Reagent and method for detecting mercury content in gas
By using sulfite reagent coated with silicon carbide particles, the mercury ions in the flue gas are reduced to atomic mercury, which solves the problem of easy decomposition of stannous chloride in the prior art at high temperatures, and achieves efficient and accurate online mercury ion detection.
Patent Information
- Application Number
- CN202510110297.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-23
- Publication Date
- 2025-04-18
AI Technical Summary
In the quantitative analysis of detecting mercury ions in flue gas, stannous chloride is easy to decompose at high temperatures, resulting in the inability to adapt to the high-temperature flue gas environment, which is difficult to achieve, complex operation, and cannot convert in real time. It consumes time and effort for a single monitoring, and is not suitable for online flue gas total mercury monitoring.
A reagent is provided, including silicon carbide particles and a wall material coated on its surface, including sulfite as a reducing agent for reducing mercury ions in the gas to be tested at a temperature of 180-200°C to atomic mercury.
Through the use of this reagent, mercury ions can be stably reduced to atomic mercury under high temperature environments, real-time detection is achieved, the accuracy and efficiency of detection are improved, and operational complexity and energy consumption are reduced.
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Figure CN119845692A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of detection technology, and in particular relates to a reagent and a method for detecting mercury content in gas. Background Art
[0002] With the increasing demand for energy and the rising oil prices due to the global economic development, coal has become an important resource to ease the global energy shortage. When coal is mined, a considerable amount of waste rock and gangue must be removed. The sulfide in the gangue slowly oxidizes and generates heat. If the heat dissipation is poor or the air is not isolated, it will spontaneously combust and release harmful substances such as carbon dioxide and sulfur dioxide. Coal mines may be associated with heavy metal elements such as mercury. As they burn, heavy metal elements such as mercury will enter the flue gas after combustion in several forms. Although people will treat the flue gas, trace amounts of mercury will still remain. These mercury elements mainly exist in the following two forms: atomic mercury and mercury ions (also known as ionic mercury). The quantitative analysis of atomic mercury can adopt the more mature spectral analysis method, and can achieve online real-time detection. However, the quantitative analysis of mercury ions generally relies on laboratory analysis, through on-site sampling, and then using wet chemical methods to reduce mercury ions to atomic mercury, and then perform spectral analysis. However, the wet chemical reduction method uses a saturated solution of stannous chloride to treat the gas, and stannous chloride is easily decomposed at high temperatures, making it unable to adapt to the high-temperature flue gas environment. The flue gas must be cooled before reacting with stannous chloride, which is difficult to implement and complicated to operate. It cannot be converted in real time, and single monitoring is time-consuming and labor-intensive, making it unsuitable for online flue gas total mercury monitoring.
[0003] There are also methods that use high-temperature cracking to quantitatively analyze mercury ions. However, mercury ions will crack into mercury atoms at 900°C. When the flue gas is heated to 900°C, mercury ions will be thermally cracked into mercury atoms. This method is difficult to implement, and high temperature will increase the danger level on site and increase energy consumption; furthermore, sulfur dioxide in flue gas has similar absorption peaks to mercury atoms, and additional sulfur dioxide absorption devices need to be added to reduce interference in the later detection of mercury atom content; in addition, mercury atoms generated after mercury ion cracking react with oxygen in the air under heating conditions to generate mercuric oxide, which will crack into mercury and oxygen at above 500°C, but when cooled to 300-350°C, mercury atoms are easily combined with oxygen to generate mercuric oxide, affecting the accuracy of detection. Summary of the invention
[0004] In view of this, the present invention provides a reagent and a method for detecting mercury content in gas to solve the above-mentioned problem that stannous chloride is easily decomposed at high temperature in the quantitative analysis of mercury ions in flue gas by wet chemical method, resulting in its inability to adapt to the high-temperature flue gas environment, great difficulty in implementation, complex operation, and inability to be converted in real time. Single monitoring is time-consuming and labor-intensive, and is not suitable for online flue gas total mercury monitoring; the mercury ions present in the quantitative analysis of mercury ions by high-temperature cracking method will be cracked into mercury atoms at 900°C, which is difficult to implement, and high temperature will increase the degree of danger on site and increase energy consumption. Sulfur dioxide in flue gas has similar absorption peaks to mercury atoms, and an additional device for absorbing sulfur dioxide is required. Mercury atoms generated after the cracking of mercury ions react with oxygen in the air under heating conditions to generate mercuric oxide, which will be cracked into mercury and oxygen at above 500°C, but when cooled to 300-350°C, mercury atoms are easily combined with oxygen again to generate mercuric oxide, affecting the accuracy of detection and other technical problems.
[0005] To achieve the above solution, the technical solution of the present invention is as follows:
[0006] In a first aspect, the present application provides a reagent, which includes silicon carbide particles and a wall material coated on the surface of the silicon carbide particles, the wall material includes a reducing agent, and the reducing agent includes sulfite.
[0007] Optionally, the reagent is used to reduce mercury ions in the gas to be tested at a temperature of 180-200° C. to atomic mercury.
[0008] Optionally, the diameter of the silicon carbide particles is 2-4 mm, preferably 2.5-3.5 mm.
[0009] Optionally, the sulfite is selected from at least one of lithium sulfite, sodium sulfite, potassium sulfite and ferrous sulfite.
[0010] Optionally, the wall material further includes an adhesive.
[0011] Optionally, the binder is selected from calcium carbonate.
[0012] Illustratively, the method for preparing the reagent as described above comprises the following steps:
[0013] The silicon carbide is added to a saturated solution of sulfite and dried to obtain the reagent.
[0014] Optionally, the molar ratio of the sulfite to the silicon carbide is 1-2:2-3, preferably 1.5-2:2-3.
[0015] Optionally, the drying temperature is 350-450°C, preferably 380-420°C.
[0016] When the wall material further contains the adhesive, the preparation method of the reagent comprises the following steps:
[0017] The binder and the silicon carbide are added to a saturated solution of sulfite and dried to obtain the reagent.
[0018] Optionally, the molar ratio of the sulfite, the binder and the silicon carbide is 1-2:1-2:2-3, preferably 1.5-2:1.5-2:2-3.
[0019] In a second aspect, the present application also provides a method for detecting mercury content in gas, the detection method comprising the following steps:
[0020] The gas to be tested is brought into contact with the reagent as described above to undergo an oxidation-reduction reaction to generate mercury atoms, wherein the gas to be tested contains mercury ions;
[0021] Detecting the mercury atomic content in the gas to be tested after the redox reaction;
[0022] The mercury atomic content is determined as the mercury content.
[0023] Optionally, the temperature of the gas to be measured is 180-200°C.
[0024] Optionally, the gas to be tested also contains acidic gas.
[0025] It should be noted that, in the present application, the acidic gas includes gaseous sulfur dioxide and / or gaseous hydrogen chloride.
[0026] Optionally, the gas to be tested is flue gas.
[0027] Optionally, the temperature of the redox reaction is 200-300°C.
[0028] In the redox reaction process, the mercury ions in the gas to be tested react with the sulfite in the reagent to generate mercury atoms and sulfates, and the calcium carbonate in the reagent reacts with the gaseous sulfur dioxide and other substances in the gas to be tested to generate calcium sulfite, and the calcium sulfite then reacts with the mercury ions in the gas to be tested to generate mercury atoms and sulfates. The reaction equation is as follows:
[0029]
[0030] In the present application, cold atomic absorption method, fluorescence method and the like can be used to detect the mercury atomic content in the gas to be tested.
[0031] As described above, the reagent and the method for detecting mercury content in gas of the present invention have the following beneficial effects:
[0032] The present application utilizes silicon carbide particles with strong chemical stability under high temperature conditions and irregular external shapes of the particles, which are conducive to the passage of airflow and can enable the mercury ions in the gas to be tested to fully contact the wall material attached to the surface of the silicon carbide particles; the sulfite in liquid state at a temperature of 200-300°C can improve the reduction efficiency of mercury ions; under the joint action of the above substances, the mercury ions in the gas to be tested are reduced to atomic mercury, and the reagent is in an environment of 200-300°C, which can prevent the condensation of water vapor in the sample gas and affect the detection, and can also prevent the mercury atoms from combining with oxygen again, thereby improving the accuracy of the detection.
[0033] In the present application, calcium carbonate is used as a binder to make sulfite adhere to the surface of silicon carbide particles. At the same time, calcium carbonate can react with acidic gases such as sulfur dioxide and hydrogen chloride in the gas to be tested to prevent atomic mercury from reacting with the acidic gas to generate mercury ions again. The generated calcium sulfite and other substances can be used as a supplement to sulfite, and can reduce mercury ions to atomic mercury, thereby extending the service life of the reagent and reducing the content of sulfur dioxide in the gas to be tested, thereby avoiding interference caused by sulfur dioxide and improving detection accuracy. In addition, the adhesion performance of calcium carbonate prevents liquid sulfite from detaching from the surface of the silicon carbide particles.
[0034] After the gas to be tested (containing mercury ions) is treated with the reagent of the present application, the mercury content in the gas to be tested is detected, which is not easily interfered by substances such as gaseous sulfur dioxide, and has high accuracy, high precision and strong stability.
[0035] The reagent of the present application is used to treat the gas to be tested (containing mercury ions), and the reaction efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Figure 1 Schematic diagram of the structure of the reagent of this application. DETAILED DESCRIPTION
[0037] The present invention is further described below through specific examples, but it should be pointed out that the specific material ratios, process conditions and results described in the embodiments of the present invention are only used to illustrate the present invention and cannot be used to limit the scope of protection of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.
[0038] like Figure 1 As shown, an embodiment of the present application provides a reagent for reducing mercury ions in a gas to be tested at a temperature of 180-200° C. to atomic mercury, the reagent comprising silicon carbide particles (i.e., silicon carbide carriers) having a diameter of 2-4 mm and a wall material coated on the surface of the silicon carbide particles, the wall material comprising a reducing agent and a binder, the reducing agent comprising a sulfite, the sulfite being selected from at least one of lithium sulfite, sodium sulfite, potassium sulfite and ferrous sulfite, and the binder being selected from calcium carbonate;
[0039] The present application utilizes silicon carbide which has strong chemical stability at high temperature and irregular particle external shape, which is conducive to the passage of airflow and enables mercury ions in the high-temperature sample gas (i.e., the gas to be detected) to fully contact the wall material attached to the surface of the silicon carbide particles;
[0040] Calcium carbonate as a binder can make sulfite adhere to the surface of silicon carbide particles. At the same time, calcium carbonate can react with acidic gases such as gaseous sulfur dioxide and gaseous hydrogen chloride in the sample gas to prevent atomic mercury (i.e., mercury atoms) from reacting with acidic gases to generate mercury ions again. The generated calcium sulfite and other substances can be used as a supplement to sulfite to reduce mercury ions to atomic mercury, thereby extending the service life of the reagent and reducing the content of sulfur dioxide in the sample gas to avoid interference caused by sulfur dioxide, thereby improving the detection accuracy. Sulfite in liquid state at a temperature of 200-300°C can improve the reduction efficiency of mercury ions, and due to the adhesion of calcium carbonate, liquid sulfite will not separate from the surface of the reducing agent. Under the joint action of the above substances, the mercury ions in the test are reduced to atomic mercury, and the reagent is in an environment of 200-300°C to react with other substances to be tested, which can prevent water vapor in the sample gas from condensing and affecting the detection, and can also prevent mercury atoms from combining with oxygen again, thereby improving the accuracy of the detection.
[0041] Another embodiment of the present application further provides a method for detecting mercury content in gas, wherein the gas to be detected contains mercury ions and acidic gas, the acidic gas includes gaseous sulfur dioxide and / or gaseous hydrogen chloride, and the gas to be detected is flue gas, and the detection method comprises the following steps:
[0042] The gas to be tested at a temperature of 180-200° C. is brought into contact with the reagent as described above to undergo an oxidation-reduction reaction at a temperature of 200-300° C. to generate mercury atoms;
[0043] Detecting the mercury atomic content in the gas to be tested after the redox reaction;
[0044] The mercury atomic content was determined as the mercury content.
[0045] The present invention is described in detail below by specific examples. It should also be understood that the following examples are only used to specifically illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values exemplified below.
[0046] It should be understood that in the following embodiments, only sodium sulfite is listed as the specific case of the sulfite, and those skilled in the art may also select other sulfites besides sodium sulfite, such as at least one of lithium sulfite, potassium sulfite, ferric sulfite, or a mixture of sodium sulfite and at least one of lithium sulfite, potassium sulfite, and ferric sulfite.
[0047] Example 1
[0048] A reagent for detecting mercury content in gas is prepared by using the following raw materials according to the following steps:
[0049] Calcium carbonate and silicon carbide (3 mm in diameter) were added to a saturated solution of sodium sulfite, with the molar ratio of sulfite, calcium carbonate and silicon carbide being 1:1:2;
[0050] The product was dried at 450°C to obtain a reagent.
[0051] Example 2
[0052] A reagent for detecting mercury content in gas is prepared by using the following raw materials according to the following steps:
[0053] Calcium carbonate and silicon carbide (3 mm in diameter) were added to a saturated solution of sodium sulfite, with a molar ratio of sulfite, calcium carbonate and silicon carbide of 1:2:2;
[0054] The product was dried at 350°C to obtain a reagent.
[0055] Comparative Example 1
[0056] The difference between this comparative example and Example 1 is that the diameter of the silicon carbide is 5 mm.
[0057] Comparative Example 2
[0058] The difference between this comparative example and Example 1 is that the diameter of the silicon carbide is 1 mm.
[0059] Comparative Example 3
[0060] The difference between this comparative example and Example 1 is that zeolite (with a diameter of 3 mm) is used instead of silicon carbide.
[0061] Comparative Example 4
[0062] The difference between this comparative example and Example 1 is that 4A molecular sieve (with a diameter of 3 mm) is used instead of silicon carbide.
[0063] Comparative Example 5
[0064] The difference between this comparative example and Example 1 is that potassium sulfite is used instead of sodium sulfite.
[0065] Test 1
[0066] The reagents prepared in Examples 1-2 and Comparative Examples 1-5 were used to detect the mercury content in the gas, and the specific method was as follows:
[0067] Using the HovaCAL gas-liquid mixing gas distributor, nitrogen was mixed with the evaporated mercuric chloride solution (specifically, a solution containing 1 wt% hydrochloric acid and 100 ppm mercuric chloride) to obtain a solution containing 75 ug / m 3 The standard gas of mercury ions is controlled at 180°C to prevent condensation of the solution;
[0068] The reagent sample is loaded into the reaction chamber, the temperature in the reaction chamber is set to 250°C, and the standard gas is sent into the reaction chamber to perform an oxidation-reduction reaction. During this process, the mercury ions in the standard gas undergo an oxidation-reduction reaction with the sodium sulfite in the reagent to generate mercury atoms and sodium sulfate, and the calcium carbonate in the reagent reacts with the gaseous sulfur dioxide and other substances in the standard gas to generate calcium sulfite, and the calcium sulfite then reacts with the mercury ions in the standard gas to generate mercury atoms and sulfate. The reaction equation is as follows:
[0069]
[0070] Then, the standard gas is discharged from the reaction chamber under the pressure difference;
[0071] The mercury atomic content in the standard gas discharged from the reaction chamber was detected by cold atomic absorption method, and the relative error between the calculated and theoretical values was shown in Table 1.
[0072] The above standard gas was treated and the mercury content was tested by using each reagent 6 times (including the above test), and the standard error and relative standard deviation between the repeated test results of each reagent were calculated. The results are shown in Table 1.
[0073] Table 1 Relative error, standard error and relative standard deviation test results
[0074] Group Relative error Standard error Relative standard deviation Example 1 4.07％ 0.153894 0.21％ Example 2 4.06％ 0.159185 0.22％ Comparative Example 1 10.70％ 0.25782 0.38％ Comparative Example 2 3.46％ 0.192302 0.27％ Comparative Example 3 51.45％ 4.80368 13.19％ Comparative Example 4 59.59％ 4.372094 14.42％ Comparative Example 5 4.38％ 0.150885 0.21％
[0075] As shown in Table 1, the relative error of Example 1-2 is less than 4.10%, the standard error is less than 0.16, and the relative standard deviation is less than 0.22%. The results show that the reagent of the present application is used to detect the mercury content in the gas with high accuracy, high precision and strong stability.
[0076] As shown in Table 1, compared with Comparative Example 1 (using 5 mm silicon carbide) and Comparative Example 2 (using 1 mm silicon carbide), the indicators of Comparative Example 1 are slightly worse than those of Example 1, and there are no significant differences between the indicators of Comparative Example 2 and those of Example 1. This result shows that the present application selects a specific size carrier (specifically silicon carbide particles), and when the particle size is 5 mm, the gas is not in sufficient contact with the reducing agent due to the large particles, and the reduction efficiency is slightly poor. When the particle size is 1 mm, its reduction efficiency is not significantly different from that of Example 1.
[0077] As can be seen from Table 1, compared with Comparative Example 3 (using zeolite instead of silicon carbide) and Comparative Example 4 (using molecular sieve instead of silicon carbide), the relative error of Example 1 is smaller, indicating that its reduction efficiency is higher, and indicators such as the standard deviation and relative standard deviation of multiple measurements are also significantly better. This is because acidic gases such as HCL can react chemically with zeolite and molecular sieves, affecting their stability. As the use time increases, the reduction efficiency becomes worse and worse. And in the actual measurement process, the sample gas usually contains acidic gases such as hydrogen chloride, which will affect the reduction efficiency. The result shows that the present application can improve the high temperature stability of the carrier by selecting a specific carrier (specifically silicon carbide particles with a diameter of less than 5 mm), and avoid the reaction of the carrier with acidic substances such as HCL in the gas, thereby affecting the accuracy of the detection.
[0078] As can be seen from Table 1, compared with Comparative Example 5 (using potassium sulfite instead of sodium sulfite), Example 1 has no significant difference. This result shows that the present application can effectively reduce mercury ions in the gas and achieve accurate measurement of mercury atoms by selecting a reducing agent (specifically sulfite).
[0079] Test 2
[0080] The rising response time and falling response time of the reagents prepared in Example 1 and Comparative Examples 1-2 were respectively detected, and the specific steps were as follows:
[0081] The time from the introduction of the above standard gas to the time when the detection value reaches 90% of the theoretical value is the rising response time;
[0082] The above-mentioned standard gas is introduced, and when the system detection value is stable (that is, two adjacent detection values are the same), the introduction of standard gas is stopped and replaced with nitrogen. The time until the detection value drops to 10% of the theoretical value is the decline response time. The results are shown in Table 2.
[0083] Table 2 Response time test results
[0084] Group Rise response time Falling response time Example 1 160s 152s Comparative Example 1 143s 145s Comparative Example 2 201s 199s
[0085] As can be seen from Table 2, the response time of Comparative Example 1 is the shortest, followed by Example 1, and Comparative Example 2 is the worst. This result shows that the size of silicon carbide particles is related to the response speed of the system. Combining the results of Table 1 and Table 2, it can be seen that Comparative Example 1 has the fastest response, but the relative error is large. There is no obvious difference in the relative error between Example 1 and Comparative Example 2, but the response speed of Example 1 is better than that of Comparative Example 2, which shows that Example 1 can effectively balance the response time and reduction efficiency.
[0086] Test 3
[0087] Use a gas mixer to mix gaseous sulfur dioxide into the standard gas in test 1 so that the concentration of sulfur dioxide in the mixed gas is 200 mg / m 3 , in order to simulate the upper limit of sulfur dioxide concentration in flue gas emissions stipulated by the state.
[0088] The reagent prepared in Example 1 was tested again in the same manner as in Test 1 except that the standard gas was replaced by the mixed gas, and the results were compared with those of Test 1. The results are shown in Table 3.
[0089] Table 3 Test results of sulfur dioxide impact
[0090] Group Relative error Standard error Relative standard deviation Example 1 (Test 1) 4.07％ 0.153894 0.21％ Example 1 (Test 3) 4.52％ 0.162345 0.22％
[0091] It can be seen from Table 3 that when sulfur dioxide exists in the gas to be measured, the relative error of the measurement result is within 0.5%, and its influence is small. This result shows that when the reagent of the present application is used to detect the mercury content in the gas, the interference effect of sulfur dioxide in the gas is small.
[0092] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.
Claims
1. A reagent, characterized in that The reagent comprises silicon carbide particles and a wall material coated on the surface of the silicon carbide particles, the wall material comprises a reducing agent, and the reducing agent comprises sulfite.
2. The reagent according to claim 1, characterized in that The reagent is used to reduce mercury ions in the gas to be tested at a temperature of 180-200° C. to atomic mercury.
3. The reagent according to claim 1, characterized in that The diameter of the silicon carbide particles is 2-4 mm.
4. The reagent according to claim 1, characterized in that The sulfite is selected from at least one of lithium sulfite, sodium sulfite, potassium sulfite and ferrous sulfite.
5. The reagent according to claim 1, characterized in that The wall material further comprises an adhesive.
6. The reagent according to claim 5, characterized in that The binder is selected from calcium carbonate.
7. A method for detecting mercury content in gas, characterized in that: The detection method comprises the following steps: Contacting the gas to be tested with the reagent according to any one of claims 1 to 6 to perform an oxidation-reduction reaction to generate mercury atoms, wherein the gas to be tested contains mercury ions; Detecting the mercury atomic content in the gas to be tested after the redox reaction; The mercury atomic content is determined as the mercury content.
8. The detection method according to claim 7, wherein the temperature of the gas to be detected is 180-200°C; And / or, the gas to be tested also contains acidic gas.
9. The detection method according to claim 8, wherein the gas to be detected is flue gas.
10. The detection method according to claim 7, wherein the temperature of the redox reaction is 200-300°C.