A sintering method for controlled migration of bismuth element

Abstract

This invention discloses a sintering method for controlled migration of bismuth. By independently granulating bismuth-containing materials using a chlorine- and carbon-rich process and distributing the granules to the lower middle part of the sintering layer during sintering, a localized high-chlorine, high-reducing atmosphere micro-region can be created during sintering. This promotes the concentrated stripping of bismuth from the sintered mineral phase. Simultaneously, segmented dust collection of the sintering flue gas allows for the concentrated capture of flue gas dust during the peak bismuth volatilization phase, resulting in high-bismuth flue gas dust. The sintering method of this invention is simple, easy to control, and achieves efficient collection of bismuth, overcoming the bottleneck of dispersed and difficult-to-recover bismuth in existing technologies. It is applicable to most existing sintering production lines, requiring no additional independent production line, resulting in low overall investment costs and facilitating rapid market promotion and application.

Description

Technical Field

[0001] This invention relates to the treatment of bismuth-containing solid waste, specifically to a sintering method for controlled migration of bismuth, belonging to the technical field of bismuth-containing solid waste treatment. Background Technology

[0002] In the iron and steel smelting process, iron ore raw materials often contain various trace metallic elements, among which bismuth (Bi) is one. Bismuth is a harmful impurity in steel products, easily leading to hot brittleness and affecting product quality. In the traditional iron ore sintering-blast furnace ironmaking process, during the sintering process of bismuth-containing iron ore, some bismuth volatilizes into the sintering flue gas and is eventually captured in the sintering machine head ash; the remaining bismuth enters the blast furnace with the sintered ore, where it further volatilizes under the high-temperature reducing atmosphere and accumulates in the blast furnace smelting ash. This "two-stage dispersion" results in sparse distribution and large fluctuations in the content of bismuth in both types of flue dust, making efficient recovery difficult and increasing the difficulty of flue dust treatment and environmental risks. With increasingly complex mineral resources and stricter environmental requirements, how to achieve source control and efficient enrichment of rare metals such as bismuth has become an important issue for the comprehensive utilization of resources in the iron and steel industry.

[0003] Currently, the conventional methods for handling bismuth elements during smelting are mainly two modes: "centralized return of flue dust to sintering" and "returning to sintering after pre-removal of conventional harmful impurities". The specific implementation methods are as follows: (1) The flue dust mixing and recycling process is to mix bismuth-containing flue dust such as sintering machine head ash and blast furnace bag ash with other raw materials such as sintering return ore, iron ore powder, flux and coke powder, and then evenly distribute it into the sintering material layer for sintering. This method aims to achieve the recycling of metals in flue dust through recycling. (2) Returning to sintering after pre-removal of conventional harmful impurities is to remove alkali metals such as potassium and sodium from sintering machine head ash by pre-washing with water, and remove zinc from blast furnace smelting ash by reduction roasting, and then return the dealkali- and dezincified iron material to the sintering batch for use.

[0004] Although the above-mentioned existing technologies can reduce the amount of dust and recover some metals, they have significant shortcomings in the directional separation and enrichment of bismuth: (1) The direction of bismuth is uncontrollable and the dispersion is aggravated: Under the conditions of mixed granulation and uniform material distribution, bismuth is in an oxidizing atmosphere during sintering and it is difficult to effectively convert it into volatile chlorides or metals. Its direction still diffuses with the mainstream flue gas, resulting in the bismuth being dispersed in the dust and having a low grade. (2) Lack of local reaction micro-zones: Chlorine (usually from additives such as calcium chloride) is evenly distributed in the mixed material layer and has a low concentration, making it impossible to form a local high chlorine environment; in addition, the dispersion of coke powder also makes the local reducing atmosphere intensity insufficient, which is not conducive to the efficient chlorination volatilization (generating BiCl3) or reduction volatilization (generating metallic bismuth vapor) of bismuth. (3) Mixed dust collection and low enrichment efficiency: All sintering wind box flue gas is mixed for dust collection, and the bismuth volatilized at different sintering stages is mixed with other metal dust, alkali metal salts, etc., making it impossible to obtain directional dust with high bismuth content, and the subsequent separation and purification costs are high. Summary of the Invention

[0005] To address the low efficiency of bismuth collection in existing technologies, this invention provides a sintering method for controlled bismuth migration. By independently granulating bismuth-containing materials into chlorine- and carbon-rich particles and distributing them to the lower middle part of the sintering layer during the sintering process, a localized high-chlorine, high-reducing atmosphere micro-zone can be created during sintering. This promotes the concentrated stripping of bismuth from the sintered mineral phase. Simultaneously, segmented dust collection of the sintering flue gas allows for the concentrated capture of flue gas dust during the peak bismuth volatilization phase, resulting in high-bismuth flue gas dust. This method achieves highly efficient bismuth collection, overcoming the bottleneck of dispersed and difficult-to-recover bismuth in existing technologies, and providing a new approach for the resource utilization of rare and dispersed metals in steel smelting.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0007] A sintering method for controlled migration of bismuth element, the sintering method comprising the following steps:

[0008] 1) Bismuth-containing materials, high-chlorine materials, and reducing agents are mixed and granulated to obtain bismuth-containing granules.

[0009] 2) Bismuth-containing granules are mixed with some conventional sintering materials to obtain bismuth-containing mixtures.

[0010] 3) The bismuth-containing mixture is laid between the base material and the conventional sintering material layer (i.e., the remaining conventional sintering material) and sintered.

[0011] 4) During the sintering process, dust is collected from the flue gas in the sintering front section to obtain sintering dust, and dust is collected from the flue gas in the sintering back section to obtain high bismuth dust.

[0012] Preferably, the bismuth-containing material includes, but is not limited to, bismuth-containing dust and / or bismuth-containing waste ore powder. Preferably, the bismuth content in the bismuth-containing material is not higher than 5000 g / t, and more preferably 1~5000 g / t.

[0013] Preferably, the high-chlorinated material includes, but is not limited to, chloride or chloride-containing dust (e.g., sintering machine head ash after potassium and sodium removal by water washing, or other chloride-containing materials that can decompose to produce hydrogen chloride gas at high sintering temperatures), preferably one or more of calcium chloride, magnesium chloride, sodium chloride, and potassium chloride. Preferably, the chlorine content in the high-chlorinated material is not less than 1% by mass.

[0014] Preferably, the reducing agent is a carbonaceous reducing agent, preferably one or more of carbon powder, coke powder, and coal powder.

[0015] Preferably, the mass ratio of bismuth-containing material, high-chlorine material, and reducing agent is 50~80:30~15:20~5, and more preferably 60~70:25~20:15~10.

[0016] Preferably, water is added during the granulation process in step 1). Preferably, the amount of water added is such that the moisture content of the bismuth-containing granules is 2-10% by mass.

[0017] Preferably, the particle size of the bismuth-containing granules is 1~15mm, and more preferably 3~8mm.

[0018] Preferably, in the bismuth-containing mixture, the mixing mass ratio of bismuth-containing granules to conventional sintering material is 5~50:95~50, and more preferably 10~30:90~70.

[0019] Preferably, the conventional sintering material includes iron-containing raw materials (including iron-containing dust or mineral powder, etc.), flux (including limestone, dolomite, silica, fluorite, etc.), fuel (including coke powder, coal powder, carbon powder, etc.), and water. Preferably, the mixing mass ratio of iron-containing raw materials, flux, fuel, and water is 60~90:5~20:2~10:2~10. The particle size of the conventional sintering material is 4~25mm, preferably 6~20mm.

[0020] Preferably, the thickness of the base material is 70-100mm, and more preferably 80-90mm.

[0021] Preferably, the thickness of the bismuth-containing mixture layer is 20-300 mm, and more preferably 100-200 mm.

[0022] Preferably, the thickness of the conventional sintering material layer is 600~1000mm, and more preferably 700~1000mm.

[0023] Preferably, the sintering rear section air boxes are the 1st to 10th air boxes at the tail of the sintering machine, more preferably the 1st to 8th air boxes, and more preferably the 1st to 4th air boxes. The remaining air boxes are the sintering front section air boxes.

[0024] Preferably, the bismuth content in the obtained high-bismuth flue dust is 0.5-20% by mass.

[0025] Preferably, the obtained sintering dust is washed and desalted before being used as a raw material for bismuth-containing granules or as a raw material for conventional sintering materials.

[0026] Preferably, the sintering temperature is 1000~1200℃, more preferably 1050~1150℃. The sintering time is 0.5~10h, more preferably 1~5h.

[0027] In this invention, in view of the defects of the prior art, this invention aims to provide a sintering method for the controllable migration of bismuth element. Its core objectives include: (1) achieving directional volatilization and enrichment of bismuth: by separately granulating bismuth-containing materials with high-chlorine materials and reducing agents (such as coke powder) and distributing them in the lower part of the sintering material layer, a local high-chlorine, high-reducing atmosphere micro-region is constructed to promote the preferential conversion of bismuth into BiCl3 or metallic bismuth for volatilization, thereby concentrating and stripping bismuth from the sintering mineral phase. (2) enhancing the spatial enrichment of bismuth in flue dust: by collecting sintering flue dust in segments, especially by separately collecting dust from the flue gas in the windbox section after the disappearance of the over-wet zone, the flue dust at the peak of bismuth volatilization is captured to obtain high bismuth content dust, which greatly improves the economic efficiency of subsequent recovery. (3) overcoming the problem of dispersed distribution: by controlling the direction of bismuth from the source, the secondary dispersion of bismuth in the blast furnace process is avoided, and the purpose of "concentrated volatilization and primary enrichment in the sintering stage" is achieved, simplifying the entire process recovery process. (4) Improve process compatibility and environmental friendliness: Reduce the negative impact of bismuth on the quality of sintered ore, and at the same time reduce the overall flue gas treatment load through segmented collection, which is conducive to the green and efficient recovery of rare and dispersed metals in steel plants. This invention solves the bottleneck of difficult recovery of dispersed bismuth in the prior art by coupling micro-zone atmosphere control and process segmented capture, and provides a new idea for the resource utilization of rare and dispersed metals in the steel smelting process.

[0028] In this invention, bismuth-containing materials include, but are not limited to, bismuth-containing flue dust and / or bismuth-containing waste ore powder. These are generally secondary bismuth-containing materials such as sintering machine head ash and blast furnace bag ash. These materials have low bismuth content, making direct separation and purification difficult, but they also cannot be directly used as sintering feedstock in the sintering process (bismuth is difficult to collect centrally). Therefore, this invention pre-treats the bismuth-containing materials: bismuth-containing secondary bismuth-containing materials such as sintering machine head ash and blast furnace bag ash are mixed with high-chlorine materials and a reducing agent to obtain a granulation mixture. Then, water is selectively added or not added for molding to obtain bismuth-containing granules (for example, the granulation mixture is granulated in a cylindrical pelletizer or a disc pelletizer to obtain bismuth-containing granules with a particle size of 1-15 mm, preferably 3-8 mm). The high-chlorine material includes one or more of the following: sintering machine head ash after potassium and sodium removal by water washing, calcium chloride, magnesium chloride, sodium chloride, potassium chloride, or other chlorine-containing compounds that can decompose to produce hydrogen chloride (HCl) gas at high sintering temperatures. The reducing agent is a solid carbonaceous reducing agent such as coke powder or anthracite powder. By independently molding the bismuth-containing material, high-chlorine material, and reducing agent, the three form an independent whole. This facilitates placement after the sintering process, allowing the high-chlorine material and reducing agent to create a localized high-chlorine, high-reducing atmosphere micro-zone in the concentrated area of ​​the bismuth-containing material. This promotes and enhances the concentrated removal of bismuth from the sintered ore phase and its entry into the flue gas in the later stage of sintering for centralized collection. Research has shown that in the preferred embodiment of this invention, when the mixing mass ratio of bismuth-containing material, high-chlorine material, and reducing agent is 50~80:30~15:20~5 (preferably 60~70:25~20:15~10), the concentrated volatilization and stripping of bismuth can be better achieved.

[0029] In this invention, conventional sintering material refers to spherical, blocky, or columnar sintering material with a particle size of 5-25 mm (preferably 8-20 mm) obtained by any existing iron-containing raw material (including iron dust or mineral powder, etc.) and any additives (such as limestone, dolomite, silica, fluorite, etc. fluxes, coke powder, coal powder, carbon powder, etc. fuels, and water, etc.) using any known means (such as granulation, pelletizing, briquetting, etc.).

[0030] In this invention, a layered material distribution method is used to couple and sinter bismuth-containing granules with conventional sintering materials. Specifically, this involves layered material distribution on a sintering machine trolley. First, a conventional base material is laid on the sintering trolley. Then, a bismuth-containing mixture obtained in step 1) and a portion of the conventional sintering material are evenly mixed and distributed on the surface of the base material to form a specific reaction layer (i.e., the bismuth-containing mixture layer). Finally, the remaining conventional sintering material is evenly distributed on the surface of the bismuth-containing mixture layer, followed by ignition and sintering. Mixing the bismuth-containing granules with a portion of the conventional sintering material to form the bismuth-containing mixture layer ensures that the quality difference between the sintered ore from the bismuth-containing mixture layer and the rest of the sinter is small, preventing significant component segregation and avoiding a decline in the overall performance of the sinter. It should be noted that if too much conventional sintering material is mixed into the bismuth-containing mixture layer, the bismuth-containing layer will become thicker, weakening the reducing atmosphere and resulting in poor reduction and volatilization, even with the total amount of bismuth-containing material remaining constant. Conversely, if too little conventional sintering material is mixed in, the quality of the sinter from the bismuth-containing mixture layer will be relatively poor. Research has shown that a mixing mass ratio of bismuth-containing granules to conventional sintering material of 5-50:95-50 can ensure the quality of the sinter without affecting the reduction and volatilization of bismuth. In a preferred embodiment of the present invention, the thickness of the bottom layer is 70-100 mm (preferably 80-90 mm), the thickness of the bismuth-containing mixture layer is 20-300 mm (preferably 100-200 mm), and the thickness of the conventional sintering material (i.e., the pure sintering material layer located on top of the entire sintering material layer) is 600-1000 mm (preferably 700-1000 mm).

[0031] In this invention, during the sintering process, as the combustion zone moves downwards, a localized high-temperature, strongly reducing atmosphere is formed inside the lower bismuth-containing granular balls. Simultaneously, the high-chlorine material decomposes and releases HCl gas, which reacts with bismuth oxides in this localized micro-region to generate volatile bismuth trichloride (BiCl3) gas, which enters the flue gas in the later stage of sintering. The main reaction includes: Bi2O3 + 6HCl = 2BiCl 3(g) +3H2O (g) Bi2O3+3CO (g) =2Bi+3CO 2(g) 4Bi + 12HCl (g) +3O 2(g) =4BiCl 3(g) +6H2O (g) In other words, this invention achieves efficient chlorination and volatilization of bismuth by constructing a micro-region reaction with localized high temperature, high reduction, and high chlorine, laying the foundation for the subsequent collection of high-bismuth fumes.

[0032] In this invention, due to the layered sintering method, bismuth-containing granules are laid in the lower middle part of the entire sintering layer. Therefore, in the early stage of sintering, the temperature of the bismuth-containing mixture layer is relatively low, making it difficult to form a high-chlorine environment. As a result, bismuth hardly volatilizes and detaches. That is to say, the sintering flue gas in the early stage of sintering contains only a small amount of low-bismuth dust formed from the volatilization of bismuth in conventional sintering materials (along with other metal elements such as lead and zinc). This part of the flue gas is treated separately for dust removal to avoid the low-bismuth dust affecting the quality of the subsequent high-bismuth dust. In the later stage of sintering, that is, in the rear section of the sintering machine, a separate pipeline and dust removal system are specially set up to collect the flue gas generated by the wind boxes (e.g., the third to the last wind boxes at the tail of the sintering machine) corresponding to the high-temperature, high-chlorine reaction stage of the bismuth-containing reaction layer (bismuth-containing mixture layer). The dust collected therein is the high-bismuth dust, which can significantly improve the economics of subsequent bismuth element recovery and the value of bismuth products.

[0033] In this invention, the core steps of the sintering method are as follows: bismuth-containing materials, high-chlorine additives, and reducing agents are granulated separately → distributed in the lower part of the sintering bed → bismuth volatilization is promoted using local micro-regions → segmented and independent dust collection of flue gas at specific stages. The key process parameters and materials refer to the type of high-chlorine material (especially substances that release HCl), the amount of reducing agent (coke powder), the particle size range of the bismuth-containing granules, and their placement in the bed (lower part). The specific dust collection method is specially designed to achieve bismuth enrichment; independent flue gas ducts and dust collection devices are set up for specific windbox sections after the disappearance of the over-wet zone during sintering to achieve independent collection of high-bismuth dust.

[0034] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0035] 1. Compared to existing technologies where bismuth exhibits uncontrollable dispersion under conventional sintering atmospheres, ultimately dispersing into large amounts of mixed dust, resulting in extremely high separation and extraction costs and virtually no independent recovery value, this invention creates localized high-temperature, high-chlorine reduction micro-regions. This actively converts over 90% of the bismuth into a gaseous phase, causing it to volatilize and be precisely captured in specific dust particles. This directly yields a high-grade intermediate product that can be used as a raw material for bismuth smelting, significantly improving the economic feasibility of recovery.

[0036] 2. Compared to existing technologies that return bismuth-containing flue dust to the main raw materials, where bismuth accumulates in the sintering-blast furnace system, potentially affecting the strength of the sinter and ultimately damaging the steel's properties, this invention efficiently removes and extracts bismuth in a single step during the sintering process. This is equivalent to providing a "detoxification and purification" step for the main steelmaking process. This not only avoids the negative impact of bismuth on subsequent processes and produces purer sinter, but also allows a large amount of other conventional flue dust to be recycled more safely due to the reduced bismuth content.

[0037] 3. Compared to existing technologies that address the dispersed distribution of bismuth across various types of dust and multiple processing steps, subsequent recovery requires separating and extracting trace amounts of bismuth from a large volume of mixed dust, resulting in complex processes and high energy and material consumption. This invention achieves both the "separation" and "enrichment" of bismuth in one step at the source (sintering process) through atmosphere control and segmented collection. Subsequent processing only requires handling a small amount of high-bismuth ash, greatly simplifying the entire recycling process and reducing overall energy consumption and environmental pressure. It represents a classic source reduction and resource recovery technology.

[0038] 4. The sintering method of the present invention has a simple process and is easy to control. It can be applied to most existing sintering production lines without the need to build an additional independent production line. The overall investment cost is low, which makes it easy to promote and apply it to the market quickly. Attached Figure Description

[0039] Figure 1 This is a simplified process flow diagram of the sintering method described in this invention. Detailed Implementation

[0040] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments.

[0041] like Figure 1 As shown, a sintering method for controlled migration of bismuth element is disclosed, the sintering method comprising the following steps:

[0042] 1) Bismuth-containing materials, high-chlorine materials, and reducing agents are mixed and granulated to obtain bismuth-containing granules.

[0043] 2) Bismuth-containing granules are mixed with some conventional sintering materials to obtain bismuth-containing mixtures.

[0044] 3) The bismuth-containing mixture is laid between the base material and the conventional sintering material layer (i.e., the remaining conventional sintering material) and sintered.

[0045] 4) During the sintering process, dust is collected from the flue gas in the sintering front section to obtain sintering dust, and dust is collected from the flue gas in the sintering back section to obtain high bismuth dust.

[0046] In another preferred embodiment of the present invention, the bismuth-containing material includes, but is not limited to, bismuth-containing dust and / or bismuth-containing waste mineral powder.

[0047] In another preferred embodiment of the present invention, the bismuth content in the bismuth-containing material is 1~5000 g / t.

[0048] In another preferred embodiment of the present invention, the high-chlorine material includes, but is not limited to, chloride or chloride-containing dust (e.g., sintering machine head ash after water washing to remove potassium and sodium, or other chlorine-containing materials that can decompose to produce hydrogen chloride gas at high sintering temperatures).

[0049] In another preferred embodiment of the present invention, the high-chlorine material is one or more of calcium chloride, magnesium chloride, sodium chloride, and potassium chloride.

[0050] In another preferred embodiment of the present invention, the mass content of chlorine in the high-chlorine material is not less than 1%.

[0051] In another preferred embodiment of the present invention, the reducing agent is a carbonaceous reducing agent.

[0052] In another preferred embodiment of the present invention, the reducing agent is one or more of carbon powder, coke powder, and coal powder.

[0053] In another preferred embodiment of the present invention, the mixing mass ratio of bismuth-containing material, high-chlorine material, and reducing agent is 50~80:30~15:20~5.

[0054] In another preferred embodiment of the present invention, the mixing mass ratio of bismuth-containing material, high-chlorine material, and reducing agent is 60~70:25~20:15~10.

[0055] In another preferred embodiment of the invention, water is added during the granulation process in step 1).

[0056] In another preferred embodiment of the present invention, the amount of water added is such that the moisture content of the bismuth-containing granules is 2-10% by mass.

[0057] In another preferred embodiment of the present invention, the particle size of the bismuth-containing granules is 1~15 mm.

[0058] In another preferred embodiment of the present invention, the particle size of the bismuth-containing granules is 3-8 mm.

[0059] In another preferred embodiment of the present invention, the mixing mass ratio of bismuth-containing granules to conventional sintering material in the bismuth-containing mixture is 5~50:95~50.

[0060] In another preferred embodiment of the present invention, the mixing mass ratio of bismuth-containing granules to conventional sintering material in the bismuth-containing mixture is 10~30:90~70.

[0061] In another preferred embodiment of the present invention, the conventional sintering material includes iron-containing raw materials (including iron-containing dust or mineral powder, etc.), flux (including limestone, dolomite, silica, fluorite, etc.), fuel (including coke powder, coal powder, carbon powder, etc.) and water.

[0062] In another preferred embodiment of the present invention, the mixing mass ratio of iron-containing raw materials, flux, fuel, and water is 60~90:5~20:2~10:2~10. The particle size of the conventional sintered material is 4~25mm.

[0063] In another preferred embodiment of the present invention, the particle size of the conventional sintering material is 6~20mm.

[0064] In another preferred embodiment of the present invention, the thickness of the base material layer is 70~100mm.

[0065] In another preferred embodiment of the present invention, the thickness of the base material layer is 80~90mm.

[0066] In another preferred embodiment of the present invention, the thickness of the bismuth-containing mixture layer is 20~300mm.

[0067] In another preferred embodiment of the present invention, the thickness of the bismuth-containing mixture layer is 100~200mm.

[0068] In another preferred embodiment of the present invention, the thickness of the conventional sintering material layer is 600~1000mm.

[0069] In another preferred embodiment of the present invention, the thickness of the conventional sintering material layer is 700~1000mm.

[0070] In another preferred embodiment of the present invention, the sintering rear section air box is the 1st to 10th air box at the tail of the sintering machine, and the remaining air boxes are the sintering front section air boxes.

[0071] In another preferred embodiment of the present invention, the sintering rear section air box is the first to eighth air box at the tail of the sintering machine, and the remaining air boxes are the sintering front section air boxes.

[0072] In another preferred embodiment of the present invention, the sintering rear section air box is the first to fourth air box at the tail of the sintering machine, and the remaining air boxes are the sintering front section air boxes.

[0073] In another preferred embodiment of the present invention, the bismuth content in the obtained high-bismuth flue dust is 0.5-20% by mass.

[0074] In another preferred embodiment of the present invention, the obtained sintering dust is washed and desalted and then used as a raw material for bismuth-containing granules or as a raw material for conventional sintering materials.

[0075] In another preferred embodiment of the present invention, the sintering temperature is 1000~1200℃, and the sintering time is 0.5~10h.

[0076] In another preferred embodiment of the present invention, the sintering temperature is 1050~1150℃, and the sintering time is 1~5h.

[0077] Example 1

[0078] Bismuth-containing materials (solid waste with a bismuth content of approximately 46.2 g / t collected from steel plants), high-chlorine materials (washed machine head ash), and reducing agent (coke powder) were mixed at a mass ratio of 60:25:15 to obtain a granulation mixture. The granulation mixture was added to a disc granulator and water was added for granulation to obtain bismuth-containing granules with an average particle size of approximately 2 mm (moisture content of approximately 7.5 wt%). Iron-containing raw materials, limestone, dolomite, quicklime, fuel (coke powder), and water were added to a pelletizer at a mass ratio of 77.9:4.1:2.7:4.6:3.3:7.4 to mix and pelletize, resulting in conventional sintered material with an average particle size of approximately 4.5 mm.

[0079] Bismuth-containing granules were mixed with a portion of conventional sintering material at a mass ratio of 20:80 to obtain a bismuth-containing mixture. An 80mm layer of base material was first laid in the sintering machine trolley, followed by a 150mm layer of the bismuth-containing mixture on top of the base material, and then a 750mm layer of conventional sintering material on top of the bismuth-containing mixture. Finally, sintering was performed (sintering temperature: 1350℃). During sintering, dust was collected from the flue gas in the first sintering wind boxes (the 1st to the 4th from the bottom) to obtain sintering dust (bismuth content approximately 27.5g / t), and dust was collected from the flue gas in the second sintering wind boxes (the 1st to the 3rd from the bottom) to obtain high-bismuth dust (bismuth content approximately 23427.3g / t). Testing showed that the bismuth removal rate in the bismuth-containing material was approximately 88.2%.

[0080] Example 2

[0081] Bismuth-containing materials (solid waste with a bismuth content of approximately 46.2 g / t collected from steel plants), high-chlorine materials (washed machine head ash), and reducing agent (coke powder) were mixed at a mass ratio of 60:25:15 to obtain a granulation mixture. The granulation mixture was added to a disc granulator and water was added for granulation to obtain bismuth-containing granules with an average particle size of approximately 5 mm (moisture content of approximately 7.5 wt%). Iron-containing raw materials, limestone, dolomite, quicklime, fuel (coke powder), and water were added to a pelletizer at a mass ratio of 77.9:4.1:2.7:4.6:3.3:7.4 to mix and pelletize, resulting in conventional sintered material with an average particle size of approximately 4.5 mm.

[0082] Bismuth-containing granules were mixed with a portion of conventional sintering material at a mass ratio of 12:88 to obtain a bismuth-containing mixture. An 80mm layer of base material was first laid in the sintering machine trolley, followed by a 250mm layer of the bismuth-containing mixture on top of the base material, and then a 650mm layer of conventional sintering material on top of the bismuth-containing mixture. Finally, sintering was performed (sintering temperature: 1350℃). During sintering, dust was collected from the flue gas in the first sintering wind boxes (the 1st to the 6th from the bottom) to obtain sintering dust (bismuth content approximately 32.6 g / t), and dust was collected from the flue gas in the second sintering wind boxes (the 1st to the 5th from the bottom) to obtain high-bismuth dust (bismuth content approximately 14247.3 g / t). Testing showed that the bismuth removal rate in the bismuth-containing material was approximately 89.4%.

[0083] Example 3

[0084] Bismuth-containing materials (solid waste with a bismuth content of approximately 46.2 g / t collected from steel plants), high-chlorine materials (washed machine head ash), and reducing agent (coke powder) were mixed at a mass ratio of 60:25:15 to obtain a granulation mixture. The granulation mixture was added to a disc granulator and water was added for granulation to obtain bismuth-containing granules with an average particle size of approximately 5 mm (moisture content of approximately 7.5 wt%). Iron-containing raw materials, limestone, dolomite, quicklime, fuel (coke powder), and water were added to a pelletizer at a mass ratio of 77.9:4.1:2.7:4.6:3.3:7.4 to mix and pelletize, resulting in conventional sintered material with an average particle size of approximately 4.5 mm.

[0085] Bismuth-containing granules were mixed with a portion of conventional sintering material at a mass ratio of 20:80 to obtain a bismuth-containing mixture. An 80mm layer of base material was first laid in the sintering machine trolley, followed by a 150mm layer of the bismuth-containing mixture on top of the base material, and then a 750mm layer of conventional sintering material on top of the bismuth-containing mixture. Finally, sintering was performed (sintering temperature: 1350℃). During sintering, dust was collected from the flue gas in the first sintering fan (the 1st to the 4th from the bottom) to obtain sintering dust (bismuth content approximately 23.4 g / t), and dust was collected from the flue gas in the second sintering fan (the 1st to the 3rd from the bottom) to obtain high-bismuth dust (bismuth content approximately 24569.4 g / t). Testing showed that the bismuth removal rate in the bismuth-containing material was approximately 92.5%.

[0086] Example 4

[0087] Bismuth-containing materials (solid waste with a bismuth content of approximately 46.2 g / t collected from steel plants), high-chlorine materials (washed machine head ash), and reducing agent (coke powder) were mixed at a mass ratio of 60:25:15 to obtain a granulation mixture. The granulation mixture was added to a disc granulator and water was added for granulation to obtain bismuth-containing granules with an average particle size of approximately 5 mm (moisture content of approximately 7.5 wt%). Iron-containing raw materials, limestone, dolomite, quicklime, fuel (coke powder), and water were added to a pelletizer at a mass ratio of 77.9:4.1:2.7:4.6:3.3:7.4 to mix and pelletize, resulting in conventional sintered material with an average particle size of approximately 4.5 mm.

[0088] Bismuth-containing granules were mixed with a portion of conventional sintering material at a mass ratio of 30:70 to obtain a bismuth-containing mixture. An 80mm layer of base material was first laid in the sintering machine trolley, followed by a 150mm layer of the bismuth-containing mixture on top of the base material, and then a 750mm layer of conventional sintering material on top of the bismuth-containing mixture. Finally, sintering was performed (sintering temperature: 1350℃). During sintering, dust was collected from the flue gas in the first sintering fan (the 1st to the 4th from the bottom) to obtain sintering dust (bismuth content approximately 28.2 g / t), and dust was collected from the flue gas in the second sintering fan (the 1st to the 3rd from the bottom) to obtain high-bismuth dust (bismuth content approximately 34901.0 g / t). Testing showed that the bismuth removal rate in the bismuth-containing material was approximately 87.6%.

[0089] Example 5

[0090] Bismuth-containing materials (solid waste with a bismuth content of approximately 46.2 g / t collected from steel plants), high-chlorine materials (washed machine head ash), and reducing agent (coke powder) were mixed at a mass ratio of 60:25:15 to obtain a granulation mixture. The granulation mixture was added to a disc granulator and water was added for granulation to obtain bismuth-containing granules with an average particle size of approximately 5 mm (moisture content of approximately 7.5 wt%). Iron-containing raw materials, limestone, dolomite, quicklime, fuel (coke powder), and water were added to a pelletizer at a mass ratio of 77.9:4.1:2.7:4.6:3.3:7.4 to mix and pelletize, resulting in conventional sintered material with an average particle size of approximately 4.5 mm.

[0091] Bismuth-containing granules were mixed with a portion of conventional sintering material at a mass ratio of 5:95 to obtain a bismuth-containing mixture. An 80mm layer of base material was first laid in the sintering machine trolley, followed by a 150mm layer of the bismuth-containing mixture on top of the base material, and then a 750mm layer of conventional sintering material on top of the bismuth-containing mixture. Finally, sintering was performed (sintering temperature: 1350℃). During sintering, dust was collected from the flue gas in the first sintering fan (the fourth fan from the bottom) to obtain sintering dust (bismuth content approximately 29.1g / t), and dust was collected from the flue gas in the second sintering fan (the third fan from the bottom) to obtain high-bismuth dust (bismuth content approximately 5744.5g / t). Testing showed that the bismuth removal rate in the bismuth-containing material was approximately 86.5%.

[0092] Comparative Example 1

[0093] Bismuth-containing material (solid waste with a bismuth content of approximately 46.2 g / t collected from steel plants) was mixed with iron ore at a mass ratio of 4:96 to form an iron-containing raw material. The iron-containing raw material, limestone, dolomite, quicklime, fuel (coke powder), and water were added to a pelletizer at a mass ratio of 77.9:4.1:2.7:4.6:3.3:7.4 to mix and pelletize, resulting in sintered material with an average particle size of approximately 4.5 mm.

[0094] Then, an 80mm layer of base material is laid in the sintering machine trolley, followed by a 900mm layer of sintering material, and finally sintering is performed (sintering temperature is 1350℃). During the sintering process, dust from all the flue gas in the sintering machine's air boxes is collected to obtain sintering dust (bismuth content approximately 230.2g / t). After testing, the bismuth removal rate in the bismuth-containing material is approximately 5.2%.

[0095] Comparative Example 2

[0096] Bismuth-containing materials (solid waste with a bismuth content of approximately 46.2 g / t collected from steel plants), high-chlorine materials (washed machine head ash), and reducing agent (coke powder) were mixed at a mass ratio of 60:25:15 to obtain a granulation mixture. The granulation mixture was added to a disc granulator and water was added for granulation to obtain bismuth-containing granules with an average particle size of approximately 5 mm (moisture content of approximately 7.5 wt%). Iron-containing raw materials, limestone, dolomite, quicklime, fuel (coke powder), and water were added to a pelletizer at a mass ratio of 77.9:4.1:2.7:4.6:3.3:7.4 to mix and pelletize, resulting in conventional sintered material with an average particle size of approximately 4.5 mm.

[0097] Bismuth-containing granules were mixed with a portion of conventional sintering material at a mass ratio of 3.3:96.7 to obtain a bismuth-containing mixture. An 80mm layer of base material was first laid in the sintering machine trolley, followed by a 900mm layer of the bismuth-containing mixture on top of the base material layer. Finally, sintering was performed (sintering temperature: 1350℃). During the sintering process, dust was collected from all the flue gas in the sintering machine's air boxes to obtain sintering dust (bismuth content approximately 456.0 g / t). Testing showed that the bismuth removal rate from the bismuth-containing material was approximately 10.3%.

[0098] Comparative Example 3

[0099] Bismuth-containing materials (solid waste with a bismuth content of approximately 46.2 g / t collected from steel plants), high-chlorine materials (washed machine head ash), and reducing agent (coke powder) were mixed at a mass ratio of 60:25:15 to obtain a granulation mixture. The granulation mixture was added to a disc granulator and water was added for granulation to obtain bismuth-containing granules with an average particle size of approximately 5 mm (moisture content of approximately 7.5 wt%). Iron-containing raw materials, limestone, dolomite, quicklime, fuel (coke powder), and water were added to a pelletizer at a mass ratio of 77.9:4.1:2.7:4.6:3.3:7.4 to mix and pelletize, resulting in conventional sintered material with an average particle size of approximately 4.5 mm.

[0100] Bismuth-containing granules were mixed with a portion of conventional sintering material at a mass ratio of 20:80 to obtain a bismuth-containing mixture. An 80mm layer of base material was first laid in the sintering machine trolley, followed by a 750mm layer of conventional sintering material on top of the base material, and then a 150mm layer of the bismuth-containing mixture on top of the conventional sintering material. Finally, sintering was performed (sintering temperature: 1350℃). During the sintering process, dust was collected from the flue gas in the first four sintering boxes to obtain high-bismuth flue gas (bismuth content approximately 6135.7 g / t), and dust was collected from the flue gas in the last sintering boxes (fifth to penultimate sintering boxes) to obtain sintering flue gas (bismuth content approximately 38.1 g / t). Testing showed that the bismuth removal rate in the bismuth-containing material was approximately 23.1%.

[0101] Comparative Example 4

[0102] Bismuth-containing materials (solid waste with a bismuth content of approximately 46.2 g / t collected from steel plants) and reducing agent (coke powder) were mixed at a mass ratio of 85:15 to obtain a granulation mixture. The granulation mixture was added to a disc granulator and water was added for granulation to obtain bismuth-containing granules with an average particle size of approximately 5 mm (moisture content of approximately 7.5 wt%). Iron-containing raw materials, limestone, dolomite, quicklime, fuel (coke powder), and water were added to a pelletizer at a mass ratio of 77.9:4.1:2.7:4.6:3.3:7.4 to mix and pelletize, resulting in conventional sintered material with an average particle size of approximately 4.5 mm.

[0103] Bismuth-containing granules were mixed with a portion of conventional sintering material at a mass ratio of 20:80 to obtain a bismuth-containing mixture. An 80mm layer of base material was first laid in the sintering machine trolley, followed by a 150mm layer of the bismuth-containing mixture on top of the base material, and then a 750mm layer of conventional sintering material on top of the bismuth-containing mixture. Finally, sintering was performed (sintering temperature: 1350℃). During sintering, dust was collected from the flue gas in the first sintering fan (the 1st to the 4th from the bottom) to obtain sintering dust (bismuth content approximately 27.6 g / t), and dust was collected from the flue gas in the second sintering fan (the 1st to the 3rd from the bottom) to obtain high-bismuth dust (bismuth content approximately 4303.0 g / t). Testing showed that the bismuth removal rate in the bismuth-containing material was approximately 16.2%.

[0104] Comparative Example 5

[0105] Bismuth-containing materials (solid waste with a bismuth content of approximately 46.2 g / t collected from steel plants) and high-chlorine materials (washing machine head ash) were mixed at a mass ratio of 75:25 to obtain a granulation mixture. The granulation mixture was then added to a disc granulator with water for granulation to obtain bismuth-containing granules with an average particle size of approximately 5 mm (moisture content of approximately 7.5 wt%). Iron-containing raw materials, limestone, dolomite, quicklime, fuel (coke powder), and water were added to a pelletizer at a mass ratio of 77.9:4.1:2.7:4.6:3.3:7.4 to mix and pelletize, resulting in conventional sintered material with an average particle size of approximately 4.5 mm.

[0106] Bismuth-containing granules were mixed with a portion of conventional sintering material at a mass ratio of 20:80 to obtain a bismuth-containing mixture. An 80mm layer of base material was first laid in the sintering machine trolley, followed by a 150mm layer of the bismuth-containing mixture on top of the base material, and then a 750mm layer of conventional sintering material on top of the bismuth-containing mixture. Finally, sintering was performed (sintering temperature: 1350℃). During sintering, dust was collected from the flue gas in the first sintering wind boxes (the 1st to the 4th from the bottom) to obtain sintering dust (bismuth content approximately 35.4g / t), and dust was collected from the flue gas in the second sintering wind boxes (the 1st to the 3rd from the bottom) to obtain high-bismuth dust (bismuth content approximately 9349.7g / t). Testing showed that the bismuth removal rate in the bismuth-containing material was approximately 35.2%.

[0107] Comparative Example 6

[0108] Bismuth-containing materials (solid waste with a bismuth content of approximately 46.2 g / t collected from steel plants), high-chlorine materials (washed machine head ash), and reducing agent (coke powder) were mixed at a mass ratio of 60:25:15 to obtain a granulation mixture. The granulation mixture was added to a disc granulator and water was added for granulation to obtain bismuth-containing granules with an average particle size of approximately 5 mm (moisture content of approximately 7.5 wt%). Iron-containing raw materials, limestone, dolomite, quicklime, fuel (coke powder), and water were added to a pelletizer at a mass ratio of 77.9:4.1:2.7:4.6:3.3:7.4 to mix and pelletize, resulting in conventional sintered material with an average particle size of approximately 4.5 mm.

[0109] In the sintering machine trolley, an 80mm layer of base material is first laid, followed by a 30mm layer of bismuth-containing granules on top of the base material layer. Then, an 870mm layer of conventional sintering material is laid on top of the bismuth-containing granules layer, and finally, sintering is performed (sintering temperature: 1350℃). During the sintering process, dust from the flue gas in the first-stage sintering wind boxes (the 1st to the 4th from the bottom) is collected to obtain sintering dust (bismuth content approximately 31.4g / t), and dust from the flue gas in the second-stage sintering wind boxes (the 1st to the 3rd from the bottom) is collected to obtain high-bismuth dust (bismuth content approximately 9596.0g / t). Testing shows that the bismuth removal rate in the bismuth-containing material is approximately 36.2%.

Claims

1. A sintering method for controlled migration of bismuth element, characterized in that: The sintering method includes the following steps: 1) Bismuth-containing materials, high-chlorine materials, and reducing agents are mixed and granulated to obtain bismuth-containing granules; 2) Bismuth-containing granules are mixed with some conventional sintering materials to obtain a bismuth-containing mixture; 3) The bismuth-containing mixture is laid between the base material and the conventional sintering layer and then sintered. 4) During the sintering process, dust is collected from the flue gas in the blast box before sintering to obtain sintering dust, and dust is collected from the flue gas in the blast box after sintering to obtain high bismuth dust.

2. The sintering method according to claim 1, characterized in that: The bismuth-containing materials include, but are not limited to, bismuth-containing dust and / or bismuth-containing waste ore powder; preferably, the bismuth content in the bismuth-containing materials is not higher than 5000 g / t.

3. The sintering method according to claim 1 or 2, characterized in that: The high-chlorinated material includes, but is not limited to, chlorides or chloride-containing dust, preferably one or more of calcium chloride, magnesium chloride, sodium chloride, and potassium chloride; preferably, the mass content of chlorine in the high-chlorinated material is not less than 1%.

4. The sintering method according to any one of claims 1-3, characterized in that: The reducing agent is a carbonaceous reducing agent, preferably one or more of carbon powder, coke powder, and coal powder; Preferably, the mass ratio of bismuth-containing material, high-chlorine material, and reducing agent is 50~80:30~15:20~5, and more preferably 60~70:25~20:15~10.

5. The sintering method according to any one of claims 1-4, characterized in that: Water is also added during the granulation process in step 1); preferably, the amount of water added is such that the moisture content of the bismuth-containing granules is 2-10% by mass. Preferably, the particle size of the bismuth-containing granules is 1~15mm, and more preferably 3~8mm.

6. The sintering method according to any one of claims 1-5, characterized in that: In the bismuth-containing mixture, the mixing mass ratio of bismuth-containing granules to conventional sinter is 5~50:95~50, preferably 10~30:90~70; Preferably, the conventional sintering material includes iron-containing raw materials, flux, fuel and water; preferably, the mixing mass ratio of iron-containing raw materials, flux, fuel and water is 60~90:5~20:2~10:2~10; the particle size of the conventional sintering material is 4~25mm, preferably 6~20mm.

7. The sintering method according to any one of claims 1-6, characterized in that: The thickness of the base material layer is 70-100mm, preferably 80-90mm; and / or The thickness of the bismuth-containing mixture layer is 20-300 mm, preferably 100-200 mm; and / or The thickness of the conventional sintering material layer is 600~1000mm, preferably 700~1000mm.

8. The sintering method according to any one of claims 1-7, characterized in that: The sintering rear section air box is the 1st to 10th air box at the tail of the sintering machine, preferably the 1st to 8th air box, and more preferably the 1st to 4th air box; the remaining air boxes are the sintering front section air boxes.

9. The sintering method according to any one of claims 1-8, characterized in that: The bismuth content in the obtained high-bismuth flue dust is 0.5%~20% by mass; Preferably, the obtained sintering dust is washed and desalted before being used as a raw material for bismuth-containing granules or as a raw material for conventional sintering materials.

10. The sintering method according to any one of claims 1-8, characterized in that: The sintering temperature is 1000~1200℃, preferably 1050~1150℃; the sintering time is 0.5~10h, preferably 1~5h.

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