A method and system for calcining cement clinker using microwaves and infrared radiation.

Abstract

This invention provides a method and system for calcining cement clinker using microwave and infrared radiation, belonging to the field of cement production technology. The method includes the following steps: preheating cement raw materials in a preheater to obtain preheated material; decomposing the preheated material in a decomposition furnace under infrared heating and a first microwave heating condition to obtain decomposed material; calcining the decomposed material in a rotary kiln under a second microwave heating condition; and cooling the resulting calcined material in a cooler to obtain cement clinker. This invention utilizes infrared heating and microwave heating to convert electrical energy into thermal energy, thereby replacing the energy generated by burning natural carbonaceous fossil fuels. This not only reduces CO2 emissions from fossil fuel combustion, achieving low-carbon operation, but also significantly reduces the amount of air required for combustion, achieving a high solid-to-gas ratio process in the preheater system, thus greatly improving the preheater system's raw material processing capacity.

Description

Technical Field

[0001] This invention belongs to the field of cement production technology, specifically relating to a method and system for calcining cement clinker using microwaves and infrared rays. Background Technology

[0002] The cement industry is a traditional major energy consumer and carbon emitter, especially in the calcination process of cement clinker, which requires the use of large amounts of fossil fuels, greatly increasing the amount of carbon dioxide emissions into the atmosphere.

[0003] Reducing the use of fossil fuels in the cement industry is of great significance for reducing the total emissions of the greenhouse gas carbon dioxide. Replacing some or all of fossil fuels with clean energy such as electricity is a direction that the cement industry should focus on and research.

[0004] There are currently two ways to convert electrical energy into heat energy. One is microwaves, which, as a heating medium, have the advantages of uniform heating and high efficiency, but microwaves are only effective for polar molecules. The other is infrared radiation, which is the opposite of microwave heating. Microwaves heat from the inside out, while infrared heats from the outside in, and the heat receptors for infrared radiation are not limited to polar molecules. Therefore, heating materials with microwaves and infrared radiation separately or in combination to reduce the use of fossil fuels can help reduce carbon emissions in the cement industry. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for calcining cement clinker using microwaves and infrared radiation. The method provided by this invention reduces CO2 emissions from the combustion of fossil fuels.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for calcining cement clinker using microwaves and infrared radiation, comprising the following steps:

[0008] The cement raw meal is preheated in a preheater to obtain preheated material;

[0009] The infrared heating device and the first microwave generating device are turned on, and the preheated material is decomposed in the decomposition furnace under the conditions of infrared heating and first microwave heating to obtain the decomposed material.

[0010] The second microwave generator and the rotary kiln head burner are turned on, and the decomposed material is calcined in the rotary kiln under the second microwave heating condition. The calcined material is then cooled in a cooler to obtain cement clinker.

[0011] Preferably, the raw materials for preparing the cement raw meal include calcareous raw materials, silica-alumina raw materials, and ferrous raw materials.

[0012] Preferably, in the cement raw material, the mass fraction of CaO is 61-66%, the mass fraction of SiO2 is 19-21%, the mass fraction of Al2O3 is 5.0-6.5%, and the mass fraction of Fe2O3 is 2.5-4.5%.

[0013] Preferably, the cement raw meal has a fineness of 0.08–0.10 mm and a moisture content of <1.0%.

[0014] Preferably, the preheating temperature is 850–920°C; the decomposition treatment conditions include: the temperature inside the decomposition furnace is 900–950°C, and the holding time is 10–15 seconds.

[0015] Preferably, the calcination conditions include: the calcination temperature of the rotary kiln is 1400-1450℃.

[0016] This invention provides a system for calcining cement clinker using microwaves and infrared rays, comprising a preheater, a decomposition furnace, a rotary kiln, a cooler, an infrared heating device, a first microwave generating device, a second microwave generating device, and a rotary kiln head burner; the preheater, decomposition furnace, rotary kiln, and cooler are connected sequentially; the first microwave generating device and the infrared heating device are respectively connected to the decomposition furnace for heating the decomposition furnace; the second microwave generating device is connected to the rotary kiln head burner for heating the rotary kiln.

[0017] Preferably, it also includes a waste heat power generation system and a waste heat boiler; the preheater and cooler are respectively connected to the air inlet of the waste heat boiler; the waste heat steam outlet of the waste heat boiler is connected to the waste heat power generation system; the waste heat power generation system is respectively connected to an infrared heating device, a first microwave generating device and a second microwave generating device.

[0018] Preferably, it also includes a non-waste heat power supply system; the non-waste heat power supply system is connected to the infrared heating device, the first microwave generating device, and the second microwave generating device, respectively.

[0019] Preferably, it also includes a wind power generation device, a photovoltaic power generation device, or an external power grid system, wherein the non-waste heat power supply system is connected to the wind power generation device, the photovoltaic power generation device, or the external power grid system respectively.

[0020] This invention provides a method for calcining cement clinker using microwave and infrared radiation, comprising the following steps: preheating cement raw materials in a preheater to obtain preheated material; activating an infrared heating device and a first microwave generating device, and decomposing the preheated material in a decomposition furnace under infrared heating and the first microwave heating conditions to obtain decomposed material; activating a second microwave generating device and a rotary kiln head burner, and calcining the decomposed material in a rotary kiln under the second microwave heating conditions; and cooling the obtained calcined material in a cooler to obtain cement clinker. This invention utilizes infrared heating and microwave heating to convert electrical energy into heat energy, thereby replacing the energy generated by burning natural carbonaceous fossil fuels, reducing CO2 emissions from fossil fuel combustion, and achieving low-carbon operation.

[0021] Furthermore, this invention utilizes the waste heat generated during the calcination of cement clinker to generate electricity, which is then converted into microwave and infrared heat energy that can be used for heating. This heat is then used in a first microwave generating device and an infrared heating device to heat the preheated material, promoting the decomposition of carbonates in the raw material and reducing the amount of natural fossil fuels used in the decomposition furnace to provide heat for carbonate decomposition. Simultaneously, a second microwave generating device is used in the rotary kiln to generate microwaves, which, together with the flames generated by the combustion of fossil fuels in the rotary kiln head burner, calcine the decomposed material into cement clinker. The method for calcining cement clinker provided by this invention is not only environmentally friendly, but also significantly reduces the amount of air required for combustion due to the reduced use of fossil fuels. Fossil fuel combustion requires oxygen, but oxygen only accounts for 21% of the air, while nitrogen, which makes up 78% of the air, does not participate in the reaction. This means that fossil fuel combustion not only removes a large amount of heat but also occupies a significant amount of space for chemical reactions. This demonstrates that replacing fossil fuels with electricity not only reduces carbon dioxide emissions after calcination but also significantly reduces kiln tail gas emissions. Simultaneously, it increases the solid-to-gas ratio of the preheater system, substantially increasing its hourly output and thus greatly enhancing its raw material processing capacity. In this respect, it reduces the amount of material used per unit of output, indirectly contributing to carbon emission reduction. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the system device structure in Example 1;

[0024] Figure 2The flowchart shows the process of calcining cement clinker using the system in Example 1. Detailed Implementation

[0025] This invention provides a method for calcining cement clinker using the system described above, comprising the following steps:

[0026] The cement raw meal is preheated in a preheater to obtain preheated material;

[0027] The infrared heating device and the first microwave generating device are turned on, and the preheated material is decomposed in the decomposition furnace under the conditions of infrared heating and first microwave heating to obtain the decomposed material.

[0028] The second microwave generator and the rotary kiln head burner are turned on, and the decomposed material is calcined in the rotary kiln under the second microwave heating condition. The calcined material is then cooled in a cooler to obtain cement clinker.

[0029] Unless otherwise specified, all raw materials used in this invention are commercially available products well known to those skilled in the art.

[0030] This invention preheats cement raw materials in a preheater to obtain preheated material. In this invention, the raw materials for preparing the cement raw materials preferably include calcareous raw materials, aluminosilicate raw materials, and ferrous raw materials. In this invention, the mass fraction of CaO in the cement raw materials is preferably 61-66%, the mass fraction of SiO2 is preferably 19-21%, the mass fraction of Al2O3 is preferably 5.0-6.5%, and the mass fraction of Fe2O3 is preferably 2.5-4.5%. 。 In this invention, the fineness of the cement raw meal is preferably 0.08-0.10 mm, more preferably 0.09 mm; the moisture content is preferably <1.0%. The preheating temperature in this invention is preferably 850-920℃, more preferably 900℃.

[0031] After obtaining the preheated material, the present invention decomposes the preheated material in a decomposition furnace under infrared heating and first microwave heating conditions to obtain decomposed material. In the present invention, the decomposition conditions preferably include: the temperature in the decomposition furnace is preferably 900-950℃, more preferably 920-930℃; the holding time is preferably 10-15s, more preferably 12-13s.

[0032] After obtaining the decomposed material, the present invention calcines the decomposed material in a rotary kiln under a second microwave heating condition, and cools the resulting calcined material in a cooler to obtain cement clinker. In the present invention, the preferred calcination conditions include: the calcination temperature of the rotary kiln is preferably 1400–1450°C, more preferably 1420–1430°C. The present invention does not have special requirements for the cooling method and conditions; cooling methods well known to those skilled in the art can be used.

[0033] The present invention also provides a system for calcining cement clinker using microwaves and infrared rays, comprising a preheater, a decomposition furnace, a rotary kiln, a cooler, an infrared heating device, a first microwave generating device, a second microwave generating device, and a rotary kiln head burner; the preheater, decomposition furnace, rotary kiln, and cooler are connected sequentially; the first microwave generating device and the infrared heating device are respectively connected to the decomposition furnace for heating the decomposition furnace; the second microwave generating device is connected to the rotary kiln head burner for heating the rotary kiln.

[0034] In an embodiment of the present invention, the system further includes a waste heat power generation system and a waste heat boiler. The preheater and cooler are respectively connected to the air inlet of the waste heat boiler. The waste heat steam outlet of the waste heat boiler is preferably connected to the waste heat power generation system. The waste heat power generation system is preferably connected to an infrared heating device, a first microwave generating device, and a second microwave generating device.

[0035] In an embodiment of the present invention, the system further includes a decomposition furnace burner; the decomposition furnace burner is connected to the decomposition furnace.

[0036] In an embodiment of the present invention, the system further includes a non-waste heat power supply system, which is connected to the infrared heating device, the first microwave generating device, and the second microwave generating device, respectively.

[0037] In embodiments of the present invention, the system further includes a wind power generation device, a photovoltaic power generation device, or an external power grid system, and the non-waste heat power supply system is connected to the wind power generation device, the photovoltaic power generation device, or the external power grid system respectively.

[0038] In an embodiment of the present invention, the system further includes a waste gas treatment system, wherein the waste heat steam outlet of the waste heat boiler is connected to the waste gas treatment system.

[0039] This invention utilizes the steam generated during the calcination of cement clinker to generate electricity, which is then converted into microwave and infrared heat energy for heating. This heat energy is then used by a first microwave generator and an infrared heating device to heat the preheated material, promoting the decomposition of carbonates in the raw material and reducing the amount of natural fossil fuels used in the decomposition furnace to provide heat for carbonate decomposition. Simultaneously, a second microwave generator in the rotary kiln produces microwaves, which, together with the flames generated by the combustion of fossil fuels in the kiln head burner, calcine the decomposed material into cement clinker. This invention achieves the conversion of electrical energy into heat energy through infrared heating and microwave generation, replacing the energy generated by the combustion of natural carbonaceous fossil fuels. This not only reduces CO2 emissions from fossil fuel combustion, achieving low-carbon operation, but also significantly reduces the amount of air required for combustion due to the reduced use of fossil fuels, achieving a high solid-to-gas ratio process in the preheater system, thereby greatly improving the raw material processing capacity of the preheater system.

[0040] Furthermore, the electrical energy for the first microwave generating device, the second microwave generating device, and the infrared heating device of this invention comes from two sources: a waste heat power generation system and a non-waste heat power generation system. When the electrical energy generated by the waste heat power generation system is insufficient to supply the system's operation, this invention uses a non-waste heat power supply system to power the entire system, such as a wind power generation device, a photovoltaic power generation device, or an external power grid. The technical advantage of this invention is that, regardless of whether the electrical energy comes from the waste heat power generation system, the wind power generation device, the photovoltaic power generation device, or the external power grid, the technical route for converting electrical energy into heat energy is simple, easy to control and operate, and does not pollute the environment.

[0041] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0042] The raw materials used in the preparation of cement raw materials in the examples include calcareous raw materials, siliceous aluminous raw materials and ferrous raw materials. In the cement raw materials obtained therefrom, the mass fraction of CaO is 61-66%, the mass fraction of SiO2 is 19-21%, the mass fraction of Al2O3 is 5.0-6.5%, and the mass fraction of Fe2O3 is 2.5-4.5%.

[0043] Example 1

[0044] This embodiment of the system for calcining cement clinker using microwave and infrared radiation includes a preheater, a decomposition furnace, a rotary kiln, a cooler, an infrared heating device, a first microwave generating device, a second microwave generating device, a rotary kiln head burner, a waste heat power generation system, a waste heat boiler, a decomposition furnace burner, a non-waste heat power supply system, and a waste gas treatment system. The preheater, decomposition furnace, rotary kiln, and cooler are connected sequentially. The first microwave generating device and the infrared heating device are respectively connected to the decomposition furnace, and the second microwave generating device is connected to the rotary kiln head burner. The preheater and the cooler are respectively connected to... The waste heat boiler's air inlet is connected to the waste heat steam outlet, which is connected to a waste heat power generation system. The waste heat power generation system is connected to an infrared heating device, a first microwave generator, and a second microwave generator. The decomposition furnace burner is connected to the decomposition furnace. The non-waste heat power supply system is connected to the infrared heating device, the first microwave generator, and the second microwave generator. The non-waste heat power supply system is connected to a wind power generation device, a photovoltaic power generation device, or an external power grid. The waste heat steam outlet of the waste heat boiler is connected to a waste gas treatment system. A schematic diagram of the system structure is shown below. Figure 1 As shown.

[0045] The specific operation of calcining cement clinker using the system in Example 1 is as follows:

[0046] Calcium, silica-alumina, and ferrous raw materials are mixed in a mass ratio of 80:18:2 to obtain cement raw meal (fineness 0.09mm, moisture <1.0%). The cement raw meal is then fed into a preheater to obtain preheated material at 900℃. The preheated material is then fed into a decomposition furnace, and the infrared heating device and the first microwave generator are turned on. Under the conditions of infrared heating and the first microwave heating, the material is decomposed at 900℃ for 12s to obtain decomposed material. The decomposed material is then fed into a rotary kiln, and the second microwave generator and the rotary kiln head burner are turned on. The material is then calcined at 1450℃ under the conditions of the second microwave heating. Finally, the calcined material is cooled in a cooler to obtain cement clinker.

[0047] Figure 2 The flowchart shows the process of calcining cement clinker using the system in Example 1.

[0048] The method provided by this invention for cement calcination can reduce the amount of natural fossil fuels used to 50% of the original amount, while reducing CO2 emissions by at least 20%, thus achieving low-carbon operation. Furthermore, the method provided by this invention for cement calcination can increase the raw material processing capacity of the preheater system by more than 30%.

[0049] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for calcining cement clinker by using microwave and infrared, comprising the following steps: preheating cement raw meal in a preheater to obtain preheated material; turning on an infrared heating device and a first microwave generating device, and preheating the preheated material in a decomposing furnace under the conditions of infrared heating and first microwave heating to obtain decomposed material; turning on a second microwave generating device and a rotary kiln head burner, and calcining the decomposed material in a rotary kiln under the conditions of second microwave heating to obtain calcined material, and cooling the calcined material in a cooler to obtain cement clinker; the raw materials for preparing the cement raw meal include calcareous raw materials, siliceous and aluminous raw materials and ferruginous raw materials; in the cement raw meal, the mass fraction of CaO is 61-66%, the mass fraction of SiO2 is 19-21%, the mass fraction of Al2O3 is 5.0-6.5%, and the mass fraction of Fe2O3 is 2.5-4.5%; the fineness of the cement raw meal is 0.08-0.10 mm, and the moisture is less than 1.0%; the preheating temperature is 850-920℃; the conditions for the preheating process include that the temperature in the decomposing furnace is 920-930℃, and the holding time is 10-15 s; the conditions for the calcining process include that the calcining temperature of the rotary kiln is 1400-1450℃.

2. A system for implementing the method of claim 1, comprising a preheater, a decomposing furnace, a rotary kiln, a cooler, an infrared heating device, a first microwave generating device, a second microwave generating device and a rotary kiln head burner; the preheater, the decomposing furnace, the rotary kiln and the cooler are sequentially communicated; the first microwave generating device and the infrared heating device are connected with the decomposing furnace respectively for heating the decomposing furnace; the second microwave generating device is connected with the rotary kiln head burner for heating the rotary kiln. It further comprises a waste heat power generation system and a waste heat boiler; the preheater and the cooler are communicated with the gas inlet of the waste heat boiler respectively; the waste heat steam outlet of the waste heat boiler is communicated with the waste heat power generation system; the waste heat power generation system is connected with the infrared heating device, the first microwave generating device and the second microwave generating device respectively. It further comprises a non-waste heat power supply system; the non-waste heat power supply system is connected with the infrared heating device, the first microwave generating device and the second microwave generating device respectively. It further comprises a wind power generation device, a photovoltaic power generation device or an external power grid system; the non-waste heat power supply system is connected with the wind power generation device, the photovoltaic power generation device or the external power grid system respectively. ​ ​ ​ ​ ​ 3. The system of claim 2, wherein, ​ 4. The system of claim 3, wherein, ​ 5. The system of claim 4, wherein, ​

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