Method and system for preparing low-carbon cement through graded gradient utilization of coal gasification ash

Abstract

The invention provides a method and a system for preparing low-carbon cement by grading gradient utilization of coal gasification ash. The method comprises the following steps: dividing the coal gasification ash into carbon-rich ash, medium-carbon ash and carbon-poor ash according to the carbon content; feeding the carbon-rich ash and feed coal into a pulverized coal preparation workshop to prepare a first mixture serving as clinker calcination fuel; metering the medium-carbon ash residue, feeding the medium-carbon ash residue and other raw material components into a raw material preparation workshop, and grinding and drying; decomposing and calcining the uniformly mixed second mixture, and cooling to obtain clinker; and feeding a mixture of the clinker, other cement components and carbon-poor ash into a cement preparation workshop to prepare finished cement. Coal gasification ash materials with different characteristics are obtained by grading the carbon content of the coal gasification ash, and are respectively used in three process sections of cement raw material grinding, clinker calcining and cement grinding in combination with the characteristics of a cement production process, so that the coal gasification ash realizes large-dosage and large-scale utilization in the aspect of building material resources; the carbon emission in the cement clinker production process is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of cement preparation, and more specifically to a method and system for preparing low-carbon cement by quality-based and tiered utilization of coal gasification ash. Background Art

[0002] Coal gasification technology is the leader in the development of the modern coal chemical industry and one of the important technologies for achieving clean and efficient use of coal. Coal gasification ash is waste slag produced in the process of coal gasification production, with an average annual output of more than 60 million tons. Since coal gasification ash is difficult to degrade, it has not yet been applied on a large scale, and its utilization rate is about 8%. A large amount of coal gasification ash can only be piled up or landfilled, which not only occupies a large amount of land resources and causes soil and water pollution, but also causes dust and fine particles, posing a hidden danger to human health. Coal gasification ash contains rich components such as residual carbon and silicon aluminum oxides, which lays the foundation for its resource utilization.

[0003] As a basic building material, cement has always occupied an important position in the national economy. According to data from the National Bureau of Statistics, my country's cement production in 2023 was 2.038 billion tons, ranking first in the world for more than 20 consecutive years. According to relevant data, carbon emissions from my country's cement industry account for about 13.5% of the current national total carbon emissions, second only to steel in the industrial sector (carbon emissions account for 15%).

[0004] Carbon emissions from cement production mainly come from indirect carbon emissions from clinker production and electricity consumption, of which clinker production accounts for more than 95%. According to the 2018 International Energy Agency Cement Sustainable Development Promotion Association's "Technology Roadmap - Low-Carbon Transformation of the Cement Industry", the carbon emission intensity of cement can be reduced by replacing clinker and reducing the proportion of clinker used in cement. Clinker replacement alone accounts for 37% of carbon reduction measures. Therefore, how to reduce clinker carbon emissions and reduce the proportion of clinker used in cement has become a hot issue of international concern.

[0005] Cement production systems and grinding equipment have mature technologies, clear processes, and are widely used. However, due to the different material properties of coal gasification ash, the following problems exist in cement production applications:

[0006] (1) Since coal gasification ash contains a certain average carbon content (>10%), when it is directly used as a mixture to replace clinker and applied to cement, the water requirement of cement increases and the strength decreases. This is because coal gasification ash contains carbon, which is a porous organic matter. During the cement hydration process, the surface contact between CSH gel and carbon particles is very weak, resulting in coal gasification ash cannot be directly used as a cement mixture, and the resource utilization of coal gasification ash building materials is difficult.

[0007] (2) Since coal gasification ash contains rich residual carbon and silicon-aluminum oxides and other components, it has a certain average calorific value (600-900 kCal / kg) and can be used as a fuel to replace cement production. However, compared with traditional cement fuel (4500-6000 kCal / kg), its calorific value is too low. When it is burned together with traditional fuels, the combustion time is short, resulting in incomplete combustion of the ash, residual carbon in the cement clinker, and substandard quality. Summary of the invention

[0008] In view of the above problems, the present invention provides a method and system for preparing low-carbon cement through the quality-based and tiered utilization of coal gasification ash, which is used to solve the problems in the prior art that it is difficult to utilize coal gas ash as building materials as resources, and that when the calorific value of coal gasification ash is low and it is burned together with traditional fuels, the combustion time is short, resulting in incomplete combustion of ash, residual carbon in cement clinker, and substandard quality.

[0009] The present invention provides a method for preparing low-carbon cement by using coal gasification ash in different qualities and stages, comprising the following steps:

[0010] Step 1, classifying the coal gasification slag according to the carbon content into carbon-rich slag with a carbon content greater than or equal to 75%, medium-carbon slag with a carbon content greater than or equal to 30% and less than 75%, and carbon-poor slag with a carbon content less than or equal to 5%;

[0011] Step 2, the carbon-rich ash is weighed and sent to a coal powder preparation workshop together with the raw coal, or the carbon-rich ash is sent alone to dry and grind to obtain a first mixture;

[0012] The medium carbon ash is weighed and sent to a raw material preparation workshop with calcium material, silicon material, iron material and aluminum material for drying and grinding to obtain a second mixture;

[0013] The second mixture is metered as a raw material for clinker calcination and sent to a preheating decomposition furnace and a rotary kiln for decomposition and calcination; the first mixture, after being metered, is sent to the kiln head of the rotary kiln and the preheating decomposition furnace as a fuel for clinker calcination, and then enters a grate cooler for cooling to obtain clinker;

[0014] Step 3: Mix the measured carbon-poor ash, clinker, gypsum and admixtures, and send the mixture as the third mixture to the cement preparation workshop for grinding and drying to obtain finished cement.

[0015] Optionally, in the particle size distribution of the first mixture, the proportion of particles with a particle size greater than 80 μm is less than 10%, and the moisture content is less than 1%;

[0016] In the particle size distribution of the second mixture, particles with a particle size greater than 80 μm account for less than 30%, particles with a particle size greater than 200 μm account for less than 2%, and the moisture content is less than 1%;

[0017] The specific surface area of ​​the finished cement is greater than 300m 2 / kg, particles with a size greater than 45μm account for 5% to 15% of the particle size distribution, and the moisture content is less than 1%.

[0018] Optionally, the coal gasification slag is classified according to the carbon content, with only the carbon content being required and no requirement being placed on the particle size.

[0019] Optionally, when the coal powder preparation workshop adopts vertical mill equipment for grinding, the carbon-rich ash has no moisture requirement;

[0020] When air-swept ball mill equipment is used in the coal powder preparation workshop, the moisture content of the carbon-rich ash is required to be less than or equal to 8%.

[0021] Optionally, when the raw material preparation workshop adopts a roller press or a vertical mill for grinding, the medium carbon ash has no moisture requirement.

[0022] Optionally, the cement preparation workshop adopts a grinding system combining a roller press and a ball mill, or adopts vertical mill grinding.

[0023] The present invention also provides a system for preparing low-carbon cement by stepwise utilization of coal gasification ash, which is applied to the method for preparing low-carbon cement by stepwise utilization of coal gasification ash described in the present invention. The system comprises:

[0024] A pulverized coal preparation system, a raw meal preparation system, a cement kiln calcining system and a cement preparation system; the cement kiln calcining system is connected with the pulverized coal preparation system, the raw meal preparation system and the cement preparation system and continuously provides hot air;

[0025] The pulverized coal preparation system includes a pulverized coal preparation workshop, which is provided with a grinding device; the pulverized coal preparation workshop is used to grind the raw coal and the carbon-rich ash mixture into a first mixture, or to grind the carbon-rich ash alone;

[0026] The raw material preparation system comprises a raw material preparation workshop; the raw material preparation workshop is used to grind the mixture of calcareous material, siliceous material, ferrous material, aluminum material and medium carbon ash into a second mixture;

[0027] The cement kiln calcining system comprises a preheating decomposition furnace, a rotary kiln, and a grate cooler; the preheating decomposition furnace is connected to the rotary kiln, and the rotary kiln is connected to the grate cooler; a first burner is arranged at the kiln head of the rotary kiln, and a second burner is arranged in the preheating decomposition furnace; the first burner and the second burner are respectively used to decompose and calcine the second mixture using the first mixture as fuel; the grate cooler is used to cool the calcined second mixture to prepare clinker;

[0028] The cement preparation system comprises a cement preparation workshop, which is used for grinding a third mixture of clinker, admixture, gypsum and carbon-poor ash with a carbon content of less than or equal to 5% to prepare finished cement.

[0029] Optionally, the pulverized coal preparation system further includes a fuel silo and a plurality of fuel component repositories;

[0030] The multiple fuel component repositories are used to store raw coal and carbon-rich ash with a carbon content greater than or equal to 75%, respectively, and the fuel silo is used to store the first mixture;

[0031] The grinding equipment is a vertical mill or an air-swept ball mill.

[0032] Optionally, the cement kiln calcining system further comprises a raw meal homogenization warehouse, a plurality of raw meal component warehouses and a clinker warehouse for storing clinker;

[0033] A plurality of raw material component libraries are respectively used to store calcareous materials, siliceous materials, ferrous materials, aluminum materials and medium carbon ash with a carbon content greater than or equal to 30% and less than 75%;

[0034] The raw material homogenizing reservoir is used to evenly mix and store the second mixture, and the top feed port of the preheating decomposition furnace is connected to the raw material homogenizing reservoir.

[0035] Optionally, the cement preparation system further comprises a cement silo for storing the finished cement.

[0036] The present invention has at least the following beneficial effects:

[0037] The present invention provides a method and system for preparing low-carbon cement by using gasification ash in different qualities and in different stages. The gasification slag is divided into carbon-rich slag with a carbon content of 75% or more, medium-carbon slag with a carbon content of 30% or more and less than 75%, and poor-carbon slag with a carbon content of 5% or less according to the carbon content. The carbon-rich slag is used as a substitute for fuel coal, the medium-carbon slag replaces natural resources as part of the raw material of raw materials, and the poor-carbon slag replaces clinker and other cement components and is ground together to prepare low-carbon cement. That is, the carbon content of the gasification slag is regulated and graded to obtain gasification slag materials with different characteristics. Then, combined with the characteristics of the cement production process, the gasification slag after quality classification is used in the three process stages of cement raw material grinding, clinker calcination, and cement grinding process, respectively, to synergistically prepare low-carbon cement, maximize the characteristics of different gasification slag materials, and achieve large-scale utilization of gasification slag in terms of building materials resources. At the same time, the use of coal gasification ash reduces carbon emissions from the cement clinker production process, reduces the proportion of clinker in cement, and significantly reduces the carbon emission intensity of cement.

[0038] 1. Classify the coal gasification ash according to the carbon content and utilize it according to its quality, so that the coal gasification ash can be utilized as a resource, which is beneficial to protecting the ecological environment and promoting the construction of ecological civilization.

[0039] 2. Classify the coal gasification ash according to the carbon content to make full use of it, improve the resource utilization efficiency of the coal gasification ash, abandon the simple and extensive development mode, and benefit the high-quality development of the industry.

[0040] 3. Different material properties of coal gasification ash are used to realize different material functions in cement production, which greatly saves natural resources such as coal and limestone.

[0041] 4. The resource utilization of gasification ash after separation reduces the amount of clinker in the cement preparation process and reduces the carbon emission intensity of cement production.

[0042] 5. The utilization of coal gasification ash by different qualities, coupled with environmental protection and material preparation technologies, improves the technological integration between industries and is beneficial to the scientific and technological progress of society. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 A schematic diagram of a system for preparing low-carbon cement by quality-based and stepwise utilization of coal gasification ash provided in an embodiment of the present invention.

[0045] Reference numerals:

[0046] 1. Raw material preparation workshop; 2. Raw material homogenization warehouse; 3. Preheating decomposition furnace; 4. Rotary kiln; 5. First burner; 6. Second burner; 7. Grate cooler; 8. Clinker warehouse; 9. Coal powder preparation workshop; 10. Fuel silo; 11. Cement preparation workshop; 12. Cement silo. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] The present invention provides a method for preparing low-carbon cement by using coal gasification ash in a graded and graded manner, comprising the following steps:

[0049] Step 1, classifying the coal gasification slag according to the carbon content into carbon-rich slag with a carbon content greater than or equal to 75%, medium-carbon slag with a carbon content greater than or equal to 30% and less than 75%, and carbon-poor slag with a carbon content less than or equal to 5%;

[0050] Step 2, the carbon-rich ash is weighed and sent together with the raw coal, or the carbon-rich ash is sent alone to the coal powder preparation workshop 9 for drying and grinding to obtain a first mixture;

[0051] The medium carbon ash is weighed and sent to the raw material preparation workshop 1 for drying and grinding with the calcium material, silicon material, iron material and aluminum material to obtain a second mixture;

[0052] The second mixture is metered as a raw material for clinker calcination and sent to the preheating decomposition furnace 3 and the rotary kiln 4 for decomposition and calcination. The first mixture, which has been metered separately, is sent to the kiln head of the rotary kiln 4 and the preheating decomposition furnace 3 as a fuel for clinker calcination, and then enters the grate cooler 7 for cooling to obtain clinker;

[0053] Step 3: Mix the measured carbon-poor ash, clinker, gypsum and admixtures, and send the mixture as the third mixture to the cement preparation workshop 11 for grinding and drying to obtain finished cement.

[0054] Specifically, step 1, the coal gasification ash is classified or enriched according to the carbon content into: carbon-rich ash with a carbon content greater than or equal to 75%, carbon content greater than or equal to 30% and less than 75%, medium carbon ash and carbon-poor ash. The classification refers to the directional classification and grading of the coal gasification ash according to the preset specific material characteristics, so that the components with different carbon contents and different ash contents in the ash are effectively separated.

[0055] Step 2, the carbon-rich ash is metered and sent to the coal powder preparation workshop 9 together with the raw coal, or the carbon-rich ash is metered and sent to the coal powder preparation workshop 9 alone, and the material is dried under the action of the hot air at the kiln head, and the first mixture obtained after grinding is used for clinker calcination. The medium-carbon ash is metered and ground together with the calcium material, silicon material, iron material, and aluminum material, and the material is dried under the action of the hot air at the kiln tail. The second mixture obtained after grinding is mixed evenly and used as a raw material for clinker calcination. The metered carbon-rich ash and coal, or the carbon-rich ash alone, are metered and respectively enter the rotary kiln 4 and the preheating decomposition furnace 3, and are used as fuel for clinker decomposition and calcination.

[0056] The uniformly mixed second mixture is metered and enters the preheating decomposition furnace 3 and the rotary kiln 4 for decomposition and calcination, and then enters the grate cooler 7 from the rotary kiln 4 for cooling to obtain clinker.

[0057] Step 3: After the measured carbon-poor ash is mixed with clinker, gypsum and other mixed materials, the obtained third mixture is added to the cement preparation workshop 11 for grinding, and the material is dried by the clinker temperature, grinding heat, and system waste heat. The qualified finished materials after grinding are stored in the cement silo 12 for use as cement products.

[0058] In a possible embodiment, in the particle size distribution of the first mixture, particles with a particle size of less than 80 μm account for less than 10%, and the moisture content is less than 1%;

[0059] The second mixture has a particle size distribution in which particles with a particle size greater than 80 μm account for less than 30%, particles with a particle size less than 200 μm account for less than 2%, and a moisture content of less than 1%;

[0060] The specific surface area of ​​the finished cement is greater than 300m 2 / kg, particles with a size greater than 45μm account for 5% to 15% of the particle size distribution, and the moisture content is less than 1%.

[0061] Specifically, in the particle size distribution of the first mixture, the proportion of particles with a particle size greater than 80 μm is less than 10%, and the moisture content is less than 1%, that is, the particle size of the first mixture is R 80μm <10%, moisture <1%.

[0062] In the particle size distribution of the second mixture, the proportion of particles with a particle size greater than 80 μm is less than 30%, the proportion of particles with a particle size greater than 200 μm is less than 2%, and the moisture content is less than 1%, that is, the particle size of the second mixture is R 80μm <30%、R 200μm <2%, moisture <1%;

[0063] The specific surface area of ​​the finished cement prepared from the third mixture is greater than 300m 2 / kg, the proportion of particles larger than 45μm in the particle size distribution is 5% to 15%, and the moisture content is less than 1%, that is, the particle size of the finished cement is specific surface area> 300m 2 / kg, R 45μm 5~15%, moisture <1%.

[0064] In a possible implementation, the coal gasification slag is classified according to the carbon content, with only the carbon content being required and no requirement being placed on the particle size.

[0065] Specifically, coal gasification slag is classified into different categories or grades based on the carbon content, without considering or needing to consider the particle size (i.e., the size of the particles) of the slag. That is, no matter what the particle size of the coal gasification slag is, as long as their carbon content meets a certain standard or range, they will be classified into the same category or grade. This classification method helps to manage and utilize coal gasification slag more accurately.

[0066] In a possible implementation, when the vertical mill is used for grinding in the coal powder preparation workshop 9, the carbon-rich ash has no moisture requirement;

[0067] When the air-swept ball mill is used in the pulverized coal preparation workshop 9, the moisture content of the carbon-rich ash is required to be less than or equal to 8%.

[0068] Specifically, in a vertical mill, since the material is subjected to greater extrusion and shear forces, its grinding efficiency is higher and the requirement for the moisture content of the material is relatively low. Therefore, when a vertical mill is used to grind carbon-rich ash, there is usually no specific requirement for the moisture content of the carbon-rich ash.

[0069] The air-swept ball mill uses the steel balls in the ball mill to impact and grind the materials, and uses wind power to blow out the fine powder. The moisture content of the material has a great influence on the grinding effect and product quality. If the moisture content of the carbon-rich ash is too high, the material will stick together in the ball mill, affecting the grinding efficiency and product quality. Therefore, when using the air-swept ball mill to grind carbon-rich ash, the moisture content of the carbon-rich ash needs to be strictly controlled, and the moisture content is generally required to be less than or equal to 8%.

[0070] In a possible implementation, when the raw material preparation workshop 1 adopts a roller press or a vertical mill for grinding, the medium carbon ash has no moisture requirement.

[0071] In a possible implementation, the cement preparation workshop 11 adopts a grinding system combining a roller press and a ball mill, or adopts a vertical mill for grinding.

[0072] The present invention also provides a system for preparing low-carbon cement by using coal gasification ash in a stepwise manner, and a method for preparing low-carbon cement by using coal gasification ash in a stepwise manner in the present invention, wherein the system comprises: a pulverized coal preparation system, a raw material preparation system, a cement kiln calcining system and a cement preparation system; the cement kiln calcining system is connected to the pulverized coal preparation system, the raw material preparation system and the cement preparation system and continuously provides hot air;

[0073] The pulverized coal preparation system includes a pulverized coal preparation workshop 9; the pulverized coal preparation workshop 9 is used to grind the raw coal and the carbon-rich ash mixture into a first mixture, or to grind the carbon-rich ash alone;

[0074] The raw material preparation system comprises a raw material preparation workshop 1; the raw material preparation workshop 1 is used to grind the mixture of calcareous material, siliceous material, ferrous material, aluminum material and medium carbon ash into a second mixture;

[0075] The cement kiln calcining system comprises a preheating decomposition furnace 3, a rotary kiln 4, and a grate cooler 7; the preheating decomposition furnace 3 is connected to the rotary kiln 4, and the rotary kiln 4 is connected to the grate cooler 7; a first burner 5 is provided at the kiln head of the rotary kiln 4, and a second burner 6 is provided in the preheating decomposition furnace 3; the first burner 5 and the second burner 6 are respectively used to calcine the second mixture using the first mixture as fuel; the grate cooler 7 is used to cool the calcined second mixture to prepare clinker;

[0076] The cement preparation system comprises a cement preparation workshop 11; the cement preparation workshop 11 is used to grind a third mixture of clinker, admixture, gypsum and carbon-poor ash with a carbon content of less than or equal to 5% to prepare finished cement.

[0077] Specifically, the system for preparing low-carbon cement by using coal gasification ash in a graded manner mainly includes a pulverized coal preparation system, a raw material preparation system, a cement kiln calcination system and a cement preparation system. The hot air generated in the cement kiln calcination system can enter the pulverized coal preparation system, the raw material preparation system and the cement preparation system respectively.

[0078] In the pulverized coal preparation system, the pulverized coal fuel is pure carbon-rich ash, or a mixture of carbon-rich ash and raw coal. The pulverized coal raw material is sent to the pulverized coal preparation workshop 9 for grinding. During the grinding, the kiln head hot air in the cement calcining system dries the material. After grinding and drying, a first mixture is obtained.

[0079] In the raw material preparation system, calcium materials, silicon materials, iron materials, aluminum materials and medium carbon ash are respectively metered according to a certain ratio and then enter the raw material preparation workshop 1 for grinding, and the second mixture is obtained after grinding. In the cement calcination system, the first mixture is used as the fuel for decomposing and calcining the second mixture and then enters the first burner 5 and the second burner 6 of the rotary kiln 4 after being metered. The second mixture is decomposed and calcined in the preheating decomposition furnace 3 and the rotary kiln 4 in turn, and then cooled by the grate cooler 7 to obtain clinker.

[0080] In the cement preparation system, clinker, admixture, gypsum and carbon-poor ash with a carbon content of less than or equal to 5% are respectively measured and mixed according to a specific ratio, and the obtained third mixture is added to the cement preparation workshop 11 for grinding, and the finished cement is obtained after grinding.

[0081] In a possible implementation, the pulverized coal preparation system further includes a fuel silo and a plurality of fuel component repositories;

[0082] The multiple fuel component repositories are used to store raw coal and carbon-rich ash with a carbon content greater than or equal to 75%, respectively, and the fuel silo is used to store the first mixture;

[0083] The grinding equipment is a vertical mill or an air-swept ball mill.

[0084] Specifically, if the raw materials constituting the pulverized coal include raw coal and carbon-rich ash, the raw coal and the carbon-rich ash are stored in two different fuel component libraries respectively. If the raw materials constituting the pulverized coal only include carbon-rich ash, the carbon-rich ash is stored in one fuel component library. The fuel silo 10 stores the first mixture, and the first burner 5 in the rotary kiln 4 and the second burner 6 in the preheating decomposition furnace 3 are respectively connected to the fuel silo 10. The first mixture in the fuel silo 10 enters the first burner 5 and the second burner 6 of the rotary kiln 4 after being metered respectively. The grinding equipment in the grinding workshop can be a vertical mill or an air-swept ball mill.

[0085] In a possible implementation, the cement kiln calcining system further includes a raw meal homogenization warehouse and a plurality of raw meal component warehouses, and the cement kiln calcining system further includes a clinker warehouse for storing clinker;

[0086] A plurality of raw material component libraries are respectively used to store calcareous materials, siliceous materials, ferrous materials, aluminum materials and medium carbon ash with a carbon content greater than or equal to 30% and less than 75%;

[0087] The raw material homogenizing reservoir is used to evenly mix and store the second mixture, and the top feed port of the preheating decomposition furnace is connected to the raw material homogenizing reservoir.

[0088] Specifically, each raw material component warehouse stores calcium materials, silicon materials, iron materials, aluminum materials and medium carbon ash with a carbon content greater than or equal to 30% and less than 75%. The raw material homogenization warehouse 2 mixes the second mixture after grinding and stores it as a raw material for clinker calcination. The feed port of the preheating decomposition furnace 3 is connected to the raw material homogenization warehouse 2, and the second mixture that is evenly mixed after metering by the raw material homogenization warehouse 2 enters the preheating decomposition furnace 3 through the feed port of the preheating decomposition furnace 3. After the second mixture in the cement kiln calcination system is calcined and cooled in sequence, clinker is prepared, and the clinker enters the clinker warehouse 8 for storage and waiting for use.

[0089] In a possible implementation, the cement preparation system further includes a cement silo 12 for storing the finished cement.

[0090] Specifically, the materials after grinding and drying from the cement preparation workshop 11 are transported to the cement silo 12 for storage.

[0091] In summary, the present invention has the following beneficial effects:

[0092] 1. The coal gasification ash is classified according to the carbon content into: carbon-rich ash, carbon content ≥75%; medium-carbon ash, carbon content ≥30%; and carbon-poor ash, carbon content ≤5%. This allows the coal gasification ash to be utilized as a resource to the greatest extent, solving the problem of difficulty in resource utilization of coal gasification ash. At the same time, classification according to carbon content improves the efficiency of resource utilization of coal gasification ash.

[0093] 2. Use carbon-rich ash to replace fuel coal and enter the coal powder preparation system; medium-carbon ash to replace natural resources and enter the raw material mill preparation system; and carbon-poor ash to replace clinker and enter the cement mill preparation system. The material properties are used to realize different material functions in cement production, which greatly saves natural resources such as coal and limestone. At the same time, the use of carbon-poor ash reduces the clinker in cement and reduces the carbon emissions of cement production. Carbon-poor ash replaces part of the mixed materials and saves natural resources.

[0094] 3. According to the carbon content, material characteristics, and multi-point coupling, ash slag is used to prepare low-carbon cement and improve the utilization rate of coal gasification ash slag. This is conducive to protecting the ecological environment, promoting the construction of ecological civilization, and promoting the high-quality development of enterprises and industries.

[0095] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0096] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing low-carbon cement by using coal gasification ash in different qualities and stages, characterized in that: The steps include: Step 1, classifying the coal gasification slag according to the carbon content into carbon-rich slag with a carbon content greater than or equal to 75%, medium-carbon slag with a carbon content greater than or equal to 30% and less than 75%, and carbon-poor slag with a carbon content less than or equal to 5%; Step 2, the carbon-rich ash is weighed and sent to a coal powder preparation workshop together with the raw coal, or the carbon-rich ash is sent alone to dry and grind to obtain a first mixture; The medium carbon ash is weighed and sent to a raw material preparation workshop with calcium material, silicon material, iron material and aluminum material for drying and grinding to obtain a second mixture; The second mixture is metered as a raw material for clinker calcination and sent to a preheating decomposition furnace and a rotary kiln for decomposition and calcination; the first mixture, after being metered, is sent to the kiln head of the rotary kiln and the preheating decomposition furnace as a fuel for clinker calcination, and then enters a grate cooler for cooling to obtain clinker; Step 3: Mix the measured carbon-poor ash, clinker, gypsum and admixtures, and send the mixture as the third mixture to the cement preparation workshop for grinding and drying to obtain finished cement.

2. The method for preparing low-carbon cement by graded utilization of coal gasification ash according to claim 1, characterized in that: The first mixture has a particle size distribution in which particles with a particle size greater than 80 μm account for less than 10% and a moisture content of less than 1%; In the particle size distribution of the second mixture, particles with a particle size greater than 80 μm account for less than 30%, particles with a particle size greater than 200 μm account for less than 2%, and the moisture content is less than 1%; The specific surface area of ​​the finished cement is greater than 300m 2 / kg, particles with a size greater than 45μm account for 5% to 15% of the particle size distribution, and the moisture content is less than 1%.

3. The method for preparing low-carbon cement by graded utilization of coal gasification ash according to claim 1, characterized in that: The coal gasification slag is classified according to the carbon content, with only the carbon content being required and no requirement on the particle size.

4. The method for preparing low-carbon cement by graded utilization of coal gasification ash according to claim 1, characterized in that: When the vertical mill is used for grinding in the coal powder preparation workshop, the carbon-rich ash has no moisture requirement; When air-swept ball mill equipment is used in the coal powder preparation workshop, the moisture content of the carbon-rich ash is required to be less than or equal to 8%.

5. The method for preparing low-carbon cement by graded utilization of coal gasification ash according to claim 1, characterized in that: When the raw material preparation workshop adopts a roller press or a vertical mill for grinding, the medium carbon ash has no moisture requirement.

6. The method for preparing low-carbon cement by graded utilization of coal gasification ash according to claim 1, characterized in that: The cement preparation workshop adopts a grinding system combining a roller press and a ball mill, or adopts vertical mill grinding.

7. A system for preparing low-carbon cement by using coal gasification ash in different qualities and stages, characterized in that: Applied to the method according to any one of claims 1 to 6, the system comprises: A pulverized coal preparation system, a raw meal preparation system, a cement kiln calcining system and a cement preparation system; the cement kiln calcining system is connected with the pulverized coal preparation system, the raw meal preparation system and the cement preparation system and continuously provides hot air; The pulverized coal preparation system includes a pulverized coal preparation workshop, which is provided with a grinding device; the pulverized coal preparation workshop is used to grind the raw coal and the carbon-rich ash mixture into a first mixture, or to grind the carbon-rich ash alone; The raw material preparation system comprises a raw material preparation workshop; the raw material preparation workshop is used to grind the mixture of calcareous material, siliceous material, ferrous material, aluminum material and medium carbon ash into a second mixture; The cement kiln calcining system comprises a preheating decomposition furnace, a rotary kiln, and a grate cooler; the preheating decomposition furnace is connected to the rotary kiln, and the rotary kiln is connected to the grate cooler; a first burner is arranged at the kiln head of the rotary kiln, and a second burner is arranged in the preheating decomposition furnace; the first burner and the second burner are respectively used to decompose and calcine the second mixture using the first mixture as fuel; the grate cooler is used to cool the calcined second mixture to prepare clinker; The cement preparation system comprises a cement preparation workshop, which is used for grinding a third mixture of clinker, admixture, gypsum and carbon-poor ash with a carbon content of less than or equal to 5% to prepare finished cement.

8. The system for preparing low-carbon cement by graded utilization of coal gasification ash according to claim 7, characterized in that: The pulverized coal preparation system also includes a fuel silo and a plurality of fuel component repositories; The multiple fuel component repositories are used to store raw coal and carbon-rich ash with a carbon content greater than or equal to 75%, respectively, and the fuel silo is used to store the first mixture; The grinding equipment is a vertical mill or an air-swept ball mill.

9. The system for preparing low-carbon cement by graded utilization of coal gasification ash according to claim 7, characterized in that: The cement kiln calcining system also includes a raw material homogenization warehouse, a plurality of raw material component warehouses and a clinker warehouse for storing clinker; A plurality of raw material component libraries are respectively used to store calcareous materials, siliceous materials, ferrous materials, aluminum materials and medium carbon ash with a carbon content greater than or equal to 30% and less than 75%; The raw material homogenizing reservoir is used to evenly mix and store the second mixture, and the top feed port of the preheating decomposition furnace is connected to the raw material homogenizing reservoir.

10. The system for preparing low-carbon cement by graded utilization of coal gasification ash according to claim 7, characterized in that: The cement preparation system further comprises a cement silo for storing the finished cement.

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