Cement raw material pulverization device and pulverization method, and cement manufacturing method

Abstract

To improve pulverization efficiency by effective use of waste heat of a cement pulverization mill and to stabilize cement quality.SOLUTION: A device includes a hopper for storing a cement raw material, a mill for pulverization of the cement raw material in the hopper, a classifier for classification of pulverized grains of the cement raw material having been pulverized by the mill, a dust collector for collecting dust from an exhaust gas from the classifier, and an exhaust gas circulation duct for transporting at least a part of the exhaust gas from the dust collector to the mill, wherein the hopper is provided with a jacket covering at least a part of an outer peripheral surface thereof, and the exhaust gas circulation duct is connected to the mill via the jacket.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cement raw material grinding device and grinding method for grinding cement raw materials such as cement clinker and gypsum, and a cement manufacturing method. [Background technology]

[0002] In cement manufacturing facilities, cement is produced by adding gypsum as a set modifier to cement clinker burned in a cement kiln and grinding it in a grinding device. To activate the gypsum added to this cement, the temperature inside the cement raw material grinding device must be maintained at 95°C to 125°C. Cement clinker generates heat due to impact and friction during grinding, causing the temperature inside the grinding device to rise. However, when the cement clinker is transported to a different location after burning and ground, or during winter, the temperature of the cement clinker fed into the cement raw material grinding device drops, making it difficult for the temperature inside the grinding device to rise. Furthermore, installing a preliminary grinder also helps prevent the temperature inside the grinding device from rising.

[0003] Patent Document 1 discloses a method of controlling temperature by introducing exhaust gas (70 to 75°C) from a separator installed downstream of the cement mill into the cement mill. In this case, the temperature is controlled by controlling the amount of exhaust gas introduced using a damper and a control device, and it is described that the temperature can be maintained at 95 to 125°C, which is necessary for activating the gypsum, using the heat generated by the exothermic reaction between cement clinker and gypsum. However, because the exhaust gas at the mill outlet contains a lot of moisture, it is released into the atmosphere and is not used as a heat source.

[0004] Meanwhile, Patent Document 2 discloses a method of controlling the temperature inside the mill by providing an air seal damper at the raw material inlet of a tube mill that grinds cement raw materials and an air bleed damper at the air bleed inlet, and connecting an exhaust gas circulation duct to the air bleed inlet, thereby circulating part of the exhaust gas (80-90°C) from the tube mill into the tube mill. In this case, there is the problem of condensation inside the piping and mill, and utilization of the exhaust gas from the cement grinding mill as a heat source is limited to about 50%. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-126644 [Patent Document 2] Japanese Patent Application Publication No. 6-31188 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the exhaust gas (80 to 90°C) from the cement grinding mill contains a lot of moisture due to water spraying inside the mill, which causes problems such as condensation on the inner walls of the equipment through which the exhaust gas passes. As taught in Patent Document 2, it is not possible to circulate the entire amount through the cement grinding mill, which results in insufficient utilization of waste heat.

[0007] The present invention has been made in view of the above circumstances, and aims to effectively utilize the waste heat of a cement grinding mill to improve grinding efficiency and stabilize the quality of cement. [Means for solving the problem]

[0008] The cement raw material grinding device of the present invention includes a hopper that stores cement raw materials including cement clinker and gypsum, a mill that grinds the cement raw materials in the hopper, a classifier that classifies the ground particles of the cement raw materials ground in the mill, a dust collector that collects dust from exhaust gas from the classifier, and an exhaust gas circulation duct that transports at least a portion of the exhaust gas from the dust collector to the mill, and the hopper is provided with a jacket that covers at least a portion of the outer circumferential surface of the hopper, and the exhaust gas circulation duct is connected to the mill via the jacket.

[0009] Because exhaust gas is supplied to the jacket attached to the hopper through the exhaust gas circulation duct, the cement raw material in the hopper can be indirectly heated through the hopper wall. Therefore, the heated cement raw material is supplied to the mill, making it easier to raise the temperature inside the mill to a level favorable for gypsum activation. Meanwhile, even if the exhaust gas from the classifier contains moisture, it condenses through heat exchange between the jacket and the hopper, and the moisture-reduced exhaust gas is introduced into the mill, preventing condensation in the piping leading to the mill.

[0010] In the cement raw material grinding device of the present invention, the hoppers may include a clinker hopper for storing cement clinker and a gypsum hopper for storing gypsum, and the jacket may be provided on at least the gypsum hopper.

[0011] Since the gypsum can be directly heated by the exhaust gas, the activation of the gypsum can be further promoted.

[0012] In the cement raw material grinding apparatus of the present invention, the mill may be provided with a sprinkler that supplies water to the cement raw material, and a water recovery pipe that recovers water generated inside the jacket may be connected to the bottom of the jacket, and the water recovery pipe may be connected to the sprinkler of the mill.

[0013] The heat from the exhaust gas is supplied to the cement raw materials in the hopper, and at the same time, the moisture in the exhaust gas is cooled inside the jacket to become water, which can be recovered through water recovery piping and supplied to the mill's water sprinklers.In addition, the grinding aid that has volatilized in the exhaust gas is also recovered at the same time and supplied to the mill, allowing for effective use of the grinding aid.

[0014] In the cement raw material grinding device of the present invention, a calcination facility exhaust gas transfer pipe for supplying moisture-containing exhaust gas from a cement clinker calcination facility may be connected to the exhaust gas circulation duct at a position upstream of the jacket.

[0015] By supplying moisture-containing exhaust gases such as preheater exhaust gases from cement firing equipment, chlorine bypass system exhaust, cooler bleed air, and exhaust dryer exhaust to the jacket, some of the moisture can be removed inside the jacket before the exhaust gases are supplied to the mill, allowing them to be effectively used as a heat source.

[0016] The cement raw material grinding method of the present invention is a cement raw material grinding method in which cement raw materials containing cement clinker and gypsum taken out from a hopper are ground in a mill, the hopper being provided with a jacket that covers at least a part of the hopper, and at least a part of the exhaust gas generated in the mill being circulated to the mill via the jacket.

[0017] In the cement raw material grinding method of the present invention, the hoppers have a clinker hopper for storing cement clinker and a gypsum hopper for storing gypsum, and the jacket is preferably provided on at least the gypsum hopper.

[0018] In the cement raw material grinding method of the present invention, it is preferable that the water generated inside the jacket is recovered and sprayed into the mill.

[0019] The cement production method of the present invention is a method for producing cement by removing cement raw materials, including cement clinker and gypsum produced in cement firing equipment, from a hopper that stores the cement raw materials and mixing and grinding them in a mill, wherein the hopper is provided with a jacket that covers at least a portion of its outer periphery, and at least a portion of the exhaust gas generated in the mill is circulated to the mill via the jacket. [Effects of the Invention]

[0020] According to the present invention, exhaust gas is supplied from the exhaust gas circulation duct to the jacket installed in the hopper, so the cement raw material in the hopper can be indirectly heated through the wall of the hopper, and the heated cement raw material is supplied to the mill, making it easier to raise the temperature inside the mill to a temperature favorable for gypsum activation, thereby improving grinding efficiency and stabilizing cement quality. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic diagram of a cement raw material grinding device according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram showing an example of clinker burning equipment for producing cement clinker. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0023] 1 shows one embodiment of a cement raw material grinding apparatus 1. This cement raw material grinding apparatus 1 has hoppers 2A and 2B for storing cement raw materials, a mill 3 for grinding the cement raw materials in the hoppers 2A and 2B, a classifier (separator) 4 for classifying the ground particles of the cement raw materials ground in the mill 3, a dust collector 5 for collecting dust from the exhaust gas from the classifier 4, and an exhaust gas circulation duct 6 for transporting at least a portion of the exhaust gas from the dust collector 5 to the mill 3. Hopper 2B is provided with a jacket 7 that covers at least a portion of its outer circumferential surface, and the exhaust gas circulation duct 6 is connected to the mill 3 via the jacket 7.

[0024] In this case, the hoppers 2A, 2B include a clinker hopper 2A for storing cement clinker and a gypsum hopper 2B for storing gypsum. In addition to these hoppers 2A, 2B, a secondary raw material hopper (not shown) for storing secondary raw materials may also be provided.

[0025] Mill 3 mixes cement clinker with gypsum and grinds it to produce cement. For example, it is configured as a ball mill using iron balls, and grinds the cement clinker and gypsum by the impact and friction of the iron balls while rotating the outer cylinder. The impact and friction during grinding generate heat, and as mentioned above, to activate the gypsum, it is necessary to maintain the temperature inside mill 3 at 95°C to 125°C. Temperature control will be described later.

[0026] The classifier 4 separates the mixed powder of cement clinker and gypsum pulverized in the mill 3 into fine and coarse powder particles, and a cyclone separator, for example, is used. This classifier 4 is supplied with compressed air from a fan 11 to generate convection inside, and the separated fine powder particles are taken out from the classifier 4 via a cement product discharge pipe 12 and stored separately as cement products. Meanwhile, the coarse powder particles are sent back to the mill 3 via a coarse particle return pipe 13 and are pulverized again.

[0027] The compressed air supplied into the classifier 4 is sent to the dust collector 5 via an exhaust gas transport pipe 14. This exhaust gas also contains fine cement product powder, which the dust collector 5 collects by passing the exhaust gas through a bag filter. The collected fine powder is discharged as cement products via a cement product discharge pipe 12 together with the fine powder and granular material removed from the classifier 4.

[0028] The exhaust gas from the dust collector 5 is then released into the atmosphere through exhaust gas discharge pipe 16 by fan 15, but a portion of the gas is led to exhaust gas circulation duct 6. This exhaust gas circulation duct 6 branches off midway through the exhaust gas discharge pipe 16 from the dust collector 5 and is connected to a jacket 7 provided on the gypsum hopper 2B. This jacket 7 covers almost the entire outer peripheral surface of the gypsum hopper 2B, forming a gap between itself and the outer peripheral surface, and the exhaust gas supplied from the exhaust gas circulation duct 6 flows through this gap. In addition, near the branching point of the exhaust gas discharge pipe 16 and the exhaust gas circulation duct 6, dampers 17 and 18 for adjusting the flow rate are provided.

[0029] Then, in the jacket 7, the heat of the exhaust gas is transferred to the wall of the hopper 2B and exchanges heat with the gypsum inside, heating the gypsum. After this heat exchange, the exhaust gas in the jacket 7 is sent to the mill 3. Meanwhile, inside the jacket 7, the temperature of the exhaust gas drops due to heat exchange with the gypsum, causing the moisture contained in the exhaust gas to condense. A water recovery pipe 20 for recovering water generated inside the jacket 7 is connected to the bottom of the jacket 7, and this water recovery pipe 20 is connected to a sprinkler 21 inside the mill 3 so that it is used as part of the water used by the sprinkler 21. The sprinkler 21 adjusts the temperature by appropriately spraying water inside the mill 3. The water recovery pipe 20 is provided with an air seal valve 22 for adjusting the flow rate and a pump 23 for pressure feeding.

[0030] The exhaust gas generated in the mill 3 is sent to a coarse particle separator 25 via a gas exhaust pipe 24, where the coarse particles are separated. The separated coarse particles are sent to a classifier 4 together with the powder and granular material sent from the mill 3. The exhaust gas from the coarse particle separator 25 is sent to a dust collector 5 via an exhaust gas transport pipe 14 together with the exhaust gas from the classifier 4.

[0031] In the cement raw material grinding device 1 configured as described above, exhaust gas is supplied from the exhaust gas circulation duct 6 to the jacket 7 provided in the gypsum hopper 2B, so that the gypsum in the gypsum hopper 2B can be indirectly heated through the wall of the hopper 2B. The exhaust gas sent through the exhaust gas circulation duct 6 has a temperature of, for example, 70°C to 100°C, and therefore, the gypsum heated by this exhaust gas is supplied to the mill 3, making it easier to raise the temperature inside the mill 3 to a temperature (95°C to 125°C) that is advantageous for activating the gypsum.

[0032] For example, in winter, the temperature of stored gypsum is around 0°C to 10°C. On the other hand, cement clinker is hot immediately after production, but after being stored in a silo for several weeks, when it is transferred to Mill 3 and the required amount of cement is produced, the temperature drops to around 30°C to 60°C. If this cooled gypsum and cement clinker are crushed as is, the temperature inside Mill 3 will not reach 100°C, making it difficult to reach the crushing temperature of 95°C to 125°C, which is necessary to ensure the fluidity of the high-performance water-reducing agent by dehydrating the water adhering to the gypsum and increasing the hemihydration rate (maintaining the slump of concrete).

[0033] In the cement raw material grinding device 1 of this embodiment, exhaust gas at about 70°C to 100°C inside the mill 3 is used, and by passing this exhaust gas through the jacket 7 of the gypsum hopper 2B, the gypsum inside the hopper 2B is heated and the heated gypsum is supplied to the mill 3, and the exhaust gas inside the jacket 7 is also supplied to the mill 3. Therefore, with the addition of heat generated by grinding inside the mill 3, it is possible to raise the temperature inside the mill 3 to about 95°C to 125°C.

[0034] In this embodiment, the jacket 7 is formed on the gypsum hopper 2B to heat the gypsum in the gypsum hopper 2B, but the jacket 7 may be formed on the clinker hopper 2A to heat the cement clinker, and the heated cement clinker and gypsum can be mixed to effectively activate the gypsum. For this reason, it is sufficient to form a jacket 7 on either the clinker hopper 2A or the gypsum hopper 2B to supply the exhaust gas, but it is also possible to form a jacket 7 on both of them. By forming the jacket 7 on the gypsum hopper 2B as in the present embodiment, the gypsum can be directly heated, thereby further promoting the activation of the gypsum.

[0035] When the gypsum hopper 2B is heated by the exhaust gas in this manner, even if the exhaust gas from the classifier 4 contains moisture, the moisture is condensed by heat exchange with the hopper 2B in the jacket 7, and the exhaust gas with reduced moisture is introduced into the mill 3. Therefore, it is possible to prevent condensation from occurring between the jacket 7 and the mill 3, etc.

[0036] Then, while the heat of the exhaust gas is supplied to the gypsum in the hopper 2B, the moisture in the exhaust gas is cooled in the jacket 7 to become water, which is recovered in the water recovery pipe 20 and supplied to the sprinkler 21 of the mill 3. In this case, the exhaust gas extracted from the dust collector 5 may contain volatilized grinding aid that was added to improve the grinding efficiency, and this volatilized grinding aid is also recovered at the same time and supplied to the mill 3, so that the grinding aid can be used effectively.

[0037] FIG. 2 shows a cement clinker burning facility for producing cement clinker, and the moisture-containing exhaust gas generated therein may be supplied to the exhaust gas circulation duct 6 of the cement raw material crushing device 1. In the cement clinker calcination facility 30, raw materials from a raw material hopper 31 that stores limestone, clay, silica stone, iron raw materials, etc. are crushed and dried in a raw material mill 32, and then sent to a cement kiln 34 while being preheated in a preheater 33, where the raw materials are calcined. The resulting cement clinker is then cooled in a clinker cooler 35 to produce cement clinker as a product. The cement clinker produced in this cement clinker calcination facility 30 is stored in the clinker hopper 2A of the cement raw material crushing device 1 directly or indirectly via a storage silo.

[0038] In this cement clinker calcination apparatus 30, a chlorine bypass system 37 is provided to remove chlorine by extracting part of the exhaust gas from the end 36 of the cement kiln 34 to prevent chlorine components from circulating between the preheater 33 and the cement kiln 34. In addition, industrial waste including waste plastics is dried in a waste hopper 38 and then sent to a burner 39 of the cement kiln 34 as, for example, a part of the heat source.

[0039] In this cement clinker calcination facility 30, exhaust gases containing moisture are generated, such as exhaust gas from the preheater 33, exhaust from filter 40 of the chlorine bypass system 37, bleed air from the clinker cooler 35, and exhaust from the exhaust dryer (waste hopper 38). By supplying these exhaust gases via the calcination facility exhaust gas transfer pipe 41 to the exhaust gas circulation duct 6 at a position upstream of the jacket 7 of the cement raw material grinding device 1, as shown by the two-dot chain line in FIG. 1, for example, the exhaust gases containing moisture can be used as a heat source for heating gypsum, and the moisture can also be effectively used for the sprinklers 21 of the mill 3.

[0040] As described above, in this cement raw material grinding device 1, exhaust gas is supplied from the exhaust gas circulation duct 6 to the jacket 7 provided in the hopper 2B, so that the gypsum in the hopper 2B can be indirectly heated through the wall of the hopper 2B, and the heated gypsum is supplied to the mill 3, making it easier to raise the temperature in the mill 3 to a temperature favorable for activating the gypsum. This makes it possible to improve grinding efficiency and stabilize the quality of cement. [Explanation of symbols]

[0041] 1. Cement raw material grinding equipment 2A Clinker Hopper 2B Gypsum Hopper 3 mil 4 Classifier 5. Dust collector 6 Exhaust gas circulation duct 7. Jacket 11 Fan 12 Cement product discharge pipe 13 Coarse particle return pipe 14 Exhaust gas transport pipe 15 Fans 16 Exhaust gas exhaust pipe 17,18 Damper 20 Water recovery piping 21 Sprinkler 22 Air seal valve 23 Pump 24 Gas exhaust pipe 25 Coarse powder separator 30 Cement clinker burning equipment 33 Preheater 34 Cement Kiln 35 Clinker cooler 37 Chlorine Bypass System 38 Waste hopper (dryer) 41 Burner exhaust gas transfer pipe

Claims

1. 1. A cement raw material grinding device comprising: a hopper for storing cement raw materials including cement clinker and gypsum; a mill for grinding the cement raw materials in the hopper; a classifier for classifying the ground particles of the cement raw materials ground in the mill; a dust collector for collecting dust from exhaust gas from the classifier; and an exhaust gas circulation duct for transporting at least a portion of the exhaust gas from the dust collector to the mill, wherein the hopper is provided with a jacket covering at least a portion of its outer circumferential surface, and the exhaust gas circulation duct is connected to the mill via the jacket.

2. 2. The cement raw material grinding device according to claim 1, wherein the hoppers include a clinker hopper for storing cement clinker and a gypsum hopper for storing gypsum, and the jacket is provided on at least the gypsum hopper.

3. 2. The cement raw material grinding apparatus according to claim 1, wherein the mill is provided with a sprinkler that supplies water to the cement raw material, and a water recovery pipe that recovers water generated inside the jacket is connected to the bottom of the jacket, and the water recovery pipe is connected to the sprinkler of the mill.

4. 2. The cement raw material grinding device according to claim 1, wherein a burning equipment exhaust gas transfer pipe for supplying moisture-containing exhaust gas from a cement clinker burning equipment is connected to the exhaust gas circulation duct at a position upstream of the jacket.

5. A cement raw material grinding method in which cement raw materials containing cement clinker and gypsum taken out from a hopper are ground in a mill, the method comprising providing a jacket covering at least a part of the hopper, and circulating at least a part of exhaust gas generated in the mill to the mill via the jacket.

6. 6. The cement raw material grinding method according to claim 5, wherein the hoppers include a clinker hopper for storing cement clinker and a gypsum hopper for storing gypsum, and the jacket is provided on at least the gypsum hopper.

7. 6. The method for grinding cement raw materials according to claim 5, wherein water generated inside the jacket is collected and sprayed into the mill.

8. A method for producing cement by removing cement raw materials, including cement clinker and gypsum produced in a cement clinker burning facility, from a hopper that stores the cement raw materials, and mixing and grinding the cement raw materials in a mill, the method comprising providing a jacket on the hopper that covers at least a portion of the outer periphery of the hopper, and circulating at least a portion of the exhaust gas generated in the mill to the mill via the jacket.

Images