COLOR OPTIMIZATION OF ACTIVATED TONES WITH AMMONIA

Description

[0001] The invention relates to a method for color optimization of activated tones.

[0002] To reduce their CO₂ footprint, the building materials industry is increasingly using activated clays as binders and substitutes for cement clinker. Unlike the production of clinker from limestone, this process releases little to no carbon dioxide from the raw material, the clay. However, most clays contain a certain amount of iron, which is typically oxidized to iron(III) during activation, giving the product an undesirable red color. Therefore, the still-hot activated clay is color-optimized immediately after activation. This color optimization usually takes place in a color optimization unit downstream of the activation unit. For color optimization, substances such as coal or hydrocarbons, like propane, are used. However, this process also generates carbon dioxide.

[0003] From WO 2016 / 173 795 A1 a plant and a process for the thermal treatment of aircraft-grade raw material are known.

[0004] A clinker substitute made of aluminium silicate and dolomite is known from WO 2017 / 202 849 A1.

[0005] Energy recovery during the cooling of color-optimized clays is known from DE 10 2020 211 750 A1.

[0006] From DE 10 2008 020 600 B4 a process and a plant for the heat treatment of fine-grained mineral solids are known.

[0007] From DE 10 2022 209 826 A1, the avoidance of emissions in the production of artificial pozzolans from mineral material, in particular clays, is known.

[0008] From WO 2024 / 079 675 A1, an electrical activation system and a method for the electrical activation and provision of a cement additive are known. The object of the invention is to provide a device and a method for color optimization of activated clays, which avoids carbon dioxide emissions. This object is achieved by the method with the features specified in claim 1.

[0009] Advantageous further developments result from the subclaims, the following description and the drawing.

[0010] A device for carrying out the process according to the invention serves to activate clays. The device is designed for activation and color optimization. Such devices are widely known in the prior art. The device comprises an activation device for thermal activation and a color optimization device downstream of the activation device. The activation device can, for example, consist of a preheater and a fluidized bed calciner. The color optimization device can, for example, consist of a fluidized bed reactor. The exact design of the activation device and the color optimization is arbitrary for the purposes of the invention and is known to those skilled in the art in a wide variety of embodiments. The advantage is that these are two separate process steps in two separate components, which can therefore be optimized independently of each other.In particular, the activation device can be operated in an oxidizing environment, for example, to safely combust alternative fuels. Color optimization in the color optimization device is achieved by supplying ammonia in a reducing atmosphere. The separate design also allows for optimal temperature control. Specifically, the use of ammonia (NH₃) or NH₃-containing compounds as reducing agents allows for significantly lower temperatures in the color optimization device compared to carbon-based reducing agents, such as coal dust.

[0011] According to the invention, the device, preferably the color optimization device, has a feed for ammonia or NH3-containing compounds. Crucially, this allows ammonia or NH3-containing compounds to be supplied to the color optimization device as a reducing agent. This eliminates the need for carbon-containing reducing agents such as coal or propane. Ammonia or NH3-containing compounds are increasingly being produced sustainably, i.e., without carbon dioxide as a byproduct or greenhouse gas. Therefore, the use of ammonia or NH3-containing compounds enables carbon dioxide-free color optimization. It has been shown that ammonia or NH3-containing compounds are particularly suitable as reducing agents for the color-imparting iron(III) centers and are capable of converting them into gray-colored magnetite.Another advantage of using ammonia is that any unused ammonia in the process can be used either as a carbon dioxide-free fuel and / or for the non-catalytic reduction of nitrogen oxides. Thus, ammonia or NH3-containing compounds are also advantageous compared to, for example, regeneratively produced hydrogen, which at least has no positive effect on nitrogen oxides. Furthermore, the storage and handling of ammonia or NH3-containing compounds are simpler.

[0012] According to the invention, the color optimization device has a gas outlet. The activation device has a gas inlet. The gas outlet and the gas inlet are connected to each other for the transfer of unreacted ammonia or NH3-containing compounds. This allows the ammonia or the NH3-containing compound to be used either as fuel or, preferably, after the actual combustion, for example and especially of a substitute fuel, to be supplied for the non-catalytic reduction of nitrogen oxides produced during combustion.

[0013] In a further embodiment of the invention, the color optimization device is a fluidized bed reactor. The fluidized bed reactor has proven to be particularly suitable for color optimization with ammonia or NH3-containing compounds.

[0014] In another embodiment of the invention, the color optimization device is a tubular reactor.

[0015] In another embodiment of the invention, the color optimization device is a separate flow reactor.

[0016] The invention relates to a method for optimizing the color of an activated clay in a device according to the invention. The method comprises a first oxidatively carried out activation step and a second subsequent color optimization step. Performing the steps separately in separate components allows for the separate optimization of the two steps.

[0017] For color optimization in the color optimization step, ammonia or an NH3-containing compound is added to the activated clay. Coal, propane, or a comparable carbon-based reducing agent, which produces the greenhouse gas carbon dioxide as a byproduct, is not added. This makes color optimization climate-neutral. Furthermore, this combination of activated clay with ammonia or NH3-containing compounds has proven advantageous. Presumably, the iron components of the clay act catalytically on the decomposition of the ammonia or NH3-containing compounds to produce hydrogen. In any case, the use of ammonia or NH3-containing compounds allows for significantly lower temperatures compared to the use of carbon-based reducing agents. This also leads to energy savings and ultimately to the avoidance of carbon dioxide emissions.

[0018] In a further embodiment of the invention, color optimization is carried out at temperatures between 450 °C and 900 °C. Successful color optimization can thus be achieved even within the temperature range of 450 to 550 °C, which is energetically advantageous compared to the usual higher temperature range of 800 to 900 °C. This also reduces the problems and risks of re-oxidation during cooling. In a further embodiment of the invention, the ammonia or NH3-containing compounds not reacted during color optimization are fed from the activation device. This allows the ammonia or NH3-containing compounds to be used as fuel and / or as an agent for SNCR, with the SNCR reaction preferably also being carried out within a temperature range of 800 °C to 900 °C, for example, in the middle or at the end of a fluidized bed calciner as part of the activation device.

[0019] In a further embodiment of the invention, the ammonia or NH3-containing compounds are supplied in a gas mixture, preferably in a gas mixture containing carbon dioxide. For example, exhaust gas is used as the carbon dioxide-containing gas mixture.

[0020] In the process according to the invention, ammonia or an NH3-containing compound is used to optimize the color of an activated clay. Previously, carbon or hydrocarbon compounds or hydrogen were used for color optimization. The use of ammonia or NH3-containing compounds, in particular green-derived ammonia or NH3-containing compounds, is not only particularly well-suited for color optimization, but is also particularly well-suited for carbon dioxide-free color optimization.

[0021] The device according to the invention is explained in more detail below with reference to an embodiment shown in the drawing. Fig. 1 Exemplary device

[0022] In Fig. 1 An exemplary device is shown in a highly schematic form, which also serves as an example to illustrate the procedure.

[0023] The clay to be activated is fed into a preheater 10 via material feed 11, preheated, and from there transferred to a calciner 20, where the thermal activation of the clay takes place. A gas stream, which can originate from the material cooler 40, is supplied to the calciner 20 via a gas feed, and fuel is supplied via the fuel feed 22. A secondary fuel, such as biomass, can be used as fuel. The activated clay 23 is transferred to the color optimization device 30, for example, a fluidized bed reactor. Ammonia is supplied to the color optimization device 30 via an ammonia feed 31. The ammonia reacts with the iron(III) compounds, leading to a decolorization / graying of the product.Unused ammonia is transferred via the ammonia transfer unit 32 into the calcinator 20, for example, also into a combustion chamber of the calcinator 20, where, for example, alternative fuels are burned at a temperature of 850 °C for at least 2 seconds to convert the nitrogen oxides produced there non-catalytically. The activated and color-optimized clay is transferred from the color optimization device 30 into a material cooler 40 and removed from it as the finished product 41. Reference sign

[0024] 10 Preheater 11 Material feed 12 Exhaust outlet 20 Calcinator 21 Gas feed 22 Fuel feed 23 Activated clay 30 Color optimization device 31 Ammonia feed 32 Ammonia transfer 40 Material cooler 41 Product

Claims

1. Method for color optimization of an activated clay (23) in a device, wherein the device is for activation of clays, wherein the device is designed for activation and for color optimization, wherein the device comprises an activation device for thermal activation and a color optimization device (30) downstream of the activation device, wherein the color optimization device (30) comprises a feed for ammonia or an NH3-containing compound (31), wherein the method comprises a first oxidatively carried out activation step and a second subsequent color optimization step, wherein for color optimization in the color optimization step ammonia or an NH3-containing compound is supplied to the activated clay (23), characterized in that the color optimization device (30) comprises a gas outlet, wherein the activation device comprises a gas inlet, wherein the gas outlet and the gas inlet are connected to one another for transfer of unreacted ammonia or NH3-containing compounds.

2. Method according to claim 1, characterized in that the color optimization device (30) is a fluidized bed reactor.

3. Method according to one of the preceding claims, characterized in that the color optimization device (30) is a tubular reactor.

4. Method according to one of the preceding claims, characterized in that the color optimization device (30) is a separate entrained flow reactor.

5. Method according to one of the preceding claims, characterized in that the color optimization is carried out at 450 °C to 900 °C, preferably at 450 to 550 °C.

6. Method according to one of the preceding claims, characterized in that the ammonia or NH3-containing compounds not reacted during the color optimization are supplied from the activation device.

7. Method according to one of the preceding claims, characterized in that the ammonia or NH3-containing compounds are supplied in a gas mixture, preferably in a carbon dioxide-containing gas mixture.