CN109054915B - Natural gas dehydration system and method for throttling pre-dehydration and entrainer regeneration - Google Patents
Natural gas dehydration system and method for throttling pre-dehydration and entrainer regeneration Download PDFInfo
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- CN109054915B CN109054915B CN201810748102.XA CN201810748102A CN109054915B CN 109054915 B CN109054915 B CN 109054915B CN 201810748102 A CN201810748102 A CN 201810748102A CN 109054915 B CN109054915 B CN 109054915B
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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
- C10L3/106—Removal of contaminants of water
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1425—Regeneration of liquid absorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1493—Selection of liquid materials for use as absorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/18—Absorbing units; Liquid distributors therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/26—Drying gases or vapours
- B01D53/263—Drying gases or vapours by absorption
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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
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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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2252/00—Absorbents, i.e. solvents and liquid materials for gas absorption
- B01D2252/20—Organic absorbents
- B01D2252/202—Alcohols or their derivatives
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2256/00—Main component in the product gas stream after treatment
- B01D2256/24—Hydrocarbons
- B01D2256/245—Methane
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/80—Water
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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
- 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
Abstract
The invention belongs to the technical field of natural gas treatment, and particularly relates to a natural gas dehydration system and method for throttling pre-dehydration and entrainer regeneration. A Laval spray pipe and a gas-liquid separator are arranged in front of the absorption tower to pre-dehydrate the natural gas. The entrainer is injected into the reboiler from the azeotropic regeneration loop, the top of the regeneration tower is provided with an outlet, high-temperature gas containing the entrainer and water is led out, the entrainer, the water and the gas are separated through the three-phase separator after the heat exchange between the heat exchanger and the barren solution, and the separated entrainer is dried by the entrainer dryer and then is conveyed to the reboiler through the circulating pump, so that the recycling of the entrainer is realized. The gas-gas flow divider is arranged behind the absorption tower, most of the dry gas dried by the absorption tower is output, and the other small part of the gas reaches the bottom of the stripping column to be used as stripping gas. The invention solves the problems of low efficiency, high energy consumption and incapability of meeting the deep dehydration requirement in the operation process of the existing triethylene glycol dehydration device.
Description
Technical Field
The invention belongs to the technical field of natural gas treatment, and particularly relates to a natural gas dehydration system and method for throttling pre-dehydration and entrainer regeneration.
Background
The natural gas flowing out of the wellhead is almost saturated with gas phase water and even carries a certain amount of liquid water. The presence of moisture in natural gas often has serious consequences: containing CO2And H2The natural gas of S forms acid in the presence of water to corrode pipelines and equipment; forming natural gas hydrates under certain conditions to block valves, pipelines and equipment; reducing the pipeline transportation capacity and causing unnecessary power consumption. Moisture is a very unfavorable event in the presence of natural gas, and therefore, the requirement for dehydration is more stringent. The main methods for dehydrating natural gas include low-temperature separation, solvent absorption, solid adsorption, and membrane separation.
Dehydrating by a low-temperature separation method: the temperature of natural gas containing water is reduced under a certain pressure by means of the temperature difference of natural gas and water vapour condensed into liquid, so that the water vapour and heavy hydrocarbon are condensed into liquid, and then gravity separation is carried out by means of the relative density difference and mutual insolubility of liquid hydrocarbon and water, so that the water is removed. The low-temperature separation method is used for separating out water in the natural gas through throttling expansion cooling or external refrigeration. The natural gas water dew point after dehydration mainly depends on the gas temperature after throttling, and the investment and the operation cost of the device are higher if pressurization or external refrigeration is needed. The method is generally used for dehydrating high-pressure natural gas with available pressure energy (pressure drop), and can control the water dew point and the hydrocarbon dew point of the natural gas at the same time. The main technical problems are as follows: 1) inhibitor (commonly used methanol or ethylene glycol) is required to be injected to prevent natural gas hydrate, and an inhibitor injection and regeneration system is required to be built; 2) the problems of difficult separation of alcohol and hydrocarbon, loss of inhibitor and the like exist; 3) the system has more equipment and complex process flow.
Solid adsorption and dehydration: the natural gas dehydration method has the advantages that certain solid substances have strong adsorption effect and selectivity on water vapor in the natural gas, so that the water vapor in the natural gas is adsorbed on the surface of the solid substances, and other components are not adsorbed or are less adsorbed, so that the natural gas dehydration is realized. The adsorption dehydrating agents commonly used in industry are active alumina, silica gel and molecular sieves, wherein the molecular sieves are most widely used for dehydration. The water content of the dehydrated natural gas can be reduced to 1ppm, the water dew point can reach 120 ℃, and the method is mainly used in deep dehydration places such as CNG gas filling stations, natural gas condensate recovery devices, natural gas liquefaction devices and the like. The technical problems of the dehydration by the adsorption method are as follows: 1) for large-scale devices, the equipment investment is large, and the operation cost is high; 2) the adsorbent has short service life, and can be replaced after being used for three years, so that the cost is increased; 4) high energy consumption, large regeneration gas amount and more obvious low treatment capacity.
Membrane separation dehydration: the preferential permeability of the membrane material to water vapor in natural gas is utilized, and when natural gas flows through the surface of the membrane, the water vapor preferentially permeates the membrane to be removed, so that the water vapor in the natural gas is removed. Compared with the traditional dehydration method, the membrane method dehydration has the advantages of simple process, easy operation, no additional solvent, no secondary pollution, small pressure loss and the like, but the natural gas membrane separation dehydration is industrially applied in countries such as America, Japan, Canada and the like at present. In 1998, the Dajunghuan of Chinese academy of sciences and the Changqing oil and gas general company collaborated to develop an industrial experimental device for membrane dehydration of natural gas, and operated for 1700 hours. The daily throughput of the device is (3-15) × 104Nm3The dew point temperature of the product gas is controlled between minus 28 ℃ and minus 8 ℃ (the conveying pressure is less than 4.6MPa), the recovery rate of methane is more than or equal to 98 percent, and the membrane performance is stable. The main technical problems of membrane separation dehydration are as follows: 1) the gas separation membrane is in a research and development stage at home, and the price of an imported device is higher; 2) the film material has poor reliability and limited bearing capacity; 3) the investment of the device is higher than that of triethylene glycol dehydration.
Solvent absorption and dehydration: the method is to remove the water vapor in the natural gas by utilizing the good absorption and dissolution performance of certain liquid substances on the water vapor in the natural gas. The dehydrated solution has low vapor pressure and can be regenerated and recycled. The solvent absorption dehydration method is a common method used in the dehydration of natural gas at present, wherein the dehydration by triethylene glycol is widely applied in the dehydration of natural gas, the water dew point of the natural gas can reach 40 ℃, and the requirements of the medium and shallow cooling process for the pipeline transportation and the recovery of natural gas condensate on the water dew point can be met. The triethylene glycol dehydration system comprises a separator, an absorption tower and a triethylene glycol regeneration system. The main technical problems of triethylene glycol dehydration are as follows: 1) the system is complex, and the energy consumption of the regeneration process of the triethylene glycol solution is large; 2) triethylene glycol solution is lost and contaminated, requiring replenishment and purification; 3) triethylene glycol can generate oxidation reaction when contacting with air, and corrosive organic acid is generated. Triethylene glycol has the advantages of strong water absorption capacity, low solubility, high boiling point, easiness in regeneration, low investment and the like, is most widely applied to the conventional dehydration process, but the concentration of triethylene glycol barren solution obtained in the conventional triethylene glycol dehydration process is low when the temperature of a reboiler reaches 200 ℃ under one atmospheric pressure, so that the dehydration process cannot meet the dehydration requirement under the condition of high dehydration depth requirement.
Disclosure of Invention
The invention aims to provide a novel efficient throttling pre-dehydration and azeotropic regeneration dehydration system and a novel efficient throttling pre-dehydration and azeotropic regeneration method, which solve the problems of low efficiency and high energy consumption of the existing triethylene glycol dehydration system in the operation process, and particularly solve the problems that when the temperature of a reboiler reaches 200 ℃, the triethylene glycol lean solution obtained in the conventional triethylene glycol dehydration process has low concentration and cannot meet the deep dehydration requirement.
The technical scheme of the invention is as follows:
a natural gas dehydration system with throttling pre-dehydration and entrainer regeneration comprises a gas-liquid separator and an absorption tower which are sequentially connected, wherein gas separated from the gas-liquid separator enters the absorption tower after being heated by a heater, gas in the absorption tower enters a gas-gas splitter through a top outlet, liquid in the absorption tower enters a flash tank through a bottom liquid outlet through a pipeline, the bottom liquid outlet of the flash tank is connected with a regeneration tower, the regeneration tower is connected with a reboiler, the reboiler is connected with a stripping column, and wet natural gas enters the gas-liquid separator through a Laval spray pipe; the liquid outlet of the stripping column is connected with the absorption tower through a pipeline; an outlet at the top of the regeneration tower is connected with the three-phase separator after heat exchange through a heat exchanger through a pipeline; gas in the three-phase separator is discharged through a gas outlet, liquid is discharged through a liquid outlet, and the separated entrainer is dried by an entrainer dryer and then enters a reboiler for recycling; and part of gas of the gas-gas splitter enters the stripping column after being heated by the heat exchanger.
Specifically, a first heat exchanger is arranged between the outlet at the top of the absorption tower and the gas-gas splitter.
Specifically, a third heat exchanger and a first circulating pump are arranged on a pipeline between a liquid outlet of the stripping column and the absorption tower and pass through the first heat exchanger.
Specifically, liquid in the absorption tower enters the flash tank after being heated by the second heat exchanger through a bottom liquid outlet through a pipeline, and a throttling valve is arranged on the pipeline.
A method of dehydrating natural gas using a system as described above, comprising the steps of:
firstly, the wet natural gas from a gas gathering station is subjected to adiabatic expansion of fluid through a Laval nozzle to create a low-temperature environment, so that heavy hydrocarbon and moisture in the natural gas are condensed into liquid drops, and preliminary gas-liquid separation is realized through a gas-liquid separator;
heating the natural gas subjected to pre-dehydration by a heater, feeding the natural gas into the lower part of an absorption tower, naturally floating due to low density of the gas relative to glycol solution, fully contacting with triethylene glycol barren solution in the absorption tower from top to bottom, removing part of water, changing the water into dry gas to meet the requirement of natural gas outward transportation, and then outward transporting the natural gas through an outer discharge port of a gas-gas splitter by a dry gas outward transportation pipeline;
thirdly, enabling triethylene glycol rich liquid to flow out of the bottom of the absorption tower, throttling and depressurizing the triethylene glycol rich liquid, exchanging heat with gas flowing out of the upper part of a regeneration tower, increasing the temperature, enabling the triethylene glycol rich liquid to enter a flash tank, removing most of light hydrocarbon components such as methane in the triethylene glycol rich liquid in the flash tank, throttling and depressurizing the stabilized rich liquid again, exchanging heat with high-temperature lean liquid in a stripping column, enabling the triethylene glycol rich liquid to enter the regeneration tower, enabling the triethylene glycol rich liquid to flow back through a stripping section, a rectifying section and the top of the tower in the regeneration tower, reboiling the triethylene glycol rich liquid through a reboiler to obtain a triethylene glycol solution with higher concentration, further purifying the triethylene glycol rich liquid through the stripping column to reach the concentration of 99.3%, meeting the dehydration concentration of triethylene glycol, pressing the triethylene glycol;
fourthly, high-temperature gas flowing out of the top of the regeneration tower contains water and an entrainer, in order to realize the recycling of the entrainer, the gas is not discharged and exhausted randomly, the gas exchanges heat with barren solution, then passes through a three-phase separator to realize the separation of the entrainer, the water and the gas, and the separated entrainer is dried by an entrainer dryer and then is conveyed to a reboiler through a circulating pump to realize the recycling of the entrainer;
and fifthly, heating the other part of the gas branched out by the gas-gas splitter by a heater, then, enabling the other part of the gas to reach a stripping column, injecting the lean solution part from the bottom of the stripping column, and enabling the lean solution part to be used as stripping gas to be co-heated with the triethylene glycol solution in the stripping column, wherein the flow directions of the stripping gas and the triethylene glycol solution are opposite and fully contacted, and reducing the partial pressure of water vapor on the surface of the solution so as to improve the mass fraction of the ethylene glycol solution to be more.
The invention has the beneficial effects that: 1. the triethylene glycol barren solution obtained by the dehydration system provided by the invention has higher concentration, and because the entrainer in the regeneration dehydration process is insoluble in water and triethylene glycol, the loss amount of the triethylene glycol barren solution in the dehydration process is less, and the loss amount of the triethylene glycol barren solution in the regeneration dehydration process is about 10% of that of the traditional triethylene glycol dehydration process; 2. because the triethylene glycol loss amount in the system and the method provided by the invention is small, the concentration of the reclaimed triethylene glycol barren solution is high, and the dew point of the dry natural gas water dehydrated by the azeotropic regeneration dehydration system is about 38 ℃ lower than that of the traditional triethylene glycol dehydration process; 3. in the system provided by the invention, when the temperature of the reboiler reaches 200 ℃, the mass fraction of the glycol solution is improved to more than 99.8 percent, and the deep dehydration requirement can be met; 4. the dehydration system provided by the invention has the advantages that the dehydration efficiency of the whole system is effectively improved after the pre-dehydration is carried out by the Laval nozzle, the energy consumption of the device is reduced, and the saving and the environmental protection are facilitated.
Drawings
FIG. 1 is a schematic diagram of the system architecture of the present invention;
FIG. 2 is a schematic diagram of the azeotropic regeneration circuit.
1 wet natural gas, 2Laval spray pipes, 3 gas-liquid separators, 4 throttle valves, 5 drainage pipelines, 6 heaters, 7 absorption towers, 8-1 heat exchanger I, 8-2 heat exchanger II, 8-3 heat exchanger III, 9 gas-gas splitters, 10 dry gas outward conveying pipelines, 11 flash tanks, 12 top gas outlets, 13 regeneration towers, 14 reboilers, 15 stripping columns, 16 gas outlets, 17-1 circulating pump I, 17-2 circulating pump II, 18 entrainer dryers, 19 three-phase separators and 20 liquid outlets.
Detailed Description
As shown in fig. 1, the natural gas dehydration system comprises a gas-liquid separator 3 and an absorption tower 7 which are connected in sequence, wherein gas separated from the gas-liquid separator 3 enters the absorption tower 7 after being heated by a heater 6, gas in the absorption tower 7 enters a gas-gas splitter 9 through a top outlet, and a heat exchanger I8-1 is arranged between the top outlet of the absorption tower 7 and the gas-gas splitter 9; liquid in the absorption tower 7 enters a flash tank 11 after being heated by a bottom liquid outlet through a second heat exchanger 8-2 through a pipeline, a throttling valve 4 is arranged on the pipeline, the bottom liquid outlet of the flash tank 11 is connected with a regeneration tower 13, the regeneration tower 13 is connected with a reboiler 14, the reboiler 14 is connected with a stripping column 15, and the wet natural gas 1 enters a gas-liquid separator 3 through a Laval spray pipe 2; a liquid outlet of the stripping column 15 is connected with the absorption tower 7 through a pipeline, and a heat exchanger III 8-3 and a circulating pump I17-1 are arranged on the pipeline between the liquid outlet of the stripping column 15 and the absorption tower 7 and pass through the heat exchanger I8-1; an outlet at the top of the regeneration tower 13 is connected with a three-phase separator 19 after heat exchange is carried out through a heat exchanger 8-2 through a pipeline; gas in the three-phase separator 19 is discharged through a gas outlet 16, liquid is discharged through a liquid outlet 20, and the separated entrainer is dried by an entrainer dryer 18 and then enters the reboiler 14 for recycling; part of gas of the gas-gas splitter 9 enters a stripping column 15 after being heated by a heat exchanger 6.
A method of dehydrating natural gas using a system as described above, comprising the steps of:
firstly, the wet natural gas 1 from a gas gathering station is subjected to adiabatic expansion of fluid through a Laval nozzle 2 to create a low-temperature environment, so that heavy hydrocarbon and moisture in the natural gas are condensed into liquid drops, and preliminary gas-liquid separation is realized through a gas-liquid separator 3;
heating the natural gas subjected to pre-dehydration by a heater 6, feeding the natural gas into the lower part of an absorption tower 7, naturally floating due to low density of the gas relative to glycol solution, fully contacting with triethylene glycol barren solution in the absorption tower 7 from top to bottom, removing part of water to obtain dry gas, meeting the requirement of natural gas outward transportation, and then outward transporting the natural gas by an outer discharge port of a gas-gas splitter 9 through a dry gas outward transportation pipeline 10;
the triethylene glycol rich solution flows out of the bottom of the absorption tower 7, after throttling and pressure reduction, the triethylene glycol rich solution exchanges heat with gas flowing out of the upper part of the regeneration tower 13, the temperature is raised, the triethylene glycol rich solution enters the flash tank 11, most of light hydrocarbon components such as methane in the triethylene glycol rich solution are removed from the flash tank 11, the stabilized rich solution is throttled and pressure reduced again, exchanges heat with high-temperature lean solution in the stripping column 15, then enters the regeneration tower 13, flows back in the regeneration tower 13 through a stripping section, a rectifying section and a tower top, and is reboiled through the reboiler 14 to obtain a triethylene glycol solution with a higher concentration, the triethylene glycol solution is further purified through the stripping column 15 to reach a concentration of 99.3 percent, the triethylene glycol solution meets the triethylene glycol dehydration concentration, and is pressed into the absorption tower 7 through a circulating pump pressure 17-1 to be circulated;
and fourthly, the entrainer is injected into the reboiler 13 from the azeotropic regeneration loop, and the lean glycol water volume fraction in the reboiler 13 can be greatly reduced under the same reboiler temperature condition. The high temperature gas flowing out from the top of the regeneration tower 13 contains water and entrainer, in order to realize the recycling of the entrainer, the gas is not discharged and emptied randomly, the gas exchanges heat with lean solution, then passes through a three-phase separator 19 to realize the separation of the entrainer, the water and the gas, the separated entrainer is dried by an entrainer drier 18 and then is conveyed to a reboiler 14 by a circulating pump 17-2 to realize the recycling of the entrainer, the boiling point of the water in the reboiler can be greatly reduced by adding an azeotropic regeneration loop, so that the volume fraction of the water in the lean glycol can be reduced from 0.1 percent to about 10 multiplied by 10-6；
Fifthly, heating the other part of the gas branched out by the gas-gas splitter 9 by the heater 6, then leading the heated gas to the stripping column 15, injecting the lean solution part from the bottom of the stripping column 15, using the heated gas as stripping gas to be co-heated with the triethylene glycol solution in the stripping column 15, leading the heated gas and the triethylene glycol solution to be in reverse flow directions and fully contacting, reducing the water vapor partial pressure on the surface of the solution, and improving the mass fraction of the ethylene glycol solution to be more than 99.8%.
The invention aims to solve the problems that the existing triethylene glycol dehydration device has low efficiency and high energy consumption in the operation process and can not meet the requirement of deep dehydration. The Laval spray pipe 2 and the gas-liquid separator 3 are arranged in front of the absorption tower 7, and water separated by the gas-liquid separator 3 is discharged from the bottom water discharge outlet 5 to pre-dehydrate natural gas. The entrainer is pumped into the reboiler 14 from the azeotropic regeneration loop, and the boiling point of water is reduced under the same temperature condition of the reboiler 14, so that the volume fraction of the glycol-lean water in the reboiler 14 is greatly reduced. An outlet is arranged at the top of the regeneration tower 7, high-temperature gas containing the entrainer and water is led out, the high-temperature gas exchanges heat with the barren solution through the heat exchanger 6, then the high-temperature gas passes through the three-phase separator 19 to realize the separation of the entrainer, the water and the gas, the separated entrainer is dried through the entrainer dryer 18 and then is conveyed to the reboiler 14 through the circulating pump 17-2 to realize the recycling of the entrainer. The gas-gas flow divider 9 is arranged behind the absorption tower 7, most of dry gas dried by the absorption tower 7 is output, the other small part of gas is depressurized by the throttle valve 4 and heated by the heater 6 and reaches the bottom of the stripping column 15 to be used as stripping gas, and the gas flow can be adjusted in the gas-gas flow divider 9 to meet the requirement of the stripping column 15.
Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and not to limit the same; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art will understand that: modifications to the specific embodiments of the invention or equivalent substitutions for parts of the technical features may be made; without departing from the spirit of the present invention, it is intended to cover all aspects of the invention as defined by the appended claims.
Claims (5)
1. A throttling pre-dehydration and entrainer regeneration natural gas dehydration system comprises a gas-liquid separator (3) and an absorption tower (7) which are sequentially connected, wherein gas separated from the gas-liquid separator (3) enters the absorption tower (7) after being heated by a heater (6), gas in the absorption tower (7) enters a gas-gas splitter (9) through a top outlet, liquid in the absorption tower (7) enters a flash tank (11) through a bottom liquid outlet through a pipeline, a bottom liquid outlet of the flash tank (11) is connected with a regeneration tower (13), the regeneration tower (13) is connected with a reboiler (14), and the reboiler (14) is connected with a stripping column (15), and the throttling pre-dehydration and entrainer regeneration natural gas dehydration system is characterized in that wet natural gas (1) enters the gas-liquid separator (3) through a Laval spray pipe (2); the liquid outlet of the stripping column (15) is connected with the absorption tower (7) through a pipeline; an outlet at the top of the regeneration tower (13) is connected with a three-phase separator (19) after heat exchange through a heat exchanger (8-2) through a pipeline; gas in the three-phase separator (19) is discharged through a gas outlet (16), liquid is discharged through a liquid outlet (20), and the separated entrainer is dried by an entrainer dryer (18) and then enters a reboiler (14) for recycling; and part of gas of the gas-gas splitter (9) enters a stripping column (15) after being heated by the heat exchanger (6).
2. The natural gas dehydration system with throttling pre-dehydration and entrainer regeneration according to claim 1, characterized in that a first heat exchanger (8-1) is arranged between the top outlet of the absorption tower (7) and the gas splitter (9).
3. The natural gas dehydration system with throttling pre-dehydration and entrainer regeneration according to claim 2, characterized in that a third heat exchanger (8-3) and a first circulating pump (17-1) are arranged on the pipeline between the liquid outlet of the stripping column (15) and the absorption tower (7) and pass through the first heat exchanger (8-1).
4. The natural gas dehydration system with throttling pre-dehydration and entrainer regeneration according to claim 1, characterized in that the liquid in the absorption tower (7) enters a flash tank (11) after being heated by a second heat exchanger (8-2) through a pipeline from a bottom liquid outlet, and the pipeline is provided with a throttling valve (4).
5. A method for dehydrating natural gas in a system according to any of the preceding claims, comprising the steps of:
firstly, wet natural gas (1) from a gas gathering station is subjected to adiabatic expansion of fluid through a Laval spray pipe (2) to create a low-temperature environment, so that heavy hydrocarbon and water in the natural gas are condensed into liquid drops, and primary gas-liquid separation is realized through a gas-liquid separator (3);
heating the natural gas subjected to pre-dehydration by a heater (6), feeding the heated natural gas into the lower part of an absorption tower (7), and enabling the natural gas to float upwards naturally due to low density relative to glycol solution, fully contacting with triethylene glycol barren solution in the absorption tower (7) from top to bottom, removing part of water to be changed into dry gas, meeting the natural gas outward transportation requirement, and then externally transporting the dry gas through a dry gas outward transportation pipeline (10) by an outer discharge port of a gas-gas splitter (9);
thirdly, triethylene glycol rich liquid flows out of the bottom of an absorption tower (7), after throttling and pressure reduction, heat exchange is carried out on the triethylene glycol rich liquid and gas flowing out of the upper part of a regeneration tower (13), the temperature is raised, the triethylene glycol rich liquid enters a flash tank (11), most light hydrocarbon components in the triethylene glycol rich liquid are removed in the flash tank (11), the stabilized rich liquid is subjected to throttling and pressure reduction again, the stabilized rich liquid enters a regeneration tower (13) after heat exchange with high-temperature barren liquid in a stripping column (15), the regeneration tower (13) is subjected to reflux through a stripping section, a rectifying section and a tower top, then reboiling is carried out through a reboiler (14), a triethylene glycol solution with higher concentration is obtained, the triethylene glycol solution is further purified through the stripping column (15) and can reach 99.3% concentration, the triethylene glycol dehydration concentration is met, and is pressed into the absorption tower (7) through a circulating pump pressure (17-1);
fourthly, high-temperature gas flowing out of the top of the regeneration tower (13) contains water and an entrainer, in order to realize the recycling of the entrainer, the gas is not discharged and emptied randomly, the gas exchanges heat with barren liquor and then passes through a three-phase separator (19) to realize the separation of the entrainer, the water and the gas, and the separated entrainer is dried by an entrainer dryer (18) and then is conveyed to a reboiler (14) by a circulating pump (17-2) to realize the recycling of the entrainer;
fifthly, heating the other part of the gas branched out by the gas-gas splitter (9) by a heater (6), then enabling the other part of the gas to reach a stripping column (15), injecting the lean solution part from the bottom of the stripping column (15) as stripping gas which is in the same heat with the triethylene glycol solution in the stripping column (15), enabling the stripping gas and the triethylene glycol solution to be in reverse flow directions and fully contact with each other, reducing the water vapor partial pressure on the surface of the solution, and enabling the mass fraction of the ethylene glycol solution to be improved to be more than 99.8%.
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