METHOD AND DEVICE FOR THE PRODUCTION OF CEMENT CLINKER

Abstract

A process for producing cement clinker may involve preheating raw meal in a preheater, calcining the preheated raw meal in a calciner, burning the preheated and calcined raw meal in a furnace to give cement clinker, cooling the cement clinker in a cooler, branching off a portion of the furnace offgases flowing out of the furnace as bypass gas, cooling the bypass gas in a mixing chamber with a cooling gas, and separating out dust present in the bypass gas. The cooling gas is formed at least partly or completely from the bypass gas and/or the calciner offgas and/or the preheater offgas. The cooling gas is introduced into the mixing chamber in a ratio of 2-10:1 relative to the bypass gas.

Claims

1.-12. (canceled)

13. A process for producing cement clinker, the process comprising: preheating raw meal in a preheater; calcining in a calciner the raw meal that has been preheated; burning in a furnace the raw meal that has been preheated and calcined to give cement clinker; cooling the cement clinker in a cooler; branching off a portion of furnace offgases flowing out of the furnace as bypass gas; and cooling the bypass gas in a mixing chamber with a cooling gas and separating out dust present in the bypass gas, wherein the cooling gas is formed at least partly or completely from at least one of the bypass gas, a calciner offgas, or a preheater offgas, wherein the cooling gas is introduced into the mixing chamber in a ratio of 2-10:1 relative to the bypass gas.

14. The process of claim 13 wherein the cooling gas is formed partly or completely from a portion of the bypass gas that has been dedusted and cooled, wherein a portion of the bypass gas that is not fed to the mixing chamber is fed to at least one of the calciner, the furnace, or the cooler.

15. The process of claim 13 wherein the bypass gas is branched off between the furnace and the calciner.

16. The process of claim 13 wherein the bypass gas is branched off downstream of the calciner.

17. The process of claim 13 wherein the cooling gas is cooled in a second cooler prior to entry into the mixing chamber.

18. The process of claim 17 wherein the second cooler that is upstream of the mixing chamber is an evaporative cooler or a gas-gas heat exchanger.

19. The process of claim 13 wherein at least a portion of the bypass gas that is cooled and dedusted is fed to at least one of the calciner, the furnace, or the cooler.

20. The process of claim 13 comprising supplying the furnace and the calciner with a combustion gas that has an oxygen content of more than 20.5%.

21. The process of claim 13 comprising supplying the furnace and the calciner with a combustion gas that has an oxygen content of more than 95%.

22. A cement production plant comprising: a preheater configured to preheat raw meal; a calciner configured to calcine the raw meal that has been preheated; a furnace configured to burn the raw meal to give cement clinker; a cooler configured to cool the cement clinker; a bypass system including: a bypass conduit that is connected downstream of the furnace in a flow direction of furnace offgases, the bypass conduit configured to branch off a portion of the furnace offgases as a bypass gas, a mixing chamber configured to cool the bypass gas with a cooling gas, and a dust separator configured to separate out dust present in the bypass gas, wherein at least one of the dust separator, the preheater, or the calciner is connected to the mixing chamber for introducing cooling gas into the mixing chamber, wherein the mixing chamber is configured such that the cooling gas is introducible into the mixing chamber in a ratio of 2-10:1 relative to the bypass gas.

23. The cement production plant of claim 22 wherein the bypass system includes a branch that is configured to branch off a portion of the bypass gas that is downstream of the dust separator and is connected to the mixing chamber for guiding of a portion of the bypass gas and connected to the calciner, the furnace, and/or the cooler for guiding of another portion of the bypass gas.

24. The cement production plant of claim 22 wherein the bypass conduit is disposed between the furnace and the calciner.

25. The cement production plant of claim 22 wherein the bypass conduit is disposed downstream of the calciner.

26. The cement production plant of claim 22 wherein the bypass system has a second cooler upstream of the mixing chamber.

27. The cement production plant of claim 26 wherein the second cooler is an evaporative cooler or a gas-gas heat exchanger.

Description

DESCRIPTION OF THE DRAWINGS

[0045] The invention is elucidated in detail hereinafter by multiple working examples with reference to the appended figures.

[0046] FIG. 1 shows a schematic diagram of a cement production plant with a bypass system according to a working example.

[0047] FIG. 2 shows a schematic diagram of a cement production plant with a bypass system according to a further working example.

[0048] FIG. 3 shows a schematic diagram of a cement production plant with a bypass system.

[0049] FIG. 1 shows a cement production plant 10 with a preheater 12 for preheating of raw meal, a calciner 14 for calcining of the raw meal, a furnace 16, especially a rotary furnace, for burning of the raw meal to give clinker, and a cooler 18 for cooling the clinker burnt in the furnace 16.

[0050] The preheater 12 comprises a multitude of cyclones 20 for separation of the raw meal out of the raw meal gas stream. By way of example, the preheater 12 has five cyclones 20 arranged in four cyclone stages one below another. The preheater 12 has a material inlet (not shown) for introduction of the raw meal into the uppermost cyclone stage of the preheater 12 that comprises two cyclones 20. The raw meal flows successively through the cyclones 20 of the cyclone stages in countercurrent to the furnace offgas and is heated as a result. The calciner 14 is disposed between the last and penultimate cyclone stages. The calciner 14 has a riser with at least one burner for heating of the raw meal, such that the raw meal is calcined in the calciner 14. In addition, the calciner 14 has a fuel inlet for introducing fuel into the riser. The calciner 14 also has a combustion gas inlet for introducing combustion gas into the riser of the calciner 14. The combustion gas is, for example, pure oxygen or a gas having an oxygen content of at least 85%. The calciner offgas is introduced into the preheater 12, preferably into the last cyclone stage, and leaves the preheater 12 beyond the uppermost cyclone stage as preheater offgas 22.

[0051] Connected downstream of the preheater 12 in flow direction of the raw meal is the furnace 16, such that the raw meal preheated in the preheater 12 and calcined in the calciner 14 flows into the furnace 16. The furnace gas outlet 24, especially material inlet, of the furnace 16 is connected directly to the riser of the calciner 14, such that the furnace offgas flows into the calciner 14 and subsequently into the preheater 12. The furnace 16 is, by way of example, a rotary furnace having a rotary tube rotatable about its longitudinal axis, arranged at a slightly declining angle. The furnace 12 has a burner 28 and a corresponding fuel inlet 30 at the material outlet end within the rotary tube. The material outlet from the furnace 16 is disposed at the opposite end of the rotary tube from the material inlet, such that the raw meal is conveyed within the rotary tube by the rotation of the rotary tube in the direction of the burner 28 and of the material outlet. The raw meal is burnt within the furnace 16 to give cement clinker, with the raw meal being heated, for example, in the first third of the rotary tube and burnt, especially sintered, in the downstream region of the rotary tube. The region within the rotary tube in which the raw meal is sintered, especially melted, is referred to as sintering zone 32. The sintering zone 32 comprises the far region of the rotary tube on the material outlet side, preferably the rear third in material flow direction, especially the rear two thirds of the rotary tube.

[0052] Following on from the material outlet of the furnace 16 is the cooler 18 for cooling of the clinker. The cooler 18 has a cooling gas space 34 in which the clinker is cooled by a cooling gas stream. The clinker is conveyed in conveying direction F through the cooling gas space 34. The cooling gas space 34 has a first cooling gas space section 36, and a second cooling gas space section 38 which follows on in conveying direction F from the first cooling gas space section 36. The furnace 16 is connected to the cooler 18 via the material outlet of the furnace 16, such that the clinker burnt in the rotary furnace 20 falls into the cooler 18.

[0053] The first cooling gas space section 36 is disposed beneath the material outlet of the furnace 16, such that the clinker falls from the furnace 16 into the first cooling gas space section 36. The first cooling gas space section 36 constitutes an intake region for the cooler 18 and preferably has a static grid 40 that receives the clinker exiting from the furnace 16. The static grid 40 is especially disposed entirely within the first cooling gas space section 36 of the cooler 10. The clinker preferably falls out of the furnace 16 directly onto the static grid 40. The static grid 40 extends preferably completely at an angle of 10° to 35°, preferably 14° to 33°, especially 21 to 25, to the horizontal, such that the clinker slides along the static grid 40 in conveying direction.

[0054] Following on from the first cooling gas space section 36 is the second cooling gas space section 38 of the cooler 18. In the first cooling gas space section 36 of the cooler 18, the clinker is especially cooled to a temperature of less than 1100° C., the cooling being effected in such a way that liquid phases present in the clinker are fully solidified to solid phases. When it leaves the first cooling gas space section 36 of the cooler 18, the clinker is preferably completely in the solid phase and at a temperature of not more than 1100° C. In the second cooling gas space section 38 of the cooler 18, the clinker is cooled down further, preferably to a temperature of less than 100° C. The second cooling gas stream can preferably be divided into multiple gas substreams having different temperatures.

[0055] The static grid of the first cooling gas space section 36 has, for example, passages through which a cooling gas enters the cooler 18 and the clinker. The cooling gas is generated, for example, by means of at least one ventilator disposed beneath the static grid 40, such that a first cooling gas stream 42 flows from below through the static grid into the first cooling gas space section 36. The first cooling gas stream 42 is, for example, pure oxygen or a gas having a proportion of 15% by volume or less of nitrogen and a proportion of 50% by volume or more of oxygen. The first cooling gas stream 42 flows through the clinker and then flows into the furnace 16. The first cooling gas stream forms, for example, a portion or the entirety of the combustion gas for the furnace 16. The high proportion of oxygen in the combustion gas leads to a furnace offgas consisting essentially of CO2, oxygen and water vapor.

[0056] Within the cooler 18, the clinker to be cooled is moved in conveying direction F. The second cooling gas section 38 preferably has a dynamic, especially movable, grid 44 which follows on from the static grid 40 in conveying direction F. The dynamic grid 44 especially has a conveying unit that transports the clinker in conveying direction F. The conveying unit is, for example, a moving floor conveyor having a multitude of conveying elements for transport of the bulk material. The conveying elements in a moving floor conveyor are a multitude of planks, preferably grid planks, that form a ventilated floor. The conveying elements are disposed alongside one another and are movable in conveying direction F and counter to conveying direction F. It is preferably possible for cooling gas stream to flow through the conveying elements in the form of conveying planks or grid planks, and these are disposed over the entire length of the second cooling gas section 38 of the cooler 18 and form the surface on which the clinker lies. The conveying unit may also be a moving conveyor, in which case the conveying unit has a stationary ventilated floor through which cooling gas stream can flow and a multitude of conveying elements movable relative to the ventilated floor. The conveying elements of the moving conveyor are preferably disposed above the ventilated floor and have entrainers that run transverse to conveying direction. For transport of the clinker along the ventilated floor, the conveying elements are movable in conveying direction F and counter to conveying direction F. The conveying elements of the moving conveyor and of the moving floor conveyor may be movable by the “walking floor principle”, wherein the conveying elements are all moved simultaneously in conveying direction and non-simultaneously counter to conveying direction. Alternatively, other conveying principles from bulk material technology are also conceivable.

[0057] Beneath the dynamic grid 44 are disposed, by way of example, a multitude of ventilators by means of which the second cooling gas stream 46 is blown from below through the dynamic grid 44. The second cooling gas stream 46 is, for example, air.

[0058] Following on from the dynamic grid 44 of the second cooling gas space section 38 in FIG. 1, by way of example, is a comminuting device 48. The comminuting device 48 is, for example, a crusher having at least two crusher rolls that are rotatable in opposing directions and a crusher nip formed between them, in which the comminution of the material takes place. Following on from the comminuting device 48 is a further dynamic grid 50 beneath the comminuting device 48. The cold clinker 52 on departure from the cooler 18 is preferably at a temperature of 100° C. or less.

[0059] The cement production plant 10 of FIG. 1 additionally has a bypass system 56. The bypass system 56 comprises a bypass conduit 58 for branching off a portion of the furnace offgases flowing to the calciner as bypass gas. The bypass conduit 58 is connected to the furnace offgas outlet 24, such that a portion of the offgas discharged from the furnace 24 is guided into the calciner 14 and another portion is guided into the bypass conduit 58. In addition, the bypass system comprises a cooling device 60 for cooling of the bypass gas with a cooling gas. The cooling device 60 is directly connected to the furnace offgas outlet 24 via the bypass conduit 58. The cooling device 60 is, for example, a mixing chamber. For example, the cooling device 60 has a cooling gas inlet for introducing cooling gas into the cooling device 60, and a bypass gas outlet for discharging the cooled bypass gas from the cooling device 60. The cooled bypass gas leaving the cooling device 60 has, for example, a temperature of 200° C. to 600° C., especially 400-500° C., and is guided into a dust separator 62 downstream of the cooling device 60. The dust separator has a solids outlet for discharging the separated dust 64, and a gas outlet for discharging the dedusted and cooled bypass gas. Following on from the dust separator 62 is a fan for accelerating the cooled and dedusted bypass gas. The bypass system 56 additionally has, downstream of the fan, a branch 68 for branching off a portion of the dedusted and cooled bypass gas, which is connected to the calciner 14 and a cooler 70, such that a portion of the dedusted and cooled bypass gas is guided into the calciner 14 and the other portion into the cooler 70. The cooler is, for example, an evaporative cooler or a gas-gas heat exchanger. The dedusted and cooled bypass gas fed to the calciner 14 is at a temperature, for example, of 200° C. to 600° C., especially 400-500° C. The cooler 10 is connected to the cooling device 60, which is in the form of a mixing chamber by way of example. The branched-off, cooled and dedusted bypass gas leaves the cooler 70 as cooling gas 72 and is fed to the cooling device 60 for cooling of the bypass gas branched off from the furnace offgas outlet 24. The cooling gas 72 is at a temperature, for example, of 100° C. to 200° C., especially 100-120° C.

[0060] In the working example of FIG. 1, the cooling gas for cooling of the bypass gas in the cooling device 60 is formed by the in flow direction of the bypass gas beyond the cooling device 60 and the separator 62 bypass gas, which is additionally cooled further by means of a cooler 70. Thus, the additional introduction of cooling air into the cooling device 60 is dispensed with, such that the proportion of uncondensable gases in the bypass gas does not rise and, for example, the CO2 content of the bypass gas recycled into the calciner remains constant and high.

[0061] FIG. 2 shows a further embodiment of the cement production plant 10 that corresponds essentially to the cement production plant shown in FIG. 1. Identical elements are given the same reference numerals. By contrast with FIG. 1, FIG. 2 shows a cement production plant 10 with a bypass conduit 58 connected to the preheater 12. In particular, the bypass conduit 58, in flow direction of the furnace offgas, is disposed beyond the lowermost cyclone stage, preferably between the calciner 14 and the second-from-last cyclone stage. The offgas flowing through the preheater at this point is preferably at a temperature of 920° C. It is likewise conceivable to dispose the bypass conduit 58 at another position within the preheater 12, preferably upstream of the uppermost cyclone stage.

[0062] FIG. 3 shows a further embodiment of the cement production plant 10, which corresponds essentially to the cement production plant shown in FIG. 1. Identical elements are given the same reference numerals. By contrast with FIG. 1, FIG. 3 shows a cement production plant 10, wherein the cooling gas 72 flowing into the cooling device 60 is formed by a from the preheater offgas 22 gas stream. The branch 68, by contrast with FIG. 1, is disposed upstream of the preheater 12 for branching-off of a portion of the preheater offgas 22. The branched-off preheater offgas is guided into the cooler 70 of the bypass system 56 and preferably cooled to a temperature of 100° C. to 200° C., especially 100 to 120° C. Subsequently, it is introduced into the cooling device 60 designed as a mixing chamber for cooling of the bypass gas branched off from the furnace offgas outlet.

[0063] Optionally, the cooled and dedusted bypass gas, in FIGS. 1 to 3, in addition to being fed to the calciner 14, is fed partly to the furnace 16 and/or the cooler 18. For sake of clarity, the corresponding conduits are not shown in FIGS. 1 to 3. The cooled and dedusted bypass gas is fed, for example, to the first cooling gas space section 36 and at least partly forms the first cooling gas stream 42. It is likewise conceivable to feed a portion of the cooled and dedusted bypass gas to the furnace 16, preferably to the furnace head and/or to the sintering zone 32.

LIST OF REFERENCE NUMERALS

[0064] 10 cement production plant

[0065] 12 preheater

[0066] 14 calciner

[0067] 16 furnace

[0068] 18 cooler

[0069] 20 cyclone

[0070] 22 preheater offgas

[0071] 24 furnace offgas outlet

[0072] 28 furnace burner

[0073] 30 furnace fuel outlet

[0074] 32 sintering zone

[0075] 34 cooling gas space

[0076] 36 first cooling gas space section

[0077] 38 second cooling gas space section

[0078] 40 static grid

[0079] 42 first cooling gas stream

[0080] 44 dynamic grid

[0081] 46 second cooling gas stream

[0082] 48 comminuting device

[0083] 50 dynamic grid

[0084] 52 cold clinker

[0085] 54 cooler output air

[0086] 56 bypass system

[0087] 58 bypass conduit

[0088] 60 mixing chamber

[0089] 62 dust separator

[0090] 64 separated dust

[0091] 66 fan

[0092] 68 branch

[0093] 70 cooler

[0094] 72 cooling gas