A modified mercury removal adsorbent based on active coke, and a preparation method and application thereof

Abstract

The application belongs to the field of pollutant control, and specifically discloses a modified activated coke-based mercury removal adsorbent and a preparation method and application thereof. The preparation method is to heat the activated coke to 300-600 DEG C under a mixed atmosphere of inert gas and SO2 for pyrolysis modification, and to obtain the modified activated coke-based mercury removal adsorbent by cooling after the reaction. The application reduces the SO2 activated coke modification temperature to 300-600 DEG C, can change the mercury removal principle of the prepared mercury removal adsorbent, and makes it suitable for low-temperature mercury removal working conditions. Good mercury removal effect and sulfur resistance can still be achieved at a lower reaction temperature.

Description

Technical Field

[0001] This application belongs to the field of pollutant control, and more specifically, relates to a mercury removal adsorbent based on activated coke modification, its preparation method and application. Background Technology

[0002] Mercury is one of the most volatile substances produced by coal-fired boilers, and it has attracted widespread attention due to its toxicity, cumulative effects on the biosphere, and potential harm to humans and animals. Reducing mercury emissions from flue gas is an urgent task, and currently, mercury removal adsorbents are mainly used for mercury removal treatment of flue gas.

[0003] Traditional coal-fired power plants remove mercury and other conventional pollutants using methods such as SCR, ESP, and WFGD. However, with increasingly stringent emission standards, near-zero emissions are required. Existing technologies have proposed Cold Oxidation Adsorption Process (COAP) for coal-fired pollutant removal, which can achieve near-zero emissions from coal-fired flue gas. In power plants using COAP technology, existing methods for modifying mercury removal adsorbents, including impregnation with halogens, impregnation with metal compounds, and mechanochemical modification, pose risks such as increased operating costs and the generation of hazardous waste. CN107737581A discloses a method for preparing modified petroleum coke-based mercury removal adsorbents. This method uses delayed coking petroleum coke as raw material and SO2 gas as an active modifier, resulting in a mercury removal adsorbent with well-developed pores and a surface rich in sulfur-containing functional groups. However, this method requires a high modification temperature, making it unsuitable for application in COAP technology. Meanwhile, current research on mercury adsorption removal in COAP technology mainly focuses on temperatures between 30℃ and 160℃. There is currently no research on the mercury adsorption effect of common modification methods at low temperatures (0-40℃), which is not conducive to the practical implementation of COAP technology. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a mercury removal adsorbent based on activated carbon modification, its preparation method, and its application, aiming to solve the problems of high cost and incompatibility with COAP technology in existing modification methods.

[0005] According to one aspect of this application, a method for preparing a mercury removal adsorbent based on activated carbon modification is provided. The method specifically involves heating activated carbon to 300°C to 600°C in a mixed atmosphere of inert gas and SO2 for pyrolysis modification, and cooling it after the reaction is completed to obtain the mercury removal adsorbent based on activated carbon modification.

[0006] Compared with the prior art, the technical solution conceived in this application reduces the temperature of SO2 activated coke modification to 300℃~600℃, which can change the mercury removal principle of the prepared mercury removal adsorbent, making it suitable for low-temperature mercury removal conditions, thereby adapting to a wider range of mercury removal environments.

[0007] As a further preferred option, the pyrolysis time is 30 min to 180 min.

[0008] As a further preferred embodiment, the volume fraction of SO2 in the mixed atmosphere is 5% to 45%.

[0009] As a further preferred embodiment, the volume fraction of SO2 in the mixed atmosphere is 25% to 35%.

[0010] As a further preferred option, the flow rate of the mixed atmosphere is 200 ml / min to 2000 ml / min.

[0011] As a further preferred embodiment, the particle size of the activated coke is 40 mesh to 100 mesh.

[0012] According to another aspect of this application, a mercury removal adsorbent prepared using the above-described preparation method is provided.

[0013] According to another aspect of this application, a method for improving mercury removal efficiency in a power plant is provided. The power plant includes a boiler, a dust collector, a cascade cooling tower, a low-temperature adsorption tower, and a regeneration tower connected in sequence. Deactivated activated coke in the low-temperature adsorption tower is fed into the regeneration tower, and the tail gas from the regeneration tower is returned to the regeneration tower to form a mixed atmosphere of inert gas and SO2. At the same time, the temperature of the regeneration tower is maintained at 300℃ to 600℃, thereby achieving SO2 modification of the deactivated activated coke and returning the modified activated coke to the low-temperature adsorption tower.

[0014] As a further preferred embodiment, the volume fraction of SO2 in the regeneration tower is 5-45%.

[0015] As a further preferred embodiment, the volume fraction of SO2 in the regeneration tower is 25% to 35%.

[0016] In summary, compared with the prior art, the technical solutions conceived in this application have the following main technical advantages:

[0017] 1. This application reduces the modification temperature of SO2 activated coke to 300℃~600℃, which can change the mercury removal principle of the prepared mercury removal adsorbent, making it suitable for low-temperature mercury removal conditions. It can still achieve good mercury removal effect and sulfur resistance at a lower reaction temperature, thus having a wider range of applicable temperature and stronger adaptability.

[0018] 2. At the same time, this application optimizes the volume fraction of SO2 in the mixed atmosphere, which can further improve the mercury removal efficiency of the mercury removal adsorbent;

[0019] 3. Furthermore, this application applies the preparation method to power plants using COAP technology, which can match the temperature of the regeneration tower, thereby further reducing the preparation cost of modified activated coke. Moreover, the modified activated coke can adapt to mercury removal environments over a wide temperature range and still has high mercury removal efficiency at 0–40°C, which is conducive to the implementation of COAP technology. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a power plant using COAP technology provided in an embodiment of this application;

[0021] Figure 2 This is a comparison chart of the mercury removal efficiency of the mercury removal adsorbents obtained under different SO2 concentrations at a pyrolysis temperature of 400℃ and a pyrolysis time of 60min, as provided in the embodiments of this application.

[0022] Figure 3 This is a comparison chart of the mercury removal efficiency of the mercury removal adsorbents obtained at different pyrolysis times in a mixed atmosphere of 75% N2 + 25% SO2 and a pure N2 atmosphere at a pyrolysis temperature of 400℃, according to the embodiments of this application.

[0023] Figure 4 This is a comparison chart of the mercury removal efficiency of the mercury removal adsorbents obtained at different pyrolysis temperatures in a mixed atmosphere of 75% N2 + 25% SO2 and a pure N2 atmosphere with a pyrolysis time of 60 min, according to the embodiments of this application.

[0024] Figure 5 This is a comparison chart of the mercury removal efficiency of the mercury removal adsorbents prepared in Example 1 and Comparative Example 1 of this application at different mercury removal temperatures;

[0025] Figure 6 This is a comparison chart of the mercury removal efficiency of the mercury removal adsorbent prepared in Example 1 of this application under different atmospheric environments at mercury removal temperatures of 20°C and 140°C.

[0026] Figure 7 The XPS results of the mercury removal adsorbent prepared in Example 1 of this application after mercury removal at mercury removal temperatures of -20°C and 140°C under different atmospheric conditions are shown.

[0027] Figure 8 This is a diagram of the equipment for preparing the mercury removal adsorbent based on activated carbon modification provided in the embodiments of this application;

[0028] Figure 9 This is a schematic diagram of the test bench used for wide-temperature mercury removal tests in this application.

[0029] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0030] 1-Boiler, 2-Dust collector, 3-Step cooling tower, 4-Low-temperature adsorption tower, 5-Regeneration tower, 6-Mixed gas cylinder, 7-Tube furnace, 8-Flue gas cooling pipe, 9-Low-temperature water bath. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0032] This application provides a method for preparing a mercury removal adsorbent based on activated carbon modification. The method involves heating activated carbon to 300℃~600℃ in a mixed atmosphere of inert gas and SO2 for pyrolysis modification, and cooling after the reaction to obtain the mercury removal adsorbent based on activated carbon modification.

[0033] Specifically, the steps include the following:

[0034] S1 Crushing and Screening: The activated coke is washed, crushed, and screened to obtain activated coke particles with a particle size distribution of 40 mesh to 100 mesh.

[0035] S2 drying process involves sending the pre-selected activated coke particles into a 105℃ oven and drying them for 12 hours to ensure the evaporation of moisture.

[0036] S3 insulation modification, such as Figure 8 As shown, the tubular furnace 7 is heated to 300℃~600℃. Inert gas and SO2 are mixed in the mixing bottle 6 and then introduced into the tubular furnace 7. The previously dried activated coke particles are purged for a period of time in the mixed atmosphere of inert gas and SO2 to ensure that there is no oxygen. Then, they are quickly put into the tubular furnace and kept at the same temperature for a period of time in the same mixed atmosphere before being taken out. Finally, they are cooled in the mixed atmosphere to obtain the mercury removal adsorbent based on activated coke modification.

[0037] This application utilizes sulfur dioxide thermal reduction modification of activated carbon, effectively increasing the active sites on the activated carbon surface. The attacked active sites mitigate the slow reaction rate caused by low temperatures and reduce the negative impact of SO2 on mercury control, giving the adsorbent excellent anti-sulfur and mercury removal properties under low-temperature conditions. More importantly, this application lowers the SO2-modified activated carbon temperature to 300℃~600℃, achieving higher mercury removal efficiency compared to existing high-temperature modification techniques, while still maintaining good mercury removal and anti-sulfur performance at lower reaction temperatures.

[0038] Furthermore, the pyrolysis time is 30 min to 180 min. The mercury removal efficiency first increases and then decreases with the pyrolysis time, reaching its peak at 2 hours. Therefore, the pyrolysis time is further preferably 60 min to 120 min, within which the mercury removal efficiency of the mercury removal adsorbent is the highest.

[0039] Furthermore, the volume fraction of SO2 in the mixed atmosphere is 5%–45%. The mercury removal efficiency first increases and then decreases with the SO2 concentration, reaching its peak at a sulfur dioxide concentration of 35%. Therefore, the preferred volume fraction of SO2 in the mixed atmosphere is 25%–35%, within which the mercury removal efficiency of the mercury removal adsorbent is highest. The flow rate of the mixed atmosphere is 200 ml / min–2000 ml / min.

[0040] According to another aspect of this application, a mercury removal adsorbent prepared using the above-described preparation method is provided.

[0041] According to another aspect of this application, a method for improving the mercury removal efficiency of a power plant is provided. The power plant includes a boiler 1, a dust collector 2, a cascade cooling tower 3, a low-temperature adsorption tower 4, and a regeneration tower 5 connected in sequence. The cascade cooling tower 3 can achieve enhanced removal of particulate matter, SO3, and heavy metals through cascade cooling. The low-temperature adsorption tower 4 uses modified activated coke to achieve efficient adsorption of gaseous pollutants and deep removal of particulate pollutants. The deactivated activated coke after the reaction is sent to the regeneration tower 5 for thermal regeneration. Considering that most sulfur dioxide will be released from the activated coke at low temperatures (as shown in Table 1), and that the modification of activated coke in an SO2 atmosphere at low temperatures can effectively improve its mercury removal performance and is more suitable for low-temperature mercury removal reaction conditions.

[0042] Table 1 Main components of flue gas in the regeneration tower

[0043]

[0044] Therefore, the method provided in this application returns the tail gas from regeneration tower 5 to regeneration tower 5 to form a mixed atmosphere of inert gas and SO2, and ensures that the temperature of regeneration tower 5 is between 300℃ and 600℃, thereby achieving in-situ modification of deactivated activated carbon by sulfur dioxide. The modified activated carbon obtained is then returned to low-temperature adsorption tower 4. Under these reaction conditions, the modified activated carbon can exhibit better mercury adsorption performance at low temperatures (0-40℃), making it more suitable for the temperature of low-temperature adsorption tower 4 in COAP technology.

[0045] Furthermore, the volume fraction of SO2 in the mixed atmosphere is 5% to 45%, and more preferably, the volume fraction of SO2 in the mixed atmosphere is 25% to 35%, within which the mercury removal efficiency of the mercury removal adsorbent is the highest.

[0046] The technical solutions provided in this application will be further described below with reference to specific embodiments.

[0047] Example 1

[0048] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distribution between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, which is then placed in a mixed atmosphere of 200ml / min total gas flow and 75% N2 + 25% SO2. The mixture is then pyrolyzed at 400℃ for 60 minutes. After natural cooling, the mercury removal adsorbent based on activated coke modification is obtained.

[0049] Example 2

[0050] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, which is then placed in a mixed atmosphere of 200ml / min total gas flow and 95% N2 + 5% SO2. The mixture is then pyrolyzed at 400℃ for 60 minutes. After natural cooling, the mercury removal adsorbent based on activated coke modification is obtained.

[0051] Example 3

[0052] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, which is then placed in a mixed atmosphere of 200ml / min total gas flow and 85% N2 + 15% SO2. The mixture is then pyrolyzed at 400℃ for 60 minutes. After natural cooling, the mercury removal adsorbent based on activated coke modification is obtained.

[0053] Example 4

[0054] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, which is then placed in a mixed atmosphere of 200ml / min total gas flow and 65% N2 + 35% SO2. The mixture is then pyrolyzed at 400℃ for 60 minutes. After natural cooling, the mercury removal adsorbent based on activated coke modification is obtained.

[0055] Example 5

[0056] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, which is then placed in a mixed atmosphere of 200ml / min total gas flow and 55% N2 + 45% SO2. The mixture is then pyrolyzed at 400℃ for 60 minutes. After natural cooling, the mercury removal adsorbent based on activated coke modification is obtained.

[0057] Example 6

[0058] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, which is then placed in a mixed atmosphere of 200ml / min total gas flow and 75% N2 + 25% SO2. The mixture is then pyrolyzed at 400℃ for 30 minutes. After natural cooling, the mercury removal adsorbent based on activated coke modification is obtained.

[0059] Example 7

[0060] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distribution between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, which is then placed in a mixed atmosphere of 200ml / min total gas flow and 75% N2 + 25% SO2. The mixture is then pyrolyzed at 400℃ for 120 minutes. After natural cooling, the mercury removal adsorbent based on activated coke modification is obtained.

[0061] Example 8

[0062] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, which is then placed in a mixed atmosphere of 200ml / min total gas flow and 75% N2 + 25% SO2. The mixture is then pyrolyzed at 400℃ for 180 minutes. After natural cooling, the mercury removal adsorbent based on activated coke modification is obtained.

[0063] Example 9

[0064] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distribution between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, which is then placed in a mixed atmosphere of 200ml / min total gas flow and 75% N2 + 25% SO2. The mixture is then pyrolyzed at 300℃ for 60 minutes. After natural cooling, the mercury removal adsorbent based on activated coke modification is obtained.

[0065] Example 10

[0066] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, which is then placed in a mixed atmosphere of 200ml / min total gas flow and 75% N2 + 25% SO2. The mixture is then pyrolyzed at 600℃ for 60 minutes. After natural cooling, the mercury removal adsorbent based on activated coke modification is obtained.

[0067] Example 11

[0068] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, which is then placed in a mixed atmosphere of 200ml / min total gas flow and 75% N2 + 25% SO2. The mixture is then pyrolyzed at 500℃ for 60 minutes. After natural cooling, the mercury removal adsorbent based on activated coke modification is obtained.

[0069] Comparative Example 1

[0070] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, placed in a pure N2 atmosphere with a total gas flow of 200ml / min, and pyrolyzed at 400℃ for 60 minutes. After natural cooling, the mercury removal adsorbent is obtained.

[0071] Comparative Example 2

[0072] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, placed in a pure N2 atmosphere with a total gas flow of 200ml / min, and pyrolyzed at 600℃ for 60 minutes. After natural cooling, the mercury removal adsorbent is obtained.

[0073] Comparative Example 3

[0074] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distribution between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, placed in a pure N2 atmosphere with a total airflow of 200ml / min, and pyrolyzed at 400℃ for 120 minutes. After natural cooling, the mercury removal adsorbent is obtained.

[0075] Comparative Example 4

[0076] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, placed in a pure N2 atmosphere with a total gas flow of 200ml / min, and pyrolyzed at 400℃ for 30 minutes. After natural cooling, the mercury removal adsorbent is obtained.

[0077] Comparative Example 5

[0078] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, placed in a pure N2 atmosphere with a total gas flow of 200ml / min, and pyrolyzed at 400℃ for 180 minutes. After natural cooling, the mercury removal adsorbent is obtained.

[0079] Comparative Example 6

[0080] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, placed in a pure N2 atmosphere with a total gas flow of 200ml / min, and pyrolyzed at 300℃ for 60 minutes. After natural cooling, the mercury removal adsorbent is obtained.

[0081] Comparative Example 7

[0082] First, the activated coke raw material is crushed and sieved to obtain particles that meet the sieve standards, with the particle size distributed between 40 and 100 mesh. The activated coke particles are dried at 105℃ for 12 hours. 3g of activated coke particles are weighed and placed in a tube furnace, placed in a pure N2 atmosphere with a total gas flow of 200ml / min, and pyrolyzed at 500℃ for 60 minutes. After natural cooling, the mercury removal adsorbent is obtained.

[0083] The prepared mercury-removing adsorbent is then... Figure 9 Mercury removal tests were conducted on the wide-temperature mercury removal test bench shown. O2, SO2, N2 and NO were mixed to simulate flue gas and sent through flue gas cooling pipe 8 into a U-shaped tube filled with mercury removal adsorbent. Both flue gas cooling pipe 8 and U-shaped tube were placed in a low-temperature water bath 9 to adjust the mercury removal temperature. The low-temperature water bath 9 can be adjusted within the temperature range of -40℃ to 200℃, thereby realizing the wide-temperature mercury removal test.

[0084] Mercury removal tests were conducted on mercury removal adsorbents obtained under different SO2 concentrations at a pyrolysis temperature of 400℃ and a pyrolysis time of 60 min, including the mercury removal adsorbents prepared in Examples 1-5 and Comparative Example 1. The results are as follows: Figure 2As shown, the mercury removal efficiency first increases and then decreases with SO2 concentration, reaching its peak at a sulfur dioxide concentration of 35%, with an average adsorption efficiency of 92.3% and a maximum of 100%. Testing the sulfur content of various mercury removal adsorbents revealed that the sulfur content in activated coke modified with different SO2 concentrations also showed a trend of first increasing and then decreasing, reaching its highest level of 5.507% at a modification concentration of 35%. Therefore, the mercury removal efficiency of the adsorbent is highest when the SO2 volume fraction is between 25% and 35%.

[0085] Mercury removal tests were conducted on mercury removal adsorbents obtained at different pyrolysis times in a mixed atmosphere of 75% N2 + 25% SO2 and a pure N2 atmosphere at a pyrolysis temperature of 400℃. These tests included mercury removal adsorbents prepared in Examples 1, 6-8, and Comparative Examples 1 and 3-5. The results are as follows: Figure 3 As shown, at 400℃, a holding time of 0.5 hours resulted in an adsorption efficiency of nearly 50%, indicating that short-term holding can still effectively improve mercury removal efficiency. Furthermore, the mercury removal efficiency first increased and then decreased with pyrolysis time, reaching its peak at 2 hours of holding. Tests on the sulfur content of various mercury removal adsorbents revealed that the sulfur content in activated coke at different pyrolysis times also showed a trend of first increasing and then decreasing, with the total sulfur content in the activated coke at 2 hours of holding being 5.205%. However, prolonged holding may cause the functional groups on the sulfur-containing surface to break bonds and form gaseous molecules, resulting in a decrease in sulfur content and thus a decrease in removal efficiency.

[0086] Mercury removal tests were conducted on mercury removal adsorbents obtained at different pyrolysis temperatures in a mixed atmosphere of 75% N2 + 25% SO2 and a pure N2 atmosphere for 60 min of pyrolysis. These included mercury removal adsorbents prepared in Examples 1, 9-11, and Comparative Examples 1, 2, 6, and 7. The results are as follows: Figure 4 As shown, under the same atmosphere and pyrolysis time conditions, the mercury removal efficiency increases with increasing temperature. At a pyrolysis temperature of 400℃, the average mercury removal efficiency is >80%, which meets the industrial requirements for mercury removal. On the one hand, the total sulfur content increases with increasing temperature, so the relative content of active sulfur-containing functional groups also increases. On the other hand, the increase in temperature is conducive to the carbothermic reduction of sulfur dioxide, causing more sulfur dioxide molecules to be reduced to form small-molecule sulfur-containing substances, thereby improving the mercury removal efficiency.

[0087] Mercury removal tests were conducted on the mercury removal adsorbents prepared in Example 1 and Comparative Example 1 at different mercury removal temperatures, and the results are as follows: Figure 5As shown, the mercury removal efficiency under different mercury removal temperatures exhibits a trend of first increasing and then decreasing. It shows an increasing trend within the range of ~30 to 0℃, reaching its peak around ~10℃ or 0℃, and then decreasing. Meanwhile, the mercury removal adsorbent prepared in Comparative Example 1 is particularly significantly affected by temperature, while the mercury removal adsorbent prepared in Example 1 is relatively less affected by temperature. Since the mercury removal adsorbent prepared in Comparative Example 1 basically does not contain sulfur-related functional groups, it cannot effectively convert physical adsorption to chemical adsorption under low-temperature conditions, resulting in poor adsorption capacity. As the temperature increases, a dynamic equilibrium between physical and chemical adsorption is reached around ~10 to 0℃, resulting in the highest adsorption efficiency, with an average adsorption efficiency of approximately 71.34%. However, with further increases in temperature, although chemical adsorption is promoted, physical adsorption is inhibited, making it impossible to effectively adsorb elemental mercury. The mercury removal adsorbent prepared in Example 1 contains a large number of sulfur-containing functional groups, which results in a good average adsorption efficiency of ≥80% even at low temperatures; however, the mercury removal efficiency decreases at high temperatures, with a minimum average mercury removal efficiency of ≥50%. Therefore, the mercury removal adsorbent prepared in this application is well adapted to the low-temperature mercury removal conditions in COAP technology.

[0088] The mercury removal adsorbent prepared in Example 1 was subjected to mercury removal tests at mercury removal temperatures of -20°C and 140°C in different atmospheric environments. The mercury removal efficiency was as follows: Figure 6 As shown, at -20℃, 500 ppm SO2 can achieve 100% mercury removal efficiency, and the removal efficiency first increases and then decreases with increasing SO2 concentration. In contrast, at 140℃, although the trend is similar, the highest mercury removal efficiency (90.27%) appears at 1000 ppm, indicating that SO2 is more readily adsorbed than mercury at low temperatures. At -20℃, this modified activated coke exhibits good sulfur resistance, and at 1500 ppm, the mercury adsorption efficiency is comparable to or even higher than that at the original temperature under pure nitrogen atmosphere.

[0089] The mercury removal adsorbent prepared in Example 1 was subjected to mercury removal tests at different mercury removal temperatures. XPS analysis was performed on the mercury removal adsorbent before mercury removal (Fresh) and after mercury removal at different temperatures (Used - mercury removal temperature). The results are as follows: Figure 7 As shown, at the same time Figure 7 The corresponding valence distributions are shown in Table 2.

[0090] Table 2. S-morphological distribution

[0091]

[0092] As the temperature increases, the relative content of RSS- increases after the reaction, and R-SO- X(x＝1，2) The relative content of SO4 is constantly decreasing. 2-The continuously increasing content indicates that within the temperature range of -20 to 140℃, RSS- and R-SO play the main roles in mercury removal. X(x＝1，2) However, as the temperature increases, the dominant functional group gradually changes from RSS- to R-SO. X(x＝1，2) Comparing the results of Hg-TPD, it can be found that the Hg atoms bound by RSS- mainly react to form HgS (black), while R-SO X(x＝1，2) The main reaction involves combining Hg atoms to generate HgS(red) and HgSO4. In existing technologies, when the modification temperature is above 600℃, the sulfur dioxide-modified activated coke contains a large number of sulfur atoms or low-valence sulfur-containing functional groups. Moreover, in this application, the modification results are mainly dominated by oxidized sulfur-containing functional groups, resulting in a different reaction product compared to existing mercury removal adsorbents.

[0093] The overall reaction equation is:

[0094] Hg (g) →Hg (ads) (1)

[0095] Lowering the temperature tends to lead to the following equation:

[0096] Hg (ads) +RSS-→HgS(black) (ads) +RS-(2)

[0097] Increasing the temperature tends to lead to the following equation:

[0098] 4R-SO X(x＝1，2) +4Hg (ads) →(4-x)HgS(red) (ads) +xHgSO 4(ads) +2R-R(3)

[0099] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for improving mercury removal efficiency in a power plant, the power plant comprising a boiler (1), a dust collector (2), a cascade cooling tower (3), a low-temperature adsorption tower (4), and a regeneration tower (5) connected in sequence, characterized in that, The deactivated activated carbon in the low-temperature adsorption tower (4) is sent to the regeneration tower (5), and the tail gas of the regeneration tower (5) is sent back to the regeneration tower (5) to form a mixed atmosphere of inert gas and SO2. At the same time, the temperature of the low-temperature adsorption tower (4) is kept at -30℃ to 20℃, and the temperature of the regeneration tower (5) is kept at 300℃ to 600℃. The activated carbon is heated to 300℃ to 600℃ in the mixed atmosphere of inert gas and SO2 to carry out pyrolysis modification. After the reaction is completed, the activated carbon is cooled to obtain a mercury removal adsorbent based on activated carbon modification. This achieves SO2 modification of deactivated activated carbon and the obtained modified activated carbon is sent back to the low-temperature adsorption tower (4).

2. The method as described in claim 1, characterized in that, The volume fraction of SO2 in the regeneration tower (5) is 5-45%.

3. The method as described in claim 1, characterized in that, The volume fraction of SO2 in the regeneration tower (5) is 25% to 35%.

4. The method as described in claim 1, characterized in that, The pyrolysis time is 30 min to 180 min.

5. The method as described in claim 1, characterized in that, The flow rate of the mixed atmosphere is 200 ml / min to 2000 ml / min.

6. The method according to any one of claims 1 to 5, characterized in that, The particle size of the activated coke is 40 mesh to 100 mesh.

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