Oxy-fuel combustion white cement firing system and method thereof
By optimizing the white cement clinker calcination process through full oxygen combustion technology and a two-stage cooling system, the problems of difficult white cement clinker calcination and high carbon dioxide capture cost have been solved, efficient carbon dioxide capture and heat energy recovery have been achieved, and the calcination quality and combustion efficiency of white cement clinker have been improved.
Patent Information
- Application Number
- CN202510874103.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-27
- Publication Date
- 2025-09-12
AI Technical Summary
It is difficult to form a liquid phase during the calcination process of white cement clinker, and its flammability becomes worse, requiring the consumption of more fuel, resulting in a low concentration of carbon dioxide in the flue gas at the kiln tail, and the cost of direct capture is high.
The full oxygen combustion technology is adopted to exchange heat between the mixed gas with high oxygen concentration and the white cement clinker. Combined with the two-stage cooling and waste heat power generation system, the composition of the combustion-supporting gas is optimized, the carbon dioxide concentration in the kiln tail gas is increased, and the heat consumption and fuel consumption of the system are reduced.
It effectively increases the carbon dioxide concentration in the flue gas at the kiln tail, reduces the cost of carbon dioxide capture, improves the calcination temperature and quality of white cement clinker, realizes the recovery and utilization of heat enthalpy, and reduces the system heat consumption and the generation of nitrogen oxide pollutants.
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Figure CN120627685A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of white cement burning, in particular to a full oxygen combustion white cement burning system and a method thereof. Background Art
[0002] With the national goals of "carbon peak" and "carbon neutrality", carbon emission reduction in the cement industry is imminent. Carbon dioxide emissions from the cement industry mainly come from three parts: carbon dioxide formed by the decomposition of carbonates in raw materials, carbon dioxide formed by fuel combustion, and carbon dioxide emitted indirectly from electricity consumption. Since the concentration of carbon dioxide emitted by the cement industry is relatively low, the volume ratio of carbon dioxide in the kiln tail chimney is generally 20-25%. The cost of capturing carbon dioxide directly in the kiln tail chimney is relatively high. Oxygen-enriched and full oxygen combustion can increase the carbon dioxide concentration of the kiln tail flue gas, which helps reduce the cost of carbon dioxide capture and purification.
[0003] In order to ensure the whiteness of white cement clinker, a bleaching process is required during the preparation process. Usually, water spraying or water mist is used to bleach and quench the high-temperature white cement clinker leaving the rotary kiln. Since the system lacks the process of heat exchange between the oxygen supply air entering the decomposition furnace and the rotary kiln and the high-temperature white cement clinker leaving the kiln to form high-temperature secondary air and tertiary air, white cement clinker can only be fed into the rotary kiln and decomposition furnace with cold air or secondary and tertiary air with lower temperature. In addition, the white cement clinker ingredients require low iron content and high values of limestone saturation coefficient, aluminum silicate and aluminum oxygen rate. Therefore, it is difficult to form liquid during the calcination process of white cement clinker. The calcination temperature of white cement clinker is often 150-200℃ higher than that of ordinary Portland cement clinker, which leads to higher heat consumption of white cement burning system. The calcination of white cement clinker requires more fuel, which increases the proportion of carbon dioxide emitted by fuel combustion, and ultimately makes the carbon dioxide concentration in the flue gas at the kiln tail lower than that of the flue gas at the kiln tail of ordinary Portland clinker burning system. Compared with the direct capture of carbon dioxide at the kiln tail of ordinary Portland clinker, the cost of direct capture and purification of carbon dioxide at the kiln tail of white cement clinker is higher.
[0004] In order to provide a higher flame temperature and enhance the calcination intensity for the rotary kiln calcining of white cement, and to reduce the cost of carbon dioxide capture and purification in the flue gas at the kiln tail of the white cement clinker burning system, the use of oxygen-enriched or full oxygen combustion is a better solution. It can increase the oxygen concentration of the combustion-supporting gas, reduce the heat consumption of the system, and increase the carbon dioxide concentration in the flue gas at the kiln tail, providing favorable conditions for reducing the carbon capture and purification costs of the white cement clinker production line. Therefore, a new full oxygen combustion white cement burning system and its working principle are proposed. Summary of the Invention
[0005] (1) Technical problems solved
[0006] In response to the deficiencies in the prior art, the present invention provides a full oxygen combustion white cement firing system and method, which solves the problem that the current white cement clinker calcination process is difficult to form a liquid phase, the burnability deteriorates, more fuel is consumed, and the proportion of carbon dioxide emitted by fuel combustion increases, ultimately making the carbon dioxide concentration in the kiln tail flue gas lower than the carbon dioxide concentration in the kiln tail flue gas of an ordinary silicate clinker firing system. Compared with directly capturing carbon dioxide at the kiln tail of an ordinary silicate clinker, the cost of directly capturing and purifying carbon dioxide at the kiln tail of the white cement clinker is higher.
[0007] Second technical solution
[0008] To achieve the above object, the present invention provides the following technical solutions:
[0009] A full oxygen combustion white cement burning system includes a preheater system, a decomposition furnace, a rotary kiln, a bleaching machine, a grate cooler, a dust collection system 1, a dust collection system 2, a white cement clinker storage, and a raw material mill. It also includes a heat exchanger 1, a circulating fan, a carbon capture system, an oxygen production system, a heat exchanger 2, a water spray system, and a water vapor exhaust fan. The preheater system, the decomposition furnace, the rotary kiln, the bleaching machine, the grate cooler, and the white cement clinker storage are connected in sequence according to the material path; the oxygen production system, the grate cooler, Heat exchanger 1, rotary kiln, decomposition furnace, preheater system, heat exchanger 1, dust collection system 1, circulation fan and carbon capture system are connected in sequence; the circulation fan outlet is divided into two branches, the first branch is connected to the carbon capture system, the second branch is connected in parallel with the oxygen production system and connected to the grate cooler together; the mixed gas outlet air duct of heat exchanger 1 is divided into two routes, one is connected to the rotary kiln, and the other is connected to the decomposition furnace; the grate cooler is divided into two sections for air supply cooling, the rear section of the grate cooler is supplied with air, and the front section of the grate cooler is supplied with air. The oxygen produced by the oxygen production system and the recycled flue gas from the kiln tail gas form a mixed gas. The oxygen content of the mixed gas is sufficient for fuel combustion and burnout in the rotary kiln and precalciner. After heat exchange with the white cement clinker in the grate cooler, the mixed gas enters the first heat exchanger, where it indirectly exchanges heat with the flue gas discharged from the preheater system. After the temperature is raised, it is divided into two paths: one entering the rotary kiln and the other entering the precalciner. The air blown into the rear section of the grate cooler heats up after heat exchange with the white cement clinker and enters the raw material mill for drying. The water spray system, bleaching machine, heat exchanger 2, dust collection system 2, and water vapor exhaust fan are connected in sequence. The water spray system in the bleaching machine sprays and cools the white cement clinker, generating medium-high temperature water vapor that enters heat exchanger 2 and indirectly exchanges heat with the air entering heat exchanger 2. The cooled water vapor is discharged into the atmosphere through the dust collector and water vapor exhaust fan. The heated air enters the raw material mill and, together with the hot air discharged from the rear section of the grate cooler, is used for drying the raw material mill.
[0010] Furthermore, the concentration of oxygen produced by the oxygen production system is not less than 90%, and the oxygen concentration of the mixed flue gas formed after mixing with the circulating flue gas is not less than 25%.
[0011] On the basis of the above scheme, an isolation device is designed above the front and rear material beds of the grate cooler. The mixed flue gas blown in from the front and the air blown in from the rear are separated by the isolation device after heat exchange with the white cement clinker in the grate cooler, and are discharged from the grate cooler through the front and rear air outlets respectively.
[0012] As a further solution of the present invention, the heat exchanger is provided with two sets of gas inlets and outlets, and the flue gas at the outlet of the preheater system and the mixed gas at the outlet of the front section of the grate cooler are subjected to indirect countercurrent heat exchange in the heat exchanger. After the heat exchange, the mixed gas at the outlet of the front section of the grate cooler is raised to not less than 300°C, and the flue gas at the outlet of the preheater system is reduced to not more than 260°C.
[0013] Furthermore, the water spray system forms water mist to bleach and cool the white cement clinker in the bleaching machine, reducing the temperature of the white cement clinker to no more than 650°C, and the generated medium-high temperature water vapor passes through the second heat exchanger to heat the air to no less than 200°C and reduce the medium-high temperature water vapor to no more than 220°C.
[0014] On the basis of the above scheme, a waste heat power generation system is set between the dust collection system and the circulating fan to realize waste heat power generation while further reducing the carbon dioxide-rich kiln tail flue gas to no more than 100°C, and then sending it to the carbon capture system and the front section of the grate cooler in a certain proportion.
[0015] The present invention also proposes a process principle of a full-oxygen combustion white cement burning system, including a material circuit process and a gas circuit process. The material circuit process is as follows: the white cement raw material is fed into the preheater system to realize raw material preheating, the preheated raw material enters the decomposition furnace to realize raw material decomposition, the decomposed raw material enters the rotary kiln, and high-temperature calcination is realized in the rotary kiln. The oxygen concentration of the kiln gas is not less than 25%, forming high-temperature white cement clinker at about 1400°C, and then enters the bleaching machine for spray bleaching and rapid cooling, cooling to no more than 650°C, and then entering the grate cooler for two-stage gas cooling. The front stage uses a mixed flue gas composed of full oxygen with a concentration of no less than 90% and the circulating flue gas of the preheater system for cooling, and the rear stage uses air for cooling. The temperature of the white cement clinker is cooled to no more than 100°C and discharged from the grate cooler, and then sent to the white cement clinker storage through a conveying device.
[0016] The gas path process includes three parts. The first part of the gas is the oxygen supply gas with an oxygen concentration of not less than 25% entering the white cement burning system, which is a mixed gas composed of the circulating flue gas at the outlet of the preheater system and the total oxygen with an oxygen concentration of not less than 90% prepared by the oxygen production system; the second part is the air entering the rear section of the grate cooler; the third part is the water vapor generated in the bleaching machine; the specific process principle is as follows: the first part of the gas: the circulating flue gas at the outlet of the preheater system is mixed with the total oxygen to form a carbon dioxide-rich mixed gas with an oxygen concentration of not less than 25%, which enters the front section of the grate cooler and forms a mixed gas with a temperature of not less than 200°C after heat exchange with the white cement clinker, and then enters the heat exchanger 1 to perform indirect countercurrent heat exchange with the preheater outlet flue gas entering the heat exchanger 1 at the same time, and is heated to not less than 300°C, and then is divided into two paths, one path goes to the rotary kiln for kiln internal combustion The flue gas is sent to the preheater for heat exchange with the raw material, and then enters the heat exchanger 1 for indirect countercurrent heat exchange with the mixed gas from the front section of the grate cooler. The temperature of the carbon dioxide-rich medium-temperature flue gas in the preheater system is further reduced, and the temperature of the mixed gas from the front section of the grate cooler is further increased. The carbon dioxide-rich flue gas leaving the heat exchanger 1 is divided into two routes: one route enters the carbon capture system; the other route is mixed with the full oxygen prepared by the oxygen production system in a certain proportion, and enters the firing system from the front section of the grate cooler for recycling.
[0017] The second part of gas: The air entering the rear section of the grate cooler exchanges heat with the white cement clinker, reducing the temperature of the white cement clinker to no more than 100°C. After heat exchange, hot air of 100-200°C is formed, which serves as the heat source for raw material grinding and drying.
[0018] The third part of gas: The high-temperature white cement clinker from the rotary kiln is spray-bleached and cooled in the bleaching machine through the water spray system. The medium-high temperature water vapor formed in the high-temperature clinker environment enters the second heat exchanger for indirect countercurrent heat exchange with the air entering simultaneously, heating the air entering the second heat exchanger to no less than 200°C. This hot air serves as another drying heat source for the raw material mill; at the same time, the water vapor is reduced to no more than 220°C and discharged into the atmosphere through the second dust collection system and the water vapor exhaust fan.
[0019] Three beneficial effects
[0020] Compared with the prior art, the present invention provides a full oxygen combustion white cement burning system and method, which has the following beneficial effects:
[0021] 1. In the present invention, a mixed gas composed of total oxygen with a high oxygen concentration and a portion of the kiln tail flue gas rich in carbon dioxide replaces air and enters the grate cooler. After heat exchange with the bleached white cement clinker, the mixed gas enters the heat exchanger 1 for indirect heat exchange with the kiln tail flue gas. After the temperature is raised to no less than 300°C, the mixed gas enters the rotary kiln and the decomposition furnace to be used as fuel for combustion in the firing system. This effectively reduces the nitrogen content in the flue gas of the white cement firing system, helps to increase the carbon dioxide concentration in the kiln tail flue gas, and reduces the subsequent carbon dioxide capture cost.
[0022] 2. The present invention increases the oxygen content in the combustion-supporting gas in the rotary kiln to no less than 25% by adjusting the ratio of total oxygen to the circulating flue gas at the kiln tail. This not only helps to increase the flame temperature of the rotary kiln burner and the calcination temperature of white cement clinker, but also helps to calcine white cement clinker and improve the quality of white cement clinker.
[0023] 3. The present invention reduces the temperature of the kiln tail flue gas to no more than 100°C through the heat exchanger and the waste heat power generation system, which facilitates subsequent low-temperature carbon capture, realizes waste heat utilization and improves the heat-resistant environment of the front-end equipment components of the grate cooler.
[0024] 4. The present invention uses a bleaching machine and a grate cooler to perform two-stage cooling on the high-temperature white cement clinker leaving the rotary kiln, which not only ensures the water spray bleaching effect, but also realizes partial heat recovery of the white cement clinker, increases the temperature of the oxygen supply mixed gas entering the rotary kiln and decomposition furnace, and further increases the temperature of the oxygen supply mixed gas through the heat exchanger. This not only facilitates the combustion of fuel in the firing system, but also reduces the heat consumption and fuel consumption of the system.
[0025] 5. The present invention reduces the nitrogen content in the white cement burning system through full oxygen combustion and recycling of high-carbon dioxide kiln tail flue gas, thereby reducing the waste gas volume and heat consumption of the burning system. The dual effects of low nitrogen environment and low fuel consumption not only increase the carbon dioxide concentration in the kiln tail flue gas, but also reduce the cost of subsequent carbon capture and purification, while also reducing the generation of nitrogen oxide pollutants in the system.
[0026] 6. The medium- and high-temperature water vapor generated by the bleaching machine of the present invention is used to heat a certain amount of air through heat exchanger 2. Combined with the other part of hot air obtained by heat exchange between the air in the rear section of the grate cooler and the white cement clinker, both parts of hot air can be used as heat sources for raw material grinding and drying, fully realizing the heat recovery and utilization of the system. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 This is a schematic diagram of the process structure of a full oxygen combustion white cement burning system proposed by the present invention;
[0028] Figure 2 This is a schematic diagram of the isolation device installed above the grate cooler material bed;
[0029] Figure 3 Process flow diagram for optimization implementation.
[0030] In the figure: 1. Preheater system; 2. Decomposition furnace; 3. Rotary kiln; 4. Bleaching machine; 5. Grate cooler; 5-1. Isolation device; 6. Heat exchanger 1; 7. Dust collection system 1; 8. White cement clinker silo; 9. Water spray system; 10. Circulating fan; 10-1. First branch; 10-2. Second branch; 11. Carbon capture system; 12. Oxygen production system; 13. Heat exchanger 2; 14. Dust collection system 2; 15. Water vapor exhaust fan; 16. Raw material mill; 17. Waste heat power generation system. DETAILED DESCRIPTION
[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.
[0032] Example 1
[0033] Reference Figure 1-Figure 3A full oxygen combustion white cement burning system includes a preheater system 1, a decomposition furnace 2, a rotary kiln 3, a bleaching machine 4, a grate cooler 5, a dust collection system 7, a white cement clinker storage 8, and a raw material mill 16. It also includes a heat exchanger 6, a water spray system 9, a circulating fan 10, a carbon capture system 11, an oxygen production system 12, a heat exchanger 13, a dust collection system 14, and a water vapor exhaust fan 15. According to the material path: the preheater system 1, the decomposition furnace 2, the rotary kiln 3, the bleaching machine 4, the grate cooler 5, and the white cement clinker storage 8 are connected in sequence; according to the gas path: the oxygen production system 12, the grate cooler 5, and the white cement clinker storage 8 are connected in sequence. The cooling machine 5, heat exchanger 6, rotary kiln 3, decomposition furnace 2, preheater system 1, heat exchanger 6, dust collection system 7, circulating fan 10, and carbon capture system 11 are connected in sequence; the outlet of the circulating fan 10 is divided into two branches, the first branch 10-1 is connected to the carbon capture system, and the second branch 10-2 is connected in parallel with the oxygen production system 12 and connected to the grate cooler 5; the mixed gas outlet duct of the heat exchanger 6 is divided into two routes, one route enters the rotary kiln 3, and the other route enters the decomposition furnace 2; the grate cooler 5 is divided into two sections of cooling air supply, the rear section of the grate cooler 5 is supplied with air, and the front section of the grate cooler 5 is supplied with The wind is a mixture of full oxygen prepared by the oxygen production system 12 and the circulating flue gas at the kiln tail. The oxygen content in the mixed gas is sufficient for the combustion and exhaustion of the fuel in the rotary kiln 3 and the decomposition furnace 2. The mixed gas and the white cement clinker are heat-exchanged in the grate cooler 5 and then enter the heat exchanger 6. In the heat exchanger 6, indirect heat exchange is carried out with the flue gas discharged from the preheater system 1. After the temperature is increased, it is divided into two paths, one entering the rotary kiln 3 and the other entering the decomposition furnace 2; the air blown into the rear section of the grate cooler 5 exchanges heat with the clinker, and the temperature is increased before entering the raw material mill 16 for drying the raw materials; the water spray system 9, bleaching The machine 4, the heat exchanger 2 13, the dust collecting system 2 14, and the water vapor exhaust fan 15 are connected in sequence. The bleaching machine 4 is equipped with a water spray pipe and a nozzle. The pipe is connected to the water spray system. The nozzle is used to spray bleach and cool the high-temperature white cement clinker, reducing the temperature of the white cement clinker to no more than 650°C. The medium-temperature water vapor formed enters the heat exchanger 2 13 and indirectly exchanges heat with the air entering the heat exchanger 2 13, heating the air to no less than 200°C. The water vapor temperature drops to no more than 220°C and is discharged into the atmosphere through the dust collector 214. The heated air enters the raw material mill 16.
[0034] In order to increase the calcination temperature of white cement clinker and ensure the calcination quality of white cement clinker, the oxygen production system 12 prepares total oxygen with an oxygen concentration of not less than 90%, and controls the oxygen concentration of the mixed flue gas formed by mixing it with the circulating flue gas at the kiln tail to not less than 25%, which can increase the combustion rate of the fuel in the rotary kiln 3. In addition, in order to prevent the flame temperature in the kiln from being too high, it is appropriate to control the oxygen concentration of the mixed flue gas entering the kiln to 25-35%. The oxygen concentration control is achieved by adjusting the ratio of total oxygen to the circulating flue gas at the kiln tail.
[0035] In order to increase the temperature of the carbon dioxide-rich and oxygen-rich mixed flue gas entering the firing system and reduce the temperature of the flue gas at the kiln tail, so as to optimize the implementation effect, a heat exchanger 6 is added between the outlet of the preheater system 1 and the front air outlet of the grate cooler 5. The flue gas discharged from the preheater system 1 and the mixed gas discharged from the front air outlet of the grate cooler 5 are indirectly countercurrently exchanged in the heat exchanger 6. After the heat exchange, the mixed flue gas at the front outlet of the grate cooler 5 rises to not less than 300°C, and the flue gas at the outlet of the preheater system 1 is reduced to not more than 260°C.
[0036] In order to achieve the bleaching and cooling effect of white cement clinker, the heat of white cement clinker is reasonably recovered and utilized. The white cement clinker after spray bleaching and cooling is sent to the grate cooler 5 for relay cooling at a temperature not exceeding 650°C. After cooling to a temperature not exceeding 100°C, it is sent to the white cement clinker storage. The hot air at the rear outlet of the grate cooler 5 is used as the heat source for drying the raw materials, and is supplied to the raw material mill 16 together with the hot air at the outlet of the heat exchanger 2 13 for drying the raw materials.
[0037] In order to optimize the implementation effect of the present invention, an isolation device 5-1 is designed above the material bed of the front and rear sections of the grate cooler 5. The mixed flue gas blown in from the front section, i.e., the combination of full oxygen and circulating flue gas, and the air blown in from the rear section are separated by the isolation device after heat exchange with the white cement clinker in the grate cooler 5, and are discharged from the grate cooler 5 through two air outlets respectively, to ensure that the two gases for cooling the white cement clinker do not mix with each other, to ensure that nitrogen in the air in the rear section does not enter the firing system, and to avoid the overflow of carbon dioxide enriched in the firing system.
[0038] Carbon dioxide capture requires that the flue gas temperature be further reduced from no more than 260°C to no more than 100°C. In order to further improve the implementation effect of the present invention, a waste heat power generation system 17 is set between the dust collection system 7 and the circulating fan 10. While realizing waste heat power generation 17, the flue gas rich in carbon dioxide is further reduced to no more than 100°C, and then sent to the carbon capture system 11 and the front section of the grate cooler 5, providing favorable conditions for low-temperature carbon capture of the flue gas enriched in carbon dioxide, so that the equipment components of the front section of the grate cooler are protected from the high temperature environment.
[0039] The present invention also proposes a method for producing white cement using oxyfuel combustion. To ensure the whiteness of the white cement clinker, raw materials with low coloring matter content are generally selected, primarily controlling the Fe2O3 and transition metal oxide contents. Controlling the Fe2O3 content is crucial for improving the whiteness of the white cement clinker. Furthermore, fuels with low ash content and few coloring elements are selected, with petroleum and natural gas being preferred. Low-ash petroleum coke can also be used to produce white cement clinker. After the raw materials are batched according to the required ratio, they are dried and ground to a desired fineness using high-quality alloy equipment—a grinding machine designed to minimize wear and ensure raw material whiteness.
[0040] Material circuit process: The prepared white cement raw meal is fed into the preheater system 1 to achieve raw meal preheating, and the preheated raw meal enters the decomposition furnace 2 to achieve raw meal decomposition. The decomposed raw meal enters the rotary kiln 3, and the high-temperature calcination of the white cement clinker is achieved in the rotary kiln 3. Part of the flue gas discharged from the preheater system 1 is circulated and mixed with total oxygen to form a mixed gas. The oxygen concentration is controlled at 25-35%, which is easier to increase the calcination temperature than air combustion, which is conducive to the high-temperature calcination of white cement, forming high-temperature white cement clinker at about 1400℃. After leaving the rotary kiln 3, it enters the bleaching machine 4 for spray bleaching and rapid cooling to form clinker not exceeding 650℃, and then enters the grate cooler 5 for two-stage cooling. The front stage uses a mixed flue gas composed of total oxygen with a concentration of not less than 90% and the circulating flue gas of the preheater system 1 for cooling, and the back stage uses air for cooling. The white cement clinker temperature is cooled to not more than 100℃ and discharged from the grate cooler 5 and sent to the white cement clinker storage 8.
[0041] Gas path process: The gas path system consists of three parts. The first part is the oxygen supply gas with an oxygen concentration of not less than 25% entering the white cement burning system. It is a mixed gas composed of the circulating flue gas at the outlet of the preheater system 1 and the full oxygen with an oxygen concentration of not less than 90% prepared by the oxygen production system 12. The entire system contains very little nitrogen. The flue gas at the outlet of the preheater system 1 is a flue gas with a high carbon dioxide concentration formed by the decomposition of raw materials and combustion of fuel in the system; the second part is the air entering the rear section of the grate cooler 5; the third part is the water vapor generated in the bleaching machine 4.
[0042] The first part of the gas path is the main gas path: the circulating flue gas at the outlet of the preheater system 1 is mixed with the total oxygen to form an oxygen-rich and carbon dioxide-rich gas with an oxygen concentration of not less than 25%, which enters the front section of the grate cooler 5 and exchanges heat with the white cement clinker to form a gas with a temperature of not less than 200°C. It passes through the heat exchanger 6 and is heated to not less than 300°C by the flue gas at the outlet of the preheater. Then it is divided into two paths, one to the rotary kiln 3 for fuel combustion in the rotary kiln 3, and the other to the decomposition furnace 2 to mix with the flue gas from the rotary kiln 3 in the decomposition furnace 2 for fuel combustion in the decomposition furnace 2. , while the white cement raw material is decomposed in the decomposition furnace 2, a high-temperature flue gas rich in carbon dioxide of 850-950°C is generated, which then enters the preheater system 1 for heat exchange with the raw material. While preheating the raw material, the flue gas temperature is reduced; the flue gas leaving the preheater system 1 enters the heat exchanger 1 6 and is indirectly heat exchanged with the mixed flue gas from the grate cooler 5. The flue gas temperature of the preheater system 1 is further reduced, and the temperature of the oxygen-rich and carbon dioxide-rich mixed flue gas is further increased; taking the preheater composed of five-stage cyclones as an example, the carbon dioxide-rich flue gas leaving the preheater system 1 The flue gas temperature is about 380℃. Through indirect heat exchange in heat exchanger 6, the oxygen-rich and carbon dioxide-rich mixed gas at the outlet of the front section of the grate cooler 5 can be heated from about 200℃ to not less than 300℃, and the carbon dioxide-rich flue gas leaving the preheater system 1 will be reduced to not more than 260℃; the carbon dioxide-rich flue gas leaving the heat exchanger 6 is divided into two paths: one path enters the carbon capture system 11 to capture carbon dioxide; the other path is mixed with the full oxygen prepared by the oxygen production system 12 in a certain proportion and enters the front section of the grate cooler 5 of the white cement burning system for circulation. Circular utilization; In order to improve the implementation effect of the present invention and further reduce the outlet flue gas temperature of the preheater system 1, a waste heat power generation system 17 is set between the dust collection system 7 and the circulating fan 10, which can further cool the outlet flue gas of the preheater system 1 rich in carbon dioxide to no more than 100°C, providing favorable conditions for the subsequent carbon capture system to capture carbon dioxide at low temperature, and also realizing the resource utilization of waste heat, reducing the temperature of the mixed flue gas blown in from the front section of the grate cooler 5, so that the equipment components and oil circuits of the front section of the grate cooler 5 are protected from the high-temperature flue gas environment.
[0043] The second part: The cooling air entering the rear section of the grate cooler 5 cools the white cement clinker again. The temperature of the white cement clinker is reduced to no more than 100°C through heat exchange between the air and the white cement clinker. After heat exchange, hot air of 100-200°C is formed, and then enters the raw material grinding system 16 for drying and grinding of the raw materials.
[0044] The third part: The water vapor generated by bleaching is sprayed on the high-temperature white cement clinker from the rotary kiln 3 in the bleaching machine 4 through the water spray system 9 to perform bleaching and cooling. In the high-temperature clinker environment, medium-high temperature water vapor of 400-500°C is formed. The medium-high temperature water vapor enters the heat exchanger 2 13 and indirectly exchanges heat with the air. The air entering the heat exchanger 2 13 can be heated to no less than 200°C. The heated hot air can be used as another drying heat source for the raw material mill 16. At the same time, the water vapor temperature of the heat exchanger 2 13 is reduced to no more than 220°C, and the dust is collected by the dust collection system 2 14. Finally, it is discharged into the atmosphere through the water vapor exhaust fan 15. By adjusting the ratio of total oxygen and the circulating flue gas at the kiln tail, the oxygen content in the combustion-supporting gas in the rotary kiln is increased to not less than 25%. This can not only help to increase the flame temperature of the rotary kiln burner and the calcination temperature of white cement clinker, but also help to calcine white cement clinker and improve the quality of white cement clinker. The flue gas at the kiln tail is reduced to no more than 100°C through the heat exchanger 1 and the waste heat power generation system, which is convenient for subsequent low-temperature carbon capture, realizes the utilization of waste heat and improves the heat-resistant environment of the front-end equipment components of the grate cooler.
[0045] Taking the kiln tail of the five-stage preheater system as an example, the total oxygen and the circulating flue gas at the kiln tail form a gas with an oxygen concentration of 25%. When passing through the grate cooler, it exchanges heat with the white cement clinker at about 600℃ after bleaching and cooling, and the temperature is increased to about 200℃. It enters the heat exchanger 6 and then indirectly exchanges heat with the flue gas at about 380℃ at the outlet of the preheater system 1. The temperature is further increased to about 300℃, and then enters the decomposition furnace 2 and the rotary kiln 3 for fuel combustion; the flue gas of the preheater system 1 at about 250℃ at the heat exchanger 6 is cooled to about 100℃ through the waste heat power generation system 17 and is divided into two routes. One path is sent to the carbon capture system 11, and the other path is mixed with full oxygen as circulating flue gas and enters the white cement clinker burning system through the front section of the grate cooler 5; the high-temperature white cement clinker leaving the rotary kiln 3 is bleached and cooled by the bleaching machine 4 and cooled by the two gases of the grate cooler 5 respectively. After the temperature is reduced to no more than 100°C, it is sent to the white cement clinker storage, and the hot air generated in the rear section enters the raw material mill for drying the raw materials; the water vapor of about 400°C generated in the bleaching machine 4 is indirectly heat-exchanged with the air through the second heat exchanger 13, and is discharged into the atmosphere after the temperature is reduced. The heated air enters the raw material mill for drying the raw materials.
[0046] Example 2
[0047] Reference Figure 1-Figure 3A full oxygen combustion white cement burning system includes a preheater system 1, a decomposition furnace 2, a rotary kiln 3, a bleaching machine 4, a grate cooler 5, a dust collection system 1 7, a dust collection system 2 14, a white cement clinker silo 8, and a raw material mill 16. It also includes a heat exchanger 1 6, a circulating fan 10, a carbon capture system 11, an oxygen production system 12, a heat exchanger 2 13, a water spray system 9, and a water vapor exhaust fan 15. The preheater system 1, the decomposition furnace 2, the rotary kiln 3, the bleaching machine 4, the grate cooler 5, and the white cement clinker silo 8 are sequentially connected according to the material path; the oxygen production system is connected according to the gas path. 12, grate cooler 5, heat exchanger 6, rotary kiln 3, decomposition furnace 2, preheater system 1, heat exchanger 6, dust collection system 7, circulating fan 10 and carbon capture system 11 are connected in sequence; the outlet of circulating fan 10 is divided into two branches, the first branch 10-1 is connected to the carbon capture system 11, and the second branch 10-2 is connected in parallel with the oxygen production system 12 and connected to the grate cooler 5 together; the mixed gas outlet duct of heat exchanger 6 is divided into two routes, one is connected to the rotary kiln 3, and the other is connected to the decomposition furnace 2; the grate cooler 5 is divided into two sections for air supply cooling, and the rear section of the grate cooler 5 is supplied with air The air supply at the front of the grate cooler 5 is a mixed gas composed of the full oxygen prepared by the oxygen production system 12 and the circulating flue gas at the kiln tail. The oxygen content in the mixed gas satisfies the combustion and exhaustion of the fuel in the rotary kiln 3 and the decomposition furnace 2. The mixed gas exchanges heat with the white cement clinker in the grate cooler 5 and then enters the heat exchanger 6. In the heat exchanger 6, indirect heat exchange is carried out with the flue gas discharged from the preheater system 1. After the temperature is increased, it is divided into two paths, one entering the rotary kiln 3 and the other entering the decomposition furnace 2. The air blown into the rear of the grate cooler 5 exchanges heat with the white cement clinker to increase its temperature. The raw materials enter the raw mill 16 for drying; the water spray system 9, the bleaching machine 4, the heat exchanger 2 13, the dust collection system 2 14, and the water vapor exhaust fan 15 are connected in sequence. The white cement clinker in the bleaching machine 4 is spray-bleached and cooled by the water spray system 9. The medium-high temperature water vapor generated enters the heat exchanger 2 13 and indirectly exchanges heat with the air entering the heat exchanger 2 13. The cooled water vapor is discharged into the atmosphere through the dust collector 2 and the water vapor exhaust fan 15. The heated air enters the raw mill 16 and is used for drying in the raw mill 16 together with the hot air discharged from the rear section of the grate cooler 5.
[0048] In the present invention, it should be noted that the oxygen concentration prepared by the oxygen production system 12 is not less than 90%, and the oxygen concentration in the mixed flue gas formed after mixing with the circulating flue gas is not less than 25%. An isolation device 5-1 is designed above the front and rear sections of the grate cooler 5. The mixed flue gas blown in from the front section and the air blown in from the rear section are separated by the isolation device 5-1 after heat exchange with the white cement clinker in the grate cooler 5, and are discharged from the grate cooler 5 through the front and rear air outlets respectively. The heat exchanger 16 is provided with two sets of gas inlets and outlets. The flue gas at the outlet of the preheater system 1 and the mixed gas at the outlet of the front section of the grate cooler 5 are indirectly countercurrently exchanged in the heat exchanger 16. After heat exchange, the mixed gas at the outlet of the front section of the grate cooler 5 is raised to not less than 300°C, and the flue gas at the outlet of the preheater system 1 is reduced to not more than 260°C. The water spray system 9 forms water mist in the drift The white cement clinker is bleached and cooled in the bleaching machine 4, and the temperature of the white cement clinker is reduced to no more than 650°C. The medium and high temperature water vapor formed is passed through the heat exchanger 2 13 to heat the air to no less than 200°C and the medium and high temperature water vapor is reduced to no more than 220°C. A waste heat power generation system is set between the dust collection system 1 7 and the circulating fan 10 to realize waste heat power generation while further reducing the carbon dioxide-rich kiln tail flue gas to no more than 100°C, and then sent to the carbon capture system 11 and the front end of the grate cooler 5 according to a certain proportion. The medium and high temperature water vapor generated by the bleaching machine is passed through the heat exchanger 2 to achieve a certain amount of air heating. Combined with the other part of hot air obtained by heat exchange between the air in the rear end of the grate cooler and the white cement clinker, both parts of hot air can be used as heat sources for raw material grinding and drying, fully realizing the thermal enthalpy recovery and utilization of the system.
[0049] The present invention also proposes a full oxygen combustion white cement burning system process raw material, including a material circuit process and a gas circuit process. The material circuit process is that the white cement raw material is fed into the preheater system 1 to realize raw material preheating, the preheated raw material enters the decomposition furnace 2 to realize raw material decomposition, and the decomposed raw material enters the rotary kiln 3 to realize high-temperature calcination in the rotary kiln 3. The oxygen concentration of the kiln gas is not less than 25%, forming a high-temperature white cement clinker of about 1400°C, and then enters the bleaching machine 4 for spray bleaching and rapid cooling, cooling to no more than 650°C, and then enters the grate cooler 5 for two-stage gas cooling. The front stage uses a mixed flue gas composed of full oxygen with a concentration of no less than 90% and the circulating flue gas of the preheater system 1 for cooling, and the rear stage uses air for cooling. The temperature of the white cement clinker is cooled to no more than 100°C and discharged from the grate cooler 5, and then sent to the white cement clinker storage through a conveying device.
[0050] The gas path process is as follows: the system gas path consists of three parts. The first part is the oxygen supply gas with an oxygen concentration of not less than 25% entering the white cement burning system. It is a mixed gas composed of the circulating flue gas at the outlet of the preheater system 1 and the total oxygen with an oxygen concentration of not less than 90% prepared by the oxygen production system 12. The entire system contains very little nitrogen, among which the flue gas at the outlet of the preheater system 1 is the carbon dioxide-rich flue gas formed by the decomposition of the raw material and the combustion of the fuel in the system; the second part is the air entering the rear section of the grate cooler 5; and the third part is the water vapor generated in the bleaching machine 4.
[0051] The first part of the gas is the main gas path: the circulating flue gas at the outlet of the preheater system 1 is mixed with the total oxygen to form an oxygen-rich and carbon dioxide-rich mixed gas with an oxygen concentration of not less than 25%, which enters the front section of the grate cooler 5 and forms a mixed gas with a temperature of not less than 200°C after heat exchange with the white cement clinker. It then enters the heat exchanger 16 and undergoes indirect countercurrent heat exchange with the flue gas at the outlet of the preheater that enters the heat exchanger 16 at the same time, and is heated to not less than 300°C. It is then divided into two paths, one to the rotary kiln 3 for fuel combustion in the kiln, and the other to the calciner 2 and the flue gas from the rotary kiln 3 to be mixed in the calciner 2 for fuel combustion in the calciner 2. While the white cement raw material is decomposed in the calciner 2, 850- The high-temperature flue gas rich in carbon dioxide at 950°C then enters the preheater system 1 to exchange heat with the raw meal. While heating the raw meal, the flue gas temperature is reduced to form medium-temperature flue gas; the medium-temperature flue gas rich in carbon dioxide exiting the preheater system 1 enters the heat exchanger 6 to perform indirect countercurrent heat exchange with the mixed gas from the front section of the grate cooler 5. The temperature of the medium-temperature flue gas rich in carbon dioxide in the preheater system 1 is further reduced, and the temperature of the mixed gas from the front section of the grate cooler 5 is further increased; the carbon dioxide-rich flue gas exiting the heat exchanger 6 is divided into two paths: one path enters the carbon capture system 11; the other path is mixed with the full oxygen prepared by the oxygen production system 12 in a certain proportion, and enters the firing system from the front section of the grate cooler 5 for recycling.
[0052] The second part of gas: the air entering the rear section of the grate cooler 5 exchanges heat with the white cement clinker, reducing the temperature of the white cement clinker to no more than 100°C. After heat exchange, it forms hot air of 100-200°C, which serves as the drying heat source for the raw material mill 16.
[0053] The third part of gas: The high-temperature white cement clinker from the rotary kiln 3 is spray-bleached and cooled in the bleaching machine 4 through the water spray system 9. The medium-high temperature water vapor formed in the high-temperature clinker environment enters the heat exchanger 2 13 for indirect countercurrent heat exchange with the air entering simultaneously, heating the air entering the heat exchanger 2 13 to no less than 200°C. This hot air serves as another drying heat source for the raw material mill 16; at the same time, the water vapor is reduced to no more than 220°C and discharged into the atmosphere through the dust collection system 2 14 and the water vapor exhaust fan 15. A mixed gas composed of total oxygen with a high oxygen concentration and a portion of the kiln tail flue gas rich in carbon dioxide replaces the air and enters the grate cooler. After heat exchange with the bleached white cement clinker, it enters the heat exchanger 1 for indirect heat exchange with the kiln tail flue gas. After the temperature is raised to no less than 300°C, it enters the rotary kiln and the decomposition furnace for fuel combustion in the firing system. This effectively reduces the nitrogen content in the flue gas of the white cement firing system, helps to increase the carbon dioxide concentration in the kiln tail flue gas, and reduces the subsequent carbon dioxide capture cost.
[0054] In the description herein, it should be noted that relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Furthermore, the terms "include," "comprise," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.
Claims
1. A full oxygen combustion white cement burning system, comprising a preheater system (1), a decomposition furnace (2), a rotary kiln (3), a bleaching machine (4), a grate cooler (5), a dust collection system (7), a dust collection system (14), a white cement clinker storage (8), and a raw material mill (16), characterized in that: The system further comprises a heat exchanger 1 (6), a circulating fan (10), a carbon capture system (11), an oxygen production system (12), a heat exchanger 2 (13), a water spray system (9), and a steam exhaust fan (15). The preheater system (1), the decomposition furnace (2), the rotary kiln (3), the bleaching machine (4), the grate cooler (5), and the white cement clinker storage (8) are sequentially connected according to the material path; the oxygen production system (12), the grate cooler (5), the heat exchanger 1 (6), the rotary kiln (3), the decomposition furnace (2), the preheater system (1), the heat exchanger 1 (6), the dust collection system 1 (7) are sequentially connected according to the gas path. ), a circulating fan (10) and a carbon capture system (11) are connected in sequence; the outlet of the circulating fan (10) is divided into two branches, the first branch (10-1) is connected to the carbon capture system (11), and the second branch (10-2) is connected in parallel with the oxygen production system (12) and connected to the grate cooler (5); the mixed gas outlet air duct of the heat exchanger (6) is divided into two paths, one path is connected to the rotary kiln (3), and the other path is connected to the decomposition furnace (2); the grate cooler (5) is divided into two sections for air supply cooling, the air supply of the rear section of the grate cooler (5) is air, and the air supply of the front section of the grate cooler (5) is full oxygen prepared by the oxygen production system (12) The mixed gas is composed of the circulating flue gas at the kiln tail, and the oxygen content in the mixed gas satisfies the combustion and exhaustion of the fuel in the rotary kiln (3) and the decomposition furnace (2). The mixed gas and the white cement clinker are heat-exchanged in the grate cooler (5) and then enter the heat exchanger 1 (6). In the heat exchanger 1 (6), indirect heat exchange is achieved with the flue gas discharged from the preheater system (1). After the temperature is increased, it is divided into two paths, one entering the rotary kiln (3) and the other entering the decomposition furnace (2); the air blown in from the rear section of the grate cooler (5) exchanges heat with the white cement clinker and the temperature is increased, and then enters the raw material mill (16) for drying the raw materials; the water spray system The system (9), the bleaching machine (4), the heat exchanger 2 (13), the dust collecting system 2 (14), and the water vapor exhaust fan (15) are connected in sequence. The white cement clinker is spray-bleached and cooled by the water spraying system (9) in the bleaching machine (4). The medium-high temperature water vapor generated enters the heat exchanger 2 (13) and indirectly exchanges heat with the air entering the heat exchanger 2 (13). The cooled water vapor is discharged into the atmosphere through the dust collector (2) and the water vapor exhaust fan (15). The heated air enters the raw material mill (16) and is used for drying the raw material mill (16) together with the hot air discharged from the rear section of the grate cooler (5).
2. The oxy-combustion white cement burning system according to claim 1, characterized in that: The concentration of oxygen produced by the oxygen production system (12) is not less than 90%, and the oxygen concentration in the mixed flue gas formed after mixing with the circulating flue gas is not less than 25%.
3. The oxy-combustion white cement burning system according to claim 1, characterized in that: An isolation device (5-1) is designed above the front and rear material beds of the grate cooler (5). The mixed flue gas blown in from the front and the air blown in from the rear are separated by the isolation device (5-1) after heat exchange with the white cement clinker in the grate cooler (5), and are discharged from the grate cooler (5) through the front and rear air outlets respectively.
4. The oxy-combustion white cement burning system according to claim 1, characterized in that: The heat exchanger (6) is provided with two sets of gas inlets and outlets. The flue gas at the outlet of the preheater system (1) and the mixed gas at the outlet of the front section of the grate cooler (5) are subjected to indirect countercurrent heat exchange in the heat exchanger (6). After the heat exchange, the mixed gas at the outlet of the front section of the grate cooler (5) is raised to not less than 300°C, and the flue gas at the outlet of the preheater system (1) is lowered to not more than 260°C.
5. The oxy-combustion white cement burning system according to claim 1, characterized in that: The water spray system (9) forms water mist to bleach and cool the white cement clinker in the bleaching machine (4), reducing the temperature of the white cement clinker to no more than 650°C. The generated medium-high temperature water vapor passes through the second heat exchanger (13) to heat the air to no less than 200°C and reduce the medium-high temperature water vapor to no more than 220°C.
6. The oxy-combustion white cement burning system according to claim 1, characterized in that: The waste heat power generation system is arranged between the dust collecting system (7) and the circulating fan (10), which realizes waste heat power generation while further reducing the carbon dioxide-rich kiln tail flue gas to no more than 100°C, and then sends it to the carbon capture system (11) and the front section of the grate cooler (5) in a certain proportion.
7. A full oxygen combustion white cement burning system process principle, characterized in that: Including material path technology and gas path technology; The material circuit process is as follows: white cement raw material is fed into a preheater system (1) to realize raw material preheating; the preheated raw material enters a decomposition furnace (2) to realize raw material decomposition; the decomposed raw material enters a rotary kiln (3) to realize high-temperature calcination in the rotary kiln (3); during calcination, an oxygen concentration of not less than 25% is introduced into the rotary kiln to form high-temperature white cement clinker of about 1400°C; then the raw material enters a bleaching machine 4 for spray bleaching and rapid cooling to not more than 650°C; and then enters a grate cooler 5 for two-stage gas cooling; the front stage uses a mixed flue gas composed of total oxygen with a concentration of not less than 90% and the circulating flue gas of the preheater system (1) for cooling; the rear stage uses air for cooling; the temperature of the white cement clinker is cooled to not more than 100°C and discharged from the grate cooler (5), and then sent to the white cement clinker storage through a conveying device. The gas path process comprises three parts: the first part is the oxygen supply gas with an oxygen concentration of not less than 25% entering the white cement burning system, which is a mixed gas composed of the circulating flue gas at the outlet of the preheater system and the total oxygen with an oxygen concentration of not less than 90% prepared by the oxygen production system; the second part is the air entering the rear section of the grate cooler (5); and the third part is the water vapor generated in the bleaching machine (4); The specific process principle is as follows: the first part of the gas: the circulating flue gas at the outlet of the preheater system (1) is mixed with the total oxygen to form a carbon dioxide-rich mixed gas with an oxygen concentration of not less than 25%, which enters the front section of the grate cooler (5) and forms a mixed gas with a temperature of not less than 200°C after heat exchange with the white cement clinker. Then, it enters the heat exchanger 1 (6) and performs indirect countercurrent heat exchange with the preheater outlet flue gas entering the heat exchanger 1 (6) at the same time, and is heated to not less than 300°C. Then, it is divided into two paths, one path goes to the rotary kiln (3) for fuel combustion in the kiln, and the other path goes to the decomposition furnace (2) and is mixed with the flue gas from the rotary kiln (3) in the decomposition furnace (2) for fuel combustion in the decomposition furnace (2). While the white cement raw material is decomposed in the decomposition furnace (2), 850 The high-temperature flue gas rich in carbon dioxide at -950°C then enters the preheater system (1) for heat exchange with the raw meal. While heating the raw meal, the flue gas temperature is reduced to form medium-temperature flue gas. The medium-temperature flue gas rich in carbon dioxide exiting the preheater system (1) enters the heat exchanger 1 (6) for indirect countercurrent heat exchange with the mixed gas from the front section of the grate cooler (5). The temperature of the medium-temperature flue gas rich in carbon dioxide in the preheater system (1) is further reduced, and the temperature of the mixed gas from the front section of the grate cooler (5) is further increased. The carbon dioxide-rich flue gas exiting the heat exchanger 1 (6) is divided into two paths: one path enters the carbon capture system (11); the other path is mixed with the total oxygen prepared by the oxygen production system (12) in a certain proportion and enters the firing system from the front section of the grate cooler (5) for recycling. The second part of gas: the air entering the rear section of the grate cooler (5) exchanges heat with the white cement clinker, reducing the temperature of the white cement clinker to no more than 100°C. After the heat exchange, hot air of 100-200°C is formed, which serves as a drying heat source for the raw material mill (16). The third part of gas: The high-temperature white cement clinker from the rotary kiln (3) is spray-bleached and cooled in the bleaching machine (4) through the water spray system (9). The medium-high temperature water vapor formed in the high-temperature clinker environment enters the heat exchanger 2 (13) and performs indirect countercurrent heat exchange with the air entering simultaneously. The air entering the heat exchanger 2 (13) is heated to not less than 200°C. The hot air serves as another part of the drying heat source for the raw material mill (16); at the same time, the water vapor is reduced to not more than 220°C and discharged into the atmosphere through the dust collection system 2 (14) and the water vapor exhaust fan (15).