Cascade separation device and method for multi-component heavy metals in metallurgical flue gas

Abstract

The invention provides a gradient separation device and method for multi-component heavy metal in metallurgical flue gas. The cascade separation device comprises a catalytic oxidation unit, a bipolar pre-charge unit, a turbulent flow agglomeration unit, an electric precipitation unit, a coordination adsorption unit, a wet washing device and a filtering separation device which are sequentially communicated along the flow direction of the flue gas, a catalyst and a two-fluid spray gun are arranged in the catalytic oxidation unit, and the two-fluid spray gun is used for spraying HCl-containing waste acid so as to convert zero-valent mercury in the flue gas into gaseous mercuric chloride; the working temperature of the electric precipitation unit is configured to be higher than the boiling point of gaseous mercuric chloride, and the electric precipitation unit is used for intercepting solid lead and zinc particles and allowing the gaseous mercuric chloride to penetrate through; the coordination adsorption unit is used for adsorbing gaseous mercuric chloride penetrating through the electric precipitation unit and unreacted zero-valent mercury. According to the invention, gaseous gradient separation of lead, zinc and other solid heavy metals from mercury in the metallurgical flue gas is realized, and cyclic utilization of waste acid is realized at the same time.

Description

Technical Field

[0001] This invention relates to a device and method for separating heavy metals in metallurgical flue gas, specifically to a stepwise separation device and method for multi-component heavy metals in metallurgical flue gas, belonging to the field of flue gas particulate matter control technology. Background Technology

[0002] The non-ferrous metallurgical industry emits heavy metals such as lead, zinc, and mercury into the atmosphere annually, making it a significant contributor to heavy metal pollution in my country's atmosphere. During the fluidized bed smelting and roasting process of lead-zinc ore, zinc and lead primarily form oxide particles, while mercury directly generates mercury vapor at high temperatures. Simultaneously, sulfur exists in the form of sulfur dioxide and sulfur trioxide. Therefore, the heavy metals in non-ferrous metallurgical flue gas are composed of both non-volatile metals such as zinc and lead and volatile metals such as mercury.

[0003] Existing metallurgical flue gas purification processes are mainly based on a combination of electrostatic precipitators (ESPs) and wet scrubbing. Because non-ferrous metallurgical flue gases contain high concentrations of sulfur dioxide and sulfur trioxide, and have low acid dew point temperatures, ESPs need to operate at temperatures above 260°C. However, high temperatures cause a significant drop in the operating voltage of the ESP, leading to a decrease in dust removal efficiency. In particular, submicron-sized fine particles enriched with volatile metals such as mercury are more likely to penetrate the ESP. To reduce the entry of heavy metal particles into the acid production system, the industry commonly uses wet scrubbing for secondary dust removal. However, this results in a large amount of heavy metals being lost into the scrubbing liquid, forming contaminated acid. Even after wet scrubbing, elemental zero-valent mercury is still difficult to purify effectively, leading to a large amount of highly toxic mercury entering the acid production system, contaminating sulfuric acid products, and causing environmental pollution with the use of sulfuric acid.

[0004] Therefore, how to effectively separate non-volatile metals from volatile metals in metallurgical flue gas, while simultaneously realizing the resource utilization of waste acid, has become a key problem that urgently needs to be solved in the field of heavy metal treatment of non-ferrous metallurgical flue gas. Summary of the Invention

[0005] Based on the above background, the purpose of this invention is to provide a stepwise separation device and method for multi-component heavy metals in metallurgical flue gas. Through the synergistic effect of phase change separation, coagulation and agglomeration and coordination adsorption, the stepwise separation of solid heavy metals such as lead and zinc from gaseous mercury is achieved, while the recycling of waste acid is realized. This solves the technical problems in the prior art, such as low high-temperature dust removal efficiency, difficulty in heavy metal separation, high cost of waste acid treatment, and mercury pollution of acid production systems.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A cascade separation device for multi-component heavy metals in metallurgical flue gas includes a catalytic oxidation unit, a bipolar pre-charge unit, a turbulent agglomeration unit, an electrostatic precipitator, a coordination adsorption unit, a wet scrubbing device, and a filtration and separation device, which are connected sequentially along the flue gas flow direction.

[0008] The inlet of the catalytic oxidation unit is used to connect to the external smelting furnace flue. The catalytic oxidation unit is equipped with a catalyst and a dual-fluid spray gun. The dual-fluid spray gun is used to spray HCl-containing waste acid to convert zero-valent mercury in the flue gas into gaseous mercuric chloride.

[0009] The bipolar precharged unit has parallel positive corona charging channels and negative corona charging channels inside. A grounded porous plate is provided between the positive corona charging channels and the negative corona charging channels. The porous plate is used for charged particles to pass through.

[0010] The turbulent agglomeration unit is equipped with an eddy current generator and a rectifier.

[0011] The operating temperature of the electrostatic precipitator is configured to be higher than the boiling point of the gaseous mercuric chloride. The electrostatic precipitator is used to trap solid lead and zinc particles while allowing the gaseous mercuric chloride to pass through.

[0012] The coordination adsorption unit contains an adsorbent and is used to adsorb the gaseous mercuric chloride and unreacted zero-valent mercury that have penetrated the electrostatic precipitator.

[0013] The inlet of the wet scrubbing device is connected to the outlet of the coordination adsorption unit, and the wet scrubbing device is provided with a waste acid discharge outlet.

[0014] The inlet of the filtration and separation device is connected to the waste acid outlet of the wet washing device. The filtration and separation device is provided with a filtrate outlet, which is connected to the dual-fluid spray gun of the catalytic oxidation unit.

[0015] By incorporating a catalytic oxidation unit with a catalyst and a dual-fluid spray gun, HCl-containing (hydrogen chloride)-injected waste acid is converted into gaseous mercuric chloride in the flue gas under the action of the catalyst. This utilizes the different volatility characteristics of mercuric chloride compared to lead and zinc oxides, creating conditions for subsequent staged separation. A bipolar pre-charging unit, with parallel positive and negative corona charging channels, charges particulate matter positively and negatively, respectively. A grounded porous plate between the two channels allows charged particles to pass through, causing mixing and collision between positively and negatively charged particles, increasing the size of submicron particles. A turbulent agglomeration unit, with an internal eddy current generator, produces turbulent disturbances to promote further collision and agglomeration of charged particles. A rectifier assembly ensures a uniform and stable airflow entering the downstream electrostatic precipitator unit. By configuring the operating temperature of the electrostatic precipitator (ESP) unit above the boiling point of gaseous mercuric chloride, solid lead and zinc particles are effectively retained, while gaseous mercuric chloride can penetrate the ESP unit, thus achieving initial separation of lead, zinc, and mercury. A coordination adsorption unit is then installed, with an adsorbent added inside, to directionally adsorb and capture the gaseous mercuric chloride that has penetrated the ESP unit, as well as unreacted zero-valent mercury. A wet scrubbing device further purifies the flue gas, and a filtration and separation device filters and separates the waste acid discharged from the wet scrubbing device. The separated filtrate is recycled back to the dual-fluid spray gun of the catalytic oxidation unit, significantly reducing the consumption of fresh acid and achieving resource utilization of the waste acid.

[0016] Preferably, the catalyst is an integral catalyst, which is installed in a quick-release structure, and pressure sensors are provided on both the front and rear sides of the integral catalyst; the liquid injection direction of the dual-fluid spray gun is parallel to the flue gas flow direction, the outer layer of the dual-fluid spray gun is provided with a sleeve, and an annular air duct is formed between the sleeve and the dual-fluid spray gun, and the annular air duct is used to introduce compressed air.

[0017] The quick-release design facilitates maintenance and replacement. A pressure sensor monitors pressure drop changes before and after the catalyst in real time, allowing for timely detection of blockages. The dual-fluid spray gun's liquid injection direction ensures that the hydrogen chloride-containing acid penetrates deep into the catalyst and makes full contact with the flue gas. Compressed air is introduced into the annular duct to form a cooling film on the spray gun surface, effectively isolating high-temperature flue gas and blowing away accumulated ash.

[0018] Preferably, the bipolar pre-charged unit includes a charging section shell, an insulator, a discharge electrode, and a grounding electrode; the discharge electrode is provided in both the positive corona charging channel and the negative corona charging channel; the perforated plate has an opening ratio of less than or equal to 9.4%, and the perforated plate is configured as the grounding electrode; the discharge electrode is connected to the insulator, the insulator is installed on the charging section shell, the insulator includes a through-shell sleeve with an inner cavity and an insulator pressure plate, and an insulating and corrosion-resistant layer is deposited on the surface of the insulator; an airflow distribution plate is provided at the inlet of the bipolar pre-charged unit, and the airflow distribution plate is a vertical parallel plate grid with an opening ratio greater than 80%.

[0019] Preferably, the vortex generator is arranged on the front side of the rectifier assembly, the vortex generator includes multiple blades, the blades are installed at an angle relative to the incoming flow direction, and the multiple blades have different tilt directions; the rectifier assembly includes multiple parallel rectifier plates.

[0020] Multiple vanes are used to generate complex turbulent flow fields to promote particle collisions, while multiple parallel fairings are used to stabilize the flow field.

[0021] Preferably, the coordination adsorption unit includes a quench tower, a rotary atomizing spray gun, a washing liquid circulation pipeline, and a metering pump. The rotary atomizing spray gun is located inside the quench tower, the washing liquid circulation pipeline is connected to the rotary atomizing spray gun, and the metering pump is connected to the washing liquid circulation pipeline. The metering pump is used to quantitatively add the adsorbent to the washing liquid circulation pipeline. The adsorbent is a metal sulfide-based adsorbent, which includes copper sulfide and / or molybdenum disulfide.

[0022] Preferably, the filtration and separation device includes a sedimentation tank, a filter press, and an evaporator connected in sequence. The inlet of the sedimentation tank serves as the inlet of the filtration and separation device, and the sedimentation tank, the filter press, and the evaporator are connected in sequence along the flow direction of the waste acid.

[0023] A method for separating multi-component heavy metals in metallurgical flue gas using a cascade separation device as described in any of the preceding claims, the method comprising the following steps:

[0024] S1. Metallurgical flue gas is introduced into the catalytic oxidation unit, and HCl-containing waste acid is sprayed in through the dual-fluid spray gun, so that the zero-valent mercury in the metallurgical flue gas is converted into gaseous mercuric chloride under the action of the catalyst.

[0025] S2. Metallurgical flue gas enters the bipolar pre-charged unit, and is diverted into the positive corona charging channel and the negative corona charging channel, so that positively charged particles and negatively charged particles pass through the porous plate and then enter the turbulent agglomeration unit.

[0026] S3. Metallurgical flue gas enters the electrostatic precipitator unit, and the operating temperature of the electrostatic precipitator unit is controlled to be higher than the boiling point of the gaseous mercuric chloride. The electrostatic precipitator unit traps solid lead and zinc particles, while allowing the gaseous mercuric chloride to pass through.

[0027] S4. The metallurgical flue gas that penetrates the electrostatic precipitator enters the coordination adsorption unit, and the gaseous mercuric chloride and unreacted zero-valent mercury are adsorbed by spraying a washing liquid containing adsorbent.

[0028] S5. Metallurgical flue gas enters the wet scrubbing device for washing. The waste acid discharged from the wet scrubbing device enters the filtration and separation device for filtration and separation. The separated filtrate is returned to the dual-fluid spray gun as the HCl-containing waste acid mentioned in step S1 for recycling.

[0029] Preferably, in step S1, the injection amount of the HCl-containing waste acid is controlled so that the HCl concentration in the flue gas in the catalytic oxidation unit is greater than 100 ppm.

[0030] Control the amount of polluted acid containing hydrogen chloride injected to ensure the full oxidation and conversion of zero-valent mercury.

[0031] Preferably, in step S2, the discharge voltage of the negative corona charging channel is -15kV, and the discharge voltage of the positive corona charging channel is 9kV~12kV.

[0032] Controlling the discharge voltage of the negative corona charging channel and the positive corona charging channel can optimize particle agglomeration.

[0033] Preferably, in step S4, the adsorbent is defective MoS2 nanosheets, and the operating temperature of the coordination adsorption unit is controlled at 150°C; in step S5, the filter residue separated by the filtration separation device is subjected to thermal desorption treatment at a temperature higher than 200°C.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] This invention discloses a cascade separation device and method for multi-component heavy metals in metallurgical flue gas. It converts zero-valent mercury into gaseous mercuric chloride through catalytic oxidation and utilizes the difference in phase transition temperatures between mercuric chloride and lead and zinc particles, combined with temperature control of the electrostatic precipitator unit, to achieve cascade separation of solid heavy metals and gaseous mercury. This invention effectively promotes the increase in particle size of submicron fine particles through the synergistic effect of bipolar pre-charging and turbulent agglomeration, significantly improving the removal efficiency of the electrostatic precipitator unit for fine particles. Furthermore, this invention uses a coordination adsorption unit to deeply capture gaseous mercuric chloride and residual zero-valent mercury, preventing mercury from entering the subsequent acid production system. The filtration and separation device enables the recycling of waste acid, significantly reducing treatment costs and minimizing secondary pollution. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of a multi-component heavy metal separation device for metallurgical flue gas according to the present invention.

[0038] Figure 2 This is a graph showing the conversion rate of zero-valent mercury on the surface of a 1% V2O5 / TiO2 catalyst;

[0039] Figure 3 This is a schematic diagram of the structure of the bipolar pre-charged unit, the turbulent agglomeration unit, and the electrostatic precipitator unit in this invention;

[0040] Figure 4 This is a graph showing the particle coagulation and reinforcement coefficients under different porosities;

[0041] Figure 5 This is a schematic diagram of the turbulent agglomeration unit in this invention;

[0042] Figure 6 This is a graph showing the particle grading and removal efficiency of the device of the present invention;

[0043] Figure 7 This is a graph showing the mercury adsorption performance of defective molybdenum disulfide nanosheets as an adsorbent.

[0044] In the diagram: 10, Catalytic oxidation unit; 20, Bipolar pre-charged unit; 21, Positive corona charging channel; 22, Negative corona charging channel; 23, Porous electrode plate; 24, Discharge electrode; 25, Airflow distribution plate; 30, Turbulent agglomeration unit; 31, Vortex generator; 311, Vane; 32, Rectifier assembly; 321, Rectifier plate; 40, Electrostatic precipitator unit; 50, Coordination adsorption unit; 60, Wet scrubbing device; 70, Filtration and separation device. Detailed Implementation

[0045] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any modifications and / or alterations made to the present invention will fall within the protection scope of the present invention.

[0046] In this invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art. Unless otherwise specified, the components or equipment in the following embodiments are general standard parts or components known to those skilled in the art, and their structures and principles can be learned by those skilled in the art through technical manuals or conventional experimental methods.

[0047] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In this detailed description, numerous specific details are set forth to facilitate explanation and provide a thorough understanding of the embodiments of the present invention. However, one or more embodiments may be practiced by those skilled in the art without these specific details.

[0048] like Figure 1 As shown, an embodiment of the present invention discloses a cascade separation device for multi-component heavy metals in metallurgical flue gas. The device includes a catalytic oxidation unit 10, a bipolar pre-charged unit 20, a turbulent agglomeration unit 30, an electrostatic precipitator 40, a coordination adsorption unit 50, a wet scrubbing device 60, and a filtration separation device 70, connected sequentially along the flue gas flow direction. The inlet of the catalytic oxidation unit 10 is connected to an external smelting furnace flue, and its outlet is connected to the inlet of the bipolar pre-charged unit 20. The outlet of the bipolar pre-charged unit 20 is connected to the inlet of the turbulent agglomeration unit 30. The outlet of the turbulent agglomeration unit 30 is connected to the inlet of the electrostatic precipitator 40. The outlet of the electrostatic precipitator 40 is connected to the inlet of the coordination adsorption unit 50. The outlet of the coordination adsorption unit 50 is connected to the inlet of the wet scrubbing device 60. The waste acid discharge outlet of the wet scrubbing device 60 is connected to the inlet of the filtration separation device 70. The filtration and separation device 70 is provided with a filtrate outlet, which is connected to the catalytic oxidation unit 10 through a pipeline to form a waste acid recycling loop.

[0049] The catalytic oxidation unit 10 contains a catalyst and a two-fluid spray gun. The catalyst is one or more of SCR catalysts, carbon-based catalysts, and metal oxide catalysts. Typical catalysts include V₂O₅ / TiO₂ catalysts, V₂O₅ / AC (activated carbon) catalysts, and catalysts with MnO as the active component. x Alternatively, catalysts supported on CuO, Al2O3, TiO2, and SiO2, such as MnO. x / Al2O3. The reaction mechanism for the conversion of mercury speciation in the catalyst is as follows: at an appropriate reaction temperature, HCl reacts with the catalyst to produce Cl2, and the generated Cl2 then reacts with zero-valent mercury in the flue gas to form mercuric chloride. The specific reaction process is shown below:

[0050]

[0051]

[0052] The conversion rate of zero-valent mercury on the surface of a 1% V2O5 / TiO2 catalyst is as follows: Figure 2 As shown. The reaction conditions were: a concentration of zero-valent mercury of 18.5 μg / m³. 3 The reaction temperature was 380℃ and the space velocity was 7200 h⁻¹. -1 HCl strongly promotes the oxidation of mercury, and the conversion rate of zero-valent mercury increases with increasing HCl concentration. At an HCl concentration of 0%, the conversion rate of zero-valent mercury is only 36.8%; however, when the HCl concentration increases to 100 ppm, the conversion rate increases to over 99%. Therefore, the amount of waste acid injected should ensure that the HCl concentration in the flue gas exceeds 100 ppm.

[0053] The integral catalyst is installed within a quick-release structure, which consists of a sleeve and a flange connecting to the pipeline. The integral catalyst is housed within the sleeve, which is coaxially sealed to the flue gas pipeline via a flange. A sealing gasket is installed at the connection to prevent flue gas escape. Pressure sensors are installed on both the front and rear sides of the integral catalyst to monitor pressure drop changes after the flue gas passes through the catalyst. When the detected pressure exceeds a threshold, the quick-release structure can be removed, and compressed air can be used to backflush the integral catalyst to remove deposited particles.

[0054] The dual-fluid spray gun is used to spray waste acid containing hydrogen chloride. It has independent gas and liquid interfaces. The liquid interface is connected to the filtrate from the filtration and separation device 70, and the gas interface is connected to compressed air at a pressure of 0.3~0.8MPa. The dual-fluid spray gun has an internal swirling mixing chamber to ensure thorough mixing of the gas and liquid phases. The nozzle is conical or fan-shaped. The liquid spray direction of the dual-fluid spray gun is parallel to the flue gas flow direction to ensure that the liquid can be sprayed into the integral catalyst. The dual-fluid spray gun is made of austenitic stainless steel or nickel-based alloy and has an outer sleeve. An annular air duct is formed between the sleeve and the dual-fluid spray gun. The annular air duct is used to continuously introduce compressed air, forming a cooling air film on the surface of the gun body, thereby isolating high temperatures and blowing away accumulated dust.

[0055] like Figure 3As shown, the bipolar pre-charged unit 20 includes a charged section shell, an insulator, a discharge electrode 24, and a grounding electrode. The bipolar pre-charged unit 20 internally has parallel positive corona charging channels 21 and negative corona charging channels 22. A grounded porous plate 23 is provided between the positive and negative corona charging channels 21 and 22, serving as the grounding electrode and allowing charged particles to pass through. Both the positive and negative corona charging channels 21 and 22 contain discharge electrodes 24, which can be palm-shaped, sawtooth-shaped, helical rod, or round rod electrodes, made of a corrosion-resistant alloy. The discharge electrodes 24 are connected to either a positive or negative high-voltage power supply via a 10MΩ protective resistor. The discharge voltage of the negative corona charging channel 22 is configured as -15kV, and the discharge voltage of the positive corona charging channel 21 is configured as 9kV~12kV. The discharge electrode 24 is connected to the insulator, which is installed on the outer shell of the charging section. The insulator includes a through-shell bushing with an inner cavity and an insulator pressure plate. It can be made of alumina ceramic material, and its surface is coated with a dense single or composite coating of alumina, silicon dioxide, and titanium dioxide by magnetron sputtering as an insulating and corrosion-resistant layer to slow down corrosion under high sulfur content flue gas. The insulator can be equipped with an externally heated air purging system, which keeps the surface temperature above the flue gas dew point to prevent condensation and creepage. The inlet of the bipolar pre-charging unit 20 is provided with an airflow distribution plate 25, which is a vertical parallel plate grid with an opening ratio of more than 80%, used to uniformly distribute the flue gas and ensure sufficient stability of the particulate charging process.

[0056] To measure particle agglomeration, an ELPI+ (Electrostatic Low-Voltage Impactor) was used at the outlet of the bipolar precharged unit 20 to measure particle concentration and size distribution. The ELPI+ can achieve online measurement of the number concentration of 14 levels of particles smaller than 10 μm. In the ELPI+, particles are initially charged by ions generated in the positive polarity charger. Then, particles are graded according to their aerodynamic diameter in the ELPI+. Each level is connected to an electrometer current amplifier; the induced current value is proportional to the number of particles, and the instrument converts this into a number concentration distribution using known particle charge and the particle number dependence of each level. Considering that particle agglomeration is usually accompanied by an increase in median particle size (i.e., agglomeration produces larger particles), R was defined. ae R is the agglomeration enhancement factor, which is the ratio of the increase in median particle size before and after particle agglomeration. ae A value greater than 1 indicates that the unit promotes particle agglomeration and growth. The formula for calculating the agglomeration enhancement coefficient is as follows:

[0057] ;

[0058] Where D0 is the average particle size (µm) of the particles before passing through the bipolar precharged unit 20, D aggIt is the average particle size (µm) of the particulate matter after passing through the bipolar precharged unit 20.

[0059] The average particle size of the particulate matter was calculated using the following formula:

[0060] ;

[0061] Where, N i It is the number of particulate matter at each level detected by ELPI+, D i It is the diameter corresponding to each level of particles.

[0062] To obtain a suitable voltage matching configuration for the pre-charged unit while ensuring sufficient particle charging, this invention sets the negative channel discharge voltage to -15 kV and the positive channel voltage to 9 kV to 15 kV to evaluate the electrocoagulation effect under different voltage matching configurations. The particle coagulation enhancement coefficient R under different voltage matching configurations is... ae like Figure 4 As shown, when the positive voltage increases from 9kV to 12kV, the increase in positive discharge voltage increases R. ae This indicates that a high discharge voltage increases the positive charge on the particles, leading to better mixing under the influence of Coulomb force and further aggregation with negatively charged particles. However, when the positive discharge voltage exceeds 12 kV, R... ae The value decreased from 1.33 to 1.10. This finding can be inferred from the collision and coalescence of submicron particles with neutral particles in the positive channel due to polarization. When the positive corona discharge voltage is too high, too many positive ions are generated, thus suppressing the collision and coalescence between charged particles and neutral particles.

[0063] The ion wind generated near the discharge electrode 24 can produce strong turbulence on the ground electrode, which has a significant impact on the flow field and particle migration. To utilize the ion wind for agglomeration enhancement, a porous electrode plate 23 is used between the positive and negative channels in the pre-charged unit. In this way, the ion wind-induced turbulence can drive particles toward the ground electrode and through the holes in the plate into another channel of opposite polarity. Therefore, the chances of mixing and colliding between positively and negatively charged particles increase. The porous electrode plate 23 utilizes the ion wind generated by corona discharge in the pre-charged unit, allowing the turbulence caused by the ion wind to promote the mixing and collision of positively and negatively charged particles in the pre-charger.

[0064] The porous electrode plate 23 typically has circular perforations with diameters of 6 mm, 8 mm, and 10 mm, corresponding to porosity ratios of 9.4%, 16.7%, and 26.2%, respectively. Considering the porosity under different voltage matching conditions, compared with a smooth electrode plate without perforations, a porous plate with a porosity ratio below 9.4% can achieve better particle agglomeration effect. That is, a porous plate with appropriate porosity can promote airflow exchange and particle collision agglomeration within the precharger, while an excessively high porosity reduces the agglomeration effect because large pores in the plate cause uneven discharge field and excessive neutralization of positive and negative ions. Therefore, in this embodiment, the porosity of the porous electrode plate 23 is less than or equal to 9.4%, and a porous plate with a circular perforation diameter of 6 mm is used to achieve an porosity of 9.4%. Preferably, the discharge voltage of the negative corona charging channel 22 is configured as -15 kV, and the discharge voltage of the positive corona charging channel 21 is configured as 12 kV.

[0065] The turbulent agglomeration unit 30 is equipped with a vortex generator 31 and a flow rectifier assembly 32. The vortex generator 31 is arranged in front of the flow rectifier assembly 32. The vortex generator 31 includes multiple vanes 311. The size of the vanes 311 is 1 to 3 times the thickness of the boundary layer of the flue gas duct. The shape can be trapezoidal, triangular, or rectangular. They are installed at an angle of 10° to 20° relative to the incoming flow direction. The multiple vanes 311 have different tilt directions and can be installed in pairs in a V-shape or array on one or more sections in the incoming flow direction to generate a complex vortex field to promote particle collision. The flow rectifier assembly 32 includes multiple parallel flow rectifier plates 321. The flow rectifier plates 321 can be in the form of guide plates or guide vanes, with a rectangular or airfoil cross-section, to stabilize the flow field and ensure uniform airflow entering the downstream electrostatic precipitator unit 40.

[0066] The operating temperature of the electrostatic precipitator unit 40 is configured to be higher than the boiling point of gaseous mercuric chloride, specifically above 310°C. The electrostatic precipitator unit 40 is used to trap solid lead and zinc particles while allowing gaseous mercuric chloride to pass through. The electrostatic precipitator unit 40 is equipped with a negative high-voltage power supply with an operating voltage of -25kV to capture particulate matter after it has been processed by the aforementioned unit.

[0067] The particle classification and removal efficiency of the entire device can be calculated using the following formula after measuring the initial particle concentration and the outlet concentration of the electrostatic precipitator unit 40:

[0068] ;

[0069] Where η is the removal efficiency of particles at each stage, and N inlet The initial concentration of particles at each level (particles / cm³) 3 ), N outlet The particle concentration at the outlet of the electrostatic precipitator unit 40 (particles / cm³) 3 ).

[0070] like Figure 6 As shown, the particle removal efficiency of the device can be effectively improved by using a pre-charged unit combined with turbulent agglomeration before the electrostatic precipitator unit 40.

[0071] The coordination adsorption unit 50 includes a quench tower, a rotary atomizing spray gun, a washing liquid circulation pipeline, and a metering pump. The rotary atomizing spray gun is located inside the quench tower, and the washing liquid circulation pipeline is connected to the rotary atomizing spray gun. The metering pump is connected to the washing liquid circulation pipeline. The metering pump is used to quantitatively add adsorbent to the washing liquid circulation pipeline. The operating temperature of the coordination adsorption unit 50 is controlled at approximately 150°C. The washing liquid containing the adsorbent is atomized and sprayed into the flue gas through the rotary atomizing spray gun, contacting the flue gas and adsorbing gaseous mercuric chloride and unreacted zero-valent mercury while cooling the gas. The composition of the washing liquid in the coordination adsorption unit 50 is the same as that used in the wet scrubbing device 60, and the washing liquid in the coordination adsorption unit 50 can be periodically discharged to the wet scrubbing device 60.

[0072] The adsorbent is a metal sulfide-based adsorbent, including copper sulfide and / or molybdenum disulfide. In particular, defective molybdenum disulfide nanosheets can be used as the adsorbent, and their mercury adsorption performance is as follows: Figure 7 As shown. This adsorbent at 150℃ is effective against Hg. 0 It exhibits excellent adsorption performance. Steady-state analysis results show that the defective molybdenum disulfide nanosheets exhibit excellent adsorption performance in Hg. 0 It exhibits excellent adsorption performance, with a removal efficiency approaching 100%. When the temperature rises above 200℃, the adsorbed Hg... 0 Desorption can occur, with the desorption-to-adsorption ratio exceeding 99.4%. This indicates that the defective molybdenum disulfide nanosheets can be easily regenerated at high temperatures. Compared to traditional activated carbon adsorption, defective molybdenum disulfide nanosheets are technically and economically superior as adsorbents. Furthermore, defective molybdenum disulfide nanosheets can also capture Hg... 0 As a means of efficient resource recycling.

[0073] Dilute sulfuric acid can be used as the washing liquid in the wet scrubbing device 60, with the concentration controlled between 10% and 20%, to further separate heavy metals from high-sulfur flue gas. During the scrubbing process, fluorides, chlorides, and heavy metal ions dissolve in the washing liquid. Therefore, it is necessary to periodically discharge a portion of the washing liquid (i.e., waste acid) to the filtration and separation device 70 and replenish it with clean water or dilute sulfuric acid to maintain the concentration.

[0074] The filtration and separation device 70 includes a sedimentation tank, a filter press, and an evaporator connected in sequence. The inlet of the sedimentation tank serves as the inlet of the filtration and separation device 70. The sedimentation tank, filter press, and evaporator are connected in sequence along the flow direction of the waste acid. The waste acid containing saturated adsorbent first enters the sedimentation tank for settling, and then undergoes solid-liquid separation through the filter press. The filtrate is mainly a solution containing hydrogen chloride and sulfuric acid, and is recycled back to the two-fluid spray gun of the catalytic oxidation unit 10 for reuse through the filtrate outlet. The filter residue is mainly saturated adsorbent, which can be thermally desorbed at a temperature above 200°C to achieve mercury recovery and adsorbent regeneration.

[0075] The embodiments of the present invention also disclose a step-by-step separation method using the above-mentioned step-by-step separation device for multi-component heavy metals in metallurgical flue gas, the specific steps of which are as follows.

[0076] First, metallurgical flue gas is introduced into the catalytic oxidation unit 10. Waste acid containing hydrogen chloride is injected through a dual-fluid spray gun, with the injection rate controlled to ensure a hydrogen chloride concentration in the flue gas greater than 100 ppm. Under the action of the catalyst, zero-valent mercury in the flue gas undergoes a catalytic oxidation reaction to convert into gaseous mercuric chloride. The reaction temperature is controlled at approximately 380℃. During this process, hydrogen chloride in the waste acid reacts on the catalyst surface to generate chlorine gas, which then reacts with zero-valent mercury to form gaseous mercuric chloride. This converts the difficult-to-capture zero-valent mercury into an easily adsorbed gaseous form of mercuric chloride, while simultaneously utilizing the acidic components in the waste acid to inhibit other competing reactions.

[0077] Subsequently, the metallurgical flue gas enters the bipolar pre-charged unit 20. The gas flow is first evenly distributed by the gas distribution plate 25, then splits into the positive corona charging channel 21 and the negative corona charging channel 22. In the negative corona charging channel 22, particles acquire a negative charge under the influence of a -15kV negative high-voltage corona. In the positive corona charging channel 21, particles acquire a positive charge under the influence of a 9kV~12kV positive high-voltage corona. The positively and negatively charged particles are carried by the gas flow through the grounded porous plate 23. Since the porosity of the porous plate 23 is less than or equal to 9.4%, the turbulence induced by the ion wind drives the particles through the pores into channels of opposite polarity, resulting in thorough mixing of the positively and negatively charged particles. Under the influence of Coulomb force, particles with opposite charges collide and coalesce, significantly increasing their size. Simultaneously, some particles also contribute to the coalescence process due to collisions with neutral particles caused by polarization.

[0078] Next, the metallurgical flue gas enters the turbulent agglomeration unit 30. Under the action of the vanes 311 of the vortex generator 31, the flue gas generates turbulent disturbances, further promoting collisions and agglomeration between charged particles and between particles and neutral particles. Because the vanes 311 have different tilt directions, the generated vortex structure is complex and varied, effectively breaking particle following behavior and increasing the collision probability. After passing through the vortex generator 31, the flue gas undergoes rectification by the rectifying component 32, resulting in a uniform and stable flow field before entering the electrostatic precipitator unit 40.

[0079] In the electrostatic precipitator unit 40, the operating temperature is controlled above 310°C, which is higher than the boiling point of gaseous mercuric chloride (302°C). At this temperature, heavy metals such as lead and zinc exist as solid particulate matter, while mercury exists as gaseous mercuric chloride. The electrostatic precipitator unit 40 uses a high-voltage electrostatic field to capture solid lead and zinc particles, while gaseous mercuric chloride can easily penetrate the unit, thus achieving preliminary separation of lead, zinc, and mercury. After passing through the electrostatic precipitator unit 40, the removal efficiency of solid heavy metal particles is significantly improved, especially the removal efficiency of submicron particles, which is greatly enhanced through the aforementioned agglomeration process.

[0080] The metallurgical flue gas passing through the electrostatic precipitator unit 40 then enters the coordination adsorption unit 50, where its temperature is rapidly cooled to approximately 150°C in a quench tower by sprayed washing liquid containing adsorbent. At this temperature, the defective molybdenum disulfide nanosheet adsorbent exhibits a strong chemical affinity for gaseous mercuric chloride and residual zero-valent mercury. The unsaturated sulfur sites on the adsorbent surface can form stable mercuric sulfide chemical bonds with mercury atoms, while the abundant porous structure provides physical adsorption, thereby achieving deep capture of mercury. The washing liquid containing adsorbed mercury is periodically discharged into the wet scrubbing unit 60.

[0081] Finally, the metallurgical flue gas enters the wet scrubbing unit 60 for final washing to remove residual acidic gases and trace particulate matter. The waste acid discharged from the wet scrubbing unit 60 enters the filtration and separation unit 70. After sedimentation, pressure filtration and evaporation, the filtrate rich in hydrogen chloride is recycled back to the dual-fluid spray gun of the catalytic oxidation unit 10, while the filter residue rich in mercury is desorbed to recover mercury and regenerate the adsorbent.

[0082] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A stepped separation device for multi-component heavy metals in metallurgical flue gas, characterized in that: The multi-component heavy metal separation device for metallurgical flue gas includes a catalytic oxidation unit (10), a bipolar pre-charged unit (20), a turbulent agglomeration unit (30), an electrostatic precipitator (40), a coordination adsorption unit (50), a wet scrubbing device (60), and a filtration and separation device (70) connected sequentially along the flue gas flow direction. The inlet of the catalytic oxidation unit (10) is used to connect to the external smelting furnace flue. The catalytic oxidation unit (10) is equipped with a catalyst and a dual-fluid spray gun. The dual-fluid spray gun is used to spray HCl-containing waste acid so that the zero-valent mercury in the flue gas is converted into gaseous mercuric chloride. The bipolar precharged unit (20) has parallel positive corona charging channels (21) and negative corona charging channels (22) inside. A grounded porous plate (23) is provided between the positive corona charging channel (21) and the negative corona charging channel (22). The porous plate (23) is used to allow charged particles to pass through. The turbulent agglomeration unit (30) is equipped with an eddy generator (31) and a rectifier assembly (32). The operating temperature of the electrostatic precipitator (40) is configured to be higher than the boiling point of the gaseous mercuric chloride. The electrostatic precipitator (40) is used to trap solid lead and zinc particles and allow the gaseous mercuric chloride to pass through. An adsorbent is added to the coordination adsorption unit (50), which is used to adsorb the gaseous mercuric chloride and unreacted zero-valent mercury that penetrate the electrostatic precipitator (40). The inlet of the wet scrubbing device (60) is connected to the outlet of the coordination adsorption unit (50), and the wet scrubbing device (60) is provided with a waste acid discharge outlet. The inlet of the filtration and separation device (70) is connected to the waste acid outlet of the wet washing device (60), and the filtration and separation device (70) is provided with a filtrate outlet, which is connected to the dual-fluid spray gun of the catalytic oxidation unit (10).

2. The stepwise separation device for multi-component heavy metals in metallurgical flue gas according to claim 1, characterized in that: The catalyst is an integral catalyst, which is installed in a quick-release structure, and pressure sensors are provided on both the front and rear sides of the integral catalyst; the liquid injection direction of the dual-fluid spray gun is parallel to the flue gas flow direction, the outer layer of the dual-fluid spray gun is provided with a sleeve, and an annular air duct is formed between the sleeve and the dual-fluid spray gun, and the annular air duct is used to introduce compressed air.

3. The stepwise separation device for multi-component heavy metals in metallurgical flue gas according to claim 1, characterized in that: The bipolar precharged unit (20) includes a charged section shell, an insulator, a discharge electrode (24), and a grounding electrode; the discharge electrode (24) is provided in both the positive corona charging channel (21) and the negative corona charging channel (22); the perforated plate (23) has an opening ratio of less than or equal to 9.4%, and the perforated plate (23) is configured as the grounding electrode; the discharge electrode (24) is connected to the insulator, the insulator is installed on the charged section shell, the insulator includes a shell sleeve with an inner cavity and an insulator pressure plate, and the surface of the insulator is deposited with an insulating and corrosion-resistant layer; an airflow distribution plate (25) is provided at the inlet of the bipolar precharged unit (20), and the airflow distribution plate (25) is a vertical parallel plate grid with an opening ratio of greater than 80%.

4. The stepwise separation device for multi-component heavy metals in metallurgical flue gas according to claim 1, characterized in that: The vortex generator (31) is arranged on the front side of the rectifier assembly (32). The vortex generator (31) includes multiple blades (311), which are installed at an angle relative to the incoming flow direction, and the multiple blades (311) have different tilt directions. The rectifier assembly (32) includes multiple parallel rectifier plates (321).

5. The stepwise separation device for multi-component heavy metals in metallurgical flue gas according to claim 1, characterized in that: The coordination adsorption unit (50) includes a quench tower, a rotary atomizing spray gun, a washing liquid circulation pipeline, and a metering pump. The rotary atomizing spray gun is located inside the quench tower. The washing liquid circulation pipeline is connected to the rotary atomizing spray gun. The metering pump is connected to the washing liquid circulation pipeline. The metering pump is used to quantitatively add the adsorbent to the washing liquid circulation pipeline. The adsorbent is a metal sulfide-based adsorbent, which includes copper sulfide and / or molybdenum disulfide.

6. The stepwise separation device for multi-component heavy metals in metallurgical flue gas according to claim 1, characterized in that: The filtration and separation device (70) includes a sedimentation tank, a filter press and an evaporator connected in sequence. The inlet of the sedimentation tank serves as the inlet of the filtration and separation device (70). The sedimentation tank, the filter press and the evaporator are connected in sequence along the flow direction of the waste acid.

7. A step-by-step separation method using a step-by-step separation device for multi-component heavy metals in metallurgical flue gas as described in any one of claims 1-6, characterized in that: The method includes the following steps: S1. Metallurgical flue gas is introduced into the catalytic oxidation unit (10), and HCl-containing waste acid is sprayed into it through the dual-fluid spray gun, so that the zero-valent mercury in the metallurgical flue gas is converted into gaseous mercuric chloride under the action of the catalyst. S2. Metallurgical flue gas enters the bipolar pre-charged unit (20), and is diverted into the positive corona charging channel (21) and the negative corona charging channel (22), so that the positively charged particles and the negatively charged particles pass through the porous plate (23) and then enter the turbulent agglomeration unit (30). S3. Metallurgical flue gas enters the electrostatic precipitator (40), and the working temperature of the electrostatic precipitator (40) is controlled to be higher than the boiling point of the gaseous mercuric chloride. The electrostatic precipitator (40) traps solid lead and zinc particles and allows the gaseous mercuric chloride to pass through. S4. The metallurgical flue gas that penetrates the electrostatic precipitator (40) enters the coordination adsorption unit (50) and adsorbs the gaseous mercuric chloride and unreacted zero-valent mercury by spraying a washing liquid containing adsorbent. S5. Metallurgical flue gas enters the wet scrubbing device (60) for scrubbing. The waste acid discharged from the wet scrubbing device (60) enters the filtration and separation device (70) for filtration and separation. The separated filtrate is returned to the dual-fluid spray gun as the HCl-containing waste acid mentioned in step S1 for recycling.

8. The method for stepwise separation of multi-component heavy metals in metallurgical flue gas according to claim 7, characterized in that: In step S1, the injection amount of the HCl-containing waste acid is controlled so that the HCl concentration in the flue gas in the catalytic oxidation unit (10) is greater than 100 ppm.

9. The method for staged separation of multi-component heavy metals in metallurgical flue gas according to claim 7, characterized in that: In step S2, the discharge voltage of the negative corona charging channel (22) is -15kV, and the discharge voltage of the positive corona charging channel (21) is 9kV~12kV.

10. The method for stepwise separation of multi-component heavy metals in metallurgical flue gas according to claim 7, characterized in that: In step S4, the adsorbent is defective MoS2 nanosheets, and the operating temperature of the coordination adsorption unit (50) is controlled at 150°C; in step S5, the filter residue separated by the filtration separation device (70) is subjected to thermal desorption treatment at a temperature higher than 200°C.

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