A method for removing heavy metals from iron slag to produce high-grade iron powder

Abstract

The present invention provides a method for removing heavy metals from iron slag to produce high-grade iron powder, belonging to the field of utilization of hazardous waste-containing iron slag. In the present invention, the iron slag is pretreated to obtain primary iron powder, which is then mixed with lignite, sodium bicarbonate, calcium fluoride and sodium-based bentonite. After pelletizing, it is subjected to reduction treatment to obtain reduced metal pellets. The reduced metal pellets are subjected to first ball milling and first magnetic separation to obtain reduced materials; the reduced materials are screened to obtain oversize materials and undersize materials; the oversize materials are subjected to second ball milling and then screened continuously; the undersize materials are subjected to impurity removal and second magnetic separation to obtain high-grade iron powder. The present invention solves the problem that the heavy metal content in the product after direct deep reduction of iron-containing metallurgical tailings seriously exceeds the standard and does not meet the requirements of steelmaking through pretreatment, making harmful substances such as sulfur, phosphorus, arsenic, antimony and bismuth in steelmaking less than 0.0003%, and saving resources and increasing production, which is applicable to industrial production.

Description

Technical Field

[0001] The present invention belongs to the field of utilization of hazardous waste iron slag, and particularly relates to a method for removing heavy metals from iron slag to produce high-grade iron powder. Background Art

[0002] Iron slag refers to materials with iron content higher than 21% and heavy metal content higher than 0.1% produced during the smelting process. Iron slag is widely sourced from non-ferrous metal smelting processes. For example, in the hydrometallurgy process of gold, the pyrometallurgy process of copper, the pyrometallurgical process for producing sulfuric acid in sulfuric acid plants, and the pyrometallurgical process for extracting sulfur, a large amount of iron slag is produced. In gold cyanide slag, the total iron content accounts for 21 - 30% of the slag content, and the contents of arsenic and antimony are 0.315% and 0.2% respectively, and some are even higher; in sulfur slag, the total iron content accounts for 18 - 27% of the slag content, and the contents of arsenic and antimony are 0.2% and 0.15% respectively; in sulfuric acid slag, the total iron content is the highest, which can account for 50 - 62% of the slag content, and the contents of arsenic and antimony are 0.12% and 0.1% respectively. This is because the raw materials for producing sulfuric acid are high-purity sulfur iron minerals obtained after flotation. After the sulfur element is extracted by pyrometallurgy, iron is enriched and remains in the tailings; the total iron content of the iron slag produced in the pyrometallurgy process of copper slag generally accounts for about 40% of the slag, the content of arsenic is greater than 0.22%, and the content of antimony is greater than 0.014%.

[0003] Although these slag have been subjected to high-temperature roasting, most of the residual heavy metal elements such as arsenic remain in sulfides and other basic oxides, and the content in iron-containing substances is extremely small. Although the iron content of some slag is higher than the required standard of iron ore in China, they all have heavy metal exceedances such as arsenic. If not pretreated and removed, it will cause the iron and steel industry to be unable to utilize them.

[0004] Gold smelters, sulfuric acid plants, sulfur plants, and copper smelters in China produce 3 billion tons of waste slag every year. The industry predicts that in the next 2 to 3 years, industrial solid waste tailings will exceed 4 billion tons, and the accumulated iron-containing slag produced in the past exceeds 1 billion tons. At present, through simple ore dressing, iron-rich slag with iron content above 55% can be produced. Although the iron grade has reached the requirements for ironmaking, due to its high content of harmful substances for ironmaking such as arsenic, antimony, and bismuth, it cannot be used as a direct raw material for ironmaking. If it is stacked outdoors for a long time without recycling, it will not only cause waste of resources but also environmental pollution. Therefore, removing and recovering arsenic from iron slag to make the iron-rich slag meet the requirements for ironmaking has important economic and environmental benefits.

[0005] Arsenic, antimony, bismuth, tin, etc. are harmful elements in steel, which have a series of adverse effects on the performance of steel. For example, in the case of arsenic-containing steel under normal rolling process conditions, that is, long-term high-temperature heating in an oxidizing atmosphere, a surface enrichment layer will appear, causing surface cracking during hot processing. It segregates severely in steel, promotes the development of banded structure in steel, reduces the impact toughness of steel, and easily causes steel to crack during hot processing. In addition, most arsenic and its compounds are highly toxic substances, which will bring serious environmental problems to the treatment of arsenic-containing minerals. Currently, there are two main methods for the treatment of iron slag containing heavy metals such as arsenic, antimony, and bismuth: one is the pyrometallurgical method, that is, treatment is carried out by oxidation roasting, reduction roasting, vacuum roasting, etc., so that the arsenic in the slag is recovered in the form of arsenic trioxide; the other is the hydrometallurgical method, that is, treatment is carried out by methods such as acid leaching, alkali leaching, or salt leaching. First, arsenic is separated from the slag, and then arsenic is further recovered or harmlessly treated. Among these treatment methods, the oxidation roasting pyrometallurgical treatment cannot reduce the arsenic content to less than 0.1% because high-temperature pyrometallurgical arsenic removal of heavy metals such as antimony easily causes the arsenic and other heavy metals originally remaining in sulfides and basic oxides to vaporize at high temperatures. This vapor reacts with iron oxides or elemental iron to regenerate stable compounds and accumulate in iron minerals, resulting in serious over-standard of arsenic and other heavy metal contents in iron minerals. During the high-temperature pyrometallurgical treatment process, the cost is low and the treatment capacity is large, but heavy metal oxides such as arsenic trioxide are extremely likely to cause secondary environmental pollution and safety problems, and the removal of heavy metals is not complete. The hydrometallurgical method does not generate dust, can meet environmental requirements, and has the advantages of low energy consumption, less pollution, and high efficiency. However, the process is relatively complex, the treatment cost is relatively high, and it is difficult to carry out industrial production.

[0006] Therefore, conducting research on the removal of heavy metals from iron slag is of great significance for reducing the harm of arsenic, antimony, bismuth, and tin in the iron-making system and realizing the comprehensive utilization of iron ore resources containing heavy metals. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for removing heavy metals from iron slag to produce high-grade iron powder, which can remove heavy metals from iron slag to obtain high-grade iron powder for industrial applications, can treat iron slag that has been piled up for many years, can improve production capacity, and is energy-saving, pollution-free, and waste-free.

[0008] To achieve the above purpose, the present invention provides the following technical solutions:

[0009] A method for removing heavy metals from iron slag to produce high-grade iron powder, comprising the following steps:

[0010] 1) Pretreat the iron slag to obtain primary iron powder;

[0011] 2) Mix the primary iron powder in step 1) with lignite, sodium bicarbonate, calcium fluoride, and sodium-based bentonite, pelletize, and then carry out reduction treatment to obtain reduced metal pellets;

[0012] 3) Subject the reduced metal balls in step 2) to first ball milling and first magnetic separation to obtain a reduced material;

[0013] 4) Screen the reduced material in step 3) to obtain an oversize material and an undersize material;

[0014] 5) Subject the undersize material in step 4) to impurity removal and second magnetic separation in sequence to obtain high-grade iron powder.

[0015] Preferably, the iron slag in step 1) is iron red slag and / or iron black slag; the percentage content of iron(III) oxide in the iron red slag is 30 - 85%, and the percentage content of iron(II,III) oxide is 5 - 8%; the content of iron(III) oxide in the iron black slag is 5 - 7%, and the percentage content of iron(II,III) oxide is 51 - 58%.

[0016] Preferably, the pretreatment method of the iron red slag is: mix the iron red slag with lignite and then carry out magnetization reduction, ball milling and magnetic separation in sequence to obtain primary iron powder.

[0017] Preferably, the mass of the lignite is 3 - 5% of the mass of the iron red slag.

[0018] Preferably, the pretreatment method of the iron black slag is: subject the iron black slag to elutriation, ball milling and magnetic separation in sequence to obtain primary iron powder.

[0019] Preferably, the mass ratio of the primary iron powder, lignite, sodium bicarbonate, calcium fluoride and sodium-based bentonite in step 2) is 100:10 - 20:1 - 3:1 - 3:0.5 - 2.

[0020] Preferably, the reduction temperature in step 2) is 1000 - 1200 °C, and the reduction time is 1 - 2 h.

[0021] Preferably, the magnetic field intensity of the first magnetic separation in step 3) is 200 - 300 MT.

[0022] Preferably, the second magnetic separation in step 5) is divided into a first stage and a second stage in sequence. The magnetic field intensity of the first stage is 150 - 200 TM, and the magnetic field intensity of the second stage is 70 - 100 MT.

[0023] Preferably, the total iron content of the high-grade iron powder is 94 - 96.3%, the metallization rate is greater than 96%, the silicon dioxide is less than 2%, and the harmful substances such as sulfur, phosphorus, arsenic, antimony and bismuth are less than 0.0003%.

[0024] The beneficial technical effects of the present invention:

[0025] The present invention pre-treats iron slag to obtain primary iron powder, then mixes it with lignite, sodium bicarbonate, calcium fluoride and sodium-based bentonite, pelletizes it and then conducts a reduction treatment to obtain reduced metal pellets, and subjects the reduced metal pellets to first ball milling and first magnetic separation to obtain a reduced material; the reduced material is screened to obtain an oversize material and an undersize material; the oversize material is subjected to second ball milling and then screened continuously; the undersize material is subjected to impurity removal and second magnetic separation to obtain high-grade iron powder.

[0026] The present invention solves the problem that the heavy metals in the product after directly deep-reducing iron-containing metallurgical tailings slag seriously exceed the standard and do not meet the requirements of steelmaking through pre-treatment, making harmful substances such as sulfur, phosphorus, arsenic, antimony and bismuth in steelmaking less than 0.0003%. Compared with directly deep-reducing iron-containing tailings slag, the energy consumption cost is saved by two-fifths. For example, for copper-smelting tailings slag without pre-treatment, the specific heat capacity of the slag is detected to be 0.85 kJ / (kg·°C), and if it is pre-treated, the specific heat capacity of the iron powder is measured to be 0.45 kJ / (kg·°C). Due to different specific heat capacities, the heat energy consumed is also different, and the latter saves two-fifths of the heat energy compared with the former. Due to different iron contents, the specific gravities are also different, and the production efficiency is also increased by 1.2 times through rotary furnace test detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flow chart for producing high-grade iron powder by removing heavy metals from iron slag. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention provides a method for producing high-grade iron powder by removing heavy metals from iron slag, comprising the following steps:

[0029] 1) Pre-treat the iron slag to obtain primary iron powder;

[0030] 2) Mix the primary iron powder in step 1) with lignite, sodium bicarbonate, calcium fluoride and sodium-based bentonite, pelletize them and then conduct a reduction treatment to obtain reduced metal pellets;

[0031] 3) Subject the reduced metal pellets in step 2) to first ball milling and first magnetic separation to obtain a reduced material;

[0032] 4) Screen the reduced material in step 3) to obtain an oversize material and an undersize material;

[0033] 5) Subject the undersize material in step 4) to impurity removal and second magnetic separation in sequence to obtain high-grade iron powder.

[0034] The present invention pre-treats the iron slag to obtain primary iron powder.

[0035] In the present invention, the iron slag is preferably iron red slag and / or iron black slag; the percentage content of iron(III) oxide in the iron red slag is 30 - 85%, and the percentage content of iron(II,III) oxide is 5 - 8%; the content of iron(III) oxide in the iron black slag is 5 - 7%, and the percentage content of iron(II,III) oxide is 51 - 58%.

[0036] In the present invention, the pretreatment method of the iron red slag is as follows: mix the iron red slag with lignite and then perform magnetization reduction, ball milling, and magnetic separation in sequence to obtain primary iron powder.

[0037] In the present invention, the mass of the lignite is preferably 3 - 5% of the mass of the iron red slag, more preferably 4%.

[0038] In the present invention, the temperature of the magnetization reduction is preferably 550 - 580 °C, more preferably 580 °C; the reduction time is preferably 15 - 30 min; the magnetization reduction is preferably carried out in a magnetization reduction furnace; the rotation speed of the reduction furnace is preferably 3 r / min, and the filling rate of the reduction furnace is preferably 10 - 20%, more preferably 15%.

[0039] In the present invention, the ball milling method is preferably wet milling, and the concentration of the obtained pulp after wet milling is preferably 30 - 40%, more preferably 35%; the ball milling time is preferably 5 - 10 min, more preferably 8 min; the ball milling particle size is preferably -200 mesh.

[0040] In the present invention, the magnetic field strength of the magnetic separation is preferably 100 - 200 MT, more preferably 150 - 180 MT.

[0041] In the present invention, the pretreatment method of the iron red slag further includes pressure filtration dehydration and drying after magnetic separation to obtain primary iron powder.

[0042] In the present invention, the percentage content of iron(III) oxide in the primary iron powder is 5 - 10, the percentage content of Fe3O4 is 80 - 85%, the total iron content is 60 - 65%, and the content of arsenic, antimony, bismuth, and tin is less than 0.0003%.

[0043] The iron red slag described in the present invention is red in color, indicating a relatively high content of ferric oxide. Pyrometallurgical copper slag, pyrometallurgical sulfuric acid slag, pyrometallurgical sulfur slag, and cyanide slag all contain heavy metals such as arsenic, antimony, bismuth, and tin to varying degrees. For the above-mentioned smelting slag raw materials, although the iron slag has been treated at high temperature, most of the heavy metal elements remain in the sulfide basic oxides, and only a very small amount remains in the iron. After washing pretreatment and low-temperature pretreatment, the vast majority of heavy metals such as arsenic and antimony enter the tailings, and only an extremely small amount of heavy metals enter the iron powder. If the iron-containing slag is directly subjected to deep reduction without pretreatment, the heavy metals remaining in the sulfide will decompose again at high temperature, and the gas oxides generated after decomposition have a very strong affinity for elemental iron, and will form heavy metal and iron compounds such as iron arsenate and iron arsenide again, remaining in the product and being enriched, so that the heavy metal element content in the product reaches several times that of the original slag. The magnetization reduction temperature is controlled at 550 - 580 °C, which can not only meet the simple magnetization of ferric oxide, but also avoid the re-decomposition of heavy metal-containing sulfides (the decomposition temperature of heavy metal sulfides is greater than 600 °C) and the combination with iron oxides to form stable heavy metal iron salts, which are brought into the deep reduction iron powder. The heat energy of the deep reduction tail gas can fully meet the heat energy required for pretreatment without additional heating. The carbon monoxide in the tail gas can also be supplemented into the magnetization reduction furnace, saving the consumption of coal in the pretreatment magnetization reduction.

[0044] In the present invention, the pretreatment method for the iron black slag is as follows: the iron black slag is successively subjected to washing, ball milling, and magnetic separation to obtain primary iron powder.

[0045] In the present invention, the washing time is preferably 5 - 15 min, more preferably 10 min; the washing is preferably carried out in a magnetic reconnection washing device.

[0046] In the present invention, the ball milling is preferably wet milling; the concentration of the slurry obtained by ball milling is preferably 25 - 35%, more preferably 30%; the ball milling time is preferably 5 - 15 min, more preferably 8 min; the particle size of the ball milling is -200 mesh.

[0047] In the present invention, the magnetic field strength of the magnetic separation is preferably 100 - 200 MT, more preferably 150 - 180 MT.

[0048] In the present invention, the pretreatment method for the iron black slag further includes pressure filtration dehydration and drying after magnetic separation to obtain primary iron powder.

[0049] Tail slag is also generated after the magnetic separation in the present invention, and the tail slag enters the thickener.

[0050] In the present invention, the content of ferric oxide in the black iron slag is relatively low. During pretreatment, only washing, ball milling, and magnetic separation are required to achieve slag-iron separation. Most of the heavy metal-containing substances enter the tail slag, and the iron-containing substances are dried for the next step of deep reduction.

[0051] The obtained primary iron powder is mixed with lignite, sodium bicarbonate, calcium fluoride and sodium-based bentonite to form pellets, and then subjected to reduction treatment to obtain reduced metal pellets.

[0052] In the present invention, the mass ratio of the primary iron powder to lignite, sodium bicarbonate, calcium fluoride and sodium-based bentonite is preferably 100:10 - 20:1 - 3:1 - 3:0.5 - 2, and more preferably 100:15:1.5:1.5:1.

[0053] In the present invention, the reduction temperature is preferably 1000 - 1200 °C, and more preferably 1150 °C; the reduction time is preferably 1 - 2 h, and more preferably 1.5 h. The reduction treatment of the present invention is preferably carried out in an externally fired rotary kiln, and the rotation speed of the externally fired rotary kiln is preferably 3 r / min.

[0054] In the present invention, the pellet diameter of the reduced metal pellets is preferably 3 - 5 cm, and more preferably 4 cm.

[0055] In the present invention, lignite is used as a reducing agent, sodium bicarbonate is used as a catalyst, and calcium fluoride is used as a flux desulfurizer. This usage ratio can not only ensure the reduction effect and desulfurization effect, but also further remove harmful metals, save raw materials and control costs.

[0056] After obtaining the reduced metal pellets, the present invention subjects the reduced metal pellets to first ball milling and first magnetic separation to obtain a reduced material.

[0057] In the present invention, before the first ball milling, it also includes crushing the reduced metal pellets; the particle size after crushing is preferably 0.5 - 1 cm, and more preferably 0.8 cm.

[0058] In the present invention, the first ball milling is preferably wet milling; the pulp concentration obtained by wet milling is preferably 10 - 20 wt%, and more preferably 15 wt%; the magnetic field intensity of the first magnetic separation is preferably 200 - 300 MT, and more preferably 240 MT.

[0059] Tailings are also obtained after the first magnetic separation of the present invention, and the tailings enter the thickener.

[0060] After obtaining the reduced material, the present invention screens the reduced material to obtain oversize material and undersize material.

[0061] In the present invention, the particle size of the undersize material is preferably -150 mesh.

[0062] The present invention preferably subjects the oversize material to second ball milling and then returns it for continued screening.

[0063] After obtaining the undersize material, the present invention sequentially performs impurity removal and second magnetic separation on the undersize material to obtain high-grade iron powder.

[0064] In the present invention, the impurity removal is preferably carried out in a elutriator. In the present invention, impurities are removed by magnetic reconnection separation, and the impurities are carried away by water flow and enter the thickener.

[0065] In the present invention, the second magnetic separation is sequentially divided into a first stage and a second stage. The magnetic field strength in the first stage is preferably 150-200 MT, more preferably 160 MT, and the magnetic field strength in the second stage is more preferably 80 MT.

[0066] After the second magnetic separation in the present invention, it is also preferably to include dehydrating the target product obtained by the second magnetic separation.

[0067] In the present invention, the total iron content of the high-grade iron powder is 94-96.3 wt%, the metallization rate is greater than 96 wt%, the silica is less than 2 wt%, and other impurities are less than 0.0003%. The other impurities in the present invention preferably include at least one of sulfur, phosphorus, arsenic, antimony and bismuth.

[0068] In the present invention, it is preferred to carry out briquetting on the high-grade iron powder. By the briquetting treatment in the present invention, secondary oxidation can be prevented from reducing the iron grade and affecting the product quality.

[0069] The second magnetic separation in the present invention also produces tailings, and the tailings enter the thickener.

[0070] In almost all processes of the present invention, there is no waste. All tailings enter the thickener after passing through the tailing iron recovery machine, and then enter the vacuum belt filter through the thickening equipment for dehydration. After dehydration, the materials are sent to the cement plant as cement clinker, and the recovered iron concentrate powder is returned as reduction material. All waste water flows into the reservoir for recycling. The deep reduction tail gas is sent into the pretreatment environment through the exhaust pipe as heat source or for drying iron powder. Finally, the low-temperature tail gas passes through the three-stage dust removal equipment and reacts in a closed sodium hydroxide solution pool (for waste gas separation). Carbon monoxide is discharged from the closed solution pool, collected and sent to the magnetization equipment or used as fuel for reuse. Carbon dioxide and sulfur-containing gases react in the sodium hydroxide solution pool to form sodium bicarbonate, which is fished out, dried and used as a raw material additive. In the whole process, almost no waste gas is discharged.

[0071] To better understand the present invention, the content of the present invention will be further illustrated below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments.

[0072] Example 1

[0073] The main component of Yunnan sulfuric acid residue is iron oxide, with a dark red color. Its total iron content is 56%, arsenic content is 0.5%, antimony content is 0.14%, bismuth content is 0.014%, and tin content is 0.001%.

[0074] 1) Take 100 kg of the sulfuric acid residue, mix it with 4 kg of lignite, and add it to the magnetization reduction furnace using a screw feeder. Use the tail gas of the direct reduction equipment as the heating source, control the temperature at 580 °C, the rotational speed of the external heating reduction furnace is 3 revolutions per minute, the filling rate is 15%, the reduction time is 20 minutes. After the calcined material is cooled, it is sent to the ball mill through a slag scraper, the pulp concentration is adjusted to 35%, the ball milling time is 8 minutes, the ball milling particle size is -200 mesh, and the overflow of the ball milled pulp enters the ore pond, and is sent to a semi-countercurrent magnetic separator with a magnetic field intensity of 160 MT for magnetic separation by a slurry pump. The magnetic separation concentrate flows into a stirring filter press for pressure filtration and drying, and primary iron powder is obtained after drying, and the tail slag is collected at the same time.

[0075] 2) Mix the primary iron powder with 15% of its mass of lignite, 1.5% of sodium bicarbonate, 1.5% of calcium fluoride, and 1% of sodium-based bentonite, and make it into balls, and send it to an external-fired rotary furnace through a feeder, the temperature is set at 1150 °C, the time is set at 1.5 hours, the rotational speed is set at 3 r / min, and the reduced metal balls are obtained after roasting.

[0076] 3) Cool the reduced metal balls through a cooler, simply crush them and send them into a ball mill through a feeder, adjust the pulp concentration to 15%, ball mill to a particle size of -100 mesh, and perform magnetic separation on the obtained ball milled pulp at a magnetic field intensity of 240 MT to obtain reduced materials, and collect the tail slag at the same time.

[0077] 4) Send the reduced materials to a screening device, the oversize materials are returned to the second grinding device for continuous grinding, and after grinding, they re-enter the screening device. The undersize materials are washed by a elutriator and impurities are removed through magnetic and gravity combined separation. The impurities are carried away by the water flow into the tail slag. The magnetic iron-containing materials are first magnetically separated at a magnetic field intensity of 160 MT and then magnetically separated at a magnetic field intensity of 80 MT to select high-grade iron powder, and the high-grade iron powder enters a disk filter for dehydration and briquetting.

[0078] 5) Put all the tail slag into a thickener to recover the residual iron concentrate powder as reduced materials; all the waste water flows into a reservoir for recycling; the deep reduction tail gas is sent to a pretreatment environment through an exhaust pipe as a heat source or for drying iron powder. Finally, the low-temperature tail gas passes through a three-stage dust removal device, enters a closed sodium hydroxide solution pool for reaction, carbon monoxide is discharged from the closed solution pool, collected and sent to a magnetization device or used as fuel for reuse, carbon dioxide and sulfur-containing gases are sent to a sodium hydroxide solution pool for reaction to form sodium bicarbonate, which is fished out and dried for use as a raw material additive.

[0079] Example 2

[0080] The main components of the gold smelting slag in Henan are iron(III) oxide, with a dark red color. Its total iron content is 25%, arsenic content is 0.5%, antimony content is 0.14%, bismuth content is 0.014%, and tin content is 0.001%.

[0081] 1) Take 100 kg of the smelting slag, mix it with 3 kg of lignite, and add it to the magnetization reduction furnace using a screw feeder. Use the tail gas of the direct reduction equipment as the heating source, control the temperature at 550 °C, the external heating reduction furnace rotates at 3 revolutions per minute, the filling rate is 10%, the reduction time is 15 minutes. After the roasting material is cooled, it is sent to the ball mill through a slag skimmer, the pulp concentration is adjusted to 30%, the ball milling time is 5 minutes, the ball milling particle size is -200 mesh, and the overflow of the ball milled pulp enters the ore pool and is sent to a semi-countercurrent magnetic separator with a magnetic field intensity of 200 MT for magnetic separation. The magnetic separation concentrate flows into the agitation filter press for pressure filtration and drying, and primary iron powder is obtained after drying. At the same time, the tail slag is collected.

[0082] 2) Mix 10% of lignite, 1% of sodium bicarbonate, 1% of calcium fluoride, and 2% of sodium-based bentonite by mass with the primary iron powder, and make it into spheres. Then send it to the external firing rotary furnace through a feeder, set the temperature at 1100 °C, the time at 2 hours, and the rotation speed at 3 r / min. After roasting, the reduced metal balls are obtained.

[0083] 3) Cool the reduced metal balls through a cooler, simply crush them and then send them to the ball mill through a feeder. Adjust the pulp concentration to 20%, ball mill to a particle size of -150 mesh, and perform magnetic separation on the obtained ball milled pulp at a magnetic field intensity of 300 MT to obtain the reduced material. At the same time, the tail slag is collected.

[0084] 4) Send the reduced material to the screening equipment. The oversize material is returned to the second grinding equipment for further grinding, and after grinding, it re-enters the screening device. The undersize material is washed with a elutriator and the impurities are removed through magnetic and gravity combined separation. The impurities are carried away by the water flow and enter the tail slag. The magnetic iron-containing material is first magnetically separated at a magnetic field intensity of 200 MT and then at a magnetic field intensity of 100 MT to select high-grade iron powder, and the high-grade iron powder enters the disk filter for dehydration and briquetting.

[0085] 5) Put all the tail slag into the thickener to recover the residual iron concentrate powder as the reduced material; all the waste water flows into the reservoir for recycling; the deep reduction tail gas is sent through the exhaust pipe to the pretreatment environment as a heat source or for drying the iron powder. Finally, the low-temperature tail gas passes through a three-stage dust removal equipment and reacts in a closed sodium hydroxide solution pool. Carbon monoxide is discharged from the closed solution pool, collected and sent to the magnetization equipment or used as fuel for reuse. Carbon dioxide and sulfur-containing gases react in the sodium hydroxide solution pool to form sodium bicarbonate, which is fished out and dried for use as a raw material additive.

[0086] Example 3

[0087] The main components of the Yunnan sulfuric acid slag are iron(III) oxide, with a dark red color. Its total iron content is 56%, arsenic content is 0.5%, antimony content is 0.14%, bismuth content is 0.014%, and tin content is 0.001%.

[0088] 1) Take 100 kg of the sulfuric acid residue, mix it with 5 kg of lignite, and add it to the magnetization reduction furnace using a screw feeder. Use the tail gas of the direct reduction equipment as the heating source, control the temperature at 580 °C, the rotational speed of the external heating reduction furnace is 3 revolutions per minute, the filling rate is 20%, the reduction time is 30 minutes. After the calcined material is cooled, it is sent to the ball mill through a slag scraper, the pulp concentration is adjusted to 40%, the ball milling time is 10 minutes, the ball milling particle size is -200 mesh, and the overflow of the ball milled slurry enters the ore pond and is sent to a semi-countercurrent magnetic separator with a magnetic field intensity of 100 MT for magnetic separation by a slurry pump. The magnetic separation concentrate flows into a stirring filter press for pressure filtration and drying, and primary iron powder is obtained after drying, and the tail slag is collected at the same time.

[0089] 2) Mix the primary iron powder with 20% of its mass of lignite, 3% of sodium bicarbonate, 3% of calcium fluoride, and 0.5% of sodium-based bentonite, and make it into balls, then send it to an external burning rotary furnace through a feeder, set the temperature at 1200 °C, the time at 2 hours, and the rotational speed at 3 r / min. After roasting, reduced metal balls are obtained.

[0090] 3) Cool the reduced metal balls through a cooler, simply crush them and then send them into a ball mill through a feeder, adjust the pulp concentration to 10%, ball mill to a particle size of -100 mesh, and the obtained ball milled slurry is magnetically separated at a magnetic field intensity of 200 MT to obtain reduced materials, and the tail slag is collected at the same time.

[0091] 4) Send the reduced materials to a screening device, the oversize materials are returned to the second grinding device for continuous grinding, and after grinding, they re-enter the screening device. The undersize materials are washed by a washing machine and the sundries are removed through magnetic and gravity combined separation. The sundries are carried away by the water flow and enter the tail slag. The magnetic iron-containing materials are first magnetically separated at a magnetic field intensity of 150 MT and then at a magnetic field intensity of 70 MT to select high-grade iron powder, and the high-grade iron powder enters a disc filter for dehydration and briquetting.

[0092] 5) Put all the tail slag into a thickener to recover the residual iron concentrate powder as reduced materials; all the waste water flows into a reservoir for recycling; the deep reduction tail gas is sent through an exhaust pipe to a pretreatment environment as a heat source or for drying iron powder. Finally, the low-temperature tail gas passes through a three-stage dust removal device and reacts in a closed sodium hydroxide solution pool. Carbon monoxide is discharged from the closed solution pool, collected and sent to a magnetization device or used as fuel for reuse. Carbon dioxide and sulfur-containing gases react in the sodium hydroxide solution pool to form sodium bicarbonate, which is fished out, dried and used as a raw material additive.

[0093] Example 4

[0094] The main components of the copper smelting slag in Yuncheng, Shanxi are magnetite and iron silicate, with a black color. Its total iron content is 45%, arsenic content is 0.03%, antimony content is 0.014%, bismuth content is 0%, and tin content is 0%.

[0095] 1) Take 100 kg of the smelting slag and feed it into the magnetic reconnection washing equipment using a feeder. Conduct gravity separation for 10 minutes. Adopt a continuous production method to settle and recover the iron-containing substances. The iron-free impurities are carried away by the water flow at the overflow port and enter the tailings pond. The iron-containing minerals are adjusted to a concentration of 30% by pulp mixing, and then pumped into an overflow ball mill using a slurry pump for ball milling for 8 minutes. The overflow slurry flows into a semi-countercurrent magnetic separator and is subjected to magnetic separation at a magnetic field intensity of 160 MT. Then, it is subjected to pressure filtration, dehydration, and drying to obtain primary iron powder, and at the same time, the tail slag is collected.

[0096] 2) Mix the primary iron powder with 15% of its mass of lignite, 1.5% of sodium bicarbonate, 1.5% of calcium fluoride, and 1% of sodium-based bentonite, and make it into spherical shapes. Feed it into an external-firing rotary kiln using a feeder. Set the temperature to 1150 °C, the time to 1.5 hours, and the rotation speed to 3 r / min. After roasting, the reduced metal balls are obtained.

[0097] 3) Cool the reduced metal balls through a cooler, simply crush them, and then feed them into a ball mill using a feeder. Adjust the slurry concentration to 15%, and ball mill until the particle size reaches -150 mesh. The obtained ball-milled slurry is subjected to magnetic separation at a magnetic field intensity of 240 MT to obtain the reduced materials, and at the same time, the tail slag is collected.

[0098] 4) Feed the reduced materials into a screening device. The oversize materials are returned to the second grinding equipment for continuous grinding, and after grinding, they re-enter the screening device. The undersize materials are washed using a elutriator and the impurities are removed through magnetic reconnection separation. The impurities are carried away by the water flow and enter the tail slag. The magnetic iron-containing substances are first subjected to magnetic separation at a magnetic field intensity of 160 MT and then at a magnetic field intensity of 80 MT to select high-grade iron powder. The high-grade iron powder enters a disk filter for dehydration and briquetting.

[0099] 5) Put all the tail slag into a thickener to recover the residual iron concentrate powder as the reduced materials; all the wastewater flows into a reservoir for recycling; the deep reduction tail gas is sent into a pretreatment environment through an exhaust pipe as a heat source or for drying the iron powder. Finally, the low-temperature tail gas passes through a three-stage dust removal equipment and reacts in a closed sodium hydroxide solution pool. Carbon monoxide is discharged from the closed solution pool, collected and sent to a magnetization equipment or used as fuel for reuse. Carbon dioxide and sulfur-containing gases react in the sodium hydroxide solution pool to form sodium bicarbonate, which is fished out, dried, and used as a raw material additive.

[0100] Example 5

[0101] The main components of the copper smelting slag in Yuling, Henan are magnetite and iron silicate, with a black color. Its total iron content is 42.7%, arsenic content is 0.2%, antimony content is 0.345%, bismuth content is 0.012%, and tin content is 0%.

[0102] 1) Take 100 kg of the smelting slag and feed it into the magnetic and gravity combined washing equipment using a feeder. Conduct gravity separation for 10 minutes. Adopt a continuous production method to settle and recover the iron-containing substances. The iron-free impurities are carried away by the overflow water through the overflow port and enter the tailings pond. The iron-containing minerals are adjusted to a concentration of 30% by pulp mixing, and then pumped into an overflow ball mill using a slag pump for ball milling for 8 minutes. The overflow pulp flows into a semi-countercurrent magnetic separator and is magnetically separated under a magnetic field intensity of 160 MT. Then, it is filtered, dewatered, and dried to obtain primary iron powder, and the tailing slag is collected simultaneously.

[0103] 2) Mix 20% of lignite, 3% of sodium bicarbonate, 3% of calcium fluoride, and 0.5% of sodium-based bentonite by mass into the primary iron powder and make it into spheres. Feed the spheres into an external firing rotary kiln through a feeder. Set the temperature to 1200 °C, the time to 2 hours, and the rotation speed to 3 r / min. After roasting, reduced metal balls are obtained.

[0104] 3) Cool the reduced metal balls through a cooler, simply crush them, and then feed them into a ball mill through a feeder. Adjust the pulp concentration to 10%, and ball mill until the particle size reaches -150 mesh. The obtained ball mill pulp is magnetically separated under a magnetic field intensity of 200 MT to obtain reduced materials, and the tailing slag is collected simultaneously.

[0105] 4) Feed the reduced materials into a screening device. The oversize materials are returned to the second grinding equipment for continuous grinding, and after grinding, they re-enter the screening device. The undersize materials are washed by a elutriator and the impurities are removed through magnetic and gravity combined separation. The impurities are carried away by the water flow and enter the tailing slag. The magnetic iron-containing substances are first magnetically separated under a magnetic field intensity of 150 MT and then under a magnetic field intensity of 70 MT to select high-grade iron powder. The high-grade iron powder enters a disk filter for dehydration and briquetting.

[0106] 5) Put all the tailing slag into a thickener to recover the residual iron concentrate powder as reduced materials; all the wastewater flows into a reservoir for recycling; the deep reduction tail gas is sent into a pretreatment environment through an exhaust pipe as a heat source or for drying the iron powder. Finally, the low-temperature tail gas passes through a three-stage dust removal device and reacts in a closed sodium hydroxide solution pool. Carbon monoxide is discharged from the closed solution pool, collected, sent to a magnetization device or used as fuel for reuse. Carbon dioxide and sulfur-containing gases react in the sodium hydroxide solution pool to form sodium bicarbonate, which is fished out, dried, and used as a raw material additive.

[0107] Example 6

[0108] The main components of Yunnan sulfuric acid slag are iron(III) oxide, with a dark red color. Its total iron content is 56%, arsenic content is 0.5%, antimony content is 0.14%, bismuth content is 0.014%, and tin content is 0.001%.

[0109] 1) Mix the sulfuric acid residue with 15% of its mass of lignite, 1.5% of sodium bicarbonate, 1.5% of calcium fluoride, and 1% of sodium-based bentonite, make it into spheres after mixing evenly, and send it into the external firing rotary kiln through a feeder. Set the temperature to 1150 °C, the time to 1.5 hours, and the rotation speed to 3 r / min. After roasting, reduced metal balls are obtained.

[0110] 2) Cool the reduced metal balls through a cooler, simply crush them and send them into a ball mill through a feeder. Adjust the pulp concentration to 15%, grind to a particle size of -200 mesh. The obtained ball-milled pulp is subjected to magnetic separation at a magnetic field intensity of 240 MT to obtain reduced materials, and at the same time, tailings are collected.

[0111] 3) Send the reduced materials into a screening device. The oversize materials are returned to the second grinding device for continuous grinding, and after grinding, they re-enter the screening device. The undersize materials are washed with a washer and impurities are removed through magnetic and gravity combined separation. The impurities are carried away by the water flow and enter the tailings. The magnetic iron-containing materials are first subjected to magnetic separation at a magnetic field intensity of 160 MT and then at a magnetic field intensity of 80 MT to select high-grade iron powder. The high-grade iron powder enters a disk filter for dehydration and briquetting.

[0112] 4) Put all the tailings into a thickener to recover the residual iron concentrate powder as reduced materials; all the waste water flows into a reservoir for recycling; the deeply reduced tail gas is sent into a pretreatment environment through an exhaust pipe as a heat source or for drying iron powder. Finally, the low-temperature tail gas passes through a three-stage dust removal device and reacts in a closed sodium hydroxide solution pool. Carbon monoxide is discharged from the closed solution pool, collected and sent to a magnetization device or used as fuel for reuse. Carbon dioxide and sulfur-containing gases react in the sodium hydroxide solution pool to form sodium bicarbonate, which is fished out and dried for use as a raw material additive.

[0113] Measure the products obtained from the above examples, and the measurement results are shown in Table 1:

[0114] Table 1 Analysis Table of Measurement Results

[0115]

[0116]

[0117] The above is only the preferred implementation mode of the present invention. It should be pointed out that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for removing heavy metals from iron slag to produce high-grade iron powder, characterized in that, It includes the following steps: 1) Pretreat the iron slag to obtain primary iron powder; 2) Mix the primary iron powder in step 1) with lignite, sodium bicarbonate, calcium fluoride and sodium-based bentonite, pelletize them, and then perform reduction treatment to obtain reduced metal pellets; 3) Perform first ball milling and first magnetic separation on the reduced metal pellets in step 2) to obtain reduced materials; 4) Screen the reduced materials in step 3) to obtain oversize materials and undersize materials; 5) Perform impurity removal and second magnetic separation on the undersize materials in step 4) in sequence to obtain high-grade iron powder; The iron slag in step 1) is iron red slag; The pretreatment method of the iron red slag is: mix the iron red slag with lignite, and then perform magnetization reduction, ball milling and magnetic separation in sequence to obtain primary iron powder; The mass of the lignite is 3-5% of the mass of the iron red slag; The temperature of the magnetization reduction is 550-580°C; the reduction time is 15-30 min.

2. The method according to claim 1, characterized in that, In step 2), the mass ratio of the primary iron powder to lignite, sodium bicarbonate, calcium fluoride and sodium-based bentonite is 100:10-20:1-3:1-3:0.5-2.

3. The method according to claim 1, characterized in that, In step 2), the reduction temperature is 1000-1200°C, and the reduction time is 1-2 h.

4. The method according to claim 1, characterized in that, In step 3), the magnetic field intensity of the first magnetic separation is 200-300 MT.

5. The method according to claim 1, characterized in that, In step 5), the second magnetic separation is divided into a first stage and a second stage in sequence. The magnetic field intensity of the first stage is 150-200 TM, and the magnetic field intensity of the second stage is 70-100 MT.

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