Method to activate clay with secondary fuels

Description

1 / 10 METHOD FOR ACTIVATING CLAYS WITH SECONDARY FUELS

[001] The invention relates to a method for activating clays with secondary fuel.

[002] Cement clinker as a base for concrete requires production by calcination of limestone (CaCO3), in which carbon dioxide (CO2) is formally expelled from the limestone so that quicklime (CaO) is formed, and a subsequent sintering of the quicklime with silicate rock (CaSiO3) at high temperature. The generation of high temperatures requires a correspondingly high fuel consumption, which also produces carbon dioxide (CO2) from the fuel. The carbon dioxide balance in cement clinker production is quite high and, with regard to the quantities used in civil construction and municipal infrastructure building, is now so high that efforts are being made to use other building materials as a complete replacement or as an additive to reduce carbon dioxide emissions, during the production of which less carbon dioxide is released.

[003] The use of thermally activated clay as a substitute or additive for cement clinker as a building material is known. Thermally activated clay does not require formal expulsion of carbon dioxide (CO2) from the raw clay and the activation temperature of 800 °C is lower than the calcination temperature of cement clinker. A necessary sintering temperature of 1,450 °C, which is required for the production of cement clinker, is completely eliminated.

[004] Although thermally activated clays do not achieve the strength of concrete that is based on cement clinker, the properties of activated clays as a building material are sufficient for a large number of construction projects where a special performance of the building material is not important, as is Petition 870250084756, dated 09 / 19 / 2025, p. 13 / 30 2 / 10 is the case, for example, with prestressed concrete bridges or, as is the case with extremely tall buildings well beyond the 100 m limit.

[005] In order to further improve the carbon dioxide balance of activated clay, which is also called “calcined clay”, it is desirable to replace primary fossil fuels, gas, oil and coal, with biogenic or at least partially biogenic fuels as secondary fuels. In contrast to the classic clinker burning process, however, the lower temperature is a decisive disadvantage in this case: only very finely processed secondary fuels can be implemented at 800 °C within 3 s 5 s in an entrained flow reactor such as a calciner or activation reactor. Since no rotary tubular kiln for sintering is connected downstream in this method described here, unburned material cannot be residually burned in the rotary tubular kiln either. However, fine processing of alternative fuels with particles as secondary fuels demands a lot of energy and is sometimes not feasible.The initially superficial advantage of a lower firing temperature for the calciner / activation reactor again proves to demand a lot of energy at an upstream location due to the processing required during conventional use of the calciner / activation reactor.

[006] It is therefore the object of the invention to propose a method for activating clays with secondary fuel in which the energy-intensive processing required to use the fuel in a calciner / activation reactor can be bypassed, or in which at least a large part of the secondary fuel does not require energy-intensive processing.

[007] The objective according to the invention is achieved by a method having the characteristics according to claim 1. An installation for carrying out the method is specified in claim 9. Other advantageous configurations of the method are specified in claims Petition 870250084756, dated 09 / 19 / 2025, page 14 / 30 3 / 10 dependent on claim 1.

[008] According to the invention concept, a fluidized bed reactor is used alongside the entrained flow reactor to calcine / activate the clay. This fluidized bed reactor is used to slowly burn secondary fuels at a temperature of approximately 800 °C. For this purpose, a fluidized bed of preheated process air, an intermediate product of clay grinding and / or a portion of already thermally activated clay is generated in the fluidized bed reactor, and secondary fuel is burned in it, wherein the residence time of the fluidized fuel and clay mixture in the preheated process air totals between 1 and 20 s. Depending on the method configuration, the total residence time ranges from 5 to 15 s.The method is based on the following steps: drying and grinding moist clay as feedstock; thermally activating the dried and ground clay in an entrained flow reactor, where a first portion of the clay is fluidized along with secondary fuel in a fluidized bed reactor, and the secondary fuel is burned there in the presence of this first portion of clay; introducing the exhaust gas from the fluidized bed reactor, which carries with it the first portion of clay, into the entrained flow reactor, where a second portion of the clay is thermally activated along with the first portion of clay in the entrained flow reactor to form thermally activated clay. The combustion of the fuel in the fluidized bed reactor along with the provided clay enables slow combustion at temperatures around 800 °C, where the clay found in the fluidized bed is already activated within it.The hot exhaust gases from the fluidized bed reactor are then passed, along with the clay that is at least partially activated, to a conventional entrained flow reactor, where a known type of calcination / activation takes place. For this, it is provided that a fine fraction of the crushed clay is fed to the entrained flow reactor. On the other hand, the fluidized bed reactor... Petition 870250084756, dated 09 / 19 / 2025, page 15 / 30 4 / 10 of the fluidized bed is fed with a mixture of a coarser fraction of crushed clay and a fine fraction. The stability of the fluidized bed can be controlled by adjusting the clay mixture of the clay fed to the fluidized bed reactor. The exhaust gases inseparable from the fluidized bed reactor are provided in an adjustable quantity to the entrained flow reactor, and the remaining portion is cooled and classified as thermally activated clay.

[009] Depending on the temperature reached in the fluidized bed reactor, it can be provided that the exhaust gas from the fluidized bed reactor mixed with clay and waste fuel is combined with the already activated clay from the entrained bed reactor for heat recovery in order to transfer the heat from the activated clay to the exhaust gas. In a cyclone-like recuperator stage, all the clay is separated from the exhaust gas before the exhaust gas reaches the entrained bed reactor. The separated and activated clay, on the other hand, can be routed to a cooling stage. There, the cooling of the activated fine fraction can be carried out with fresh gas, where the now heated fresh gas is passed under a nozzle base of the fluidized bed reactor after cooling the activated fine fraction. This procedure enables maximum use of heat in the process.The fluidized bed reactor may contain non-volatile substances from the burned fuel and also, if applicable, excessively large pieces of clay in the crushed clay. To separate these non-volatile substances, a discharge of non-volatile impurities from the secondary fuel and / or oversized ash particles from the fluidized bed may be provided at the height of a fluidized bed reactor nozzle base.

[010] In the best possible implementation of the method according to the invention, the following method steps are provided: drying and grinding moist clay as raw material in a drying and grinding device, sieving the dried and ground clay in a sieve with an outlet. Petition 870250084756, dated 09 / 19 / 2025, p. 16 / 30 5 / 10 for an average fraction, a) wherein a coarse sieved fraction of the dry and crushed clay is passed back to the device for drying and crushing, b) the medium sieved fraction of the dry and crushed clay is passed to a fluidized bed reactor, and c) a fine sieved fraction of the dry and crushed clay and crushed clays suspended in the sieving air are passed to a dust collector, collecting the dust from the sieving air in the dust collector, wherein a) the fine fraction of the sieving air is passed to a heat exchanger, b) a first part of the dust-free sieving air is discarded as exhaust gas, and c) a second part of the dust-free sieving air is passed back to the device for drying and crushing, preheating the fine fraction in the heat exchanger with exhaust gas from an entrained flow reactor,The process involves sieving the preheated fine fraction and thermally activating it in the entrained flow reactor to form activated clay. The activated clay from the previous step is then sieved, with a first portion introduced as thermally activated clay into a recuperator, and a second portion introduced as thermally activated clay into the fluidized bed reactor along with the medium fraction of dry, crushed clay from the sieve. Heat is recovered from the thermally activated clay in a cyclone stage as a recuperator, where heat is transmitted from the thermally activated clay to an exhaust gas from the fluidized bed reactor, cooling the thermally activated clay. The aforementioned exhaust gas is then passed from the fluidized bed reactor to the entrained flow reactor. The thermally activated clay is then cooled in a cyclone stage operated with fresh gas.whose exhaust gas is passed as heated fresh gas a) with a first part to the fluidized bed reactor, b) with a second part to the entrained flow reactor, c) with a third part to a heating device and d) with a fourth part to the recuperator, wherein an exhaust gas from the heating device is passed back to the device to, Petition 870250084756, dated 09 / 19 / 2025, p. 17 / 30 6 / 10 drying and grinding, in which in the fluidized bed reactor the clay introduced there is fluidized together with secondary fuel and the secondary fuel is ignited there, in which the exhaust gas inseparable from the fluidized bed reactor is passed a) with a first part to the entrained flow reactor and b) with a second part to the cyclone stage as a recuperator.

[011] The invention will be explained in more detail with reference to the following figures. It is shown: Fig. 1 is a diagram of an installation for calcining / activating clay to carry out the method according to the invention. Fig. 2 is a flowchart of the installation shown in Figure 1 with individual method steps.

[012] Figure 1 shows a diagram of an installation for calcining / activating clay to carry out the method according to the invention. In this diagram, the material flow is shown as line arrows, while the gas flow is shown as thick arrows with black borders, as shown in the legend. The fuel is shown as a thick black arrow. Raw material 1 is provided through a hopper 150 via a conveying system in a circuit of a drying and grinding device 270. There, the raw material 1, wet clay, is dried and ground. From the drying and grinding device 270, a pneumatic conveying line for dry and ground clay 100 leads to a cyclone screen 250 with an outlet for intermediate material 120.Cyclone 250 passes the fine sieved fraction 130 through a pneumatic conveying line to a dust collector 210, the medium sieved fraction 120 through a line to a fluidized bed reactor 200, and the coarse sieved fraction 110 back to the device 270 for drying and grinding. The fine material 130 is separated from the sieving air in the dust collector 210 and passed to a heat exchanger 220. The sieving air is passed from the dust collector 220 to a gas line. Petition 870250084756, dated 09 / 19 / 2025, page 18 / 30 7 / 10 exhaust that branches and takes back a portion of the screening air instead of exhaust gas to device 270 for drying and grinding. The fine material 130 arrives at heat exchanger 220 and there is preheated by exhaust gas 231 from an entrained flow reactor 230 and separated by a cyclone at reference number (6), which represents the “screening” method step, and taken to the lower inlet of the entrained flow reactor 230, where the fine material 130 is thermally treated to form thermally activated clay 131. The thermally activated clay 131 is then separated with a cyclone at reference number (8), which also represents the “screening” method step, and provided to a recuperator 240 where the thermally activated clay with a first portion as thermally activated clay 133 releases its heat into process gas by recovery.Another portion of the thermally activated clay 131 is passed as thermally activated clay 132 to the fluidized bed reactor 200 behind the cyclone at reference number (8) in the material flow direction. The first portion of the thermally activated clay 133 is then cooled with fresh gas in an additional cyclone stage 260 and leaves the installation as activated clay. The fresh gas heated by the cooling of the activated clay is passed through a compressor with a first portion to the fluidized bed reactor. An additional portion of the heated fresh gas is passed to a heating device 280, which further heats the fresh gas and leads to device 270 for drying and grinding. A third portion of the heated fresh gas, on the other hand, is taken to the lower inlet of the entrained flow reactor.In the fluidized bed reactor 220, combined medium fraction clay 120 and thermally activated clay 132 are fluidized together with fuel, here biogenic fuel as a secondary fuel, in contrast to high-quality primary fuels such as oil, coal and gas, and there the secondary fuel is burned. The residence time of the fluidized bed in the fluidized bed reactor 220 totals between 1 and 20 s. Petition 870250084756, dated 09 / 19 / 2025, page 19 / 30 8 / 10 preferably between 5 and 15 s. The inseparable exhaust gas from the fluidized bed reactor is split and carried, on one side, to the recuperator 240 and, on the other side, carried directly to the lower inlet of the entrained flow reactor 230. The relative quantities of the inseparable exhaust gases from the fluidized bed reactor 220 can be adjusted by the corresponding devices.

[013] Figure 2 shows a flowchart of the installation shown in Figure 1 with individual method steps. In this diagram, material flow is shown as line arrows, while gas flow is shown as thick arrows with black borders, as shown in the legend. Fuel is shown as a thick black arrow. Raw material 1 is dried and crushed in a device 270 for combined drying and crushing as method step 2. From there, gas is carried along with the dried and crushed clay to sieving in method step 3. From the sieving stage in method step 3, a coarse fraction is returned to device 270 for drying and crushing. A medium fraction is sent to a fluidized bed reactor 200 in method step 12. The fine material from method step 3, on the other hand, is sent to have the dust collected as method step 4.The dust-free exhaust gas is, on the one hand, discarded and, on the other hand, returned to device 270 for drying and grinding. The fine material is further preheated by dust collection in step 4 of method. The gas from step 5 of method, preheating, is, on the one hand, passed for recovery in step 9 of method and, on the other hand, passed back for heating in step 11 of method. After preheating, the fine material is sieved in the counterflow gas in step 6 of method and taken for thermal activation in step 7 of method. After thermal activation in step 7 of method, sieving follows in step 8 of method. The thermally activated clay is taken, on the one hand, to the fluidized bed reactor 200 and, on the other hand, for recovery in step 11 of method 200. Petition 870250084756, dated 09 / 19 / 2025, page 20 / 30 9 / 10 method 9. From the recovery in step 9 of method, the thermally activated clay arrives for cooling in step 10 of method and then, at the end of the method, exits as activated clay. In step 10 of method, fresh gas enters the method, where the heated fresh gas is taken, on one side, to the fluidized bed reactor 220 and, on the other side, to step 11 of method for heating the fresh gas. The heated gas arrives at device 270 for drying and heating. Gas from step 9 of method, recovery, is passed to the entrained flow reactor, step 7 of method. The gas from the previous step 8 of method, in the material flow direction, is passed to the screen in step 6 of method. Finally, the exhaust gas inseparable from the fluidized bed reactor 200 arrives, on one side, at the entrained flow reactor in step 7 of method and, on the other side, at step 9 of method, recovery.In this material flow-centered method diagram, the gas paths take interwoven routes in order to return as much heat as possible to the process and lose as little heat as possible with the exhaust gas leaving the plant in method step 4. List of reference numbers 1 Raw material 131 Activated clay 2 Crushing / drying 132 Clay 3 Sieves 133 Clay 4 Dust collector 150 Hopper 5 Preheating 200 Fluidized bed reactor 6 Sieves 205 Nozzle base 7 Thermal activation 210 Dust collector 8 Sieves 220 Heat exchanger 9 Recovery 230 Entrained flow reactor 10 Cooling 231 Exhaust gas Petition 870250084756, dated 09 / 19 / 2025, page 21 / 30 10 / 10 11 Heating 12 Fluidization / heat treatment 100 Crushed clay 110 Coarse fraction 120 Medium fraction 130 Fine fraction 240 Recovery unit 250 Screen 260 Cyclone stage 270 Crushing device 280 Heating device 290 Screen Petition 870250084756, dated 09 / 19 / 2025, page 22 / 30

Claims

1 / 5 CLAIMS 1. Method for activating clays with secondary fuel characterized in that it comprises the following steps: drying and grinding (2) wet clay as feedstock (1), thermally activating (7) the dry and ground clay (100) in a entrained flow reactor (230), wherein a first part of the clay (120, 132) is fluidized in a fluidized bed reactor (200) together with secondary fuel and the secondary fuel is burned there in the presence of that first part of the clay (120, 132), introducing the exhaust gas from the fluidized bed reactor (200), which carries with it the first part of the clay (120, 132), into the entrained flow reactor (230), where a second part of the clay (130) is thermally activated together with the first part of the clay (120, 132) in the entrained flow reactor (230) to form thermally activated clay (131).

2. Method, according to claim 1, characterized in that it comprises extracting the first part of the clay (132) from a sieve (290) disposed behind the entrained flow reactor (230) in the direction of material flow.

3. Method according to claim 1, characterized in that it comprises extracting the first part of the clay (120) from a sieve (250) disposed behind a device (270) for drying and grinding in the direction of material flow.

4. Method, according to any one of claims 1 to 3, characterized in that a residence time of the secondary fuel in the fluidized bed reactor (200) totals between 1 and 20 s, preferably between 5 and 15 s. Petition 870250084756, dated 19 / 09 / 2025, page 23 / 30 2 / 5 5. Method, according to any one of claims 1 to 4, characterized in that it comprises recovering heat from a portion of thermally activated clay (131) as thermally activated clay (133) in a cyclone stage as recuperator (240).

6. Method according to claim 5, characterized in that it comprises cooling thermally activated clay (133) with a fresh gas which, after cooling the thermally activated clay (133), is passed under a nozzle base (205) of the fluidized bed reactor (200).

7. Method, according to any one of claims 1 to 6, characterized in that it comprises discharging non-volatile secondary fuel impurities and / or oversized ash particles from the fluidized bed at the height of a nozzle base (205) of the fluidized bed reactor (200).

8. Method, according to any one of claims 1 to 7, characterized in that it comprises drying and grinding (2) moist clay as raw material (1) in a device (270) for drying and grinding, sieving (3) the dry and ground clay (100) in a sieve (250) with an outlet for a medium fraction (120), wherein a) a coarse sieved fraction (110) of the dry and ground clay (100) is taken back to the device (270) for drying and grinding, b) the medium sieved fraction (120) of the dry and ground clay (100) is passed to a fluidized bed reactor (200) and c) a fine sieved fraction (130) of the dry and ground clay (100) suspended in the sieving air is passed to a dust collector. Petition 870250084756, dated 19 / 09 / 2025, p. 24 / 30 3 / 5 (210), remove dust (4) from the screening air in the dust collector (210), wherein a) the fine fraction (130) is passed from the screening air to a heat exchanger (220),b) a first part of the dust-free screening air is discarded as exhaust gas; c) a second part of the dust-free screening air is passed back to the device (270) for drying and grinding, preheating (5) the fine fraction (130) in the heat exchanger (220) with exhaust gas (231) from an entrained flow reactor (230), screening (6) the preheated fine fraction (130) and thermally activating (7) the preheated fine fraction (130) in the entrained flow reactor (230) to form activated clay (131), screening (8) the activated clay (131) in the previous step and introducing a first part of this activated clay (131) as thermally activated clay (133) into a recuperator (240) and introducing a second part of this activated clay (131) as thermally activated clay (132) into the fluidized bed reactor (200) together with the average fraction (120) of dry and crushed clay (100) from the sieve (250),recover (9) the heat from the thermally activated clay (133) in a cyclone stage as recuperator (240), wherein the heat is transmitted from the thermally activated clay (133) to an exhaust gas from the fluidized bed reactor (200) and cools the thermally activated clay (133) and wherein the aforementioned exhaust gas is passed from the fluidized bed reactor (200) to the entrained flow reactor (230), cool (10) the thermally activated clay (133) in a cyclone stage (260) operated with fresh gas, whose exhaust gas is passed as heated fresh gas Petition 870250084756, dated 19 / 09 / 2025, page. 25 / 30 4 / 5 a) with a first part for the fluidized bed reactor (200), b) with a second part for the entrained flow reactor (230), c) with a third part for a heating device (280) d) with a fourth part for the recuperator (240),wherein an exhaust gas from the heating device (280) is passed back to the device (270) for drying and grinding, wherein the clay (120, 132) introduced therein is fluidized together with the secondary fuel in the fluidized bed reactor (200) and therein the secondary fuel is ignited, wherein the inseparable exhaust gas is passed from the fluidized bed reactor (200) a) with a first part to the entrained flow reactor (230) and b) with a second part to the cyclone stage as recuperator (240).

9. Installation for carrying out the method for thermal activation of clays with secondary fuel as defined in any of claims 1 to 8 characterized in that it comprises: a device (270) for drying and grinding wet clay as raw material (1), a entrained flow reactor (230) for thermally activating the dry and ground clay (100), a fluidized bed reactor (200) for combustion of secondary fuel in the presence of clay, wherein the device (270) for drying and grinding in the direction of material flow a) connected to the entrained flow reactor (230) through a heat exchanger (220) and Petition 870250084756, dated 19 / 09 / 2025, p.26 / 30 5 / 5 b) connected to the fluidized bed reactor (200) via a line for a mean fraction (120) and the fluidized bed reactor (200) a) is connected by an exhaust gas line to the entrained flow reactor (230) and b) an exhaust gas line is connected to a recuperator (240) that returns heat from the thermally activated clay (133) of the entrained flow reactor (230) to the entrained flow reactor (230) with a gas and c) connected with a clay supply line to a heat exchanger cyclone (220). Petition 870250084756, dated 19 / 09 / 2025, page 27 / 30.

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