DE-112024002230-T5 - System and process for the production of low-CO2 cement by staged and separate grinding

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Abstract

System and method for producing low-carbon cement by classification and subsequent 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 separator (29), and a first exhaust fan (30), which are connected sequentially. The first conveying device serves to transport materials from the first elevator to the vertical mill. The grinding system further includes a first dust separator, a ball mill (31), a second elevator (32), a separator (33), a second dust separator (34), and a conveying chute (36), which are connected sequentially. The grinding system can effect a relative mixing of the materials in opposite directions, thereby improving the mixing efficiency of the materials, and by means of the system equipped with the vertical mill and the ball mill, the comminution can be carried out according to the properties of the different components of the low-carbon cement, ensuring that all components of the low-carbon cement achieve the optimal degree of grinding, improving the performance of the cement, reducing the amount of clinker and decreasing the carbon emission intensity of the cement.

Inventors

Wenhai Nie
Xin Du
Di Liu
Chang Liu
Zhonghua Qin
XIONG HUANG
Minghao Liu

Assignees

TIANJIN CEMENT INDUSTRY DESIGN & RESEARCH INSTITUTE CO., LTD

Dates

Publication Date: 20260513
Application Date: 20240912
Priority Date: 20240508

Claims (15)

A system for producing low- CO2 cement by staged and separate grinding, characterized in that the system comprises a grinding system and a mixing system, wherein the grinding system comprises a first bucket elevator, a first conveying device, a vertical mill, a first dust separator, and a first exhaust fan connected in series, wherein the first conveying device is used to convey material from the first bucket elevator to the vertical mill, wherein the grinding system also comprises a first dust separator, a ball mill, a second bucket elevator, a classifier, a second dust separator, and an air conveying trough connected in series, wherein the second dust separator is also connected to a second exhaust fan, wherein the vertical mill is also connected to a second conveying device used to convey material to the first bucket elevator, wherein the ball mill is also connected to a third dust separator connected to a third exhaust fan, wherein the third dust separator is also connected to the air conveying trough, the air conveying trough being connected to a first silo, a third silo, and a fourth silo, wherein the first dust separator is also connected to a second silo, wherein the first silo, the second silo, the third silo, and the fourth silo are used for storing different goods, wherein the mixing system comprises a mixer, several buffer tanks, and several metering devices, each of the buffer tanks being connected to a metering device, wherein the mixer comprises a housing, a feed device, and a discharge opening, wherein the first silo, the second silo, the third silo, and the fourth silo are each connected to a corresponding buffer tank, wherein the housing is inclined upwards from the discharge opening side to the feed device side at an angle of 2° to 10°, wherein the feed device is located in the upper region of the first end of the housing, wherein the discharge opening is located on the side surface of the second end of the housing, wherein the metering device is connected to the feed device via a feed line, and the material from each silo is discharged after metering by the corresponding Metering device, the product is transferred via the feed line into the mixer for stirring and mixing, wherein a first agitator is arranged in the housing parallel to the housing, wherein the first agitator comprises a main shaft driven by a main shaft drive device, and wherein the main shaft is provided with several agitators mounted continuously along the axial direction of the main shaft, each agitator comprising two gear bevel gears and a main shaft bevel gear running coaxially to the main shaft, two gear spur gears, two large rim gears and two hollow shafts, wherein the two gear bevel gears are arranged symmetrically on both sides of the main shaft and mesh simultaneously with the main shaft bevel gears mounted and fastened on the main shaft, wherein the two gear spur gears are each arranged on the outside of their corresponding gear bevel gears and are each connected to the two gear bevel gears via a gear shaft, wherein the two large rim gears are supported by a rim gear support cylinder, wherein the two gear spur gears are located between the two large rim gears and each of the The gear spur gears are each engaged with the two large ring gears, the axial direction of the ring gear support cylinder being parallel to the main shaft, and both ends of the ring gear support cylinder being attached to the side surface of the first and second ends of the mixer, each of the hollow shafts being rigidly connected to a large ring gear, and the two hollow shafts being closely fitted to each other at a coupling position to prevent the material from being transferred into the agitator, each of the hollow shafts being provided with several first vanes, the two hollow shafts rotating in opposite directions under the rotation of the main shaft to stir and mix the material in the housing, the number of teeth of the respective main shaft bevel gear of each agitator on the main shaft being different, so that the first agitator stirs the material at different speeds at different positions in the housing.
System for the production of low- CO2 cement by staged and separate grinding according to Claim 1 , characterized in that the system also includes a hot air oven that supplies the entire system with hot air.
System for the production of low- CO2 cement by staged and separate grinding according to Claim 1 , characterized in that the first wing has a uniform overall sectional thickness indicates, with the first wing having a wave-like structure and being used to move the material in multiple directions at variable speed.
System for the production of low- CO2 cement by staged and separate grinding according to Claim 3 , characterized in that the first wing comprises a root and a tip, wherein the tip is located at the upper end of the first wing, wherein the root is connected to the outer surface of the hollow shaft, and wherein the tip faces the output opening.
System for the production of low- CO2 cement by staged and separate grinding according to Claim 1 , characterized in that the bottom and sides of the housing are also provided with air injection devices to adjust the travel path and residence time of the goods in the housing.
System for the production of low- CO2 cement by staged and separate grinding according to Claim 5 , characterized in that the air injection devices are connected to an air mixing chamber which is connected to an air supply fan, wherein the air supply fan is used to supply the air mixing chamber with air pressure, wherein the air mixing chamber is used to supply the air injection devices with air pressure, wherein the air injection device comprises several air inlet pipes, wherein an air inlet pipe comprises an air inlet pipe shell, a dust sealing ring, a dust deflector plate and a flap valve, wherein the air outlet port of the air inlet pipe faces the interior of the housing, wherein the inner surface of the top of the air outlet port is provided with a dust sealing ring and several dust deflector plates located in the center of the dust sealing ring and connected to the same pivot axis, wherein the dust deflector plates are semicircular and their diameter corresponds to the inner diameter of the dust sealing ring, wherein the dust deflector plates are flipped up and down under the influence of the air pressure, wherein the air inlet port of the air inlet pipe is connected to the air mixing chamber and a flap valve is provided at a connection where the air inlet connection is connected to the air mixing chamber, wherein the flap valve is connected to the flap valve control, wherein the flap valve control controls the amount of air entering the air inlet pipe by controlling the pivot dimension of the flap valve.
System for the production of low- CO2 cement by staged and separate grinding according to Claim 1 , characterized in that the feeding device comprises an inlet opening and an airlock structure mounted in the inlet opening, wherein the airlock structure comprises an airlock housing, an airlock drive device, an airlock rotating shaft and an airlock leaf, wherein the airlock rotating shaft is mounted horizontally in the inlet opening and is driven to rotate by the airlock drive device, wherein several airlock leaves are mounted on the axial circumference of the airlock rotating shaft, wherein one end face of the airlock leaf is connected to the airlock rotating shaft and the other end faces each bear against the airlock housing, wherein during feeding the airlock rotating shaft drives the airlock leaves so that the airlock leaves rotate and convey the material into the housing, or wherein the feeding device comprises a screw feeder, wherein the screw feeder comprises a screw feeder housing, wherein the inlet opening of the screw feeder is inclinedly mounted on the screw feeder housing and communicates with the screw feeder housing, wherein the bottom of the screw feeder housing communicates with the interior of the housing, wherein a screw spindle and spirally distributed screw wings, which are attached to the screw spindle, are arranged vertically in the screw feed housing, wherein a grid plate is attached to the bottom of the screw spindle, the grid plate comprising several L-shaped grid bars, the L-shaped grid bars comprising vertical sides and inclined sides, the vertical sides being located above the inclined sides, one end of the inclined sides being connected to the screw spindle and the other end being connected to a lower end of the vertical sides.
System for the production of low- CO2 cement by staged and separate grinding according to Claim 1 , characterized in that four first agitators are present in the housing and the four first agitators are divided into an upper level and a lower level, with two agitators arranged on each level.
System for the production of low- CO2 cement by staged and separate grinding according to Claim 8 , characterized in that several groups of locking units are distributed along the main shaft in the housing, the locking units dividing the interior of the housing into several mixing chambers, each locking unit comprising an upper locking structure and a lower locking structure arranged one above the other, the upper locking structure and the lower locking structure being on the same vertical plane, each locking structure comprising a lower fixed locking plate and an upper movable locking plate, with which the quantity of material in the mixing chamber is controlled and transferred to an adjacent mixing chamber.
System for the production of low- CO2 cement by staged and separate grinding according to Claim 9 , characterized in that a guide plate is arranged on the top of each mixing chamber, wherein the vertical height of the guide plate is complementary to the vertical distance from the top of the corresponding locking unit to the ceiling surface in the housing, wherein the guide plate is used to further control the residence time of the material in the mixing chamber.
System for the production of low- CO2 cement by staged and separate grinding according to Claim 9 , characterized in that at least one vertical agitator is provided on the top of each mixing chamber, wherein the rotational speed of the vertical agitator can be adjusted according to the mixing conditions in the mixing chamber.
A process for producing low- CO2 cement by staged and separate grinding, characterized in that the process is based on the system for producing low- CO2 cement by staged and separate grinding according to one of the Claims 1 until 11 is carried out and comprises the following steps: Step 1: Production of desired material components for low- CO2 cement, comprising: an early self-activating gelling component, a medium-term self-activating gelling component, a long-term self-activating gelling component, and a rheologically active material component, wherein the early self-activating gelling component comprises silicate cement clinker, granulated blast furnace slag, and grinding aids, wherein the process for producing the early self-activating gelling component is as follows: conveying a metered mixture of silicate cement clinker, granulated blast furnace slag, and grinding aids via the first bucket elevator to the first conveying device and then through the first conveying device into the vertical mill for grinding, wherein the material obtained in the vertical mill, with a specific surface area of 400 m² /kg - 500 m² /kg, is collected in the first dust collector under the action of the first exhaust fan and subsequently conveyed to the ball mill for further grinding, sorting of the material by the classifier, After the material has been milled again by the ball mill, the resulting material with a specific surface area of 1150 m² /kg - 1250 m² /kg is collected by the second dust collector under the action of the second exhaust fan and then transported by the air conveying trough into the second silo, wherein the medium-term self-activating gelling component comprises a silicate cement clinker and a gypsum, wherein the process for producing the medium-term self-activating gelling component proceeds as follows: a metered mixture of the silicate cement clinker and the gypsum is fed into the first bucket elevator, wherein the mixture is transferred by the first bucket elevator into the first conveying device and then transported to the vertical mill for milling, wherein the material with a specific surface area of 380 m² /kg to 400 m² /kg is collected after milling by the vertical mill under the action of the first exhaust fan in the first dust collector and then transferred to the first silo, wherein the long-term self-activating The gelling component comprises one or more of fly ash, steel slag, furnace slag, phosphorus slag, and coal grit, wherein the process for producing the long-term self-activating gelling component proceeds as follows: A metered long-term self-activating gelling component, after being filled into the first bucket elevator, is conveyed by the first conveying device into the vertical mill for grinding, wherein, after grinding, the material with a specific surface area of 400 m² /kg - 450 m² /kg is collected by the first dust collector under the suction action of the first exhaust fan and then transferred to the ball mill for further grinding and then by the second bucket elevator into the classifier, wherein the material obtained from the classifier with a specific surface area of 480 m² /kg - 550 m² /kg is collected by the second dust collector under the action of the second exhaust fan and then transferred by the air conveying trough into the third silo, wherein the rheologically active material component is quartz sand or limestone is, whereby the procedure for The production of the rheologically active material component proceeds as follows: The metered rheologically active material component is filled into the first bucket elevator and then conveyed by the first conveying device to the vertical mill for grinding. After grinding, the resulting material, with a specific surface area of 200 m² /kg to 240 m² /kg, is collected by the first dust separator under the suction action of the first exhaust fan. The material collected by the first dust separator is transferred to the ball mill for further grinding. After re-grinding in the ball mill, the material is then transferred via the second bucket elevator to the classifier. The material obtained from the classifier, with a specific surface area of 240 m² /kg to 300 m² /kg, is collected by the second dust separator under the action of the second exhaust fan and then transferred through the air conveying trough to the fourth silo. Step 2: Transfer of the material in each silo first to the corresponding buffer tank, after all material components are produced, the material is dosed with the appropriate dosing device and then transferred to the mixer for mixing, resulting in the desired low- CO2 cement after mixing.
Process for the production of low- CO2 cement by staged and separate grinding according to Claim 12 , characterized in that , in the production of the early self-activating gelling component, the material obtained after milling by the vertical mill with a specific surface area of less than 400 m² /kg is transported again to the first bucket elevator via the second conveying device; in the production of the medium-term self-activating gelling component, the material obtained after milling by the vertical mill with a specific surface area of less than 380 m² /kg is transported again to the first bucket elevator via the second conveying device; in the production of the long-term self-activating gelling component, the material obtained after milling by the vertical mill with a specific surface area of less than 400 m² /kg is transported again to the first bucket elevator via the second conveying device; and in the production of the rheologically active material component, the material obtained after milling by the vertical mill with a specific surface area of less than 200 m² /kg is transported again to the first bucket elevator via the second conveying device.
Process for the production of low- CO2 cement by staged and separate grinding according to Claim 12 , characterized in that , in the production of the early self-activating gelling component, the material with a specific surface area of less than 1150 m² /kg is fed into the ball mill for re-grinding after sorting by the classifier, in the production of the long-term self-activating gelling component, the material with a specific surface area of less than 480 m² /kg is fed into the ball mill for re-grinding after sorting by the classifier, and in the production of the rheologically active material component, the material with a specific surface area of less than 240 m² /kg is fed into the ball mill for re-grinding after sorting by the classifier.
Process for the production of low- CO2 cement by staged and separate grinding according to Claim 12 , characterized in that , during the production of the early self-activating gelling component, the material collected by the third dust separator connected to the ball mill is transported directly into the first silo by the third exhaust fan, during the production of the long-term self-activating gelling component, the material collected by the third dust separator connected to the ball mill is transported directly into the third silo by the third exhaust fan, and during the production of the rheologically active material component, the material collected by the third dust separator connected to the ball mill is transported directly into the fourth silo by the third exhaust fan.

Description

TECHNICAL AREA The present invention relates to the technical field of cement production and more specifically to a system and a method for producing low- CO2 cement by staged and separate grinding. STATE OF THE ART In the cement industry, different materials are fed into the mixing device in a specific ratio via a metering device. Mixing is carried out mechanically or pneumatically, with uniform stirring over a specific period achieving the goal of a homogeneous mixture. Currently, commercially available mixing devices can be broadly divided into two categories: continuous and intermittent. Due to the steady material feed and long mixing time, the intermittent mixing device exhibits good mixing efficiency and high homogeneity, exceeding 99%. Compared to a pneumatic-mechanical combination mixing device, homogeneity is improved by approximately 5%. However, because the intermittent mixing device requires several mixing tanks with relatively large volumes and has a long mixing time, it occupies a large footprint, has limited production capacity, and cannot be promoted and used on a large scale. Regarding pneumatic, mechanical, or pneumatic-mechanical combination mixing devices, the most common types of powder mixers currently available on the market are horizontal or spiral vertical mixers. The operating principle of a horizontal mixer is to mechanically stir the powder using blades mounted on the drive shaft. The fixed circular motion and axial movement of the material are the primary means of achieving the desired mixing effect. Existing horizontal mixers generally operate at a single speed within the mixing chamber and cannot mix the material in multiple stages within the same chamber. This results in low mixing efficiency and a poor mixing result. At the same time, sufficient power is required to overcome the resistance of the material during the work process. This leads to problems such as high installed power, high energy consumption, low production efficiency, a large footprint, and low flexibility in process arrangement. When filling the mixer with material, "material overflow" and other phenomena can easily occur. The material is discharged from the mixer without being mixed, leading to large fluctuations in the uniformity of the mixture. This results in an uneven composition, impairs subsequent process design and the improvement of the performance of the final cement product, leads to a continuous increase in cement production costs, and hinders further energy savings and consumption reduction in the cement industry. For products with similar powder particle sizes, it is not easy to separate particles of the same size during mixing to ensure uniform and smooth blending. However, for products with large differences in powder particle size, the following applies: the smaller the particle size and the finer the powder, the more likely it is to float to the surface during mixing. Conversely, the larger the particle size and the coarser the powder, the more likely it is to sink. This leads to segregation, which complicates mixing. With existing equipment, problems frequently occur during the mixing process, such as dead zones, dead spots, agglomeration, and clumping. This results in segregation and significant clumping of the product after mixing, leading to large variations in composition and a large CaO standard deviation. In ultrafine material mixtures with a size of 1000 or 2000 mesh or more, the fineness itself is relatively small, and the gravitational constraint on the individual particles becomes so negligible that the particles exhibit a certain degree of mobility due to suspension. Simultaneously, the material absorbs a large amount of mechanical or thermal energy during the comminution process; therefore, the surface of the newly formed ultrafine particles has a very high surface energy, and the material is in an extremely unstable state. To reduce surface energy, particles often clump together to reach a stable state, which can easily lead to particle agglomeration. Therefore, the particles tend to agglomerate with each other and are difficult to mix, making homogeneous mixing challenging. With sticky materials, at a relative humidity above 65%, water vapor begins to condense on the surface of the particles and between the particles, and the formation of liquid bridges between the particles significantly increases the agglomeration effect. Continuous and stable feed from the raw material storage, precise dosing, stable material transport, and uniform mixing are some of the key factors for the mixing effect. The mixer's performance is reflected in the mixing quality, energy consumption, and maintenance requirements. The main purpose of the mixing process is to obtain a mixture in which the various components are evenly distributed. The mixer's function is to blend the material uniformly. The more uniform the components of the output mixture, the better the mixing effect. In industrial applicat