regeneration system includes a regeneration gas compressor, which is respectively connected to a dehydration tower and a regeneration gas heat exchanger; the regeneration gas heat exchanger is connected to a regeneration gas heat transfer oil heat exchanger and connected to a connecting pipeline between the dehydration tower and the regeneration gas compressor; the dehydration tower is also connected to a regeneration gas waste heat exchanger, a regeneration gas air cooler, a waste heat recovery water cooler, a water scrubber, and an emptying and separating tank in sequence; the upper part of the water scrubber is connected to a gas collecting and distribution area;

[0009] The regeneration gas thermal oil heat exchanger exchanges heat through circulating thermal oil; the regeneration gas waste heat exchanger exchanges heat through circulating water; and the regenerator chilled water heat exchanger exchanges heat through circulating chilled water.

[0010] The second technical solution adopted by the present invention is: a method of eluting methanol with molecular sieve and circulating water, wherein the raw natural gas containing methanol is sent to an adsorption system for filtration, dehydration and mercury removal by a molecular sieve dryer to obtain dry gas; the dry gas enters a regeneration system to realize cyclic adsorption and regeneration of the molecular sieve, and the alcohol-containing water in the raw natural gas is separated; the specific operation steps are as follows:

[0011] Step 1, feeding the raw natural gas containing methanol into the first dust filter separator for filtration, the filtered raw natural gas enters the dehydration tower containing the molecular sieve dryer from the top for dehydration, and the dried gas passes through the second dust filter separator, the demercuration tower, and the third dust filter separator in sequence to form dry gas;

[0012] Step 2, the dry gas treated in step 1 is pressurized by a regeneration gas compressor to form rich regeneration gas, and the rich regeneration gas passes through a dehydration tower that has just completed the regeneration process from bottom to top to cool the tower; then the regeneration gas passes through a regeneration gas heat exchanger to exchange heat with the rich regeneration gas, and then enters a regeneration gas heat transfer oil heat exchanger to heat and heat up with the heat transfer oil;

[0013] Step 3, the heated regeneration gas enters the bottom of the dehydration tower, flows from bottom to top, desorbs the water adsorbed by the dehydration tower in step 1, and enters the regeneration gas heat exchanger for cooling together with the regeneration gas, and then enters the regeneration gas waste heat exchanger for further cooling;

[0014] Step 4, the regenerated gas and analytical water cooled in step 3 enter the regenerated gas air cooler for cooling, then enter the waste heat recovery water cooler for heat exchange with chilled water, and finally enter the water washing tower to separate the alcohol-containing water to the entrance of the methanol recovery device.

[0015] The present invention is also characterized in that:

[0016] There are multiple dehydration towers, which can realize cyclic operation.

[0017] In step 2, cooling is considered to be completed when the outlet temperature of the cooling bed in the dehydration tower is 50°C; the regenerated gas is heated to 140°C by heat exchange with rich regenerated gas in the regeneration heat exchanger, and is heated to 285°C by heat exchange with heat transfer oil in the regeneration gas heater.

[0018] In step 3, after the heated regeneration gas has resolved the water adsorbed by the molecular sieve in the dehydration tower, it first enters the regeneration gas heat exchanger to be cooled to 180°C, and then is cooled to 85°C in the regeneration gas waste heat exchanger.

[0019] In steps 1-3, the molecular sieve dryers in the multiple dehydration towers are operated periodically. When the device is operated at the normal design processing capacity, three of the dryers are in dry absorption, and one is in a cold blowing state or a hot blowing state. The regenerated gas can achieve the purpose of cold blowing and hot blowing at the same time. The system is fully automated. By comparing the processing capacity of the device, the cycle time can be adjusted to maximize the efficiency of the device.

[0020] In step 4, the regenerated gas after preliminary cooling in the regenerated gas waste heat exchanger enters the regenerated gas air cooler and is cooled to 50°C, and finally enters the waste heat recovery water cooler to exchange heat with chilled water and be cooled to 25°C.

[0021] The purpose of separating alcohol-containing water in the water scrubber is to prevent methanol from accumulating in the molecular sieve of the dehydration tower and affecting the dehydration effect of the molecular sieve. The upper part of the water scrubber is filled with fillers, desalted water enters from the upper part of the water scrubber, and methanol-containing regeneration gas enters from the bottom of the water scrubber. The gas rises, the liquid phase descends, and the gas and liquid contact in reverse to dilute and remove the methanol in the methanol-containing regeneration gas.

[0022] When the methanol-rich liquid in the dehydration tower accumulates to a certain level, liquid is formed from the lower part of the methanol water washing tower filler and flows into the bottom of the water washing tower; deionized water continuously enters the water washing tower through the top of the tower and the internal filler, and the water in the tower is continuously circulated and sent out through the circulating pump.

[0023] The beneficial effects of the present invention are:

[0024] 1. The present invention adopts a multi-tower molecular sieve adsorption method for dehydration, and uses the dehydrated dry natural gas as the molecular sieve regeneration gas. The rich regeneration gas is cooled by a cooler to condense most of the water therein into liquid. The cooled regeneration gas separates water in the regeneration gas water washing tower and then enters the inlet of the methanol recovery device.

[0025] 2. Aiming at the special situation that the raw natural gas contains methanol, the present invention fully combines the actual production of the industry, utilizes the existing dehydration device to combine the molecular sieve dehydration with the circulating water elution methanol process, and maximizes the production and operation efficiency through the four-tower adsorption dehydration and dealcoholization method, with low manufacturing cost and convenient operation. This process device adopts circulating water cooling technology, and the removed methanol is sent to the distillation device for recovery to maximize utilization.

[0026] 3. The present invention uses chilled water generated by waste heat recovery to cool the regenerated gas to 25°C, which is the same as the raw gas inlet temperature, to avoid operating fluctuations caused by the inconsistency between the molecular sieve cooling temperature and the raw gas inlet temperature, thereby achieving energy saving and consumption reduction.

[0027] 4. The regenerated gas of the present invention adds a regenerated gas water washing tower to separate the alcohol-containing water (to prevent the accumulation of methanol in the molecular sieve and affect the dehydration effect of the molecular sieve).

[0028] 5. The present invention adopts a modular structure, occupies a compact area, and is convenient and flexible to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the structure of the regeneration system of the present invention.

[0030] Figure 2 It is a schematic diagram of the structure of the adsorption system of the present invention.

[0031] In the figure: 1. Regeneration gas compressor; 2. Dehydration tower; 3. Regeneration gas heat exchanger; 4. Regeneration gas thermal oil heat exchanger; 5. Regeneration gas waste heat heat exchanger; 6. Regeneration gas air cooler; 7. Waste heat recovery water cooler; 8. Water washing tower; 9. Venting separator tank; 10. Dust filter separator; 11. Mercury removal tower. DETAILED DESCRIPTION

[0032] The following is a detailed description of an embodiment of the present invention in conjunction with the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0033] Example 1

[0034] The molecular sieve and circulating water eluting methanol system of the present invention is as follows: Figure 1-2 As shown, it includes an adsorption system and a regeneration system; the adsorption system is used to filter, dehydrate and remove mercury from the raw natural gas containing methanol through a molecular sieve dryer to obtain dry gas; the regeneration system uses the dry gas to realize the cyclic adsorption and regeneration of the molecular sieve to separate the alcohol-containing water in the raw natural gas.

[0035] Example 2

[0036] The difference from Example 1 is that

[0037] The adsorption system comprises three stages of dust filter separators 10 connected in series, a dehydration tower 2 is connected in series between the first dust filter separator and the second dust filter separator, and a demercuration tower 11 is connected in series between the second dust filter separator and the third dust filter separator.

[0038] The adsorption system includes three stages of dust filter separators 10 connected in series, a dehydration tower 2 is connected in series between the first dust filter separator and the second dust filter separator, and a demercuration tower 11 is connected in series between the second dust filter separator and the third dust filter separator;

[0039] The regeneration system includes a regeneration gas compressor 1, which is respectively connected to a dehydration tower 2 and a regeneration gas heat exchanger 3; the regeneration gas heat exchanger 3 is connected to a regeneration gas heat transfer oil heat exchanger 4 and connected to a connecting pipeline between the dehydration tower 2 and the regeneration gas compressor 1; the dehydration tower 2 is also sequentially connected to a regeneration gas waste heat exchanger 5, a regeneration gas air cooler 6, a waste heat recovery water cooler 7, a water scrubber 8, and an emptying and separating tank 9; the upper part of the water scrubber 8 is connected to a gas collecting and distribution area;

[0040] The regeneration gas heat transfer oil heat exchanger 4 exchanges heat through circulating heat transfer oil; the regeneration gas waste heat exchanger 5 exchanges heat through circulating water; and the regenerator chilled water heat exchanger 7 exchanges heat through circulating chilled water.

[0041] Example 3

[0042] The method of eluting methanol with molecular sieve and circulating water is to send the raw natural gas containing methanol into the adsorption system for filtration, dehydration, and mercury removal to obtain cooling gas; the cooling gas enters the regeneration system to separate the alcohol-containing water for methanol removal. The specific operation steps are as follows:

[0043] Step 1, feeding the raw natural gas containing methanol into the first dust filter separator for filtration, the filtered raw natural gas enters the dehydration tower containing the molecular sieve dryer from the top for dehydration, and then passes through the second dust filter separator, the demercuration tower, and the third dust filter separator in sequence to form dry gas;

[0044] Step 2, the dry gas treated in step 1 is used as cooling gas and pressurized by a regeneration gas compressor to form rich regeneration gas, and the rich regeneration gas passes through a dehydration tower from bottom to top to cool the tower; then the regeneration gas passes through a regeneration gas heat exchanger to exchange heat with the rich regeneration gas, and then enters a regeneration gas heat transfer oil heat exchanger to exchange heat with the heat transfer oil to increase the temperature;

[0045] Step 3, the heated regeneration gas enters the bottom of the dehydration tower, flows from bottom to top, desorbs the water adsorbed by the dehydration tower in step 1, and enters the regeneration gas heat exchanger for cooling together with the regeneration gas, and then enters the regeneration gas waste heat exchanger for further cooling;

[0046] Step 4, the regenerated gas and analytical water cooled in step 3 enter the regenerated gas air cooler for cooling, then enter the waste heat recovery water cooler for heat exchange with chilled water, and finally enter the water washing tower to separate the alcohol-containing water to the entrance of the methanol recovery device.

[0047] There are multiple dehydration towers, which can realize cyclic operation.

[0048] In step 2, cooling is considered to be completed when the outlet temperature of the cooling bed in the dehydration tower is 50°C; the regenerated gas is heated to 140°C by heat exchange with rich regenerated gas in the regeneration heat exchanger, and is heated to 285°C by heat exchange with heat transfer oil in the regeneration gas heater.

[0049] In step 3, after the heated regeneration gas has resolved the water adsorbed by the molecular sieve in the dehydration tower, it first enters the regeneration gas heat exchanger to be cooled to 180°C, and then is cooled to 85°C in the regeneration gas waste heat exchanger.

[0050] In step 4, the regenerated gas after preliminary cooling in the regenerated gas waste heat exchanger enters the regenerated gas air cooler and is cooled to 50°C, and finally enters the waste heat recovery water cooler to exchange heat with chilled water and be cooled to 25°C.

[0051] When the methanol-rich liquid in the dehydration tower accumulates to a certain level, liquid is formed from the lower part of the methanol water washing tower filler and flows into the bottom of the water washing tower; deionized water continuously enters the water washing tower through the top of the tower and the internal filler, and the water in the tower is continuously circulated and sent out through the circulating pump.

[0052] Example 4

[0053] The method for eluting methanol with molecular sieve and circulating water disclosed in Example 4 of the present invention comprises the following steps: in the adsorption process, the raw natural gas containing methanol is sent to the dust filter separator for filtration, the filtered raw natural gas enters the molecular sieve dehydration tower from the top, and the dehydrated gas enters the demercuration tower after passing through the molecular sieve dust filter; in the regeneration process, the dry gas after molecular sieve dehydration is used as cooling gas, which is pressurized by the regeneration gas compressor, and the cooling gas passes through the molecular sieve dehydration tower from bottom to top to cool the tower. Then the cooling gas exchanges heat with the rich regeneration gas through the regeneration heat exchanger, and then enters the regeneration gas heater to heat and heat the heat with the heat transfer oil; the heated regeneration gas enters the bottom of the adsorption tower, flows from bottom to top, and the water adsorbed by the molecular sieve is analyzed out, and first enters the regeneration gas heat exchanger with the regeneration gas for cooling, and then enters the regeneration gas waste heat exchanger for further cooling; the regeneration gas after preliminary cooling and the analyzed water enter the regeneration gas air cooler for cooling, and then enters the waste heat recovery water cooler for heat exchange with chilled water, and finally enters the regeneration gas water washing tower to separate the alcohol-containing water to the entrance of the methanol recovery device.

[0054] The present invention has multiple dehydration towers, each of which has a molecular sieve dryer. The four molecular sieve dryers operate in cycles. When the device operates at the normal design processing capacity, three of the dryers are in dry absorption, and one is in a cold blowing state and a hot blowing state. The regenerated gas achieves the purpose of cold blowing and hot blowing at the same time. The system operates fully automatically, and by comparing the processing capacity of the device, the cycle time can be adjusted to achieve the maximum efficiency of the device.

Claims

1. A system for eluting methanol with molecular sieve and circulating water, characterized in that: It includes an adsorption system and a regeneration system; the adsorption system is used to filter, dehydrate and remove mercury from raw natural gas containing methanol through a molecular sieve dryer to obtain dry gas; the regeneration system uses dry gas to realize cyclic adsorption and regeneration of the molecular sieve to separate the alcohol-containing water in the raw natural gas.

2. The system for eluting methanol with molecular sieve and circulating water according to claim 1, characterized in that: The adsorption system comprises three stages of dust filter separators (10) connected in series, a dehydration tower (2) being connected in series between the first dust filter separator and the second dust filter separator, and a demercuration tower (11) being connected in series between the second dust filter separator and the third dust filter separator; there are a plurality of dehydration towers (2), each of which is provided with a molecular sieve dryer.

3. The system for eluting methanol with molecular sieve and circulating water according to claim 2, characterized in that: The regeneration system comprises a regeneration gas compressor (1), wherein the regeneration gas compressor (1) is respectively connected to a dehydration tower (2) and a regeneration gas heat exchanger (3); the regeneration gas heat exchanger (3) is connected to a regeneration gas heat transfer oil heat exchanger (4) and is connected to a connecting pipeline between the dehydration tower (2) and the regeneration gas compressor (1); the dehydration tower (2) is also sequentially connected to a regeneration gas waste heat exchanger (5), a regeneration gas air cooler (6), a waste heat recovery water cooler (7), a water scrubber (8), and an emptying and separating tank (9); the upper part of the water scrubber (8) is connected to a gas collecting and distribution area; The regenerated gas heat transfer oil heat exchanger (4) exchanges heat through circulating heat transfer oil; the regenerated gas waste heat exchanger (5) exchanges heat through circulating water; and the regenerator chilled water heat exchanger (7) exchanges heat through circulating chilled water.

4. A method for eluting methanol using molecular sieve and circulating water, characterized in that: The raw natural gas containing methanol is sent to the adsorption system for filtration, dehydration and mercury removal through the molecular sieve dryer to obtain dry gas; the dry gas enters the regeneration system to realize the cyclic adsorption and regeneration of the molecular sieve, and separates the alcohol-containing water in the raw natural gas.

5. The method for eluting methanol using molecular sieve and circulating water according to claim 4, characterized in that: The specific steps are as follows: Step 1, feeding the raw natural gas containing methanol into the first dust filter separator for filtration, the filtered raw natural gas enters the dehydration tower containing the molecular sieve dryer from the top for dehydration, and then passes through the second dust filter separator, the demercuration tower, and the third dust filter separator in sequence to form dry gas; Step 2, the dry gas treated in step 1 is used as cooling gas and pressurized by a regeneration gas compressor to form rich regeneration gas, and the rich regeneration gas passes through a dehydration tower from bottom to top to cool the tower; then the regeneration gas passes through a regeneration gas heat exchanger to exchange heat with the rich regeneration gas, and then enters a regeneration gas heat transfer oil heat exchanger to exchange heat with the heat transfer oil to increase the temperature; Step 3, the heated regeneration gas enters the bottom of the dehydration tower, flows from bottom to top, desorbs the water adsorbed by the dehydration tower in step 1, and enters the regeneration gas heat exchanger for cooling together with the regeneration gas, and then enters the regeneration gas waste heat exchanger for further cooling; Step 4, the regenerated gas and analytical water cooled in step 3 enter the regenerated gas air cooler for cooling, then enter the waste heat recovery water cooler for heat exchange with chilled water, and finally enter the water washing tower to separate the alcohol-containing water to the entrance of the methanol recovery device.

6. The method for eluting methanol using molecular sieve and circulating water according to claim 5, characterized in that: There are multiple dehydration towers, which can realize periodic circulation operation.

7. The method for eluting methanol using molecular sieve and circulating water according to claim 5, characterized in that: In step 2, cooling is considered to be completed when the outlet temperature of the cooling bed in the dehydration tower is 50°C; the regenerated gas is heated to 140°C by heat exchange with rich regenerated gas in the regeneration heat exchanger, and is heated to 285°C by heat exchange with heat transfer oil in the regeneration gas heater.

8. The method for eluting methanol using molecular sieve and circulating water according to claim 5, characterized in that: In step 3, after the heated regeneration gas has resolved the water adsorbed by the molecular sieve in the dehydration tower, it first enters the regeneration gas heat exchanger to be cooled to 180°C, and then is cooled to 85°C in the regeneration gas waste heat exchanger.

9. The method for eluting methanol using molecular sieve and circulating water according to claim 5, characterized in that: In step 4, the regenerated gas after preliminary cooling in the regenerated gas waste heat exchanger enters the regenerated gas air cooler and is cooled to 50°C, and finally enters the waste heat recovery water cooler to exchange heat with chilled water and be cooled to 25°C.

10. The method for eluting methanol using molecular sieve and circulating water according to claim 5, characterized in that: When the methanol-rich liquid in the dehydration tower accumulates to a certain level, liquid is formed from the lower part of the methanol water washing tower filler and flows into the bottom of the water washing tower; deionized water continuously enters the water washing tower through the top of the tower and the internal filler, and the water in the tower is continuously circulated and sent out through the circulating pump.

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