Method for detecting chlorine ion content in blast furnace gas and gas sampling device

Abstract

The invention relates to a method for detecting the content of chloride ions in blast furnace gas and a gas sampling device, which comprises the following steps: firstly, completely absorbing chlorine in a fixed volume of gas and converting the chlorine into chloride ions, and simultaneously absorbing interferent hydrogen sulfide and a small amount of carbon dioxide; all sulfur ions with strong reducibility and interference are oxidized into non-interference sulfate ions, and carbonate ions are removed at the same time; and calculating the mass of chloride ions in the absorption liquid according to the titration results of the absorption liquid and the blank sample. And finally, calculating the chlorine content in the blast furnace gas according to the collected gas volume and the measured chlorine ion mass. According to the invention, interference of other ions in the absorption liquid on subsequent titration results is effectively avoided, and the detection accuracy is ensured.

Description

Technical Field

[0001] This invention relates to a method for detecting chloride ion content in blast furnace gas and a gas sampling device, belonging to the field of chloride ion determination technology in gas. Background Technology

[0002] In the process of blast furnace gas purification and utilization, hydrogen chloride (HCl) and ammonium chloride (HCl) are used. Chlorides such as nitrogen oxides (NOx) are key factors causing equipment corrosion and product quality degradation. These substances precipitate out during gas transportation and cooling, forming highly corrosive solutions that seriously endanger the safe and stable operation of systems such as gas pipelines, TRT power generation units, and hot blast furnaces.

[0003] Currently, the industry commonly uses solution absorption to determine chloride ion content for risk assessment. This method leverages the water solubility of chloride ions, using alkaline solutions or deionized water to absorb chloride ions from coal gas, followed by titration or ion chromatography for detection. However, if strong alkaline solutions such as sodium hydroxide are used as the absorbent, they will react with the abundant hydrogen sulfide present in the coal gas while absorbing the target chloride. ) and carbon dioxide ( This will trigger a significant competitive response. It reacts with alkaline solution to produce carbonate ions ( ) and bicarbonate ( ), It then transforms into sulfide ions ( These reaction products severely interfere with subsequent chloride ion determination. Clearly, the alkaline solution absorption method described above lacks an effective and standardized procedure for removing interfering substances. Current methods for removing interfering substances have several drawbacks: the manual heating oxidation method is difficult to control precisely, leading to incomplete removal of interfering substances; the solution pH adjustment process is crude, directly affecting the accuracy of titration endpoint determination; furthermore, while ion-selective electrode methods have some application, they require repeated pH adjustments and electrode cleaning to a stable state, making the process cumbersome and lacking stability, resulting in detection results that do not accurately reflect the total chloride content.

[0004] For example, application CN120294241A discloses a method for determining the chloride ion content in coal gas. This method involves absorbing chloride ions from the coal gas with ultrapure water, then using Mohr's titration method to determine the chloride ion content in the solution, and finally calculating the chloride ion content in the coal gas. However, this method has two drawbacks: firstly, the absorption efficiency of ultrapure water for chloride ion absorption is low, leading to lower actual test results; secondly, the absorption solution is not pretreated before titration, resulting in problems during sampling. and It will also dissolve in water and interfere with the titration results during the detection process.

[0005] Therefore, there is a need for a complete analytical method that can achieve absorption and thorough impurity removal to improve the accuracy and precision of chlorine concentration detection in blast furnace gas, and which can be operated with the conditions of a conventional chemical analysis laboratory. Summary of the Invention

[0006] This invention provides a method for detecting chloride ion content in blast furnace gas and a gas sampling device, which solves the problems of instability and reliance on expensive detection equipment in current methods for detecting chloride ions in gas. It can objectively and accurately determine the chloride ion content in gas and is suitable for testing gas in conventional chemical laboratories at production sites.

[0007] The technical solution adopted by this invention to solve its technical problem is: A method for detecting chloride ion content in blast furnace gas, comprising the following steps: Step S1, will A series of absorption bottles Integer and ≥2, one end of the gas sampling tube extends into the first absorption bottle, and the other end of the gas sampling tube is connected to the gas pipeline through the gas sampling port. Each absorption bottle is connected to a drying bottle, and a gas flow meter is installed on the connecting pipe at the outlet of the drying bottle; Step S2, in the first to the second The first absorption bottle contains the prepared sodium carbonate solution. Each absorption bottle contains silver nitrate solution; Step S3: Blast furnace gas is introduced into the absorption bottle for sampling, and the sampling start time is recorded. , No. Sampling time per absorption bottle and blast furnace gas flow rate ; Step S4, after sampling is completed, All the sodium carbonate solution in the absorption bottle was transferred to the conical flask. At the same time, the absorption bottle after the sodium carbonate solution was transferred was washed multiple times with deionized water, and the washed deionized water was then transferred to the conical flask. Step S5: Acidify the solution in the conical flask as a pretreatment. ， Heat the conical flask until the pH of the solution drops to neutral or weakly acidic, continue heating for the preset time, and then cool to room temperature. Step S6: Add hydrogen peroxide to the solution after acidification pretreatment to carry out oxidation treatment until no more bubbles are generated in the solution, thus completing the oxidation process. Step S7: Continue heating the conical flask for the preset time until all excess oxidant is decomposed, and then cool the solution to room temperature. Step S8: Add dilute nitric acid solution dropwise into the conical flask to adjust the pH of the solution to between 7 and 10; Step S9: Perform absorption titration on the solution after pH adjustment in step S8. Add potassium chromate solution as an indicator to the solution, and titrate with a silver nitrate standard titrant of known precise concentration. Record the volume of silver nitrate standard titrant consumed at the titration endpoint. ; Step S10: Perform a blank titration on the solution after pH adjustment in step S8. Add potassium chromate solution as an indicator, add calcium carbonate powder until the solution becomes turbid, and titrate with a silver nitrate standard titrant of known precise concentration. Record the volume of silver nitrate standard titrant consumed at the titration endpoint. ; Step S11, calculate the mass of chloride ions, using the following formula: (1) In formula (1), This represents the concentration of the silver nitrate standard titrant, in mol / L. The molar mass of chlorine is 35.45 g / mol. Step S12: Based on the data collected in step S3 and combined with the chloride ion mass calculated in step S11, the chlorine content in the blast furnace gas is finally calculated. The formula for calculating the chlorine content is as follows: (2) In formula (2), This refers to the chlorine content in blast furnace gas, expressed in mg / m³. The mass of chloride ions calculated using formula (1) is expressed in mg. This refers to the blast furnace gas flow rate, expressed in L / min. This is the start time of sampling, in minutes. For the first Sampling time per absorption bottle, in minutes; Furthermore, in step S2, the concentration of the prepared sodium carbonate solution is 0.05 mol / L, and the concentration of the silver nitrate solution is 0.005 mol / L; Furthermore, in step S5, the step of acidifying the solution in the conical flask is as follows: ， Step S51: Add dilute nitric acid or dilute sulfuric acid dropwise into the conical flask; Step S52: Add phenolphthalein as an indicator to the conical flask, and gently shake the conical flask until the pH of the solution drops to between 6 and 7. Step S53: Place the conical flask on a hot plate or water bath and heat it. Set the heating temperature to 60~80℃ and continue heating for 10~15 minutes. Then cool it to room temperature. Furthermore, in step S6, 30% hydrogen peroxide is slowly added dropwise to the solution after acidification pretreatment, and gently stirred or shaken. During the addition of hydrogen peroxide, bubbles are generated in the solution. The addition continues until no more bubbles are generated in the solution. Furthermore, in step S7, the conical flask is placed on a hot plate or water bath for heating, the heating temperature is set to 60~80℃, and the heating is continued for 10~15 minutes, and then cooled to room temperature; Furthermore, in step S9, 1 mL of 50 g / L potassium chromate is added to the solution after the pH value was adjusted in step S8. Potassium chromate is used as an indicator, and the solution is yellow. Titration is performed using silver nitrate standard titrant of precise concentration. The titration is continued while the conical flask is shaken continuously until a stable light reddish-brown precipitate appears in the solution and the light reddish-brown color no longer fades. This is the titration endpoint of the absorption solution. Furthermore, in step S10, 1 mL of 50 g / L potassium chromate is added to the solution after adjusting the pH value in step S8, and calcium carbonate powder is added until the solution becomes turbid. Titration is performed with silver nitrate standard titrant of known precise concentration. The titration is continued while shaking the conical flask until a light reddish-brown precipitate appears in the solution and the light reddish-brown color no longer fades. This is the titration endpoint of the blank sample titration. A gas sampling device for the method of detecting chloride ion content in blast furnace gas includes several absorption bottles, each containing a porous glass plate. The absorption bottles are connected in series, and adjacent bottles are connected by connecting pipes. One end of a gas sampling tube extends into the first absorption bottle, and the other end extends into the gas pipeline through a gas sampling port. A sampling valve is installed on the gas sampling tube located between the gas sampling port and the first absorption bottle. The absorption bottle at the end is connected to the drying bottle via a connecting pipe, and a gas flow meter is installed on the connecting pipe at the outlet of the drying bottle; The last absorption bottle is filled with silver nitrate solution, and the remaining absorption bottles are filled with sodium carbonate solution, wherein the concentration of sodium carbonate solution is 0.05 mol / L and the concentration of silver nitrate solution is 0.005 mol / L.

[0008] By employing the above technical solutions, the present invention has the following beneficial effects compared to the prior art: 1. The method for detecting chloride ion content in blast furnace gas provided by this invention fully considers the subsequent design to improve the accuracy of chloride ion determination. Sodium carbonate solution is selected for absorption during the sampling and absorption stage. Sodium carbonate solution is a strong base-weak acid salt, and becomes alkaline after dissolving in water, thus effectively absorbing acidic substances in blast furnace gas and converting both chloride and sulfur into ionic form. , , It exists in the absorption liquid, as well as a small amount of dissolved carbonate ions, which avoids the introduction of other interfering ions and lays a solid foundation for the subsequent thorough removal of interfering substances. 2. The method for detecting chloride ion content in blast furnace gas provided by the present invention innovatively designs a sample pretreatment process, which oxidizes all sulfur ions with strong reducing and interfering properties into non-interfering sulfate ions. Combined with the heating step, it accurately removes residual carbonate ions and excess oxidant, creating a pure environment for subsequent determination and improving the accuracy of subsequent determination. 3. The method for detecting chloride ion content in blast furnace gas provided by this invention, based on the design of sampling and absorption and sample pretreatment procedures, adopts silver nitrate titration for quantification. The operation process is clear, the whole method has simple equipment requirements, and is reproducible, which greatly reduces the implementation cost and technical threshold. Attached Figure Description

[0009] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0010] Figure 1 This is a schematic diagram of the gas sampling and testing process provided by the present invention; Figure 2 This is a schematic diagram of the gas sampling device provided by the present invention.

[0011] In the diagram: 1 is the gas pipeline, 2 is the gas sampling port, 3 is the gas sampling pipe, 4 is the sampling valve, 5 is the absorption bottle, 6 is the drying bottle, and 7 is the gas flow meter. Detailed Implementation

[0012] The invention will now be described in further detail with reference to the accompanying drawings.

[0013] As described in the background section, traditional techniques use strong alkaline solutions as absorbents. While absorbing the target chloride, these solutions also generate numerous reactants that interfere with subsequent chloride ion determination. Furthermore, current interference removal processes lack effectiveness and standardization, resulting in cumbersome and unstable chloride ion analysis methods, thus failing to accurately reflect the total chloride content.

[0014] To address the aforementioned problems, this application provides a method for detecting chloride ion content in blast furnace gas, such as... Figure 1 As shown, the entire process mainly consists of three parts: sampling, sample pretreatment, and titration detection. This complete detection process—absorption, pretreatment, and then determination—improves the accuracy and precision of chlorine concentration detection in blast furnace gas, and the entire detection method is feasible under the conditions of a conventional chemical analysis laboratory.

[0015] The specific steps involved in the detection method are as follows: Step S1, will A series of absorption bottles Integer and ≥2, one end of the gas sampling tube extends into the first absorption bottle, and the other end of the gas sampling tube is connected to the gas pipeline through gas sampling port 2. Each absorption bottle is connected to a drying bottle, and a gas flow meter is installed on the connecting pipe at the outlet of the drying bottle; Step S2, in the first to the second Each absorption bottle contains a 0.05 mol / L sodium carbonate solution. Each absorption bottle contains a 0.005 mol / L silver nitrate solution, used to detect whether chloride ions have been completely absorbed; Step S3: Blast furnace gas is introduced into the absorption bottle for sampling, and the sampling start time is recorded. , No. Sampling time per absorption bottle and blast furnace gas flow rate ; The purpose of steps S1-S3 is to remove hydrogen chloride (HCl) and ammonium chloride (HCl) from a fixed volume of blast furnace gas. ) and other substances are completely absorbed and converted into chloride ions, while the interfering substances hydrogen sulfide () are also absorbed. ) and a small amount of carbon dioxide ( The following chemical reactions mainly occur during the above absorption process: (Absorption of chlorine) (Absorbs hydrogen sulfide, producing sodium hydrosulfide and sodium bicarbonate) At this point, chlorine and sulfur exist in the absorbent in ionic form, along with a small amount of dissolved carbonate ions.

[0016] Step S4, after sampling is completed, All sodium carbonate solution in each absorption bottle was transferred to an Erlenmeyer flask. The absorption bottle was then washed multiple times with deionized water, and the washed deionized water was then transferred to the Erlenmeyer flask to ensure complete sample transfer.

[0017] The following steps, S5-S7, represent the most innovative design aspect of this application: sample pretreatment. This design is based on the sample collection and absorption process in steps S1-S3. Chlorine and sulfur both exist in ionic form in the absorption solution. During sample pretreatment, the highly reducing and interfering sulfur ions are completely oxidized to non-interfering sulfate ions. This is because the solubility of the sulfate ions involved (silver sulfate Ag₂SO₄) is much greater than that of silver chloride (AgCl) and silver chromate (Ag₂CrO₄). During titration, Ag… + It will preferentially react with Cl, which has lower solubility. - and CrO4 2- They combine to form a precipitate, while Ag in the solution... + The concentration never reached the threshold at which Ag2SO4 begins to precipitate. The remaining interfering substances existed in the form of carbonate ions, so there was no need to worry about interference from other products during treatment, ensuring complete removal of the interfering substances.

[0018] Specifically, step S5, the step of acidifying and pretreating the solution in the conical flask, is as follows: ， Step S51: Add dilute nitric acid or dilute sulfuric acid dropwise into the conical flask; Step S52: Add phenolphthalein as an indicator to the conical flask, gently shake the conical flask until the pH value of the solution drops to neutral or weakly acidic. When measuring the solution with a pH meter, the pH value is between 6 and 7. Step S53: Place the conical flask on a hot plate or water bath and heat it. Set the heating temperature to 60~80℃ and continue heating for 10~15 minutes. Then cool it to room temperature.

[0019] The purpose of step S5 is to neutralize excess sodium carbonate in the sample and prevent it from reacting with hydrogen peroxide in subsequent oxidation steps. The reaction during neutralization is... This will produce bubbles. Once the bubbles have mostly stopped, it means the pH value is close to neutral.

[0020] Step S6: Slowly add 30% hydrogen peroxide solution dropwise to the solution after acidification pretreatment, and gently stir or shake. Bubbles will be generated in the solution during the addition of hydrogen peroxide. Continue adding until no more bubbles are generated in the solution, indicating that the oxidation reaction has been completed.

[0021] Step S7: Place the conical flask on a hot plate or water bath and heat it at 60-80°C for 10-15 minutes to promote the reaction of excess unreacted substances in the solution. It completely decomposes into water and oxygen, and then is cooled to room temperature.

[0022] After step S7 is completed, the main interfering substances in the solution It has been completely transformed into an interference-free environment. Excessive It has also been removed.

[0023] After sample processing, the interfering substances are removed, and the next step is titration testing. The titration test used in this application is Mohr's titration. First, in step S8, dilute nitric acid solution is added dropwise to the conical flask to adjust the pH value of the solution to between 7 and 10, which is the optimal pH range for Mohr's titration of chloride ions.

[0024] Step S9: Add 1 mL of 50 g / L potassium chromate to the solution after pH adjustment in step S8. Potassium chromate acts as an indicator, and the solution turns yellow. Titrate with a precise concentration of silver nitrate standard titrant, continuously titrating while shaking the conical flask until a stable light reddish-brown precipitate appears. When the light reddish-brown color no longer fades, this is the titration endpoint of the absorption solution titration. Record the volume of silver nitrate standard titrant consumed at the titration endpoint. ; Step S10: Add 1 mL of 50 g / L potassium chromate to the solution after adjusting the pH in step S8, and continue adding calcium carbonate powder until the solution becomes turbid. Titrate with a known accurate concentration of silver nitrate standard titrant, continuously titrating while shaking the conical flask until a light reddish-brown precipitate appears in the solution. When the light reddish-brown color no longer fades, this is the titration endpoint for the blank sample titration. Record the volume of silver nitrate standard titrant consumed at the titration endpoint. Adding a small amount of calcium carbonate as a precipitate is to minimize the precipitation of silver chloride during the titration of the absorbent sample, ensuring a consistent endpoint. It also eliminates color differences caused by the transparency of water, allowing for better observation of the light reddish-brown precipitate and thus accurate determination of the titration endpoint.

[0025] Next, in step S11, the mass of chloride ions is calculated using the following formula: (1) In formula (1), This represents the concentration of the silver nitrate standard titrant, in mol / L. The molar mass of chlorine is 35.45 g / mol. In the final step S12, based on the data collected in step S3 and combined with the chloride ion mass calculated in step S11, the chlorine content in the blast furnace gas is finally calculated. The formula for calculating the chlorine content is as follows: (2) In formula (2), This refers to the chlorine content in blast furnace gas, expressed in mg / m³. The mass of chloride ions calculated using formula (1) is expressed in mg. This refers to the blast furnace gas flow rate, expressed in L / min. This is the start time of sampling, in minutes. For the first Sampling time for each absorption bottle, in minutes.

[0026] The method for detecting chloride ion content in blast furnace gas provided in this application first detects the chloride ion content in a fixed volume of blast furnace gas. , (etc.) are completely absorbed and converted into chloride ions ( ), while absorbing interfering substances And a small amount of CO2. Then, sulfur ions (which have strong reducing and interfering properties) are introduced. ⁻, All are oxidized to unaffected sulfate ions ( ), while removing CO3 2- The mass of chloride ions in the absorbent is then calculated using titration results with the absorbent and blank samples. Finally, the chloride content in the blast furnace gas is calculated based on the collected gas volume and the measured chloride ion mass. Using a weakly alkaline sodium carbonate solution as the absorbent improves the chloride ion absorption efficiency. Simultaneously, pretreatment methods such as pH adjustment and oxidation of interfering ions effectively avoid interference from other ions in the absorbent, ensuring detection accuracy.

[0027] This application also provides a gas sampling device for the method of detecting chloride ion content in blast furnace gas. Figure 2 As shown, the system includes several absorption bottles 5, each equipped with a porous glass plate to significantly increase the gas-liquid contact area and improve absorption efficiency. Several absorption bottles are connected in series, with adjacent bottles linked by connecting pipes. One end of a gas sampling pipe 3 extends into the first absorption bottle, and the other end extends into the gas pipeline 1 through a gas sampling port. A sampling valve 4 is installed on the gas sampling pipe located between the gas sampling port and the first absorption bottle. The last absorption bottle is connected to a drying bottle 6 via a connecting pipe, and a gas flow meter 7 is installed on the connecting pipe at the outlet of the drying bottle. Silver nitrate solution is placed in the last absorption bottle, while sodium carbonate solution is placed in the remaining absorption bottles. The silver nitrate solution at the end can detect whether chloride ions in the blast furnace gas have been completely absorbed, thereby adjusting the number of absorption bottles connected in series. The concentration of the sodium carbonate solution is 0.05 mol / L, and the concentration of the silver nitrate solution is 0.005 mol / L.

[0028] To verify the feasibility of this application, embodiments are provided for verification. Example

[0029] First, prepare a 0.05 mol / L sodium carbonate solution ( The solution was prepared by connecting two porous glass plate absorption bottles in series, with 50 ml of sodium carbonate solution added to each bottle. After the last absorption bottle, a silver nitrate solution containing 0.005 mol / L was connected. Finally, a drying bottle and a gas flow meter were connected in sequence, and the gas flow rate was controlled at 1 L / min. At this time, a white turbidity was found in the last absorption bottle, indicating that chloride ions in the blast furnace gas were not completely absorbed, and the sampling conditions need to be adjusted.

[0030] Next, prepare 0.05 mol / L sodium carbonate ( The solution consisted of two porous glass plate absorption bottles connected in series. Each absorption bottle contained 50 ml of sodium carbonate solution. After the last absorption bottle, a silver nitrate solution containing 0.005 mol / L was connected to detect whether chloride ions were completely absorbed. Finally, a drying bottle and a gas flow meter were connected in sequence, and the gas flow rate was controlled at 0.5 L / min. No turbidity was found in the last absorption bottle after the sampling started, and the sampling continued. The sampling start time was recorded as 0 min and the sampling end time as 120 min.

[0031] Transfer all the absorption liquid from the absorption bottle to a 250 mL Erlenmeyer flask, wash the absorption bottle several times with a small amount of deionized water, and combine all the washing liquid into the Erlenmeyer flask.

[0032] Add dilute nitric acid dropwise to the combined sample while gently shaking until the pH of the solution drops to 6.5. Heat the conical flask to 80°C in a water bath for 15 minutes, then cool to room temperature. Next, perform oxidation treatment: slowly add 30% hydrogen peroxide solution dropwise to the acidified sample while gently stirring, continuing until no more bubbles are produced in the solution. Finally, remove excess oxidant from the absorbent: heat the conical flask to 80°C in a water bath for 15 minutes to remove excess unreacted oxidant from the solution. It completely decomposes into water and oxygen. After cooling the solution, it is ready for titration.

[0033] Adjust the pH of the absorption solution to 8.0, and add 1 mL of 50 g / L potassium chromate to the sample. The solution is used as an indicator, and the solution is yellow. Titrate with 0.005 mol / L silver nitrate standard titrant, continuously titrating while shaking the conical flask, until a stable pale reddish-brown precipitate appears. When the solution stops fading, the titration endpoint is reached. Record the volume of silver nitrate standard solution consumed at this point as 28 ml. Similarly, the volume of silver nitrate consumed in the blank sample titration is 3 ml.

[0034] The mass of chloride ions in the absorbent is calculated as m = 4.43 mg according to formula (1), and the chloride ion content in the gas is calculated as C = 73.96 mg / m³ according to formula (2).

[0035] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0036] The meaning of "and / or" as used in this application includes situations where each exists alone or both exist simultaneously.

[0037] The term "connection" as used in this application can mean a direct connection between components or an indirect connection between components through other components.

[0038] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for detecting chloride ion content in blast furnace gas, characterized in that: Includes the following steps: Step S1, will A series of absorption bottles Integer and ≥2, one end of the gas sampling tube extends into the first absorption bottle, and the other end of the gas sampling tube is connected to the gas pipeline through the gas sampling port. Each absorption bottle is connected to a drying bottle, and a gas flow meter is installed on the connecting pipe at the outlet of the drying bottle; Step S2, in the first to the second The first absorption bottle contains the prepared sodium carbonate solution. Each absorption bottle contains silver nitrate solution; Step S3: Blast furnace gas is introduced into the absorption bottle for sampling, and the sampling start time is recorded. , No. Sampling time per absorption bottle and blast furnace gas flow rate ; Step S4, after sampling is completed, All the sodium carbonate solution in the absorption bottle was transferred to the conical flask. At the same time, the absorption bottle after the sodium carbonate solution was transferred was washed multiple times with deionized water, and the washed deionized water was then transferred to the conical flask. Step S5: Acidify the solution in the conical flask as a pretreatment. ， Heat the conical flask until the pH of the solution drops to neutral or weakly acidic, continue heating for the preset time, and then cool to room temperature. Step S6: Add hydrogen peroxide to the solution after acidification pretreatment to carry out oxidation treatment until no more bubbles are generated in the solution, thus completing the oxidation process. Step S7: Continue heating the conical flask for the preset time until all excess oxidant is decomposed, and then cool the solution to room temperature. Step S8: Add dilute nitric acid solution dropwise into the conical flask to adjust the pH of the solution to between 7 and 10; Step S9: Perform absorption titration on the solution after pH adjustment in step S8. Add potassium chromate solution as an indicator to the solution, and titrate with a silver nitrate standard titrant of known precise concentration. Record the volume of silver nitrate standard titrant consumed at the titration endpoint. ; Step S10: Perform a blank titration on the solution after pH adjustment in step S8. Add potassium chromate solution as an indicator, add calcium carbonate powder until the solution becomes turbid, and titrate with a silver nitrate standard titrant of known precise concentration. Record the volume of silver nitrate standard titrant consumed at the titration endpoint. ; Step S11, calculate the mass of chloride ions, using the following formula: （1） In formula (1), This represents the concentration of the silver nitrate standard titrant, in mol / L. The molar mass of chlorine is 35.45 g / mol. Step S12: Based on the data collected in step S3 and combined with the chloride ion mass calculated in step S11, the chlorine content in the blast furnace gas is finally calculated. The formula for calculating the chlorine content is as follows: （2） In formula (2), This refers to the chlorine content in blast furnace gas, expressed in mg / m³. The mass of chloride ions calculated using formula (1) is expressed in mg. This refers to the blast furnace gas flow rate, expressed in L / min. This is the start time of sampling, in minutes. For the first Sampling time for each absorption bottle, in minutes.

2. The method for detecting chloride ion content in blast furnace gas according to claim 1, characterized in that: In step S2, the concentration of the prepared sodium carbonate solution is 0.05 mol / L and the concentration of the silver nitrate solution is 0.005 mol / L.

3. The method for detecting chloride ion content in blast furnace gas according to claim 1, characterized in that: In step S5, the step of acidifying the solution in the conical flask is as follows: ， Step S51: Add dilute nitric acid or dilute sulfuric acid dropwise into the conical flask; Step S52: Add phenolphthalein as an indicator to the conical flask, and gently shake the conical flask until the pH of the solution drops to between 6 and 7. Step S53: Place the conical flask on a hot plate or water bath and heat it. Set the heating temperature to 60~80℃ and continue heating for 10~15 minutes, then cool it to room temperature.

4. The method for detecting chloride ion content in blast furnace gas according to claim 1, characterized in that: In step S6, 30% hydrogen peroxide is slowly added dropwise to the solution after acidification pretreatment, and the solution is gently stirred or shaken. Bubbles are generated in the solution during the addition of hydrogen peroxide. The addition continues until no more bubbles are generated in the solution.

5. The method for detecting chloride ion content in blast furnace gas according to claim 1, characterized in that: In step S7, the conical flask is placed on a hot plate or water bath for heating. The heating temperature is set to 60~80℃ and heated for 10~15 minutes. Then it is cooled to room temperature.

6. The method for detecting chloride ion content in blast furnace gas according to claim 1, characterized in that: In step S9, 1 mL of 50 g / L potassium chromate is added to the solution after the pH value was adjusted in step S8. Potassium chromate is used as an indicator, and the solution is yellow. Titration is performed using silver nitrate standard titrant of precise concentration. The titration is continued while the conical flask is shaken continuously until a stable light reddish-brown precipitate appears in the solution and the light reddish-brown color no longer fades. This is the titration endpoint of the absorption solution titration.

7. The method for detecting chloride ion content in blast furnace gas according to claim 1, characterized in that: In step S10, add 1 mL of 50 g / L potassium chromate to the solution after adjusting the pH value in step S8, and continue to add calcium carbonate powder until the solution becomes turbid. Titrate with silver nitrate standard titrant of known precise concentration, continue titrating and shaking the conical flask until a light reddish-brown precipitate appears in the solution and the light reddish-brown color no longer fades. This is the titration endpoint of the blank sample titration.

8. A gas sampling device for the method of detecting chloride ion content in blast furnace gas according to any one of claims 1-7, characterized in that: It includes several absorption bottles, each containing a porous glass plate. The absorption bottles are connected in series, and adjacent bottles are connected by a connecting pipe. One end of a gas sampling tube extends into the first absorption bottle, and the other end extends into the gas pipeline through a gas sampling port. A sampling valve is installed on the gas sampling tube located between the gas sampling port and the first absorption bottle. The absorption bottle at the end is connected to the drying bottle via a connecting pipe, and a gas flow meter is installed on the connecting pipe at the outlet of the drying bottle; The last absorption bottle is filled with silver nitrate solution, and the remaining absorption bottles are filled with sodium carbonate solution, wherein the concentration of sodium carbonate solution is 0.05 mol / L and the concentration of silver nitrate solution is 0.005 mol / L.

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