Vacuum low-temperature reduction method for putty powder bonded steel solid waste pellets and application

Abstract

The invention discloses a vacuum low-temperature reduction method for putty powder bonded steel solid waste pellets and application, and belongs to the field of metallurgical pellet production. The vacuum low-temperature reduction method comprises the following steps: uniformly mixing zinc-containing steel solid waste, a reducing agent and putty powder to obtain a first mixture, adding water into the first mixture, uniformly mixing to obtain a second mixture, pelletizing the second mixture to obtain pellets, and drying the pellets to obtain pellets for reduction; and the pellets for reduction are subjected to segmented pressure control reduction in the vacuum atmosphere, and dezincized pellets and crude zinc blocks are obtained. The binder used in the invention is interior wall crack-resistant putty powder or waste putty powder regenerated material, has wide source and low price, and can also treat waste with waste. The reduced pellets can directly enter a converter to be used as raw materials, and crude zinc obtained through condensation is high in added value. The method is suitable for industrial production, wide in application prospect and suitable for large-scale popularization and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgical pellet production, and particularly relates to a vacuum low-temperature reduction method and application of putty powder for bonding iron and steel solid waste pellets. Background Art

[0002] The iron and steel industry, as a typical resource- and energy-intensive industry, consumes a large amount of resources in the production process to produce finished steel products and generates a large amount of solid waste. During the production process of iron and steel enterprises, about 8-12% of the metallurgical dust and sludge is produced, mainly from the dust removal devices and the dust and sludge discharged from the wastewater treatment during the iron and steel production processes such as sintering, smelting, and rolling, and usually contains elements such as iron and zinc. Among them, electric furnace dust is listed as hazardous solid waste, and improper disposal will have a huge impact on the environment.

[0003] As a secondary resource with great utilization value, developing a suitable process to recycle the useful elements in these dusts and sludges can replace ironmaking raw materials, reduce China's dependence on imported iron ore, and solve the environmental pollution problems caused by iron and steel enterprise dust.

[0004] In the prior art, patent CN110317950B discloses a method for reducing and dezincifying zinc-containing dust, wherein the zinc-containing dust is heated with water and then mixed with a binder, pelletized and dried, and then calcined at high temperature in a rotary kiln, and then cooled in a protective atmosphere after reduction to obtain reduced dezincified balls. In this patent, a rotary kiln is used to treat zinc-containing dust, and the final product is secondary zinc oxide, which has a low added value. In addition, a composite binder is used as the binder, and high-value polyacrylamide is used for immediate use, which adds a process and increases the cost. Patent CN109022808A discloses a comprehensive recovery method for zinc-containing steel metallurgical dust, wherein various zinc-containing steel metallurgical dusts are ground and mixed with a reducing agent, coke powder, until the zinc content in the mixture reaches more than 10%, and the mixture is made into a pellet or brick shape using pulp or clay as a binder, and then vacuum reduction smelting is performed to obtain metallized pellets containing metallic zinc and mainly iron and carbon. In this patent, the binder used to improve the strength of the pellets is pulp or clay, and the amount used is as high as 4% to 6%, which makes the pelletizing cost high and the economic benefit low. Patent CN106399700A discloses a method and system for treating zinc-containing dust, wherein the zinc-containing dust, reducing agent and binder are mixed, milled, pelletized and dried, and then high-temperature roasted in a ring roasting furnace, and the high-temperature flue gas generated enters the zinc recovery system to collect the valuable metal dust, and the tailings are treated to obtain metal iron powder. The liquid binder used in this patent is not conducive to the addition and mixing during the pelletizing process, which may eventually lead to uneven strength of the finished balls, unable to meet the furnace entry standards, or easy to pulverize the pellets into powder after entering the furnace, resulting in a bonding effect, so that the pellets are powdery after reduction and cannot be directly used as raw materials in the converter. It is generally found in the above patents that in the treatment technology of zinc-containing steel solid waste, there are problems such as large amount of binder used, resulting in high cost of pelletizing, or uneven strength of pellets caused by the use of liquid binder, which affects the stable operation of the dezincification process, or secondary zinc oxide is produced in the rotary hearth furnace and rotary kiln, and the reduction affects the economic benefits of the dezincification process. Therefore, it is very necessary to adopt a new direct reduction dezincification technology to treat zinc-containing steel solid waste on a large scale, increase the added value of zinc products, and increase the strength of iron-containing products after reduction, so as to solve the solid waste treatment problem and ensure the sustainable development of the steel industry. Summary of the invention

[0005] In order to solve the problems of high cost and uneven pellet strength caused by the use of liquid binders in the treatment of zinc-containing steel solid waste, which in turn affects the stability of the dezincification process and the dezincification effect, the present invention provides a vacuum low-temperature reduction method for bonding steel solid waste pellets with putty powder and its application. The method has low price and good pellet performance, can meet the strength requirements of the raw pellet transportation process and the strength requirements of the dry pellet entering the furnace, and the pellets have high strength after reduction and can be directly used as steelmaking raw materials, thereby improving the economic benefits of the products.

[0006] The present invention adopts the following technical solutions to solve the above technical problems: The present invention provides a vacuum low-temperature reduction method for putty powder to bond iron and steel solid waste pellets, including: Mix zinc-containing iron and steel solid waste, a reducing agent, and putty powder evenly to obtain a first mixture, add water to the first mixture and mix evenly to obtain a second mixture, pelletize the second mixture to obtain pellets, and dry the pellets to obtain reduction pellets; Reduce the reduction pellets under controlled pressure in segments in a vacuum atmosphere to obtain de-zincified pellets and crude zinc blocks.

[0007] The zinc-containing iron and steel solid waste includes any one of converter fume or OG sludge, and electric furnace dry dedusting ash; By mass percentage, the zinc-containing iron and steel solid waste includes 47% - 61% of Fe2O3, 9% - 18% of ZnO, 2% - 4% of SiO2, 1% - 3% of Al2O3, 1% - 6% of MgO, 4% - 8% of CaO, and the rest are impurities; the particle size of the zinc-containing iron and steel solid waste is 120 - 200 mesh.

[0008] The reducing agent is semi-coke or coke powder, the particle size of the reducing agent is 40 - 80 mesh, and the fixed carbon content in the reducing agent is ≥75%; the dosage of the reducing agent is 1.05 - 1.2 times the total molar mass of iron and zinc in the zinc-containing iron and steel solid waste for complete reduction.

[0009] The putty powder is an interior wall crack-resistant putty powder that meets the JG / T 298-2010 standard or recycled waste putty powder; by mass percentage, the putty powder includes 42% - 60% of CaCO3, 12% - 28% of 3MgO·4SiO2·H2O, 15% - 30% of CaSO4·2H2O, 1% - 5% of redispersible latex powder; the dosage of the putty powder accounts for 1.5% - 3% of the mass of the first mixture.

[0010] The recycled waste putty powder needs to be pretreated before use. The pretreatment includes: screening the waste putty powder to remove impurity particles with a particle size > 1mm; roasting the screened waste putty powder at 200 - 400°C for 1 - 2 hours, then grinding it, and screening it through a 200-mesh sieve to obtain the recycled waste putty powder.

[0011] The dosage of water is 8wt% - 10wt% of the second mixture.

[0012] The step of reducing the reduction pellets under controlled pressure in segments in a vacuum atmosphere to obtain de-zincified pellets and crude zinc blocks is specifically as follows: in the initial stage, place the reduction pellets in a vacuum environment of 50 Pa; in the heating stage, in a vacuum environment of 20 - 50 Pa, gradually heat up to 800 - 1020°C; in the heat preservation stage, in a vacuum environment of ≤20 Pa, keep the temperature at 1020 - 1070°C for 30 - 120 min to obtain de-zincified pellets and crude zinc blocks.

[0013] The segmented pressure-controlled reduction process is carried out in a vacuum furnace. A ceramic filter screen and a collector are arranged in the upper part of the vacuum furnace. The ceramic filter screen is used to filter impurity particles accompanied by volatile metal vapors, and the collector is used to collect the produced crude zinc blocks.

[0014] 3 - 5 layers of ceramic filter screens are arranged in the upper part of the vacuum furnace. The collector is a collection frame with a downward inclination angle from the inside to the outside, and the inclination angle is 5 - 8°.

[0015] The present invention also provides an application of the vacuum low-temperature reduction method for bonding steel solid waste pellets with putty powder in the treatment of zinc-containing steel solid waste.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The binder used in the present invention is ordinary interior wall putty powder, which has a wide source, a lower market price than other binders, is environmentally friendly and has a wide application range. Using waste putty powder (construction waste) as a low-cost binder not only reduces the landfill of construction waste but also reduces the raw material cost, which conforms to the concept of circular economy. Moreover, the main components of putty powder, such as calcium carbonate, can be used as a sulfur-fixing agent after high-temperature decomposition, and gypsum dehydrates at high temperature to generate CaSO4, and the released water vapor can promote the formation of pores inside the pellets, enhance the air permeability, thereby shortening the roasting time and reducing the energy consumption. The vacuum reduction is carried out by adopting a segmented pressure control adjustment process. Maintaining a lower vacuum degree during the heating period can promote the escape of CO and enhance the reaction kinetics. Increasing the high vacuum degree during the heat preservation period can accelerate the aggregation of the metal phase, which can significantly improve the reduction efficiency and the quality of the product. The product is crude zinc blocks, whose value is higher than that of the secondary zinc oxide produced by rotary kilns and rotary hearth furnaces, and the economic benefit is good. Moreover, the technical process and binder of the present invention can also be applied to other fields of alkaline carbon-containing pellet production and are suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 It is a process flow chart of the vacuum low-temperature reduction method for bonding steel solid waste pellets with putty powder of the present invention; Figure 2 It is a schematic diagram of filtration and collection inside the vacuum furnace used for vacuum reduction of the present invention; In the figure, 1, filter screen; 2, collector; 3, inclination angle. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the following further details this application in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0020] In this application, the term "and / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0021] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one (item)" or its similar expression refers to any combination of these items, including any combination of single item (item) or plural items (items). For example, "at least one (item) of a, b, or c", or, "at least one (item) of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or plural respectively.

[0022] It should be understood that in various embodiments of this application, the size of the serial numbers of the above processes does not mean the sequence of execution. Some or all steps can be executed in parallel or sequentially. The execution sequence of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0023] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms "a", "the", and "said" used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0024] The weight of the relevant components mentioned in the specification of the embodiments of this application not only can refer to the specific content of each component, but also can represent the proportional relationship of the weights between the components. Therefore, as long as the content of the relevant components in the specification of the embodiments of this application is enlarged or reduced in proportion, it is within the scope disclosed in the specification of the embodiments of this application. Specifically, the mass described in the specification of the embodiments of this application can be mass units well-known in the chemical industry such as μg, mg, g, kg, etc.

[0025] Such as Figure 1As shown in the figure, the vacuum low-temperature reduction method for putty powder to bond iron and steel solid waste pellets provided by the present invention includes: uniformly mixing zinc-containing iron and steel solid waste, a reducing agent, and putty powder to obtain a first mixture, adding water to the first mixture and mixing uniformly to obtain a second mixture, pelletizing the second mixture to obtain pellets, and drying the pellets to obtain reduction pellets; subjecting the reduction pellets to staged pressure-controlled reduction in a vacuum atmosphere to obtain de-zincified pellets and crude zinc blocks.

[0026] As Figure 2 shown in the figure, the entire process of staged pressure-controlled reduction in a vacuum atmosphere is carried out in a vacuum furnace. The staged pressure-controlled reduction technology controls the pressure in the furnace at different stages to ensure the stability and efficiency of the reduction reaction, optimizes the reduction effect, and improves the economy and environmental protection of the overall process. During this process, a filtration and collection system is provided in the vacuum furnace. A ceramic filter screen 1 and a collector 2 are provided in the upper-middle part of the vacuum furnace. The ceramic filter screen 1 is used to filter impurity particles accompanied by volatile metal vapors. 3-5 layers of ceramic filter screens 1 are provided in the upper part of the vacuum furnace; the collector 2 is used to collect the produced crude zinc blocks. The collector 2 is a collection box with a downward inclination angle 3 from the inside to the outside, and the inclination angle 3 is 5-8°.

[0027] In the following examples, unless otherwise specified, all materials used can be obtained through ordinary channels; the testing methods adopted are conventional methods in the art. The interior wall crack-resistant putty powder in the examples complies with the JG / T 298-2010 standard.

[0028] Comparative Example 1 Prepare pellets according to conventional binders and processes and carry out conventional vacuum reduction, including the following steps: Using converter dust as raw material, by mass percentage, the components in the converter dust are 47.12% Fe2O3, 9.33% ZnO, 2.27% SiO2, 1.15% Al2O3, 1.06% MgO, 4.52% CaO, and the rest are impurities, with a particle size of 120 mesh. Add semi-coke with a particle size of 80 mesh to the converter dust so that C:O = 1.1, then add 4wt% of calcium-based bentonite and stir evenly, and then add 10wt% of water and stir evenly to obtain a mixed material. Press the mixed material into balls and dry to obtain reduction pellets; put the reduction pellets into a vacuum furnace, evacuate to a pressure of 50 Pa, heat up to 1050 °C, react for 60 min, and then break the vacuum and cool with nitrogen as a protective gas to obtain reduction de-zincified pellets and crude zinc blocks.

[0029] Comparative Example 2 Prepare pellets according to conventional binders and processes and carry out vacuum reduction, including the following steps: Using the dried OG mud as raw material, by mass percentage, the composition of the OG mud contains 55.43% of Fe2O3, 13.76% of ZnO, 3.18% of SiO2, 1.97% of Al2O3, 3.56% of MgO, 6.42% of CaO, and the rest are impurities. The particle size is 160 mesh. Add coke powder with a particle size of 100 mesh to the raw material to make the C:O = 1.2, then add 4wt% of sodium bentonite and stir evenly, and then add 10wt% of water and stir evenly to obtain a uniformly mixed material. Press the uniformly mixed material into balls and dry to obtain pellets for reduction; put the pellets for reduction into a vacuum furnace, evacuate to a pressure of 50 Pa, heat up to 1050 °C, react for 60 min, and then use nitrogen as a protective gas to break the vacuum and cool to obtain reduced dezinced pellets and crude zinc blocks.

[0030] Example 1 Pelletize and perform vacuum reduction according to the preparation method provided by the present invention, including the following steps: In this example, first, converter dust is selected as the zinc-containing steel waste as the main raw material. By mass percentage, the composition of the converter dust contains 47.12% of Fe2O3, 9.33% of ZnO, 2.27% of SiO2, 1.15% of Al2O3, 1.06% of MgO, 4.52% of CaO, and the rest are impurities. The particle size of the converter dust is 120 mesh; add semi-coke with C:O = 1.05 and interior wall anti-cracking putty powder to the converter dust and stir evenly to obtain a first mixed material. The particle size of the semi-coke is 80 mesh, the fixed carbon content is 75%, and the ash content is 2.1%; the addition amount of the interior wall anti-cracking putty powder accounts for 1.5wt% of the first mixed material. By mass percentage, the composition of the interior wall anti-cracking putty powder includes 60% of CaCO3, 23% of CaSO4·2H2O, 5% of redispersible latex powder (Vac / E), and 12% of 3MgO·4SiO2·H2O; add water to the first mixed material and continue to stir to obtain a second mixed material. The water addition amount accounts for 8wt% of the second mixed material; press the second mixed material into balls and dry to obtain pellets for reduction; put the pellets for reduction into a vacuum furnace and evacuate to 50 Pa. When the temperature in the furnace reaches 800 °C, control the pressure in the furnace to be 50 Pa. When the reduction temperature reaches 1020 °C, control the pressure in the furnace to be 20 Pa, and the holding time is 30 min; the metal vapor generated in real time during the process passes through three layers of filter screens 1 to reach the collector 2, and the inclination angle of the collector 2 is 5°; after the reaction, use nitrogen as a protective gas to break the vacuum and cool to obtain reduced dezinced pellets and crude zinc blocks.

[0031] Example 2 Pelletize and perform vacuum reduction according to the preparation method provided by the present invention, including the following steps: In this embodiment, first, the zinc-containing iron and steel solid waste as the main raw material is selected as the dried OG sludge. By mass percentage, the components of the OG sludge are 55.43% Fe2O3, 13.76% ZnO, 3.18% SiO2, 1.97% Al2O3, 3.56% MgO, 6.42% CaO, and the rest are impurities. The particle size of the OG sludge is 160 mesh; pulverized coal with a C:O ratio of 1.1 and interior wall anti-cracking putty powder are added to the OG sludge and stirred evenly to obtain the first mixture. The particle size of the pulverized coal is 90 mesh, the fixed carbon content is 80%, and the ash content is 4.5%; the addition amount of the interior wall anti-cracking putty powder accounts for 2.2 wt% of the first mixture. By mass percentage, the components of the interior wall anti-cracking putty powder include 48% CaCO3, 26% CaSO4·2H2O, 22% 3MgO·4SiO2·H2O, and 4% redispersible latex powder (Vac / E); water is added to the first mixture and then stirred continuously to obtain the second mixture. The water addition amount accounts for 9 wt% of the second mixture; the second mixture is pressed into balls and then dried to obtain the pellets for reduction; the pellets for reduction are loaded into a vacuum furnace and evacuated to 50 Pa. When the furnace temperature reaches 800 °C, the furnace pressure is controlled at 30 Pa. When the reduction temperature reaches 1050 °C, the furnace pressure is controlled at 10 Pa, and the holding time is 60 min; the metal vapor generated in real time during the process passes through the 4-layer filter screen 1 to reach the collector 2. The inclination angle of the collector 2 is 6°; after the reaction, nitrogen is used as the protective gas to break the vacuum and cool, obtaining the reduced de-zinc pellets and crude zinc blocks.

[0032] Example 3 Pellets are made and vacuum reduction is carried out according to the preparation method provided by the present invention, including the following steps: In this embodiment, first, the zinc-containing iron and steel solid waste as the main raw material is selected as the electric furnace dry dust removal ash. By mass percentage, the components of the electric furnace dry dust removal ash are 60.88% Fe2O3, 17.79% ZnO, 3.97% SiO2, 2.79% Al2O3, 5.81% MgO, 7.65% CaO, and the rest are impurities. The particle size of the electric furnace dry dust removal ash is 200 mesh; Add semi-coke with a C:O ratio of 1.2 and interior wall anti-cracking putty powder to the electric furnace dry dust removal ash and stir evenly to obtain the first mixture. The particle size of the semi-coke is 100 mesh, the fixed carbon content is 85%, and the ash content is 5.7%; The addition amount of the interior wall anti-cracking putty powder accounts for 3wt% of the first mixture. The components of the interior wall anti-cracking putty powder include 55% CaCO3, 27% CaSO4·2H2O, 3% redispersible latex powder (Vac / E), and 15% 3MgO·4SiO2·H2O. Add water to the first mixture and continue to stir to obtain the second mixture. The water addition amount accounts for 10wt% of the second mixture; Press the second mixture into balls and dry to obtain the pellets for reduction; Load the pellets for reduction into a vacuum furnace, evacuate to 50 Pa, when the furnace temperature reaches 800 °C, control the furnace pressure to 20 Pa, when the reduction temperature reaches 1070 °C, control the furnace pressure to 1 Pa, and the holding time is 120 min. The metal vapor generated in real time during the process passes through the 5-layer filter screen 1 to reach the collector 2, and the inclination angle of the collector 2 is 8°. After the reaction, use nitrogen as the protective gas to break the vacuum and cool to obtain the reduced de-zinc pellets and crude zinc blocks.

[0033] Example 4 Pelletize according to the preparation method provided by the present invention and perform vacuum reduction, including the following steps: In this embodiment, first, the zinc-containing iron and steel solid waste as the main raw material is selected as the electric furnace dry dust removal ash. By mass percentage, the components of the electric furnace dry dust removal ash are 60.88% of Fe2O3, 17.79% of ZnO, 3.97% of SiO2, 2.79% of Al2O3, 5.81% of MgO, 7.65% of CaO, and the rest are impurities. The particle size of the electric furnace dry dust removal ash is 200 mesh; after collecting the waste putty powder, the impurity particles with a particle size > 1 mm are screened out and calcined at 200 °C for 2 hours, and then passed through a 200-mesh sieve to obtain the recycled waste putty powder; the semi-coke with a C:O ratio of 1.2 and the recycled waste putty powder are added to the electric furnace dry dust removal ash. The particle size of the semi-coke is 100 mesh, the fixed carbon content is 85%, and the ash content is 5.7%; the addition amount of the recycled waste putty powder accounts for 3 wt% of the first mixture. The components of the recycled waste putty powder include 50% of CaCO3, 20% of 3MgO·4SiO2·H2O, 28% of CaSO4·2H2O, and 2% of redispersible latex powder (Vac / E). Water is added to the first mixture and then stirred continuously to obtain the second mixture. The water addition amount accounts for 10 wt% of the second mixture; the second mixture is pressed into balls and then dried to obtain the pellets for reduction; the pellets for reduction are loaded into a vacuum furnace and evacuated to 50 Pa. When the furnace temperature reaches 800 °C, the furnace pressure is controlled at 20 Pa. When the reduction temperature reaches 1070 °C, the furnace pressure is controlled at 1 Pa, and the holding time is 120 min. The metal vapor generated in real time during the process passes through the 5-layer filter screen 1 to reach the collector 2, and the inclination angle of the collector 2 is 8°; after the reaction, nitrogen is used as the protective gas to break the vacuum and cool, and the reduced de-zinc pellets and crude zinc blocks are obtained.

[0034] Example 5 Pellets are made and vacuum reduction is carried out according to the preparation method provided by the present invention, including the following steps: In this embodiment, first, converter dust, which is a zinc-containing steel solid waste as the main raw material, is selected. By mass percentage, the components of converter dust are 47.12% Fe2O3, 9.33% ZnO, 2.27% SiO2, 1.15% Al2O3, 1.06% MgO, 4.52% CaO, and the rest are impurities. The particle size of the converter dust is 200 mesh. After collecting the waste putty powder, impurities with a particle size > 1 mm are removed by screening, and then it is calcined at 400 °C for 1 hour and passed through a 200-mesh sieve to obtain the recycled waste putty powder. Semi-coke with a C:O ratio of 1.2 and the recycled waste putty powder are added to the converter dust. The particle size of the semi-coke is 100 mesh, the fixed carbon content is 85%, and the ash content is 5.7%. The addition amount of the recycled waste putty powder accounts for 3 wt% of the first mixture. The components of the recycled waste putty powder include 42% CaCO3, 25% CaSO4·2H2O, 5% redispersible latex powder (Vac / E), and 28% 3MgO·4SiO2·H2O. After adding water to the first mixture and continuing to stir, a second mixture is obtained. The water addition amount accounts for 10 wt% of the second mixture. The second mixture is pressed into balls and then dried to obtain the pellets for reduction. The pellets for reduction are loaded into a vacuum furnace, and the vacuum is pumped to 50 Pa. When the furnace temperature reaches 800 °C, the furnace pressure is controlled at 20 Pa. When the reduction temperature reaches 1070 °C, the furnace pressure is controlled at 1 Pa, and the holding time is 120 min. The metal vapor generated in real time during the process passes through the 5-layer filter net 1 to reach the collector 2, and the inclination angle of the collector 2 is 8°. After the reaction, nitrogen is used as the protective gas to break the vacuum and cool, obtaining the reduction de-zincified pellets and the crude zinc blocks.

[0035] The production processes of the above embodiments and comparative examples are shown in Table 1, and the performance tests of the finished balls and reduction products are carried out. The test results are shown in Table 2: Table 1 Experimental parameter record table of the embodiments and comparative examples

[0036] Table 2 Product performance test table of the embodiments and comparative examples

[0037] Pellets manufactured by conventional processes represented by conventional binders (such as bentonite, etc.) generally have a green pellet drop strength of generally 3 - 4 times / 0.5m, a dry pellet drop strength of 0 - 1 time / 2m, and a compressive strength of 30 - 80 N / pellet. The pellet strength and reduction effect of the preferred embodiments of the present invention are higher than those of conventional processes, the binder addition amount is much smaller than that of conventional processes, and the pellet effects of using putty powder recycled materials (Examples 4 and 5) are the same as those of interior wall putty powder (Examples 1, 2, and 3), indicating that it is feasible to use construction waste as a low-cost binder to achieve the purpose of "treating waste with waste", the process cost is significantly reduced, and the residual zinc content in the reduced metallized pellets is significantly reduced, and there is no pulverization, and the strength exceeds 800 N / pellet, meeting the requirements for charging into a converter. Therefore, the metallized pellets can be directly used as raw materials in the converter.

[0038] In the ranges disclosed in the present invention, the endpoints and any values of the ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. In the following text, in principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be regarded as specifically disclosed herein.

[0039] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still modify the specific implementation manners of the present invention or make equivalent substitutions. Any such modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of the claims of the present invention awaiting approval.

Claims

1. A vacuum low-temperature reduction method for putty powder to bond iron and steel solid waste pellets, characterized in that Including: Mix zinc-containing iron and steel solid waste, a reducing agent, and putty powder evenly to obtain a first mixture. Add water to the first mixture and mix evenly to obtain a second mixture. Pelletize the second mixture to obtain pellets, and dry the pellets to obtain pellets for reduction; Reduce the pellets for reduction under segmented pressure control in a vacuum atmosphere to obtain de-zincified pellets and crude zinc blocks.

2. The vacuum low-temperature reduction method for putty powder to bond iron and steel solid waste pellets according to claim 1, characterized in that, The zinc-containing iron and steel solid waste includes any one of converter fume or OG mud, and dry electric furnace dedusting ash; By mass percentage, the zinc-containing iron and steel solid waste includes 47% - 61% of Fe2O3, 9% - 18% of ZnO, 2% - 4% of SiO2, 1% - 3% of Al2O3, 1% - 6% of MgO, 4% - 8% of CaO, and the rest are impurities; The particle size of the zinc-containing iron and steel solid waste is 120 - 200 mesh.

3. The vacuum low-temperature reduction method for putty powder to bond iron and steel solid waste pellets according to claim 1, characterized in that, The reducing agent is semi-coke or coke powder. The particle size of the reducing agent is 40 - 80 mesh, and the fixed carbon content in the reducing agent is ≥75%; The addition amount of the reducing agent is 1.05 - 1.2 times the total molar mass of iron and zinc in the zinc-containing iron and steel solid waste for complete reduction.

4. The vacuum low-temperature reduction method for putty powder to bond iron and steel solid waste pellets according to claim 1, characterized in that, The putty powder is an interior wall crack-resistant putty powder that meets the JG / T 298 - 2010 standard or recycled waste putty powder; By mass percentage, the putty powder includes 42% - 60% of CaCO3, 12% - 28% of 3MgO·4SiO2·H2O, 15% - 30% of CaSO4·2H2O, and 1% - 5% of redispersible latex powder; The addition amount of the putty powder accounts for 1.5% - 3% of the mass of the first mixture.

5. The vacuum low-temperature reduction method for putty powder to bond iron and steel solid waste pellets according to claim 4, characterized in that The recycled waste putty powder needs to be pretreated before use. The pretreatment includes: Screen the waste putty powder to remove impurity particles with a particle size > 1mm; roast the screened waste putty powder at 200 - 400°C for 1 - 2 hours, grind it after roasting, and screen it through a 200-mesh sieve to obtain recycled waste putty powder.

6. The vacuum low-temperature reduction method for putty powder to bond iron and steel solid waste pellets according to claim 1, characterized in that The addition amount of water is 8wt% - 10wt% of the second mixture.

7. The vacuum low-temperature reduction method for putty powder to bond iron and steel solid waste pellets according to claim 1, characterized in that, The reduction of the pellets for reduction under segmented pressure control in a vacuum atmosphere to obtain de-zincified pellets and crude zinc blocks is specifically as follows: In the initial stage, place the pellets for reduction in a vacuum environment of 50 Pa; in the heating stage, in a vacuum environment of 20 - 50 Pa, gradually heat up to 800 - 1020°C; in the holding stage, in a vacuum environment of ≤20 Pa, hold the temperature at 1020 - 1070°C for 30 - 120 min to obtain de-zincified pellets and crude zinc blocks.

8. The vacuum low-temperature reduction method for putty powder to bond iron and steel solid waste pellets according to claim 1, characterized in that, The segmented pressure control reduction process is carried out in a vacuum furnace. A ceramic filter screen (1) and a collector (2) are arranged in the upper part of the vacuum furnace. The ceramic filter screen (1) is used to filter impurity particles accompanying volatile metal vapors, and the collector (2) is used to collect the generated crude zinc blocks.

9. The vacuum low-temperature reduction method for putty powder to bond iron and steel solid waste pellets according to claim 8, characterized in that, 3 - 5 layers of ceramic filter screens (1) are arranged in the upper part of the vacuum furnace. The collector (2) is a collection frame with a downward inclination angle from the inside to the outside, and the inclination angle is 5 - 8°.

10. The vacuum low-temperature reduction method for putty powder-bonded iron and steel solid waste pellets according to any one of claims 1 - 9 is applied to the treatment of zinc-containing iron and steel solid waste.

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