METHOD OF CALCINING A RAW MATERIAL TO OBTAIN A CEMENTITIOUS MATERIAL

Abstract

A method of calcining a raw material to obtain a cementitious material, includes providing a flow of raw material containing a metal carbonate, such as CaCO.sub.3 to a calcination system, introducing the flow of raw material into a first thermal reactor and at least partially decarbonating the raw material in the first thermal reactor by subjecting the raw material to a first heat treatment at a first temperature of at least 650 C. in order to obtain an at least partly decarbonated material and CO.sub.2, wherein the first thermal reactor is heated by electrical energy, and obtaining the cementitious material as a result of the first heat treatment.

Claims

1. A method of calcining a raw material to obtain a cementitious material, comprising: providing a flow of raw material containing a metal carbonate to a calcination system, introducing the flow of raw material into a first thermal reactor and at least partially decarbonating the raw material in the first thermal reactor by subjecting the raw material to a first heat treatment at a first temperature of at least 650 C. in order to obtain an at least partly decarbonated material and CO.sub.2, wherein the first thermal reactor is heated by electrical energy, optionally introducing the at least partly decarbonated material into a second thermal reactor and subjecting the at least partly decarbonated material to a second heat treatment at a second temperature lying above the first temperature, and obtaining the cementitious material as a result of the first and optionally the second heat treatment.

2. The method according to claim 1, wherein the flow of raw material is preheated before being introduced into the first thermal reactor, wherein preheating is carried out by bringing a heat exchanging fluid into a heat exchanging relationship with the raw material, while the heat exchanging fluid is cooled.

3. The method according to claim 2, wherein an exhaust gas is withdrawn from the first thermal reactor, and said exhaust gas is used as said heat exchanging fluid to preheat the raw material.

4. The method according to claim 3, wherein preheating the raw material comprises introducing the exhaust gas into a heat exchanger and preheating the raw material in said heat exchanger.

5. The method according to claim 2, wherein an exhaust gas is withdrawn from the first thermal reactor, and the heat exchanging fluid is heated by bringing the exhaust gas into a heat exchanging relationship with the heat exchanging fluid, while the exhaust gas is cooled.

6. The method according to claim 2, wherein the cementitious material is introduced into a cooling device, in which the cooled heat exchanging fluid is used to cool the cementitious material, while the cooled heat exchanging fluid is re-heated.

7. The method according to claim 6, wherein the re-heated heat exchanging fluid that is withdrawn from the cooling device is used to provide thermal energy to the first or second heat treatment.

8. The method according to claim 7, wherein the re-heated heat exchanging fluid that is withdrawn from the cooling device is heated before being used for providing thermal energy to the first or second thermal reactor.

9. The method according to claim 7, wherein the re-heated heat exchanging fluid that is withdrawn from the cooling device is introduced into the second thermal reactor to provide thermal energy to the second heat treatment and wherein the heat exchanging fluid is withdrawn from the second thermal reactor and introduced into the first thermal reactor to provide thermal energy to the first heat treatment.

10. The method according to claim 9, wherein the heat exchanging fluid that is withdrawn from the second thermal reactor is heated before being introduced into the first thermal reactor.

11. The method according to claim 8, wherein the heating of the heat exchanging fluid is performed by means of a heating device that transforms electrical energy into thermal energy.

12. The method according to claim 1, wherein the second thermal reactor is heated by electrical energy and/or by combusting a renewable fuel and/or by combusting hydrogen.

13. The method according to claim 1, wherein the raw material consists of or comprises clay and/or a recycled concrete material and/or a recycled plasterboard material.

14. The method according to claim 1, wherein the metal carbonate is CaCO.sub.3.

15. The method according to claim 3, wherein said exhaust gas contains at least 80 vol. % CO.sub.2.

16. The method according to claim 5, wherein said exhaust gas contains at least 80 vol. % CO.sub.2.

17. The method according to claim 7, wherein the re-heated heat exchanging fluid that is withdrawn from the cooling device is used to provide thermal energy to the first or second heat treatment by introducing the re-heated heat exchanging fluid into the first or second thermal reactor.

18. The method according to claim 5, wherein the cementitious material is introduced into a cooling device, in which the cooled exhaust gas is used to cool the cementitious material, while the cooled exhaust gas is re-heated.

19. The method according to claim 18, wherein the re-heated exhaust gas that is withdrawn from the cooling device is used to provide thermal energy to the first or second heat treatment.

20. The method according to claim 19, wherein the re-heated exhaust gas that is withdrawn from the cooling device is used to provide thermal energy to the first or second heat treatment by introducing the re-heated exhaust gas into the first or second thermal reactor.

21. The method according to claim 19, wherein the re-heated exhaust gas that is withdrawn from the cooling device is heated before being used for providing thermal energy to the first or second thermal reactor.

22. The method according to claim 19, wherein the re-heated exhaust gas that is withdrawn from the cooling device is introduced into the second thermal reactor to provide thermal energy to the second heat treatment and wherein the exhaust gas is withdrawn from the second thermal reactor and introduced into the first thermal reactor to provide thermal energy to the first heat treatment.

23. The method according to claim 22, wherein the exhaust gas that is withdrawn from the second thermal reactor is heated before being introduced into the first thermal reactor.

24. The method according to claim 21, wherein the heating of the exhaust gas is performed by means of a heating device that transforms electrical energy into thermal energy.

Description

[0055] The invention will now be described in more detail with reference to the attached drawings.

[0056] FIG. 1 is a schematic illustration of a first embodiment of a calcination system and

[0057] FIG. 2 is a schematic illustration of a second embodiment of a calcination system.

[0058] In FIG. 1 a first thermal reactor 1 is shown that is heated by electrical energy 2. The first thermal reactor is fed by raw material 3 that is first preheated in a preheater 4. Raw material is subjected to heat treatment in said first thermal reactor 1 to obtain a cementitious material that is extracted from the first thermal reactor 1 and conveyed to a cooling device 5 via line 6. The final cementitious product is obtained at 7.

[0059] As a result of the decarbonation of the raw material within the first thermal reactor 1, CO.sub.2 is produced so that a CO.sub.2 rich exhaust gas is withdrawn from the first thermal reactor 1 via line 8 and used in the preheater 4 to preheat the raw material 3. The CO.sub.2 rich exhaust gas may contain >80 vol.-% CO.sub.2, preferably >90 vol.-% CO.sub.2. The exhaust gas that has been cooled in the preheater 4 can be deployed at 9 and/or recirculated via recirculation line 10. The recirculated exhaust gas is used in the cooling device 5 as a cooling fluid for cooling the cementitious material that comes from the first thermal reactor 1. By being in heat exchanging relationship with the cementitious material, the exhaust gas is re-heated wherein said heat can be recovered by introducing the re-heated exhaust gas into the first thermal reactor via line 11. Additional heat can be introduced by heating the exhaust gas by means of electrical energy 12.

[0060] In the alternative embodiment of FIG. 2 same reference numerals are used for the same components as in FIG. 1. In FIG. 2 a second thermal reactor 13 is provided that is used to provide a second heat treatment to the raw material that has already been subjected to the first heat treatment in the first thermal reactor 1. The cementitious material that is discharged from the second thermal reactor 13 is fed to the cooling device via line 14. The second thermal reactor 13 is heated by electric energy 15. Further, the recirculated exhaust gas that is re-heated in the cooling device 5 is first introduced into the second thermal reactor 13 via line 11 and then introduced into the first thermal reactor 1. Before being introduced into the first thermal reactor 1, the exhaust gas may be subjected to an optional heating step 16.