A suspension calcination system and method for preparing a high-activity grey supplementary cementitious material from a clay mineral

Abstract

The application discloses a kind of clay mineral preparation high-activity gray auxiliary cementitious material suspension calcining system and method, the suspension calcining system includes suspension preheating system, suspension calcining activation system, suspension decoloring system and suspension cooling system;Material is reduced after calcination in suspension calcining activation system, and the material after reaction flows into suspension decoloring system and suspension cooling system in turn;Suspension decoloring system includes low-temperature low-oxygen reducing gas producer and reduction decoloring furnace.The application introduces the discharge of calcining furnace into low-temperature reduction furnace, and is cooled with low-oxygen content flue gas in the reduction process, both Fe2O3 in calcined product is reduced to Fe3O4 again, and the product is rapidly cooled down.Cone part of calcining furnace is arranged with biomass gasification vortex chamber, which can achieve energy-saving effect of alternative fuel, and effectively assist in controlling the color of product by using the characteristics of easy generation of reducing gas.

Description

Technical Field

[0001] This invention relates to the field of calcination and activation of clay minerals, and more particularly to a suspension calcination system and method for preparing highly active gray auxiliary cementitious materials from clay minerals. Background Technology

[0002] In the international cement industry's technology roadmap for energy conservation, emission reduction, and environmentally friendly development, the application of auxiliary cementitious materials to replace clinker is currently recognized internationally as one of the three major technological approaches to low-carbon development in the cement industry. Using low-carbon emission admixtures with cementitious or potential cementitious properties to replace high-carbon emission clinker in cement not only has a good CO2 emission reduction effect, but these cementitious admixtures also contribute positively to the final performance of cement. Materials that can be used as admixtures include blast furnace slag, fly ash, natural volcanic ash, and limestone powder. However, due to the dual limitations of the quality and availability of these industrial wastes in various countries, clinker replacement technologies either have low replacement volumes or significantly reduce cement strength after large-scale replacement. This situation hinders the further development of low-carbon cement. Looking at the overall development trend of the cement industry, the international cement market is still in a state of slight growth, with strong demand for cement in emerging markets, mainly developing countries, especially in South Asia, Central Asia, Southeast Asia, Africa, and South America. Cement production capacity and output are insufficient to meet the needs of infrastructure construction and urbanization. Limited by the lagging economic and industrial development of developing countries, the scarcity of auxiliary cementitious materials such as fly ash and mineral powder restricts the rapid growth of cement production capacity, resulting in poor cement performance and high costs. This problem urgently needs to be solved. A new type of low-carbon cement prepared by calcining and activating clay minerals, which have wide reserves and distribution globally, can not only overcome the technical bottleneck of traditional cement admixture dosage while ensuring the performance of cement concrete, significantly replacing clinker, but also greatly reducing the carbon emissions per unit of cement. The calcination and activation technology of clay minerals has broad application prospects. Existing clay calcination methods include fixed-bed kilns (such as tunnel kilns, down-draft kilns, shuttle kilns, pusher kilns, and insulated cylinders), semi-fixed-bed kilns (such as vertical kilns, rotary kilns, and multi-layer open-hearth furnaces), and fluidized-bed kilns (in the laboratory stage). Among these, using rotary kilns to calcine and activate clay is a commonly used method; however, this type of kiln suffers from problems such as high heat consumption, small processing capacity, reddish color of finished products, and difficulty in controlling product quality. Therefore, developing a low-energy-consumption clay mineral suspension calcination activation process that is adaptable to different clay minerals and has controllable activity and color can effectively solve the obstacles to its use as an auxiliary cementing material. Summary of the Invention

[0003] Objective of the Invention: To overcome the problems of high heat consumption, small scale, and difficulty in controlling the color and quality of finished products in existing clay mineral calcination and activation technologies, the objective of this invention is to provide a suspension preheating calcination cooling activation system for large-scale production of clay minerals with low heat consumption and controllable color and activity. Another objective of this invention is to provide a method for preparing activated clay using this calcination system.

[0004] Technical Solution: This invention provides a suspension calcination system for preparing highly active gray auxiliary cementitious materials from clay minerals. The suspension calcination system includes a suspension preheating system, a suspension calcination activation system, a suspension decolorization system, and a suspension cooling system. After calcination in the suspension calcination activation system, the material undergoes a reduction reaction. The reacted material then flows sequentially into the suspension decolorization system and the suspension cooling system. The suspension decolorization system includes a low-temperature, low-oxygen reducing gas generator and a reduction decolorization furnace connected to the low-temperature, low-oxygen reducing gas generator. The low-temperature, low-oxygen reducing gas generator generates low-temperature, low-oxygen reducing gas, and the reduction decolorization furnace receives the reducing gas generated by the low-temperature, low-oxygen reducing gas generator and re-reduces the material that has been reduced and re-oxidized in the suspension calcination activation system.

[0005] As a further improvement to the above scheme, the flue gas outlet of the suspension calcination activation system is connected to the flue gas inlet of the suspension preheating system, the flue gas outlet of the suspension preheating system is connected to the flue gas inlet of the suspension decolorization system, and the flue gas outlet of the suspension decolorization system is connected to the flue gas inlet of the suspension calcination activation system.

[0006] One air outlet of the suspension cooling system is connected to the air inlet of the suspension decolorization system, and the other air outlet of the suspension cooling system is connected to the flue gas inlet of the suspension decolorization system.

[0007] As a further improvement to the above solution, the suspension preheating system is used to receive and dry the material, and the dried material flows into the suspension calcination activation system;

[0008] The suspension calcination activation system is connected to the suspension preheating system and is used to receive the dried material flowing out of the suspension preheating system. The dried material undergoes a reduction reaction in the suspension calcination activation system, where the ferric iron in the clay minerals is reduced. The flue gas generated during the reduction reaction flows into the suspension preheating system to provide a heat source for drying. The material after the reaction flows into the suspension decolorization system.

[0009] The suspension decolorization system is connected to the suspension calcination activation system, the suspension preheating system and the suspension cooling system respectively. It is used to receive the material flowing out of the suspension calcination activation system and the flue gas flowing out of the suspension preheating system. The material is reduced at low temperature in the suspension decolorization system, and the Fe2O3 in the material that is oxidized again is reduced to Fe3O4 to achieve decolorization.

[0010] The suspension cooling system is connected to the suspension calcination activation system and the suspension decolorization system respectively. The suspension cooling system is used to receive the material flowing out of the suspension decolorization system and to provide low-temperature air to the suspension calcination activation system and the suspension decolorization system respectively.

[0011] As a further improvement to the above scheme, the suspension calcination activation system includes a vortex gasification furnace, a calcination furnace, a fuel injection system, and a raw material feeding device. The vortex gasification furnace is used to gasify biomass fuel to generate reducing gas. The calcination furnace is connected to the vortex gasification furnace. The raw material feeding device is connected to the feeding ports of the vortex gasification furnace and the calcination furnace respectively. The fuel injection system is located at the bottom of the vortex gasification furnace.

[0012] As a further improvement to the above scheme, the calcining furnace includes a reduction zone located above the biomass vortex gasification furnace, an oxidation zone located above the reduction zone, and the reduction zone is equipped with several ring-shaped fuel spray guns.

[0013] As a further improvement to the above scheme, the suspension calcination system includes a fifth cyclone, the flue gas outlet of the fifth cyclone is connected to the flue gas inlet of the suspension preheating system, the flue gas inlet of the fifth cyclone is connected to the flue gas outlet of the calcining furnace, the material inlet of the fifth cyclone is connected to the material outlet of the calcining furnace, and the material outlet of the fifth cyclone is connected to the material inlets of the suspension decolorization system and the suspension cooling system respectively through a tee.

[0014] As a further improvement to the above scheme, the suspension cooling system includes several stages of fluidized bed coolers and several stages of cyclone cooling devices.

[0015] As a further improvement to the above scheme, the suspension decolorization system includes a low-temperature, low-oxygen reducing gas generator and a reduction decolorization furnace.

[0016] On the other hand, the present invention provides a suspension calcination method for preparing highly active gray auxiliary cementitious materials from clay minerals, wherein the clay minerals are transported via material routes and flue gas routes to prepare highly active gray auxiliary cementitious materials.

[0017] Material route:

[0018] (1) The material enters the suspension preheating system for drying; the dried material flows into the raw material feeding device of the suspension calcination activation system.

[0019] (2) The raw material feeding device distributes the dried material to the vortex vaporization furnace and the calcining furnace. The dried material is calcined in the suspension calcination activation system and undergoes a reduction reaction in the reduction zone of the calcining furnace. The trivalent iron in the clay mineral is reduced to generate gray magnetite.

[0020] When magnetite enters the oxidation zone of the calcining furnace, some of the iron in the magnetite is re-oxidized to ferric iron, thus obtaining the calcined product.

[0021] The calcined product flows into a reduction and decolorization furnace, or the calcined product flows into a fluidized bed cooler for direct cooling;

[0022] (3) If the calcined product flows into the reduction and decolorization furnace, then low-temperature reduction and decolorization will be carried out; the discharged material will enter the fluidized bed cooler.

[0023] (4) The material is cooled in a fluidized bed cooler to obtain a gray auxiliary cementitious material;

[0024] Smoke route:

[0025] (1) Biomass fuel is gasified to produce flue gas containing reducing gases, and the air required for gasification is provided by a suspension cooling system;

[0026] (2) The flue gas enters the suspension preheating system to provide a heat source. The flue gas flows from bottom to top through the various cyclones in the suspension preheating system and then flows into the suspension decolorization system.

[0027] (3) The low-temperature low-oxygen reducing gas generator in the suspension decolorization system generates reducing gas through low-temperature oxygen-deficient gas. The low-temperature oxygen-deficient gas comes from the flue gas in the suspension preheating system and the low-temperature air in the suspension cooling system. The flue gas discharged from the suspension decolorization system flows into the calcining furnace for flue gas circulation.

[0028] Preferably, the flue gas path satisfies one or more of the following conditions:

[0029] In step (2), the flue gas temperature of the flue gas flowing into the suspension decolorization system from the suspension preheating system is 200-250℃ and the oxygen content is 1-3%.

[0030] In step (3), the reaction temperature of the low-temperature, low-oxygen reducing gas generator is 450-600℃, and the oxygen content is about 0.5% to 3%.

[0031] In step (3), the reducing gas is one or more of CO, H2 and CH4.

[0032] The principle of this invention:

[0033] It is known that in the preparation of highly active cementitious materials by suspension calcination of clay minerals, when the iron content of the clay raw material is high, the finished product often has a reddish tint. The conventional approach is to create a reducing atmosphere in the calcination furnace, so that hematite (Fe2O3) and goethite (FeO(OH)) in the clay minerals are reduced to gray magnetite Fe3O4. During the cooling stage, the calcined product is rapidly cooled to below 400°C using quenching or water cooling to minimize the amount of Fe3O4 in the product being re-oxidized by O2 in the cooling air, thereby controlling the color of the finished product. However, because Fe3O4 is inevitably re-oxidized to red Fe2O3 in the oxygen-rich zone of the calcination furnace and when it encounters the high concentration of O2 (21%) in the quenching air, the implementation effect is inevitably less than satisfactory.

[0034] Beneficial Effects: Compared with the prior art, the present invention has the following significant advantages: The present invention introduces the discharge from the calcining furnace into a low-temperature reduction furnace, and cools it with flue gas of low oxygen content (3%) during the reduction process. This not only reduces the Fe2O3 that has been re-oxidized in the calcined product back to Fe3O4, but also rapidly cools the product. Simultaneously, a biomass gasification vortex chamber is arranged in the cone section of the calcining furnace, which not only achieves the energy-saving effect of replacing fuel, but also effectively assists in controlling the color of the finished product by utilizing its characteristic of easily generating reducing gases. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0036] Figure 2 This is a schematic diagram of the suspension preheating system of the present invention.

[0037] Figure 3 This is a schematic diagram of the suspension calcination activation system of the present invention.

[0038] Figure 4 This is a schematic diagram of the suspension decolorization system of the present invention.

[0039] Figure 5 This is a schematic diagram of the suspension cooling system of the present invention.

[0040] The attached figures are labeled as follows: 1. Suspension preheating system; 11. Cyclone; 12. Connecting air duct; 13. Flip valve; 2. Suspension calcination activation system; 3. Suspension decolorization system; 4. Suspension cooling system; 21. Vortex vaporization furnace; 22. Calcination furnace; 23. Fuel injection system; 24. Raw material feeding device; 31. Low-temperature low-oxygen reducing gas generator; 32. Reduction decolorization furnace; 41. Fluidized bed cooler; C1. First cyclone; C2. Second cyclone; C3. Third cyclone; C4. Fourth cyclone; C5. Fifth cyclone; C6. Sixth cyclone; C7. Seventh cyclone; C8. Eighth cyclone. Detailed Implementation

[0041] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0042] like Figure 1 As shown, this embodiment of the invention provides a suspension calcination system for preparing highly active gray cementitious materials from clay minerals, comprising a suspension preheating system 1, a suspension calcination activation system 2, a suspension decolorization system 3, and a suspension cooling system 4. The material undergoes a reduction reaction after calcination in the suspension calcination activation system 2, and the reacted material sequentially flows into the suspension decolorization system 3 and the suspension cooling system 4. The flue gas outlet of the suspension calcination activation system 2 is connected to the flue gas inlet of the suspension preheating system 1, the flue gas outlet of the suspension preheating system 1 is connected to the flue gas inlet of the suspension decolorization system 3, and the flue gas outlet of the suspension decolorization system 3 is connected to the flue gas inlet of the suspension calcination activation system 2. One air outlet of the suspension cooling system 4 is connected to the air inlet of the suspension decolorization system 3, and the other air outlet of the suspension cooling system 4 is connected to the flue gas inlet of the suspension decolorization system 3.

[0043] like Figure 2 As shown, the suspension preheating system 1 includes several cyclones 11, each with a connecting duct 12 at its outlet and a flap valve 13 connected to the bottom of each cyclone 11. This embodiment uses five cyclones 11 as an example. Following the air inlet sequence, the fifth cyclone C5, fourth cyclone C4, third cyclone C3, second cyclone C2, and first cyclone C1 are connected sequentially. Air enters the suspension preheating system 1 through the fifth cyclone C5 and exits through the outlet of the first cyclone C1. Material enters through the outlet duct of the second cyclone C2, passes through each cyclone sequentially, and finally enters the suspension calcination activation system 2 from the bottom of the fourth cyclone C4.

[0044] like Figure 3 As shown, the suspension calcination activation system 2 includes a biomass vortex gasification furnace 21 and a calcination furnace 22 with reduction and oxidation zones, a fuel injection system 23, and a raw material feeding device 24. The vortex gasification furnace 21 is used to gasify biomass fuel to generate reducing gas. The calcination furnace 22 is connected to the vortex gasification furnace 21. The raw material feeding device 24 is connected to the feeding ports of the vortex gasification furnace 21 and the calcination furnace 22 respectively. The fuel injection system 23 is located at the bottom of the vortex gasification furnace 21.

[0045] like Figure 4 As shown, the suspension decolorization system 3 includes a low-temperature, low-oxygen reducing gas generator 31 and a reduction decolorization furnace 32.

[0046] like Figure 5As shown, the suspension cooling system 4 includes a fluidized bed cooler 41 and a three-stage cyclone cooling device. The three-stage cyclone cooling device includes a sixth cyclone C6, a seventh cyclone C7, and an eighth cyclone C8. The sixth cyclone C6 is connected to the fifth cyclone C5, the vortex vaporization furnace 21, the calcining furnace 22, the seventh cyclone C7, and the fluidized bed cooler 41, respectively. The seventh cyclone C7 is connected to the sixth cyclone C6, the low-temperature low-oxygen reducing gas generator 31, and the fluidized bed cooler 41, respectively. The eighth cyclone C8 is connected to the downstream air and the seventh cyclone C7.

[0047] Specifically, the inlet of the fifth cyclone C5 of the suspension preheating system 1 is connected to the outlet of the suspension calcination activation system 2. The discharge port of the fifth cyclone C5 of the suspension preheating system 1 is connected to the lower inlet of the low-temperature, low-oxygen reducing gas generator 31 of the suspension decolorization system 3. The discharge port of the fifth cyclone C5 of the suspension preheating system is directly connected to the inlet pipe of the sixth cyclone C6 of the suspension cooling system 4 via a three-way switch. The discharge port of the fourth cyclone C4 of the suspension preheating system 1 is connected to the feeding ports of the vortex vaporization furnace 21, the reduction zone, and the oxidation zone calcination furnace 22 of the suspension calcination activation system 2. The outlet of the first cyclone C1 of the suspension preheating system 1 is connected to the reduction decolorization furnace 32 via a duct. Preferably, the flue gas temperature at the outlet of the first cyclone C1 of the suspension preheating system 1 is 200-250℃, and the oxygen content is 1-3%.

[0048] The suspension cooling system 4 for preparing highly active gray cementitious materials from clay minerals. The suspension calcination activation system 2 includes a biomass vortex gasification furnace at the bottom, a reduction zone in the middle, and a calcination furnace 22 in the upper oxidation zone. The inlet of the biomass vortex gasification furnace 21 of the suspension calcination activation system 2 is connected to the outlet of the sixth cyclone C6 of the suspension cooling system 4. The biomass vortex gasification furnace 21 of the suspension calcination activation system 2 is connected to a biomass feeding port, which can process biomass fuel to provide a heat source and also utilize it to generate reducing gases required for partial decolorization reaction under an oxygen-deficient environment. The feeding port of the reduction zone of the suspension calcination activation system 2 is connected to the lower outlet of the fourth cyclone C4 of the suspension preheating system 1. The air inlet of the reduction zone of the suspension calcination activation system 2 is the vortex chamber air inlet. The reduction zone of the suspension calcination activation system 2 is equipped with 2-4 ring-shaped fuel spray guns. The inlet of the oxidation zone of the suspension calcination activation system 2 is connected to the upper outlet of the fourth cyclone C4 of the suspension preheating system 1. The air inlet of the oxidation zone of the suspension calcination activation system 2 is connected to the air outlet of the reduction zone and the upper outlet of the sixth cyclone C6 of the suspension cooling system 4. The oxidation zone of the suspension calcination activation system is equipped with 2-4 ring-shaped fuel spray guns. The biomass processed in the vortex chamber can be straw, fruit shells, wood chips, cocoa powder, domestic waste, etc. Preferably, the oxygen content of the gasifier is controlled at 0.5% to 1.5%.

[0049] The suspension cooling system 4 for preparing highly active gray cementitious materials from clay minerals. The suspension decolorization system 3 includes a low-temperature, low-oxygen reducing gas generator 31 and a reduction decolorization furnace 32. The outlet of the reduction decolorization furnace 32 is connected to the oxidation zone of the suspension calcination furnace. The discharge port of the reduction decolorization furnace 32 is connected to the inlet pipe of the sixth cyclone C6 of the suspension cooling system. The conical inlet pipe of the low-temperature, low-oxygen reducing gas generator 31 is connected to the outlet of the first cyclone C1 of the suspension preheating system 1 and to the outlet pipe of the seventh cyclone C7 of the suspension cooling system 4. The conical part of the low-temperature, low-oxygen reducing gas generator 3 is equipped with a fuel injection device for generating reducing gas. Preferably, the reaction temperature of the low-temperature, low-oxygen reducing gas generator 31 is about 450-600℃, and the oxygen content is about 0.5% to 3%. The reducing gas generated by the reaction in the low-temperature, low-oxygen reducing gas generator 31 is CO, H2, CH4, etc. The main reaction occurring in the reduction decolorization furnace 32 of the suspension decolorization system is the reduction of red iron oxide to gray iron(III) oxide.

[0050] The suspension cooling system 4 for preparing highly active gray cementitious materials from clay minerals comprises a first- and second-stage fluidized bed cooler 41 and a first- and third-stage cyclone cooling device. The outlet of the suspension cooling system 4 is connected to the lower part of the vortex vaporization furnace in the suspension calcination activation system 2. The fluidized bed feed inlet of the suspension cooling system 4 is connected to the outlet of the sixth cyclone C6, and the air inlet of the fluidized bed cooler is connected to the outlet of the exhaust fan of the cooling system. The fluidized bed cooler is equipped with a fluidizing fan. The fluidized bed cooler has a long gas-solid heat exchange time, good cooling effect, and can also serve as a temporary safety storage silo in case of tower material risk.

[0051] This invention provides a suspension calcination method for preparing highly active gray cementitious materials from clay minerals. Raw materials with suitable particle size and moisture content are fed into the inlet of a suspension preheating system 1 via a bucket elevator or pneumatic conveying device. The inlet is located at the outlet duct of the second cyclone C2 in the suspension preheating system 1, or the outlet duct of another cyclone can be selected based on the moisture content of the raw material. After the raw material undergoes N-stage (2-6 stages) counter-current heat exchange with the hot flue gas from the suspension calcination activation system 2 in the preheater, it is fed into different areas of the suspension calcination activation system 2 via a distribution valve from the outlet of the fourth cyclone C4 cone in the suspension preheating system 1 for calcination activation. The suspension calcination activation system 2 is equipped with a biomass vortex gasification furnace 21 and calcination furnaces 22 with reduction and oxidation zones. Biomass fuel is added from the top of the vortex gasification furnace 21, supplied by the outlet duct of the seventh cyclone C7 of the air suspension cooling system 4. In the vortex chamber, the biomass fuel generates reducing gases such as CO, H2, and C required for the reduction reaction under an oxygen-deficient environment, reducing the iron content in the raw material to gray Fe3O4. Other fuels required for calcination and decomposition are injected from 2-4 spray guns arranged in a ring in the reduction and oxidation zones of the calcination furnace. The air required for combustion in the calcination furnace and gasification chamber is also supplied by the outlet of the seventh cyclone C7 of the suspension cooling system 4, with the flow rate regulated by valves. Precise control of the material, gas, and fuel achieves a uniform temperature field within the calcination furnace, thus meeting the activation quality control requirements. After gas-solid separation by the cyclone, the material from the outlet of the suspension calcination activation system 2 enters the suspension decolorization system 3, while the flue gas enters the suspension preheating system 1 to preheat the incoming material. The suspension decolorization system 3 includes a low-temperature, low-oxygen reducing gas generator 31 and a reduction decolorization furnace 32. The low-temperature, low-oxygen reducing gas generator 31 is equipped with a fuel spray gun in its cone section. The low-temperature, oxygen-deficient gas that stimulates the combustion of fuel in an oxygen-deficient environment to generate reducing gases is mainly drawn from the flue gas (oxygen content less than 3%, water vapor content greater than 20%) at the outlet of the first cyclone C1 of the suspension preheating system 1 and the low-temperature air from the suspension cooling system 4. In the reduction decolorization furnace, the high-temperature material (700-850℃) from the suspension calcination activation system 2 and the low-temperature, reducing gases CO, H2, and CH4 generated by the reducing gas generator come into close contact to carry out the reduction reaction of Fe2O3. At this point, the Fe2O3 content of the product is almost completely converted into Fe3O4, thus completing the color control. The product is cooled to 400-600℃ during the reduction process. The material collected from the outlet of the reduction decolorization furnace in the suspension decolorization system 3 enters the outlet duct of the seventh cyclone C7 in the suspension cooling system 4 to exchange heat with the downstream air. After secondary rapid cooling of the product here, it undergoes solid-gas separation and enters the fluidized bed cooler 41 and the first to third stage cyclone cooling devices in the suspension cooling system 4. The fluidized bed cooler has a long gas-solid heat exchange time and good cooling effect, and can also serve as a safety temporary storage silo in case of tower material risk in the system.The low-temperature finished product from the fluidized bed is carried downstream by air to the second and third stage cyclone cooling units for further cooling and gas-solid separation. The solid material is then transported to the finished product storage warehouse by a zipper conveyor. At this point, the production of the highly active gray cementitious material prepared from clay minerals is complete. The gas is then discharged after passing through a bag filter dust collector to meet emission standards.

[0052] Specifically, the suspension calcination method for preparing highly active gray cementitious materials from the aforementioned clay minerals includes two routes: material and flue gas.

[0053] The material routing includes the following steps:

[0054] (1) The material enters the suspension preheating system 1 from the outlet air pipe of the second cyclone C2 or the third cyclone C3 to remove the moisture in the material and obtain dry material.

[0055] The dried material flows into the raw material feeding device 24 in the suspension calcination activation system 2 through the fourth cyclone C4;

[0056] (2) The raw material feeding device 24 distributes the dried material to the vortex gasification furnace 21 and the calcining furnace 22. The dried material is calcined in the suspension calcination activation system 2 and undergoes a reduction reaction. The hematite (Fe2O3) and goethite (FeO(OH)) in the clay minerals are reduced to generate gray magnetite Fe3O4.

[0057] Magnetite flows into reduction and decolorization furnace 32 via fifth cyclone C5, or magnetite flows into fluidized bed cooler 41 via sixth cyclone C6 for direct cooling;

[0058] The tee at the fifth cyclone C5 can be used to enter different systems depending on whether the raw material needs to be decolorized. If decolorization is required, it enters the fluidized bed cooler 41; if not, it enters the sixth cyclone C6. In addition, the decolorization depth can be adjusted by adjusting the proportion of raw materials flowing into different systems.

[0059] (3) The magnetite is subjected to low-temperature reduction and decolorization in the reduction and decolorization furnace 32, and the discharged material enters the fluidized bed cooler 41 through the seventh cyclone C7 and the sixth cyclone C6.

[0060] (4) The material is cooled in the fluidized bed cooler 41 and the cyclone cooling device.

[0061] The path of the flue gas:

[0062] (1) Biomass fuel is gasified to generate flue gas containing reducing gases. The air required for gasification is provided by the outlet duct of the seventh cyclone C7.

[0063] (2) The flue gas enters the suspension preheating system 1 through the fifth cyclone C5 to provide a heat source for the dried material. The flue gas flows into the low temperature and low oxygen reducing gas generator 31 after passing through the fifth cyclone C5, the fourth cyclone C4, the third cyclone C3, the second cyclone C2, and the first cyclone C1 in sequence.

[0064] (3) The low-temperature low-oxygen reducing gas generator 31 generates reducing gas. The low-temperature oxygen-deficient gas comes from the flue gas and low-temperature air flowing into the suspension preheating system 1 through the first cyclone C1. The low-temperature air in the fluidized bed cooler 41 flows into the bottom of the low-temperature low-oxygen reducing gas generator 31 through the seventh cyclone C7. After the flue gas in the fluidized bed cooler 41 is mixed with the flue gas flowing into the suspension preheating system 1 through the first cyclone C1, it flows into the reduction and decolorization furnace 32.

[0065] (4) The suspension cooling system 4 does not receive the flue gas generated in the suspension preheating system 1, the suspension calcination activation system 2, and the suspension decolorization system 3. After entering the fluidized bed cooler 41 of the suspension cooling system 4, the flue gas enters the inlet duct of the eighth cyclone C8 and exchanges heat with the downstream air. The product undergoes secondary rapid cooling here and then solid-gas separation.

[0066] The above embodiments provide a detailed description of the present invention. However, the content described is merely a description of the technical solution of the present invention and is not intended to limit it. It should not be considered as limiting the scope of the present invention. All improvements made in accordance with the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A suspension calcination system for preparing highly active gray auxiliary cementitious materials from clay minerals, characterized in that, The suspension calcination system includes a suspension preheating system (1), a suspension calcination activation system (2), a suspension decolorization system (3), and a suspension cooling system (4). After calcination in the suspension calcination activation system (2), the material undergoes a reduction reaction, and the reacted material flows into the suspension decolorization system (3) and the suspension cooling system (4) in sequence. The suspension decolorization system (3) includes a low-temperature low-oxygen reducing gas generator (31) and a reduction decolorization furnace (32) connected to the low-temperature low-oxygen reducing gas generator (31). The low-temperature low-oxygen reducing gas generator (31) is used to generate low-temperature low-oxygen reducing gas, and the reduction decolorization furnace (32) is used to receive the reducing gas generated by the low-temperature low-oxygen reducing gas generator (31) and reduce the material that has been re-oxidized after reduction in the suspension calcination activation system (2) again.

2. The suspension calcination system for preparing highly active gray auxiliary cementitious materials from clay minerals according to claim 1, characterized in that, The flue gas outlet of the suspension calcination activation system (2) is connected to the flue gas inlet of the suspension preheating system (1), the flue gas outlet of the suspension preheating system (1) is connected to the flue gas inlet of the suspension decolorization system (3), and the flue gas outlet of the suspension decolorization system (3) is connected to the flue gas inlet of the suspension calcination activation system (2). One air outlet of the suspension cooling system (4) is connected to the air inlet of the suspension decolorization system (3), and the other air outlet of the suspension cooling system (4) is connected to the flue gas inlet of the suspension decolorization system (3).

3. The suspension calcination system for preparing highly active gray auxiliary cementitious materials from clay minerals according to claim 1, characterized in that, The suspension preheating system (1) is used to receive and dry the material, and the dried material flows into the suspension calcination activation system (2); The suspension calcination activation system (2) is connected to the suspension preheating system (1) and is used to receive the dried material flowing out of the suspension preheating system (1). The dried material undergoes a reduction reaction in the suspension calcination activation system (2), where the ferric iron in the clay mineral is reduced. The flue gas generated during the reduction reaction flows into the suspension preheating system (1) to provide a heat source for drying. The material after the reaction flows into the suspension decolorization system (3). The suspension decolorization system (3) is connected to the suspension calcination activation system (2), the suspension preheating system (1) and the suspension cooling system (4) respectively. It is used to receive the material flowing out of the suspension calcination activation system (2) and the flue gas flowing out of the suspension preheating system (1). The material is reduced at low temperature in the suspension decolorization system (3), and the Fe2O3 that is oxidized again in the material is reduced back to Fe3O4 to achieve decolorization. The suspension cooling system (4) is connected to the suspension calcination activation system (2) and the suspension decolorization system (3) respectively. The suspension cooling system (4) is used to receive the material flowing out of the suspension decolorization system (3) and to provide low-temperature air to the suspension calcination activation system (2) and the suspension decolorization system (3) respectively.

4. The suspension calcination system for preparing highly active gray auxiliary cementitious materials from clay minerals according to claim 1, characterized in that, The suspension calcination activation system (2) includes a vortex gasification furnace (21), a calcination furnace (22), a fuel injection system (23), and a raw material feeding device (24). The vortex gasification furnace (21) is used to gasify biomass fuel to generate reducing gas. The calcination furnace (22) is connected to the vortex gasification furnace (21). The raw material feeding device (24) is connected to the feeding ports of the vortex gasification furnace (21) and the calcination furnace (22) respectively. The fuel injection system (23) is located at the bottom of the vortex gasification furnace (21).

5. The suspension calcination system for preparing highly active gray auxiliary cementitious materials from clay minerals according to claim 4, characterized in that, The calcining furnace (22) includes a reduction zone located above the vortex gasification furnace and an oxidation zone located above the reduction zone. The reduction zone is equipped with several ring-shaped fuel spray guns.

6. The suspension calcination system for preparing highly active gray auxiliary cementitious materials from clay minerals according to claim 4, characterized in that, The suspension calcination system includes a fifth cyclone C5. The flue gas outlet of the fifth cyclone C5 is connected to the flue gas inlet of the suspension preheating system (1). The flue gas inlet of the fifth cyclone C5 is connected to the flue gas outlet of the calcining furnace (22). The material inlet of the fifth cyclone C5 is connected to the material outlet of the calcining furnace (22). The material outlet of the fifth cyclone C5 is connected to the material inlets of the suspension decolorization system (3) and the suspension cooling system (4) respectively through a tee.

7. The suspension calcination system for preparing highly active gray auxiliary cementitious materials from clay minerals according to claim 1, characterized in that, The suspension cooling system (4) includes several stages of fluidized bed coolers (41) and several stages of cyclone cooling devices.

8. A suspension calcination method for preparing highly active gray auxiliary cementitious materials from clay minerals, characterized in that, Clay minerals are used to prepare highly active gray auxiliary cementitious materials via material and flue gas routes: Material route: (1) The material enters the suspension preheating system for drying; the dried material flows into the raw material feeding device of the suspension calcination activation system. (2) The raw material feeding device distributes the dried material to the vortex vaporization furnace and the calcining furnace. The dried material is calcined in the suspension calcination activation system and undergoes a reduction reaction in the reduction zone of the calcining furnace. The trivalent iron in the clay mineral is reduced to generate gray magnetite. When magnetite enters the oxidation zone of the calcining furnace, some of the iron in the magnetite is re-oxidized to ferric iron, thus obtaining the calcined product. The calcined product flows into a reduction and decolorization furnace, or the calcined product flows into a fluidized bed cooler for direct cooling; If the calcined product flows into the reduction and decolorization furnace, it undergoes low-temperature reduction and decolorization; the discharged material then enters the fluidized bed cooler. Cooling yields a gray auxiliary cementitious material; Smoke route: (1) Biomass fuel is gasified to produce flue gas containing reducing gases, and the air required for gasification is provided by a suspension cooling system; (2) The flue gas enters the suspension preheating system to provide a heat source. The flue gas flows from bottom to top through the various cyclones in the suspension preheating system and then flows into the suspension decolorization system. (3) The low-temperature low-oxygen reducing gas generator in the suspension decolorization system generates reducing gas through low-temperature oxygen-deficient gas. The low-temperature oxygen-deficient gas comes from the flue gas in the suspension preheating system and the low-temperature air in the suspension cooling system. The flue gas discharged from the suspension decolorization system flows into the calcining furnace for flue gas circulation.

9. The suspension calcination method for preparing highly active gray auxiliary cementitious materials from clay minerals according to claim 8, characterized in that, The flue gas path meets one or more of the following conditions: In step (2), the flue gas temperature of the flue gas flowing into the suspension decolorization system from the suspension preheating system is 200-250℃ and the oxygen content is 1-3%. In step (3), the reaction temperature of the low-temperature, low-oxygen reducing gas generator is 450-600℃, and the oxygen content is 0.5% to 3%. In step (3), the reducing gas is one or more of CO, H2 and CH4.

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