A renewable Hg 2+ Selective adsorbents, methods of making and using the same

Abstract

The application provides a renewable Hg 2+ The selective adsorbent is mainly composed of graphite phase carbon nitride; a nitrogen-rich carbon precursor is calcined to obtain a block solid, namely graphite phase carbon nitride, which is ground and sieved to obtain the renewable Hg 2+ The selective adsorbent is mainly composed of graphite phase carbon nitride; a nitrogen-rich carbon precursor is calcined to obtain a block solid, namely graphite phase carbon nitride, which is ground and sieved to obtain the renewable Hg 2+ The selective adsorbent is mainly composed of graphite phase carbon nitride; a nitrogen-rich carbon precursor is calcined to obtain a block solid, namely graphite phase carbon nitride, which is ground and sieved to obtain the renewable Hg 0 The selective adsorbent is mainly composed of graphite phase carbon nitride; a nitrogen-rich carbon precursor is calcined to obtain a block solid, namely graphite phase carbon nitride, which is ground and sieved to obtain the renewable Hg 2+ The selective adsorbent is mainly composed of graphite phase carbon nitride; a nitrogen-rich carbon precursor is calcined to obtain a block solid, namely graphite phase carbon nitride, which is ground and sieved to obtain the renewable Hg 2+ The selective adsorbent is mainly composed of graphite phase carbon nitride; a nitrogen-rich carbon precursor is calcined to obtain a block solid, namely graphite phase carbon nitride, which is ground and sieved to obtain the renewable Hg 2+ The selective adsorbent is mainly composed of graphite phase carbon nitride; a nitrogen-rich carbon precursor is calcined to obtain a block solid, namely graphite phase carbon nitride, which is ground and sieved to obtain the renewable Hg 0 The selective adsorbent is mainly composed of graphite phase carbon nitride; a nitrogen-rich carbon precursor is calcined to obtain a block solid, namely graphite phase carbon nitride, which is ground and sieved to obtain the renewable Hg 2+ The selective adsorbent is mainly composed of graphite phase carbon nitride; a nitrogen-rich carbon precursor is calcined to obtain a block solid, namely graphite phase carbon nitride, which is ground and sieved to obtain the renewable Hg

Description

Technical Field

[0001] This invention belongs to the technical field of mercury speciation separation and valence state measurement in industrial mercury-containing flue gas, specifically relating to a renewable Hg... 2+ Selective adsorbents and their preparation methods also involve a renewable Hg. 2+ Application of selective adsorbents in measuring mercury concentration in mercury-containing flue gas. Background Technology

[0002] Mercury, a heavy metal, is a highly toxic pollutant that poses a significant threat to the ecological environment and human health. It exhibits characteristics such as inter-regional migration, bioaccumulation, food chain toxicity transfer, and strong latency. With the rapid pace of industrial development, mercury emissions have exacerbated pollution problems. To control mercury emissions, many countries and regions worldwide have developed mercury monitoring methods and systems.

[0003] Currently, there are three main methods for measuring mercury concentration in mercury-containing flue gas generated during industrial processes: the Ontario Method (OHM), the adsorption tube method (EPA Method 30B), and the continuous emission monitoring system (Hg-CEMS). The Hg-CEMS is a rapidly developing and technologically advanced method for monitoring mercury in flue gas, capable of real-time monitoring of gaseous elemental mercury (Hg) in flue gas. 0 (g), vapor-phase oxidized mercury Hg 2+ (g) and total mercury in the gas phase (Hg) T (g) Concentration. The main components of Hg-CEMS include: a flue gas sample pretreatment module, a mercury valence state separation module, a mercury concentration analysis and detection module, an instrument self-calibration module, an instrument external calibration module, and a real-time data display. The mercury valence state separation module is responsible for separating Hg from the flue gas. 2+ (g) undergoes selective adsorption and reacts with Hg 0 (g) Separation, thereby measuring Hg separately 0 (g) and Hg T The concentration of (g) is then calculated, and the difference between the two is used to obtain Hg. 2+ The concentration of (g). Because the two different forms of mercury have different effects on the ecological environment and human health, the detection of different speciation of mercury is particularly important.

[0004] Currently, conventional mercury detection instruments typically only detect zero-valent mercury. The usual method for speciation detection involves splitting the mercury in the flue gas into two paths: one path selectively adsorbs valence mercury using an adsorbent, allowing only zero-valent mercury to pass through, thus obtaining the zero-valent mercury concentration; the other path reduces valence mercury to zero-valent mercury through high-temperature pyrolysis, yielding the total mercury concentration. The difference between the two paths gives the concentration of valence mercury. This indirect method of obtaining valence mercury concentration is prone to significant errors due to factors such as the reduction efficiency of valence mercury and the adsorption efficiency of zero-valent mercury, making it impossible to accurately measure the content of valence mercury. Existing adsorbents capable of selectively adsorbing valence mercury, including alkaline adsorbents (such as calcium oxide) or alkaline earth metal adsorbents (such as potassium chloride and sodium chloride), while able to adsorb valence mercury, are easily affected by flue gas components. Furthermore, these adsorbents lack regeneration capabilities, becoming ineffective after adsorption saturation, resulting in low adsorption efficiency, poor accuracy, and poor economic benefits.

[0005] Based on this, the present invention provides a suitable method for treating Hg. 2+ (g) Selective adsorption is a key technology and means to achieve accurate monitoring of the concentration of mercury in the valence state separation module of mercury in Hg-CEMS system, and it is also a technical problem that researchers urgently need to solve. Summary of the Invention

[0006] One of the objectives of this invention is to provide a renewable Hg 2+ Selective adsorbents and their preparation methods.

[0007] The second objective of this invention is to provide a renewable Hg 2+ Selective adsorbent.

[0008] The third objective of this invention is to provide a renewable Hg 2+ Application of selective adsorbents in measuring mercury concentration in industrial mercury-containing flue gas.

[0009] One of the technical solutions adopted to achieve the objective of this invention is: to provide a renewable Hg 2+ A method for preparing a selective adsorbent includes the following steps:

[0010] The nitrogen-rich carbon precursor was calcined at a target temperature according to a certain heating rate, and then ground and sieved to obtain Hg. 2+ Selective adsorbent;

[0011] The Hg 2+ Selective adsorbents for targeted adsorption of Hg 2+ ; Hg after inactivation 2+ Selective adsorbents can be regenerated by heat treatment for a certain period of time.

[0012] The renewable Hg provided by this invention 2+ The general approach to preparing selective adsorbents is as follows:

[0013] Nitrogen-rich carbon precursors, after calcination and grinding / sieving, yield carbon nitride. Carbon nitride contains a heptaazine ring structure composed of several atoms, which exhibits physical adsorption for both valence-state and zero-valence mercury, primarily through van der Waals forces. However, due to the valence-state mercury (Hg... 2+ It has a linear triatomic structure, and zero-valent mercury (Hg) 0 Mercury (Hg) is a single atom, and its triatomic structure makes it easier for it to bond with more atoms in carbon nitride, resulting in a strong bonding ability. Zero-valent mercury, being a single atom, has limited bonding with atoms in carbon nitride, leading to a weaker bonding ability. When gaseous elemental mercury (Hg) is present in flue gas... 0 ) and oxidized mercury (Hg) 2+ When Hg is used, because valenced mercury has a stronger binding force with carbon nitride, carbon nitride cannot adsorb zero-valent mercury, thus achieving selective adsorption and speciation detection of mercury. Furthermore, after a certain period of time, Hg... 2+ The adsorption capacity of selective adsorbents will decrease significantly (i.e., deactivate). At this point, a simple heat treatment can disrupt the physical bond between valence mercury and carbon nitride, allowing the valence mercury to escape from the adsorbent and achieve Hg release. 2+ Regeneration of selective adsorbents.

[0014] Furthermore, the nitrogen-rich carbon precursor includes a substance that can produce graphitic carbon nitride through a thermal polymerization reaction. Preferably, the nitrogen-rich carbon precursor includes one or more combinations of urea, melamine, melamine thiocyanate, cyanamide, dicyandiamide, and thiourea.

[0015] Furthermore, the heating rate is 2–5 °C / min. Since the process of the nitrogen-rich precursor transforming into graphitic carbon nitride is stepwise, as the temperature gradually increases, the precursor first continuously condenses into other intermediate products before becoming the final substance. By controlling the heating rate and heating slowly, sufficient time can be ensured for the formation of intermediate products, thereby increasing the content of carbon nitride in the final product.

[0016] Furthermore, the target temperature is 450–600℃, and the calcination time is 2–6 hours. Studies have shown that when the calcination temperature is too low, the desired carbon nitride crystals cannot be synthesized; if the calcination temperature is too high (above 650℃), it will cause the carbon nitride to decompose, affecting the adsorption effect of the adsorbent. Preferably, the target temperature is 500–600℃.

[0017] Furthermore, the calcination treatment is carried out in air or a protective atmosphere; preferably, the calcination treatment is carried out in a nitrogen atmosphere.

[0018] Furthermore, the Hg 2+ The selective adsorbent has a particle size of 40–60 mesh. In this invention, the prepared Hg... 2+ Selective adsorbents have smaller particle sizes, which can increase their contact area with flue gas and thus improve adsorption efficiency.

[0019] Furthermore, the heat treatment temperature is 450–550°C, and the heat treatment time is 0.5–1.5 h. Studies have found that when the heat treatment temperature exceeds 600°C, it leads to the decomposition of carbon nitride; while controlling the heat treatment time to around 1 h allows for the desorption of mercury in all valence states.

[0020] The second technical solution adopted by the present invention to achieve the objective is: to provide a renewable Hg 2+ Selective adsorbent, the Hg 2+ The selective adsorbent is prepared by the preparation method described in one of the objectives of this invention.

[0021] The third technical solution adopted by the present invention is: to provide a renewable Hg according to the second objective of the present invention. 2+ The application of selective adsorbents includes: [the process of] using the Hg [as an adsorbent]. 2+ The adsorbent was selected for use in the Hg-CEMS online measurement system for mercury concentration in industrial mercury-containing flue gas, for the purpose of measuring Hg. 2+ To achieve targeted adsorption of Hg 0 With Hg 2+ Morphological detection.

[0022] Furthermore, the application also includes: inactivating Hg 2+ The selective adsorbent was heat-treated at 450–550℃ for 0.5–1.5 h to obtain regenerated Hg. 2+ Selective adsorbent.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) Compared with the Ontario process (OHM), the renewable Hg provided by this invention... 2+ Selective adsorbents are applied to online measurement systems for mercury concentration in industrial mercury-containing flue gas (Hg-CEMS), enabling online monitoring of mercury in flue gas. The operation is simple, with minimal human-introduced errors, and the post-processing and analysis are straightforward, making it more suitable for widespread application.

[0025] (2) The renewable Hg provided by the present invention 2+This selective adsorbent possesses a strong adsorption capacity for oxidized mercury, enabling the measurement of mercury in different speciations. Simultaneously, it adsorbs little or no SO2, HCl, and other flue gas components, making it adaptable to complex flue gas conditions. Furthermore, this adsorbent exhibits excellent thermal regeneration performance, allowing for continuous long-term operation, thus possessing broader industrial application prospects and commercial value. Attached Figure Description

[0026] Figure 1 The renewable Hg obtained in Examples 1 and 2 of this invention 2+ Selective adsorbents for Hg 0 Experimental results regarding adsorption;

[0027] Figure 2 The renewable Hg obtained in Examples 1 and 2 of this invention 2+ Selective adsorbents for Hg 2+ Adsorption capacity test results;

[0028] Figure 3 The renewable Hg obtained in Example 1 of this invention 2+ Fresh, deactivated, and regenerated samples of selective adsorbents for Hg 2+ A comparison chart of adsorption capacities. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0031] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0032] The main raw materials and parameters involved in the various embodiments of the present invention are shown in Table 1 below.

[0033] Table 1

[0034]

[0035] Example 1

[0036] (1) Weigh 10g of melamine using an analytical balance and place it evenly into a porcelain boat;

[0037] (2) Place the above sample in a muffle furnace and slowly heat it to 550°C at a heating rate of 2.3°C / min under a nitrogen atmosphere, and hold it for 3 hours.

[0038] (3) The calcined sample was ground in a mortar and passed through a 40-60 mesh sieve to obtain renewable Hg with a particle size range of 0.25 mm to 0.425 mm. 2+ Selective adsorbent particles.

[0039] Example 2

[0040] (1) Weigh 10g of thiourea using an analytical balance and place it evenly into a porcelain boat;

[0041] (2) Place the above sample in a muffle furnace and slowly heat it to 550°C at a heating rate of 2.3°C / min under a nitrogen atmosphere, and hold it for 3 hours.

[0042] (3) The calcined sample was ground in a mortar and passed through a 40-60 mesh sieve to obtain renewable Hg with a particle size range of 0.25 mm to 0.425 mm. 2+ Selective adsorbent particles.

[0043] Example 3

[0044] (1) Weigh 10g of urea using an analytical balance and place it evenly into the porcelain boat;

[0045] (2) Place the above sample in a muffle furnace and slowly heat it to 600°C at a heating rate of 5°C / min under a nitrogen atmosphere, and hold it for 2 hours.

[0046] (3) The calcined sample was ground in a mortar and passed through a 40-60 mesh sieve to obtain renewable Hg with a particle size range of 0.25 mm to 0.425 mm. 2+ Selective adsorbent particles.

[0047] Example 4

[0048] (1) Weigh 10g of melamine using an analytical balance and place it evenly into a porcelain boat;

[0049] (2) Place the above sample in a muffle furnace and slowly heat it to 500°C at a heating rate of 2.5°C / min under a nitrogen atmosphere, and hold it at that temperature for 4 hours.

[0050] (3) The calcined sample was ground in a mortar and passed through a 40-60 mesh sieve to obtain renewable Hg with a particle size range of 0.25 mm to 0.425 mm. 2+ Selective adsorbent particles.

[0051] Example 5

[0052] (1) Weigh 10g of cyanamide using an analytical balance and place it evenly into a porcelain boat;

[0053] (2) Place the above sample in a muffle furnace and slowly heat it to 500°C at a heating rate of 4°C / min under a nitrogen atmosphere, and keep it at that temperature for 2 hours.

[0054] (3) The calcined sample was ground in a mortar and passed through a 40-60 mesh sieve to obtain renewable Hg with a particle size range of 0.25 mm to 0.425 mm. 2+ Selective adsorbent particles.

[0055] Example 6

[0056] (1) Weigh 10g of dicyandiamide using an analytical balance and place it evenly into a porcelain boat;

[0057] (2) Place the above sample in a muffle furnace and slowly heat it to 550°C at a heating rate of 3°C / min under a nitrogen atmosphere, and hold it for 6 hours.

[0058] (3) The calcined sample was ground in a mortar and passed through a 40-60 mesh sieve to obtain renewable Hg with a particle size range of 0.25 mm to 0.425 mm. 2+ Selective adsorbent particles.

[0059] Application Example 1

[0060] The renewable Hg obtained in Examples 1 and 2 2+ The selective adsorbent was tested on a fixed-bed adsorption experimental platform to verify its Hg content. 0 Adsorption capacity.

[0061] like Figure 1 As shown, two types of renewable Hg 2+ Hg of selective adsorbents 0 Adsorption experiment results. Inlet mercury concentration was 70 ± 2 μg / m³. 3 The quartz tube reactor has an inner diameter of 10 mm, an adsorbent dosage of 100 mg, an adsorption temperature of 120 ℃, an adsorption time of 1 min, and a total gas flow rate of 1 L / min.

[0062] from Figure 1 It can be seen that the adsorbents prepared using melamine and thiourea as precursors do not adsorb Hg at all. 0 .

[0063] Application Example 2

[0064] The renewable Hg obtained in Examples 1 and 2 2+ The selective adsorbent was tested on a fixed-bed adsorption experimental platform to verify its Hg content.2+ Adsorption capacity.

[0065] The quartz tube reactor has an inner diameter of 10 mm, uses 100 mg of adsorbent, has an adsorption temperature of 120 °C, a total gas flow rate of 1 L / min, and a HgCl2 concentration of approximately 160 μg / m³. 3 Hg was measured using a two-stage method consistent with EPA 30B sampling. 2+ Adsorption experiment. The first stage is the adsorption stage, with an adsorbent dosage of 100 mg; the second stage is the breakthrough test stage, with the same adsorbent dosage of 100 mg. Hg 2+ The adsorption performance of Hg 2+ Defined by penetration rate, it is expressed as the amount of Hg adsorbed in the second adsorbent. 2+ The ratio of the mass of the adsorbent to the total adsorption mass of the two adsorbent sections. Figure 2 The renewable Hg obtained in Examples 1 and 2 2+ Hg of selective adsorbent under pure N2 atmosphere 2+ Adsorption experiment results. Figure 2 It can be seen that the adsorbent exhibits good Hg performance. 2+ Adsorption capacity, Hg of the adsorbent 2+ The adsorption rate is over 98%.

[0066] Furthermore, under the same experimental conditions described above, the renewable Hg obtained in Examples 3-6 was tested. 2+ Selective adsorbents for Hg 2+ The adsorption capacity was tested, and the results are shown in Table 2 below:

[0067] Table 2

[0068]

[0069] As can be seen from the above table,

[0070] Renewable Hg prepared in Examples 1-6 of this invention 2+ Selective adsorbents for Hg 2+ The selective adsorption efficiencies of all samples were above 98%, and the Hg prepared in Example 3 was also above 98%. 2+ Selective adsorbents exhibit the best adsorption efficiency, reaching 99.3%.

[0071] Application Example 3

[0072] The renewable Hg obtained in Example 1 2+ The selective adsorbent was used in simulated flue gas components (6% O2 + 12% CO2 + 20ppm HCl + 200ppm SO2 + 300ppm NO, HgCl2 concentration approximately 120 μg / m³). 3The inactivation process was performed by heating the inactivated sample in a tube furnace at 450°C for 1 hour, and then verifying its Hg content on a fixed-bed adsorption experimental platform. 2+ Adsorption capacity.

[0073] The quartz tube reactor has an inner diameter of 10 mm, an adsorbent dosage of 100 mg, an adsorption temperature of 120 °C, and a total gas flow rate of 1 L / min. Hg was collected using a two-stage method consistent with that used in 30B sampling. 2+ Adsorption experiment. The first stage is the adsorption stage, with an adsorbent dosage of 100 mg; the second stage is the breakthrough test stage, with the same adsorbent dosage of 100 mg. Hg 2+ The adsorption performance of Hg 2+ Defined by penetration rate, it is expressed as the amount of Hg adsorbed in the second adsorbent. 2+ The ratio of the mass of the adsorbent to the total adsorption mass of the two adsorbent sections. Figure 3 Hg in fresh samples, inactivated samples, and regenerated samples 2+ Adsorption experiment results.

[0074] from Figure 3 It can be seen that the adsorption capacity of the deactivated adsorbent is significantly reduced, only about 7% of that of the fresh adsorbent. The regenerated adsorbent showed good Hg performance. 2+ The adsorption capacity is almost identical to that of fresh samples.

[0075] In summary, this paper proposes a renewable Hg... 2+ The selective adsorbent and its preparation method, compared with the prior art, the Hg of the present invention 2+ The selected adsorbent can be applied to the online measurement system of mercury concentration in industrial mercury-containing flue gas (Hg-CEMS), which enables online monitoring of valence mercury in flue gas. The operation steps are simple, the human-introduced error is small, and the post-processing and analysis are simple, making it suitable for widespread promotion and application.

[0076] The above are merely preferred embodiments of the present invention and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should recognize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. Application of a renewable HgCl2 selective adsorbent, characterized in that, the HgCl2 selective adsorbent is applied to an on-line measurement system Hg-CEMS for mercury concentration in industrial mercury-containing flue gas for directional adsorption of HgCl2; a preparation method of the HgCl2 selective adsorbent comprises: calcining melamine or thiourea at a temperature increasing rate of 2.3 ℃ / min to 450-600 ℃ for 2-6 h, and then grinding and screening to obtain a HgCl2 selective adsorbent with a particle size of 40-60 mesh; the HgCl2 selective adsorbent is carbon nitride with a heptazine ring structure; the application further comprises: placing the deactivated HgCl2 selective adsorbent in heat treatment at 450-550 ℃ for 0.5-1.5 h to obtain a regenerated HgCl2 selective adsorbent.

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