Method and apparatus for activating clay

Abstract

The invention relates to a method and an apparatus for activating clay. The invention provides that a clay raw material is divided into a coarse fraction and a fine fraction, the fine fraction is preheated in a preheater, then the fine fraction is activated in a fluidized bed reactor and / or an air flow reactor, the activated hot fine fraction is united with the separated cold coarse fraction, whereby the hot activated clay fraction is rapidly cooled, and the united clay fraction is discharged from the reactor. The advantage of carrying out the method is that the activated clay is not oxidized and thereby does not turn red. In addition, the previous sieving saves a lot of thermal energy, and the rapid cooling of the hot activated clay stabilizes the overall product against undesired redness.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method and a device for activating clay. BACKGROUND

[0002] As a replacement material for cement bricks as a building material, the use of thermally activated clay is known. Although thermally activated clay does not reach the strength of concrete based on cement bricks, the properties of activated clay as a building material are sufficient for many building projects which do not depend on special properties of the building material, such as prestressed concrete bridges, or extremely high buildings which far exceed the 100 m limit, for example.

[0003] Clay building has been known since the time of the ancient Greeks and Romans. Houses built of burnt clay and clay exhibit the typical red color, which can reach the color tone of terra-cotta brick panels.

[0004] Clay minerals which are suitable for processing as a building material by developing hydraulic properties through thermal treatment can be changed significantly in their chemical composition, mineral composition and in their physical properties. The natural occurrence of the clay minerals additionally contains fractions which are usually different from the clay minerals in terms of hydraulic properties, which relate to inert components, such as quartz, feldspar, flint. Purely naturally occurring clay minerals from different origins are usually distinguished from one another by different properties, such as particle size, density and humidity. In addition to the external properties, clay minerals from different origins are also distinguished from one another by the contained inorganic impurities, such as iron, titanium, manganese.

[0005] These chemically combined metal accompanying substances determine the color of the activated clay through their change in oxidation state upon thermal treatment of the clay minerals. Iron impurities can occur as structural iron (part of the structure of the kaolinite or additional minerals) and as free iron in the form of oxides, hydroxides, carbonates and sulfides. The titanium content and the content of oxidic iron are related to the colorimetric parameters and the color saturation of the red color. Upon oxidation, manganese exhibits a brown color in the structure of manganese oxides. It is known that the red color is caused by iron (III) compounds. The content of impurities such as iron, titanium in the naturally occurring clay minerals likewise leads to an undesired red color which occurs as a result of the thermal treatment of the activated clay minerals upon calcination under oxidizing conditions and subsequent cooling in the air of the atmosphere.

[0006] Clay is a naturally occurring substance which consists mainly of clay mineral particles and which is generally deformable in a plastic manner and brittle upon drying or burning, if the water content is sufficient. Although clay usually contains layered silicates, it also contains other substances which impart plasticity to it and which harden upon drying or burning. As relevant phases, clay can contain substances which do not impart plasticity to it, such as quartz, calcite, dolomite, feldspar and organic substances.

[0007] Unlike the previous definitions, the definition of AIPEA (Association International Pour L'Etudes Des Argiles, International Association for the Study of Clays) and CMS (Clay Minerals Society) does not determine the exact particle size of the clay components, since different rules here lead to their own conclusions. At the level of geological science, according to the standard EN ISO 14688, clay particles are particles smaller than 2 μιη (in some cases also smaller than 4 μιη), at the level of colloid chemistry, clay particles are particles smaller than 1 μιη.

[0008] Within the scope of the present application, clay refers to a naturally occurring substance which consists mainly of clay mineral particles and thereby has more than 50% of clay mineral particles, but also consists of decomposable substances from clay mineral layers, which have less than 50%, up to only 10% to 20% of clay mineral particles. The rest consists of sand, silt, quartz, calcite, dolomite, feldspar and, in certain cases, also of gravel. The larger substance fraction which is not clay mineral particles is chemically largely inert, abrasive and cannot be thermally activated. The last-mentioned clay thereby resembles clay. SUMMARY

[0009] The task of the present application is to provide an apparatus and a method for thermal activation of clay, in which the undesired reddening phenomenon does not occur.

[0010] The task underlying the present application is solved by an apparatus having the features according to embodiment 1, dependent embodiments 2 to 4, and by a method according to embodiments 6 to 10.

[0011] The method according to the application provides that the clay raw material is divided into a coarse fraction and a fine fraction, the fine fraction is then preheated in a preheater, the fine fraction is then activated in a fluidized bed reactor and / or an air flow reactor. The thermal treatment of the fine fraction takes place in the fluidized bed reactor and / or the air flow reactor. The still hot fine fraction after thermal activation is unified with the separated cold coarse fraction, and the unified clay fraction is discharged from the reactor.

[0012] Corresponding to the method, the invention also provides a plant having at least one fluidized bed reactor and / or gas flow reactor and at least one cyclone heat exchanger, wherein the cyclone heat exchanger follows the fluidized bed reactor and / or gas flow reactor in the direction of gas flow, and wherein a feed device for the clay to be activated is provided at the upper end of the cyclone heat exchanger, characterized in that a sifter is in fluid connection upstream in the direction of material flow with the gas feed device for the fluidized bed reactor and / or gas flow reactor with the coarse material discharge opening of the sifter and in that the sifter is in fluid connection upstream in the direction of material flow with the feed device for the clay to be activated with the fine material discharge opening of the sifter. The plant allows the treatment of clay in accordance with the aforementioned method.

[0013] The surprising insight on which the invention is based is that the reddening of clays is a phenomenon that occurs only in the fine fraction of natural clays through oxidation of the iron contained in the clay minerals to iron (III) in combination with other chemically combined metal components during activation. In contrast, the coarse fraction of natural clays has no tendency to become red. The insight on which the invention is based is that the fine fraction of the clay can be activated by heat treatment. If the heat treatment activation is carried out under strongly reducing chemical conditions, then iron (III) does not occur in the clay, but rather precisely iron (II) that is combined in the clay minerals and is greenish or even colorless. The clay fraction activated under chemically reducing conditions thus appears gray or even anthracitic in combination with all the accompanying substances. The fine fraction of the natural clay activated by heat treatment is initially in a state that is very sensitive to oxidation in atmospheric air. In order to avoid oxidation, the fine, heat-activated clay fraction is rapidly cooled at the end of the reactor for heat activation from a temperature of 600 to 1000 °C to a temperature that is significantly below 600 °C by a temperature of 600 to 1000 °C. However, this rapid thermal cooling cannot be carried out with atmospheric air, otherwise undesirable iron (III) would occur. The rapid cooling must be carried out under chemically neutral conditions. The coarse fraction separated from the natural clay in the first step of the method is suitable for this. The coarse fraction is almost chemically inert and can absorb a large amount of heat without itself being oxidized. The invention is therefore also based on the separation of the clay minerals into a fine fraction that is heat-activated and a coarse fraction that is not heated as inert material. The surprising effect is that the separation into a coarse fraction and a fine fraction results in a clay-poor and inert coarse fraction and a clay-rich fine fraction. After the heat activation of the still hot, oxidation-sensitive fine fraction, the activated fine fraction is rapidly cooled using the previously separated coarse fraction, which is significantly cooler. In the rapidly cooled state, the chemically combined iron (II) is protected from oxidation. The clay minerals treated in this way appear gray or even anthracitic in color.

[0014] It is advantageous to discharge the activated, grey or even anthracite-colored mineral from the reactor. To this end, the material flow outlet of the cyclone heat exchanger can be provided in fluid connection at the lower end with a gas feed device for the gas flow reactor, wherein the activated clay is united at this location with the coarse material from the coarse material discharge opening of the sifter. The gas feed device can be present in the form of a cyclone, from which the carrier gas escapes through a dip tube, and the solid material as dust suspended in the carrier gas exits from a generally downwardly directed cone.

[0015] The temperature influences the activated product not only during activation, but also after activation. It has been established in tests that the integration of the thermally activated fine material portion with the coarse material portion of the raw material at a final temperature of 350°C to 600°C in the temperature window of 600°C to 1000°C makes the fine material portion of the activated clay insensitive to discoloration by oxidation in atmospheric air having natural air humidity.

[0016] The separation of the natural clay into a fine material portion and a coarse material portion and the thermal activation of only the separated fine material portion, and the subsequent rapid cooling with the previously separated coarse material portion, has a number of advantages. First, the activated fine material portion can be rapidly cooled under chemically inert conditions, which stabilizes the activated clay portion against reddening. Furthermore, by thermal activation in portions, only a small portion of the heat is required, which saves fuel and resources. A further advantage is also the surprising insight that the thermally activatable fine material portion has significantly less abrasiveness than the coarse material portion. The coarse material portion contains quartz, feldspar and flint. By separating off the coarse material portion, the equipment subjected to the thermal load is subjected to less abrasive dust, which extends the service life and the service duration of the equipment. By using a wind sifter, in particular a V-shaped sifter, the extent of exposure of moving machine parts to abrasive clay portions is minimized. BRIEF DESCRIPTION OF DRAWINGS

[0017] The application is further illustrated by means of the following drawings. In the drawings:

[0018] Figure 1 An apparatus for activating clay according to the application is shown. DETAILED DESCRIPTION

[0019] The foregoing description of the solution according to the application thus includes, inter alia, various feature combinations defined by the subsequently numbered embodiments:

[0020] 1. An apparatus for activating clay, having

[0021] + at least one fluidized bed reactor and / or gas stream reactor (110),

[0022] - at least one cyclone heat exchanger (120), wherein the cyclone heat exchanger (120) follows the fluidized bed reactor and / or gas stream reactor (110) in the direction of gas flow,

[0023] wherein a feed device (200) for clay to be activated is arranged at the upper end of the cyclone heat exchanger (120),

[0024] wherein a sifter (40) is in fluid connection upstream in the direction of material flow with a gas feed device for the fluidized bed reactor and / or gas stream reactor (110), preferably in the form of a cyclone (100), at the coarse material outlet opening of the sifter (40) and wherein the sifter (40) is in fluid connection upstream in the direction of material flow with the feed device (200) for clay to be activated at the fine material outlet opening of the sifter (40).

[0025] 2. The apparatus according to embodiment 1,

[0026] wherein the material flow outlet of the cyclone heat exchanger (120) is in fluid connection at the lower end with a gas feed device for the fluidized bed reactor and / or gas stream reactor (110), preferably in the form of a cyclone (100),

[0027] wherein activated clay is unified at this location with coarse material from the coarse material outlet opening of the sifter (40).

[0028] 3. The apparatus according to any one of embodiments 1 or 2,

[0029] wherein a gas line (220) of a gas feed device for the fluidized bed reactor and / or gas stream reactor (110), preferably in the form of a cyclone (100), is connected with a gas line (130) that serves as a gas discharge line of the cyclone heat exchanger (120),

[0030] wherein the unified gas lines flow into a hot gas generator (140) and wherein the hot gas generator (140) is connected in the downstream direction of the gas stream with a gas inlet of the sifter (40).

[0031] 4. The apparatus according to any one of embodiments 1 to 3,

[0032] wherein the coarse material outlet opening of the sifter (40) is connected with the raw material inlet of the sifter (40) by means of a material turnout (60).

[0033] 5. The apparatus according to any one of embodiments 1 to 4,

[0034] wherein the sizer (40) is a vertical sizer.

[0035] 6. A method for activating clay,

[0036] wherein,

[0037] + the clay feedstock is divided into a coarse fraction and a fine fraction,

[0038] + the fine fraction is preheated in a preheater, and then

[0039] + the fine fraction is activated in a fluidized bed reactor and / or an airlift reactor (110),

[0040] + the activated hot fine fraction is unified with the separated cold coarse fraction,

[0041] + the unified clay fraction is discharged from the reactor.

[0042] 7. The method for activating clay according to embodiment 6,

[0043] wherein the activated hot fine fraction having a temperature of 600°C to 1000°C is unified with the separated cold coarse fraction which is significantly colder.

[0044] 8. The method according to any one of embodiments 6 or 7,

[0045] wherein,

[0046] - the fine fraction is activated in a fluidized bed reactor and / or an airlift reactor (110) under conditions of chemical reduction and when the oxygen content of the carrier gas is less than 4%.

[0047] 9. The method according to any one of embodiments 6 or 8,

[0048] wherein the unified clay fraction is discharged from the reactor by a cyclone.

[0049] 10. The method according to embodiment 9,

[0050] wherein the unified clay fraction is discharged from the reactor when the temperature is 50°C to a maximum of 200°C, preferably when the temperature is 90°C to 120°C.

[0051] 11. The method according to any one of embodiments 6 to 10,

[0052] wherein the cold coarse fraction is treated by filtering, sieving and / or crushing / compacting before the cold coarse fraction is unified with the activated fine fraction for rapid cooling.

[0053] 12. The method according to any one of embodiments 6 to 10,

[0054] wherein a share of the relative amounts of coarse fraction and activated fine fraction in the unified clay fraction is set.

[0055] Figure 1 An apparatus for activating clay according to the present application is shown. In the sketch, moist raw material is taken through the apparatus from a feed hopper 10 in the upper left corner of the sketch until the activated product, which is the finished product, leaves the apparatus shown here through a conveyor 240 in the lower right corner of the sketch. Fresh air enters the apparatus through a cyclone 230 in the lower right corner of the sketch and leaves the apparatus as exhaust air in the sketch through a compressor 180 in the upper right corner of the sketch.

[0056] The raw material is conveyed from the feed hopper 10 by a conveyor 20 to a conditioned conveyor 30, where the raw material is united with the material in the circulation of the classifier. From the conditioned conveyor 30 the material falls into a classifier 40, which is a vertical classifier here, in which the material rolls on a stepped cascade, where the material is no longer agglomerated, and is released from the fine material fraction by the classification gas, which in the sketch enters the classifier 40 from the left. At this point the path of the coarse material fraction and the path of the fine material fraction diverge. The path of the coarse material fraction is described first. The coarse material from the classifier 40 falls from the classifier 40 onto a conditioned conveyor 50, and is conveyed by this conveyor 50 to the left in the sketch. At the left side of the conveyor 50 the coarse material falls into a conditioned material switch 60. A first part of the coarse material is transported by the material switch 60 to a further conveyor 70 up to a lift 80, which throws the classified material in circulation again onto the conveyor 30 described at the beginning, where the classified material in circulation is united with the raw material. A second part of the coarse material from the classifier 40, which is inert material, is transported by a conveyor 90 to the right in the sketch, and there is united with the activated fine material of the raw material. Along the transport path of the conveyor 90 there can also be provided a treatment device 92, for example in the form of a sieve device 92 or a grinding device, which can be reached by the lift 91, in order to sieve out the coarser constituents of the natural clay, in order to set the share of the relative amount of activated clay and inert material in the end product. Furthermore, there can also be provided an optional water application device 93, which moistens the coarse material before it is united with the activated clay, in order to increase the heat absorption capacity of the coarse material. At this point the coarse material has an atmospheric temperature of at most 150°C by virtue of the temperature of the classifier gas in the classifier 40. The path of the fine material from the raw material from the classifier 40 leads into the gas line 160, in which the fine material is carried by the classification gas. In a dust separator 170 the fine material is separated from the classification gas. As described at the beginning, the classification gas leaves the plant as exhaust gas towards the upper right by means of the compressor 180. A conveyor 190, which conveys the fine material fraction into a feed device 200, is located below the dust separator 170. The fine material falls from the feed device 200 into the uppermost gas guide up to the heat exchanger cyclone 123 of the heat exchanger 120 shown here with three cyclones. It is likewise possible to drive a plant with another number of cyclones in the heat exchanger line. The fine material fraction is suspended in the gas in the gas guide up to the cyclone 123, and is warmed up in the hot gas of the heat exchanger 120.In the uppermost heat exchanger cyclone 123, the fine fraction is directed to the gas input up to the penultimate cyclone 122, where the heating and the subsequent separation are repeated. At the outlet of the penultimate cyclone 122, the preheated fine fraction falls into the lower region of the gas stream reactor shown here, which is configured like a calciner of a plant for the production of cement bricks. But at this location a fluidized bed reactor can also be provided. In the rising hot gas of the gas stream reactor 110, the fine fraction of clay is thermally activated into a hydraulic binder that hardens when mixed with water, wherein the hot gas can be heated in a combustion position, but also in other hot process gases of industrial processes. After the hot gas in the gas stream reactor 110 reaches the upper return point, the fuel from the gas stream reactor is burnt out. The free oxygen content in the gas stream reactor should not exceed 4%. The flame of the burner in the gas stream reactor 110 is therefore driven in a strongly reducing manner, which can be done by an oxygen supply below the stoichiometric ratio or a fuel supply above the stoichiometric ratio. The heat exchanger 120 follows the descending branch of the gas stream reactor 110. The hot activated fine fraction of clay suspended in the hot gas is separated by the lowermost cyclone 121 of the heat exchanger 120 and has a temperature of between 600°C and 1000°C at this location. The flow direction of the hot gas in the heat exchanger 120 is opposite to the flow direction of the new fine fraction. In contrast thereto, the new hot activated clay fraction leaves the heat exchanger through the solids material line of the lowermost cyclone 121 and is there combined with the inert cold coarse fraction of clay that has been separated in the sifter 40.

[0057] The newly activated clay with a temperature of 600 to 1000°C, when delivered together with the cold coarse fraction, cools rapidly in the case of intensive mixing to a temperature of approximately 350 to 600°C and is separated from the hot line of the plant in the cyclone 100. In order to cause a strong temperature drop, the cold coarse fraction can be watered before it is united with the hot activated clay fraction. The united clay fractions flow into the gas guide of the cyclone 230, where the flow direction of these fractions is opposite to the flow direction of the new atmospheric air. The fraction, which is cooled to approximately 80 to 120°C, leaves the plant as a finished product via the solids line of the cyclone 230 and via the conveying device 240. In contrast thereto, the fresh air, which enters the plant, is conveyed via the compressor 210 to the gas line 220 and as a gas supply to the cyclone 100, where it receives the rapidly cooled and united clay fraction in the gas chamber. The fresh air, which arrives there, serves as combustion air for the burners in the gas stream reactor 110 and also as carrier air. A further portion of this fresh air flows to the T-junction with the exhaust line 130, which guides the hot heat exchanger exhaust gas from the heat exchanger 130 to the hot gas generator 140. The united gas fraction is heated in the hot gas generator 140, and after the hot gas generator 140, the gas line 150 guides the heated gas as a screening gas and drying gas to the screener 40, where all the gas circulation ends together with the material circulation and / or all the flows end.

[0058] List of reference signs

[0059] 10 feed hopper

[0060] 20 conveying device

[0061] 30 conveying device

[0062] 40 screener

[0063] 50 conveying device

[0064] 60 material turnout

[0065] 70 conveying device

[0066] 80 elevator

[0067] 90 conveying device

[0068] 91 elevator

[0069] 92 treatment device

[0070] 93 water application device

[0071] 100 cyclone

[0072] 110 gas flow reactor

[0073] 120 heat exchanger

[0074] 121 second lower heat exchanger cyclone

[0075] 122 lowermost heat exchanger cyclone

[0076] 123 uppermost heat exchanger cyclone

[0077] 130 gas line

[0078] 140 hot gas generator

[0079] 150 gas line

[0080] 160 gas line

[0081] 170 dust separator

[0082] 180 compressor

[0083] 190 conveying device

[0084] 200 feed device

[0085] 210 compressor

[0086] 220 gas line

[0087] 230 cyclone

[0088] 240 conveying device

Claims

1. A method for activating clay, Its features are, - Divide the clay raw materials into coarse and fine components. - Preheat the fine material portion in the preheater, and then... - Under chemical reduction conditions and when the oxygen content of the carrier gas is less than 4%, the fine material portion is thermally activated in a fluidized bed reactor and / or a gas flow reactor (110). - This integrates the thermally activated, hot fine material portion with a temperature of 600°C to 1000°C with the separated, cold coarse material portion with an atmospheric temperature below 150°C. - The integrated clay portion is discharged from the reactor.

2. The method according to claim 1, Its features are, The combined clay portion is discharged from the reactor via a hydrocyclone.

3. The method according to claim 2, Its features are, When the temperature is between 50°C and a maximum of 200°C, the integrated clay portion is discharged from the reactor.

4. The method according to claim 2, Its features are, When the temperature is between 90°C and 120°C, the integrated clay portion is discharged from the reactor.

5. The method according to any one of claims 1-4, Its features are, The cold coarse material portion is processed by filtration, screening, and / or crushing / rolling before being integrated with the activated fine material portion for rapid cooling.

6. The method according to any one of claims 1-4, Its features are, Set the relative proportions of coarse and activated fine materials in the integrated clay portion.

7. The method according to claim 5, Its features are, Set the relative proportions of coarse and activated fine materials in the integrated clay portion.

8. An apparatus for activating clay by any one of claims 1-7, comprising: -At least one fluidized bed reactor and / or gas flow reactor (110) with a burner, -At least one swirl heat exchanger (120), wherein, The swirl heat exchanger (120) follows the fluidized bed reactor and / or gas flow reactor (110) in the gas flow direction. The feeding device (200) for the clay to be activated by heat is located at the upper end of the cyclone heat exchanger (120). Its features are, The screen (40) is fluidly connected upstream in the material flow direction to the gas feed device for the fluidized bed reactor and / or the gas flow reactor (110) via the coarse material discharge opening of the screen (40), and wherein the screen (40) is fluidly connected upstream in the material flow direction to the feed device (200) for the clay to be activated via the fine material discharge opening of the screen (40).

9. The device according to claim 8, Its features are, The material outlet of the swirl heat exchanger (120) is in fluid connection at its lower end with a gas feed device for the fluidized bed reactor and / or the gas flow reactor (110). The activated clay is combined with the coarse material from the coarse material discharge opening of the screen (40) at the lower end.

10. The device according to claim 8, Its features are, The first gas line (220) for the gas feed device of the fluidized bed reactor and / or gas flow reactor (110) is connected to the second gas line (130) that serves as the exhaust line of the swirl heat exchanger (120). The integrated gas pipeline converges into the hot gas generator (140), and the hot gas generator (140) is connected to the gas inlet of the sieve (40) in the downstream direction of the gas flow.

11. The device according to claim 9, Its features are, The first gas line (220) for the gas feed device of the fluidized bed reactor and / or gas flow reactor (110) is connected to the second gas line (130) that serves as the exhaust line of the swirl heat exchanger (120). The integrated gas pipeline converges into the hot gas generator (140), and the hot gas generator (140) is connected to the gas inlet of the sieve (40) in the downstream direction of the gas flow.

12. The device according to any one of claims 8-11, Its features are, The gas feeding device is in the form of a cyclone separator.

13. The device according to any one of claims 8-11, Its features are, The coarse material discharge opening of the screen (40) is connected to the raw material inlet of the screen (40) through a material switch (60).

14. The device according to claim 12, Its features are, The coarse material discharge opening of the screen (40) is connected to the raw material inlet of the screen (40) through a material switch (60).

15. The device according to any one of claims 8-11 and 14, Its features are, The screen (40) is a vertical screen.

16. The device according to claim 12, Its features are, The screen (40) is a vertical screen.

17. The device according to claim 13, Its features are, The screen (40) is a vertical screen.

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