Red mud reduction system
By combining a gasifier, a reduction reaction unit, a material collection unit, and a magnetic separation unit, red mud is reduced using raw coal gas and secondary flue gas. This solves the problems of high energy consumption and secondary pollution in existing technologies, and achieves efficient recovery of iron from red mud and effective utilization of resources.
Patent Information
- Application Number
- CN202510870635.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-26
- Publication Date
- 2025-11-18
AI Technical Summary
The existing technology for reducing iron oxide in red mud is energy-intensive and produces a lot of secondary pollution, resulting in low utilization of red mud and low treatment efficiency.
A combined system of gasifier, reduction reaction unit, material collection unit, magnetic separation unit and heat exchange unit is adopted to reduce red mud using raw coal gas and secondary flue gas. Through fluidized bed technology and magnetic separation, combined with waste heat recovery and purification treatment, the iron in red mud is efficiently recovered.
It reduces energy consumption, increases the yield and utilization rate of iron in red mud, reduces secondary pollution, and achieves efficient reduction of red mud and effective utilization of resources.
Smart Images
Figure CN120961573A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of red mud recovery, and particularly relates to a red mud reduction system. BACKGROUND
[0002] Red mud is a red-brown powder-like solid waste in the production of alumina, and with the rapid development of global alumina industry, the amount of red mud emission is also rapidly increasing. A large amount of red mud is stored in the open air, and its main pollutants have exceeded the national emission standard (Non-ferrous Metal Industry Solid Waste Pollution Control Standard GB5058-85) of China, causing serious resource waste and environmental pollution. A large amount of red mud cannot be fully and effectively utilized, and can only be stacked in a large area, occupying a large amount of land and causing serious pollution to the environment. Other red mud treatment technologies include using red mud as a filler for rubber and plastic, using red mud as a paving material, preparing unfired red mud fly ash bricks, preparing alkali slag-red mud cement, and applying red mud to cement concrete, etc. However, the composition structure of red mud is relatively complex, and most of the methods have low utilization rate of red mud, low treatment efficiency or high economic cost, and are difficult to be industrialized.
[0003] At present, in the process of recovering and treating iron oxide in red mud, the energy consumption is high, and the secondary pollution is more. SUMMARY
[0004] The application provides a red mud reduction system, which comprises:
[0005] A gasification furnace is configured to produce raw coal gas by using coal, oxygen and water vapor;
[0006] A reduction reaction device is configured to reduce initial red mud by using the raw coal gas;
[0007] The reduction reaction device is internally provided with a fluidized bed;
[0008] A material trapping device is configured to separate secondary red mud and secondary flue gas containing hydrogen from the primary flue gas discharged from the reduction reaction device;
[0009] The reduction reaction device is further configured to reduce initial red mud by using the raw coal gas and part of the secondary flue gas;
[0010] A magnetic separation device is configured to screen ferroferric oxide in the reduced red mud to obtain tertiary red mud.
[0011] Further, the material trapping device is further configured to separate part of the secondary flue gas to collect hydrogen and tertiary flue gas containing carbon dioxide, respectively.
[0012] Further, the hydrogen obtained by separating the secondary flue gas is provided to the reduction reaction device.
[0013] Further, the third-stage flue gas is provided to the gasification furnace.
[0014] Further, the reducing reaction device is provided with a fluidized bed, which can make the initial red mud in a fluidized state.
[0015] The secondary flue gas or the raw coal gas is used as a gas source for generating fluidizing gas for the fluidized bed.
[0016] Further, a waste heat recovery device is arranged upstream of the material trapping device, and is used for recovering heat of the first-stage flue gas.
[0017] Further, a first heat exchange device is arranged, which is used for preheating oxygen or steam required by the gasification furnace by using heat of the recovered first-stage flue gas.
[0018] The first heat exchange device is used for dehydrating and preheating the initial red mud by using heat of the recovered first-stage flue gas.
[0019] Further, the system further comprises a raw coal gas purification device and a second heat exchange device.
[0020] The raw coal gas purification device is used for purifying the raw coal gas produced by the gasification furnace.
[0021] The second heat exchange device is used for absorbing heat of the raw coal gas by using a heat exchange medium, so that the heat is reduced to a temperature required by the reduced red mud.
[0022] Further, the second heat exchange device is used for producing industrial steam by absorbing heat of the raw coal gas.
[0023] Further, the magnetic separation device comprises a coarse material magnetic separation device and a fine material magnetic separation device.
[0024] The coarse material magnetic separation device is arranged below the waste heat recovery device, and is used for absorbing magnetite in the red mud deposited in the waste heat recovery process.
[0025] The fine material magnetic separation device is arranged below the material trapping device, and is used for absorbing magnetite in the secondary red mud.
[0026] The above technical solutions of the present application have at least the following beneficial technical effects:
[0027] The present application uses low-calorific-value raw materials to produce raw coal gas, and uses hydrogen and carbon monoxide in the raw coal gas to reduce Fe2O3 in red mud, the reaction temperature is low, 650-750℃, the reaction time is short, the yield of iron is 70-80%, the utilization rate of hydrogen and carbon monoxide is 70-90% and 40-70%, and the phase of the reduced substance is Fe3O4 with strong magnetism. By recycling the secondary flue gas containing unreacted raw coal gas to the reduction reaction device as fluidizing gas to make the initial red mud fully react, the raw coal gas is fully utilized, the secondary flue gas is recycled to participate in the reaction, the energy consumption is reduced, and secondary pollution is reduced. BRIEF DESCRIPTION OF DRAWINGS
[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort on the basis of these drawings.
[0029] Figure 1 It is a structural diagram of a red mud reduction system in an embodiment of the present application.
[0030] Among them, Figure 1 The correspondence between the reference signs in the drawings and the component names is as follows:
[0031] 1, gasification furnace; 2, raw coal gas purification device; 3, pressure fan; 4, reduction reaction device; 5, waste heat recovery device; 6, material trapping device; 7, induced draft fan; 8, chimney; 9, fine material magnetic separation device; 10, coarse material magnetic separation device; DETAILED DESCRIPTION
[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the embodiments of the present application will be described in detail below with reference to the drawings. However, those skilled in the art can understand that in the embodiments of the present application, many technical details are proposed in order to make the readers better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed by the present application can be implemented. The division of the following embodiments is for the convenience of description, and should not constitute any limitation on the specific implementation of the present application, and the embodiments can be combined with each other and mutually quoted under the premise of not contradicting each other.
[0033] At present, in the prior art, in the process of recovering and processing iron oxide in red mud, the energy consumption is high, and there is more secondary pollution.
[0034] To solve the above problems, an embodiment of the present application provides a red mud reduction system, as shown in Figure 1 the figure, comprising:
[0035] The gasifier 1 can convert coal into raw gas by using oxygen (air, rich or pure oxygen) and water vapor; the raw coal feeding method of the gasifier 1 is divided into dry and wet methods, in order to avoid the water in the raw coal in the wet feeding method to absorb a large amount of heat, affecting the stability of the temperature rise of the gasifier 1, the dry feeding method is selected in the embodiment. The gasifier 1 can adopt the K-T gasifier 1 structure. After the raw coal is ground into coal powder and dried, it is transported into the gasifier 1 by screw feeding or pneumatic feeding. The form of the gasifier 1 is not limited to this, as long as it can produce enough coal gas required by the process. The necessary condition for the gasifier 1 is that the raw gas discharged from the gasifier 1 is not less than 850℃, so that the raw gas after purification can be maintained at above 300℃, and the temperature of the raw gas after purification is also adjustable. The temperature is maintained above 300℃ in order to maintain the temperature of the reduction reaction device 4 stable, and save the heat released by the reduction consumption of the raw gas. The main reactions and reactants involved in the gasifier 1 are shown in the following formula:
[0036] (1) Drying and pyrolysis (100-400℃): coal powder removes water, and volatile matter is split and released (such as CH4, tar, etc.).
[0037] (2) Oxidation reaction (>700℃)
[0038] Carbon and oxygen burn violently, releasing heat: C+O2→CO2 (high-temperature exothermic), providing energy for the subsequent reduction reaction.
[0039] (3) Reduction reaction (above 800℃)
[0040] C+CO2→2CO (Boudouard reaction)
[0041] C+H2O→CO+H2 (water gas reaction).
[0042] The raw gas outlet of the gasifier 1 is communicated with the raw gas inlet of the reduction reaction device 4, in the reduction reaction device 4, the raw gas can reduce the initial red mud into magnetically recyclable magnetite (Fe3O4) from the initial ferric oxide (Fe2O3); catalysts such as nickel-based catalysts can be used in the reduction process. The reduced red mud in the application is produced by the Bayer process for producing alumina, and the Fe2O3 therein is relatively high, accounting for about 50% of the total weight of the red mud.
[0043] The reduction reaction device 4 is provided with a fluidized bed, which uses fluidizing gas to blow the red mud into a fluidized state, so as to facilitate the full contact of the red mud and the crude gas and reduce the overall reaction time. Optionally, the reduction reaction device 4 is provided with a coal gas burner for burning the crude gas to maintain the temperature. The coal gas burner is isolated from the space where the red mud is reduced by the crude gas. Preferably, the reduction reaction device 4 discharges the primary flue gas containing the gas-solid mixture of the red mud, and the secondary flue gas obtained by separating the red mud from the primary flue gas can be used as the gas source for generating the fluidizing gas of the fluidized bed; or the crude gas can be used as the gas source for generating the fluidizing gas of the fluidized bed.
[0044] The primary flue gas discharged from the reduction reaction device 4 is a gas-solid mixture containing the red mud, the unreacted crude gas and the flue gas after reaction. The primary flue gas outlet of the reduction reaction device 4 is communicated with the primary flue gas inlet of the material trapping device 6, so as to separate the secondary red mud and the secondary flue gas containing hydrogen from the primary flue gas;
[0045] The reduction reaction device 4 also uses the crude gas and part of the secondary flue gas to reduce the initial red mud. Preferably, the material trapping device 6 is provided with an induced draft fan 7, which is communicated with the secondary flue gas outlet of the material trapping device 6 and the crude gas inlet of the reduction reaction device 4. By controlling the flow rate, part of the secondary flue gas is returned to the reduction reaction device 4 to continue to participate in the reduction of the red mud. The induced draft fan 7 and the fluidized bed fully mix and fluidize the crude gas and the returned secondary flue gas, and the flow rate is controlled at 1-2 m / s. The contact time of the red mud and the crude gas generated by the gasification furnace 1 can be 5-15 s. In the case of 5 s of contact, the residence time of the red mud in the reduction reaction device 4 is short, which is not conducive to the reduction of Fe2O3 in the red mud, and the reduction rate is about 60%. In the case of 15 s of contact, the residence time of the red mud in the reduction reaction device 4 is long, which is about 5% higher than that in the case of 10 s of residence time, but the reduction efficiency of Fe2O3 in the red mud is not significantly improved. The long residence time of the red mud in the reduction reaction device 4 will reduce the treatment efficiency of the red mud in the whole process and increase the energy consumption. The residence time of about 10 s can complete the reduction rate of 95%.
[0046] The magnetic separation device is used to separate the magnetite in the reduced red mud to obtain the tertiary red mud. The magnetic separation device includes a coarse material magnetic separation device 10 and a fine material magnetic separation device 9 for grading magnetic separation.
[0047] In an embodiment, the gasification furnace 1 is further provided with a gas separation device downstream of the gasification furnace, between the raw gas outlet of the gasification furnace and the pressurized air blower 3; the gas separation device separates hydrogen and carbon monoxide from part of the raw gas, and the separation method can use physical adsorption.
[0048] In an embodiment, the material trapping device 6 also separates part of the secondary flue gas, and the adsorption assembly in the material trapping device 6 separates hydrogen using physical adsorption, and collects hydrogen and the tertiary flue gas containing carbon dioxide. Alternatively, the hydrogen separated from the secondary flue gas is provided from the hydrogen outlet of the material trapping device 6 to the raw gas inlet of the reduction reaction device 4 to continue to participate in the reduction of red mud. Alternatively, the tertiary flue gas is provided from the tertiary flue gas outlet of the material trapping device 6 to the oxygen inlet (or air inlet) of the gasification furnace 1, and because the tertiary flue gas contains more carbon dioxide, the tertiary flue gas has a certain temperature and less nitrogen content compared with air, and after being transported into the gasification furnace 1, the raw coal reacts with carbon dioxide to generate carbon monoxide, and less ammonia by-products are generated.
[0049] In an embodiment, the system further comprises a waste heat recovery device 5 between the primary flue gas outlet of the reduction reaction device 4 and the primary flue gas inlet of the material trapping device 6, for recovering the heat of the primary flue gas, and the waste heat recovery device 5 comprises a heat exchange cavity and a heat exchange tube bundle arranged in the heat exchange cavity, the heat exchange cavity flows through flue gas, and the heat exchange tube bundle flows through water to form industrial steam after absorbing heat. Alternatively, the waste heat recovery device 5 is provided with a desulfurization and decarbonization component for desulfurization and denitrification treatment of the primary flue gas to reduce secondary pollution.
[0050] Preferably, during the process of recovering the heat of the primary flue gas or desulfurization and denitrification, most of the red mud is deposited, so the coarse material magnetic separation device 10 is arranged below the waste heat recovery device 5 to adsorb the magnetite in the deposited red mud during the waste heat recovery process. After coarse magnetic separation, the content of Al2O3 in the remaining red mud can be increased to 35%, and the content of Fe2O3 is reduced to 3%, and the component can be adjusted to be used as a raw material for producing high-alumina cement.
[0051] The fine material magnetic separation device 9 is arranged below the material trapping device 6 to adsorb the magnetite in the secondary red mud.
[0052] In one embodiment, the system further comprises a first heat exchange device (not shown) which can be arranged in the waste heat recovery device 5 and uses the heat of the recovered first flue gas to preheat the oxygen or steam required by the gasifier 1; the first flue gas releases heat through the shell side of the first heat exchange device; the tube side of the first heat exchange device is arranged on the oxygen pipeline or steam pipeline of the gasifier 1, and the oxygen or steam absorbs heat through the tube side of the first heat exchange device and then enters the gasifier 1. Alternatively, the first heat exchange device uses the heat of the recovered first flue gas to dehydrate and preheat the initial red mud.
[0053] In one embodiment, the system further comprises a raw gas cleaning device 2 and a second heat exchange device (not shown);
[0054] The raw gas cleaning device 2 can be arranged between the raw gas outlet of the gasifier and the pressurized air blower 3, and is used to clean the raw gas produced by the gasifier 1.
[0055] The second heat exchange device can be arranged in the raw gas cleaning device 2, and is used to absorb the heat of the raw gas by using a heat exchange medium, so that the temperature of the raw gas is reduced to the temperature required for reduction of the red mud.
[0056] Preferably, the heat exchange medium is water, and the second heat exchange device is connected to an industrial steam pipeline, and the second heat exchange device directly produces industrial steam by using the heat of the raw gas.
[0057] In an optional embodiment of the present application, the red mud produced in the Bayer process for extracting alumina has strong alkaline substances such as NaOH, CaO, NaAlO2, etc., and only a small amount of alkaline substances is converted in the process of reducing the red mud. In order to reduce the alkalinity of the red mud, the system is also provided with an alkalinity neutralizing device (not shown) for neutralizing the alkalinity of the third-stage red mud after magnetic separation by using the third-stage flue gas. The alkalinity neutralizing device can be arranged downstream of the fine material magnetic separation device 9; a conveying belt is arranged between the alkalinity neutralizing device and the fine material magnetic separation device 9, and the conveying belt is used to transport the third-stage red mud after magnetic separation to the alkalinity neutralizing device. The alkalinity neutralizing device can be a tank, and the third-stage red mud is placed in the tank. A stirring paddle is arranged in the tank for stirring; an air inlet pipe and a water inlet are arranged on one side of the tank, and an air outlet pipe is arranged on the other side of the tank; wherein one end of the air inlet pipe is located outside the tank, and this end is connected to the third-stage flue gas outlet of the material trapping device 6; the other end of the air inlet pipe is located inside the tank and close to the bottom of the tank, and can directly introduce the third-stage flue gas into the mixture of the third-stage red mud and water in the tank. One end of the air outlet pipe is located inside the tank and close to the upper part, and the other end of the air outlet pipe is located outside the tank and communicates with the chimney 8. The neutralization process is as follows: the second-stage flue gas is separated to obtain hydrogen gas, and the third-stage flue gas contains a large amount of carbon dioxide; the third-stage red mud is the remaining red mud after screening the magnetite; the third-stage flue gas is introduced into the mixed slurry of the third-stage red mud and water, and the gas-liquid-solid three-phase reaction (CO2, water and alkaline substances) is promoted by stirring; or the diffusion rate of the third-stage flue gas in the mixed slurry and the reaction rate are improved by ultrasonic waves; the process can be carried out at normal temperature and pressure, and in order to improve the reaction speed, the temperature can be increased to 60-80°C, and the pressure can be reduced to 1-3 bar.
[0058] Optionally, the flue gas recovered by the waste heat and the red mud trapping device can be discharged through the chimney 8.
[0059] It should be understood that the above specific embodiments of the present application are only used for illustrative or explanatory purposes of the principles of the present application, and do not constitute a limitation on the present application. Therefore, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present application shall be included in the protection scope of the present application. In addition, the claims attached to the present application are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.
Claims
1. A red mud reduction system, characterized in that, include: Gasifier (1), used to produce raw coal gas using coal, oxygen and steam; The reduction reaction device (4) is used to reduce the initial red mud using the raw coal gas; The reduction reaction device (4) is equipped with a fluidized bed; Material collection device (6) is used to separate secondary red mud and secondary flue gas containing hydrogen from the primary flue gas discharged from the reduction reaction device (4); The reduction reaction device (4) is also used to reduce the initial red mud using the raw coal gas and part of the secondary flue gas; A magnetic separator is used to screen the reduced red mud for ferric oxide to obtain grade III red mud.
2. The red mud reduction system according to claim 1, characterized in that, The material collection device (6) is also used to separate a portion of the secondary flue gas and collect hydrogen and tertiary flue gas containing carbon dioxide, respectively.
3. The red mud reduction system according to claim 2, characterized in that, The hydrogen obtained from the secondary flue gas separation is supplied to the reduction reaction device (4).
4. The red mud reduction system according to claim 2, characterized in that, The third-stage flue gas is supplied to the gasifier (1).
5. The red mud reduction system according to claim 1, characterized in that, The reduction reaction device (4) is equipped with a fluidized bed, which enables the initial red mud to be in a fluidized state; The secondary flue gas or the raw coal gas serves as the gas source for generating fluidizing gas in the fluidized bed.
6. The red mud reduction system according to claim 1, characterized in that, It also includes a waste heat recovery device (5), which is located upstream of the material collection device (6) for recovering the heat of the primary flue gas.
7. The red mud reduction system according to claim 6, characterized in that, It also includes a first heat exchange device for preheating the oxygen or steam required by the gasifier (1) using the heat from the recovered primary flue gas; or, It is used to dehydrate and preheat the initial red mud using the heat from the recovered primary flue gas.
8. The red mud reduction system according to claim 1, characterized in that, Also includes: Raw coal gas purification device (2) and second heat exchange device; The raw coal gas purification device (2) is used to purify the raw coal gas produced by the gasifier (1); The second heat exchange device is used to absorb the heat of the raw coal gas using a heat exchange medium, thereby reducing it to the temperature required for the reduction of red mud.
9. The red mud reduction system according to claim 8, characterized in that, The second heat exchanger is used to absorb the heat from raw coal gas to produce industrial steam.
10. The red mud reduction system according to claim 1, characterized in that, The magnetic separation device includes a coarse material magnetic separation device (10) and a fine material magnetic separation device (9); The coarse magnetic separator (10) is located below the waste heat recovery device (5) and is used to adsorb iron tetroxide in the red mud deposited during the waste heat recovery process. The fine material magnetic separator (10) is located below the material collection device (6) and is used to adsorb iron tetroxide in the secondary red mud.