GB2588364A

GB2588364A - Method for recycling zinc by comprehensively utilizing steelmaking dust

Info

Publication number: GB2588364A
Application number: GB2101494.9A
Authority: GB
Inventors: Huang Run; Wu Qinghi; Lv Xiaodong; Wu Qinzhi; Zhao Shifan; Xu Benjun; Zhang Jinzhu
Original assignee: Guizhou University
Current assignee: Guizhou University
Priority date: 2018-11-26
Filing date: 2019-01-11
Publication date: 2021-04-21
Anticipated expiration: 2039-01-11
Also published as: CN109554550A; WO2020107669A1; CN109554550B; GB202101494D0; GB2588364B

Abstract

A method for recycling zinc by comprehensively utilizing steelmaking dust. Steelmaking dust is mixed with a reducing agent and an additive and is pressed into pellets, the pellets are fed into a vacuum carbon tube furnace to perform vacuum roasting to obtain a gaseous elemental zinc volatile matter, the gaseous elemental zinc volatile matter passes through a condensation collector to be condensed to a solid, and the solid is obtained as a high-purity zinc ingot. The method promotes the reduction of zinc in the steelmaking dust and implements recycling utilization of the steelmaking dust, so that the high-quality zinc ingot is obtained, energy consumption during the control of vacuum condition in the steelmaking dust treatment process is reduced, the process is simple, and the operation is simple and convenient.

Description

METHOD FOR COMPREHENSIVE UTILIZATION AND RECOVERY OF ZINC FROM STEEL-MAKING DUST

TECHNICAL FIELD

The invention belongs to the technical field of comprehensive utilization of secondary resources, and particularly relates to a method for comprehensive utilization of steelmaking dust to recover zinc.

BACKGROUND

Iron and steel enterprises produce a large amount of dust in various processes such as iron-making, steel-making and steel rolling, accounting for about 10% of the total steel output. It is one of the main pollution sources of iron and steel plants, and also a potential secondary resource. Due to the different levels of raw materials and fuels in various iron and steel enterprises, the dust not only contains high iron content, but also contains high zinc content. If it is directly returned to sintering as an ingredient, the zinc will be continuously recycled and enriched, which will bring harmful effects such as furnace nodulation, tuyere upwarping and damage, and seriously endanger the smooth operation of iron and steel smelting process.

However, the amount of zinc resource in China is small and the consumption is large, so it is necessary to increase the utilization of recycled zinc. Iron and steel metallurgical dust is an important source of recycled zinc. However, because the quality of zinc-containing dust is far less than that of traditional zinc smelting raw materials, the value of zinc extraction is limited, and it cannot be directly used by zinc smelting enterprises, so how to effectively use zinc-containing dust has always been an important problem in the industry.

The traditional zinc-containing dust treatment methods are mainly wet method and fire method. The wet treatment process is complex, difficult to control, low economic efficiency, and produces a lot of chemical waste, causing environmental pollution, and is difficult to optimize and cannot be used on a large scale. Therefore, at present, the treatment of zinc-containing dust is concentrated on Pyrometallurgical process, but pyrometallurgical process requires higher processing temperature, higher consumption and larger equipment investment.

At present, there are some documents on the recovery of zinc from steel-making dust for secondary utilization, such as: 1. Patent application CN201710643213. X discloses a method for recycling steelmaking dust and a vacuum reduction electric furnace equipment for its use. In this method, steel-making dust, coke powder, calcium oxide and water are mixed in the proportion of 53:20:15:12 to make pre reduction pellets, which are then put into a rotary furnace, and the pre reduction temperature is controlled at 1050 °C for reduction for 60min to collect the waste gas and slag (the first iron-containing slag) of the first high temperature furnace. The first zinc containing dust is obtained by filtering the waste gas of the first high temperature furnace; then the first iron containing slag is crushed and mixed with coke powder, calcium oxide and water in the proportion of 55:18:15:12 to make a secondary reduction pellet, which is put into the electric furnace for secondary reduction, and the pre reduction temperature is controlled at 1150 °C for reduction for 50min, and the waste gas of the second high temperature furnace of the rotary furnace is collected. The second zinc containing dust is obtained by filtering the waste gas of the-second-high temperature furnace. Finally, the coarse zinc oxide dust (prepared by mixing the first zinc containing dust and the second zinc containing dust) or the fine zinc oxide dust (the second zinc containing dust) and the iron powder are mixed evenly according to the molar ratio of 1:1-1.2, pressed into blocks, and then placed in the high-frequency induction heating furnace at 1100 °C for 2h for oxidation-reduction reaction, finally condensed and collected to obtain elemental zinc blocks. Finally, the extraction rate of zinc can reach more than 95%, and the iron content of iron slag can reach more than 60%, and this method is economic and environmental protection, which can achieve the purpose of waste recycling. It can be seen that the patent application adopts the pre-reduction treatment first, and the pre-reduction step and the reduction roasting treatment step are carried out separately, thus prolonging the whole process, and the temperature in the pre-reduction step is higher, and the energy consumption is larger; and the secondary pre-reduction treatment is also required in the treatment process, which further increases the cost.

2. Patent application CN201010237178. X discloses a process for recovering zinc and iron from steel-making dust of waste galvanized sheet. The steel-making dust of waste galvanized sheet is used as the raw material and is crushed and screened to obtain leaching material. Zinc oxide in leaching material is leached by weak acid at room temperature, while zinc ferrite is leached by strong acid at high temperature. The leaching rate of zinc in the whole leaching process is higher than 95%. The iron precipitation rate can reach 99% by using phosphoric acid iron precipitation process; the purified zinc rich liquid is extracted and electrodeposited to obtain electrodeposited zinc; the iron phosphate obtained by phosphoric acid iron precipitation process can be further hydrolyzed to form Fe(OH)3 and HP042-, and the Fe(OH)3 generated by reaction can be used as raw material for iron and steel plant, while HP042-can realize the recycling of iron precipitation agent phosphoric acid. The invention can not only recover metal zinc and metal iron from steel-making dust of waste galvanized sheet, but also realize the recycling of iron precipitant phosphoric acid. However, the patent application adopts the wet treatment process, which is complex and difficult to control. If it is used on a large scale, a lot of chemical waste will be produced, causing environmental pollution and low economic benefits.

3. Patent application CN201710639195.8 discloses a method for extracting lead and zinc from crude zinc oxide recovered from steel-making dust. The method includes the following steps: 1) making crude zinc oxide into spherical particles and adding them into an oxidation smelting furnace for heating and oxidation refining; 2) volatilizing zinc and lead elements in the furnace body in gaseous form, changing into dust after meeting oxygen, and collecting zinc and lead with a container 3) put the above dust into hydrochloric acid solution for stirring and dissolving, and the zinc component exists in the form of zinc ion solution and the lead component exists in the form of lead chloride solid; 4) add sodium carbonate solution into zinc ion solution to produce zinc carbonate, and lead chloride add sodium carbonate solution to produce lead carbonate; 5) wash and dry with water. The process of the invention is simple and the operation is convenient. The purity of PbCO3 and ZnCO3 can reach more than 98%, the purity of Pb0 and ZnO can reach more than 99%, and the purity of Zn and Pb can reach more than 99.9%. However, the patent application first adopts reduction roasting treatment, and then adopts wet process treatment. The whole process is divided into two steps, the overall process is more complex, energy consumption is larger, and control is more difficult, such as large-scale use will produce more chemical waste, and environmental pollution.

Therefore, how to effectively recycle the zinc in the zinc-containing steel-making dust, and the obtained residue can also be used as an ingredient for secondary utilization is a key problem.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the invention provides a method for comprehensively utilizing and recovering zinc from steel-making dust. The application promotes the reduction of zinc in steel-making dust by adding additives, realizes the recovery and utilization of steel-making dust, obtains high-quality zinc ingot, reduces the energy consumption of vacuum condition control in the process of steel-making dust treatment, and has the advantages of simple process and simple operation. The vacuum can effectively evaporate zinc in steel-making dust, so as to achieve the purpose of condensing and collecting elemental zinc, so that the recovery rate of zinc in steel-making dust is as high as 97.76%, which effectively solves the problems of high cost, heavy pollution, high energy consumption and large output of three wastes in the treatment of zinc-containing steel-making dust in the existing technology, and finally realizes the purpose of waste recycling.

In order to achieve the above purpose, the invention adopts the following technical scheme: A method for comprehensive utilization and recovery of zinc from steel-making dust, comprising the following steps: (1) the steel-making dust is mixed with reducing agent, additives, and water, in which the steel-making dust, the reducing agent, the additive and water are mixed according to the following weight proportion: 100 units of the steel-making dust, 6-8 units of the reducing agent, 0-2 units of the additive and 0.4-0.7 units of water, and then sent into a mold with a diameter of 20.01-30mm and a pressure of 11-19MPa to form pellets; the additive is boron trioxide, the reducing agent is coke powder; (2) the pellets in step (1) are sent into a vacuum carbon tube furnace for vacuum roasting to obtain volatiles; the vacuum roasting conditions are as follows: the reaction temperature is controlled to 850-950 °C under the vacuum degree of 10-100pa, and the constant temperature treatment time is 80-100min, (3) the volatiles obtained in step (2) are gaseous elemental zinc, which is condensed into a solid after passing through a condensing collector, and the solid is collected to obtain a high-purity zinc ingot.

Further, in step (1), the method of mixing raw materials before pressing into pellets is as follows: firstly, the steel-making dust and the reducing agent are evenly mixed, and then they are sent to a grinder to grind into powder with a mesh size of 80-120 mesh, and then the additives and water are added for mixing.

Further, before the steel-making dust and the reducing agent are mixed, the steelmaking dust is ball-milled with a ball mill to form a powder with a mesh size of 30-60 10 mesh Further, in step (2), before the pellets are sent into the vacuum carbon tube furnace for vacuum roasting, the formed pellets are sent to the drying oven for drying treatment until the moisture content is 0.

Further, the drying temperature is 120°C and the drying time is 1-3 hours.

The paper "Experimental Study on zinc recovery from electric furnace dust", Journal of iron and steel research, Du Guangbao, Zhang Mei, Guo min, October 15, 2010, disclosed that part of the dust has agglomerated during stacking and transportation, and its water content is 1.94%. The test pellets (8-15mm in diameter) are prepared by crushing, drying, carbon mixing, pelletizing (adding binder) and drying the dust.

The pellets are put into the alumina crucible, and then put into the constant temperature zone of the furnace at the test temperature. The test pellets are roasted at high temperature under the protection of nitrogen gas. The test pellets are put into the furnace, and the iron and zinc are gradually reduced by carbon and CO at high temperature. The results show that when the C / 0 ratio is 1.2, the roasting temperature is 1100 °C, and the reduction time is 10min, the pellets with metallization rate of 84.95% can be obtained, and the metallic zinc can be collected. Both the paper and the application recover zinc by adding substances to the dust, pelletizing and roasting. After zinc is reduced by carbon and CO, there will be CO and other elements in the gas in addition to zinc, so that the final condensed material is not necessarily pure zinc, and the process also needs to be carried out under the protection of nitrogen gas, which will increase the cost of recovery and treatment. However, the application makes the reduction process of zinc easier by adding additive (boron trioxide); in addition, the application selects reasonable vacuum degree for vacuum reduction roasting of steel-making dust, which greatly reduces the reaction temperature, does not need inert gas protection, and reduces the energy consumption in the treatment process; and in the application, the steel-making dust is pulverized and uniformly mixed with the reducing agent and additives so that the steel-making dust can fully contact with the reducing agent and additives, which makes the reaction fully carried out in the reduction roasting process, because the reaction mainly occurs in the surface layer of particles, and the dynamic conditions are good; the addition of water makes the test block easier to form; the constant temperature treatment time is reasonable, and the energy saving at the same time ensures that the reduction process is fully carried out, so that the zinc can be volatilized completely, and then condensed and collected to obtain zinc ingot.

Reaction principle of the application: the method of the application uses coke powder as reducing agent, reduces zinc in steel-making dust pellet into elemental substance by reduction roasting method and discharges it in gaseous form, while valuable metals such as iron and other components in steel-making dust pellet are left in vacuum furnace, so as to separate zinc, zinc vapor is condensed and collected to obtain high-purity zinc ingot, and the excess tail gas is discharged after the activated carbon adsorption treatment, which avoids secondary pollution during the recovery process. The method of the application first mixes the steel-making dust, reducing agent, additive and water evenly, and then makes the pellet under the pressure of 11-19MPa, so as to increase the binding force of the block, so that the zinc oxide powder in the steel-making dust can fully contact with the coke powder and boron trioxide, and the zinc oxide in the block can be reduced to the zinc element as much as possible. In addition, the reduction roasting conditions are set as follows: the reaction temperature is 850-950 °C and the constant temperature treatment is 80-100min under the vacuum degree of 10-100Pa; if the vacuum degree is higher than 100Pa, the temperature is lower than 850 °C and the treatment time is less than 80min, the zinc oxide cannot be fully reduced and the zinc monomer cannot completely escape from the block; if the vacuum degree is lower than 10Pa, the temperature is higher than 950 °C and the treatment time is longer than 100 min, zinc oxide cannot be fully reduced to zinc, resulting in waste of resources. Through the comprehensive utilization and zinc recovery method of steel-making dust in the invention, the final zinc recovery rate is as high as 97.76%, and the iron content of the obtained iron bearing material is more than 59.16%, which can be directly reused as iron concentrate, so that the resources can be fully recovered and utilized.

EFFECT OF THE INVENTION

Since the invention adopts the above technical scheme, it has the following beneficial effects: (1) In order to solve the above defects, in the present invention, the steel-making dust, the reducing agent and the additives are mixed and pressed into pellets, and then the pellets are send into a vacuum carbon tube furnace for reduction roasting treatment. The whole treatment process is an integral treatment with low reduction temperature, and can fully volatilize zinc from the steel-making dust, thus reducing the large energy consumption required for heating up in two pre-reduction processes. It not only reduces the cost of comprehensive utilization of steel-making dust, but also reduces the energy consumption and the emission of three wastes.

(2) Through the reasonable control of vacuum degree, the gas pressure in the vacuum carbon tube furnace is low, which can promote the gasification and evaporation of metal, the decomposition and reduction of metal compounds, and degassing of molten metal, so that zinc can be fully volatilized in the reduction roasting process, the recovery rate of elemental zinc can be improved, the reaction speed can be accelerated and the reaction temperature can be reduced, so that metallurgical operations can be carried out at low temperatures to reduce energy consumption. For example, when the pressure of the system is 100 Pa, the starting temperature of the carbothermal reduction of MgO to magnesium vapor is 1476 K (i.e. 1203 °C); under normal pressure, the starting temperature of the carbothermal reduction of MgO to magnesium vapor is 2154 K (i.e. 1881 °C).

(3) The application reasonably controls the temperature in combination with the vacuum degree, so that the zinc can be fully volatilized in the reduction roasting process, further improving the recovery rate of elemental zinc, avoiding that the zinc in the steel-making dust is difficult to volatilize at too low temperature, and avoiding the volatilization of metal magnesium or manganese at too high temperature, so as to reduce the energy consumption in the reduction roasting process.

(4) By reasonably controlling the process parameters of vacuum reduction roasting, the zinc is volatilized in the form of steam and other substances cannot be volatilized, thus forming high-purity zinc ingot in the condensation process.

(5) The application promotes the reduction of zinc in steel-making dust by adding additives, realizes the recovery and utilization of steel-making dust, obtains high-quality zinc ingot, reduces the energy consumption of vacuum condition control in the process of steel-making dust treatment, and has the advantages of simple process and simple operation. Vacuum can effectively evaporate zinc in steel-making dust, so as to achieve the purpose of condensing and collecting elemental zinc, which makes the process more convenient. The recovery rate of zinc in steel-making dust is as high as 97.76%, which effectively solves the problems of high cost, heavy pollution, high energy consumption and large output of three wastes in the treatment of zinc-containing steel-making dust in the existing technology.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The specific embodiments of the invention are further described in detail below, but the invention is not limited to these embodiments. Any improvement or substitution in the basic spirit of the embodiment still belongs to the scope of protection claimed in the claims of the invention.

The embodiment of the application adopts the steel-making dust produced in the production process of a factory in Guizhou, analyzes its chemical composition, and obtains the mass fraction of its composition as shown in Table 1 Table 1 Chemical composition and content of steel-making dust Composition TFe Si02 Mg0 A1203 MnO Zn Cu As Content(wt%) 58.98 1.10 2.10 0.07 0.590 6.35 0.03 0.057 The main raw materials and dosage of embodiments 1-5 of the application are shown

in Table 2 below:

Table 2 Main raw materials and dosage of embodiments 1-5 Steel-making dust / kg Coke powder / kg Boron trioxide / kg Embodiment 1 100 6 0 Embodiment 2 100 8 0 Embodiment 3 100 8 2 Embodiment 4 100 7 1 Embodiment 5 100 7 1.5 Embodiment A method for comprehensively utilizing and recovering zinc from steel-making dust comprises the following steps: (1)after mixing the steel-making dust with the reducing agent and the water, the steel-making dust is pressed into pellets; the reducing agent is coke powder; the steelmaking dust, the reducing agent and the water are evenly mixed before being sent to a mold with a diameter of 20.01mm to press the pellets; the pressure of the pressed pellets is 11MPa; the steel-making dust, the reducing agent and the water are mixed according to the following weight proportion: 100 units of the steel-making dust, 6 units of the reducing agent and 0.4 units of the water; before pelletizing, the steelmaking dust is milled by a ball mill to form 30 mesh powder, which is evenly mixed with the reducing agent, then grinded into 80 mesh powder by a grinding machine, and then mixed with the water; (2)the pellets obtained in step (1) are sent to the vacuum carbon tube furnace for vacuum roasting to obtain volatiles and residues, and the residues are the solid residues in the vacuum carbon tube furnace; the vacuum roasting conditions are as follows: the reaction temperature is controlled to 850 °C under the vacuum degree of 10Pa, and the constant temperature treatment time is 100min; before the pellets are sent to the vacuum carbon tube furnace for vacuum roasting, the formed pellets are sent to the drying oven for drying treatment until the moisture content is 0;the drying temperature is a. 120°C and the drying time is 1h; (3) the residue in step (2) is crushed and ball milled to obtain iron bearing material with improved grade; the volatile matter in step (2) is gaseous elemental zinc, which is condensed into solid after passing through a condensing collector, and the solid is collected to obtain high-purity zinc ingot.

The chemical composition and content of the steel-making dust are shown in Table 1, and the dosage ratio of the steel-making dust, the reducing agent, the additive and the water is shown in Table 2.

Embodiment 2 A method for comprehensively utilizing and recovering zinc from steel-making dust comprises the following steps: (1)after mixing the steel-making dust with the reducing agent and the water, the steel-making dust is pressed into pellets; the reducing agent is coke powder; the steelmaking dust, the reducing agent and the water are evenly mixed before being sent to a mold with a diameter of 30mm to press the pellets; the pressure of the pressed pellets is 19MPa; the steel-making dust, the reducing agent and the water are mixed according to the following weight proportion: 100 units of steel-making dust, 8 units of the reducing agent and 0.7 units of the water; before pelletizing, the steel-making dust is milled by a ball mill to form 60 mesh powder, which is evenly mixed with the reducing agent, then grinded into 120 mesh powder by a grinding machine, and then mixed with water; (2)the pellets in step (1) are sent to the vacuum carbon tube furnace for vacuum roasting to obtain volatiles and residues, and the residues are the solid residues in the vacuum carbon tube furnace; the vacuum roasting conditions are as follows: the reaction temperature is controlled to 950 °C under the vacuum degree of 100Pa, and the constant temperature treatment time is 80min; before the pellets are sent to the vacuum carbon tube furnace for vacuum roasting, the formed pellets are sent to the drying oven for drying treatment until the moisture content is 0; the drying temperature is 120 °C and the drying time is 3h; (3) the residue in step (2) is crushed and ball milled to obtain iron bearing material with improved grade; the volatile matter in step (2) is gaseous elemental zinc, which is condensed into solid after passing through a condensing collector, and the solid is collected to obtain high-purity zinc ingot.

Embodiment 3 A method for comprehensively utilizing and recovering zinc from steel-making dust comprises the following steps: (1)after mixing the steel-making dust with the reducing agent and the water, the steel-making dust is pressed into pellets; the additive is boron trioxide; the reducing agent is coke powder; the steel-making dust, the reducing agent, the additive and the water are evenly mixed before being sent to a mold with a diameter of 21.05mm to press the pellets; the pressure of the pressed pellets is 12MPa; the steel-making dust, the reducing agent and the water are mixed according to the following weight proportion: 100 units of steel-making dust, 8 units of reducing agent, 2 units of additive and 0.5 units of water; before pelletizing, steel-making dust is milled by a ball mill to form 40 mesh powder, which is evenly mixed with the reducing agent, then grinded into 90 mesh powder by a grinding machine, and then mixed with additive and water; (2)the pellets in step (1) are sent to the vacuum carbon tube furnace for vacuum roasting to obtain volafiles and residues, and the residues are the solid residues in the vacuum carbon tube furnace; the vacuum roasting conditions are as follows: the reaction temperature is controlled to 890 °C under the vacuum degree of 20Pa, and the constant temperature treatment time is 89min; before the pellets are sent to the vacuum carbon tube furnace for vacuum roasting, the formed pellets are sent to the drying oven for drying treatment until the moisture content is 0; the drying temperature is a. 120°C and the drying time is 1.5h; (3) the residue in step (2) is crushed and ball milled to obtain iron bearing material with improved grade; the volatile matter in step (2) is gaseous elemental zinc, which is condensed into solid after passing through a condensing collector, and the solid is collected to obtain high-purity zinc ingot.

The chemical composition and content of the steel-making dust are shown in Table 1, and the dosage ratio of the steel making dust, the reducing agent, the additive and the water is shown in Table 2.

Embodiment 4 A method for comprehensively utilizing and recovering zinc from steel-making dust comprises the following steps: (1)After mixing the steel-making dust with the reducing agent and the water, the steel-making dust is pressed into pellets; the additive is boron trioxide; the reducing agent is coke powder; the steel-making dust, reducing agent, additive and water are evenly mixed before being sent to a mold with a diameter of 29.01mm to press the pellets; the pressure of the pressed pellets is 18MPa; the steel-making dust, reducing agent and water are mixed according to the following weight proportion: 100 units of steel-making dust, 7 units of reducing agent, 1 units of additive and 0.6 units of water; before pelletizing, the steel-making dust is milled by a ball mill to form 50 mesh powder, which is evenly mixed with the reducing agent, then grinded into 110 mesh powder by a grinding machine, and then mixed with the additive and the water; (2)the pellets in step (1) are sent to the vacuum carbon tube furnace for vacuum roasting to obtain volatiles and residues, and the residues are the solid residues in the vacuum carbon tube furnace; the vacuum roasting conditions are as follows: the reaction temperature is controlled to 930 °C under the vacuum degree of 90Pa, and the constant temperature treatment time is 85min; before the pellets are sent to the vacuum carbon tube furnace for vacuum roasting, the formed pellets are sent to the drying oven for drying treatment until the moisture content is 0; the drying temperature is 120 °C and the drying time is 1.5h; (3) tThe residue in step (2) is crushed and ball milled to obtain iron bearing material with improved grade; the volatile matter in step (2) is gaseous elemental zinc, which is condensed into solid after passing through a condensing collector, and the solid is collected to obtain high-purity zinc ingot.

Embodiment 5 A method for comprehensively utilizing and recovering zinc from steel-making dust comprises the following steps: (1)after mixing the steel-making dust with the reducing agent and the water, the steelmaking dust is pressed into pellets; the additive is boron trioxide; the reducing agent is coke powder; the steel-making dust, the reducing agent, the additive and the water are evenly mixed before being sent to a mold with a diameter of 25mm to press the pellets; the pressure of the pressed pellets is 15MPa; the steel-making dust, the reducing agent and the water are mixed according to the following weight proportion: 100 units of the steel-making dust, 7 units of the reducing agent, 1.5 units of the additive and 0.5 units of the water; before pelletizing, the steel-making dust is milled by a ball mill to form 45 mesh powder, which is evenly mixed with the reducing agent, then grinded into 100 mesh powder by a grinding machine, and then mixed with the additive and the water; (2)the pellets in step (1) are sent to the vacuum carbon tube furnace for vacuum roasting to obtain volatiles and residues, and the residues are the solid residues in the vacuum carbon tube furnace; the vacuum roasting conditions are as follows: the reaction temperature is controlled to 900 °C under the vacuum degree of 50Pa, and the constant temperature treatment time is 90min; before the pellets are sent to the vacuum carbon tube furnace for vacuum roasting, the formed pellets are sent to the drying oven for drying treatment until the moisture content is 0; the drying temperature is 120 °C and the drying time is 2h; (3) the residue in step (2) is crushed and ball milled to obtain iron bearing material with improved grade; the volatile matter in step (2) is gaseous elemental zinc, which is condensed into solid after passing through a condensing collector, and the solid is collected to obtain high-purity zinc ingot.

Comparative example 1 The difference from embodiments 1-5 is that the pressure is controlled to 1 atm during the roasting process, and other conditions remain unchanged.

Comparative example 2 The difference from embodiments 1-5 is that the temperature is controlled at 800 °C during the vacuum roasting process, and other conditions remain unchanged.

Comparative example 3 Follow the embodiment in patent application CN201710643213. X. Comparative example 4 Follow the embodiment in patent application CN201010237178. X. Embodiments 1-5 and comparative examples 1-4 of the application are respectively tested for zinc recovery and utilization of steel-making dust, and the zinc recovery rate, iron content of iron bearing materials and total cost after treating 100kg steel-making dust by different methods are recorded. The test results are shown in Table 3 below.

Table 3 Experimental results of 100kg steel-making dust treated by different methods Groups Zinc recovery Iron content in Total cost ferrous materials Embodiment 1 93.70% 61.69% 117 yuan Embodiment 2 95.43% 59.16% 122 yuan Embodiment 3 97.76% 60.67% 168 yuan Embodiment 4 96.25% 61.08% 143 yuan Embodiments 96.97% 61.96% 154 yuan Comparative example 1 48.03% 58.23% 156 yuan Comparative example 2 90.26% 59.21% 138 yuan Comparative example 3 96.00% 60.00% 496 yuan Comparative example 4 95.00% 62.56% 473 yuan It can be seen from the experimental data in Table 3 that in the process of recycling zinc from steel-making dust, the recovery rate of zinc and the iron content of iron-bearing materials are equivalent to those of Comparative example 3 and Comparative example 4. However, when the amount of steel-making dust is the same, the cost of Comparative example 3 and Comparative example 4 is obviously higher than that of the application method. Therefore, the application method has obvious advantages in recycling zinc from steel-making dust.

To sum up, the application promotes the reduction of zinc in steel-making dust through the addition of additives, realizes the recycling of steel-making dust, obtains high-quality zinc ingot, reduces the energy consumption of vacuum condition control in the process of steel-making dust treatment, and has simple process and operation. Vacuum reduction can effectively evaporate zinc in steel-making dust, so as to achieve the purpose of condensing and collecting elemental zinc. The recovery rate of zinc in steel-making dust is as high as 97.76%, which effectively solves the problems of high cost, heavy pollution, high energy consumption and large output of three wastes in the treatment of zinc-containing steel-making dust in the existing technology, and finally realizes the purpose of waste recycling.

For those skilled in the art, it is obvious that the invention is not limited to the details of the above exemplary embodiments, and can be realized in other specific forms without departing from the spirit or basic features of the invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the invention is defined by the attached claims rather than the above description. Therefore, it is intended to include all changes within the meaning and scope of the claims in the scope of protection of the invention.

Claims

CLAIMS1. A method for comprehensive utilization and recovery of zinc from steel-making dust, characterized in that it comprises the following steps: (1) the steel-making dust is mixed with reducing agent, additives and water, in which the steel-making dust, the reducing agent, the additive and the water are mixed according to the following weight proportion: 100 units of the steel-making dust, 7-8 units of the reducing agent, 0-2 units of the additive and 0.4-0.7 units of the water, and then sent into a mold with a diameter of 20.01-30mm and a pressure of 11-19MPa to form pellets; the additive is boron trioxide, the reducing agent is coke powder; (2) the pellets in step (1) are sent into a vacuum carbon tube furnace for vacuum roasting to obtain volatiles; the vacuum roasting conditions are as follows: the reaction temperature is controlled to 850-950 °C under the vacuum degree of 10-100pa, and the constant temperature treatment time is 80-100min; (3) the volatiles obtained in step (2) are gaseous elemental zinc, which is condensed into a solid after passing through a condensing collector, and the solid is collected to obtain a high-purity zinc ingot.
2. A method for comprehensive utilization of steel-making dust and recovery of zinc according to claim 1, characterized in that: in step (1), the method of mixing raw materials before pressing into pellets is as follows: firstly, the steel-making dust and the reducing agent are evenly mixed, and then they are sent to a grinder to grind into powder with a mesh size of 80-120 mesh, and then the additives and the water are added for mixing.
3. A method for comprehensive utilization of steel-making dust and recovery of zinc according to claim 2, characterized in that: before the steel-making dust and the reducing agent are mixed, the steel-making dust is ball-milled with a ball mill to form a powder with a mesh size of 30-60 mesh.
4. A method for comprehensive utilization of steel-making dust and recovery of zinc according to claim 1, characterized in that: in step (2), before the pellets are sent into the vacuum carbon tube furnace for vacuum roasting, the formed pellets are sent to the drying oven for drying treatment until the moisture content is 0.
5. A method for comprehensive utilization of steel-making dust to recover zinc according to claim 4, characterized in that: the drying temperature is a120°C and the drying time is 1-3 hours.