Desulfurization, denitration and demercuration method for CO2-rich flue gas

Abstract

The invention relates to a CO2-rich flue gas desulfurization, denitrification and demercuration method which comprises the following steps: S1, introducing CO2-rich flue gas into a pressurizing device for pressurizing treatment to obtain high-pressure CO2-rich flue gas; and S2, under high pressure, introducing the high-pressure CO2-rich flue gas into a washing tower to be in contact with washing water, and carrying out desulfurization, denitrification and demercuration reaction. According to the method disclosed by the invention, efficient desulfurization, denitrification and demercuration can be realized, the flue gas purification effect is excellent and stable, and a high-pressure condition is provided for subsequent carbon capture and storage processes.

Description

Technical Field

[0001] The present application relates to the field of flue gas treatment, and in particular, to a method for desulfurization, denitrification and demercurization of CO2-rich flue gas. Background Art

[0002] Carbon capture technology is being closely watched by researchers at home and abroad. Generally speaking, carbon capture technology for coal-fired power plants is divided into pre-combustion capture, post-combustion capture and oxygen-enriched combustion technology. Among them, oxygen-enriched combustion technology uses high-purity oxygen produced by the air separation unit to replace air to enter the combustion chamber and burn with fuel. After passing through the flue gas recirculation system, flue gas containing high concentrations of CO2 can be directly obtained, which is convenient for compression, purification and separation of CO2 to achieve its storage or utilization. Oxygen-enriched combustion technology has good process adaptability, and has great advantages over other carbon capture technologies in terms of capture cost and ease of scalability. Therefore, it is also considered to be one of the carbon capture technologies with the most promising industrial application prospects.

[0003] Sulfide, nitrogen oxides and mercury in flue gas are one of the main sources of atmospheric pollution, which cause serious harm to air quality and human health. In addition, impurities such as sulfide, nitrogen oxide and mercury in flue gas will also increase the cost of CO2 purification and corrode CO2 transportation pipelines. Therefore, it is of great significance to develop an efficient flue gas desulfurization, denitrification and demercuration method.

[0004] Traditional flue gas desulfurization and denitrification methods mainly use limestone slurry and catalytic reduction as desulfurization agents and denitrification methods. However, when traditional methods treat CO2-rich flue gas, the high concentration of CO2 in the flue gas will be absorbed by the alkaline solution, producing complex by-products. At the same time, NO x There are also certain difficulties in removing mercury. These problems affect the purification effect of flue gas and increase the treatment cost. Summary of the invention

[0005] The purpose of the present invention is to provide a method for desulfurization, denitrification and demercuration of CO2-rich flue gas. The method of the present invention can achieve efficient desulfurization, denitrification and demercuration, the flue gas purification effect is excellent and stable, and high-pressure conditions are provided for subsequent carbon capture and storage processes.

[0006] In order to achieve the above object, the present disclosure provides a method for desulfurization, denitrification and demercuration of CO2-rich flue gas, the method comprising: S1, introducing the CO2-rich flue gas into a pressurizing device for pressurization treatment to obtain high-pressure CO2-rich flue gas; S2. Under high pressure, the high-pressure CO2-rich flue gas is introduced into a washing tower to contact with washing water for washing to carry out desulfurization, denitrification and demercuration reactions.

[0007] Optionally, the pressure of the high-pressure CO2-rich flue gas is 1.5-3 MPa, preferably 2.5-3 MPa.

[0008] Optionally, the pressure in the washing tower is 1.5-4 MPa, preferably 2.5-4 MPa.

[0009] Optionally, the flow rate of the washing water is 1.38-3.33 kg / s, the temperature of the washing water is 30-40°C, and the inlet flow rate of the high-pressure CO2-rich flue gas is 5000-12000 Nm 3 / h.

[0010] Optionally, the usage ratio of the high-pressure CO2-rich flue gas to the scrubbing water per unit time is 0.5-1.7 kg water / Nm 3 Flue gas, preferably 0.6-1.6 kg water / Nm 3 Smoke.

[0011] Optionally, the method further comprises: collecting the washing wastewater in step S2, and returning part of the washing wastewater to the washing tower as washing water for continued use.

[0012] Optionally, the volume flow ratio of the fresh washing water introduced into the washing tower to the washing wastewater is 1:(0.11-9), and the circulation ratio of the washing wastewater is 0.1-0.7.

[0013] Optionally, in step S2, a washing water spraying device is provided in the washing tower, and the nozzle outlet pressure of the washing water spraying device is 2.5-4 MPa.

[0014] Optionally, the method further comprises: introducing the CO2-rich flue gas after the desulfurization, denitrification and demercuration reactions into a CO2 compression and purification device to obtain purified CO2.

[0015] Optionally, the CO2-rich flue gas contains 450-1000 ppm NO, 45-100 ppm NO, 900-2000 ppm SO, 20-80% CO, and 0.3-0.7 ppb Hg.

[0016] Through the above technical solution, the method disclosed in the present invention has the following advantages: (1) The method disclosed herein uses water as an absorbent and can effectively remove sulfur oxides, nitrogen oxides and mercury from flue gas under high pressure conditions. The flue gas purification effect is good and stable and efficient.

[0017] (2) The method disclosed in the present invention has low operating costs and waste liquid treatment costs, and can avoid secondary environmental pollution caused by the use of related reagents.

[0018] (3) In the method disclosed in the present invention, the CO2-rich flue gas is still in a high-pressure state after compression and washing, which can provide high-pressure conditions for the carbon dioxide liquefaction link in the process of carbon dioxide transportation and utilization, thereby realizing the integrated utilization of energy in the carbon reduction process.

[0019] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings: Figure 1 It is a process simulation flow chart in Example 1 of the present disclosure.

[0021] Figure 2 This is a schematic diagram of the experimental apparatus used for desulfurization, denitrification and demercurization of CO2-rich flue gas used in Examples 5 and 6 of the present disclosure.

[0022] Description of Reference Numerals 1. O2 cylinder 2. CO2 cylinder 3. Mixed gas cylinder 4. Pressure reducing valve 5. Mass flow controller 6. High pressure reactor 7. Deionized water 8. Flue gas analyzer 9. Stop valve DETAILED DESCRIPTION The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0023] The present disclosure provides a method for desulfurization, denitrification and demercuration of CO2-rich flue gas, which comprises: S1, introducing the CO2-rich flue gas into a pressurizing device for pressurization treatment to obtain high-pressure CO2-rich flue gas; S2, introducing the high-pressure CO2-rich flue gas into a washing tower under high pressure to contact with washing water to carry out desulfurization, denitrification and demercuration reactions.

[0024] In the method disclosed in the present invention, the CO2-rich flue gas is pressurized and washed with water. Under high pressure conditions, NO in the flue gas reacts with O2 to generate NO2 that is easily soluble in water. NO2 dissolves in water and is removed; SO2 also dissolves in water, and the high pressure also promotes this dissolution process; mercury reacts homogeneously with NO2 to form a water-soluble compound that is removed by water washing. The CO2-rich flue gas desulfurization, denitrification and demercuration method of the present application can effectively transfer sulfur oxides, nitrogen oxides and mercury in the flue gas to the liquid phase, reduce the concentration of pollutants in the flue gas, achieve efficient removal of pollutants, and obtain high-pressure flue gas, which is beneficial to the subsequent compression and purification of CO2 in the flue gas. In addition, the CO2-rich flue gas is washed with water and the pollutants are dissolved in water to remove the pollutants. There is no need to use other desulfurizers and denitrifiers, which can save operating costs, reduce waste liquid treatment costs, and avoid secondary environmental pollution caused by the use of related reagents.

[0025] According to the present disclosure, the pressurizing device is well known to those skilled in the art, and may be, for example, a compressor, a pump, a high-pressure container, etc., and the present disclosure does not make any specific limitation on this.

[0026] In a specific embodiment of the present disclosure, the pressure of the high-pressure CO2-rich flue gas is 1.5-3 MPa, preferably 2.5-3 MPa. Within the above pressure range, the method of the present disclosure has a better effect of removing pollutants.

[0027] According to the present disclosure, the pressure in the scrubber is also high pressure, and the pressure in the scrubber is greater than the pressure of the high pressure CO2-rich flue gas, and the pressure can vary within a wide range. In a specific embodiment of the present disclosure, the pressure in the scrubber is 1.5-4MPa, preferably 2.5-4MPa. In the present disclosure, the pressure in the scrubber can be monitored by a pressure gauge and controlled by a controller connected to the pressure gauge signal.

[0028] According to the present disclosure, the ratio of the amount of high-pressure CO2-rich flue gas to the amount of washing water can vary within a wide range. In a specific embodiment, the amount of high-pressure CO2-rich flue gas to the amount of washing water per unit time is 0.5-1.7 kg water / Nm 3 Flue gas, preferably 0.6-1.6 kg water / Nm 3 Flue gas. Under the above conditions, the method disclosed in the present invention has a better effect of removing nitrogen oxides, sulfur oxides and mercury from flue gas.

[0029] According to the present disclosure, the flow rate of the washing water can vary in a wide range, for example, it can be 1.38-5.55 kg / s, preferably 1.38-3.33 kg / s, and the flow rate of the washing water can be regulated by a liquid pump. In the present disclosure, the temperature of the washing water can vary in a wide range. In a specific embodiment, the temperature of the washing water can be 30-90°C, preferably 30-40°C. The inlet flow rate of the high-pressure CO2-rich flue gas can also vary in a wide range, for example, it can be 5000-20000 Nm 3 / h, preferably 5000-12000Nm 3 / h.

[0030] In a preferred specific embodiment of the present disclosure, the method further includes: collecting the washing wastewater in step S2, and returning part of the washing wastewater to the washing tower for continued use as washing water. In the present disclosure, high-pressure CO2-rich flue gas is introduced into the washing tower to contact with the washing water for washing, and the pollutants in the CO2-rich flue gas are absorbed by the washing water to form washing wastewater. In the method of the present disclosure, by recycling part of the washing wastewater, the use of washing water can be greatly reduced, achieving the purpose of water use and cost reduction. Preferably, the remaining washing wastewater is purified so that the washing wastewater meets the discharge standards to reduce harm to the environment.

[0031] In order to ensure the absorption of pollutants in the CO2-rich flue gas and further reduce the amount of washing water, in a specific embodiment, the ratio of the volume flow of fresh washing water introduced into the washing tower to the washing wastewater is 1: (0.11-9), preferably 1: (0.11-7), and the circulation ratio of the washing wastewater is 0.1-0.9, preferably 0.1-0.7. In the present disclosure, the circulation ratio refers to the ratio of the washing wastewater recycled back to the washing tower to the total washing wastewater. In this embodiment, the amount of washing water can be minimized, resources are more conserved, and the environment is more friendly.

[0032] In order to make the CO2-rich flue gas fully contact with the washing water, in a specific embodiment of the present disclosure, in step S2, a washing water spray device is provided in the washing tower, and the nozzle outlet pressure of the washing water spray device is 1.5-4MPa, preferably 2.5-4MPa. In this embodiment, the washing water spray device can spray washing water into the washing tower or even form water mist to contact and wash the CO2-rich flue gas, so as to more fully and effectively remove pollutants in the flue gas. The present disclosure does not limit the specific setting method of the washing water spray device. For example, the washing water spray device can be arranged layer by layer along the axial direction of the washing tower. Those skilled in the art can select the specific type of the washing water spray device as needed.

[0033] In order to achieve continuous removal of pollutants in CO2-rich flue gas, in a specific embodiment of the present disclosure, in step S2, a water storage section is provided in the scrubbing tower. Preferably, a liquid level meter and a controller connected to the liquid level meter signal are provided to control the water output and water inflow in the water storage section, so that the method of the present disclosure can be carried out continuously.

[0034] In a specific embodiment of the present disclosure, the method further comprises: introducing the CO2-rich flue gas after the desulfurization, denitrification and demercuration reaction into a CO2 compression and purification device to obtain purified CO2. The method of the present disclosure is particularly suitable for treating CO2-rich flue gas, which is still in a high-pressure state after compression and washing, providing high-pressure conditions for subsequent carbon capture and storage processes, and realizing the integrated utilization of energy in the carbon reduction process.

[0035] The method disclosed in the present invention can achieve the removal of pollutants such as sulfur oxides, nitrogen oxides and mercury in CO2-rich flue gas generated in different application fields by adjusting process-related parameters. In a specific embodiment of the present invention, the content of NO in the CO2-rich flue gas is 450-1000ppm, the content of NO2 is 45-100ppm, the content of SO2 is 900-2000ppm, the content of CO2 is 20-80% by volume, and the content of Hg is 0.3-0.7ppb. According to the present disclosure, the CO2-rich flue gas can be oxygen-enriched cement industry, power plant boilers, blast furnace ironmaking industry, etc.

[0036] The present disclosure is further illustrated below by way of examples, but the present disclosure is not limited thereby.

[0037] Example 1 Aspen Plus was used for simulation calculations, and the process flow chart was established as follows: Figure 1 As shown, the composition of the CO2-rich flue gas to be treated is 494 ppm NO, 49.4 ppm NO2, 988 ppm SO2, 3.95 volume % O2, 79.0 volume % CO2, 6.92 volume % H2O, 9.88 volume % N2, and 2.96 ppb Hg.

[0038] Among them, the flow rate of the flue gas inlet of the flue gas compression device is 8410Nm 3 / h, the pressure is 0.1 MPa, the pressure of the outlet high-pressure CO2-rich flue gas is 2.5 MPa, the pressure in the washing tower is 2.5 MPa, the height of the washing tower is 12m, the diameter is 4m, the flow rate of washing water is 2.2kg / s, the water temperature is 25°C, the volume flow rate ratio of fresh washing water and washing waste water introduced into the washing tower is 1:2.33, the circulation ratio is 0.7, and the usage ratio of the high-pressure CO2-rich flue gas to the washing water per unit time is 0.94.

[0039] The concentration of each pollutant in the outlet flue gas is calculated by simulation: NO is 23.6ppm, NO2 is 1.68ppm, SO2 is 21.9ppm, N2O is 3.14ppm, and Hg is 0.282ppb. Pollutant removal rate: NO x 95.1%, SO x The total amount of washing water used was 84.24 kg.

[0040] Example 2 The same simulation process flow as in Example 1 was adopted, except that the circulation ratio was 0.8.

[0041] The concentration of each pollutant in the outlet flue gas is calculated by simulation: NO is 23.89ppm, NO2 is 1.77ppm, SO2 is 22.3ppm, N2O is 3.15ppm, and Hg is 0.288ppb. Pollutant removal rate: NO x 94.8%, SO x The total amount of washing water used was 56.16 kg.

[0042] Example 3 The same simulation process flow as in Example 1 was adopted, the only difference being that the pressure of the high-pressure CO2-rich flue gas was 2 MPa and the pressure in the scrubbing tower was 2 MPa.

[0043] The concentration of each pollutant in the outlet flue gas is calculated by simulation: NO is 28.2ppm, NO2 is 2.41ppm, SO2 is 28.1ppm, N2O is 3.19ppm, and Hg is 0.31ppb. Pollutant removal rate: NO x 93.8%, SO x The total amount of washing water used was 84.24 kg.

[0044] Example 4 The same simulation process as in Example 1 was used, except that the flow rate of the imported CO2-rich flue gas was 8414 Nm 3 / h, the flow rate of washing water is 1.17kg / s, and the ratio of high-pressure CO2-rich flue gas to washing water per unit time is 0.50.

[0045] The concentration of each pollutant in the outlet flue gas is calculated by simulation: NO is 30.2ppm, NO2 is 3.8ppm, SO2 is 41ppm, N2O is 3.33ppm, and Hg is 0.39ppb. Pollutant removal rate: NO x 93.11%, SO xThe total amount of washing water used was 42.1 kg.

[0046] Example 5 In such Figure 2 The experiment of desulfurization, denitrification and demercuration of CO2-rich flue gas was carried out in the system shown in the figure. The specific method is as follows: (1) First check whether all instruments are normal, whether all pipelines are airtight, and turn on the indoor ventilation facilities. Then open the high-pressure reactor 6, wipe off dust and other impurities with cotton balls to ensure that the reactor is clean and pollution-free, add 250mL of deionized water 7 into the reactor, and finally close the reactor.

[0047] (2) Open the mass flow controller 5 to the cleaning position, open the CO2 cylinder 2 and introduce CO2 until the pressure in the autoclave reaches 1 MPa, then discharge the carbon dioxide in the autoclave to normal pressure, repeat three times to drive away the air in the pipeline and reactor. If N2 atmosphere is required, flush with N2.

[0048] (3) Set the temperature in the reactor and turn on the circulating cooling water. When the temperature reaches the preset value, open the pressure reducing valve 4 of the O2 cylinder 1, CO2 cylinder 2 and mixed gas cylinder 3, adjust the mass flow controller 5 to the measuring position and adjust the flow rate to the required size, open the stop valve 9 to simulate the introduction of flue gas, record the ventilation time, observe the reactor pressure gauge, and close the air inlet valve after reaching 1.6MPa.

[0049] (4) After a period of reaction, open the stop valve 9 at the reactor outlet and pass the reacted gas into the pre-opened flue gas analyzer 8 for gas composition analysis, mainly measuring the contents of NO, NO2 and SO2 in the outlet gas, and record the experimental data.

[0050] (5) Open the inlet and outlet valves of the reactor to release the remaining gas in the system.

[0051] (6) Open the reactor and collect the absorption liquid sample in the reactor. The sample is collected in a high-density polyethylene bottle washed with deionized water and left for ion chromatography analysis and detection, mainly measuring NO3 － 、SO4 2－ If the collected samples cannot be analyzed on the same day, they should be protected and sealed. The samples can be filtered with a 0.45μm filter membrane and then sealed with a black polyethylene bottle. Otherwise, the bacteria in the bottles may cause the sample concentration to change over time.

[0052] (7) Clean the reactor, shut down all experimental instruments according to the regulations, and end the experiment.

[0053] The experimental parameters are as follows: Simulated flue gas components: NO 919.6ppm, SO22800.6ppm, O25%, the rest is CO2 Pressure in reactor: 1.6MPa Stay time: 5min Water volume in the reactor: 250mL Temperature: 13℃ Outlet flue gas components: SO20ppm, NO 23ppm Removal rate: SO2 100%, NO 97.5% Example 6 In the system shown in Example 5, an experiment of desulfurization, denitrification and demercuration of CO2-rich flue gas was carried out. The only difference is that the experimental parameters are different. The experimental parameters of this example are as follows: Simulated flue gas components: NO 800ppm, SO21000ppm, O23%, Hg 0 The concentration was controlled at 30 μg / m 3 About 2000 tons, the rest is CO2 and N2 Pressure in reactor: 2MPa Pollutant outlet concentration: NO 80ppm, SO20ppm Removal rate: NO X 90.00%, SO X 100%, Hg 90.24% It can be seen from the above that the method disclosed in the present invention can achieve efficient desulfurization, denitrification and demercuration, the flue gas purification effect is excellent and stable, and high-pressure conditions are provided for the subsequent carbon capture and storage process.

[0054] The preferred embodiments of the present disclosure are described in detail above; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0055] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0056] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for desulfurization, denitrification and demercuration of CO2-rich flue gas, characterized in that: The method includes: S1, introducing the CO2-rich flue gas into a pressurizing device for pressurization treatment to obtain high-pressure CO2-rich flue gas; S2. Under high pressure, the high-pressure CO2-rich flue gas is introduced into a washing tower to contact with washing water to carry out desulfurization, denitrification and demercuration reactions.

2. The method according to claim 1, wherein: The pressure of the high-pressure CO2-rich flue gas is 1.5-3MPa, preferably 2.5-3MPa.

3. The method according to claim 1, wherein: The pressure in the washing tower is 1.5-4 MPa, preferably 2.5-4 MPa.

4. The method according to claim 1, wherein: The flow rate of the washing water is 1.38-3.33 kg / s, the temperature of the washing water is 30-40°C, and the inlet flow rate of the high-pressure CO2-rich flue gas is 5000-12000 Nm 3 / h.

5. The method according to claim 1, wherein: The usage ratio of the high-pressure CO2-rich flue gas to the washing water per unit time is 0.5-1.7 kg water / Nm 3 Flue gas, preferably 0.6-1.6g water / Nm 3 Smoke.

6. The method according to claim 1, wherein: The method further comprises: collecting the washing wastewater in step S2, and returning part of the washing wastewater to the washing tower as washing water for continued use.

7. The method according to claim 6, wherein: The volume flow ratio of the fresh washing water introduced into the washing tower to the washing wastewater is 1:(0.11-9), and the circulation ratio of the washing wastewater is 0.1-0.

9.

8. The method according to claim 1, wherein: In step S2, a washing water spraying device is provided in the washing tower, and the nozzle outlet pressure of the washing water spraying device is 2.5-4 MPa.

9. The method according to claim 1, wherein: The method also includes: introducing the CO2-rich flue gas after the desulfurization, denitrification and demercuration reactions into a CO2 compression and purification device to obtain purified CO2.

10. The method according to claim 1, wherein: The CO2-rich flue gas contains 450-1000 ppm NO, 45-100 ppm NO, 900-2000 ppm SO, 20-80% CO, and 0.5-3 ppb Hg.

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