A method for calcification reduction and dealkalization of vanadium extraction tailings

Abstract

The present invention provides a vanadium extraction tailings calcification reduction dealkalization method. The method comprises the following steps: pre-treating the vanadium extraction tailings with a composite low-temperature curing agent for pelletization to prepare a silicon-free pellet raw material that releases CO2 at high temperature; adopting a hot air drying-microwave consolidation process to strengthen the strength of the pellets; and then using a rotary kiln for reduction roasting, so that the alkali metals in the vanadium extraction tailings enter the gas phase and are removed through dust removal. The obtained slag phase has high iron and vanadium metallization rates and can be directly used in a blast furnace. The alkali metals in the vanadium extraction tailings are effectively removed, enabling the recycling of the vanadium extraction tailings in the ironmaking process, improving the recovery rate of valuable elements in the vanadium extraction tailings, and increasing the blast furnace's ability to process the vanadium extraction tailings.

Description

Technical Field

[0001] The invention relates to a method for treating vanadium-extracting tailings, in particular to a method for treating vanadium-extracting tailings by adopting a reduction method, and belongs to the technical fields of solid waste treatment and metallurgy. Background Art

[0002] The iron-rich tailings in vanadium extraction are mostly oxidized to hematite. Current methods for utilizing this iron include magnetization roasting, spiral laundering, magnetic separation, and flotation. Research on iron recovery from tailings has primarily focused on pyrometallurgical and hydrometallurgical methods. Some steel mills sinter or pelletize their tailings before returning them to the blast furnace, but blast furnaces cannot fully utilize their tailings. The reasons for this are: first, the low iron content in vanadium extraction tailings reduces the overall iron grade fed to the furnace and increases the coke ratio. Second, the alkali metal content in vanadium extraction tailings exceeds the blast furnace's tolerance limit, thereby degrading the permeability of the blast furnace charge column and hindering smooth operation. Third, the tailings contain toxic hexavalent chromium and pentavalent vanadium, posing a potential risk of secondary pollution during the recovery process. Consequently, non-blast furnace ironmaking technologies have attracted considerable attention, with reduction grinding being the most studied. This involves reducing roasting to reduce the trivalent iron in the tailings to metallic iron particles, followed by grinding and magnetic separation to recover the iron. The wet process for recovering iron from tailings involves pressure leaching with sulfuric acid. The iron in the tailings dissolves during the pressure leaching process and crystallizes out of the solution as green vitriol. Spherical nano-iron oxide is then synthesized hydrothermally using glucose as a substrate. However, these methods only recover a portion of the valuable elements in the vanadium-extracting tailings, still generating significant amounts of waste, and fail to address the high alkali metal content in the vanadium-containing tailings, which makes recycling difficult.

[0003] The main methods for extracting vanadium from tailings include sodium roasting-water leaching and direct acid leaching. The basic principle of the sodium roasting-water leaching process is to add sodium salt to the roasting process to convert low-valent vanadium into water-soluble pentavalent vanadium. Analysis of the tailings after sodium roasting shows that some vanadium-containing spinel remains unoxidized due to the presence of silicates. Some smaller vanadium particles enter the vitreous body and become insoluble vanadium-containing compounds. Therefore, a large amount of vanadium remains after secondary vanadium extraction from the tailings. Another method is direct acid leaching, which can be performed at atmospheric pressure or under pressure. The leaching agent is generally sulfuric acid, with a small amount of oxidant and catalyst. The use of high-concentration sulfuric acid can increase equipment corrosion. Hydrogen fluoride is often used as a catalyst in this process, which increases environmental risks. Pressure leaching is an acid leaching reaction using sulfuric acid as the leaching agent and hydrogen peroxide as the oxidant. Compared with atmospheric pressure acid leaching, it has disadvantages such as higher equipment requirements and lower processing capacity.

[0004] In the study of dealkalization of vanadium tailings, some researchers have proposed adding calcium oxide or magnesium oxide to leaching under pressure and heat to destroy the sodium-containing phase, so that the sodium can be leached into the solution and then removed. The main phases in vanadium tailings are pyroxene solid solution, iron oxide and olivine. Whether using normal pressure in and out or pressure leaching, the sodium removal rate is not high. In addition, the process requires pressure leaching, which requires high equipment investment and discontinuous operation, increasing the investment and processing costs of enterprises. Existing research on the utilization of vanadium tailings is mostly focused on extracting and utilizing some of the valuable elements in it. However, a large amount of waste is still generated during the extraction process, which is harmful to the environment and does not fundamentally solve the problem of comprehensive resource utilization of vanadium tailings.

[0005] Traditional reduction roasting and volatilization methods require high temperatures and long times to remove alkali metals. High reduction temperatures can lead to severe agglomeration and ringing during the reduction process. If agglomeration is not performed before reduction, the large amount of powder will result in severe agglomeration and ringing. If agglomeration is performed, the amount of binder added, such as traditional bentonite, will be very large. Bentonite has a high silicon content, which reacts with vanadium extraction tailings at high temperatures to form compounds that increase the difficulty of alkali metal removal. Traditional reduction volatilization methods are unable to remove alkali metals from complex stable solid solutions containing multiple elements, such as sodium, potassium, silicon, titanium, iron, magnesium, aluminum, and manganese. Summary of the Invention

[0006] The vanadium extraction tailings produced by the existing vanadium industry contain not only large amounts of iron and vanadium, but also high levels of alkali metals. During the return process to the sintering and blast furnace, the high alkali metal content can cause the sintered ore to have a low melting point and stick to the grate bars. During the blast furnace reduction process, this high alkali metal content can also damage the tuyere and corrode the furnace lining, among other process phenomena. The existing reduction roasting and volatilization methods used to remove alkali metals require high temperatures, long times, and high reduction temperatures. This incomplete alkali metal removal can lead to severe agglomeration and ringing during the reduction process, impacting blast furnace operation and iron grade. The existing pretreatment processes used to treat the vanadium extraction tailings, such as pelletizing or agglomeration, introduce new impurities such as silicon and cause pellets to be weak and prone to bursting. To solve the above problems, the present invention proposes a calcification reduction dealkalization method for vanadium extraction tailings. The method comprises the following steps: pre-treating the vanadium extraction tailings with a composite low-temperature curing agent for pelletization to prepare a silicon-free pellet raw material that releases CO2 at high temperature; adopting a hot air drying-microwave consolidation process to strengthen the strength of the pellets; and then using a rotary kiln for reduction roasting, so that the alkali metals in the vanadium extraction tailings enter the gas phase and are removed through dust removal. The obtained slag phase has a high iron and vanadium metallization rate and can be directly used in a blast furnace. The alkali metals in the vanadium extraction tailings are effectively removed, enabling the recycling of the vanadium extraction tailings in the ironmaking process, improving the recovery rate of valuable elements in the vanadium extraction tailings, and increasing the blast furnace's ability to process the vanadium extraction tailings.

[0007] According to the technical solution provided by the present invention, a method for dealkalization of vanadium-extracting tailings by calcification reduction is provided.

[0008] A vanadium extraction tailings calcification reduction dealkalization method, the method comprising the following steps:

[0009] 1) uniformly mixing the vanadium extraction tailings and the composite low-temperature curing agent, forming pellets to obtain green pellets;

[0010] 2) The green pellets are sequentially subjected to hot air drying and microwave consolidation to obtain consolidated pellets;

[0011] 3) The consolidated pellets are transported to a rotary kiln for reduction roasting. The dust-laden tail gas discharged from the rotary kiln undergoes a first dust removal treatment, a reburning reaction, waste heat utilization, a second dust removal treatment, and a desulfurization treatment in sequence. The reduced material obtained after the reduction roasting in the rotary kiln is cooled and screened to obtain the ferrovanadium raw material.

[0012] Preferably, the tail gas after desulfurization treatment in step 3) is CO2-containing waste gas, and the CO2-containing waste gas is divided into two parts, one part of the CO2-containing waste gas is transported to the rotary kiln; the other part of the CO2-containing waste gas is transported to the microwave consolidation process, and the gas discharged from the microwave consolidation process is transported to the hot air drying process.

[0013] Preferably, the CO2-containing waste gas entering the rotary kiln is input from the middle part of the rotary kiln body.

[0014] Preferably, the cooling in step 3) is performed by semi-dry cooling, specifically:

[0015] 301) passing water through an atomization system to obtain atomized water;

[0016] 302) The reduced material is conveyed into a semi-dry cooling device, and atomized water is introduced into the semi-dry cooling device; the atomized water cools the reduced material, absorbs heat in the reduced material, and reacts with the residual carbon in the reduced material to produce water gas to obtain hot gas containing CO and H2, and the hot gas containing CO and H2 is conveyed to a waste heat utilization process for waste heat utilization and / or the hot gas containing CO and H2 is conveyed to a rotary kiln for reduction of consolidated pellets.

[0017] Preferably, a portion of the CO2-containing waste gas is transported to a rotary kiln; a portion of the CO2-containing waste gas is transported to a microwave consolidation process, and the gas discharged from the microwave consolidation process is transported to a hot air drying process; the remaining CO2-containing waste gas is transported to an atomization device, and CO2 is dissolved in the atomized water; the atomized water dissolved in CO2 is reformed through a semi-dry cooling device, CO2 reacts with the residual carbon in the reducing material to produce a Boudolf reaction, and the atomized water reacts with the residual carbon in the reducing material to produce a water-gas reaction to obtain hot gas containing CO and H2, and the hot gas containing CO and H2 is transported to a waste heat utilization process for waste heat utilization and / or the hot gas containing CO and H2 is transported to a rotary kiln for reduction of consolidated pellets.

[0018] In the present invention, the screening in step 3) is magnetic separation, and the ferrovanadium raw material and residual carbon are obtained through magnetic separation.

[0019] Preferably, the waste heat utilization is waste heat power generation.

[0020] Preferably, the residual carbon is screened to obtain fine-grained coke powder and coarse-grained coke powder. The fine-grained coke powder is used as a sintering ingredient, while the coarse-grained coke powder is transported to a rotary kiln. The ferrovanadium raw material is transported to a blast furnace. Alkali-containing dust is obtained through the first and second dust removal processes.

[0021] In the present invention, the composite low-temperature curing agent in step 1) is obtained by mixing one or more of calcium oxide, calcium hydroxide, calcium carbonate, calcium chloride, and calcium sulfate with one or more of starch, coal tar, and molasses.

[0022] In the present invention, the mixing weight ratio of the vanadium extraction tailings and the composite low-temperature curing agent is 1:0.1-1, preferably 1:0.2-0.8.

[0023] In the present invention, the moisture content of the green balls is 5 to 20% by weight, preferably 8 to 12% by weight.

[0024] In the present invention, the particle size of the green balls is 2 to 12 mm, preferably 3 to 8 mm.

[0025] Preferably, in step 2), a gas containing CO2 and water vapor is introduced into the microwave consolidation process, the gas containing CO2 and water vapor is transported to the microwave consolidation process, and the gas discharged from the microwave consolidation process is transported to the hot air drying process.

[0026] Preferably, the gas containing CO2 and water vapor is any one of hot air with added water vapor and CO2, hot tail gas after combustion of blast furnace gas, coke oven gas or converter gas, direct reduction hot tail gas, and lime kiln hot tail gas.

[0027] In the present invention, the CO 2 concentration in the gas containing CO 2 and water vapor is 10% to 50%, preferably 20% to 40%.

[0028] In the present invention, the humidity of the gas containing CO2 and water vapor is 10g / m 3 ~100g / m 3 , preferably 20g / m 3 ~50g / m 3 .

[0029] In the present invention, in step 3), the consolidated pellets and coke powder are mixed and then transported to a rotary kiln for reduction roasting. The weight ratio of the consolidated pellets to the coke powder is 1:0.1 to 1.5, preferably 1:0.2 to 1.

[0030] Preferably, during the reduction roasting step, coal is injected from the kiln head of the rotary kiln, and the weight ratio of the injected coal to the weight of the consolidated pellets is 0.1 to 1:1, preferably 0.2 to 0.5:1.

[0031] Preferably, the hot air drying process is a two-stage hot air drying process, including hot air drying stage I and hot air drying stage II.

[0032] Preferably, the microwave consolidation process is a two-stage microwave consolidation process, including microwave consolidation stage I and microwave consolidation stage II.

[0033] The raw balls are sequentially subjected to hot air drying stage I, hot air drying stage II, microwave consolidation stage I, and microwave consolidation stage II to obtain consolidated pellets.

[0034] Preferably, the drying temperature in hot air drying stage I is 60-100°C, and the drying time is 2-20 minutes. The drying temperature in hot air drying stage II is 100-250°C, and the drying time is 2-20 minutes. After the hot air drying process, the moisture content in the pellets is 2% to 8%, preferably 4% to 6%.

[0035] Preferably, the temperature of microwave consolidation stage I is 250-350°C, and the pellet residence time is 2-20 minutes. The temperature of microwave consolidation stage II is 350-500°C, and the pellet residence time is 2-20 minutes. The microwave power density in the microwave consolidation process is 5 kW / m 3 ~50kw / m 3 , preferably 20kw / m 3 ~30kw / m 3 .

[0036] Preferably, the rotary kiln is a direct reduction rotary kiln.

[0037] A direct reduction rotary kiln comprises a kiln head, a kiln body, and a kiln tail. A burner is provided at the kiln head. The direct reduction rotary kiln is cylindrical in structure, with the kiln body sidewalls constructed of refractory bricks. Gas delivery pipes are provided within the refractory bricks of the kiln body sidewalls. A nozzle is provided on the inner sidewall of the kiln body. The nozzle connects the gas delivery pipe to the inner chamber of the direct reduction rotary kiln.

[0038] In the invention, the nozzle is arranged at the middle kiln body of the direct reduction rotary kiln.

[0039] Preferably, a plurality of gas delivery pipes are provided in the kiln body parallel to the axis direction of the direct reduction rotary kiln.

[0040] Preferably, 2-100 gas delivery pipelines are provided in the kiln body, and more preferably, 4-50 gas delivery pipelines are provided in the kiln body.

[0041] A plurality of gas conveying pipelines are evenly arranged in the side wall of the direct reduction rotary kiln.

[0042] Preferably, each gas delivery pipeline is provided with a plurality of nozzles.

[0043] Preferably, each gas delivery pipeline is provided with 2-20 nozzles, and more preferably, each gas delivery pipeline is provided with 3-10 nozzles.

[0044] Preferably, the gas delivery pipeline is a spiral pipeline, which is perpendicular to the axis of the direct reduction rotary kiln 1 and is wound inside the refractory bricks of the kiln body.

[0045] Preferably, a plurality of nozzles are provided on the spiral gas delivery pipe.

[0046] Preferably, the spiral gas delivery pipeline is provided with 2-100 nozzles, and more preferably, the spiral gas delivery pipeline is provided with 3-50 nozzles.

[0047] In the present invention, the air inlet end of the gas delivery pipeline is connected to the blower.

[0048] Preferably, a gas release valve is provided at the end of the gas delivery pipeline, and the gas release valve is located downstream of the nozzle.

[0049] Preferably, the gas delivery pipeline is a variable diameter pipeline. The inner diameter of the gas delivery pipeline gradually decreases from the air inlet end to the location where the nozzle is arranged.

[0050] Preferably, the inner diameter of the gas delivery pipe gradually increases from the location where the nozzle is set to the location of the gas release valve.

[0051] Preferably, the ratio of the inner diameter of the gas delivery pipe at the nozzle position to the inner diameter of the gas delivery pipe inlet end is 1:1.5-4, preferably 1:2-3.

[0052] Preferably, a pressurized anti-backflow fin is provided on the inner wall of the gas delivery pipeline.

[0053] Preferably, the cross section of the pressurization anti-backflow fin is an "eight-shaped" structure. The end of the pressurization anti-backflow fin of the "eight-shaped" structure is connected to the inner wall of the gas delivery pipe and is located upstream.

[0054] Preferably, the angle between the pressurization anti-backflow fin and the inner wall of the gas delivery pipe is 20-80°, preferably 30-60°.

[0055] Preferably, a temperature measuring element is provided on the inner wall of the gas delivery pipeline.

[0056] Preferably, temperature measuring elements are independently provided on the inner walls of the gas delivery pipeline at each section of the kiln head, kiln body and kiln tail of the direct reduction rotary kiln.

[0057] In the present invention, the vanadium extraction tailings are pelletized, dried, and consolidated to obtain consolidated pellets, which are then reduced and roasted in a rotary kiln. In the rotary kiln, the alkali metals have a low boiling point and enter the gas phase, and are discharged from the rotary kiln along with the flue gas; the flue gas discharged from the rotary kiln undergoes dust removal treatment (settling chamber) to obtain sedimentation ash containing alkali metals. The oxides of iron and vanadium are reduced in the rotary kiln to obtain elemental iron and vanadium, or are reduced to low-valent iron (+2) and low-valent vanadium (+3), enter the slag phase, and are discharged from the kiln head of the rotary kiln; and then cooled to obtain reduced materials containing iron and vanadium. The reduced materials containing iron and vanadium can be directly used as raw materials for blast furnaces.

[0058] The present invention proposes a method for calcification reduction and dealkalization of vanadium-extracting tailings. Compared with the common reduction volatilization method, the composite small balls (raw balls) used in the present invention have the characteristics of faster and more uniform carbonation reaction, higher pellet strength and higher production efficiency. A composite low-temperature curing agent (obtained by mixing one or more of calcium oxide, calcium hydroxide, calcium carbonate, calcium chloride and calcium sulfate with one or more of starch, coal tar and molasses) is used. The composite low-temperature curing agent does not contain silicon and releases CO2 under medium and high temperature conditions for calcification of the calcium binder to form calcium carbonate with higher strength, thereby improving the hardness and consolidation of the pellets. The calcification reduction volatilization de-sodiumization method provided by the present invention has the characteristics of higher de-sodiumization rate and more stable production, and the semi-dry cooling method adopted has the characteristics of higher waste heat utilization rate and faster cooling speed.

[0059] The reasons are:

[0060] (1) The present invention contains a carbon-based composite binder in the composite low-temperature curing agent added during the pelletizing process. During the drying and consolidation process, the carbon-based composite binder between the raw material particles is converted into CO2, which directly provides the CO2 gas required for the carbonation reaction. This changes the previous unreacted core model and avoids the situation in which traditional CO2 needs to diffuse from the outside of the pellet to the inside. The outside and inside of the pellet are carbonated simultaneously, and there is no outer dense calcium carbonate film that hinders gas diffusion. As a preference, the use of 3-8 mm small balls (raw balls) can also reduce the diffusion resistance of CO2 inside the pellet.

[0061] (2) The composite low-temperature curing agent of the present invention contains calcium oxide / calcium hydroxide and a carbon-based composite binder. In the pelletizing stage, the colloidal calcium hydroxide and the carbon-based composite binder can ensure the strength of the pellets; in the drying and consolidation process, under high temperature conditions, although the bonding strength of the dried calcium hydroxide is low, the carbon-based composite binder can still provide a certain strength for the pellets after dehydration. Moreover, because there is a large amount of newly generated CO2 inside the pellets, the carbonation reaction speed is also accelerated. The amount of newly generated calcium carbonate crystallites is more than that of conventional methods. The combination of the two can ensure the strength of the pellets during the high-temperature drying process. The production efficiency can be improved by increasing the reaction temperature and increasing the material layer height, so as to achieve a balance between strength and production efficiency.

[0062] (3) The carbonation consolidation process of the present invention adopts the method of hot air drying + microwave heating drying consolidation. Microwave heating consolidation has the characteristic of heating from the inside and outside of the pellet together. The temperature and CO2 atmosphere conditions are met inside and outside the pellet. The carbonation reaction rate is consistent, and there will be no double-layer structure with a hard outside and a loose inside. In addition, the carbon-based composite binder has a very strong wave absorption characteristic. Under microwave radiation, a microwave hot spot phenomenon will appear. The temperature will be significantly higher than the ambient temperature. A high temperature phenomenon will appear in the local micro-region with the carbon-based composite binder. In the micro-region, the carbon-based composite binder is converted into CO2 and water vapor to react with calcium hydroxide at a relatively high temperature. A high temperature, high CO2, high water vapor, and high calcium reaction environment is formed in the micro-region. The carbonation reaction proceeds rapidly to generate calcium carbonate microcrystals. Under the non-thermal effect of microwaves, the formed calcium carbonate microcrystals will drive the migration of particles. The microcrystals will grow rapidly, tightly connecting adjacent particles together, providing high strength guarantee for the pellets.

[0063] (4) The multi-nozzle rotary kiln (a rotary kiln with air intake through the kiln body) used in the present invention is used for reduction roasting. The temperature field in the kiln can be effectively adjusted through the multi-nozzle kiln body. By supplying air to the high-temperature zone, the temperature in the high-temperature zone is reduced to prevent the material from melting and forming rings due to excessive temperature. By supplying air to the section from the middle of the kiln to the tail of the kiln, the combustion efficiency of the reducing gas in the kiln is improved, the gas temperature in the direction of the kiln tail is increased, and the high-temperature zone is effectively extended, providing a longer-term high-temperature roasting environment for material reduction.

[0064] (5) The semi-dry cooling method adopted by the present invention can deliver atomized water to the hot reduction product for countercurrent direct heat exchange cooling. In addition, the reduction product contains some unburned high-temperature residual coal (residual carbon or residual coke), which will undergo an endothermic reaction during contact with water vapor and CO2:

[0065] C + CO2 = 2CO

[0066] C+H2O=H2+CO

[0067] The temperature of the reduction product is further reduced by the endothermic reaction of the coal gas reforming reaction and the Boudol reaction, so that the reduction product is cooled quickly to obtain a reduction material containing iron and vanadium with a high metallization rate.

[0068] In view of the technical problem that in the prior art, CO2 gas can only diffuse from the outside of the pellet to the inside of the pellet during the drying and consolidation process, resulting in the binder (such as calcium hydroxide) in the outer layer of the outer pellet preferentially reacting with CO2 to form a dense calcium carbonate layer, which hinders the CO2 gas from continuing to diffuse into the interior of the pellet, resulting in the inability to form calcium carbonate inside the pellet, affecting the overall strength of the pellet. The present invention adds a composite low-temperature curing agent (obtained by mixing one or more of calcium oxide, calcium hydroxide, calcium carbonate, calcium chloride, and calcium sulfate with one or more of starch, coal tar, and molasses) during the pelletizing process. During the pellet drying and consolidation process, the carbon-based composite binder (starch, coal tar, molasses) in the inner core (inside) of the pellet can release CO2 and H2O under the low-temperature conditions of drying and consolidation, and the released CO2 and H2O react with the binder (such as calcium hydroxide) in the pellet to form a calcium carbonate consolidation structure uniformly throughout the pellet; so that calcium carbonate consolidation with higher strength is formed at each position in the entire pellet, thereby improving the strength of the entire pellet. In the technical solution of the present invention, the carbon-based composite binder between the raw material particles is converted into CO2 and H2O during the drying and consolidation process, directly providing the CO2 gas and H2O vapor environment required for the carbonation reaction inside the pellets, changing the previous unreacted core model, avoiding the situation where the traditional CO2 needs to diffuse from the outside of the pellet to the inside, and the outside and inside of the pellets are carbonated simultaneously, without the influence of the outer dense calcium carbonate film hindering gas diffusion, thereby reducing the diffusion resistance of CO2 inside the pellets. In addition, from the analysis of reaction kinetics, compared with the diffusion of CO2 gas from the outside of the pellets to the inside of the pellets, the technical solution of the present invention is used to release CO2 and H2O from the inside of the pellets, and the CO2 and H2O inside the pellets are much easier to diffuse outward, thereby making it easier for the binder (such as calcium hydroxide) in the pellets to react with CO2 in the presence of water vapor, and the resulting calcium carbonate consolidation material is more uniform.

[0069] In the present invention, the carbon-based composite binder (starch, coal tar, molasses) is solid or liquid at room temperature. During the drying and consolidation process, the carbon-based composite binder (starch, coal tar, molasses) is thermally decomposed to release carbon dioxide and / or water during the heating process. The released carbon dioxide reacts with the binder in the pellets under the action of water vapor to form a compound that has a consolidating effect. For example, the starch used in this application begins to decompose at 180-200°C, releasing CO2 and H2O; coal tar begins to decompose at around 80°C, releasing volatiles; and waste molasses begins to decompose at 280°C, releasing CO2 and H2O. The carbon-based composite binder (starch, coal tar, molasses) is solid or liquid at room temperature, making it easy to mix with vanadium-extraction tailings to form pellets. After the carbon-based composite binder (starch, coal tar, molasses) is mixed with vanadium-extraction tailings and other additives to form pellets, the pellets gradually begin to decompose under the elevated temperature conditions of the drying and consolidation process, releasing CO2 and H2O. This achieves the technical effect of the pellets self-releasing CO2 and H2O during the drying and consolidation process. Moreover, unlike the method of introducing CO2 and H2O from the outside, the pellets of the present invention release CO2 and H2O from the inside of the pellets, and the consolidation process is carried out simultaneously inside and outside the pellets. As a result, the pellets after drying and consolidation have a structure with uniform strength from the inside to the outside, overcoming the technical problem of "hard outside and loose inside". At the same time, the decomposition temperature of the carbon-based composite binder (starch, coal tar, molasses) used in the present invention cannot be too high, because the drying temperature of the pellets is generally controlled below 500°C (preferably 400°C). If a binder with a decomposition temperature that is too high (over 500°C) is used, it cannot decompose and release CO2 and H2O during the drying and consolidation process, thereby failing to achieve the technical purpose and effect of releasing CO2 and H2O from the interior of the pellets. Through continuous experiments by the inventors, it was found that starch, coal tar, molasses, or a combination thereof, can be added during the preparation of the pellets. Such substances can release CO2 and H2O within the temperature range of the pellet drying and consolidation process. The decomposition temperature of such substances coincides with the temperature of the drying and consolidation process. Under the temperature conditions of the drying and consolidation process, they begin to release CO2 and H2O, providing the CO2 and H2O required for consolidation to the interior of the pellets.

[0070] In the prior art, hot air drying and consolidation are generally used to dry and consolidate the pellets. Hot air drying results in a higher temperature on the surface of the pellets and a lower temperature inside the pellets, resulting in a large temperature difference. In order to achieve the drying effect inside the pellets, the temperature outside the pellets needs to be further increased, which causes the CO2 on the surface of the pellets to react quickly with the binder to form a dense calcium carbonate layer, further hindering the formation of the consolidation structure inside the pellets. In the preferred embodiment of the present invention, a drying and consolidation technology of hot air drying + microwave consolidation is used. Compared with hot air drying, which is only a physical heat, the pellets are dried and consolidated by heat transfer. Microwaves are an energy field that can directly act on the interior of the pellets to stimulate the decomposition of the carbon-based composite binder inside the pellets. Therefore, the microwave heating drying and consolidation method can ensure that the temperature of the outside and inside of the pellets is uniform, so that the outside and inside of the pellets can be dried and consolidated at the same time. Through microwave heating, combined with the addition of a carbon-based composite binder within the pellets, microwaves directly act on the carbon-based composite binder, simultaneously decomposing it to release CO2 and H2O. This allows for simultaneous drying and consolidation. Microwaves not only heat the pellets but also ensure uniform temperature inside and outside the pellets, thereby ensuring simultaneous decomposition of the carbon-based composite binder at different locations. This allows for simultaneous consolidation across all locations, resulting in composite pellets with uniform strength.

[0071] The carbonation consolidation process of the present invention adopts a consolidation method under the action of microwaves. Under the action of microwaves, the carbon-based composite binder inside the pellet is evenly decomposed and converted into CO2 and H2O, avoiding the problem of asynchronous reaction between the outer layer and the internal material of the pellet caused by the traditional heat conduction method from the outside to the inside. In this way, the temperature and CO2 atmosphere conditions are met inside and outside the pellet, the carbonation reaction rate is consistent, and a double-layer structure with a hard outside and a loose inside will not appear. In addition, under the action of microwaves, a high-temperature, high-CO2, high-water vapor, and high-calcium reaction environment is formed in the micro-region inside the pellet. The carbonation reaction proceeds rapidly to generate calcium carbonate microcrystals. The microwaves drive the migration of particles, and the microcrystals grow rapidly, tightly connecting adjacent particles together, providing high strength protection for the pellets.

[0072] Therefore, through the technical means of microwave consolidation + carbon-based composite binder, the composite pellets are made into a homogeneous structure, avoiding the technical problem of uneven quality caused by pellet stratification, while ensuring that the inside and outside of the pellets are high-strength structures, which plays a synergistic role.

[0073] The inventors further discovered through experiments that, compared to the methods of hot air drying and consolidation alone or microwave drying and consolidation alone, the drying and consolidation method using hot air + microwaves is particularly effective. If hot air drying and consolidation is used alone, the pellets are dried and consolidated by physical heat transfer, which results in a technical problem of uneven temperature inside and outside the pellets, and the consolidation strength inside the pellets is low. If microwave drying and consolidation is used alone, the moisture inside the pellets themselves is lost too quickly, and the moisture in the gaps between the molecules in the pellets is suddenly lost, which also affects the consolidation effect between the molecules in the pellets. Through experiments, it was found that first, the pellets were dried by hot air drying, so that the moisture in the gaps between the molecules in the pellets evaporated at a slower rate, and the molecules in the material slowly gathered together, reducing the distance between the molecules in the material; then, through the action of microwaves, the CO2 and H2O released by the carbon-based composite binder reacted with the binder to form a consolidation structure between the molecules of the material. The strength of the composite pellets obtained by combining hot air drying and microwave consolidation was greatly improved.

[0074] Further experiments revealed that by using a drying and consolidation method of hot air drying + microwave consolidation, the pellets are first dried by hot air drying until the moisture content in the pellets is 2% to 8% (preferably 4% to 6%), and then dried and consolidated by an electromagnetic field, the strength of the resulting composite pellets can reach above 300N / P.

[0075] In the present invention, the flue gas discharged from the rotary kiln in step 3) is subjected to dust removal treatment (obtaining sedimentation ash containing alkali metals), reburning reaction (further burning the unreacted reducing gas CO in the flue gas to release heat), and waste heat utilization (sensible heat resource utilization), and then desulfurization treatment. The gas obtained after desulfurization is a CO2-containing waste gas. A portion of the CO2-containing waste gas is transported to microwave consolidation and hot air drying to provide a CO2 atmosphere in the peripheral environment of the green balls during the drying and consolidation processes. The CO2 reacts with the calcium binder in the green balls to generate calcium carbonate with higher strength, thereby increasing the strength of the green balls and preventing the pellets from bursting in the rotary kiln, thereby reducing the amount of dust generated. The hot air drying and microwave drying processes just require CO2-containing gas, and the rotary kiln process of this process just produces CO2-containing gas, realizing resource utilization within the process. A portion of the CO2-containing waste gas is transported to the rotary kiln (preferably input through the kiln body position in the middle of the rotary kiln). In the rotary kiln, the CO2-containing waste gas reacts with the carbon (coal or coke powder) in the pellets to generate reducing CO. CO directly reduces the metal oxides in the pellets, thereby improving the reduction rate and reduction efficiency of the pellets in the rotary kiln and improving the metallization rate of iron and vanadium in the reduced material. Moreover, the CO2-containing waste gas is transported into the rotary kiln, which reduces the oxidizing atmosphere in the rotary kiln, thereby reducing the probability of iron and vanadium being reduced to elemental or low-priced substances and being oxidized again, thereby improving the metallization rate of iron and vanadium in the reduced material. This application uses the characteristics of CO2 contained in the exhaust gas discharged from the rotary kiln, combined with the characteristics that CO2 is required in the drying and consolidation process of this process, and further combined with the role that can be played by transporting the CO2-containing gas to the rotary kiln, to transport the generated CO2-containing gas to the required process, thereby realizing the reuse of waste gas and improving the resource utilization value of this process.

[0076] The inventors discovered that the reduced material discharged from the rotary kiln has the characteristics of high temperature and high carbon residue. Compared with the prior art method of directly using gas to cool the reduced material, the inventors found through experiments that the semi-dry cooling process using atomized water to cool the reduced material has an excellent cooling effect. Moreover, the gas after the atomized water has undergone the semi-dry cooling process has a high content of reducing gases (CO and H2), and this gas has a high preheating utilization value. The present invention uses atomized water as a cooling medium to perform a semi-dry cooling process on the reduced material. The atomized water cools the reduced material, and the atomized water absorbs heat from the reduced material, thereby achieving a better cooling effect on the reduced material. The atomized water reacts with the carbon residue in the reduced material to produce hot gas containing CO and H2. The hot gas containing CO and H2 is transported to the waste heat utilization process for waste heat utilization and / or the hot gas containing CO and H2 is transported to the rotary kiln for reduction of consolidated pellets.

[0077] Preferably, the gas obtained after desulfurization is a waste gas containing CO2. Based on the amount of gas required for the drying and consolidation process and the rotary kiln reduction and burning process, the excess waste gas containing CO2 is transported to an atomizing device, where the CO2 dissolves in water to form atomized water containing CO2. The atomized water containing CO2 is transported to a semi-dry cooling device, which cools the reducing material. At the same time, the reducing material reforms the atomized water containing CO2, and the CO2 reacts with the residual carbon in the reducing material to form a Boudolf reaction, and the atomized water reacts with the residual carbon in the reducing material to form a water-gas reaction, thereby obtaining hot gas containing CO and H2. The hot gas containing CO and H2 is transported to a waste heat utilization process for waste heat utilization and / or the hot gas containing CO and H2 is transported to a rotary kiln for reduction of the consolidated pellets.

[0078] The present invention provides a vanadium extraction tailings calcification reduction dealkalization method, specifically comprising:

[0079] (1) One or more calcium salts such as calcium oxide, calcium hydroxide, calcium carbonate, calcium chloride, and calcium sulfate are mixed with a carbon-based composite binder such as starch, coal tar, and molasses to form a composite low-temperature curing agent. The calcium salt particle size is preferably ≥50% of -200 mesh, and preferably ≥80% of -325 mesh. The ratio of the calcium salt to the carbon-based composite binder can be adjusted according to the type of the two. The mixing equipment can be a drum mixer, a powerful mixer, or the like.

[0080] (2) The vanadium extraction tailings and the composite low-temperature curing agent are mixed and then pelletized, wherein the mixing ratio of the vanadium extraction tailings and the composite low-temperature curing agent is 1:0 to 1:1; the mixing equipment can be a drum mixer, a strong mixer, etc.; the moisture content of the raw materials after mixing is 5% to 20%; the pelletizing equipment can be a disc pelletizing machine or a strong disturbance pelletizing machine, and the pellet size is preferably 3mm to 8mm. The disc pelletizing process uses atomized water as the water adding method, and atomized water is added to the raw material distribution area and the 2mm to 4mm particle size area in the ball disc respectively. The amount of atomized water added is determined according to the moisture content of the raw materials and the pelletizing state.

[0081] (3) The green pellets are pre-dried and consolidated by hot air and then dried and consolidated by microwaves. During the drying and consolidation process, a gas containing CO2 and water vapor is introduced. Drying and consolidation can be carried out by a chain grate machine, a steel mesh belt machine, etc. combined with microwaves. The material height is 10 mm to 200 mm, preferably 100 mm to 150 mm. The gas can be hot air with added water vapor and CO2, hot exhaust gas after combustion of blast furnace gas / coke oven gas / converter gas, direct reduction hot exhaust gas, lime kiln hot exhaust gas, etc. The CO2 concentration is 0% to 50% and the humidity is 10 g / m 3 ~100g / m 3 , better, 20g / m 3 ~50g / m 3 ;The gas flow rate is 0.1m / s~5m / s.

[0082] (4) The consolidated pellets are mixed with coke powder and then enter a multi-nozzle rotary kiln for reduction roasting. During the reduction roasting process, CO2-containing waste gas is introduced through the multi-nozzle at the bottom of the material layer with the highest temperature. The CO2 in the waste gas reacts with the coal in the material layer to produce CO (C+CO2=CO), which enhances the reducing atmosphere in the material layer. In addition, the heat exchange and reaction endothermic effect of the introduced waste gas effectively reduce the temperature of the material layer and prevent ringing. Air is introduced through the multi-nozzle at the top of the material layer. A large amount of reducing gas in the top of the material layer reacts with the air to replenish the heat in the kiln and improve the utilization efficiency of the reducing gas. During the reduction process, a certain amount of coal is sprayed from the kiln head to ensure a reducing atmosphere in the material layer. Among them, the ratio of consolidated pellets to coke powder is 1:0~1:1.5, the coke powder particle size is 0~15mm, the ratio of the amount of coal sprayed into the kiln head to the consolidated balls is 0~1:1, the coal particle size is 0~15mm, the highest temperature of the reduction process is 1100℃-1300℃, and the residence time of materials with a temperature exceeding 1100℃ is 1~3h.

[0083] (5) During the reduction roasting process, the exhaust gas at the kiln tail passes through the settling chamber to remove dust, and obtains sedimentation ash 1, which is then burned in the reburning chamber, and then used for waste heat power generation to collect sedimentation ash 2. The dust removal system collects the dust ash, and the exhaust gas after dust removal is desulfurized to become CO2-containing exhaust gas. Part of the exhaust gas returns to the multi-nozzle rotary kiln and enters from the bottom of the material layer in the highest temperature section. Part of the exhaust gas is heated and used for carbonation consolidation, and the rest of the exhaust gas is discharged through the chimney.

[0084] (6) After the reduction and dealkalization, the pellets and residual coal are discharged from the kiln head and enter the semi-dry cooling equipment. After direct heat exchange cooling with atomized water in the countercurrent, magnetic separation is performed to separate the residual coke and ash. The hot gas after the semi-dry cooling and heat exchange is combined with the tail gas after the reburning chamber and enters the waste heat power generation system. After the residual coke and ash are screened, the fine residual coke powder is used as sintering solid fuel, and the coarse residual coke powder is returned to the multi-nozzle rotary kiln for reduction roasting.

[0085] In the present invention, a gas delivery pipe is provided in the refractory bricks of the side wall of the rotary kiln, and CO2-containing waste gas is input into the gas delivery pipe. The gas in the gas delivery pipe absorbs the heat in the rotary kiln. The heated CO2-containing waste gas is then sprayed into the inner cavity of the rotary kiln through a nozzle. The CO2-containing waste gas participates in the reduction of minerals in the rotary kiln. The direct reduction rotary kiln provided in the present application has the following functions through the arrangement of the gas delivery pipeline: 1. CO2-containing waste gas is input into the gas delivery pipeline, and the CO2-containing waste gas can absorb the heat on the inner wall of the rotary kiln, thereby protecting the rotary kiln and extending the service life of the rotary kiln; compared with the heat preservation device provided on the outer wall of the rotary kiln, the gas delivery pipeline in the present application is closer to the inner cavity of the rotary kiln, and can dissipate the heat of the inner wall of the rotary kiln evenly, thereby better protecting the rotary kiln; 2. By arranging the gas delivery pipeline in the inner wall of the rotary kiln, the CO2-containing waste gas in the gas delivery pipeline absorbs the heat dissipated in the inner cavity of the rotary kiln, thereby realizing the waste heat utilization of the sensible heat of the rotary kiln; 3. After absorbing the heat, the CO2-containing waste gas in the gas delivery pipeline is directly sprayed into the inner cavity of the rotary kiln through the nozzle at the position of the rotary kiln body, and the CO2-containing waste gas undergoes Boudol reaction with the carbon in the material in the rotary kiln. , generating CO, CO acts as a reducing agent to directly reduce the material, thereby improving the reduction efficiency; Fourth, through the introduction of CO2-containing waste gas, there is a "solid-solid reduction" of carbon-material in the rotary kiln; at the same time, the CO2-containing waste gas reacts with carbon to generate reducing CO, and CO reduces the material at the same time, so that there is a "gas-solid reduction" of the material in the rotary kiln, thereby improving the efficiency of material reduction and shortening the reduction time; Fifth, the present application increases the amount of reducing agent by injecting CO2-containing waste gas, CO2 reacts with 1 mole of carbon to generate 2 moles of CO, and the prior art uses 1 mole of reducing agent carbon to reduce the material. After adopting the technical solution of the present application, 1 mole of reducing agent carbon becomes 2 moles of reducing agent (CO), which reduces the same amount of material and saves the consumption of reducing agent carbon. Therefore, the technical solution of the present application is adopted to achieve the technical effect of reducing carbon consumption.

[0086] In the present invention, the reduction of the material within the rotary kiln occurs in the middle section of the rotary kiln. Therefore, as a preferred embodiment, the nozzle is positioned in the middle section of the direct reduction rotary kiln. The middle section of the rotary kiln experiences high temperatures of 800-1200°C. The CO₂-containing waste gas injected into the rotary kiln directly undergoes a Boudall reaction with the carbon in the material, and the resulting CO product directly reduces the material. If the CO₂-containing waste gas is injected at the head or tail of the rotary kiln, the temperature there is relatively low, preventing the CO₂ from undergoing a reduction reaction with the carbon in the material. Furthermore, even if a Boudall reaction occurs, the resulting CO product at the head or tail is insufficient to directly reduce the material. Experiments have shown that when the CO₂-containing waste gas is injected from the head or tail, the majority of the CO₂ enters the flue gas within the rotary kiln cavity. A very small portion of the CO₂ undergoes a Boudall reaction with the carbon in the material, producing CO product that also enters the flue gas within the rotary kiln cavity and is then discharged directly from the kiln tail along with the flue gas, failing to reduce the material. Through experiments, it was found that injecting CO2-containing waste gas from the kiln head or kiln tail has no obvious effect on promoting the reduction efficiency of the material in the rotary kiln, and has no obvious effect on improving the metallization rate of iron in the reduced material.

[0087] In the preferred technical solution of the present invention, a gas release valve is provided at the end of the gas delivery pipeline, and the gas release valve is located downstream of the nozzle. Depending on the actual process, excess CO2-containing waste gas is discharged through the gas release valve. If the amount of CO2-containing waste gas required by the rotary kiln is small and the temperature inside the rotary kiln is high, the amount of CO2-containing waste gas introduced into the gas delivery pipeline can be increased. After the CO2-containing waste gas is heated in the gas delivery pipeline, a portion is sprayed into the inner cavity of the rotary kiln through the nozzle, and the remaining CO2-containing waste gas is discharged through the gas release valve. This technical means not only meets the rotary kiln's demand for CO2-containing waste gas, but also protects the rotary kiln system by increasing the input amount of CO2-containing waste gas.

[0088] Furthermore, the inventors discovered through experiments that because a rotary kiln is used to reduce minerals, the kiln experiences high temperatures of 800-1200°C, resulting in relatively high pressure inside the kiln. Furthermore, the rotary kiln is a closed system, and the pressure inside the kiln is controlled based on actual process requirements. The inventors discovered that if the pressure inside the kiln is too high, the amount of CO2-containing waste gas in the gas delivery pipeline that is injected into the kiln through the nozzle is very limited due to the excessive pressure inside the kiln. As the pressure inside the kiln increases, the amount of CO2-containing waste gas injected decreases. When the pressure inside the kiln is high, simply increasing the blower power has little effect on the amount of CO2-containing waste gas injected. To address this technical problem, the inventor unexpectedly discovered that by changing the diameter of the gas delivery pipeline, designing the gas delivery pipeline as a variable diameter pipeline, and using a blower to deliver CO2-containing waste gas into the gas delivery pipeline, the volume of the CO2-containing waste gas increases after being heated by the heat in the rotary kiln. At the same time, the variable diameter pipeline increases the pressure of the CO2-containing waste gas in the gas delivery pipeline, significantly increasing the amount of CO2-containing waste gas injected into the rotary kiln. The variable diameter pipeline technology achieves automatic pressurization of the CO2-containing waste gas in the gas delivery pipeline, increasing the pressure of the CO2-containing waste gas in the gas delivery pipeline, and making it easier for the CO2-containing waste gas to enter the rotary kiln cavity.

[0089] Preferably, the inner diameter of the gas delivery pipe gradually decreases from the air inlet end to the location where the nozzle is installed. This change in the inner diameter of the gas delivery pipe increases the pressure of the CO2 waste gas within the pipe. The inventors further discovered through experiments that when the ratio of the inner diameter of the gas delivery pipe at the nozzle location to the inner diameter of the gas delivery pipe at the air inlet end is greater than 1:1.5, as the inner diameter ratio increases, the pressure of the CO2 waste gas within the gas delivery pipe gradually increases, and the amount of CO2 waste gas entering the rotary kiln also gradually increases. When the ratio of the inner diameter of the gas delivery pipe at the nozzle location to the inner diameter of the gas delivery pipe at the air inlet end is greater than 1:3, as the inner diameter ratio increases, the amount of CO2 waste gas entering the rotary kiln begins to decrease due to the excessive pressure of the CO2 waste gas within the gas delivery pipe. When the ratio of the inner diameter of the gas delivery pipe at the nozzle location to the inner diameter of the gas delivery pipe at the air inlet end is greater than 1:4, the amount of CO2 waste gas entering the rotary kiln significantly decreases, hindering the entry of CO2 waste gas into the rotary kiln. Therefore, the ratio of the inner diameter of the gas delivery pipe at the nozzle position to the inner diameter of the gas delivery pipe inlet end is controlled to be 1:1.5-4, preferably 1:2-3; this is conducive to the entry of CO2-containing waste gas into the rotary kiln, ensuring the amount of CO2-containing waste gas entering the rotary kiln, and further ensuring that the CO2-containing waste gas participates in the reduction of minerals in the rotary kiln.

[0090] When the pressure inside the rotary kiln is too high, the inventors discovered through experiments that installing pressurized anti-backflow fins on the inner wall of the gas delivery pipe can also increase the pressure of the CO2 waste gas within the gas delivery pipe. By installing pressurized anti-backflow fins, the CO2 waste gas achieves the technical effect of automatically pressurizing the gas delivery pipe. As the CO2 waste gas passes through the gas delivery pipe equipped with pressurized anti-backflow fins, its volume increases due to heat, further increasing its pressure through the pressurized anti-backflow fins, allowing the CO2 waste gas to enter the rotary kiln cavity more smoothly.

[0091] The inventors further discovered through experiments that as the angle between the booster anti-backflow fins and the inner wall of the gas delivery pipe increases, the pressure of the CO2-containing waste gas in the gas delivery pipe gradually increases. Under the same blower power and rotary kiln conditions, the amount of CO2-containing waste gas entering the rotary kiln gradually increases. However, when the angle between the booster anti-backflow fins and the inner wall of the gas delivery pipe exceeds 60°, the amount of CO2-containing waste gas entering the rotary kiln begins to decrease due to the excessive pressure of the CO2-containing waste gas in the gas delivery pipe. When the angle between the booster anti-backflow fins and the inner wall of the gas delivery pipe exceeds 80°, the amount of CO2-containing waste gas entering the rotary kiln significantly decreases, hindering the entry of CO2-containing waste gas into the rotary kiln. Therefore, the angle between the pressurized anti-backflow fin and the inner wall of the gas delivery pipe is controlled to be 20-80°, preferably 30-60°; this is conducive to the entry of CO2-containing waste gas into the rotary kiln, ensuring the amount of CO2-containing waste gas entering the rotary kiln, and further ensuring that the CO2-containing waste gas participates in the reduction of minerals in the rotary kiln.

[0092] In the present invention, the cross section of the pressurization anti-backflow fin is an "eight-shaped" structure, and the end of the pressurization anti-backflow fin 3 of the "eight-shaped" structure is connected to the inner wall of the gas delivery pipe. That is to say, the end of the pressurization anti-backflow fin with a larger opening in the "eight-shaped" structure is connected to the inner wall of the gas delivery pipe and is located upstream of the gas delivery pipe (upstream of the flow direction of CO2 exhaust gas); the end of the pressurization anti-backflow fin with a smaller opening in the "eight-shaped" structure is located inside the gas delivery pipe, separated from the inside of the gas delivery pipe, and is located downstream of the gas delivery pipe. (such as Figure 4 shown)

[0093] In a preferred embodiment of the present invention, a gas delivery pipeline employing a variable diameter pipe has an inner diameter that gradually decreases from the air inlet end to the nozzle location and then increases from the nozzle location to the gas release valve location. This technical approach allows the inner diameter of the gas delivery pipeline to gradually decrease from the air inlet end to the nozzle location, increasing the pressure of the CO2 waste gas within the pipeline and facilitating its entry into the rotary kiln cavity. Furthermore, the inner diameter of the gas delivery pipeline gradually increases from the nozzle location to the gas release valve location. Controlling the gas release valve allows the amount of CO2 waste gas entering the rotary kiln cavity to be controlled. When the demand for CO2 waste gas in the rotary kiln decreases, the gas release valve allows the CO2 waste gas to be preferentially discharged from the gas release valve due to the gradually increasing inner diameter of the gas delivery pipeline from the nozzle location to the gas release valve location. Therefore, simply controlling the opening of the gas release valve can control the amount of CO2 waste gas discharged, and thus the amount of CO2 waste gas entering the rotary kiln.

[0094] In the preferred embodiment of the present invention, a pressurized anti-backflow fin is provided inside the gas delivery pipe. The gas delivery pipe from the air inlet end to the nozzle setting position is provided with a pressurized anti-backflow fin, and the gas delivery pipe from the nozzle setting position to the gas release valve position is not provided with a pressurized anti-backflow fin. By providing the pressurized anti-backflow fin, the inner diameter of the gas delivery pipe gradually decreases from the air inlet end to the nozzle position, thereby increasing the pressure of the CO2 waste gas in the gas delivery pipe, which is beneficial for the CO2 waste gas to enter the rotary kiln cavity; from the nozzle position to the gas release valve position, there is no obstruction of the pressurized anti-backflow fin, and the pressure of the CO2 waste gas in this position is relatively low, which is beneficial for the discharge of the CO2 waste gas. By controlling the gas release valve, the amount of CO2 waste gas entering the rotary kiln cavity can be controlled. When the amount of CO2-containing waste gas required by the rotary kiln decreases, the CO2-containing waste gas is discharged preferentially from the gas release valve because there are no pressurized backflow prevention fins in the gas transmission pipeline from the nozzle to the gas release valve. Therefore, simply controlling the opening of the gas release valve can control the amount of CO2-containing waste gas discharged, and thus the amount of CO2-containing waste gas entering the rotary kiln.

[0095] Another technical problem in the prior art is that, because the rotary kiln is a high-temperature environment and is constantly rotating, the material constantly contacts and rubs against the inner wall of the rotary kiln. Therefore, measuring the temperature of the rotary kiln has always been a technical problem in this field. The present invention provides a gas delivery pipe inside the side wall of the rotary kiln, and a temperature measuring element is provided on the inner wall of the gas delivery pipe. The temperature of the gas in the gas delivery pipe is detected by the temperature measuring element, and the temperature in the rotary kiln at the corresponding position can be inferred based on actual working experience. Because the gas in the gas delivery pipe is heated by the heat in the rotary kiln, the temperature in the rotary kiln can be inferred from the temperature of the water vapor in the gas. The temperature measuring element is arranged on the inner wall of the gas delivery pipe. Compared with the wear of solid materials in the rotary kiln, the wear of the gas on the temperature measuring element is much less because the gas flowing in the gas delivery pipe is in a gaseous state. Therefore, the technical problem in the prior art of inconveniently detecting the temperature in the rotary kiln due to the wear of the temperature measuring element by the material is solved.

[0096] The present invention proposes a method for calcification reduction dealkalization of vanadium extraction tailings. The green balls have a diameter of 1-20 mm (preferably 2-10 mm, more preferably 3-8 mm), and are consolidated by carbonation. Compared with conventional carbonation low-temperature consolidation, the green balls of the present invention, which are consolidated by a composite low-temperature curing agent, have faster and more uniform carbonation reactions, higher pellet strength, and higher production efficiency.

[0097] Compared with the prior art, the technical solution provided by the present invention has the following beneficial technical effects:

[0098] 1. The present invention adds a composite low-temperature curing agent to the composite pellets. The composite low-temperature curing agent can release CO2 and H2O during the low-temperature drying and consolidation process, and can significantly improve the carbonation consolidation efficiency and the strength of the dried consolidated pellets;

[0099] 2. The present invention adopts a carbonation consolidation method of hot air drying + microwave drying for drying and consolidation of composite pellets. Under the action of microwaves, the composite low-temperature curing agent inside the pellets is evenly decomposed and converted into CO2 and H2O, avoiding the problem of asynchronous reaction between the outer layer and the inner material of the pellet caused by the traditional outside-to-inside heat conduction method, thus providing high strength guarantee for the pellets.

[0100] 3. Upgrade and renovate the existing rotary kiln structure, embed a gas delivery pipeline in the refractory material, and the gas in the gas delivery pipeline can achieve efficient recovery of the unorganized heat dissipation of the kiln wall; at the same time, it plays a protective role for the rotary kiln.

[0101] 4. The gas transported to the rotary kiln through the gas transmission pipeline undergoes Boudol reaction with the fuel in the rotary kiln to produce a large amount of reducing gas CO; the reduction reaction speed is increased, low-temperature rapid reduction is achieved, and the carbon consumption per unit material reduction is reduced.

[0102] 5. The kiln body air-inlet rotary kiln reduction roasting adopted in the present invention can effectively adjust the temperature field in the kiln through the multiple nozzles in the kiln body, reduce the temperature in the high-temperature zone by supplying air to the high-temperature zone, and prevent the material temperature from being too high to melt and form rings. By supplying air to the section from the middle of the kiln to the tail of the kiln, the combustion efficiency of the reducing gas in the kiln is improved, the gas temperature in the direction of the kiln tail is increased, and the high-temperature zone area is effectively extended, providing a longer-term high-temperature roasting environment for material reduction.

[0103] 6. The present invention uses atomized water as a cooling medium to perform semi-dry cooling on the reducing material, which has a good cooling effect. In addition, the atomized water is reformed by utilizing the high temperature and high residual carbon characteristics of the reducing material to obtain a gas containing reducing gases CO and H2, thereby improving the resource utilization of the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0104] Figure 1 This is a process flow chart of a vanadium extraction tailings calcification reduction dealkalization method of the present invention;

[0105] Figure 2 This is an optimized process flow chart of a vanadium extraction tailings calcification reduction dealkalization method of the present invention;

[0106] Figure 3 Schematic diagram of the structure of the direct reduction rotary kiln of the present invention;

[0107] Figure 4 This is a schematic structural diagram of a direct reduction rotary kiln of the present invention, in which the gas delivery pipeline is a variable diameter pipeline;

[0108] Figure 5 This is a structural schematic diagram of a direct reduction rotary kiln according to the present invention, in which a pressurized backflow prevention fin is provided in a gas delivery pipeline;

[0109] Figure 6 This is a process diagram of a direct reduction rotary kiln used for mineral reduction according to the present invention.

[0110] Reference numerals:

[0111] 1: Direct reduction rotary kiln; 101: Kiln head; 102: Kiln body; 103: Kiln tail; 10101: Burner; L1: Gas delivery pipeline; 10201: Nozzle; 2: Gas release valve; 3: Pressurized anti-backflow fin; 4: Temperature measuring element. DETAILED DESCRIPTION

[0112] The technical solutions of the present invention are illustrated below with examples, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0113] Example 1

[0114] A vanadium extraction tailings calcification reduction dealkalization method, the method comprising the following steps:

[0115] 1) uniformly mixing the vanadium extraction tailings and the composite low-temperature curing agent, forming pellets to obtain green pellets;

[0116] 2) The green pellets are sequentially subjected to hot air drying and microwave consolidation to obtain consolidated pellets;

[0117] 3) The consolidated pellets are transported to a rotary kiln for reduction roasting. The dust-laden tail gas discharged from the rotary kiln undergoes a first dust removal treatment, a reburning reaction, waste heat utilization, a second dust removal treatment, and a desulfurization treatment in sequence. The reduced material obtained after the reduction roasting in the rotary kiln is cooled and screened to obtain the ferrovanadium raw material.

[0118] The composite low-temperature curing agent is a mixture of calcium hydroxide and starch in a weight ratio of 1:1, and the weight ratio of the vanadium extraction tailings to the composite low-temperature curing agent is 1:0.5. The moisture content of the green balls is 10% by weight, and the average particle size of the green balls is 5 mm.

[0119] Example 2

[0120] A vanadium extraction tailings calcification reduction dealkalization method, the method comprising the following steps:

[0121] 1) uniformly mixing the vanadium extraction tailings and the composite low-temperature curing agent, forming pellets to obtain green pellets;

[0122] 2) The green pellets are sequentially subjected to hot air drying and microwave consolidation to obtain consolidated pellets;

[0123] 3) The consolidated pellets and coke powder are mixed and transported to a rotary kiln for reduction roasting. The dust-laden exhaust gas from the rotary kiln undergoes a primary dust removal process, reburning, waste heat utilization, a secondary dust removal process, and desulfurization. The reduced material obtained from the rotary kiln reduction roasting is cooled and screened to obtain ferrovanadium raw material. The desulfurized exhaust gas contains CO2, which is split into two parts. One portion is transported to the rotary kiln from the middle of the kiln body; the other portion is transported to the microwave consolidation process. The exhaust gas from the microwave consolidation process is then transported to the hot air drying process.

[0124] The composite low-temperature curing agent is a mixture of calcium hydroxide and starch in a weight ratio of 1:1, and the weight ratio of the vanadium extraction tailings to the composite low-temperature curing agent is 1:0.5. The green pellets have a moisture content of 10% by weight and an average particle size of 5 mm. The weight ratio of the consolidated pellets to the coke powder is 1:0.3.

[0125] Example 3

[0126] Repeat Example 2, except that the cooling in step 3) adopts semi-dry cooling, specifically:

[0127] 301) passing water through an atomization system to obtain atomized water;

[0128] 302) The reduced material is conveyed into a semi-dry cooling device, and atomized water is introduced into the semi-dry cooling device; the atomized water cools the reduced material, absorbs heat in the reduced material, and reacts with the residual carbon in the reduced material to produce water gas to obtain hot gas containing CO and H2, and the hot gas containing CO and H2 is conveyed to a waste heat utilization process for waste heat utilization and / or the hot gas containing CO and H2 is conveyed to a rotary kiln for reduction of consolidated pellets.

[0129] Example 4

[0130] Example 3 is repeated, except that the tail gas after desulfurization treatment is CO2-containing waste gas, and the CO2-containing waste gas is divided into three parts, one part of the CO2-containing waste gas is conveyed to the rotary kiln; one part of the CO2-containing waste gas is conveyed to the microwave consolidation process, and the gas discharged from the microwave consolidation process is conveyed to the hot air drying process; the remaining CO2-containing waste gas is conveyed to the atomization device, and CO2 is dissolved in the atomized water; the atomized water dissolved in CO2 is reformed through a semi-dry cooling device, CO2 reacts with the residual carbon in the reducing material to produce a Boudol reaction, and the atomized water reacts with the residual carbon in the reducing material to produce a water-gas reaction to obtain hot gas containing CO and H2, and the hot gas containing CO and H2 is conveyed to the waste heat utilization process for waste heat utilization and / or the hot gas containing CO and H2 is conveyed to the rotary kiln for reduction of consolidated pellets.

[0131] Example 5

[0132] Example 4 was repeated, except that the screening in step 3) was performed using magnetic separation. The magnetic separation yielded the ferrovanadium raw material and residual carbon. The residual carbon was screened to yield fine-grained coke powder and coarse-grained coke powder. The fine-grained coke powder was used as a sintering ingredient, while the coarse-grained coke powder was transported to a rotary kiln. The ferrovanadium raw material was transported to a blast furnace. Alkali-containing dust was obtained through the first and second dust removal processes. The waste heat utilization was specifically waste heat power generation.

[0133] Example 6

[0134] Example 5 was repeated, except that the composite low-temperature curing agent was a mixture of calcium oxide and coal tar in a weight ratio of 1:1, and the weight ratio of the vanadium extraction tailings to the composite low-temperature curing agent was 1:0.4. The moisture content of the green balls was 10% by weight, and the average particle size of the green balls was 5 mm.

[0135] Example 7

[0136] Example 5 was repeated, except that the composite low-temperature curing agent was a mixture of calcium carbonate and molasses in a weight ratio of 1:1, and the weight ratio of the vanadium extraction tailings to the composite low-temperature curing agent was 1:0.6. The moisture content of the green balls was 10% by weight, and the average particle size of the green balls was 5 mm.

[0137] Example 8

[0138] Example 5 was repeated, except that in step 2), a gas containing CO2 and water vapor was introduced into the microwave consolidation process, the gas containing CO2 and water vapor was transported to the microwave consolidation process, and the gas discharged from the microwave consolidation process was transported to the hot air drying process. The gas containing CO2 and water vapor was hot air with added water vapor and CO2, the CO2 concentration in the gas containing CO2 and water vapor was 30%, and the humidity of the gas containing CO2 and water vapor was 30 g / m 3 .

[0139] Example 9

[0140] Example 5 was repeated, except that in step 2), a gas containing CO2 and water vapor was introduced into the microwave consolidation process, the gas containing CO2 and water vapor was transported to the microwave consolidation process, and the gas discharged from the microwave consolidation process was transported to the hot air drying process. The gas containing CO2 and water vapor was the hot exhaust gas after the combustion of blast furnace gas. The CO2 concentration in the gas containing CO2 and water vapor was 35%, and the humidity of the gas containing CO2 and water vapor was 25 g / m 3 .

[0141] Example 9

[0142] Example 5 was repeated, except that in step 3), the weight ratio of the consolidated pellets to the coke powder was 1:0.4. During the reduction roasting step, coal was injected into the rotary kiln head. The weight ratio of the injected coal to the consolidated pellets was 0.3:1.

[0143] Example 10

[0144] Example 5 was repeated, except that the hot air drying process was a two-stage hot air drying process, comprising hot air drying stage I and hot air drying stage II. The microwave consolidation process was a two-stage microwave consolidation process, comprising microwave consolidation stage I and microwave consolidation stage II. The raw pellets sequentially passed through hot air drying stage I, hot air drying stage II, microwave consolidation stage I, and microwave consolidation stage II to obtain consolidated pellets.

[0145] Example 11

[0146] Example 10 was repeated, except that the drying temperature in hot air drying stage I was 80°C and the drying time was 10 minutes. The drying temperature in hot air drying stage II was 200°C and the drying time was 10 minutes. After the hot air drying process, the moisture content of the pellets was 4% by weight.

[0147] The temperature of microwave consolidation stage I is 300℃, and the pellet residence time is 10min. The temperature of microwave consolidation stage II is 450℃, and the pellet residence time is 10min. The microwave power density in the microwave consolidation process is 25kw / m 3 .

[0148] Example 12

[0149] Example 5 was repeated, except that a direct reduction rotary kiln was used for the roasting reduction in step 3. The direct reduction rotary kiln 1 comprises a kiln head 101, a kiln body 102, and a kiln tail 103. A burner 10101 is provided at the kiln head 101. The direct reduction rotary kiln 1 is cylindrical in structure, and the sidewalls of the kiln body 102 are constructed of refractory bricks. A gas delivery pipe L1 is provided within the refractory bricks of the sidewalls of the kiln body 102. A nozzle 10201 is provided on the inner sidewall of the kiln body 102. The nozzle 10201 connects the gas delivery pipe L1 to the inner chamber of the rotary kiln 1. The nozzle 10201 is located in the middle section of the kiln body of the rotary kiln 1.

[0150] Example 13

[0151] Example 12 is repeated, except that a gas release valve 2 is provided at the end of the gas delivery pipeline L1, and the gas release valve 2 is located downstream of the nozzle 10201.

[0152] Example 14

[0153] Repeat Example 13, except that the gas delivery pipeline L1 is a variable diameter pipeline; the inner diameter of the gas delivery pipeline L1 gradually decreases from the air inlet end to the setting position of the nozzle 10201; the inner diameter of the gas delivery pipeline L1 gradually increases from the setting position of the nozzle 10201 to the position of the gas release valve 2; the ratio of the inner diameter of the gas delivery pipeline at the nozzle position to the inner diameter of the gas delivery pipeline at the air inlet end is 1:2.

[0154] Example 15

[0155] Example 13 was repeated, except that a pressurization backflow prevention fin 3 was provided on the inner wall of the gas delivery pipe L1. The cross-section of the pressurization backflow prevention fin 3 was an "eight" structure. The distal end of the "eight" structure was connected to the inner wall of the gas delivery pipe L1 and located upstream. The angle between the pressurization backflow prevention fin and the inner wall of the steam pipe was 30°.

[0156] Comparative Example 1

[0157] A vanadium extraction tailings calcification reduction dealkalization method, the method comprising the following steps:

[0158] 1) uniformly mixing vanadium extraction tailings and calcium hydroxide, forming balls to obtain green balls;

[0159] 2) Drying and consolidating the green pellets in turn through hot air to obtain consolidated pellets;

[0160] 3) The consolidated pellets are transported to a rotary kiln for reduction roasting. The dust-laden tail gas discharged from the rotary kiln undergoes a first dust removal treatment, a reburning reaction, waste heat utilization, a second dust removal treatment, and a desulfurization treatment in sequence. The reduced material obtained after the reduction roasting in the rotary kiln is cooled and screened to obtain the ferrovanadium raw material.

[0161] The weight ratio of the vanadium extraction tailings to calcium hydroxide is 1:0.5. The moisture content of the green balls is 10% by weight, and the average particle size of the green balls is 5 mm.

[0162] Comparative Example 2

[0163] A vanadium extraction tailings calcification reduction dealkalization method, the method comprising the following steps:

[0164] 1) uniformly mixing vanadium extraction tailings and calcium hydroxide, forming balls to obtain green balls;

[0165] 2) The green pellets are sequentially subjected to hot air drying and microwave consolidation to obtain consolidated pellets;

[0166] 3) The consolidated pellets are transported to a rotary kiln for reduction roasting. The dust-laden tail gas discharged from the rotary kiln undergoes a first dust removal treatment, a reburning reaction, waste heat utilization, a second dust removal treatment, and a desulfurization treatment in sequence. The reduced material obtained after the reduction roasting in the rotary kiln is cooled and screened to obtain the ferrovanadium raw material.

[0167] The weight ratio of the vanadium extraction tailings to calcium hydroxide is 1:0.5. The moisture content of the green balls is 10% by weight, and the average particle size of the green balls is 5 mm.

[0168] Comparative Example 3

[0169] A vanadium extraction tailings calcification reduction dealkalization method, the method comprising the following steps:

[0170] 1) uniformly mixing the vanadium extraction tailings and the composite low-temperature curing agent, forming pellets to obtain green pellets;

[0171] 2) Drying and consolidating the green pellets in turn through hot air to obtain consolidated pellets;

[0172] 3) The consolidated pellets are transported to a rotary kiln for reduction roasting. The dust-laden tail gas discharged from the rotary kiln undergoes a first dust removal treatment, a reburning reaction, waste heat utilization, a second dust removal treatment, and a desulfurization treatment in sequence. The reduced material obtained after the reduction roasting in the rotary kiln is cooled and screened to obtain the ferrovanadium raw material.

[0173] The composite low-temperature curing agent is a mixture of calcium hydroxide and starch in a weight ratio of 1:1, and the weight ratio of the vanadium extraction tailings to the composite low-temperature curing agent is 1:0.5. The moisture content of the green balls is 10% by weight, and the average particle size of the green balls is 5 mm.

[0174] The technical solutions of Examples 1, 2, 3, 4, 11, 12, 14, and 15 and Comparative Examples 1, 2, and 3 were used to verify the effects. The vanadium extraction tailings used were all sodium-containing vanadium extraction tailings from the same batch, and the starch was industrial starch from the same batch. The coking coal was all raw materials from the same batch. The calcium hydroxide was obtained by digesting the same batch of quicklime through the same process. The mixing equipment, disc pelletizer, chain grate drying system (for hot air drying), microwave system, and rotary kiln used in Examples 1, 2, 3, 4, 11 and Comparative Examples 1, 2, and 3 were all the same equipment. Experiments and effect verification were carried out, and the results are as follows:

[0175]

[0176]

[0177] In the present invention, the compressive strength of the consolidated pellets is tested according to the GB / T14201-93 standard. The drop strength of the consolidated pellets is tested according to the GB / T14201-93 standard.

[0178] The content of alkali metals in ferrovanadium raw materials is accurately determined by sampling and analytical chemistry in the laboratory.

[0179] The metallization rate of iron in ferrovanadium raw materials refers to the weight percentage of elemental iron in the total iron component in the entire reduced material (slag phase).

[0180] The vanadium metallization rate in the ferrovanadium raw material refers to the weight percentage of elemental vanadium in the total vanadium element components in the entire reduced material (slag phase).

Claims

1. A method for calcification reduction and dealkalization of vanadium extraction tailings, the method comprising the following steps: 1) uniformly mixing the vanadium extraction tailings and the composite low-temperature curing agent, forming pellets to obtain green pellets; 2) The green pellets are sequentially subjected to hot air drying and microwave consolidation to obtain consolidated pellets; 3) The consolidated pellets are transported to a rotary kiln for reduction roasting. The dust-laden tail gas discharged from the rotary kiln undergoes a first dust removal treatment, a reburning reaction, waste heat utilization, a second dust removal treatment, and a desulfurization treatment in sequence. The reduced material obtained after the reduction roasting in the rotary kiln is cooled and screened to obtain the ferrovanadium raw material. The hot air drying process is a two-stage hot air drying process, including hot air drying stage I and hot air drying stage II; the microwave consolidation process is a two-stage microwave consolidation process, including microwave consolidation stage I and microwave consolidation stage II; the raw balls are sequentially subjected to hot air drying stage I, hot air drying stage II, microwave consolidation stage I, and microwave consolidation stage II to obtain consolidated pellets; the drying temperature of hot air drying stage I is 60-100°C, and the drying time is 2-20 minutes; the drying temperature of hot air drying stage II is 100-250°C, and the drying time is 2-20 minutes; the temperature of microwave consolidation stage I is 250-350°C, and the pellet residence time is 2-20 minutes; the temperature of microwave consolidation stage II is 350-500°C, and the pellet residence time is 2-20 minutes; after the hot air drying process, the moisture content of the pellets is 2%-8% by mass; the microwave power density in the microwave consolidation process is 5 kW / m 3 ~50kw / m 3 .

2. The vanadium extraction tailings calcification reduction dealkalization method according to claim 1, characterized in that: The tail gas after desulfurization treatment in step 3) is CO2-containing waste gas, which is divided into two parts. One part of the CO2-containing waste gas is transported to the rotary kiln; the other part of the CO2-containing waste gas is transported to the microwave consolidation process, and the gas discharged from the microwave consolidation process is transported to the hot air drying process.

3. The vanadium extraction tailings calcification reduction dealkalization method according to claim 2, characterized in that: The CO2-containing waste gas entering the rotary kiln is input from the middle part of the rotary kiln body.

4. The vanadium extraction tailings calcification reduction dealkalization method according to claim 2, characterized in that: The cooling described in step 3) adopts semi-dry cooling, specifically: 301) passing water through an atomization system to obtain atomized water; 302) The reduced material is conveyed into a semi-dry cooling device, and atomized water is introduced into the semi-dry cooling device; the atomized water cools the reduced material, absorbs heat in the reduced material, and reacts with the residual carbon in the reduced material to produce water gas to obtain hot gas containing CO and H2, and the hot gas containing CO and H2 is conveyed to a waste heat utilization process for waste heat utilization and / or the hot gas containing CO and H2 is conveyed to a rotary kiln for reduction of consolidated pellets.

5. The vanadium extraction tailings calcification reduction dealkalization method according to claim 4, characterized in that: The remaining CO2-containing waste gas is transported to the atomization device, and CO2 is dissolved in the atomized water; the atomized water containing CO2 is reformed through a semi-dry cooling device, CO2 reacts with the residual carbon in the reducing material to produce a Boudolf reaction, and the atomized water reacts with the residual carbon in the reducing material to produce a water-gas reaction to obtain hot gas containing CO and H2, and the hot gas containing CO and H2 is transported to the waste heat utilization process for waste heat utilization and / or the hot gas containing CO and H2 is transported to the rotary kiln for reduction of consolidated pellets.

6. The vanadium extraction tailings calcification reduction dealkalization method according to any one of claims 1 to 5, characterized in that: The screening in step 3) is magnetic separation, and the ferrovanadium raw material and residual carbon are obtained through magnetic separation; and / or The waste heat utilization is specifically waste heat power generation.

7. The vanadium extraction tailings calcification reduction dealkalization method according to claim 6, characterized in that: The residual carbon is screened to obtain fine-grained coke powder and coarse-grained coke powder. The fine-grained coke powder is used as sintering ingredient, and the coarse-grained coke powder is transported to the rotary kiln; the iron-vanadium raw material is transported to the blast furnace; and the alkali-containing dust is obtained through the first and second dust removal treatments.

8. The vanadium extraction tailings calcification reduction dealkalization method according to any one of claims 1 to 5, characterized in that: The composite low-temperature curing agent in step 1) is obtained by mixing one or more of calcium oxide, calcium hydroxide, calcium carbonate, calcium chloride, and calcium sulfate with one or more of starch, coal tar, and molasses; and / or The mixing weight ratio of vanadium extraction tailings and composite low-temperature curing agent is 1:0.1-1; the water weight content of green balls is 5-20%; and the particle size of green balls is 2-12 mm.

9. The vanadium extraction tailings calcification reduction dealkalization method according to claim 8, characterized in that: The mixing weight ratio of vanadium extraction tailings and composite low-temperature curing agent is 1:0.2-0.8; the water weight content of green balls is 8-12%; and the particle size of green balls is 3-8 mm.

10. The vanadium extraction tailings calcification reduction dealkalization method according to any one of claims 1 to 5, characterized in that: In step 2), a gas containing CO2 and water vapor is introduced into the microwave consolidation process, the gas containing CO2 and water vapor is transported to the microwave consolidation process, and the gas discharged from the microwave consolidation process is transported to the hot air drying process.

11. The vanadium extraction tailings calcification reduction dealkalization method according to claim 10, characterized in that: The gas containing CO2 and water vapor is any one of hot air with added water vapor and CO2, hot tail gas after combustion of blast furnace gas, coke oven gas or converter gas, direct reduction hot tail gas, and lime kiln hot tail gas; the CO2 concentration in the gas containing CO2 and water vapor is 10% to 50%; the humidity of the gas containing CO2 and water vapor is 10g / m 3 ~100g / m 3 .

12. The vanadium extraction tailings calcification reduction dealkalization method according to claim 11, characterized in that: The CO2 concentration in the gas containing CO2 and water vapor is 20% to 40%; the humidity of the gas containing CO2 and water vapor is 20g / m 3 ~50g / m 3 .

13. The vanadium extraction tailings calcification reduction dealkalization method according to any one of claims 1 to 5, characterized in that: In step 3), the consolidated pellets and coke powder are mixed and then transported to a rotary kiln for reduction roasting; the weight ratio of the consolidated pellets to the coke powder is 1:0.1 to 1.

5.

14. The vanadium extraction tailings calcification reduction dealkalization method according to claim 13, characterized in that: The weight ratio of consolidated pellets to coke powder is 1:0.2~1.

15. The vanadium extraction tailings calcification reduction dealkalization method according to claim 13, characterized in that: In the reduction roasting process, coal is sprayed from the kiln head of the rotary kiln; the weight ratio of the sprayed coal to the weight of the consolidated pellets is 0.1 to 1:

1.

16. The vanadium extraction tailings calcification reduction dealkalization method according to claim 13, characterized in that: The weight ratio of the injected coal to the weight of the consolidated pellets is 0.2 to 0.5:

1.

17. The vanadium extraction tailings calcification reduction dealkalization method according to any one of claims 1 to 5, characterized in that: After the hot air drying process, the moisture content of the pellets is 4% to 6%; the microwave power density in the microwave consolidation process is 20kw / m 3 ~30kw / m 3 .

18. The method for dealkalization of vanadium extraction tailings by calcification reduction according to any one of claims 1-5, 7, 9, 11-12, and 14-16, characterized in that: The rotary kiln (1) is a direct reduction rotary kiln, comprising a kiln head (101), a kiln body (102), and a kiln tail (103); a burner (10101) is provided at the kiln head (101); the direct reduction rotary kiln (1) is a cylindrical structure, and the side walls of the kiln body (102) of the direct reduction rotary kiln (1) are made of refractory bricks; a gas delivery pipeline (L1) is provided in the refractory bricks of the side walls of the kiln body (102); a nozzle (10201) is provided on the inner side wall of the kiln body (102); the nozzle (10201) is connected to the gas delivery pipeline (L1) and the inner chamber of the rotary kiln (1); and the nozzle (10201) is arranged at the middle kiln body of the rotary kiln (1).

19. The vanadium extraction tailings calcification reduction dealkalization method according to claim 18, characterized in that: A gas release valve (2) is provided at the end of the gas delivery pipeline (L1), and the gas release valve (2) is located downstream of the nozzle (10201).

20. The vanadium extraction tailings calcification reduction dealkalization method according to claim 19, characterized in that: The gas delivery pipeline (L1) is a variable diameter pipeline; the inner diameter of the gas delivery pipeline (L1) gradually decreases from the air inlet end to the location where the nozzle (10201) is set; and the inner diameter of the gas delivery pipeline (L1) gradually increases from the location where the nozzle (10201) is set to the location of the gas release valve (2); and / or A pressurized anti-backflow fin (3) is provided on the inner wall of the gas delivery pipeline (L1); the cross section of the pressurized anti-backflow fin (3) is an "eight-shaped" structure, and the end of the pressurized anti-backflow fin (3) with the "eight-shaped" structure is connected to the inner wall of the gas delivery pipeline (L1) and is located upstream.

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