Oxygen-fuel combustion-suspension calcination coupled activation process for clay

Abstract

Disclosed in the present invention is an oxygen-fuel combustion-suspension calcination coupled activation process for clay. The process comprises: using flue gas obtained by oxygen-fuel combustion as a combustion gas, conveying same to a hot blast furnace, allowing the obtained high-temperature flue gas to enter a suspension calcination furnace for heat exchange with a clay raw material coming from a preheating section, then subjecting the flue gas that has been subjected to heat exchange to heat transfer with a dried clay raw material, and then allowing same to enter a raw material drying system for heat recovery and then enter a gas treatment system, so as to obtain a high-concentration CO2 gas; and recycling part of the high-concentration CO2 gas back to the front end to be mixed with pure oxygen, feeding the resulting mixture into an oxygen-fuel firing system, and allowing the other part to enter a carbon capture system. Compared with the single suspension calcination of clay, flue gas at the tail end can be returned to an oxygen-fuel combustion production line and enter the carbon capture system, thereby truly achieving the production of zero-carbon calcined clay.

Description

Clay activation process coupled with full-oxygen combustion and suspension calcination TECHNICAL FIELD

[0001] The present disclosure 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

[0002] The existing full-oxygen combustion clinker line produces high-purity oxygen gas (oxygen concentration higher than 99.5%) in the production process through an air separation device. However, nitrogen, argon and other remaining gas components cannot be effectively utilized in the cement production process because they have no suitable use in the cement plant, resulting in waste of resources and energy.

[0003] Calcined clay is a low-carbon cementitious material, which can achieve low carbon dioxide emissions in the activation process. Moreover, its raw material availability, high cementitious 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, because the high-iron-content clay will turn into red-brown in the traditional calcination process, which will affect the color of the cement and make it unacceptable in the 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 the product color to be gray. Meanwhile, when using traditional air calcination directly, the combustion effect of the substitute fuel is generally poor, which cannot fully utilize the low-grade substitute fuel heat value, and the air needs to be heated from room temperature, and the heat cannot be completely recovered at the back end, resulting in a certain waste of heat. SUMMARY

[0004] To solve the above technical problems, the present disclosure provides a clay activation process coupled with full-oxygen combustion and suspension calcination, which uses the flue gas of full-oxygen combustion as the combustion gas, avoids the heat loss of heating low-temperature air, controls the oxygen content in the flue gas, improves the combustion effect of the substitute fuel, maintains the reducing atmosphere, and ensures the product color to be gray.

[0005] To achieve the technical purpose, the present disclosure adopts the following solutions:

[0006] The clay activation process coupled with full-oxygen combustion and suspension calcination is based on the combination of the full-oxygen combustion clinker production line and the suspension calcination clay system, and includes the following steps:

[0007] S1, air is treated by an air separation system to obtain high-purity oxygen gas and nitrogen mixed gas, the nitrogen mixed gas enters the cooling part of the suspension calcination clay system through a pipeline, and the high-purity oxygen gas is divided into two parts: pure oxygen I mixed with circulating CO2 gas, which enters the full-oxygen firing system to change the air firing atmosphere of the clinker and increase the CO2 concentration in the flue gas; and pure oxygen II delivered to the hot blast stove of the suspension calcination clay system;

[0008] S2, the full oxygen firing system generates flue gas I containing high CO2 and flue gas II, flue gas I is transported into the hot blast furnace, mixed with pure oxygen II, the oxygen proportion in the gas is adjusted, the high temperature flue gas III obtained is introduced into the suspension calcining furnace, and the clay raw material falling from the preheating part is subjected to heat exchange, the flue gas IV after heat exchange is introduced into the preheating part to exchange heat with the dried clay raw material, the flue gas V is obtained, the flue gas V is mixed with the flue gas II to obtain the flue gas VI, after heat recovery in the drying system, it goes to the gas treatment system, after dust removal, desulfurization and denitrification, and water removal, high concentration CO2 gas is obtained;

[0009] S3, part of the high concentration CO2 gas is recycled to the front end and mixed with pure oxygen I to enter the full oxygen firing system, another part enters the carbon capture system to capture, purify and liquefy CO2 to obtain liquid CO2 for storage or use, and the remaining gas is directly discharged through the chimney;

[0010] S4, the dried clay raw material is introduced from the upper part into the preheating part of the suspension calcining clay system, and after heat exchange with the flue gas IV through multiple cyclone cylinders, it is introduced into the suspension calcining furnace, and after heat exchange, calcination and dehydroxylation are completed, high temperature calcined clay is obtained, and then the high temperature calcined clay is introduced downward into the cooling part to exchange heat with the nitrogen mixed gas to complete the oxygen-free cooling, and the gray calcined clay product is obtained;

[0011] S5, the heat exchanged nitrogen mixed gas enters the drying system to release heat for drying the raw material, and then is discharged into the atmosphere through the chimney.

[0012] After coupling, the energy consumption of full oxygen combustion can be efficiently utilized and the product can be additionally utilized, avoiding waste of energy and materials and improving the cost performance of full oxygen combustion; compared with single suspension calcining clay, oxygen-free environment cooling and reducing atmosphere calcination can be realized without additional means, and the use of alternative fuel can be further improved, and the tail end flue gas can also return to the full oxygen combustion production line and enter the carbon capture system, realizing zero carbon calcined clay production; realizing the optimal allocation of resources and efficient use of energy, solving the high carbon emission problem of traditional cement production, realizing zero carbon cement preparation, significantly reducing carbon emissions in the cement industry and reducing environmental impact.

[0013] Further, the full oxygen combustion clinker production line comprises 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 with the full oxygen firing system, the full oxygen firing system is connected with the raw material drying system, the raw material drying system is connected with the gas treatment system, and the gas treatment system is connected with the carbon capture system.

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

[0015] Further, the full-oxygen firing system is an O2 and CO2 firing atmosphere, mainly a 3-5 stage cyclone.

[0016] Further, the suspension calcination clay system comprises a hot blast furnace, a suspension calcination furnace, a preheating part and a cooling part, the hot blast furnace is connected between the full-oxygen firing system and the suspension calcination furnace, the feeding port of the suspension calcination furnace is communicated with the preheating part, and the discharging port of the suspension calcination furnace is communicated with the cooling part.

[0017] Further, 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] Further, the hot blast furnace burns air 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 fuel is used to start the hot blast furnace in advance.

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

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

[0021] Further, the S4 high-temperature calcination temperature is 700-800℃, and the temperature of the final product after cooling is below 120℃.

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

[0023] (1) The nitrogen gas generated by the air separation system (ASU) at the front end of the full-oxygen combustion clinker production line is reused as a cooling gas for the suspension calcination clay, ensuring that the high-temperature calcined clay is rapidly cooled in an oxygen-free environment, and obtaining a gray calcined clay product;

[0024] (2) The high-temperature flue gas and pure oxygen mixed gas are used to replace air for combustion in the hot blast furnace of the suspension calcination clay system, saving fuel consumption, and improving the combustion effect of low-grade alternative fuels;

[0025] (3) The flue gas of the suspension calcination device is mixed with the flue gas of the full-oxygen combustion clinker line again, and after gas treatment, it enters the carbon capture device, truly realizing the production of zero-carbon emission calcined clay and zero-carbon cement. BRIEF DESCRIPTION OF DRAWINGS

[0026] Fig. 1 is a whole process flow diagram of the clay activation process coupled with full-oxygen combustion and suspension calcination provided by the present disclosure;

[0027] Fig. 2 is a flow diagram of the full-oxygen combustion clinker production line provided by the present disclosure;

[0028] Figure 3 is a flow chart of the suspension calcination clay production provided by the present disclosure;

[0029] Figure 4 is a flow chart of the flue gas drying raw material provided by the present disclosure;

[0030] Figure 5 is a column chart of carbon emission values of a traditional process. DETAILED DESCRIPTION

[0031] For the purpose of fully understanding the present disclosure, its features and effects, the present disclosure is described in detail below, but the present disclosure is not limited to this.

[0032] As shown in Figures 1 to 4, the present disclosure provides a clay activation process coupled with full-oxygen combustion and suspension calcination, which is based on a coupling system of a full-oxygen combustion clinker production line and a 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. The gas treatment system is connected to the carbon capture system. The air separation system is any one of a low-temperature separation, a membrane separation, and a 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 calcination clay system includes a hot blast stove, a suspension calcination furnace, a preheating part, and a cooling part. The hot blast stove is connected between the full-oxygen firing system and the suspension calcination furnace. The feed inlet of the suspension calcination furnace is communicated with the preheating part. The discharge outlet of the suspension calcination furnace is communicated with 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 stove mainly uses alternative fuel to provide heat, and a small part of fossil fuel is used to start the hot blast stove in the early stage.

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

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

[0036] S2, the full-oxygen firing system generates flue gas I containing high CO2 (CO2 concentration of 60-80% on a wet basis) and flue gas II, flue gas I is transported into the hot blast furnace, mixed with pure oxygen II, the oxygen proportion in the gas is adjusted, high-temperature flue gas III is obtained, enters the suspension calcining furnace, and exchanges heat with the preheated clay raw material, the heat-exchanged flue gas IV enters the preheating part upward and exchanges heat with the dried clay raw material, flue gas V is obtained, flue gas V is mixed with flue gas II to obtain flue gas VI, after heat recovery in the drying system, flue gas VI is transported to the gas treatment system, after dust removal, desulfurization and denitrification, and water removal, high-concentration CO2 gas (CO2 concentration of 75-80% on a dry basis) is obtained.

[0037] S3, part of the high-concentration CO2 gas is recycled to the front end and mixed with pure oxygen I to enter the full-oxygen firing system, another part enters the carbon capture system, CO2 is captured, purified and liquefied to obtain liquid CO2 for storage or use, and the remaining gas is directly discharged through a chimney.

[0038] S4, the dried clay raw material is fed from the upper part into the preheating part of the suspension calcining clay system, exchanges heat with flue gas IV through multiple cyclones, and then enters the suspension calcining furnace, and after heat exchange, the calcination and dehydroxylation are completed, high-temperature (700-800°C) calcined clay is obtained, then the high-temperature calcined clay enters the cooling part downward and exchanges heat with the nitrogen mixed gas to complete the oxygen-free cooling, the final product is cooled to a temperature below 120°C, and the gray calcined clay finished product is obtained.

[0039] S5, the heat-exchanged nitrogen mixed gas enters the drying system to release heat for drying the raw material, and then is discharged into the atmosphere through a chimney.

[0040] The gray calcined clay product and the clinker produced by the full-oxygen firing system enter the cement production system, and after adding mixed materials and gypsum, various labels of zero-carbon cement can be prepared.

[0041] In order to prove the influence of calcination atmosphere on the color change of the sample, according to the national standard GB / T 5950-2008, the whiteness of the calcined clay product obtained by the method and the calcined product obtained by the simple suspension calcining process (the raw material, ratio, amount, calcination temperature 800°C, time and other parameters are the same as those in the suspension calcining part of the coupled method provided by the present disclosure) were tested, and the results are shown in Table 1. It can be seen that the whiteness of the product obtained by the coupled process is the same as or even better than that of the product obtained by the simple suspension calcining process.

[0042] Table 1: Whiteness test results

[0043]

[0044] Figure 5 shows that the CO2 emission value of calcined clay produced by the traditional process is about one fourth of that of clinker, and the tail-end flue gas of calcined clay produced by the present process is treated by a carbon capture facility to achieve zero-carbon emission product production, achieving a significant emission reduction effect.

[0045] Finally, it should be noted that the above are only preferred embodiments of the present disclosure, and of course those skilled in the art can modify and change the present disclosure, provided that these modifications and changes are within the scope of the claims of the present disclosure and their equivalent technologies, and should be considered as the protection scope of the present disclosure.

Claims

1. A clay activation process coupling a full oxy-combustion and a suspension calcination, characterized in that, Based on the combination of full-oxygen combustion clinker production line and suspension calcination clay system, comprising the following steps: S1, air is treated by air separation system to obtain high-purity oxygen gas and nitrogen mixed gas, the nitrogen mixed gas enters the cooling part of the suspension calcination clay system through the pipeline; the high-purity oxygen gas is divided into two parts: pure oxygen I is mixed with circulating CO2 gas and enters the full-oxygen firing system to change the air firing atmosphere of clinker and improve the CO2 concentration in the flue gas; pure oxygen II is transported to the hot blast furnace of the suspension calcination clay system; S2, the full-oxygen firing system generates flue gas I containing high CO2 and flue gas II, flue gas I is transported into the hot blast furnace and mixed with pure oxygen II to adjust the oxygen proportion in the gas, the obtained high-temperature flue gas III enters the suspension calcination furnace and exchanges heat with the clay raw materials falling from the preheating part, the flue gas IV after heat exchange enters the preheating part and exchanges heat with the dried clay raw materials, the flue gas V is obtained, the flue gas V and the flue gas II are mixed to obtain the flue gas VI, which enters the drying system to complete heat recovery, then goes to the gas treatment system, after dust removal, desulfurization and denitrification, water removal and related operations, high-concentration CO2 gas is obtained; S3, part of the high-concentration CO2 gas is recycled to the front end and mixed with pure oxygen I to enter the full-oxygen firing system, another part enters the carbon capture system to capture, purify and liquefy CO2 to obtain liquid CO2 for easy storage or utilization, and the remaining gas is directly discharged through the chimney; S4, the dried clay raw materials are fed from the upper part into the preheating part of the suspension calcination clay system, and after heat exchange with flue gas IV through multiple cyclones, they enter the suspension calcination furnace, complete calcination and dehydroxylation after heat exchange, and obtain high-temperature calcined clay, then the high-temperature calcined clay enters the cooling part downward and exchanges heat with the nitrogen mixed gas to complete oxygen-free cooling and obtain gray calcined clay products; S5, the nitrogen mixed gas after heat exchange enters the drying system to release heat for drying raw materials, and then is discharged into the atmosphere through the chimney.

2. The coupled oxy-combustion and suspension calcination clay activation process of claim 1, wherein, 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 with the full-oxygen firing system, the full-oxygen firing system is connected with the raw material drying system, the raw material drying system is connected with the gas treatment system, and the gas treatment system is connected with the carbon capture system.

3. The coupled oxy-combustion and suspension calcination clay activation process of claim 2, wherein, The air separation system is any one of low-temperature separation, membrane separation and PSA air separation process equipment.

4. The coupled oxy-combustion and clay activation process of claim 2, wherein, The full-oxygen firing system is an O2 and CO2 firing atmosphere, mainly 3-5 stage cyclones.

5. The coupled oxy-combustion and suspension calcination clay activation process according to claim 1, wherein, The suspension calcination clay system includes a hot blast furnace, a suspension calcination furnace, a preheating part and a cooling part, the hot blast furnace is connected between the full-oxygen firing system and the suspension calcination furnace, the feeding port of the suspension calcination furnace is communicated with the preheating part, and the discharging port of the suspension calcination furnace is communicated with the cooling part.

6. The coupled oxy-combustion and suspension calcination clay activation process according to claim 1, wherein, The preheating part is 3 or 4 stage cyclones; and / or the cooling part is 3 or 4 stage cyclones.

7. The coupled oxy-combustion and suspension calcination clay activation process according to claim 1, wherein, The hot blast furnace uses air from pure oxygen gas and flue gas generated by the full-oxygen firing system for combustion, mainly uses alternative fuel to provide heat, and a small part of fossil fuel is used to start the hot blast furnace in the early stage.

8. The coupled oxy-combustion and suspension calcination clay activation process according to claim 1, wherein, The CO2 wet basis concentration in flue gas I and flue gas II is 60-80%.

9. The coupled oxy-combustion and suspension calcination clay activation process according to claim 1, wherein, The S2 gas treatment system rear flue gas dry basis CO2 concentration is 75 ~ 80%.

10. The coupled oxy-combustion and suspension calcination clay activation process according to claim 1, wherein, The S4 high-temperature calcination temperature is 700 ~ 800 DEG C, and the final product cooling temperature is below 120 DEG C.

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