System for producing thermally activated materials

Abstract

The present invention relates to a system (10) for producing thermally activated materials, wherein: the system (10) has a thermal activation device (20); the thermal activation device (20) has a material cooler (24); the thermal activation device (20) has a feed for oxygen-enriched gas (30); the system (10) has an air separation system (40); the air separation system (40) has an oxygen outlet (41) for oxygen-enriched gas and a nitrogen outlet (42) for nitrogen-enriched gas; the oxygen outlet (41) is connected to the feed for oxygen-enriched gas (30); the system (10) has a combustible material processing device (50, 55, 56); the combustible material processing device (50, 55, 56) has a protective gas inlet (52), characterised in that the nitrogen outlet (42) and the protective gas inlet (52) are connected together directly or via a gas heating device, wherein the material cooler (24) is connected at least partially as the gas heating device.

Description

[0001] PLANT FOR THE PRODUCTION OF THERMALLY ACTIVATED MATERIALS

[0002] The invention relates to a plant, for example for the production of cement clinker, according to the oxyfuel process with a safe preparation of fuels without dilution of the enriched carbon dioxide exhaust gas stream.

[0003] Plants for the thermal treatment of materials, such as cement production plants, contain a multitude of devices, which are often complexly interconnected. For example, such plants typically have a grinding device for fuels, such as coal, but also alternative fuels, such as biomass. To prevent the ignition of these materials during grinding, the exhaust gas from the actual thermal treatment is usually used, in which the oxygen has largely been converted to carbon dioxide. Due to the residual heat, this gas is also suitable for drying the fuel, particularly with moist fuels.

[0004] As part of the effort to avoid carbon dioxide emissions and mitigate climate change, plants are increasingly being redesigned. A key approach is the so-called oxyfuel process. By using the purest possible oxygen, the exhaust gas produced is almost pure carbon dioxide (after water separation), eliminating the need for complex nitrogen separation. To make this process efficient, it is important to prevent other gases from secondary air sources, such as ambient nitrogen, from entering the exhaust gas.

[0005] Such oxyfuel processes are known from DE 10 2018 206 673 A1 and DE 10 2018 206 674 A1.

[0006] The combustion of coal dust is known from JP S59 24115 A.

[0007] WO 94 / 24484 A1 discloses a method for reducing emissions during waste incineration. US 2014 / 238281 A1 discloses a method for supplying pulverized fuel to a combustion device using the oxyfuel process.

[0008] This means, however, that it is unfavorable to channel such carbon dioxide-enriched exhaust gas through a mill, as the mill's unavoidable inlet air leads to unwanted dilution of the exhaust gas. This, in turn, means that this protective gas is no longer available for the grinding devices, especially for grinding fuels.

[0009] The object of the invention is to provide an atmosphere suitable for the grinding of combustible materials throughout the entire plant network.

[0010] This object is achieved by the system having the features specified in claim 1. Advantageous further developments emerge from the subclaims, the following description, and the drawings.

[0011] The plant according to the invention is used to produce thermally activated materials. Examples of such plants can be found, for example, in the cement industry, for example in the production of clinker from limestone or in the thermal activation of clays. Such plants can also be found in ore processing, for example in the roasting of lithium ores. The plant comprises a device for thermal activation. This can have any embodiment according to the prior art, and a multitude of different embodiments are familiar to those skilled in the art. The device for thermal activation has a supply for oxygen-enriched gas. The device for thermal activation is thus operated according to the oxyfuel process in order to have the purest possible carbon dioxide as exhaust gas, which eliminates the need for a complex carbon dioxide separation process and saves investment and energy.The plant features an air separation unit. This provides the oxygen-rich gas stream for oxyfuel operation. The air separation unit has an oxygen outlet for oxygen-enriched gas and a nitrogen outlet for nitrogen-enriched gas. The oxygen outlet is connected to the oxygen-enriched gas supply. The plant also features a processing device for combustible materials. Combustible materials can be, for example, coal or alternative fuels such as biomass. When processing combustible materials, for example during grinding, dusts in particular can generate highly flammable or even explosive mixtures, making an oxygen-depleted atmosphere advantageous or even necessary. For example, the processing device for combustible materials prepares the fuel required in the thermal activation device.The processing device for flammable materials has a protective gas inlet.

[0012] According to the invention, the nitrogen outlet and the protective gas inlet are connected via a gas heating device. This means that the gas depleted by combustion in the thermal activation device is no longer used in the combustible material processing device, as was previously the case, so that this carbon dioxide-containing gas is not diluted by secondary air in the combustible material processing device. Instead, the nitrogen-enriched gas stream from the air separation plant is used. For this purpose, the nitrogen-enriched gas stream from the air separation plant is passed through a gas heating device and preheated.

[0013] According to the invention, the device for thermal activation comprises a material cooler. The material cooler is at least partially connected as a gas heating device, i.e., arranged between the nitrogen outlet and the protective gas inlet. In some cases, it is preferred, and in particular, the material cooler is divided into three zones. The first zone is the hottest, into which the hot material enters. In this first zone, cooling takes place with the oxygen-rich gas in order to preheat it to the maximum for the thermal treatment and thus retain as much heat as possible in the process. The second zone is connected to the nitrogen outlet and serves to preheat the nitrogen-enriched gas. This utilizes this low-calorific energy, which is also sufficiently warm for drying a material. In the last and coldest third zone, for example, a final cooling takes place with ambient air.

[0014] In a further embodiment of the invention, the processing device for combustible materials is a grinding device and / or a drying device. The processing device can be a simple mill, for example, for producing coal dust. The processing device can be a grinding or crushing device followed by a riser dryer, i.e., a combination of grinding device and drying device. This is advantageous, for example, for wood as a substitute fuel. Or it can be a pure drying device, for example, to initially sufficiently dewater biomass. Two processing devices can also be provided: one as a pure drying device and one as a combination of grinding device and drying device.

[0015] In a further embodiment of the invention, the thermal activation device has an exhaust gas outlet. The exhaust gas outlet can, for example, be arranged downstream of a preheater. It is the point at which the gas stream leaves the thermal activation device. The exhaust gas outlet is connected to a heat exchanger. The heat exchanger is connected as a gas heating device. This means that the heat exchanger has a first inlet on one side, which is connected to the exhaust gas outlet. The outlet of the first side can, for example, be connected to a carbon dioxide liquefaction plant. The other side is for the heat-absorbing gas, specifically the nitrogen-enriched gas, and therefore the inlet of the second side is connected to the nitrogen outlet and the outlet of the second side is connected to the protective gas inlet. The heat exchanger is preferably a recuperative heat exchanger or a regenerating heat exchanger.The heat exchanger is particularly preferably a rotary heat exchanger.

[0016] In a further embodiment of the invention, the air separation plant is a cryogenic air separation plant. While air separation using the membrane process or pressure swing adsorption is also conceivable, cryogenic air separation is currently still advantageous for the required amount of oxygen and the desired purity.

[0017] The system according to the invention is explained in more detail below with reference to exemplary embodiments shown in the drawings. Fig. 1 first example according to the invention

[0018] Fig. 2 second alternative example

[0019] Fig. 1 shows a first example of a plant 10 according to the invention. The plant comprises a thermal activation device 20. The thermal activation device 20 comprises, for example, a material feed 28 through which limestone, for example, is fed. This supplied material is preheated in the preheater 21, calcined in the calciner 22, and fired in the rotary kiln 23. The product is cooled in a material cooler 24 and removed via the product discharge.

[0020] One thermal activation device 20 is operated according to the oxyfuel process, i.e., preferably with the highest possible oxygen content in order to ultimately obtain the highest possible carbon dioxide content. For this purpose, the plant comprises an air separation plant 40, from which oxygen-enriched gas, for example, with over 95 vol.% oxygen, is fed from an oxygen outlet 41 to an oxygen-enriched gas feed 30, in this case the first zone 25 of the material cooler 24. There, the oxygen-rich gas is preheated and then transferred to the rotary kiln 23. The gas exiting the preheater 21 is transferred to a carbon dioxide liquefaction plant 60 via an exhaust outlet 61.

[0021] The nitrogen-enriched gas stream is fed via the nitrogen outlet 42 to the second zone 26 of the material cooler 24, where it is preheated. The preheated nitrogen-enriched gas stream is fed via the protective gas inlet 52 to a first processing device for combustible materials 50, for example, a mill with a connected riser dryer. A fuel is supplied via a fuel supply 51, crushed and dried, and then fed, for example, to the calciner 22.

[0022] Fig. 2 shows a second example of an alternative plant 10. The thermal activation device 20 corresponds to the first example. The oxygen-enriched gas is fed directly and without preheating to the rotary kiln 23 via the oxygen-enriched gas feed 30. The exhaust gases from the preheater 21 are first fed to a heat exchanger 70 via the exhaust gas outlet 61 before entering the carbon dioxide liquefaction plant 60. The nitrogen-containing gas stream passes from the nitrogen outlet 42 into the heat exchanger 70 and is heated there. For the use of very moist fuels, the plant 10 has a second combustible material processing device 55 in the form of a dryer and a third combustible material processing device 56 in the form of a mill.Both the second combustible material processing device 55 and the third combustible material processing device 56 have a protective gas inlet 52 and are supplied with nitrogen-containing gas heated in the preheater 70.

[0023] Reference symbol

[0024] 10 Plant for the production of thermally activated materials

[0025] 20 Device for thermal activation

[0026] 21 preheaters

[0027] 22 Calciner

[0028] 23 rotary kilns

[0029] 24 material coolers

[0030] 25 first zone

[0031] 26 second zone

[0032] 27 third zone

[0033] 28 Material supply

[0034] 29 Product removal

[0035] 30 Supply for oxygen-enriched gas

[0036] 40 air separation plant

[0037] 41 Oxygen outlet

[0038] 42 Nitrogen outlet

[0039] 50 first processing device for combustible substances

[0040] 51 Fuel supply

[0041] 52 Shielding gas inlet

[0042] 55 second processing device for combustible substances

[0043] 56 third processing device for combustible substances

[0044] 60 carbon dioxide liquefaction plant

[0045] 61 Exhaust outlet

[0046] 70 heat exchangers

Claims

Patent claims 1. Plant (10) for producing thermally activated materials, wherein the plant (10) comprises a device for thermal activation (20), wherein the device for thermal activation (20) comprises a material cooler (24), wherein the device for thermal activation (20) comprises a supply for oxygen-enriched gas (30), wherein the plant (10) comprises an air separation plant (40), wherein the air separation plant (40) comprises an oxygen outlet (41) for oxygen-enriched gas and a nitrogen outlet (42) for nitrogen-enriched gas, wherein the oxygen outlet (41) is connected to the supply for oxygen-enriched gas (30), wherein the plant (10) comprises a processing device for combustible substances (50, 55, 56), wherein the processing device for combustible substances (50, 55, 56) comprises a protective gas inlet (52), characterized in thatthat the nitrogen outlet (42) and the protective gas inlet (52) are connected to each other via a gas heating device, wherein the material cooler (24) is at least partially connected as a gas heating device.

2. Plant (10) according to claim 1, characterized in that the processing device for combustible substances (50, 55, 56) is a grinding device and / or a drying device.

3. Plant (10) according to one of the preceding claims, characterized in that the device for thermal activation (20) has an exhaust gas outlet (61), wherein the exhaust gas outlet (61) is connected to a heat exchanger (70), wherein the heat exchanger (70) is connected as a gas heating device.

4. Plant (10) according to claim 3, characterized in that the heat exchanger (70) is a recuperative heat exchanger (70) or a regenerating heat exchanger (70).

5. System (10) according to claim 3, characterized in that the heat exchanger (70) is a rotary heat exchanger.

6. Plant (10) according to one of the preceding claims, characterized in that the air separation plant (40) is a cryogenic air separation plant (40).

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