A method for comprehensively treating zinc-containing sulfuric acid residue and blast furnace bag dust

Abstract

The present invention discloses a method for comprehensively treating zinc-containing sulfuric acid residue and blast furnace bag dust. The zinc-containing sulfuric acid residue, blast furnace bag dust, calcium-based additive, and carbonaceous reducing agent are proportioned and mixed evenly according to the weight ratio of 10:3-5:2.5-4:1.5-3, and then subjected to high-temperature roasting. The flue dust generated by roasting is subjected to oxidation dust removal, cooling separation, and desulfurization treatment to obtain zinc oxide, sulfuric acid, and sulfite; the roasted material is cooled by water and then crushed and ground, and subjected to strong magnetic separation and weak magnetic separation in sequence to obtain high-value reduced iron powder. The final iron grade can reach more than 95%, and the sulfur and zinc content is less than 0.1%. This method can convert industrial solid waste sulfuric acid residue and blast furnace bag dust into high-value reduced iron powder, realizing the comprehensive recovery and utilization of resources, and avoiding environmental and soil pollution caused by stacking.

Description

Technical Field

[0001] This application relates to the technical field of comprehensive utilization of solid waste. Specifically, it relates to a method for comprehensively treating zinc-containing sulfuric acid residue and blast furnace bag dust. Background Art

[0002] Sulfuric acid residue is an industrial solid waste generated during the production of sulfuric acid using pyrite as raw material, with a TFe content of over 50%. Currently, the disposal methods of sulfuric acid residue mainly include separating iron concentrate, making cement admixture, bricklaying, and iron-based pigments. In addition, most of the sulfuric acid residue remains untreated and is stockpiled or landfilled, which not only occupies land but also causes pollution and damage to the soil and environment.

[0003] The iron grade in sulfuric acid residue is relatively high. Most iron and steel enterprises in China often use 5-10% sulfuric acid residue to replace iron ore powder for ironmaking. In addition, sulfuric acid residue can also be prepared into iron concentrate powder by beneficiation methods for pelletizing and sintering. However, due to the mutual encapsulation and intergrowth of various minerals in sulfuric acid residue, it is difficult to achieve ideal indexes for the recovered iron using traditional beneficiation methods such as magnetic separation and flotation. At the same time, the iron loss is relatively large, and the sulfur content in the product is relatively high, which is subject to certain limitations in the ironmaking process. For zinc-containing sulfuric acid residue, due to its relatively high zinc and sulfur content, it is difficult to remove zinc and sulfur elements using conventional beneficiation and acid leaching / alkali leaching methods.

[0004] At present, more research has been carried out on the recovery of iron elements from sulfuric acid slag by pyrometallurgical processes. Patent application CN113122703A discloses an "apparatus and method for integrated treatment of arsenic removal, zinc removal and reduction roasting of sulfuric acid slag", which uses a microwave reduction roasting furnace to carry out reduction roasting on sulfuric acid slag, and has obvious arsenic and zinc removal effects, but the final iron grade is only about 80%, with a relatively low grade; Patent application CN111809041A discloses a "method for preparing high-grade iron concentrate from sulfuric acid slag", which uses the method of calcination and magnetic separation to treat sulfuric acid slag, and the final iron grade is relatively low, only a little over 60%; Patent application CN102796839A discloses a "process method for reduction roasting of sulfuric acid slag to produce direct reduced iron and synchronous desulfurization", which obtains higher-grade direct reduced iron powder through adding a mixed desulfurizer and reducing agent of sodium carbonate and calcium carbonate, high-temperature roasting and magnetic separation. Its iron grade reaches 90%, and the sulfur removal rate reaches more than 96%. However, the sodium carbonate used has a relatively high cost and will introduce alkali metals into the final product, affecting the quality of the final product; Patent application CN112080635A discloses a "method for preparing iron concentrate powder by self-reduction of sulfuric acid slag based on biomass", which mixes sulfuric acid slag, biomass carbon and binder, presses them into blocks, and carries out direct reduction under nitrogen protection to finally obtain high-purity direct reduced iron powder. This process requires a protective gas atmosphere, has high requirements for equipment and process, and is difficult to realize industrial application; Patent application CN102925612A discloses a "method for extracting sponge iron from sulfuric acid slag by reduction roasting in a tunnel kiln", which mixes sulfuric acid slag raw materials, reducing agent and desulfurizing agent, presses the mixed raw materials into hollow bricks and arranges them in a tunnel kiln for reduction roasting. This process adds an excessive amount of reducing agent, significantly increasing the treatment cost. At the same time, this process does not treat the soot during the roasting process, and the soot generated during the roasting process will cause secondary pollution to the environment.

[0005] In addition to the above patents, the "method for producing iron concentrate powder from sulfuric acid slag" disclosed in Patent CN103088203B; the "method for preparing iron-rich pellets from sulfuric acid slag" disclosed in Patent Application CN118127317A; the "method for producing iron concentrate powder from sulfuric acid slag" disclosed in Patent Application CN106435171A; the "method for producing high-purity iron concentrate from sulfuric acid slag" disclosed in Patent Application CN106755949A, etc. are all based on the recovery and utilization of iron elements in sulfuric acid slag. Although these patent applications can achieve the recovery of iron elements, they are prone to cause relatively large iron losses during the treatment process, the final iron grade is not high, and the high-value utilization of products cannot be achieved. Moreover, the requirements for equipment and operation are relatively high, and it is difficult to realize industrial application.

[0006] The blast furnace bag dust is a high-temperature mixture of iron ore powder, coke, limestone and other iron-making raw materials, which is obtained by collecting the dry bag dust of blast furnace gas. The main components are carbon and iron oxide, accounting for 60-70% in total. In addition, it also contains some harmful elements to blast furnace smelting, among which zinc element accounts for 5-10% and chlorine element accounts for 2-5%. At present, the main treatment methods of blast furnace bag dust include extracting zinc oxide, separating carbon, iron and zinc, direct roasting and landfill. Among them, the energy consumption is relatively large in the process of extracting zinc oxide and the iron in the blast furnace bag dust is not effectively utilized; the value of the products obtained by separating carbon, iron and zinc is not high and the high-value utilization of blast furnace bag dust cannot be realized; direct roasting is only to obtain building materials and the effective utilization of blast furnace bag dust cannot be realized; direct landfill will cause pollution to the environment and soil and occupy a large amount of land. Therefore, combining the roasting characteristics of sulfuric acid slag and the characteristics of blast furnace bag dust, formulating relevant process to treat zinc-containing sulfuric acid slag and blast furnace bag dust, effectively separating the harmful elements therein, recycling the valuable element iron therein, and simultaneously preparing high-value reduced iron powder, so as to achieve the comprehensive recovery of sulfuric acid slag and blast furnace bag dust has important economic and environmental protection values. Summary of the Invention

[0007] The purpose of the present invention is to solve the problems of poor treatment effect, low product added value and inability to be utilized on a large scale of the current zinc-containing sulfuric acid slag and blast furnace bag dust. This method can achieve the purpose of efficiently removing zinc and sulfur from sulfuric acid slag and blast furnace bag dust, and can recycle the iron element in zinc-containing sulfuric acid slag and blast furnace bag dust to obtain high-value reduced iron powder, realize the high-value utilization of zinc-containing sulfuric acid slag and blast furnace bag dust, reduce environmental pollution, and can treat zinc-containing sulfuric acid slag and blast furnace bag dust on a large scale.

[0008] In order to achieve the above purpose, the present invention provides a method for comprehensively treating zinc-containing sulfuric acid slag and blast furnace bag dust, and the method comprises the following steps:

[0009] (1) Mix zinc-containing sulfuric acid slag, blast furnace bag dust, calcareous additive and carbonaceous reducing agent according to the weight ratio of 10: 3-5: 2.5-4: 1.5-3;

[0010] (2) Roast the materials fully mixed in step (1) at high temperature. The dust generated during the roasting process undergoes oxidation dust removal, cooling separation and desulfurization processes to obtain zinc oxide, sulfuric acid and sulfite;

[0011] The high-temperature environment during the roasting process volatilizes and removes zinc and sulfur in the zinc-containing sulfuric acid residue and blast furnace bag dust into the soot. After oxidation, zinc oxides and sulfur oxides are formed. During the subsequent cooling process, the zinc oxides condense and solidify to form particulate deposits, and the sulfur oxides form sulfuric acid and sulfites through the desulfurization process. The carbon powder in the blast furnace bag dust acts as a carbonaceous reducing agent, reducing the iron oxides in the sulfuric acid residue and blast furnace bag dust to metallic iron during the high-temperature roasting process, reducing the addition of the carbonaceous reducing agent.

[0012] (3) Introduce the roasted material in step (2) into a cooling pond for water cooling, and crush and grind the water-cooled slag material;

[0013] (4) Perform high-intensity magnetic separation on the slag material crushed and ground in step (3) to separate the iron-containing phases, and then perform a low-intensity magnetic separation process on the separated iron-containing phases to obtain high-value reduced iron powder.

[0014] Preferably, the calcium additive is limestone or dolomite;

[0015] The carbonaceous reducing agent is coke powder, lignite or semi-coke;

[0016] The roasting temperature is 1200 - 1300 °C, and the roasting time is 0.5 - 3 h;

[0017] The zinc-containing sulfuric acid residue, blast furnace bag dust, calcium additive, and carbonaceous reducing agent are in a weight ratio of 10 : 4 : 3 : 2.5;

[0018] In the oxidation and dust removal in step (2), the zinc in the high-temperature soot is oxidized into zinc oxide and zinc suboxide, and at the same time, dust is removed to reduce the dust content in the flue gas;

[0019] The cooling and separation is to condense and separate zinc oxide and zinc suboxide in the flue gas from sulfur oxides, and the cooling temperature is below 850 °C;

[0020] The desulfurization is to remove sulfur oxides in the tail gas through a desulfurization device to form sulfuric acid and sulfites.

[0021] In step (3), the slag material is ground to a particle size of less than 75 μm, and the proportion reaches between 95% and 98%;

[0022] The high-intensity magnetic separation magnetic field strength is 160 - 210 KA / m, and the low-intensity magnetic separation magnetic field strength is 80 - 120 KA / m;

[0023] The sulfuric acid residue is the waste residue discharged during the sulfuric acid production process from pyrite;

[0024] The blast furnace bag dust is the dust removed during the blast furnace production process of iron and steel enterprises.

[0025] More preferably, the chemical composition of the sulfuric acid residue contains 55-65% TFe, 8-12% SiO 2 , 1-7% Al 2 O 3 , 1-5% MgO, 0.2-1.5% Zn, 0.5-1.5% S; the chemical composition of the blast furnace bag dust contains 30-40% TFe, 5-8% SiO 2 , 4-6% CaO, 2-5% Al 2 O 3 , 3-5% Zn, 18-25% C.

[0026] In the step (2), the fuel used in the roasting process is natural gas, blast furnace gas or heavy oil.

[0027] In the step (2) and step (4), the dust obtained by oxidation dust removal and the tailings obtained by strong magnetic separation and weak magnetic separation can both be used as subgrade and building materials.

[0028] The present invention provides a method for comprehensively treating zinc-containing sulfuric acid residue and blast furnace bag dust. The beneficial effects of the present invention include:

[0029] In the method for comprehensively treating zinc-containing sulfuric acid residue and blast furnace bag dust provided by the present invention, blast furnace bag dust is added. As a solid waste generated during the blast furnace ironmaking process, the blast furnace bag dust contains a large amount of coke powder, which can be used as a reducing agent to reduce iron oxides in the sulfuric acid residue, and other components in the blast furnace bag dust will not have other effects on the roasting process of the sulfuric acid residue; by adding blast furnace bag dust, the use of carbonaceous reducing agents can be reduced, and energy consumption can be saved; in addition, adding blast furnace bag dust can increase the zinc content in the soot during the roasting process, thereby improving the final zinc oxide and zinc suboxide grades; therefore, this method realizes the purpose of converting these two industrial solid wastes, sulfuric acid residue and blast furnace bag dust, into high-value-added products, and solves the problems of large-scale stacking and resource waste of sulfuric acid residue and blast furnace bag dust.

[0030] The present invention separates zinc and sulfur during the roasting process by oxidizing dust removal, cooling separation and desulfurization treatment of the soot generated during the roasting process, and obtains roasted by-products zinc-containing oxides, sulfuric acid and sulfites; separates elemental iron in the roasted slag through strong magnetic separation and weak magnetic separation processes, and obtains a grade of more than 95%, in which the sulfur and zinc content is reduced to less than 0.1%. This treatment method is simple, the by-product products are stable, and high-purity, high-grade high-value-added reduced iron powder can be obtained. At the same time, the iron recovery rate is high, and the zinc and sulfur contents are low. This method not only disposes of industrial solid wastes but also improves economic benefits, and at the same time reduces the solid waste treatment pressure for enterprises, having good economic and social benefits. Description of the Drawings

[0031] Figure 1 Process flow chart of the method for comprehensively treating zinc-containing sulfuric acid residue and blast furnace bag dust provided by the present invention. Specific embodiments

[0032] The present invention will be further described and illustrated below in conjunction with embodiments. However, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the present invention and the embodiments, all other inventions and embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0033] Unless otherwise specified, the experimental methods used in the following embodiments are all conventional methods.

[0034] Unless otherwise specified, the materials, reagents, etc. used in the following embodiments can all be obtained from commercial channels.

[0035] Embodiment 1. A method for comprehensively treating zinc-containing sulfuric acid residue and blast furnace bag dust

[0036] In this embodiment, the sulfuric acid residue used is the residue discharged after pyrite acid making, and the blast furnace bag dust used is the dust removed during the blast furnace production process. The chemical components are shown in Table 1; in this embodiment, coke powder (with a fixed carbon content > 85% and a volatile content of 10%) is selected as the carbonaceous reducing agent, and the calcium additive used is limestone.

[0037] Table 1 Main chemical components (wt.%) of sulfuric acid residue and blast furnace bag dust used in Embodiment 1

[0038]

[0039] As Figure 1 shown, the specific implementation steps of the method for comprehensively treating zinc-containing sulfuric acid residue and blast furnace bag dust are as follows:

[0040] (1) Thoroughly mix the zinc-containing sulfuric acid residue, blast furnace bag dust, limestone, and coke powder in a weight ratio of 10:4:3:2.5;

[0041] (2) Subject the mixed material in step (1) to high-temperature roasting at a roasting temperature of 1250 °C for 1 h. Oxidize and remove the dust generated during the roasting process, oxidize the zinc in the high-temperature dust into zinc oxide and zinc suboxide, and at the same time reduce the dust content in the flue gas through the dust removal equipment; then separate the zinc oxide and zinc suboxide in the flue gas by condensation at 750 °C from sulfur oxides; further remove the sulfur oxides in the tail gas through a desulfurization absorption tower to form sulfuric acid and sulfites;

[0042] (3) The material calcined in step (2) is directly poured into a cooling pool for cooling, the water-cooled material is introduced into a crusher for crushing, and the crushed material is ground until the particle size is less than 75 μm, accounting for 96%;

[0043] (4) The slag after crushing and grinding in step (3) is magnetically separated from the iron-containing phase on a magnetic separator with a magnetic field strength of 210KA / m, and then the separated iron-containing phase is magnetically separated on a weak magnetic separator with a magnetic field strength of 100kA / m to obtain high-value reduced iron powder.

[0044] The final reduced iron powder after treatment by this process has an iron grade of 97%, a mesh size of less than 200 meshes, a S content of 0.06%, a Zn content of 0.09%, a sulfur removal rate of 92%, and a zinc removal rate of 80%, and has a high economic value.

[0045] Example 2: A method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash

[0046] The sulfuric acid slag used in this embodiment is the slag discharged after the pyrite acid is made, and the blast furnace bag ash used is the dust ash produced in the blast furnace production process, and the chemical composition is shown in Table 2; in this embodiment, blue charcoal (wherein the fixed carbon content is> 80%) is selected as the carbonaceous reducing agent, and dolomite is the calcium additive (CaO:MgO=3:2);

[0047] Table 2 Main chemical components of sulfuric acid slag and blast furnace bag ash used in Example 2 (wt.%)

[0048]

[0049] like Figure 1 As shown, the specific implementation steps of the method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash are as follows:

[0050] (1) fully mixing zinc-containing sulfate slag, blast furnace bag ash, dolomite and semi-coke in a weight ratio of 10:3:2.5:2;

[0051] (2) The mixed material in step (1) is subjected to high temperature roasting at a roasting temperature of 1300° C. for a roasting time of 0.5 h, and the smoke generated during the roasting process is subjected to oxidation and dust removal, and the zinc in the high-temperature smoke is oxidized into zinc oxide and zinc suboxide, and the dust content in the flue gas is reduced by dust removal equipment; the zinc oxide and zinc suboxide in the flue gas are then condensed at 750° C. to separate them from sulfur oxides; and the sulfur oxides in the tail gas are removed by a desulfurization absorption tower to form sulfuric acid and sulfite;

[0052] (3) Directly pour the material after roasting in step (2) into a cooling pond for cooling, import the water-cooled material into a crusher for crushing, and grind the crushed material until the proportion of particles with a particle size below 75 μm reaches 97%;

[0053] (4) Magnetically separate the iron-containing phase from the slag material after crushing and grinding in step (3) on a magnetic separator with a magnetic field intensity of 180 kA / m, and then magnetically separate the obtained iron-containing phase on a weak magnetic separator with a magnetic field intensity of 90 kA / m to obtain high-value reduced iron powder.

[0054] The final reduced iron powder after being treated by this process has an iron grade of 95%, a mesh number lower than 200 mesh, an S content of 0.09%, a Zn content of 0.05%, a sulfur removal rate of 90%, and a zinc removal rate of 78%, and has high economic value.

Claims

1. A method for comprehensively treating zinc-containing sulfate slag and blast furnace bag ash, characterized in that: The method comprises the following steps: (1) mixing zinc-containing sulfate slag, blast furnace bag ash, calcium additive, and carbonaceous reducing agent in a weight ratio of 10:3-5:2.5-4:1.5-3; (2) subjecting the fully mixed materials of step (1) to high temperature roasting, and subjecting the smoke generated during the roasting process to oxidation dust removal, cooling separation and desulfurization processes to obtain zinc oxide, sulfuric acid and sulfite; (3) water cooling the material after roasting in step (2), and crushing and grinding the slag after water cooling; (4) subjecting the crushed and ground slag in step (3) to strong magnetic separation to separate the iron-containing phase, and then subjecting the separated iron-containing phase to weak magnetic separation to obtain high-value reduced iron powder; The sulfuric acid slag is waste slag discharged from the pyrite acid production process, and the chemical composition of the sulfuric acid slag contains 55-65% TFe, 8-12% SiO2, 1-7% Al2O3, 1-5% MgO, 0.2-1.5% Zn, 0.5-1.5% S; the blast furnace bag ash is dust removal ash generated in the blast furnace production process of a steel enterprise, and the chemical composition of the blast furnace bag ash contains 30-40% TFe, 5-8% SiO2, 4-6% CaO, 2-5% Al2O3, 3-5% Zn, 18-25% C; In the step (2), the fuel used in the roasting process is natural gas, blast furnace gas or heavy oil; the oxidation dust removal is to oxidize the zinc in the high-temperature smoke into zinc oxide and zinc suboxide, and at the same time reduce the dust content in the flue gas by dust removal; the cooling separation is to condense the zinc oxide and zinc suboxide in the flue gas and separate them from the sulfur oxides, and the temperature of the cooling separation is below 850°C.

2. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to claim 1, characterized in that: The calcium additive is limestone or dolomite; the carbonaceous reducing agent is coke powder, lignite or blue charcoal.

3. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to claim 1, characterized in that: The calcination temperature is 1200-1300°C, and the calcination time is 0.5-3 h.

4. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to claim 1, characterized in that: The zinc-containing sulfate slag, blast furnace bag ash, calcium additive and carbonaceous reducing agent are in a weight ratio of 10:4:3:2.

5.

5. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to claim 1, characterized in that: The desulfurization is to remove sulfur oxides in the tail gas by desulfurization equipment to form sulfuric acid and sulfite.

6. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to claim 1, characterized in that: In the step (3), the slag is ground to a particle size of 95-98% below 75 μm.

7. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to claim 1, characterized in that: The strong magnetic separation magnetic field strength is 160~210KA / m, and / or the weak magnetic separation magnetic field strength is 80~120KA / m.

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