Online monitoring and control system for amine liquid thermal stable salt content

Abstract

The invention discloses an amine liquid thermal stable salt content on-line monitoring and control system, which comprises an automatic control valve, a pretreatment unit, an analysis detection unit, a data analysis and control unit, an anion content correction unit and an amine liquid purification unit, a rich amine liquid inlet arranged on the pretreatment unit is connected with a to-be-treated liquid source through the automatic control valve; a rich amine liquid outlet is also formed; the analysis and detection unit is provided with a to-be-detected liquid inlet connected with the amine-rich liquid outlet, and is also provided with a detection liquid outlet; a to-be-analyzed liquid inlet connected with the detection liquid outlet and an analysis liquid outlet are formed in the data analysis and control unit; a correction liquid inlet connected with the analysis liquid outlet and a correction liquid outlet are formed in the anion content correction unit, and the correction liquid outlet is connected with the data analysis and control unit; and the amine liquid purification unit is provided with a to-be-purified liquid inlet connected with the analysis liquid outlet. Real-time monitoring and content control of the thermal stable salt can be achieved, and long-period operation of the device is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of amine liquid purification, and particularly relates to an on-line monitoring and control system for the content of heat-stable salts in amine liquid. Background Art

[0002] Alkanolamines are currently the most widely used gas purifying agents in the petrochemical and natural gas industries, mainly including monoethanolamine, diethanolamine, diisopropanolamine, and methyldiethanolamine, etc. However, during the use of alkanolamine absorbents, degradation inevitably occurs, such as oxidative degradation and thermal degradation, generating a series of organic or inorganic anions that form salts with alkanolamines. Since they cannot release alkanolamines during the regeneration process, they are called heat-stable salts. The enrichment of heat-stable salts in the alkanolamine process system will lead to a series of problems such as a decline in the purification efficiency of the system, solution foaming, and equipment corrosion. Therefore, in order to reduce the energy consumption of the equipment operation and ensure the long-term operation of the equipment, it is necessary to monitor and control the change in the content of heat-stable salts in the amine liquid.

[0003] At present, there are two methods for detecting heat-stable salts in the laboratory, ion exchange and ion chromatography. Among them, the ion exchange analysis process is relatively complex and it is difficult to achieve on-line monitoring. While the ion chromatography method has a fast analysis speed and has the basis for realizing on-line monitoring. For example, Patent CN 103454367A discloses a method for detecting methylamine using ion chromatography. Although this method can directly detect the sample, during ion chromatography analysis, the sample needs to be pretreated. At the same time, carbonate, nitrate, and phosphate in the sample will cause certain interference to the target substances in the ion chromatography analysis, resulting in poor repeatability and reproducibility of the analysis data. Therefore, how to quickly and accurately realize the on-line detection of the change in the content of heat-stable salts in amine liquid and conduct control is an urgent problem to be solved at present. Summary of the Invention

[0004] The main object of the present invention is to provide an on-line monitoring and control system for the content of heat-stable salts in amine liquid, which can realize real-time monitoring and control of the content of heat-stable salts in amine liquid, and has the advantages of high automation degree, fast and accurate, and simple control.

[0005] To achieve the above object, the present invention provides an on-line monitoring and control system for the content of heat-stable salts in amine liquid, including:

[0006] An automatic control valve;

[0007] A pretreatment unit, the rich amine liquid inlet provided on the pretreatment unit is connected to the liquid source to be treated through the automatic control valve, and the pretreatment unit is also provided with a rich amine liquid outlet;

[0008] An analysis and detection unit, the liquid to be detected inlet connected to the rich amine liquid outlet is provided on the analysis and detection unit, and the analysis and detection unit is also provided with a detection liquid outlet;

[0009] A data analysis and control unit, on which there is an inlet for the liquid to be analyzed connected to the outlet of the detection liquid, and there is also an outlet for the analysis liquid on the data analysis and control unit;

[0010] An anion content correction unit, on which there is an inlet for the liquid to be corrected connected to the outlet of the analysis liquid, and there is also an outlet for the correction liquid on the anion content correction unit, and the outlet of the correction liquid is connected to the data analysis and control unit; and,

[0011] An amine liquid purification unit, which has an inlet for the liquid to be purified connected to the outlet of the analysis liquid.

[0012] Optionally, the pretreatment unit includes:

[0013] A mechanical impurity removal device, the medium of which is at least one of quartz sand, porous ceramics, polyethylene, and polypropylene porous plastics; and,

[0014] A chemical impurity removal device, the medium of which is at least one of activated carbon, silica gel, and hollow fiber membranes.

[0015] Optionally, the analysis and detection unit includes:

[0016] A first ion chromatograph, which includes an automatic sampling device and an automatic elution device;

[0017] A second ion chromatograph, which includes an automatic sampler; and,

[0018] An on-line pH meter, which is used to detect the pH value of the amine liquid.

[0019] Optionally, the data analysis and control unit includes:

[0020] An anion content calculation model, the model formula is y n =a m x n +b m , where x n is the area of the anion chromatogram, y n is the mass fraction of the anion, a m and b m are constants;

[0021] An alkanolamine content calculation model, the model formula is f = ex + g, where x is the area of the alkanolamine chromatogram, f is the alkanolamine concentration, and e and g are constants; and,

[0022] Thermal stability salt content calculation model, the model formula is m = [(Mn′ / M n )*y n , where Mn′ is the relative molecular mass of different types of thermal stability salts, M n is the relative molecular mass of the anion of the thermal stability salt, and y n is the anion mass fraction.

[0023] Optionally, the data analysis and control unit further includes a controller, and the outlet of the controller is connected to the inlet of the liquid to be purified in the amine liquid purification unit.

[0024] Optionally, in the calculation process of the thermal stability salt content calculation model, the cation is uniformly the ammonium ion of the main absorbent, and the control threshold of the thermal stability salt content in the amine liquid is between 0.5 and 1.0 wt%.

[0025] Optionally, the anion content correction unit includes a pH correction model, and the influence model of the anion content on the pH value of the alkanolamine solution is pH y = p 1 x 1 + p 2 x 2 + p 3 x 3 + …… p n x n + Z, where p, q, and Z are all constants.

[0026] Optionally, the amine liquid purification unit adopts at least one of the processes of ion resin exchange, electrodialysis, and electrode adsorption.

[0027] Optionally, the data analysis and control unit sets the analysis frequency to be 6 - 24 h / time when the thermal stability salt exceeds the standard.

[0028] Optionally, the data analysis and control unit sets the analysis frequency to be 12 - 48 h / time when the thermal stability salt does not exceed the standard.

[0029] The beneficial effects of the present invention are as follows:

[0030] The technical solution of the present invention removes substances such as solid particles, corrosion products, and organic hydrocarbons in the amine solution by using a pretreatment unit; uses an analysis and detection unit to detect the anion content, alkanolamine content, and pH value of the purified amine solution to obtain spectral data of different types of anion contents, alkanolamine contents, and pH values; uses a data analysis and control unit to perform model fitting calculations on the contents of different types of anions and alkanolamines; uses an anion content correction unit to perform model iterative calculations and corrections. After reaching the set accuracy, relatively accurate anion content data is output to the data analysis and control unit. After calculating the heat stable salt content, an instruction is issued through the controller to remove the heat stable salt, thereby controlling the heat stable salt in the amine solution within an appropriate range. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0032] Figure 1 It is a system logic schematic diagram of an embodiment of the on-line monitoring and control system for the heat stable salt content of the amine solution of the present invention.

[0033] The reference numeral descriptions of the embodiments provided by the present invention are as follows:

[0034]

[0035] The realization, functional features, and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0037] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative position relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0038] In addition, if the descriptions such as "first" and "second" are involved in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and / or" appearing throughout the text includes three parallel scenarios. Taking "A and / or B" as an example, it includes Scenario A, or Scenario B, or the scenario where both A and B are satisfied simultaneously. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0039] In view of the problems of slow detection speed and inaccurate results existing in the existing online detection system for amine liquid heat stable salts, the present invention proposes an online monitoring and control system for the content of amine liquid heat stable salts. Refer to Figure 1 , Figure 1 which is the system logic schematic diagram of an embodiment of the online monitoring and control system for the content of amine liquid heat stable salts of the present invention.

[0040] The present invention proposes an online monitoring and control system 100 for the content of amine liquid heat stable salts. As Figure 1 shown, it includes an automatic control valve 1, a pretreatment unit 2, an analysis and detection unit 3, a data analysis and control unit 4, an anion content correction unit 5, and an amine liquid purification unit 6. The rich amine liquid inlet provided on the pretreatment unit 2 is connected to the liquid source to be treated through the automatic control valve 1, and a rich amine liquid outlet is also provided on the pretreatment unit 2; a liquid to be detected inlet connected to the rich amine liquid outlet is provided on the analysis and detection unit 3, and a detection liquid outlet is also provided on the analysis and detection unit 3; a liquid to be analyzed inlet connected to the detection liquid outlet is provided on the data analysis and control unit 4, and an analysis liquid outlet is also provided on the data analysis and control unit 4; a liquid to be corrected inlet connected to the analysis liquid outlet is provided on the anion content correction unit 5, and a correction liquid outlet is also provided on the anion content correction unit 5. The correction liquid outlet is connected to the data analysis and control unit 4; the amine liquid purification unit 6 is provided with a liquid to be purified inlet connected to the analysis liquid outlet.

[0041] The technical solution of the present invention introduces the rich amine liquid collected online into the pretreatment unit 2 through the automatic control valve 1 to remove substances such as solid particles, corrosion products, and organic hydrocarbons in the amine liquid; the analysis and detection unit 3 is used to detect the anion content, alkanolamine content, and pH value of the purified amine liquid to obtain the spectral data of different types of anion content, alkanolamine content, and pH value; the data analysis and control unit 4 uses model fitting to calculate the content of different types of anions and alkanolamines; the anion content correction unit 5 performs model iteration calculation and correction. After reaching the set accuracy, it outputs relatively accurate anion content data to the data analysis and control unit 4. After calculating the heat stable salt content, an instruction is issued through the controller 44 to remove the heat stable salt, so as to control the heat stable salt in the amine liquid within an appropriate range.

[0042] Preferably, the pretreatment unit 2 includes a mechanical impurity removal device and a chemical impurity removal device. The medium of the mechanical impurity removal device is at least one of quartz sand, porous ceramics, polyethylene, and polypropylene porous plastics, preferably porous ceramics. This mechanical impurity removal device can remove suspended solid particles and corrosion products in the amine liquid; the medium of the chemical impurity removal device is at least one of activated carbon, silica gel, and hollow fiber membranes, preferably activated carbon. This device can selectively adsorb organic hydrocarbons mixed in the amine liquid. After being processed by the pretreatment unit 2, the impurities in the amine liquid are removed, making the detection result of the heat stable salt more accurate.

[0043] Further, the analysis and detection unit 3 includes a first ion chromatograph, a second ion chromatograph, and an online pH meter. The first ion chromatograph includes an automatic sampling device and an automatic elution device, and the first ion chromatograph is used to detect the anion content in the amine liquid; the second ion chromatograph includes an automatic sampler, and the second ion chromatograph is used to detect the alkanolamine concentration in the amine liquid; the online pH meter is used to detect the pH value of the amine liquid.

[0044] Preferably, please refer to Figure 1 , the data analysis and control unit embeds three models, including an anion content calculation model 41, an alkanolamine content calculation model 42, and a heat stable salt content calculation model 43. The anions involved in the anion content calculation model 41 include, but are not limited to, formate ions, acetate ions, chloride ions, sulfate ions, oxalate ions, sulfite ions, glycolate ions, malonate ions, thiosulfate ions, succinate ions, and thiocyanate ions. The model formula is y n =a m x n +b m , where x n is the anion spectrum area, y n is the anion mass fraction, a m and bm is a constant. The model formula is finally obtained by curve fitting of the data obtained through parallel analysis of different gradient anion contents for more than 10 times; the formula of the alkanolamine content calculation model 42 is f = ex + g, where x is the alkanolamine spectrum area, f is the alkanolamine concentration, and e and g are constants. Similarly, this model formula is finally obtained by curve fitting of the data obtained through parallel analysis of different gradient alkanolamine concentrations for more than 10 times; the formula of the heat stable salt content calculation model 43 is m = [(M n ′ / M n )*y n , where Mn′ is the relative molecular mass of different types of heat stable salts, M n is the relative molecular mass of the anion of the heat stable salt, y n is the anion mass fraction, and the heat stable salt cation in the amine solution is uniformly the ammonium ion of the main absorbent.

[0045] In an embodiment of the present invention, please refer to Figure 1 . The data analysis and control unit 4 further includes a controller 44. The outlet of the controller 44 is connected to the inlet of the liquid to be purified of the amine liquid purification unit 6, and the inlet of the controller 44 is connected to the outlet of the data analysis and control unit 4. After calculating the heat stable salt content through the heat stable salt content calculation model 43 of the data analysis and control unit 4, an instruction is sent through the controller 44 to remove the heat stable salt, so as to control the heat stable salt in the amine liquid within an appropriate range.

[0046] Further, please refer to Figure 1 . In the calculation process of the heat stable salt content calculation model 43, the cation is uniformly the ammonium ion of the main absorbent. The control threshold of the heat stable salt content in the amine liquid is between 0.5 and 1.0 wt%. By removing the heat stable salt and controlling the system circulation, the heat stable salt is controlled within this range, which is beneficial to ensuring the purification efficiency of the system.

[0047] Preferably, please refer to Figure 1 . The anion content correction unit 5 includes a pH correction model. The influence model of the anion content on the pH value of the alkanolamine solution is pH y = p 1 x 1 + p 2 x 2 + p 3 x 3 + …… p n x n + Z, where p, q, and Z are all constants. When the ratio of the iteratively calculated pH y to (pH 实际 - pH 浓度 ) reaches more than 90%, the parameters can be output, where pH实际 is the value detected online by the pH meter, pH 浓度 is the value of the pure alkanolamine solution at a certain concentration; when the pH value corresponding to the iterative calculation of the anion content reaches 90-95% of the model pH value, the parameters can be output.

[0048] Further, the amine solution purification unit 6 adopts at least one of the processes of ion resin exchange, electrodialysis, and electrode adsorption, that is, the amine solution purification unit 6 can adopt ion resin exchange, or electrodialysis, or electrode adsorption, or any combination of two processes, or all three processes at the same time. By adopting the amine solution purification unit 6, interfering ions such as carbonate ions, nitrate ions, and phosphate ions can be removed.

[0049] Further, the data analysis and control unit 4 sets the analysis frequency to be 6-24 h / time, preferably 12 h / time when the heat-stable salt exceeds the standard, and the analysis frequency to be 12-48 h / time, preferably 24 h / time when the heat-stable salt does not exceed the standard.

[0050] The following is the working mode of an embodiment of the online monitoring and control system 100 for the content of heat-stable salts in amine solution: The rich amine solution collected online is introduced into the pretreatment unit 2 through the automatic control valve 1 to remove solid particles, corrosion products, organic hydrocarbons and other substances in the amine solution; the analysis and detection unit 3 detects the anion content, alkanolamine content and pH value of the purified amine solution to obtain the content map data and pH value of different types of anions and alkanolamines; the above data is imported into the data analysis and control unit 4, and the content of different types of anions and alkanolamines is calculated by model fitting; then the data is imported into the anion content correction unit 5 for model iterative calculation and correction, and after reaching the set accuracy, relatively accurate anion content data is output to the data analysis and control unit 4. After calculating the content of heat-stable salts, an instruction is sent through the controller 44 to remove the heat-stable salts, so as to control the heat-stable salts in the amine solution within an appropriate range.

[0051] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made under the inventive concept of the present invention, or direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. An on-line monitoring and control system for the content of heat-stable salts in amine solution, characterized in that, it comprises: an automatic control valve (1); a pretreatment unit (2), the rich amine solution inlet provided on the pretreatment unit (2) is connected to the liquid source to be treated through the automatic control valve (1), and a rich amine solution outlet is also provided on the pretreatment unit (2); an analysis and detection unit (3), the liquid to be detected inlet connected to the rich amine solution outlet is provided on the analysis and detection unit (3), and a detection liquid outlet is also provided on the analysis and detection unit (3); a data analysis and control unit (4), the liquid to be analyzed inlet connected to the detection liquid outlet is provided on the data analysis and control unit (4), and an analysis liquid outlet is also provided on the data analysis and control unit (4); an anion content correction unit (5), the liquid to be corrected inlet connected to the analysis liquid outlet is provided on the anion content correction unit (5), and a correction liquid outlet is also provided on the anion content correction unit (5), and the correction liquid outlet is connected to the data analysis and control unit (4); and, an amine solution purification unit (6), the liquid to be purified inlet connected to the analysis liquid outlet is provided on the amine solution purification unit (6).

2. The on-line monitoring and control system for the content of heat-stable salts in amine solution according to claim 1, characterized in that, the pretreatment unit (2) comprises: a mechanical removal device, the medium of the mechanical removal device is at least one of quartz sand, porous ceramics, polyethylene, and polypropylene porous plastics; and, a chemical impurity removal device, the medium of the chemical impurity removal device is at least one of activated carbon, silica gel, and hollow fiber membranes.

3. The on-line monitoring and control system for the content of heat-stable salts in amine solution according to claim 1, characterized in that, the analysis and detection unit (3) comprises: a first ion chromatograph, the first ion chromatograph includes an automatic sampling device and an automatic elution device; a second ion chromatograph, the second ion chromatograph includes an automatic sampler; and, an on-line pH meter, the on-line pH meter is used to detect the pH value of the amine solution.

4. The on-line monitoring and control system for the content of heat-stable salts in amine solution according to claim 1, characterized in that, the data analysis and control unit (4) comprises: Anion content calculation model (41), the model formula is y n = a m x n + b m , where x n is the anion spectrum area, y n is the anion mass fraction, a m and b m are constants; an alkanolamine content calculation model (42), the model formula is f = ex + g, where x is the alkanolamine chromatogram area, f is the alkanolamine concentration, and e and g are constants; and, Thermal stability salt content calculation model (43), the model formula is m = [(M n ˊ / M n ) * y n , where M n ˊ is the relative molecular mass of different kinds of thermal stability salts, M n is the relative molecular mass of the anion of the thermal stability salt, and y n is the anion mass fraction.

5. The on-line monitoring and control system for the content of heat-stable salts in amine solution according to claim 4, characterized in that, the data analysis and control unit (4) further comprises a controller (44), and the outlet of the controller (44) is connected to the liquid to be purified inlet of the amine solution purification unit (6).

6. The on-line monitoring and control system for the content of heat-stable salts in amine solution according to claim 4, characterized in that, in the calculation process of the heat-stable salt content calculation model (43), the cations are uniformly the ammonium ions of the main absorbent, and the control threshold of the heat-stable salt content in the amine solution is between 0.5 and 1.0 wt%.

7. The on-line monitoring and control system for the content of heat-stable salts in amine solution according to claim 1, characterized in that, The anion content correction unit (5) includes a pH correction model. The influence model of the anion content on the pH value of the alkanolamine solution is pH y = p 1 x 1 + p 2 x 2 + p 3 x 3 + …… p n x n + Z, where p, q, and Z are all constants.

8. The online monitoring and control system for the content of amine liquid heat-stable salts as described in claim 1, characterized in that, the amine liquid purification unit (6) adopts at least one of the processes of ion resin exchange, electrodialysis, and electrode adsorption.

9. The online monitoring and control system for the content of amine liquid heat-stable salts as described in claim 1, characterized in that, the data analysis and control unit (4) sets the analysis frequency to be 6 - 24 h / time when the heat-stable salts exceed the standard.

10. The online monitoring and control system for the content of amine liquid heat-stable salts as described in claim 1, characterized in that, the data analysis and control unit (4) sets the analysis frequency to be 12 - 48 h / time when the heat-stable salts do not exceed the standard.

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