阅读说明：本技术 一种基于含铁物料加热致裂强化还原焙烧的方法 (Method for strengthening reduction roasting based on heating and cracking of iron-containing material ) 是由 韩跃新 高鹏 张琦 袁帅 李艳军 孙永升 于 2020-06-03 设计创作，主要内容包括：一种基于含铁物料加热致裂强化还原焙烧的方法,按以下步骤进行：(1)将含铁物料破碎磨矿制成矿粉；(2)将矿粉输送到预氧化焙烧炉,在悬浮状态被加热进行预氧化焙烧,然后进入旋风分离器；(3)经旋风分离排放到蓄热还原焙烧炉,在悬浮状态与还原气进行还原焙烧；(4)还原物料输送至一级冷却旋风分离器,在氮气气氛条件下旋风分离并冷却至200～300℃；(5)冷却还原物料经流动密封阀进入二级冷却旋风分离器,在空气气氛下旋风分离并发生再氧化反应；(6)再氧化物料磨矿制成二次矿粉；进行弱磁选。本发明的方法增加了铁矿物的反应活性位点,提升反应速率,降低还原反应表观活化能,从而强化还原效果。(A method for strengthening reduction roasting based on iron-containing material heating cracking comprises the following steps: (1) crushing and grinding the iron-containing material to prepare mineral powder; (2) conveying the mineral powder to a pre-oxidation roasting furnace, heating the mineral powder in a suspension state for pre-oxidation roasting, and then entering a cyclone separator; (3) the mixture is discharged to a heat storage reduction roasting furnace through cyclone separation, and is reduced and roasted with reducing gas in a suspension state; (4) conveying the reduced material to a primary cooling cyclone separator, performing cyclone separation under the condition of nitrogen atmosphere, and cooling to 200-300 ℃; (5) the cooled and reduced material enters a secondary cooling cyclone separator through a flow seal valve, is subjected to cyclone separation in the air atmosphere and undergoes reoxidation reaction; (6) re-oxidizing the material and grinding to obtain secondary mineral powder; and carrying out low-intensity magnetic separation. The method increases the reactive active sites of the iron minerals, improves the reaction rate, and reduces the apparent activation energy of the reduction reaction, thereby strengthening the reduction effect.)

1. A method for strengthening reduction roasting based on iron-containing material heating cracking is characterized by comprising the following steps:

(1) crushing the iron-containing material to the particle size of 2-15 mm, and grinding the iron-containing material to the oreThe part with the particle size of-0.074 mm accounts for 30-55% of the total mass and is prepared into mineral powder; the iron-containing material is complex iron ore, the iron grade TFe is 25-40%, and the material contains SiO according to the mass percentage₂25～55％；

(2) The method comprises the steps of adopting a pre-oxidation roasting furnace with a burner and an air inlet at the bottom, arranging a feed inlet at the lower part of the pre-oxidation roasting furnace, communicating the upper part with a cyclone separator through a material channel, communicating an exhaust port of the cyclone separator with an induced draft fan through a pipeline, introducing combustion flue gas generated by combustion of natural gas introduced into the burner into the pre-oxidation roasting furnace, introducing air into the pre-oxidation roasting furnace under the condition of starting the induced draft fan, conveying mineral powder into the pre-oxidation roasting furnace from the lower part of the pre-oxidation roasting furnace, keeping the mineral powder in a suspension state in the pre-oxidation suspension roasting furnace under the action of negative pressure and air flow, heating the mineral powder to 750-850 ℃ for pre-oxidation roasting, removing adsorbed water, crystal water and other volatile components in the mineral powder, and converting the mineral phases of different₂O₃And because the thermal expansion coefficients of the gangue and the iron ore are different, microcracks and holes are generated in the mineral powder particles in the heating process; the pre-oxidized product obtained after the pre-oxidation roasting is a pre-oxidation roasting material and enters a cyclone separator under the action of airflow;

(3) under the condition of introducing nitrogen and reducing gas into the regenerative reduction roasting furnace, the preoxidized roasting material is subjected to cyclone separation in the cyclone separator, is discharged into the regenerative reduction roasting furnace, is in a suspension state under the action of negative pressure and air flow, and is subjected to reduction roasting with the reducing gas at the temperature of 500-600 ℃, α -Fe₂O₃Is reduced to produce Fe₃O₄(ii) a Reducing products obtained after the reduction roasting are reducing materials and are discharged from a side discharge hole of the heat storage reduction roasting furnace;

(4) conveying the reducing material discharged from the heat storage reduction roasting furnace to a primary cooling cyclone separator; introducing nitrogen from a feed inlet of the primary cooling cyclone separator, and discharging the nitrogen from an air outlet of the primary cooling cyclone separator; carrying out cyclone separation on the reduced material under the condition of nitrogen atmosphere, cooling to 200-300 ℃ to obtain a cooled reduced material, and discharging from a discharge hole of a primary cooling cyclone separator;

(5) the cooled reducing material discharged from the primary cooling cyclone separator enters a flow seal valve, and enters a secondary cooling cyclone separator after being discharged from the flow seal valve; at the moment, air is introduced from a feed inlet of the secondary cooling cyclone separator, and the air is discharged from an air outlet of the secondary cooling cyclone separator; the cooled and reduced material is separated in cyclone in air atmosphere and is reoxidized to produce Fe₃O₄Oxidized to generate ferromagnetic mineral gamma-Fe₂O₃Reducing the temperature of the obtained roasted product to be less than or equal to 100 ℃, and discharging the formed reoxidized material from a discharge hole of the secondary cooling cyclone separator;

(6) grinding the reoxidation material until the part with the particle size of-0.074 mm accounts for 75-95% of the total mass to prepare secondary mineral powder; and carrying out low-intensity magnetic separation on the secondary mineral powder, wherein the magnetic field intensity is 1000-2000 Oe, and the obtained magnetic product is iron ore concentrate.

2. The method for heating, cracking, strengthening and reducing roasting based on the iron-containing material according to claim 1, wherein in the step (2), the retention time of the solid material in the pre-oxidation roasting furnace is 2-10 min.

3. The method for strengthening reduction roasting based on heating cracking of iron-containing material according to claim 1, wherein in the step (3), the reducing gas is CO or H₂Or coal gas; the amount of reducing gas is determined according to the CO/H required by the complete reaction of reduction roasting₂1: 1-1.3 times of theoretical amount, and the reaction formula for complete reaction is as follows:

Fe₂O₃+H₂/CO→Fe₃O₄+H₂O/CO₂。

4. the method for heating, cracking and strengthening reduction roasting based on the iron-containing material according to claim 1, wherein in the step (3), the volume flow ratio of nitrogen to reducing gas in the regenerative reduction roasting furnace is (1-7): 1.

5. The method for heating, cracking, strengthening and reducing roasting of iron-containing materials according to claim 1, wherein in the step (3), the retention time of the solid materials in the regenerative reducing roasting furnace is 10-60 min.

6. The method of claim 1, wherein the iron grade TFe of the iron ore concentrate is not less than 60%.

7. The method for the heating, cracking, strengthening, reducing and roasting of the iron-containing materials according to claim 1, wherein the recovery rate of Fe is more than or equal to 85%.

8. The method for heating, cracking, strengthening, reducing and roasting the iron-containing material according to claim 1, wherein in the step (4), the retention time of the reduced material in the primary cooling cyclone separator is 2-5 min.

9. The method for heating, cracking, strengthening, reducing and roasting the iron-containing material according to claim 1, wherein in the step (5), the retention time of the cooled and reduced material in the secondary cooling cyclone separator is 1-3 min.

Technical Field

The invention belongs to the technical field of mineral processing, and particularly relates to a method for heating, cracking, strengthening, reducing and roasting iron-containing materials.

Background

The resource utilization rate of the low-grade complex refractory iron ore is low, so that the large-scale efficient utilization of the low-grade complex refractory iron ore resource is realized, and the situation of insufficient iron ore resource supply is relieved.

Patent CN104593588 discloses a method for roasting lean iron ore in a rotary kiln, which proposes that iron ore with iron content of about 40% is used as a raw material, and the contained iron is roasted and recovered by the rotary kiln; the method can realize the utilization of iron resources and reduce the coal consumption to a certain extent, but adopts the conventional calcining equipment of a rotary kiln, the oxidation atmosphere and the reduction atmosphere in the system coexist, the heating and the reduction are carried out simultaneously, the process has low processing capacity, the product quality is poor, a coal injection device needs to be assembled, and the process flow is complex.

Patent CN 107630139 discloses a fluidized suspension preheating prereduction device and method for iron ore, which can recover a large amount of heat in waste gas in the smelting link, save preheating heat and reduce energy loss; the method can reduce energy consumption to a certain extent, but the iron phase in the complex iron ore is complex, the reduction speed of iron minerals is different, and the quality of a roasted product is influenced and the production efficiency is reduced by heating and reducing the materials simultaneously; the same problem exists in patent CN 105316476.

Patent CN 107930843 discloses a method for re-roasting refractory iron ore in a suspension roasting dry-type pre-separation tailing return furnace; the method can recover the iron minerals in the complex ores, but the product needs to be roasted twice, and has the defects of high energy consumption, complex process flow, difficult separation of the iron minerals and the gangue in the reduction product, low concentrate grade and the like.

Patent CN108396134A discloses an iron ore roasting device and method with oxidation preheating and fluidization reduction, which can realize oxidation preheating of materials, but the preheating temperature is low, and it is difficult to efficiently realize complete oxidation and cracking of iron ore; then the materials are heated and reduced at high temperature, and because the reduction speeds of different iron minerals are different, the materials are heated and reduced at the same time, so that the quality and the production efficiency of the roasted product are influenced.

Disclosure of Invention

Aiming at the problems of the existing complex refractory iron ore processing technology, the invention provides a method for strengthening reduction roasting based on heating and cracking of iron-containing materials.

The method of the invention is carried out according to the following steps:

1. crushing the iron-containing material to a particle size of 2-15 mm, and then grinding the iron-containing material until the part with the particle size of-0.074 mm accounts for 30-55% of the total mass to prepare mineral powder; the iron-containing material is complex iron ore, the iron grade TFe is 25-40%, and the material contains SiO according to the mass percentage₂25～55％；

2. The method comprises the steps of adopting a pre-oxidation roasting furnace with a burner and an air inlet at the bottom, arranging a feed inlet at the lower part of the pre-oxidation roasting furnace, communicating the upper part with a cyclone separator through a material channel, communicating an exhaust port of the cyclone separator with an induced draft fan through a pipeline, introducing combustion flue gas generated by combustion of natural gas introduced into the burner into the pre-oxidation roasting furnace, introducing air into the pre-oxidation roasting furnace under the condition of starting the induced draft fan, conveying mineral powder into the pre-oxidation roasting furnace from the lower part of the pre-oxidation roasting furnace, keeping the mineral powder in a suspension state in the pre-oxidation suspension roasting furnace under the action of negative pressure and air flow, heating the mineral powder to 750-850 ℃ for pre-oxidation roasting, removing adsorbed water, crystal water and other volatile components in the mineral powder, and converting the mineral phases of different₂O₃And because the thermal expansion coefficients of the gangue and the iron ore are different, microcracks and holes are generated in the mineral powder particles in the heating process; the pre-oxidized product obtained after the pre-oxidation roasting is a pre-oxidation roasting material and enters a cyclone separator under the action of airflow;

3. the discharge hole of the cyclone separator is communicated with the feed inlet of the heat storage reduction roasting furnace, the bottom of the heat storage reduction roasting furnace is provided with a nitrogen inlet and a reducing gas inlet, and the side part of the heat storage reduction roasting furnace is provided with a discharge hole; under the condition of introducing nitrogen and reducing gas into the heat-accumulating reduction roasting furnace, the preoxidized roasted material is separated by cyclone in the cyclone separator and dischargedPlacing the mixture into a heat storage reduction roasting furnace, keeping the mixture in a suspension state under the action of negative pressure and airflow, and carrying out reduction roasting on the mixture with reduction gas at the temperature of 500-600 ℃, wherein α -Fe₂O₃Is reduced to produce Fe₃O₄(ii) a Reducing products obtained after the reduction roasting are reducing materials and are discharged from a side discharge hole of the heat storage reduction roasting furnace;

4. conveying the reducing material discharged from the heat storage reduction roasting furnace to a primary cooling cyclone separator; introducing nitrogen from a feed inlet of the primary cooling cyclone separator, and discharging the nitrogen from an air outlet of the primary cooling cyclone separator; carrying out cyclone separation on the reduced material under the condition of nitrogen atmosphere, cooling to 200-300 ℃ to obtain a cooled reduced material, and discharging from a discharge hole of a primary cooling cyclone separator;

5. the cooled reducing material discharged from the primary cooling cyclone separator enters a flow seal valve, and enters a secondary cooling cyclone separator after being discharged from the flow seal valve; at the moment, air is introduced from a feed inlet of the secondary cooling cyclone separator, and the air is discharged from an air outlet of the secondary cooling cyclone separator; the cooled and reduced material is separated in cyclone in air atmosphere and is reoxidized to produce Fe₃O₄Oxidized to generate ferromagnetic mineral gamma-Fe₂O₃Reducing the temperature of the obtained roasted product to be less than or equal to 100 ℃, and discharging the formed reoxidized material from a discharge hole of the secondary cooling cyclone separator;

6. grinding the reoxidation material until the part with the particle size of-0.074 mm accounts for 75-95% of the total mass to prepare secondary mineral powder; and carrying out low-intensity magnetic separation on the secondary mineral powder, wherein the magnetic field intensity is 1000-2000 Oe, and the obtained magnetic product is iron ore concentrate.

The main phases of the complex iron ores are goethite, hematite, limonite, siderite or pyrite.

The particle size of the complex iron ore is 5-200 mm.

In the step 1, a jaw crusher or a disc crusher is selected for crushing.

In the steps 1 and 6, a high-pressure roller mill or an ore mill is selected for grinding.

In the step 2, the main reaction formula of the pre-oxidation roasting is as follows:

Fe₂O₃·nH₂O→Fe₂O₃+H₂O、

FeCO₃+O₂→Fe₂O₃+CO₂and

Fe₃O₄+O₂→Fe₂O₃+CO₂。

in the step 2, the retention time of the solid materials in the pre-oxidation roasting furnace is 2-10 min.

In the step 3, the reducing gas is CO or H₂Or coal gas; the amount of reducing gas is determined according to the CO/H required by the complete reaction of reduction roasting₂1: 1-1.3 times of theoretical amount, and the reaction formula for complete reaction is as follows:

Fe₂O₃+H₂/CO→Fe₃O₄+H₂O/CO₂。

in the step 3, the volume flow ratio of the nitrogen to the reducing gas in the regenerative reduction roasting furnace is (1-7): 1.

In the step 3, the retention time of the solid materials in the heat-storage reduction roasting furnace is 10-60 min.

In the step 5, the main reaction formula of the reoxidation reaction is as follows:

Fe₃O₄+O₂→γ-Fe₂O₃。

the iron grade TFe of the iron ore concentrate is not less than 60 percent.

In the method, the recovery rate of Fe is more than or equal to 85 percent.

In the step 6, the low-intensity magnetic separation adopts a wet low-intensity magnetic separator or a dry magnetic separator.

In the step 4, the retention time of the reduced materials in the primary cooling cyclone separator is 2-5 min.

In the step 5, the retention time of the cooling and reducing material in the secondary cooling cyclone separator is 1-3 min.

In the step 4, the tubular heat exchanger is arranged in the primary cooling cyclone separator, and the sensible heat of the reduced material is recovered by the tubular heat exchanger.

In the step 5, the tubular heat exchanger is arranged in the secondary cooling cyclone separator, and sensible heat of the cooled and reduced material and latent heat released by reoxidation reaction are recovered by the tubular heat exchanger.

The principle of the invention is as follows: the mineral powder is in quick contact with high-temperature flue gas in a pre-oxidation roasting furnace, on one hand, the mineral powder is separated from adsorption water, crystal water and other volatile components in the material to form, on the other hand, various types of iron minerals such as goethite, limonite, siderite and magnetite in the mineral are heated and oxidized to generate dehydration, pyrolysis, oxidation reaction and the like, and the iron minerals are converted into Fe with uniform components₂O₃(ii) a Meanwhile, the thermal expansion coefficients of different minerals are different, and the materials are influenced by oxidation reaction and thermal expansion in the high-temperature heating process, so that a large number of micro-cracks and hole porosities generated by particles are greatly increased, the crystal structure is damaged, the iron-containing materials form a loose structure, and the particle strength is reduced; after the iron ore enters the heat storage reduction roasting furnace, in the reduction process, the increase of the porosity increases the reaction active sites of the iron ore, reduces the apparent activation energy of the reduction reaction, and improves the reaction rate, thereby strengthening the reduction effect; the reduced material is cooled in the nitrogen atmosphere, and the iron phase is not changed; then cooling in air, contacting air to make Fe₃O₄Reacting with oxygen to generate ferromagnetic mineral gamma-Fe with low coercive force₂O₃To reduce the magnetic agglomeration phenomenon; at this stage, a non-contact heat exchanger can be adopted to recover sensible heat and latent heat for power generation; the preheated gas can be used for preheating materials, and the energy consumption of system heating is reduced.

The invention has the characteristics and advantages that: compared with the conventional magnetic separation and flotation process, the method can efficiently recover iron from the iron ore containing the composite iron mineral, and the iron mineral can be goethite, hematite, limonite, siderite, pyrite and the like, so that the efficient separation of iron and gangue can be realized; before reduction roasting, a pre-oxidation roasting method is adopted to convert the complex iron ore into a product with more uniform properties; a large amount of microcracks and holes are generated in the high-temperature heating process, the crystal structure is damaged, the reactive sites of iron minerals are increased, the reaction rate is improved, and the apparent activation energy of the reduction reaction is reduced, so that the reduction effect is enhanced.

Drawings

FIG. 1 is an SEM scanning electron microscope of the ore powder before and after pre-oxidation roasting treatment in example 1 of the present invention;

FIG. 2 is a schematic flow chart of a method for strengthening reduction roasting based on iron-containing material heating cracking in the embodiment of the invention;

fig. 3 is a schematic view of the structure of the flow seal valve in the embodiment of the present invention.

Detailed Description

The iron grade TFe of the complex iron ore adopted in the embodiment of the invention is 25-40%, and the complex iron ore contains SiO according to the mass percentage₂25～55％。

The main phases of the complex iron ores adopted in the embodiment of the invention are goethite, hematite, limonite, siderite or pyrite.

The particle size of the complex iron ore adopted in the embodiment of the invention is 5-200 mm.

The crusher used in the embodiment of the present invention is a jaw crusher or a disc crusher.

The ore mill adopted in the embodiment of the invention is a high-pressure roller mill or a ball mill.

In the embodiment of the invention, a wet low-intensity magnetic separator or a dry magnetic separator is adopted for low-intensity magnetic separation.

The reducing gas in the embodiment of the invention is CO and H₂Or coal gas.

The structural principle of the flow seal valve adopted in the embodiment of the invention is shown in fig. 3, a baffle plate is arranged in the flow seal valve to divide the interior of the flow seal valve into a feeding chamber and a discharging chamber, the top edge and the side edge of the baffle plate are fixedly connected with the interior of the flow seal valve, and a gap is formed between the bottom edge of the baffle plate and the bottom of the flow seal valve to serve as a horizontal channel; a feeding hole is formed in the side wall of the feeding chamber, a discharging hole is formed in the side wall of the discharging chamber, the feeding hole and the discharging hole are both positioned above the bottom edge of the baffle, and the feeding hole is higher than the discharging hole; the top of the discharging chamber is also provided with an air outlet pipe; the bottom plate of the feeding chamber is provided with a loosening air inlet communicated with the air inlet pipeline 1, and the bottom plate of the discharging chamber is provided with a fluidizing air inlet communicated with the air inlet pipeline 2; the air inlet pipeline 1 and the air inlet pipeline 2 are respectively communicated with an air source.

The working method of the flow seal valve in the embodiment of the invention comprises the following steps: solid materials entering from the feeding hole are gradually accumulated, when the horizontal channel is closed by the solid materials, gas is introduced into the feeding chamber through the gas inlet pipeline 1 to serve as loosening wind, and gas is introduced into the discharging chamber through the gas inlet pipeline 2 to serve as fluidized wind, so that the solid materials in the feeding chamber move towards the discharging chamber under the action of gas flow; along with the solid materials are gradually accumulated in the feeding chamber and the discharging chamber, when the top surface of the solid materials in the discharging chamber is lifted to the position of the discharging port, the solid materials in the discharging chamber are discharged from the discharging port under the action of air flow.

In the embodiment of the invention, an air pipeline 1 and an air inlet pipeline 2 of the flow seal valve are respectively communicated with a nitrogen source, and nitrogen is used as loosening air and fluidizing air; and the nitrogen discharged from the gas outlet pipe at the top of the flow seal valve enters a feed inlet of the primary cooling cyclone separator to form a nitrogen atmosphere.

In the embodiment of the invention, the feed inlet of the secondary cooling cyclone separator is communicated with the air compressor through a pipeline, and air is blown in through the air compressor to form air atmosphere.

In the embodiment of the invention, the tubular heat exchanger is arranged in the primary cooling cyclone separator, and the sensible heat of the reduced material is recovered by the tubular heat exchanger.

In the embodiment of the invention, the tubular heat exchanger is arranged in the secondary cooling cyclone separator, and sensible heat of the cooled and reduced material and latent heat released by reoxidation reaction are recovered by the tubular heat exchanger.

In the embodiment of the invention, the air discharged from the air outlet of the secondary cooling cyclone separator is transmitted to the air inlet at the bottom of the pre-oxidation roasting furnace to be used as combustion-supporting gas.