A system and process for producing low carbon cement by separate grinding in stages

Abstract

The application provides a system and a process for preparing low-carbon cement by grading and separately grinding, which comprises a grinding system and a mixing system, wherein the grinding system is sequentially connected with a first elevator, a first conveying device, a vertical mill, a first dust collector and a first tail exhaust fan; the first conveying device is used for conveying the material in the first elevator to the vertical mill; and the system further comprises a first dust collector, a ball mill, a second elevator, a powder selector, a second dust collector and a conveying chute which are sequentially connected. The system can not only realize relative disturbance of the mixed material in opposite directions and improve the stirring efficiency of the mixed material, but also can grind different components of the low-carbon cement according to the characteristics of the different components by simultaneously arranging the vertical mill and the ball mill, so that the grinding degree of each component of the low-carbon cement is ensured to be optimal, the low-carbon cement with ideal cement particle size distribution is obtained after mixing by the mixer, the performance of the cement is improved, the clinker consumption in the cement is reduced, and the carbon emission intensity of the cement is reduced.

Description

A system and process for preparing low-carbon cement by graded and separate grinding Technical Field

[0001] This invention relates to the field of cement preparation technology, and more specifically to a system and process for preparing low-carbon cement by graded grinding. Background Technology

[0002] In the cement industry, different types of materials are metered and fed into a mixing device in a specific ratio. The materials are then mixed mechanically or pneumatically for a set time to achieve uniform mixing. Currently, mixing devices on the market can be broadly categorized into continuous and intermittent types. Intermittent mixing devices, due to their static feeding and long mixing time, offer superior mixing results and uniformity, exceeding 99%. Compared to pneumatic-mechanical composite mixing devices, this represents an approximately 5% improvement in uniformity. However, intermittent mixing devices require several large mixing tanks and have a long mixing time, resulting in a large footprint and limited production capacity, hindering large-scale application.

[0003] For pneumatic, mechanical, or pneumatic-mechanical composite mixing devices, most powder material mixing equipment widely used in the market are horizontal mixers or spiral vertical mixers. The working principle of a horizontal mixer is to mechanically agitate the powder material using blades mounted on a drive shaft, achieving the mixing purpose based on the fixed circumferential and axial motion of the material. Existing horizontal mixers generally agitate at a single speed within the mixing chamber, failing to achieve multi-stage mixing of materials within the same chamber, resulting in low mixing efficiency and poor mixing effect. Furthermore, sufficient power is required to overcome material resistance during operation, leading to problems such as high installed power, high energy consumption, low production efficiency, large footprint, and poor process layout flexibility. Material feeding into the mixer can easily cause "cross-contamination," with unmixed material being discharged, resulting in large fluctuations in mixing uniformity and uneven material composition. This affects subsequent process design and the improvement of cement product performance, leading to continuous increases in cement production costs and hindering further energy conservation and emission reduction in the cement industry.

[0004] For materials with similar particle sizes, segregation is less likely to occur during mixing, ensuring smooth and uniform mixing. However, for materials with significantly different particle sizes, smaller particles tend to float during mixing, while larger particles tend to sink. This segregation makes mixing difficult. Existing equipment is prone to problems such as dead zones, dead spots, agglomeration, and pelleting during mixing, leading to severe segregation and agglomeration of the mixed material, resulting in large fluctuations in composition and a large standard deviation in CaO.

[0005] For mixtures of ultrafine materials with a mesh size of 1000 or 2000 mesh or larger, the gravitational binding of individual particles becomes negligible due to their fineness, resulting in a certain degree of buoyancy. Simultaneously, the material absorbs a significant amount of mechanical or thermal energy during the crushing process, giving the newly formed ultrafine particles a considerably high surface energy, placing the material in a highly unstable state. To reduce surface energy, particles often aggregate and move closer together to achieve a stable state, which also easily leads to particle agglomeration. Therefore, the material particles are prone to agglomeration and difficult to mix, posing challenges to uniform mixing.

[0006] For viscous materials, when the relative humidity of the air exceeds 65%, water vapor begins to condense on the surface of the particles and between the particles, and the agglomeration effect is greatly enhanced due to the formation of liquid bridges between the particles.

[0007] Continuous and stable feeding, accurate metering, stable material conveying, and uniform mixing are key factors affecting mixing efficiency. The performance of a mixer can be reflected in mixing quality, power consumption, and maintenance. The main purpose of mixing is to obtain a mixture with uniformly distributed components. The function of a mixer is to mix materials evenly; the more uniform the components of the output material, the better the mixing effect. In industrial applications, the feed rate of each material to be mixed may fluctuate, resulting in fluctuations in the components of the output material from the mixer at different times. Therefore, a rationally designed, accurately metered, and highly efficient mixing process system is urgently needed.

[0008] In addition, in existing technologies, the main types of cement produced are 42.5 grade cement and 32.5 grade cement, which together account for over 95% of total cement production. Specifically, 42.5 grade cement contains 70-80% clinker, while 32.5 grade cement contains 60-70% clinker. During cement production, clinker, gypsum, slag, limestone, and other materials are simultaneously fed into a grinding unit and ground together to a certain fineness (specific surface area 320-400 m²). 2 / kg is cement.

[0009] Cement production systems and grinding equipment are technologically mature, with clear processes and wide applications. However, due to differences in material grindability, hydration activity, and hydration processes, the following problems exist in their application:

[0010] (1) Clinker is more difficult to grind than limestone. During co-grinding, clinker cannot be ground sufficiently while limestone is ground very finely. Because clinker cannot be ground sufficiently during co-grinding, clinker particles >32μm are not fully hydrated. In order to ensure the strength and other properties of cement, the proportion of clinker used can only be increased, resulting in clinker waste, high carbon emission intensity of cement, and high production cost.

[0011] (2) High-activity auxiliary cementitious materials (taking slag as an example) and low-activity auxiliary cementitious materials (taking limestone as an example) were not utilized properly. Because high-activity auxiliary cementitious materials are usually harder to grind than clinker, while low-activity auxiliary cementitious materials are easier to grind than clinker, when they are ground together: the hard-to-grind, high-activity auxiliary cementitious materials cannot be ground finely, resulting in their inability to exert their activity well and material waste; the easy-to-grind, low-activity auxiliary cementitious materials are ground too finely, resulting in high cement water demand, poor performance, and high power consumption in production.

[0012] (3) The cement particle size distribution is not ideal. The traditional grinding of cement has a narrow particle size distribution, resulting in a high cement water demand. Summary of the Invention

[0013] To address the aforementioned problems, this invention provides a system and process for preparing low-carbon cement through graded and separate grinding. Based on graded and separate grinding technology, the system optimizes the particle size distribution and gelling activity matching of cement raw materials, maximizing the gelling activity and synergistic activation capabilities of each cement component at different ages. This achieves a gradient self-activation effect from early to long ages, ensuring the mechanical properties of low-carbon cement throughout its entire service life. Simultaneously, it solves the problems of unstable material feeding, poor uniformity, uneven mixing, low mixing efficiency due to single-speed mixing, high water demand in the prepared cement, and poor performance in existing technologies.

[0014] This invention provides a system for preparing low-carbon cement by graded grinding, comprising a grinding system and a mixing system. The grinding system includes a first elevator, a first conveying device, a vertical mill, a first dust collector, and a first exhaust fan connected in sequence. The first conveying device is used to convey the material in the first elevator to the vertical mill.

[0015] The grinding system further includes a first dust collector, a ball mill, a second elevator, a classifier, a second dust collector, and a conveying chute connected in sequence; the second dust collector is also connected to a second tail exhaust fan; the vertical mill is also connected to a second conveying device for conveying materials to the first elevator;

[0016] The ball mill is also connected to a third dust collector, which is connected to a third tail exhaust fan and is also connected to the conveying chute.

[0017] The conveying chutes are respectively connected to the first storage silo, the third storage silo, and the fourth storage silo; the first dust collector is also connected to the second storage silo; the first storage silo, the second storage silo, the third storage silo, and the fourth storage silo are used to store different materials;

[0018] The mixing system includes a mixer, multiple buffer silos, and multiple metering devices; each buffer silo is connected to a corresponding metering device; the mixer includes a housing, a feeding device, and a discharge port; the first storage silo, the second storage silo, the third storage silo, and the fourth storage silo are respectively connected to the corresponding buffer silos; the housing is inclined upward from the discharge port side to the feeding device side, with an inclination angle of 2 to 10°; the feeding device is located on the upper part of the first end of the housing, and the discharge port is located on the side of the second end of the housing;

[0019] The metering device is connected to the feeding device through the feeding pipe. After the material in each storage silo is metered by the corresponding metering device, it enters the mixer through the feeding pipe for stirring and mixing.

[0020] A first stirring mechanism is arranged parallel to the box body inside the box. The first stirring mechanism includes a main shaft driven by a main shaft drive device, and a plurality of stirrers are continuously installed on the main shaft along the main shaft axis.

[0021] Each of the agitators includes two drive bevel gears, a main shaft bevel gear coaxial with the main shaft, two drive round gears, two large gear rings, and two hollow shafts.

[0022] Two drive bevel gears are symmetrically arranged on both sides of the main shaft and simultaneously mesh with the main shaft bevel gear sleeved and fixed on the main shaft; two drive round teeth are respectively arranged on the outside of their respective drive bevel gears and are respectively connected to the two drive bevel gears through drive gear shafts; two large gear rings are supported by gear ring support cylinders, and the two drive round teeth are located between the two large gear rings, with each drive round tooth meshing with the two large gear rings respectively; the axial direction of the gear ring support cylinder is parallel to the main shaft, and its two ends are respectively fixed to the first end side and the second end side of the mixer;

[0023] Each hollow shaft is fixedly connected to a large gear ring, and the two hollow shafts are tightly fitted at the joint to prevent material from entering the agitator; each hollow shaft is provided with multiple first blades, and the two hollow shafts rotate in opposite directions under the rotation of the main shaft to stir and mix the material in the box.

[0024] The number of teeth on the main shaft of each agitator is different, so that the first agitation mechanism agitates the material at different positions in the box at different speeds.

[0025] Optionally, it may also include a hot air furnace that provides hot air to the entire system.

[0026] Optionally, the thickness of the entire cross-section of the first blade is uniform;

[0027] The first blade has a wave-shaped structure, which is used to make the material move at different speeds in multiple dimensions.

[0028] Optionally, the first blade includes a blade root and a blade tip;

[0029] The blade tip is located at the top of the first blade, the blade root is connected to the outer surface of the hollow shaft, and the blade tip faces the discharge port.

[0030] Optionally, the bottom and sides of the box are also equipped with jetting devices to adjust the material movement trajectory and residence time inside the box.

[0031] Optionally, the jet device is connected to a mixing box, and the mixing box is connected to a blower; the blower is used to provide air pressure to the mixing box; the mixing box is used to provide air pressure to the jet device.

[0032] The jet device includes multiple air inlet pipes; each air inlet pipe includes an air inlet pipe shell, a dustproof ring, dustproof blades, and a flap valve;

[0033] The air outlet of the air inlet pipe faces the inside of the housing; a dustproof ring and multiple dustproof blades connected to the same flip axis are provided on the top inner surface of the air outlet; the dustproof blades are semi-circular and have the same diameter as the inner diameter of the dustproof ring, and can flip up and down under air pressure.

[0034] The air inlet port of the air inlet duct is connected to the mixing box, and a flap valve is provided at the port where the air inlet port is connected to the mixing box. The flap valve is connected to a flap valve controller. The flap valve controller controls the air volume entering the air inlet duct by controlling the degree of flap valve flipping.

[0035] Optionally, the feeding device includes a feeding port and an airlock structure installed in the feeding port;

[0036] The airlock structure includes an airlock housing, an airlock drive device, an airlock rotating shaft, and airlock blades;

[0037] The airlock shaft is horizontally fixed inside the feed inlet and is driven to rotate by the airlock drive device. Multiple airlock blades are mounted circumferentially on the airlock shaft. One end face of each airlock blade is connected to the airlock shaft, and the other end faces are respectively attached to the airlock housing. During feeding, the airlock shaft drives the airlock blades to rotate and feed the material into the box.

[0038] Alternatively, the feeding device may include a screw feed mechanism;

[0039] The spiral feeding mechanism includes a spiral feeding mechanism housing, a spiral feeding mechanism inlet that is obliquely fixed to the spiral feeding mechanism housing and communicates with the spiral feeding mechanism housing, and the bottom of the spiral feeding mechanism housing is connected to the inside of the box.

[0040] The spiral feeding mechanism housing contains a vertically arranged spiral feeding mechanism rotating shaft and spiral blades fixedly distributed on the spiral feeding mechanism rotating shaft; a grid plate is fixedly installed at the bottom of the spiral feeding mechanism rotating shaft, the grid plate includes multiple L-shaped grid bars, each L-shaped grid bar includes a vertical side and an inclined side, the vertical side being located above the inclined side; one end of the inclined side is connected to the spiral feeding mechanism rotating shaft, and the other end is connected to the bottom end of the vertical side.

[0041] Optionally, there are four first stirring mechanisms inside the box, arranged in two layers, with two mechanisms in each layer.

[0042] Optionally, multiple sets of baffle units are distributed inside the box along the main axis direction, and the baffle units divide the internal space of the box into multiple mixing chambers;

[0043] The baffle unit includes upper and lower baffles; the upper and lower baffles are located on the same vertical plane; the baffles include a fixed baffle located below and a movable baffle located above, which are used to control the amount of material in the mixing chamber entering the adjacent mixing chamber.

[0044] Optionally, each of the mixing chambers is provided with a guide plate at the top. The vertical height of the guide plate is complementary to the vertical distance from the top of the corresponding baffle unit to the top surface of the inner chamber. The guide plate is used to further control the residence time of the material in the mixing chamber.

[0045] Optionally, each of the mixing chambers is provided with at least one vertical stirring mechanism at its top, and the rotation speed of the vertical stirring mechanism can be adjusted according to the mixing conditions of the mixing chamber.

[0046] This invention also provides a process for preparing low-carbon cement by graded and separate grinding based on a system for graded and separate grinding, comprising the following steps:

[0047] Step 1: Prepare the target low-carbon cement raw material components, including: early-age self-activated cementitious material components, middle-age self-activated cementitious material components, long-age self-activated cementitious material components, and rheology-active material components;

[0048] The early-age self-activating cementitious material components include silicate cement clinker, granulated blast furnace slag, and a particle modifier. The preparation process of the early-age self-activating cementitious material components is as follows:

[0049] A mixture of pre-proportioned silicate cement clinker, granulated blast furnace slag, and granular modifier is fed into a first conveying device via a first elevator, and then into a vertical mill for grinding. The resulting material has a specific surface area of ​​400–500 m². 2 Materials between / kg are collected in the first dust collector under the action of the first exhaust fan, and then transported to the ball mill for further grinding;

[0050] The material, after being further ground in the ball mill, is separated by an air classifier to obtain a specific surface area of ​​1150–1250 m². 2 Materials between / kg are collected by the second dust collector under the action of the second tail exhaust fan, and then enter the first storage silo through the conveying chute;

[0051] The middle-aged self-activating cementitious material component includes silicate cement clinker and gypsum. The preparation process of the middle-aged self-activating cementitious material component is as follows:

[0052] The proportioned silicate cement clinker and gypsum mixture is fed into the first elevator, then enters the first conveying device, and is subsequently sent to the vertical mill for grinding. After grinding in the vertical mill, the specific surface area is 380–400 m². 2 The material at a rate of / kg is collected in the first dust collector by the action of the first tail exhaust fan, and then enters the second storage silo.

[0053] The long-term self-activating material components include one or more of fly ash, steel slag, furnace slag, phosphorus slag, and coal gangue. The preparation process of the long-term self-activating cementitious material components is as follows:

[0054] The pre-mixed long-term self-activated cementitious material components are fed into the first elevator and then conveyed to the vertical mill for grinding via the first conveying device; the specific surface area obtained after grinding is 400-450 m². 2 Materials with a specific surface area between 0.5 kg and 0.6 kg are collected by the first dust collector under the suction of the first exhaust fan, then further ground in the ball mill, and finally fed into the classifier via the second elevator; the classifier separates materials with a specific surface area of ​​480–550 m². 2 Materials between / kg are collected by the second dust collector under the action of the second tail exhaust fan, and then enter the third storage silo through the conveying chute;

[0055] The rheologically active material component is either quartz sand or limestone, and the preparation process of the rheologically active material component is as follows:

[0056] After being fed into the first elevator, the metered rheologically active material components are conveyed to the vertical mill for grinding via the first conveying device; the specific surface area obtained after grinding is 200-240 m². 2 / kg of material is collected by the first dust collector under the suction of the first tail exhaust fan;

[0057] The material collected by the first dust collector enters the ball mill for further grinding, and after being ground again in the ball mill, it enters the classifier via the second elevator; the classifier separates the material into particles with a specific surface area of ​​240–300 m². 2 Materials between / kg are collected by the second dust collector under the action of the second tail exhaust fan, and then enter the fourth storage silo through the conveying chute;

[0058] Step 2: After all the raw material components have been prepared, the materials in each storage silo first enter the corresponding buffer silo, are measured by the corresponding metering device, and then enter the mixer together for mixing. After mixing, the target low-carbon cement is obtained.

[0059] Optionally, in the preparation of the early-age self-excited cementitious material component, the specific surface area obtained after grinding with the vertical mill is less than 400 m². 2 The material at a rate of / kg is conveyed back to the first elevator via the second conveying device;

[0060] In the preparation of the middle-aged self-activated cementitious material components, the specific surface area obtained after grinding in the vertical mill is less than 380 m². 2 The material at a rate of / kg is conveyed again to the first elevator via the second conveying device;

[0061] In the preparation of the long-term self-activated cementitious material components, the specific surface area obtained after grinding in the vertical mill is less than 400 m². 2 The material at a rate of / kg is conveyed back to the first elevator via the second conveying device;

[0062] In the preparation of the rheologically active material component, the specific surface area obtained after grinding by the vertical mill is less than 200 m². 2 The material at a rate of / kg is conveyed back to the first elevator via the second conveying device.

[0063] Optionally, in the preparation of the early-age self-excited cementitious material components, after separation by the air classifier, the specific surface area is less than 1150 m². 2 / kg of material is fed into the ball mill for further grinding;

[0064] During the preparation of the middle-aged self-activated cementitious material components, after separation by the air classifier, the specific surface area is less than 480 m². 2 / kg of material is fed into the ball mill for further grinding;

[0065] During the preparation of the rheologically active material components, after separation by the powder classifier, the specific surface area is less than 240 m². 2 / kg of material is fed into the ball mill for further grinding.

[0066] Optionally, during the preparation of the early-age self-excited cementitious material components, the material collected by the third dust collector connected to the ball mill under the action of the third tail exhaust fan directly enters the first storage tank.

[0067] During the preparation of the long-term self-excited cementitious material components, the material collected by the third dust collector connected to the ball mill under the action of the third tail exhaust fan directly enters the third storage tank.

[0068] During the preparation of the rheologically active material components, the material collected by the third dust collector connected to the ball mill under the action of the third tail exhaust fan directly enters the fourth storage tank.

[0069] The present invention has at least the following beneficial effects:

[0070] The system and process for preparing low-carbon cement by graded grinding in this invention utilizes a mixer with multiple sections of agitators rotating in opposite directions. This not only achieves relative disturbance of the mixed materials in opposite directions but also extends the residence time of the materials within this region, improving mixing efficiency and reducing ineffective mixing power consumption. By setting different numbers of bevel teeth on the differential speed agitator on the main shaft, gradient mixing is achieved along the mixing axis, improving mixing efficiency and uniformity while reducing energy consumption and increasing production efficiency, which is beneficial for large-scale equipment. The inclusion of a buffer silo and metering device before feeding prevents unstable feeding, effectively controlling feeding stability and improving metering accuracy. Furthermore, by incorporating both a vertical mill and a ball mill, the system can grind different components of the low-carbon cement separately according to their characteristics, ensuring that each component reaches its optimal grinding degree. After mixing in the mixer, the resulting low-carbon cement has an ideal particle size distribution, improving cement performance. Attached Figure Description

[0071] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0072] Figure 1 is a schematic diagram of a system for preparing low-carbon cement by graded grinding according to an embodiment of the present invention;

[0073] Figure 2 is a schematic diagram of the external appearance of the mixer provided in an embodiment of the present invention;

[0074] Figure 3 is a schematic diagram of the internal structure of the mixer provided in an embodiment of the present invention;

[0075] Figure 4 is a schematic diagram of the internal structure of the stirrer provided in an embodiment of the present invention;

[0076] Figure 5 is a schematic diagram of the internal structure of the stirrer provided in an embodiment of the present invention;

[0077] Figure 6 is a schematic diagram of the internal structure of the mixer provided in an embodiment of the present invention;

[0078] Figure 7 is a schematic diagram of the intake pipe structure provided in an embodiment of the present invention;

[0079] Figure 8 is a schematic diagram of the airlock device provided in an embodiment of the present invention;

[0080] Figure 9 is a schematic diagram of the screw feeding mechanism provided in an embodiment of the present invention;

[0081] Figure 10 is a schematic diagram of the vertical stirring mechanism provided in an embodiment of the present invention;

[0082] Figure 11 is a schematic diagram of the material blocking unit provided in an embodiment of the present invention.

[0083] Figure label:

[0084] 1-Box body; 2-Feeding device; 3-Discharge port; 3-1-Breathable filter cloth; 4-First stirring mechanism; 4-1 Main shaft; 4-2-Main shaft drive device; 4-3-Agitator; 4-3-1-Transmission bevel gear; 4-3-2-Main shaft bevel gear; 4-3-3-Transmission gear shaft; 4-3-4-Gear bearing seat; 4-3-5-Gear ring support cylinder; 4-3-6-Large gear ring; 4-3-7-Hollow shaft; 4-3-8-Transmission round gear; 5-First blade; 6-Mixing box; 6-1-Blower; 7-Inlet 7-1-Inlet duct housing; 7-2-Dustproof ring; 7-3-Dustproof blade; 7-4-Flap valve; 7-5-Flap valve controller; 7-6-Pressure sensor; 8-Air lock housing; 9-Air lock drive device; 10-Air lock shaft; 11-Air lock blade; 12-Screw feed mechanism; 12-1-Screw feed mechanism housing; 12-2-Screw feed mechanism inlet; 12-3-Screw feed mechanism rotating shaft; 12-4-Screw blade; 12-5-Grate plate; 13-Blocking unit; 13-1 13-Fixed baffle; 13-2-Modible baffle; 13-3-Upper screw; 13-4-Lower screw; 13-5-Rotator; 13-6-Rotator support; 14-Guide plate; 15-Vertical stirring mechanism; 15-1-Rotary shaft of vertical stirring mechanism; 15-2-Driver of vertical stirring mechanism; 15-3-Second blade; 16-1-Second storage tank; 16-2-First storage tank; 16-3-Third storage tank; 16-4-Fourth storage tank; 17-Metering device; 18-Buffer tank; 19-Feed pipe; 20 - Discharge pipe; 21- Uniformity detection system; 22- Mixer controller; 23- Product storage warehouse; 24- Third elevator; 25- First elevator; 26- First conveying device; 27- Vertical mill; 28- Second conveying device; 29- First dust collector; 30- First tail exhaust fan; 31- Ball mill; 32- Second elevator; 33- Air classifier; 34- Second dust collector; 35- Second tail exhaust fan; 36- Conveying chute; 37- Third dust collector; 38- Third tail exhaust fan; 39- Discharge port. Detailed Implementation

[0085] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0086] The present invention provides a system for preparing low-carbon cement by graded grinding, comprising a grinding system and a mixing system. The grinding system includes a first elevator 25, a first conveying device 26, a vertical mill 27, a first dust collector 29, and a first exhaust fan 30 connected in sequence. The first conveying device 26 is used to convey the material in the first elevator 25 to the vertical mill 27.

[0087] The grinding system also includes a first dust collector 29, a ball mill 31, a second elevator 32, a classifier 33, a second dust collector 34, and a conveying chute 36 connected in sequence; the second dust collector 34 is also connected to a second tail exhaust fan 35; the vertical mill 27 is also connected to a second conveying device 28 for conveying materials to the first elevator 25.

[0088] The ball mill 31 is also connected to the third dust collector 37, which is connected to the third tail exhaust fan 38. The third dust collector 37 is also connected to the conveying chute 36.

[0089] The conveying chute 36 is connected to the first storage tank 16-2, the third storage tank 16-3, and the fourth storage tank 16-4 respectively; the first dust collector 29 is also connected to the second storage tank 16-1; the first storage tank 16-2, the second storage tank 16-1, the third storage tank 16-3, and the fourth storage tank 16-4 are used to store different materials;

[0090] The mixing system includes a mixer, multiple buffer silos 18, and multiple metering devices 17; each buffer silo 18 is connected to a corresponding metering device 17; the mixer includes a housing 1, a feeding device 2, and a discharge port 3; the first storage silo 16-2, the second storage silo 16-1, the third storage silo 16-3, and the fourth storage silo 16-4 are respectively connected to the corresponding buffer silos 18; the housing 1 is inclined upward from the discharge port 3 side to the feeding device 2 side, with an inclination angle of 2 to 10°; the feeding device 2 is located at the upper part of the first end of the housing 1, and the discharge port 3 is located on the side of the second end of the housing 1;

[0091] The metering device 17 is connected to the feeding device 2 through the feeding pipe 19; after being metered by the metering device 17, the single material enters the mixer through the feeding pipe 19 for stirring and mixing.

[0092] A first stirring mechanism 4 is arranged parallel to the box body 1 inside the box body 1. The first stirring mechanism 4 includes a main shaft 4-1 driven by a main shaft drive device 4-2, and a plurality of stirrers 4-3 are continuously installed on the main shaft 4-1 along the axial direction of the main shaft 4-1.

[0093] Each of the stirrers 4-3 includes two drive bevel gears 4-3-1, a main shaft bevel gear 4-3-2 coaxial with the main shaft 4-1, two drive round gears 4-3-8, two large gear rings 4-3-6, and two hollow shafts 4-3-7.

[0094] Two transmission bevel gears 4-3-1 are symmetrically arranged on both sides of the main shaft 4-1, and simultaneously mesh with the main shaft bevel gear 4-3-2 sleeved and fixed on the main shaft 4-1; two transmission round gears 4-3-8 are respectively arranged on the outer side of their respective transmission bevel gears 4-3-1, and are respectively connected to the two transmission bevel gears 4-3-1 through transmission gear shafts 4-3-3; two large gear rings 4-3-6 are supported by gear ring support cylinders 4-3-5, and the two transmission round gears 4-3-8 are located between the two large gear rings 4-3-6, and each transmission round gear 4-3-8 meshes with the two large gear rings 4-3-6 respectively; the gear ring support cylinders 4-3-5 are axially parallel to the main shaft 4-1, and their two ends are respectively fixed to the first end side and the second end side of the mixer.

[0095] Each hollow shaft 4-3-7 is fixedly connected to a large gear ring 4-3-6, and the two hollow shafts 4-3-7 are tightly fitted at the mating position to prevent material from entering the agitator 4-3; each hollow shaft 4-3-7 is provided with multiple first blades 5, and under the rotation of the main shaft 4-1, the two hollow shafts 4-3-7 rotate in opposite directions to stir and mix the material in the box 1;

[0096] The number of teeth on the main shaft bevel gears 4-3-2 of each agitator 4-3 on the main shaft 4-1 is different, so that the first agitation mechanism 4 agitates the material at different positions in the box 1 at different speeds.

[0097] Specifically, the first conveying device 26 mainly feeds the material from the first elevator 25 into the vertical mill 27, and the second conveying device 28 mainly conveys the unfinished material from the vertical mill 27 back to the first elevator 25, where it is fed back into the vertical mill 27 for grinding together with the unground raw materials. In this embodiment of the invention, both the first conveying device 26 and the second conveying device 28 are belt conveyors, which are characterized by high efficiency, continuous operation, strong adaptability, economy, practicality, safety, and reliability. Furthermore, in this invention, each dust collector is equipped with a tail exhaust fan at its rear end to ensure that the ground powder and exhaust gas can smoothly enter the dust collector, thereby allowing the powder to be collected. Simultaneously, the fan can adjust its speed and volume as needed to adapt to different stages, enabling the corresponding dust collector to collect materials with different specific surface areas.

[0098] As shown in Figure 1, different materials are prepared and enter different storage tanks, each corresponding to a buffer silo 18 and a metering device 17. Each storage tank has a certain volume according to the mixing output requirements. A certain amount of material is released from the storage tank and stored in the buffer silo 18. The buffer silo 18 is a small storage tank with a certain volume, smaller than the corresponding storage tank. The metering device 17 is connected to the buffer silo 18, and the material in the buffer silo 18 is stably fed into the metering device 17 according to the feed rate determined by the metering device 17. Various materials enter the feed pipe 19 connected to the feeding device in a certain amount through the metering device 17, and then are fed into the mixing tank 1 from the feeding device 2 at the upper part of the first end of the tank 1 through the feed pipe 19. After stirring, they flow out from the discharge port 3 set on the side of the second end of the tank 1. Each material is independently equipped with a multi-stage steady-flow mixing system, which can be set to mix different types of materials as needed, making it highly operable. In this application, the measuring device is configured as a rotor scale, and more preferably, as a double-layer rotor scale, ensuring a measuring accuracy within ±0.5%. The volume of the buffer chamber 18 is set to 2 to 5 times the maximum capacity of the measuring scale.

[0099] As shown in Figure 2, the housing 1 is inclined upwards from the discharge port 3 side to the feeding device 2 side, with an inclination angle of 2-10°, so that the material moves as a whole towards the outlet side under the action of gravity, reducing discharge resistance. Furthermore, the inclination angle should not be too small or too large; too small an angle may lead to discharge difficulties, while too large an angle will result in the material being discharged from the discharge port 3 before being evenly mixed due to insufficient mixing time in the housing 1. The top of the discharge port 3 housing has an opening covered by a breathable filter cloth 3-1, ensuring smooth material flow within the housing 1 while preventing material overflow from the opening. The mixing machine housing 1 is supported by a bottom support device. Additionally, several glass observation doors are provided on the side of the housing 1 to observe the mixing process and the material's trajectory. In this application, the mixing machine capacity is 1.0 to 2.0 times the mixing volume.

[0100] As shown in Figures 3, 4, and 5, a first stirring mechanism 4 is arranged parallel to the housing 1 inside the housing 1. The first stirring mechanism 4 includes a main shaft 4-1, with its two ends respectively mounted on two end faces along the length of the housing 1. Each main shaft 4-1 is independently driven by a main shaft drive device 4-2. The main shaft drive device 4-2 includes a drive motor and a coupling, wherein the drive motor is a permanent magnet motor. The permanent magnet motor in this application is a reversible motor, capable of rotating in both directions to prevent feed blockage.

[0101] The main shaft drive device 4-2 is located on the outer side of the housing 1 near the feeding device 2. The head end of the main shaft 4-1 is connected to the main shaft drive device 4-2, and the tail end of the main shaft 4-1 is supported by a bearing located at the other end of the mixing housing 1. The bearing is fixed to the mixing housing 1 by a bracket, and each main shaft 4-1 is provided with multiple agitators 4-3 continuously installed along the axial direction of the main shaft 4-1. Two drive bevel gears 4-3-1 in the agitator 4-3 are symmetrically arranged on both sides of the main shaft 4-1 and simultaneously mesh with the main shaft bevel gears 4-3-2 sleeved and fixed on the main shaft 4-1. The main shaft bevel gears 4-3-2 are conical and fixed on the main shaft 4-1. Through gear meshing, they drive the drive bevel gears 4-3-1 with a certain number of teeth in the radial direction to rotate. Two drive round teeth 4-3-8 are respectively located on the outer side of their respective drive bevel gears 4-3-1 and are respectively connected to the two drive bevel gears 4-3-1 through the drive gear shaft 4-3-3. The transmission round teeth 4-3-8 are connected to the gear ring support cylinder 4-3-5 via gear bearing seats 4-3-4. Two large gear rings 4-3-6 are supported by the gear ring support cylinder 4-3-5. The two transmission round teeth 4-3-8 are located between the two large gear rings 4-3-6, and each transmission round tooth 4-3-8 meshes with one of the two large gear rings 4-3-6. The gear ring support cylinder 4-3-5 is parallel to the main shaft 4-1, and its two ends are fixed to the first and second end sides of the mixer, respectively. The two large gear rings 4-3-6 meshing with the two transmission round teeth 4-3-8 are fixed on the outer circumferential direction of the gear ring support cylinder 4-3-5. Both the first and second end sides are vertical surfaces.

[0102] Each hollow shaft 4-3-7 is fixedly connected to a large gear ring 4-3-6, and the two hollow shafts 4-3-7 are tightly fitted together to prevent material from entering the agitator 4-3. Multiple first blades 5 are provided on the outer side of each hollow shaft 4-3-7. With the rotation of the main shaft 4-1, the two hollow shafts 4-3-7 rotate around the main shaft 4-1 in different directions, driving the first blades 5 on the two hollow shafts 4-3-7 to rotate in opposite directions, thus mixing the material inside the housing 1. The number of teeth on the main shaft bevel gears 4-3-2 of each agitator 4-3 on the main shaft 4-1 is different. By setting different numbers of teeth on the main shaft bevel gears 4-3-2, the transmission speed is also different when the transmission is carried out through the main shaft bevel gears 4-3-2. Therefore, the first agitation mechanism 4 can agitate the material at different positions inside the housing 1 at different speeds.

[0103] Each agitator 4-3 includes a first blade 5 rotating in opposite directions. During the mixing process, it generates more complex and intense fluid motion, thereby enhancing the mixing effect of materials within the housing 1. This ensures that materials are fully mixed in all directions, reducing dead zones and improving mixing uniformity. Furthermore, because they rotate in opposite directions, they cooperate to form a more efficient mixing force field. This force field accelerates the flow and mixing of materials within the mixing drum, thus shortening mixing time and improving production efficiency.

[0104] Multiple agitators 4-3 are installed on the mixing shaft 4-1, each rotating in opposite directions. Within a certain mixing zone, this not only achieves relative disturbance of the mixed materials in opposite directions but also extends the residence time of the materials within this zone, improving mixing efficiency and reducing ineffective mixing power consumption. Furthermore, the multiple agitators 4-3 continuously installed on the shaft 4-1 operate at different speeds. The varying numbers of beveled teeth on the agitators 4-3 ensure more effective and uniform mixing of the materials. This design of different mixing speeds increases the contact area and contact time between materials, promoting interaction and diffusion, thereby improving mixing efficiency. Additionally, gradient mixing allows the materials to experience different mixing environments and conditions within the mixing chamber 1, thus more comprehensively meeting mixing requirements. By gradually increasing the number of beveled teeth on the agitators 4-3, a transition from coarse to fine mixing can be achieved, gradually bringing the materials to a uniform mixing state. This helps improve mixing quality, making the product more stable and reliable. Gradually increasing the number of beveled teeth on the agitators 4-3 allows for different mixing effects at different stages, avoiding unnecessary energy consumption, helping to reduce production costs and improve economic efficiency.

[0105] In summary, the mixer in the system and process for preparing low-carbon cement by graded grinding of the present invention, by setting multiple agitators with opposite rotation directions, not only achieves relative disturbance of the mixed materials in opposite directions, but also prolongs the residence time of the mixed materials in this area, improves the mixing efficiency, and reduces ineffective mixing power consumption. By setting different numbers of bevel teeth on the differential speed agitator on the main shaft, gradient mixing is carried out along the mixing axis of the material during the mixing process, improving mixing efficiency and uniformity while reducing energy consumption and increasing production efficiency, which is conducive to the large-scale development of equipment. In addition, by setting a buffer silo and a metering device before feeding, unstable feeding can be prevented, feeding stability can be effectively controlled, and metering accuracy can be improved. Furthermore, by setting up a system that simultaneously incorporates a vertical mill and a ball mill, different components of low-carbon cement can be ground separately according to their characteristics, ensuring that each component of low-carbon cement reaches the optimal grinding degree. After being mixed by the mixer, low-carbon cement with an ideal particle size distribution is obtained, improving the performance of the cement.

[0106] In one possible implementation, a hot air furnace is also included to provide hot air to the entire system.

[0107] Specifically, the system also includes a hot air furnace, which provides hot air to the grinding production line. This hot air is primarily used for drying materials. During the process of graded grinding to prepare cement, materials typically require drying to remove excess moisture and ensure the smooth operation of the grinding process. The hot air provided by the hot air furnace effectively meets this requirement, improving the efficiency and effectiveness of material drying.

[0108] In one possible implementation, the thickness of the entire cross-section of the first blade is uniform.

[0109] The first blade has a wave-shaped structure, which is used to make the material move at different speeds in multiple dimensions.

[0110] Specifically, the first blade 5 has a uniform thickness and a wavy structure. When multiple wavy blades are installed on the stirring shaft and rotate with the main shaft 4-1, eddies and shear forces are generated, causing the material to undergo variable-speed motion in multiple dimensions. As the wavy blades rotate, they continuously change the contact area and direction with the material. This constantly changing contact generates a shear force, pushing and mixing the material in a direction perpendicular to the rotation axis. Additionally, as the blades rotate, the material is subjected to centrifugal force, causing it to be pushed outwards. The combined effect of this centrifugal force and shear force causes the material to undergo variable-speed motion in multiple dimensions. Furthermore, as the blades rotate, the material circulates under the push of the blades, forming eddies. These eddies generate vortices and mixing within the material, contributing to the uniform mixing and dispersion of the material.

[0111] In one possible implementation, the first blade includes a blade root and a blade tip;

[0112] The blade tip is located at the top of the first blade, the blade root is connected to the outer surface of the hollow shaft, and the blade tip faces the discharge port.

[0113] Specifically, the root of the first blade 5 is connected to the outer surface of the hollow shaft 2, while the tip of the blade faces the discharge port 3, causing the material to further tend to flow towards the discharge port 3 during the stirring process. In this invention, the angle between the first blade 5 and the axis of the hollow shaft 4-3-7 is 30° to 60°.

[0114] In one possible implementation, the bottom and sides of the container are also equipped with jetting devices for adjusting the material movement trajectory and residence time inside the container.

[0115] Specifically, as shown in Figure 3, jet spraying devices are installed at the bottom and sides of the mixing chamber 1. This allows for repeated movement paths during the material's rising and settling process, ensuring thorough mixing and agitation. The jet spraying devices also adjust the material's trajectory and residence time within the chamber 1. The jet spraying devices create a convective impact and dispersion of the material within the chamber 1, particularly subjecting finer materials to forces from different directions within the movement space, thus ensuring thorough mixing and agitation. Simultaneously, it prevents localized settling of material at the bottom, improving the uniformity of material mixing and reducing the standard deviation of the mixing effect.

[0116] In one possible implementation, the jet device is connected to a mixing box, which is used to supply air pressure to the jet device;

[0117] The jet device includes multiple air inlet pipes; each air inlet pipe includes an air inlet pipe shell, a dustproof ring, dustproof blades, and a flap valve;

[0118] The air outlet of the air inlet pipe faces the inside of the housing; a dustproof ring and multiple dustproof blades connected to the same flip axis are provided on the top inner surface of the air outlet; the dustproof blades are semi-circular and have the same diameter as the inner diameter of the dustproof ring, and can flip up and down under air pressure.

[0119] The air inlet port of the air inlet duct is connected to the mixing box, and a flap valve is provided at the port where the air inlet port is connected to the mixing box. The flap valve is connected to a flap valve controller. The flap valve controller controls the air volume entering the air inlet duct by controlling the degree of flap valve flipping.

[0120] Specifically, as shown in Figures 6 and 7, the jet device is connected to the mixing box 6, which in turn is connected to the air supply fan 6-1. The air supply fan 6-1 provides compressed air to the mixing box 6, which in turn supplies the compressed air to the jet device. The jet device includes several air inlet pipes 7, each comprising an air inlet pipe housing 7-1, a dustproof ring 7-2, dustproof blades 7-3, and a flap valve 7-4. The air outlet of the air inlet pipe 7 faces the interior of the housing 1. A dustproof ring 7-2 is provided on the inner surface of the top of the air outlet. Multiple dustproof blades 7-3 connected to the same rotating shaft are also provided at the center of the dustproof ring 7-2. The dustproof blades 7-3 are semi-circular, with the same diameter as the inner diameter of the dustproof ring 7-2. Under air pressure, the dustproof blades 7-3 can rotate up and down.

[0121] The air inlet port of the air inlet duct 7 is connected to the mixing box 6, and a flap valve 7-4 is installed at the port where the air inlet port connects to the mixing box 6. The flap valve 7-4 is electrically connected to the flap valve controller 7-5. The air inlet duct 7 is also equipped with a pressure sensor 7-6, which is electrically connected to the flap valve controller 7-5 and feeds back the detected airflow of the air inlet duct 7 to the flap valve controller 7-5. The flap valve controller 7-5 controls the degree of flap valve 7-4 to flip according to the received airflow of the air inlet duct 7, so that the airflow in the air inlet duct 7 reaches the target airflow. The gas in the mixing box 6 is ambient air, and more preferably, it can also be hot air with a certain temperature, so that the air and materials are more thoroughly mixed.

[0122] In one possible implementation, the feeding device includes a feed inlet and an airlock structure installed within the feed inlet;

[0123] The airlock structure includes an airlock housing, an airlock drive device, an airlock rotating shaft, and airlock blades;

[0124] The airlock shaft is horizontally fixed inside the feed inlet and is driven to rotate by the airlock drive device. Multiple airlock blades are mounted circumferentially on the airlock shaft. One end face of each airlock blade is connected to the airlock shaft, and the other end faces are respectively attached to the airlock housing. During feeding, the airlock shaft drives the airlock blades to rotate and feed the material into the box.

[0125] Specifically, as shown in Figure 6, the feeding device 2 is located on the upper side of the box 1, and an airlock device is installed in the feeding port of the feeding device 2. As shown in Figure 8, the airlock device is cylindrical, and the airlock shaft 10 in the airlock device is located in the internal space of the feeding port and is horizontally arranged. The airlock drive device 9 is located outside the outer shell of the feeding port and is connected to the airlock shaft 10 to drive the airlock shaft 10 to rotate. The material enters the airlock cavity through the feeding port. The airlock shaft 10 is perpendicular to the main shaft 4-1, with one end connected to the airlock drive device 9 and the other end fixed to the side of the outer shell of the airlock device. The airlock blades 11 are fixed in the axial direction of the airlock shaft 10. One end face of the airlock blades 11 is connected to the airlock shaft 10, and the other end faces of the airlock blades 11 are in contact with the airlock shell 8. That is, the gap between the other end faces of the airlock blades 11 and the airlock shell 8 is extremely small, and they can rotate freely relative to the airlock shell 8. Under the drive of the airlock drive device 9, the airlock shaft 10 rotates. During feeding, the airlock shaft 10 rotates, driving the airlock blades 11 to rotate and feed the material into the housing 1. At the same time, the airlock blades 11 also prevent external air from entering the housing 1 and affecting the airflow distribution inside the housing. The minimum distance between the airlock blades 11 and the airlock housing 8 is 5-10 mm.

[0126] The feeding device includes a screw feeding mechanism;

[0127] The spiral feeding mechanism includes a spiral feeding mechanism housing, the feed port is obliquely fixed on the spiral feeding mechanism housing and communicates with the spiral feeding mechanism housing, and the bottom of the spiral feeding mechanism housing is connected to the inside of the box;

[0128] The spiral feeding mechanism housing contains a vertically arranged spiral feeding mechanism rotating shaft and spiral blades fixedly distributed on the spiral feeding mechanism rotating shaft; a grid plate is fixedly installed at the bottom of the spiral feeding mechanism rotating shaft, the grid plate includes multiple L-shaped grid bars, each L-shaped grid bar includes a horizontal side and a vertical side, the vertical side being located above the horizontal side; one end of the horizontal side is connected to the spiral feeding mechanism rotating shaft, and the other end is connected to the vertical side.

[0129] Specifically, as shown in Figure 9, the feeding device 2 includes a screw feeding mechanism 12. The screw feeding mechanism inlet 12-2 is obliquely fixed to the screw feeding mechanism housing 12-1 and communicates with the housing of the screw feeding mechanism 12. The counterclockwise angle between the screw feeding mechanism inlet 12-2 and the horizontal plane is 45-80°. The bottom of the screw feeding mechanism housing 12-1 is embedded in the internal space of the box 1 and communicates with the inside of the box 1. After the material is fed in from the outside through the screw feeding mechanism inlet 12-2, it enters the screw feeding mechanism 12 and then enters the box 1 of the mixer from the screw feeding mechanism 12.

[0130] A spiral feeding mechanism rotating shaft 12-3 is vertically installed inside the outer casing 12-1. Spiral blades 12-4 are fixed on the rotating shaft 12-3, spirally distributed around the rotating shaft 12-3. The minimum distance between the edge of the spiral blades 12-4 and the outer casing 12-1 is 5-10 mm. This ensures that, while allowing the spiral blades 12-4 to rotate normally, it effectively prevents external airflow from entering the casing and affecting the airflow distribution within the casing, thus impacting the mixing effect. Additionally, it can guide the path of materials entering from the feed inlet. A grid plate 12-5 is fixedly installed at the bottom of the rotating shaft 12-3 of the screw feeding mechanism. The grid plate 12-5 includes multiple L-shaped grid bars, each with an inclined side and a vertical side, with the vertical side located above the inclined side. One end of the inclined side is connected to the rotating shaft 12-3 of the screw feeding mechanism, and the other end is connected to the bottom of the vertical side. All the inclined and vertical sides form a cylindrical shape, and the diameter of the cylinder is larger than the outer shell of the screw feeding device 12, ensuring that all materials entering the housing 1 from the screw mechanism pass through the grid plate 12-5. The rotating shaft 12-3 of the screw feeding mechanism is connected to a drive motor. Driven by the drive motor, the rotating shaft 12-3 of the screw feeding mechanism rotates, causing the screw blades 12-4 and the grid to rotate. During the rotation, the grid disperses the material guided down along the screw blades 12-4.

[0131] In one possible implementation, there are four first stirring mechanisms inside the box, arranged in two layers, with two mechanisms in each layer.

[0132] Specifically, as shown in Figure 6, four parallel first stirring mechanisms 4 are arranged inside the housing 1, divided into upper and lower layers, with two mechanisms in each layer, to stir materials at different heights within the housing 1. In other embodiments, other numbers of first stirring mechanisms 4 can be set according to actual mixing requirements. In other embodiments, the two shafts in the upper layer are main shafts 4-1, and the two shafts in the lower layer are secondary shafts. The diameters of the two main shafts 4-1 are larger than those of the two secondary shafts, and the corresponding multi-stage speed difference agitator 4-3 and vortex disturbance type stirring blades are also larger than the secondary shafts. The diameter of the main shafts 4-1 is 2 to 5 times the diameter of the secondary shafts.

[0133] In one possible implementation, multiple sets of baffle units are distributed inside the box along the main axis direction, and the baffle units divide the internal space of the box into multiple mixing chambers;

[0134] The baffle unit includes upper and lower baffles; the upper and lower baffles are located on the same vertical plane; the baffles include a fixed baffle located below and a movable baffle located above, which are used to control the amount of material in the mixing chamber entering the adjacent mixing chamber.

[0135] Specifically, as shown in Figure 6, the interior of the housing 1 is equipped with multiple sets of baffle units 13, which divide the interior of the housing 1 into multiple spaces, each of which can be considered a mixing chamber. Each baffle unit 13 consists of upper and lower baffles located on the same vertical plane. Each baffle consists of a fixed baffle 13-1 and a movable baffle 13-2. By adjusting the position of the movable baffle 13-2, the mixing volume and residence time of each mixing chamber can be controlled. The baffle units 13 are made of wear-resistant material. In this embodiment, the base material is cast steel ZG20SiMn, and the wear-resistant layer is a weld overlay material. Additionally, the top height of each baffle unit can also be set in the form of louvers, i.e., a panel with multiple slits, allowing material to pass only through the slits, preventing excessive material overflow and reducing the material's residence time.

[0136] The volume of the box is determined based on the material feeding rate, bulk density, and number of cycles, using the following formula:

[0137]

[0138] In formula (1), V is the volume of the box, in meters. 3 P is the feed rate of the material, in t / h, and ρ0 is the bulk density of the mixture, in kg / m³. 3 k is the number of loop iterations.

[0139] Specifically, for materials with a specific long-term mixing ratio, the volume of chamber 1 can be set based on the bulk density of the uniformly mixed material, the hourly feeding weight, and the number of times the material is circulated and stirred within chamber 1. A reasonable design of chamber 1's volume aims to reduce unnecessary space occupation and cost consumption while ensuring uniform mixing. The number of cycles k is adjusted according to the required precision of the mixed product, with an optimal value of 1 to 5. The length-to-diameter ratio of chamber 1 is set to 2 to 10.

[0140] In one possible implementation, each of the mixing chambers is provided with a guide plate at the top, the vertical height of which is complementary to the vertical distance from the top of the corresponding baffle unit to the top surface of the inner chamber, and the guide plate is used to further control the residence time of the material in the mixing chamber.

[0141] Specifically, as shown in Figure 3, the baffle unit 13 divides the interior of the housing 1 into multiple mixing chambers. Each mixing chamber has a guide plate 14 at its top, and the vertical distance from the top of each guide plate 14 to the inner top surface of the housing 1 is complementary to that of the corresponding baffle unit 13. The corresponding baffle unit 13 is downstream in the material inflow direction, and the vertical height of the guide plate 14 closest to the outlet 3 is complementary to that of the upstream baffle unit 13 in the material inflow direction. The guide plate 14 further controls the time it takes for material to enter the downstream mixing chamber from the current mixing chamber, increasing the residence time of the material in the mixing chamber, ensuring that the material entering the housing 1 is fully mixed before flowing out from the outlet 3. In other embodiments, where there is no baffle unit 13 or no jetting device is provided on the bottom and sides of the box, multiple baffles are provided on the inner wall of the box 1 along the stirring direction of the main shaft 4-1. The positions of the baffles within the box 1 are opposite to the projection positions of the connection points of every two agitators 4-3 on the side wall of the box 1. The side of the baffle facing the feeding device 2 is inclined, and the side of the baffle facing the discharge port 3 is vertical. The vertical surface is used to prevent material from flowing back towards the feeding device 2.

[0142] In one possible implementation, at least one vertical stirring mechanism is provided at the top of each mixing chamber, and the rotation speed of the vertical stirring mechanism can be adjusted according to the mixing conditions of each mixing chamber.

[0143] Specifically, as shown in Figure 6, each mixing chamber formed by the baffle unit 13 includes at least four agitators 4-3 in the upper and lower layers, and the four agitators 4-3 belong to different first mixing mechanisms 4.

[0144] A vertical stirring mechanism 15 is installed at the top of the mixing chamber to further achieve gradient mixing of the materials in the mixing chamber in the vertical direction. The stirring speed of the corresponding vertical stirring mechanism 15 in each mixing chamber can be adjusted according to the actual mixing situation.

[0145] The vertical stirring mechanism includes a vertical stirring mechanism rotating shaft, a vertical stirring mechanism drive, and a plurality of second blades distributed circumferentially around the vertical stirring mechanism rotating shaft;

[0146] The second blade includes two vertical edges and is connected to the rotating shaft of the vertical stirring mechanism through one of the vertical edges. The area between the two vertical edges is a vertical curved surface. The vertical stirring mechanism is driven and disposed outside the top surface of the housing and connected to the top end of the rotating shaft of the vertical stirring mechanism. The vertical stirring mechanism drives the rotating shaft of the vertical stirring mechanism to rotate, causing the second blade to rotate in the horizontal direction.

[0147] Specifically, as shown in Figure 10, the vertical stirring mechanism 15 has a vertically arranged rotating shaft 15-1, and multiple second blades 15-3 are arranged circumferentially on the rotating shaft 15-1. The second blades 15-3 are vertically arranged curved surfaces, and one vertical edge of the curved surface is connected to the vertical stirring mechanism rotating shaft 15-1. The vertical stirring mechanism drive 15-2 is located outside the top surface of the box 1 and is connected to the top of the vertical stirring mechanism rotating shaft 15-1. Under the action of the vertical stirring mechanism drive 15-2, the vertical stirring mechanism rotating shaft 15-1 drives the second blades 15-3 to rotate and perform horizontal rotational stirring of the material located at the top of the box 1.

[0148] The fixed baffle located below has two protrusions at its top, through which the two main shafts pass; the bottom of the movable baffle above has a groove that complements the shape of the protrusions, and the width of the groove is greater than the diameter of the main shaft.

[0149] The upper movable baffle is connected to the top plate of the box via an upper screw, and the lower movable baffle is connected to the top plate of the box via a lower screw. The upper and lower screws drive the corresponding movable baffles to move vertically up and down.

[0150] Specifically, as shown in Figures 6 and 11, the baffle unit 13 includes upper and lower baffles. Each baffle includes an upper movable baffle 13-2 and a lower fixed baffle 13-1. Two main shafts 4-1 pass through the fixed baffle 13-1, and the top of the fixed baffle 13-1 is provided with two protrusions. The sides of both the upper and lower fixed baffles 13-1 are in close contact with the inner wall of the box body 1, and the bottom surface of the lower fixed baffle 13-1 is in close contact with the bottom surface of the box body 1 to prevent material from passing through the gap between the lower fixed baffle 13-1 and the bottom of the box body 1 without sufficient mixing. The bottom of the movable baffle 13-2, corresponding to the fixed baffle 13-1, is provided with a groove. The shape of the groove is complementary to the protrusion on the corresponding fixed baffle 13-1. The width of the groove is greater than the diameter of the main shaft 4-1, allowing the movable baffle 13-2 to be moved to a position where it is tightly against the corresponding fixed baffle 13-1. The two grooves of the movable baffle 13-2 are respectively engaged with the two main shafts 4-1. At this point, the obstruction of material from entering other mixing chambers is minimized. When the groove of the movable baffle 13-2 fully engages with the protrusion of the corresponding movable baffle 13-2, the obstruction of material is maximized, extending the residence time of the material in the mixing chamber. In this application, the total height of each baffle is less than the height of the mixer housing 1.

[0151] In the material blocking unit 13, the movement of the upper movable baffle 13-2 is achieved by the upper screw 13-3 installed on the top plate of the box 1, and the movement of the lower movable baffle 13-2 is achieved by the lower screw 13-4 installed on the top plate of the box 1. The top ends of the upper and lower screws 13-4 pass through the corresponding rotating wheels 13-5 on the outside of the top of the box 1, respectively. A rotating wheel support 13-6 is provided between the rotating wheel 13-5 and the outer surface of the top of the box 1 to support the rotating wheel 13-5. The rotation of the rotating wheel 13-5 drives the corresponding screw to move vertically upward or downward, and the screw drives the corresponding movable baffle 13-2 to move vertically up and down, thereby controlling the residence time of the material in the mixing chamber.

[0152] The bottom surface of the mixing chamber is divided into four equally spaced areas in a grid pattern; the maximum time interval Δt between two adjacent areas in the bottom region of the mixing chamber is calculated using the following formula:

[0153]

[0154] In formula (2), h is the height of the retaining unit between the mixing chamber and the next mixing chamber along the material conveying direction, and g is the acceleration due to gravity, which is 9.8 m / s². 2 .

[0155] Specifically, the bottom of each mixing chamber is divided into four equal areas in a grid pattern. An interval of Δt is set between each pair of adjacent areas in these four areas. Within the same time interval, the material experiences different pressures as it passes through each area of ​​the bottom of the mixing chamber, resulting in different falling speeds from the top. This process increases the probability of mixing and enhances the mixing effect. Additionally, the jet volume can be reduced while maintaining the same mixing effect. In formula (2), h is the height of the baffle unit between the mixing chamber and the next mixing chamber along the material conveying direction. The height of the baffle unit of the mixing chamber closest to the outlet is based on the height of the baffle unit between the mixing chambers adjacent to it.

[0156] The minimum blowing force of the mixer is greater than the weight of the heaviest material in the mixture.

[0157] Specifically, the minimum blowing force of the mixer is greater than the weight of the heaviest material in the mixture, to ensure that each material can be blown up and that no mixing dead zone is formed at the bottom of the mixing chamber, thereby further promoting the mixing of materials.

[0158] The mixing system also includes a uniformity detection system; the uniformity detection system is installed on the discharge pipe and is used to detect the uniformity of the material discharged from the mixing machine; the uniformity detection system is electrically connected to the mixing machine controller; the uniformity detection system is used to detect the component uniformity of the mixed materials and feed back the measured uniformity data to the mixing machine controller; the mixing controller is used to control the air volume of the jet device and the rotational speed of the main shaft according to the uniformity data.

[0159] Specifically, as shown in Figure 1, a uniformity detection system 21 is also installed on the discharge pipe 20 connected to the discharge port of the mixer to detect the uniformity of the material discharged from the discharge port. The uniformity data after detection is transmitted to the mixer controller 22. In this application, by real-time monitoring of the CaO in the material discharged from the mixer, relevant information is promptly fed back to the mixer controller 22. The mixer controller 22 adjusts and controls the air volume in the jet device and the speed of the main shaft according to the uniformity data to ensure the uniformity of the material mixing in the mixer, so that the composition of the finished product fluctuates within a certain range.

[0160] As shown in Figure 1, the mixed material discharged from the outlet is transported to the hopper of the third elevator 24 through the discharge pipe 20. The third elevator 24 lifts the hopper and pours the material into the product storage bin 23 for storage.

[0161] This invention also provides a process for preparing low-carbon cement by graded grinding, which is implemented using the system of this invention for preparing low-carbon cement by graded grinding, and includes the following steps:

[0162] Step 1: Prepare the target low-carbon cement raw material components, including: early-age self-activated cementitious material components, middle-age self-activated cementitious material components, long-age self-activated cementitious material components, and rheology-active material components;

[0163] The early-age self-activating cementitious material components include silicate cement clinker, granulated blast furnace slag, and a particle modifier. The preparation process of the early-age self-activating cementitious material components is as follows:

[0164] The mixture of silicate cement clinker, granulated blast furnace slag, and granular modifier, prepared in proportion, is fed into the first conveying device 26 via the first elevator 25, and then into the vertical mill 27 for grinding. The resulting material in the vertical mill 27 has a specific surface area of ​​400-500 m². 2 Materials between / kg are collected in the first dust collector 29 under the action of the first exhaust fan 30, and then transported to the ball mill 31 for further grinding.

[0165] The material, after being re-ground by the ball mill 31, is separated by the classifier 33, resulting in a specific surface area of ​​1150–1250 m². 2 Materials between / kg are collected by the second dust collector 34 under the action of the second tail exhaust fan 35, and then enter the first storage silo 16-2 through the conveying chute 36;

[0166] The middle-aged self-activating cementitious material component includes silicate cement clinker and gypsum. The preparation process of the middle-aged self-activating cementitious material component is as follows:

[0167] The proportioned silicate cement clinker and gypsum mixture is fed into the first elevator 25, then enters the first conveying device 26, and is then sent to the vertical mill 27 for grinding; after grinding in the vertical mill 27, the specific surface area is 380-400 m². 2 The material at a rate of / kg enters the first dust collector 29 under the action of the first tail exhaust fan 30 and is collected, and then enters the second storage silo 16-1;

[0168] The long-term self-activating material components include one or more of fly ash, steel slag, furnace slag, phosphorus slag, and coal gangue. The preparation process of the long-term self-activating cementitious material components is as follows:

[0169] The pre-mixed long-term self-activated cementitious material components are fed into the first elevator 25 and then conveyed to the vertical mill 27 for grinding via the first conveying device 26; the specific surface area obtained after grinding is 400-450 m². 2Materials in the range of / kg are collected by the first dust collector 29 under the suction of the first exhaust fan 30, and then enter the ball mill 31 for further grinding. After grinding, they enter the classifier 33 through the second elevator 32. The classifier 33 separates materials with a specific surface area of ​​480-550m². 2 Materials between / kg are collected by the second dust collector 34 under the action of the second tail exhaust fan 35, and then enter the third storage 16-3 through the conveying chute 36;

[0170] The rheologically active material component is either quartz sand or limestone, and the preparation process of the rheologically active material component is as follows:

[0171] The metered rheologically active material components are fed into the first elevator 25 and then conveyed to the vertical mill 27 via the first conveying device 26 for grinding; the specific surface area obtained after grinding is 200-240 m². 2 / kg of material is collected by the first dust collector 29 under the suction of the first tail exhaust fan 30;

[0172] The material collected by the first dust collector 29 enters the ball mill 31 for further grinding. After being ground again in the ball mill 31, it enters the classifier 33 via the second elevator 32. The classifier 33 separates the material into particles with a specific surface area of ​​240–300 m². 2 Materials between / kg are collected by the second dust collector 34 under the action of the second tail exhaust fan 35, and then enter the fourth storage 16-4 through the conveying chute 36;

[0173] Step 2: After all the raw material components have been prepared, the materials in each storage silo first enter the corresponding buffer silo, are measured by the corresponding metering device, and then enter the mixer together for mixing. After mixing, the target low-carbon cement is obtained.

[0174] In one possible implementation, during the preparation of the early-age self-excited cementitious material component, the specific surface area obtained after grinding by the vertical mill 27 is less than 400 m². 2 The material of / kg is conveyed again to the first elevator 25 via the second conveying device 28;

[0175] In the preparation of the middle-aged self-activated cementitious material components, the specific surface area obtained after grinding by the vertical mill 27 is less than 380m². 2 The material at a rate of / kg is conveyed again to the first elevator 25 via the second conveying device 28;

[0176] In the preparation of the long-term self-activated cementitious material components, the specific surface area obtained after grinding by the vertical mill 27 is less than 400 m². 2The material of / kg is conveyed again to the first elevator 25 via the second conveying device 28;

[0177] In the preparation of the rheologically active material component, the specific surface area obtained after grinding by the vertical mill 27 is less than 200 m². 2 The material at a rate of / kg is conveyed again to the first elevator 25 via the second conveying device 28.

[0178] In one possible implementation, during the preparation of the early-age self-excited cementitious material component, after separation by the air classifier 33, the specific surface area is less than 1150 m². 2 / kg of material is fed into the ball mill 31 for further grinding;

[0179] During the preparation of the middle-aged self-activated cementitious material components, after separation by the air classifier 33, the specific surface area is less than 480 m². 2 / kg of material is fed into the ball mill 31 for further grinding;

[0180] During the preparation of the rheologically active material component, after separation by the classifier 33, the specific surface area is less than 240 m². 2 / kg of material is fed into the ball mill 31 for further grinding.

[0181] In one possible implementation, during the preparation of the early-age self-excited cementitious material component, the material collected by the third dust collector 37 connected to the ball mill 31 under the action of the third tail exhaust fan 38 directly enters the first storage 16-2.

[0182] During the preparation of the long-term self-excited cementitious material component, the material collected by the third dust collector 37 connected to the ball mill 31 under the action of the third tail exhaust fan 38 directly enters the third storage 16-3.

[0183] During the preparation of the rheologically active material components, the material collected by the third dust collector 37 connected to the ball mill 31 under the action of the third tail exhaust fan 38 directly enters the fourth storage tank 16-4.

[0184] Specifically, the low-carbon cement prepared in this application is a self-activated low-carbon cement, comprising the following raw materials in parts by weight: 15-20 parts of early-age self-activated cementitious material component, 45-50 parts of middle-age self-activated cementitious material component, 20-25 parts of long-age self-activated cementitious material component, and 10-15 parts of rheology-active material component.

[0185] The early-age self-excited cementitious material comprises silicate cement clinker, granulated blast furnace slag, and a particle modifier in a mass ratio of 1:3:0.002, with a particle size range of 0.1–10 μm and a particle specific surface area of ​​1150–1250 m². 2 / kg, uniformity coefficient >1.1;

[0186] The particle modifier is one of industrial-grade diethanol monoisopropanolamine or diisopropylethylamine, with an effective ingredient content of ≥85%.

[0187] The middle-aged self-activating cementitious material comprises silicate cement clinker and gypsum in a mass ratio of 95:5, with a particle specific surface area of ​​380–400 m². 2 / kg, uniformity coefficient > 1.1, R 45μm Residue on sieve <5%;

[0188] The long-term self-activating cementitious material is one or more of fly ash, steel slag, furnace slag, phosphorus slag, and coal gangue, with a particle specific surface area of ​​480–550 m². 2 / kg, uniformity coefficient > 1.1, R 45μm Residue on sieve <2%.

[0189] The rheologically active material is either quartz sand or limestone, with a particle specific surface area of ​​240–300 m². 2 / kg, uniformity coefficient > 0.9, R 45μm Residue on sieve <40%.

[0190] The early-age self-activated cementitious material has a 3-day activity index ≥ 100%; the long-age self-activated cementitious material has a 28-day activity index of 65%–80%; and the rheologically active material has no activity requirement.

[0191] The process for preparing gradient self-excited low-carbon cement using a graded separate grinding system is as follows:

[0192] Components for preparing early-age self-excited cementitious materials:

[0193] Silicate cement clinker, granulated blast furnace slag, and granular modifier are metered and fed into the first elevator 25 through the feed inlet 39, and then conveyed into the vertical mill 27 via the first conveying device 26 for grinding. Under the negative pressure of the first exhaust fan 30, a 400-500m³ particle size is obtained after grinding. 2 Fine powder of / kg is drawn into the first dust collector 29 for collection, and the purified gas from the first dust collector 29 is discharged from the first exhaust fan 30. After grinding by the vertical mill 27, the particle specific surface area is less than 400m². 2The material, at a rate of / kg, is conveyed via the second conveyor 28, along with the proportioned silicate cement clinker, granulated blast furnace slag, and granular modifier, into the first elevator 25 for secondary grinding. This grinding process is repeated until the specific surface area of ​​the powder reaches 400–500 m². 2 / kg is collected by the first dust collector 29.

[0194] The 400-500m³ collected by the first dust collector 29 2 The fine powder, at a density of / kg, is conveyed to ball mill 31 for further grinding. The material after grinding in ball mill 31 is discharged from the mill head into the second elevator 32, and then enters the classifier 33 for separation. The particles separated by classifier 33 have a specific surface area of ​​1150–1250 m². 2 / The material, weighing kg, is collected by the second dust collector 34 under the negative pressure of the second exhaust fan 35. The material collected by the second dust collector 34 enters the first storage silo 16-2 through the conveying chute 36. After separation by the air classifier 33, the particle specific surface area is less than 1150 m². 2 / The material (kg) is returned to ball mill 31 for further grinding until the particle specific surface area reaches 1150–1250 m². 2 The powder is collected by the second dust collector 34 after being discharged at a rate of / kg. The internal ventilation of the ball mill 31 is purified by the third dust collector 37. The fine powder collected by the third dust collector 37 directly enters the first product warehouse, and the gas purified by the third dust collector 37 is discharged from the third tail exhaust fan.

[0195] In addition, before preparing the components of the early-age self-activated cementitious material, the granulated blast furnace slag in the raw materials of the early-age self-activated cementitious material is made of mineral powder ground to a certain fineness, with a specific surface area of ​​400-450 m². 2 / kg, mineral powder grinding can be carried out using a ball mill final grinding system. Mineral powder of a certain fineness, along with silicate cement clinker ground by vertical mill 27 and particle modifier, are metered and then fed into ball mill 31 for further grinding. The material ground by ball mill 31 is then separated by air classifier 33 to obtain particles with a specific surface area of ​​1150–1250 m². 2 / kg of early-age self-initiated cementitious material composition. After separation by a 33-stage air classifier, the particle specific surface area is less than 1150 m². 2 / kg of material is returned to ball mill 31 for further grinding.

[0196] Components for preparing middle-aged self-activated cementitious materials:

[0197] The proportioned silicate cement clinker and gypsum are metered and fed into the first elevator 25 through the discharge port 39, and then into the vertical mill 27 via the first conveying device 26 for grinding. The material is ground inside the vertical mill 27. After grinding, a specific surface area of ​​380-400 m² is obtained. 2Fine powder of / kg enters the first dust collector 29 for collection, and the purified gas from the first dust collector 29 is discharged from the first tail exhaust fan 30. After grinding by the vertical mill 27, the particle specific surface area is less than 380m². 2 The material, at a rate of / kg, is conveyed via the second conveyor 28, and together with the proportioned silicate cement clinker and gypsum, enters the first elevator 25 for secondary grinding. This grinding process is repeated until the specific surface area of ​​the particles reaches 380–400 m². 2 / kg is collected by the first dust collector 29, and the material collected by the first dust collector 29 is sent to the second product warehouse.

[0198] Components for preparing long-term self-excited materials:

[0199] A mixture of one or more materials, including fly ash, steel slag, furnace slag, phosphorus slag, and coal gangue, is metered and fed into the first elevator 25 through the discharge port 39, and then conveyed to the vertical mill 27 via the first conveying device 26 for grinding. The resulting product has a specific surface area of ​​400–450 m². 2 Fine powder of / kg enters the first dust collector 29 under the negative pressure of the first exhaust fan 30 and is collected. The gas purified by the first dust collector 29 is discharged from the first exhaust fan 30. The particle specific surface area after grinding by the vertical mill 27 is less than 400m². 2 The material, at a rate of / kg, is conveyed via the second conveying device 28 and fed into the first elevator 25 along with a pre-mixed mixture of one or more materials, including fly ash, steel slag, furnace slag, phosphorus slag, and coal gangue, for secondary grinding. This grinding process is repeated until the particle specific surface area reaches 400–450 m². 2 / kg.

[0200] The particle specific surface area in the first dust collector 29 is 400-450 m². 2 The fine powder, at a density of / kg, is fed into ball mill 31 for further grinding. The material after grinding in ball mill 31 is discharged from the mill head and enters classifier 33 for separation. Classifier 33 separates the powder to obtain particles with a specific surface area of ​​480–550 m². 2 The material at a density of / kg is collected by the second dust collector 34 under the negative pressure of the second exhaust fan 35. The material collected by the second dust collector 34 enters the third storage silo 16-3 from the conveying chute 36. After separation by the classifier 33, the material with a specific surface area of ​​less than 480m² is... 2 The material at a density of / kg is returned to ball mill 31 for further grinding until the specific surface area of ​​the material reaches 480-550m². 2 / kg. The internal ventilation of the ball mill 31 is purified by the third dust collector 37. The fine powder collected by the third dust collector 37 directly enters the third storage silo 16-3. The gas purified by the third dust collector 37 is discharged from the third tail exhaust fan 38.

[0201] In addition, when the raw materials for long-term materials are in powder form, a ball mill final grinding system can be directly used. The well-proportioned materials of a certain fineness are then further ground in ball mill 31. The material ground in ball mill 31 then enters classifier 33 for separation, yielding a specific surface area of ​​480–550 m². 2 The finished long-aged self-excited material, at a rate of / kg, is processed by a classifier. Materials that fail the classification are returned to the ball mill for further grinding until the specific surface area reaches 480–550 m². 2 / kg.

[0202] Material components for preparing rheologically active materials:

[0203] One of the following, quartz sand or limestone, is metered and fed into the first elevator 25 through the feed inlet 39, and then enters the vertical mill 27 for grinding. The specific surface area obtained after grinding in the vertical mill 27 is 200-240 m². 2 Fine powder of / kg is collected in the first dust collector 29 under the negative pressure of the first exhaust fan 30, and the purified gas from the first dust collector 29 is discharged from the first exhaust fan 30. After grinding in the vertical mill 27, the specific surface area is less than 200m². 2 The material, at a density of / kg, is conveyed to the elevator via the second conveying device 28, and then fed into the first elevator 25 along with quartz sand or limestone through the discharge port 39 for secondary grinding until the specific surface area of ​​the material reaches 200-240m². 2 / kg is collected by the first dust collector 29.

[0204] The dust collected in the first dust collector 29 has a specific surface area of ​​200-240 m². 2 The material at a density of / kg is fed into ball mill 31 for further grinding. The material after grinding in ball mill 31 is discharged from the mill head and then fed into classifier 33 via second elevator 32 for separation. Classifier 33 separates the material to obtain particles with a specific surface area of ​​240–300 m². 2 The material, at a density of / kg, is collected by the second dust collector 34 under the negative pressure of the second exhaust fan 35, and then sent to the fourth storage silo 16-4 through the conveying chute 36. After separation by the classifier 33, the material with a specific surface area of ​​less than 240m² is... 2 The material at a density of / kg is returned to ball mill 31 for further grinding until it reaches a density of 240-300 mg / kg. 2 The material is collected by the second dust collector 34 after passing through the ball mill 31. The gas inside the ball mill 31 is purified by the third dust collector 37. The material collected by the third dust collector 37 enters the fourth storage silo 16-4 directly through the conveying chute 36. The gas purified by the third dust collector 37 is discharged from the third tail exhaust fan 38.

[0205] The early-age self-activated cementitious material components, middle-age self-activated cementitious material components, long-age self-activated cementitious material components and rheology-active material components in each storage silo enter the corresponding buffer silo 18, and are measured by the corresponding metering device 17 according to the preset weight. They are then fed into the mixing machine box 1 through the feeding device 2 for mixing and homogenization, and discharged from the discharge port 3, finally producing gradient self-activated low-carbon cement.

[0206] It should be noted that, based on vertical mill grinding, the rheology-active materials are further ground and shaped using a ball mill grinding system to obtain better sphericity and further improve fineness.

[0207] This invention proposes a novel design and preparation concept for low-carbon cement. By controlling particle size and cementitious activity, it prepares early-, mid-, and long-term self-activated cementitious materials in a graded manner, and constructs a gradient self-activated low-carbon cement system through matched optimization design. In its hydration process, this low-carbon cement initially relies on the vigorous hydration reaction of the early-age self-activated cementitious materials to rapidly develop early strength, compensating for the slow early strength development caused by low clinker content. Simultaneously, it releases a large number of silicon / aluminum tetrahedral units, increasing the early ion activity and supersaturation of the pore solution, promoting the nucleation and growth of hydration products, and stimulating the hydration reaction of the mid-age self-activated cementitious materials, accelerating the mid-term strength development of the low-carbon cement. This process continues, further increasing the alkalinity of the pore solution in the later stages of hydration, promoting the depolymerization of inert aluminosilicate tetrahedra in the long-age self-activated cementitious materials, synergistically stimulating the reaction of the long-age self-activated cementitious materials, strengthening the low-carbon cement matrix, achieving stable long-term strength growth, and improving the durability of cement-based materials.

[0208] By setting up a combined vertical mill and ball mill grinding system, different types of materials can be ground using vertical mill, ball mill in closed-circuit grinding, or a combination of vertical mill and ball mill, depending on the particle size distribution characteristics of the materials. This allows for the utilization of the respective grinding process characteristics, resulting in self-activated cementitious materials with different fineness and gradations with minimal energy consumption and maximum output. After mixing in a mixer, low-carbon cement with an ideal particle size distribution is obtained, thus improving the performance of the cement.

[0209] The present invention also has the following advantages and technical effects:

[0210] (1) Compared with traditional cement production methods, the gradient self-excited low-carbon cement prepared by this invention can significantly reduce clinker usage and overall carbon emissions, while also possessing the mechanical properties of rapid early and mid-term strength development and stable long-term strength development.

[0211] (2) The introduction of particle modifiers significantly improves the grinding efficiency of early-age self-excited cementitious materials, reduces the energy consumption of preparation, and utilizes the strong ionic complexation effect of organic particle modifiers to fully stimulate the activity of early-age self-excited cementitious materials and promote the early strength development of low-carbon cement.

[0212] (3) Introducing rheological active materials broadens the particle size distribution of low-carbon cement, optimizes particle gradation, reduces the water demand of low-carbon cement, and improves workability.

[0213] This invention, by setting up multiple sections of agitators with opposite rotation directions, not only achieves relative disturbance of the mixture in opposite directions but also extends the residence time of the mixture in this region, improving mixing efficiency and reducing ineffective mixing power consumption. By setting different numbers of bevel teeth on the differential speed agitator on the main shaft, gradient mixing is achieved along the mixing axis, improving mixing efficiency and uniformity while reducing energy consumption and increasing production efficiency, which is beneficial for large-scale equipment. By setting up a buffer silo and metering device before feeding, unstable feeding can be prevented, effectively controlling feeding stability and improving metering accuracy. By setting up a system that integrates both a vertical mill and a ball mill, different components of low-carbon cement can be ground separately according to their characteristics, ensuring that each component of the low-carbon cement reaches the optimal grinding degree. After mixing in the mixer, low-carbon cement with an ideal particle size distribution is obtained, improving the cement's performance.

[0214] The present invention will now be further illustrated by the following embodiments:

[0215] The system and process for preparing low-carbon cement by graded grinding in this invention were used to prepare early-, middle-, and long-age self-activated cementitious materials and rheologically active materials. After being mixed in specific proportions, the properties of cements with different configurations were measured. The test results are shown in Tables 1 to 4.

[0216] Table 1. Experiment 1 on self-excited low-carbon cement with particle size classification gradient.

[0217]

[0218] Table 2. Experiment 2 on self-excited low-carbon cement with particle size classification gradient.

[0219]

[0220] Table 3. Experiment 3 on self-excited low-carbon cement with particle size classification gradient.

[0221]

[0222]

[0223] Table 4. Experiment 4 on self-excited low-carbon cement with particle size classification gradient.

[0224]

[0225] The GB175-2007 standard for general-purpose Portland cement specifies a 3-day compressive strength of 17 MPa and a 28-day compressive strength of 42.5 MPa for ordinary Portland cement. As shown in Tables 1-4 above, the system and process for preparing low-carbon cement using the graded grinding method described in this invention, when used to prepare early-, mid-, and long-term self-activated cementitious materials and rheologically active materials, and mixed in a specific ratio, yields 3-day and 28-day compressive strengths that are superior to the GB175-2007 standard for ordinary Portland cement (PO.42.5). Furthermore, the uniformity coefficients are all less than 0.9, indicating a wider particle size distribution, reduced cement water demand, and improved cement performance.

[0226] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0227] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A system for preparing low-carbon cement by graded and separately grinding, characterized in that, The system includes a grinding system and a mixing system. The grinding system comprises a first elevator, a first conveying device, a vertical mill, a first dust collector, and a first tail exhaust fan connected in sequence. The first conveying device is used to convey material from the first elevator to the vertical mill. The grinding system also includes a first dust collector, a ball mill, a second elevator, a classifier, a second dust collector, and a conveying chute connected in sequence. The second dust collector is also connected to a second tail exhaust fan. The vertical mill is also connected to a second conveying device for conveying material to the first elevator. The ball mill is also connected to a third dust collector, which is connected to a third tail exhaust fan and the conveying chute. The conveying chute is connected to a first storage silo, a third storage silo, and a first tail exhaust fan, respectively. The four storage silos are connected; the first dust collector is also connected to the second storage silo; the first, second, third, and fourth storage silos are used to store different materials; the mixing system includes a mixer, multiple buffer silos, and multiple metering devices; each buffer silo is connected to a corresponding metering device; the mixer includes a housing, a feeding device, and a discharge port; the first, second, third, and fourth storage silos are respectively connected to their corresponding buffer silos; the housing is inclined upwards from the discharge port side to the feeding device side, with an inclination angle of 2~10°; the feeding device is located at the upper part of the first end of the housing, and the discharge port is located on the side of the second end of the housing; the metering device is connected to the feeding device through a feeding pipe. Next, the materials in each storage silo are metered by the corresponding metering device and then enter the mixer through the feed pipe for mixing. A first stirring mechanism is arranged parallel to the housing body. The first stirring mechanism includes a main shaft driven by a main shaft drive device, and multiple stirrers are continuously installed on the main shaft along its axial direction. Each stirrer includes two drive bevel gears, a main shaft bevel gear coaxial with the main shaft, two drive circular gears, two large gear rings, and two hollow shafts. The two drive bevel gears are symmetrically arranged on both sides of the main shaft and simultaneously mesh with the main shaft bevel gears sleeved and fixed on the main shaft. The two drive circular gears are respectively arranged outside their respective drive bevel gears and are respectively connected to the two drive bevel gears via drive gear shafts. The system features a toothed connection; two large gear rings are supported by a gear ring support cylinder, with two transmission round teeth located between the two large gear rings, each meshing with one of the two large gear rings; the axial direction of the gear ring support cylinder is parallel to the main shaft, and its two ends are fixed to the first and second end sides of the mixer, respectively; each hollow shaft is fixedly connected to a large gear ring, and the two hollow shafts are tightly fitted together to prevent material from entering the agitator; each hollow shaft is equipped with multiple first blades, and under the rotation of the main shaft, the two hollow shafts rotate in opposite directions to stir and mix the material inside the box; the number of teeth on the main shaft bevel gears of each agitator on the main shaft is different, so that the first stirring mechanism stirs the material at different positions inside the box at different speeds.

2. The system for preparing low-carbon cement by graded grinding according to claim 1, characterized in that, It also includes a hot air furnace that provides hot air for the entire system.

3. The system for preparing low-carbon cement by graded grinding according to claim 1, characterized in that, The first blade has a uniform cross-sectional thickness; the first blade has a wave-shaped structure, which is used to make the material move at different speeds in multiple dimensions.

4. The system for preparing low-carbon cement by graded grinding according to claim 3, characterized in that, The first blade includes a blade root and a blade tip; the blade tip is located at the top of the first blade, the blade root is connected to the outer surface of the hollow shaft, and the blade tip faces the discharge port.

5. The system for preparing low-carbon cement by graded grinding according to claim 1, characterized in that, The bottom and sides of the box are also equipped with jetting devices to adjust the material movement trajectory and residence time inside the box.

6. The system for preparing low-carbon cement by graded grinding according to claim 5, characterized in that, The jet device is connected to a mixing box, which is connected to a blower; the blower provides air pressure to the mixing box; the mixing box provides air pressure to the jet device; the jet device includes multiple air inlet pipes; each air inlet pipe includes an air inlet pipe housing, a dustproof ring, dustproof blades, and a flap valve; the air outlet of the air inlet pipe faces the interior of the housing; the top inner surface of the air outlet is provided with a dustproof ring and multiple dustproof blades connected to the same flip axis, located at the center of the dustproof ring; The dustproof blade is semi-circular and its diameter is the same as the inner diameter of the dustproof ring. Under the action of air pressure, the dustproof blade can flip up and down. The air inlet port of the air inlet pipe is connected to the mixing box, and a flap valve is provided at the port where the air inlet port is connected to the mixing box. The flap valve is connected to a flap valve controller. The flap valve controller controls the air volume entering the air inlet pipe by controlling the degree of flipping of the flap valve.

7. The system for preparing low-carbon cement by graded grinding according to claim 1, characterized in that, The feeding device includes a feed inlet and a lock structure installed inside the feed inlet; the lock structure includes a lock housing, a lock drive device, a lock shaft, and lock blades; the lock shaft is horizontally fixed inside the feed inlet and is driven to rotate by the lock drive device; multiple lock blades are circumferentially mounted on the lock shaft; one end face of each lock blade is connected to the lock shaft, and the other end faces are respectively attached to the lock housing; during feeding, the lock shaft drives the lock blades to rotate and feed the material into the box; or, the feeding device includes a screw feeding mechanism; the screw feeding mechanism includes a screw feeding mechanism housing. The feed inlet of the screw feed mechanism is obliquely fixed to the outer shell of the screw feed mechanism and communicates with the outer shell. The bottom of the outer shell of the screw feed mechanism is connected to the inside of the box. A screw feed mechanism rotating shaft and helical blades fixed on the rotating shaft are vertically arranged inside the outer shell of the screw feed mechanism. A grid plate is fixedly arranged at the bottom of the rotating shaft of the screw feed mechanism. The grid plate includes multiple L-shaped grid bars. The L-shaped grid bars include a vertical side and an inclined side. The vertical side is located above the inclined side. One end of the inclined side is connected to the rotating shaft of the screw feed mechanism, and the other end is connected to the bottom end of the vertical side.

8. The system for preparing low-carbon cement by graded grinding according to claim 1, characterized in that, The first stirring mechanism inside the box consists of four parts, arranged in two layers, with two parts in each layer.

9. The system for preparing low-carbon cement by graded grinding according to claim 8, characterized in that, Multiple sets of baffle units are distributed along the main axis inside the box, and the baffle units divide the internal space of the box into multiple mixing chambers; the baffle unit includes upper and lower baffles; the upper and lower baffles are located on the same vertical plane; the baffles include a fixed baffle at the bottom and a movable baffle at the top, which are used to control the amount of material in the mixing chamber entering the adjacent mixing chamber.

10. The system for preparing low-carbon cement by graded grinding according to claim 9, characterized in that, Each of the mixing chambers is provided with a guide plate at the top. The vertical height of the guide plate is complementary to the vertical distance from the top of the corresponding baffle unit to the top surface of the inner chamber. The guide plate is used to further control the residence time of the material in the mixing chamber.

11. The system for preparing low-carbon cement by graded grinding according to claim 9, characterized in that, Each of the mixing chambers is equipped with at least one vertical stirring mechanism at its top, and the rotation speed of the vertical stirring mechanism can be adjusted according to the mixing conditions of the mixing chamber.

12. A process for preparing low-carbon cement by graded and separately grinding, characterized in that, This process is based on the system for preparing low-carbon cement by graded grinding according to any one of claims 1 to 11, and includes the following steps: Step 1: Prepare the target low-carbon cement raw material components, including: early-age self-activated cementitious material components, middle-age self-activated cementitious material components, long-age self-activated cementitious material components, and rheology-active material components; the early-age self-activated cementitious material components include silicate cement clinker, granulated blast furnace slag, and particle modifier. The preparation process of the early-age self-activated cementitious material components is as follows: the mixture of silicate cement clinker, granulated blast furnace slag, and particle modifier is fed into the first conveying device through the first elevator, and then fed into the vertical mill for grinding. The resulting vertical mill has a specific surface area of ​​400-500 m². 2 Materials in the range of / kg are collected by the first dust collector under the action of the first exhaust fan, and then conveyed to the ball mill for further grinding; the material after further grinding in the ball mill is separated by an air classifier to obtain a specific surface area of ​​1150~1250m². 2 Materials in the range of / kg are collected by the second dust collector under the action of the second tail exhaust fan, and then enter the first storage silo through the conveying chute; the middle-aged self-activated cementitious material component includes silicate cement clinker and gypsum, and the preparation process of the middle-aged self-activated cementitious material component is as follows: the proportioned silicate cement clinker and gypsum mixture is fed into the first elevator, enters the first conveying device through the first elevator, and is then sent to the vertical mill for grinding; after grinding by the vertical mill, the specific surface area is 380~400m². 2 The material at a rate of / kg is collected by the first dust collector under the action of the first tail exhaust fan, and then enters the second storage silo; the long-term self-activated cementitious material component includes one or more of fly ash, steel slag, furnace slag, phosphorus slag, and coal gangue. The preparation process of the long-term self-activated cementitious material component is as follows: the proportioned long-term self-activated cementitious material component is fed into the first elevator and then conveyed to the vertical mill for grinding through the first conveying device; the specific surface area obtained after grinding is 400~450m². 2 Materials with a specific surface area between 0.5 kg and 0.6 kg are collected by the first dust collector under the suction of the first exhaust fan, then further ground in the ball mill, and finally fed into the classifier via the second elevator; the classifier separates materials with a specific surface area of ​​480~550 m². 2 Materials in the range of / kg are collected by the second dust collector under the action of the second tail exhaust fan, and then enter the third storage tank through the conveying chute; the rheological active material component is one of quartz sand or limestone, and the preparation process of the rheological active material component is as follows: the metered rheological active material component is fed into the first elevator and then conveyed to the vertical mill for grinding through the first conveying device; the specific surface area obtained after grinding is 200~240m². 2 The material at a density of / kg is collected by the first dust collector under the suction of the first exhaust fan; the material collected by the first dust collector enters the ball mill for further grinding, and after further grinding in the ball mill, it enters the classifier via the second elevator; the classifier separates the material into particles with a specific surface area of ​​240~300m². 2 Materials between / kg are collected by the second dust collector under the action of the second tail exhaust fan, and then enter the fourth storage silo through the conveying chute; Step 2: After all the raw material components are prepared, the materials in each storage silo first enter the corresponding buffer silo, are measured by the corresponding metering device, and then enter the mixer together for mixing. After mixing, the target low-carbon cement is obtained.

13. The process for preparing low-carbon cement by graded grinding according to claim 12, characterized in that, In the preparation of the early-age self-excited cementitious material components, the specific surface area obtained after grinding in the vertical mill is less than 400 m². 2 / kg of material is conveyed again to the first elevator via the second conveying device; during the preparation of the middle-aged self-excited cementitious material components, the specific surface area obtained after grinding by the vertical mill is less than 380m². 2 The material at a density of / kg is conveyed again to the first elevator via the second conveying device; during the preparation of the long-term self-activated cementitious material component, the specific surface area obtained after grinding by the vertical mill is less than 400m². 2 The material at a density of / kg is conveyed again to the first elevator via the second conveying device; during the preparation of the rheologically active material component, the specific surface area obtained after grinding by the vertical mill is less than 200m². 2 The material at a rate of / kg is conveyed back to the first elevator via the second conveying device.

14. The process for preparing low-carbon cement by graded grinding according to claim 12, characterized in that, During the preparation of the early-age self-excited cementitious material components, after separation by the air classifier, the specific surface area is less than 1150 m². 2 / kg of material is fed into the ball mill for further grinding; during the preparation of the long-term self-activated cementitious material component, after separation by the air classifier, the specific surface area is less than 480m². 2 / kg of material is fed into the ball mill for further grinding; during the preparation of the rheologically active material component, after separation by the classifier, the specific surface area is less than 240m². 2 / kg of material is fed into the ball mill for further grinding.

15. The process for preparing low-carbon cement by graded grinding according to claim 12, characterized in that, In the preparation of the early-age self-activated cementitious material component, the material collected by the third dust collector connected to the ball mill under the action of the third tail exhaust fan directly enters the first storage tank; in the preparation of the long-age self-activated cementitious material component, the material collected by the third dust collector connected to the ball mill under the action of the third tail exhaust fan directly enters the third storage tank; in the preparation of the rheology-active material component, the material collected by the third dust collector connected to the ball mill under the action of the third tail exhaust fan directly enters the fourth storage tank.

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