Online skid-mounted integrated triethylene glycol barren solution desalting device and method

Abstract

The invention discloses an online skid-mounted integrated triethylene glycol barren solution desalting device and method. The device comprises a cold clear precipitation device, a fine filter and three-stage series electrodialysis devices, the three parts are connected in series, cooling is carried out, chemical agents are added for precipitation, fine filtration and electrodialysis, impurities and inorganic salt in the triethylene glycol barren solution are removed through the device in sequence, and long-period recycling of the triethylene glycol barren solution is achieved. According to the invention, continuous desalination of the high-salt-content triethylene glycol barren solution can be realized, and the technological process is accelerated. In addition, the device is low in energy consumption, convenient to operate, arranged in a prying manner, convenient to drag and convenient for indirect desalination of triethylene glycol dehydration devices in different stations.

Description

Technical Field

[0001] The present invention relates to the technical field of surface engineering - oil and gas treatment station technology - separation and recovery technology, and is mainly used for the impurity removal and recovery of the dehydrating agent triethylene glycol. In particular, it relates to an on-line skid-mounted integrated desalting device and method for lean triethylene glycol. Background Technique

[0002] The methods for natural gas purification and dehydration mainly include solvent absorption method (mainstream process), solid adsorption method, and chemical reaction method. Among them, the most commonly used solvent absorption method for natural gas dehydration is the dehydration with triethylene glycol solution. The wet purified natural gas (or synthesis gas or saturated gas) enters the bottom of the dehydration device absorption tower and contacts countercurrently with the lean triethylene glycol entering from the top of the tower in the dehydration absorption tower. In this way, part of the saturated water in the natural gas is absorbed by the triethylene glycol and removed, meeting the requirements of the exported gas quality. The dehydrated natural gas comes out from the top of the absorption tower, and the lean liquid that has absorbed water becomes rich liquid and flows out from the bottom of the absorption tower and enters the regeneration system for regeneration to realize the recycling of the triethylene glycol solution.

[0003] At present, there are 20 triethylene glycol dehydration devices in Qinghai Oilfield, which are basically in operation all year round. The main users are the Third Gas Production Plant and the First Gas Production Plant. The single alcohol filling volume of each triethylene glycol dehydration device is 4950L, and the average consumption during the normal operation of the dehydration device is 220L / month. At present, the maintenance of the triethylene glycol dehydration device is carried out 2 times a year. The main work is to manually clean the impurities inside devices such as the reboiler, lean liquid storage tank, rectifying column, mechanical filter, cartridge filter, and absorption tower (inorganic salts account for 95%, muddy silt accounts for 3%, and coking substances account for 2%), and fill new triethylene glycol. The two factories consume about 250 tons of glycol per year, with a cost of about 4 million yuan, and the ineffective triethylene glycol is directly scrapped.

[0004] During the normal operation process, it is found that there are problems in the triethylene glycol dehydration device such as easy foaming of the system, excessive inorganic salts, cracking and polymerization reactions caused by too high temperature, unqualified natural gas water dew point, difficult treatment of excessive tail gas, increased solution loss, and unstable operation of the device; during the maintenance, a large amount of inorganic salts are attached to the flue pipes of the reboiler and the heat exchange coils of the lean liquid tank, affecting the heating efficiency of the burner, blocking the heat exchange coils, reducing the heat exchange efficiency of the lean liquid coils, and there are also problems such as perforation of the flue pipes and coils; there are problems such as triethylene glycol polymers and inorganic salts in the rectifying column, mechanical filter, cartridge filter, and absorption tower. The unqualified natural gas water dew point affects the quality of the exported natural gas, causing internal corrosion of the downstream long-distance pipeline and natural gas metering disputes; equipment corrosion perforation and pipeline scaling and blockage pose potential safety hazards and running with diseases for the equipment operation, bringing huge challenges to the safety production management.

[0005] The total content of suspended solids in the TEG lean solution was 358 mg / L, the total content of heat-stable salts was 935 mg / L, and the total content of organic impurities was 455 mg / L. The suspended solids, heat-stable salts, and impurities caused the TEG solution to become ineffective, and a large amount of ineffective TEG had to be regularly discarded and replaced, resulting in a huge waste of resources.

[0006] During normal operation, it was found that triethylene glycol had problems such as pollution and foaming, excessive inorganic salts, cracking and polymerization caused by excessive temperature, and substandard natural gas water dew point. The total content of solid suspended matter in triethylene glycol lean liquid was 358 mg / L, the total content of thermally stable salts was 935 mg / L, and the total content of organic impurities was 455 mg / L. During maintenance, it was found that there were many inorganic salts in the burner of the reboiler and the heat exchange coil of the lean liquid tank, which affected the heating efficiency of the burner, blocked the pipeline, the heat exchange efficiency of the lean liquid coil, and the corrosion and perforation of the pyrotechnic tube and coil.

[0007] TEG dehydration technology is the mainstream natural gas dehydration method at present. All large gas fields are faced with problems such as excessive inorganic salts in TEG, pollution and foaming, and exhaust gas treatment and emission compliance. Research on TEG lean liquid dehydration method is of great significance for treating TEG system prone to foaming, weak dehydration ability, exhaust gas treatment and emission compliance, and poor equipment operation stability. It can improve equipment efficiency, reduce operating costs, improve device operation stability, achieve "safe, stable, full and excellent" device operation, reduce maintenance frequency and labor intensity, ensure external quality requirements and achieve safe production control.

[0008] Through equipment maintenance twice a year, the deposited salt on the reboiler is manually removed and triethylene glycol is replaced to meet the needs of the production process.

[0009] At present, the main separation technologies are: vacuum distillation; chemical precipitation; membrane separation; anion and cation resin exchange.

[0010] Patent CN200810041693.3 discloses a method for continuous distillation and purification of coked phenol, which includes two steps of preliminary separation in a first vacuum distillation tower and main separation in a second vacuum distillation tower. Continuous distillation and purification of coked phenol is achieved by selecting parameters such as the number of theoretical plates, reflux ratio and operating parameters of the first vacuum distillation tower and the second vacuum distillation tower. The present invention also discloses a device for realizing the above-mentioned continuous distillation and purification method of coked phenol. The technical key points of the device are that it mainly includes a feed heat exchange device, a first vacuum distillation tower, a second vacuum distillation tower, a condensing device, a heating device and related pipelines. The present invention solves the problems of low processing capacity, low process stability, high energy consumption and high operating labor intensity in the current intermittent distillation and purification of coked phenol. The present invention is suitable for producing coked phenol with 90%-95% phenol fraction in the phenol recovery system of the coking industry.

[0011] Patent CN200910030760.6 discloses a method for simultaneously recovering phosphorous acid and glyphosate from glyphosate production wastewater by chemical precipitation method: (1) adjusting the pH value of glyphosate production wastewater with hydrochloric acid; (2) adding CaCl2 solution to form calcium glyphosate and calcium phosphite filter cake; (3) adding water to the filter cake for blending, adding a certain amount of Na2CO3 to the blending solution, and generating CaCO3 precipitate after stirring and reacting; (4) filtering and separating the precipitated CaCO3; after the filtrate is concentrated twice to remove NaCl, a concentrated solution of glyphosate and phosphorous acid is obtained, where the concentration of glyphosate is 84.72 g / l and the concentration of phosphorous acid is 251.40 g / l. The total recovery rates of glyphosate and phosphorous acid are 88% and 89% respectively. The recovery and treatment method of the present invention can simultaneously recover glyphosate and phosphorous acid from wastewater, and obtain a concentrated solution of glyphosate and phosphorous acid. The total recovery rates of glyphosate and phosphorous acid are 88% and 89% respectively.

[0012] The triethylene glycol dehydration unit is in a perennial operation state and does not stop except for maintenance. The operating temperature of the lean triethylene glycol solution is 120 °C, the operating temperature of the rich solution is 180 °C, and the operating temperature of the absorption tower is 20 °C. Problems such as foaming of triethylene glycol, non-compliance of water dew point, equipment corrosion and perforation are caused by heat-stable salts and impurities in the solution. Summary of the Invention

[0013] To solve the above problems, the present technical solution provides a desalination device and method for triethylene glycol solution with high recovery rate, low energy consumption and no environmental pollution. Without affecting the operation of the device, the heat-stable salts and impurities in the device are removed, the circulating operation time of triethylene glycol is increased, the water dew point is ensured to meet the production requirements, and the maintenance frequency is reduced.

[0014] The present invention adopts the following technical solutions:

[0015] 3. An on-line skid-mounted integrated lean triethylene glycol desalination device, including a cold precipitation device, a fine filter and an electrodialysis device in series of three stages; the three parts are in series relationship, for cooling, adding chemical agents for precipitation, fine filtration, and electrodialysis. The cold precipitation device includes a triethylene glycol transfer pump, a cooling and sedimentation chamber, a formation water transfer pump, a formation water filter, and a formation water storage tank. The inlet of the triethylene glycol transfer pump is connected to the lean triethylene glycol storage tank, and the outlet is connected to the cooling and sedimentation chamber. The cooling and sedimentation chamber is provided with a housing, and a sodium hydroxide dosing chamber and a sodium carbonate dosing chamber are arranged on the housing. A stirring device, a heat exchange coil, and zeolite are arranged in the housing. The formation water transfer pump, the formation water filter, and the formation water storage tank are connected in series to form an integral body. The outlet of the formation water storage tank is connected to the electrodialysis device.

[0016] The fine filter includes adsorption resin, decolorizing resin, a fine filtration chamber, and a housing.

[0017] The electrodialysis device is provided with a housing, in which an anode plate and a cathode plate are arranged. The anode plate and the cathode plate are connected to the positive and negative poles of a power supply to form a closed loop. A conductivity meter is arranged between the anode plate and the positive pole of the power supply. A cation exchange membrane and an anion exchange membrane are arranged in the housing and are alternately arranged between the anode plate and the cathode plate.

[0018] The integrated method for desalting lean triethylene glycol solution comprises the following steps:

[0019] Step 1: The outlet of the lean triethylene glycol solution is connected to a chemical precipitation chamber, and the temperature is controlled at 30 - 35 °C. Sodium hydroxide and sodium carbonate are added to the chemical precipitation chamber to adjust the appropriate pH value, and a chemical reaction occurs to generate magnesium hydroxide and calcium carbonate precipitates. Zeolite is added in the precipitation chamber, which has good adsorption for the precipitates and other impurities and is more convenient for cleaning. The feeding speed is 800 - 1000 L / h, which is designed according to the normal operation circulation volume of the triethylene glycol dehydration device. In this process, the pH value of the solution is mainly adjusted and 98% of divalent metal ions are removed. The temperature control is completed by the water circulation of the heat exchange coil.

[0020] Step 2: Enter the fine filter, control the feeding speed at 5 - 10 L / s, and maintain the operating pressure at 0.2 - 0.3 MPa. The fine filter is provided with a backwashing device, which is convenient for cleaning and removing impurities from the fine filter and can be recycled. The adsorption resin and decolorizing resin complete the absorption of the remaining impurities and triethylene glycol polymers to prevent contamination of the anion and cation exchange membranes.

[0021] Step 3: Enter the electrodialysis device to remove monovalent anions and cations. Pretreated formation water is introduced into the concentration chamber, and sodium sulfate solution is introduced into the cathode chamber and the anode chamber. Among them, a once-through water supply method is adopted in both the desalination chamber and the concentration chamber, while a circulating water supply method is adopted in the cathode chamber and the anode chamber. The formation water with a salt content is sequentially introduced into the concentration chamber of the electrodialysis device, the lean solution is introduced into the desalination chamber, and 3% sodium sulfate solution is introduced into the anode chamber and the cathode chamber at a flow rate of 80 L / h.

[0022] It is operated in a constant pressure mode, and the operating voltage is 110 V. The inorganic salt ions in the lean solution respectively pass through the anion and cation exchange membranes under the action of the electric field and enter the concentration chamber. The lean solution molecules are not charged and are thus not affected by the electric field and flow out with the solution, thereby obtaining the desalted lean triethylene glycol solution.

[0023] The outlet end of the desalination chamber of the three-stage electrodialysis device is the product liquid. The device can operate continuously for a long time. When the salt content of the lean solution is detected to be reduced to less than 3%, the reaction terminates, and the power supply is cut off in sequence. The concentration of triethylene glycol in the lean triethylene glycol solution is > 98%. Both the cation exchange membrane and the anion exchange membrane are composite ion exchange membranes with high cross-linking degree characteristics. The water streamline velocity in the desalination chamber, the concentration chamber, the cathode chamber, and the anode chamber is 0.1 - 0.3 cm / s; the current density is 3 - 15 mA / cm².

[0024] The object of the present invention is to address the deficiencies of the prior art. The cooling precipitation + fine filter + three - stage series electrodialysis device provided by the present invention can achieve one - pass continuous desalination of high - salinity triethylene glycol lean liquid through the design of the process, accelerating the process. In addition, the volume of a single electrodialysis membrane stack is small, and it is arranged in a skid - mounted form, which is convenient for shipping, realizing indirect desalination of triethylene glycol dehydration devices at different stations.

[0025] First, sodium hydroxide and sodium carbonate are added to the device of the present invention for precipitation to reduce the hardness of the solution. The fine filter uses adsorption resin to further reduce the solution hardness and prevent the precipitation of corresponding inorganic salts due to temperature changes, which may block the membrane sheets used in electrodialysis. It can operate online, ensure that the device does not stop production, and can operate at full load. Divalent ions are mainly Ca 2+ 、Mg 2+ which are easy to precipitate, and chemical precipitation is used to remove divalent ions; fine filtration is used to further remove impurities and decolorize, protecting the anion - cation exchange membranes; the electrodialysis device removes Na + 、K + 、Cl - monovalent ions. Anion - cation exchange membranes are more conducive to the passage of monovalent ions, and it is not easy to achieve chemical precipitation of these ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic flow diagram of the present invention;

[0027] Figure 2 is a schematic diagram of the principle of the electrodialysis device of the present invention;

[0028] Reference numerals: The cooling precipitation device includes 1 - pump, 2 - filter, 3 - formation water storage tank, 4 - chemical precipitation chamber, 5 - sodium hydroxide, 6 - sodium carbonate, 10 - zeolite, 11 - stirring device, 12 - housing; the fine filtration device includes 7 - adsorption resin, 8 - decolorizing resin, 9 - fine filtration chamber, 13 - housing; the electrodialysis device includes 1 - anode plate, 2 - cathode plate, 3 - concentration chamber, 4 - desalination chamber, 5 - anode chamber, 6 - cathode chamber, 7 - cation exchange membrane, 8 - cation exchange membrane, 9 - housing. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] As shown in the accompanying drawings, the anode plate and the cathode plate are respectively connected to the positive and negative poles of a DC power supply to form a stable constant - voltage DC electric field. Under the action of the constant electric field, charged particles in the solution move directionally. Positive - valence ions move towards the negative pole, and negative - valence ions move towards the positive pole, passing through the anion - cation exchange membranes and entering the formation water chamber to achieve solution desalination.

[0030] The method of the present invention mainly includes chemical precipitation + fine filtration + three - stage series electrodialysis device.

[0031] The main components of the chemical precipitation chamber are the sodium hydroxide dosing chamber, the sodium carbonate dosing chamber, the heat exchange coil, and the zeolite. Sodium hydroxide and sodium carbonate are added to adjust the appropriate pH value, and a chemical reaction occurs to generate magnesium hydroxide and calcium carbonate precipitates, and the divalent ions are removed. Zeolite has good adsorption capacity for precipitates and impurities, and does not generate new pollution, so it is easy to clean.

[0032] 2NaOH+MgSO4=Na2SO4+Mg(OH)2↓

[0033] CaCl2+Na2CO3=2NaCl+CaCO3↓

[0034] The main components of the fine filter are adsorption resin and decolorization resin, and the backwash device uses the high adsorption of the adsorption resin to adsorb the remaining impurities, and the decolorization resin decolorizes the triethylene glycol lean solution to prevent contamination of the anion and cation exchange membrane.

[0035] The main components of the electrodialysis device are anode plates, cathode plates, power supplies, cation exchange membranes, anion exchange membranes, and backwash devices. The monovalent ions are removed. An anode chamber is provided between the anode plate and the repeating unit, and a cathode chamber is provided between the cathode plate and the repeating unit. Each repeating unit contains two compartments, namely: a desalination chamber and a concentration chamber, and an ion exchange membrane is provided between adjacent compartments. The inlet and outlet liquid ends of the electrodialysis device are provided with ancillary equipment such as a conductivity meter, a power supply, and a flow meter. The cathode plate is fixedly connected to the negative pole of the power supply, and the anode plate is fixedly connected to the positive pole of the power supply. Both the anode plate and the cathode plate are titanium-coated ruthenium flat electrodes.

[0036] The feed end pipeline of the device is connected to the lean liquid storage tank of the triethylene glycol dehydration device, and the finished product is returned to the lean liquid storage tank for recycling. The inlet and outlet of the formation water storage tank are connected to the station water injection system, and the inlet and outlet of the backwash device are connected to the water injection system, so no new waste is generated.

[0037] The steps include:

[0038] Step 1: The outlet of the triethylene glycol lean solution is connected to a chemical precipitation chamber, and the temperature is controlled at 30-35°C. Sodium hydroxide and sodium carbonate are added to the chemical precipitation chamber to adjust the appropriate pH value, and a chemical reaction occurs to generate magnesium hydroxide and calcium carbonate precipitation. Zeolite is added to the precipitation chamber, which has good adsorption of precipitates and other impurities and is easier to clean. The feed rate is 800-1000L / h, which is designed according to the normal production cycle of the triethylene glycol dehydration unit. This process mainly adjusts the pH value of the solution and removes 98% of divalent metal ions. Temperature control is completed by heat exchange coil water circulation.

[0039] Step 2: Enter the fine filter, control the feeding speed at 5 - 10 L / s, maintain the operating pressure at 0.2 - 0.3 MPa. The fine filter is equipped with a backwashing device to facilitate cleaning and impurity removal, and for recycling use. The adsorption resin and decolorizing resin complete the absorption of the remaining impurities and triethylene glycol polymers, preventing contamination of the anion and cation exchange membranes.

[0040] Step 3: Enter the electrodialysis device to remove monovalent anions and cations. Pretreated formation water is introduced into the concentration chamber, and sodium sulfate solution is introduced into the cathode chamber and the anode chamber. Among them, a once-through water supply method is adopted in both the desalination chamber and the concentration chamber, while a circulating water supply method is adopted in the cathode chamber and the anode chamber.

[0041] The desalination operation method includes the following steps:

[0042] Open the control valve, and the lean triethylene glycol enters the chemical sedimentation chamber. Sodium hydroxide and sodium carbonate are added to adjust the appropriate pH value, and at the same time, magnesium hydroxide and calcium carbonate precipitates are generated. The feeding speed is 800 - 1000 L / h, designed according to the normal operation circulation volume of the triethylene glycol dehydration device. The chemical addition speed requires manual intervention and dynamic adjustment. Then it enters the fine filter, control the feeding speed at 5 - 10 L / s, maintain the operating pressure at 0.2 - 0.3 MPa, and then enter the electrodialysis device.

[0043] Sequentially introduce formation water with a certain salt content into the concentration chamber of the electrodialysis device, introduce lean liquid into the desalination chamber, and introduce 3% sodium sulfate solution into the anode chamber and the cathode chamber at a flow rate of 80 L / h.

[0044] Operate in a constant pressure mode with an operating voltage of 110 V. The inorganic salt ions in the lean liquid penetrate through the anion and cation exchange membranes into the concentration chamber under the action of the electric field. The lean liquid molecules are not charged and thus are not affected by the electric field and flow out with the solution, thereby obtaining desalted lean triethylene glycol. The outlet end of the desalination chamber of the three-stage electrodialysis device is the product liquid, and the equipment can operate continuously for a long time. When the detected salt content in the lean liquid is reduced to less than 3%, the reaction terminates, and the power supply is cut off in sequence. The concentration of triethylene glycol in the lean triethylene glycol is > 98%. Both the cation exchange membrane and the anion exchange membrane are composite ion exchange membranes with high cross-linking degree characteristics. The water streamline velocity in the desalination chamber, concentration chamber, cathode chamber, and anode chamber is 0.1 - 0.3 cm / s; the current density is 3 - 15 mA / cm².

Claims

1. An on-line skid-mounted integrated desalination device for triethylene glycol lean liquid, characterized in that: It includes a cold precipitation device, a fine filter, and a three-stage series electro-dialysis device; the three parts are in series relationship, for cooling, adding chemical agents for precipitation, fine filtration, and electro-dialysis. The cold precipitation device includes a triethylene glycol transfer pump, a cooling and sedimentation chamber, a formation water transfer pump, a formation water filter, and a formation water storage tank. The inlet of the triethylene glycol transfer pump is connected to the lean triethylene glycol storage tank, and the outlet is connected to the cooling and sedimentation chamber. The cooling and sedimentation chamber is provided with a housing, on which a sodium hydroxide dosing chamber and a sodium carbonate dosing chamber are provided. Inside the housing, there are a stirring device, a heat exchange coil, and zeolite; the formation water transfer pump, the formation water filter, and the formation water storage tank are connected in series to form an integral whole.

2. The on-line skid-mounted integrated triethylene glycol lean liquid desalination device according to claim 1, characterized in that: The outlet of the formation water storage tank is connected to the electro-dialysis device.

3. An on-line skid-mounted integrated desalination device for triethylene glycol lean liquid according to claim 1, characterized in that: The fine filter includes an adsorption resin, a decolorizing resin, a fine filtration chamber, and a housing. The inlet of the fine filter is connected to the outlet of the cold precipitation device, and the outlet is connected to the electro-dialysis device. Inside the fine filter, there is a fine filtration chamber, and the adsorption resin and the decolorizing resin are arranged inside.

4. An on-line skid-mounted integrated desalination device for triethylene glycol lean liquid according to claim 1, characterized in that: The electro-dialysis device is provided with a housing, inside which an anode plate and a cathode plate are arranged. The anode plate and the cathode plate are connected to the positive and negative poles of the power supply to form a closed loop. An electrical conductivity meter is arranged between the anode plate and the positive pole of the power supply. Inside the housing, a cation exchange membrane and an anion exchange membrane are arranged, which are alternately arranged between the anode plate and the cathode plate.

5. An on-line skid-mounted integrated method for desalting triethylene glycol lean liquid using the device according to claim 1, characterized in that It includes the following steps: Step 1: The outlet of the lean triethylene glycol is connected to a chemical precipitation chamber, and the temperature is controlled at 30 - 35 °C. Sodium hydroxide and sodium carbonate are added to the chemical precipitation chamber to adjust the appropriate pH value, and a chemical reaction occurs to generate magnesium hydroxide and calcium carbonate precipitates. Zeolite is added to the precipitation chamber, which has good adsorption for the precipitates and other impurities and is more convenient for cleaning. The feeding speed is 800 - 1000 L / h, designed according to the normal operation circulation volume of the triethylene glycol dehydration device. This process mainly adjusts the pH value of the solution and removes 98% of divalent metal ions. The temperature control is completed by the water circulation of the heat exchange coil; Step 2: Enter the fine filter, control the feeding speed at 5 - 10 L / s, and maintain the operating pressure at 0.2 - 0.3 MPa. The fine filter is provided with a backwashing device to facilitate the cleaning and impurity removal of the fine filter for recycling. The adsorption resin and the decolorizing resin complete the absorption of the remaining impurities and triethylene glycol polymers to prevent pollution of the cation and anion exchange membranes; Step 3: Enter the electro-dialysis device to remove monovalent cations and anions. Pretreated formation water is introduced into the concentration chamber, and sodium sulfate solution is introduced into the cathode chamber and the anode chamber; among them, a once-through water supply method is adopted in both the desalination chamber and the concentration chamber, while a circulating water supply method is adopted in the cathode chamber and the anode chamber.

6. An on-line skid-mounted integrated method for desalting triethylene glycol lean liquid according to claim 5, characterized in that, The formation water with salt content is introduced into the concentration chamber of the electro-dialysis device in sequence, the lean liquid is introduced into the desalination chamber, and 3% sodium sulfate solution is introduced into the anode chamber and the cathode chamber, with the sodium sulfate solution at 80 L / h.

7. An on-line skid-mounted integrated method for desalting triethylene glycol lean liquid according to claim 5, characterized in that, It is operated in a constant pressure mode, with an operating voltage of 110 V. The inorganic salt ions in the lean liquid respectively pass through the anion and cation exchange membranes under the action of the electric field and enter the concentration chamber. The lean liquid molecules are not charged and are not affected by the electric field, and flow out with the solution, thus obtaining the desalted lean triethylene glycol.

8. An on-line skid-mounted integrated desalination method for triethylene glycol lean liquid according to claim 5, characterized in that, The outlet end of the desalination chamber of the three-stage electrodialysis device is the product liquid. The device can operate continuously for a long time. When the salt content of the lean liquid detected is reduced to less than 3%, the reaction terminates, and the power supply is cut off in sequence.

9. An on-line skid-mounted integrated method for desalting triethylene glycol lean liquid according to claim 5, characterized in that, The concentration of triethylene glycol in the triethylene glycol lean liquid > 98%. Both the cation exchange membrane and the anion exchange membrane are composite ion exchange membranes with high cross-linking degree characteristics.

10. An on-line skid-mounted integrated method for desalting triethylene glycol lean liquid according to claim 5, characterized in that, The water flow linear velocity in the desalination chamber, concentration chamber, cathode chamber, and anode chamber is 0.1 - 0.3 cm / s; the current density is 3 - 15 mA / cm2.

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