Method and system for partitioned regulation and reinforced reduction of metallurgical kiln

Abstract

The invention provides a method and system for partitioned regulation and control and enhanced reduction of a metallurgical kiln, and belongs to the technical field of energy, metallurgy and CO2 emission reduction. The method for partitioned regulation and reinforced reduction of the metallurgical kiln comprises the following steps: introducing solid fuel and a gasifying agent into a gasifier for gasification reaction to obtain unconverted carbon and gas fuel with reducibility; gas fuel, unconverted carbon and to-be-smelted dry ore are introduced into the rotary kiln, an oxidizing agent is introduced into a plurality of preset areas of the rotary kiln in a staged mode, so that the gas fuel, the unconverted carbon and the oxidizing agent are subjected to staged combustion reaction in the preset areas, and the to-be-smelted dry ore is smelted under the effect of heat released by the combustion reaction. And performing multi-stage reduction roasting on the to-be-smelted dry ore by using the unconverted carbon, unoxidized reducing gas in the gas fuel and reducing gas generated by oxygen-deficient combustion of the unconverted carbon to obtain roasted sand and first flue gas.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy, metallurgy and CO2 emission reduction, and in particular to a method and system for zoning control and enhanced reduction of a metallurgical furnace. Background Art

[0002] The metallurgical industry is an important support for economic development, and it is also the main industry for coal consumption and carbon emissions. It is urgent to reduce the coal consumption and carbon emissions of the metallurgical industry.

[0003] RKEF (Rotary Kiln Electric Furnace) is an important process for the pyrometallurgical smelting of laterite nickel ore. In the existing RKEF process, coal powder is used as fuel and sprayed into the rotary kiln through a burner. The poor combustion uniformity affects the uniformity of the temperature and reducing atmosphere distribution in the rotary kiln. In order to ensure the combustion efficiency of coal powder in the rotary kiln, a large amount of oxidant enters the rotary kiln, resulting in an oxidizing atmosphere in the rotary kiln. The pre-reduction rate of metal oxides in the rotary kiln is low, and the reduction smelting is mainly completed by the downstream ore-fired furnace, resulting in a high overall energy consumption. Summary of the invention

[0004] In view of this, the present disclosure provides a method and system for zoning control and enhanced reduction of a metallurgical furnace, in order to at least partially solve the above technical problems. In this regard, the technical solution provided by the present disclosure is as follows.

[0005] As a first aspect of the present disclosure, the present disclosure provides a method for zoning control and enhanced reduction of a metallurgical kiln, comprising: introducing solid fuel and a gasifying agent into a gasifier for gasification reaction to obtain unconverted carbon and gas fuel with reducing properties; introducing the gas fuel, unconverted carbon and dry ore to be smelted into a rotary kiln, and introducing an oxidant in stages into multiple predetermined areas of the rotary kiln so that the gas fuel, unconverted carbon and the oxidant undergo a staged combustion reaction in the multiple predetermined areas, and under the action of heat released by the combustion reaction, the dry ore to be smelted is subjected to multi-stage reduction roasting using the unconverted carbon, the unoxidized reducing gas in the gas fuel, and the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon to obtain roasted sand and a first flue gas.

[0006] According to an embodiment of the present disclosure, a solid reducing agent is also added to the dry ore to be smelted, and the solid reducing agent partly participates in graded combustion, oxygen-deficient combustion and multi-stage reduction roasting of the dry ore to be smelted; wherein the solid reducing agent includes at least one of lignite, anthracite or biomass carbon.

[0007] According to an embodiment of the present disclosure, the method further includes: introducing the first flue gas and combustion-supporting air into a hot blast furnace for a complete combustion reaction to generate a second flue gas that does not contain combustibles.

[0008] According to an embodiment of the present disclosure, it also includes: passing the second flue gas and the wet ore to be smelted into a drying kiln for heat exchange to obtain the dry ore to be smelted and the third flue gas; and passing the dry ore to be smelted into a rotary kiln; wherein the dry ore to be smelted is dry laterite nickel ore, and the wet ore to be smelted is wet laterite nickel ore.

[0009] According to an embodiment of the present disclosure, it also includes: passing part of the third flue gas into the gasifier; and / or passing part of the third flue gas into multiple predetermined areas of the rotary kiln in stages; wherein the third flue gas includes CO2.

[0010] According to an embodiment of the present disclosure, the multiple predetermined areas of the rotary kiln include, in sequence: a kiln head area, N kiln body areas and a kiln tail area, where N≥1.

[0011] According to an embodiment of the present disclosure, the staged introduction of oxidants into a plurality of predetermined areas of a rotary kiln for staged combustion reaction comprises: introducing a first oxidant into the kiln head area so that the first oxidant and a portion of the gas fuel undergo a first combustion reaction in the kiln head area, and under the action of heat released by the first combustion reaction, reduction roasting of the dry ore to be smelted is carried out using unconverted carbon, unoxidized reducing gas in the gas fuel, and reducing gas generated by the oxygen-deficient combustion of the unconverted carbon.

[0012] According to an embodiment of the present disclosure, the stepwise introduction of oxidants into a plurality of predetermined areas of a rotary kiln for a stepwise combustion reaction comprises: introducing a second oxidant into N kiln body areas respectively, so that the second oxidant, the remaining portion of unconverted carbon and the gas fuel undergo a second combustion reaction in each kiln body area, and under the action of heat released by the second combustion reaction, the remaining portion of unconverted carbon, the unoxidized reducing gas in the gas fuel, and the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon are used to carry out stepwise reduction roasting of the dry ore to be smelted.

[0013] According to an embodiment of the present disclosure, the staged introduction of oxidants into multiple predetermined areas of the rotary kiln for staged combustion reaction includes: introducing a third oxidant into the kiln tail area so that the third oxidant and the combustible gas and unconverted carbon in the gas fuel remaining in the rotary kiln undergo a third combustion reaction in the kiln tail area, and utilizing the heat released by the third combustion reaction to roast the dry ore to be smelted.

[0014] According to an embodiment of the present disclosure, the temperature of the kiln head area is 950-1100°C, the temperature of the kiln body area is 900-1000°C, and the temperature of the kiln tail area is 250-600°C.

[0015] According to an embodiment of the present disclosure, the gasifying agent includes air, oxygen-enriched air, and water vapor; and the carbon conversion rate in the gasifier is controlled at 30%-80%.

[0016] According to an embodiment of the present disclosure, the gas fuel includes CH4, CO and H2, the volume ratio of H2 to CO is controlled at 0.8-1.5, and the temperature of the gas fuel is 250-900°C.

[0017] According to an embodiment of the present disclosure, the first oxidant, the second oxidant, and the third oxidant are combustion aids or a mixture of a combustion aid and a third flue gas, the combustion aid is air, oxygen-enriched air, or oxygen; the combustion-supporting wind is air or oxygen-enriched air; wherein the volume content of oxygen in the first oxidant, the second oxidant, and the third oxidant is each independently 15%-50%.

[0018] As a second aspect of the present disclosure, a system for zoning control and enhanced reduction of a metallurgical furnace is provided, comprising: a gasification furnace and a rotary kiln connected in sequence.

[0019] The gasifier is used for gasification reaction of solid fuel and gasifying agent in the gasifier to obtain unconverted carbon and gas fuel with reducing properties.

[0020] The rotary kiln is used for performing a staged combustion reaction of gas fuel, unconverted carbon and an oxidant introduced in stages through a plurality of predetermined areas of the rotary kiln, and under the action of the heat released by the combustion reaction, the unconverted carbon, the unoxidized reducing gas in the gas fuel and the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon are used to perform multi-stage reduction roasting on the dry ore to be smelted introduced into the rotary kiln, so as to obtain roasted sand and the first flue gas.

[0021] According to an embodiment of the present disclosure, the system further comprises a hot blast furnace; the hot blast furnace is used for completely burning the first flue gas with the combustion-supporting air introduced into the hot blast furnace to generate a second flue gas free of combustibles.

[0022] According to an embodiment of the present disclosure, the system further comprises a drying kiln; the drying kiln is used to exchange waste heat of the second flue gas with the wet ore to be smelted introduced into the drying kiln to obtain dry ore to be smelted and third flue gas.

[0023] According to an embodiment of the present disclosure, the system further includes: a pipeline for connecting the drying kiln and the gasifier to pass part of the third flue gas into the gasifier.

[0024] According to an embodiment of the present disclosure, air distribution units are provided on multiple predetermined areas of the rotary kiln for introducing the oxidant into the multiple predetermined areas of the rotary kiln in stages; wherein the multiple predetermined areas of the rotary kiln include a kiln head area, N kiln body areas and a kiln tail area in sequence, and N≥1.

[0025] According to an embodiment of the present disclosure, an air distribution unit is arranged in the kiln head area for introducing the first oxidant; and / or air distribution units are respectively arranged in N kiln body areas for introducing the second oxidant in stages; and / or an air distribution unit is arranged in the kiln tail area for introducing the third oxidant.

[0026] According to an embodiment of the present disclosure, a plurality of bypasses are arranged on the pipeline; the bypasses are connected to air distribution units arranged on a plurality of predetermined areas of the rotary kiln, and are used to pass part of the third flue gas into the air distribution units.

[0027] Based on the above technical solution, the present disclosure provides a method and system for zoning control and enhanced reduction of a metallurgical kiln, which has at least one of the following beneficial effects:

[0028] (1) In the embodiments of the present disclosure, solid fuel and gasifying agent are introduced into a gasifier for gasification reaction. On the one hand, the solid fuel is thermally converted into reducing unconverted carbon and gas fuel by utilizing the gasifying agent, thereby expanding the adaptability of the solid fuel and the range of selectable solid fuels. On the other hand, by adjusting the carbon conversion rate in the gasifier to control the ratio of the solid fuel thermally converted into gas fuel and unconverted carbon, the flame length and temperature distribution in the rotary kiln can be regulated.

[0029] (2) In the embodiments of the present disclosure, the oxidant is introduced into a plurality of predetermined areas of the rotary kiln in stages, and the gas fuel and unconverted carbon introduced into the rotary kiln are burned in stages and zones, so as to avoid that the reducing gas in the gas fuel entering the rotary kiln is completely consumed in the kiln head area, so as to achieve the control of the temperature, combustion reaction and reducing atmosphere in different areas of the rotary kiln, thereby strengthening the pre-reduction of the metal oxides in the dry ore to be smelted in the rotary kiln. In addition, the staged introduction of the oxidant can reduce the consumption of the oxidant in the kiln head area of ​​the rotary kiln, which is beneficial to control the temperature in the kiln head area and prevent ring formation, and there is no need to introduce excessive air to reduce the temperature in the kiln head area. The staged introduction of the oxidant can also improve the uniformity of the temperature distribution in the rotary kiln, effectively shorten the reduction roasting time of the rotary kiln, and make it possible to shorten the length of the reduction roasting kiln.

[0030] (3) In the embodiments of the present disclosure, the first flue gas generated in the rotary kiln is introduced into the hot blast furnace for combustion reaction to obtain the second flue gas without combustibles, which can be used as a drying heat source for the wet ore to be smelted (such as wet laterite nickel ore) in the drying kiln.

[0031] (4) In the embodiments of the present disclosure, the third flue gas after heat exchange is introduced into the gasifier and / or rotary kiln, which can effectively reduce CO2 gas emissions and realize resource utilization of the third flue gas, such as carbon enrichment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the process of zone control and enhanced reduction of a metallurgical furnace in one embodiment of the present disclosure;

[0033] Figure 2 It is a schematic diagram of the process of zoning control and enhanced reduction of a metallurgical furnace in another embodiment of the present disclosure.

[0034] Reference numerals

[0035] 1-gasifier, 2-rotary kiln, 3-hot furnace air, 4-drying kiln, S1-pipeline, S2-bypass;

[0036] A-solid fuel, B-gasifying agent, C-unconverted carbon, D-gaseous fuel, E-oxidant, F-dry ore to be smelted, G-roasted sand, H-first flue gas, I-combustion-supporting air, J-second flue gas, K-wet ore to be smelted, L-third flue gas. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0038] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0039] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0040] When using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc. When using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.

[0041] In view of the RKEF process of the prior art, the rotary kiln has the problems of fuel combustion, uneven temperature distribution, and low pre-reduction efficiency in the rotary kiln. The present disclosure provides a hot gas fuel process based on the RKEF process. First, solid fuel is introduced into the gasifier to generate a gas fuel with reducing properties, and then the gas fuel is introduced into the rotary kiln, which can solve the problem of low fuel combustion efficiency in the rotary kiln. By introducing the oxidant in stages, a staged and zoned combustion reaction can be achieved, so that the reducing gas in the gas fuel is prevented from being completely consumed in the kiln head area of ​​the rotary kiln, the uniformity of the temperature distribution in the rotary kiln is improved, and the reducing atmosphere distribution in a wide area of ​​the rotary kiln is achieved to enhance the pre-reduction efficiency in the rotary kiln. Furthermore, part of the flue gas generated by the rotary kiln is circulated into the gasifier and / or the rotary kiln, completely or partially replacing the N2 in the air, and then mixed with O2 and enters the gasifier and / or the rotary kiln, thereby increasing the CO2 concentration in the final exhaust gas, so that the CO2 in the exhaust gas can be used and processed without separation, thereby effectively reducing the emission of the generated CO2 into the atmosphere.

[0042] Figure 1 It is a schematic diagram of the process of zoning control and enhanced reduction of a metallurgical furnace in one embodiment of the present disclosure.

[0043] like Figure 1 As shown, in the first embodiment of the present disclosure, the method for zoning control and enhanced reduction of a metallurgical kiln includes: introducing solid fuel A and gasifying agent B into a gasifier 1 for gasification reaction to obtain unconverted carbon C and gas fuel D with reducing properties; introducing gas fuel D, unconverted carbon C and dry ore F to be smelted into a rotary kiln 2, and introducing oxidant E into multiple predetermined areas of the rotary kiln 2 in stages, so that the gas fuel D, unconverted carbon C and oxidant E undergo staged combustion reaction in multiple predetermined areas, and under the action of heat released by the combustion reaction, the unconverted carbon C, the unoxidized reducing gas in the gas fuel D, and the reducing gas generated by the under-oxygen combustion of the unconverted carbon C are used to perform multi-stage reduction roasting on the dry ore F to be smelted, so as to obtain roasted sand G and the first flue gas H.

[0044] In the first embodiment of the present disclosure, solid fuel A is first introduced into the gasifier 1 for gasification and then introduced into the rotary kiln 2 to participate in the reduction roasting reaction. The advantages are that, on the one hand, the adaptability of solid fuel A and the selectable range of solid fuel A can be expanded, for example, raw materials with high water content and poor grindability can be selected; on the other hand, solid fuel A and gasifying agent B undergo gasification reaction in the gasifier 1, and the carbon conversion rate in the gasifier 1 is regulated by adjusting the amount of gasifying agent B, generating gas fuel D and unconverted carbon C (i.e., part of the unconverted solid fuel), thereby achieving the regulation of flame length, temperature distribution, etc. in the rotary kiln 2. Solid fuel A is converted into gas fuel D through the gasification reaction of the gasifier 1 and then introduced into the rotary kiln 2. The combustion effect of gas fuel D is better than that of solid fuel A, and the combustion is easy to organize and control, which can effectively reduce the excess air coefficient in the rotary kiln 2 and reduce heat loss. In the rotary kiln 2, by utilizing the difference in reaction rates between the gas fuel D and the unconverted carbon C, the oxidant E is introduced in stages to achieve staged and zoned combustion, and the CO2 gas in the unconverted carbon C and the oxidant E and / or the CO2 gas generated by the combustion reaction is used to carry out a CO2 reduction reaction and release CO gas, and the unconverted carbon C and the H2O generated by roasting the dry ore F to be smelted in the rotary kiln 2 are used to react with water gas to release H2 and CO gases, thereby regulating the uniformity of fuel combustion, temperature and reducing atmosphere distribution in the rotary kiln 2, and at the same time, the reducing properties of the gas fuel D, the unconverted carbon C and the generated CO and H2 gases are used to pre-reduce the metal oxides in the dry ore F to be smelted in the rotary kiln 2, which can effectively shorten the reduction roasting time of the rotary kiln 2 and make it possible to shorten the length of the reduction roasting kiln.

[0045] In the first embodiment of the present disclosure, solid fuel A includes carbon-containing fuels such as coal and biomass, or a mixed fuel of coal and biomass. Gasifying agent B includes at least one of air, oxygen-enriched air, and water vapor. By controlling the amount of gasifying agent B, the carbon conversion rate in the gasifier 1 is controlled at 30%-80%, preferably at 40%-50%, and the gasification reaction temperature in the gasifier 1 is controlled at 600-1000°C. By controlling the carbon conversion rate and then controlling the ratio of gas fuel D including CH4, CO and H2 and unconverted carbon C generated by solid fuel A through gasification reaction, the flame length and temperature distribution in the rotary kiln 2 are regulated. Furthermore, by controlling the water vapor content in the gasifying agent B, the content of H2 and CO in the gas fuel D can be controlled. Considering that H2 has a better reduction effect on metal oxides in the dry ore F to be smelted than CO, the excessive H2 generation in the gasifier 1 affects the cold gas efficiency. Therefore, it is preferred to control the volume ratio of H2 to CO in the gas fuel D to be 0.8-1.5. In order to ensure that the gas fuel D is easy to ignite after entering the rotary kiln 2, it is preferred to control the temperature of the gas fuel D to be 250-900°C, and the calorific value of the gas fuel D is not less than 1000 kcal / m 3, to ensure that the gas fuel D can burn stably after entering the rotary kiln 2.

[0046] In the prior art, the oxidant E is generally introduced into the rotary kiln 2 all at once. This method of introducing the oxidant E easily causes the reducing gas in the rotary kiln 2 to be completely consumed in the kiln head area, thereby reducing the reduction efficiency of the rotary kiln 2 for metal oxides; or there are problems of uneven distribution of temperature and reducing atmosphere in the rotary kiln 2, which affects the reduction roasting effect; or it is necessary to increase the amount of cold air to cool the high-temperature area of ​​concentrated combustion at the kiln head to control the temperature, thereby affecting the energy efficiency.

[0047] In this regard, in the first embodiment of the present disclosure, the rotary kiln 2 is divided into a plurality of predetermined areas, and the oxidant E is introduced into the plurality of predetermined areas respectively, wherein the plurality of predetermined areas of the rotary kiln 2 sequentially include a kiln head area, N kiln body areas and a kiln tail area, and N ≥ 1. The stepwise introduction of the oxidant E into the plurality of predetermined areas of the rotary kiln 2 for a stepwise combustion reaction includes: introducing a first oxidant into the kiln head area so that the first oxidant and a portion of the gas fuel D undergo a first combustion reaction in the kiln head area, and under the action of the heat released by the first combustion reaction, the unconverted carbon C, the unoxidized reducing gas (CO, H2, CH4, etc.) in the gas fuel D, and the reducing gas generated by the under-oxygen combustion of the unconverted carbon C are used to carry out reduction roasting of the dry ore F to be smelted.

[0048] In the first embodiment of the present disclosure, a first oxidant is introduced into the kiln head area, and by utilizing the difference in reaction rates between the gas fuel D and the unconverted carbon C in the kiln head area, the first oxidant can cause part of the combustible gas (such as CH4) in the gas fuel D to produce CO2 gas through combustion reaction, and the heat released causes the kiln head area to reach the required reduction roasting temperature, while the unburned gas fuel D keeps the kiln head area in a reducing atmosphere. During the combustion reaction, the unconverted carbon C in the kiln can undergo a reduction reaction with the CO2 gas to release CO gas, and then, under the action of the heat released by the first combustion reaction, the unconverted carbon C and part of the CO and H2 gases in the gas fuel D, as well as the reducing gas (such as CO gas) generated by the oxygen-deficient combustion of the unconverted carbon C, are used to perform reduction roasting on the dry ore F to be smelted, thereby achieving pre-reduction of the metal oxides in the dry ore F to be smelted.

[0049] The second embodiment of the present disclosure is different from the first embodiment in that the method of introducing the oxidant E into the rotary kiln 2 for the staged combustion reaction is different. Specifically, introducing the oxidant E into the multiple predetermined areas of the rotary kiln 2 for the staged combustion reaction includes: introducing the second oxidant into the N kiln body areas respectively, so that the second oxidant, the remaining part of the unconverted carbon C and the gas fuel D undergo a second combustion reaction in each kiln body area, and under the action of the heat released by the second combustion reaction, the remaining part of the unconverted carbon C, the unoxidized reducing gas (such as CO, H2, CH4, etc.) in the gas fuel D and the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon C are used to perform staged reduction roasting on the dry ore F to be smelted. It should be noted that the second embodiment can be implemented independently, that is, only the oxidant E is introduced into the kiln body area in stages, and the fuel combustion, temperature and reducing atmosphere in the rotary kiln 2 can also be regulated, but there may be a problem of low pre-reduction efficiency. Therefore, it is preferred to implement the technical solution in the second embodiment on the basis of the first embodiment, that is, to introduce the oxidant E in stages into the kiln head area and N kiln body areas for staged combustion reaction, to pre-reduce the metal oxides and improve the metal pre-reduction rate.

[0050] In the second embodiment of the present disclosure, the first oxidant is introduced into the kiln head area to achieve pre-reduction of the metal oxide. As the endothermic reduction reaction of the metal oxide proceeds and the kiln body area dissipates heat, the temperature in the rotary kiln 2 gradually decreases. From the kiln head area to the kiln tail area of ​​the rotary kiln 2, to the position where the second oxidant is introduced into the kiln body area, the freshly introduced second oxidant and the remaining gas fuel D and unconverted carbon C in the rotary kiln 2 undergo a second combustion reaction in each kiln body area and release heat, so that the temperature in the rotary kiln 2 is raised again, providing the required high temperature environment for the reduction roasting reaction. During the second combustion reaction, the unconverted carbon C in the kiln may also undergo a reduction reaction with CO2 gas to release CO gas, and the unconverted carbon C may also undergo a water-gas reaction with H2O generated by roasting the dry ore F to be smelted to release CO and H2 gases, and then under the action of the heat released by the second combustion reaction, the CO and H2 gases in the unconverted carbon C and part of the gas fuel D, as well as the CO and H2 gases generated by the CO2 reduction reaction and the water-gas reaction, are used to reduce and roast the dry ore F to be smelted. In this way, by introducing the second oxidant in stages, a multi-stage reduction roasting reaction is carried out in the kiln body area, and the metal oxides in the kiln body area are reduced in stages, which helps to improve the metal recovery rate.

[0051] In the third embodiment of the present disclosure, the oxidant is introduced into a plurality of predetermined areas of the rotary kiln 2 in stages for staged combustion reaction, including: introducing a third oxidant into the kiln tail area so that the third oxidant and the combustible gas and unconverted carbon C in the gas fuel D remaining in the rotary kiln 2 undergo a third combustion reaction in the kiln tail area, and utilizing the heat released by the third combustion reaction to roast the dry ore F to be smelted.

[0052] In the third embodiment of the present disclosure, only a small amount of combustible gas (such as CH4) and unconverted carbon C remain in the rotary kiln 2 near the kiln tail area. At this time, the third oxidant is introduced to perform a third combustion reaction with the unconverted carbon C remaining in the rotary kiln 2 and the combustible gas in the gas fuel D and release heat, and the heat released by the third combustion reaction is used to roast the dry ore to be smelted. As the dry ore F to be smelted absorbs heat during the reduction roasting reaction, the temperature of the kiln tail area gradually decreases, and the first flue gas H generated can be used to dry the wet ore K to be smelted, realizing resource utilization and reducing system CO2 gas emissions.

[0053] By introducing the oxidant E (i.e., the first oxidant, the second oxidant, and the third oxidant) step by step from the kiln head area to the kiln tail area, it is avoided that the reducing gas in the gas fuel entering the rotary kiln 2 from the kiln head area is completely consumed in the kiln head area, thereby achieving a wide area distribution of the reducing atmosphere in the rotary kiln 2, which is helpful to strengthen the reduction of the reducing gas (such as CO, H2) and unconverted carbon C in the rotary kiln 2 to the dry ore F to be smelted; on the other hand, reducing the amount of oxidant in the kiln head area is conducive to controlling the reduction roasting temperature in the kiln head area, and there is no need to introduce excessive air to reduce the temperature in the kiln head area. In addition, the graded introduction of the oxidant E can improve the uniformity of the temperature and reducing atmosphere distribution in the rotary kiln 2, which can effectively shorten the time required for reduction roasting and make it possible to shorten the length of the reduction roasting kiln.

[0054] The basis for the amount of oxidant E introduced from the kiln head area to the kiln tail area is: (1) the temperature in the rotary kiln 2 is not higher than the temperature required for safe and stable generation operation, while meeting the reduction roasting requirements; (2) the kiln head area needs to be a reducing atmosphere, and the oxidant E is introduced in stages from the kiln head area to the kiln tail area, so that the combustible gas in the gas fuel D in the rotary kiln 2 is gradually consumed, and the reducing gas in the rotary kiln 2 is gradually reduced.

[0055] In the first to third embodiments of the present disclosure, the temperature of the kiln head area is 950-1100°C, the temperature of the kiln body area is 900°C-1000°C, and the temperature of the kiln tail area is 250-600°C. The first oxidant, the second oxidant, and the third oxidant are combustion aids, wherein the combustion aid is air, oxygen-enriched air or oxygen. Further, the volume content of oxygen in the first oxidant, the second oxidant, and the third oxidant is independently 15%-50%. Specifically, the volume content of oxygen in the first oxidant is 15%-35%, the volume content of oxygen in the second oxidant is 21%-50%, and the volume content of oxygen in the third oxidant is 21%-50%.

[0056] According to an embodiment of the present disclosure, a solid reducing agent is also added to the dry ore F to be smelted, and the solid reducing agent partly participates in graded combustion, oxygen-deficient combustion and multi-stage reduction roasting of the dry ore to be smelted; wherein the solid reducing agent includes at least one of lignite, anthracite or biomass carbon.

[0057] In the first to third embodiments, in order to control the amount of oxidant E entering the rotary kiln 2, it is necessary to reduce the air leakage in the kiln body area and control the pressure in the kiln head area of ​​the rotary kiln 2 to be close to 0 kPa (gauge pressure). The speed at which the second oxidant and the third oxidant are introduced into the rotary kiln 2 is ≥15 m / s. At this speed, the dry ore F to be smelted in the rotary kiln 2 can be fluidized and stirred, and the mixing with the reducing gas in the rotary kiln 2 can be enhanced, thereby enhancing the reducing effect of the reducing gas on the metal oxides in the dry ore F to be smelted.

[0058] Furthermore, the unconverted carbon C and the gas fuel D undergo a combustion reaction in the rotary kiln 2 to release a first flue gas H. By controlling the amount of the oxidant E, although the combustibles (such as CH4, H2, CO and unconverted carbon C) in the rotary kiln 2 can be effectively consumed, combustibles (such as unconverted carbon C) may still remain in the first flue gas H. In view of this, the present disclosure proposes to pass the first flue gas H into the hot blast furnace 3 for combustion, and at the same time use the obtained second flue gas J without combustibles as a heat source for the drying kiln 4 to realize the utilization of the energy in the second flue gas J.

[0059] Figure 2 It is a schematic diagram of the process of zoning control and enhanced reduction of a metallurgical furnace in another embodiment of the present disclosure.

[0060] like Figure 2 As shown, the fourth embodiment of the present disclosure is different from the above-mentioned first to third embodiments in that the method for zoning control and enhanced reduction of a metallurgical kiln also includes: introducing the first flue gas H and the combustion-supporting air I into the hot blast furnace 3 for a complete combustion reaction to generate a second flue gas J that does not contain combustibles, wherein the combustion-supporting air I is air or oxygen-enriched air.

[0061] In the fourth embodiment of the present disclosure, the first flue gas H is introduced into the hot blast furnace 3 for complete combustion reaction, and the combustibles (such as CH4, H2, CO and unconverted carbon C) in the first flue gas H are consumed to obtain the second flue gas J without combustibles, which is used as the heat source of the drying kiln 4. The temperature of the second flue gas J is 250-400°C.

[0062] The fifth embodiment of the present disclosure is different from the fourth embodiment described above in that the method for zoning control and enhanced reduction of a metallurgical kiln further includes: passing the second flue gas J and the wet ore K to be smelted into the drying kiln 4 for heat exchange to obtain the dry ore F to be smelted and the third flue gas L; and passing the dry ore F to be smelted into the rotary kiln 2; wherein the dry ore F to be smelted is a laterite nickel ore dry ore, and the wet ore K to be smelted is a laterite nickel ore wet ore. In the fifth embodiment of the present disclosure, the second flue gas J is passed into the drying kiln 4, and the waste heat of the second flue gas J is used to exchange heat with the wet ore K to be smelted passed into the drying kiln 4 to obtain the third flue gas L and the dry ore F to be smelted, thereby realizing energy utilization of the flue gas.

[0063] The sixth embodiment of the present disclosure is different from the fifth embodiment described above in that the method for zoning control and enhanced reduction of a metallurgical kiln further includes: introducing a portion of the third flue gas L into the gasifier 1, wherein the third flue gas includes CO2. It can be understood that solid fuel A, gasifying agent B and the third flue gas L from the drying kiln 4 are introduced into the gasifier 1 for gasification reaction to obtain unconverted carbon C with reducing properties and gas fuel D, wherein the gas fuel D is rich in CO gas. It should be noted that a portion of the third flue gas L can be introduced into the gasifier 1 independently, or a portion of the third flue gas L can be mixed with the gasifying agent B and introduced into the gasifier 1, wherein the volume content of oxygen in the mixed gas introduced into the gasifier 1 by the portion of the third flue gas L and the gasifying agent B is 13%-50%.

[0064] In the sixth embodiment of the present disclosure, part of the third flue gas L is introduced into the gasification furnace 1, and the heat released by the gasification reaction of the gasifying agent B and the solid fuel A is used to allow the unconverted carbon C to undergo a reduction reaction with the CO2 gas (derived from the CO2 gas produced by the gasification reaction and / or the CO2 gas in the third flue gas L) to release CO gas, thereby preparing a gas fuel D rich in CO gas, which can effectively solve the problem of CO2 gas emissions; at the same time, the gas fuel D rich in CO gas enters the rotary kiln 2, and by organizing combustion, the pre-reduction rate of metal oxides in the dry ore F to be smelted in the rotary kiln 2 can be effectively improved.

[0065] Furthermore, the gas fuel D, the unconverted carbon C and the dry ore F to be smelted are introduced into the rotary kiln 2, and the oxidant E is introduced into multiple predetermined areas of the rotary kiln 2 in stages, so that the gas fuel D, the unconverted carbon C and the oxidant E are subjected to staged combustion reactions in multiple predetermined areas to release heat, and at the same time, under the action of heat, the dry ore F to be smelted is subjected to multi-stage reduction roasting by the gas fuel D and the unconverted carbon C to obtain roasted sand G and the first flue gas H. By introducing the gas fuel D rich in CO gas into the rotary kiln 2 and burning it with the oxidant E in stages and zones, the temperature, reaction atmosphere and reduction reaction in different areas of the rotary kiln 2 can be controlled, thereby enhancing the pre-reduction effect of the rotary kiln 2 on the metal oxides in the dry ore F to be smelted.

[0066] The seventh embodiment of the present disclosure is different from the fifth embodiment or the sixth embodiment described above in that: the method for zoning control and enhanced reduction of the metallurgical kiln also includes: passing part of the third flue gas L into multiple predetermined areas of the rotary kiln 2 in stages, wherein the multiple predetermined areas of the rotary kiln 2 include the kiln head area, N kiln body areas and the kiln tail area in sequence, and N≥1. It can be understood that: the new oxidant (i.e., the oxidant formed by the third flue gas L and the combustion aid) is mixed and passed into the kiln head area, the kiln body area and the kiln tail area of ​​the rotary kiln 2. It should be noted that the seventh embodiment of the present disclosure can be implemented in combination with the fifth embodiment or the sixth embodiment, and the technical solutions implemented can increase the CO2 concentration in the final exhaust gas, achieve carbon enrichment, and make the CO2 in the exhaust gas available and processed without separation, thereby effectively reducing the emission of CO2 generated by the present disclosure into the atmosphere. The reaction of the third flue gas L in the multiple predetermined areas of the rotary kiln 2 is the same as the mechanism in the above embodiment.

[0067] Specifically, new oxidant E (composed of a third flue gas and a combustion aid (air, oxygen or oxygen-enriched air)) is introduced into the kiln head area, the kiln body area and the kiln tail area respectively for staged combustion reaction, including: introducing a first oxidant into the kiln head area so that the first oxidant and part of the gas fuel D undergo a first combustion reaction in the kiln head area, and under the action of heat released by the first combustion reaction, the dry ore F to be smelted is reduction roasted using unconverted carbon C, unoxidized reducing gas in the gas fuel D, and reducing gas generated by the under-oxygen combustion of the unconverted carbon C.

[0068] The second oxidant is introduced into N kiln body areas respectively, so that the second oxidant, the remaining unconverted carbon C and the gas fuel D undergo a second combustion reaction in each kiln body area. Under the action of the heat released by the second combustion reaction, the remaining unconverted carbon C, the unoxidized reducing gas in the gas fuel D, and the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon C are used to carry out graded reduction roasting of the dry ore F to be smelted.

[0069] A third oxidant is introduced into the kiln tail area so that the third oxidant and the combustible gas and unconverted carbon C in the gas fuel D remaining in the rotary kiln 2 undergo a third combustion reaction in the kiln tail area, and the heat released by the third combustion reaction is used to roast the dry ore F to be smelted.

[0070] In the seventh embodiment of the present disclosure, the temperature of the kiln head area is 950-1100°C, the temperature of the kiln body area is 900-1000°C, and the temperature of the kiln tail area is 250-600°C. The first oxidant, the second oxidant, and the third oxidant are a mixture of a combustion aid and a third flue gas, and the combustion aid is air, oxygen, or oxygen-enriched air; the volume content of oxygen in the first oxidant, the second oxidant, and the third oxidant is independently 15%-50%. Specifically, the volume content of oxygen in the first oxidant is 15%-35%, the volume content of oxygen in the second oxidant is 21%-50%, and the volume content of oxygen in the third oxidant is 21%-50%.

[0071] As a second aspect of the present disclosure, a system for zone control and enhanced reduction of a metallurgical furnace is provided, which is used to execute the method for zone control and enhanced reduction of a metallurgical furnace in the above-mentioned embodiment.

[0072] The first embodiment of the present disclosure provides a metallurgical furnace zoning control and enhanced reduction system, such as Figure 1 The system shown comprises: a gasification furnace 1 and a rotary kiln 2 which are connected in sequence.

[0073] The gasifier 1 is provided with a solid material inlet for introducing solid fuel A, a gasifying agent inlet for introducing gasifying agent B, and a gas material outlet for discharging solid fuel A and gasifying agent B. The gasifier 1 is used for gasifying the solid fuel A and the gasifying agent B in the gasifier 1 to obtain unconverted carbon C with reducing properties and gas fuel D.

[0074] The rotary kiln 2 is provided with a gas material inlet for the gas fuel D and the unconverted carbon C, a dry ore inlet for the dry ore F to be smelted, a first flue gas outlet for discharging the first flue gas H, and a roasted sand outlet for discharging the roasted sand G. The rotary kiln 2 can be divided into a plurality of predetermined areas, including: a kiln head area, N kiln body areas (N≥1) and a kiln tail area, and a plurality of oxidant inlets for the oxidant E to enter are provided on the rotary kiln 2. The rotary kiln 2 is used for the gas fuel D, the unconverted carbon C and the oxidant E introduced in stages through the plurality of predetermined areas of the rotary kiln 2 to carry out staged combustion reaction, and under the action of the heat released by the combustion reaction, the unconverted carbon C, the unoxidized reducing gas in the gas fuel D, and the reducing gas generated by the under-oxygen combustion of the unconverted carbon C are used to carry out multi-stage reduction roasting on the dry ore F to be smelted introduced into the rotary kiln 2, so as to obtain the roasted sand G and the first flue gas H.

[0075] Furthermore, in the first embodiment of the present disclosure, an air distribution unit (not shown) is provided on multiple predetermined areas of the rotary kiln 2, for passing the oxidant E into the multiple predetermined areas of the rotary kiln 2 in a graded manner; wherein the multiple predetermined areas of the rotary kiln 2 include a kiln head area, N kiln body areas and a kiln tail area in sequence, N ≥ 1, and the air distribution unit includes air distribution holes or air distribution hoods.

[0076] In which, an air distribution unit is arranged in the kiln head area for introducing the first oxidant to utilize the difference in reaction rates between the gas fuel D and the unconverted carbon C in the kiln head area. The first oxidant can cause part of the combustible gas (such as CO, H2, CH4, etc.) in the gas fuel to produce CO2 gas through combustion reaction, and the released heat makes the kiln head area reach the required reduction roasting temperature, while the reducing gas in the unburned gas fuel D keeps the kiln head area in a reducing atmosphere. During the combustion reaction, the unconverted carbon C in the kiln can undergo a reduction reaction with the CO2 gas to release CO gas, and then under the action of heat, the unconverted carbon C, the unoxidized reducing gas (such as CO, H2, CH4 gas) in the gas fuel D, and the reducing gas (such as CO gas) generated by the under-oxygen combustion of the unconverted carbon C are used to perform reduction roasting on the dry ore F to be smelted, thereby realizing the pre-reduction of the metal oxides in the dry ore F to be smelted.

[0077] In the second embodiment of the present disclosure, air distribution units are respectively arranged in N kiln body areas for introducing the second oxidant in stages, so that the second oxidant, the remaining unconverted carbon C and the gas fuel D undergo a second combustion reaction in each kiln body area, and under the action of the heat released by the second combustion reaction, the remaining unconverted carbon C, the unoxidized reducing gas in the gas fuel D (such as CO, H2, CH4, etc.), and the reducing gas (such as CO) generated by the oxygen-deficient combustion of the unconverted carbon C are used to carry out graded reduction roasting of the dry ore F to be smelted, thereby achieving graded reduction of metal oxides in the kiln body area, which helps to improve the metal recovery rate.

[0078] In the third embodiment of the present disclosure, a small amount of combustible gas (such as CH4) and unconverted carbon C remain in the rotary kiln 2 near the kiln tail area. An air distribution unit is provided in the kiln tail area for introducing a third oxidant. The third oxidant can undergo a third combustion reaction with the unconverted carbon C remaining in the rotary kiln 2 and the combustible gas in the gas fuel D, and the heat released by the third combustion reaction is used to roast the dry ore to be smelted.

[0079] In the first to third embodiments, the first oxidant, the second oxidant and the third oxidant introduced into the rotary kiln 2 are combustion aids, and the combustion aids are air, oxygen or oxygen-enriched air.

[0080] The fourth embodiment of the present disclosure provides another system for zone control and enhanced reduction of a metallurgical furnace, such as Figure 2 As shown, the system further includes a hot blast furnace 3, wherein the gasification furnace 1, the rotary kiln 2 and the hot blast furnace 3 are sequentially connected. The hot blast furnace 3 is used for the first flue gas H to completely burn with the combustion-supporting air I introduced into the hot blast furnace 3 to generate a second flue gas J without combustibles.

[0081] Continue as Figure 2As shown, in the fifth embodiment of the present disclosure, the above-mentioned system for zoned control and enhanced reduction of metallurgical kilns further includes: a drying kiln 4. The drying kiln 4 is used for heat exchange between the waste heat of the second flue gas J and the wet ore K to be smelted introduced into the drying kiln 4 to obtain the dry ore F to be smelted and the third flue gas L. By utilizing the waste heat of the second flue gas J to dry the wet ore K to be smelted, the energy utilization of the flue gas is realized, which helps to reduce the energy consumption of metallurgy.

[0082] Continue as Figure 2 As shown, in the sixth embodiment of the present disclosure, the system for zoning control and enhanced reduction of the metallurgical kiln further includes: a pipeline S1, which is used to connect the drying kiln 4 and the gasifier 1 to pass part of the third flue gas L into the gasifier 1. Part of the third flue gas L in the drying kiln 4 is passed into the gasifier 1 through the pipeline S1, and the heat released by the gasification reaction of the solid fuel A and the gasifying agent B is utilized, and under this heat, a reduction reaction is carried out with the unconverted carbon C and CO2 gas in the gasifier 1 to generate CO gas, thereby obtaining a gaseous fuel rich in CO gas.

[0083] Continue as Figure 2 As shown, in the seventh embodiment of the present disclosure, a plurality of bypasses S2 are arranged on the pipeline S1; the bypasses S2 are connected to the air distribution units arranged on a plurality of predetermined areas of the rotary kiln 2, and are used to pass part of the third flue gas L into the air distribution units. The third flue gas L is mixed with the combustion-supporting agent to form a new first oxidant, a new second oxidant, and a new third oxidant, which are then passed through the plurality of air distribution units on the rotary kiln into the kiln head area, the kiln body area, and the kiln tail area of ​​the rotary kiln 2 for staged combustion reaction and carbon dioxide reduction reaction, which can effectively utilize CO2 gas and achieve carbon enrichment at the same time.

[0084] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. The scope of the present disclosure is defined by the attached claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A method for zoning control and enhanced reduction of a metallurgical furnace, characterized in that: The method comprises: The solid fuel and the gasifying agent are introduced into the gasifier for gasification reaction to obtain unconverted carbon and gas fuel with reducing properties; The gas fuel, unconverted carbon and dry ore to be smelted are introduced into a rotary kiln, and an oxidant is introduced into a plurality of predetermined areas of the rotary kiln in a staged manner, so that the gas fuel, the unconverted carbon and the oxidant undergo a staged combustion reaction in the plurality of predetermined areas, and under the action of heat released by the combustion reaction, the unconverted carbon, the unoxidized reducing gas in the gas fuel, and the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon are used to perform multi-stage reduction roasting on the dry ore to be smelted, so as to obtain roasted sand and a first flue gas.

2. The method according to claim 1, characterized in that A solid reducing agent is also added to the dry ore to be smelted, and a part of the solid reducing agent participates in the staged combustion, the oxygen-deficient combustion and the multi-stage reduction roasting of the dry ore to be smelted; Wherein, the solid reducing agent includes at least one of lignite, anthracite or biomass carbon.

3. The method according to claim 1, characterized in that Also includes: The first flue gas and combustion-supporting air are introduced into a hot blast furnace for complete combustion reaction to generate a second flue gas free of combustibles.

4. The method according to claim 3, characterized in that Also includes: Passing the second flue gas and the wet ore to be smelted into a drying kiln for heat exchange to obtain the dry ore to be smelted and the third flue gas; as well as Passing the dry ore to be smelted into the rotary kiln; Wherein, the dry ore to be smelted is laterite nickel ore dry ore, and the wet ore to be smelted is laterite nickel ore wet ore.

5. The method according to claim 4, characterized in that Also includes: Passing part of the third flue gas into the gasifier; and / or Passing part of the third flue gas into a plurality of predetermined areas of the rotary kiln in a staged manner; Wherein, the third flue gas includes CO2.

6. The method according to any one of claims 1 to 5, characterized in that The multiple predetermined areas of the rotary kiln include: a kiln head area, N kiln body areas and a kiln tail area in sequence, where N≥1.

7. The method according to claim 6, characterized in that The step of introducing oxidant into a plurality of predetermined areas of the rotary kiln in stages to perform a staged combustion reaction comprises: A first oxidant is introduced into the kiln head area so that the first oxidant and part of the gas fuel undergo a first combustion reaction in the kiln head area, and under the action of the heat released by the first combustion reaction, the unconverted carbon, the unoxidized reducing gas in the gas fuel, and the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon are used to reduction roast the dry ore to be smelted.

8. The method according to claim 7, characterized in that The step of introducing oxidant into a plurality of predetermined areas of the rotary kiln in stages to perform a staged combustion reaction comprises: A second oxidant is introduced into each of the N kiln body areas, so that the second oxidant, the remaining part of the unconverted carbon and the gas fuel undergo a second combustion reaction in each of the kiln body areas, and under the action of the heat released by the second combustion reaction, the remaining part of the unconverted carbon, the unoxidized reducing gas in the gas fuel, and the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon are used to perform graded reduction roasting on the dry ore to be smelted.

9. The method according to claim 8, characterized in that The step of introducing oxidant into a plurality of predetermined areas of the rotary kiln in stages to perform a staged combustion reaction comprises: A third oxidant is introduced into the kiln tail area so that the third oxidant undergoes a third combustion reaction with the combustible gas and unconverted carbon in the gas fuel remaining in the rotary kiln in the kiln tail area, and the heat released by the third combustion reaction is used to roast the dry ore to be smelted.

10. The method according to claim 6, characterized in that The temperature of the kiln head area is 950-1100°C, the temperature of the kiln body area is 900-1000°C, and the temperature of the kiln tail area is 250-600°C.

11. The method according to claim 1, characterized in that: The gasifying agent includes air, oxygen-enriched air, and water vapor; The carbon conversion rate in the gasifier is controlled at 30%-80%.

12. The method according to claim 1, characterized in that: The gas fuel includes CH4, CO and H2, the volume ratio of H2 to CO is controlled at 0.8-1.5, and the temperature of the gas fuel is 250-900°C.

13. The method according to claim 9, characterized in that: The first oxidant, the second oxidant and the third oxidant are combustion aids or a mixture of the combustion aid and the third flue gas, and the combustion aid is air, oxygen-enriched air or oxygen; The combustion-supporting air is air or oxygen-enriched air; The volume content of oxygen in the first oxidant, the second oxidant and the third oxidant is independently 15%-50%.

14. A system for zone control and enhanced reduction of metallurgical furnaces, characterized in that: The system comprises: A gasifier, for gasifying solid fuel and gasifying agent to undergo gasification reaction in the gasifier to obtain reducing gas fuel and unconverted carbon; A rotary kiln is used for performing a staged combustion reaction on the gas fuel, the unconverted carbon and the oxidant introduced in stages through a plurality of predetermined areas of the rotary kiln, and under the action of the heat released by the combustion reaction, the unconverted carbon, the unoxidized reducing gas in the gas fuel and the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon are used to perform multi-stage reduction roasting on the dry ore to be smelted introduced into the rotary kiln to obtain roasted sand and the first flue gas.

15. The system according to claim 14, characterized in that The system further comprises: The hot blast furnace is used for completely burning the first flue gas with the combustion-supporting air introduced into the hot blast furnace to generate the second flue gas without combustibles.

16. The system according to claim 13, characterized in that The system also includes: a drying kiln; The drying kiln is used for heat exchange between the waste heat of the second flue gas and the wet ore to be smelted introduced into the drying kiln, so as to obtain the dry ore to be smelted and the third flue gas.

17. The system according to claim 16, characterized in that The system further includes: a pipeline for connecting the drying kiln and the gasifier to pass part of the third flue gas into the gasifier.

18. The system according to claim 14, characterized in that An air distribution unit is provided on a plurality of predetermined areas of the rotary kiln, for introducing the oxidant into the plurality of predetermined areas of the rotary kiln in stages; The multiple predetermined areas of the rotary kiln include a kiln head area, N kiln body areas and a kiln tail area in sequence, and N≥1.

19. The system according to claim 18, characterized in that: The air distribution unit is arranged in the kiln head area for introducing the first oxidant; and / or Air distribution units are respectively arranged in the N kiln body areas for introducing the second oxidant in stages; and / or An air distribution unit is arranged in the kiln tail area for introducing the third oxidant.

20. The system according to claim 18, characterized in that The pipeline is provided with a plurality of bypasses; The bypass is communicated with the air distribution units arranged on a plurality of predetermined areas of the rotary kiln, and is used for passing the third flue gas into the air distribution units.

Images