METHOD OF PRODUCING CLINKER FROM CEMENT RAW MEAL

Abstract

A method of producing clinker from cement raw meal, includes preheating cement raw meal in a preheater string, the preheater string including a plurality of preheater stages, pre-calcining preheated raw meal in a pre-calciner to obtain a pre-calcined product, introducing the pre-calcined product into a rotary kiln for calcining the pre-calcined product to obtain cement clinker, wherein a partial flow of at least partly preheated raw meal is diverted from the preheater string, introduced into a calcination device and at least partially decarbonated in the calcination device in order to obtain an at least partially decarbonated product and CO.sub.2, wherein the calcination device is heated by electrical energy, and wherein the at least partially decarbonated product is fed into the rotary kiln and the CO.sub.2 is drawn off from the calcination device.

Claims

1. A method of producing clinker from cement raw meal, comprising: preheating cement raw meal in a preheater string, said preheater string comprising a plurality of preheater stages, pre-calcining preheated raw meal in a pre-calciner to obtain a pre-calcined product, introducing the pre-calcined product into a rotary kiln for calcining the pre-calcined product to obtain cement clinker, wherein a partial flow of at least partly preheated raw meal is diverted from the preheater string, introduced into a calcination device and at least partially decarbonated in the calcination device in order to obtain an at least partially decarbonated product and CO.sub.2, wherein the calcination device is heated by electrical energy, and wherein the at least partially decarbonated product is fed into the rotary kiln and the CO.sub.2 is drawn off from the calcination device.

2. The method according to claim 1, wherein the at least partly preheated raw meal is extracted from the preheater string at a temperature of 650-750 C.

3. The method according to claim 1, wherein the at least partly preheated raw meal is heated to a temperature of 750-950 C. in the calcination device.

4. The method according to claim 1, wherein decarbonating the at least partly preheated raw meal comprises converting limestone into CaO and CO.sub.2.

5. The method according to claim 1, wherein the least partly preheated raw meal is transported through the calcination device by means of a screw conveyor while being at least partially decarbonated.

6. The method according to claim 1, wherein the calcination device is configured as a screw conveyor.

7. The method according to claim 6, wherein a conveyor screw of the screw conveyor is configured as a heating element that is heated by electrical energy, such as by resistance heating.

8. The method according to claim 1, wherein the CO.sub.2 drawn off from the calcination device is fed through a heat exchanger, in which a fluid or gaseous medium is heated by heat exchange with the CO.sub.2.

9. The method according to claim 8, wherein heat obtained by heat exchange with the CO.sub.2 is used in a thermodynamic cycle to evaporate a working fluid of said thermodynamic cycle.

10. The method according to claim 9, wherein the thermodynamic cycle is designed as a gas turbine process or as an Organic Rankine Cycle.

11. The method according to claim 10, wherein a gas turbine of the gas turbine process or of the Organic Rankine Cycle is used to generate electrical energy by means of an electrical generator and wherein the electrical energy is optionally fed to the calcination device for electrically heating the same.

12. The method according to claim 1 any one of claim 1, wherein the CO.sub.2 drawn off from the calcination device is fed to a reactor, in which CO.sub.2 and further reactants are transformed into a synthetic fuel.

13. A device for carrying out a method according to claim 1, comprising: a preheater string for preheating cement raw meal, said preheater string comprising a plurality of preheater stages, a pre-calciner for pre-calcining preheated raw meal to obtain a pre-calcined product, a rotary kiln for calcining the pre-calcined product to obtain cement clinker, a calcination device having electrical heating means, said calcination device comprising an inlet that is connected to the preheater string to divert a partial flow of at least partly preheated raw meal from the preheater string and introduce the same into the calcination device in order to obtain an at least partially decarbonated product and CO.sub.2, said calcination device comprising an outlet that is connected to the rotary kiln for feeding the at least partially decarbonated product into the rotary kiln, and said calcination device comprising a CO.sub.2 discharge opening for drawing off the CO.sub.2 from the calcination device.

14. The device according to claim 13, wherein the calcination device comprises at least one contact heating element that is arranged to be in heat exchanging contact with the at least partly preheated raw meal while the same is being conveyed from the inlet to the outlet, wherein said at least one contact heating element is configured to be heated by the electrical heating means.

15. The device according to claim 13, wherein the calcination device comprises a screw conveyor for conveying the at least partly preheated raw meal from the inlet to the outlet.

16. The device according to claim 15, wherein a conveyor screw of the screw conveyor is configured as the at least one contact heating element.

17. The device according to claim 13, wherein the electrical heating means is configured as a resistance heating.

18. The device according to claim 13, wherein the CO.sub.2 discharge opening is connected to a heat exchanger, in which a fluid or gaseous medium is heated by heat exchange with the CO.sub.2.

19. The device according to claim 13, wherein a thermodynamic cycle is provided, which comprises an evaporator and which is arranged so that heat obtained by heat exchange with the CO.sub.2 is used in the thermodynamic cycle to evaporate a working fluid of said thermodynamic cycle in said evaporator.

20. The device according to claim 19, wherein the thermodynamic cycle is designed as a gas turbine process or as an Organic Rankine Cycle.

21. The device according to claim 20, wherein a gas turbine of the gas turbine process or of the Organic Rankine Cycle is connected to an electrical generator and wherein the electrical energy generated by said electrical generator is optionally fed to the calcination device for electrically heating the same.

22. The method according to claim 2, wherein the at least partly preheated raw meal is extracted from the preheater string at a temperature of 680-720 C.

23. The method according to claim 3, wherein the at least partly preheated raw meal is heated to a temperature of 800-950 C.

24. The method according to claim 23, wherein the at least partly preheated raw meal is heated to a temperature of 850-900 C.

Description

[0052] The invention will now be described in more detail with reference to the attached drawing.

[0053] FIG. 1 schematically illustrates a cement production process, into which the inventive method has been incorporated. In the cement clinker production plant ground raw meal is charged into a preheater string 1, where it is preheated in counter-current to the hot exhaust gases coming from a rotary clinker kiln 2. The preheater string 1 comprises a plurality of interconnected cyclone suspension-type preheater stages 3, 4, 5 and 6. Further, a pre-calciner 7 is provided that is heated by burning a fuel.

[0054] The preheated and pre-calcined raw meal is then introduced into the rotary kiln 2, where it is calcined to obtain cement clinker. The clinker leaves the rotary kiln 2 and is cooled in a clinker cooler (not shown).

[0055] At least partially preheated raw meal is taken from the preheater string 1 directly downstream of the second lowest preheater 5 at a temperature of approximately 700 C. and fed into a divider 8, where the raw meal is divided into a first partial flow and a second partial flow. The first partial flow is fed into the pre-calciner 7 and the second partial flow is introduced into the electrically heated calcination device 9, where the raw meal is heated to approximately 900 C. and at least partially decarbonated while producing CO.sub.2. The at least partially decarbonated product that leaves the calcination device 9 is fed into the kiln 2 via lines 10 and 11. The CO.sub.2 is withdrawn from the calcination device 9 and fed into a heat recovery device 12 via line 13.

[0056] In the heat recovery device 12, CO.sub.2 is cooled, wherein the heat draw from the CO.sub.2 is used to produce electrical energy, such as by means of a thermodynamic cycle. The electrical energy is fed to the heating means of the electrical calcination device 9 via electrical lines 14 and 15. The electrical energy may also be used in other devices.

[0057] Further, the cooled CO.sub.2 exiting the heat recovery device 12 may be introduced into a storage 16 for further processing.