Clay activation process by coupling oxy-fuel combustion and suspension calcination

Abstract

The present invention discloses a clay activation process coupled with full oxygen combustion and suspension calcination, and relates to the technical field of cement raw material processing. A clay activation process coupled with full oxygen combustion and suspension calcination uses the flue gas of full oxygen combustion as combustion gas, avoids the heat loss of heating low-temperature air, and can also control the oxygen content in the flue gas, improve the combustion effect of alternative fuels, and maintain a reducing atmosphere; at the same time, compared with single suspension calcined clay, it can achieve anaerobic environment cooling and reducing atmosphere calcination without adding additional means, and can further improve the use of alternative fuels, and the tail end flue gas can also return to the full oxygen combustion production line and enter the carbon capture system, truly realizing the production of zero-carbon calcined clay; while realizing the optimal allocation of resources and efficient use of energy, it solves the high carbon emission problem of traditional cement production, realizes the preparation of zero-carbon cement, significantly reduces the carbon emissions of the cement industry, and reduces environmental impact.

Description

Technical Field

[0001] The invention relates to the technical field of cement raw material processing, in particular to a clay activation process coupled with full oxygen combustion and suspension calcination. Background Art

[0002] The existing oxy-fuel combustion clinker lines produce high-purity oxygen gas (oxygen concentration higher than 99.5%) through air separation devices during the production process. However, the remaining gas components such as nitrogen and argon have no suitable uses in cement plants and are not effectively utilized during the cement production process, resulting in a waste of resources and energy.

[0003] Calcined clay is a low-carbon cementitious material that can achieve low carbon dioxide emissions during the activation process. Its easy availability of raw materials, high gelling activity and low cost make it an ideal choice to replace traditional clinker. However, the color of the product needs to be controlled when producing calcined clay. This is because clay with a high iron content will turn into a reddish brown color during the traditional calcination process, which affects the color of cement when preparing cement and is not accepted in the sales market. The iron phase transformation of clay during firing and cooling can be avoided by reducing the calcination atmosphere and the oxygen-free cooling environment, thereby ensuring that the product color is gray. At the same time, when directly using traditional air calcination, the combustion effect of the alternative fuel is general, and the calorific value of the low-grade alternative fuel cannot be fully utilized. At the same time, the air must be heated from room temperature, and it cannot be fully recovered at the back end, resulting in a certain amount of heat waste. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a clay activation process that couples full oxygen combustion and suspended calcination, using the flue gas from full oxygen combustion as combustion gas to avoid heat loss from heating low-temperature air, and also to control the oxygen content in the flue gas, thereby improving the combustion effect of alternative fuels, maintaining a reducing atmosphere, and ensuring that the product does not change color from gray.

[0005] To achieve this technical purpose, the present invention adopts the following scheme:

[0006] The clay activation process of coupling oxyfuel combustion and suspension calcination is based on the combination of oxyfuel combustion clinker production line and suspension calcination clay system, including the following steps:

[0007] S1. The air is processed by the air separation system to obtain a high-purity oxygen gas and nitrogen mixed gas. The nitrogen mixed gas enters the cooling part of the suspension calcined clay system through a pipeline; the high-purity oxygen gas is divided into two parts: pure oxygen I is mixed with the circulating CO2 gas and enters the full oxygen calcining system to change the clinker air calcining atmosphere and increase the CO2 concentration in the flue gas; pure oxygen II is transported to the hot air furnace of the suspension calcined clay system;

[0008] S2. The full oxygen calcining system produces flue gas Ⅰ and flue gas Ⅱ containing high CO2. Flue gas Ⅰ is transported to the hot blast furnace and mixed with pure oxygen Ⅱ. The oxygen ratio in the gas is adjusted. The obtained high-temperature flue gas Ⅲ enters the suspension calcining furnace and exchanges heat with the clay raw material coming down from the preheating part. The flue gas Ⅳ after the heat exchange enters the preheating part upward to exchange heat with the dried clay raw material to obtain flue gas Ⅴ. Flue gas Ⅴ is mixed with flue gas Ⅱ to obtain flue gas Ⅵ. After entering the drying system to complete heat recovery, it goes to the gas treatment system and obtains high-concentration CO2 gas after dust removal, desulfurization, denitrification, and water removal.

[0009] S3. Part of the high-concentration CO2 gas is circulated back to the front end, mixed with pure oxygen I and entered into the full oxygen combustion system. The other part enters the carbon capture system to capture, purify and liquefy CO2 to obtain liquid CO2 for easy storage or utilization. The remaining gas is directly discharged through the chimney;

[0010] S4, the dried clay raw material is put into the preheating part of the suspension calcination clay system from the top, and enters the suspension calcination furnace after heat exchange with the flue gas IV through the multi-stage cyclone, and completes calcination and dehydroxylation after heat exchange to obtain high-temperature calcined clay, and then the high-temperature calcined clay enters the cooling part downward, performs heat exchange with the nitrogen mixed gas, completes oxygen-free cooling, and obtains a gray calcined clay product;

[0011] S5. The nitrogen mixed gas after heat exchange enters the drying system, releases heat to dry the raw materials, and is then discharged into the atmosphere through the chimney.

[0012] After coupling, efficient energy utilization of oxy-fuel combustion and additional utilization of products can be achieved, thus avoiding waste of energy and materials and improving the cost-effectiveness of oxy-fuel combustion. At the same time, compared with single suspended calcined clay, anaerobic environment cooling and reducing atmosphere calcination can be achieved without adding additional means, which can further improve the use of alternative fuels, and the tail flue gas can also return to the oxy-fuel combustion production line and enter the carbon capture system, thus truly realizing the production of zero-carbon calcined clay. While achieving optimal allocation of resources and efficient utilization of energy, it solves the problem of high carbon emissions in traditional cement production, realizes the preparation of zero-carbon cement, significantly reduces carbon emissions in the cement industry, and reduces environmental impact.

[0013] Furthermore, the oxy-fuel combustion clinker production line includes an air separation system, an oxy-fuel burning system, a carbon capture system, a raw material drying system and a gas treatment system. The air separation system is connected to the oxy-fuel burning system, the oxy-fuel burning system is connected to the raw material drying system, the raw material drying system is connected to the gas treatment system, and the gas treatment system is connected to the carbon capture system.

[0014] Furthermore, the air separation system is any one of low-temperature separation, membrane separation, and PSA air separation process equipment.

[0015] Furthermore, the full oxygen firing system has an O2 and CO2 firing atmosphere, mainly a 3-5 level cyclone.

[0016] Furthermore, the suspension calcining clay system includes a hot blast furnace, a suspension calcining furnace, a preheating part and a cooling part. The hot blast furnace is connected between the full oxygen sintering system and the suspension calcining furnace. The feed port of the suspension calcining furnace is connected to the preheating part, and the discharge port of the suspension calcining furnace is connected to the cooling part.

[0017] Furthermore, the preheating part is a 3-stage or 4-stage cyclone; and / or the cooling part is a 3-stage or 4-stage cyclone.

[0018] Furthermore, the air used for combustion in the hot blast furnace comes from pure oxygen gas and flue gas generated by the full oxygen firing system. The hot blast furnace mainly uses alternative fuels to provide heat, and a small amount of fossil fuels is used to start the hot blast furnace in the early stage.

[0019] Furthermore, the wet basis concentration of CO2 in flue gas I and flue gas II is 60~80%.

[0020] Furthermore, the dry basis CO2 concentration of flue gas after the S2 gas treatment system is 75~80%.

[0021] Furthermore, the high temperature calcination temperature of S4 is between 700 and 800°C, and the temperature of the final product after cooling is below 120°C.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] (1) Reuse the nitrogen and other gases generated by the air separation system (ASU) at the front end of the oxyfuel combustion clinker production line as cooling gas for suspended calcined clay, ensuring that the high-temperature calcined clay is quickly cooled in an oxygen-free environment to obtain a gray calcined clay product;

[0024] (2) In the hot blast furnace of the suspension calcined clay system, a mixture of high-temperature flue gas and pure oxygen is used to replace air for combustion, saving fuel loss and improving the combustion effect of low-grade alternative fuels;

[0025] (3) The flue gas from the suspended calcining device is mixed again with the flue gas from the oxy-fuel combustion clinker line and enters the carbon capture device after gas treatment, thus truly realizing the production of zero-carbon emission calcined clay and zero-carbon cement. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The overall flow chart of the clay activation process coupled with full oxygen combustion and suspension calcination provided by the present invention;

[0027] Figure 2 A flow chart of the oxy-fuel combustion clinker production line provided by the present invention;

[0028] Figure 3The production flow chart of suspended calcined clay provided by the present invention;

[0029] Figure 4 A flow chart of flue gas drying raw materials provided by the present invention;

[0030] Figure 5 This is a bar chart of carbon emission values ​​for traditional processes. DETAILED DESCRIPTION

[0031] In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific implementation methods, but the present invention is not limited thereto.

[0032] like Figures 1 to 4 As shown, the present invention provides a clay activation process coupled with full oxygen combustion and suspension calcination, based on the coupling system of the full oxygen combustion clinker production line and the suspension calcination clay system, the full oxygen combustion clinker production line includes an air separation system, a full oxygen firing system, a carbon capture system, a raw material drying system and a gas treatment system, the air separation system is connected to the full oxygen firing system, the full oxygen firing system is connected to the raw material drying system, the raw material drying system is connected to the gas treatment system, and the gas treatment system is connected to the carbon capture system. The air separation system is any one of low temperature separation, membrane separation, and PSA air separation process equipment. The full oxygen firing system is an O2 and CO2 firing atmosphere, mainly a 3-5 stage cyclone.

[0033] The suspension calcined clay system includes a hot blast furnace, a suspension calcining furnace, a preheating part and a cooling part. The hot blast furnace is connected between the full oxygen calcining system and the suspension calcining furnace. The feed port of the suspension calcining furnace is connected to the preheating part, and the discharge port of the suspension calcining furnace is connected to the cooling part. The preheating part is a 3-stage or 4-stage cyclone; and / or the cooling part is a 3-stage or 4-stage cyclone. The hot blast furnace mainly uses alternative fuels to provide heat, and a small amount of fossil fuels is used to start the hot blast furnace in the early stage.

[0034] The steps of clay activation process are as follows:

[0035] S1. Air is processed through the air separation system to obtain a high-purity oxygen gas and nitrogen mixed gas. The nitrogen mixed gas enters the cooling part of the suspension calcined clay system through a pipeline; the high-purity oxygen gas is divided into two parts: pure oxygen I is mixed with the circulating CO2 gas and enters the full oxygen firing system to change the clinker air firing atmosphere and increase the CO2 concentration in the flue gas; pure oxygen II is transported to the hot air furnace of the suspension calcined clay system through a pipeline.

[0036] S2. The full oxygen calcining system produces flue gas Ⅰ and flue gas Ⅱ containing high CO2 (CO2 wet basis concentration 60~80%). Flue gas Ⅰ is transported to the hot blast furnace and mixed with pure oxygen Ⅱ. The oxygen ratio in the gas is adjusted. The obtained high-temperature flue gas Ⅲ enters the suspension calcining furnace and exchanges heat with the clay raw material coming down from the preheating part. The flue gas Ⅳ after the heat exchange enters the preheating part upward to exchange heat with the dried clay raw material to obtain flue gas Ⅴ. Flue gas Ⅴ is mixed with flue gas Ⅱ to form flue gas Ⅵ. After entering the drying system to complete heat recovery, it goes to the gas treatment system. After dust removal, desulfurization, denitrification, and water removal related operations, high-concentration CO2 gas (dry basis CO2 concentration 75~80%) is obtained.

[0037] S3. Part of the high-concentration CO2 gas is circulated back to the front end, mixed with pure oxygen I and entered into the full oxygen combustion system. The other part enters into the carbon capture system to capture, purify and liquefy the CO2 to obtain liquid CO2 for easy storage or utilization. The remaining gas is directly discharged through the chimney.

[0038] S4. The dried clay raw material is put into the preheating part of the suspended calcined clay system from the top, and enters the suspended calcining furnace after heat exchange with the flue gas IV through the multi-stage cyclone. After heat exchange, calcination and dehydroxylation are completed to obtain high-temperature (700℃~800℃) calcined clay. After that, the high-temperature calcined clay enters the cooling part downward, exchanges heat with the nitrogen mixed gas, and completes oxygen-free cooling. The temperature of the final product after cooling is below 120℃, and a gray calcined clay product is obtained.

[0039] S5. The nitrogen mixed gas after heat exchange enters the drying system, releases heat to dry the raw materials, and is then discharged into the atmosphere through the chimney.

[0040] The finished gray calcined clay products and the clinker produced by the full oxygen firing system enter the cement production system. After adding admixtures and gypsum, various grades of zero-carbon cement can be prepared.

[0041] In order to prove the influence of calcination atmosphere on the color change of samples, according to the national standard GB / T 5950-2008 whiteness measurement method for building materials and non-metallic mineral products, whiteness test tests were carried out on the calcined clay products obtained by the present method and the calcined products obtained by the simple suspension calcination process (the parameters such as raw materials, proportion, dosage, calcination temperature of 800°C, time and the like are the same as those of the suspension calcination part in the coupling method provided by the present invention). The results are shown in Table 1. It can be seen that the whiteness of the products obtained by the coupling process is the same as or even better than that of the products obtained by the single suspension calcination.

[0042] Table 1 Whiteness test results

[0043]

[0044] Figure 5It shows that the CO2 emission value of calcined clay produced by traditional process is about one-fourth of that of clinker. The tail flue gas of calcined clay produced by this process passes through carbon capture facilities to achieve zero-carbon emission product production, achieving significant emission reduction effects.

[0045] Finally, it should be noted that the above are only preferred embodiments of the present invention. Of course, those skilled in the art can make changes and modifications to the present invention. If these modifications and variations fall within the scope of the claims of the present invention and their equivalent technologies, they should be considered to be within the scope of protection of the present invention.

Claims

1. A clay activation process coupled with full oxygen combustion and suspension calcination, characterized in that: Based on the combination of oxyfuel combustion clinker production line and suspension calcined clay system, it includes the following steps: S1. The air is processed by the air separation system to obtain a high-purity oxygen gas and nitrogen mixed gas. The nitrogen mixed gas enters the cooling part of the suspension calcined clay system through a pipeline; the high-purity oxygen gas is divided into two parts: pure oxygen I is mixed with the circulating CO2 gas and enters the full oxygen calcining system to change the clinker air calcining atmosphere and increase the CO2 concentration in the flue gas; pure oxygen II is transported to the hot air furnace of the suspension calcined clay system; S2. The full oxygen calcining system produces flue gas Ⅰ and flue gas Ⅱ containing high CO2. Flue gas Ⅰ is transported to the hot blast furnace and mixed with pure oxygen Ⅱ. The oxygen ratio in the gas is adjusted. The obtained high-temperature flue gas Ⅲ enters the suspension calcining furnace and exchanges heat with the clay raw material coming down from the preheating part. The flue gas Ⅳ after the heat exchange enters the preheating part upward to exchange heat with the dried clay raw material to obtain flue gas Ⅴ. Flue gas Ⅴ is mixed with flue gas Ⅱ to obtain flue gas Ⅵ. After entering the drying system to complete heat recovery, it goes to the gas treatment system and obtains high-concentration CO2 gas after dust removal, desulfurization, denitrification, and water removal. S3. Part of the high-concentration CO2 gas is circulated back to the front end, mixed with pure oxygen I and entered into the full oxygen combustion system. The other part enters the carbon capture system to capture, purify and liquefy CO2 to obtain liquid CO2 for easy storage or utilization. The remaining gas is directly discharged through the chimney; S4, the dried clay raw material is put into the preheating part of the suspension calcination clay system from the top, and enters the suspension calcination furnace after heat exchange with the flue gas IV through the multi-stage cyclone, and completes calcination and dehydroxylation after heat exchange to obtain high-temperature calcined clay, and then the high-temperature calcined clay enters the cooling part downward, performs heat exchange with the nitrogen mixed gas, completes oxygen-free cooling, and obtains a gray calcined clay product; S5. The nitrogen mixed gas after heat exchange enters the drying system, releases heat to dry the raw materials, and is then discharged into the atmosphere through the chimney.

2. The clay activation process of coupling oxyfuel combustion and suspension calcination according to claim 1, characterized in that: The oxy-fuel combustion clinker production line includes an air separation system, an oxy-fuel burning system, a carbon capture system, a raw material drying system and a gas treatment system. The air separation system is connected to the oxy-fuel burning system, which is connected to the raw material drying system. The raw material drying system is connected to the gas treatment system, which is connected to the carbon capture system.

3. The clay activation process of coupling full oxygen combustion and suspension calcination according to claim 2, characterized in that: The air separation system is any one of low temperature separation, membrane separation and PSA air separation process equipment.

4. The clay activation process of coupling oxyfuel combustion and suspension calcination according to claim 2, characterized in that: The full oxygen firing system uses O2 and CO2 firing atmospheres, mainly 3~5 level cyclones.

5. The clay activation process of coupling oxyfuel combustion and suspension calcination according to claim 1, characterized in that: The suspension calcined clay system includes a hot blast furnace, a suspension calcining furnace, a preheating part and a cooling part. The hot blast furnace is connected between the full oxygen sintering system and the suspension calcining furnace. The feed port of the suspension calcining furnace is connected to the preheating part, and the discharge port of the suspension calcining furnace is connected to the cooling part.

6. The clay activation process of coupling oxyfuel combustion and suspension calcination according to claim 1, characterized in that: The preheating part is a 3-stage or 4-stage cyclone; and / or the cooling part is a 3-stage or 4-stage cyclone.

7. The clay activation process of coupling oxyfuel combustion and suspension calcination according to claim 1, characterized in that: The air used for hot blast furnace combustion comes from pure oxygen gas and flue gas produced by the full oxygen combustion system. The hot blast furnace mainly uses alternative fuels to provide heat, and a small amount of fossil fuels is used to start the hot blast furnace in the early stage.

8. The clay activation process of coupling oxyfuel combustion and suspension calcination according to claim 1, characterized in that: The wet basis concentration of CO2 in flue gas I and flue gas II is 60~80%.

9. The clay activation process of coupling oxyfuel combustion and suspension calcination according to claim 1, characterized in that: The dry basis CO2 concentration of flue gas after the S2 gas treatment system is 75~80%.

10. The clay activation process of coupling oxyfuel combustion and suspension calcination according to claim 1, characterized in that: The high temperature calcination temperature of S4 is between 700 and 800°C, and the temperature of the final product after cooling is below 120°C.

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