Recycling method of denitration slag
By mixing the waste SCR denitrification catalyst with high concentration strong alkali, vanadium and tungsten products are extracted, and the problem of recycling and utilization of waste catalysts is solved, achieving efficient utilization of resources and environmental protection.
Patent Information
- Application Number
- CN202510364132.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-26
- Publication Date
- 2025-06-27
AI Technical Summary
The prior art is difficult to effectively recycle and utilize waste SCR denitrification catalysts, resulting in waste of resources and environmental pollution.
By fully mixing the waste denitrification slag catalyst with high concentration and strong alkali, solid-liquid separation is performed, vanadium and tungsten products are extracted, and the denitrification slag is washed and calcined, proportioned with titanium slag, treated with chlorination reaction and molten salt chlorination furnace, and resources are recycled and utilized.
The effective recycling and utilization of waste SCR denitrification catalysts is achieved, which reduces production costs, reduces environmental pollution, and improves resource utilization efficiency.
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Figure CN120210556A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of chemical engineering technology, and particularly relates to a method for recycling denitrification slag. Background Art
[0002] There are many reasons for air pollution, and nitrogen oxides (NOx) are one of the main culprits. It mainly includes nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (N2O), dinitrogen trioxide (N2O3), etc. When nitrogen oxides (NOx) dissolve in rainwater, they will become acid rain, corrode buildings, denature the soil, and harm the ecological environment. In addition, NOx undergoes a photochemical reaction under the action of ultraviolet light to form photochemical smog, which poses a threat to the environment and human health. Therefore, reducing the emissions of NOx in the industrial production process has extremely important practical significance.
[0003] Among many nitrogen oxide NOx emission control technologies, the selective catalytic reduction (SCR) denitrification technology is one of the most widely used, technically mature and efficient denitrification technologies in the world. It has a high denitrification rate for flue gas containing nitrogen oxides, can perfectly solve the problem of tail gas denitrification, and make the flue gas meet the relevant emission standards, and has been widely applied industrially.
[0004] Metal oxide-based catalysts are used as a new generation of SCR denitrification catalysts due to their excellent performance and lower price, mainly using metal oxides such as V2O5, WO3, Fe2O3, NiO, CuO, MoO3 as active components.
[0005] Currently, vanadium-based catalysts with anatase TiO2 as the carrier are commonly used in the tail gas denitrification process of coal-fired power plants, and their main component ratios are shown in Table 1:
[0006] Table 1 Content of each active component in the V2O5 / TiO2 catalyst
[0007]
[0008] Generally speaking, the service life of the catalyst is about 2 to 3 years, and then it is decided whether to recycle and regenerate according to its damaged condition. For severely damaged or poisoned catalysts, the high regeneration cost and the poorly active regenerated catalysts often make such waste often landfilled underground. However, the accumulated landfilling will not only make it a serious environmental pollution source, but also cause waste of resources such as titanium, tungsten, vanadium, and silicon in it. In recent years, various uses have been developed for derivatives containing these elements, and the prices have been rising continuously. Therefore, the recovery of waste SCR denitrification catalysts is extremely important. Summary of the Invention
[0009] The object of the present invention is to provide a method for recycling denitrification slag, which is used to solve the problem of recycling and utilization of waste SCR denitrification catalysts generated during the power generation process in thermal power plants, and avoid waste of resources.
[0010] To achieve the above object of the invention, the present invention provides the following technical solutions:
[0011] A method for recycling denitrification slag includes the following steps:
[0012] 1) The waste denitrification slag catalyst is fully mixed with high-concentration strong alkali and leached. After the leaching is completed, the liquid is subjected to solid-liquid separation to separate the leachate and the leached residue;
[0013] 2) The leachate is refined to extract vanadium and tungsten to obtain vanadium products and tungsten products;
[0014] 3) The leached residue is washed with H2SO4, and after washing, it is calcined to obtain an anatase-type denitrification slag product, and the various indexes of the denitrification slag product must be measured;
[0015] 4) The denitrification slag and titanium slag are proportioned according to a ratio, and after proportioning, they are fully mixed; for the said ratio, various slag proportioning schemes are determined according to the indexes, and several feed bins are prepared. The feed bins include different titanium slag feed bins and denitrification slag feed bins. The feed bins are equipped with a loss-in-weight weighing system. The denitrification slag and titanium slag are respectively loaded into the corresponding feed bins, and are proportioned by weighing according to the proportioning scheme. The proportioned materials fall onto the scraper conveyor, enter the bucket elevator after being dried in the fluidized bed, are transported to the transfer bin by the bucket elevator, and finally transported to the intermediate bin. The slag intermediate bin is also equipped with a loss-in-weight weighing system;
[0016] 5) The petroleum coke and sodium chloride are transported to the intermediate bin; the petroleum coke and sodium chloride feed bins are prepared, and the petroleum coke and sodium chloride are respectively loaded into the corresponding feed bins. The feed bins are equipped with a loss-in-weight weighing system. After weighing, they are transported to their respective corresponding intermediate bins through the scraper and bucket elevator;
[0017] 6) According to the material consumption proportioning scheme, the slag, petroleum coke, and sodium chloride are proportioned, and after proportioning, they are fully mixed; for the said material consumption proportioning scheme, the loss-in-weight weighing of the intermediate bin is used to weigh and mix the slag, petroleum coke, and sodium chloride. After proportioning is completed, it falls onto the scraper conveyor and is transported to the furnace front bin, where it is fully mixed in the furnace front bin. After mixing, the material is continuously fed into the molten salt chlorination furnace through a screw feeder;
[0018] 7) Chlorination reaction: The materials in the molten salt chlorination furnace react with chlorine supplied through a chlorine gas spray gun. The waste molten salt generated from the chlorination reaction is discharged from the salt discharge pipe of the molten salt chlorination furnace. The titanium tetrachloride vapor and gas mixture generated from the chlorination reaction pass through a dust collector, where some high-boiling chlorides are condensed and co-settled with solid particles to form dust, which is collected as dust collection slag. The uncondensed titanium tetrachloride and gas mixture are sprayed and condensed to form liquid crude titanium tetrachloride, which is sent to the refining process for refining, and the tail gas is sent to the tail gas treatment process through a fan.
[0019] 8) Recover salt and titanium from the waste molten salt, and recover petroleum coke and titanium from the dust collection slag. The recovered petroleum coke and sodium chloride are recycled to the molten salt chlorination furnace.
[0020] As a preferred technical solution, in step 1), the waste denitrification slag catalyst is the waste after being used for denitrification of the SCR denitrification catalyst in a thermal power plant; the high-concentration strong base is one of NaOH and KOH; in step 1), the solid-liquid separation is one or more of pressure filtration, filtration, centrifugation, and precipitation.
[0021] As a preferred technical solution, in step 1), the solid-liquid separation is the separation of solid and liquid in the leaching liquid.
[0022] As a preferred technical solution, in step 2), the refining of the leaching solution is that the leaching solution undergoes a chemical precipitation method, and precipitation reactions are carried out using ammonium salts and calcium salts to obtain NH4VO3 filter residue and CaWO4 filter residue respectively; the vanadium extraction is that the NH4VO3 filter residue is calcined at high temperature to obtain vanadium products; the tungsten extraction is that CaWO4 is obtained as tungsten products after pickling and calcination processes.
[0023] As a preferred technical solution, in step 3), the H2SO4 is the waste sulfuric acid after electrolytic purification of chlorine in magnesium chloride electrolysis.
[0024] The indicators in step 3) include composition, particle size, bulk density, fluidity, moisture content, and rutile content.
[0025] As a preferred technical solution, in step 4), the proportioning scheme requires that the proportion of the -200 mesh in the mixed slag after proportioning is less than 30%.
[0026] The drying hot gas used in the fluidized bed drying in step 4) is one or more of the reduction waste heat in the production of sponge titanium in the workshop or the cooling waste heat of the titanium ingot in the production of sponge titanium in the workshop.
[0027] As a preferred technical solution, in step 5), the petroleum coke is one or more of the petroleum coke purchased from outside the workshop, the petroleum coke recovered from the dust collection slag of the molten salt chlorination furnace and the fluidized bed chlorination furnace, and the sodium chloride is one or more of the sodium chloride purchased from outside the workshop, the sodium chloride recovered from the waste molten salt, or the sodium chloride produced by titanium white MVR.
[0028] In step 5), the moisture content of the petroleum coke in the petroleum coke batching bin is required to be < 0.1%; the moisture content of the sodium chloride in the sodium chloride batching bin is required to be < 0.1%.
[0029] As a preferred technical solution, in step 7), during the chlorination reaction, it is necessary to observe the changes in the molten salt composition, waste molten salt composition and liquid level during the production process and adjust the production at any time.
[0030] As a preferred technical solution, in step 8), for the recovery of salt and titanium from the waste molten salt, the waste molten salt is dissolved in water and then the filtrate is purified to obtain sodium chloride, and the filter residue is recovered for titanium dioxide by ore dressing methods;
[0031] In step 8), for the recovery of petroleum coke and titanium from the dust collecting residue, the dust collecting residue is slurried and then the petroleum coke and titanium dioxide are recovered by ore dressing methods.
[0032] As a preferred technical solution, the conveying method is one of using a scraper and a bucket elevator to convey the materials or conveying them by a belt conveyor. The belt of the belt conveyor is one of a U-shaped belt or a circular belt; the proportioning adopts a blending method, and the blending method is applicable to the proportioning and use of denitrification slag, other titanium-rich materials, petroleum coke, and sodium chloride.
[0033] The present invention also discloses the following steps: 1) The waste denitration slag catalyst is fully mixed with a high-concentration strong base and leached. After the leaching is completed, the liquid is subjected to solid-liquid separation to separate the leaching solution and the leaching residue; 2) The leaching solution is refined to extract vanadium and tungsten to obtain vanadium products and tungsten products; 3) The leaching residue is washed with H2SO4, and then calcined to obtain an anatase-type denitration slag product, and various indexes of the denitration slag product must be measured; 4) The denitration slag and titanium slag are proportioned according to a ratio, and after proportioning, they are fully mixed; for the said proportioning, various slag proportioning schemes are determined according to the indexes, and several stock bins are prepared. The stock bins include different titanium slag stock bins and denitration slag stock bins. The stock bins are equipped with a loss-in-weight weighing system. The denitration slag and titanium slag are respectively loaded into the corresponding stock bins, and proportioning is carried out by weighing according to the proportioning scheme. The proportioned materials fall onto a scraper conveyor, enter a bucket elevator after being dried in a fluidized bed, are transported to a transfer bin by the bucket elevator, and finally transported to an intermediate bin. The slag intermediate bin is also equipped with a loss-in-weight weighing system; 5) Petroleum coke and sodium chloride are transported to an intermediate bin; stock bins for petroleum coke and sodium chloride are prepared, and petroleum coke and sodium chloride are respectively loaded into the corresponding stock bins. The stock bins are equipped with a loss-in-weight weighing system. After weighing, they are transported to their respective corresponding intermediate bins through a scraper and a bucket elevator; 6) According to the material consumption proportioning scheme, the slag, petroleum coke, and sodium chloride are proportioned and fully mixed after proportioning; for the said material consumption proportioning scheme, the loss-in-weight weighing of the intermediate bin is used to weigh and proportion the mixed slag, petroleum coke, and sodium chloride. After proportioning is completed, they fall onto a scraper conveyor and are transported to a furnace front bin, where they are fully mixed. After mixing, the materials are continuously fed into a molten salt chlorination furnace through a screw feeder; 7) Chlorination reaction: The materials in the molten salt chlorination furnace react with chlorine supplied through a chlorine lance. The waste molten salt generated by the chlorination reaction is discharged from the salt discharge pipe of the molten salt chlorination furnace. The titanium tetrachloride vapor and gas mixture generated by the chlorination reaction pass through a dust collector, where part of the high-boiling chlorides are condensed and co-sedimented with solid particles to form dust and are collected as dust-containing slag. The uncondensed titanium tetrachloride and gas mixture are sprayed and condensed to form liquid crude titanium tetrachloride, and the liquid crude titanium tetrachloride is sent to a refining process for refining. The tail gas is sent to a tail gas treatment process through a fan. 8) The waste molten salt is subjected to the recovery of salt and titanium, and the dust-containing slag is subjected to the recovery of petroleum coke and titanium. The recovered petroleum coke and sodium chloride are recycled to the molten salt chlorination furnace.
[0034] Advantages of the present invention:
[0035] Since most of the TiO2 in the denitration slag is anatase type and only a small part is rutile type, for molten salt chlorination, the temperature is sufficient to chlorinate it;
[0036] The contents of CaO and MgO in the denitration slag are relatively low, which will not affect the viscosity of the molten salt and will not affect the progress of the chlorination reaction;
[0037] The blending of particle sizes can fully meet the production requirements and will not affect production due to unqualified particle sizes.
[0038] By using the denitrification slag in a proportionate manner, waste materials are effectively utilized, reducing production costs.
[0039] In the denitrification catalyst of the present invention, vanadium has been recycled and utilized in the early stage, and the content of vanadium oxychloride produced by chlorination is relatively low. This can reduce the usage of vanadium removal oil in the purification stage of titanium tetrachloride, thereby reducing the C content in titanium tetrachloride, further controlling the C content in sponge titanium, and improving the quality of sponge titanium.
[0040] The present invention reduces environmental pollution and meets the requirements of the concept of green development. BRIEF DESCRIPTION OF THE DRAWINGS
[0041] Figure 1 is the process flow chart of the present invention;
[0042] Figure 2 is the XRD pattern of the denitrification slag in Example 1 of the present invention;
[0043] Figure 3 is the process equipment framework diagram of the present invention;
[0044] 1 - Intermediate bin for mixed slag; 2 - Transfer bin; 3 - Bucket elevator; 4 - Fluidized bed; 5 - Scraper conveyor; 6 - Titanium slag preparation bin; 7 - Denitrification slag preparation bin; 8 - Loss-in-weight scale; 9 - Valve; 10 - Intermediate bin for sodium chloride; 11 - Intermediate bin for petroleum coke; 12 - Intermediate bin for mixed slag; 13 - Bin before furnace; 14 - Screw feeder; 15 - Chlorination furnace. DETAILED DESCRIPTION OF THE INVENTION
[0045] In order to make the technical means, creative features, achieved purposes and functions of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.
[0046] Example 1
[0047] 1) The waste denitrification slag catalyst is fully mixed with high-concentration strong alkali and leached. After the leaching is completed, the liquid is subjected to solid-liquid separation to separate the leaching solution and the leaching residue;
[0048] 2) The leaching solution is refined to extract vanadium and tungsten to obtain vanadium products and tungsten products;
[0049] 3) The leaching residue is washed with H2SO4 and then calcined to obtain an anatase denitrification slag product, and the various indexes of the denitrification slag product must be measured;
[0050] The indexes of the denitrification slag:
[0051] Analysis of the composition of the denitrification slag:
[0052] Elemental Analysis of Denitrification Slag in Table 2
[0053]
[0054] The TiO2 grade of the denitrification slag sample is 88.571%, and the content of CaO + MgO is 2.47%.
[0055] XRD Analysis of Denitrification Slag
[0056] As Figure 2 shown, it can be known from the XRD scanning analysis that most of the crystal forms of titanium in the denitrification slag sample are anatase type, with a small amount of rutile type. Among them, the anatase type content is 94.7%, and the rutile type content is 5.3%.
[0057] Particle Size Analysis of Denitrification Slag
[0058] Particle Size Analysis of Denitrification Slag in Table 3
[0059] Mesh number +60 mesh -60 to +120 mesh -120 to +160 mesh -160 to +200 mesh -200 mesh Proportion (%) 4.33 5.62 12.56 41.44 36.05
[0060] It can be known from the particle size analysis that the proportion of the sample below -160 mesh is 90.05%, and the proportion of -200 mesh is 36.05%.
[0061] 4) Mix the denitrification slag and titanium slag in proportion, and fully mix them after proportioning; for the said proportioning, determine various slag proportioning schemes according to the indexes, prepare several stock bins, the said stock bins include different titanium slag stock bins and denitrification slag stock bins, the stock bins are equipped with a loss-in-weight weighing system, load the denitrification slag and titanium slag into the corresponding stock bins respectively, conduct proportioning by weighing according to the proportioning scheme, the proportioned materials fall onto the scraper conveyor, enter the bucket elevator after being dried in the fluidized bed, are transported to the transfer bin by the bucket elevator, and finally transported to the intermediate bin, and the slag intermediate bin is also equipped with a loss-in-weight weighing system;
[0062] Particle Size Analysis of Mixed Slag in Table 4
[0063]
[0064]
[0065] The proportion of -200 mesh of the mixed slag is 19.85%.
[0066] 5) Transport the petroleum coke and sodium chloride to the intermediate bin; prepare the petroleum coke and sodium chloride stock bins, load the petroleum coke and sodium chloride into the corresponding stock bins respectively, the stock bins are equipped with a loss-in-weight weighing system, and after weighing, transport them to their respective corresponding intermediate bins through the scraper and bucket elevator;
[0067] 6) According to the material consumption ratio plan, conduct the ratio of slag, petroleum coke, and sodium chloride, and fully mix them after the ratio; for the material consumption ratio plan, the loss-in-weight weigher in the intermediate bunker weighs to conduct the ratio of mixed slag, petroleum coke, and sodium chloride. After the ratio is completed, it falls onto the scraper conveyor and is transported to the bin in front of the furnace. It is fully mixed in the bin in front of the furnace, and after mixing, the material is continuously fed into the molten salt chlorination furnace through a screw feeder;
[0068] 7) Chlorination reaction: The materials in the molten salt chlorination furnace react with chlorine supplied through a chlorine lance. The waste molten salt generated by the chlorination reaction is discharged from the salt discharge pipe of the molten salt chlorination furnace. The titanium tetrachloride vapor and gas mixture generated by the chlorination reaction pass through a dust collector, where some high-boiling chlorides are condensed and co-settled with solid particles to form dust, which is collected to obtain collected dust slag. The uncondensed titanium tetrachloride and gas mixture are sprayed and condensed to form liquid crude titanium tetrachloride, and the liquid crude titanium tetrachloride is sent to the refining process for refining, and the tail gas is sent to the tail gas treatment process through a fan.
[0069] 8) Recover salt and titanium from the waste molten salt, and recover petroleum coke and titanium from the collected dust slag. The recovered petroleum coke and sodium chloride are recycled to the molten salt chlorination furnace.
[0070] In step 1), the waste denitrification slag catalyst is the waste after the SCR denitrification catalyst in a thermal power plant is used for denitrification; the high-concentration strong base is NaOH.
[0071] In step 1), the solid-liquid separation is the separation of solid and liquid in the leaching liquid.
[0072] In step 2), the refining of the leaching liquid is that the leaching liquid undergoes a chemical precipitation method, using ammonium salts and calcium salts for precipitation reactions to obtain NH4VO3 filter residue and CaWO4 filter residue respectively; the vanadium extraction is that the NH4VO3 filter residue is calcined at high temperature to obtain vanadium products; the tungsten extraction is that CaWO4 obtains tungsten products after pickling and calcination processes;
[0073] In step 3), the H2SO4 is the waste sulfuric acid after the electrolytic purification of chlorine in magnesium chloride;
[0074] The indicators in step 3) include composition, particle size, bulk density, fluidity, moisture content, and rutile content.
[0075] In step 4), the ratio plan requires that the proportion of the mixed slag -200 mesh after the ratio is less than 30%;
[0076] In step 4), the drying hot gas used in the fluidized bed drying is one or more of the reduction waste heat in the production of sponge titanium in the workshop or the cooling waste heat of the titanium ingot in the production of sponge titanium in the workshop.
[0077] In step 5), the petroleum coke is the petroleum coke purchased from outside the workshop, the petroleum coke recovered from the collected dust slag of the molten salt chlorination furnace, and the fluidized bed chlorination furnace;
[0078] In step 5), the moisture content requirement of the petroleum coke in the petroleum coke stock bin is <0.1%; the moisture content requirement of the sodium chloride in the sodium chloride stock bin is <0.1%.
[0079] In step 7), for the chlorination reaction, it is necessary to observe the changes in the molten salt composition, waste molten salt composition and liquid level during the production process and adjust the production at any time.
[0080] In step 8), for the recovery of salt and titanium from the waste molten salt, the waste molten salt is dissolved in water and then the filtrate is purified to obtain sodium chloride, and the filter residue is recovered for titanium dioxide through ore dressing methods;
[0081] In step 8), for the recovery of petroleum coke and titanium from the dust collection residue, the dust collection residue is slurried and then the petroleum coke and titanium dioxide are recovered through ore dressing methods.
[0082] The conveying method is to convey the materials by a scraper and a bucket elevator; the proportioning adopts a blending method, and the blending method is applicable to the proportioning of denitrification slag, other titanium-rich materials, petroleum coke and sodium chloride.
[0083] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for recycling denitrification slag, characterized in that: The following steps are involved: 1) The waste denitration residue catalyst is fully mixed with a high concentration of strong alkali, and leached. After the leaching is completed, the liquid is solid-liquid separated to separate the leaching liquid and the leaching residue; 2) Refining the leaching solution to extract vanadium and tungsten to obtain vanadium products and tungsten products; 3) washing the leached residue with H2SO4, and then roasting it to obtain anatase denitrification residue product, and the denitrification residue product must be measured for various indicators; 4) Denitrification slag and titanium slag are proportioned and fully mixed after proportioning; the proportioning is to determine various slag proportioning schemes according to the indicators, and prepare several preparation bins, including different titanium slag preparation bins and denitrification slag preparation bins, and the preparation bins are equipped with loss-in-weight scale systems. The denitrification slag and titanium slag are respectively loaded into corresponding preparation bins, and proportioned by weighing according to the proportioning scheme. The proportioned materials fall onto the scraper conveyor, enter the bucket elevator after being dried on the fluidized bed, and are transported to the transfer bin by the bucket elevator, and finally transported to the intermediate bin. The slag intermediate bin is also equipped with a loss-in-weight scale system; 5) Transporting petroleum coke and sodium chloride to the intermediate silo; preparing petroleum coke and sodium chloride preparation silos, loading petroleum coke and sodium chloride into corresponding preparation silos respectively, the preparation silos are equipped with a loss-in-weight scale system, and after weighing, they are transported to their corresponding intermediate silos via scrapers and fighter elevators; 6) According to the material consumption ratio scheme, slag, petroleum coke and sodium chloride are proportioned, and the proportions are fully mixed; in the material consumption ratio scheme, the intermediate silo is weighed by a weight loss scale to mix the slag, petroleum coke and sodium chloride, and after the proportions are completed, they fall onto a scraper conveyor and are transported to the silo in front of the furnace, where they are fully mixed, and after mixing, the materials are continuously fed into the molten salt chlorination furnace through a screw feeder; 7) Chlorination reaction, the material in the molten salt chlorination furnace undergoes chlorination reaction with chlorine supplied by a chlorine spray gun, the waste molten salt produced by the chlorination reaction is discharged from the salt discharge pipe of the molten salt chlorination furnace, the titanium tetrachloride vapor and gas mixture produced by the chlorination reaction pass through a dust collector, wherein part of the high-boiling point chloride is condensed and precipitated together with solid particles to form dust to be collected, and dust collecting residue is obtained, the titanium tetrachloride and gas mixture that has not been condensed are sprayed and condensed to form liquid crude titanium tetrachloride, the liquid crude titanium tetrachloride is sent to a refining process for refining, and the tail gas is sent to a tail gas treatment process through a blower; 8) The waste molten salt is used to recover salt and titanium, and the dust slag is used to recover petroleum coke and titanium. The recovered petroleum coke and sodium chloride are reused in the molten salt chlorination furnace.
2. The method for recycling denitrification slag according to claim 1, characterized in that: The waste denitration slag catalyst in step 1) is the waste of SCR denitration catalyst in thermal power plants after denitration; the high-concentration strong alkali is one of NaOH and KOH; the solid-liquid separation in step 1) is one or more of filter pressing, filtration, centrifugation, and precipitation.
3. A method for recycling denitrification slag according to claim 1 or 2, characterized in that: The solid-liquid separation in the step 1) is solid-liquid separation of the leaching liquid.
4. The method for recycling denitrification slag according to claim 1, characterized in that: In the step 2), the leachate is refined by chemical precipitation, using ammonium salt and calcium salt to react to obtain NH4VO3 filter residue and CaWO4 filter residue respectively; the vanadium extraction is to obtain vanadium products by high-temperature roasting of NH4VO3 filter residue; the tungsten extraction CaWO4 is to obtain tungsten products after acid washing and calcination.
5. The method for recycling denitrification slag according to claim 1, characterized in that: In the step 3), H2SO4 is waste sulfuric acid after chlorine is purified by electrolysis of magnesium chloride; The indicators in step 3) include composition, particle size, bulk density, fluidity, moisture, and rutile content.
6. The method for recycling denitrification slag according to claim 1, characterized in that: The proportioning scheme in step 4) requires that the proportion of mixed slag-200 mesh is less than 30% after proportioning; The drying hot air used for fluidized bed drying in step 4) is one or more of the reduction waste heat from the production of titanium sponge in the workshop or the cooling waste heat from the production of titanium sponge in the workshop.
7. The method for recycling denitrification slag according to claim 1, characterized in that: The petroleum coke in step 5) is one or more of petroleum coke purchased from the workshop, petroleum coke recovered from dust residue of a molten salt chlorination furnace, and boiling chlorination furnace, and the sodium chloride is one or more of sodium chloride purchased from the workshop, sodium chloride recovered from waste molten salt, or sodium chloride produced by titanium dioxide MVR; In the step 5), the moisture content of the petroleum coke in the petroleum coke preparation bin is required to be less than 0.1%; the moisture content of the sodium chloride in the sodium chloride preparation bin is required to be less than 0.1%.
8. The method for recycling denitrification slag according to claim 1, characterized in that: In the chlorination reaction in step 7), it is necessary to observe the changes in the molten salt composition, the waste molten salt composition and the liquid level during the production process, and make production adjustments at any time.
9. The method for recycling denitrification slag according to claim 1, characterized in that: In the step 8), the waste molten salt is used to recover salt and titanium, and the filtrate is purified to extract sodium chloride after the waste molten salt is dissolved, and the filter residue is used to recover titanium dioxide through a mineral processing method; In the step 8), the dust collected is used to recover petroleum coke and titanium by pulping the dust collected and then recovering petroleum coke and titanium dioxide through a mineral processing method.
10. The method for recycling denitrification slag according to claim 1, characterized in that: The conveying method is one of conveying materials by a scraper and bucket elevator or conveying by a belt conveyor, and the belt of the belt conveyor is one of a U-shaped belt and a round belt; the proportioning adopts a blending method, and the blending method is suitable for the proportioning of denitrification slag, other titanium-rich materials, petroleum coke, and sodium chloride.