A carbonate raw material decomposition device in a high carbon dioxide partial pressure environment

Abstract

This invention discloses a carbonate raw meal decomposition device in a high carbon dioxide partial pressure environment. It includes a high carbon dioxide partial pressure furnace, a raw meal buffer silo, a cyclone separator, and a waste heat boiler. The high carbon dioxide partial pressure furnace is connected to the raw meal buffer silo. The high carbon dioxide partial pressure furnace includes a reaction chamber and a vertical combustion furnace body, which are connected. A circulating separator is installed in the vertical combustion furnace body, and the circulating separator is connected to the side of the cyclone separator. The top of the cyclone separator is connected to the waste heat boiler. This invention's device is suitable for the continuous decomposition process of carbonate raw meal in a high carbon dioxide environment, and a material decomposition device has been developed to match the process design. This device can achieve a carbonate raw meal decomposition rate of over 85% at an 80% carbon dioxide concentration, ensuring the quality of cement clinker products after oxygen-enriched / pure oxygen combustion in cement kilns.

Description

Technical Field

[0001] This invention relates to the field of cement clinker manufacturing, and more specifically to a carbonate raw meal decomposition device in a high carbon dioxide partial pressure environment. Background Technology

[0002] The cement manufacturing industry is an energy- and carbon-intensive industry, and in China, the amount of carbon dioxide emitted by cement production is second only to the power industry. Currently, the cement industry is actively implementing energy-saving and carbon-reduction technology upgrades, hoping to reduce carbon emissions during production through advanced technology and equipment. Oxygen-enriched combustion technology is a powerful measure to address carbon emission reduction. This approach mainly involves equipping cement plants with an oxygen production system to obtain gas with an oxygen concentration of 25-40%. Because this gas has a significantly higher oxygen content than air, it can significantly improve combustion efficiency and flame temperature during the combustion process with pulverized coal, and significantly reduce the enthalpy carried by the exhaust gas, thereby reducing the consumption of traditional fossil fuels and achieving the goal of energy conservation and carbon reduction. Building on oxygen-enriched combustion, to further improve energy utilization and reduce pollutant emissions, the industry has proposed the pure oxygen combustion technology approach, which uses oxygen with a concentration of over 95% as the combustion-supporting gas, enabling the fuel to be converted into heat energy to a large extent for direct use in the calcination of cement clinker.

[0003] The application of oxygen-enriched / pure oxygen combustion technology in cement firing systems faces the following limitations:

[0004] ① The main chemical reactions in a cement decomposition furnace fall into three categories: first, the reaction of pulverized coal with oxygen to produce carbon dioxide (C + O₂ → CO₂); second, the decomposition of carbonate raw materials, primarily calcium carbonate, to produce carbon dioxide (CaCO₃ → CaO + CO₂). This results in a high concentration of CO₂ gas in the decomposition furnace. Theoretical research indicates that the decomposition of CaCO₃ is a reversible chemical reaction. The decomposition process in the container is influenced by the equilibrium partial pressure of CaCO₃ and the partial pressure of the CO₂ environment. Excessive CO₂ concentration directly inhibits the decomposition of carbonate raw materials, negatively impacting cement production. Therefore, oxygen-enriched / pure oxygen combustion technology in the cement industry, due to the high concentration of CO₂ gas in the decomposition furnace hindering the decomposition of carbonate raw materials, makes it difficult to obtain the desired cement clinker product, thus affecting production stability.

[0005] ② Regarding pure oxygen combustion technology, it has previously been widely used in industries such as float glass kilns, fiberglass kilns, and steel smelting. There are currently no application cases of combining pure oxygen with pulverized coal directly for calcination in cement kilns. This is mainly because the cement industry lacks dedicated burners, industrial decomposition furnaces, and process design schemes compatible with pure oxygen combustion, and issues such as intensity control under high combustion efficiency of pure oxygen have not yet been resolved. Summary of the Invention

[0006] The purpose of this invention is to provide a carbonate raw meal decomposition device in a high carbon dioxide partial pressure environment, solving the following problems: ① Unlike conventional decomposition furnaces, this patent can effectively adapt to the requirements of rapid ignition of pulverized coal under oxygen-enriched / pure oxygen combustion conditions, concentrating energy release, making it a dedicated decomposition device for high-efficiency combustion technology. ② From a process design perspective, by matching air, coal, and materials, the inhibitory effect of high carbon dioxide partial pressure on material decomposition is weakened, ensuring that the chemical reaction process proceeds in the direction of carbonate decomposition. ③ From an equipment design perspective, sufficient reaction space is created for carbonate raw meal decomposition, improving the material decomposition rate and ensuring the quality of cement clinker products.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a carbonate raw material decomposition device in a high carbon dioxide partial pressure environment, comprising a high carbon partial pressure furnace, a raw material buffer silo, a cyclone separator, and a waste heat boiler. The high carbon partial pressure furnace is connected to the raw material buffer silo. The high carbon partial pressure furnace includes a reaction chamber and a vertical combustion furnace body, which are connected. The vertical combustion furnace body is equipped with a circulating separator, which is connected to the side of the cyclone separator. The top of the cyclone separator is connected to the waste heat boiler, and the branch pipe of the waste heat boiler is connected to the high carbon partial pressure furnace.

[0009] Furthermore, the upper half of the reaction chamber of the high-carbon partial pressure furnace is cylindrical, and the lower half is a triangular constriction structure. A combustion-supporting gas conveying pipe is provided at the bottom of the reaction chamber, and the combustion-supporting gas conveying pipe is connected to several small injection devices. An ash discharge port is also provided at the bottom of the reaction chamber of the high-carbon partial pressure furnace.

[0010] Furthermore, a secondary flue gas inlet is provided at the upper part of the reaction chamber of the high-carbon partial pressure furnace. The secondary flue gas inlet is connected to the waste heat boiler, and a set of pulverized coal conveying pipes are provided at both the upper and lower ends of the secondary flue gas inlet.

[0011] Furthermore, the vertical combustion furnace body is provided with three material inlets, including a cold and hot mixed raw material inlet, a hot raw material inlet, and an inlet for undecomposed raw material. The cold and hot mixed raw material inlet is located at the bottom of the vertical combustion furnace body and is connected to the buffer chamber.

[0012] Furthermore, the hot raw material inlet is also located at the bottom of the vertical combustion furnace body, staggered with the cold and hot mixed raw material inlets, and the hot raw material inlet is connected to the cement kiln preheater.

[0013] Furthermore, the inlet for the undecomposed raw material is located opposite the inlet for the hot raw material and is connected to the circulating separator.

[0014] Furthermore, the upper part of the circulating separator is a cylinder and the lower part is a cone. The upper end of the circulating separator is connected to the outlet of the vertical combustion furnace, and its lower end is connected to the inlet of the incompletely decomposed raw material in the lower section of the vertical combustion furnace through a pipe.

[0015] Based on the above technical solution, the embodiments of the present invention can produce at least the following technical effects:

[0016] This device can achieve a carbonate raw meal decomposition rate of over 85% under an 80% carbon dioxide environment concentration, ensuring the quality of cement clinker products after oxygen-enriched / pure oxygen combustion in cement kilns.

[0017] Construct a secondary decomposition system for materials. Add a circulating separator at the top of the high-carbon partial pressure furnace. First, it can be regarded as an extension of the device, increasing the residence time of materials in the furnace for decomposition and improving the decomposition rate of raw materials in a high-concentration carbon dioxide atmosphere. Second, after applying the circulating separator, some of the incompletely reacted raw material particles are returned to the high-carbon partial pressure furnace for further heating and decomposition.

[0018] This device can adapt to both oxygen-enriched and pure oxygen combustion processes, providing a systematic alternative to the current use of high-concentration oxygen for combustion in cement kiln decomposition furnaces. It effectively expands the application scenarios of new energy rationalization in cement production lines and achieves the goals of energy conservation and carbon reduction. Attached Figure Description

[0019] Figure 1 This is a structural schematic diagram of an embodiment of the present invention;

[0020] In the diagram: 1. High-carbon partial pressure furnace; 101. Combustion gas conveying pipe; 102. Ash discharge port; 103. Pulverized coal conveying pipe; 104. Secondary flue gas inlet; 105. Cold and hot mixed raw meal inlet; 106. Hot raw meal inlet; 107. Incompletely decomposed raw meal inlet; 109. Circulating separator; 2. Raw meal buffer bin; 3. Cyclone separator; 4. Waste heat boiler. Detailed Implementation

[0021] This invention provides a carbonate raw material decomposition device in a high carbon dioxide partial pressure environment, comprising a high carbon partial pressure furnace 1, a raw material buffer silo 2, a cyclone separator 3, and a waste heat boiler 4. The high carbon partial pressure furnace 1 is connected to the raw material buffer silo 2. The high carbon partial pressure furnace 1 includes a reaction chamber and a vertical combustion furnace body, which are connected. The vertical combustion furnace body is equipped with a circulating separator 109, which is connected to the side of the cyclone separator 3. The top of the cyclone separator 3 is connected to the waste heat boiler 4, and the branch pipes of the waste heat boiler 4 are connected to the high carbon partial pressure furnace 1.

[0022] The upper half of the high-carbon partial pressure furnace reaction chamber is cylindrical, while the lower half has a triangular constriction structure. A combustion-supporting gas conveying pipe 101 is located at the bottom of the reaction chamber, connected to several small injection devices. An ash discharge port 102 is also provided at the bottom of the reaction chamber. High-concentration oxygen is injected through the combustion-supporting gas conveying pipe 101 at the bottom of the reaction chamber. The total amount of combustion-supporting gas can be evenly distributed to the small injection devices, achieving multi-point injection of oxygen-enriched / pure oxygen gas into the reaction chamber. Part of the gas from the waste heat boiler 4 enters the reaction chamber through a branch pipe at the secondary flue gas inlet 104 at a wind speed of 10-15 m / s. Powdered coal is conveyed using oxygen or carbon dioxide at a wind speed of 28-35 m / s through the powdered coal conveying pipe 103 into the reaction chamber. The conveying of secondary flue gas helps to create an upward flow of raw materials in the vertical combustion furnace section, constructing a suspended calcination reaction flow field and stabilizing the material suspension wind speed. The mixing ratio of secondary flue gas can be 0-60%. The ash discharge port 102 is mainly used to clean up the small amount of ash and slag accumulated at the bottom of the reaction chamber, including ash and slag produced after pulverized coal combustion and carbonate raw material decomposition, to prevent ash and slag from clogging the combustion gas conveying channel.

[0023] A secondary flue gas inlet 104 is provided at the upper part of the reaction chamber of the high-carbon partial pressure furnace. The secondary flue gas inlet 104 is connected to the waste heat boiler 4. A set of pulverized coal conveying pipes 103 is provided at both the upper and lower ends of the secondary flue gas inlet 104. The pulverized coal conveying pipes 103 are located on the upper and lower sides of the secondary flue gas inlet 104 for two reasons: First, the pulverized coal will quickly mix with the secondary flue gas to form a solid-gas mixture and be fully dispersed inside the reaction chamber, avoiding local accumulation of combustibles. Second, since this reaction chamber is an oxygen-enriched / pure oxygen combustion zone, the combustion speed can be controlled by arranging the pulverized coal conveying pipes 103 in layers, avoiding excessive local heat radiation intensity that could damage the reaction chamber.

[0024] The vertical combustion furnace body is provided with three material inlets, including a cold and hot mixed raw material inlet 105, a hot raw material inlet 106, and an inlet for undecomposed raw material 107. The cold and hot mixed raw material inlet 105 is located at the bottom of the vertical combustion furnace body and is connected to the buffer chamber 2.

[0025] The hot raw material inlet 106 is also located at the bottom of the vertical combustion furnace body, and is arranged in a staggered manner with the cold and hot mixed raw material inlet 105. The hot raw material inlet 106 is connected to the cement kiln preheater.

[0026] The inlet 107 for undecomposed raw meal is located above the hot raw meal inlet 106 and is connected to the circulating separator 109. The vertical combustion furnace is the main area for carbonate raw meal decomposition, with an internal air velocity of 7-13 m / s. The residence time of carbonate raw meal in this combustion furnace is controlled at 50-100 s. Under pure oxygen combustion conditions, the mixing ratio of cold and hot raw meal in the raw meal buffer bin 2 can be selectively adjusted according to the temperature inside the vertical combustion furnace. The appropriate mass of raw meal is conveyed to the cold and hot mixed raw meal inlet 105 through the distribution valve and finally flows into the vertical combustion furnace for carbonate decomposition. Undecomposed raw meal with high enthalpy flows into the vertical combustion furnace through the hot raw meal inlet 106 for carbonate decomposition. The cold and hot raw meal inlet 105 and the hot raw meal inlet 106 are arranged in a staggered manner. The process principle is that the decomposition of carbonates is an endothermic reaction. The raw meal is introduced at the junction of the reaction chamber and the vertical combustion furnace body, which helps to absorb the high-temperature heat generated by oxygen-enriched / pure oxygen combustion during the decomposition process, control the combustion intensity inside the device, and allow the heat energy to be directly used for raw meal decomposition. In particular, the amount of cold raw meal added can be adjusted according to production needs by controlling the amount added, thereby regulating the reaction temperature inside the device. This ensures both the decomposition of carbonate raw meal in a high carbon dioxide partial pressure environment and avoids localized high temperature damage to the device.

[0027] The upper part of the circulating separator 109 is cylindrical and the lower part is conical. The upper end of the circulating separator 109 is connected to the outlet of the vertical combustion furnace, and its lower end is connected to the inlet 107 of the incompletely decomposed raw material in the lower section of the vertical combustion furnace through a pipe.

[0028] High-carbon dioxide partial pressure gas from the vertical combustion furnace carries decomposed solid particles and incompletely decomposed raw material particles, forming a solid-gas mixture that enters the circulating separator via a side-swirling shearing motion. As the solid-gas mixture continuously swirls downwards, it separates the flue gas and some solid particles. Finally, some solid particles return to the vertical combustion furnace through the inlet 107 for incompletely decomposed raw material, forming a third stream of material entering the furnace, separate from the mixed raw material and hot raw material. High-carbon dioxide partial pressure gas and some solid particles exit from the top of the circulating separator and enter the next stage cyclone separator 3. The gas-solid mixture from the high-carbon partial pressure furnace 1 enters the cyclone separator 3 from the side. The ambient gas, primarily composed of carbon dioxide, exits from the top of the cyclone separator 3 and enters the next stage (waste heat boiler 4), while the solid particles return to the cement kiln preheater.

[0029] The functions of the waste heat boiler 4 are twofold: first, to reduce the temperature of the high-temperature ambient gas to below 200°C, and the steam generated by the heat exchange can be incorporated into the waste heat power generation system of the cement production line to achieve energy recovery and utilization; second, to provide a cooling medium, controlling the temperature within the system's fan conveying capacity, and then providing some of the secondary flue gas back to the high-carbon partial pressure furnace 1 through the branch pipe.

[0030] Inside the high-carbon partial pressure furnace 1, oxygen-enriched / pure oxygen is used as a combustion aid and pulverized coal is used as fuel. The two react with each other to quickly form a high-temperature heat source. Carbonate raw materials are introduced into the furnace, and the carbonate components decompose in the high-temperature environment to produce CO2 gas. This CO2 gas will continuously accumulate in the rising pipe of the high-carbon partial pressure furnace 1, eventually forming a high CO2 partial pressure environment in which the material is continuously decomposed and CO2 is continuously accumulated. A circulation separation device 109 is set at the top of the rising pipe. Some of the incompletely decomposed carbonate raw materials will be directly returned to the high-carbon partial pressure furnace 1 through the incompletely decomposed raw material inlet 107, realizing the material circulation and decomposition.

[0031] The present invention will now be described in detail with reference to the accompanying drawings.

[0032] Example 1

[0033] like Figure 1 As shown, oxygen-enriched gas with a concentration of 30-45% is introduced into the combustion-supporting gas conveying pipe 101 at the bottom of the device. The pulverized coal uses oxygen-enriched and carbon dioxide-enriched conveying media. The two are mixed and burned to generate a high-temperature heat source. By adjusting the amount of combustibles and secondary flue gas, the temperature in the high-carbon partial pressure furnace is controlled at 850-900℃. Finally, at the outlet of the device, when the carbon dioxide concentration in the flue gas reaches 50-60%, the thermal decomposition rate of carbonate raw materials can be controlled at over 93%.

[0034] Example 2

[0035] Pure oxygen gas with a concentration of over 95% is introduced through the combustion gas conveying pipe 101 at the bottom of the device. Coal powder is conveyed using carbon dioxide as the medium. The two are mixed and burned to generate a high-temperature heat source. By adjusting the amount of combustibles and secondary flue gas, the temperature in the high-carbon partial pressure furnace is controlled at 900-980℃. Finally, at the outlet of the device, when the carbon dioxide concentration in the flue gas reaches 80% or above, the thermal decomposition rate of carbonate raw materials can be controlled at 85-93%.

Claims

1. A carbonate raw material decomposition device in a high carbon dioxide partial pressure environment, characterized in that, Including high carbon partial pressure furnace (1), raw material buffer bin (2), cyclone (3), waste heat boiler (4), the high carbon partial pressure furnace (1) is connected with raw material buffer bin (2), the high carbon partial pressure furnace (1) includes reaction chamber and vertical combustion furnace body, reaction chamber and vertical combustion furnace body are connected, vertical combustion furnace body is provided with circulating separator (109), the circulating separator (109) is connected with the side of cyclone (3), the top of cyclone (3) is connected with waste heat boiler (4), the branch pipe of waste heat boiler (4) is connected with high carbon partial pressure furnace (1);The upper half of the reaction chamber of the high carbon partial pressure furnace (1) is cylindrical, the lower half is a kind of triangle neck-in structure, combustion-supporting gas delivery pipe (101) is equipped at the bottom of reaction chamber, the combustion-supporting gas delivery pipe (101) is connected with several small injection devices, the bottom of high carbon partial pressure furnace reaction chamber is also provided with ash outlet (102); The upper portion of the reaction chamber of the high carbon partial pressure furnace (1) is provided with secondary flue gas inlet (104), the secondary flue gas inlet (104) is connected with waste heat boiler (4), and a group of coal powder conveying pipes (103) is arranged at the upper and lower ends of the secondary flue gas inlet (104); The vertical combustion furnace body is provided with three material inlets, including cold, hot mixed raw material inlet (105), hot raw material inlet (106) and incompletely decomposed raw material inlet (107), the cold, hot mixed raw material inlet (105) is arranged at the bottom of the vertical combustion furnace body and is connected with the buffer bin (2); The hot raw material inlet (106) is also arranged at the bottom of the vertical combustion furnace body, is arranged in staggered layers with the cold, hot mixed raw material inlet (105), and the hot raw material inlet (106) is connected with the cement kiln preheater.

2. The apparatus according to claim 1, wherein The incompletely decomposed raw material inlet (107) is arranged at the side of the hot raw material inlet (106) and is connected with the circulating separator (109).

3. The apparatus according to claim 1, wherein The upper half of the circulating separator (109) is a cylinder, and the lower half is a cone, the upper end of the circulating separator (109) is connected with the outlet of the vertical combustion furnace body, and the lower end is connected with the incompletely decomposed raw material inlet (107) in the middle and lower section of the vertical combustion furnace body through a pipeline.

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