WO2020077851A1

WO2020077851A1 - Method for recovering iron by means of copper slag calcination and modification

Info

Publication number: WO2020077851A1
Application number: PCT/CN2018/123841
Authority: WO
Inventors: 姜平国; 刘金生; 廖春发; 邱廷省; 曾颜亮
Original assignee: 江西理工大学
Priority date: 2018-10-17
Filing date: 2018-12-26
Publication date: 2020-04-23
Also published as: CN109207715B; CN109207715A

Abstract

A method for recovering iron by means of copper slag calcination and modification. The method comprises: (2) maintaining a calcination temperature and inert gas protection, communicating a calcination system with ambient air, simultaneously introducing CO and CO₂ gases into the calcination system in step (1) with the volume percentage of CO in the total gas components of CO and CO₂ being 0-5%, oxidizing free ferrous oxide into ferroferric oxide, and enabling crystals of ferroferric oxide to grow; and (3) performing cooling after calcination is finished, performing ore grinding and grading to obtain modified slag of different particle sizes, and performing magnetic separation under a magnetic field to obtain iron ore concentrate and magnetic separation tailings. According to the method, iron in copper slag can be efficiently recovered by using industrial waste gases CO and CO₂, so as to obtain iron ore concentrate suitable for use as an iron melting raw material and magnetic separation tailings suitable for use as a raw material for building materials such as cement.

Description

Method for recovering iron by roasting copper slag

Technical field

The invention relates to a process for recovering iron in copper slag, in particular to a method for recovering iron by roasting copper slag.

Background technique

According to statistics, in 2017, China's refined copper output reached 8.889 million tons. Copper slag was produced during the copper smelting process, mainly during the copper smelting and smelting process. According to the general slag copper ratio of 2.2: 1 To calculate, the amount of copper slag produced in China in 2017 alone was as high as 17.778 million tons. The typical composition of copper slag is Fe 30% -40%, Cu 0.2% -5%, SiO ₂ 35% -40%, Al ₂ O ₃ and CaO content are both below 10%, there is a small amount of zinc, Metal elements such as nickel and cobalt show that the iron content in copper slag is very high. The copper matte smelting process has complex physical and chemical reactions. The slagging reaction is part of the smelting process. The ferrous oxide and the added quartz stone flux in the slag forming process react to produce ferric silicate. Fayalite (2FeO · SiO ₂ ) is formed. In the process of making matte, it is carried out under an oxidizing atmosphere, so the copper slag is over-oxidized and there is more Fe ₃ O _{4 in the} slag. Therefore, iron in copper slag mainly exists as fayalite and magnetite (Fe ₃ O ₄ ).

The average industrial grade of iron ore in China is 29.1%, and copper slag actually meets the iron grade requirements of iron ore as a kind of "artificial ore". However, at present, the domestic utilization rate of copper in copper slag is less than 12%, and the utilization rate of iron is less than 1%. Most of the copper slag is piled up in the slag yard, which occupies land and pollutes the environment, and is also a huge waste of resources , Has become an important factor hindering the continuous development of copper smelting enterprises. If all the iron in copper slag can be recycled, it not only solves the environmental pollution problem of copper slag accumulation, but also provides a new raw material for the iron smelting industry, reduces the cost of iron smelting, and enables copper smelting enterprises to achieve sustainable development And circular economy requirements.

Summary of the invention

The purpose of the present invention is to provide a method for recovering iron by roasting copper slag, which solves the problem of copper slag utilization, and can efficiently recover iron in copper slag by using industrial waste gas CO and CO _{2 to} obtain iron concentrate .

In order to achieve the above object, the present invention provides a method for recovering iron by roasting and modifying copper slag. The method includes:

(1) The desiliconization modifier and copper slag are heated to the calcination temperature under the protection of inert gas to free the ferrous oxide in the iron olivine in the copper slag;

(2) Maintain the roasting temperature and inert gas protection, the roasting system is connected to the outside atmosphere, and CO and CO ₂ gases are simultaneously introduced into the roasting system in step (1), the volume percentage of CO in the total gas composition of CO and CO ₂ 0 ～ 5%, oxidize the free ferrous oxide to ferric oxide, and make the magnetic ferric oxide crystal grow;

(3) After the roasting is completed, the temperature is lowered, and the modified slag with different particle sizes is obtained through the grinding and classification process, which is separated by magnetic separation under a magnetic field to obtain iron concentrate and magnetic separation tailings.

Preferably, in step (1), the calcination temperature is 800-1200 ° C.

Preferably, in step (1), the inert gas includes any one or two or more of nitrogen, argon and carbon dioxide.

Preferably, in step (1), the desilication modifier comprises: slaked lime.

Preferably, in step (1), the mass ratio of the desiliconization modifier to copper slag is 1:10 to 3:10.

Preferably, in step (2), during the constant-temperature roasting, the total flow rate of the intake air of CO and CO ₂ is 150 mL / min to 250 mL / min; when the temperature is raised to a constant roasting temperature and the temperature is lowered after the roasting ends, The inlet flow rate of the inert gas is 250 mL / min.

Preferably, in step (2), the gas flow rates of CO and CO ₂ are 0-10 mL / min and 190-200 mL / min, respectively.

Preferably, in step (3), a ball mill or a vibration mill is used for the grinding; a vibration screen is used for the classification; and a magnetic separator is used for the magnetic separation.

Preferably, in step (3), the particle size of the modified slag is 38-100 μm.

Preferably, in step (3), the intensity of the magnetic field is 80mT-130mT.

The method for roasting and modifying recovered iron of copper slag of the present invention solves the problem of utilization rate of copper slag and has the following advantages:

The method of the present invention utilizes industrial waste gas CO and CO ₂ and slaked lime to recover iron in waste copper slag. The process is short, the equipment is simple, does not cause secondary pollution, and can obtain iron concentrate directly from copper slag at a lower cost The iron ore with an iron grade of more than 60% and a recovery rate of more than 98% can be obtained from the ore. The recovered iron concentrate can meet the requirements of blast furnace iron raw materials and significantly improve economic efficiency.

detailed description

The technical solutions of the present invention will be further described below in conjunction with embodiments.

A method for roasting and modifying copper slag to recover iron, the method includes:

(3) After the roasting is completed, the temperature is lowered, and the modified slag with different particle sizes is obtained through the grinding and classification process, which is separated by magnetic separation under the magnetic field to obtain iron concentrate and magnetic tailings. The iron concentrate is dried and used as a blast furnace Iron raw materials, magnetic separation tailings are dried as raw materials for making cement or breathable bricks.

The present invention considers that there is a large amount of CO and CO ₂ gas in industrial waste gas. For economic and environmental protection purposes, the CO and CO ₂ gas is used to recover iron in copper slag. When CO and CO ₂ gases are introduced, the gas composition ratio of the two gases in the heat preservation roasting is controlled by adjusting the respective gas flow rates of the two gases under the premise that the total gas flow velocity is constant, and CO is controlled in the total gas composition of CO and CO ₂ The volume percentage is below 5%. By passing inert gas, the air is discharged from the roasting system. The oxidation of iron olivine in the copper slag to ferric oxide requires weak oxidizing conditions. The weak oxidizing atmosphere of the system can be adjusted by CO and CO _2. As much as possible, the iron olivine is oxidized to ferric oxide, and the proportion of CO in the total gas composition cannot exceed 5%. The roasting system of the present invention is in communication with the outside atmosphere, and in a dynamic state, the total amount of gas introduced and discharged is the same, so the inert gas will not affect the overall roasting system.

Further, in step (1), the firing temperature is 800-1200 ° C.

Further, in step (1), the inert gas includes any one or two or more of nitrogen, argon and carbon dioxide.

Further, in step (1), the desiliconization modifier includes any one or two or more of sodium carbonate, calcium sulfate and slaked lime. The role of desiliconizer in the oxidation recovery of fayalite in copper slag is mainly to react with the SiO ₂ component in fayalite and adjust the alkalinity of the system.

Further, in step (1), the mass ratio of the desilication modifier and copper slag is 1:10 to 3:10, so that the molar mass ratio of calcium and silicon in the desilication agent and copper slag is as much as possible It is 1: 1, and the iron in the copper slag is recovered as efficiently as possible.

Further, in step (2), during the constant-temperature roasting, the total flow rate of the intake air of CO and CO ₂ is 150 mL / min to 250 mL / min. There is no strict requirement on the total flow of CO and CO ₂ intake air. The effect on the separation effect of the present invention is related to the volume ratio of CO and CO ₂ , but due to the requirements of economy and controllability, the limits of CO and CO ₂ are limited. The total flow of intake air is 150mL / min ～ 250mL / min.

Further, when the temperature is raised to a constant calcination temperature and the temperature is lowered after the end of the calcination, the flow rate of the inert gas is 250 mL / min.

Further, in step (2), the gas flow rates of CO and CO ₂ are 0 to 10 mL / min and 190 to 200 mL / min, respectively.

Further, in step (3), a ball mill or a vibration mill is used for grinding; a vibrating screen is used for classification; and a magnetic separator is used for magnetic separation. Grinding is mainly to grind the modified slag to meet the particle size of magnetic separation. Therefore, as long as the grinding slag can be used to grind the modified slag to the required particle size, the grinding equipment can be used. The particle size classification can be used as long as it can meet the classification accuracy of the classification equipment. The present invention considers economy and universality, so it chooses a vibrating screen, a magnetic separator, and a ball mill or vibrating mill.

Further, in step (3), the particle size of the modified slag is 38-100 μm.

Further, in step (3), the strength of the magnetic field is 80 mT to 130 mT.

In step (2), the ball mill or vibration mill is used for grinding; the vibrating screen is used for classification; and the magnetic separator is used for magnetic separation.

In step (2), the particle size of the modified slag is 38-100 μm. Through the selection of the particle size of the modified slag to facilitate subsequent magnetic separation. When the particle size of the magnetic separation is too large or too small, it will cause the loss of magnetic concentrate in the process of magnetic separation recovery. After research, it is found that when the particle size of the modified slag is 38 ～ 100μm, the recovery loss of iron concentrate less.

In step (2), the strength of the magnetic field is 80mT ~ 130mT to separate into iron concentrate with high iron grade and tailings with low iron grade. Magnetic field strength is also an important factor influencing the recovery rate of iron concentrate recovered by magnetic separation. Too low or too high magnetic field strength will cause the loss of recovered iron concentrate. After research, it was found that when the strength of the magnetic field is 80mT ~ 130mT, iron The recovery rate of concentrate is less.

Example 1

The dried copper slag and hydrated lime mass ratio of 1:10 under nitrogen calcined at 900 ℃ incubated at, upon firing into a mixed gas of CO and CO _2, CO and CO ₂ in the intake air flow rate of 10mL respectively / min and 190mL / min, control the proportion of CO in the total gas composition of CO and CO _{2 to} be 5%, and roast for 1 hour.

After the roasting is completed, through the grinding and classification process, a modified slag with a particle size of 38 μm is obtained, which is separated by magnetic separation under a weak magnetic field with an intensity of 120 mT.

Through the above process, the iron grade of the recovered iron concentrate (iron grade, refers to the percentage of iron metal content in the iron concentrate amount) is 60%, the recovery rate is 98.5%, magnetic separation tailings (magnetic separation recovery ratio is 1.5%, the silicon content of the magnetic separation tailings is 29.36%, which realizes the separation of iron and silicon and the recovery of iron.

Example 2

The dried copper slag and hydrated lime mass ratio of 1:10 calcined under argon, at 950 ℃ incubated, upon firing into a mixed gas of CO and CO _2, CO and CO ₂ in the intake air flow rate respectively, 10mL / min and 190mL / min, control the proportion of CO in the total gas composition of CO and CO _{2 to} be 5%, and roast for 4 hours.

After the roasting is completed, through the grinding and classification process, a modified slag with a particle size of 38-50 μm is obtained, and the magnetic separation is performed under a weak magnetic field with an intensity of 110 mT.

Through the above process, the recovered iron concentrate iron grade is 62.5%, the recovery rate is 98.83%, the recovery rate of the magnetic separation tailings is 1.17%, the silicon content in the magnetic separation tailings is 30.05%, and the separation of iron and silicon is achieved. And the recovery of iron.

Example 3

The dried copper slag and hydrated lime mass ratio of 2:10 under carbon dioxide protection calcined at 1000 ℃ incubated, upon firing into a mixed gas of CO and CO _2, CO and CO ₂ in the intake air flow rate were 5mL / min and 195mL / min, control the proportion of CO in the total gas composition of CO and CO _{2 to} be 2.5%, and roast for 8 hours.

After the roasting is completed, through the grinding and classification process, a modified slag with a particle size of 50-74 μm is obtained, and the magnetic separation is performed under a weak magnetic field with an intensity of 100 mT.

Through the above process, the recovered iron concentrate iron grade is 65.7%, the recovery rate is 99.25%, the recovery rate of the magnetic separation tailings is 0.75%, the silicon content in the magnetic separation tailings is 31.27%, and the separation of iron and silicon is achieved. And the recovery of iron.

Example 4

The dried copper slag and hydrated lime mass ratio of 2:10 under carbon dioxide protection fired at 1050 deg.] C under heat, upon firing into a mixed gas of CO and CO _2, CO and CO ₂ in the intake air flow rate were 5mL / min and 195mL / min, control the proportion of CO in the total gas composition of CO and CO _{2 to} be 2.5%, and roast for 12 hours.

After the roasting is completed, through the grinding and classification process, a modified slag with a particle size of 74-100 μm is obtained, and the magnetic separation is performed under a weak magnetic field with a strength of 90 mT.

Through the above process, the recovered iron concentrate iron grade is 65.7%, the recovery rate is 99.5%, the recovery rate of the magnetic separation tailings is 0.5%, the silicon content of the magnetic separation tailings is 32.37%, and the separation of iron and silicon is achieved. And the recovery of iron.

Example 5

The dried slaked lime and copper slag are roasted under the protection of carbon dioxide at a mass ratio of 3:10 and kept at 1100 ° C. During roasting, only CO ₂ gas is introduced, because at high temperature CO ₂ will also decompose to account for 5% of the total volume The following CO, the mixed gas formed to achieve weak oxidation treatment of ferrous oxide, control the flow rate of CO ₂ intake air flow rate 200mL / min, roasting for 24 hours.

At the end of roasting, through the grinding and classification process, a modified slag with a particle size of 100 μm is obtained, which is magnetically separated under a weak magnetic field with an intensity of 80 mT. The recovered iron concentrate iron grade is 66.5%, the recovery rate is 98.75%, magnetic The recovery rate of the tailings is 1.25%, and the silicon content of the magnetic tailings is 30.02%, which realizes the separation of iron and silicon and the recovery of iron.

In summary, the method for roasting and modifying iron recovered from copper slag of the present invention can efficiently recover iron in copper slag using industrial waste gas CO and CO _{2 to} obtain iron concentrate.

Although the content of the present invention has been described in detail through the above-described preferred embodiments, it should be recognized that the above description should not be considered as limiting the present invention. After those skilled in the art read the foregoing, various modifications and substitutions to the present invention will be apparent. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

A method for recycling modified iron by roasting copper slag, characterized in that the method comprises:

(1) The desiliconization modifier and copper slag are heated to the calcination temperature under the protection of inert gas to free the ferrous oxide in the iron olivine in the copper slag;

(2) Maintain the roasting temperature and inert gas protection, the roasting system is connected to the outside atmosphere, and CO and CO 2 gases are simultaneously introduced into the roasting system in step (1), the volume percentage of CO in the total gas composition of CO and CO 2 0 ～ 5%, oxidize the free ferrous oxide to ferric oxide, and make the magnetic ferric oxide crystal grow;

(3) After the roasting is completed, the temperature is lowered, and the modified slag with different particle sizes is obtained through the grinding and classification process, which is separated by magnetic separation under a magnetic field to obtain iron concentrate and magnetic separation tailings.
The method for roasting copper slag to modify and recover iron according to claim 1, characterized in that, in step (1), the calcination temperature is 800-1200 ° C.
The method for roasting copper slag to modify and recover iron according to claim 1, characterized in that, in step (1), the inert gas includes any one or two or more of nitrogen, argon and carbon dioxide.
The method for roasting copper slag to modify and recover iron according to claim 1, characterized in that in step (1), the desiliconization modifier comprises: slaked lime.
The method for roasting copper slag to modify and recover iron according to claim 1, characterized in that, in step (1), the mass ratio of the desiliconization modifier to copper slag is 1:10 to 3:10 .
The method for roasting copper slag to modify and recover iron according to claim 1, characterized in that, in step (2), during constant-temperature roasting, the total flow rate of the intake air of CO and CO 2 is 150 mL / min ～ 250mL / min; when the temperature is increased to a constant roasting temperature, and the temperature is reduced at the end of roasting, the inlet flow rate of the inert gas is 250mL / min.
The method for recovering iron by roasting copper slag according to claim 3, characterized in that, in step (2), the gas flow rates of CO and CO 2 are 0 to 10 mL / min and 190 to 200mL / min.
The method for roasting copper slag to modify and recover iron according to claim 1, characterized in that, in step (3), a ball mill or a vibrating mill is used for the ore grinding; a vibrating screen is used for the classification; and the magnetic Choose to use magnetic separation tube.
The method for roasting copper slag to modify and recover iron according to claim 1, characterized in that, in step (3), the particle size of the modified slag is 38-100 μm.
The method for roasting copper slag to modify and recover iron according to claim 1, characterized in that, in step (3), the strength of the magnetic field is 80mT-130mT.