Metallurgical reduction roasting method and system beneficial to CO2 capture

Abstract

The invention provides a metallurgical reduction roasting method and system beneficial to CO2 capture, and belongs to the technical field of energy. The metallurgical reduction roasting method beneficial to CO2 capture comprises the following steps: introducing a solid fuel, a gasifying agent and first flue gas from a drying kiln into a gasification furnace, and carrying out gasification reaction to obtain unconverted carbon and gas fuel with reducibility; unconverted carbon, gas fuel, to-be-smelted dry ore and a combustion improver are introduced into the rotary kiln, so that the unconverted carbon, the gas fuel and the combustion improver are subjected to a combustion reaction in the rotary kiln, and the to-be-smelted dry ore is smelted under the effect of heat released by the combustion reaction; performing reduction roasting on the to-be-smelted dry ore by using the unconverted carbon, unoxidized reducing gas in the gas fuel, reducing gas generated by oxygen-deficient combustion of the unconverted carbon and CO generated by reaction of CO2 in the combustion improver and the unconverted carbon to obtain hot roasted sand and hot flue gas; and the hot flue gas and the to-be-smelted wet ore are introduced into a drying kiln for heat exchange, and to-be-smelted dry ore and first flue gas are obtained.

Description

Technical Field

[0001] The present disclosure belongs to the field of energy and CO2 capture technology, and in particular, relates to a metallurgical reduction roasting method and system that is beneficial to CO2 capture. Background Art

[0002] The metallurgical industry is an important support for economic development, and it is also a major industry for coal consumption and carbon emissions. Under the dual carbon goals, it is urgent to reduce metallurgical coal consumption and carbon emissions.

[0003] RKEF (Rotary Kiln Electric Furnace) is an important process for the pyrometallurgical smelting of laterite nickel ore. However, the existing RKEF process has the following main problems:

[0004] (1) When pulverized coal is sprayed into the rotary kiln as fuel, the combustion uniformity is poor, which affects the uniformity of the temperature and reducing atmosphere distribution in the rotary kiln.

[0005] (2) In order to ensure the combustion efficiency of pulverized coal in the rotary kiln, a large amount of combustion-supporting agent (air or oxygen-enriched air) is introduced into 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.

[0006] (3) During the metallurgical process, the emission of CO2 gas is relatively large. Summary of the invention

[0007] In view of this, the present disclosure provides a metallurgical reduction roasting method and system that is beneficial to CO2 capture, 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.

[0008] As a first aspect of the present disclosure, a metallurgical reduction roasting method that is conducive to CO2 capture is provided, comprising: introducing solid fuel, a gasifying agent and a first flue gas from a drying kiln into a gasifier for gasification reaction to obtain reducing unconverted carbon and gaseous fuel; introducing the unconverted carbon, the gaseous fuel, the dry ore to be smelted and the combustion aid into a rotary kiln so that the unconverted carbon, the gaseous fuel and the combustion aid undergo a combustion reaction in the rotary kiln, and under the action of the heat released by the combustion reaction, the dry ore to be smelted is reduction roasted by utilizing the unconverted carbon, the unoxidized reducing gas in the gaseous fuel, the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, and the CO2 in the combustion aid and the CO generated by the reaction of the unconverted carbon with the unconverted carbon to obtain hot roasted sand and hot flue gas; and introducing the hot flue gas and the wet ore to be smelted into the drying kiln for heat exchange to obtain the dry ore to be smelted and the first flue gas; wherein the first flue gas includes CO2, and the reducing gas fuel includes CH4, CO and H2.

[0009] According to an embodiment of the present disclosure, the wet ore to be smelted is mixed with a solid reducing agent, and the solid reducing agent partially participates in combustion, oxygen-deficient combustion, and reduction roasting of the dry ore to be smelted.

[0010] According to an embodiment of the present disclosure, the gasifying agent includes at least one of air, oxygen-enriched air, and water vapor; the volume content of oxygen in the mixed gas of the gasifying agent and the first flue gas is 13%-50%; the temperature of the gas fuel is 250-900°C, and the calorific value is ≥1000kcal / m 3 .

[0011] According to an embodiment of the present disclosure, the rotary kiln is divided into a kiln head area, a kiln body area and a kiln tail area, and there are N kiln body areas, where N≥1.

[0012] According to an embodiment of the present disclosure, introducing a combustion-supporting agent into a rotary kiln for combustion reaction includes: introducing the combustion-supporting agent into the rotary kiln all at once for combustion reaction; or introducing the combustion-supporting agent into the kiln head area, the kiln body area and the kiln tail area in stages for staged combustion reaction. The combustion-supporting agent is a mixed gas of CO2 or the first flue gas and an oxidant, and the oxidant is air, oxygen or oxygen-enriched air; the volume content of oxygen in the combustion-supporting agent is 15%-50%.

[0013] According to the embodiments of the present disclosure, combustion aids are introduced into the kiln head area, the kiln body area and the kiln tail area respectively to carry out staged combustion reaction, including: introducing a first combustion aid into the kiln head area so that the first combustion aid and part of the gas fuel carry out 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 reducing gas that is not oxidized in the gas fuel, the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, and the CO2 in the combustion aid reacting with the unconverted carbon to carry out reduction roasting of the dry ore to be smelted; introducing a second combustion aid into N kiln body areas respectively so that the second combustion aid and the remaining part of the gas fuel carry out 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 reducing gas that is not oxidized in the gas fuel, the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, and the CO2 generated by the reaction of the unconverted carbon and the unconverted carbon are used for reduction roasting of the dry ore to be smelted; The gas fuel and unconverted carbon undergo a second combustion reaction in N kiln body areas, and under the action of the heat released by the second combustion reaction, the dry ore to be smelted is graded reduction roasted by using the remaining unconverted carbon, the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, the unoxidized reducing gas in the gas fuel, and the CO generated by the reaction of CO2 in the combustion aid with the unconverted carbon; and a third combustion aid is introduced into the kiln tail area so that the third combustion aid, the unconverted carbon remaining in the rotary kiln and the combustible gas in the gas fuel 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 to be smelted.

[0014] According to an embodiment of the present disclosure, the first combustion aid, the second combustion aid and the third combustion aid are a mixed gas of CO2 or the first flue gas and an oxidant, and the oxidant is air, oxygen or oxygen-enriched air; wherein the volume content of oxygen in the first combustion aid, the second combustion aid and the third combustion aid is respectively 15%-50%.

[0015] As a second aspect of the present disclosure, a metallurgical reduction roasting system that is conducive to CO2 capture is provided, including: a gasifier, a rotary kiln, a drying kiln connected in sequence, and a first pipeline for passing the first flue gas in the drying kiln into the gasifier.

[0016] The gasifier is used for gasifying solid fuel, gasifying agent and first flue gas from a drying kiln to obtain unconverted carbon and gas fuel with reducing properties.

[0017] The rotary kiln is used for the combustion reaction of unconverted carbon, gas fuel and combustion-supporting agent introduced into the rotary kiln, and under the action of the heat released by the combustion reaction, the unconverted carbon, the reducing gas in the gas fuel that is not oxidized, the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, and the CO generated by the reaction of CO2 in the combustion-supporting agent with the unconverted carbon are used to reduce and roast the dry ore to be smelted introduced into the rotary kiln to obtain hot roasted sand and hot flue gas.

[0018] The drying kiln is used for heat exchange between hot flue gas and wet ore to be smelted introduced into the drying kiln to obtain dry ore to be smelted and first flue gas; wherein the first flue gas includes CO2, and the reducing gas fuel includes CH4, CO and H2.

[0019] According to an embodiment of the present disclosure, the rotary kiln is divided into a kiln head area, a kiln body area and a kiln tail area, and there are N kiln body areas, N≥1; the above-mentioned metallurgical reduction roasting system that is conducive to CO2 capture also includes one or more air distribution units.

[0020] When there is one air distribution unit, an air distribution unit is arranged in the kiln head area for introducing a combustion aid; or when there are multiple air distribution units, air distribution units are arranged axially and radially from the kiln head area to the kiln tail area; wherein, an air distribution unit is arranged in the kiln head area for introducing a first combustion aid; air distribution units are arranged in N kiln body areas for introducing a second combustion aid in stages; and an air distribution unit is arranged in the kiln tail area for introducing a third combustion aid.

[0021] According to an embodiment of the present disclosure, a bypass is provided on the first pipeline, and the bypass is connected to the air distribution unit and is used to pass the first flue gas into the air distribution unit; wherein, there are one or more bypasses.

[0022] Based on the above technical solution, the metallurgical reduction roasting method and system for CO2 capture provided by the present disclosure has at least one of the following beneficial effects:

[0023] (1) In the embodiment of the present disclosure, solid fuel, gasifying agent and first flue gas are introduced into a gasifier for gasification reaction. On the one hand, the solid fuel is gasified into reducing gas fuel and unconverted carbon by using the gasifying agent and the first flue gas (including CO2 gas), which can expand the adaptability of solid fuel and the range of selectable solid fuels; on the other hand, by adjusting the CO2 content and carbon conversion rate in the mixed gas of the gasifying agent and the first flue gas, the reduction reaction of CO2 and carbon in the solid fuel is fully utilized to prepare unconverted carbon and gas fuel rich in CO gas, which can effectively solve the CO2 gas emission problem in the metallurgical industry and realize the regulation of flame length, temperature and reducing gas distribution in the rotary kiln. Subsequently, the unconverted carbon and gas fuel rich in CO gas are introduced into the rotary kiln. Through the regulation of combustion organization, the uniformity of combustion, reducing atmosphere and temperature distribution in the rotary kiln is improved, and the combustion efficiency is high and easy to control, thereby effectively improving the pre-reduction rate of metal oxides in the dry ore to be smelted in the rotary kiln.

[0024] (2) In the embodiment of the present disclosure, the combustion aid is introduced in stages from the kiln head area to the kiln tail area of ​​the rotary kiln, and the gas fuel introduced into the rotary kiln is burned in stages and zones to avoid the reducing gas in the gas fuel entering the rotary kiln from the kiln head area being completely consumed in the kiln head area, so as to achieve the control of the temperature, reaction atmosphere and reduction reaction of the kiln head area, kiln body area and kiln tail area of ​​the rotary kiln, thereby enhancing the reduction roasting effect of the rotary kiln on metal oxides. The staged introduction of the combustion aid can also reduce the amount of the combustion aid in the kiln head area, which is conducive to controlling the temperature in the kiln head area and preventing ringing, and there is no need to introduce excessive air to reduce the temperature in the kiln head area.

[0025] (3) In the embodiments of the present disclosure, a first flue gas containing CO2 and a combustion-supporting agent consisting of an oxidant (such as air or oxygen) are introduced into a rotary kiln. While reducing CO2 emissions, the CO gas generated by the CO2 reduction reaction in the rotary kiln can be controlled to reduce and roast the metal oxides in the kiln, thereby realizing the recycling of the first flue gas and achieving carbon enrichment, which is beneficial to the capture and utilization of CO2. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the metallurgical reduction roasting principle that is beneficial to CO2 capture in the embodiments of the present disclosure;

[0027] Figure 2 Schematic diagram of the metallurgical reduction roasting principle based on hierarchical control for CO2 capture in the embodiments of the present disclosure. DETAILED DESCRIPTION

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] In the process of implementing the inventive concept disclosed in the present invention, it is found that in the existing RKEF process, coal powder is used as fuel, and coal powder and air are burned through the kiln head burner. The temperature in the kiln head area is the highest, and it is necessary to control the amount of coal powder and air injected to control the temperature of the kiln head to prevent ringing. The temperature from the kiln head to the kiln tail decreases spontaneously through reactions such as heat absorption and heat dissipation. There is no control method, which affects the roasting effect, increases the residence time required for roasting, and indirectly increases the length of the rotary kiln. In addition, in the rotary kiln, coal powder is sprayed into the rotary kiln as fuel through the burner, and the combustion uniformity is poor, which affects the temperature in the kiln and the distribution of the reducing atmosphere; in order to ensure the combustion efficiency, a large amount of combustion-supporting air is required, resulting in an oxidizing atmosphere in the rotary kiln, and the pre-reduction rate of the metal oxides entering the rotary kiln is close to 0, which leads to the reduction smelting of the metal oxides mainly relying on the downstream ore-fired furnace, and the overall system energy consumption is high. In addition, the CO2 gas emissions generated by metallurgy cannot be effectively utilized, resulting in energy waste and increasing the environmental burden.

[0033] In this regard, the present disclosure proposes a hot gas fuel process based on the RKEF process, which first introduces solid fuel, gasifying agent and first flue gas into a gasifier, and obtains reducing unconverted carbon and CO-rich gas fuel by regulating the concentration of CO2 in the gasifier, thereby broadening the adaptability and optional range of solid fuels; the unconverted carbon and gas fuel are then introduced into a rotary kiln, which can solve the problems of uneven and uncontrollable distribution of fuel, reaction atmosphere and temperature in the rotary kiln, and can also utilize the high temperature environment (900-1100°C) in the rotary kiln to react the CO2 gas introduced into the rotary kiln with the unconverted carbon to reduce it to CO, thereby reducing CO2 emissions while strengthening the pre-reduction of metal oxides in the rotary kiln.

[0034] Figure 1 Schematic diagram of the metallurgical reduction roasting principle that is beneficial to CO2 capture in one embodiment of the present disclosure.

[0035] like Figure 1 As shown, the first embodiment of the present disclosure, a metallurgical reduction roasting method that is conducive to CO2 capture includes: passing solid fuel, gasifying agent and first flue gas from a drying kiln into a gasifier for gasification reaction to obtain reducing unconverted carbon and gas fuel; passing unconverted carbon, gas fuel, dry ore to be smelted and combustion aid into a rotary kiln so that the unconverted carbon, gas fuel and combustion aid undergo combustion reaction in the rotary kiln, and under the action of heat released by the combustion reaction, the dry ore to be smelted is reduction roasted by utilizing the unconverted carbon, the unoxidized reducing gas in the gas fuel, the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, and the CO2 in the combustion aid and the CO generated by the reaction of the unconverted carbon with the unconverted carbon to obtain hot roasted sand and hot flue gas; and passing the hot flue gas and the wet ore to be smelted into the drying kiln for heat exchange to obtain the dry ore to be smelted and the first flue gas; wherein the first flue gas includes CO2, and the reducing gas fuel includes CH4, CO and H2.

[0036] In the first embodiment of the present disclosure, the solid fuel is first introduced into the gasifier for gasification and then introduced into the rotary kiln to participate in the reduction roasting reaction. The advantages are that, on the one hand, the adaptability of the solid fuel and the selectable range of the solid fuel can be expanded, for example, raw materials with high water content and poor grindability can be selected; on the other hand, the solid fuel, the gasifying agent and the first flue gas are in the gasifier, and the carbon conversion rate in the gasifier is regulated by regulating the content of CO2 in the gasifier to ensure that there are unconverted carbon (i.e., unconverted solid fuel) with reducing properties and gas fuel rich in CO gas (including CO, CH4 and H2) in the gasifier after the gasification reaction. The solid fuel is converted into gas fuel through the gasification reaction of the gasifier and then introduced into the rotary kiln. The combustion effect of the gas fuel is higher than that of the solid fuel and the combustion organization is easy to control, which can effectively reduce the excess air coefficient in the rotary kiln and reduce heat loss. In the rotary kiln, the gas fuel and the combustion aid (including CO2) undergo a combustion reaction to release heat, and at the same time, the unconverted carbon undergoes a reduction reaction with the CO2 gas in the combustion aid to release CO gas. At the same time, under the action of the heat released by the combustion reaction in the kiln, the unoxidized reducing gas (such as CO and H2) in the gas fuel, the unconverted carbon, the reducing gas (such as CO gas) generated by the under-oxygen combustion of the unconverted carbon, and the CO generated by the reaction of CO2 in the combustion aid with the unconverted carbon are used to pre-reduce the metal oxides in the dry ore to be smelted in the rotary kiln, and obtain hot roasted sand and hot flue gas. Finally, the hot flue gas is passed into the drying kiln, and the waste heat of the hot flue gas is used to dry the wet ore to be smelted in the drying kiln, and the first flue gas and the dry ore to be smelted are obtained, realizing the utilization of the energy in the hot flue gas. The obtained first flue gas can be circulated to the gasifier to reduce the emission of CO2 gas in the system.

[0037] According to the first embodiment of the present disclosure, the solid fuel includes carbon-containing fuels such as coal and biomass, or a mixed fuel of coal and biomass. The gasifying agent includes at least one of air, oxygen-enriched air, and water vapor, and the first flue gas includes CO2, and the gas entering the gasifier is a mixed gas of the gasifying agent and the first flue gas (CO2). In other words, the mixed gas entering the gasifier can be a mixed gas of the first flue gas and air, the first flue gas and oxygen, or the first flue gas, oxygen and water vapor. By controlling the CO2 content in the mixed gas of the gasifying agent and the first flue gas in the gasifier, and then controlling the CO content in the gas fuel, the gasification reaction temperature in the gasifier is controlled at 600-1000°C. Furthermore, considering the stability of the operation of the gasifier and the effective conversion rate of CO2 in the gasifier, the volume content of oxygen in the mixed gas of the gasifying agent and the first flue gas is controlled at 13%-50%.

[0038] The solid fuel, gasifying agent and first flue gas undergo gasification reaction in the gasifier to produce reducing gas fuel including CH4, CO and H2, as well as some unconverted carbon. In order to ensure that the gas fuel is easy to ignite after entering the rotary kiln, it is preferred to control the temperature of the gas fuel to 250-900°C; the calorific value of the gas fuel is not less than 1000kcal / m 3 To ensure that the gas fuel can burn stably after entering the rotary kiln.

[0039] In the embodiments of the present disclosure, the dry ore to be smelted includes dry laterite nickel ore. The method provided in the present disclosure is suitable for smelting laterite nickel ore and improving the recovery rate of nickel iron in laterite nickel ore.

[0040] According to an embodiment of the present disclosure, the wet ore to be smelted is mixed with a solid reducing agent, and the solid reducing agent partially participates in combustion, oxygen-deficient combustion, and reduction roasting of the dry ore to be smelted.

[0041] According to the first embodiment of the present disclosure, introducing the combustion aid into the rotary kiln for combustion reaction includes: introducing the combustion aid into the rotary kiln all at once for combustion reaction, wherein the rotary kiln is divided into a kiln head area, a kiln body area and a kiln tail area, wherein the kiln body areas are N, and N≥1.

[0042] For example: a combustion aid is introduced into the kiln head area all at once for combustion reaction, so that the gas fuel, unconverted carbon and the combustion aid can undergo combustion reaction in the rotary kiln, and under the action of the heat released by the combustion reaction, the unconverted carbon, the unoxidized reducing gas (such as CO, H2 gas) in the gas fuel, the reducing gas (CO gas) generated by the oxygen-deficient combustion of the unconverted carbon, the CO2 in the combustion aid and the CO generated by the reaction of the unconverted carbon are used to reduce roast the dry ore to be smelted, and hot roasted sand and hot flue gas are obtained; wherein the combustion aid is a mixed gas of CO2 and an oxidant (i.e., air, oxygen-enriched air or oxygen), and the volume content of oxygen in the combustion aid introduced all at once into the kiln head area is 15%-50%. It can be understood as: utilizing the difference in reaction rates between gas fuel and unconverted carbon in the rotary kiln, the air or oxygen in the combustion aid first reacts with the combustible gas (such as CH4) in the gas fuel to release CO2 gas and heat, and at the same time, under the action of this heat, part of the unconverted carbon in the rotary kiln can react with the CO2 gas in the combustion aid and / or the generated CO2 gas to generate CO gas; or the unconverted carbon burns under oxygen to generate CO gas. Furthermore, the CO gas generated by the under-oxygen combustion of the unconverted carbon, the unoxidized CO gas in the gas fuel, and the CO and unconverted carbon generated by the reaction of CO2 in the combustion aid with the unconverted carbon can pre-reduce the metal oxides in the dry ore to be smelted in the rotary kiln, thereby obtaining hot roasted sand and hot flue gas.

[0043] In the first embodiment of the present disclosure, in order to control the amount of combustion-supporting agent entering the rotary kiln, 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 to be close to 0 kPa (gauge pressure). The speed at which the combustion-supporting agent enters the rotary kiln is ≥15 m / s. At this speed, the dry ore to be smelted in the rotary kiln can be fluidized and stirred, and the mixing of the dry ore to be smelted with the reducing gas in the rotary kiln can be enhanced, thereby enhancing the pre-reduction effect of the reducing gas on the metal oxides in the dry ore to be smelted.

[0044] The second embodiment of the present disclosure is different from the first embodiment in that the first flue gas is used to partially or completely replace the CO2 gas in the combustion-supporting agent to form a combustion-supporting agent composed of the first flue gas and air, oxygen-enriched air or oxygen (i.e., oxidant), wherein the volume content of oxygen in the combustion-supporting agent is 15%-50%. Subsequently, the combustion-supporting agent composed of the first flue gas and air, oxygen-enriched air or oxygen is introduced into the kiln head area all at once, so that the gas fuel, unconverted carbon and the combustion-supporting agent (including the first flue gas) are burned in the rotary kiln to release heat and CO gas, and at the same time, under the action of the heat released by the combustion reaction, the unconverted carbon, the unoxidized reducing gas (such as CO and H2) in the gas fuel and the generated CO gas (including the reducing gas generated by the unconverted carbon under-oxygen combustion, and the CO generated by the reaction of CO2 in the combustion-supporting agent and the unconverted carbon) are used to reduce roast the dry ore to be smelted, so as to obtain hot roasted sand and hot flue gas. The reaction process of the gas fuel, unconverted carbon and combustion aid (including the first flue gas) in the rotary kiln in the second embodiment is the same as the reaction process in the first embodiment, the only difference being that the CO2 gas contained in the first flue gas is used for the reaction.

[0045] In the first and second embodiments of the present disclosure, the combustion-supporting agent is introduced into the kiln head area of ​​the rotary kiln at one time, which easily leads to the complete consumption of the reducing gas entering the rotary kiln at the kiln head, resulting in uneven distribution of temperature and reducing atmosphere in the rotary kiln, thus affecting the pre-reduction effect of the rotary kiln. Therefore, the present disclosure provides a metallurgical reduction roasting method based on hierarchical control to facilitate CO2 capture.

[0046] Figure 2 Schematic diagram of the metallurgical reduction roasting principle based on hierarchical control for CO2 capture in the embodiments of the present disclosure.

[0047] The third embodiment of the present disclosure adopts the same metallurgical kiln reduction roasting method as the first and second embodiments, except that the third embodiment has a different method for introducing the combustion aid into the rotary kiln. That is, introducing the combustion aid into the rotary kiln for combustion reaction includes: introducing the combustion aid into the kiln head area, the kiln body area and the kiln tail area in stages for staged combustion reaction (such as Figure 2 as shown).

[0048] Specifically, the step of introducing combustion aids into the kiln head area, the kiln body area and the kiln tail area respectively for staged combustion reaction comprises: introducing a first combustion aid into the kiln head area so that the first combustion aid and a part of the gas fuel undergo a first combustion reaction, and under the action of the heat released by the first combustion reaction, utilizing the reducing gas (such as CO gas) generated by the oxygen-deficient combustion of unconverted carbon, a part of the unconverted carbon, the reducing gas in the gas fuel that is not oxidized, and the CO generated by the reaction of CO2 in the combustion aid and the unconverted carbon to carry out reduction roasting on the dry ore to be smelted; introducing a second combustion aid into N kiln body areas respectively so that the second combustion aid, the reducing gas generated by the oxygen-deficient combustion of the remaining part of the gas fuel and the unconverted carbon undergo a second combustion reaction in the N kiln body areas, and under the action of the heat released by the second combustion reaction, utilizing the remaining part The unoxidized reducing gas, unconverted carbon, unoxidized reducing gas in the unconverted carbon (such as CO, H2 gas, etc.) in the gas fuel, and CO generated by the reaction of CO2 in the combustion aid with the unconverted carbon are used to perform graded reduction roasting on the dry ore to be smelted; and a third combustion aid is introduced into the kiln tail area so that the third combustion aid and the unconverted carbon remaining in the rotary kiln and the combustible gas (such as CH4) in the gas fuel 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 to be smelted; wherein the first combustion aid, the second combustion aid and the third combustion aid are mixed gases of CO2 and an oxidant (i.e., air, oxygen or oxygen-enriched air), and the volume content of oxygen in the first combustion aid, the second combustion aid and the third combustion aid is 15%-50%, preferably 20%-40%.

[0049] In the third embodiment of the present disclosure, by utilizing the difference in reaction rates between gas fuel and unconverted carbon in the rotary kiln, the first combustion aid is introduced into the kiln head area, so that part of the combustible gas (such as CH4) in the gas fuel can be burned, and the heat released makes the kiln head area reach the required reduction roasting temperature, while the reducing gas and unconverted carbon in the unburned gas fuel keep the kiln head area in a reducing atmosphere. During the combustion reaction, the unconverted carbon can undergo a reduction reaction with the CO2 gas in the first combustion aid to release CO gas, and then under the action of the heat released by the first combustion reaction, the CO gas generated by the oxygen-deficient combustion of the unconverted carbon, part of the unconverted carbon, the unoxidized reducing gas (CO gas, H2) in the gas fuel, and the CO generated by the reaction of CO2 in the combustion aid with the unconverted carbon are used to perform reduction roasting on the dry ore to be smelted, thereby achieving the pre-reduction of the metal oxides in the dry ore to be smelted. As the endothermic reduction reaction of the metal oxide proceeds and the kiln body area dissipates heat, the temperature in the rotary kiln gradually decreases. From the kiln head area to the kiln tail area of ​​the rotary kiln, to the position where the second combustion-supporting agent is fed to the kiln body area (i.e., the next level), the freshly fed second combustion-supporting agent undergoes a second combustion reaction with the remaining gas fuel and unconverted carbon in the rotary kiln. The heat released by the second combustion reaction raises the temperature in the rotary kiln again, providing the required high-temperature environment for the reduction roasting reaction of the metal oxide. During the second combustion reaction, the unconverted carbon in the rotary kiln may also undergo a reduction reaction with CO2 gas to release CO gas, and the unconverted carbon may also undergo a water-gas reaction with H2 generated by roasting the dry ore to be smelted to release CO gas and H2 gas. Then, under the high-temperature environment of the kiln body area, the unconverted carbon, the unoxidized reducing gas (such as CO, H2) in the gas fuel, and the CO gas and H2 gas generated by the CO2 reduction reaction and the water-gas reaction can be used to pre-reduce the metal oxides in the dry ore to be smelted in the kiln body area. In this way, the second combustion-supporting agent is introduced in stages, and a multi-stage reduction roasting reaction is carried out in the kiln body area, so that the metal oxides in the kiln body area are graded reduced, which helps to improve the metal recovery rate and reduction rate. When it reaches the vicinity of the kiln tail area, the combustible gas (such as CH4) in the gas fuel in the rotary kiln is basically consumed. Due to the difference in the reaction rate of the gas fuel and the unconverted carbon, some unconverted carbon and combustible gas in the gas fuel may remain in the kiln tail area at this time. At this time, the third combustion aid is introduced to react with the unconverted carbon and gas fuel remaining in the rotary kiln for combustion. At the same time, the heat released by the third combustion reaction is used to roast the dry ore to be smelted to obtain hot roasted sand and hot flue gas. As the roasting reaction of the dry ore to be smelted absorbs heat, the temperature in the kiln tail area gradually decreases. Despite this, the hot flue gas in the kiln tail area still has a certain amount of waste heat. It is introduced into the drying kiln and heat-exchanged with the wet ore to be smelted (such as laterite nickel wet ore) introduced into the drying kiln to obtain the dry ore to be smelted and the first flue gas, thereby realizing the utilization of the waste heat of the hot flue gas.The exhausted first flue gas can be circulated to the gasifier and / or rotary kiln again for reaction, thereby reducing the emission of CO2 gas in the first flue gas and realizing the resource utilization of CO2.

[0050] In addition, the combustion-supporting agent is introduced into the rotary kiln head area and the kiln tail area in stages. On the one hand, it prevents the reducing gas in the gas fuel entering the rotary kiln from the kiln head area from being completely consumed in the kiln head area, thereby realizing the wide distribution of the reducing atmosphere in the rotary kiln, which helps to strengthen the reduction of the dry ore to be smelted by the reducing gas in the gas fuel; on the other hand, it reduces the amount of the combustion-supporting agent in the kiln head area, which is conducive to controlling the reduction roasting temperature (950-1100℃) in the kiln head area, and there is no need to introduce excessive air to reduce the temperature in the kiln head area. The staged introduction of the combustion-supporting agent can also improve the uniformity of the temperature and reducing atmosphere distribution in the rotary kiln, which can effectively shorten the time required for reduction roasting and make it possible to shorten the length of the reduction roasting kiln.

[0051] The basis for the amount of combustion aid introduced from the kiln head area to the kiln tail area is: (1) the temperature in the rotary kiln should not be higher than the temperature required for safe and stable operation, and at the same time meet the reduction roasting requirements; (2) the kiln head area needs to be a reducing atmosphere, and the combustion aid is introduced in stages from the kiln head area to the kiln tail area. The combustible gas in the gas fuel in the rotary kiln is gradually consumed, and the reducing gas in the rotary kiln is gradually reduced.

[0052] According to the third 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 volume content of oxygen in the first combustion aid is 15%-35%, the volume content of oxygen in the second combustion aid is 21%-50%, and the volume content of oxygen in the third combustion aid is 21%-50%. The speed at which the second combustion aid and the third combustion aid are introduced into the rotary kiln is ≥15m / s. At this speed, the dry ore to be smelted in the rotary kiln can be fluidized and stirred, and the mixing with the reducing gas in the rotary kiln can be strengthened, thereby strengthening the reducing effect of the reducing gas on the metal oxides in the dry ore to be smelted.

[0053] The fourth embodiment of the present disclosure is different from the third embodiment in that the first flue gas is used to partially or completely replace the CO2 gas in the combustion-supporting agent to form a combustion-supporting agent composed of the first flue gas and air, oxygen or oxygen-enriched air, so as to realize the recycling of CO2 in the first flue gas and reduce the emission of CO2 gas in the first flue gas. It should be noted that the first flue gas partially or completely replaces the CO2 gas in the combustion-supporting agent and is introduced into the rotary kiln in stages, and the reaction process in the rotary kiln is the same.

[0054] As a second aspect of the present disclosure, the present disclosure also provides a metallurgical reduction roasting system that is conducive to CO2 capture, which is used to execute the metallurgical reduction roasting method that is conducive to CO2 capture in the above-mentioned embodiment.

[0055] In the first embodiment of the present disclosure, a metallurgical reduction roasting system that is conducive to CO2 capture includes: a gasifier, a rotary kiln, a drying kiln connected in sequence, and a first pipeline for passing the first flue gas in the drying kiln into the gasifier.

[0056] The gasifier is provided with a solid material inlet for solid fuel, a mixed gas inlet for gasifying agent and first flue gas, and a gas material outlet for discharging unconverted carbon and gas fuel. The gasifier is used for gasifying solid fuel, gasifying agent and first flue gas from a drying kiln to obtain unconverted carbon and gas fuel with reducing properties, wherein the first flue gas includes CO2, and the gas fuel with reducing properties includes CH4, CO and H2.

[0057] The rotary kiln includes a kiln head area, N kiln body areas (N≥1) and a kiln tail area. The kiln head area of ​​the rotary kiln is provided with a gas material inlet for gas fuel and unconverted carbon, and a roasted sand outlet for discharging hot roasted sand; the kiln tail area is provided with a dry ore inlet for the dry ore to be smelted, and a hot flue gas outlet for discharging hot flue gas; and a combustion agent inlet for the combustion agent is provided on the rotary kiln. The rotary kiln is used for the combustion reaction of unconverted carbon, gas fuel and the combustion agent introduced into 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, the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, and the CO generated by the reaction of CO2 in the combustion agent with the unconverted carbon are used to reduce and roast the dry ore to be smelted introduced into the rotary kiln to obtain hot roasted sand and hot flue gas.

[0058] The drying kiln is provided with a wet ore inlet for the wet ore to be smelted to enter, a first flue gas outlet for discharging the first flue gas, a hot flue gas inlet for the hot flue gas to enter, and a dry ore outlet for discharging the dry ore to be smelted. The drying kiln is used for the hot flue gas to exchange heat with the wet ore to be smelted introduced into the drying kiln, and obtain the dry ore to be smelted and the first flue gas.

[0059] In the first embodiment of the present disclosure, the solid fuel enters the gasifier through the solid material inlet. The gasifier and the first flue gas enter the gasifier through the mixed gas inlet. In the gasifier, the solid fuel, the gasifier and the first flue gas undergo a gasification reaction to obtain unconverted carbon and gas fuel with reducing properties. The solid fuel is converted into gas fuel by the gasifier, which broadens the range of solid fuel options. At the same time, by regulating the oxygen content in the mixed gas of the gasifier and the first flue gas, and making full use of the reduction reaction of CO2 and unconverted carbon, a gas fuel rich in CO gas is prepared. Combining the gasifier with the rotary kiln and introducing the gas fuel into the rotary kiln improves the combustion reaction, the uniformity of the reducing atmosphere and the temperature in the rotary kiln, making the combustion efficiency in the rotary kiln higher and easier to control. At the same time, the unconverted carbon and CO2 gas in the rotary kiln undergo a reduction reaction to generate CO gas. The unconverted carbon, the unoxidized reducing gas in the gas fuel, the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, and the CO generated by the reaction of the CO2 in the combustion aid with the unconverted carbon can effectively pre-reduce the metal oxides in the smelting dry ore.

[0060] According to the first embodiment of the present disclosure, the metallurgical reduction roasting system that is beneficial to CO2 capture further includes an air distribution unit, and the number of the air distribution units is one or more, wherein the air distribution unit includes air distribution holes or air distribution hoods.

[0061] In the first embodiment of the present disclosure, when there is only one air distribution unit, an air distribution unit is provided in the kiln head area for introducing a combustion aid. For example, by providing an air distribution unit in the kiln head area of ​​the rotary kiln, the combustion aid can be introduced into the kiln head area of ​​the rotary kiln through the air distribution unit at one time for combustion reaction, so that the combustion aid reacts with the gas fuel and unconverted carbon entering the kiln head area, and under the action of the heat released by the combustion reaction, the unconverted carbon, the reducing gas of the gas fuel that is not oxidized, the reducing gas (CO) generated by the oxygen-deficient combustion of the unconverted carbon, and the CO generated by the reaction of CO2 in the combustion aid with the unconverted carbon are used for reduction roasting of the dry ore to be smelted, and hot roasted sand and hot flue gas are obtained; wherein the combustion aid is a mixed gas of CO2 and an oxidant (i.e., air, oxygen or oxygen-enriched air), wherein the volume content of oxygen in the combustion aid introduced into the rotary kiln at one time is 15%-50%. The speed at which the combustion aid enters the rotary kiln is ≥15m / s. In other words, the speed at which the combustion aid leaves the air distribution hole or the air distribution hood is ≥15m / s to avoid blockage of the air distribution hole. At the same time, it plays a certain role in fluidizing and stirring the dry ore to be smelted in the rotary kiln, as well as mixing with the reducing gas, thereby strengthening the reduction of metal oxides in the dry ore to be smelted.

[0062] According to the second embodiment of the present disclosure, when there are multiple air distribution units, the following method is adopted: Figure 2The metallurgical reduction and roasting system based on hierarchical control that is conducive to CO2 capture is different from the metallurgical kiln reduction and roasting system in the first embodiment in that an air distribution unit is arranged axially and radially from the kiln head area to the kiln tail area, wherein the air distribution unit is an air distribution hole or an air distribution hood.

[0063] In the second embodiment of the present disclosure, a plurality of air distribution units are arranged in the axial and radial directions from the kiln head area to the kiln tail area of ​​the rotary kiln, and the combustion aid can be introduced into the rotary kiln in stages through the air distribution units, thereby avoiding that the reducing gas in the gas fuel entering the rotary kiln 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, which helps to strengthen the reducing atmosphere in the gas fuel, and the reduction of the CO gas generated by the reduction reaction of the unconverted carbon and CO2 gas and the unconverted carbon on the dry ore to be smelted; at the same time, reducing the amount of the combustion aid in the kiln head area is beneficial to controlling the temperature in the kiln head area.

[0064] Specifically, air distribution units are arranged in the axial and radial directions from the kiln head area to the kiln tail area, and the combustion aid is introduced in stages from the kiln head area to the kiln tail area of ​​the rotary kiln through the air distribution units to carry out a staged combustion reaction, including: air distribution units are arranged in the axial and radial directions of the kiln head area, and a first combustion aid is introduced into the kiln head area so that the first combustion aid 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, the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, and the CO generated by the reaction of CO2 in the combustion aid with the unconverted carbon are reduction roasted on the dry ore to be smelted; air distribution units are arranged in the axial and radial directions of N kiln head areas, and a second combustion aid is introduced into N kiln body areas respectively, so that the second combustion aid, the remaining part of the gas fuel and the unconverted carbon undergo a second combustion reaction in the N kiln body areas. , and under the action of the heat released by the second combustion reaction, the remaining unconverted carbon, the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, the unoxidized reducing gas in the gaseous fuel, and the CO2 in the combustion aid reacting with the unconverted carbon to perform graded reduction roasting on the dry ore to be smelted; and an air distribution unit is arranged in the axial and radial directions of the kiln tail area to introduce a third combustion aid into the kiln tail area, so that the third combustion aid and the residual unconverted carbon in the rotary kiln and the combustible gas in the gaseous fuel 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 to be smelted; wherein the first combustion aid, the second combustion aid, and the third combustion aid are mixed gases of CO2 and an oxidant (i.e., air, oxygen or oxygen-enriched air), and the volume content of oxygen in the first combustion aid, the second combustion aid, and the third combustion aid is 15%-50%, preferably 20%-40%, respectively.

[0065] In the second 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 speed at which the first combustion aid, the second combustion aid, and the third combustion aid enter the rotary kiln is ≥15 m / s.

[0066] In the third embodiment of the present disclosure, a bypass is provided on the first pipeline, and the bypass is connected to the air distribution unit, and is used to pass the first flue gas into the air distribution unit; wherein, there are one or more bypasses. Wherein, in the case where there is one bypass, the first flue gas can be mixed with oxygen, oxygen-enriched air or air and then passed into the air distribution unit. In the case where there are multiple bypasses, the multiple bypasses can be connected to the multiple air distribution units on the rotary kiln to pass the first flue gas into the kiln head area, N kiln body areas and the kiln tail area, wherein the first flue gas can be mixed with oxygen, oxygen-enriched air or air and then passed into the air distribution unit.

[0067] 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 metallurgical reduction roasting method for CO2 capture, characterized in that: The method comprises: Passing solid fuel, gasifying agent and first flue gas from a drying kiln into a gasifier for gasification reaction to obtain unconverted carbon and gas fuel with reducing properties; The unconverted carbon, the gas fuel, the dry ore to be smelted, and the combustion improver are introduced into a rotary kiln so that the unconverted carbon, the gas fuel, and the combustion improver are subjected to a combustion reaction in the rotary kiln, and under the action of the heat released by the combustion reaction, the dry ore to be smelted is reduction roasted by using the unconverted carbon, the unoxidized reducing gas in the gas fuel, the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, and the CO2 in the combustion improver and the CO generated by the reaction of the unconverted carbon to obtain hot roasted sand and hot flue gas; and Passing the hot flue gas and the wet ore to be smelted into the drying kiln for heat exchange to obtain the dry ore to be smelted and the first flue gas; Wherein, the first flue gas includes CO2, and the reducing gas fuel includes CH4, CO and H2.

2. The method according to claim 1, characterized in that The wet ore to be smelted is mixed with a solid reducing agent, and the solid reducing agent partially participates in the combustion, the oxygen-deficient combustion and the reduction roasting of the dry ore to be smelted.

3. The method according to claim 1, characterized in that: The gasifying agent includes at least one of air, oxygen-enriched air, and water vapor, and the volume content of oxygen in the mixed gas of the gasifying agent and the first flue gas is 13%-50%; The temperature of the gas fuel is 250-900°C, and the calorific value is ≥1000kcal / m 3 .

4. The method according to claim 1 or 2, characterized in that: The rotary kiln is divided into a kiln head area, a kiln body area and a kiln tail area, and the number of the kiln body areas is N, where N≥1.

5. The method according to claim 4, characterized in that The step of introducing a combustion-supporting agent into the rotary kiln for combustion reaction comprises: introducing all of the combustion-supporting agent into the rotary kiln at once for combustion reaction; or The combustion-supporting agent is introduced into the kiln head area, the kiln body area and the kiln tail area in stages to carry out staged combustion reaction; Wherein, the combustion-supporting agent is a mixed gas of CO2 or the first flue gas and an oxidant, and the oxidant is air, oxygen or oxygen-enriched air; The volume content of oxygen in the combustion-supporting agent is 15%-50%.

6. The method according to claim 5, characterized in that The step of introducing the combustion-supporting agent into the kiln head area, the kiln body area and the kiln tail area respectively for staged combustion reaction comprises: A first combustion-supporting agent is introduced into the kiln head area so that the first combustion-supporting agent 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, the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, and the CO generated by the reaction of CO2 in the combustion-supporting agent and the unconverted carbon are used to reduce roast the dry ore to be smelted; A second combustion-supporting agent is introduced into the N kiln body regions respectively, so that the second combustion-supporting agent, the remaining part of the gas fuel and the unconverted carbon undergo a second combustion reaction in the N kiln body regions, and under the action of the heat released by the second combustion reaction, the remaining part of the unconverted carbon and the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, the unoxidized reducing gas in the gas fuel, and the CO generated by the reaction of CO2 in the combustion-supporting agent and the unconverted carbon are used to perform graded reduction roasting on the dry ore to be smelted; and A third combustion aid is introduced into the kiln tail area so that the third combustion aid undergoes a third combustion reaction with the unconverted carbon remaining in the rotary kiln and the combustible gas in the gas fuel in the kiln tail area, and the dry ore to be smelted is roasted using the heat released by the third combustion reaction.

7. The method according to claim 6, characterized in that: The first combustion aid, the second combustion aid and the third combustion aid are a mixed gas of CO2 or the first flue gas and an oxidant, and the oxidant is air, oxygen or oxygen-enriched air; Among them, the volume content of oxygen in the first combustion aid, the second combustion aid and the third combustion aid is 15%-50% respectively.

8. A metallurgical reduction roasting system that is beneficial to CO2 capture, characterized in that: The system comprises: a gasifier, a rotary kiln, a drying kiln connected in sequence, and a first pipeline for passing the first flue gas in the drying kiln into the gasifier; The gasifier is used for gasifying solid fuel, gasifying agent and first flue gas from a drying kiln to obtain unconverted carbon and gas fuel with reducing properties; The rotary kiln is used for the unconverted carbon, the gas fuel and the combustion-supporting agent introduced into the rotary kiln to carry out combustion reaction, and under the action of the heat released by the combustion reaction, the unconverted carbon, the reducing gas in the gas fuel that is not oxidized, the reducing gas generated by the oxygen-deficient combustion of the unconverted carbon, and the CO2 in the combustion-supporting agent reacting with the unconverted carbon to carry out reduction roasting on the dry ore to be smelted introduced into the rotary kiln to obtain hot roasted sand and hot flue gas; The drying kiln is used for heat exchange between the hot flue gas and the wet ore to be smelted introduced into the drying kiln to obtain the dry ore to be smelted and the first flue gas; Wherein, the first flue gas includes CO2, and the reducing gas fuel includes CH4, CO and H2.

9. The system according to claim 8, characterized in that The rotary kiln is divided into a kiln head area, a kiln body area and a kiln tail area, and the number of kiln body areas is N, where N≥1; The system further includes an air distribution unit, which includes one or more air distribution units; In the case where there is one air distribution unit, the air distribution unit is arranged in the kiln head area for introducing the combustion aid; or In the case where there are multiple air distribution units, the air distribution units are arranged in the axial direction and radial direction from the kiln head area to the kiln tail area; Wherein, the air distribution unit is arranged in the kiln head area for introducing the first combustion aid; The air distribution units are arranged in N kiln body areas to introduce the second combustion-supporting agent in stages; The air distribution unit is arranged in the kiln tail area for introducing the third combustion-supporting agent.

10. The system according to claim 9, characterized in that A bypass is provided on the first pipeline, the bypass is connected to the air distribution unit, and is used to pass the first smoke into the air distribution unit; There are one or more bypasses.

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