A method for producing a low carbon emission cement

Abstract

This application discloses a low-carbon emission cement production method, belonging to the field of cement production. The production method includes the following steps: uniformly mixing iron-containing materials, a carbon source, and calcium carbonate-containing raw materials to obtain cement raw meal; thermally decomposing and calcining the cement raw meal to convert it into cement clinker. By introducing carbon during the high-temperature decomposition of calcium carbonate, carbon dioxide emissions are reduced while carbon monoxide is produced. The introduction of carbon can significantly convert the carbon dioxide emitted during cement production into carbon monoxide, reducing total carbon dioxide emissions in traditional cement processes by 50-60%. Simultaneously, the flue gas produced by the method mainly consists of carbon monoxide, nitrogen, and a small amount of carbon dioxide. The separated carbon monoxide can be used directly as fuel or as a component of syngas for further chemical production, achieving certain economic benefits while reducing carbon dioxide emissions during cement production.

Description

Technical Field

[0001] This application relates to a method for producing cement with low carbon emissions, and belongs to the field of cement production. Background Technology

[0002] Cement is a crucial material in the construction industry, widely used in building, bridge, road, and infrastructure construction. However, cement production is an energy-intensive and emission-prone process, a significant source of global carbon dioxide (CO2) emissions. CO2 emissions from the cement industry primarily originate from two sources: first, the decomposition of calcium carbonate (CaCO3) into calcium oxide (CaO) during high-temperature calcination, releasing CO2—a process known as "process emissions"; and second, CO2 produced by the combustion of fossil fuels in cement kilns, known as "fuel emissions." In 2020, my country's cement industry emitted approximately 1.4 billion tons of CO2, with "process emissions" accounting for about 60% and "combustion emissions" accounting for about 40%.

[0003] Against the backdrop of global efforts to address climate change and reduce carbon emissions, reducing CO2 emissions during cement production has become a key challenge for the sustainable development of the cement industry. Existing technologies for reducing CO2 emissions in the cement industry include using alternative raw materials, improving thermal efficiency, adopting low-carbon fuels, and carbon capture and storage (CCS) technology. However, these methods often suffer from high technical complexity, high economic costs, and difficulty in implementation, especially for the treatment of CO2 generated directly from the decomposition of calcium carbonate, for which a more economical and effective solution is still lacking. Summary of the Invention

[0004] This invention utilizes the reaction of calcium carbonate and carbon at high temperatures (CaCO3 + C → CaO + 2CO). By introducing carbon during the high-temperature decomposition of calcium carbonate, CO2 emissions are reduced while CO is generated. The purpose of this patent is to provide a method for the combined production of cement and chemicals to reduce CO2 emissions during cement production.

[0005] We propose a method for emission reduction that involves introducing a chemical reaction between carbon and calcium carbonate to reduce direct CO2 emissions. Carbon reacts with calcium carbonate at high temperatures to produce carbon monoxide (CO) and calcium oxide (CaO), as shown in the following equation: CaCO3 + C → CaO + 2CO. The core advantage of this reaction is that CO2, which would otherwise be directly released into the atmosphere, is converted into CO, thereby reducing direct CO2 emissions. The generated carbon monoxide (CO) can also be used as fuel or a feedstock for syngas, enabling further energy recovery and resource utilization.

[0006] According to one aspect of this application, a low-carbon emission cement production method is provided. This method utilizes the reaction of calcium carbonate and carbon-rich substances at high temperature (CaCO3 + C → CaO + 2CO) to produce cement. By introducing carbon during the high-temperature decomposition of calcium carbonate, carbon dioxide emissions are reduced while carbon monoxide is produced. The introduction of carbon can significantly convert the carbon dioxide emitted during cement production into carbon monoxide, reducing total carbon dioxide emissions in traditional cement processes by 50-60%. Simultaneously, the flue gas from the decomposition furnace system in this method mainly consists of carbon monoxide, nitrogen, and a small amount of carbon dioxide. The separated carbon monoxide can be used directly as fuel or as a component of syngas for further chemical production, achieving certain economic benefits while reducing carbon dioxide emissions during cement production.

[0007] A method for producing low-carbon-emission cement, the method comprising the following steps:

[0008] Iron-containing substances, carbon sources, and calcium carbonate-containing raw materials are mixed evenly to obtain cement raw meal. The cement raw meal is then thermally decomposed and calcined to transform it into cement clinker.

[0009] Optionally, the calcium carbonate-containing raw material is selected from limestone and / or calcium carbonate.

[0010] Optionally, the carbon source is selected from at least one of coal, petroleum coke, and biochar.

[0011] Optionally, the coal is selected from at least one of lignite, bituminous coal, anthracite, and sub-bituminous coal.

[0012] Optionally, the iron-containing substance is used as a catalyst, and the iron-containing substance is selected from at least one of iron ore, iron oxide, iron nitrate, iron hydroxide, and iron carbonate.

[0013] Optionally, the molar ratio of calcium carbonate to carbon in the calcium carbonate-containing raw material is 2 to 0.5.

[0014] Optionally, the molar ratio of calcium carbonate in the calcium carbonate-containing raw material to carbon in the carbon source is independently selected from any value or a range between 2, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, and 0.5.

[0015] Optionally, the iron-containing substance accounts for 1 to 6 wt.% of the mass of the cement raw meal.

[0016] Optionally, the content of iron-containing substances as a percentage of the cement raw meal mass is independently selected from any value or a range between 1 wt.%, 1.5 wt.%, 2 wt.%, 2.5 wt.%, 3 wt.%, 3.5 wt.%, 4.0 wt.%, 4.5 wt.%, 5.0 wt.%, 5.5 wt.%, and 6.0 wt.%.

[0017] Optionally, the iron-containing material further comprises a catalyst additive;

[0018] The catalyst additive is selected from at least one of potassium carbonate, sodium carbonate, potassium chloride, sodium chloride, zinc chloride, aluminum chloride, aluminum oxide, and magnesium oxide.

[0019] Preferably, the catalyst additive is at least one selected from potassium carbonate, sodium carbonate, potassium chloride, sodium chloride, and magnesium oxide.

[0020] Optionally, the catalyst promoter is 0.5 to 6.0 wt.% of the iron-containing substance.

[0021] Optionally, the catalyst additive is an iron-containing substance whose mass percentage is independently selected from any value or a range between 0.5 wt.%, 1 wt.%, 1.5 wt.%, 2 wt.%, 2.5 wt.%, 3 wt.%, 3.5 wt.%, 4.0 wt.%, 4.5 wt.%, 5.0 wt.%, 5.5 wt.%, and 6.0 wt.%.

[0022] Optionally, the thermal decomposition includes preheating decomposition and high-temperature decomposition;

[0023] The preheating decomposition temperature is 700–850°C, and the time is 5–20 minutes;

[0024] The high-temperature decomposition is carried out at a temperature of 800–950°C for 10–60 minutes.

[0025] Optionally, the temperature of the preheating decomposition is independently selected from any value or a range between 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃, 840℃, and 850℃.

[0026] Optionally, the preheating decomposition time is independently selected from any value or a range between any two of 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, and 20 min.

[0027] Optionally, the temperature for high-temperature decomposition is independently selected from any value or a range between any two of 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, and 950℃.

[0028] Optionally, the time for high-temperature decomposition is independently selected from any value or a range between 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, and 60 min.

[0029] Optionally, preheating decomposition and high-temperature decomposition are combined into high-temperature decomposition in a fluidized bed decomposition furnace.

[0030] Optionally, the calcination temperature is 1300–1500°C.

[0031] Optionally, the flue gas from cement production processes is rich in CO, which can be separated to obtain CO.

[0032] Alternatively, preheating decomposition can be carried out in a preheater, high-temperature decomposition can be carried out in a decomposition furnace, and high-temperature calcination can be carried out in a rotary kiln.

[0033] Optionally, the preheating and high-temperature decomposition processes can be carried out in a fluidized bed reactor.

[0034] In one preferred embodiment, the production method includes the following steps:

[0035] 1) Mix iron-containing substances and carbon-rich substances evenly in a certain proportion;

[0036] 2) The materials from step 1) and cement raw materials such as calcium carbonate, clay and rock sand are crushed and mixed evenly in a certain proportion to obtain cement raw meal;

[0037] 3) The raw materials obtained in step 2) are preheated, decomposed at high temperature, and calcined at high temperature to be converted into cement clinker.

[0038] Optionally, in step 2), other raw materials are mixed in a certain proportion to ensure that the chemical composition of the final product meets the requirements.

[0039] Optionally, the preheating decomposition process, the high-temperature decomposition process, and the high-temperature calcination process are carried out in a preheating furnace, a decomposition furnace, and a rotary kiln, respectively.

[0040] Optionally, the preheating decomposition process and the high-temperature decomposition process can be carried out in a fluidized bed decomposition furnace.

[0041] Optionally, the flue gas from the decomposition furnace system mainly consists of carbon monoxide, nitrogen, and a small amount of carbon dioxide.

[0042] This invention provides a fluidized bed decomposer applied to the decomposition process in cement production. By using a fluidized bed decomposer, finely ground cement raw materials come into contact with a high-temperature gas flow within the fluidized bed, rapidly completing the decomposition reaction from CaCO3 to CaO, while simultaneously generating CO. This rapid and efficient decomposition method helps improve the production capacity of the kiln system and reduces the load on the rotary kiln. Furthermore, due to the uniform temperature within the fluidized bed, the thermal efficiency of the decomposition process is significantly improved.

[0043] After being decomposed in a fluidized bed decomposer, the mixed raw materials are transferred to a cement rotary kiln system for further high-temperature calcination. By combining fluidized bed technology with a cement rotary kiln system, a more efficient, low-carbon, and environmentally friendly cement production process can be achieved; the fluidized bed technology also facilitates flue gas separation.

[0044] In this invention, by introducing carbon to react with calcium carbonate, calcium carbonate and carbon monoxide are generated. This reduces the carbon dioxide concentration around the calcium carbonate, which can promote the shift of the CaCO3→CaO+CO2 reaction equilibrium towards calcium oxide. This promotes the decomposition of calcium carbonate, lowers the temperature of the decomposition reaction, accelerates the decomposition rate, and reduces the energy consumption of the calcium carbonate decomposition process. Simultaneously, the introduced carbon can also react directly with the CO2 generated during decomposition (CO2+C→2CO), further reducing CO2 emissions, resulting in cement production with lower carbon emissions and lower energy consumption.

[0045] The introduction of carbon can significantly convert CO2 emitted during the process into CO, which can reduce CO2 emissions in traditional cement production by 50-60%.

[0046] The flue gas from the decomposition furnace system mainly consists of carbon monoxide, nitrogen, and a small amount of carbon dioxide. The separated carbon monoxide can be used directly as fuel or as a component of syngas for further chemical production, thereby reducing carbon dioxide emissions during cement production and achieving certain economic benefits.

[0047] This invention provides a method for reducing carbon dioxide emissions during cement production. By introducing carbon and calcium carbonate for high-temperature decomposition, it solves the problem of carbon dioxide emissions generated during the decomposition of calcium carbonate in traditional cement production. Simultaneously, by coupling cement production with the production of chemicals such as carbon monoxide, it achieves a shift towards low-carbon, low-energy-consumption, and high-profit cement production.

[0048] The beneficial effects that this application can produce include:

[0049] 1) The method provided by this invention can significantly reduce carbon dioxide emissions from the decomposition of calcium carbonate during cement production, achieving a carbon monoxide / carbon monoxide + carbon dioxide ratio greater than 4:1 in the flue gas at the decomposition furnace outlet. Overall, it can reduce carbon dioxide emissions by approximately 50-60% during cement production, which is beneficial to the energy transformation path of cement production towards low-carbon development.

[0050] 2) The method provided by this invention uses carbon-rich raw materials, such as coal, petroleum coke, and biochar, which are inexpensive and readily available.

[0051] 3) The method provided by this invention uses an iron-based catalyst that can be derived from iron ore, which is itself a raw material for cement production. The efficient catalytic reaction between calcium carbonate and carbon can be achieved simply by adjusting the mixing order.

[0052] 4) The method provided by this invention produces flue gas rich in carbon monoxide at the outlet of the decomposition furnace. Carbon monoxide can be used directly as a raw material and as an important component of syngas to further generate chemicals. This couples cement production and chemical production, promoting coordinated development across various industries. Detailed Implementation

[0053] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0054] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially.

[0055] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0056] It should be noted that the embodiments of the present invention mainly focus on the high-temperature decomposition process of cement production. The solid products produced by the decomposition furnace are added with cement raw materials that need to be balanced, and then fed into a commercial cement rotary kiln for calcination to obtain cement clinker.

[0057] Example 1

[0058] Using lignite as the carbon source, iron oxide as the iron-containing substance, and analytical grade calcium carbonate, the raw meal is ground and mixed evenly. The iron oxide content is 2 wt.% of the raw meal mass, and the molar ratio of carbon in limestone and lignite is 2.0. The raw meal is preheated at 750℃ for 15 minutes and then decomposed at 900℃ for 30 minutes. The ratio of carbon monoxide to carbon dioxide in the produced flue gas is 1.7, and the calcium oxide accounts for more than 95% of the solid product. Cement raw materials that need to be balanced are added to the solid product, and then it is fed into a commercial cement rotary kiln for calcination to obtain cement clinker.

[0059] Example 2

[0060] Using lignite as the carbon source, iron oxide as the iron-containing substance, and magnesium oxide as a catalyst, analytical grade calcium carbonate is ground and mixed evenly to form the raw meal. The iron oxide content is 2 wt.% of the raw meal mass, the magnesium oxide content is 2 wt.% of the iron oxide mass, and the molar ratio of carbon in limestone and lignite is 2.0. The raw meal is preheated at 750℃ for 15 minutes and then decomposed at 900℃ for 30 minutes. The ratio of carbon monoxide to carbon dioxide in the produced flue gas is 2.6, and the calcium oxide accounts for more than 95% of the solid product. Cement raw materials that need to be balanced are added to the solid product, and then it is fed into a commercial cement rotary kiln for calcination to obtain cement clinker.

[0061] Example 3

[0062] Activated carbon was used as the carbon source, ferric hydroxide as the iron-containing substance, and sodium carbonate as a catalyst additive. The ferric hydroxide, sodium carbonate, and activated carbon were mixed using an impregnation method. Then, analytical grade calcium carbonate was ground and mixed evenly to form the raw meal. The ferric hydroxide content was 2 wt.% of the raw meal mass, the sodium carbonate content was 1.5 wt.% of the ferric oxide mass, and the molar ratio of carbon in limestone and lignite was 1.0. A fluidized bed decomposer was used to decompose the raw meal at 900℃ for 40 minutes. The ratio of carbon monoxide to carbon dioxide in the produced flue gas was 11.2, and the calcium oxide content in the produced solid product was over 95%. Cement raw materials requiring balancing were added to the solid product, and then the mixture was fed into a commercial cement rotary kiln for calcination to obtain cement clinker.

[0063] Example 4

[0064] Activated carbon was used as the carbon source, and ferric hydroxide was used as the iron-containing substance. The ferric hydroxide and activated carbon were mixed using an impregnation method. Then, analytical grade calcium carbonate was ground and mixed evenly to form the raw meal. The ferric hydroxide content was 2 wt.% of the raw meal mass, and the molar ratio of carbon in limestone and lignite was 1.0. A fluidized bed decomposer was used to decompose the raw meal at 900℃ for 40 minutes. The ratio of carbon monoxide to carbon dioxide in the produced flue gas was 9.2, and the calcium oxide content in the produced solid product was over 95%. Cement raw materials requiring balancing were added to the solid product, and then the mixture was fed into a commercial cement rotary kiln for calcination to obtain cement clinker.

[0065] Example 5

[0066] Using bituminous coal as the carbon source and ferric nitrate as the iron-containing substance, the ferric nitrate and bituminous coal are mixed by impregnation. Then, analytical grade calcium carbonate is ground and mixed evenly to form the raw meal. The ferric nitrate content is 5 wt.% of the raw meal mass, and the carbon molar ratio in limestone and bituminous coal is 0.8. The raw meal is preheated at 800℃ for 10 minutes and then decomposed at 930℃ for 60 minutes. The ratio of carbon monoxide to carbon dioxide in the produced flue gas is 18.4, and the calcium oxide content in the produced solid product is over 90%. Cement raw materials requiring balancing are added to the solid product, and then it is fed into a commercial cement rotary kiln for calcination to obtain cement clinker.

[0067] Example 6

[0068] Petroleum coke was used as the carbon source, iron ore as the iron-containing substance, and analytical grade calcium carbonate were ground and mixed evenly as raw materials. The iron ore content was 4 wt.% of the raw material mass, and the molar ratio of carbon in limestone and lignite was 1.0. The raw materials were preheated at 850℃ for 10 minutes and then decomposed at 900℃ for 40 minutes. The ratio of carbon monoxide to carbon dioxide in the produced flue gas was 4.7, and the calcium oxide content in the produced solid products was over 90%. Cement raw materials that needed to be balanced were added to the solid products, and then the mixture was fed into a commercial cement rotary kiln for calcination to obtain cement clinker.

[0069] Example 7

[0070] Petroleum coke was used as the carbon source, iron ore as the iron-containing substance, and potassium carbonate was added as a catalyst. Analytical grade calcium carbonate was ground and mixed evenly to form the raw meal. The iron ore content was 4 wt.% of the raw meal mass, the potassium carbonate content was 2 wt.% of the iron ore mass, and the molar ratio of carbon in limestone and lignite was 1.0. The raw meal was preheated at 850℃ for 10 minutes and then decomposed at 900℃ for 40 minutes. The resulting flue gas had a carbon monoxide to carbon dioxide ratio of 6.8, and the solid product contained over 90% calcium oxide. Cement raw materials requiring balancing were added to the solid product, and then the mixture was fed into a commercial cement rotary kiln for calcination to obtain cement clinker.

[0071] Example 8

[0072] Using bamboo charcoal as the carbon source and ferric nitrate as the iron-containing substance, the ferric nitrate and bamboo charcoal are mixed by impregnation. Then, analytical grade calcium carbonate is ground and mixed evenly to form the raw meal. The ferric nitrate content is 1 wt.% of the raw meal mass, and the molar ratio of carbon in limestone and lignite is 1.0. A fluidized bed decomposer is used to decompose the raw meal at 920℃ for 30 minutes. The ratio of carbon monoxide to carbon dioxide in the produced flue gas is 11.1, and the calcium oxide content in the solid product is over 95%. Cement raw materials requiring balancing are added to the solid product, and then the mixture is fed into a commercial cement rotary kiln for calcination to obtain cement clinker.

[0073] Example 9

[0074] Using bamboo charcoal as the carbon source, ferric nitrate as the iron-containing substance, and potassium carbonate as a catalyst, ferric nitrate, potassium carbonate, and bamboo charcoal are mixed by impregnation. Then, analytical grade calcium carbonate is ground and mixed evenly to form the raw meal. The ferric nitrate content is 1 wt.% of the raw meal mass, the potassium carbonate content is 2 wt.% of the ferric nitrate content, and the molar ratio of carbon in limestone and lignite is 1.0. A fluidized bed decomposer is used to decompose the raw meal at 920℃ for 30 minutes. The ratio of carbon monoxide to carbon dioxide in the produced flue gas is 19.2, and the calcium oxide content in the produced solid product is over 95%. Cement raw materials requiring balancing are added to the solid product, and then the mixture is fed into a commercial cement rotary kiln for calcination to obtain cement clinker.

[0075] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for producing cement with low carbon emissions, characterized in that, The production method includes the following steps: Iron-containing substances, carbon sources, and calcium carbonate-containing raw materials are mixed evenly to obtain cement raw meal. The cement raw meal is then thermally decomposed and calcined to transform it into cement clinker.

2. The production method according to claim 1, characterized in that, The calcium carbonate-containing raw material is selected from limestone and / or calcium carbonate.

3. The production method according to claim 1, characterized in that, The carbon source is selected from at least one of coal, petroleum coke and biochar; Preferably, the coal is selected from at least one of lignite, bituminous coal, anthracite, and sub-bituminous coal.

4. The production method according to claim 1, characterized in that, The iron-containing substance is used as a catalyst, and the iron-containing substance is selected from at least one of iron ore, iron oxide, iron nitrate, iron hydroxide, and iron carbonate.

5. The production method according to claim 1, characterized in that, The molar ratio of calcium carbonate to carbon in the calcium source in the calcium carbonate-containing raw material is 2 to 0.

5.

6. The production method according to claim 1, characterized in that, The iron content of the raw cement meal is 1-6 wt.%.

7. The production method according to claim 1, characterized in that, The iron-containing substance also includes a catalyst additive; The catalyst additive is selected from at least one of potassium carbonate, sodium carbonate, potassium chloride, sodium chloride, zinc chloride, aluminum chloride, aluminum oxide, and magnesium oxide. Preferably, the catalyst additive is 0.5 to 6.0 wt.% of the iron-containing substance.

8. The production method according to claim 1, characterized in that, The thermal decomposition includes preheating decomposition and high-temperature decomposition; The preheating decomposition temperature is 700–850°C, and the time is 5–20 minutes; The high-temperature decomposition is carried out at a temperature of 800–950°C for 10–60 minutes.

9. The production method according to claim 8, characterized in that, Preheating decomposition and high-temperature decomposition are combined into high-temperature decomposition in the fluidized bed decomposition furnace.

10. The production method according to claim 1, characterized in that, The calcination temperature is 1300–1500℃.