A method for treating steel dust sludge by sintering process and regulating migration of valuable metals

Abstract

This invention relates to the technical field of solid waste treatment, specifically disclosing a method for treating steel dust and sludge and controlling the migration of valuable metals through a sintering process. The method involves producing carbon-core dust sludge pellets with superior pelletizing properties through a graded coupling of sintering fuel and layered pelletizing of steel dust and sludge. These carbon-core dust sludge pellets are then used as an intermediate layer between the sintering mixture and the base material during sintering, thereby facilitating the rapid reduction of elements such as Zn, Pb, K, Na, In, Ge, and Tl, which migrate from the solid phase into the gas phase. Furthermore, targeted oxygen supplementation at the sintering endpoint in the bellows further enhances the purity and recovery efficiency of the oxides of each element. The method of this invention features a simple process flow, is easy to operate, has high efficiency in treating fine particulate fuel and steel dust and sludge, exhibits excellent treatment results, and is suitable for large-scale promotion and application.

Description

Technical Field

[0001] This invention relates to the treatment of steel dust and fine sintered fuel, specifically to a method for treating steel dust and controlling the migration of valuable metals through a sintering process, belonging to the technical field of synergistic treatment of steel dust and fine sintered fuel. Background Technology

[0002] During the operation of long-process ironmaking, a large amount of dust and sludge is collected through electrostatic precipitators, gravity dust collectors, bag filters, and wet scrubbers. This includes sintering machine head ash, blast furnace bag filter ash, and converter ash, accounting for approximately 10% of steel production. The main components are a mixture of metal oxides (primarily Fe), flux, and coke powder, as well as small amounts of harmful impurities such as Pb, Zn, K, and Na. In some stages, the dust particles may also contain precious and rare metals such as silver (Ag), indium (In), germanium (Ge), and thallium (Tl). Currently, the mainstream method for disposing of steel dust and sludge is to directly return it to the sintering process for recycling. However, this method can lead to problems such as deteriorating sintering granulation, affecting the stability of sintering production conditions, and increasing the content of harmful elements in the sintered ore. Furthermore, there is no special treatment for rare and precious metals. The recycling of Pb, K, Na, and other rare and precious metals with the dust and sludge in the sintering process causes these elements to accumulate continuously during production, resulting in a low level of comprehensive utilization of the dust and sludge. For example, CN109055731A proposes a dust granulation process and an iron ore sintering process. The dust granulation process uses a dust pelletizing method to form larger-sized green dust pellets from the dust generated during the blast furnace and sintering process. These green dust pellets are then combined with the mixed ore in existing sintering processes for sintering. The skeletal effect of the green dust pellets improves the permeability of the sintering bed. In existing technologies, the migration of both valuable and harmful metals is random, making it impossible to effectively control valuable metal elements and achieve efficient enrichment of rare and precious metal elements and targeted separation of harmful elements.

[0003] On the other hand, because both excessively coarse and excessively fine particle sizes of sintered solid fuels lead to low sintering utilization efficiency and high energy consumption in sintering production, the reasonable particle size range for sintered solid fuels is generally 0.5mm to 3mm to ensure sintering effectiveness. However, during the processing and crushing of sintered fuels, fine-grained fuel particles smaller than 0.5mm are inevitably generated, and the more times the crushing is performed, the higher the content of fine-grained fuel particles becomes. Production practice has shown that the content of particles <0.5mm in sintered fuels after crushing reaches approximately 20%. Introducing a fuel screening system is an effective way to solve the problem of excessive fine-grained fuel content in sintered fuels, and many implementation schemes already exist. However, given the special requirements for fuel particle size and combustion properties in various processes of blast furnace ironmaking, how to utilize the -0.5mm fine-grained fuel particles generated by sintered fuel screening has become a new challenge. Patent application CN104313313A proposes a method for pre-granulating fine particulate fuel for iron ore sintering. This method involves collecting particulate fuel with a particle size of -0.5 mm through a graded sieve, adding a binder, mixing, and then using a pelletizer to prepare fine particulate fuel with a particle size >0.5 mm. This is then mixed with 0.5 mm to 3 mm particulate fuel and returned to the sintering batching process, thus solving the problem of excessively fine particle size in the sintered fuel. Although this method achieves artificial granulation of fine particulate fuel, its relatively low strength means that it is still prone to breakage and pulverization at various stages such as subsequent sintering batching, mixing, secondary granulation, and material distribution. Therefore, it cannot completely eliminate the negative impact on sintering.

[0004] To address the challenges of fine-particle fuel pulverization and disordered migration of metal elements, there is an urgent need to develop composite pelleting technology that combines high mechanical strength with functional controllability to enhance the migration control and subsequent utilization of valuable elements. Summary of the Invention

[0005] To address the problem of poor utilization efficiency in existing technologies where steel dust and fine fuel are independently returned to the sintering process, this invention provides a method for treating steel dust and controlling the migration of valuable metals through sintering. This method involves graded coupling of sintering fuel with layered pelletizing of steel dust to produce carbon-core dust pellets with superior pelletizing properties. These carbon-core dust pellets are then used as an intermediate layer between the sintering mixture and the base material during sintering, thereby facilitating the rapid reduction and controlled migration of elements such as Zn, Pb, K, Na, In, Ge, and Tl. Furthermore, targeted oxygen supplementation at the sintering endpoint in the bellows further enhances the purity and recovery efficiency of oxides of various elements. The carbon-core dust pellets, with graded fine fuel as the core and an outer layer of steel dust and binder mixture, are formed through multi-stage grinding and pelletizing to create composite particles with a gradient structure, significantly improving their mechanical strength and thermal stability. This method not only solves the problem of fine fuel pulverization but also achieves gradient separation and directional enrichment of valuable metals in the steel dust, improving the permeability and combustion efficiency of the sintering layer.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A method for treating steel dust and controlling the migration of valuable metals through a sintering process, the method comprising the following steps: 1) The sintering fuel is sorted into coarse fuel, fine fuel and particulate fuel; 2) The coarse fuel particles are mixed with the sintering raw materials and granulated (i.e., conventional mixing and granulation in the sintering process) to obtain the sintered mixture; 3) Fine fuel particles are mixed with molding aids and molded to obtain molded fuel pellets; 4) First, the particulate fuel and steel dust are mixed and ground to obtain carbon-containing dust powder. Then, the carbon-containing dust powder is mixed with shaped fuel particles to form pellets, resulting in carbon-core dust pellets. 5) The base material, carbon core dust balls, and sintering mixture are laid sequentially from bottom to top on the sintering trolley, and then sintered to obtain sintered ore. During the sintering process, oxygen-containing gas is injected into the wind box at the sintering endpoint, and the dust in the flue gas from that part of the wind box is collected to obtain element-rich dust.

[0007] Preferably, in step 1), the sintering fuel is a solid carbonaceous fuel. The coarse-particle fuel has a particle size greater than 0.5 mm. The fine-particle fuel has a particle size of 0.1–0.5 mm. The particulate fuel has a particle size less than 0.1 mm.

[0008] Preferably, in step 2), the sintering raw materials include iron-containing raw materials, flux, and water. More preferably, the mixing mass ratio of iron-containing raw materials, flux, and water is 76.0~82.0:10.0~15.5:7.0~9.0.

[0009] Preferably, the iron-containing raw material includes iron-containing ore powder and / or iron-containing solid waste. The flux includes one or more of limestone, dolomite, serpentine, and quicklime.

[0010] Preferably, in step 2), the mass ratio of coarse fuel to sintering raw material is 3.0~4.5:95.5-97.0.

[0011] Preferably, in step 2), the average particle size of the sintered mixture is not greater than 12 mm, and more preferably 4 to 12 mm.

[0012] Preferably, in step 3), the molding aid is an organic binder, and more preferably, the organic binder is a starch aqueous solution with a mass concentration of 30% to 70%.

[0013] Preferably, in step 3), the amount of molding aid is 1% to 10% of the total mass of the fine particulate fuel, preferably 2% to 6%.

[0014] Preferably, in step 3), the particle size of the formed fuel particles is 2-6 mm, more preferably 3-5 mm.

[0015] Preferably, in step 4), the steel dust includes one or more of the following: sintering machine head ash, blast furnace bag filter ash, converter ash, and electric field dust collector ash.

[0016] Preferably, in step 4), the mixing mass ratio of particulate fuel to steel dust is 5~15:85~95.

[0017] Preferably, in step 4), the grinding process specifically involves mixing particulate fuel and steel dust and then grinding them until the mass percentage of particles smaller than 0.075 mm is not less than 80%, preferably not less than 85%.

[0018] Preferably, in step 4), the pelletizing process specifically involves adding carbon-containing dust and sludge micropowder and shaped fuel particles to a pelletizing machine at a mass ratio of 55-75:25-45, and spraying an atomized liquid medium during the pelletizing process. Preferably, the liquid medium includes one or more of water, starch solution, and plant sludge (generally sludge generated by wet dust removal). The particle size of the carbon core dust and sludge pellets is 8-12 mm.

[0019] Preferably, in step 5), the thickness of the base material layer is 70-100 mm, and more preferably 80-90 mm.

[0020] Preferably, in step 5), the thickness of the carbon core dust pellet layer is 20-60 mm, more preferably 30-50 mm.

[0021] Preferably, in step 5), the thickness of the sintering mixture layer is 600-1000 mm, more preferably 700-900 mm.

[0022] Preferably, the base material is recycled ore and / or natural lump ore.

[0023] Preferably, in step 5), the sintering endpoint wind box is the 1st to 10th wind box at the tail of the sintering machine (and the 1st to 10th wind box from the bottom of the sintering machine according to the direction of the sintering material), preferably the 1st to 8th wind box at the tail of the sintering machine (and the 1st to 8th wind box from the bottom of the sintering machine according to the direction of the sintering material), and more preferably the 1st to 5th wind box at the tail of the sintering machine (and the 1st to 5th wind box from the bottom of the sintering machine according to the direction of the sintering material).

[0024] Preferably, in step 5), the amount of oxygen-containing gas injected is such that the oxygen mass concentration in the bellows is not less than 300 mg / L, preferably not less than 310 mg / L.

[0025] Preferably, in step 5), the oxygen-containing gas is injected into the upper part of the inner cavity of the bellows.

[0026] Preferably, the oxygen-containing gas is preheated before injection so that the temperature difference between it and the flue gas in the blower is no more than 100°C.

[0027] This invention demonstrates that in the current research and development of harmful element removal technologies for steel dust, the resource-based removal of Zn has received considerable attention. However, since Zn compounds undergo rapid reduction reactions at 800℃~900℃, the removal of Zn through carbon reduction of zinc compounds has reached a relatively high level. This involves preparing zinc-containing steel dust into carbon-coated microspheres and placing them in a sintering layer for sintering, which can achieve Zn removal to a certain extent. However, the significant reduction reactions of Pb, K, Na, In, and Ge compounds generally require temperatures reaching 1200℃~1400℃, thus demanding a higher redox atmosphere. Conventional sintering processes struggle to provide such a sustained high-temperature environment and reducing atmosphere. Tl compounds can be carbon-reduced above 600℃, but require a specific reaction environment. Furthermore, the precious metal Ag in steel dust typically exists as chlorides or hypochlorous acid compounds that volatilize at high temperatures. During sintering, these compounds volatilize layer by layer into the sintering flue gas as the combustion zone moves downwards, resulting in inefficient utilization. In this invention, steel dust and fine particulate fuel are granulated into carbon core dust pellets using a special granulation method and then used as the intermediate material layer for sintering. When the sintering combustion zone moves to the carbon core dust pellet layer and the temperature of the material layer reaches above 900°C, the outer layer of the carbon core dust pellets begins to undergo a Zn reduction and removal reaction. As the combustion zone moves further down, the temperature of the carbon core dust pellet layer increases further, the outer layer of the pellets begins to melt, and the internal fuel particles (i.e., carbon cores) begin to ignite and release heat intensely. This significantly increases the combustion zone temperature from the highest temperature of no more than 1350°C in conventional processes to above 1400°C, thereby reaching the temperature range where compounds such as Pb, K, Na, In, Ge, and Tl are efficiently reduced, and a reduction and removal reaction begins. Meanwhile, the presence of fuel particles in the core of the small spheres and the fuel powder in the outer layer of the double-layer structure creates a strong reducing atmosphere in the local area of ​​the material layer, which promotes the rapid reduction of elements such as Zn, Pb, K, Na, In, Ge, and Tl. Ultimately, these elements are removed in the form of gaseous elements and enter the high-temperature sintering flue gas.

[0028] Furthermore, when the high-temperature sintering flue gas rich in the aforementioned gaseous elements leaves the high-temperature zone and enters the blower box, oxygen is promptly added to the flue gas to increase the oxygen concentration from ≤200mg / L to ≥300mg / L. This efficiently promotes the rapid conversion of gaseous elements such as Zn, Pb, K, Na, In, Ge, and Tl into oxides, preventing the formation of cyanides (such as KCN and NaCN) or chlorides from the aforementioned elements or some of them with components such as CO, N2, and Cl in the flue gas. This ensures the purity of the oxides of each element in the subsequent dust collection products and improves the element recovery rate. The high-temperature flue gas after oxidation can be filtered by a cloth dust collector equipped with a separate auxiliary fan to remove dust particles rich in the aforementioned valuable element compounds, obtaining raw materials for non-ferrous metallurgy. At the same time, the high-temperature flue gas after filtration is transported back to the middle section of the sintering main flue to avoid the high-temperature flue gas being drawn out separately, which would cause the flue gas temperature in the front section of the sintering main flue to be too low, resulting in condensation and affecting the subsequent flue gas purification process. This recycling strategy not only effectively recovers various valuable elements such as Zn, Pb, K, Na, In, Ge, and Tl, but also significantly improves the thermal energy utilization rate of the sintering system.

[0029] In this invention, sintering fuels are classified into three grades according to their specifications: greater than 0.5 mm (maximum not exceeding 3 mm), 0.1–0.5 mm, and less than 0.1 mm, namely coarse-grained fuel, fine-grained fuel, and particulate fuel. Among them, coarse-grained fuel has a larger particle size and higher strength, and can be directly used as fuel for conventional sintering feedstock. However, fine-grained fuel and particulate fuel have relatively smaller particle sizes, and their direct use as fuel for sintering feedstock is not conducive to the normal operation of sintering. In order to realize the utilization of fine-grained fuel and particulate fuel, the fine-grained fuel is first mixed with a molding aid and rolled into small particles (i.e., molded fuel particles) as the core. At the same time, the particulate fuel is mixed with steel dust and sludge and finely ground to obtain micro powder, which is used as the adhesive layer. After being pelletized by a disc, a double-layer structure pellet (i.e., carbon core dust and sludge pellet) is formed with the molded fuel as the core and the carbon-containing dust and sludge micro powder as the outer layer. In the subsequent sintering process, the carbon core dust and sludge pellet is placed between the sintering mix layer and the base layer. The resulting carbon core dust pellets do not need to participate in the batching, mixing, and secondary granulation processes of sintering, thus avoiding the problem of secondary processing and breakage. Furthermore, during the sintering process, the carbon dust pellet layer will not react when the upper sintering mixture layer is sintered, but it can improve the air permeability of the entire sintering layer.

[0030] The process of this invention is carried out in steps, including: First, sorting and classifying the sintering fuel (maximum particle size not exceeding 3 mm) to obtain coarse fuel with a particle size of 0.5 mm or more, fine fuel with a particle size of 0.1 mm to 0.5 mm, and particulate fuel with a particle size of less than 0.1 mm. Second, mixing the coarse fuel with a particle size of 0.5 mm or more with sintering raw materials such as iron-containing raw materials and flux according to the conventional sintering process ratio, and then processing it through cylindrical mixing, granulation, and other processes to finally obtain a sintered mixture. Third, adding a molding aid to the fine fuel with a particle size of 0.1 mm to 0.5 mm and then rolling it to obtain shaped fuel pellets. The molding aid is an aqueous solution of an organic binder (or adhesive), preferably with a concentration of 30% to 70%, and preferably with an amount of 1% to 10% of the total mass of the fine fuel; the particle size of the shaped fuel pellets is preferably 2 to 6 mm. The fourth step involves mixing and finely grinding particulate fuel with a particle size of less than 0.1 mm with steel dust and sludge in a certain ratio to obtain carbon-containing dust and sludge powder. The steel dust and sludge includes sintering machine head ash, blast furnace bag filter ash, converter ash, and electric field dust collector ash. The preferred mass ratio of steel dust and sludge to particulate fuel is 85-95:5-15. The preferred particle size of the carbon-containing dust and sludge powder is that particles with a diameter of -0.075 mm account for ≥80% (mass fraction). The fifth step involves feeding the carbon-containing dust and sludge powder and shaped fuel particles into a pelletizer for pelletizing. During the pelletizing process, an atomized liquid medium is sprayed in to obtain carbon-core dust and sludge pellets with shaped fuel particles as the core and carbon-containing dust and sludge powder as the adhesive layer. The atomized liquid medium sprayed during the pelletizing process can be water, a specific concentration of organic binder solution, or plant slurry. The preferred particle size of the carbon-core dust and sludge pellets is 8-12 mm. Step 6: The carbon core dust pellets and sintering mixture are sintered and distributed. First, the carbon core dust pellets are placed above the sintering base layer, and then the sintering mixture is placed above the carbon core dust pellet layer. In a preferred embodiment, the thicknesses of the three layers from bottom to top are 70mm–100mm for the base layer, 20mm–60mm for the carbon core dust pellet layer, and 600mm–1000mm for the sintering mixture layer. Step 7: Ignition and sintering with exhaust are performed to obtain sintered ore. Simultaneously, oxygen-containing gas or pure oxygen is injected into the upper part of a specific number of bellows (e.g., 1–10 bellows before the sintering endpoint) near the bottom of the sintering trolley. The flue gas from these bellows is then recovered to obtain non-ferrous metallurgical raw materials (i.e., element-rich dust) rich in oxides of K, Na, Zn, Pb, and rare and dispersed precious metal compounds. The element-rich dust was tested and found to be significantly enriched in valuable elements such as K, Na, Zn, and Pb, making it a high-quality raw material for subsequent extraction of rare and precious metals.

[0031] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1. This invention uses fine particulate fuel and steel dust to form pellets in layers, and then uses them as a separate sintering material layer for direct distribution. This achieves efficient utilization of fine particulate fuel without affecting the normal operation of sintering. At the same time, it also helps to achieve efficient reduction of valuable elements in steel dust, thereby improving the removal efficiency of valuable elements.

[0032] 2. This invention is based on the process of co-sintering of fine particulate fuel with steel dust and sludge. It also improves the recovery rate and compound purity of valuable elements such as iron, zinc and lead in the subsequent flue gas by providing oxygen at a specific location in the wind box. This improves the efficiency of resource-based removal of valuable elements and can achieve a win-win situation for economic, environmental and social benefits.

[0033] 3. This invention effectively regulates the temperature field and atmosphere distribution during sintering through the synergistic effect of layered material distribution and directional oxygen supplementation, promoting the volatilization and enrichment of low-melting-point valuable metal oxides while inhibiting their residue in sintered ore, thus significantly improving the comprehensive utilization rate of resources. It achieves efficient separation of valuable elements and synergistic optimization of sintered ore quality, solving the technical problems of low utilization rate of fine particulate fuel and difficulty in recovering valuable elements from dust and sludge in traditional processes, and has significant economic and environmental benefits.

[0034] 4. The method of the present invention has a simple process flow, is easy to operate, and has high efficiency and excellent effect in the treatment of fine particulate fuel and steel dust and sludge, and is easy to promote and apply on a large scale. Attached Figure Description

[0035] Figure 1 This is a simplified process flow diagram of the method described in this invention. Detailed Implementation

[0036] 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.

[0037] Example 1 like Figure 1 As shown, a method for treating steel dust and controlling the migration of valuable metals through a sintering process includes the following steps: 1) The sintering fuel is sorted into coarse fuel, fine fuel and particulate fuel.

[0038] 2) Mix coarse fuel with sintering raw materials and granulate to obtain sintering mixture.

[0039] 3) Fine fuel particles are mixed with molding aids and then pressed into shape to obtain molded fuel pellets.

[0040] 4) First, mix and grind the particulate fuel with steel dust to obtain carbon-containing dust powder; then mix the carbon-containing dust powder with shaped fuel particles to form pellets to obtain carbon core dust pellets.

[0041] 5) The base material, carbon core dust balls, and sintering mixture are laid sequentially from bottom to top on the sintering trolley, followed by sintering to obtain sintered ore. During the sintering process, oxygen-containing gas is injected into the wind box at the sintering endpoint, and the flue gas in that part of the wind box is collected to obtain element-rich dust.

[0042] Example 2 Repeat Example 1, except that in step 1), the sintering fuel is a solid carbonaceous fuel. The coarse-grained fuel has a particle size greater than 0.5 mm. The fine-grained fuel has a particle size of 0.1–0.5 mm. The particulate fuel has a particle size less than 0.1 mm. In step 2), the sintering raw materials include iron-containing raw materials, flux, and water; the mixing mass ratio of iron-containing raw materials, flux, and water is 80.0:12.5:7.5; the iron-containing raw materials include iron ore powder; the flux is limestone; the mixing mass ratio of coarse-grained fuel to sintering raw materials is 4.0:96.0, and the particle size of the sintered mixture is 6–10 mm.

[0043] Example 3 Repeat Example 2, except that in step 3), the molding aid is a starch aqueous solution with a mass concentration of 70%, and the amount of molding aid used is 3% of the total mass of fine fuel particles; the particle size of the molded fuel particles is 2-6 mm.

[0044] Example 4 Repeat Example 2, except that in step 3), the molding aid is a starch aqueous solution with a mass concentration of 30%, and the amount of molding aid is 8% of the total mass of fine particulate fuel; the particle size of the molded fuel particles is 2-6 mm, and the mixing and grinding specifically involves mixing the particulate fuel and steel dust and grinding until the mass percentage of particles with a particle size of less than 0.075 mm is not less than 80%.

[0045] Example 5 Repeat Example 3, except that in step 4), the steel dust includes one or more of the following: sintering machine head ash, blast furnace bag ash, converter ash, and electric field dust collector ash; the mixing mass ratio of particulate fuel to steel dust is 15:85.

[0046] Example 6 Repeat Example 5, except that in step 4), the mixing mass ratio of particulate fuel and steel dust is 10:90; the grinding specifically refers to grinding the particulate fuel and steel dust until the mass percentage of particles smaller than 0.075mm is not less than 85%.

[0047] Example 7 Example 5 is repeated, except that in step 4), the pelletizing process specifically involves adding carbon-containing dust and sludge micropowder and shaped fuel particles to a pelletizing machine at a mass ratio of 65:35, and spraying an atomized liquid medium during the pelletizing process. The liquid medium is [missing information - likely a specific component or ingredient]. The particle size of the carbon-core dust and sludge pellets is 8–12 mm.

[0048] Example 8 Repeat Example 5, except that in step 5), the thickness of the base material layer is 100 mm. The thickness of the carbon core dust pellet layer is 50 mm. The thickness of the sintering mixture layer is 1000 mm.

[0049] Example 9 Repeat Example 5, except that in step 5), the thickness of the base material layer is 80 mm. The thickness of the carbon core dust pellet layer is 30 mm. The thickness of the sintering mixture layer is 700 mm.

[0050] Example 10 Repeat Example 8, except that the base material is natural ore.

[0051] Example 11 Repeat Example 8, except that in step 5), the sintering endpoint wind box is one to ten wind boxes at the tail of the sintering machine.

[0052] Example 12 Repeat Example 8, except that in step 5), the sintering endpoint wind box is one to eight wind boxes at the tail of the sintering machine.

[0053] Example 13 Repeat Example 8, except that in step 5), the sintering endpoint wind boxes are 1 to 5 wind boxes at the tail of the sintering machine.

[0054] Example 14 Repeat Example 11, except that in step 5), the amount of oxygen-containing gas injected is such that the oxygen mass concentration in the 1 to 10 air boxes at the tail of the sintering machine is not less than 310 mg / L.

[0055] Example 15 Repeat Example 14, except that in step 5), the oxygen-containing gas is injected into the upper part of the inner cavity of the bellows. The oxygen-containing gas is preheated before injection so that the temperature difference between it and the flue gas in the bellows is no more than 100°C.

[0056] Application Example 1 Sintered fuel with a maximum particle size not exceeding 3 mm is screened and classified to obtain coarse fuel with a particle size of more than 0.5 mm, fine fuel with a particle size of 0.1 mm to 0.5 mm, and particulate fuel with a particle size of less than 0.1 mm.

[0057] Coarse-grained fuel, natural iron ore powder, recycled ore, quicklime, limestone, dolomite, and water were mixed in a mass ratio of 3.7:53.9:24.1:2.1:5.2:3.5:7.5, and then mixed and granulated in a cylindrical drum to obtain a sintered mixture with an average particle size of about 4.5 mm.

[0058] Starch slurry with a mass concentration of 30% is added to fine-particle fuel at a solid-liquid mass ratio of 100:3, and then formed into shaped fuel pellets with a diameter of approximately 5 mm by roller molding. Microparticle fuel is mixed with steel dust at a mass ratio of 10:90, and then finely ground in a grinding device until the mass content of -0.075 mm is greater than 80%, obtaining carbon-containing dust micropowder. The carbon-containing dust micropowder and shaped fuel pellets are fed into a disc pelletizer at a mass ratio of 65:35 for pelletizing. Water mist is sprayed during the pelletizing process to promote pellet growth, ultimately obtaining carbon-core dust pellets with a particle size of approximately 10 mm.

[0059] First, a base layer of approximately 80mm thick sintering return ore is laid on the sintering trolley. Then, carbon core dust pellets are laid on top of the base layer to form a layer of approximately 40mm thick carbon core dust pellets. Finally, a sintering mixture is laid on top of the carbon core dust pellet layer to form a layer of approximately 750mm thick sintering mixture. The sintering machine is started, and the ignition and exhaust sintering processes are completed sequentially. After the sintering process is completed, qualified sintered ore is obtained. During the sintering process, oxygen is injected into the upper part of the 1st to 5th air boxes near the bottom of the sintering trolley before the sintering endpoint to ensure that the oxygen concentration in the flue gas in the air boxes is not less than 310mg / L. Then, the flue gas in these 5 air boxes is separately led out through the air box branch pipes, and the dust in the flue gas is recovered to obtain element-rich dust (rich in Pb, Zn, K, Na, In, Ge, Tl, Ag, etc.). The dust-removed flue gas is returned to the main sintering flue through the flue pipe.

[0060] In Application Example 1, the following results were obtained: the Zn removal rate of the steel dust was approximately 90.42%, the Pb removal rate was approximately 80.04%, and the alkali metal removal rate was approximately 65.88%. The resulting element-rich dust contained approximately 44.77% ZnO, 15.91% PbO, 6.42% K₂O, 4.13% Na₂O, 481.12 g / t In, 426.46 g / t Ag, 286.06 g / t Ge, and 405.87 g / t Tl. The sintering utilization coefficient (i.e., the yield of sintered ore per unit area per unit time) was approximately 1.53 t / (m²). 2 ·h).

[0061] Application Example 2 The same method as Example 1 was used, except that the mass ratio of particulate fuel to steel dust was 5:95.

[0062] In application example 2, the following results were obtained: the Zn removal rate of the steel dust was approximately 86.12%, the Pb removal rate was approximately 75.65%, and the alkali metal removal rate was approximately 60.33%. The resulting element-rich dust contained approximately 42.64% ZnO, 15.03% PbO, 5.88% K₂O, 3.78% Na₂O, 377.41 g / t In, 413.05 g / t Ag, 217.64 g / t Ge, and 385.91 g / t Tl. The sintering utilization coefficient was approximately 1.52 t / (m²). 2 ·h).

[0063] Application Example 3 The application of Example 1 is repeated, except that the thickness of the base material is about 80 mm, the thickness of the carbon core dust ball material layer is about 50 mm, and the thickness of the sintered mixed material layer is about 850 mm.

[0064] In application example 3, the following results were obtained: the Zn removal rate of the steel dust was approximately 92.04%, the Pb removal rate was approximately 83.56%, and the alkali metal removal rate was approximately 67.89%. The resulting element-rich dust contained approximately 45.57% ZnO, 16.61% PbO, 6.61% K₂O, 4.25% Na₂O, 501.24 g / t In, 428.56 g / t Ag, 290.45 g / t Ge, and 433.69 g / t Tl. The sintering utilization coefficient was approximately 1.56 t / (m²). 2 ·h).

[0065] Comparative Example 1 The operating procedure of Example 1 was repeated, with the following adjustments: the sintering fuel was directly added to the sintering batch without screening, and steel dust was directly added to the sintering mixture without a designated dust collection point. The test results of Comparative Example 1 showed that Zn, Pb, and alkali metals in the steel dust were not effectively removed, and rare and precious metals were not effectively recovered. The sintering utilization coefficient was approximately 1.40 t / (m³). 2 ·h).

[0066] Comparative Example 2 Example 1 was repeated, except that oxygen supplementation was not performed on the first to fifth air boxes before the sintering endpoint. In Comparative Example 2, the following results were obtained: Zn removal rate of steel dust was approximately 91.03%, Pb removal rate was approximately 79.85%, and alkali metal removal rate was approximately 65.01%. The resulting element-rich dust contained approximately 40.34% ZnO, 12.23% PbO, 2.45% K2O, 1.95% Na2O, 473.26 g / t In, 413.28 g / t Ag, 262.34 g / t Ge, and 398.43 g / t Tl, with a sintering utilization coefficient of approximately 1.52 t / (m 2 ·h).

[0067] Comparative Example 3 The operation process of Example 1 was repeated, except that carbon core dust pellets were directly used as one of the sintering raw materials. Sintering batching, mixing, granulation, and material distribution were performed sequentially, without dust collection at a specific location. In Comparative Example 3, the Zn removal rate of the steel dust was approximately 35.53%, the Pb removal rate was approximately 10.05%, and the alkali metal removal rate was approximately 5.02%. Rare and precious metals were not effectively recovered. The sintering utilization coefficient was approximately 1.46 t / (m³). 2 ·h).

Claims

1. A method for treating steel dust and controlling the migration of valuable metals through a sintering process, characterized in that: The method includes the following steps: 1) The sintering fuel is sorted into coarse-grained fuel, fine-grained fuel, and particulate fuel; the coarse-grained fuel has a particle size greater than 0.5 mm; the fine-grained fuel has a particle size of 0.1–0.5 mm; and the particulate fuel has a particle size less than 0.1 mm. 2) The coarse fuel particles are mixed with the sintering raw materials and granulated to obtain a sintering mixture; 3) Fine fuel particles are mixed with molding aids and molded to obtain molded fuel pellets; 4) First, the particulate fuel and steel dust are mixed and ground to obtain carbon-containing dust powder; then, the carbon-containing dust powder is mixed with shaped fuel particles to form pellets to obtain carbon core dust pellets; the mixing mass ratio of particulate fuel and steel dust is 5~15:85~95; the mixing mass ratio of carbon-containing dust powder and shaped fuel particles is 55~75:25~45. 5) Lay the base material, carbon core dust balls and sintering mixture sequentially from bottom to top on the sintering trolley, and then carry out sintering treatment to obtain sintered ore; during the sintering process, oxygen-containing gas is injected into the wind box at the end of the sintering process and the dust in the flue gas of this part of the wind box is collected to obtain element-rich dust; the amount of oxygen-containing gas injected is such that the oxygen mass concentration in the wind box is not less than 300 mg / L.

2. The method according to claim 1, characterized in that: In step 1), the sintering fuel is a solid carbonaceous fuel.

3. The method according to claim 1, characterized in that: In step 2), the sintering raw materials include iron-containing raw materials, flux and water; the mixing mass ratio of iron-containing raw materials, flux and water is 76.0~82.0:10.0~15.5:7.0~9.

0.

4. The method according to claim 3, characterized in that: The iron-containing raw materials include iron ore powder, recycled ore and / or iron-containing solid waste; the flux includes one or more of limestone, dolomite, serpentine and quicklime.

5. The method according to claim 1, characterized in that: In step 2), the mixing mass ratio of coarse fuel to sintering raw materials is 3.0~4.5:95.5-97.0; and / or In step 2), the average particle size of the sintered mixture is no greater than 12 mm.

6. The method according to claim 1, characterized in that: In step 3), the molding aid is an organic binder.

7. The method according to claim 6, characterized in that: The molding aid is a starch aqueous solution with a mass concentration of 30% to 70%.

8. The method according to claim 1, characterized in that: In step 3), the amount of molding aid used is 1% to 10% of the total mass of the particulate fuel; and / or In step 3), the particle size of the formed fuel particles is 2 to 6 mm.

9. The method according to claim 8, characterized in that: In step 3), the amount of molding aid used is 2% to 6% of the total mass of the particulate fuel; and / or In step 3), the particle size of the formed fuel particles is 3-5 mm.

10. The method according to claim 1, characterized in that: In step 4), the steel dust includes one or more of the following: sintering machine head ash, blast furnace bag filter ash, converter ash, and electric field dust collector ash.

11. The method according to any one of claims 1-2, 4, 7, and 9, characterized in that: In step 4), the mixing and grinding specifically involves mixing particulate fuel and steel dust and grinding them until the mass percentage of particles smaller than 0.075 mm is not less than 80%. In step 4), the pelletizing process specifically involves adding carbon-containing dust and sludge powder and shaped fuel particles into a pelletizing machine, and spraying atomized liquid medium during the pelletizing process.

12. The method according to claim 11, characterized in that: The specific process involves mixing particulate fuel and steel dust, then grinding them until the mass percentage of particles smaller than 0.075 mm is not less than 85%; and / or The liquid medium includes one or more of water, starch solution, and plant slurry; the particle size of the carbon core dust spheres is 8-12 mm.

13. The method according to any one of claims 1-2, 4, 7, 9, and 12, characterized in that: In step 5), the thickness of the base material layer is 70–100 mm; and / or In step 5), the thickness of the carbon core dust pellet layer is 20–60 mm; and / or In step 5), the thickness of the sintered mixture layer is 600-1000 mm.

14. The method according to claim 13, characterized in that: In step 5), the thickness of the base material layer is 80–90 mm; and / or In step 5), the thickness of the carbon core dust pellet layer is 30–50 mm; and / or In step 5), the thickness of the sintered mixture layer is 700-900 mm.

15. The method according to any one of claims 1-2, 4, 7, 9, 12, and 14, characterized in that: In step 5), the base material is recycled ore and / or natural lump ore.

16. The method according to any one of claims 1-2, 4, 7, 9, 12, and 14, characterized in that: In step 5), the sintering endpoint position wind box is the 1st to 10th wind box at the tail of the sintering machine.

17. The method according to claim 16, characterized in that: In step 5), the sintering endpoint position wind box is the first to eighth wind box at the tail of the sintering machine.

18. The method according to claim 17, characterized in that: In step 5), the sintering endpoint position wind box is the 1st to 5th wind box at the tail of the sintering machine.

19. The method according to any one of claims 1-2, 4, 7, 9, 12, 14, 17, and 18, characterized in that: In step 5), the amount of oxygen-containing gas injected is such that the oxygen mass concentration in the bellows is not less than 310 mg / L.

20. The method according to any one of claims 1-2, 4, 7, 9, 12, 14, 17, and 18, characterized in that: The oxygen-containing gas is injected into the upper part of the bellows' inner cavity.

21. The method according to claim 20, characterized in that: The oxygen-containing gas was preheated before being injected so that the temperature difference between it and the flue gas in the bellows was no more than 100°C.

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