Treatment method of regenerated amine liquid

Abstract

The invention relates to the technical field of amine liquid purification, and discloses a treatment method of regenerated amine liquid. The method comprises the following steps: (1) performing electrodialysis on regenerated amine liquid, and dissolving salt separated from the regenerated amine liquid by using carrier water to obtain strong brine and purified amine liquid; (2) carrying out reduced pressure distillation on the strong brine to respectively obtain acid gas, regenerated distillate water, recovered organic amine and concentrated salt; and (3) returning the regenerated distillate water to the electrodialysis to be used as carrier water. According to the method provided by the invention, electrodialysis and reduced pressure distillation are coupled, and the concentrated brine in the electrodialysis process is recovered by using the reduced pressure distillation, so that the problem that a large amount of wastewater is generated in the traditional technology for removing the thermally stable salt is solved, meanwhile, the resource waste can be reduced, the production cost is reduced, and the method is suitable for industrial popularization.

Description

Technical Field

[0001] The invention relates to the technical field of regenerated amine liquid purification, and in particular to a method for treating regenerated amine liquid. Background Art

[0002] In the process of desulfurization using organic amines, organic amines will degrade, resulting in a continuous increase in the content of heat-stable salts in the amine solution. Heat-stable salts will not only cause the loss of organic amines, but also cause problems such as foaming of the organic amine solution and corrosion of pipelines, further promoting the degradation and deterioration of the amine solution, forming a vicious cycle, thereby reducing the ability of the amine solution to remove acidic gases or even making it unusable.

[0003] Therefore, the current organic amine desulfurization process generally includes three units. First, the organic amine solution is used to absorb the acidic gas in the absorption unit to form a rich amine liquid. Then, the rich amine liquid is regenerated at high temperature in the regeneration unit to obtain a regenerated amine liquid. Then, the regenerated amine liquid is purified in the purification unit to remove impurities such as heat-stable salts to obtain a purified amine liquid, and the purified amine liquid is returned to the absorption unit for repeated use.

[0004] Among them, the purification of the regenerated amine solution can be carried out by electrodialysis. However, during the electrodialysis treatment process, a large amount of water is consumed to dissolve the heat-stable salt, resulting in a large amount of wastewater. In addition, when the electrodialysis treatment is used to regenerate the amine solution, the loss of organic amines usually exceeds 5wt%, and the wastewater containing organic amines is difficult to treat and has heavy environmental pressure.

[0005] Therefore, there is an urgent need to provide a method for treating regenerated amine liquid with substantially no waste liquid generated and low organic amine loss. Summary of the invention

[0006] The purpose of the present invention is to solve the problems of large wastewater discharge and large organic amine loss in the regenerated amine liquid purification method in the prior art, and to provide a regenerated amine liquid treatment method with basically no waste liquid generation, low energy consumption and small organic amine loss.

[0007] In order to achieve the above object, the present invention provides a method for purifying a regenerated amine solution, wherein the method comprises the following steps:

[0008] (1) subjecting the regenerated amine solution to electrodialysis, using carrier water to dissolve the salt separated from the regenerated amine solution to obtain concentrated brine and purified amine solution;

[0009] (2) subjecting the concentrated brine to reduced pressure distillation to obtain acidic gas, regenerated distillate water, recovered organic amine and concentrated salt, respectively;

[0010] (3) Returning the regenerated distillate water to the electrodialysis for use as the carrier water.

[0011] Through the above technical solution, the excellent technical effects achieved by the present invention are as follows:

[0012] 1) The purification method of the regenerated amine solution provided in the present invention couples electrodialysis and vacuum distillation, and utilizes vacuum distillation to recover the waste liquid in the electrodialysis process, thereby solving the problem that the traditional heat-stable salt removal technology generates a large amount of wastewater, and at the same time can reduce resource waste and production costs, and is suitable for industrial promotion;

[0013] 2) The purification method of the regenerated amine solution provided in the present invention can also recover the organic amine in the concentrated brine discharged during the electrodialysis process, further reducing the loss of organic amine and lowering the production cost;

[0014] 3) The purification method of the regenerated amine solution provided in the present invention can not only improve the desalination rate, but also remove the acidic gas contained in the non-thermally stable salt in the concentrated brine, thereby avoiding the harm of the acidic gas emission to the environment and human body, and achieving zero emission of acidic gas. DETAILED DESCRIPTION

[0015] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0016] The present invention provides a method for treating a regenerated amine solution, wherein the method comprises the following steps:

[0017] (1) subjecting the regenerated amine solution to electrodialysis, using carrier water to dissolve the salt separated from the regenerated amine solution to obtain concentrated brine and purified amine solution;

[0018] (2) subjecting the concentrated brine to reduced pressure distillation to obtain acidic gas, regenerated distillate water, recovered organic amine and concentrated salt, respectively;

[0019] (3) Returning the regenerated distillate water to the electrodialysis for use as the carrier water.

[0020] Wherein, in the present invention, electrodialysis is carried out in an electrodialyzer. The electrodialyzer includes a concentrated water chamber and a concentrated water chamber, the regenerated amine solution enters the fresh water chamber, and the carrier water enters the concentrated water chamber. As the electrodialysis proceeds, the salt contained in the regenerated amine solution continuously passes through the ion exchange membrane into the concentrated water chamber and dissolves in the carrier water. As the salt leaves, the regenerated amine solution slowly turns into a purified amine solution that is almost salt-free. The carrier water gradually turns into concentrated brine due to the dissolution of a large amount of salt. When the concentrated brine is close to saturation, the carrier water is replaced again, and the discharged concentrated brine is subjected to reduced pressure distillation to separate the regenerated distillate water. The separated regenerated distillate water can be returned to the electrodialysis as carrier water, thereby solving the technical problem that traditional electrodialysis requires the use of a large amount of carrier water and produces a large amount of wastewater.

[0021] In step (1),

[0022] In one embodiment of the present invention, the regenerated amine solution has a well-known meaning in the art, and is a solution obtained by regenerating the rich amine solution after absorbing the acidic gas, wherein the acidic gas includes but is not limited to H2S, CO2, SO2, CS2, HCN, COS and the like.

[0023] In one embodiment of the present invention, the salt includes a heat-stable salt and a heat-instability salt. The heat-stable salt has a well-known meaning in the art, and is a substance generated by thermal degradation, chemical degradation, oxidative degradation, etc. after the organic amine is contaminated by materials during long-term heating and cooling processes such as desulfurization and analysis. These substances are stable in the process of thermal regeneration of rich amine liquid, so they are called heat-stable salts, including formates, acetates, oxalates, sulfates, sulfites, thiosulfates, chlorides, etc. The heat-instability salt also has a well-known meaning in the art, and is a salt generated by the reaction of organic amines and acidic gases.

[0024] In one embodiment of the present invention, the regenerated amine solution further comprises an organic amine. Preferably, the organic amine is selected from one or more of ethanolamine, diethanolamine, N-methyldiethanolamine, triethanolamine, N-methylethylenediamine, diisopropanolamine, N,N-dibutylethanolamine, ethylenediamine, diethylamine, tetramethylethylenediamine and hydroxyethylpiperazine, preferably N-methyldiethanolamine.

[0025] In one embodiment of the present invention, based on the total mass of the regenerated amine solution, the regenerated amine solution comprises: 10-50wt% of organic amine, 1-10wt% of heat-stable salt, 0.1-1.5wt% of non-heat-stable salt, and 50-80wt% of water.

[0026] In one embodiment of the present invention, the operating conditions of the electrodialysis include: the electrodialysis membrane voltage is 0.5-1.2V, the current density is 50-150mA / m 2, the electrodialysis temperature is 5-40℃.

[0027] In the present invention, the electrodialysis membrane voltage can be 0.5V, 0.6V, 0.7V, 0.8V, 0.9V, 1V, 1.1V, 1.2V, and any value in the range formed by any two of these point values. The current density can be 50mA / m 2 、60mA / m 2 , 70mA / m 2 、80mA / m 2 , 90mA / m 2 , 100mA / m 2 , 110mA / m 2 , 120mA / m 2 , 130mA / m 2 , 140mA / m 2 , 150mA / m 2 , and any value in the range formed by any two of these point values. The electrodialysis temperature can be 5°C, 6°C, 8°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, and any value in the range formed by any two of these point values.

[0028] In one embodiment of the present invention, the operating conditions of the electrodialysis further include: before the electrodialysis, adding a desalting aid to the regenerated amine solution, wherein the desalting aid is an inorganic base selected from sodium hydroxide and / or potassium hydroxide.

[0029] Among them, in the present invention, the desalination aid reacts with the heat-stable salt to generate organic amine and auxiliary salt (sodium salt or potassium salt). Not only can the removal of the heat-stable salt be accelerated, but the organic amine bound by the heat-stable salt can also be released, which helps to reduce the loss of the organic amine. The generated auxiliary salt can enter the concentrated brine under the action of electric current.

[0030] In one embodiment of the present invention, the mass ratio of the regenerated amine solution to the desalination aid is 100:0.1-5, preferably 100:0.5-3.

[0031] In one embodiment of the present invention, the concentrated brine contains a heat-stable salt, a non-heat-stable salt and an optional auxiliary salt, wherein the content of the organic amine is 0.5-5wt%, preferably 2-4wt%.

[0032] During the electrodialysis process, a small amount of organic amines will also pass through the ion exchange membrane and enter the carrier water, causing the loss of organic amines. In order to reduce the loss of organic amines, the existing electrodialysis generally controls the operating conditions so that the content of organic amines in the concentrated brine is not higher than 0.5wt%. In order to achieve this effect, it is necessary to reduce the membrane voltage of the electrodialysis, thereby having the defect that the desalination speed (desalination amount per unit time) is slow. However, in the present invention, the inventor has found through research that by increasing the content of organic amines in the concentrated brine and coupling with vacuum distillation, not only can the loss of organic amines be solved, but also the desalination speed can be improved.

[0033] In step (2):

[0034] In the present invention, non-heat-stable salts in concentrated brine will generate organic amines and acidic gases during the process of vacuum distillation. By using vacuum distillation to treat concentrated brine, acidic gases, regenerated distillate water, organic amines and concentrated salts can be separated from the concentrated brine. The concentrated salt is a heat-stable salt, and the regenerated distillate water is water separated from the concentrated brine.

[0035] In one embodiment of the present invention, the vacuum distillation is carried out in a vacuum distillation tower. The present invention does not specifically limit the number of vacuum distillation towers, and there may be one tower, from which acidic gas, regenerated distillate water, organic amines and concentrated salts are respectively extracted from the tower top, side line and bottom, or there may be three towers, and the specific cutting order may be determined according to actual needs.

[0036] In one embodiment of the present invention, the present invention does not specifically limit the specific operating conditions of the vacuum distillation. According to the cutting scheme and the specific selection of the organic amine in the concentrated brine, the concentrated brine can be divided into four components of acid gas, regenerated distillate water, recovered organic amine and concentrated salt according to conventional operations. Among them, the bottom temperature of the vacuum distillation is closely related to the type of organic amine contained in the treated concentrated brine and the tower bottom pressure. Generally, the boiling point ±5°C of the organic amine under the tower bottom pressure can be used as the bottom temperature. When the concentrated brine contains multiple organic amines, the boiling point ±5°C of the organic amine with the highest boiling point under the tower bottom pressure is selected as the bottom temperature.

[0037] In one embodiment of the present invention, a distillation aid is added to the concentrated brine during the reduced pressure distillation treatment, wherein the distillation aid includes a metal hydroxide and a defoaming agent.

[0038] In one embodiment of the present invention, the metal hydroxide is selected from NaOH and / or KOH, and the defoaming agent is selected from methyl silicone oil and / or dimethyl silicone oil.

[0039] In one embodiment of the present invention, the mass ratio of the concentrated brine, NaOH and methyl silicone oil is 1000:1-10:0.01-0.1.

[0040] In one embodiment of the present invention, the acid gas is treated according to a known method to prevent the acid gas from polluting the environment and avoid the harm to the environment and human body caused by the emission of toxic gases. The recovered organic amine is returned to the absorption unit in the organic amine desulfurization process for reuse, which can further reduce the loss of organic amine and reduce production costs. The obtained concentrated salt is treated as solid waste according to a known method to prevent solid waste pollution.

[0041] In one embodiment of the present invention, the total loss of organic amine in the treatment method is ≤0.5%, preferably ≤0.2%.

[0042] In step (3):

[0043] In the present invention, the regenerated distillate water is returned to the electrodialysis as the carrier water, which can reduce the amount of water used in the electrodialysis process and significantly reduce the water consumption in the electrodialysis. The recovered amine is returned to the desulfurization system for recycling, which can reduce the loss of organic amine.

[0044] The purification method of the regenerated amine liquid provided in the present invention couples electrodialysis and vacuum distillation, and utilizes vacuum distillation to recover the waste liquid in the electrodialysis process, which can not only reduce the energy consumption of the entire process and fully recycle water resources, but also reduce the loss of organic amines, avoid organic amines and acidic gases from polluting the environment, and is suitable for industrial promotion.

[0045] The present invention will be described in detail below through examples. It should be understood that the following examples are only used to further explain and illustrate the contents of the present invention, but are not used to limit the present invention.

[0046] In the following examples, the regenerated amine solution comes from the solvent regeneration system of Beihai Refining and Chemical, and includes: 30 wt% N-methyldiethanolamine, 3 wt% heat-stable salt, 66.5 wt% water and 0.5 wt% non-heat-stable salt. The content of organic amine is determined by chromatography.

[0047] Example 1

[0048] (1) First, sodium hydroxide was added to the regenerated amine solution, and then the regenerated amine solution and carrier water were introduced into the fresh water chamber and concentrated water chamber of the electrodialyzer respectively. The voltage between the electrodialysis membranes was 0.8 V and the current density was 80 mA / m 2 , electrodialysis is performed at an electrodialysis temperature of 35°C to obtain concentrated brine and purified amine solution; wherein the mass ratio of the regenerated amine solution to sodium hydroxide is 100:1, and it is found through testing that the concentrated brine contains 3.5wt% of organic amine;

[0049] (2) adding NaOH and methyl silicone oil to the brine, and then introducing the brine into a vacuum distillation tower for vacuum distillation to obtain acidic gas, regenerated distillate water, recovered organic amine and concentrated salt, respectively; wherein the mass ratio of the concentrated brine, NaOH and methyl silicone oil is 1000:5:0.05;

[0050] (3) returning the regenerated distillate water to the electrodialysis system for recycling as carrier water, and returning the recovered amine to the desulfurization system for recycling.

[0051] According to calculation, when the above method is used to treat the regenerated amine liquid, the desalination rate of the electrodialyzer is 40kg / h, the energy consumption of the electrodialysis process is 5kwh of electricity for every ton of regenerated amine liquid treated, and the water vapor consumption at 150°C in the vacuum distillation process is 0.2 tons; the total loss rate of organic amine is 0.3%, and except for concentrated salt, there is basically no waste liquid discharge.

[0052] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for treating a regenerated amine solution, characterized in that: The method comprises the following steps: (1) subjecting the regenerated amine solution to electrodialysis, using carrier water to dissolve the salt separated from the regenerated amine solution to obtain concentrated brine and purified amine solution; (2) subjecting the concentrated brine to reduced pressure distillation to obtain acidic gas, regenerated distillate water, recovered organic amine and concentrated salt, respectively; (3) Returning the regenerated distillate water to the electrodialysis for use as the carrier water.

2. The processing method according to claim 1, wherein: The salts include heat-stable salts and heat-instability salts.

3. The processing method according to claim 2, wherein: The regenerated amine solution also includes organic amine.

4. The processing method according to claim 3, wherein: The organic amine is selected from one or more of ethanolamine, diethanolamine, N-methyldiethanolamine, triethanolamine, N-methylethylenediamine, diisopropanolamine, N,N-dibutylethanolamine, ethylenediamine, diethylamine, tetramethylethylenediamine and hydroxyethylpiperazine.

5. The processing method according to claim 3 or 4, wherein: Based on the total mass of the regenerated amine solution, the regenerated amine solution comprises: 10-50wt% of organic amine, 1-10wt% of heat-stable salt, 0.1-1.5wt% of non-heat-stable salt and 50-80wt% of water.

6. The processing method according to any one of claims 1 to 5, wherein: The operating conditions of the electrodialysis include: the electrodialysis membrane voltage is 0.5-1.2V, the current density is 50-150mA / m 2 , the electrodialysis temperature is 5-40℃.

7. The processing method according to claim 6, wherein: The operating conditions of the electrodialysis also include: before the electrodialysis, adding a desalting aid to the regenerated amine solution.

8. The processing method according to claim 7, wherein: The desalination aid is an inorganic base selected from sodium hydroxide and / or potassium hydroxide; Preferably, the mass ratio of the regenerated amine solution to the desalination aid is 100:0.1-5, preferably 100:0.5-3.

9. The purification method according to any one of claims 1 to 8, wherein: A distillation aid is added to the concentrated brine during the reduced pressure distillation process; wherein the distillation aid includes a metal hydroxide and a defoaming agent.

10. The purification method according to claim 9, wherein: The metal hydroxide is selected from NaOH and / or KOH, and the defoaming agent is selected from methyl silicone oil and / or dimethyl silicone oil.