CN116678214A - System and method for preparing metakaolin regenerated by technological process - Google Patents
System and method for preparing metakaolin regenerated by technological process Download PDFInfo
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- CN116678214A CN116678214A CN202310511713.3A CN202310511713A CN116678214A CN 116678214 A CN116678214 A CN 116678214A CN 202310511713 A CN202310511713 A CN 202310511713A CN 116678214 A CN116678214 A CN 116678214A
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- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 title claims abstract description 103
- 238000000034 method Methods 0.000 title claims abstract description 36
- 230000008569 process Effects 0.000 title claims abstract description 25
- 238000001816 cooling Methods 0.000 claims abstract description 140
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 91
- 239000003546 flue gas Substances 0.000 claims abstract description 91
- 239000000463 material Substances 0.000 claims abstract description 69
- 239000000725 suspension Substances 0.000 claims abstract description 63
- 239000000446 fuel Substances 0.000 claims abstract description 53
- 239000002994 raw material Substances 0.000 claims abstract description 41
- 238000002360 preparation method Methods 0.000 claims abstract description 30
- 239000007789 gas Substances 0.000 claims abstract description 12
- 230000009467 reduction Effects 0.000 claims abstract description 8
- 230000003647 oxidation Effects 0.000 claims abstract description 4
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 4
- 239000002826 coolant Substances 0.000 claims description 31
- 238000001354 calcination Methods 0.000 claims description 20
- 238000002485 combustion reaction Methods 0.000 claims description 19
- 229910052760 oxygen Inorganic materials 0.000 claims description 16
- 239000001301 oxygen Substances 0.000 claims description 16
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 14
- 235000012054 meals Nutrition 0.000 claims description 12
- 238000009826 distribution Methods 0.000 claims description 11
- 239000002918 waste heat Substances 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 238000010791 quenching Methods 0.000 claims description 9
- 230000000171 quenching effect Effects 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 8
- 239000000428 dust Substances 0.000 claims description 8
- 239000000498 cooling water Substances 0.000 claims description 5
- 230000001590 oxidative effect Effects 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 238000012544 monitoring process Methods 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 13
- 238000005265 energy consumption Methods 0.000 abstract description 4
- 239000005995 Aluminium silicate Substances 0.000 description 39
- 235000012211 aluminium silicate Nutrition 0.000 description 39
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 25
- 239000004568 cement Substances 0.000 description 17
- 239000007787 solid Substances 0.000 description 16
- 239000000843 powder Substances 0.000 description 10
- 238000000926 separation method Methods 0.000 description 9
- 238000000354 decomposition reaction Methods 0.000 description 5
- 239000003921 oil Substances 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 239000000779 smoke Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 229910052595 hematite Inorganic materials 0.000 description 2
- 239000011019 hematite Substances 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- LIKBJVNGSGBSGK-UHFFFAOYSA-N iron(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Fe+3].[Fe+3] LIKBJVNGSGBSGK-UHFFFAOYSA-N 0.000 description 2
- 239000006028 limestone Substances 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 235000019738 Limestone Nutrition 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- AXCZMVOFGPJBDE-UHFFFAOYSA-L calcium dihydroxide Chemical compound [OH-].[OH-].[Ca+2] AXCZMVOFGPJBDE-UHFFFAOYSA-L 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 238000001879 gelation Methods 0.000 description 1
- 229910052598 goethite Inorganic materials 0.000 description 1
- 239000010440 gypsum Substances 0.000 description 1
- 229910052602 gypsum Inorganic materials 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
- 238000006703 hydration reaction Methods 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- AEIXRCIKZIZYPM-UHFFFAOYSA-M hydroxy(oxo)iron Chemical compound [O][Fe]O AEIXRCIKZIZYPM-UHFFFAOYSA-M 0.000 description 1
- 230000002779 inactivation Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 229910021646 siderite Inorganic materials 0.000 description 1
- 239000003469 silicate cement Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
- F27B17/00—Furnaces of a kind not covered by any preceding group
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/20—Silicates
- C01B33/36—Silicates having base-exchange properties but not having molecular sieve properties
- C01B33/38—Layered base-exchange silicates, e.g. clays, micas or alkali metal silicates of kenyaite or magadiite type
- C01B33/40—Clays
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B7/00—Hydraulic cements
- C04B7/36—Manufacture of hydraulic cements in general
- C04B7/38—Preparing or treating the raw materials individually or as batches, e.g. mixing with fuel
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B7/00—Hydraulic cements
- C04B7/36—Manufacture of hydraulic cements in general
- C04B7/43—Heat treatment, e.g. precalcining, burning, melting; Cooling
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B7/00—Hydraulic cements
- C04B7/36—Manufacture of hydraulic cements in general
- C04B7/43—Heat treatment, e.g. precalcining, burning, melting; Cooling
- C04B7/44—Burning; Melting
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D13/00—Apparatus for preheating charges; Arrangements for preheating charges
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
- F27D17/004—Systems for reclaiming waste heat
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
- F27D17/008—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases cleaning gases
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Ceramic Engineering (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Environmental & Geological Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Dispersion Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
Abstract
The invention discloses a preparation system and a preparation method of metakaolin regenerated in a process flow, wherein the preparation system comprises a suspension preheating system, a preheating furnace, a modifying furnace, a first cooling system and a second cooling system, wherein the preheating furnace is directly connected with the modifying furnace, an outlet of the modifying furnace is connected with an inlet of a final cyclone preheater, a material outlet of the final cyclone preheater is connected with a material inlet of the first cooling system, a discharge port of a penultimate cyclone preheater is connected with a raw material feeding port of the modifying furnace, no raw material feeding port is arranged on the preheating furnace, and fuel feeding ports are respectively arranged on the preheating furnace and the modifying furnace; the suspension preheating system flue gas outlet is connected with the first cooling system flue gas inlet, the first cooling system flue gas outlet is connected with the preheating furnace flue gas inlet, and the second cooling system gas outlet is connected with the middle combustion-supporting air inlet of the modifying furnace; the lower part of the preheating furnace and the modifying furnace is internally provided with a reduction zone, and the upper part of the modifying furnace is internally provided with an oxidation zone. The invention can produce metakaolin meeting the requirements of color and activity index, and has low system energy consumption.
Description
Technical Field
The invention relates to the technical field of metakaolin preparation, in particular to a metakaolin preparation system and a metakaolin preparation method regenerated by a process flow.
Background
Kaolin (Al) 2 O 3 ·2SiO 2 ·2H 2 O，AS 2 H 2 ) Is a common mineral in natural kaolin or kaolin tailings, and can generate a plurality of structural changes when heated in air, and the layered structure of the kaolin is destroyed by the removal of hydroxyl groups when heated to about 600 ℃ to form amorphous transition phase-metakaolin (Al) 2 O 3 ·2SiO 2 ，AS 2 ). Metakaolin has irregular molecular arrangement, presents thermodynamic prepositive state, has gelation property under alkali excitation, and can be matched with calcium hydroxide (Ca (OH) 2 ) The water reacts with the pozzolan to produce a hydration product similar to cement.
By utilizing the characteristics, the mixed material is prepared by calcining the kaolin containing the kaolin and the aluminum-silicon minerals with similar structures, and then the mixed material is compounded with gypsum, silicate cement clinker or limestone to prepare the calcined kaolin-based composite cement, so that the calcined kaolin-based composite cement becomes a research hot spot in the international cement and concrete industry in recent years. The clinker consumption of the cement can be reduced from 75% to 45% -50% by adopting the calcined kaolin with higher activity instead of clinker, the compressive strength of the cement for 28 days is kept not to be reduced, the flexural strength can be improved by more than 20%, and the technical targets of low clinker coefficient, low carbon emission and high strength in the cement preparation process are realized.
Because the preparation cost of the calcined kaolin is lower than that of the clinker, CO in the preparation process of the calcined kaolin 2 The emission is lower than CO in the clinker preparation process 2 The emission and the raw materials of kaolin are very widely available, and the use of calcined kaolin in the concrete and cement industries to replace clinker in large amounts has a significant competitive advantage in reducing the clinker dosage in the cement in the context of the positive advancement of carbon emission reduction in the building concrete and cement industries.
Currently, existing calcined kaolin preparation methods mainly comprise fixed bed type, semi-fixed bed type, fluidized bed type and the like. The method for preparing the calcined kaolin by adopting the rotary kiln calcination is generally adopted, but the problems of high system heat consumption, easy overburning and inactivation of products, difficult quality control and the like often exist when the rotary kiln calcination is adopted. On the other hand, kaolin materials typically contain some amount of iron, mainly in the form of goethite, hematite, siderite, and the like. The iron phase undergoes decomposition reaction during the calcination of the kaolin and finally exists in the form of red hematite, so that the calcined kaolin presents obvious red color. The direct use of red calcined kaolin to prepare cement affects the color of the finished cement product, and is easily mistaken as inferior cement by the market to affect sales. Therefore, the calcined kaolin which has high activity and consistent color with cement clinker is produced with lower energy consumption and higher efficiency by adopting reasonable process technology, and becomes the key of large-scale production and wide application of the calcined kaolin and the calcined kaolin-limestone composite cement.
Therefore, based on market demands and the key technical problems faced by the market demands, the preparation system and the preparation method of the metakaolin reconstructed by the process flow, which fully consider the requirements of the cement concrete industry on the color control and the activity index control of the calcined kaolin and solve the problems of high energy consumption, small processing capacity, difficult control of product quality and the like of the calcined kaolin preparation system, have important practical significance.
Disclosure of Invention
The invention provides a preparation system and a preparation method of metakaolin regenerated by a process flow, which can fully consider the control requirements of the cement concrete industry on the color and activity index of a metakaolin finished product, produce metakaolin meeting the control requirements of the color and activity index, and solve the problems of high energy consumption, small processing capacity, difficult control of the product quality and the like of the metakaolin preparation system.
The invention is realized in such a way that a metakaolin preparation system for reconstructing a process flow comprises a suspension preheating system, a calciner system, a first cooling system and a second cooling system, wherein the calciner system comprises a preheating furnace and a modifying furnace, the bottom of the preheating furnace is a flue gas inlet, the top outlet of the preheating furnace is directly connected with the bottom inlet of the modifying furnace, the top outlet of the modifying furnace is connected with the inlet of a final cyclone preheater of the suspension preheating system, the material outlet at the bottom of the final cyclone preheater of the suspension preheating system is connected with the material inlet of the first cooling system, the discharge port of the penultimate cyclone preheater of the suspension preheating system is connected with the raw material inlet of the modifying furnace, the preheating furnace is not provided with a raw material feeding port, and the preheating furnace and the modifying furnace are respectively provided with a fuel feeding port;
the top flue gas outlet of the suspension preheating system is connected with the flue gas inlet of the indirect heat exchanger, the flue gas outlet of the indirect heat exchanger is connected with the flue gas inlet of the first cooling system, the first cooling system is used for quenching materials to a temperature range of 300-350 ℃ and below, the flue gas outlet of the first cooling system is connected with the flue gas inlet of the preheating furnace, and the oxygen content in the flue gas discharged from the top of the suspension preheating system is 1-3%; the material outlet of the first cooling system is connected with the material inlet of the second cooling system, and the gas outlet of the second cooling system is connected with the combustion-supporting air inlet in the middle of the modifying furnace;
the interior of the middle lower part of the preheating furnace and the modifying furnace is a reduction zone, and the interior of the middle upper part of the modifying furnace is an oxidation zone.
Preferably, the modifying furnace is composed of a modifying furnace cone and a modifying furnace cylinder from bottom to top in sequence, the middle lower part of the modifying furnace cone, the modifying furnace cylinder and the middle part of the modifying furnace cylinder are respectively provided with a fuel feeding port, the fuel feeding port in the middle part of the modifying furnace cylinder is positioned above a combustion air inlet of the modifying furnace, and raw material feeding ports are respectively arranged above the fuel feeding ports of the modifying furnace.
Preferably, the preheating furnace and the modifying furnace are provided with a plurality of temperature measuring points for monitoring the temperature distribution in the preheating furnace and the modifying furnace in real time in a layered manner in the height direction, and the temperature distribution in the preheating furnace and the modifying furnace is controlled in a reasonable range by adjusting the fuel quantity fed into the preheating furnace and the fuel quantity, the raw material quantity and the combustion-supporting air quantity fed into the modifying furnace.
Preferably, the indirect heat exchanger is used for indirectly cooling the flue gas discharged by the suspension preheating system to 80-120 ℃, the bottom of the indirect heat exchanger is provided with a cooling medium inlet and a flue gas outlet, the top of the indirect heat exchanger is provided with a flue gas inlet and a cooling medium outlet, so that the flue gas and the cooling medium exchange heat in a countercurrent way, and the cooling medium channel of the indirect heat exchanger is internally communicated with the cooling medium.
Further preferably, the cooling medium of the indirect heat exchanger is cooling water, cooling oil or other suitable cooling medium.
Preferably, a flue gas circulating fan is respectively arranged between the indirect heat exchanger and the first-stage cyclone preheater of the suspension preheating system and between the indirect heat exchanger and the first cooling system.
Preferably, the gas outlet of the second cooling system is connected with the combustion air inlet in the middle of the modifying furnace through the dust collector and the combustion air circulating fan in sequence.
Preferably, the second cooling system comprises at least one stage of cyclone cooler for cooling the material to below 100 ℃.
Preferably, the flue gas outlet of the suspension preheating system and the gas outlet of the second cooling system are also connected with a drying crusher or other waste heat utilization equipment.
The method for preparing metakaolin by adopting the system comprises the steps that raw materials enter a modifying furnace after being preheated by a suspension preheating system, decomposed materials leave the modifying furnace and enter a final cyclone preheater of the suspension preheating system, and materials separated by the final cyclone preheater of the suspension preheating system enter a first cooling system; the flue gas discharged from the top of the suspension preheating system enters the first cooling system after being cooled by the indirect heat exchanger, exchanges heat with materials entering the first cooling system, and enters the preheating furnace, the gas discharged from the second cooling system enters the middle upper part of the modifying furnace for supporting combustion, and the fuel quantity fed into the preheating furnace, the fuel quantity fed into the modifying furnace, the raw meal quantity and the combustion-supporting air quantity are regulated, so that the fuel in the middle lower part of the preheating furnace and the modifying furnace is incompletely combusted to form a reducing atmosphere, and the fuel in the middle upper part of the modifying furnace is fully combusted to form an oxidizing atmosphere; the first cooling system quenches the material to a temperature range of 300-350 ℃ and below, then enters the second cooling system, and is cooled to below 100 ℃ by the second cooling system, so that the finished product of the metakaolin with controllable color is obtained.
Preferably, the calcination temperatures in the preheating furnace and the middle and lower part of the modifying furnace are 600-800 ℃, and the calcination temperature in the middle and upper part of the modifying furnace is 700-900 ℃; the residence time of the flue gas in the calciner system is 2-10 seconds.
Preferably, the excess air coefficient of the outlet of the modifying furnace is 1.05-1.2.
Preferably, the cooling medium of the first cooling system is flue gas with the temperature of 80-120 ℃ after being cooled by an indirect heat exchanger, and the oxygen content in the flue gas is 1-3%; the cooling medium of the second cooling system is normal temperature air.
The specific principle of the invention is as follows:
the key of the color control of the metakaolin finished product is calcination control and cooling control, wherein the calcination control needs to strictly control the calcination atmosphere and the calcination temperature; the cooling control requires a comprehensive control of the cooling atmosphere and the cooling temperature. In order to control the color of the finished metakaolin, the invention controls the excessive air coefficient of the outlet of the modifying furnace in the process of decomposing and forming metakaolin, thereby realizing that the oxygen content in the kiln tail flue gas of the outlet of the suspension preheating system is within the preferable oxygen content range, and considering the ideal range that the oxygen content in the kiln tail flue gas of the outlet of the suspension preheating system is 1-3%, the preheating furnace and the modifying furnace can be easily enabled by controlling the fuel consumption of the preheating furnace and the modifying furnaceThe fuel in the lower part of the furnace is incompletely combusted to form a reducing atmosphere, so that Fe in the kaolin raw material is further reduced 3+ Fully reduce to Fe 2+ The method comprises the steps of carrying out a first treatment on the surface of the Meanwhile, by supplementing a proper amount of combustion air into the middle upper part of the modifying furnace, the full burnout of fuel and the full release of heat energy can be ensured. In the cooling process of high-temperature metakaolin, the cooling atmosphere and the cooling temperature control need to be comprehensively considered. As proved by detailed experimental study, if the cooling medium of metakaolin is inert gas (such as N 2 Etc.) or low-oxygen flue gas (the oxygen concentration in the flue gas is preferably controlled to be 1-3%), and Fe in the metakaolin prepared by reduction and calcination 2+ Will not be oxidized into Fe again in the cooling link 3+ The method comprises the steps of carrying out a first treatment on the surface of the And has experimental study to verify that Fe in the metakaolin prepared by reduction calcination 2+ Is stable at 300-350deg.C and below, and will not be oxidized to Fe again even in contact with conventional air 3+ . Based on the theoretical research work, considering that the oxygen concentration in the outlet flue gas of the suspension preheating system can be controlled to be 1-3%, the suspension preheating system is a very ideal cooling medium and can be used for realizing the first-stage quenching of hot materials, the invention firstly sufficiently cools the outlet flue gas of the suspension preheating system, then cools the hot materials entering the first cooling system, and can realize the quenching of the hot materials to a temperature range of 300-350 ℃ and below through detailed theoretical calculation. The material after the first-stage quenching enters a second cooling system and is cooled to about 100 ℃ by normal-temperature air.
The key of the activity control of the metakaolin finished product is that the temperature field in the modifying furnace is uniformly controlled, a first burner is arranged in a preheating furnace, a second burner is arranged at the cone part of the modifying furnace, a third burner is arranged at the middle lower part of the modifying furnace, and a fourth burner is arranged in the middle part of the modifying furnace (more burners can be arranged according to the field condition in the actual production process), and the temperature of each area in the calcining furnace is ensured to be within the preferential calcining temperature of the calcining furnace by reasonably controlling the fuel quantity of each burner and the feeding quantity of each feeding point, so that the metakaolin is fully decomposed to form the metakaolin (i.e. the 'under-burning') and the crystallization precipitation of the metakaolin is avoided to lose activity (i.e. the 'over-burning') is avoided, so that the activity index of the metakaolin finished product meets the subsequent production requirement.
In the process, according to the material flow direction, the kaolin raw material is subjected to a raw material pretreatment procedure to obtain raw material powder meeting the production requirement. The raw meal powder is fed into a suspension preheating system after being subjected to gas-solid separation by a feeding device or a cyclone separator through a raw meal lifting machine. The suspension preheating system comprises a multi-stage cyclone preheater, a high-efficiency material scattering device, a connecting pipeline and the like. The raw meal powder is preheated and gas-solid separated in the cyclone preheater, and the raw meal powder subjected to multiple heat exchange and gas-solid separation enters the modification furnace from the discharging pipe of the second last cyclone preheater of the suspension preheating system. The calciner system comprises a high-efficiency material scattering device, a flue gas inlet pipeline, a preheating furnace, a first burner arranged on the preheating furnace, a modifying furnace, a second burner arranged on the cone part of the modifying furnace, a third burner arranged on the middle lower part of the modifying furnace cylinder, a fourth burner arranged on the middle part of the modifying furnace cylinder, a flue gas outlet pipeline and the like. The temperature distribution in the preheating furnace and the modifying furnace is monitored in real time by arranging a plurality of temperature measuring points in layers in the height direction of the preheating furnace and the modifying furnace, the temperature distribution in the preheating furnace and the modifying furnace is controlled in a reasonable range by adjusting the fuel quantity fed into the preheating furnace and the fuel quantity and the material quantity fed into the modifying furnace, the reasonable temperature distribution in the preheating furnace and the modifying furnace can ensure the full combustion of fuel and the full decomposition of kaolin, meanwhile, the kaolin is ensured not to be over-burned, and the activity index of the finished product metakaolin meets the subsequent production requirement. The fuel combustion in the calciner system releases a large amount of heat for decomposing kaolin, and the decomposed hot materials leave the modifying furnace and then enter the first cooling system after being separated from hot flue gas in the final cyclone preheater of the suspension preheating system. The first cooling system comprises one-stage or multi-stage cyclone coolers, a high-efficiency material scattering device, a connecting pipeline and the like. The hot material is cooled and gas-solid separated in a cyclone cooler of the first cooling system, and the material cooled by the first cooling system enters the second cooling system after gas-solid separation. The second cooling system comprises one-stage or multi-stage cyclone coolers, a high-efficiency material scattering device, a connecting pipeline and the like. The material is further cooled and gas-solid separated in the cyclone cooler of the second cooling system, and finally leaves from the discharging pipe of the cyclone cooler of the lowest stage of the second cooling system and fallsAnd (5) feeding the finished products into a finished product zipper machine to finally obtain the finished products meeting the requirements. According to the air flow direction, normal-temperature air enters a second cooling system, then materials entering the second cooling system are cooled, heat exchange-completed air leaves from an air outlet of the upmost cyclone cooler of the second cooling system, then metakaolin finished products contained in the air are separated into a finished product zipper machine by a dust collector, and air at an outlet of the dust collector is divided into the following two paths: the first path enters the modifying furnace to support combustion through the middle part of the modifying furnace, and the second path enters a drying crusher to dry raw materials or perform other forms of waste heat utilization. The fuel quantity entering the preheating furnace and the fuel quantity and the raw material quantity at the middle and lower parts of the modifying furnace are reasonably controlled, so that the fuel in the preheating furnace and the fuel in the middle and lower parts of the modifying furnace are incompletely combusted to form a reducing atmosphere, and Fe in the kaolin raw material is further reduced 3+ Fully reduce to Fe 2+ The method comprises the steps of carrying out a first treatment on the surface of the The fuel quantity, the raw material quantity and the combustion-supporting air quantity entering the middle and upper parts of the modifying furnace are reasonably controlled, so that the full burnout of the fuel and the full release of heat energy are ensured; the hot flue gas formed by decomposing kaolin is used for carrying out preheating and gas-solid separation on raw material powder fed into a suspension preheating system for multiple times, and finally leaves from an air outlet of the uppermost cyclone preheater of the suspension preheating system, and then is divided into the following two paths: one path of the flue gas enters an indirect heat exchanger through a flue gas circulating fan, the indirect heat exchanger sufficiently cools the flue gas by adopting cooling water, cooling oil or other applicable cooling mediums, the sufficiently cooled flue gas enters a first cooling system, then high-temperature materials entering the first cooling system are cooled, and cooled circulating flue gas leaves from an air outlet of an uppermost stage cyclone cooler of the first cooling system and then enters a preheating furnace; and the second path is fed into a drying crusher to dry the raw materials or perform other forms of waste heat utilization, and the raw materials are discharged into the atmosphere after being treated by smoke.
Compared with the prior art, the invention has the advantages and positive effects that:
1. the invention considers O in the flue gas at the outlet of the suspension preheating system 2 The concentration is easy to control to be at a lower level of 1-3%, and the indirect heat exchanger is adopted to cool the circulating flue gas to a proper temperature range, and then the circulating flue gas is used for carrying out primary quenching on high-temperature metakaolin, so that Fe in the metakaolin can be avoided 2+ Is re-oxidized to Fe by contact with an oxygen-containing cooling medium 3+ Further losing control over the color of the finished metakaolin product; meanwhile, the circulating flue gas after heat exchange is due to O 2 The concentration is lower, and a local reducing atmosphere is easy to form at the middle and lower parts of the modifying furnace, so that Fe in the kaolin raw material is reduced 3+ Fully reduce to Fe 2+ . Namely, the circulating flue gas of the invention can be simultaneously used for primary quenching of high-temperature metakaolin, and greatly reduces Fe in the metakaolin from the source 3+ The concentration effectively reduces the difficulty of controlling the color of the finished metakaolin product.
2. The invention designs a calciner system into a preheating furnace and a modifying furnace in a sectional way for preparing a metakaolin finished product with an activity index meeting the subsequent requirements. Because the decomposition reaction of the kaolin is a strong endothermic reaction, the invention adopts the preheating furnace to only feed fuel and not feed raw materials for combustion reaction with the circulating flue gas fed into the preheating furnace in consideration of the lower temperature of the circulating flue gas fed into the preheating furnace, thereby preheating the circulating flue gas to a reasonable temperature range of 800-1000 ℃ so as to be beneficial to the subsequent fuel burnout and the full decomposition work of the kaolin. Then, circulating flue gas enters a modifying furnace, fuel and raw materials are fed into the modifying furnace in multiple points (or multiple stages), combustion-supporting air is introduced into the middle upper part of a cylinder of the modifying furnace, so that a uniform temperature distribution field is created in the modifying furnace, further, the kaolin is fully decomposed to form metakaolin, and meanwhile, the metakaolin is prevented from crystallizing and precipitating to lose activity;
3. the invention sequentially sets the first cooling system and the second cooling system, and the two cooling systems have definite function positioning. Wherein, the first cooling system fully utilizes the low-oxygen flue gas at the outlet of the suspension preheating system to carry out primary cooling on the metakaolin, so as to avoid Fe in the metakaolin 2+ Is oxidized to Fe in contact with an oxygen-containing cooling medium (such as air at normal temperature) during cooling 3+ . Meanwhile, the low oxygen smoke quantity which is reasonably designed can cool the metakaolin to a safe temperature range of 300-350 ℃ and below. The second cooling system fully utilizes normal-temperature air to cool the metakaolin to about 100 ℃;
4. the suspension preheating system outlet flue gas and the second cooling system outlet air both consider full waste heat recycling, so that the system heat consumption can be effectively reduced, and the production cost is reduced.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a system flow diagram of a process flow reconstituted metakaolin preparation system provided by an embodiment of the invention.
Wherein: 1. a suspension preheating system; 1-1, a cyclone preheater; 2. a calciner system; 2-1, preheating furnace; 2-2, a modifying furnace; 3. a first cooling system; 3-1, a first cyclone cooler; 4. a second cooling system; 4-1, a second cyclone cooler; 4-2, a third cyclone cooler; 6. an indirect heat exchanger; 7. a dust collector.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the description of the present invention, it should be noted that the positional or positional relationship indicated by the terms such as "upper", "lower", "top", "bottom", "inner", "outer", etc. are based on the positional or positional relationship shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or element in question must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
Examples
Referring to fig. 1, an embodiment of the present invention provides a process flow reconstituted metakaolin preparation system, which includes a suspension preheating system 1, a calciner system 2, a first cooling system 3, and a second cooling system 4.
The suspension preheating system 1 comprises a multi-stage cyclone preheater 1-1, a high-efficiency material scattering device, a connecting pipeline and the like, wherein the cyclone preheater 1-1 of the suspension preheating system 1 has three-seven preferred stages for preheating raw materials; in this embodiment, the cyclone preheater 1-1 of the suspension preheating system 1 is preferably five stages, namely, the first, second, third, fourth and fifth cyclone preheaters. The calciner system 2 comprises a high-efficiency material scattering device, a flue gas inlet pipeline, a preheating furnace 2-1, a first burner arranged on the preheating furnace 2-1, a modifying furnace 2-2, a second burner arranged on the conical part of the modifying furnace 2-2, a third burner arranged on the middle lower part of a column body of the modifying furnace 2-2, a fourth burner arranged on the middle part of the column body of the modifying furnace 2-2, a flue gas outlet pipeline and the like. The preferred number of the cyclone cooler of the first cooling system 3 is one-four, in this embodiment, a first cyclone cooler is selected, and the first cooling system 3 includes a first cyclone cooler 3-1, a high-efficiency material scattering device, a connecting pipeline, and the like. The preferred number of the cyclone coolers of the second cooling system 4 is one-four, in this embodiment, two-stage cyclone coolers are selected, and the second cooling system 4 comprises a second cyclone cooler 4-1, a third cyclone cooler 4-2, a high-efficiency material scattering device, a connecting pipeline and the like.
The bottom of the preheating furnace 2-1 is a flue gas inlet, the top outlet of the preheating furnace 2-1 is directly connected with the bottom inlet of the modifying furnace 2-2, the top outlet of the modifying furnace 2-2 is connected with the inlet of a fifth cyclone preheater of the suspension preheating system 1, the material outlet at the bottom of the fifth cyclone preheater of the suspension preheating system 1 is connected with the material inlet of a first cyclone cooler 3-1 of a first cooling system 3, the discharge port of a fourth cyclone preheater of the suspension preheating system 1 is connected with a raw material feeding port of the modifying furnace 2-2, the raw material feeding port is not arranged on the preheating furnace 2-1, and fuel feeding ports are respectively arranged on the preheating furnace 2-1 and the modifying furnace 2-2; the middle lower parts of the preheating furnace 2-1 and the modifying furnace 2-2 are internally provided with a reduction zone, and the middle upper part of the modifying furnace 2-2 is internally provided with an oxidation zone. Specifically, the modifying furnace 2-2 is composed of a modifying furnace cone and a modifying furnace cylinder from bottom to top in sequence, fuel feeding ports are respectively arranged at the middle lower part of the modifying furnace cone and the modifying furnace cylinder and the middle part of the modifying furnace cylinder, the fuel feeding ports at the middle part of the modifying furnace cylinder are positioned above combustion air inlets of the modifying furnace 2-2, and raw material feeding ports are respectively arranged above the fuel feeding ports of the modifying furnace 2-2. The preheating furnace 2-1 and the modifying furnace 2-2 are provided with a plurality of temperature measuring points in layers in the height direction, the temperature distribution in the preheating furnace 2-1 and the modifying furnace 2-2 is controlled within a reasonable range by adjusting the fuel quantity fed into the preheating furnace 2-1 and the fuel quantity, the raw meal quantity and the combustion-supporting air quantity fed into the modifying furnace 2-2.
The top flue gas outlet of the suspension preheating system 1 is connected with the flue gas inlet of the indirect heat exchanger 6, the indirect heat exchanger 6 is used for indirectly cooling the flue gas discharged by the suspension preheating system 1 to 80-120 ℃, the bottom of the indirect heat exchanger 6 is provided with a cooling medium inlet and a flue gas outlet, the top of the indirect heat exchanger 6 is provided with a flue gas inlet and a cooling medium outlet, so that the flue gas and the cooling medium exchange heat in a countercurrent way, and the cooling medium channel of the indirect heat exchanger 6 is internally filled with the cooling medium. The cooling medium of the indirect heat exchanger 6 is cooling water, cooling oil or other suitable cooling medium.
Considering that the oxygen content in the flue gas at the outlet of the suspension preheating system 1 can be controlled to be 1-3%, the system can be used for realizing the primary quenching of hot materials in the first cooling system 3, the flue gas outlet of the indirect heat exchanger 6 is connected with the flue gas inlet of the first cooling system 3, the first cooling system 3 is used for quenching the materials to a temperature range of 300-350 ℃ and below, the flue gas outlet of the first cooling system 3 is connected with the flue gas inlet of the preheating furnace 2-1, and the flue gas after heat exchange is sent to the preheating furnace 2-1.
The material outlet of the first cooling system 3 is connected with the material inlet of the second cooling system 4, the cooling medium of the second cooling system 4 is normal-temperature air, the second cooling system 4 is used for cooling the material to below 100 ℃, and the gas outlet of the second cooling system 4 is connected with the combustion-supporting air inlet in the middle part of the modifying furnace 2-2 sequentially through the dust collector 7 and the combustion-supporting air circulating fan and is used for supporting combustion in the middle and upper parts of the modifying furnace 2-2.
The flue gas outlet of the suspension preheating system 1 and the gas outlet of the second cooling system 4 are also connected with a drying crusher for drying raw materials or connecting other waste heat utilization equipment for carrying out other forms of waste heat utilization, so that the waste heat recycling is fully considered, the heat consumption of the system can be effectively reduced, and the production cost is reduced.
The specific method for preparing metakaolin by adopting the system comprises the following steps:
raw materials enter a modifying furnace 2-2 after being preheated by a suspension preheating system 1, decomposed materials leave the modifying furnace 2-2 and enter a final cyclone preheater 1-1 of the suspension preheating system 1, and materials separated by the final cyclone preheater 1-1 of the suspension preheating system 1 enter a first cooling system 3; flue gas with oxygen content of 1-3% discharged from the top of the suspension preheating system 1 is cooled to 80-120 ℃ by an indirect heat exchanger 6 and then enters a first cooling system 3 to exchange heat with materials entering the first cooling system 3, the flue gas discharged from the first cooling system 3 enters a preheating furnace 2-1, gas discharged from a second cooling system 4 enters the upper part of a modifying furnace 2-2 to support combustion, the fuel quantity fed into the preheating furnace 2-1 and the fuel quantity, raw meal quantity and combustion-supporting air quantity fed into the modifying furnace 2-2 are regulated, so that the fuel in the middle lower part of the preheating furnace 2-1 and the modifying furnace 2-2 is incompletely combusted to form a reducing atmosphere, the calcining temperature in the preheating furnace 2-1 and the middle lower part of the modifying furnace 2-2 is 600-800 ℃, and Fe in raw materials is fed into the modifying furnace 2-2 3+ Reduction to Fe 2+ The fuel in the upper middle part of the modifying furnace 2-2 is fully burnt out to formThe calcination temperature in the middle upper part of the modifying furnace 2-2 is 700-900 ℃ in the oxidizing atmosphere, the excess air coefficient of the outlet of the modifying furnace 2-2 is 1.05-1.2, and the kaolin is ensured not to be excessively burned; the first cooling system 3 rapidly cools the decomposed hot material (metakaolin) to a temperature of 300-350 ℃ and below to enable Fe in the metakaolin 2+ The cooling element is not oxidized into Fe again 3+ The hot materials are cooled and gas-solid separated in a first cyclone cooler 3-1 of a first cooling system 3; the materials cooled by the first cooling system 3 enter the second cooling system 4, the cooling medium of the second cooling system 4 is normal-temperature air, the materials are cooled to below 100 ℃ by the second cooling system 4, cooling and gas-solid separation are further realized in the third cyclone cooler 4-2 of the second cooling system 4, and finally the materials leave from the blanking pipe of the second cyclone cooler 4-1 and fall into a finished product zipper machine, so that the finished product meeting the requirements is obtained.
According to the material flow direction, the kaolin raw material is subjected to a raw material pretreatment procedure to obtain raw material powder meeting the production requirement. The raw meal powder is fed into a suspension preheating system 1 after being subjected to gas-solid separation by a feeding device or a cyclone separator through a raw meal lifting machine. The raw meal powder is preheated and gas-solid separated in the cyclone preheater 1-1, and the raw meal powder subjected to multiple heat exchange and gas-solid separation enters the modification furnace 2-2 from the discharging pipe of the fourth cyclone preheater 1-1 of the suspension preheating system 1. The calciner system 2 comprises a high-efficiency material scattering device, a flue gas inlet pipeline, a preheating furnace 2-1, a first burner arranged on the preheating furnace 2-1, a modifying furnace 2-2, a second burner arranged on the conical part of the modifying furnace 2-2, a third burner arranged on the middle lower part of the modifying furnace 2-2, a fourth burner arranged on the middle part of the modifying furnace 2-2, a flue gas outlet pipeline and the like. The temperature distribution in the preheating furnace 2-1 and the modifying furnace 2-2 is monitored in real time by arranging a plurality of temperature measuring points in layers in the height direction of the preheating furnace 2-1 and the modifying furnace 2-2, the temperature distribution in the preheating furnace 2-1 and the modifying furnace 2-2 is controlled in a reasonable range by adjusting the fuel quantity fed into the preheating furnace 2-1 and the fuel quantity and the material quantity fed into the modifying furnace 2-2, the reasonable temperature distribution in the preheating furnace 2-1 and the modifying furnace 2-2 can ensure the adequate combustion of fuel and the adequate decomposition of kaolin, meanwhile, the kaolin is not over-burned, and the activity index of the finished product metakaolin meets the subsequent production requirement. The kaolin is decomposed by releasing a large amount of heat after combustion in the fuel in the calciner system 2, and the decomposed hot material leaves the modifying furnace 2-2 and then enters the first cooling system 3 after being separated from the hot flue gas in the fifth cyclone preheater 1-1 of the suspension preheating system 1. The hot materials are cooled and gas-solid separated in the cyclone cooler of the first cooling system 3, and the materials cooled by the first cooling system 3 enter the second cooling system 4 through the blanking pipe of the first cyclone cooler 3-1 after gas-solid separation. The material is further cooled and gas-solid separated in the third cyclone cooler 4-2 of the second cooling system 4, finally leaves from the blanking pipe of the second cyclone cooler 4-1 of the second cooling system 4 and falls into a finished product zipper machine, and finally a finished product meeting the requirement is obtained.
According to the air flow direction, normal-temperature air enters the second cooling system 4, then the materials entering the second cooling system 4 are cooled, the air subjected to heat exchange leaves from the air outlet of the third cyclone cooler 4-2 of the second cooling system 4, then the meta-kaolin finished product contained in the air is separated into a finished product zipper machine by entering the dust collector 7, and the air at the outlet of the dust collector 7 is divided into the following two paths: the first path enters the modifying furnace 2-2 through the middle upper part of the modifying furnace 2-2 to support combustion, and the second path enters a drying crusher to dry raw materials or perform other forms of waste heat utilization. The fuel quantity entering the modifying furnace 2-2 is reasonably controlled, so that the fuels in the middle lower parts of the preheating furnace 2-1 and the modifying furnace 2-2 are incompletely combusted to form a reducing atmosphere, and Fe in the kaolin raw material is further reduced 3+ Fully reduce to Fe 2+ The method comprises the steps of carrying out a first treatment on the surface of the The amount of combustion-supporting air entering the upper middle part of the modifying furnace 2-2 is reasonably controlled, so that the full burnout of fuel and the full release of heat energy are ensured, raw material powder fed into the suspension preheating system 1 is preheated for multiple times and subjected to gas-solid separation, and finally leaves from the air outlet of the first cyclone preheater 1-1 of the suspension preheating system 1, and then is divided into the following two paths: one path of the flue gas enters the indirect heat exchanger 6 through a circulating fan, the circulating flue gas is fully cooled by adopting cooling water, cooling oil or other applicable cooling mediums, the fully cooled flue gas enters the first cooling system 3, then the high-temperature materials entering the first cooling system 3 are cooled, and the cooled circulating flue gas flows out of the first cyclone cooler of the first cooling system 33-1, leaving the air outlet, and then entering the bottom of the preheating furnace 2-1; and the second path is fed into a drying crusher to dry the raw materials or perform other forms of waste heat utilization, and the raw materials are discharged into the atmosphere after being treated by smoke.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (12)
1. The utility model provides a metakaolin preparation system that process flow was reconstituted, includes suspension preheating system, calciner system, first cooling system and second cooling system, its characterized in that: the calcination furnace system comprises a preheating furnace and a modifying furnace, wherein the bottom of the preheating furnace is a flue gas inlet, the top outlet of the preheating furnace is directly connected with the bottom inlet of the modifying furnace, the top outlet of the modifying furnace is connected with the inlet of a final cyclone preheater of the suspension preheating system, the material outlet at the bottom of the final cyclone preheater of the suspension preheating system is connected with the material inlet of the first cooling system, the discharge port of the last-last cyclone preheater of the suspension preheating system is connected with the raw material feeding port of the modifying furnace, the preheating furnace is not provided with the raw material feeding port, and the preheating furnace and the modifying furnace are respectively provided with a fuel feeding port;
the top flue gas outlet of the suspension preheating system is connected with the flue gas inlet of the indirect heat exchanger, the flue gas outlet of the indirect heat exchanger is connected with the flue gas inlet of the first cooling system, the first cooling system is used for quenching materials to a temperature range of 300-350 ℃ and below, the flue gas outlet of the first cooling system is connected with the flue gas inlet of the preheating furnace, and the oxygen content in the flue gas discharged from the top of the suspension preheating system is 1-3%; the material outlet of the first cooling system is connected with the material inlet of the second cooling system, and the gas outlet of the second cooling system is connected with the combustion-supporting air inlet in the middle of the modifying furnace;
the interior of the middle lower part of the preheating furnace and the modifying furnace is a reduction zone, and the interior of the middle upper part of the modifying furnace is an oxidation zone.
2. The system for preparing metakaolin regenerated by the process according to claim 1, wherein the modifying furnace is composed of a modifying furnace cone and a modifying furnace cylinder from bottom to top in sequence, fuel feeding ports are respectively arranged at the middle lower part of the modifying furnace cone and the modifying furnace cylinder, the fuel feeding ports at the middle part of the modifying furnace cylinder are positioned above combustion air inlets of the modifying furnace, and raw material feeding ports are respectively arranged above the fuel feeding ports of the modifying furnace.
3. The process flow reconstituted metakaolin preparation system according to claim 1, wherein the preheating furnace and the modifying furnace are layered in the height direction with a plurality of temperature measuring points for monitoring the temperature distribution in the preheating furnace and the modifying furnace in real time.
4. The process flow reconstituted metakaolin preparation system according to claim 1, wherein the indirect heat exchanger is used for indirectly cooling the flue gas discharged from the suspension preheating system to 80-120 ℃, a cooling medium inlet and a flue gas outlet are arranged at the bottom of the indirect heat exchanger, a flue gas inlet and a cooling medium outlet are arranged at the top of the indirect heat exchanger, so that the flue gas and the cooling medium exchange heat in a countercurrent manner, and the cooling medium is introduced into a cooling medium channel of the indirect heat exchanger.
5. The process flow rebuilt metakaolin preparation system according to claim 4, wherein the cooling medium of said indirect heat exchanger is cooling water, cooling oil or other suitable cooling medium.
6. The process flow rebuilt metakaolin preparation system according to claim 1, wherein flue gas circulation fans are respectively arranged between the indirect heat exchanger and the first stage cyclone preheater of the suspension preheating system and between the indirect heat exchanger and the first cooling system.
7. The process flow reconstituted metakaolin preparation system according to claim 1, wherein the gas outlet of the second cooling system is connected with the combustion air inlet in the middle part of the modifying furnace through a dust collector and a combustion air circulating fan in sequence.
8. The process flow rebuilt metakaolin preparation system according to claim 1, wherein said second cooling system comprises at least one stage cyclone cooler for cooling the material to below 100 ℃.
9. The process flow reconstituted metakaolin preparation system according to claim 1, wherein the flue gas outlet of the suspension preheating system, the gas outlet of the second cooling system are also connected with a drying crusher, or other waste heat utilization equipment.
10. A process for preparing metakaolin by using the system of any one of claims 1-9, wherein the process is characterized in that raw materials enter a modifying furnace after being preheated by a suspension preheating system, decomposed materials leave the modifying furnace and enter a final cyclone preheater of the suspension preheating system, and materials separated by the final cyclone preheater of the suspension preheating system enter a first cooling system; the flue gas discharged from the top of the suspension preheating system enters the first cooling system after being cooled by the indirect heat exchanger, exchanges heat with materials entering the first cooling system, and enters the preheating furnace, the gas discharged from the second cooling system enters the middle upper part of the modifying furnace for supporting combustion, and the fuel quantity fed into the preheating furnace, the fuel quantity fed into the modifying furnace, the raw meal quantity and the combustion-supporting air quantity are regulated, so that the fuel in the middle lower part of the preheating furnace and the modifying furnace is incompletely combusted to form a reducing atmosphere, and the fuel in the middle upper part of the modifying furnace is fully combusted to form an oxidizing atmosphere; the first cooling system quenches the material to a temperature range of 300-350 ℃ and below, then enters the second cooling system, and is cooled to below 100 ℃ by the second cooling system, so that the finished product of the metakaolin with controllable color is obtained.
11. The process flow reconstituted metakaolin preparation method according to claim 10, wherein the calcination temperature in the preheating furnace and in the middle lower part of the modifying furnace is 600-800 ℃, and the calcination temperature in the middle upper part of the modifying furnace is 700-900 ℃; the excess air coefficient of the outlet of the modifying furnace is 1.05-1.2; the residence time of the flue gas in the calciner system is 2-10 seconds.
12. The process flow reconstituted metakaolin preparation method according to claim 10, wherein the cooling medium of the first cooling system is flue gas with the temperature of 80-120 ℃ after being cooled by an indirect heat exchanger, and the oxygen content in the flue gas is 1-3%; the cooling medium of the second cooling system is normal temperature air.
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