An acid mist waste gas treatment system for a zinc-based alloy production process

Abstract

The present invention relates to the technical field of waste gas treatment, and particularly to an acid mist waste gas treatment system for a zinc-based alloy production process. The acid mist waste gas treatment system includes a gas collection system, a separation system and a spray system. Through the top suction and start-stop side suction structures of the gas collection system, the suction air flow velocity is synchronously tested, the power ratio between the side suction port and the top suction port is analyzed, and the suction power of the two suction ports of the gas collection system is distributed. After being transmitted to the separation system, the gradient temperature separation structure is used to further separate and settle aerosol particles, and finally the gas is neutralized and treated through the spray system. The present invention collects gas through the double suction ports of top suction and side suction, analyzes the influence of different suction ports on the mixed precipitation of aerosol particles to determine the optimal power distribution, and the collected gas is transmitted to the separation system for separation through the gradient inversion layer structure, improving the sedimentation efficiency of aerosol particles and ensuring the high efficiency and reliability of waste gas treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of waste gas treatment, and particularly to an acid mist waste gas treatment system for a zinc-based alloy production process. Background Art

[0002] During the production of zinc-based alloys, the pickling process is the main source of acid mist waste gas. Hydrochloric acid (concentration about 15%) is used in the pickling stage to remove metal surface oxides, generating hydrogen chloride acid mist. Its generation amount is closely related to the acid solution concentration, operating conditions, and tank size. Acid mist capture is achieved through a closed workshop, side suction at the tank edge, or a negative pressure exhaust system, and the gas collection efficiency can reach 85% - 99.5%. The acid mist is led to an alkali solution spray tower, such as a dual-source cooling tower or an acid mist absorption tower, where sodium hydroxide reacts with hydrogen chloride for neutralization.

[0003] In the pickling tank area, a closed side suction exhaust system is often used to avoid acid mist escape. However, during the pickling process, in addition to acid mist gas, a large amount of metal ions are also generated, which react with the acid solution to form aerosol particles. If these aerosol particles are directly discharged into the alkali solution spray tower after being collected, solid deposits will quickly form, not only affecting the quality of the recycled material in circulation but also requiring frequent cleaning of these solid blockages.

[0004] In order to reduce the blockage caused by solid precipitation in acid mist treatment, aerosol particle separation can be carried out in advance. However, traditional separation processes are relatively complex, and the use of a large number of consumables increases the actual production cost, and the unsatisfactory separation effect will also lead to poor waste gas treatment efficiency. Summary of the Invention

[0005] In order to solve the above problems in the prior art, the purpose of the present invention is to provide an acid mist waste gas treatment system for a zinc-based alloy production process, and the specific technical solution adopted is as follows:

[0006] The present invention provides an acid mist waste gas treatment system for a zinc-based alloy production process, including a gas collection system, a separation system, and a spray system; the gas collection system includes a top suction port, a start-stop side suction port, and a temporary storage area;

[0007] In the gas collection system, different preset inhalation speeds are set, and continuous tests are carried out in ascending order. In each test, the preset inhalation speeds of the top suction port and the side suction port are the same; in each test, the bottom layer waste gas turbidity of the temporary storage area, the gas dispersion degree of each sampling point, and the gas dispersion degree of each moment in the local area during the shutdown of the side suction port are obtained; the hydrogen chloride concentration and aerosol concentration in the inhaled gas of the top suction port and the side suction port are respectively obtained;

[0008] In each test, the gas static separation rate is obtained according to the change degree of gas divergence during the shutdown of the side suction port and the distribution of gas escape rate in the temporary storage area; the mutual interference coefficient of each test is obtained according to the change situation of the bottom waste gas disturbance during continuous tests; by the ratio between the hydrogen chloride concentration and aerosol concentration at different suction ports during the test, as well as the gas static separation rate and the mutual interference coefficient, the influence of the preset inhalation speed on the states of different suction ports is analyzed to obtain the final power ratio between the side suction port and the top suction port;

[0009] The gas collection system distributes the power of the two suction ports based on the final power ratio and transmits the collected gas to the separation system; the separation system further separates the collected gas through the gradient inversion layer structure of the tower temperature, and then the gas is transmitted to the spray system for neutralization treatment.

[0010] Further, the method for obtaining the gas static separation rate includes:

[0011] For any test, during the shutdown of the side suction port, the difference between the gas divergence at the last moment and the gas divergence at the initial moment is subjected to negative correlation mapping and normalization processing to obtain the inertial escape coefficient of this test;

[0012] Calculate the mean value of the gas escape rate at all sampling points in this test as the average natural escape rate; the difference between the average natural escape rate and the minimum gas escape rate among all sampling points is used as the basic separation speed of this test;

[0013] Taking the inertial escape coefficient of this test as the numerator and the sum value of the preset inhalation speed and the basic separation speed corresponding to this test as the denominator, the gas static separation rate of this test is obtained.

[0014] Further, the method for obtaining the mutual interference coefficient includes:

[0015] During continuous tests, the difference in the bottom waste gas disturbance between the subsequent test and the previous test for every two adjacent tests is taken, and the average value of all differences is used as the disturbance change degree;

[0016] The difference in the bottom waste gas disturbance between each test and the previous test is used as the disturbance difference degree of each test; the difference between the disturbance difference degree of each test and the disturbance change degree is used as the mutual interference coefficient of each test.

[0017] Further, the method for obtaining the final power ratio includes:

[0018] According to the ratio situation of the hydrogen chloride concentration and aerosol concentration at the top suction port during the test, combined with the gas static separation rate, the gas collection state index of the top suction port is obtained;

[0019] According to the ratio of the hydrogen chloride concentration to the aerosol concentration at the side suction port during the test, and in combination with the interference coefficient, the gas collection state index of the side suction port is obtained;

[0020] Take the ratio of the gas collection state index of the side suction port to the gas collection state index of the top suction port as the final power ratio.

[0021] Furthermore, the method for obtaining the gas collection state index of the top suction port includes:

[0022] Take the ratio of the hydrogen chloride concentration to the aerosol concentration corresponding to the top suction port in each test as the top suction gas collection ratio;

[0023] Take the preset inhalation speed corresponding to the test when the top suction gas collection ratio is the largest as the top suction ideal speed; take the preset inhalation speed corresponding to the test with the largest gas static separation rate as the first critical speed;

[0024] Take the gas static separation rate corresponding to the test as the weight, and perform weighted averaging on the top suction ideal speed and the first critical speed to obtain the gas collection state index of the top suction port.

[0025] Furthermore, the method for obtaining the gas collection state index of the side suction port includes:

[0026] Take the ratio of the hydrogen chloride concentration to the aerosol concentration corresponding to the side suction port in each test as the side suction gas collection ratio;

[0027] Take the preset inhalation speed corresponding to the test when the side suction gas collection ratio is the smallest as the side suction ideal speed; take the preset inhalation speed corresponding to the test with the smallest interference coefficient as the second critical speed;

[0028] Take the interference coefficient corresponding to the test as the weight, and perform weighted averaging on the side suction ideal speed and the second critical speed to obtain the gas collection state index of the side suction port.

[0029] Furthermore, the method for obtaining the bottom waste gas disturbance degree includes:

[0030] In each test, obtain the acid mist gas flow rate at each horizontal sampling point at each moment at a preset height above the bottom of the temporary storage area;

[0031] For any horizontal sampling point, take the average flow rate of the acid mist gas flow rate in the vertical direction at all moments of this sampling point as the vertical reference flow rate of this sampling point; calculate the difference between the flow rate of the acid mist gas flow rate in the vertical direction at each moment of this sampling point and the vertical reference flow rate as the pulsation speed of this sampling point;

[0032] Normalize the ratio between the standard deviation of the pulsation speeds of all horizontal sampling points and the average value of all vertical reference flow rates to obtain the bottom waste gas disturbance degree of each test.

[0033] Further, the method for obtaining the gas divergence includes:

[0034] At any given moment, obtain the gas flow velocities in each axis direction of a preset local area of the side suction port in a three-dimensional coordinate system;

[0035] Sum up the derivatives of all gas flow velocities and perform normalization processing to obtain the gas divergence at each moment.

[0036] Further, the direction of the top suction port is vertically downward, and the direction of the side suction port is at an inclined angle with the wall of the temporary storage area.

[0037] Further, the separation system includes an upper high-temperature section, a middle transition section, and a lower low-temperature section. The electric heating temperature control device is located in the upper high-temperature section and is used to raise the separated gas. The humidity control device is located in the middle transition section and is used to liquefy and block aerosol particles. The water circulation temperature control device is located in the lower low-temperature section and is used for the sedimentation of aerosol particles.

[0038] The present invention has the following beneficial effects:

[0039] Through the top suction and start-stop side suction structure of the gas collection system, the present invention conducts synchronous tests on the suction flow rates. According to the static separation rate of acid mist under different test suction speeds and the mutual interference between the two suction ports, the preferred influence of the suction rate is analyzed. Combining with the preferred state of the ratio between the inhaled hydrogen chloride concentration and the aerosol concentration, the power ratio is obtained for the suction power distribution of the gas collection system. Through the comprehensive influence of static separation and mutual interference, while ensuring the collection efficiency of acid mist waste gas, the stable state of the acid mist waste gas is maintained. While the double gas collection ports operate synchronously, space is reserved for the upward dispersion of gas and the sedimentation of aerosol particles, promoting the continuous and stable collection and preliminary separation of acid mist waste gas. In the subsequent separation system, the gradient temperature separation structure is used to promote the further separation and sedimentation of high-concentration aerosol particles, reduce the influence of aerosol particles on subsequent processing, and enable the gas to be efficiently neutralized by the spray system. Through the double suction port gas collection of top suction and side suction, the present invention analyzes the influence of different suction ports on the mixed precipitation of aerosol particles to determine the preferred power distribution. The gas is collected and transmitted to the separation system for separation through the gradient inversion layer structure, improving the sedimentation efficiency of aerosol particles and ensuring the high efficiency and reliability of waste gas treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0041] Figure 1The structural diagram of an acid mist waste gas treatment system for a zinc-based alloy production process provided by an embodiment of the present invention;

[0042] Figure 2 The schematic diagram of a processing procedure flow provided by an embodiment of the present invention;

[0043] Figure 3 The schematic diagram of the structural distribution of a gas collection system provided by an embodiment of the present invention;

[0044] Figure 4 The schematic diagram of the suction port gas collection process in a gas collection system provided by an embodiment of the present invention;

[0045] Figure 5 The flow chart of the method for obtaining the final power ratio of the side suction port and the top suction port in a gas collection system provided by an embodiment of the present invention;

[0046] Figure 6 The structural diagram of a separation system provided by an embodiment of the present invention;

[0047] Figure 7 The schematic diagram of the structure of a spray system provided by an embodiment of the present invention. Detailed implementation manners

[0048] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following, in combination with the accompanying drawings and preferred embodiments, details the specific implementation manners, structures, features and effects of an acid mist waste gas treatment system for a zinc-based alloy production process proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs.

[0050] The following specifically describes the specific solution of an acid mist waste gas treatment system for a zinc-based alloy production process provided by the present invention with reference to the accompanying drawings.

[0051] The main process flow of hot-dip galvanizing of zinc-based alloys includes: pre-plated parts, alkaline degreasing, water washing, pickling, water washing, solvent fluxing, drying, hot-dip galvanizing, cooling, post-treatment and other processes. Please refer to Figure 2 , which shows the schematic diagram of a processing procedure flow provided by an embodiment of the present invention.

[0052] Among them, the pickling process will generate a large amount of acid mist waste gas that escapes. The pickling process uses strong acids to remove oxides and rust on the metal surface, usually hydrochloric acid or sulfuric acid, and hydrochloric acid is used in this application. When the acid solution reacts with the metal, hydrogen is released and acidic gases volatilize, forming acid mist.

[0053] Therefore, the main component of the acid mist waste gas is hydrogen chloride. In addition, hydrogen, metal chloride aerosol, corrosion inhibitor volatiles, surfactant residues, water vapor, etc. may also be generated; unqualified galvanized parts will be returned for re-pickling, and the pickling of returned workpieces is usually more intense, which may lead to an accelerated metal dissolution rate, releasing more ions in a short time, exacerbating the generation of aerosol particles and escaping together with the acid mist. These aerosol particles are doped in the hydrogen chloride gas to form acid mist waste gas.

[0054] The acid mist waste gas is introduced into the alkali spray absorption tower through the air duct. After passing through the packing layer, the acid mist waste gas and the sodium hydroxide absorption liquid carry out a full contact absorption and neutralization reaction in the gas-liquid two-phase. After the acid mist waste gas is purified, it is dehydrated and demisted by the demisting plate and then discharged into the atmosphere by the fan. The absorption liquid is pressurized by the water pump at the bottom of the tower and sprayed down from the top of the tower, and finally returns to the bottom of the tower for recycling.

[0055] However, in the above process, the acid mist waste gas may contain metal ions, such as zinc and iron ions. When neutralizing with sodium hydroxide, the precipitate may block the packing or circulation pipeline of the absorption tower, and directly mixing and neutralizing will result in the loss of recoverable HCl, such as directly generating waste salt of NaCl, which is difficult to purify.

[0056] To make the treatment of acid mist after pickling more efficient, please refer to Figure 1 , which shows the structural diagram of an acid mist waste gas treatment system for a zinc-based alloy production process provided by an embodiment of the present invention. The system includes: a gas collection system, a separation system, and a spray system.

[0057] The gas collection system includes a top suction port, a start-stop side suction port, and a temporary storage area. Based on the final power ratio, the power of the top suction port and the side suction port is allocated, and the collected gas is transmitted to the separation system. The separation system further separates the collected gas through the gradient inversion layer structure of the tower temperature, and then the gas is transmitted to the spray system for neutralization treatment.

[0058] In the gas collection system, in order to collect the pickling mist, a closed room is used as a compartment above the pickling tank to form a temporary storage area to isolate the air inside and outside the pickling tank. The temporary storage area is equipped with a negative pressure exhaust system, with 15-20 air changes per hour. On the basis of side suction gas collection, top suction is added. That is, most of the existing gas collection systems use the side suction method, that is, an exhaust port is opened on the side of the pickling tank against the wall. Since a certain amount of heat is released during the pickling process, it promotes the upward movement of the bottom air to form convection. Now, following the original air flow trajectory, a top exhaust gas collection port is added.

[0059] In the embodiment of the present invention, two air collecting ports, namely a side suction port and a top suction port, are provided. The space height is greater than 2.5 m. The bottom side suction port is 0.3 - 0.5 m from the ground, and the top suction port is 0.2 m from the ceiling. The direction of the top suction port is vertically downward, and the direction of the side suction port is at an inclined angle with the wall of the temporary storage area. In this embodiment, the included angle between the side suction port and the wall is 60 degrees, that is, an inclination angle of 30 degrees downward. Please refer to Figure 3 , which shows a schematic structural distribution diagram of an air collecting system provided by an embodiment of the present invention.

[0060] The top suction port at the top sucks air slowly and uniformly, with the characteristics of continuous slow rate and low disturbance. The suction flow rate of the top suction port is relatively low, maintaining a laminar flow state to avoid disturbing the bottom aerosol.

[0061] The side suction port at the bottom is of pulse start-stop type, with the characteristics of high rate and high disturbance in pulse mode. The air pump of the side suction port is equipped with an automatic start-stop device and adopts the method of intermittent air collection. The instantaneous flow rate during the start-stop stage needs to be relatively high to overcome the inertial resistance of aerosol particles. In the embodiment of the present invention, a pulse mode of 5 seconds on / 5 seconds off is adopted to reserve the particle sedimentation time. In other embodiments, it can also be set to a mode of 10 seconds on / 10 seconds off. The implementer can adjust according to the specific implementation situation and is not limited here.

[0062] The suction force of the side suction port in the air collecting system is greater than that of the top suction port. When the top suction port and the side suction port operate in coordination with a suitable power ratio, the top suction port continuously and uniformly sucks air, always forming a low-pressure area in the upper space of the room to promote the rise of the bottom gas. When the side suction port starts, the bottom acid mist mixed waste gas will move briefly in the direction of the side suction port. When the side suction port closes, the sudden stagnation of the large amount of acid mist mixed waste gas movement will form an acid mist retention area in the direction close to the side suction port. Under static conditions, the aerosol particles will naturally sink or slowly float with the gas, and the acid mist gas will float upward. The upper top suction port will uniformly suck away the gas in the upper layer. The floating speed of the aerosol particles is relatively slow. At this time, the side suction port will be reopened to suck away the acid mist waste gas with a large concentration of aerosol particles in the lower layer of the retention area and drag down the floating aerosol particles.

[0063] In this way, there are very few aerosol particles in the acid mist gas collected by the top suction port, which is basically gas, such as hydrogen chloride, hydrogen and water vapor, etc. And the aerosol particles have a large mass and are more easily captured by the airflow in a specific direction. Therefore, there are relatively more aerosol particles in the acid mist gas collected by the bottom side suction port. The combination of the two can initially stratify the acid mist waste gas in the air collecting system. Please refer to Figure 4 , which shows a schematic diagram of the air collection process of the suction ports in an air collecting system provided by an embodiment of the present invention.

[0064] Therefore, in order to ensure the stable operation of the gas collection system in the embodiments of the present invention and effectively preliminarily stratify the aerosol particles and gases in the acid mist, it is necessary to calculate the power ratio between the side suction and top suction gas collection ports. Please refer to Figure 5 , which shows a flowchart of a method for obtaining the final power ratio between the side suction port and the top suction port in a gas collection system provided by an embodiment of the present invention. The method includes the following steps:

[0065] S1: In the gas collection system, set different preset inhalation speeds and conduct continuous tests in ascending order. In each test, the preset inhalation speeds of the top suction port and the side suction port are the same; in each test, obtain the disturbance of the bottom layer of waste gas in the temporary storage area, the gas escape degree of each sampling point, and the gas divergence degree of each moment in the local area during the shutdown of the side suction port; respectively obtain the hydrogen chloride concentration and aerosol concentration in the inhaled gas of the top suction port and the side suction port.

[0066] Set different inhalation speeds for testing and analyze the preferred situation of gas collection in the temporary storage area. In the embodiments of the present invention, take the preset inhalation speed of 0.1 m / s as the initial speed, and the inhalation speed in subsequent tests is adjusted and increased with a step size of 0.1 m / s until the preset inhalation speed reaches 10 m / s. The inhalation speeds of the top suction port and the side suction port during uniform operation in each test are the corresponding preset inhalation speeds. It should be noted that the specific number of tests and the setting of inhalation speeds can be adjusted by the implementer according to the specific implementation scenario and are not limited here.

[0067] In each test at the preset inhalation speed, use a hot-wire anemometer to obtain the natural escape speed of the acid mist gas components under the experimental conditions, that is, directly take the gas flow rate at each sampling point in the closed space above the pickling tank as the gas escape degree of the acid mist gas. At the same time, collect and analyze the disturbance of the bottom layer of acid mist waste gas at the preset inhalation speed of the top suction port. Since the influence of the inhalation speed of the top suction port on the disturbance of the bottom layer of acid mist waste gas is in the vertical direction, the disturbance is the turbulent intensity in the vertical direction.

[0068] In the embodiments of the present invention, the method for obtaining the disturbance of the bottom layer of waste gas includes:

[0069] In each test, obtain the acid mist gas flow rate at each horizontal sampling point at a preset height above the bottom layer of the temporary storage area, and collect it using a hot-wire anemometer. In this embodiment, set the preset height to 0.5 m. The bottom layer of the temporary storage area is the pickling tank, and the horizontal sampling points are sampling points at the same horizontal height at a position 0.5 m above the pickling tank. Set the selection quantity to 10, and the specific values can be adjusted by the implementer himself.

[0070] For any horizontal sampling point, the average flow velocity of the acid mist gas flow velocity at all times in the vertical direction at this sampling point is used as the vertical reference flow velocity of this sampling point. Calculate the difference between the flow velocity of the acid mist gas flow velocity in the vertical direction and the vertical reference flow velocity at each moment at this sampling point, which is used as the pulsation velocity of this sampling point. The pulsation velocity reflects the randomness and volatility of fluid motion, and reflects the turbulence characteristics through the deviation between the instantaneous flow velocity and the average flow velocity at each moment.

[0071] Furthermore, the ratio between the standard deviation of the pulsation velocities of all horizontal sampling points and the average value of all vertical reference flow velocities is normalized to obtain the bottom-layer exhaust gas perturbation degree for each test, which is also the turbulence intensity, reflecting the disturbance condition of the air flow.

[0072] It should be noted that normalization is a technical means well-known to those skilled in the art. The choice of normalization can be linear normalization or standard normalization, etc. The specific normalization method is not limited here.

[0073] In the embodiment of the present invention, the side suction port operates at the same suction speed. After closing, the side suction port takes a local area of 1 square meter as the preset local area, and analyzes the gas divergence in the area. Divergence represents the volume change rate of a unit volume of fluid, including expansion or contraction.

[0074] In the embodiment of the present invention, for any moment, the gas flow velocities in each coordinate axis direction in the three-dimensional coordinate system within the preset local area of the side suction port are obtained. For example, the gas flow velocity is . The derivatives of all gas flow velocities are summed and normalized to obtain the gas divergence at each moment.

[0075] To reflect the different stratification quality conditions of gas collection by the top suction port and the side suction port, that is, the aerosol distribution situation, in each test, samples are taken in the pipeline after the top suction port and the side suction port inhale the acid mist exhaust gas. The hydrogen chloride concentration is measured by a gas measuring instrument, and the aerosol concentration is measured by an electrostatic precipitator or a filtration membrane method.

[0076] S2: In each test, according to the change degree of the gas divergence during the shutdown of the side suction port and the distribution situation of the gas escape degree in the temporary storage area, the gas static separation rate is obtained; according to the change related situation of the bottom-layer exhaust gas perturbation degree between consecutive tests, the mutual interference coefficient of each test is obtained; by the ratio between the hydrogen chloride concentration and the aerosol concentration at different suction ports during the test, as well as the gas static separation rate and the mutual interference coefficient, analyze the influence situation of the preset suction speed on the states of different suction ports, and obtain the final power ratio between the side suction port and the top suction port.

[0077] First, in each test, the top suction port mainly promotes the natural separation of gas. Therefore, it is necessary to analyze the gas separation efficiency at different suction speeds. Preferably, in the embodiment of the present invention, the method for obtaining the gas static separation rate includes:

[0078] For any single test, during the period when the side suction port is closed, the difference between the gas divergence at the last moment and the gas divergence at the initial moment is subjected to negative correlation mapping and normalization to obtain the inertial dispersion coefficient of this test. The change deviation of the gas divergence during the closing period reflects the movement of the acid mist gas under the influence of inertia after the sudden stop of the suction force of the side suction port. The smaller the change in gas divergence, the larger the inertial dispersion coefficient, and the slower the outward diffusion of the acid mist retention area.

[0079] It should be noted that negative correlation mapping is a technical means well-known to those skilled in the art, and it can adopt the form of negative exponential power or inverse proportion, and no limitation is made here.

[0080] Furthermore, calculate the mean value of the gas dispersion of all sampling points in this test as the average natural dispersion. The difference between the average natural dispersion and the minimum gas dispersion among all sampling points is used as the basic separation speed of this test. The mean value of the dispersion represents the overall natural dispersion speed of the acid mist waste gas, and the minimum gas dispersion in the space represents the natural dispersion speed closest to the aerosol particles in the acid mist waste gas. The difference between the average dispersion and the minimum dispersion of the acid mist waste gas reflects the difference in the natural dispersion speeds of the acid mist gas and the aerosol particles.

[0081] Finally, take the inertial dispersion coefficient of this test as the numerator and the sum value of the preset inhalation speed and the basic separation speed corresponding to this test as the denominator to obtain the gas static separation rate of this test. The denominator is the sum of the top suction port speed and the separation speed, and the inertial dispersion direction is opposite to the top suction direction. Therefore, the larger the denominator and the smaller the numerator, it indicates that the suction force of the top suction port fails to overcome the inertial dispersion force of the acid mist retention area, and the gas static separation rate is smaller.

[0082] Since the acid mist waste gas is continuously subjected to an upward natural dispersion due to the top suction force in the vertical direction, and after the side suction port is opened, it is necessary to minimize the impact on the natural dispersion of the acid mist waste gas at the bottom of the pickling tank without disturbing the gas and particles in the acid mist waste gas, so as to achieve the purpose of continuous and uniform stratification of gas and aerosol particles.

[0083] Because theoretically, the disturbance relationship between the change in the top suction speed and the acid mist waste gas at the bottom is approximately regarded as a linear relationship, that is, the greater the inhalation speed of the top suction port, the greater the possible disturbance to the acid mist waste gas. Therefore, further analyze the mutual interference coefficient of the mutual interference between the two suction ports in each test through the continuous change of the disturbance degree of the bottom waste gas. Preferably, in the embodiment of the present invention, the method for obtaining the mutual interference coefficient includes:

[0084] In continuous tests, the difference in the disturbance degree of the bottom waste gas between the subsequent test and the previous test for every two adjacent tests is taken, and the average value of all differences is used as the degree of change in disturbance, which reflects the overall general change in continuous change.

[0085] The difference in the underlying exhaust gas disturbance between each test and the previous test is taken as the disturbance difference degree of each test, and the difference between the disturbance difference degree of each test and the disturbance change degree is taken as the mutual disturbance coefficient of each test. The greater the deviation between the single disturbance change and the overall change, the higher the non - correlation of the single test, and the higher the non - correlation, the more likely the gas disturbance generated by the opening and closing of the side suction port exists. Its influence range is not only the acid mist retention area, but may be larger, and the higher the interference situation generated.

[0086] Finally, while ensuring the gas collection efficiency based on the gas static separation rate and the mutual disturbance coefficient, the gas quality preference degree of gas collection transmission is controlled by the ratio between the hydrogen chloride concentration and the aerosol concentration, obtaining a more preferred ratio of the inhalation power situation, making the actual inhalation effect better, improving the purity of subsequent complete separation, and reducing the influence of aerosol particles.

[0087] Preferably, in the embodiment of the present invention, the method for obtaining the final power ratio includes:

[0088] First, according to the ratio of the hydrogen chloride concentration and the aerosol concentration in the test of the top suction port, combined with the gas static separation rate, the gas collection state index of the top suction port is obtained. In the embodiment of the present invention, the ratio of the hydrogen chloride concentration and the aerosol concentration corresponding to the top suction port in each test is taken as the top suction gas collection ratio, which reflects the presence of aerosol in the gas collection of the top suction port in each test. The higher the top suction gas collection ratio, the lower the aerosol particle content. The preset inhalation speed corresponding to the test with the maximum top suction gas collection ratio is taken as the top suction ideal speed. When the aerosol particles in the gas collection of the top suction port are lower, the inhalation speed - assisted stratification result is more ideal.

[0089] The preset inhalation speed corresponding to the test with the maximum gas static separation rate is taken as the first critical speed. The greater the gas static separation rate, the higher the inhalation efficiency of the top suction port. Taking the gas static separation rate corresponding to the test as the weight, the top suction ideal speed and the first critical speed are weighted and averaged to obtain the gas collection state index of the top suction port, and the situation of the gas static separation rate corresponding to the speed is used for constraint to obtain the expected flow velocity degree of the top suction port.

[0090] As an example, the expression of the gas collection state index of the top suction port is: ; In the formula, represents the gas collection state index of the top suction port, represents the top suction ideal speed, represents the gas static separation rate corresponding to the test of the top suction ideal speed, represents the maximum gas static separation rate, represents the first critical speed.

[0091] Secondly, according to the ratio of the hydrogen chloride concentration to the aerosol concentration at the side suction port during the test, combined with the interference coefficient, the gas collection state index of the side suction port is obtained. In the embodiment of the present invention, the ratio of the hydrogen chloride concentration to the aerosol concentration corresponding to the side suction port in each test is used as the side suction gas collection ratio, which reflects the presence of aerosols in the gas collection at the side suction port during each test. The smaller the side suction gas collection ratio, the higher the aerosol particle content. The preset inhalation speed corresponding to the test when the side suction gas collection ratio is the smallest is used as the ideal side suction speed. The lower the side suction gas collection ratio, the better the preliminary stratification effect of the bottom aerosol particles, and the more ideal the inhalation speed of the side suction port.

[0092] The preset inhalation speed corresponding to the test with the smallest interference coefficient is used as the second critical speed. The smaller the interference coefficient, the smaller the disturbance effect of the double suction ports, and the more stable the gas collection process. The interference coefficient corresponding to the test is used as the weight, and the ideal side suction speed and the second critical speed are weighted and averaged to obtain the gas collection state index of the side suction port. With the interference coefficient corresponding to the speed as the constraint, the expected flow velocity degree of the side suction port is obtained.

[0093] As an example, the expression of the gas collection state index of the side suction port is: ; in the formula, represents the gas collection state index of the side suction port, represents the ideal side suction speed, represents the interference coefficient corresponding to the test of the ideal side suction speed, represents the smallest interference coefficient, represents the second critical speed.

[0094] Finally, the ratio of the gas collection state index of the side suction port to the gas collection state index of the top suction port is used as the final power ratio. By preferentially allocating the inhalation power according to the power ratio, while ensuring the collection efficiency of the acid mist waste gas, maintaining the stable state of the acid mist waste gas, it can reserve space for the upward dispersion of gas and the settlement of aerosol particles while the top suction and side suction double gas collection ports are operating synchronously, promoting the continuous and stable collection and preliminary stratification of the acid mist waste gas.

[0095] As an example, the inhalation rate distribution of the top suction port in the test result is 0.4 m / s, and the inhalation rate distribution of the side suction port is 8 m / s. Then, the air volume and air pressure are rechecked, and a waste gas is transported through an air duct with a suitable pipe diameter. Through the air curtain function, when the workpiece enters and exits the pickling area, an air curtain is used to isolate the internal and external air and prevent the acid mist waste gas from escaping.

[0096] A separation system is added between the gas collection system and the spray purification tower. The separation system forms a gradient inversion layer by constructing a tower-type temperature structure. Please refer to Figure 6, which shows the structural diagram of a separation system provided by an embodiment of the present invention. The separation system includes: a top suction port 1, a side suction port 2, a top suction outlet 3, a side suction outlet 4, a porthole 5, a baffle 6, a first electric heating temperature control device 7, a first water circulation temperature control device 8, a second water circulation temperature control device 9, a second electric heating temperature control device 10, a conveying pipeline 11, and a waste liquid collector 12.

[0097] The separation system includes an upper high-temperature section, a middle transition section, and a lower low-temperature section. Two electric heating temperature control devices, the first electric heating temperature control device 7 and the second electric heating temperature control device 10, are used to control the upper space to form the upper high-temperature section. The second electric heating temperature control device 10 and the second water circulation temperature control device 9 are used to control the temperature of the intermediate transition layer space to form the middle transition section. Two water circulation temperature control devices, the first water circulation temperature control device 8 and the second water circulation temperature control device 9, are used to control the temperature of the bottom space to form the lower low-temperature section, and finally form a gradient inversion layer.

[0098] The top suction outlet 3 is located at a position slightly above the second water circulation device 9, and the outlet pipe directly conveys the gas to the upper high-temperature section of the separation tower. The high temperature will accelerate the rise of the acid mist gas. The side suction outlet 4 is located at the bottom space position below the first water circulation temperature control device 8, and the outlet pipe orifice outputs in the lower low-temperature section. The aerosol particles in the acid mist waste gas will settle downward or diffuse horizontally.

[0099] The electric heating temperature control device has a fast temperature response and is suitable for the upper high-temperature section. The water circulation temperature control device has a gentle temperature change and is suitable for the natural rise of the lower acid mist gas.

[0100] The first electric heating temperature control device 7 and the second electric heating temperature control device 10 are located in the upper high-temperature section. Their function is to accelerate the upward separation of the acid mist gas. The temperature is maintained by electric heating or steam coils at 50 - 80 °C. Under standard conditions, the density of HCl gas is about 1.49 g / L. When the upper temperature is slightly higher, the gas expands due to heat and the density further decreases, prompting HCl to float upward to the collection area. At the same time, a gas-liquid separation membrane or a porous diffusion plate is installed to accelerate the separation of HCl from light gases such as H2 gas. In particular, an explosion-proof ventilation opening needs to be set at the top of the high-temperature section to prevent gas accumulation and danger in case of a malfunction.

[0101] The space between the second electric heating temperature control device 10 and the second water circulation temperature control device 9 is the middle transition section, which is used to receive the acid mist gas rising from the lower layer and liquefy and block the remaining aerosol particles. A spiral baffle is set to extend the residence time of the gas flow and separate the aerosol particles by centrifugal force. The temperature of this space position is set between 20 - 50 °C, and the temperature of the second water circulation temperature control device 9 is dynamically adjusted using a PID controller.

[0102] An additional humidity control device is provided on the lower surface of the baffle 6 with humidity adjustment function, which can maintain the humidity between 60% and 80% in the transition section from the bottom layer space to the middle layer, causing water vapor to condense into liquid droplets and the rising aerosol particles to attach to the liquid and settle down.

[0103] The first water circulation temperature control device 8 and the second water circulation temperature control device 9 are located in the lower low-temperature section, which are used to control the escape speed of acid mist waste gas at the side suction outlet and settle aerosol particles. Metal chlorides or acid mist aerosol particles have a large mass and a density usually > 2 g / cm³, and are more likely to settle by gravity in a low-temperature environment. Therefore, a circulating cooling water system is adopted. To avoid the condensation of hydrogen chloride gas, the temperature is set at 15 - 30 °C, increasing the density of heavy components such as metal chloride aerosols and corrosion inhibitor volatiles, promoting the condensation of metal chloride aerosols into solid particles, and collecting them through a gravity settling tank.

[0104] It should be noted that if the acid mist waste gas is not separated and input into the separation system using the gas collection system, when an inversion layer occurs, the vertical movement of the gas in the cylinder will be inhibited and usually will not naturally accumulate upward. Instead, it may accumulate below or in the middle layer. The acid mist waste gas passing through the separation system directly passes through the suction device with a constant power at the top and is discharged into the alkali liquid spray tower through the conveying pipeline 11 for neutralization treatment.

[0105] In the embodiment of the present invention, please refer to Figure 7 which shows a schematic structural diagram of a spray system provided by an embodiment of the present invention. In the spray system, first, by cooling, the condensation temperature needs to be maintained at 5 - 10 °C, so that HCL in the acid mist condenses into liquid acid and is recycled to the pickling tank to avoid crystallization caused by supercooling when strong acid is replaced with sulfuric acid. Then, the dosing ratio of the neutralizing agent is controlled, and the molar ratio of Ca(OH)2 to Zn 2+ is 1.2:1 to ensure the complete precipitation of Zn(OH)2. Finally, sludge dewatering is carried out. Adding polyacrylamide (PAM, 0.1% - 0.3%) can reduce the moisture content of the sludge from 95% to below 70%. Through hierarchical treatment, more than 90% of HCL and Zn2+ in the acid mist waste gas can be recycled resourcefully, while meeting the environmental protection emission requirements.

[0106] In summary, the present invention performs synchronous testing of the suction air flow rate through the top suction and start-stop side suction structures of the gas collection system. According to the static separation rate of acid mist and the mutual interference between the two suction ports at different tested suction speeds, the preferred influence of the suction rate is analyzed. Combining with the preferred state of the ratio between the inhaled hydrogen chloride concentration and the aerosol concentration, the power ratio is obtained to allocate the suction power of the gas collection system. Through the comprehensive influence of static separation and mutual interference, while ensuring the collection efficiency of acid mist waste gas, the stable state of the acid mist waste gas is maintained. While the double gas collection ports operate synchronously, a space for gas to escape upward and aerosol particles to settle is reserved, promoting the continuous and stable collection and preliminary separation of acid mist waste gas. In the subsequent separation system, the gradient temperature separation structure is used to promote the further separation and settlement of high-concentration aerosol particles, reducing the impact of aerosol particles on subsequent treatment, and enabling the gas to be efficiently neutralized through the spray system. The present invention uses a double suction port gas collection of top suction and side suction, analyzes the influence of different suction ports on the mixed precipitation of aerosol particles to determine the preferred power distribution, and the gas collection is transmitted to the separation system for separation through the gradient inversion layer structure, improving the sedimentation efficiency of aerosol particles and ensuring the high efficiency and reliability of waste gas treatment.

[0107] It should be noted that the above sequence of embodiments of the present invention is only for description and does not represent the superiority or inferiority of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0108] Each embodiment in this specification is described in a progressive manner. The same or similar parts between the embodiments can be referred to each other, and the key point of each embodiment is to illustrate the differences from other embodiments.

Claims

1. An acid mist exhaust gas treatment system for a zinc-based alloy production process, characterized in that, It includes a gas collection system, a separation system and a spray system; the gas collection system includes a top suction port, a start-stop side suction port, and a temporary storage area; In the gas collection system, different preset inhalation speeds are set and continuous tests are carried out in ascending order. In each test, the preset inhalation speeds of the top suction port and the side suction port are the same; in each test, the bottom layer waste gas turbulence in the temporary storage area, the gas dispersion degree at each sampling point, and the gas dispersion degree at each moment in the local area during the shutdown of the side suction port are obtained; the hydrogen chloride concentration and aerosol concentration in the inhaled gas of the top suction port and the side suction port are respectively obtained; In each test, according to the degree of change in the gas dispersion degree during the shutdown of the side suction port and the distribution of the gas dispersion degree in the temporary storage area, the gas static separation rate is obtained; according to the change related situation of the bottom layer waste gas turbulence between continuous tests, the mutual interference coefficient of each test is obtained; through the ratio between the hydrogen chloride concentration and aerosol concentration of different suction ports in the test, as well as the gas static separation rate and the mutual interference coefficient, the influence of the preset inhalation speed on the states of different suction ports is analyzed, and the final power ratio of the side suction port and the top suction port is obtained; The gas collection system distributes the power of the two suction ports based on the final power ratio and transmits the collected gas to the separation system; the separation system further separates the collected gas through the gradient inversion layer structure of the tower temperature, and then the gas is transmitted to the spray system for neutralization treatment.

2. The acid mist waste gas treatment system for the zinc-based alloy production process according to claim 1, characterized in that, The method for obtaining the gas static separation rate includes: For any test, during the shutdown of the side suction port, the difference between the gas dispersion degree at the last moment and the gas dispersion degree at the initial moment is subjected to negative correlation mapping and normalization processing to obtain the inertial dispersion coefficient of this test; Calculate the mean value of the gas dispersion degrees of all sampling points in this test as the average natural dispersion degree; the difference between the average natural dispersion degree and the minimum gas dispersion degree among all sampling points is used as the basic separation speed of this test; Taking the inertial dispersion coefficient of this test as the numerator and the sum value of the preset inhalation speed and the basic separation speed corresponding to this test as the denominator, the gas static separation rate of this test is obtained.

3. The acid mist waste gas treatment system for a zinc-based alloy production process according to claim 1, characterized in that, The method for obtaining the mutual interference coefficient includes: In continuous tests, the difference in the bottom layer waste gas turbulence between the next test and the previous test among every two adjacent tests is taken, and the average value of all differences is used as the turbulence change degree; The difference in the bottom layer waste gas turbulence between each test and the previous test is used as the turbulence difference degree of each test; the difference between the turbulence difference degree of each test and the turbulence change degree is used as the mutual interference coefficient of each test.

4. The acid mist waste gas treatment system for a zinc-based alloy production process according to claim 1, characterized in that, The method for obtaining the final power ratio includes: According to the ratio of the hydrogen chloride concentration and aerosol concentration of the top suction port in the test, combined with the gas static separation rate, the gas collection state index of the top suction port is obtained; According to the ratio of the hydrogen chloride concentration and aerosol concentration of the side suction port in the test, combined with the mutual interference coefficient, the gas collection state index of the side suction port is obtained; Taking the ratio of the gas collection state index of the side suction port to the gas collection state index of the top suction port as the final power ratio.

5. The acid mist waste gas treatment system for a zinc-based alloy production process according to claim 4, characterized in that, The method for obtaining the gas collection state index of the top suction port includes: Taking the ratio of the hydrogen chloride concentration and aerosol concentration corresponding to the top suction port in each test as the top suction gas collection ratio; Take the preset inhalation speed corresponding to the maximum top suction air collection ratio during the test as the ideal top suction speed; take the preset inhalation speed corresponding to the maximum gas static separation rate during the test as the first critical speed; Take the gas static separation rate corresponding to the test as the weight, and perform weighted averaging on the ideal top suction speed and the first critical speed to obtain the air collection state index of the top suction port.

6. The acid mist waste gas treatment system for a zinc-based alloy production process according to claim 4, wherein, The method for obtaining the air collection state index of the side suction port includes: Take the ratio of the hydrogen chloride concentration and the aerosol concentration corresponding to the side suction port in each test as the side suction air collection ratio; Take the preset inhalation speed corresponding to the minimum side suction air collection ratio during the test as the ideal side suction speed; take the preset inhalation speed corresponding to the minimum mutual interference coefficient during the test as the second critical speed; Take the mutual interference coefficient corresponding to the test as the weight, and perform weighted averaging on the ideal side suction speed and the second critical speed to obtain the air collection state index of the side suction port.

7. The acid mist waste gas treatment system for a zinc-based alloy production process according to claim 1, characterized in that, The method for obtaining the bottom waste gas disturbance includes: In each test, obtain the acid mist gas flow rate at each horizontal sampling point at each moment at a preset height above the bottom of the temporary storage area; For any horizontal sampling point, take the average flow velocity of the acid mist gas flow rate at all moments in the vertical direction at this sampling point as the vertical reference flow velocity of this sampling point; calculate the difference between the flow velocity of the acid mist gas flow rate in the vertical direction and the vertical reference flow velocity at each moment at this sampling point as the pulsation velocity of this sampling point; Normalize the ratio between the standard deviation of the pulsation velocities of all horizontal sampling points and the average value of all vertical reference flow velocities to obtain the bottom waste gas disturbance of each test.

8. The acid mist waste gas treatment system for a zinc-based alloy production process according to claim 1, characterized in that, The method for obtaining the gas divergence includes: For any moment, obtain the gas flow velocities in each coordinate axis direction in a three-dimensional coordinate system within a preset local area of the side suction port; Sum the derivatives of all gas flow velocities and perform normalization processing to obtain the gas divergence at each moment.

9. The acid mist waste gas treatment system for a zinc-based alloy production process according to claim 1, characterized in that, The direction of the top suction port is vertically downward, and the direction of the side suction port is at an inclined angle with the wall of the temporary storage area.

10. The acid mist waste gas treatment system for a zinc-based alloy production process according to claim 1, wherein, The separation system includes an upper high-temperature section, a middle transition section, and a lower low-temperature section. The electric heating temperature control device is located in the upper high-temperature section and is used to raise the separated gas. The humidity control device is located in the middle transition section and is used to liquefy and block aerosol particles. The water circulation temperature control device is located in the lower low-temperature section and is used for the sedimentation of aerosol particles.

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