Method for dehydration of aqueous triethylene glycol solution, method and apparatus for dehydration of natural gas

Abstract

The application provides a dehydration method of an aqueous triethylene glycol solution, a dehydration method and device of natural gas, and the dehydration method of the aqueous triethylene glycol solution is performed by using a dehydration device, the dehydration device comprises a stripping tower and a reboiler connected in sequence, and the dehydration method comprises the following steps: making the aqueous triethylene glycol solution enter the reboiler, and performing azeotropy with an azeotrope agent in the reboiler to obtain a dehydrated triethylene glycol system and a compatible gas product of water and the azeotrope agent generated by azeotropy respectively; wherein the azeotrope agent comprises cyclohexane; making the triethylene glycol system enter the stripping tower, and performing stripping with stripping gas entering the stripping tower in countercurrent contact, and outputting the triethylene glycol system from the stripping tower after stripping, the dehydration method can further reduce the water content of the triethylene glycol, and the dehydration method has the advantages of low toxicity, high efficiency, low energy consumption and the like.

Description

Technical Field

[0001] This invention belongs to the field of natural gas purification, specifically relating to a method for dehydrating an aqueous triethylene glycol solution, a method for dehydrating natural gas, and an apparatus. Background Technology

[0002] Natural gas is a clean and efficient energy source with a very broad prospect for development and utilization. Natural gas extracted from gas fields typically undergoes dehydration processing before being fed into the finished gas pipeline network. Natural gas dehydration processes include solvent absorption, cryogenic separation, and solid adsorption. Solvent absorption is currently the most widely used dehydration process in the natural gas industry due to its advantages such as low construction and operating costs, strong adaptability, and simple operation. Most natural gas dehydration units both domestically and internationally currently use triethylene glycol as the absorption solvent for natural gas dehydration.

[0003] The triethylene glycol solution obtained after natural gas dehydration, after the removal of natural gas, can also be called triethylene glycol-rich solution. This rich solution contains hydrocarbons, water, triethylene glycol, etc., and requires distillation for dehydration (regeneration). The dehydrated triethylene glycol solution can be called lean triethylene glycol solution, which can be recycled back to the natural gas dehydration process unit. Therefore, the dehydration requirements for aqueous triethylene glycol solutions are more stringent. Dehydration (regeneration) methods for aqueous triethylene glycol solutions include inert gas stripping, local condensation, vacuum distillation, and azeotropic distillation (e.g., the Drizo process).

[0004] Inert gas stripping is a method of removing water from triethylene glycol solution using stripping gas; local condensation utilizes the large difference between the boiling points of water and hydrocarbons and triethylene glycol, employing finger-shaped tube bundles (vertical tubes) inserted into the reboiler to condense water and hydrocarbons in the triethylene glycol solution, thereby removing water and hydrocarbons and increasing the mass fraction of triethylene glycol; vacuum distillation, under vacuum conditions, reduces the partial pressure of water vapor by lowering the total pressure of the system. However, vacuum distillation operates under negative pressure, making it susceptible to external air intrusion, which severely affects regeneration efficiency; furthermore, in the rich-liquid triethylene glycol regeneration process, the temperature of the reboiler exceeds 2... Temperatures below 00℃ will cause triethylene glycol to decompose, resulting in a low concentration of triethylene glycol that cannot meet the requirements for deep dehydration. Azeotropic distillation uses an azeotropic agent to dehydrate an aqueous triethylene glycol solution. The azeotropic agent and water form a non-uniform azeotropic mixture, the boiling point of which is lower than that of water or the azeotropic agent. Commonly used azeotropic agents are selected from isooctane, aromatics, etc. In the azeotropic distillation process, the addition process of the azeotropic agent is relatively complex, and a large amount of aromatics are used, which poses problems of toxicity and environmental pollution. The wastewater generated during the production process is also complex to treat, and the operating costs are high. Summary of the Invention

[0005] This invention provides a method for dehydrating an aqueous triethylene glycol solution, a method for dehydrating natural gas, and an apparatus. The method for dehydrating an aqueous triethylene glycol solution uses cyclohexane as an azeotropic agent, which can further reduce the water content of the dehydrated triethylene glycol, achieving the requirements for deep dehydration. Moreover, this dehydration method has advantages such as low toxicity, high efficiency, and low energy consumption, effectively overcoming the defects of the prior art.

[0006] This invention provides a method for dehydrating an aqueous triethylene glycol solution. The method employs a dehydration device comprising a stripping tower and a reboiler connected together. The dehydration method includes: introducing the aqueous triethylene glycol solution into the reboiler, where it contacts an azeotropic agent to undergo azeotrope, thereby obtaining a dehydrated triethylene glycol system and a compatible gaseous product of water and the azeotropic agent produced by the azeotrope; wherein the azeotropic agent includes cyclohexane; introducing the triethylene glycol system into the stripping tower, where it undergoes countercurrent stripping with stripping gas entering the stripping tower, and then outputting the dehydrated triethylene glycol from the stripping tower.

[0007] According to one embodiment of the present invention, the dehydration apparatus further includes a distillation column, a condenser, and a three-phase separator, with a stripping column, a reboiler, a distillation column, a condenser, and a three-phase separator connected in sequence. The dehydration method further includes: passing an aqueous triethylene glycol solution through the distillation column into the reboiler; distilling the compatible gas product into the distillation column to separate the compatible water and azeotropic agent in the compatible gas product, obtaining a mixture containing water and azeotropic agent; condensing the mixture in the condenser, and then separating it in the three-phase separator to obtain a gas phase, an aqueous phase, and an azeotropic agent phase; returning the azeotropic agent phase to the reboiler; and returning at least a portion of the aqueous phase to the distillation column.

[0008] According to one embodiment of the present invention, the temperature of the condenser is 40°C-50°C; and / or, the azeotropic agent phase is successively dried and vaporized before entering the reboiler through a stripping tower.

[0009] According to one embodiment of the present invention, the temperature of the reboiler is 95°C-180°C; and / or, the mass of the azeotropic agent is 8-12 times the mass of water in the aqueous triethylene glycol solution; and / or, the water content of the azeotropic agent is less than 0.0005%.

[0010] According to one embodiment of the present invention, the dehydration device further includes a dryer and a vaporization heater. The three-phase separator is provided with an azeotropic agent phase outlet, from which the azeotropic agent phase is discharged. The three-phase separator is sequentially connected to the dryer, the vaporization heater, and the stripping tower through the azeotropic agent phase outlet. The dehydration method further includes: allowing the azeotropic agent phase to enter the dryer for drying, then entering the vaporization heater for vaporization, and finally returning it to the reboiler through the stripping tower.

[0011] A second aspect of the present invention provides a method for dehydrating water-containing natural gas, comprising the following steps: dehydrating using a natural gas dehydration device, the natural gas dehydration device including a dehydration tower; the dehydration method comprising: introducing water-containing natural gas into the dehydration tower, contacting it with triethylene glycol in the dehydration tower to remove water from the water-containing natural gas, obtaining a water-containing triethylene glycol solution; and dehydrating the water-containing triethylene glycol solution using the above-described dehydration method for the water-containing triethylene glycol solution.

[0012] According to one embodiment of the present invention, the dehydration device further includes a flash tank, a filter, and a heat exchanger, with the dehydration tower and the heat exchanger connected in sequence. The dehydration method further includes: allowing water-containing natural gas to enter the dehydration tower and contacting it with triethylene glycol in the dehydration tower to remove water from the water-containing natural gas through contact, thereby obtaining dehydrated natural gas and a water-enriched triethylene glycol solution; allowing the triethylene glycol solution to enter the heat exchanger; the dehydrated triethylene glycol output from the stripping tower entering the heat exchanger and exchanging heat with the triethylene glycol solution entering the heat exchanger; the dehydrated triethylene glycol after heat exchange returning to the dehydration tower; and the triethylene glycol solution after heat exchange entering the reboiler for dehydration.

[0013] According to one embodiment of the present invention, the dehydration device further includes a flash tank, a filter, a first buffer tank, an glycol pump, and a cooler; the dehydration method further includes: flashing the triethylene glycol solution sequentially through the flash tank and filtering it through the filter before it enters the heat exchanger; after heat exchange, the dehydrated triethylene glycol enters the first buffer tank and then enters the cooler through the glycol pump for cooling, and after cooling, it returns to the dehydration tower.

[0014] A third aspect of the present invention provides a dehydration apparatus for implementing the above-described dehydration method for water-containing natural gas. The dehydration apparatus includes a dehydration tower, a flash tank, a filter, a heat exchanger, a distillation column, a reboiler, a stripping tower, a first buffer tank, an glycol pump, a cooler, a second buffer tank, a dryer, a vaporization heater, a three-phase separator, and a condenser. The dehydration tower, flash tank, filter, and heat exchanger are sequentially connected; the stripping tower, reboiler, and distillation column are sequentially connected; the first buffer tank, glycol pump, cooler, and dehydration tower are sequentially connected; the second buffer tank, dryer, vaporization heater, and stripping tower are sequentially connected. The dehydration tower has a wet gas inlet, a triethylene glycol inlet, a dry gas outlet, and a triethylene glycol outlet. The flash tank has a first inlet, an exhaust outlet, and a first outlet, wherein the triethylene glycol outlet of the dehydration tower is connected to the first inlet of the flash tank. The filter has a second inlet and a second outlet, and the first outlet of the flash tank is connected to the second inlet of the filter. The heat exchanger has a third inlet, a fourth inlet, a third outlet, and a fourth outlet; the second outlet of the filter is connected to the third inlet of the heat exchanger; the third inlet of the heat exchanger is connected to the third outlet of the heat exchanger; the fourth inlet of the heat exchanger is connected to the fourth outlet of the heat exchanger; the distillation column has a fifth inlet, a sixth inlet, and a fifth outlet; the third outlet of the heat exchanger is connected to the fifth inlet of the distillation column; the stripping tower and the reboiler are connected through a first connecting port, and the reboiler and the distillation column are connected through a second connecting port; the stripping tower has a sixth outlet and a seventh inlet, the sixth outlet of the stripping tower is connected to the fourth inlet of the heat exchanger, and the fourth outlet of the heat exchanger is connected to the first buffer tank; the fifth outlet of the distillation column is connected in sequence to the condenser and the three-phase separator, the three-phase separator is provided with a gas phase outlet, a water phase outlet, and an azeotropic agent phase outlet, and the azeotropic agent phase outlet is connected in sequence to the seventh inlet of the stripping tower through the second buffer tank, the dryer, and the vaporization heater.

[0015] According to one embodiment of the present invention, the dehydration device further includes a water pump, which has a seventh outlet and is connected to the aqueous phase outlet of the three-phase separator. The seventh outlet of the water pump is connected to the sixth inlet of the distillation column.

[0016] The implementation of this invention has at least the following beneficial effects:

[0017] The present invention discloses a dehydration method for an aqueous triethylene glycol solution, which uses cyclohexane as an azeotropic agent. The aqueous triethylene glycol solution is introduced into a reboiler and contacted with cyclohexane. During the contact process, cyclohexane and water in the aqueous triethylene glycol solution form a compatible gaseous product of water and cyclohexane. This compatible gaseous product of water and cyclohexane undergoes azeotroping, removing water from the aqueous triethylene glycol solution to obtain a triethylene glycol system. The triethylene glycol system is then introduced into a stripping tower and contacted countercurrently with stripping gas for stripping, further removing water from the triethylene glycol system. Using the above dehydration method to dehydrate the aqueous triethylene glycol solution can improve the dehydration efficiency, making the water content of the dehydrated triethylene glycol less than 0.001%, which can meet the requirements of deep dehydration. Moreover, the azeotropic agent has the advantages of low toxicity and low cost, which can effectively reduce energy consumption.

[0018] Furthermore, the dehydration method for aqueous triethylene glycol solution provided by this invention has the advantages of simple dehydration method, controllable process conditions, and easy operation, which is conducive to industrial production and application. Attached Figure Description

[0019] Figure 1 This is a schematic flow diagram of a dehydration device for water-containing natural gas according to an embodiment of the present invention;

[0020] Figure label:

[0021] 1-Dry gas outlet; 2-Triethylene glycol inlet; 3-Dehydration tower; 4-Triethylene glycol outlet; 5-Wet gas inlet; 6-Wastewater outlet; 7-Exhaust gas outlet; 8-Flash tank; 9-Triethylene glycol solution after flash evaporation; 10-Filter; 11-Cooler; 12-Ethylene glycol pump; 13-Heat exchanger; 14-Stripping tower; 15-Reboiler; 16-Vaporization heater; 17-First buffer tank; 18-Dehydrated triethylene glycol; 19-Azeotropic agent phase; 20-Dryer; 21-Second buffer tank; 22-Reflux liquid; 23-Residual wastewater outlet; 24-Azeotropic agent replenishment port; 25-Boost pump; 26-Three-phase separator; 27-Distillation column; 28-Stripping gas; 29-Aqueous triethylene glycol solution; 30-Mixture containing water and azeotropic agent phase; 31-Condenser; 32-Gas phase outlet; 33-Precipitated water outlet; 34-Water pump. Detailed Implementation

[0022] The specific embodiments listed below are merely descriptions of the principles and features of the present invention. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In the description of the present invention, terms such as "above," "below," "bottom," and "top" indicate positional relationships based on the positional relationships shown in the accompanying drawings and should not be construed as limitations on the present invention.

[0023] The present invention provides a method for dehydrating an aqueous triethylene glycol solution, which employs a dehydration device comprising a stripping tower and a reboiler connected together. The dehydration method includes: introducing the aqueous triethylene glycol solution into the reboiler, contacting it with an azeotropic agent in the reboiler to perform azeotropy, thereby obtaining a dehydrated triethylene glycol system and a compatible gaseous product of water and the azeotropic agent produced by the azeotropy; wherein the azeotropic agent includes cyclohexane; introducing the triethylene glycol system into the stripping tower, contacting it countercurrently with the stripping gas entering the stripping tower to perform stripping, and outputting the dehydrated triethylene glycol from the stripping tower after stripping.

[0024] In this invention, the above-mentioned dehydration method is operated under normal pressure. The aqueous triethylene glycol solution is a water-rich triethylene glycol solution obtained by dehydrating aqueous natural gas with triethylene glycol. It contains water, triethylene glycol, and a small amount of aromatics. Cyclohexane is selected as the azeotropic agent for triethylene glycol dehydration. The aqueous triethylene glycol solution and cyclohexane are contacted in a reboiler. During the contact process, hydrogen bonds are formed between the water in the aqueous triethylene glycol solution and cyclohexane, forming a compatible gaseous product of water and cyclohexane, namely a cyclohexane-water azeotropic system. Azeotrope then occurs in the reboiler, causing the cyclohexane-water azeotropic system to further dehydrate the triethylene glycol solution. The water azeotropic system is removed from the aqueous triethylene glycol solution in gaseous form to obtain a dehydrated triethylene glycol system. The triethylene glycol system is then fed into a stripping tower and stripped countercurrently with the stripping gas entering the tower. This stripping process further removes water, resulting in a triethylene glycol phase with even lower water content. The stripping gas includes cyclohexane flowing upwards within the stripping tower, which removes water from the triethylene glycol system upon contact. Furthermore, cyclohexane has good solubility for small amounts of aromatic hydrocarbons in the aqueous triethylene glycol solution, further improving the purity of the triethylene glycol during the dehydration process.

[0025] Furthermore, the dehydration device also includes a flash tank and a filter, so that the water-enriched triethylene glycol solution is first flash-treated in the flash tank to remove hydrocarbon gases and a small amount of water, and then enters the reboiler for dehydration.

[0026] Specifically, in the dehydration device, the stripping tower, reboiler, and distillation column are arranged from low to high. The dehydration method includes: the aqueous triethylene glycol solution enters the distillation column for preliminary distillation to remove a small amount of water, and then enters the reboiler, where it contacts cyclohexane for azeotropic reaction, obtaining the dehydrated triethylene glycol system and the compatible gaseous products of water and the azeotropic agent. The dehydrated triethylene glycol system then enters the stripping tower, flowing downwards and countercurrently contacting the upward-flowing stripping gas for stripping, obtaining the stripping product, i.e., the dehydrated triethylene glycol phase. The compatible gaseous product is in gaseous form; due to its density difference, the compatible gaseous product moves upwards and enters the distillation column for distillation. Distillation breaks the hydrogen bonds in the cyclohexane-water azeotropic system, separating the water and cyclohexane, resulting in a mixture containing water and cyclohexane. In the specific implementation of this invention, the dehydrated triethylene glycol is almost free of water, with a water content below 0.001%. The distillation column can also be called a regeneration tower.

[0027] In the specific implementation of this invention, the azeotropic agent can be introduced into the reboiler by a booster pump. Specifically, the azeotropic agent is pumped into the dryer by the booster pump, dried in the dryer, and then formed into azeotropic agent gas by the vaporization heater. The azeotropic agent gas enters from the bottom of the stripping tower and comes into countercurrent contact with the triethylene glycol system.

[0028] In some embodiments, the temperature of the reboiler is 95°C-180°C, for example, a range of 95°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, or any combination thereof. Controlling the temperature of the reboiler within the above range can further reduce the thermal decomposition of triethylene glycol, which can lead to its failure. Furthermore, the aqueous triethylene glycol solution is allowed to enter the reboiler through a distillation column, where it contacts the azeotropic agent to undergo azeotrope, resulting in a dehydrated triethylene glycol system and a compatible gaseous product of water and the azeotropic agent produced by the azeotrope.

[0029] In this invention, the azeotropic agent that enters the reboiler and comes into contact with the aqueous triethylene glycol solution is almost water-free. In some embodiments, the water content of the azeotropic agent (cyclohexane) is less than 0.0005%.

[0030] In some embodiments, the mass of the azeotropic agent is 8 to 12 times the mass of water in the aqueous triethylene glycol solution, for example, a range of 8, 9, 10, 11, 12 times, or any combination thereof.

[0031] In some embodiments, the dehydration apparatus further includes a condenser and a three-phase separator, and the dehydration method further includes: passing an aqueous triethylene glycol solution through a distillation column into a reboiler; distilling the compatible gas product into the distillation column to separate the compatible water and azeotropic agent in the compatible gas product, thereby obtaining a mixture containing water and azeotropic agent; condensing the mixture in the condenser, and then separating it in the three-phase separator to obtain a gas phase, an aqueous phase, and an azeotropic agent phase, respectively; returning the azeotropic agent phase to the reboiler to achieve the recycling of the azeotropic agent phase; and returning at least a portion of the aqueous phase to the distillation column for further distillation to remove water.

[0032] Specifically, the compatible gaseous products of water and azeotropic agent produced by azeotrope, namely the azeotropic agent that has absorbed water, are distilled by a distillation column to form a mixture containing water, cyclohexane, and aromatic compounds dissolved in cyclohexane. The gas phase and water phase are removed by a three-phase separator, and the cyclohexane and aromatic compounds dissolved in cyclohexane can be recycled as azeotropic agents.

[0033] In some embodiments, the temperature of the condenser is 40°C-50°C, for example, 40°C, 42°C, 45°C, 48°C, 50°C, or any combination thereof. By controlling the condenser temperature within this range, the mixture containing water and an azeotropic agent enters the condenser for condensation, and then enters a three-phase separator for separation, yielding a gas phase, an aqueous phase, and an azeotropic agent phase. The gas phase contains non-condensable gases and can be discharged to a tail gas treatment device. The aqueous phase carries a small amount of triethylene glycol, allowing at least a portion of the aqueous phase to be returned to the distillation column for further dehydration, while the remaining aqueous phase can be transported to a wastewater treatment device. The azeotropic agent phase is an oil phase, containing at least cyclohexane. Furthermore, cyclohexane has good solubility for small amounts of aromatics in the aqueous triethylene glycol solution, enabling the aromatics and cyclohexane to be returned to the reboiler as an azeotropic agent phase, effectively utilizing the hydrocarbons in the aqueous triethylene glycol solution, allowing cyclohexane to be recycled, further removing moisture, and reducing the emission of harmful gases such as aromatic compounds.

[0034] In this invention, the azeotropic agent phase output from the three-phase separator needs to be further processed before being transported to the stripping tower for recycling. In some embodiments, the azeotropic agent phase is dried and vaporized in sequence before entering the reboiler through the stripping tower. Specifically, the azeotropic agent phase is dried and vaporized in sequence before being transported to the stripping tower by a booster pump and then returned to the reboiler through the stripping tower, thus realizing the recycling of the azeotropic agent.

[0035] In some embodiments, the three-phase separator is provided with an azeotropic agent phase outlet, and the dehydration device further includes a dryer and a vaporization heater. The three-phase separator is sequentially connected to the dryer, the vaporization heater, and the stripping tower through the azeotropic agent phase outlet. In a specific implementation, the azeotropic agent phase is discharged from the azeotropic agent phase outlet, allowing the azeotropic agent phase to enter the dryer for drying, and then enter the vaporization heater for vaporization, before returning to the reboiler through the stripping tower.

[0036] Furthermore, the dehydration device also includes a second buffer tank. The three-phase separator, the second buffer tank, the dryer, the vaporization heater, and the stripping tower are connected in sequence. The azeotropic agent phase outlet of the three-phase separator is connected to the second buffer tank. The second buffer tank can be used as a storage tank to store the azeotropic agent phase, allowing the azeotropic agent phase to stand in the second buffer tank. During the standing process, the azeotropic agent phase and water are further separated, separating the azeotropic agent phase and the water that has been separated during standing. The separated water is discharged, and the azeotropic agent phase enters the dryer and the vaporization heater. The second buffer tank also plays a balancing and buffering role, making the circulation process more stable.

[0037] The present invention provides a method for dehydrating water-containing natural gas, comprising the following steps: dehydrating using a natural gas dehydration device, the natural gas dehydration device including a dehydration tower; the dehydration method comprising: introducing water-containing natural gas into the dehydration tower, contacting it with triethylene glycol in the dehydration tower to remove water from the water-containing natural gas, obtaining a water-containing triethylene glycol solution; and dehydrating the water-containing triethylene glycol solution using the above-mentioned dehydration method to obtain dehydrated triethylene glycol.

[0038] Specifically, water-containing natural gas, also known as wet natural gas (moist gas), contains water, natural gas, and a small amount of hydrocarbons. It is generally dehydrated using a natural gas dehydration unit. The water-containing natural gas enters from the bottom of the dehydration tower (also called an absorption tower) and comes into contact with triethylene glycol from the upper part of the tower. Countercurrent absorption removes the water from the water-containing natural gas, yielding dehydrated natural gas (also called dry gas) and a water-enriched triethylene glycol solution. The dry gas exits from the top of the dehydration tower, while the water-enriched triethylene glycol solution exits from the bottom. The triethylene glycol solution then enters a heat exchanger. The dehydrated triethylene glycol output from the stripping tower enters the heat exchanger and exchanges heat with the triethylene glycol solution entering the heat exchanger. The dehydrated triethylene glycol after heat exchange returns to the dehydration tower. The heat-exchanged triethylene glycol solution then enters a reboiler for further dehydration using the same method as the water-containing triethylene glycol solution, yielding dehydrated triethylene glycol.

[0039] Typically, the triethylene glycol solution enriched in water contains a small amount of hydrocarbon compounds. The triethylene glycol solution enriched in water is pretreated before being conveyed to the heat exchanger. In some embodiments, the dehydration device further includes a flash tank and a filter; the dehydration method further includes: the triethylene glycol solution enriched in water discharged from the bottom of the dehydration tower enters the flash tank, where it undergoes flash evaporation to remove hydrocarbon compounds and a small amount of water; the flash-evaporated triethylene glycol solution is then filtered through a filter to remove impurities, and finally enters the heat exchanger for heat exchange.

[0040] Normally, the dehydrated triethylene glycol can be returned to the dehydration tower for recycling. In some embodiments, the dehydration device further includes a first buffer tank, an glycol pump, and a cooler. The dehydration method further includes: after heat exchange, the dehydrated triethylene glycol passes through the first buffer tank, and then through the glycol pump and cooler back to the dehydration tower. The first buffer tank can serve as a storage tank and also play a balancing and buffering role, making the circulation process more stable.

[0041] The dehydration apparatus for water-containing natural gas provided by this invention can be used to implement the above-mentioned dehydration method for water-containing natural gas. The dehydration apparatus includes a dehydration tower, a flash tank, a filter, a heat exchanger, a distillation column, a reboiler, a stripping tower, a first buffer tank, a glycol pump, a cooler, a second buffer tank, a dryer, a vaporization heater, a three-phase separator, and a condenser; wherein the dehydration tower, flash tank, filter, and heat exchanger are connected in sequence; the stripping tower, reboiler, and distillation column are connected in sequence; the first buffer tank, glycol pump, cooler, and dehydration tower are connected in sequence; and the second buffer tank, dryer, vaporization heater, and stripping tower are connected in sequence.

[0042] Furthermore, the aforementioned dehydration tower is equipped with a moisture inlet, a triethylene glycol inlet, a dry gas outlet, and a triethylene glycol outlet. The moisture inlet of the dehydration tower is used to transport water-containing natural gas, the triethylene glycol inlet is used to transport dehydrated triethylene glycol, the dry gas outlet is used to discharge natural gas, and the triethylene glycol outlet is used to transport the triethylene glycol solution from which natural gas has been removed. The moisture inlet of the dehydration tower is located at the bottom of the dehydration tower, the triethylene glycol inlet is located at the top of the dehydration tower, the dry gas outlet is located at the top of the dehydration tower, and the triethylene glycol outlet is located at the bottom of the dehydration tower.

[0043] Furthermore, the aforementioned flash tank is equipped with a first inlet, an exhaust outlet, and a first outlet. The triethylene glycol outlet of the dehydration tower is connected to the first inlet of the flash tank, and the exhaust outlet of the flash tank is used to discharge hydrocarbon gases and a small amount of water vapor during the flash evaporation process.

[0044] Furthermore, the filter is provided with a second inlet and a second outlet, and the first outlet of the flash tank is connected to the second inlet of the filter.

[0045] The heat exchanger is provided with a third inlet, a fourth inlet, a third outlet, and a fourth outlet. The second outlet of the filter is connected to the third inlet of the heat exchanger. The third inlet of the heat exchanger is connected to the third outlet of the heat exchanger. The third inlet and the third outlet of the heat exchanger are used to transport the azeotropic agent that has absorbed water, and the fourth inlet and the fourth outlet of the heat exchanger are used to transport the azeotropic agent phase that has been dehydrated.

[0046] The distillation column is provided with a fifth inlet, a sixth inlet, and a fifth outlet. The third outlet of the heat exchanger is connected to the fifth inlet of the distillation column. The stripping column and the reboiler are connected through a first connecting port, and the reboiler and the distillation column are connected through a second connecting port.

[0047] The stripping tower is equipped with a sixth outlet and a seventh inlet. The sixth outlet of the stripping tower is connected to the fourth inlet of the heat exchanger, and the fourth outlet of the heat exchanger is connected to the first buffer tank.

[0048] The fifth outlet of the distillation column is connected in sequence to the condenser and the three-phase separator. The three-phase separator is provided with a gas phase outlet, a water phase outlet and an azeotropic agent phase outlet. The azeotropic agent phase outlet is connected in sequence to the seventh inlet of the stripping tower through the second buffer tank, the dryer and the vaporization heater. The second buffer tank is also provided with a precipitated water outlet.

[0049] In some embodiments, the dehydration apparatus further includes a water pump connected to the aqueous phase outlet of a three-phase separator, and a seventh outlet of the water pump connected to the sixth inlet of a distillation column, so that at least a portion of the aqueous phase is returned to the distillation column.

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0051] In the following embodiments, unless otherwise specified, conventional devices / instruments / structures / components in the art can be used.

[0052] Figure 1 This is a schematic diagram of the structure of the dehydration device for water-containing natural gas provided in this embodiment. The dehydration device includes at least:

[0053] The system comprises: a dehydration tower 3, a flash tank 8, a filter 10, a heat exchanger 13, a distillation column 27, a reboiler 15, a stripping tower 14, a first buffer tank 17, a glycol pump 12, a cooler 11, a second buffer tank 21, a dryer 20, a vaporization heater 16, a three-phase separator 26, and a condenser 31. The dehydration tower 3, flash tank 8, filter 10, and heat exchanger 13 are connected in sequence; the stripping tower 14, reboiler 15, and distillation column 27 are connected in sequence; the first buffer tank 17, glycol pump 12, cooler 11, and dehydration tower 3 are connected in sequence; and the second buffer tank 21, dryer 20, vaporization heater 16, and stripping tower 14 are connected in sequence.

[0054] The dehydration tower 3 is equipped with a moisture inlet 5, a triethylene glycol inlet 2, a dry gas outlet 1, a triethylene glycol outlet 4, and a wastewater outlet 6. The moisture inlet 5 of the dehydration tower is located at the bottom of the dehydration tower 3, the triethylene glycol inlet 2 of the dehydration tower is located at the top of the dehydration tower 3, the dry gas outlet 1 of the dehydration tower is located at the top of the dehydration tower 3, the triethylene glycol outlet 4 of the dehydration tower is located in the middle of the dehydration tower 3, and the wastewater outlet 6 is located at the bottom of the dehydration tower 3.

[0055] The flash tank 8 is equipped with a first inlet, an exhaust outlet 7, and a first outlet. The triethylene glycol outlet 4 of the dehydration tower is connected to the first inlet of the flash tank.

[0056] The filter 10 is provided with a second inlet and a second outlet, and the first outlet of the flash tank is connected to the second inlet of the filter;

[0057] The heat exchanger 13 is provided with a third inlet, a fourth inlet, a third outlet, and a fourth outlet. The second outlet of the filter is connected to the third inlet of the heat exchanger; the third inlet of the heat exchanger is connected to the third outlet of the heat exchanger.

[0058] The distillation column 27 is provided with a fifth inlet, a sixth inlet, and a fifth outlet. The third outlet of the heat exchanger is connected to the fifth inlet of the distillation column. The stripping column 14 and the reboiler 15 are connected through a first connecting port. The reboiler 15 and the distillation column 27 are connected through a second connecting port.

[0059] The stripping tower 14 is provided with a sixth outlet and a seventh inlet. The sixth outlet of the stripping tower is connected to the fourth inlet of the heat exchanger, and the fourth outlet of the heat exchanger is connected to the first buffer tank 17.

[0060] The fifth outlet of the distillation column is connected in sequence to the condenser 31 and the three-phase separator 26. The three-phase separator 26 is provided with a gas phase outlet 32, a water phase outlet and an azeotropic agent phase outlet. The azeotropic agent phase outlet is connected to the seventh inlet of the stripping tower in sequence through the second buffer tank 21, the dryer 20 and the vaporization heater 16. The second buffer tank is provided with an eighth inlet, an eighth outlet and a precipitated water outlet 33. The eighth outlet of the second buffer tank is connected to the dryer 20.

[0061] Water pump 34 is connected to the water phase outlet of the three-phase separator, and the seventh outlet of the water pump is connected to the sixth inlet of the distillation column, so that at least part of the water phase returns to the distillation column 27, and the remaining water phase 23 is discharged from the remaining wastewater outlet.

[0062] Azeotropic agent replenishment port 24, the azeotropic agent is replenished through azeotropic agent replenishment port 24.

[0063] The booster pump 25 is used to deliver the azeotropic agent or azeotropic phase to the second buffer tank 21.

[0064] The dehydration method for water-containing natural gas in this embodiment is briefly described as follows:

[0065] Water-containing natural gas enters through the wet gas inlet 5 of the dehydration tower 3, where it comes into contact with triethylene glycol from the triethylene glycol inlet 2 to remove moisture from the natural gas, resulting in a water-enriched triethylene glycol solution and natural gas. The natural gas exits through the dry gas outlet 1, and the water-enriched triethylene glycol solution exits through the triethylene glycol outlet 4. It then enters the flash tank 8 through the first inlet of the flash tank for flash evaporation, where hydrocarbon compounds and a small amount of water are flashed out and discharged through the exhaust outlet 7. The flashed triethylene glycol solution 9 exits through the first outlet of the flash tank and flows through the second inlet of the filter into the filter 10 for filtration to remove impurities. The filtered triethylene glycol solution enters the heat exchanger 13 through the third inlet of the heat exchanger for heat exchange and exits through the third outlet of the heat exchanger, resulting in a water-containing triethylene glycol solution.

[0066] After dehydration, triethylene glycol 18 is output from the sixth outlet of the stripping tower and enters the fourth inlet of the heat exchanger for heat exchange. After heat exchange, it is output from the fourth outlet of the heat exchanger and flows sequentially through the first buffer tank 17, glycol pump 12, and cooler 11. Finally, it enters the dehydration tower 3 from the triethylene glycol inlet 2 to achieve the recycling of triethylene glycol. The heat exchange process is as follows: after dehydration, the triethylene glycol enters the heat exchanger and exchanges heat with the filtered triethylene glycol solution. The dehydrated triethylene glycol after heat exchange returns to the dehydration tower, and the triethylene glycol solution after heat exchange enters the reboiler for dehydration.

[0067] After the aqueous triethylene glycol solution 29 is output from the third outlet of the heat exchanger, it enters the distillation column through the fifth inlet of the distillation column, and then enters the reboiler 15 through the second connecting port between the distillation column 27 and the reboiler 15. At the same time, the azeotropic agent is added through the azeotropic agent replenishment port 24, and under the action of the booster pump 25, it passes through the second buffer tank 21, is dried by the dryer 20, then vaporized by the vaporization heater 16, and enters the stripping tower 14 through the seventh inlet of the stripping tower, and then enters the reboiler 15 through the first connecting port between the stripping tower 14 and the reboiler 15. The aqueous triethylene glycol solution and the azeotropic agent contact each other in the reboiler 15 to azeotrope, obtaining the dehydrated triethylene glycol system and the compatible gaseous products of water and azeotropic agent produced by azeotroping. The azeotropic agent includes cyclohexane, the temperature of the reboiler is 180°C, and the added mass (addition amount) of the azeotropic agent is 10 times the water content in the aqueous triethylene glycol solution.

[0068] The dehydrated triethylene glycol system enters the stripping tower 27 through the first connecting port and flows from top to bottom. The stripping gas contacts the system countercurrently for stripping to obtain the dehydrated triethylene glycol phase. The stripping gas includes cyclohexane that enters the stripping tower 14 through the seventh inlet and flows from bottom to top.

[0069] The compatible gas product moves upward into the distillation column 27 for distillation. The compatible water and azeotropic agent phases in the compatible gas product are separated by distillation to obtain a mixture 30 containing water and azeotropic agent phases. The mixture 30 is output from the fifth outlet of the distillation column and enters the condenser 31 for condensation. Then it enters the three-phase separator 26 for separation to obtain the gas phase, water phase and azeotropic agent phase respectively. The temperature of the condenser is 45℃.

[0070] The azeotropic phase 19 is output from the azeotropic phase outlet and, under the action of the booster pump 25, flows through the eighth inlet of the second buffer tank. It is left to stand in the second buffer tank 21 to allow water in the azeotropic phase to precipitate out. The precipitated water is discharged from the precipitated water outlet 33. The azeotropic phase after removing the precipitated water is transported to the dryer 20 through the eighth outlet of the second buffer tank for drying, and then flows into the vaporization heater 16 for vaporization. Finally, it enters the stripping tower 14 through the seventh inlet of the stripping tower, and then returns to the reboiler 15 through the first connecting port to realize the recycling of the azeotropic phase.

[0071] Non-condensable gases in the gas phase are discharged through the gas phase outlet 32, and at least a portion of the aqueous phase is used as reflux liquid 22 to enter the distillation column 27 through the sixth inlet of the distillation column under the action of the water pump to continue dehydration. The remaining aqueous phase 23 is discharged from the remaining wastewater outlet and transported to the wastewater treatment device.

[0072] Through the above dehydration process, the water content of the dehydrated product triethylene glycol (after dehydration) can be less than 0.001%, and hydrocarbons in water-containing natural gas can be effectively utilized with a utilization rate of over 85%, reducing the emission of hydrocarbon compounds during the dehydration process. Furthermore, this dehydration method can use cyclohexane as a single azeotropic agent, which has the advantages of low toxicity, high efficiency, and low energy consumption, greatly reducing the removal cost.

[0073] The preferred embodiments and experimental verifications of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for dehydrating an aqueous triethylene glycol solution, characterized in that, Dehydration is performed using a dehydration device, which includes a stripping tower and a reboiler connected together. The dehydration method includes: An aqueous triethylene glycol solution is introduced into a reboiler and azeotropically reacted with an azeotropic agent to obtain a dehydrated triethylene glycol system and a compatible gaseous product of water and azeotropic agent produced by the azeotrope; wherein the azeotropic agent includes cyclohexane. The triethylene glycol system is introduced into the stripping tower and stripped by countercurrent contact with the stripping gas entering the stripping tower. After stripping, the system is output from the stripping tower to obtain dehydrated triethylene glycol. The temperature of the reboiler is 95℃-180℃; The mass of the azeotropic agent is 8 to 12 times the mass of water in the aqueous triethylene glycol solution; The azeotropic agent has a water content of less than 0.0005%.

2. The method for dehydrating an aqueous triethylene glycol solution according to claim 1, characterized in that, The dehydration device further includes a distillation column, a condenser, and a three-phase separator, wherein the stripping tower, reboiler, distillation column, condenser, and three-phase separator are connected in sequence, and the dehydration method further includes: The aqueous triethylene glycol solution is passed through the distillation column into the reboiler; The compatible gas product is fed into a distillation column for distillation. The distillation separates the compatible water and azeotropic agent from the compatible gas product, resulting in a mixture containing water and azeotropic agent. The mixture is condensed in the condenser and then separated in a three-phase separator to obtain a gas phase, an aqueous phase, and an azeotropic phase. The azeotropic agent phase is returned to the reboiler; This allows at least a portion of the aqueous phase to return to the distillation column.

3. The method for dehydrating an aqueous triethylene glycol solution according to claim 2, characterized in that, The temperature of the condenser is 40℃-50℃; and / or, The azeotropic agent phase is dried and vaporized sequentially, and then enters the reboiler through a stripping tower.

4. The method for dehydrating an aqueous triethylene glycol solution according to claim 2, characterized in that, The dehydration device also includes a dryer and a vaporization heater. The three-phase separator is provided with an azeotropic agent phase outlet, from which the azeotropic agent phase is discharged. The three-phase separator is connected in sequence to the dryer, the vaporization heater, and the stripping tower through the azeotropic agent phase outlet. The dehydration method further includes: drying the azeotropic agent phase in a dryer, then vaporizing it in a vaporization heater, and finally returning it to the reboiler through the stripping tower.

5. A method for dehydrating water-containing natural gas, characterized in that, Includes the following steps: Dehydration is performed using a natural gas dehydration device, which includes a dehydration tower; The dehydration method includes: The water-containing natural gas is introduced into a dehydration tower, where it comes into contact with triethylene glycol to remove the water from the natural gas, resulting in a water-containing triethylene glycol solution. The aqueous triethylene glycol solution is dehydrated using the dehydration method described in any one of claims 1-4.

6. The method for dehydrating water-containing natural gas according to claim 5, characterized in that, The dehydration device also includes a flash tank, a filter, and a heat exchanger. The dehydration tower and the heat exchanger are connected in sequence. The dehydration method also includes: allowing water-containing natural gas to enter the dehydration tower and contacting it with triethylene glycol in the dehydration tower, removing water from the water-containing natural gas through the contact, and obtaining dehydrated natural gas and a water-enriched triethylene glycol solution, respectively. The triethylene glycol solution is then introduced into the heat exchanger. The dehydrated triethylene glycol output from the stripping tower enters a heat exchanger to exchange heat with the triethylene glycol solution entering the heat exchanger. The dehydrated triethylene glycol after heat exchange returns to the dehydration tower, and the triethylene glycol solution after heat exchange enters the reboiler for dehydration.

7. The method for dehydrating water-containing natural gas according to claim 6, characterized in that, The dehydration device further includes a flash tank, a filter, a first buffer tank, a glycol pump, and a cooler; the dehydration method further includes: The triethylene glycol solution is flashed in a flash tank and filtered through a filter before entering the heat exchanger. After the heat exchanged dehydrated triethylene glycol enters the first buffer tank, it is then pumped into the cooler for cooling before returning to the dehydration tower.

8. A dehydration apparatus for implementing the dehydration method for water-containing natural gas according to any one of claims 5-7, characterized in that, Includes dehydration tower, flash tank, filter, heat exchanger, distillation column, reboiler, stripping tower, first buffer tank, glycol pump, cooler, second buffer tank, dryer, vaporization heater, three-phase separator, and condenser; The dehydration tower, flash tank, filter, and heat exchanger are connected in sequence; the stripping tower, reboiler, and distillation column are connected in sequence; the first buffer tank, glycol pump, cooler, and dehydration tower are connected in sequence; and the second buffer tank, dryer, vaporization heater, and stripping tower are connected in sequence. The dehydration tower is provided with a wet gas inlet, a triethylene glycol inlet, a dry gas outlet, and a triethylene glycol outlet; the flash tank is provided with a first inlet, an exhaust outlet, and a first outlet, wherein the triethylene glycol outlet of the dehydration tower is connected to the first inlet of the flash tank; The filter is provided with a second inlet and a second outlet, and the first outlet of the flash tank is connected to the second inlet of the filter; The heat exchanger is provided with a third inlet, a fourth inlet, a third outlet, and a fourth outlet; wherein the second outlet of the filter is connected to the third inlet of the heat exchanger; the third inlet of the heat exchanger is connected to the third outlet of the heat exchanger; wherein the fourth inlet of the heat exchanger is connected to the fourth outlet of the heat exchanger. The distillation column is provided with a fifth inlet, a sixth inlet, and a fifth outlet; the third outlet of the heat exchanger is connected to the fifth inlet of the distillation column; The stripping column is connected to the reboiler through a first connection port, and the reboiler is connected to the distillation column through a second connection port. The stripping tower is provided with a sixth outlet and a seventh inlet. The sixth outlet of the stripping tower is connected to the fourth inlet of the heat exchanger, and the fourth outlet of the heat exchanger is connected to the first buffer tank. The fifth outlet of the distillation column is connected in sequence to a condenser and a three-phase separator. The three-phase separator is provided with a gas phase outlet, a water phase outlet and an azeotropic agent phase outlet. The azeotropic agent phase outlet is connected in sequence to the seventh inlet of the stripping tower through a second buffer tank, a dryer, and a vaporization heater.

9. The dehydration apparatus according to claim 8, characterized in that, The dehydration device also includes a water pump, which has a seventh outlet. The water pump is connected to the water phase outlet of the three-phase separator, and the seventh outlet of the water pump is connected to the sixth inlet of the distillation column.

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