Method and system for preparing low-carbon cement by coal gasification ash multi-quality cascade utilization

Abstract

The application provides a method and system for preparing low-carbon cement by using coal gasification ash in a graded manner, and 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 raw coal into a coal powder preparation workshop to prepare a first mixture as a clinker calcination fuel; feeding the medium-carbon ash into a raw material preparation workshop after metering to be ground and dried together with other raw material components; preparing clinker by decomposing and calcining the second mixture after mixing uniformly and cooling; feeding the mixture of the clinker and other cement components and the carbon-poor ash into a cement preparation workshop to prepare finished cement. The carbon content of the coal gasification ash is divided in a graded manner to obtain coal gasification ash materials with different characteristics, and the cement production process characteristics are combined to be used in three process sections of raw material grinding, clinker calcination and cement grinding, so that the coal gasification ash is used in a large amount and in a large scale in the building material resources, and the carbon emission in the cement clinker production process is reduced.

Description

Technical Field

[0001] This invention relates to the field of cement preparation technology, and more specifically to a method and system for preparing low-carbon cement by utilizing coal gasification ash in a graded and progressive manner. Background Technology

[0002] Coal gasification technology is the leading technology in the modern coal chemical industry and one of the key technologies for achieving clean and efficient utilization of coal. Coal gasification ash is a waste residue generated during the coal gasification process, with an average annual output exceeding 60 million tons. Due to the difficulty in degrading coal gasification ash, it has not yet been widely applied, with a utilization rate of only about 8%. Large quantities of coal gasification ash can only be disposed of through stockpiling or landfilling, which not only occupies significant land resources and causes soil and water pollution but also generates dust and fine particulate matter, posing a threat to human health. Coal gasification ash contains abundant residual carbon and silicon-aluminum oxides, laying the foundation for its resource utilization.

[0003] Cement, as a basic building material, has always occupied an important position in the national economy. According to data from the National Bureau of Statistics, my country's cement production reached 2.038 billion tons in 2023, ranking first in the world for more than 20 consecutive years. Related data shows that the cement industry accounts for approximately 13.5% of the country's total carbon emissions, second only to steel (which accounts for 15% of carbon emissions) among industrial sectors.

[0004] Carbon emissions from cement production mainly come from indirect carbon emissions from clinker production and electricity consumption, with clinker production accounting for over 95% of these emissions. According to the 2018 International Energy Agency's Cement Sustainable Development Promotion Association's "Technology Roadmap - Low-Carbon Transformation of the Cement Industry," reducing the proportion of clinker used in cement through clinker substitution can lower the carbon intensity of cement; clinker substitution alone accounts for 37% of carbon reduction measures. Therefore, how to reduce clinker carbon emissions and the proportion of clinker used in cement has become a hot topic of international concern.

[0005] Cement production systems and grinding equipment are technologically mature, with clear processes and wide applications. However, due to the different material properties of coal gasification ash, the following problems exist in their application in cement production:

[0006] (1) Coal gasification ash contains a certain average carbon content (>10%). When it is directly used as a blending material to replace clinker in cement, it increases the water demand of cement and reduces its strength. 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, which makes it impossible to directly use coal gasification ash as a cement blending material. Therefore, the resource utilization of coal gasification ash building materials is difficult.

[0007] (2) Coal gasification ash contains abundant residual carbon and silicon aluminum oxides and has a certain average calorific value (600-900 kCal / kg), which can be used as a substitute for cement production fuel. However, compared with traditional cement fuel (4500-6000 kCal / kg), its calorific value is too low. When it is burned together with traditional fuel, the combustion time is short, resulting in incomplete combustion of ash and slag, residual carbon in cement clinker and substandard quality. Summary of the Invention

[0008] Based on the above-mentioned problems, the present invention provides a method and system for preparing low-carbon cement by utilizing coal gasification ash in a graded manner, which solves the problems of difficulty in resource utilization of coal gasification ash in building materials, low calorific value of coal gasification ash and short combustion time when co-burned with traditional fuels, resulting in incomplete combustion of ash and ash, residual carbon in cement clinker and substandard quality.

[0009] This invention provides a method for preparing low-carbon cement through the graded and cascaded utilization of coal gasification ash, comprising the following steps:

[0010] Step 1: Separate the coal gasification slag according to its carbon content into three categories: carbon-rich ash slag with a carbon content of ≥75%, medium-carbon ash slag with a carbon content of ≥30% and <75%, and carbon-poor ash slag with a carbon content of ≤5%.

[0011] Step 2: After measuring the carbon-rich ash residue, it is mixed with the raw coal, or the carbon-rich ash residue is sent separately to the coal powder preparation workshop for drying and grinding to obtain the first mixture;

[0012] The medium-carbon ash residue is metered and then sent to the raw material preparation workshop along with calcareous materials, siliceous materials, ferrous materials, and aluminum materials for drying and grinding to obtain a second mixture.

[0013] The second mixture is metered as raw material for clinker calcination and fed into a preheating decomposition furnace and a rotary kiln for decomposition and calcination. The first mixture, after being metered separately, is fed into the kiln head of the rotary kiln and the preheating decomposition furnace as fuel for clinker calcination. Then, it is cooled by a grate cooler to obtain clinker.

[0014] Step 3: Mix the metered lean carbon 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, the particle size distribution of the first mixture contains less than 10% particles larger than 80 μm and less than 1% moisture content;

[0016] The particle size distribution of the second mixture is such that the proportion of particles larger than 80 μm is less than 30%, the proportion of particles larger than 200 μm is less than 2%, and the moisture content is less than 1%.

[0017] The specific surface area of ​​the finished cement is greater than 300m². 2 / kg, particle size distribution with particles larger than 45μm accounting for 5% to 15%, and moisture content less than 1%.

[0018] Optionally, the coal gasification slag can be classified according to its carbon content, with only requirements on carbon content and no requirements on particle size.

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

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

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

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

[0023] This invention also provides a system for the graded and cascaded utilization of coal gasification ash to prepare low-carbon cement, applied to the method for the graded and cascaded utilization of coal gasification ash to prepare low-carbon cement described in this invention. The system includes:

[0024] The system includes a pulverized coal preparation system, a raw meal preparation system, a cement kiln calcination system, and a cement preparation system; the cement kiln calcination system is connected to the pulverized coal preparation system, the raw meal preparation system, and the cement preparation system and continuously provides hot air.

[0025] The coal powder preparation system includes a coal powder preparation workshop, which is equipped with grinding equipment; the coal powder preparation workshop is used to grind the material after mixing raw coal and carbon-rich ash into a first mixture, or to grind the carbon-rich ash separately.

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

[0027] The cement kiln calcination system includes 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 installed at the kiln head of the rotary kiln, and a second burner is installed 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 includes a cement preparation workshop, which is used to grind a third mixture of clinker, admixtures, 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 fuel silos and multiple fuel component storage tanks;

[0030] The multiple fuel component storage bins are used to store raw coal and carbon-rich ash with a carbon content of greater than or equal to 75%, respectively, and the fuel silos are 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 calcination system further includes a raw material homogenization silo, multiple raw material component silos, and a clinker silo for storing clinker;

[0033] Multiple raw material component storage areas are used to store calcareous materials, siliceous materials, ferrous materials, aluminous materials, and medium-carbon ash with a carbon content of ≥30% and ≤75%, respectively.

[0034] The raw material homogenization silo is used to mix the second mixture evenly and store it, and the top feed inlet of the preheating decomposition furnace is connected to the raw material homogenization silo.

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

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

[0037] This invention provides a method and system for the graded utilization of coal gasification ash to prepare low-carbon cement. The method classifies coal gasification ash into carbon-rich ash (75% or higher), medium-carbon ash (30% or higher but less than 75%), and carbon-poor ash (5% or less). The carbon-rich ash is used as a substitute for coal fuel, the medium-carbon ash is used as a partial raw material to replace natural resources, and the carbon-poor ash is used to replace clinker and other cement components in a grinding process to prepare low-carbon cement. In other words, by graded and controlled by the carbon content of the coal gasification ash, different properties of coal gasification ash materials are obtained. Combined with the characteristics of cement production processes, the graded coal gasification ash is used in three process stages: cement raw material grinding, clinker calcination, and cement grinding, to synergistically prepare low-carbon cement. This maximizes the utilization of the different characteristics of coal gasification ash materials, enabling large-scale and high-volume utilization of coal gasification ash in building materials. At the same time, the use of coal gasification ash reduces carbon emissions in the cement clinker production process, lowers the proportion of clinker used in cement, and significantly reduces the carbon emission intensity of cement.

[0038] 1. Classifying coal gasification ash and residue according to carbon content and utilizing them separately will enable the coal gasification ash and residue to be utilized as a resource, which is conducive to protecting the ecological environment and promoting the construction of ecological civilization.

[0039] 2. Classifying coal gasification ash and slag according to carbon content makes the best use of resources, improves the resource utilization efficiency of coal gasification ash and slag, abandons the simple and extensive development mode, and is conducive to the high-quality development of the industry.

[0040] 3. By utilizing the material properties of different coal gasification ash residues, different material functions can be achieved in cement production, significantly saving natural resources such as coal and limestone.

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

[0042] 5. By utilizing coal gasification ash and slag separately and integrating environmental protection and material preparation technologies, the technological integration between industries is improved, which is conducive to the scientific and technological progress of society. Attached Figure Description

[0043] 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.

[0044] Figure 1 This is a schematic diagram of a system for the graded and cascaded utilization of coal gasification ash to prepare low-carbon cement, provided in an embodiment of the present invention.

[0045] Figure label:

[0046] 1. Raw meal preparation workshop; 2. Raw meal homogenization silo; 3. Preheating decomposition furnace; 4. Rotary kiln; 5. First burner; 6. Second burner; 7. Grate cooler; 8. Clinker silo; 9. Pulverized coal preparation workshop; 10. Fuel silo; 11. Cement preparation workshop; 12. Cement silo. Detailed Implementation

[0047] 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.

[0048] This invention provides a method for preparing low-carbon cement through the graded utilization of coal gasification ash, comprising the following steps:

[0049] Step 1: Separate the coal gasification slag according to its carbon content into three categories: carbon-rich ash slag with a carbon content of ≥75%, medium-carbon ash slag with a carbon content of ≥30% and <75%, and carbon-poor ash slag with a carbon content of ≤5%.

[0050] Step 2: After measuring the carbon-rich ash residue, it is mixed with the raw coal, or the carbon-rich ash residue is sent separately to the coal powder preparation workshop 9 for drying and grinding to obtain the first mixture;

[0051] The medium-carbon ash residue is metered and then sent to the raw material preparation workshop 1 along with calcareous materials, siliceous materials, ferrous materials, and aluminum materials for drying and grinding to obtain a second mixture.

[0052] The second mixture is metered as raw material for clinker calcination and fed into the preheating decomposition furnace 3 and the rotary kiln 4 for decomposition and calcination. The first mixture, after being metered separately, is fed into the kiln head of the rotary kiln 4 and the preheating decomposition furnace 3 as fuel for clinker calcination. Then it enters the grate cooler 7 for cooling to obtain clinker.

[0053] Step 3: Mix the metered lean carbon 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 involves separating or enriching the coal gasification ash residue based on its carbon content, classifying it into: carbon-rich ash residue with a carbon content greater than or equal to 75%, medium-carbon ash residue with a carbon content greater than or equal to 30% and less than 75%, and carbon-poor ash residue. Separation refers to the targeted separation and grading of the coal gasification ash residue according to pre-defined specific material characteristics, thereby effectively separating components with different carbon and ash contents within the ash residue.

[0055] Step 2: After being metered, the carbon-rich ash slag is fed into the pulverized coal preparation workshop 9 together with the raw coal, or the carbon-rich ash slag is metered and fed into the pulverized coal preparation workshop 9 separately. The material is dried under the action of hot air at the kiln head, and the resulting first mixture after grinding is used for clinker calcination. The medium-carbon ash slag is metered and ground together with calcareous, siliceous, ferrous, and aluminous materials, while simultaneously being dried under the action of hot air at the kiln tail. The resulting second mixture after grinding is thoroughly mixed and used as raw material for clinker calcination. The metered carbon-rich ash slag and coal, or the separately metered carbon-rich ash slag, are fed into the rotary kiln 4 and the preheating decomposition furnace 3 respectively, and used as fuel for clinker decomposition and calcination.

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

[0057] Step 3: After metering, the lean carbon ash residue is mixed with clinker, gypsum, and other admixtures. The resulting third mixture is then added to the cement preparation workshop 11 for grinding. Simultaneously, the material is dried by the clinker temperature, the heat generated during grinding, and the waste heat from the system. The qualified finished material after grinding is stored in the cement silo 12 for use as cement products.

[0058] In one possible implementation, the particle size distribution of the first mixture contains less than 10% particles smaller than 80 μm and less than 1% moisture content.

[0059] The particle size distribution of the second mixture is such that the proportion of particles larger than 80 μm is less than 30%, the proportion of particles smaller than 200 μm is less than 2%, and the moisture content is less than 1%.

[0060] The specific surface area of ​​the finished cement is greater than 300m². 2 / kg, particle size distribution with particles larger than 45μm accounting for 5% to 15%, and moisture content less than 1%.

[0061] Specifically, in the particle size distribution of the first mixture, the proportion of particles larger 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] The second mixture has a particle size distribution in which particles larger than 80 μm account for less than 30%, particles larger than 200 μm account for less than 2%, and the moisture content is less than 1%. Therefore, the particle size distribution of the second mixture is R. 80μm <30%, R 200μm <2%, moisture <1%;

[0063] The finished cement prepared from the third mixture has a specific surface area greater than 300 m². 2 / kg, particle size distribution with particles larger than 45μm accounting for 5% to 15%, and moisture content less than 1%, meaning the finished cement has a particle size distribution with a specific surface area > 300m². 2 / kg, R 45μm 5~15%, moisture <1%.

[0064] In one possible implementation, the coal gasification slag is classified according to its carbon content, with only requirements on carbon content and no requirements on particle size.

[0065] Specifically, coal gasification slag will be classified into different categories or grades based on its carbon content, regardless of or without considering its particle size. That is, regardless of the particle size, as long as the carbon content meets a specific standard or range, the slag will be classified into the same category or grade. This classification method facilitates more precise management and utilization of coal gasification slag.

[0066] In one possible implementation, when the coal powder preparation workshop 9 uses a vertical mill for grinding, the carbon-rich ash residue 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 residue must be less than or equal to 8%.

[0068] Specifically, in vertical mill equipment, the material is subjected to greater extrusion and shear forces, resulting in higher grinding efficiency and relatively lower requirements for the material's moisture content. Therefore, when using vertical mill equipment to grind carbon-rich ash slag, there are usually no specific requirements regarding the moisture content of the carbon-rich ash slag.

[0069] Air-swept ball mills grind materials by impacting and grinding them with steel balls inside the mill, while airflow blows the resulting fine powder out. The moisture content of the material significantly affects grinding efficiency and product quality. If the moisture content of carbon-rich ash is too high, the material will clump together inside the mill, impacting grinding efficiency and product quality. Therefore, when using air-swept ball mills to grind carbon-rich ash, the moisture content must be strictly controlled, generally requiring a moisture content of less than or equal to 8%.

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

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

[0072] This invention also provides a system for the graded and cascaded utilization of coal gasification ash to prepare low-carbon cement, which is applied to the method for the graded and cascaded utilization of coal gasification ash to prepare low-carbon cement in this invention. The system includes: a pulverized coal preparation system, a raw meal preparation system, a cement kiln calcination system, and a cement preparation system; the cement kiln calcination system is connected to the pulverized coal preparation system, the raw meal preparation system, and the cement preparation system and continuously provides hot air.

[0073] The coal powder preparation system includes a coal powder preparation workshop 9; the coal powder preparation workshop 9 is used to grind the material after mixing raw coal and carbon-rich ash into a first mixture, or to grind the carbon-rich ash separately.

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

[0075] The cement kiln calcination system includes 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 installed at the kiln head of the rotary kiln 4, and a second burner 6 is installed 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 includes a cement preparation workshop 11; the cement preparation workshop 11 is used to grind a third mixture of clinker, admixtures, 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 the graded and cascaded utilization of coal gasification ash to produce low-carbon cement mainly includes a pulverized coal preparation system, a raw meal preparation system, a cement kiln calcination system, and a cement preparation system. The hot air generated in the cement kiln calcination system can be separately introduced into the pulverized coal preparation system, the raw meal preparation system, and the cement preparation system.

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

[0079] In the raw meal preparation system, calcareous materials, siliceous materials, ferrous materials, aluminous materials, and medium-carbon ash are metered according to a certain proportion and then fed into the raw meal preparation workshop 1 for grinding, resulting in a second mixture. In the cement calcination system, the first mixture, used as fuel for the decomposition and calcination of the second mixture, is metered and fed into the first burner 5 and the second burner 6 of the rotary kiln 4. The second mixture is then decomposed and calcined sequentially in the preheating decomposition furnace 3 and the rotary kiln 4, and finally cooled by the grate cooler 7 to obtain clinker.

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

[0081] In one possible implementation, the pulverized coal preparation system further includes a fuel silo and multiple fuel component storage tanks;

[0082] The multiple fuel component storage bins are used to store raw coal and carbon-rich ash with a carbon content of greater than or equal to 75%, respectively, and the fuel silos are 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 pulverized coal include raw coal and carbon-rich ash, the raw coal and carbon-rich ash are stored in two different fuel component bins. If the raw materials constituting pulverized coal consist only of carbon-rich ash, the carbon-rich ash is stored in one fuel component bin. Fuel silo 10 stores the first mixture. The first burner 5 in the rotary kiln 4 and the second burner 6 in the preheating decomposition furnace 3 are respectively connected to fuel silo 10. The first mixture in fuel silo 10, after being metered, enters the first burner 5 and the second burner 6 of the rotary kiln 4. The grinding equipment in the grinding workshop can be a vertical mill or an air-swept ball mill.

[0085] In one possible implementation, the cement kiln calcination system further includes a raw material homogenization silo and multiple raw material component silos, and the cement kiln calcination system also includes a clinker silo for storing clinker;

[0086] Multiple raw material component storage areas are used to store calcareous materials, siliceous materials, ferrous materials, aluminous materials, and medium-carbon ash with a carbon content of ≥30% and ≤75%, respectively.

[0087] The raw material homogenization silo is used to mix the second mixture evenly and store it, and the top feed inlet of the preheating decomposition furnace is connected to the raw material homogenization silo.

[0088] Specifically, each raw material component storage silo stores calcareous materials, siliceous materials, ferrous materials, aluminous materials, and medium-carbon ash with a carbon content greater than or equal to 30% and less than 75%, respectively. The raw material homogenization silo 2 stores the ground second mixture after homogenization, which is then used as raw material for clinker calcination. The feed inlet of the preheating decomposition furnace 3 is connected to the raw material homogenization silo 2, and the homogenized second mixture, metered and processed in the silo 2, enters the preheating decomposition furnace 3 through its feed inlet. In the cement kiln calcination system, the second mixture undergoes sequential calcination and cooling to prepare clinker, which is then stored in the clinker silo 8 for later use.

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

[0090] Specifically, the material after grinding and drying in the cement preparation workshop 11 is 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 residue is classified according to its carbon content into: high-carbon ash residue (carbon content ≥ 75%), medium-carbon ash residue (carbon content ≥ 30%), and low-carbon ash residue (carbon content ≤ 5%). This maximizes the resource utilization of coal gasification ash residue, solves the problem of difficult resource utilization of coal gasification ash residue, and improves the resource utilization efficiency of coal gasification ash residue by classifying it according to carbon content.

[0093] 2. High-carbon ash slag replaces fuel coal and enters the pulverized coal preparation system; medium-carbon ash slag replaces natural resources and enters the raw material mill preparation system; low-carbon ash slag replaces clinker and enters the cement mill preparation system. By utilizing the different material properties to achieve different functions in cement production, natural resources such as coal and limestone are significantly saved. At the same time, the utilization of low-carbon ash slag reduces the amount of clinker in cement, lowering carbon emissions from cement production. Furthermore, the replacement of some blending materials with low-carbon ash slag conserves natural resources.

[0094] 3. By utilizing ash and slag in multiple locations based on carbon content and material properties, low-carbon cement can be prepared, improving the utilization rate of coal gasification ash and slag. This is beneficial for protecting the ecological environment, promoting ecological civilization, and driving high-quality development of enterprises and industries.

[0095] 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.

[0096] 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 method for preparing low-carbon cement through the graded and cascaded utilization of coal gasification ash, characterized in that, Includes the following steps: Step 1: The coal gasification ash residue is classified according to its carbon content into three categories: carbon-rich ash residue with a carbon content of ≥75%, medium-carbon ash residue with a carbon content of ≥30% and <75%, and carbon-lean ash residue with a carbon content of ≤5%. This classification only requires a specific carbon content, not particle size. The carbon-rich ash residue is used as a substitute for coal, the medium-carbon ash residue is used as a substitute for natural resources as part of the raw material, and the carbon-lean ash residue is used to replace clinker and is ground together with other cement components to prepare low-carbon cement. Step 2: After metering, the carbon-rich ash residue is mixed with raw coal, or the carbon-rich ash residue is sent separately to the coal powder preparation workshop for drying and grinding to obtain a first mixture; the particle size distribution of the first mixture shows that the proportion of particles larger than 80μm is less than 10%, and the moisture content is less than 1%; The medium-carbon ash residue is metered and then fed with calcareous materials, siliceous materials, ferrous materials, and aluminous materials into a raw material preparation workshop for drying and grinding to obtain a second mixture. The particle size distribution of the second mixture is such that particles larger than 80 μm account for less than 30%, particles larger than 200 μm account for less than 2%, and the moisture content is less than 1%. The second mixture is metered as raw material for clinker calcination and fed into a preheating decomposition furnace and a rotary kiln for decomposition and calcination. The first mixture, after being metered separately, is fed into the kiln head of the rotary kiln and the preheating decomposition furnace as fuel for clinker calcination. Then, it is cooled by a grate cooler to obtain clinker. Step 3: The metered lean carbon ash, clinker, gypsum, and admixtures are mixed and sent to the cement preparation workshop as a third mixture for grinding and drying to obtain finished cement; the specific surface area of ​​the finished cement is greater than 300 m². 2 / kg, particle size distribution with particles larger than 45μm accounting for 5% to 15%, and moisture content less than 1%.

2. The method for preparing low-carbon cement through the graded utilization of coal gasification ash residue according to claim 1, characterized in that, When the coal powder preparation workshop uses a vertical mill for grinding, the carbon-rich ash residue has no moisture requirement; When an air-swept ball mill is used in the pulverized coal preparation workshop, the moisture content of the carbon-rich ash residue must be less than or equal to 8%.

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

4. The method for preparing low-carbon cement through the graded utilization of coal gasification ash residue according to claim 1, characterized in that, The cement preparation workshop uses a grinding system combining roller presses and ball mills, or uses vertical mills for grinding.

5. A system for the graded and cascaded utilization of coal gasification ash to prepare low-carbon cement, characterized in that, The system, applied to the method as described in any one of claims 1 to 4, comprises: The system includes a pulverized coal preparation system, a raw meal preparation system, a cement kiln calcination system, and a cement preparation system; the cement kiln calcination system is connected to the pulverized coal preparation system, the raw meal preparation system, and the cement preparation system and continuously provides hot air. The coal powder preparation system includes a coal powder preparation workshop, which is equipped with grinding equipment; the coal powder preparation workshop is used to grind the material after mixing raw coal and carbon-rich ash into a first mixture, or to grind the carbon-rich ash separately. The raw material preparation system includes a raw material preparation workshop; the raw material preparation workshop is used to grind the mixture of calcareous materials, siliceous materials, ferrous materials, aluminous materials and medium-carbon ash slag into a second mixture; The cement kiln calcination system includes 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 installed at the kiln head of the rotary kiln, and a second burner is installed 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 includes a cement preparation workshop, which is used to grind a third mixture of clinker, admixtures, gypsum, and carbon-poor ash with a carbon content of less than or equal to 5% to prepare finished cement.

6. The system for the graded and cascaded utilization of coal gasification ash to prepare low-carbon cement according to claim 5, characterized in that, The pulverized coal preparation system also includes fuel silos and multiple fuel component storage tanks; The multiple fuel component storage bins are used to store raw coal and carbon-rich ash with a carbon content of greater than or equal to 75%, respectively, and the fuel silos are used to store the first mixture. The grinding equipment is a vertical mill or an air-swept ball mill.

7. A system for the graded and cascaded utilization of coal gasification ash to prepare low-carbon cement according to claim 5, characterized in that, The cement kiln calcination system also includes a raw material homogenization silo, multiple raw material component silos, and a clinker silo for storing clinker; Multiple raw material component storage areas are used to store calcareous materials, siliceous materials, ferrous materials, aluminous materials, and medium-carbon ash with a carbon content of ≥30% and ≤75%, respectively. The raw material homogenization silo is used to mix the second mixture evenly and store it, and the top feed inlet of the preheating decomposition furnace is connected to the raw material homogenization silo.

8. A system for the graded and cascaded utilization of coal gasification ash to prepare low-carbon cement according to claim 5, characterized in that, The cement preparation system also includes cement silos for storing the finished cement.

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