A flue gas sampling pretreatment system and method based on magnetic separation and fine filtration combination

Abstract

This application provides a flue gas sampling pretreatment system and method based on the combined use of magnetic separation and fine filtration. The system includes a magnetic separation dust removal unit, a fine filtration unit, a purging system, and a temperature control system. The magnetic separation dust removal unit uses a magnetic field to adsorb magnetic particles in the flue gas sample. The outlet of the magnetic separation dust removal unit is connected to the inlet of the fine filtration unit, and the outlet of the fine filtration unit is connected to an analytical instrument. The purging system is connected to the fine filtration unit and is used to purge the pipelines of the fine filtration unit and the magnetic separation dust removal unit after sampling of the flue gas sample has stopped. The temperature control system is used to regulate the temperature of the collected flue gas sample to prevent condensation and the formation of liquid water within the magnetic separation dust removal unit and the fine filtration unit. This system and method can reduce the sampling delay of flue gas with high humidity and high concentration of magnetic dust, while simultaneously reducing the filter clogging rate and increasing its service life, exhibiting characteristics of low delay and low-frequency maintenance.

Description

Technical Field

[0001] This application relates to the field of online monitoring technology for industrial flue gas, and in particular to a flue gas sampling pretreatment system and method based on the combined use of magnetic separation and fine filtration. Background Technology

[0002] Currently, converter gas analysis technology is gradually becoming mainstream in converter blowing control technology. By using gas analyzers installed at the hot end of the converter blowing process, operators can understand the chemical reaction status within the converter in a timely manner. Furthermore, by providing gas analysis, it facilitates intelligent steelmaking, enabling intelligent control systems to achieve standardized and intelligent converter blowing, stable production operations, reduced manufacturing and management costs in the steelmaking process, and reduced labor intensity for workers. It also improves blowing efficiency and increases the final hit rate.

[0003] However, the flue gas generated by converter blowing has a high temperature of about 1600℃, and the outlet temperature of the vaporization flue at the rear end can also reach about 700℃. It also contains a large amount of iron-containing dust. The main components of the dust are iron oxide particles, iron tetroxide particles, iron particles, and some calcium oxide particles. The dust concentration can usually reach 70g / m3 to 250g / m3. The high dust concentration will cause the low-power single-wave laser generated by the laser in the commonly used in-situ laser gas analyzer installed near the hot end of the converter, i.e., near the evaporation cooler, to be scattered. Therefore, it is not possible to directly analyze the flue gas during the converter blowing process. The existing solution usually uses a sampling device to extract the flue gas generated by converter blowing, cool and filter it, and then conduct detection and analysis.

[0004] There are two main existing technologies: The first uses an in-situ laser flue gas analyzer, installed before or after the blower, approximately 200 meters or more from the converter opening. The detected flue gas components often show a delay of more than one minute, making the analysis of the converter's internal conditions only of reference value. The second uses an extraction-type flue gas analyzer, installed at the front end of the evaporative cooling system of a dry electrostatic precipitator or at the bend of the vaporization flue at the front end of the evaporative cooling system. Here, the temperature reaches 700-1000℃, or even higher, and the dust concentration reaches 120-250 g / Nm³. 3 There may even be liquid steel droplets and large dust particles, so the filter element is very easy to clog. In terms of maintenance, daily maintenance is generally adopted. In terms of materials, high temperature resistant materials must be used. In order to prevent clogging, large-diameter sampling tubes with a diameter of 40mm-100mm are generally selected.

[0005] However, existing technologies have shortcomings. First, to ensure continuous sampling, large-sized pipes and filter elements are required, with filter element and pipe diameters generally exceeding 50mm. Only larger filter elements can prevent high-concentration dust from quickly clogging them completely, ensuring a complete sampling cycle. However, larger pipe diameters and filter sizes lead to increased sampling and detection delays, with existing technologies generally achieving response times exceeding 10 seconds. Furthermore, large pipe diameters typically require smaller flow rates, which can easily mismatch with the flue gas velocity within the flue gas duct, resulting in distorted sampling and analysis data. In existing technologies, the sampling rate within large-sized sampling pipes is generally lower than the extraction rate of 10 liters of flue gas per minute, while the flue gas velocity within the duct is generally no less than 15 meters per second. Therefore, continuity and low latency are conflicting improvement directions in sampling equipment. Existing equipment requires significant daily maintenance and is gradually failing to meet the current intelligent control requirements of converter blowing processes. Second, while purging can remove most iron oxide dust particles from the filter element and pipes, some residue remains. Iron oxide dust particles easily form scale when exposed to water, making them difficult to remove and reducing filter element lifespan. Only daily maintenance can prevent blockages. However, this lack of maintenance makes continuous use impossible and is incompatible with the converter smelting cycle. Blockages during smelting hinder the guidance of converter operations. Therefore, a flue gas sampling pretreatment system and method that balances low latency and low-frequency maintenance is needed to ensure the absence of blockages in the converter blowing process and to enable intelligent monitoring to meet the current needs of intelligent control in the converter blowing process. Summary of the Invention

[0006] Purpose of the invention: This application provides a flue gas sampling pretreatment system and method based on the combined use of magnetic separation and fine filtration. When sampling flue gas with high humidity and high concentration of ferromagnetic dust, the system increases the extraction speed of the flue gas, matches and enhances the dust removal capacity, enables low-latency sampling and detection, reduces maintenance frequency, increases the service life of the filter, ensures continuous operation, and prevents sudden blockage during smelting.

[0007] This application discloses a flue gas sampling pretreatment system based on a combination of magnetic separation and fine filtration, including a first sampling tube and a precision filtration unit. The sampling port of the first sampling tube is used to draw in flue gas samples, and the system further includes: A magnetic separation dust removal unit is provided, wherein the air inlet of the magnetic separation dust removal unit is connected to the air outlet of the first sampling tube, the magnetic separation dust removal unit uses a magnetic field to adsorb magnetic particles in the flue gas sample, the air outlet of the magnetic separation dust removal unit is connected to the air inlet of a precision filtration unit, and the air outlet of the precision filtration unit is connected to an analytical instrument. A purging system, which is connected to a precision filtration unit, is used to purge the pipelines of the precision filtration unit and the magnetic separation dust removal unit after the sampling of flue gas samples has stopped.

[0008] Preferred magnetic separation dust removal units include: The second sampling tube has one end connected to the first sampling tube and the other end connected to the air inlet of the precision filter unit. A magnet, which is nested outside the second sampling tube.

[0009] Preferably, it further includes: a temperature control system, which is used to regulate the temperature of the flue gas sample entering the magnetic separation dust removal unit and / or the precision filtration unit, and / or to regulate the ambient temperature of the magnet in the magnetic separation dust removal unit.

[0010] Preferably, the magnetic field formed by the magnet moves or extends axially in the opposite direction of the flue gas sample flow during the flue gas sample collection process, and the movement or extension speed of the magnetic field is 0 or a set speed greater than 0.

[0011] Preferably, the minimum design length of the magnetic field formed by the magnet extending along the axial direction of the second sampling tube is positively correlated with the airflow velocity.

[0012] Preferably, the precision filtration unit includes a fine filter, which includes a filter element and a second housing, with a gap space between the filter element and the second housing. The second housing is provided with a fine filter inlet, which is connected to a second sampling tube. The filter element is provided with a fine filter outlet, which is connected to an analytical instrument. The second housing is provided with a gap purge port, and the purge airflow from the gap purge port moves in the direction of the fine filter inlet.

[0013] Preferably, the purging system includes a first purging unit, a second purging unit, and a third purging unit. The first purging unit includes a first purging pipe, one end of which is connected to the fine filter outlet, and the other end of which is connected to a high-pressure gas source. The first purging pipe is equipped with a third control valve. The second purging unit includes a second purging pipe, one end of which is connected to an intermittent purging port, and the other end of which is connected to a high-pressure gas source. The second purging pipe is equipped with a fourth control valve. The third purging unit includes a third purging pipe, one end of which is connected to the end of the second sampling pipe near the first sampling pipe, and the other end of which is connected to a high-pressure gas source. The third purging pipe is equipped with a fifth control valve.

[0014] Preferably, it also includes a second purging system, which includes a sixth control valve and a fourth purging tube. The sixth control valve is located at the connection between the second sampling tube and the precision filter unit, and the fourth purging tube is equipped with a seventh control valve. One end of the fourth purging tube is connected to a high-pressure liquid source, and the other end is connected to the end of the second sampling tube near the sixth control valve.

[0015] Preferably, the temperature control system includes a thermostat and a temperature sensor. The thermostat is located at the air inlet of the second purge tube or the air inlet of the precision filter unit, and the temperature sensor is located at the air outlet of the precision filter unit. The thermostat is used to adjust the temperature of the flue gas sample in the pipe at the location of the precision filter unit according to the temperature of the air outlet of the precision filter unit collected by the temperature sensor.

[0016] A flue gas sampling pretreatment method using the flue gas sampling pretreatment system based on magnetic separation and fine filtration as described above includes the following steps: Sampling stage: The first control valve is set on the first sampling tube and the second control valve is set on the third sampling tube. When the power pump is driven, the sampling port draws in the flue gas sample. The flue gas sample flows through the first sampling tube, the magnetic separation dust removal unit and the precision filtration unit in sequence, and is then transported to the analytical instrument by the third sampling tube. At the same time as the power pump is turned on, the magnetic separation dust removal unit starts to control the magnetic field formed by the magnet to move or extend in the opposite direction of the flue gas sample flow at a set speed. When sampling is started, the temperature sensor collects the temperature at the fine filter outlet. When the flue gas temperature collected by the temperature sensor is not lower than the freezing point of water, the temperature collected by the temperature sensor is fed back to the temperature controller to adjust the flue gas sample temperature in the pipe at its location until the flue gas sample temperature collected by the temperature sensor at the fine filter outlet is not lower than the set temperature. At the same time, the magnet temperature control device regulates the ambient temperature of the magnet to not be higher than the preset working temperature. When sampling is started, if the flue gas temperature collected by the temperature sensor is lower than the freezing point of water, the temperature controller stops working and does not heat the flue gas sample in the pipe at its location until the flue gas temperature collected by the temperature sensor is not lower than the freezing point of water. Non-sampling phase: After the flue gas sample is sampled, the magnetic field formed by the magnet in the magnetic separation dust removal unit is weakened or disappears, and the purging system and / or the second purging system are turned on to purge the precision filter unit and / or the magnetic separation dust removal unit until the next sampling phase begins or continues for a preset time.

[0017] Beneficial effects: First, reducing the diameter of the sampling tube can reduce sampling delay. At the same time, the magnetic separation dust removal unit uses a magnetic field to adsorb a large amount of magnetic dust in front of the precision filter unit, reducing the clogging speed of the precision filter element and increasing the single sampling time. At the same time, reducing the diameter of the sampling tube can increase the flow rate of the sampling tube, ensuring that the detection is not distorted. The movement or extension of the magnetic field can improve the adsorption efficiency of magnetic dust, and can also prevent the escape of magnetic dust in the flue gas under the condition of increased flue gas flow.

[0018] Secondly, when the ambient temperature is not lower than the freezing point of water, the temperature of the small amount of flue gas sample collected changes rapidly. Through the linkage of a temperature controller and a temperature sensor located at the outlet of the fine filter, the temperature of the flue gas sample in the magnetic separation dust removal unit and the precision filtration unit is ensured not to fall below the set temperature. The set temperature is generally the dew point of water in the current flue gas environment. This ensures that there is no condensation in the magnetic separation dust removal unit and the precision filtration unit, preventing magnetic dust particles from forming scale upon contact with water. When the ambient temperature is lower than the freezing point of water, the water vapor in the flue gas sample will condense into ice crystals. Therefore, heating is not required to prevent magnetic dust particles from forming scale upon contact with water, ensuring purging efficiency while extending the service life of the filter element.

[0019] Third, the magnetic field formed by the magnet moves or extends in the opposite direction of the flue gas sample flow during the flue gas sample collection process. This causes the dust particles adsorbed by the magnet to move or extend with the magnetic field and spread evenly on the inner surface of the second sampling tube. This prevents the dust particles from accumulating at one end of the magnetic field, which would cause airflow shock fluctuations. At the same time, the diameter of the second sampling tube is larger than that of the first sampling tube, which reserves storage space for the dust particles adsorbed by the magnet and prevents the accumulation of dust particles from causing changes in airflow. In addition, the larger diameter of the second sampling tube than that of the first sampling tube helps to slow down the airflow velocity in the second sampling tube and improve the magnetic dust adsorption efficiency.

[0020] Fourth, the ambient temperature around the magnet can be controlled within a suitable operating temperature range by the magnet temperature control device to prevent the magnet from overheating due to high-temperature flue gas, which would reduce the magnetic field strength.

[0021] Fifth, after the flue gas sample is collected, the purge airflow purges the filter element and the gap space. Purge of the filter element can remove most of the dust on the filter element, while purge of the gap space can remove the dust in the gap space. At the same time, the airflow direction for purging the gap space is towards the fine filter outlet, which can accelerate the dust discharge and also purge the junction of the second sampling tube and the fine filter, and the junction of the first sampling tube and the second sampling tube, to prevent dust from accumulating at the diameter change.

[0022] Sixth, during the interval between two samplings, the purging system can extend the purging time to ensure that the purging continues throughout the entire process of the two sampling intervals. This utilizes the purging airflow to achieve an air seal, preventing external water vapor from being adsorbed by dry dust particles and forming scale on the filter element and pipe wall, thus affecting the service life of the equipment. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of an embodiment 1 of the flue gas sampling pretreatment system based on the combined use of magnetic separation and fine filtration according to this application; Figure 2 This is a schematic diagram of the structure of Embodiment 3 of a flue gas sampling pretreatment system based on the combined use of magnetic separation and fine filtration according to this application; Figure 3 This is a schematic diagram of the structure of multiple flue gas sampling and pretreatment systems based on magnetic separation and fine filtration combined in this application when used in parallel. Figure 4 This is a schematic diagram of the structure of a fine filter in a flue gas sampling pretreatment system based on the combined use of magnetic separation and fine filtration according to this application; Explanation of the attached diagram numbers: 1. Sampling port; 2. First sampling tube; 3. Magnetic separation dust removal unit; 4. Precision filtration unit; 5. Third sampling tube; 6. Purging system; 7. Temperature control system; 21. First control valve; 31. Magnet; 34. Driver; 36. Second sampling tube; 37. Thermal insulation layer; 38. Magnetic shielding layer; 39. Magnet temperature control device; 310. First housing; 311. Air inlet; 312. Air outlet; 41. Fine filter; 42. Filter element; 43. Second housing; 44. Gap space; 45. Fine filter outlet; 46. Fine filter inlet; 47. Gap purge port; 51. Second control valve; 61. High-pressure air source; 62. First purge pipe; 63. Third control valve; 64. Second purge pipe; 65. Fourth control valve; 66. Third purge pipe; 67. Fifth control valve; 68. Sixth control valve; 69. Fourth purge pipe; 610. Seventh control valve; 71. Thermostat; 72. Temperature sensor. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0026] It should be noted that the use of designations such as [first], [second], [third], and [fourth] in this application does not represent any order, quantity, or importance; they are merely used to distinguish different parts. The directional designations such as [up], [down], [left], and [right] in this application are only for reference to the accompanying drawings. Therefore, the designations, directional designations, and positional relationship designations used are for the purpose of explaining and understanding this application, and not for limiting this application. In the drawings, structurally similar units are represented by the same labels.

[0027] Online flue gas analysis systems for converter steelmaking are essential equipment in converter steelmaking control models. They require stable operation and short data latency. Current technologies typically use fine filters to filter flue gas samples with high humidity and high concentrations of magnetic dust. However, to prevent high-temperature, high-concentration dust from clogging the fine filter, large-diameter sampling pipes and filters are necessary, which fails to meet the short latency requirement. Furthermore, the large-diameter sampling pipes require matching with low-flow flue gas, leading to detection distortion. Additionally, magnetic dust particles, primarily composed of ferric oxide and magnetite, easily form scale on the pipe and filter element surfaces upon contact with water, significantly reducing the lifespan of the fine filter.

[0028] Therefore, based on the above-mentioned shortcomings and problems, this application provides a flue gas sampling pretreatment system based on the combined use of magnetic separation and fine filtration. The following will describe this application in conjunction with specific embodiments.

[0029] Example 1: This example discloses a flue gas sampling pretreatment system based on the combined use of magnetic separation and fine filtration, such as... Figure 1 As shown, it includes a first sampling tube 2, a magnetic separation dust removal unit 3, and a precision filtration unit 4. The sampling port 1 of the first sampling tube 2 is used to draw in flue gas samples. The flue gas samples pass through the magnetic separation dust removal unit 3, which uses a magnetic field to adsorb a large amount of magnetic dust. Then, the precision filtration unit 4 filters and adsorbs fine magnetic dust particles and non-magnetic dust particles before transporting them through the third sampling tube 5 to the analytical instrument for component analysis to predict the process of converter blowing.

[0030] In this embodiment, the sampling port 1 of the first sampling tube 2 is located at the front or rear end of the evaporation cooling system of the converter blowing system, and the dust concentration after preliminary cooling can be reduced from ≥120g / m³. 3 Decreased to 50-100g / m 3 The maximum dust particle size is reduced from ≥1mm to ≤200um, and the flue gas sample temperature can be reduced to around 250℃, which reduces the temperature control load and dust amount for the flue gas sampling pretreatment system, while increasing the humidity in the flue gas.

[0031] In this embodiment, the magnetic separation dust removal unit 3 includes a magnet 31 and a second sampling tube 36. The second sampling tube 36 passes through the magnet 31, with one end connected to the first sampling tube 2 and the other end connected to the precision filter unit 4. The magnet 31 is an N50H neodymium iron boron magnet or an electromagnet with a similar magnetic field strength. In this embodiment, the magnet 31 is fixed, meaning that the movement or extension speed of the magnetic field is 0 during flue gas sample collection. The magnetic field generated by the magnet 31 can adsorb magnetic dust particles in the flue gas in the pipeline onto the pipe wall, reducing the filtration burden on the precision filter unit 4.

[0032] In this embodiment, the magnetic field strength is determined based on the required airflow velocity of the flue gas sample. The specific calculation needs to consider the drag force of the airflow on the particles, the attraction force of the magnetic field on magnetic particles represented by ferric oxide, the inertia of particle motion, and the influence of pipe wall roughness on particle sliding. It is necessary to ensure that the magnetic field attraction force is greater than the sum of the airflow drag force and the particle inertial force. Given the required flow velocity v, the magnetic field strength calculation formula for magnet 31 is as follows: ; In the formula, The minimum magnetic flux density at the pipe wall. The average velocity of the airflow inside the pipe. D is the diameter of the magnetic particle, and D is the inner diameter of the pipe. Aerodynamic viscosity, The density of magnetic particles, This is a pipe roughness correction factor; for smooth pipes, it is approximately 1.0, and for rough pipes, it can be taken as 1.2 to 1.5. The magnetic field structure coefficient is related to the magnetic susceptibility and magnetic field gradient, and is determined by the magnet structure. The magnet length is proportional to the magnetic field structure coefficient.

[0033] The finer the particles, the more difficult they are to be adsorbed due to the increased proportion of drag force. Therefore, some small magnetic particles cannot be adsorbed and will be captured by the filter element 42 in the fine filter 41 of the precision filter unit 4. These magnetic dust particles are also the main components that may cause scaling.

[0034] Since the length of a magnet is proportional to the magnetic field structure coefficient, to ensure low latency and no distortion in detection, if the magnetic field strength cannot be increased at a set high sampling flow rate, the magnet length can be extended to ensure magnetic dust adsorption efficiency. This can generally be achieved by replacing the magnet with a longer one or by splicing multiple magnets together.

[0035] In this embodiment, the precision filtration unit 4 includes a fine filter 41, such as... Figure 4As shown, the fine filter 41 includes a filter element 42 and a second housing 43, with a gap space 44 formed between the filter element 42 and the second housing 43. The second housing 43 is provided with a fine filtration inlet 46, which is connected to the second sampling tube 36. The filter element 42 is provided with a fine filtration outlet 45, which is connected to the analytical instrument. The second housing 43 is provided with a gap purge port 47, located at the end of the second housing 43 away from the fine filtration inlet 46. The purge airflow from the gap purge port 47 moves towards the fine filtration inlet 46. In this embodiment, the filter element 42 can be made of high-temperature resistant sintered titanium metal filter cartridge, with a filtration accuracy of 2. .

[0036] In this embodiment, the purging system 6 includes a first purging unit, a second purging unit, and a third purging unit. The first purging unit includes a first purging pipe 62, one end of which is connected to the fine filter outlet 45, and the other end is connected to the high-pressure gas source 61. The first purging pipe 62 is equipped with a third control valve 63. The second purging unit includes a second purging pipe 64, one end of which is connected to the gap purging port 47, and the other end is connected to the high-pressure gas source 61. The second purging pipe 64 is equipped with a fourth control valve 65. The third purging unit includes a third purging pipe 66, one end of which is connected to the end of the second sampling pipe 36 near the first sampling pipe 2, and the other end of which is connected to the high-pressure gas source 61. The third purging pipe 66 is equipped with a fifth control valve 67.

[0037] When the purging system 6 is working, the first purging unit blows towards the inside of the filter element 42, blowing away the dust particles trapped and adsorbed on the outside of the filter element. Because the porous structure of the filter element 42 disperses the airflow from the first purging unit, the dust particles blown away from the filter element will disperse within the gap space 44. Therefore, the second purging unit needs to purge the gap space 44 and the variable-diameter connection between the fine filter inlet 46 and the second sampling tube 36, which can quickly remove the dust particles from the gap space 44. Since the gap purging port 47 is located at the end of the second housing 43 away from the fine filter inlet 46, the airflow directly impacts the fine filter inlet 46, enabling... To prevent dust accumulation at the variable-diameter connection between the fine filter inlet 46 and the second sampling tube 36, in this embodiment, the purging air pressure of the first purging unit is not lower than that of the second purging unit, so as to prevent dust particles dispersed in the gap space 44 from being filtered and adsorbed again by the filter element 42 under the purging air pressure of the second purging unit; the third purging unit is used to purge the connection between the second sampling tube 36 and the first sampling tube 2, which can prevent dust accumulation at the variable-diameter connection between the second sampling tube 36 and the first sampling tube 2. The purging air pressure of the third purging unit is not higher than that of the first purging unit and the second purging unit, so as to prevent the purging airflow from flowing back.

[0038] Between two sampling intervals, the purging system can extend the purging time during the purging and dust removal process, allowing the purging to continue throughout the entire process of the two sampling intervals. The purging airflow is used to achieve an air seal, preventing external water vapor from being adsorbed by dry dust particles and forming scale on the filter element and pipe wall.

[0039] Example 2: The difference from Example 1 is that the magnetic field formed by the magnet 31 in the magnetic separation dust removal unit 3 moves or extends in the opposite direction of the flue gas sample flow during the flue gas sample collection process. Specifically, the magnet 31 is nested outside the second sampling tube 36. One end of the second sampling tube 36 is connected to the first sampling tube 2, and the other end is connected to the precision filter unit 4. The magnet 31 driver 34 is connected to the drive. The driver 34 can drive the magnet 31 to move axially along the second sampling tube 36 to realize the movement of the magnetic field at a preset speed. The driver 34 can adopt existing drive devices such as stepper motors or lead screw transmission mechanisms.

[0040] In this embodiment, the preset speed of the magnetic field movement can be calculated. Based on the sampling duration and the total distance the magnetic field travels or extends, the average moving speed or the magnetic field extension speed can be calculated. Alternatively, with a fixed sampling duration, the total distance can be divided into segments, and the speed of each segment can be set individually. For example, in the early stage of sampling, when there is less dust accumulation in the magnetic field, the average moving speed or the magnetic field extension speed can be lower than the average speed mentioned above. In the middle and later stages of sampling, when dust accumulation in the magnetic field increases, the average moving speed or the magnetic field extension speed can be higher than the average speed mentioned above.

[0041] In this embodiment, a magnetic shielding layer 38 is provided at the end of the stroke of the magnet 31 moving in the opposite direction to the flow of the flue gas sample. At this time, the gas sampling ends, the magnetic core dust particles are freed from the magnetic field constraint, and are blown out of the first sampling tube 2 when the purging system 6 is working. The magnetic shielding layer 38 can be made of permalloy, which can efficiently conduct and concentrate magnetism, forming a magnetic field shielding effect.

[0042] In this embodiment, when sampling port 1 is opened to collect flue gas samples, the driver 34 drives the magnet 31 to move in the opposite direction to the flow of the flue gas sample. At this time, the magnetic field generated by the magnet 31 also moves in the opposite direction to the flow of the flue gas sample. The magnetic dust pile accumulated at the end of the magnet 31 near the flue gas sample sampling point will move with the magnet 31 because its root is close to the magnet 31. The tip of the magnetic dust pile will slide backward under the action of airflow because the magnetic field is weaker than that at the root, but it will not slip off. Finally, the movement of the magnet 31 will cause the magnetic dust pile to be spread on the inner surface of the pipe. This avoids the accumulation of dust particles at one end of the magnetic field, which could cause blockage of the second sampling tube 36 and thus create airflow shock fluctuations.

[0043] To ensure low sampling latency, the first sampling tube 2 uses a smaller diameter pipe. In this embodiment, the diameter d1 of the first sampling tube 2 is 6mm-12mm, and the diameter d2 of the second sampling tube 36 is d1-1.5d1. The diameter of the second sampling tube 36 is larger than that of the first sampling tube 2 to reserve storage space for dust particles adsorbed by the magnet, avoiding dust particle accumulation that could cause changes in airflow. Simultaneously, the larger diameter of the second sampling tube compared to the first sampling tube helps to slow down the airflow velocity within the second sampling tube, improving the magnetic dust adsorption efficiency. The first sampling tube 2 and the second sampling tube 36 are connected at a variable diameter, and the connection point must be smoothly rounded to prevent dust accumulation at the diameter change.

[0044] In this embodiment, the second sampling tube 36 is wrapped with a heat insulation layer 37 to avoid the influence of high-temperature flue gas on the magnetic field strength of the magnet 31. At the same time, a magnet temperature control device 39 is provided on the outside of the magnet 31. The magnet temperature control device 39 includes a first housing 310 surrounding the outside of the magnet 31. The first housing 310 is provided with an air inlet 311 and an air outlet 312. The air inlet 311 is used to blow low-temperature gas into the first housing 310 to control the temperature around the magnet 31 within a suitable range.

[0045] In this embodiment, when the magnet is an N50H neodymium iron boron magnet, the maximum operating temperature of 120°C is the upper limit for safe use. Long-term use above this temperature will lead to irreversible demagnetization. Therefore, when the magnet is an N50H neodymium iron boron magnet, the magnet temperature control device 39 needs to control the temperature inside the first housing 310 below 120°C.

[0046] In this embodiment, a temperature control system 7 is also provided. The temperature control system 7 is used to regulate the temperature of the collected flue gas sample to prevent the flue gas sample from condensing into liquid water in the magnetic separation dust removal unit 3 and the precision filtration unit 4. The temperature control system 7 includes a thermostat 71 and a temperature sensor 72. The first sampling tube 2 passes through the thermostat 71, and the temperature sensor 72 is located at the fine filter outlet 45. The thermostat 71 is used to regulate the temperature of the flue gas sample in the first sampling tube 2 according to the temperature of the outlet of the precision filtration unit 4 collected by the temperature sensor 72.

[0047] In this embodiment, a sealing system is also provided, which includes a first control valve 21, a second control valve 51, a third control valve 63, a fourth control valve 65, and a fifth control valve 67. The first control valve 21 is installed on the first sampling tube 2, and the fine filter outlet 45 is connected to the analytical instrument through the third sampling tube 5. The second control valve 51 is installed on the third sampling tube 5. The sealing system is used to seal the precision filter unit 4 during the time period between the end of the purging system 6 and the start of a new round of flue gas sample collection. When the purging system 6 stops purging, the sealing system closes all pipeline valves to prevent gas exchange between the magnetic separation dust removal unit 3 and the precision filter unit 4 and the outside environment, and to prevent external moisture from being adsorbed by dry dust particles and forming scale on the filter element 42 and the tube wall.

[0048] In this embodiment, the temperature sensors, control valves, and thermostat 71 mentioned above are all equipped with electrical control units consisting of a programmable logic controller (PLC), input / output modules, solenoid valves, electrical control components, etc., which facilitates programming and control operations by customers according to their actual needs.

[0049] Example 3: Unlike Examples 1 and 2, it also includes a second purging system, such as... Figure 2 As shown, the second purging system includes a sixth control valve 68 and a fourth purging pipe 69. The sixth control valve 68 is located at the connection between the second sampling pipe 36 and the precision filter unit 4, and the fourth purging pipe 69 is equipped with a seventh control valve 610. One end of the fourth purging pipe 69 is connected to a high-pressure liquid source, and the other end is connected to the end of the second sampling pipe 36 near the sixth control valve 68. When the sampling port 1 of the first sampling tube 2 is set at the rear end of the spray water cooling system of the converter blowing system, the temperature of the flue gas sample and the average particle size of the dust are significantly reduced. However, there are a large number of liquid droplets in the flue gas sample. At this time, there is a lot of scale in the second sampling tube during the sampling process. Therefore, it is necessary to use high-pressure liquid to flush it. During operation, the passage between the second sampling tube 36 and the precision filter unit 4 is closed by the sixth control valve 68, and the seventh control valve 610 on the fourth purge tube 69 is opened. At this time, the high-pressure liquid flow dissolves and flushes the dust scale on the inner wall of the second sampling tube 36. After flushing is completed, the sixth control valve 68 and the purge system 6 are opened again to blow out the dust in the precision filter unit 4 and the liquid droplets in the second sampling tube 36, so as to prevent the liquid droplets from entering the precision filter unit 4.

[0050] The difference between this embodiment and embodiment 2 is that the thermostat 71 in the temperature control system 7 is located on the pipeline between the sixth control valve 68 and the precision filter unit 4, heating only the flue gas sample entering the precision filter unit 4 to prevent iron oxide from forming on the filter element 42. Similarly, in this embodiment, the thermostat 71 receives the signal from the temperature sensor 72 located at the fine filter outlet 45 and performs the corresponding operation to ensure that the temperature of the flue gas sample entering the precision filter unit 4 is higher than the set temperature, which is generally the dew point temperature of water in the current flue gas environment.

[0051] The difference between this embodiment and embodiment 2 is that the sealing system includes a second control valve 51, a third control valve 63, a fourth control valve 65, and a sixth control valve 68. The simultaneous closure of the above four control valves can prevent the precision filter unit 4 from exchanging gases with the outside world and prevent external moisture from being adsorbed by dry dust particles and forming scale on the filter element 42.

[0052] Example 4: The difference from Example 2 is that the magnet 31 is fixed, and a magnetic shielding layer 38 is provided between the magnet 31 and the second sampling tube 36. The driver 34 drives the magnetic shielding layer 38 to be pulled away in the opposite direction of the flue gas sample flow, so as to extend the magnetic field in the opposite direction of the flue gas sample flow. Taking advantage of the characteristic that magnetic dust particles will gather at the end of the magnetic field, as the magnetic field extends, it can also achieve the effect of spreading magnetic dust particles on the inner wall of the second sampling tube 36. After the flue gas sample is sampled, the magnetic shielding layer 38 is reset to isolate the magnetic field and improve the purging effect.

[0053] Example 5: Unlike Example 2, this example does not use a mechanically driven magnet. Instead, it uses multiple independent electromagnets to extend the magnetic field in the opposite direction of the flue gas sample flow. The structure consists of multiple independent electromagnets arranged and nested on the outside of the second sampling tube 36. When flue gas sampling begins, the multiple independent electromagnets are turned on one by one from the end furthest from the sampling port 1 to the end closest to the sampling port 1, thus extending the magnetic field in the opposite direction of the flue gas sample flow. This also achieves the effect of spreading magnetic dust particles on the inner wall of the second sampling tube 36. When the flue gas sample sampling is completed, the multiple independent electromagnets are de-energized, the magnetic field disappears, and the purging effect is improved.

[0054] Example 6: To achieve long-term continuous detection, multiple of the above-mentioned flue gas sampling pretreatment systems can be used in parallel and rotated, such as... Figure 3 As shown, the duration of continuous detection is increased.

[0055] Example 7: This example discloses a flue gas sampling pretreatment method using the above-mentioned flue gas sampling pretreatment system based on magnetic separation and fine filtration, including the following steps: Sampling stage: The first control valve 21 is set on the first sampling tube 2 and the second control valve 51 is set on the third sampling tube 5. When the power pump is driven, the sampling port 1 draws in the flue gas sample. The flue gas sample flows through the first sampling tube 2, the magnetic separation dust removal unit 3 and the precision filter unit 4 in sequence, and is then transported to the analyzer by the third sampling tube 5. At the same time as the power pump is turned on, the magnetic separation dust removal unit 3 starts to control the magnetic field formed by the magnet 31 to move or extend in the opposite direction of the flue gas sample flow at a set speed. When sampling is started, temperature sensor 72 collects the temperature at the fine filter outlet 45. When the flue gas temperature collected by temperature sensor 72 is not lower than the freezing point of water, the temperature collected by temperature sensor 72 is fed back to temperature controller 71 to adjust the flue gas sample temperature in the first sampling tube 2 until the flue gas sample temperature collected by temperature sensor 72 at the fine filter outlet 45 is not lower than the set temperature. Generally, the set temperature is the dew point temperature of water in the current flue gas environment. At the same time, magnet temperature control device 39 controls the ambient temperature of magnet 31 to not be higher than the preset working temperature. When sampling is started, if the flue gas temperature collected by temperature sensor 72 is lower than the freezing point of water, temperature controller 71 stops working and does not heat the flue gas sample in the first sampling tube 2 until the flue gas temperature collected by temperature sensor 72 is not lower than the freezing point of water. Non-sampling stage: After the flue gas sample is sampled, the magnetic field formed by the magnet 31 in the magnetic separation dust removal unit 3 is weakened or disappears, the purging system 6 is turned on, and the precision filter unit 4 and / or the magnetic separation dust removal unit 3 and / or the connection between the second sampling tube 36 and the first sampling tube 2 is purged. The purging of the purging system 6 continues until the start of the next sampling stage or continues for a preset time.

[0056] Furthermore, a sealing phase can be added. During the sealing phase, the purging system 6 stops after a preset purging time. The first control valve 21 on the first sampling tube 2, the second control valve 51 on the third sampling tube 5, the third control valve 63 on the first purging unit, the fourth control valve 65 on the second purging unit, and the fifth control valve 67 on the third purging unit are all closed until a new round of flue gas sample collection begins. The preset purging time of the purging system 6 can generally be set from 3 seconds to 300 seconds according to requirements.

[0057] The sealing system closes the first control valve 21, the second control valve 51, the third control valve 63, and the fourth control valve 65, preventing gas exchange between the magnetic separation dust removal unit and the precision filtration unit and the outside environment. This avoids external water vapor being adsorbed by dry dust particles and forming scale on the filter element and pipe wall, which would affect the service life of the equipment.

[0058] In this embodiment, when the time interval between two sampling intervals is small, the purging process continues for the entire process of the two sampling intervals. The purging airflow is used to achieve an air seal, so a sealing system is not required. When the machine is shut down for a long time, the purging stops and a sealing system is used to avoid structural damage and extend the service life of the filter element.

[0059] Example 8 discloses a flue gas sampling pretreatment method using the above-mentioned flue gas sampling pretreatment system based on magnetic separation and fine filtration. Unlike Example 7, in this example, during the sampling stage, a temperature controller 71 is installed on the pipeline between the sixth control valve 68 and the precision filter unit 4 to adjust the temperature of the flue gas sample entering the precision filter unit 4. During the non-sampling stage, after the flue gas sample is sampled, the magnetic field formed by the magnet 31 in the magnetic separation dust removal unit 3 is weakened or disappears. First, the sixth control valve 68 closes the passage between the second sampling tube 36 and the precision filter unit 4, and the seventh control valve 610 on the fourth purge tube 69 is opened. High-pressure liquid flow is used to dissolve and flush the dust and scale on the inner wall of the second sampling tube 36, and flushing is completed after a set time. Then, the sixth control valve 68 and the purge system 6 are opened to blow out the dust in the precision filter unit 4 and the liquid droplets in the second sampling tube 36. The purge system 6 continues to purge until the start of the next sampling stage or for a preset duration.

[0060] In this embodiment, the time required to dissolve and rinse the inner wall of the second sampling tube 36 using high-pressure liquid flow can be obtained experimentally to determine the shortest time to achieve the rinsing effect. Generally, the rinsing time is controlled between 3 and 300 seconds.

[0061] During the sealing stage, the second control valve 51, the third control valve 63, the fourth control valve 65, and the sixth control valve 68 are closed to prevent gas exchange between the precision filter unit and the outside environment, thereby improving the service life of the equipment.

[0062] In summary, the flue gas sampling pretreatment system and method disclosed in this application, based on the combined use of magnetic separation and fine filtration, can effectively address high humidity, high temperature, and high dust levels in converter blowing flue gas sampling and analysis systems. While utilizing ultra-fine sampling pipes to ensure low-latency sampling, the system combines a magnetic separation dust removal unit, a fine filtration unit, a purging system, a temperature control system, and a sealing system to simultaneously achieve the technical effects of magnetic adsorption of magnetic particles, reducing the filtration pressure of the fine filter, reducing scaling of magnetic particles on the filter element and pipe inner walls, and thus improving filter element lifespan. This forms a flue gas sampling pretreatment system and method with both low-latency and low-frequency maintenance characteristics, ensuring that intelligent monitoring of the converter blowing process meets the current requirements for intelligent control of the converter blowing process.

[0063] In summary, although the embodiments of this application have been described in detail above, the above embodiments are not intended to limit this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A flue gas sampling pretreatment system based on a combination of magnetic separation and fine filtration, comprising a first sampling tube (2) and a precision filtration unit (4), wherein the sampling port (1) of the first sampling tube (2) is used to draw in flue gas samples, characterized in that, Also includes: The magnetic separation dust removal unit (3) has its air inlet end connected to the air outlet end of the first sampling tube (2). The magnetic separation dust removal unit (3) uses a magnetic field to adsorb magnetic particles in the flue gas sample. The air outlet end of the magnetic separation dust removal unit (3) is connected to the air inlet end of the precision filter unit (4). The air outlet end of the precision filter unit (4) is connected to the analytical instrument. A purging system (6) is connected to a precision filter unit (4). The purging system (6) is used to purge the pipelines of the precision filter unit (4) and the magnetic separation dust removal unit (3) after the sampling of flue gas samples is stopped.

2. The flue gas sampling pretreatment system based on the combined use of magnetic separation and fine filtration according to claim 1, characterized in that, The magnetic separation dust removal unit (3) includes: The second sampling tube (36) is connected at one end to the first sampling tube (2) and at the other end to the air inlet of the precision filter unit (4). A magnet (31) is nested outside the second sampling tube (36).

3. The flue gas sampling pretreatment system based on the combined use of magnetic separation and fine filtration according to claim 2, characterized in that, Also includes: Temperature control system (7), the temperature control system (7) is used to regulate the temperature of flue gas samples entering the magnetic separation dust removal unit (3) and / or the precision filtration unit (4), and / or to regulate the ambient temperature of the magnet (31) in the magnetic separation dust removal unit (3).

4. The flue gas sampling pretreatment system based on the combined use of magnetic separation and fine filtration according to claim 2, characterized in that, The magnetic field formed by the magnet (31) moves or extends axially in the opposite direction of the flue gas sample flow during the flue gas sample collection process. The movement or extension speed of the magnetic field is 0 or a set speed greater than 0.

5. A flue gas sampling pretreatment system based on the combined use of magnetic separation and fine filtration according to claim 2, characterized in that, The minimum design length of the magnetic field formed by the magnet (31) extending along the axial direction of the second sampling tube (36) is positively correlated with the airflow velocity.

6. The flue gas sampling pretreatment system based on the combined use of magnetic separation and fine filtration according to claim 2, characterized in that, The precision filtration unit (4) includes a fine filter (41), which includes a filter element (42) and a second housing (43). A gap space (44) is formed between the filter element (42) and the second housing (43). The second housing (43) is provided with a fine filtration inlet (46), which is connected to a second sampling tube (36). The filter element (42) is provided with a fine filtration outlet (45), which is connected to an analytical instrument. The second housing (43) is provided with a gap purge port (47), and the purge airflow from the gap purge port (47) moves towards the fine filtration inlet (46).

7. A flue gas sampling pretreatment system based on the combined use of magnetic separation and fine filtration according to claim 6, characterized in that, The purging system (6) includes a first purging unit, a second purging unit, and a third purging unit. The first purging unit includes a first purging pipe (62), one end of which is connected to the fine filter outlet (45) and the other end is connected to the high-pressure gas source (61). The first purging pipe (62) is equipped with a third control valve (63). The second purging unit includes a second purging pipe (64), one end of which is connected to the gap purging port (47) and the other end is connected to the high-pressure gas source (61). The second purging pipe (64) is equipped with a fourth control valve (65). The third purging unit includes a third purging pipe (66), one end of which is connected to the end of the second sampling pipe (36) near the first sampling pipe (2), and the other end of which is connected to the high-pressure gas source (61). The third purging pipe (66) is equipped with a fifth control valve (67).

8. A flue gas sampling pretreatment system based on the combined use of magnetic separation and fine filtration according to claim 6, characterized in that, It also includes a second purging system, which includes a sixth control valve (68) and a fourth purging tube (69). The sixth control valve (68) is located at the connection between the second sampling tube (36) and the precision filter unit (4), and the fourth purging tube (69) is equipped with a seventh control valve (610). One end of the fourth purging tube (69) is connected to a high-pressure liquid source, and the other end is connected to the end of the second sampling tube (36) near the sixth control valve (68).

9. A flue gas sampling pretreatment system based on the combined use of magnetic separation and fine filtration as described in claim 8, characterized in that, The temperature control system (7) includes a thermostat (71) and a temperature sensor (72). The thermostat (71) is located at the air inlet of the second purge tube (64) or the air inlet of the precision filter unit (4). The temperature sensor (72) is located at the air outlet (45) of the precision filter. The thermostat (71) is used to adjust the temperature of the flue gas sample in the pipeline at its location according to the temperature of the air outlet of the precision filter unit (4) collected by the temperature sensor (72).

10. A flue gas sampling pretreatment method using the flue gas sampling pretreatment system based on magnetic separation and fine filtration as described in claims 1-9, characterized in that, The steps include the following: Sampling stage: The first control valve (21) is set on the first sampling tube (2) and the second control valve (51) is set on the third sampling tube (5). When the valve is opened, the sampling port (1) draws in the flue gas sample under the drive of the power pump. The flue gas sample flows through the first sampling tube (2), the magnetic separation dust removal unit (3) and the precision filter unit (4) in sequence, and is then transported to the analyzer by the third sampling tube (5). At the same time as the power pump is turned on, the magnetic separation dust removal unit (3) starts to control the magnetic field formed by the magnet (31) to move or extend in the opposite direction of the flue gas sample flow at the set speed. When sampling is started, the temperature sensor (72) collects the temperature at the fine filter outlet (45). When the flue gas temperature collected by the temperature sensor (72) is not lower than the freezing point of water, the temperature collected by the temperature sensor (72) is fed back to the temperature controller (71) to adjust the flue gas sample temperature in the pipe at its location until the flue gas sample temperature collected by the temperature sensor (72) at the fine filter outlet (45) is not lower than the specified temperature. At the same time, the magnet temperature control device (39) adjusts the ambient temperature of the magnet (31) to not be higher than the preset working temperature. When sampling is started, when the flue gas temperature collected by the temperature sensor (72) is lower than the freezing point of water, the temperature controller (71) stops working and does not heat the flue gas sample in the pipe at its location until the flue gas temperature collected by the temperature sensor (72) is not lower than the freezing point of water. Non-sampling stage: After the flue gas sample is sampled, the magnetic field formed by the magnet (31) in the magnetic separation dust removal unit (3) is weakened or disappears, the purging system (6) and / or the second purging system are turned on to purge the precision filter unit (4) and / or the magnetic separation dust removal unit (3) until the next sampling stage begins or continues for a preset time.

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