Composite inhibitor for inhibiting degradation of amine absorbent in carbon dioxide capture

Abstract

The invention discloses a composite inhibitor composed of a metal chelating agent and a free radical scavenger and application of the composite inhibitor in inhibition of degradation of an amine absorbent in CO2 capture, and belongs to the field of CO2 capture after combustion. The composite inhibitor is composed of a metal chelating agent and a free radical scavenger, the metal chelating agent refers to diethylene triamine penta (methylene phosphonic acid) (DTPMP) or diethyl triamine pentaacetic acid (DTPA), and the free radical scavenger refers to potassium iodide (KI) or sodium thiosulfate (Na2S2O3). The mass fraction of the metal chelating agent in the composite inhibitor is 10-90%, and the mass fraction of the composite inhibitor added into the amine absorbent is 0.1-1.0%. The composite inhibitor disclosed by the invention can be used for remarkably inhibiting degradation of an alcohol amine absorbent in the field of CO2 capture, and has the characteristics of strong inhibition effect, low price, good stability and high solubility. In addition, through the synergistic inhibition effect between the metal chelating agent and the free radical scavenger in the composite inhibitor, the usage amount of the composite inhibitor can be greatly reduced, and the cost of the inhibitor is reduced.

Description

Technical Field

[0001] The present invention relates to the field of post - combustion CO2 capture, and particularly to a composite inhibitor composed of a metal chelating agent and a radical scavenger and its application in inhibiting the degradation of amine absorbents during CO2 capture. Technical Background

[0002] Carbon dioxide capture, utilization and storage (CCUS) technology is the main way to achieve CO2 emission reduction and address global climate change. Common CO2 capture technologies include pre - combustion capture, oxy - fuel combustion and post - combustion capture technology. Among them, post - combustion capture technology does not change the combustion system, has the advantage of integrating desulfurization and denitrification processes, and is relatively mature in technology. It is the most promising industrialization technology route for large - scale CO2 capture and clean energy utilization.

[0003] Post - combustion CO2 capture technology mainly includes physical adsorption method, membrane separation method and chemical solvent absorption method, etc. The chemical solvent absorption method using amine absorbents has the advantages of high decarbonization efficiency, mature process, relatively low cost and being suitable for retrofitting existing power plants, etc., and is considered to be the most feasible technology at present. However, during the process of separating CO2, due to the presence of O2 and the influence of high - temperature environment, amine absorbents are prone to degradation. Degradation will cause the loss of absorbents, the degradation of CO2 absorption capacity, resulting in the system needing to supplement new absorbents irregularly, increasing the operation cost; at the same time, degradation products will cause a series of phenomena such as equipment corrosion and solution foaming, reducing the system life, and volatile degradation products will also cause environmental pollution. Summary of the Invention

[0004] The object of the present invention is to propose a composite inhibitor that can effectively inhibit the degradation of alkanolamine absorbents in view of the existing deficiencies. This composite inhibitor is composed of a metal chelating agent and a radical scavenger. The metal chelating agent can chelate metal ions in the amine solution, making the metal ions lose the function of catalyzing amine degradation; the radical scavenger can react with free radicals in the amine solution, reducing the number of free radicals in the solution, so as to achieve the purpose of inhibiting the degradation of amine absorbents. The metal chelating agent and the radical scavenger synergistically inhibit the degradation of amine absorbents, greatly improving the inhibition effect, reducing the usage amount of the inhibitor and lowering the inhibitor cost.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A composite inhibitor for inhibiting the degradation of amine absorbents, which is composed of a metal chelating agent and a radical scavenger. The metal chelating agent refers to diethylenetriamine pentamethylene phosphonic acid (DTPMP) or diethylenetriamine pentaacetic acid (DTPA), and the radical scavenger refers to potassium iodide (KI) or sodium thiosulfate (Na2S2O3).

[0007] The amine absorbent refers to an alkanolamine absorbent used to capture CO2, and the mass fraction of alkanolamine ranges from 20% to 60%.

[0008] When the alkanolamine absorbent captures CO2, the temperature ranges from 40°C to 60°C.

[0009] In the composite inhibitor, the mass fraction of the chelating agent ranges from 10% to 90%.

[0010] The mass fraction of the composite inhibitor in the amine absorbent ranges from 0.1% to 1%.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0012] 1. The present invention provides a composite inhibitor capable of effectively inhibiting amine degradation, which has the characteristics of strong inhibition effect, low price, good stability, high solubility, etc.

[0013] 2. In the composite inhibitor of the present invention, the chelating agent and the scavenger have a synergistic effect on inhibiting amine degradation. Compared with a single amine degradation inhibitor, the synergistic inhibition effect between the composite inhibitors can significantly reduce the dosage of the inhibitor, and solve the problems of amine degradation and the increase in operating costs caused by degradation from the source. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Structural formula diagrams of 1AP, DTPMP, DTPA, Na2S2O3 and KI in Examples 1-6 and Comparative Examples 2-6 of the present invention;

[0015] Figure 2 Schematic diagrams of the oxidative degradation device in Examples 1-6 and Comparative Examples 1-6 of the present invention;

[0016] Figure 3 External standard curves in Examples 1-6 and Comparative Examples 1-6 of the present invention;

[0017] Figure 4 Concentration changes of 1AP during degradation in Examples 1-6 and Comparative Examples 1-6 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] The composite inhibitor and its application of the present invention will be described in detail below with reference to the examples. Obviously, the described examples are only a part of the examples of the present invention, rather than all examples. Other examples that can be easily obtained based on the given examples also fall within the protection scope of the present invention.

[0019] Example 1

[0020] Using DTPMP + KI as the composite inhibitor, the structural formula of the composite inhibitor is as shown in the appendix Figure 1As shown, the oxidation degradation experiment of 1-amino-2-propanol (1AP) was carried out, and the experimental device is as attached Figure 2 shown.

[0021] (1) Preparation of amine absorbent

[0022] A 5.0 mol / L 1AP absorbent was prepared using a volumetric flask. CO2 was continuously introduced into the prepared amine absorbent to measure the CO2 loading of the amine absorbent, so that the final CO2 loading of the amine absorbent reached 0.4 mol / mol.

[0023] (2) Conducting the oxidation degradation experiment

[0024] Add 200 mL of amine absorbent, 0.5 mmol / L FeSO4 and 1.0 wt% composite inhibitor (DTPMP + KI) to a three-necked flask. Place the three-necked flask in a water bath, and control the reaction temperature to be maintained at 60 °C through the water bath. Control the gas composition of O2 and CO2 to be 98% O2 + 2% CO2 through a mass flow controller (MFC). The mixed gas enters the three-necked flask through a rotameter, and the flow rate of the mixed gas is 20 mL / min. A serpentine condenser is placed above the three-necked flask to condense and reflux the evaporated water. The oxidation degradation experiment was carried out for 14 days, and samples were taken for analysis at 1, 2, 4, 7, and 14 d respectively.

[0025] (3) Amine concentration measurement

[0026] Dilute the amine absorbent sample 10,000 times with deionized water, and inject the diluted sample into a cation chromatography for analysis and testing. The cation chromatography (Shine CIC-D100 system) is equipped with a SH-CC-9 analytical column (4.6 × 250 mm), a SH-G-1 guard column (4 × 50 mm), a conductivity detector, and a SHY-C-5 suppressor. The eluent uses a 3.0 mmol / L methanesulfonic acid solution. Prepare a standard amine solution with a concentration range of 1 - 50 mg / L for obtaining an external standard curve, as attached Figure 3 shown. The calculation formula for amine loss caused by degradation is as follows:

[0027]

[0028] Where:

[0029] C loss - 1AP loss caused by degradation;

[0030] A0 - Peak area of initial 1AP before the degradation experiment;

[0031] A x - Peak area of 1AP in the degraded sample;

[0032] The intercept value of the linear regression equation when establishing the external standard curve;

[0033] The slope value of the linear regression equation when establishing the external standard curve;

[0034] D - Dilution multiple;

[0035] M - Relative molecular mass of 1AP.

[0036] Example 2

[0037] Using DTPMP + Na2S2O3 as the composite inhibitor, the structural formula of the composite inhibitor is as shown in the appendix Figure 1 Carry out the 1AP oxidation degradation experiment. Add 200 mL of amine absorbent, 0.5 mmol / L FeSO4 and 0.1 wt% composite inhibitor (DTPMP + Na2S2O3) into the three-necked flask. Other degradation experiment conditions and amine concentration testing methods are the same as those in Example 1.

[0038] Example 3

[0039] Using DTPMP + Na2S2O3 as the composite inhibitor, the structural formula of the composite inhibitor is as shown in the appendix Figure 1 Carry out the 1AP oxidation degradation experiment. Add 200 mL of amine absorbent, 0.5 mmol / L FeSO4 and 0.2 wt% composite inhibitor (DTPMP + Na2S2O3) into the three-necked flask. Other degradation experiment conditions and amine concentration testing methods are the same as those in Example 1.

[0040] Example 4

[0041] Using DTPMP + Na2S2O3 as the composite inhibitor, the structural formula of the composite inhibitor is as shown in the appendix Figure 1 Carry out the 1AP oxidation degradation experiment. Add 200 mL of amine absorbent, 0.5 mmol / L FeSO4 and 1.0% composite inhibitor (DTPMP + Na2S2O3) into the three-necked flask. Other degradation experiment conditions and amine concentration testing methods are the same as those in Example 1.

[0042] Example 5

[0043] Using DTPA + Na2S2O3 as the composite inhibitor, the structural formula of the composite inhibitor is as shown in the appendix Figure 1 Carry out the 1AP oxidation degradation experiment. Add 200 mL of amine absorbent, 0.5 mmol / L FeSO4 and 1.0% composite inhibitor (DTPA + Na2S2O3) into the three-necked flask. Other degradation experiment conditions and amine concentration testing methods are the same as those in Example 1.

[0044] Example 6

[0045] Using DTPA + KI as a composite inhibitor, the structural formula of this composite inhibitor is as shown in the appendix Figure 1 and carry out the 1AP oxidation degradation experiment. Add 200 mL of amine absorbent, 0.5 mmol / L FeSO4 and 1.0% composite inhibitor (DTPA + KI) into the three-necked flask. Other degradation experiment conditions and the amine concentration measurement method are the same as those in Example 1.

[0046] Comparative Example 1

[0047] Carry out the 1AP oxidation degradation experiment without adding a composite inhibitor. Add 200 mL of amine absorbent and 0.5 mmol / L FeSO4 into the three-necked flask. Other degradation experiment conditions and the amine concentration measurement method are the same as those in Example 1.

[0048] Comparative Example 2

[0049] Using DTPMP as a single inhibitor, the structural formula of this composite inhibitor is as shown in the appendix Figure 1 and carry out the 1AP oxidation degradation experiment. Add 200 mL of amine absorbent, 0.5 mmol / L FeSO4 and 0.1% single inhibitor (DTPMP) into the three-necked flask. Other degradation experiment conditions and the amine concentration measurement method are the same as those in Example 1.

[0050] Comparative Example 3

[0051] Using DTPMP as a single inhibitor, the structural formula of this composite inhibitor is as shown in the appendix Figure 1 and carry out the 1AP oxidation degradation experiment. Add 200 mL of amine absorbent, 0.5 mmol / L FeSO4 and 1.0% single inhibitor (DTPMP) into the three-necked flask. Other degradation experiment conditions and the amine concentration measurement method are the same as those in Example 1.

[0052] Comparative Example 4

[0053] Using DTPA as a single inhibitor, the structural formula of this composite inhibitor is as shown in the appendix Figure 1 and carry out the 1AP oxidation degradation experiment. Add 200 mL of amine absorbent, 0.5 mmol / L FeSO4 and 1.0% single inhibitor (DTPA) into the three-necked flask. Other degradation experiment conditions and the amine concentration measurement method are the same as those in Example 1.

[0054] Comparative Example 5

[0055] Using KI as a single inhibitor, the structural formula of this composite inhibitor is as shown in the appendix Figure 1As shown, the 1AP oxidation degradation experiment was carried out. 200 mL of amine absorbent, 0.5 mmol / L FeSO4 and 1.0% single inhibitor (KI) were added to the three-necked flask. Other degradation experiment conditions and the amine concentration measurement method were the same as those in Example 1.

[0056] Comparative Example 6

[0057] Using Na2S2O3 as the single inhibitor, the structural formula of the composite inhibitor is as shown in the appendix Figure 1 As shown, the 1AP oxidation degradation experiment was carried out. 200 mL of amine absorbent, 0.5 mmol / L FeSO4 and 1.0% single inhibitor (Na2S2O3) were added to the three-necked flask. Other degradation experiment conditions and the amine concentration measurement method were the same as those in Example 1.

[0058] The change in 1AP concentration after adding different inhibitors is as shown in the appendix Figure 4 As shown, the data are shown in Table 1. Comparing all examples and Comparative Example 1, it was found that adding the composite inhibitor could significantly inhibit the oxidation degradation of 1AP, reducing the 1AP loss from 47.0% to less than 7.0%. Comparing Example 1, Comparative Example 3, and Comparative Example 5, adding the same concentration of the composite inhibitor showed a better inhibitory effect than the single inhibitor, reducing the 1AP loss from 10.8% (adding 1.0% DTPMP), 26.3% (adding 1.0% KI) to 6.3% (adding 1.0% DTPMP + KI). Comparing Example 4, Example 5, Example 6 and Comparative Example 3, Comparative Example 4, Comparative Example 5, Comparative Example 6, the same conclusion could also be obtained. The experimental results of Comparative Example 2 showed that the inhibitory effect of 0.1% addition amount of DTPMP was weak, only reducing the 1AP loss from 47.0% to 45.3%. While adding 0.1% composite inhibitor (DTPMP + Na2S2O3, Example 2) showed a significant inhibitory effect, reducing the 1AP loss from 47.0% to 6.1%. The above results showed that the metal chelating agent and free radical scavenger in the composite inhibitor could synergistically inhibit the oxidation degradation of 1AP, and the inhibition efficiency was significantly improved compared with the single inhibitor. A very small addition amount (0.1%) of the composite inhibitor could achieve an inhibition intensity exceeding that of more single inhibitor addition amounts (1.0%).

[0059] Table 1: Effects of adding different inhibitors on the change of 1AP concentration during degradation

[0060]

[0061] a The mass ratio of the metal chelating agent to the free radical scavenger in the composite inhibitor is 1:1.

[0062] The composite inhibitor of the present invention can significantly inhibit the degradation of amine absorbents during the CO2 capture process, reduce the amine loss caused by degradation, and the composite inhibitor shows a better inhibitory effect compared with single inhibitors. The synergistic inhibitory effect between the metal chelator and the free radical scavenger can greatly reduce the usage amount of the composite inhibitor and lower the inhibitor cost.

[0063] The above are only several specific embodiments of the present invention. Those skilled in the art can make various modifications and alterations to the embodiments of the present invention without departing from the spirit and scope of the present invention. However, the embodiments of the present invention are not limited thereto, and any changes that can be proposed by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. An application of a composite inhibitor to inhibit the degradation of an amine absorbent in CO2 capture, characterized in that: The composite inhibitor consists of a metal chelating agent and a free radical scavenger: the metal chelating agent is diethylenetriaminepenta(methylenephosphonic acid) (DTPMP) or diethyltriaminepentaacetic acid (DTPA), and the free radical scavenger is potassium iodide (KI) or sodium thiosulfate (Na2S2O3).

2. The use of the composite inhibitor according to claim 1 to inhibit the degradation of amine absorbent in CO2 capture, characterized in that: The composite inhibitor is used in the field of CO2 capture to inhibit the degradation of an alcohol amine absorbent, wherein the mass fraction of the alcohol amine absorbent ranges from 20 to 60%.

3. The use of the composite inhibitor according to claim 1 to inhibit the degradation of amine absorbent in CO2 capture, characterized in that: The temperature of the amine absorbent when capturing CO2 varies from 40 to 60°C.

4. The use of the composite inhibitor according to claim 1 to inhibit the degradation of amine absorbent in CO2 capture, characterized in that: The mass fraction of the metal chelating agent in the composite inhibitor varies from 10 to 90%.

5. The use of the composite inhibitor according to claim 1 to inhibit the degradation of amine absorbent in CO2 capture, characterized in that: The addition amount of the composite inhibitor in the alcohol amine absorbent varies from 0.1 to 1.0%.

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