Iron-containing material rotary kiln granular iron method production process

Abstract

On the basis of producing ferronickel through a laterite-nickel ore rotary kiln granular iron method, in order to produce granular iron products by adopting iron-containing materials and taking a rotary kiln as reduction equipment, the adopted production process comprises the following steps: preparing, mixing, wet-grinding and pelletizing the iron-containing materials, pulverized coal and a composite binder to obtain wet pellets, drying the wet pellets through a drying machine, screening the wet pellets through a vibrating screen, and carrying out hot pressing on the wet pellets to obtain the granular iron products. And adding the dry pellets into a rotary kiln. After the pellets are preheated and heated in the rotary kiln, iron in the materials is oxidized and subjected to a reduction reaction, slag with uniform components is generated from other components in the materials through a slagging reaction, the reduced metal iron is polymerized and grows to 1.20-30.0 mm and is uniformly suspended in the slag, the slag-iron mixture falls into water to be subjected to water quenching after being discharged from the rotary kiln in the form of viscous blocks, and the slag-iron mixture is cooled to the room temperature. And the block mass is subjected to ore grinding by an ore grinding machine and magnetic separation by a magnetic separator to obtain a granular iron product. The iron-containing material is reduced through the carbon-containing pellets, compared with a traditional iron making process, the reaction is carried out at low temperature in a short time, and high-quality granular iron can be produced.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical mineral engineering, and in particular relates to a rotary kiln granular iron production process for iron-containing materials. Background Art

[0002] At present, the rotary kiln granular iron method is a technology for producing granular metallic iron by treating unselectable low-grade acidic iron-containing materials. This technology uses non-coking coal as a reducing agent and heating energy source. The iron-containing materials are dried, preheated, and solid-state reduced in the rotary kiln, which can reduce iron oxides to metallic iron, and the gangue in the iron-containing materials is used for slag making. The metallic iron generated by reduction aggregates and grows into iron particles of 1.20 to 30.0 mm. The iron particles are suspended in the high-viscosity molten slag and discharged from the rotary kiln together with the slag. The charge discharged from the rotary kiln is then subjected to water quenching, selective crushing, gravity separation, and magnetic separation to obtain granular metallic iron.

[0003] The rotary kiln granular iron process can be divided into four parts: raw material processing, reduction and melting, slag iron separation and waste gas treatment. Raw material processing generally involves mixing ore powder and coal powder, and using a pelletizing plate or a pelletizing machine to form carbon-containing pellets or lumps. Ore powder generally uses magnetite or hematite, and can use low-grade iron ore, or even tailings powder from a beneficiation plant, but it will increase energy consumption when processing low-grade ores; coal powder can use ordinary coal or petroleum coke and other carbon-containing raw materials. The prepared carbon-containing pellets or lumps are added to the rotary kiln and under the condition of 1350-1450℃ in the kiln, the carbon-containing pellets or lumps undergo reduction and carburization reactions, and the slag iron is melted and aggregated separately. The whole process lasts for a short time. The melted and aggregated slag and metallic iron are discharged from the rotary kiln by the discharge device after oxygen-free cooling, and granular iron with a particle size of 5-25mm can be obtained. The high-temperature flue gas generated during the reduction process can be used to preheat the combustion air with a heat exchanger and then discharged after dust removal.

[0004] At present, the rotary kiln granular iron method is mainly used in the direct reduction production line of laterite nickel ore to produce low-nickel sponge iron. Its production process is as follows: (1) Drying, crushing, batching and briquetting of laterite nickel ore. The laterite nickel ore with a water content of 35-40% is dried in a drying kiln to a water content of 18-22%, and then the dried laterite nickel ore is crushed to a particle size of less than 5 mm. Finally, the crushed powder is mixed with reducing coal powder and limestone and processed into balls in a briquetting machine. (2) Roasting reduction process. The pellets are heated to 1250-1350℃ in a rotary kiln to reduce iron to about 80% and nickel to more than 95%. At the same time, the flue gas temperature at the kiln tail is controlled at 300-500℃, and the flue gas is used to dry the laterite nickel ore. (3) Crushing, grinding and magnetic separation of roasting slag. After the roasted slag is coarsely, mediumly and finely crushed, a magnetic separator is used to select nickel iron containing 7-10% nickel. The crushed roasted slag is then ground with a wet ball mill and a magnetic separator is used to select nickel iron containing 7-10% nickel.

[0005] The rotary kiln granular iron method uses pellets or briquettes with carbon inside. Since the carbon-containing pellets or briquettes use finely ground ore and coal powder, the kinetic conditions of the iron oxide reduction reaction are more advantageous than molten reduction and direct reduction. If the reduction temperature is increased to 1350-1450℃, the reduction and melting process of the carbon-containing pellets can be completed in one reaction device. The characteristics of the rotary kiln granular iron method are: the reduction temperature of iron oxides and the aggregation and growth temperature of metal particles are much lower than that of the ore-fired furnace, and the content of non-iron impurities in the product is low; cheap thermal coal is used as a reducing agent and heating fuel, and there is no need to add too many additives and slag-making agents in production, and the slag volume per unit product is low and the energy consumption is low. Compared with the ore-fired furnace method and the rotary kiln pre-reduction-electric furnace smelting method (RKEF method), it has the advantages of low energy consumption, low power consumption per ton of product, low grid capacity requirements, high iron recovery rate (about 92%), low investment, and low production cost. Disadvantages: The rotary kiln granular iron method has a complex charge handling process, poor production stability, and the material is in a semi-molten state in the rotary kiln. Any slight fluctuation in operation can easily cause faults such as adhesion and ringing in the rotary kiln. The rotary kiln is difficult to operate and difficult to automate, with a low operating rate, high consumption of refractory materials, and low single-machine production capacity.

[0006] Although the rotary kiln granular iron process has some of the above-mentioned shortcomings, with the changes in the world's iron ore resource supply conditions, from a comprehensive analysis of energy consumption, environmental friendliness, production costs, and comprehensive utilization of low-grade iron ore resources, the rotary kiln granular iron process is the most economical processing method for producing metallic iron.

[0007] The present invention is based on the existing laterite nickel ore rotary kiln granular iron method for producing nickel iron, in order to solve the above problems existing in the existing rotary kiln granular iron method, and adopts iron-containing materials to produce granular iron with a rotary kiln as a reduction device, and invents an iron-containing material rotary kiln granular iron method process. Summary of the invention

[0008] The invention relates to a granular iron production process of a rotary kiln for iron-containing materials. The main equipment used includes: a batching machine, a mixer, a damping mill, a pelletizing machine, a dryer, a vibrating screen, a reduction rotary kiln, a kiln back draft fan, a heating burner, a waste heat boiler, a cooling water pool, a ball mill, a magnetic separator, a flue gas dust collector, a smoke exhauster and a desulfurization system; the main materials used include: iron-containing powder, coal powder, a composite binder, return material, water, jet air, high-temperature and high-pressure steam, low-temperature flue gas, medium-temperature flue gas, high-temperature flue gas, pellets, powdery materials, coal powder, air, slag, granular iron, dust removal ash and flue gas emission.

[0009] The process used is: (1) After mixing the iron-containing material, coal powder, composite binder and return material in the ratio of 100:14-18:2-3:3-5, add them into the grinding machine for water grinding. The amount of water added is 7-8% of the total amount of the iron-containing material. The grinding time is 2-3 minutes. (2) Add the milled material to the ball-making plate and add water to make balls. The amount of water added is controlled to 6-7%, and the particle size of the raw balls is controlled to 8-16 mm. (3) Add the wet green balls into the drum dryer and use the 300-400℃ medium temperature flue gas discharged from the waste heat boiler to dry the wet green balls. When the moisture content of the green balls reaches below 5%, the balls are discharged from the drum dryer, and the flue gas temperature is reduced to 150-200℃; (4) The dried pellets are screened using a 5 mm vibrating screen, and the powdered material under the screen is returned to the dampening mill for use; (5) The pellets on the screen are added into the kiln from the feed end of the reduction rotary kiln. Under the action of the rotation of the reduction rotary kiln, the pellets exchange heat with the high-temperature flue gas in the kiln as they flow from the feed end to the discharge end. The pellets are dried and preheated as the temperature rises. When the temperature of the pellets rises to above 600°C, the iron oxides in the pellets are reduced step by step under the action of the reducing coal, and the iron oxides can eventually be reduced to metallic iron. (6) During the reduction process of iron ore, metallurgical gas continuously escapes from the material layer. By installing multiple combustion-supporting fans at different positions along the length of the kiln on the back of the reduction rotary kiln, normal temperature air is supplied to the iron ore reduction zone in the kiln, so that the metallurgical gas can be burned at different positions in the reduction zone in the kiln, thereby supplying heat to the rotary kiln. (7) The high-temperature flue gas generated by the combustion of metallurgical gas in the rotary kiln exchanges heat with the pellets in the countercurrent flow process, which can reduce the temperature of the high-temperature flue gas in the kiln and increase the temperature of the pellets; (8) By controlling the kiln temperature of the rotary kiln reduction zone to 1350-1400°C and the pellets in the kiln for 150-180 minutes, the pellets flow to the discharge end of the reduction rotary kiln, the temperature of the reduced pellets has reached 1250-1350°C, and the metallization rate has reached more than 96%; (9) After being discharged from the discharge end of the reduction rotary kiln, the reduced pellets enter the water cooling pool for water cooling. When the temperature of the reduced pellets drops to 70-100°C, the reduced pellets are scooped out of the water pool by a scooping machine and added to a ball mill for wet grinding. The ground materials are magnetically separated by a magnetic separator to obtain high-purity granular iron and slag; (10) The high-temperature flue gas of 600-700℃ discharged from the feeding end of the reduction rotary kiln flows into the waste heat boiler. The flue gas undergoes indirect heat exchange with normal temperature water, while producing medium-temperature and medium-pressure steam with a temperature of about 535℃ and a pressure of about 8.8MPa, which can reduce the temperature of the high-temperature flue gas to 300-400℃.

[0010] The iron-containing material of the present invention adopts iron-containing powder with an iron grade of more than 40%, CaO+MgO / SiO2 less than 0.30, and a particle size of -200 mesh accounting for more than 80%. The reduced coal adopts coal powder with a volatile matter of 25-35%, an ash content of 8-10%, and a particle size of -200 mesh accounting for more than 80%. The binder adopts a composite binder combining organic and inorganic.

[0011] The iron-containing materials of the present invention are iron concentrate, iron-containing dust, non-ferrous smelting slag, sulfuric acid slag and the like; the reduction pellets are multi-stage crushed before being ground in a ball mill, so that the particle size of the reduction pellets is reduced as much as possible before entering the ball mill.

[0012] The iron-containing material of the present invention should be pretreated before batching. There are two methods for pretreatment according to the different states of the materials entering the kiln: (1) the method of directly feeding the bulk materials into the kiln by crushing, granulating, batching and mixing the raw materials; the method of directly feeding the bulk materials into the kiln is to process the iron-containing material into particles with a particle size of less than 25 mm, and add an appropriate amount of reducing agent, slag-making agent and additive, mix them evenly, and then accurately, quantitatively and continuously add them into the rotary kiln. This method is suitable for iron-containing materials that can be directly crushed and granulated. (2) the wet briquetting or pelletizing method of crushing, granulating, batching, mixing and agglomerating the raw materials; for sedimentary iron ore with high water content, because the iron ore is mostly muddy, it is difficult to crush and granulate, and the particle size of the materials entering the kiln is difficult to control, which is easy to cause material segregation in the rotary kiln, and the wet briquetting or pelletizing method is usually used.

[0013] For sedimentary iron ore with high water content, the present invention adopts a "semi-dry briquetting" process, that is, a method in which the iron-containing material is dried, crushed, batched, briquetized, briquetized, dried and then put into the kiln.

[0014] The semi-dry briquetting or pelletizing method of the present invention comprises the following steps: the iron-containing material is dried and crushed into particles with a particle size of less than 1.0 to 2.0 mm, slag-forming agent, additive and reducing agent are added and mixed, the mixed material is briquetting and drying after adding water, and finally the block material is quantitatively and continuously added into a rotary kiln for reduction.

[0015] The present invention divides the kiln of the reduction rotary kiln into three zones: preheating zone, reduction zone and granular iron zone. (1) Preheating zone: The material is in a bulk state and is dried and preheated in the free space of the kiln using the waste heat of high-temperature flue gas. Under the rotation of the rotary kiln, the material rolls, flows and transfers heat by the friction between the kiln lining and the charge, which can increase the material temperature from room temperature to about 600°C. The length of the preheating zone is generally 20% of the total length of the rotary kiln. (2) Reduction zone: The material is reduced to iron oxides. The reduction zone starts when the iron oxides in the material begin to be reduced in large quantities and ends when the material begins to soften. Generally, more than 90% of the iron oxides can be reduced to metallic iron. Since the reduction rate of iron oxides is controlled by the diffusion rate, the reaction rate is relatively slow. The reduction process requires sufficient time, and a high reducing atmosphere and a temperature of 600-1100°C should be maintained in the material layer. The length of the reduction zone is generally 50% of the length of the rotary kiln. (3) Granular iron belt: The material continues to reduce and complete the iron oxide reduction. The remaining components in the material generate slag with uniform composition through slag-forming reaction. The reduced metallic iron aggregates and grows to 1.20-30.0 mm. The slag formed in the material is a "long slag" with high viscosity, extremely poor fluidity, and little viscosity change with temperature. The reduced metallic iron particles are evenly "suspended" in the slag, and the iron particles do not deposit in the granular iron belt. At the end of the granular iron belt, the slag-iron mixture is discharged from the rotary kiln as a viscous mass and falls into water for water quenching. The rotary kiln is a reactor for the reduction of iron oxides and the growth of iron particles. In order to complete the reduction of the material and aggregate the reduction products to a particle size of 1.20-30.0 mm, the length of the granular iron belt accounts for about 30% of the length of the rotary kiln.

[0016] In the present invention, in the high-temperature agglomerated slag-iron mixture discharged from the rotary kiln, metallic iron particles are suspended in the semi-molten slag, and the high-temperature agglomerates are water quenched, selectively crushed, and magnetically separated to obtain granular metallic iron. (1) Water quenching: The high-temperature agglomerated slag-iron mixture discharged from the rotary kiln is directly put into water for rapid cooling, and the difference in volume shrinkage between iron and slag during rapid cooling is utilized to generate gaps between the iron particles and the slag matrix, thereby reducing the energy consumption of subsequent crushing and grinding. (2) Selective crushing: The crushing of the slag-iron mixture produced by the rotary kiln should separate the iron particles and the slag around the iron particles, and maintain the original particle size of the iron particles to the maximum extent.

[0017] The reduction rotary kiln of the present invention should be a straight long kiln with a length-to-diameter ratio greater than 15, a slope less than 2.50%, and a rotation speed of 0.35 to 1.0 rpm. The two ends of the rotary kiln are provided with retaining rings of suitable height. The ratio of the diameter of the retaining rings at the feed end and the discharge end to the inner diameter of the rotary kiln is less than 0.50, so that the material filling rate in the rotary kiln can be maintained at 20 to 25%.

[0018] In the same cross section of the reduction rotary kiln of the present invention, the material is heated, reduced, and the metal particles are polymerized and grown simultaneously. An oxidation zone with high-intensity heating should be formed in the free space without material to meet the heat demand of iron oxide reduction. At the same time, a reduction zone with strong reducing atmosphere should be formed inside the material layer to ensure the reduction of iron oxide. In addition, CO gas generated by the reduction of iron oxide in the material layer continuously overflows from the material layer to form a CO gas film on the surface of the material layer, so that the CO gas film can have a stable and sufficient thickness and effectively separate the oxidizing atmosphere in the free space from the reducing atmosphere inside the material layer.

[0019] The reduction rotary kiln of the present invention uses coarse coal powder as fuel, and the coal powder is burned by a sleeve burner. The flame of the fuel combustion is long, the flame temperature is uniform, and the temperature in the kiln is easy to adjust. At the same time, the air flow disturbance during the combustion process is small, and the interference and damage to the CO gas film on the surface of the material layer are small.

[0020] The invention provides a kiln back draft fan for secondary air supply to the kiln in the low temperature reduction zone of the reduction rotary kiln, and supplies secondary air in the high temperature reduction zone of the rotary kiln by high speed jet from the kiln head.

[0021] The beneficial effects of the present invention are: (1) The present invention uses iron-containing materials to produce granular iron, which has wide adaptability to raw materials and fuels, and a wide range of choices for the types of ore and coal. Ordinary powdered ore or ordinary non-coking coal can meet the needs of the rotary kiln.

[0022] (2) The raw material pretreatment of the present invention only requires pelletizing or briquetting the iron-containing material, without the need for lump ore or coking coal, and thus without the need for sintering and coking processes, thereby greatly simplifying the ironmaking process, reducing investment costs, and simplifying the operation process.

[0023] (3) The iron-containing material of the present invention is mixed with a reducing agent and then agglomerated. The contact area between the iron oxide and the reducing agent is large, which improves the reduction kinetics of the iron-containing material. Compared with the traditional blast furnace ironmaking process, the iron oxide reaction is carried out at a low temperature and in a short time, and the energy consumption is low. It has more advantages than the traditional process in terms of energy saving and environmental protection.

[0024] (4) The present invention provides a granular iron belt in the rotary kiln, which can make the reduced metallic iron aggregate and grow to 1.20-30.0 mm. The metallic iron particles in the material are evenly "suspended" in the slag, thus creating conditions for the subsequent separation of slag and iron.

[0025] (5) The iron content of the granular iron product of the present invention is more than 97%, the carbon content is less than 2.5%, the P content is less than 0.04%, and the Mn content is less than 0.01%. The granular iron product has the same quality as blast furnace pig iron, high purity, and good melting performance. It is a better high-quality raw material for steelmaking than DRI. In addition, there is no reoxidation and pulverization problem during use, and the product is very convenient to load and unload, transport, and put into the furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart of the iron-containing material rotary kiln granular iron method of the present invention; Figure 2 To restore the structure diagram of rotary kiln equipment; Figure 3 Schematic diagram of atmosphere distribution in a reducing rotary kiln. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments: (1) Iron-containing material, coal powder, composite binder and return material are mixed in the ratio of 100:18:3:3, and then added into a grinding machine for water grinding. The amount of water added is 7% of the total amount of iron-containing material, and the grinding time is 3 minutes.

[0028] (2) Add the milled material into the ball-making plate and add water to make balls. The amount of water added is controlled to 7% and the particle size of the balls is controlled to 8-16mm.

[0029] (3) Add the wet green balls into the drum dryer and use the 350℃ medium-temperature flue gas discharged from the waste heat boiler to dry the wet green balls. When the moisture content of the green balls reaches below 5%, the balls are discharged from the drum dryer, and the flue gas temperature is reduced to 180℃.

[0030] (4) The dried pellets are screened using a 5 mm vibrating screen, and the powdered material under the screen is returned to the wet mill for use.

[0031] (5) The pellets on the screen are added into the kiln from the feed end of the reduction rotary kiln. Under the action of the rotation of the reduction rotary kiln, the pellets exchange heat with the high-temperature flue gas in the kiln as they flow from the feed end to the discharge end. The pellets are dried and preheated as the temperature rises. When the temperature of the pellets rises to above 600°C, the iron oxides in the pellets are reduced step by step under the action of the reducing coal, and the iron oxides can eventually be reduced to metallic iron.

[0032] (6) During the iron ore reduction process, metallurgical gas continuously escapes from the material layer. By installing multiple combustion-supporting fans at different positions along the length of the kiln on the back of the reduction rotary kiln, room temperature air is supplied to the iron ore reduction zone in the kiln. This allows the metallurgical gas to burn at different positions in the reduction zone in the kiln, thereby supplying heat to the rotary kiln.

[0033] (7) The high-temperature flue gas generated by the combustion of metallurgical gas in the rotary kiln exchanges heat with the pellets in the countercurrent flow process, which can reduce the temperature of the high-temperature flue gas in the kiln and increase the temperature of the pellets.

[0034] (8) By controlling the kiln temperature of the reduction zone of the rotary kiln to 1380°C and the pellet time in the kiln to 180 min, the pellets flow to the discharge end of the reduction rotary kiln. The temperature of the reduced pellets has reached 1300°C and the metallization rate has reached 96%.

[0035] (9) After being discharged from the discharge end of the reduction rotary kiln, the reduced pellets enter the water cooling pool for water cooling. When the temperature of the reduced pellets drops to 80°C, the reduced pellets are scooped out of the water pool by a scooping machine and added to a ball mill for wet grinding. The ground materials are magnetically separated by a magnetic separator to obtain high-purity granular iron and slag.

[0036] (10) The 650℃ high-temperature flue gas discharged from the feed end of the reduction rotary kiln flows into the waste heat boiler. The flue gas undergoes indirect heat exchange with normal temperature water, while producing medium-temperature and medium-pressure steam with a temperature of about 535℃ and a pressure of about 8.8MPa, which can reduce the temperature of the high-temperature flue gas to 350℃.

Claims

1. A rotary kiln granular iron production process for iron-containing materials, characterized in that: The following steps are involved: (1) The iron-containing material, coal powder, composite binder and return material are mixed in a ratio of 100:14-18:2-3:3-5, and then added into a grinding machine for water grinding. The amount of water added is 7-8% of the total weight of the iron-containing material, and the grinding time is 2-3 minutes; (2) Add the milled material to the ball-making plate, add water to make balls, and control the particle size of the balls to 8-16 mm; (3) Add the wet green balls into the drum dryer and use the 300-400℃ medium temperature flue gas discharged from the waste heat boiler to dry the wet green balls. When the moisture content of the green balls reaches below 5%, the balls are discharged from the drum dryer, and the flue gas temperature is reduced to 150-200℃; (4) The dried pellets are screened using a 5 mm vibrating screen, and the powdered material under the screen is returned to the dampening mill for use; (5) The pellets on the screen are added into the kiln from the feed end of the rotary kiln. Under the action of the rotary kiln, the pellets exchange heat with the high-temperature flue gas in the kiln as they flow from the feed end to the discharge end. The pellets are dried and preheated as the temperature rises. When the pellet temperature rises to above 600°C, the iron oxides in the pellets are gradually reduced under the action of the reducing coal, and the iron oxides can eventually be reduced to metallic iron. (6) During the iron ore reduction process, metallurgical gas continuously escapes from the material layer. By installing multiple combustion-supporting fans at different positions along the length of the kiln on the kiln back of the rotary kiln, room temperature air is supplied to the iron ore reduction zone in the kiln, so that the metallurgical gas burns at different positions in the reduction zone in the kiln, thereby supplying heat to the rotary kiln. (7) The high-temperature flue gas generated by the combustion of metallurgical gas in the rotary kiln exchanges heat with the pellets in the countercurrent flow process, which reduces the temperature of the high-temperature flue gas in the kiln and increases the temperature of the pellets; (8) By controlling the kiln temperature of the rotary kiln reduction zone to 1350-1400°C and the pellet time in the kiln to 150-180 minutes, the pellets flow to the discharge end of the rotary kiln, the temperature of the reduced pellets has reached 1250-1350°C, and the metallization rate has reached more than 96%; (9) After being discharged from the discharge end of the rotary kiln, the reduced pellets enter the water cooling pool for water cooling. When the temperature of the reduced pellets drops to 70-100°C, the reduced pellets are scooped out of the water pool by a scooping machine and added to a ball mill for wet grinding. The ground materials are magnetically separated by a magnetic separator to obtain high-purity granular iron and slag; (10) The high-temperature flue gas of 600-700℃ discharged from the feeding end of the rotary kiln flows into the waste heat boiler. The flue gas undergoes indirect heat exchange with normal temperature water, and while producing medium-temperature and medium-pressure steam, the high-temperature flue gas temperature is reduced to 300-400℃.

2. The iron-containing material rotary kiln granular iron production process according to claim 1, characterized in that: The iron-containing material uses iron grade above 40%, CaO+MgO / SiO2 less than 0.30, and particle size -200 mesh accounting for more than 80% of iron-containing powder; the reducing coal uses coal powder with volatile matter 25-35%, ash content 8-10%, and particle size -200 mesh accounting for more than 80%, and the binder uses a composite binder combining organic and inorganic.

3. The iron-containing material rotary kiln granular iron production process according to claim 1, characterized in that: There are two methods for pretreatment of iron-containing materials before batching: (1) Process the iron-containing materials into particles with a particle size of less than 25 mm, add reducing agents, slag-making agents, and additives, mix them evenly, and then add them to the rotary kiln accurately, quantitatively, and continuously. This method is suitable for iron-containing materials that can be directly crushed and granulated; (2) For sedimentary iron ore with high water content, wet briquetting or pelletizing is used.

4. The process for producing iron-containing materials by rotary kiln granular iron method according to claim 3, characterized in that: For sedimentary iron ore with high water content, the iron ore is crushed into particles with a size less than 1.0-2.0 mm after drying, and then mixed with slag-making agent, additives and reducing agent. The mixed material is pressed into blocks and dried after adding water. Finally, the block material is quantitatively and continuously added into the rotary kiln for reduction.

5. The process for producing iron-containing materials by rotary kiln granular iron method according to claim 1, characterized in that: The rotary kiln is divided into three zones: preheating zone, reduction zone and granular iron zone: (1) Preheating zone: The material is in a loose state and is dried and preheated in the free space of the kiln using the waste heat of high-temperature flue gas; under the rotation of the rotary kiln, the material rolls, flows and transfers heat due to the friction between the kiln lining and the charge, so that the material temperature rises from room temperature to 600°C. The length of the preheating zone is 20% of the total length of the rotary kiln; (2) Reduction zone: The material is reduced to iron oxides. The reduction zone starts when the iron oxides in the material begin to be reduced in large quantities and ends when the material begins to soften. More than 90% of the iron oxides are reduced to metallic iron. The reducing atmosphere and temperature conditions of 600-1100°C are maintained in the material layer. The length of the reduction zone is 50% of the length of the rotary kiln. (3) Granular iron belt: the material continues to reduce and completes the iron oxide reduction, and the remaining components in the material are slag-forming to form a uniform slag, and the reduced metallic iron aggregates and grows to a size of 1.20 to 30.0 mm; the slag formed in the material is a "long slag" with high viscosity, poor fluidity, and a small viscosity change with temperature. The reduced metallic iron particles are evenly "suspended" in the slag, and the iron particles do not deposit in the granular iron belt; at the end of the granular iron belt, the slag-iron mixture is discharged from the rotary kiln as a viscous mass and falls into water for quenching; the rotary kiln is a reactor for the reduction of iron oxides and the growth of iron particles. In order to complete the reduction of the material and the aggregation and growth of the reduction product to a particle size of 1.20 to 30.0 mm, the length of the granular iron belt accounts for 30% of the length of the rotary kiln.

6. The process for producing iron-containing materials by rotary kiln granular iron method according to claim 1, characterized in that: In the high-temperature agglomerated slag-iron mixture discharged from the rotary kiln, metallic iron particles are suspended in the semi-molten slag, and the high-temperature agglomerates are quenched by water, selectively crushed, and magnetically separated to obtain granular metallic iron; (1) Water quenching: The high-temperature agglomerated slag-iron mixture discharged from the rotary kiln is directly put into water for rapid cooling. The difference in volume shrinkage between iron and slag during rapid cooling is used to create a gap between the iron particles and the slag matrix, thereby reducing the energy consumption of subsequent crushing and grinding. (2) Selective crushing: The crushing of the slag-iron mixture produced by the rotary kiln should separate the iron particles and the slag around the iron particles, and maintain the original particle size of the iron particles to the maximum extent.

7. The process for producing iron-containing materials by rotary kiln granular iron method according to claim 1, characterized in that: The rotary kiln should be a straight long kiln with a length-to-diameter ratio greater than 15, a slope less than 2.50%, and a rotation speed of 0.35 to 1.0 rpm. There should be retaining rings at both ends of the rotary kiln. The ratio of the diameter of the retaining rings at the feed end and the discharge end to the inner diameter of the rotary kiln should be less than 0.

50. The material filling rate in the rotary kiln should be 20 to 25%.

Images