Purification treatment system and method for lepidolite roasting flue gas

Abstract

The invention belongs to the field of flue gas treatment, and provides a purification treatment system and method for lepidolite roasting flue gas. The purification treatment device comprises a pre-dedusting device, a first-stage moving bed reactor, a second-stage fluidized bed reactor, a third-stage dedusting reactor and an induced draft fan which are connected in sequence, wherein the pre-dedusting device is used for carrying out pre-dedusting treatment on roasting flue gas; the first-stage moving bed reactor is used for carrying out first-stage adsorption reaction treatment on pollutants in the pre-dedusted flue gas; the second-stage fluidized bed reactor is used for carrying out second-stage adsorption reaction treatment on pollutants in the flue gas-particle mixture I generated by the first-stage moving bed reactor; and the third-stage dust removal reactor is used for carrying out third-stage adsorption reaction and dust removal treatment on pollutants in the flue gas-particle mixture II generated by the second-stage fluidized bed reactor. According to the method, various pollutant components in the lepidolite roasting flue gas can be effectively removed, and secondary pollution problems such as waste water and chimney rain do not exist in the flue gas purification treatment process.

Description

Technical Field

[0001] The present invention belongs to the field of flue gas treatment. Specifically, a purification treatment system and method for roasting flue gas of lepidolite are provided. Background Art

[0002] With the acceleration of the global trend towards renewable energy and electrification, the element lithium, known as the "energy metal", has seen a significant increase in market demand, especially in high-tech application fields such as electric vehicles and energy storage systems. Lithium resources in nature mainly exist in the form of brine-type lithium deposits, pegmatite-type lithium deposits, etc. Among them, pegmatite-type lithium ores mainly include spodumene, lepidolite, etc. China is rich in lepidolite resources. At present, due to factors such as lithium extraction efficiency and process maturity, the process technology of extracting lithium from lepidolite ore by sulfate roasting method has become one of the main methods for obtaining lithium elements.

[0003] Due to the complex associated mineral components in lepidolite ore, the pollutant components in the flue gas generated and discharged during the high-temperature roasting process in the lithium extraction technology using the sulfate roasting method are very complex, mainly including various pollutant components such as SO2, NOx, dust, SO3, HF, heavy metals (such as thallium) and their compounds. Compared with other industrial flue gases, the flue gas generated during the lithium extraction process from lepidolite ore by the sulfate roasting method has the following flue gas characteristics: 1) The SO2 concentration is high, reaching up to 5000 mg / Nm 3 or more; 2) SO3 is relatively high, usually in the range of 150 - 250 mg / Nm 3 or even higher; 3) Nitrogen oxides (NO x ) are relatively high, reaching up to 200 mg / Nm 3 or more; 4) The fluorine element associated with lepidolite ore volatilizes during the roasting process, resulting in a certain concentration of HF in the flue gas; 5) In particular, the flue gas also includes highly toxic heavy metal thallium pollutants, and the concentration of thallium and its compounds can reach 15 mg / Nm 3 or more, and only a part of it adheres to the soot and fly ash particles in the form of solid substances such as TI2O3 and TI2O, and most of the remaining exists in the flue gas in the form of gas (aerosol) (mainly thallium halides, PM10 / PM2.5).

[0004] At present, the purification treatment of flue gas mainly adopts wet process technology, and the main process includes flue gas desulfurization treatment with liquid absorbents (such as limestone slurry, ammonia water). However, as mentioned above, the components of the flue gas from lepidolite roasting are complex and the concentrations of various pollutants are too high. The traditional wet process cannot effectively remove sulfides and thallium pollutants therein, resulting in an extremely high dust concentration in the discharged flue gas, serious system corrosion, and the slurry generated after the flue gas is treated with the absorbent in the wet process needs to be separated and subjected to secondary treatment, which is difficult. For example, CN116603385A discloses a process for removing sulfur dioxide and heavy metal thallium from the sintering flue gas of lepidolite. After the sintering flue gas of lepidolite is collected and pressurized, it is introduced into a desulfurization and thallium removal tower, and the lime slurry is sprayed to react with SO2 and thallium in the flue gas to achieve the purpose of removal and purification. Then, the slurry mixture generated in the tower is separated into waste residue and waste water for secondary treatment respectively. However, such wet processes have the following deficiencies: 1) The wet desulfurization and thallium removal tower has restrictions on the dust concentration in the inlet flue gas. However, there are often a large amount of soot and dust in the original flue gas, which easily leads to lime slurry poisoning and demister fouling, reducing the purification efficiency, resulting in an excessive dust concentration in the discharged flue gas, and increasing the difficulty of subsequent gypsum slag purification treatment and waste water treatment, etc.; 2) SO3 in the flue gas exists in the form of sulfuric acid mist aerosol in the tower, and it is difficult to remove SO3 (the SO3 removal efficiency is only 20% - 30%). Moreover, the unremoved sulfuric acid mist (SO3) is likely to cause equipment corrosion, and anti-corrosion measures for the equipment need to be considered, resulting in relatively high equipment investment and operating costs; 3) By spraying lime slurry in the tower, only the thallium compounds enriched on the larger particle soot and dust in the flue gas can be effectively removed, and there is basically no removal effect on the thallium compounds attached to a large amount of extremely fine fly ash or existing in the form of aerosol (PM10 / PM2.5); 4) A large amount of waste water generated by the wet desulfurization and thallium removal tower contains fluorine, thallium and other heavy metal pollutants, and the waste water treatment is difficult; 5) The demister at the top of the desulfurization tower is prone to fouling and blockage during long-term operation, resulting in poor demisting effect, and a large amount of gypsum slurry droplets will be entrained in the discharged flue gas. Moreover, since the flue gas after passing through the desulfurization and thallium removal tower is saturated with water, these slurry droplets will ultimately form "chimney rain" together with the condensed water vapor around the chimney outlet. The "chimney rain" accumulates on the ground nearby, causing the thallium content in the surface runoff water body in the surrounding area to exceed the standard.

[0005] In view of the problems existing in the wet purification process of lepidolite roasting flue gas, CN116651174A proposes a treatment system and method for the tail gas of a rotary roasting kiln for lithium smelting. The treatment system includes: a high-temperature filter type dust collector, which is connected to the tail gas outlet of the rotary roasting kiln and is used to filter and remove dust in the tail gas; a waste heat recovery device, which is connected to the high-temperature filter type dust collector and is used to recover the heat of the tail gas; a semi-dry acid removal device, which is connected to the waste heat recovery device and is used to set a solid desulfurizer therein to remove acidic pollutants in the tail gas; a low-temperature liquid-phase denitrification device, which is used to spray a low-temperature liquid-phase denitrification agent therein to further denitrify the tail gas after removing acidic pollutants. By adopting the coupling method of "solid denitrification + high-temperature filtration + waste heat recovery + semi-dry acid removal + low-temperature liquid-phase denitrification", the dust, SO2, and NO x in the flue gas can be effectively removed. However, the semi-dry acid removal technology adopted by this method has a low SO2 removal efficiency (97.31%), cannot meet the requirements of high SO2 concentration flue gas purification, and a solid denitrification device needs to be set at the furnace end of the roasting kiln and a low-temperature liquid-phase denitrification device needs to be separately configured after the acid removal device to achieve the denitrification purpose with two-stage denitrification devices, and the process is cumbersome. This method also needs to select a specific low-temperature liquid-phase denitrification agent and cannot effectively remove other pollutants such as heavy metal thallium. Summary of the Invention

[0006] Aiming at the defects of the existing technology, such as the difficulty in effectively purifying the lepidolite roasting flue gas with many pollution components, the purpose of the present invention is to provide a purification treatment system and method for lepidolite roasting flue gas. The present invention can effectively remove various pollutant components in the lepidolite roasting flue gas, and there are no secondary pollution problems such as "waste water" and "chimney rain" in the purification process.

[0007] The first aspect of the present invention provides a purification treatment system for lithium mica roasting flue gas, comprising: a pre-dust removal device, a first-stage moving bed reactor, a second-stage fluidized bed reactor, a third-stage dust removal reactor, and an induced draft fan, which are connected in sequence; wherein, the pre-dust removal device is used for pre-dust removal treatment of the lithium mica roasting flue gas to obtain pre-dusted flue gas; the first-stage moving bed reactor is used for performing a first-stage adsorption reaction treatment on the pollutants in the pre-dusted flue gas, and the first-stage moving bed reactor is further connected with a dry absorbent supply device and an oxidant supply device; the second-stage fluidized bed reactor is used for performing a second-stage adsorption reaction treatment on the pollutants in the flue gas-particle mixture I generated by the first-stage moving bed reactor, and the second-stage fluidized bed reactor is further connected with a cooling and humidifying device; the third-stage dust removal reaction device is used for performing a third-stage adsorption reaction and dust removal treatment on the pollutants in the flue gas-particle mixture II generated by the second-stage fluidized bed reactor to obtain purified flue gas and solid by-products; and the third-stage dust removal reactor is respectively connected with a material circulation device and a by-product collection device, the material circulation device is used for returning part of the solid by-products as circulating materials to the first-stage moving bed reactor, and the by-product collection device is used for collecting the remaining solid by-products; the induced draft fan is used for pressurizing and discharging the purified flue gas.

[0008] The purification treatment system provided by the present invention can achieve "pre-dust removal + two-stage adsorption reaction treatment + dust removal reaction treatment" of the lithium mica roasting flue gas to achieve the purpose of purifying the flue gas. The purification treatment system realizes the high-efficiency synergistic removal of various pollutant components such as SO2, NO x , dust, SO3, HF, etc., and simultaneously realizes the high-efficiency removal and stable solidification of heavy metal thallium and its compounds.

[0009] In some embodiments of the present invention, a load stability adjustment device is further provided between the outlet of the induced draft fan and the first-stage moving bed reactor. Further, the load stability adjustment device is a wind damper or butterfly valve with adjustable opening. When the load stability adjustment device is opened, using the static pressure difference between the outlet of the induced draft fan and the inlet of the first-stage moving bed reactor, the clean flue gas can automatically flow back from the outlet of the induced draft fan to the first-stage moving bed reactor.

[0010] In some embodiments of the present invention, the pre-dust removal device is an electrostatic precipitator.

[0011] In some embodiments of the present invention, the third-stage dust removal reactor is a bag filter.

[0012] In some embodiments of the present invention, the oxidant supply device includes an ozone generator and a dilution mixer connected by a pipeline. The ozone generated by the ozone generator is transported through the pipeline into the dilution gas mixture, diluted, and then enters the first-stage moving bed reactor to improve the stability and safety of ozone during transportation.

[0013] In some embodiments of the present invention, the first-stage moving bed reactor includes a cylindrical tower body. A plurality of first interfaces and second interfaces arranged alternately are uniformly provided in the circumferential direction of the cylindrical tower body. The dry absorbent supply device is connected to the first-stage moving bed reactor through each of the first interfaces, and the oxidant supply device is connected to the first-stage moving bed reactor through each of the second interfaces.

[0014] Furthermore, a flue gas inlet is connected to the bottom of the cylindrical tower body, and a flue gas outlet is connected to the top of the cylindrical tower body; the distance h1 between the first interface, the second interface and the bottom of the cylindrical tower body and the height h of the cylindrical tower body satisfy the relational expression: 0.3 < h1 / h < 0.7.

[0015] Furthermore, the number of both the first interfaces and the second interfaces is n, and 2 ≤ n ≤ 5.

[0016] Furthermore, the cross-sectional area A of the cylindrical tower body ≤ 4.9m 2 , n = 2; or

[0017] 4.9m 2 <A ≤ 20m 2 , n = 3; or

[0018] 20m 2 <A ≤ 30m 2 , n = 4.

[0019] The second aspect of the present invention provides a method for purifying and treating lithium mica roasting flue gas. This method is implemented using the purification and treatment system described in the first aspect of the present invention, and includes the following technological process:

[0020] Send the lithium mica roasting flue gas into a pre-dust removal device for pre-dust removal treatment to obtain pre-dust removal flue gas;

[0021] Send the pre-dust removal flue gas into the first-stage moving bed reactor, and add dry absorbent and oxidant to perform a first-stage adsorption reaction treatment on the pollutants in the pre-dust removal flue gas to obtain flue gas-particle mixture I;

[0022] Send the flue gas-particle mixture I into the second-stage fluidized bed reactor, and add atomized water for cooling. By performing a second-stage adsorption reaction treatment on the pollutants in the flue gas-particle mixture I, obtain flue gas-particle mixture II;

[0023] Feed the flue gas-particle mixture II into a three-stage dust removal reactor for three-stage adsorption reaction and dust removal treatment to obtain purified flue gas and solid by-products; return part of the solid by-products as recycled materials to the primary moving bed reactor, and collect the remaining solid by-products;

[0024] The purified flue gas is pressurized and discharged through a induced draft fan.

[0025] In the purification treatment method provided by the present invention, the roasting flue gas is first subjected to pre-dust removal treatment, which can remove a large amount of dust therein and thallium and its compound pollutants attached to the dust in solid form, reduce the content of heavy metals and other impurity components in the by-products of the downstream multi-stage reaction device, and avoid affecting the comprehensive utilization effect of the by-products. The pre-dust removal flue gas first enters the primary moving bed reactor, where in the presence of dry absorbent and oxidant, NO and compounds such as thallium halide are respectively adsorbed and oxidized into NO2 and Tl2O3. The obtained gas-solid materials are jointly fed into the secondary fluidized bed reactor, and then the high-density absorbent particle bed layer in the fluidized bed reactor is used to significantly improve the adsorption reaction treatment of pollutants. This combined treatment method can effectively improve the removal efficiency of pollutants, especially the removal of NOx and heavy metal thallium compounds; finally, the gas-solid materials after the two-stage adsorption reaction treatment are subjected to dust removal and adsorption reaction treatment. When the flue gas passes through the filter cake layer formed by the absorbent particles, the remaining SO2, SO3, NO2, HF, thallium and other heavy metal pollutants are further adsorbed and removed, and with the help of the particle coagulation mechanism in the upstream secondary fluidized bed reactor, the ultrafine particles (PM2.5 / PM10) in the flue gas are coagulated into large particles. The entire process using this device can effectively remove various pollutant components in the lithium mica roasting flue gas. After the flue gas is purified, it can meet the national emission standard requirements (GB 31573-2015 "Emission Standard of Pollutants for Inorganic Chemical Industry"), and no wastewater and "chimney rain" will be generated during the entire treatment process.

[0026] In some embodiments of the present invention, the concentration of SO2 in the lithium mica roasting flue gas is 2000 - 6000 mg / Nm 3 , the concentration of SO3 is 50 - 400 mg / Nm 3 , NO x concentration is 150 - 300 mg / Nm 3 , the concentration of thallium and its compounds in terms of Tl is 10 - 20 mg / Nm 3 , the concentration of HF in terms of F is 250 - 400 mg / Nm 3 , the dust concentration is 20 - 50 g / Nm 3 .

[0027] In some embodiments of the present invention, the temperature of the flue gas entering the pre-dust removal device is 150 - 200 °C.

[0028] In some embodiments of the present invention, the dust removal efficiency of the pre-dust removal treatment for the flue gas is ≥95%.

[0029] In some embodiments of the present invention, the average particle size of the dry absorbent is ≤74 μm.

[0030] In some embodiments of the present invention, the dry absorbent is a calcium-based absorbent, and the specific surface area of the calcium-based absorbent is ≥12 m 2 / g, preferably 15 - 18 m 2 / g, and the effective calcium hydroxide content is ≥80%.

[0031] In some embodiments of the present invention, relative to every 100,000 Nm 3 / h of the calcination flue gas, in the primary moving bed reactor, the dosage of the dry absorbent provided by the dry absorbent supply device is 0.4 - 1.2 t / h.

[0032] In some embodiments of the present invention, the oxidant is ozone.

[0033] In some embodiments of the present invention, relative to every 100,000 Nm 3 / h of the calcination flue gas, in the primary moving bed reactor, the dosage of the oxidant provided by the oxidant supply device is 12 - 24 Nm 3 / h.

[0034] In some embodiments of the present invention, in the secondary adsorption reaction treatment, the dosage of the atomized water is such that the temperature of the secondary fluidized bed reactor is 70 - 150 °C.

[0035] In some embodiments of the present invention, in the secondary fluidized bed reactor, the bed pressure drop formed by the particles is 1000 - 1500 Pa, and the gas flow velocity is 4 - 7 m / s.

[0036] In some embodiments of the present invention, in the tertiary adsorption reaction and dust removal treatment, the filtration air velocity is 0.5 - 0.8 m / min.

[0037] Additional aspects and advantages of the present invention will be partly given in the following description, partly will become obvious from the following description, or be understood through the practice of the present invention. Brief Description of the Drawings

[0038] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, wherein:

[0039] Figure 1 is a schematic diagram of a purification treatment system for lepidolite calcination flue gas according to an embodiment of the present invention;

[0040] Figure 2 Distribution map of the first interface and the second interface on a first-stage moving bed reactor according to an embodiment of the present invention;

[0041] Figure 3 Schematic diagram of material flow in a first-stage moving bed reactor according to an embodiment of the present invention.

[0042] Description of reference numerals

[0043] 1: Pre-dust removal device; 2: First-stage moving bed reactor; 3: Second-stage fluidized bed reactor; 4: Third-stage dust removal reactor; 5: Induced draft fan; 6: Load stability adjustment device; 7: Dry absorbent supply device; 8: Oxidant supply device; 9: Cooling and humidifying device; 10: Material circulation device; 11: By-product discharge device; 12: By-product storage bin; 2-1: Cylindrical tower body; 2-11: First interface; 2-12: Second interface. Specific embodiments

[0044] The embodiments of the present invention will be described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as a limitation to the present invention.

[0045] The "range" disclosed in the present invention is defined in the form of a lower limit and / or an upper limit. A given range is defined by selecting a lower limit and / or an upper limit. The range defined in this way may or may not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range not explicitly recorded, and any lower limit can be combined with other lower limits to form a range not explicitly recorded. Similarly, any upper limit can be combined with any other upper limit to form a range not explicitly recorded. In addition, each individually disclosed point or single value itself can be used as a lower limit or an upper limit and combined with any other point or single value or combined with other lower limits or upper limits to form a range not explicitly recorded.

[0046] If there is no special description, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution, and such a technical solution should be considered to be included in the disclosure of the present invention.

[0047] It should be noted that the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. For the sake of convenience of description, "flue gas-particle mixture I" and "flue gas-particle mixture II" respectively refer to the materials produced by the first-stage moving bed reactor and the second-stage fluidized bed reactor, and should not be construed as indicating or implying relative importance, nor as a specific composition produced under different working conditions.

[0048] In a first aspect, the present invention provides a purification treatment system for lithium mica roasting flue gas. As Figure 1 shown, in the direction of flue gas flow, the purification treatment system includes a pre-dust removal device 1, a first-stage moving bed reactor 2, a second-stage fluidized bed reactor 3, a third-stage dust removal reactor 4, and a draft fan 5 connected in sequence.

[0049] In the present invention, the pre-dust removal device 1 is used to perform pre-dust removal treatment on the roasting flue gas to obtain pre-dust removed flue gas. The roasting flue gas from the roasting kiln contains a large amount of dust, and the main component of these dusts is fine-grained lithium mica raw ore. Some thallium and its compound pollutants are attached to the dust in solid form. Before performing multi-stage adsorption reaction treatment, pre-dust collection treatment is first performed on the roasting flue gas, which can realize the recovery of dust (lithium mica raw ore) and the preliminary removal of some thallium-containing pollutants.

[0050] In the present invention, the pre-dust removal device 1 can be an electrostatic precipitator or a bag filter. To improve the operation stability, it is preferred that the pre-dust removal device 1 is an electrostatic precipitator. The type of the electrostatic precipitator can be selected according to the flue gas volume and its pollutant composition of the roasting flue gas, for example, selected from a double-field electrostatic precipitator or a triple-field electrostatic precipitator.

[0051] In the present invention, the first-stage moving bed reactor 2 is used to perform a first-stage adsorption reaction treatment on the pollutants in the pre-dust removed flue gas, and the first-stage moving bed reactor 2 is connected with a dry absorbent supply device 7 and an oxidant supply device 8 so that the first-stage adsorption reaction treatment is carried out in the presence of a dry absorbent and an oxidant. Through the first-stage adsorption reaction treatment, acidic gases in the flue gas can be preliminarily absorbed and NO and thallium halides can be oxidized. By synchronously adding a dry absorbent and an oxidant to the first-stage moving bed reactor 2 and using the dry absorbent (such as a calcium-based absorbent) to form an alkaline reaction environment, the oxidation efficiency of thallium halides in the flue gas can be improved. Thus, under the same flue gas purification efficiency, the internal space of the second-stage fluidized bed reactor 3 can be saved and the equipment investment can be reduced.

[0052] The present invention has no particular limitation on the first-stage moving bed reactor 2, and it can be selected from various moving bed reactors commonly used in dry flue gas desulfurization. The moving bed reactor can avoid the accumulation and scaling of particulate materials. As some preferred embodiments, as Figure 2 and Figure 3As shown in the figure, the first-stage moving bed reactor 2 includes a cylindrical tower body 2-1. A plurality of first interfaces 2-11 and second interfaces 2-12 which are arranged in a staggered manner are evenly provided in the circumferential direction of the cylindrical tower body 2-1. The dry absorbent supply device 7 is connected to the first-stage moving bed reactor 2 through each first interface 2-11, and the oxidant supply device 8 is connected to the first-stage moving bed reactor 2 through each second interface 2-12. In this way, the dry absorbent and the oxidant are added in a spaced and dispersed manner along the circumferential direction of the tower body, which promotes the uniform diffusion of the materials on the cross-section of the tower body, and promotes the uniform mixing of the oxidant, the absorbent and the flue gas, thereby improving the efficiency of the adsorption and oxidation reactions. It can be understood that the term "circumferentially uniform" means that the interfaces are equidistantly distributed along the circumference, and the "staggered arrangement" means that the first interfaces 2-11 and the second interfaces 2-12 are arranged alternately.

[0053] In some embodiments, the number of both the first interfaces 2-11 and the second interfaces 2-12 is n, where 2 ≤ n ≤ 5. For example, n is 2, 3, 4 or 5.

[0054] In the present invention, the number n of the interfaces can also be selected according to the cross-sectional area A of the cylindrical tower body 2-1. As some preferred examples, the cross-sectional area A of the cylindrical tower body 2-1 ≤ 4.9 m 2 , and n = 2. As some other preferred examples, 4.9 m 2 <A ≤ 20 m 2 , and n = 3. As some other preferred examples, 20 m 2 <A ≤ 30 m 2 , and n = 4.

[0055] In some embodiments, a flue gas inlet is connected to the bottom of the cylindrical tower body 2-1, and a flue gas outlet is connected to the top. Preferably, the distances from the first interfaces 2-11 and the second interfaces 2-12 to the bottom of the cylindrical tower body 2-1 are both h1, and h1 and the height h of the cylindrical tower body 2-1 satisfy the relation: 0.3 < h1 / h < 0.7. In this case, the absorbent and the oxidant can be added in the middle section of the tower body (0.3h < h1 < 0.7h). This can not only enable the absorbent and the oxidant to fully contact and mix with the flue gas and move together with the flue gas, but also avoid the interference of the flue gas entering from the bottom on the material distribution, and prevent the premature settlement of the materials due to the reduction of the gas flow velocity at the top. As some examples, h1 can be 2 to 9 m, such as 2, 3 m, 3.5 m, 4.8 m, 5 m, 7 m, 8 m, etc.

[0056] In some embodiments, at least one recycle material inlet (hereinafter referred to as "the third interface") is further provided on the cylindrical tower body 2-1. When the number of the third interfaces is greater than 1, the third interfaces are circumferentially arranged on the tower body. Preferably, the distance between the third interface and the bottom of the cylindrical tower body 2-1 is h3, and h3 > h1; more preferably, h3, h1 and h satisfy the following relationship: h3 = 0.1h + h1. The number m of the third interfaces can also be selected according to the cross-sectional area A of the cylindrical tower body 2-1. When A ≤ 3m 2 , m = 1. When 3 < A ≤ 30m 2 , m = 2. Preferably, m = 2, and the included angle between the two third interfaces is 70°.

[0057] The present invention does not particularly limit the dry absorbent supply device 7, which can be a conventional choice in existing semi-dry and dry flue gas desulfurization processes, as long as it can transport dry diluent to the primary moving bed reactor 2, for example, including but not limited to, air chute, metering feeder, etc.

[0058] As some specific examples, the oxidant supply device 8 can be an ozone supply device. For example, it can include an ozone generator and a dilution mixer connected by a pipeline, so that the ozone generated by the ozone generator enters the dilution mixer and is diluted and then enters the primary moving bed reactor 2.

[0059] In the present invention, the secondary fluidized bed reactor 3 is used to perform a secondary adsorption reaction treatment on the pollutants in the flue gas-particle mixture I from the primary moving bed reactor 2, and the secondary fluidized bed reactor 3 is connected with a cooling and humidifying device 9 for providing atomized water for the reactor. Through the secondary adsorption reaction treatment, the removal efficiency of acidic pollutants such as SO2, SO3, and HF can be further improved.

[0060] The present invention does not particularly limit the secondary fluidized bed reactor 3, which can be selected from various circulating fluidized bed reactors (CFB). Preferably, the feed inlet (i.e., the fluid inlet) of the secondary fluidized bed reactor 3 is connected with a Venturi acceleration device. The Venturi acceleration device can accelerate the raw materials and then send them into the fluidized bed reactor.

[0061] In some embodiments, the cooling and humidifying device 9 is a high-pressure water atomization spraying device, which is provided with a high-pressure water spray gun. On the one hand, water is atomized under the action of the high-pressure water spray gun and sprayed into the fluidized bed. The atomized water covers and wraps the absorbent particles, forming a local liquid film on the surface of the absorbent particles, forming a local instantaneous ionic reaction environment and improving the reaction efficiency; on the other hand, the evaporation process of water will absorb a large amount of heat, realizing the adjustment of the reaction temperature of the fluidized bed. The high-pressure water spray gun can be, for example, a single-fluid high-pressure water gun.

[0062] In some embodiments, the fluid inlet of the secondary fluidized bed reactor 3 is located at the bottom of the reactor, and an atomized water inlet is provided on the side wall of the reactor (e.g., the position area corresponding to the high-density particles in the fluidized bed layer). The inlet is connected to the water outlet of the cooling and humidifying device 9, so that the flue gas-particle mixture I enters the reactor from the bottom and contacts the atomized water. This way of adding the atomized water is more conducive to the uniform dispersion and coverage of water on the surface of the material particles in the reactor, avoiding the phenomenon of material caking and sticking to the wall caused by local over-wetting, and ensuring the more stable operation of the system.

[0063] In the present invention, the tertiary dust removal reactor 4 is used to continue the dust removal reaction treatment on the flue gas-particle mixture II generated by the secondary fluidized bed reactor 3 to obtain purified flue gas and solid by-products.

[0064] In some embodiments, the tertiary dust removal reactor 4 is a bag filter. When the flue gas-particle mixture II passes through the filter bag and the filter cake layer on its surface, the dust is filtered and removed. And when the flue gas passes through the filter cake layer, the remaining heavy metal pollutants such as SO2, SO3, NO2, HF, and thallium in the flue gas are further adsorbed and removed. To further improve the reaction efficiency of the filter cake layer of the filter bag, preferably, the tertiary dust removal reactor 4 is a low-pressure pulse rotary jet bag filter.

[0065] In the present invention, the tertiary dust removal reactor 4 is also respectively connected with a material circulation device 10 and a by-product collection device. The material circulation device 10 is used to return part of the solid by-products as circulating materials to the primary moving bed reactor 2, and the by-product collection device is used to discharge and collect the remaining solid by-products. The present invention does not particularly limit the material circulation device 10, which can be an absorbent circulation device commonly used in dry or semi-dry desulfurization processes. Specific examples thereof include, but are not limited to, air chutes. As some specific examples, the by-product collection device includes a by-product discharge device 11 and a by-product storage bin 12 connected in sequence. The by-product discharge device 11 can be a bin pump.

[0066] In the present invention, preferably, a load stability adjustment device 6 is also connected between the outlet of the induced draft fan 5 and the gas inlet of the primary moving bed reactor 2, which is used to introduce at least part of the purified flue gas into the primary moving bed reactor 2 for load adjustment. Usually, in the case of load adjustment of the upstream roasting main machine, the flue gas condition may fluctuate. To avoid phenomena such as ash falling in the fluidized bed reactor due to the condition fluctuation, by using the static pressure difference between the two ends of the connection between the outlet of the induced draft fan 5 and the gas inlet of the primary moving bed reactor 2, the purified flue gas at the outlet of the induced draft fan can be introduced back into the primary moving bed reactor 2 through the load stability adjustment device 6, ensuring that the purification treatment system of the present invention can still operate stably under different load conditions of the roasting main machine. As some embodiments, the load stability adjustment device 6 is a wind damper or butterfly valve with adjustable opening.

[0067] In a second aspect, the present invention provides a method for purifying and treating lithium mica roasting flue gas. This method is implemented using the purification and treatment system described in the first aspect of the present invention, and includes the following process:

[0068] Feed the lithium mica roasting flue gas into the pre-dust removal device 1 for pre-dust removal treatment to obtain pre-dusted flue gas;

[0069] Feed the pre-dusted flue gas into the first-stage moving bed reactor 2, and add dry absorbent and oxidant to perform a first-stage adsorption reaction treatment on the pollutants in the pre-dusted flue gas to obtain flue gas-particle mixture I;

[0070] Feed the flue gas-particle mixture I into the second-stage fluidized bed reactor 3, add atomized water for cooling, and perform a second-stage adsorption reaction treatment on the pollutants in the flue gas-particle mixture I to obtain flue gas-particle mixture II;

[0071] Feed the flue gas-particle mixture II into the third-stage dust removal reactor 4 for third-stage adsorption reaction and dust removal treatment to obtain purified flue gas and solid by-products; return part of the solid by-products as recycled materials to the first-stage moving bed reactor 2, and collect the remaining solid by-products;

[0072] The purified flue gas can be pressurized and discharged through the induced draft fan 5.

[0073] In the present invention, the lithium mica roasting flue gas can be the roasting flue gas generated in the lithium extraction process by the sulfate roasting method using lithium mica ore as the raw material, which contains multiple components of pollutants, such as HF, SO, SO3, nitrogen oxides (NO x ), heavy metals (such as Tl, Pd) and their compounds, dust (particulate matter), etc. According to some embodiments, the concentration of SO2 in the lithium mica roasting flue gas is 2000-6000 mg / Nm 3 , the concentration of SO3 is 50-400 mg / Nm 3 , the concentration of NO x is 150-300 mg / Nm 3 , the concentration of thallium and its compounds in terms of Tl is 10-20 mg / Nm 3 , the concentration of HF in terms of F is 250-400 mg / Nm 3 , and the dust concentration is 20-50 g / Nm 3 .

[0074] In some embodiments, the average amount of the roasting flue gas entering the pre-dust removal device 1 can be 100,000-400,000 Nm 3 / h.

[0075] In some embodiments, the pre-dust removal device 1 is an electrostatic precipitator, and the operating conditions for the pre-dust removal treatment include: the flue gas temperature entering the pre-dust removal device 1 is 150 - 200 °C. Additionally, the residence time of the flue gas can be 10 - 20 s. By using the electrostatic precipitator to capture the dust in the roasting flue gas, the dust concentration in the flue gas can be effectively reduced. Preferably, the dust removal efficiency of the pre-dust removal treatment for the roasting flue gas is ≥ 95%.

[0076] In the present invention, the pre-dust removal flue gas is fed into the first-stage moving bed reactor 2, where it can come into contact with the solid by-products, dry absorbent, and oxidant separated from the third-stage dust removal reactor 4, and undergo a first-stage adsorption reaction treatment to obtain the flue gas-particle mixture I. During the first-stage adsorption reaction treatment, the oxidant can oxidize NO in the flue gas into NO2, and oxidize low-valent thallium compounds (such as TICl, TIF, etc.) into thallium oxide compounds with lower toxicity, insolubility in water, and lower mobility (such as TI2O3). Moreover, in the presence of the dry absorbent and solid by-products (containing absorbent components), the preliminary absorption reactions of SO2, NO2, SO3, and HF in the flue gas are completed. Preferably, after the pre-dust removal flue gas undergoes the first-stage adsorption reaction treatment in the first-stage moving bed reactor 2, the removal rate of SO3 in the roasting flue gas is > 80%, the removal rate of HF is > 80%, the oxidation rate of NO is > 80%, and the oxidation rate of low-valent thallium compounds is > 80%.

[0077] In the present invention, by adding the dry absorbent and oxidant synchronously in advance in the first-stage moving bed reactor 2, the oxidation efficiency of thallium halide in the flue gas can be improved. The dry absorbent can be selected from various basic solid absorbents capable of adsorbing acidic gases, preferably calcium-based absorbents. As some embodiments, the specific surface area of the calcium-based absorbent is ≥ 12 m 2 / g, preferably 15 - 18 m 2 / g, and the effective calcium hydroxide content is ≥ 80%. Specific examples of the calcium-based absorbent include, but are not limited to, slaked lime and carbide slag.

[0078] In the present invention, the particle size of the dry absorbent can be selected according to the usage requirements of the moving bed and fluidized bed. Generally, the larger the particle size of the absorbent, the more conducive it is to improving the dust removal effect of the third-stage dust removal reactor, but it will reduce the efficiency of the absorption reaction. The average particle size (D50) of the dry absorbent is usually not greater than 74 μm, and preferably the average particle size (D50) of the dry absorbent is 50 - 74 μm, such as 50 μm, 55 μm, 60 μm, 63 μm, 72 μm, etc.

[0079] In the present invention, the addition amount of the dry absorbent can be selected according to the emission amount of the roasting flue gas and the concentration of acidic pollutants therein. Under the condition that the concentration of acidic pollutants and the emission standard remain unchanged, it usually increases with the increase of the emission amount of the roasting flue gas. According to some embodiments, relative to every 100,000 Nm3 The roasting flue gas is at a rate of, and the amount of dry absorbent (i.e., fresh absorbent) supplied by the dry absorbent supply device 7 is 0.4 - 1.2 t / h.

[0080] In the present invention, the oxidant can be a gaseous oxidant that can oxidize NO and thallium compounds in the lower valence state at the roasting flue gas temperature, and ozone is preferably used. The addition amount of the oxidant can be selected according to the emission amount of the roasting flue gas and the concentrations of NO x , thallium and its compounds. Under the condition that the concentrations of NO x , thallium and its compounds and the emission standard remain unchanged, it generally increases with the increase of the emission amount of the roasting flue gas. According to some embodiments, relative to every 100,000 Nm 3 / h of roasting flue gas, the amount of the oxidant (such as ozone) provided by the oxidant supply device 8 is 12 - 24 Nm 3 / h. Preferably, ozone enters the first-stage moving bed reactor 2 after being diluted by the flue gas, and the volume concentration of the diluted ozone can be 60 - 180 ppm (i.e., 0.006% - 0.018%).

[0081] In some embodiments, the gas flow velocity in the moving bed is 13 - 28 m / s, such as 13 m / s, 15 m / s, 18 m / s, 20 m / s, 21 m / s, etc. In this way, while ensuring the formation of the moving bed state, the possibility of the decrease in the adsorption reaction efficiency of multi-component pollutants and the increase in the system resistance caused by too fast moving speed can be reduced.

[0082] In the present invention, the flue gas-particle mixture I after being treated by the first-stage moving bed reactor 2 can be accelerated by a Venturi accelerating device and then enter the second-stage fluidized bed reactor 3. The flue gas-particle mixture I is converted into a highly turbulent fluidized bed state in this reactor, and an absorbent particle bed layer is formed. Preferably, the gas flow velocity in the second-stage fluidized bed reactor 3 is 4 - 7 m / s, and the bed pressure drop formed by the particles is 1000 - 1500 Pa. These particles have a huge adsorption capacity, can be in full contact with the flue gas, and can deeply and efficiently capture and adsorb each pollutant component in the flue gas. As some examples, the residence time of the material in the second-stage fluidized bed reactor 3 is 3 - 10 s, such as 4 s, 5 s, 5.3 s, 5.5 s, 6 s, 7 s, etc.

[0083] In some embodiments, the highest concentration of the local particle material in the fluidized bed is not less than 50 kg / m 3 .

[0084] In the present invention, by spraying atomized water into the fluidized bed, on the one hand, a local instantaneous liquid film can be formed on the surface of solid particles to enable ionic reactions between acid pollutants such as SO2, SO3, NO2, and HF and the absorbent within the liquid film; on the other hand, it can achieve temperature reduction and increase the reaction rate. Preferably, the amount of atomized water used is such that the temperature of the secondary fluidized bed reactor 3 is 70 - 150°C. Under this condition, during the process of secondary adsorption reaction treatment, on the one hand, the atomized water and the liquid film on the surface of the particulate material can be instantaneously evaporated in the fluidized bed, so that the material reaching the outlet position of the reactor remains in a dry state; on the other hand, when the flue gas passes through the particulate bed layer, thallium and its compounds existing in various forms in it are more likely to be captured and adsorbed. Since the oxide of thallium is insoluble in water, after oxidizing the low-valent thallium compound, it can be more stably solidified in the by-product in the form of thallium oxide and is not easily desorbed by hydrolysis.

[0085] In the present invention, generally, when the amount of atomized water used increases, it can promote the formation of a local instantaneous liquid film on the surface of solid particulate materials, promote the chemical reaction of acid pollutants, achieve temperature reduction and increase the reaction rate. However, if the amount of water used is too high, it is likely to cause problems such as too low flue gas temperature, too high flue gas moisture content, and too high material moisture content, affecting the stable operation of the system. As some preferred examples, relative to every 100,000 Nm 3 / h of flue gas volume, the amount of atomized water used is 4 - 8 t / h.

[0086] In the present invention, usually in the secondary fluidized bed reactor 3, other heavy metal pollutants such as Pb and Cr existing in the flue gas are also adsorbed and removed together. The dust concentration in the dust-containing flue gas (i.e., flue gas - particulate mixture II) obtained after passing through the fluidized bed reactor can exceed 1 kg / Nm 3 . Further, this dust-containing flue gas is sent into the tertiary dust removal reactor 4 for dust removal and adsorption reaction treatment to obtain purified flue gas and solid by-products. It is preferred to use a bag filter to treat this dust-containing flue gas. When the dust-containing flue gas passes through the filter bag and the filter cake layer on its surface, the dust is filtered and removed; at the same time, when the flue gas passes through the filter cake layer formed by absorbent particles, the remaining SO2, SO3, NO2, HF, thallium and other heavy metal pollutants in the flue gas are further absorbed and adsorbed and removed. And by means of the particle coagulation mechanism in the secondary fluidized bed reactor 3 (using the huge adsorption surface area formed by the high-density absorbent particle bed layer to absorb the extremely fine particulate dust (PM2.5 / PM10) in the flue gas, and under the condition of continuous mutual collision, friction contact and the covering liquid film of atomized water, the extremely fine particles coagulate to form larger particles), the dust removal efficiency of the bag filter is further optimized and improved to obtain purified flue gas; in addition, the soot intercepted by the filter cake layer can be collected into the ash hopper of the dust collector through the dust cleaning system in the dust collector to obtain solid by-products.

[0087] In some embodiments, in the three-stage adsorption reaction and dust removal treatment, the filtration air velocity is 0.5 - 0.8 m / min.

[0088] In the present invention, part of the solid by-products are returned to the first-stage moving bed reactor 2 through the material circulation device 10 for recycling (for example, entering the reactor through the third interface), enabling full utilization of the unreacted absorbent active components in the particulate material; the remaining solid by-products can be discharged to the by-product storage bin 12 through the by-product discharge device 11 for storage, and can be further recycled later. It can be understood that when the dry absorbent is a calcium-based absorbent, the main components of the finally obtained solid by-products are calcium sulfite, calcium sulfate, calcium nitrate, and calcium hydroxide, which can be recycled as general solid waste, for example, but not limited to, brick making, cement additive, roadbed filler, mine reclamation, etc.

[0089] The embodiments of the present invention will be described below. The embodiments described below are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention.

[0090] The following embodiments are combined with Figures 1 to 3 to treat the roasted flue gas of lepidolite. Unless otherwise specified, the pre-dust removal device 1 is selected from an electrostatic precipitator, and the three-stage dust removal reactor 4 is a low-pressure pulse rotary jet bag filter; a Venturi acceleration device is provided at the feed inlet at the bottom of the second-stage fluidized bed reactor 3, and a single-fluid high-pressure water spray gun is installed in the temperature reduction and humidity increase device 9.

[0091] Example 1

[0092] A certain enterprise newly builds a battery-grade lithium carbonate production project and supporting builds a lepidolite concentrate sulfate roasting lithium extraction device. Among them, during the production process of the lepidolite roasting kiln, the average emission flue gas volume is 131000 Nm 3 / h, the flue gas temperature is 180 °C, and the main pollution components in the flue gas: the SO2 concentration is 5000 mg / Nm 3 , the SO3 concentration is 250 mg / Nm 3 , NO x concentration is 200 mg / Nm 3 , the dust concentration is 30 g / Nm 3 , the HF (calculated as F) concentration is 300 mg / Nm 3 , the concentration of thallium and its compounds (calculated as Tl) is 15 mg / Nm 3 . The cross-sectional area A in the cylindrical tower body of the first-stage moving bed reactor 1 is 4.2 m 2, the total height h of the tower body is 3.5 m. There are a total of 4 (n = 2) first interfaces and second interfaces that are evenly distributed circumferentially on the tower body and are staggered. The interface position is h1 = 1.6 m. There are also 2 third interfaces (m = 2, the interface angle is 70°) on the circumferential direction of the tower body, and the interface position is h3 = 1.95 m. The dry calcium-based absorbent is slaked lime, with a specific surface area of 15 m 2 / g, the effective calcium hydroxide content is 88%, and the average particle size is 50 μm.

[0093] Pre-dust removal treatment: The flue gas discharged from the roasting kiln first enters the double-field electrostatic precipitator, stays for 16 s, and the electrostatic precipitator captures the dust particles in the flue gas, reducing the dust concentration to 1.5 g / Nm 3 , and the pre-dusted flue gas is discharged from the bottom of the electrostatic precipitator.

[0094] Primary adsorption reaction treatment: The pre-dusted flue gas is fed into the primary moving bed reactor from the bottom. A total of 1.2 t / h of slaked lime absorbent is evenly added into the reactor through each first interface. The gas flow velocity is controlled at 20 m / s, and ozone diluted by the flue gas (the ozone volume concentration is 150 ppm, and the total consumption in terms of ozone is 20.2 Nm 3 / h) is evenly introduced into the reactor through each second interface. A total of 110 t / h of circulating material is returned from the bottom of the bag filter hopper and evenly introduced into the reactor through each third interface to complete the preliminary treatment of multi-component pollutants in the flue gas, obtaining the flue gas-particle mixture I;

[0095] Secondary adsorption reaction treatment: The flue gas-particle mixture I is fed into the secondary fluidized bed reactor from the bottom. A particle material bed layer of 1500 Pa is established, the gas flow velocity is controlled at 4.9 m / s, and the residence time is 5.5 s. 7 t / h of atomized water is sprayed into the reactor with a single-fluid high-pressure water spray gun. The flue gas temperature at the outlet of the secondary fluidized bed reactor is maintained at about 80 °C. In the flue gas-particle mixture II obtained after the adsorption reaction treatment, the dust concentration reaches 1 kg / Nm 3 ;

[0096] Tertiary dust removal reaction: The flue gas-particle mixture II is fed into the bag filter for dust removal reaction treatment. The filtration air velocity is controlled at 0.65 m / min. When the dust-containing flue gas passes through the filter bag and the filter cake layer on its surface, the dust is filtered and removed. After passing through the bag filter, the dust concentration in the flue gas is not higher than 5 mg / Nm 3 ; At the same time, the remaining acidic pollutants and heavy metal pollutants such as thallium in the flue gas are adsorbed and removed by the absorbent in the filter cake layer. Most of the solid by-products collected in the hopper are returned to the primary moving bed reactor for recycling through the material circulation device, and the circulation material volume is 110 t / h. A small part of the particle material is discharged to the by-product bin for storage through the by-product discharge device, and the discharge amount is 1.9 t / h.

[0097] Finally, clean flue gas (i.e., purified flue gas) is discharged after three-stage dust removal reaction, pressurized by the induced draft fan, discharged to the chimney, and finally discharged into the atmosphere.

[0098] In the purified flue gas, SO2≤35mg / Nm 3 (removal efficiency higher than 99.3%), SO3≤2mg / Nm 3 (Removal efficiency is higher than 99.2%), dust ≤ 5mg / Nm 3 (removal efficiency is higher than 99.9995%), NO x ≤20mg / Nm 3 (removal efficiency higher than 90%), F≤2mg / Nm 3 (Removal efficiency higher than 99.3%), TI and its compounds ≤ 0.05 mg / Nm 3 (Removal efficiency is higher than 99.67%). During the operation of the device, when the flue gas volume emitted by the upstream roasting kiln is less than 98000Nm 3 / h, a portion of the clean flue gas after the induced draft fan is automatically led back to the inlet of the first-stage moving bed reactor through the load stabilization regulating device, ensuring that when the roasting main unit is in a low-load condition, the inlet flue gas volume of the first-stage moving bed reactor is maintained at more than about 74% of the design value, thereby maintaining the normal and stable operation of the purification treatment system of the present invention.

[0099] Example 2

[0100] A certain enterprise newly built a battery-grade lithium carbonate production project and built a new lithium mica concentrate sulfate roasting and lithium extraction device. During the production process of the lithium mica roasting kiln, the average flue gas emission was 393,000 Nm 3 / h, flue gas temperature 190℃, main pollutant in flue gas: SO2 concentration 5500mg / Nm 3 , SO3 concentration 275mg / Nm 3 , NO x Concentration 220mg / Nm 3 , dust concentration 33g / Nm 3 , HF (in F) concentration 320 mg / Nm 3 , thallium and its compounds (in terms of Tl) concentration 16 mg / Nm 3 The cross-sectional area A of the cylindrical tower body of the first-stage moving bed reactor 1 is 9.2m 2 The tower body height is h = 4.8m. There are 6 first and second interfaces (n = 3) evenly distributed around the tower body, and the interface position is h1 = 2.4m. There are also 2 third interfaces (m = 2, the interface angle is 70°) around the tower body, and the interface position is h3 = 2.88m. The dry calcium-based absorbent is slaked lime, with a specific surface area of 13m 2 / g, with an effective calcium hydroxide content of 85% and an average particle size of 63 μm.

[0101] Pre-dust removal treatment: The flue gas discharged from the roasting kiln first enters a three-field electrostatic precipitator, stays for 24 s, and the dust particles in the flue gas are captured by this electrostatic precipitator, reducing the dust concentration in the flue gas to 0.33 g / Nm 3 , and the pre-dusted flue gas is discharged from the bottom of the electrostatic precipitator.

[0102] Primary adsorption reaction treatment: The pre-dusted flue gas is fed into a primary moving bed reactor from the bottom. A total of 4.2 t / h of hydrated lime absorbent is evenly added into the reactor through each first interface, the gas flow velocity is controlled at 20.5 m / s, and ozone diluted by the flue gas (ozone volume concentration is 170 ppm, and the total ozone usage is 66.2 Nm 3 / h) is evenly introduced into the reactor through each second interface. A total of 328 t / h of recycled materials is evenly introduced into the reactor through each third interface from the bottom of the dust removal reactor hopper to complete the preliminary treatment of multi-component pollutants in the flue gas, obtaining flue gas-particle mixture I;

[0103] Secondary adsorption reaction treatment: Flue gas-particle mixture I is fed into a secondary fluidized bed reactor from the bottom, a particle material bed layer of 1400 Pa is established, the gas flow velocity is controlled at 5.2 m / s, the residence time is 5.3 s, 20 t / h of atomized water is sprayed into the reactor with a single-fluid high-pressure water spray gun, and the temperature of the flue gas at the outlet of the secondary circulating fluidized bed reactor is maintained at about 75 °C. In the flue gas-particle mixture II obtained after the adsorption reaction treatment, the dust concentration reaches 1 kg / Nm 3 ;

[0104] Tertiary dust removal reaction: Flue gas-particle mixture II is fed into a bag filter for dust removal reaction treatment, the filtration air velocity is controlled at 0.64 m / min. When the dusty flue gas passes through the filter bag and the filter cake layer on its surface, the dust is filtered and removed. After passing through the bag filter, the dust concentration in the flue gas is not higher than 5 mg / Nm 3 ; At the same time, the remaining acidic pollutants and heavy metal pollutants such as thallium in the flue gas are adsorbed and removed by the absorbent in the filter cake layer. Most of the solid by-products collected in the hopper are recycled to the primary moving bed reactor through the material circulation device, with a circulation material volume of 328 t / h, and a small part of the particle materials are discharged to the by-product silo for storage through the by-product discharge device, with a discharge volume of 6.3 t / h.

[0105] Finally, the clean flue gas discharged after the tertiary dust removal reaction is pressurized by a induced draft fan and discharged to the chimney and finally into the atmosphere.

[0106] In the purified flue gas, SO2 ≤ 32 mg / Nm 3(The removal efficiency is higher than 99.4%), SO3 ≤ 2mg / Nm 3 (The removal efficiency is higher than 99.2%), dust ≤ 5mg / Nm 3 (The removal efficiency is higher than 99.9995%), NO x ≤ 20mg / Nm 3 (The removal efficiency is higher than 90.9%), F ≤ 2mg / Nm 3 (The removal efficiency is higher than 99.3%), TI and its compounds ≤ 0.05mg / Nm 3 (The removal efficiency is higher than 99.68%). During the operation of the device, when the flue gas volume discharged from the upstream roasting kiln is less than 295000 Nm 3 / h, a part of the clean flue gas after the induced draft fan is automatically led back to the inlet of the first-stage moving bed reactor through the load stability adjustment device to ensure that when the roasting main machine is in a low-load condition, the flue gas volume at the inlet of the first-stage moving bed reactor is maintained at more than about 75% of the design value, so as to maintain the normal and stable operation of the purification treatment system of the present invention.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present invention is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A purification and treatment system for lepidolite roasting flue gas, characterized in that, It includes a pre-dust removal device, a first moving bed reactor, a second fluidized bed reactor, a third dust removal reactor and an induced draft fan connected in sequence; wherein, The pre-dust removal device is used for pre-dust removal treatment of the lepidolite roasting flue gas to obtain pre-dust removal flue gas; The first moving bed reactor is used for primary adsorption reaction treatment of the pollutants in the pre-dust removal flue gas, and a dry absorbent supply device and an oxidant supply device are also connected to the first moving bed reactor; The second fluidized bed reactor is used for secondary adsorption reaction treatment of the pollutants in the flue gas-particle mixture I generated by the first moving bed reactor, and a cooling and humidifying device is also connected to the second fluidized bed reactor for providing atomized water to the reactor; The third dust removal reactor is used for tertiary adsorption reaction and dust removal treatment of the pollutants in the flue gas-particle mixture II generated by the second fluidized bed reactor to obtain purified flue gas and solid by-products; and The third dust removal reactor is respectively connected with a material circulation device and a by-product collection device. The material circulation device is used for returning part of the solid by-products to the first moving bed reactor as circulating materials, and the by-product collection device is used for discharging and storing the remaining solid by-products; The induced draft fan is used for boosting and discharging the purified flue gas.

2. The purification treatment system according to claim 1, wherein A load stable adjustment device is also provided between the outlet of the induced draft fan and the first moving bed reactor for introducing at least part of the purified flue gas into the first moving bed reactor; Preferably, the load stable adjustment device is a wind baffle or a butterfly valve with adjustable opening.

3. The purification treatment system according to claim 1 or 2, characterized in that The pre-dust removal device is an electrostatic precipitator; and / or The third dust removal reactor is a bag filter.

4. The purification treatment system according to any one of claims 1 to 3, characterized in that The oxidant supply device includes an ozone generator and a dilution mixer connected by a pipeline, so that the ozone generated by the ozone generator enters the dilution mixer and is diluted and then enters the first moving bed reactor.

5. The purification treatment system according to any one of claims 1-4, characterized in that, The first moving bed reactor includes a cylindrical tower body. A plurality of first interfaces and second interfaces arranged alternately are uniformly provided in the circumferential direction of the cylindrical tower body. The dry absorbent supply device is connected to the first moving bed reactor through the first interface, and the oxidant supply device is connected to the first moving bed reactor through the second interface; Preferably, a flue gas inlet is connected to the bottom of the cylindrical tower body, and a flue gas outlet is connected to the top of the cylindrical tower body; the distance h1 between the first interface, the second interface and the bottom of the cylindrical tower body and the height h of the cylindrical tower body satisfy the relational expression: 0.3 < h1 / h < 0.7; Preferably, the number of the first interfaces and the second interfaces is both n, and 2 ≤ n ≤ 5; Preferably, the cross-sectional area A of the cylindrical tower body satisfies A ≤ 4.9 m 2 , n = 2; Or 4.9 m 2 <A ≤ 20 m 2 , n = 3; or 20m 2 <A≤30m 2 , n = 4.

6. A purification method for lithium mica roasting flue gas, characterized in that, This method is implemented by using the purification treatment system according to any one of claims 1-5, and includes the following technological process: Send the lepidolite roasting flue gas into the pre-dust removal device for pre-dust removal treatment to obtain pre-dust removal flue gas; Send the pre-dust removal flue gas into the first moving bed reactor, and add dry absorbent and oxidant to carry out primary adsorption reaction treatment on the pollutants in the pre-dust removal flue gas to obtain a flue gas-particle mixture I; Feed the flue gas-particle mixture I into the secondary fluidized bed reactor, add atomized water for cooling, and perform a secondary adsorption reaction treatment on the pollutants in the flue gas-particle mixture I to obtain the flue gas-particle mixture II; Feed the flue gas-particle mixture II into the tertiary dust removal reactor for tertiary adsorption reaction and dust removal treatment to obtain purified flue gas and solid by-products; return part of the solid by-products as recycled materials to the primary moving bed reactor, and discharge and store the remaining solid by-products through the by-product collection device; The purified flue gas is pressurized and discharged through a induced draft fan.

7. The purification treatment method according to claim 6, characterized in that The SO2 concentration in the roasted lepidolite flue gas is 2000 - 6000 mg / Nm 3 , the SO3 concentration is 50 - 400 mg / Nm 3 , the NO x concentration is 150 - 300 mg / Nm 3 , the concentration of thallium and its compounds calculated as Tl is 10 - 20 mg / Nm 3 , the HF concentration calculated as F is 250 - 400 mg / Nm 3 , the dust concentration is 20 - 50 g / Nm 3 ; Preferably, the temperature of the flue gas entering the pre-dust removal device is 150-200 °C; Preferably, the dust removal efficiency of the pre-dust removal device for the calcined flue gas is ≥95%; 8. The purification treatment method according to claim 6 or 7, characterized in that, The average particle size of the dry absorbent is ≤74 μm; Preferably, the dry absorbent is a calcium-based absorbent, and the specific surface area of the calcium-based absorbent is ≥ 12 m 2 / g, more preferably 15 - 18 m 2 / g, and the effective calcium hydroxide content is ≥ 80%; Preferably, relative to every 100,000 Nm 3 / h of the calcination flue gas, in the primary moving bed reactor, the dosage of the dry absorbent provided by the dry absorbent supply device is 0.4 to 1.2 t / h.

9. The purification method according to any one of claims 6-8, characterized in that, The oxidant is ozone; Preferably, relative to every 100,000 Nm 3 / h of roasting flue gas, in the first-stage moving bed reactor, the amount of the oxidant provided by the oxidant supply device is 12 - 24 Nm 3 / h.

10. The purification treatment method according to any one of claims 6-9, characterized in that, In the secondary adsorption reaction treatment, the amount of atomized water is such that the temperature of the secondary fluidized bed reactor is 70-150 °C; Preferably, in the secondary fluidized bed reactor, the bed pressure drop formed by the particles is 1000-1500 Pa, and the gas flow velocity is 4-7 m / s; Preferably, in the tertiary adsorption reaction and dust removal treatment, the filtration air velocity is 0.5-0.8 m / min.

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