Calcium oxide-based raw material for producing cement clinker based on green electric energy as well as preparation method and application of calcium oxide-based raw material

Abstract

The invention belongs to the technical field of cement, and provides a calcium oxide-based raw material based on green electric energy and a preparation method and application thereof, and the method comprises the following steps: carrying out high temperature decomposition on a limestone raw material mainly composed of limestone blocks to obtain a lime product with blocky lime as a main product; grinding the lime product to obtain the calcium oxide-based raw material; and calcining the calcium oxide-based raw material to obtain the cement clinker. Compared with the calcium carbonate-based raw material which is prepared by the traditional cement clinker production, the calcium oxide-based raw material provided by the invention not only reduces the raw material amount of a raw material mill, but also can greatly reduce the grinding energy consumption by using a porous, loose and very easy-to-grind lime product which takes blocky lime as a main product. Moreover, the lime product obtained by the method directly exchanges heat with other raw materials and is ground, so that the technological process is simplified on the basis of fully utilizing energy.

Description

Technical Field

[0001] The present invention relates to the technical field of cement, and in particular to a calcium oxide-based raw material for producing cement clinker based on green electric energy, and a preparation method and application thereof. Background Art

[0002] The main raw materials for cement production are composed of four major components of ores: calcium carbonate, silicon dioxide, aluminum oxide, and iron oxide. The four major representative ores are mainly limestone, sandstone, bauxite, and iron ore. The main production process of cement is to measure and mix the above-mentioned block ores according to the batching ratio, and then transport them into the raw mill. The material is ground into calcium carbonate-based raw material powder by the raw mill, and then calcined in a high-temperature rotary kiln at about 1450°C to form clinker. Among them, the main component of calcium carbonate-based raw material is calcium carbonate, which usually accounts for about 90%. Therefore, the grinding object of the grinding process is mainly limestone, which requires a lot of electricity to complete the grinding process. Grinding limestone is the main energy consumption factor in cement production. In view of this, the present invention is proposed. Summary of the invention

[0003] The present invention provides a calcium oxide-based raw material for producing cement clinker based on green electric energy, and a preparation method and application thereof, which are used to solve the defect of high energy consumption of grinding limestone in cement production in the prior art. By subjecting the limestone raw material mainly composed of limestone blocks to high-temperature decomposition, not only the amount of raw material for raw material grinding is reduced, but also the dense and hard limestone raw material is converted into a porous, loose and very easy-to-grind lime product with block lime as the main product, thereby greatly reducing the grinding energy consumption. Moreover, the lime product obtained by the method is directly subjected to heat exchange with other raw materials, such as sandstone, bauxite and iron ore, and then ground, which simplifies the process flow on the basis of fully utilizing energy.

[0004] Specifically, the present invention provides a method for preparing calcium oxide-based raw materials for cement clinker production, comprising: pyrolyzing a limestone raw material mainly composed of limestone blocks to obtain a lime product with block lime as the main product; and then grinding the lime product to obtain the calcium oxide-based raw material.

[0005] In the traditional cement clinker production process, limestone blocks are usually first crushed and ground into calcium carbonate-based raw material fine powder, and then heated and calcined. This process causes the cement industry to have the characteristic of high energy consumption. The present invention not only reduces the amount of raw material for raw material grinding by subjecting limestone raw materials mainly composed of limestone blocks to high-temperature decomposition to release carbon dioxide, but also converts the dense and hard limestone raw materials into porous, loose and very easy to grind lime products with block lime as the main product, greatly reducing the grinding energy consumption. For example, to obtain the same quality of cement clinker, it is originally necessary to grind 100 tons of limestone. After decomposition, only 60 tons of porous, loose, very easy to grind, and low grinding energy consumption block lime products need to be ground in the method of the present invention, thereby greatly reducing the grinding energy consumption. Moreover, the method simplifies the process flow on the basis of fully utilizing energy, and provides a new method for cement clinker production. Compared with the traditional method, the new method has the characteristics of energy saving and consumption reduction when preparing cement clinker.

[0006] The calcium oxide-based raw material is calcined to obtain the cement clinker. During grinding, other raw materials are mixed with the lime product according to the component requirements of the calcium oxide-based raw material. The other raw materials can be mixed with the lime product first and then ground together, or the lime product can be ground first and then mixed with other raw materials.

[0007] According to the method for preparing calcium oxide-based raw materials for cement clinker production provided by the present invention, a continuous thermal decomposition process is adopted, wherein the limestone raw materials are continuously introduced into a vertical or inclined decomposition furnace cavity in an upper-in and lower-out manner, and are stacked in the furnace cavity to perform heat exchange with the airflow rising from bottom to top in the decomposition furnace, thereby achieving the high-temperature decomposition;

[0008] The pressure in the furnace chamber of the decomposition furnace is -5×10 4 ~-1.5×10 5 Pa (negative pressure), CO in the decomposition furnace chamber 2 The concentration of the waste gas is 80-99%, and is discharged from the middle and upper part of the furnace cavity along with the air flow for recycling.

[0009] The present invention makes the block limestone entering the decomposition furnace in a piled state, and continuously produces in a short process mode of top-in and bottom-out. The block limestone reacts with the CO generated by decomposition and rising in the process of descending. 2 Countercurrent heat exchange is carried out. The block limestone can roll freely in the electric thermal decomposition furnace. The temperature of the limestone blocks becomes higher and higher during the descent. The gaps between the blocks provide a thermal channel for heat conduction and achieve sufficient heat exchange. At the same time, the gaps are also the CO generated by the decomposition of limestone. 2 The rising hot CO 2 The gas undergoes countercurrent heat exchange with the relatively low temperature limestone at the top of the decomposition furnace, reducing the high concentration of CO2 is extracted from the decomposition furnace and used for related CO 2 In the experiment, it was found that by controlling the pressure, temperature, reaction time and CO 2 The concentration helps to improve the decomposition and conversion of limestone to reduce the decomposition energy consumption. Obtaining high-quality lime is beneficial to the clinker calcination and manufacturing, and obtaining high-quality clinker, which is specifically reflected in: the CV value of the strength index of cement clinker is significantly reduced.

[0010] According to the method for preparing calcium oxide-based raw materials for cement clinker production provided by the present invention, the temperature in the decomposition furnace is 500-1150° C., and the temperature gradually increases from top to bottom.

[0011] The temperature in the decomposition furnace plays a key role in the decomposition of limestone blocks. The specific temperature control affects its decomposition rate. The decomposition rate is the ratio of the decomposed limestone to the initial total amount of limestone. When the decomposition furnace cavity is divided into three sections of upper, middle and lower temperature control, and the three sections are 500-700°C, 720-880°C and 900-950°C respectively, the decomposition rate can reach 88-98%, further improving the quality of cement clinker, which is specifically reflected in: the CV value of the strength index of cement clinker is significantly reduced.

[0012] According to the method for preparing calcium oxide-based raw material for cement clinker production provided by the present invention, the residence time of the limestone raw material in the decomposition furnace is 2 to 30 minutes.

[0013] When the limestone raw material is decomposed by the method of the present invention, the size of the limestone raw material and the size of the obtained lime product will not change significantly. Generally speaking, the limestone raw material containing limestone blocks with a volume ratio of more than 80% and a particle size range of 0 to 50 mm can be used.

[0014] The stacked limestone raw materials in the present invention slowly descend in the furnace cavity, and the residence time of the limestone raw materials in the decomposition furnace is controlled by the discharge amount of the bottom discharge port. It is found in experiments that when the residence time is controlled within the above range, it is beneficial to obtain higher quality cement clinker, which is specifically reflected in: the CV value of the strength index of the cement clinker is significantly reduced. If the time is too long, it will be detrimental to the improvement of the quality of the cement clinker.

[0015] According to the method for preparing calcium oxide-based raw materials for cement clinker production provided by the present invention, the airflow is discharged from the middle and upper part of the furnace cavity using a fan with adjustable exhaust volume, and no other air-extraction devices are additionally used in the process of preparing the lime product from the limestone raw materials.

[0016] In the traditional technology, since it is necessary to decompose the limestone raw materials with fine powder structure, a suspension decomposition furnace is often used for the decomposition. The method of the present invention completely abandons the technology that the suspension decomposition furnace needs a huge amount of air to complete the suspension decomposition, because this part of the high-temperature calorific value air will eventually be discharged to the atmosphere, resulting in a huge waste of heat energy. In the present invention, the decomposition furnace does not need to pull air to produce the suspension state, and all the process materials are used without any waste, and most of the heat energy is sealed in the decomposition furnace for use. A short process is achieved to simplify cement production and manufacturing, which is essentially different from the current powder suspension decomposition furnace process for cement production and manufacturing.

[0017] According to the method for preparing calcium oxide-based raw material for cement clinker production provided by the present invention, the lime product contains block lime with a volume proportion of more than 80% and a particle size range of 0 to 50 mm, the temperature of the lime product obtained by high-temperature decomposition is 800 to 1100°C, and is directly used for heat exchange with sandstone, bauxite and iron ore (that is, no intermediate links such as grinding and sorting are performed before heat exchange) and grinding to obtain the calcium oxide-based raw material.

[0018] Generally speaking, the larger the contact area, the higher the heat exchange efficiency. The present invention has found through a large number of experiments that when the lump lime in the lime product is controlled under the above conditions, it can maintain a relatively high heat exchange efficiency in the heat exchange. If the particle size of the lump lime is further increased, the heat exchange efficiency between sandstone, bauxite and iron ore and the lime product will be significantly reduced.

[0019] The method for preparing calcium oxide-based raw meal for cement clinker production provided by the present invention comprises: the heat exchange and grinding are carried out in a sorting mill, and the sorting mill returns the ground coarse slag to the sorting mill for further grinding, so that the fineness of the raw meal is 80 μm sieve residue <25%;

[0020] According to the method for preparing calcium oxide-based raw materials for cement clinker production provided by the present invention, sandstone blocks, bauxite blocks and iron ore blocks are added to the lime product for mixing and heat exchange and grinding, wherein the particle size range of the sandstone blocks is 0 to 50 mm, the particle size range of the bauxite blocks is 0 to 50 mm, and the particle size range of the iron ore blocks is 0 to 50 mm.

[0021] It was further discovered that although the temperature of the lime product obtained by the above method is high, based on the efficient heat exchange between the lime product and sandstone, bauxite and iron ore, the present invention can use a sorting grinder to perform the heat exchange and grinding to obtain powder with qualified fineness, which is then directly discharged into a high-temperature kiln for calcination. In this way, the energy utilization of the lime product under high temperature can be maximized while significantly reducing the grinding energy consumption.

[0022] The above-mentioned calcium oxide-based raw material is directly introduced into a high-temperature kiln for calcination to obtain the cement clinker. The high-temperature kiln can be equipped with a traditional rotary kiln to complete the high-temperature calcination, or a new type of electric kiln can be used to complete the high-temperature calcination. The temperature control range for converting the raw material into clinker is 900-1600°C. The specific selection and setting of the temperature depends on the type of clinker to be fired and the characteristics of the raw materials.

[0023] According to the method for preparing calcium oxide-based raw materials for cement clinker production provided by the present invention, the decomposition furnace is an electric thermal decomposition furnace, and the electric heat conversion technology adopted is microwave heating, electromagnetic induction, laser, resistive exothermic elements (such as silicon carbon rods, silicon molybdenum rods, heating wires) or infrared heating technology.

[0024] The decomposition of calcium carbonate consumes a large amount of heat energy, which accounts for up to 60% of the cement manufacturing process. Under the carbon peak policy, since the carbon emissions from cement production mainly come from the carbonate decomposition of limestone and the combustion of fossil fuels such as coal, some technologies currently use low-carbon fuels to replace coal to reduce the combustion of coal fossil fuels, but how to achieve a substantial reduction in carbon in the cement industry still urgently needs to propose new technical solutions. When an electric thermal decomposition furnace is used to decompose the limestone raw material in the present invention, not only can green electricity energy be used as a heat source for cement production, which is essentially different from the traditional use of fossil energy such as coal, oil, and gas, it can consume green electricity on a large scale, and green electricity does not produce CO at all. 2 、NO X 、SO 2 Such smog gases can significantly reduce the CO 2 Total emissions, and disposal of NO X 、SO 2 The huge cost expenditure consumed, and, for the limestone raw materials mainly composed of limestone blocks, the temperature control of the electric thermal decomposition furnace is more precise, which is more conducive to a more complete decomposition, and obtains high-quality calcium oxide-based raw materials that are conducive to clinker calcination, so as to improve the quality of cement clinker.

[0025] The present invention also provides the calcium oxide-based raw meal prepared by the method for preparing the calcium oxide-based raw meal for cement clinker production as described above.

[0026] The present invention also provides cement clinker obtained by directly introducing the above calcium oxide-based raw material into a high-temperature kiln for calcination; the performance of the cement clinker fully complies with the current GBT 21372-2008 national standard for silicate cement clinker.

[0027] During the calcination process, an electric heating system can be used. The temperature control of the electric heating system is more convenient and accurate, so that the calcination temperature can be accurately controlled, thereby realizing a new dry-process off-kiln decomposition rotary kiln calcination process that is far superior to the current traditional temperature control that is relatively extensive and fluctuating. As a result, the quality stability of the produced cement clinker is also correspondingly far superior to the clinker products of the current cement kiln.

[0028] The present invention provides a calcium oxide-based raw meal for producing cement clinker based on green electric energy, a preparation method thereof and an application thereof. By subjecting limestone raw materials mainly composed of limestone blocks to high-temperature decomposition, not only the amount of raw materials for raw meal grinding is reduced, but also the dense and hard limestone raw materials are converted into porous, loose and very easy-to-grind lime products with block lime as the main product, thereby greatly reducing the grinding energy consumption in the raw meal preparation link. Moreover, the lime product obtained by the method is directly ground after heat exchange with other raw materials, such as sandstone blocks, bauxite blocks and iron ore blocks. On the basis of fully utilizing energy, the process flow is simplified, and the investment in major equipment and operating energy consumption are reduced, which has very important technical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is a schematic diagram of the process flow of cement clinker preparation in the traditional cement industry;

[0031] Figure 2 This is one of the schematic flow diagrams of the method for preparing cement clinker provided by the present invention;

[0032] Figure 3 This is the second schematic diagram of the process of preparing cement clinker provided by the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0035] Combine the following Figure 1-Figure 3 The invention describes a calcium oxide-based raw material for producing cement clinker based on green electric energy, and a preparation method and application thereof.

[0036] The limestone raw material used in the present invention contains limestone blocks with a volume ratio of more than 80% and a particle size range of 0 to 50 mm.

[0037] The particle size range of the sandstone block used in the present invention is 0 to 50 mm.

[0038] The particle size of the bauxite block used in the present invention ranges from 0 to 50 mm.

[0039] The particle size of the iron ore block used in the present invention ranges from 0 to 50 mm.

[0040] The particle size range in the present invention refers to the distribution of the equivalent diameter R of each material satisfying: 0<R≤50mm.

[0041] The decomposition process of the decomposition furnace in the present invention can be carried out by using a suspension decomposition system.

[0042] Example 1

[0043] A method for preparing cement clinker, such as Figure 2 As shown, the process is:

[0044] First, a continuous thermal decomposition process is adopted, and the above-mentioned limestone raw materials are continuously introduced into a vertical decomposition furnace chamber in an upper-in-lower-out manner, and are in a stacked state in the furnace chamber to exchange heat with the air flow rising from bottom to top, so as to achieve high-temperature decomposition to obtain a lime product with block lime as the main product; wherein, the stacking density of the limestone raw materials in the decomposition furnace chamber is 2.5 tons / cubic meter, the temperature in the decomposition furnace is controlled in three sections, namely, upper, middle and lower, and the three sections are 600±10°C, 850±10°C and 1050±10°C respectively, and the residence time of the limestone raw materials in the decomposition furnace is 30 minutes.

[0045] The resulting CO 2 The airflow is discharged from the middle and upper part of the furnace cavity by a fan with adjustable air volume for recycling, so that the pressure of the airflow in the decomposition furnace is less than the atmospheric pressure of the local environment, ensuring that the decomposition furnace is under negative pressure to prevent the decomposition into CO 2 The CO in the decomposition furnace cavity escapes 2 The concentration is 85-96%;

[0046] The obtained lime product contains lump lime with a volume ratio of more than 80% and a particle size of 0 to 50 mm, and the temperature of the lime product is 900 to 950°C.

[0047] Then, the sandstone block, bauxite block and iron ore block are added to the lime product at a temperature of 900-950° C. and mixed in a separation mill for heat exchange and grinding. At the same time, the separation mill returns the ground coarse slag to the separation mill for further grinding, so that the fineness of the calcium oxide-based raw material is 80 μm and the sieve residue is less than 20%;

[0048] The calcium oxide-based raw material is then directly introduced into a high-temperature kiln for calcination to obtain cement clinker.

[0049] Example 2

[0050] It is basically the same as Example 1, except that the temperature in the middle and lower parts of the decomposition furnace chamber is the same, both 1050±10° C. The test found that the quality of cement clinker deteriorated, and the CV value of the strength index of cement clinker increased significantly.

[0051] Example 3

[0052] The method is basically the same as Example 1, except that the sandstone block, bauxite block and iron ore block are first ground into powder by a small auxiliary material mill and then added to a lime product at a temperature of 800 to 1100°C (such as Figure 3 The experiment found that: it is possible to achieve heat exchange between high-temperature lime powder and mixed powder of low-temperature sandstone blocks, bauxite blocks and iron ore, and reduce the temperature of lime powder output from the decomposition furnace by 50-100°C without heat loss and waste, which is conducive to the normal use temperature of raw material powder mixing equipment and prolongs the service life of the equipment.

[0053] By testing the performance of cement clinker in Examples 1 to 3, it is found that the performance of cement clinker prepared by each method fully complies with the current GBT 21372-2008 national standard for Portland cement clinker. The stability of key indicators such as clinker strength is better than that of clinker produced by the current new dry process external decomposition rotary kiln calcining process.

[0054] In addition, the present invention also found that by replacing the limestone raw material with limestone mine stripping waste ore containing more than 20% by volume and a particle size of 50 to 100 mm, the obtained lime product contains more than 30 to 40% by volume of block lime with a particle size of 50 to 100 mm. Although the calcium oxide content contained in the stripping waste ore is lower than that of qualified limestone, and the corresponding calcium oxide product has more impurities, it is still possible to produce qualified clinker through reasonable batching. This shows that the method of the present invention has a wide range of applications.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing calcium oxide-based raw material for cement clinker production, characterized in that: include: Firstly, a limestone raw material mainly composed of limestone blocks is subjected to high temperature decomposition to obtain a lime product with block lime as the main product; and then the lime product is ground to obtain the calcium oxide-based raw material.

2. The method for preparing calcium oxide-based raw material for cement clinker production according to claim 1, characterized in that: A continuous thermal decomposition process is adopted, wherein the limestone raw material is continuously introduced into a vertical or inclined decomposition furnace cavity in an upper-in-lower-out manner, and is deposited in the furnace cavity to perform heat exchange with the airflow rising from bottom to top in the decomposition furnace, thereby achieving the high-temperature decomposition; The pressure in the furnace chamber of the decomposition furnace is -5×10 4 ~-1.5×10 5 Pa, the concentration of CO2 in the furnace chamber of the decomposition furnace is 80-99%, and is discharged from the middle and upper part of the furnace chamber along with the air flow for recycling.

3. The method for preparing calcium oxide-based raw material for cement clinker production according to claim 2, characterized in that: The temperature in the decomposition furnace cavity is 500-1150° C., and the temperature gradually increases from top to bottom.

4. The method for preparing calcium oxide-based raw material for cement clinker production according to claim 3, characterized in that: The bulk density of the limestone raw material in the furnace chamber of the decomposition furnace is 1.1-2.9 ton / m 3 ; and / or, the residence time of the limestone raw material in the decomposition furnace is 2 to 30 minutes.

5. The method for preparing calcium oxide-based raw material for cement clinker production according to claim 4, characterized in that: The airflow is discharged from the middle and upper part of the furnace cavity by a fan with adjustable air volume.

6. The method for preparing calcium oxide-based raw meal for cement clinker production according to any one of claims 1 to 5, characterized in that: The lime product contains more than 80% of the volume of lump lime with a particle size range of 0 to 50 mm. The temperature of the lime product obtained by high-temperature decomposition is 800 to 1100° C., and is directly used for heat exchange and grinding with sandstone blocks, bauxite blocks and iron ore blocks to obtain the calcium oxide-based raw material.

7. The method for preparing calcium oxide-based raw material for cement clinker production according to claim 6, characterized in that: include: The heat exchange and grinding are carried out in a classifying mill, and the classifying mill returns the ground coarse slag to the classifying mill for further grinding, so that the fineness of the calcium oxide-based raw material is 80 μm sieve residue <25%; Preferably, sandstone blocks, bauxite blocks and iron ore blocks are added to the lime product for mixing and heat exchange and grinding, wherein the sandstone blocks have a particle size range of 0 to 50 mm, the bauxite blocks have a particle size range of 0 to 50 mm, and the iron ore blocks have a particle size range of 0 to 50 mm.

8. The method for preparing cement clinker according to claim 1, characterized in that: The decomposition furnace is an electric heat decomposition furnace, and the electric heat conversion technology adopted by the decomposition furnace is microwave heating, electromagnetic induction, laser, resistive heat-emitting element or infrared heating technology.

9. The calcium oxide-based raw meal obtained by the method for preparing calcium oxide-based raw meal for cement clinker production according to any one of claims 1 to 8.

10. The calcium oxide-based raw material according to claim 10 is directly introduced into a high-temperature kiln for calcination to obtain cement clinker.

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