A rotary kiln system and method for iron ore reduction and co-production of reducing gas

Abstract

The present invention discloses a rotary kiln system and method for iron ore reduction and co-production of reducing gas. The rotary kiln is sequentially divided into a drying section, a preheating section, a co-production reduction section, a roasting section, and a slow cooling section. A variable-diameter gas delivery channel and a gas injection device provided on the kiln wall effectively control the injection rhythm, injecting countercurrent steam at the bottom of the material to fully gasify the carbon to produce synthesis gas. The synthesis gas quality is also improved through temperature and flow control. The present invention couples a novel rotary kiln with a smelting reduction furnace, providing high-quality smelting reduction furnace charge with a high degree of pre-reduction to reduce smelting reduction energy consumption, and provides hydrogen-rich fuel gas for hydrogen-based smelting reduction. This improves the yield and efficiency of reduced iron, while reducing carbon emissions and saving carbon consumption, thus promoting the development of the rotary kiln-smelting reduction process.

Description

Technical Field

[0001] The present invention relates to metallurgical equipment and methods, in particular to a rotary kiln system for iron ore reduction and co-production of reducing gas and a method for iron ore reduction and co-production of reducing gas, belonging to the technical field of metallurgy. Background Art

[0002] Metallurgical rotary kilns currently have numerous applications, including the production of oxidized pellets, direct reduction of iron, and the disposal and recovery of solid waste resources. Coal-based direct reduction (DRR) is the most important, valuable, and widely used process, used for small-scale production of raw materials for electric furnace steelmaking and for treating dust and polymetallic complex ores in steel plants. However, low production output, high energy consumption, and the tendency to form rings have hampered normal rotary kiln production for many years, severely restricting the further development of rotary kiln technology. Conventional coal-based DRR can be divided into two main zones: the preheating zone and the metallization zone. These zones primarily undergo a series of complex physical and chemical reactions, including water evaporation, coal pyrolysis to release hydrocarbons, and the conversion of iron oxides (FeO) to metallic iron.

[0003] Coal gasification is the process of converting solid coal into a synthesis gas (syngas) containing combustible gases such as CO, hydrogen, and methane, and non-combustible gases such as carbon dioxide and nitrogen, through a series of chemical reactions between organic matter in the coal and a gasifying agent (such as steam, air, and / or oxygen) within specific equipment at a specific temperature and pressure. Coal gasification requires a gasifier, a gasifying agent, and heat. The process involves first introducing air into the furnace, burning a portion of the fuel and storing the heat in the fuel bed and regenerator. Steam is then introduced into the hot fuel bed to react. Because the reaction absorbs heat, the temperature of the fuel bed and regenerator drops to a certain level, and then air is introduced back into the furnace to raise the temperature, repeating the cycle.

[0004] The use of rotary kilns as metallurgical equipment has been documented in relevant literature. Patent CN210916204U proposes a coal-based hydrogen metallurgical device for iron ore rotary kilns. The iron ore reduction is primarily fueled by H2. The kiln's gas outlet is connected to the grate inlet. A dry magnetic separator is installed at the outlet of the oxygen-free cooling device. The pellet outlet of the dry magnetic separator is connected to a dry grinding and dry separation device, which also has a cold pressing device. The char outlet of the dry magnetic separator is connected to a particle size classifier. Patent CN113881842B proposes a system and method for integrated pellet roasting and reduction to produce metallized pellets. The system includes a grate, a rotary kiln, a reduction zone, and a finished product conveyor. A baffle is installed at the junction of the rotary kiln and the reduction zone, with a first hydrogen lance located below the baffle. A trolley with several second hydrogen lances is installed at the bottom of the reduction zone for hydrogen-enriched reduction of the metallized pellets. However, there are no reports of rotary kilns being used as equipment for the combined production of metallurgy and syngas. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention, based on existing rotary kiln equipment and processes, aims to develop a new type of rotary kiln equipment and realize new uses of the rotary kiln. The present invention provides a rotary kiln system for iron ore reduction and co-production of reducing gas and a method for iron ore reduction and co-production of reducing gas. The kiln body surface in the rotary kiln system is evenly distributed with kiln body gas transmission channels and embedded gas nozzles for spraying steam gasification agent and coal gas combustion-supporting air into the kiln. High-volatile coal and iron-containing raw materials (C / O=1.2-1.5:1) are also used, and the materials pass through a drying section, a preheating section, a co-production reduction section, a roasting section and a slow cooling section in sequence. In the co-production reduction section, steam is sprayed at the bottom of the material, and the steam reacts with the fixed carbon of the granular coal to produce water gas to generate H2 / CO synthesis gas, and at the same time, reduction of the iron-containing raw materials occurs. The hot air containing the synthesis gas at the kiln tail is circulated to the kiln head burner as fuel gas or to the molten reduction furnace as reducing gas. This rotary kiln system can produce synthesis gas while achieving direct reduction of iron oxides, and can also provide high-quality reducing materials for molten reduction, which is conducive to promoting the development of the rotary kiln-molten reduction process.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows:

[0007] According to a first embodiment of the present invention, a rotary kiln system for reducing iron ore and co-producing reducing gas is provided:

[0008] A rotary kiln system for reducing iron ore and co-producing reducing gas comprises a rotary kiln. The rotary kiln is a multi-stage rotary kiln. The rotary kiln comprises a drying section, a preheating section, a co-production reduction section, a roasting section, and a slow cooling section, which are sequentially connected in series from the kiln tail to the kiln head, according to the flow of material within the kiln. A gasifying agent nozzle is provided on the kiln wall of the co-production reduction section. A combustion-supporting gas nozzle is provided on the kiln wall of the roasting section. A burner is provided at the kiln head, extending into the roasting section. An exhaust port at one end of the drying section, near the kiln tail, is connected to an air inlet external to the burner via a gas circulation conduit.

[0009] Preferably, a plurality of gasifying agent nozzles are evenly arranged along the circumferential and axial directions of the kiln wall at the co-production reduction section.

[0010] Preferably, a plurality of combustion-supporting gas nozzles are evenly arranged along the circumferential and axial directions of the kiln wall at the roasting section.

[0011] Preferably, each gasifying agent nozzle and / or each oxidizing gas nozzle is independently equipped with a movable piston. As the rotary kiln rotates, the movable pistons ensure that: in the co-production reduction section, the movable piston in the gasifying agent nozzle located on the kiln wall below the material is in an open position, while the movable pistons in the gasifying agent nozzles on the other kiln walls are in a closed position. In the roasting section, the movable piston in the gasifying agent nozzle located on the kiln wall below the material is in a closed position, while the movable pistons in the gasifying agent nozzles on the other kiln walls are in an open position.

[0012] Preferably, the rotary kiln system also includes a gasifying agent delivery channel. The gasifying agent delivery channel is defined within the kiln wall of the rotary kiln and extends sequentially from the kiln tail to the kiln head, through the walls of the drying section, preheating section, and co-production reduction section, and finally connects to the gasifying agent nozzle's air inlet. The gasifying agent delivery channel comprises a plurality of air inlet ducts distributed axially along the rotary kiln. Preferably, the plurality of gasifying agent delivery channels may be interconnected or disconnected.

[0013] Preferably, the rotary kiln system further includes a combustion-supporting gas delivery channel. This channel is formed within the kiln wall of the rotary kiln and extends from the kiln head to the kiln tail, sequentially penetrating the walls of the slow cooling section and the roasting section, and then connecting to the gas inlet of the combustion-supporting gas nozzle. The combustion-supporting gas delivery channel comprises multiple inlet ducts distributed along the axial direction of the rotary kiln. Preferably, the multiple combustion-supporting gas delivery channels may or may not be interconnected.

[0014] Preferably, the aperture of the gasifying agent conveying channel gradually decreases along the direction from the kiln tail to the kiln head of the rotary kiln.

[0015] Preferably, the aperture of the combustion-supporting gas delivery channel gradually decreases along the direction from the kiln head to the kiln tail of the rotary kiln.

[0016] Preferably, both the gasifying agent delivery channel and the oxidizing gas delivery channel are provided with a pressurization check mechanism. The pressurization check mechanism is a trumpet-shaped fixed protrusion whose aperture gradually decreases along the airflow direction. Preferably, both the gasifying agent delivery channel and the oxidizing gas delivery channel are provided with multiple pressurization check mechanisms, and the apertures of the exhaust holes of the multiple pressurization check mechanisms remain constant or decrease sequentially along the airflow direction.

[0017] Preferably, a boost check mechanism is provided in both the gasifying agent delivery channel and the combustion-supporting gas delivery channel. The boost check mechanism includes fins, a limiting protrusion, and an anchor cable. The fins are fan-shaped arc pieces that match the gasifying agent delivery channel or the combustion-supporting gas delivery channel. The fins are hinged to the inner wall of the gasifying agent delivery channel or the inner wall of the combustion-supporting gas delivery channel. Depending on the direction of the airflow, the limiting protrusion is provided downstream of the fins and fixed to the inner wall of the gasifying agent delivery channel or the inner wall of the combustion-supporting gas delivery channel. One end of the anchor cable is fixedly connected to the limiting protrusion, and the other end thereof is fixedly connected to the back of the fin. The length of the anchor cable is such that when the anchor cable is extended to its maximum length, the angle formed between the fin and the inner wall of the gasifying agent delivery channel or the inner wall of the combustion-supporting gas delivery channel is 85-90°, preferably 90°.

[0018] Preferably, the boost check mechanism includes a plurality of fins, which are arranged in an annular pattern along the circumference of the inner wall of the gasifying agent delivery channel or the combustion-supporting gas delivery channel, and each fin is independently provided with a limiting protrusion and an anchor cable. When all the fins rotate in the direction of the airflow and abut against the corresponding limiting protrusions, all the fins together form a trumpet-shaped structure whose aperture gradually decreases along the direction of the airflow. Preferably, multiple boost check mechanisms are provided in both the gasifying agent delivery channel and the combustion-supporting gas delivery channel, and when the fins of the multiple boost check mechanisms form trumpet-shaped structures, the apertures of the exhaust holes of the multiple trumpet-shaped structures remain unchanged or decrease sequentially along the direction of the airflow.

[0019] Preferably, the gasifying agent delivery channel is further connected to an air inlet at the kiln tail, and a gasifying agent delivery pipeline is provided on the gasifying agent delivery pipeline.

[0020] Preferably, the combustion-supporting gas delivery channel is further connected to an oxygen-enriched gas delivery pipeline at the air inlet at the kiln head, and the oxygen-enriched gas delivery pipeline is provided with an air valve and an air pump.

[0021] Preferably, the rotary kiln system further includes a smelting reduction furnace. The kiln head discharge port of the rotary kiln is connected to the feed port of the smelting reduction furnace via a feeding device. The top exhaust port of the smelting reduction furnace is connected to the air inlet outside the burner via a top gas delivery pipeline.

[0022] Preferably, a gas circulation branch pipe is led out from the gas circulation pipeline and is connected to the air inlet of the smelting reduction furnace.

[0023] Preferably, the gas circulation pipeline is further provided with a dust removal device and a gas purification device in sequence, both of which are located upstream of the connection between the gas circulation branch pipe and the gas circulation pipeline.

[0024] According to a second embodiment of the present invention, a method for reducing iron ore and co-producing reducing gas is provided:

[0025] A method for reducing iron ore and producing reducing gas, or a method for reducing iron ore and producing reducing gas using the rotary kiln system of the first embodiment, comprising the following steps:

[0026] (S1) The iron-containing raw materials and fuel are transported to a rotary kiln, and are reduced in a drying section, a preheating section, a co-production reduction section, a roasting section, and a slow cooling section to obtain a reduced material, which is then transported to a smelting reduction furnace for deep reduction treatment.

[0027] (S2) During the reduction treatment in the rotary kiln, a gasifying agent is sprayed into the kiln through a gasifying agent nozzle on the kiln wall of the co-generation reduction section, and a combustion-supporting gas is sprayed into the kiln through a combustion-supporting gas nozzle on the kiln wall of the roasting section.

[0028] (S3) The hot air discharged from the tail of the rotary kiln is subjected to dust removal and purification treatment, and then transported to the roasting section through the gas circulation pipe and the burner to participate in the roasting treatment and / or transported to the molten reduction furnace through the gas circulation pipe and the gas circulation branch pipe to participate in the deep reduction treatment, and the top gas in the molten reduction furnace is transported to the roasting section through the top gas transportation pipe and the burner to participate in the roasting treatment.

[0029] Preferably, the iron-containing raw material is natural rich ore and / or cold-consolidated pellets. The fuel is lignite particles and / or bituminous coal particles. The addition ratio of the iron-containing raw material to the fuel is such that C / O=1.2-1.5:1.

[0030] Preferably, the particle size of the iron-containing raw material and the fuel is 2-12 mm, preferably 3-10 mm, and more preferably 4-8 mm.

[0031] Preferably, the gasifying agent is water vapor or oxygen-rich gas, and the combustion-supporting gas is air or oxygen-rich gas.

[0032] Preferably, the water vapor includes low-pressure steam and / or medium-pressure steam, wherein the low-pressure steam is water vapor with a pressure not exceeding 3 MPa and a temperature not exceeding 500° C., preferably water vapor with a pressure not exceeding 2.5 MPa and a temperature not exceeding 400° C. The medium-pressure steam is water vapor with a pressure of 2.5-8 MPa and a temperature of 400-800° C., preferably water vapor with a pressure of 3-6 MPa and a temperature of 500-700° C.

[0033] Preferably, the temperature of the drying section is 150-400°C (preferably 200-300°C). The temperature of the preheating section is 400-1000°C (preferably 500-900°C). The temperature of the co-production reduction section is 1000-1300°C (preferably 1050-1250°C). The temperature of the roasting section is 1300-1700°C (preferably 1400-1600°C). The temperature of the slow cooling section is 900-1100°C (preferably 9500-1050°C).

[0034] Preferably, the gasifying agent is sprayed into the kiln in the following manner: during the rotation of the rotary kiln, the gasifying agent is always sprayed directly into the material through the gasifying agent nozzle located below the material.

[0035] Preferably, the combustion-supporting gas is injected into the kiln in the following manner: during the rotation of the rotary kiln, the combustion-supporting gas is always directly injected into the chamber above the material through the combustion-supporting gas nozzle located above the material.

[0036] In the existing technology, the coal-based rotary kiln direct reduction process has been affecting the normal production of the rotary kiln for many years due to high energy consumption, small production scale, and easy ring formation. The annual production capacity can only reach 150,000 tons. Dust pollution is serious, the temperature field along the kiln body fluctuates greatly, and the temperature in the furnace cannot be measured and controlled in real time, resulting in easy ring formation, uneven reduction in the kiln, a large number of unqualified pellets, and unstable production. In addition, due to imperfect rotary kiln equipment design, high equipment failure rate and insufficient operating experience, almost all coal-based rotary kilns have been shut down, seriously restricting the further development of the rotary kiln technology.

[0037] In the present invention, an innovative rotary kiln system for iron ore reduction and co-production of reducing gas is proposed. The rotary kiln includes a drying section, a preheating section, a co-production reduction section, a roasting section, and a slow cooling section, which are connected in series from the kiln tail to the kiln head. High-volatile coal and iron-containing raw materials are used, with a C / O ratio of 1.2 to 1.5:1. The materials are processed in sequence through drying, preheating, gasification and co-production of reduction, roasting, and slow cooling. Steam gasification agent is sprayed into the kiln through a gasification agent nozzle set in the co-production reduction section, and coal gas combustion and combustion air is sprayed into the kiln through a combustion-supporting gas nozzle set in the roasting section. Steam is sprayed at the bottom of the material in the co-production reduction section. The steam reacts with the fixed carbon of the granular coal in the material to produce water gas to generate H2 / CO synthesis gas, and pre-reduction of the iron-containing raw materials occurs at the same time. The hot air containing synthesis gas at the kiln tail is circulated to the kiln head burner as fuel gas or to the molten reduction furnace as reducing gas. This rotary kiln equipment has the new function of producing synthesis gas, while providing high-quality pre-reduction raw materials for molten reduction, which is conducive to promoting the development of rotary kiln technology.

[0038] In the present invention, the present invention increases multiple channels (gasifying agent conveying channels, combustion-supporting gas conveying channels) uniformly distributed on the surface of the kiln body and gasifying agent nozzles embedded in the inner wall of the kiln through structural modification, changes the ratio of iron and fuel in the raw materials, develops a rotary kiln with new functions, and constructs a kiln body structure integrating a drying area, a preheating area, a gasification and reduction area, a combustion area, and a slow cooling area; in addition, by controlling the blowing rhythm, countercurrent steam is blown at the bottom of the material to fully gasify the carbon to produce synthesis gas (H2 and CO), and the quality of the synthesis gas is improved by temperature and flow control; by generating a hydrogen-rich reducing atmosphere in the kiln (under the same conditions, pure H2 atmosphere reduces iron oxides faster than pure CO atmosphere), the pre-reduction of iron oxides is promoted; the new rotary kiln is coupled with a molten reduction furnace to provide high-quality molten reduction furnace materials with high pre-reduction degree to reduce the energy consumption of molten reduction, and provides hydrogen-rich fuel gas to achieve hydrogen-based molten reduction.

[0039] In the present invention, the gasifying agent delivery channel is defined within the kiln wall of the rotary kiln and sequentially penetrates the walls of the drying section, preheating section, and co-production reduction section from the kiln tail to the kiln head, ultimately connecting to the gasification agent nozzle's air inlet. The aperture of the gasifying agent delivery channel gradually decreases from the kiln tail to the kiln head. The provision of a variable-diameter gasifying agent delivery channel increases the pressure of the gasifying agent ultimately entering the co-production reduction section. This ensures that the pressure within the gasifying agent delivery channel is higher than the kiln pressure within the co-production reduction section. This increased pressure differential not only facilitates gasifying agent injection but also prevents backflow of hot air into the gasifying agent delivery channel due to the high temperature within the kiln. This effectively ensures the occurrence of the water-gas reaction in the co-production reduction section and facilitates the generation of H2 / CO synthesis gas. Directly injecting gas into the kiln through nozzles on the kiln body requires a consistently high initial gas pressure; otherwise, backflow of the high-temperature, high-pressure airflow within the kiln is likely to occur, resulting in poor gas injection.

[0040] In the present invention, the combustion-supporting gas delivery channel is opened in the kiln wall of the rotary kiln, and passes through the kiln walls of the slow cooling section and the roasting section in sequence from the kiln head to the kiln tail of the rotary kiln, and is connected to the air inlet end of the combustion-supporting gas nozzle. The aperture size of the combustion-supporting gas delivery channel gradually decreases along the direction from the kiln head to the kiln tail of the rotary kiln. By setting up the variable-diameter combustion-supporting gas delivery channel, the pressure of the combustion-supporting gas that finally enters the roasting section can be increased, that is, in the area of ​​the roasting section, the air pressure in the combustion-supporting gas delivery channel is higher than the air pressure in the kiln. The increase in the internal and external air pressure difference is beneficial to the injection effect of the combustion-supporting gas, and can also avoid the phenomenon of hot air caused by the high temperature in the kiln flowing back to the combustion-supporting gas delivery channel, thereby ensuring the roasting treatment effect of the roasting section.

[0041] In the present invention, both the gasifying agent delivery channel and the combustion-supporting gas delivery channel are equipped with a pressurization check mechanism. The pressurization check mechanism is a trumpet-shaped fixed protrusion with a diameter that tapers along the airflow direction, or a trumpet-shaped structure composed of multiple fins. The installation of the pressurization check mechanism can further enhance the pressurization of the gasifying agent and combustion-supporting gas in the gasifying agent delivery channel and the combustion-supporting gas delivery channel, respectively, further increasing the pressure of the gasifying agent and combustion-supporting gas entering the kiln and improving the gas injection effect. In particular, the pressurization check mechanism of the fin structure can make the multiple fins distributed in the same position in the gasifying agent delivery channel or the combustion-supporting gas delivery channel rotate in the direction of the gas flow when the gas flows in the forward direction, and press against the respective corresponding limit protrusions, thereby forming a trumpet-shaped structure to achieve pressurization of the forward-flowing gas. At the same time, when the gas flows in the reverse direction, the fins rotate in the reverse direction of the gas flow under the action of the reverse flow gas. When the rotation reaches a certain degree (for example, the fins and the inner wall of the gasifying agent delivery channel 3 are in contact with each other), the fins rotate in the reverse direction of the gas flow. The angle between them or with the inner wall of the combustion-supporting gas transmission channel is 85-90°, preferably 90°), the anchor cable is pulled to its maximum length, so that the fins cannot continue to rotate further in the countercurrent direction of the gas. At this time, all the fins form a closed partition as a whole, thereby avoiding further loss of countercurrent gas. In other words, the pressurization check mechanism with a movable fin structure can automatically realize the downstream pressurization of the gas and the automatic isolation of the countercurrent gas, with timely response, no need for manipulation, strong safety, and effectively guaranteeing the smooth operation of the system.

[0042] In the present invention, a movable piston is independently provided inside any gasifier nozzle and / or any combustion-supporting gas nozzle. When the rotary kiln rotates, the movable piston is used to ensure that: in the co-generation reduction section, the movable piston in the gasifier nozzle located on the kiln wall below the material is in an open state, and the movable pistons in the gasifier nozzles on the other kiln walls are in a closed state. In the roasting section, the movable piston in the gasifier nozzle located on the kiln wall below the material is in a closed state, and the movable pistons in the gasifier nozzles on the other kiln walls are in an open state. That is, in the co-generation reduction section, the movable piston controls the gasifier to be ejected only from the gasifier nozzle located below the material into the material layer to participate in the gasification reaction. In the roasting section, the movable piston controls the oxygen-rich gas to be ejected only from the combustion-supporting gas nozzle located above the material to participate in the combustion reaction.

[0043] In the present invention, the fuel used for iron ore reduction and co-production of reducing gas in a multi-stage rotary kiln is granular coal, which is required to be young coal with high volatile matter (lignite or bituminous coal) with a volatile matter of about 30% (preferably 25% to 35%). The iron-containing raw material used is natural rich lump ore and / or cold-consolidated pellets (prepared from iron concentrate, composite ore, refractory ore and various iron-containing wastes). The iron-containing raw material is required to have good reducibility, low reducibility and high softening temperature. The proportion of granular coal is required to be higher than that of the iron-containing raw material (C / O=1.2 to 1.5:1), and the particle size of both is between 2 and 12 mm (preferably 3 to 10 mm, more preferably 4 to 8 mm). The filling rate is higher than that of a conventional rotary kiln (30 to 40%), and the material layer height is above 80 cm.

[0044] In the present invention, from the feed end to the discharge end of the rotary kiln, the materials (iron-containing raw materials and fuel) sequentially undergo a drying section (150-400°C, preferably 200-300°C), a preheating section (400-1000°C, preferably 500-900°C), a co-production reduction section (1000-1300°C, preferably 1050-1250°C), a roasting section (1300-1700°C, preferably 1400-1600°C), and a slow cooling section (900-1100°C, preferably 9500-1050°C). The iron-containing raw materials remove their free water and bound water at the drying end to prevent high-temperature cracking and the production of powder; the iron-containing raw materials complete consolidation and strengthening in the preheating section, and the granular coal completes the removal of most of the volatile matter in the preheating section, producing hydrocarbon oxides and hydrocarbon compounds.

[0045] In the present invention, after the materials (iron-containing raw materials and fuel) enter the co-production reduction section, gasification agent injection devices are evenly arranged in this area along the axial and axial directions of the rotary kiln. The gasification agent includes low-pressure or medium-pressure steam and high-oxygen gas; low-pressure steam (water vapor with a pressure of no more than 3 MPa and a temperature of no more than 500°C, preferably water vapor with a pressure of no more than 2.5 MPa and a temperature of no more than 400°C) and medium-pressure steam (water vapor with a pressure of 2.5-8 MPa and a temperature of 400-800°C, preferably water vapor with a pressure of 3-6 MPa and a temperature of 500-700°C). The gasification agent delivery channel is separated from the kiln wall by the rotary kiln cavity. The gasification agent injection device is an internal and external through-hole structure, with a movable piston on the outside and a gasification agent nozzle on the inside. The jet device rotates with the rotary kiln. When it is in the material movement range and covered by the material, the movable piston opens and the gasifying agent is injected into the material layer by the atomizing nozzle; when it leaves the material range, the movable piston closes and the gasifying agent is not sprayed to avoid affecting the composition of the synthesis gas.

[0046] Furthermore, when the gasifying agent is steam, it enters the material layer through the gasifying agent nozzle, and the steam fully contacts the granular coal. Under normal pressure and high temperature, the water-gas reaction begins to occur. The reaction formula is shown below. Each reaction is a reversible reaction. The four gases CO, H2, H2O, CO2, and CH4 are all present in the system. The overall process is highly endothermic and requires heat supply:

[0047] C+H2O=CO+H2 +131.39 KJ / mol (1)

[0048] CO+H2O=CO2+H2 -41.19 KJ / mol (2)

[0049] C+2H2=CH4 -74.90 KJ / mol (3)

[0050] In addition, as an alternative plan to adjust the conditions inside the kiln: when the heat of the water-gas reaction is insufficient, the gasifier is adjusted to water vapor containing some oxygen-rich gas or all oxygen-rich gas, which enters the material layer through the gasifier nozzle. Oxygen and granular coal undergo a combustion reaction, mainly with complete combustion, and quickly release a large amount of heat to increase the temperature of the gasification and reduction zones.

[0051] In the present invention, the iron oxides in the iron-containing raw material are completely pre-reduced to FeO and metallic iron in the co-production reduction section, which consumes some H2 and CO. Since H2 and CO can increase the concentration of the reducing atmosphere around the iron-containing raw material, the pre-reduction rate of the iron-containing raw material is increased. Therefore, this section is a highly integrated hydrogen / carbon metallurgical process in which water gasification and iron oxide reduction are carried out in a hot state. The reactions involved are:

[0052] 3Fe2O3+CO=2Fe3O4+CO2 (4)

[0053] 3Fe2O3+H2=2Fe3O4+H2O (5)

[0054] Fe3O4+CO=3FeO+CO2 (6)

[0055] Fe3O4+H2=3FeO+H2O (7)

[0056] FeO+CO=Fe+CO2 (8)

[0057] FeO+H2=Fe+H2O (9)

[0058] In the present invention, the temperature of the roasting section is between 1300-1700°C (preferably 1400-1600°C), and its main function is to provide heat for the co-production reduction section through radiation heat transfer and convection heat transfer of hot flue gas, and its heat source is the heat released by gas combustion. One part of the gas source is the top gas produced by the molten reduction furnace, and the other part is the cyclic combustion of the synthesis gas produced by the rotary kiln itself. This area is arranged with an injection device (gas-supporting gas nozzle) for combustion-supporting air injection, which provides secondary air for gas combustion, and can also moderately cool the kiln wall to reduce the risk of high-temperature ring formation. With the help of gas flushing, fine particles such as granular coal ash and iron-containing dust are prevented from adhering to the kiln wall and forming rings.

[0059] In this invention, pre-reduced iron-containing raw materials and residual coal are slowly cooled in a rotary kiln before being passed through a hot screen and used as feedstock for the smelting reduction furnace. This not only increases the material temperature but also improves the degree of reduction and metallization of the iron-containing raw materials. Synthesis gas generated in the rotary kiln is introduced into the molten bath as the reducing gas for the smelting reduction, achieving hydrogen-based smelting reduction and reducing carbon consumption during the smelting reduction process.

[0060] In the present invention, the deep reduction process of the smelting reduction furnace generates a reaction between iron oxide and carbon to generate iron, carbon monoxide and part of carbon dioxide. The specific reaction is: Fe x O(s)+C=xFe(s)+CO(g)+CO2(g). This reaction process produces high-temperature carbon monoxide and carbon dioxide gases, which are called "high-temperature coal gas" or "top gas". The high-temperature coal gas generated in the smelting furnace has a temperature greater than 1400°C, and can reach a maximum of more than 1700°C, and has a certain pressure. In addition to containing a large amount of unreacted CO and H2, it also contains a large amount of CO2 and water vapor. Its main components are CO (about 21%), CO2 (about 25%), H2 (about 4%), N2 (about 48%), and H2O (about 2%). In the technical solution of the present invention, the heat and calorific value of the high-temperature coal gas are fully utilized. A high-temperature environment is required in the rotary kiln, and a reducing gas is also required. The high-temperature top gas generated by the smelting reduction furnace in the present invention is returned to the rotary kiln. While acting as a reducing agent, it fully utilizes the heat of this part of the gas to maximize the utilization of resources.

[0061] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0062] 1: The present invention divides the rotary kiln into a drying section, a preheating section, a co-production reduction section, a roasting section and a slow cooling section in sequence, constructing a kiln structure integrating the drying zone, preheating zone, gasification and reduction zone, combustion zone and slow cooling zone; and respectively arranges a gasifying agent injection device and a combustion-supporting gas injection device on the kiln wall, thereby achieving pre-reduction of materials in the co-production reduction section and co-producing high-quality H2 / CO synthesis gas, thereby improving the reducing atmosphere in the kiln and facilitating the reduction of iron oxides.

[0063] 2: The present invention also improves the reduction degree and metallization rate of the iron-containing raw materials by circulating the high-quality synthesis gas flowing in the multi-stage rotary kiln through the gas circulation pipeline for combustion in the roasting section and the smelting reduction furnace and improving their reducing atmosphere. The smelting reduction furnace realizes hydrogen-based smelting reduction, which is beneficial to reducing the carbon consumption of the smelting reduction process.

[0064] 3: The present invention effectively controls the injection rhythm through the combined action of the variable-diameter gas delivery channel and the gas blowing device, injects countercurrent steam at the bottom of the material, fully gasifies the carbon to produce synthesis gas (H2 and CO), and improves the quality of the synthesis gas through temperature and flow control.

[0065] 4: The rotary kiln of the present invention can generate a hydrogen-rich reducing atmosphere when reducing iron oxides in the kiln, so that under the same conditions, the speed of reducing iron oxides in the H2 atmosphere is faster than that in the pure CO atmosphere, thereby promoting the pre-reduction of iron oxides.

[0066] 5: The present invention couples a new type of rotary kiln with a smelting reduction furnace to provide high-quality smelting reduction charge with a high degree of pre-reduction to reduce the energy consumption of smelting reduction, and provides hydrogen-rich fuel gas to achieve hydrogen-based smelting reduction, thereby improving the yield and efficiency of reduced iron, while reducing carbon emissions and saving carbon consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 The figure is a simplified structural diagram of the rotary kiln system of the present invention.

[0068] Figure 2 It is an enlarged structural diagram of the fixed protrusion type boost check mechanism of the present invention.

[0069] Figure 3 It is a schematic diagram of the enlarged structure of the fin-type boost check mechanism of the present invention when it is trumpet-shaped in the downstream direction.

[0070] Figure 4 It is an enlarged structural diagram of the fin-type boost check mechanism of the present invention when the reverse flow is closed.

[0071] Figure 5 This is a schematic diagram of the overall structure of the rotary kiln system of the present invention when it has a smelting reduction furnace.

[0072] Figure 6 This is a process flow chart for the iron ore reduction and co-production of reducing gas according to the present invention.

[0073] Figure markings: 1: rotary kiln; 101: drying section; 102: preheating section; 103: co-production reduction section; 104: roasting section; 105: slow cooling section; 106: gasifying agent nozzle; 107: combustion-supporting gas nozzle; 108: burner; 109: gas circulation pipeline; 110: movable piston; 111: gas circulation branch pipe; 2: molten reduction furnace; 3: gasifying agent delivery channel; 301: gasifying agent delivery pipeline; 302: throttle valve; 303: regulating pump; 4: combustion-supporting gas delivery channel; 401: oxygen-enriched gas delivery pipeline; 402: air valve; 403: air pump; 5: boost check mechanism; 501: fin; 502: limiting protrusion; 503: anchor cable; 6: feeding device; 7: furnace top gas delivery pipeline; 8: dust removal device; 9: gas purification device. DETAILED DESCRIPTION

[0074] The technical solutions of the present invention are illustrated below with examples, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0075] A rotary kiln system for reducing iron ore and co-producing reducing gas comprises a rotary kiln 1. The rotary kiln 1 is a multi-stage rotary kiln. Based on the flow of material within the kiln, the rotary kiln 1 comprises a drying section 101, a preheating section 102, a co-production reduction section 103, a roasting section 104, and a slow cooling section 105, which are sequentially connected in series from the kiln tail to the kiln head. A gasifying agent nozzle 106 is provided on the kiln wall of the co-production reduction section 103. An oxidizing gas nozzle 107 is provided on the kiln wall of the roasting section 104. A burner 108 is provided on the kiln head of the rotary kiln 1, extending into the roasting section 104. An exhaust port at one end of the drying section 101, near the kiln tail, is connected to an air inlet external to the burner 108 via a gas circulation pipe 109.

[0076] Preferably, a plurality of gasifying agent nozzles 106 are evenly arranged along the circumferential and axial directions of the kiln wall at the co-generation reduction section 103 .

[0077] Preferably, a plurality of combustion-supporting gas nozzles 107 are evenly arranged along the circumferential and axial directions of the kiln wall at the roasting section 104 .

[0078] Preferably, each gasifying agent nozzle 106 and / or each oxidizing gas nozzle 107 is independently provided with a movable piston 110. As the rotary kiln 1 rotates, the movable piston 110 causes the following conditions to occur: within the co-generation reduction section 103, the movable piston 110 within the gasifying agent nozzle 106 located on the kiln wall below the material is in an open state, while the movable pistons 110 within the gasifying agent nozzles 106 located on the other kiln walls are in a closed state. Within the roasting section 104, the movable piston 110 within the gasifying agent nozzle 106 located on the kiln wall below the material is in a closed state, while the movable pistons 110 within the gasifying agent nozzles 106 located on the other kiln walls are in an open state.

[0079] Preferably, the rotary kiln system also includes a gasifying agent delivery channel 3. The gasifying agent delivery channel 3 is provided within the kiln wall of the rotary kiln 1 and extends sequentially from the kiln tail to the kiln head through the walls of the drying section 101, preheating section 102, and co-production reduction section 103, ultimately connecting to the air inlet of the gasifying agent nozzle 106. The gasifying agent delivery channel 3 comprises a plurality of air inlet channels distributed axially along the rotary kiln 1. Preferably, the plurality of gasifying agent delivery channels 3 may be interconnected or disconnected.

[0080] Preferably, the rotary kiln system also includes a combustion-supporting gas delivery channel 4. The combustion-supporting gas delivery channel 4 is formed within the kiln wall of the rotary kiln 1 and extends from the kiln head to the kiln tail, sequentially penetrating the walls of the slow cooling section 105 and the roasting section 104, and finally connecting to the air inlet of the combustion-supporting gas nozzle 107. The combustion-supporting gas delivery channel 4 comprises a plurality of air inlet channels distributed axially along the rotary kiln 1. Preferably, the plurality of combustion-supporting gas delivery channels 4 may or may not be interconnected.

[0081] Preferably, the aperture of the gasifying agent delivery channel 3 gradually decreases along the direction from the kiln tail to the kiln head of the rotary kiln 1 .

[0082] Preferably, the aperture of the combustion-supporting gas delivery channel 4 gradually decreases along the direction from the kiln head to the kiln tail of the rotary kiln 1 .

[0083] Preferably, a pressurization check mechanism 5 is provided in both the gasifying agent delivery channel 3 and the oxidizing gas delivery channel 4. The pressurization check mechanism 5 is a trumpet-shaped fixed protrusion whose aperture gradually decreases along the airflow direction. Preferably, multiple pressurization check mechanisms 5 are provided in each of the gasifying agent delivery channel 3 and the oxidizing gas delivery channel 4, and the apertures of the exhaust holes of the multiple pressurization check mechanisms 5 remain constant or decrease sequentially along the airflow direction.

[0084] Preferably, a boost check mechanism 5 is provided in both the gasifying agent delivery channel 3 and the combustion gas delivery channel 4. The boost check mechanism 5 includes a fin 501, a limiting protrusion 502 and an anchor cable 503. The fin 501 is a fan-shaped arc plate that matches the gasifying agent delivery channel 3 or the combustion gas delivery channel 4. The fin 501 is hinged to the inner wall of the gasifying agent delivery channel 3 or the inner wall of the combustion gas delivery channel 4. According to the direction of the airflow, the limiting protrusion 502 is arranged downstream of the fin 501 and fixed on the inner wall of the gasifying agent delivery channel 3 or the inner wall of the combustion gas delivery channel 4. One end of the anchor cable 503 is fixedly connected to the limiting protrusion 502, and the other end thereof is fixedly connected to the back of the fin 501. The length of the anchor cable 503 is such that when the anchor cable 503 is extended to its maximum length, the angle formed between the fin 501 and the inner wall of the gasifying agent delivery channel 3 or the inner wall of the oxidant gas delivery channel 4 is 85-90°, preferably 90°.

[0085] Preferably, the boost check mechanism 5 includes a plurality of fins 501, which are arranged in an annular pattern along the inner wall of the gasifying agent delivery channel 3 or the oxidizing gas delivery channel 4, and each fin 501 is independently provided with a limiting protrusion 502 and an anchor cable 503. When all fins 501 rotate in the direction of the airflow and abut against the corresponding limiting protrusion 502, all fins 501 collectively form a trumpet-shaped structure with an aperture that gradually decreases along the airflow direction. Preferably, multiple boost check mechanisms 5 are provided in both the gasifying agent delivery channel 3 and the oxidizing gas delivery channel 4, and when the fins 501 of the multiple boost check mechanisms 5 form trumpet-shaped structures, the apertures of the exhaust holes of the multiple trumpet-shaped structures remain unchanged or decrease sequentially along the airflow direction.

[0086] Preferably, the gasifying agent delivery channel 3 is further connected to a gasifying agent delivery pipeline 301 at the air inlet at the kiln tail, and the gasifying agent delivery pipeline 301 is provided with a throttle valve 302 and a regulating pump 303 .

[0087] Preferably, the combustion-supporting gas delivery channel 4 is further connected to an oxygen-enriched gas delivery pipeline 401 at the air inlet at the kiln head, and the oxygen-enriched gas delivery pipeline 401 is provided with an air valve 402 and an air pump 403 .

[0088] Preferably, the rotary kiln system further includes a smelting reduction furnace 2. The kiln head discharge port of the rotary kiln 1 is connected to the feed port of the smelting reduction furnace 2 via a feeding device 6. The top exhaust port of the smelting reduction furnace 2 is connected to the air inlet outside the burner 108 via a top gas delivery pipeline 7.

[0089] Preferably, a gas circulation branch pipe 111 is led out from the gas circulation pipeline 109 and is connected to the gas inlet of the smelting reduction furnace 2.

[0090] Preferably, the gas circulation pipeline 109 is further provided with a dust removal device 8 and a gas purification device 9 in sequence. The dust removal device 8 and the gas purification device 9 are both located upstream of the connection between the gas circulation branch pipe 111 and the gas circulation pipeline 109.

[0091] Example 1

[0092] like Figure 1-5 As shown, a rotary kiln system for reducing iron ore and co-producing reducing gas includes a rotary kiln 1. The rotary kiln 1 is a multi-stage rotary kiln. According to the flow of the material in the kiln, the rotary kiln 1 includes a drying section 101, a preheating section 102, a co-production reduction section 103, a roasting section 104, and a slow cooling section 105, which are connected in series from the kiln tail to the kiln head. A gasifying agent nozzle 106 is provided on the kiln wall of the co-production reduction section 103. A combustion-supporting gas nozzle 107 is provided on the kiln wall of the roasting section 104. A burner 108 is provided on the kiln head of the rotary kiln 1 and extends into the roasting section 104. The exhaust port of the drying section 101 near the kiln tail is connected to the air inlet outside the burner 108 through a gas circulation pipe 109.

[0093] Example 2

[0094] Example 1 is repeated, except that a plurality of gasifying agent nozzles 106 are evenly arranged along the circumference and axial direction of the kiln wall at the co-generation reduction section 103 .

[0095] Example 3

[0096] Example 2 is repeated, except that a plurality of combustion-supporting gas nozzles 107 are evenly arranged along the circumferential and axial directions of the kiln wall at the roasting section 104 .

[0097] Example 4

[0098] Example 3 was repeated, except that each gasifying agent nozzle 106 and / or each oxidizing gas nozzle 107 was independently provided with a movable piston 110. As the rotary kiln 1 rotates, the movable piston 110 causes the following conditions to occur: within the co-generation reduction section 103, the movable piston 110 within the gasifying agent nozzle 106 located on the kiln wall below the material is opened, while the movable pistons 110 within the gasifying agent nozzles 106 located on the other kiln walls are closed. Within the roasting section 104, the movable piston 110 within the gasifying agent nozzle 106 located on the kiln wall below the material is closed, while the movable pistons 110 within the gasifying agent nozzles 106 located on the other kiln walls are opened.

[0099] Example 5

[0100] Example 4 was repeated, except that this rotary kiln system also included a gasifying agent delivery channel 3. The gasifying agent delivery channel 3 was opened in the kiln wall of the rotary kiln 1 and sequentially penetrated the walls of the drying section 101, preheating section 102, and co-production reduction section 103 from the kiln tail to the kiln head of the rotary kiln 1, and finally connected to the air inlet end of the gasifying agent nozzle 106. The gasifying agent delivery channel 3 consisted of multiple air inlet channels distributed along the axial direction of the rotary kiln 1.

[0101] Example 6

[0102] Example 5 is repeated, except that the plurality of gasifying agent conveying channels 3 are not connected to each other.

[0103] Example 7

[0104] Example 6 was repeated, except that this rotary kiln system also included a combustion-supporting gas delivery channel 4. The combustion-supporting gas delivery channel 4 is provided within the kiln wall of the rotary kiln 1 and sequentially penetrates the walls of the slow cooling section 105 and the roasting section 104 from the kiln head to the kiln tail of the rotary kiln 1, ultimately connecting to the air inlet of the combustion-supporting gas nozzle 107. The combustion-supporting gas delivery channel 4 comprises multiple air inlet channels distributed axially along the rotary kiln 1.

[0105] Example 8

[0106] Example 7 is repeated, except that the plurality of oxidant gas delivery channels 4 are not connected to each other.

[0107] Example 9

[0108] Example 8 was repeated, except that the aperture of the gasifying agent conveying channel 3 gradually decreased along the direction from the kiln tail to the kiln head of the rotary kiln 1 .

[0109] Example 10

[0110] Example 9 is repeated, except that the aperture of the combustion-supporting gas delivery channel 4 gradually decreases along the direction from the kiln head to the kiln tail of the rotary kiln 1 .

[0111] Example 11

[0112] Example 10 is repeated except that a pressurizing check mechanism 5 is provided in both the gasifying agent delivery channel 3 and the oxidant gas delivery channel 4. The pressurizing check mechanism 5 is a trumpet-shaped fixed protrusion with a diameter gradually decreasing along the airflow direction.

[0113] Example 12

[0114] Example 11 is repeated, except that a plurality of pressurizing check mechanisms 5 are provided in both the gasifying agent delivery channel 3 and the combustion-supporting gas delivery channel 4, and the apertures of the exhaust holes of the plurality of pressurizing check mechanisms 5 decrease sequentially along the airflow direction.

[0115] Example 13

[0116] Repeat Example 12, except that a boost check mechanism 5 is provided in both the gasifying agent delivery channel 3 and the combustion gas delivery channel 4. The boost check mechanism 5 includes a fin 501, a limiting protrusion 502, and an anchor cable 503. The fin 501 is a fan-shaped arc piece that matches the gasifying agent delivery channel 3 or the combustion gas delivery channel 4. The fin 501 is hinged to the inner wall of the gasifying agent delivery channel 3 or the inner wall of the combustion gas delivery channel 4. Depending on the direction of the airflow, the limiting protrusion 502 is provided downstream of the fin 501 and fixed on the inner wall of the gasifying agent delivery channel 3 or the inner wall of the combustion gas delivery channel 4. One end of the anchor cable 503 is fixedly connected to the limiting protrusion 502, and the other end thereof is fixedly connected to the back of the fin 501. The length of the anchor cable 503 is such that when the anchor cable 503 is extended to its maximum length, the angle formed between the fin 501 and the inner wall of the gasifying agent delivery channel 3 or the inner wall of the oxidant gas delivery channel 4 is 90°.

[0117] Example 14

[0118] Example 13 is repeated, except that the boost check mechanism 5 includes multiple fins 501, which are distributed in an annular pattern along the inner wall of the gasifying agent delivery channel 3 or the oxidizing gas delivery channel 4. Each fin 501 is independently configured with a limiting protrusion 502 and an anchor cable 503. When all fins 501 rotate in the direction of the airflow and abut against the corresponding limiting protrusion 502, all fins 501 collectively form a trumpet-shaped structure with an aperture that gradually decreases along the airflow direction. Preferably, multiple boost check mechanisms 5 are provided in both the gasifying agent delivery channel 3 and the oxidizing gas delivery channel 4, and when the fins 501 of each of the boost check mechanisms 5 form a trumpet-shaped structure, the apertures of the exhaust holes of the trumpet-shaped structures decrease sequentially along the airflow direction.

[0119] Example 15

[0120] Example 14 is repeated, except that the gasifying agent delivery channel 3 is further connected to the air inlet at the kiln tail with a gasifying agent delivery pipeline 301 , and the gasifying agent delivery pipeline 301 is provided with a throttle valve 302 and a regulating pump 303 .

[0121] Example 16

[0122] Example 15 was repeated, except that the air inlet of the combustion-supporting gas delivery channel 4 at the kiln head was further connected to an oxygen-enriched gas delivery pipeline 401 , and the oxygen-enriched gas delivery pipeline 401 was provided with an air valve 402 and an air pump 403 .

[0123] Example 17

[0124] Example 16 was repeated, except that the rotary kiln system also included a smelting reduction furnace 2. The kiln head discharge port of the rotary kiln 1 was connected to the feed port of the smelting reduction furnace 2 via a feeding device 6. The top exhaust port of the smelting reduction furnace 2 was connected to the air inlet outside the burner 108 via a top gas delivery pipe 7.

[0125] Example 18

[0126] Repeat Example 17, except that a gas circulation branch pipe 111 is extended from the gas circulation pipe 109 and connected to the gas inlet of the smelting reduction furnace 2.

[0127] Example 19

[0128] Example 18 was repeated, except that a dust removal device 8 and a gas purification device 9 were further provided in sequence on the gas circulation pipeline 109. The dust removal device 8 and the gas purification device 9 were both located upstream of the connection between the gas circulation branch pipe 111 and the gas circulation pipeline 109.

[0129] Example 20

[0130] like Figure 6 As shown, a method for reducing iron ore and producing reducing gas comprises the following steps:

[0131] (S1) The iron-containing raw material and fuel are transported to the rotary kiln 1, and are reduced in the drying section 101, the preheating section 102, the co-production reduction section 103, the roasting section 104 and the slow cooling section 105 to obtain a reduced material, which is then transported to the molten reduction furnace 2 for deep reduction treatment.

[0132] (S2) During the reduction treatment in the rotary kiln 1, a gasifying agent is sprayed into the kiln through the gasifying agent nozzle 106 on the kiln wall of the co-generation reduction section 103, and a combustion-supporting gas is sprayed into the kiln through the combustion-supporting gas nozzle 107 on the kiln wall of the roasting section 104.

[0133] (S3) The hot air discharged from the tail of the rotary kiln 1 is subjected to dust removal and purification treatment, and then transported to the roasting section 104 through the gas circulation pipe 109 and the burner 108 to participate in the roasting treatment and / or transported to the smelting reduction furnace 2 through the gas circulation pipe 109 and the gas circulation branch pipe 111 to participate in the deep reduction treatment, and the top gas in the smelting reduction furnace 2 is transported to the roasting section 104 through the top gas transportation pipe 7 and the burner 108 to participate in the roasting treatment.

[0134] The iron-containing raw materials are natural rich lump ore and cold consolidated pellets. The fuels are lignite particles and bituminous coal particles.

[0135] The particle size range of ferrous raw materials and fuels is 4-8 mm.

[0136] The gasifying agent is water vapor and the combustion-supporting gas is air.

[0137] The water vapor includes low-pressure steam and medium-pressure steam, wherein the low-pressure steam is water vapor with a pressure not exceeding 2.5 MPa and a temperature not exceeding 400°C, and the medium-pressure steam is water vapor with a pressure of 3-6 MPa and a temperature of 500-700°C.

[0138] Preferably, the temperature of the drying section 101 is 200-300°C. The temperature of the preheating section 102 is 500-900°C. The temperature of the co-production reduction section 103 is 1000-1300°C. The temperature of the roasting section 104 is 1400-1600°C. The temperature of the slow cooling section 105 is 950-1050°C.

[0139] The specific method of injecting the gasifying agent into the kiln is as follows: during the rotation of the rotary kiln 1 , the gasifying agent is always directly injected into the interior of the material through the gasifying agent nozzle 106 located below the material.

[0140] The specific method of injecting the combustion-supporting gas into the kiln is as follows: during the rotation of the rotary kiln 1 , the combustion-supporting gas is always directly injected into the chamber above the material through the combustion-supporting gas nozzle 107 located above the material.

[0141] By adopting the process method described in Example 20 to carry out reduction treatment of iron-containing raw materials multiple times and co-produce synthesis gas, the metallization rate of the obtained reduced material is increased by about 2% to 4%, and the total carbon consumption is reduced by about 60% to 80% compared with the traditional coal-based rotary kiln (without co-production synthesis gas mechanism); at the same time, the ring formation phenomenon of the rotary kiln is significantly improved, and the overall production efficiency is increased by about 10% to 20%.

Claims

1. A rotary kiln system for iron ore reduction and co-production of reducing gas, characterized by: The rotary kiln system comprises a rotary kiln (1), wherein the rotary kiln (1) is a multi-stage rotary kiln. According to the direction of the material in the kiln, the rotary kiln (1) comprises a drying section (101), a preheating section (102), a cogeneration reduction section (103), a roasting section (104), and a slow cooling section (105) which are sequentially connected in series from the kiln tail to the kiln head; a plurality of gasifying agent nozzles (106) are evenly arranged in the circumferential and axial directions of the kiln wall at the cogeneration reduction section (103); a plurality of combustion-supporting nozzles (106) are evenly arranged in the circumferential and axial directions of the kiln wall at the roasting section (104). A gas nozzle (107); a burner (108) extending into the roasting section (104) is provided on the kiln head of the rotary kiln (1); an exhaust port at one end of the drying section (101) near the kiln tail is connected to an air inlet outside the burner (108) through a gas circulation pipe (109); a movable piston (110) is independently provided inside any gasifying agent nozzle (106) and / or any combustion-supporting gas nozzle (107); when the rotary kiln (1) rotates, the movable piston (110) causes: in the co-production reduction section (103), The movable piston (110) in the gasifier nozzle (106) on the kiln wall below the material is in an open state, and the movable pistons (110) in the gasifier nozzles (106) on the other kiln walls are in a closed state; in the roasting section (104), the movable piston (110) in the gasifier nozzle (106) on the kiln wall below the material is in a closed state, and the movable pistons (110) in the gasifier nozzles (106) on the other kiln walls are in an open state; the rotary kiln system also includes a gasifier delivery channel (3); the gasifier The conveying channel (3) is opened in the kiln wall of the rotary kiln (1), and passes through the kiln walls of the drying section (101), the preheating section (102), and the co-production reduction section (103) in sequence from the kiln tail to the kiln head of the rotary kiln (1), and is connected to the air inlet end of the gasifying agent nozzle (106); the gasifying agent conveying channel (3) is a plurality of air inlet channels distributed along the axial direction of the rotary kiln (1); a pressurizing check mechanism (5) is provided in the gasifying agent conveying channel (3); the pressurizing check mechanism (5) is a trumpet-shaped fixed protrusion with an aperture gradually shrinking along the air flow direction.

2. The rotary kiln system according to claim 1, characterized in that: The rotary kiln system further comprises a combustion-supporting gas delivery channel (4); the combustion-supporting gas delivery channel (4) is opened in the kiln wall of the rotary kiln (1), and sequentially penetrates the kiln walls of the slow cooling section (105) and the roasting section (104) along the direction from the kiln head to the kiln tail of the rotary kiln (1), and is then connected to the air inlet end of the combustion-supporting gas nozzle (107); the combustion-supporting gas delivery channel (4) is a plurality of air inlet ducts distributed along the axial direction of the rotary kiln (1).

3. The rotary kiln system according to claim 2, characterized in that: Along the direction from the kiln tail to the kiln head of the rotary kiln (1), the aperture size of the gasifying agent delivery channel (3) gradually decreases; and / or Along the direction from the kiln head to the kiln tail of the rotary kiln (1), the aperture size of the combustion-supporting gas delivery channel (4) gradually decreases.

4. The rotary kiln system according to claim 2, characterized in that: A pressurization check mechanism (5) is provided in the combustion-supporting gas delivery channel (4); the pressurization check mechanism (5) is a trumpet-shaped fixed protrusion with an aperture that gradually shrinks along the airflow direction.

5. The rotary kiln system according to claim 4, characterized in that: A plurality of pressurizing check mechanisms (5) are provided in both the gasifying agent delivery channel (3) and the combustion-supporting gas delivery channel (4), and the apertures of the exhaust holes of the plurality of pressurizing check mechanisms (5) remain constant or decrease sequentially along the airflow direction.

6. The rotary kiln system according to claim 4 or 5, characterized in that: The gasifying agent delivery channel (3) and the combustion-supporting gas delivery channel (4) are both provided with a pressurizing check mechanism (5); the pressurizing check mechanism (5) comprises a fin (501), a limiting protrusion (502) and an anchor cable (503); the fin (501) is a fan-shaped arc piece matching the gasifying agent delivery channel (3) or the combustion-supporting gas delivery channel (4); the fin (501) is hinged to the inner wall of the gasifying agent delivery channel (3) or the inner wall of the combustion-supporting gas delivery channel (4); according to the direction of the airflow, the limiting protrusion (502) is hinged to the inner wall of the combustion-supporting gas delivery channel (3); 02) is arranged downstream of the fin (501) and fixed on the inner wall of the gasifying agent delivery channel (3) or the inner wall of the combustion-supporting gas delivery channel (4); one end of the anchor cable (503) is fixedly connected to the limiting protrusion (502), and the other end thereof is fixedly connected to the back surface of the fin (501); the length of the anchor cable (503) is such that when the anchor cable (503) is extended to the maximum length, the angle formed between the fin (501) and the inner wall of the gasifying agent delivery channel (3) or the inner wall of the combustion-supporting gas delivery channel (4) is 85-90°.

7. The rotary kiln system according to claim 6, characterized in that: The boost check mechanism (5) comprises a plurality of fins (501), and the plurality of fins (501) are annularly distributed along the circumference of the inner wall of the gasifying agent delivery channel (3) or the combustion-supporting gas delivery channel (4), and any fin (501) is independently provided with a limiting protrusion (502) and an anchor cable (503); when all the fins (501) rotate in the direction of the airflow and abut against the corresponding limiting protrusion (502), all the fins (501) together form a trumpet-shaped structure with an aperture gradually shrinking along the airflow direction; the gasifying agent delivery channel (3) and the combustion-supporting gas delivery channel (4) are both provided with a plurality of boost check mechanisms (5), and when the fins (501) of the plurality of boost check mechanisms (5) all form trumpet-shaped structures, the apertures of the exhaust holes of the plurality of trumpet-shaped structures remain unchanged or decrease sequentially along the airflow direction.

8. The rotary kiln system according to any one of claims 4 to 5 and 7, characterized in that: The gasifying agent delivery channel (3) is further connected to the air inlet at the kiln tail with a gasifying agent delivery pipeline (301), and the gasifying agent delivery pipeline (301) is provided with a throttle valve (302) and a regulating pump (303); and / or The combustion-supporting gas delivery channel (4) is further connected to an oxygen-enriched gas delivery pipeline (401) at the air inlet located at the kiln head. The oxygen-enriched gas delivery pipeline (401) is provided with an air valve (402) and an air pump (403).

9. The rotary kiln system according to any one of claims 1 to 5 and 7, characterized in that: The rotary kiln system also includes a smelting reduction furnace (2); the kiln head discharge port of the rotary kiln (1) is connected to the feed port of the smelting reduction furnace (2) through a feeding device (6); the top exhaust port of the smelting reduction furnace (2) is connected to the air inlet outside the burner (108) through a furnace top gas delivery pipeline (7).

10. The rotary kiln system according to claim 9, characterized in that: A gas circulation branch pipe (111) is also led out from the gas circulation pipe (109) and is connected to the gas inlet of the smelting reduction furnace (2).

11. The rotary kiln system according to claim 10, characterized in that: The gas circulation pipeline (109) is also provided with a dust removal device (8) and a gas purification device (9) in sequence; the dust removal device (8) and the gas purification device (9) are both located upstream of the connection between the gas circulation branch pipe (111) and the gas circulation pipeline (109).

12. A method for reducing iron ore and co-producing reducing gas using the rotary kiln system according to any one of claims 1 to 11, characterized in that: The method comprises the following steps: (S1) The iron-containing raw materials and fuel are transported to the rotary kiln (1), and are sequentially reduced through the drying section (101), the preheating section (102), the co-production reduction section (103), the roasting section (104), and the slow cooling section (105) to obtain reduced materials, which are then transported to the molten reduction furnace (2) for deep reduction treatment; (S2) During the reduction treatment in the rotary kiln (1), a gasifying agent is sprayed into the kiln through a gasifying agent nozzle (106) on the kiln wall of the co-generation reduction section (103), and a combustion-supporting gas is sprayed into the kiln through a combustion-supporting gas nozzle (107) on the kiln wall of the roasting section (104); (S3) The hot air discharged from the tail of the rotary kiln (1) is subjected to dust removal and purification treatment and then transported to the roasting section (104) through the gas circulation pipe (109) and the burner (108) to participate in the roasting treatment and / or transported to the molten reduction furnace (2) through the gas circulation pipe (109) and the gas circulation branch pipe (111) to participate in the deep reduction treatment, and the top gas in the molten reduction furnace (2) is transported to the roasting section (104) through the top gas transportation pipe (7) and the burner (108) to participate in the roasting treatment.

13. The method according to claim 12, wherein: The iron-containing raw material is natural rich lump ore and / or cold consolidated pellets; the fuel is lignite particles and / or bituminous coal particles; the addition ratio of the iron-containing raw material to the fuel is such that C / O=1.2~1.5:

1.

14. The method according to claim 13, wherein: The particle size of the iron-containing raw materials and fuel is 2-12 mm.

15. The method according to claim 14, characterized in that: The particle size of the iron-containing raw material and fuel is 3-10 mm.

16. The method according to claim 15, characterized in that: The particle size of the iron-containing raw materials and fuel is 4-8 mm.

17. The method according to claim 12, wherein: The gasifying agent is water vapor or oxygen-rich gas; the combustion-supporting gas is air or oxygen-rich gas.

18. The method according to claim 17, wherein: The water vapor includes low-pressure steam and / or medium-pressure steam, wherein: the low-pressure steam is water vapor with a pressure not greater than 3MPa and a temperature not higher than 500°C; the medium-pressure steam is water vapor with a pressure of 2.5-8MPa and a temperature of 400-800°C.

19. The method according to claim 18, wherein: The low-pressure steam is water vapor with a pressure not exceeding 2.5 MPa and a temperature not exceeding 400° C.; the medium-pressure steam is water vapor with a pressure of 3-6 MPa and a temperature of 500-700° C.

20. The method according to any one of claims 12 to 19, characterized in that: The temperature of the drying section (101) is 150-400°C; the temperature of the preheating section (102) is 400-1000°C; the temperature of the co-production reduction section (103) is 1000-1300°C; the temperature of the roasting section (104) is 1300-1700°C; and the temperature of the slow cooling section (105) is 900-1100°C.

21. The method according to claim 20, characterized in that: The gasifying agent is injected into the kiln specifically as follows: during the rotation of the rotary kiln (1), the gasifying agent is always injected directly into the material through the gasifying agent nozzle (106) located below the material; and / or The combustion-supporting gas is injected into the kiln specifically as follows: during the rotation of the rotary kiln (1), the combustion-supporting gas is always injected directly into the chamber located above the material via the combustion-supporting gas nozzle (107) located above the material.

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