High-calcium expanded clinker produced continuously on a rotary kiln and method for producing same

Abstract

The application discloses high calcium expanded clinker which can be continuously produced on a rotary kiln and a preparation method thereof. The high calcium expanded clinker is prepared from raw meal powder of 70-90 parts of limestone, 8-24 parts of lapis lazuli and 2-6 parts of aluminum fluoride by calcining at 1200-1300 DEG C on a rotary kiln. The application uses lapis lazuli which is not easy to decompose and rich in sulfur minerals to replace gypsum commonly used in traditional expanded clinker as a sulfur component. With the aid of the mineralization component of aluminum fluoride, the application reduces the risk of ring formation in the kiln caused by the volatilization and condensation of SO3 generated by the decomposition of gypsum on the basis of providing a sulfur phase station, significantly improves the continuity of the calcination production of the expanded clinker on the rotary kiln, greatly ensures the production quality of the expanded clinker, reduces the sintering heat consumption of the expanded clinker, saves the production cost of the expanded clinker, improves the market competitiveness of the expanded clinker, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of industrial production and preparation technology of expanded clinker, specifically, to a high-calcium expanded clinker that can be continuously produced on a rotary kiln and its preparation method. Background Technology

[0002] With the rapid development of ready-mixed concrete technology in my country, the shrinkage rate of concrete has increased from 0.04-0.06% to 0.06-0.08%, significantly increasing the risk of structural cracking. Shrinkage cracking of concrete has become a major problem plaguing contemporary cement concrete engineering, and related research has become a focus of international concrete materials research. Utilizing the volume expansion of expansive components during hydration to compensate for the shrinkage of cement concrete is one of the effective measures to suppress concrete shrinkage cracking. Expansive agents with CaO as the main expansion source have advantages such as low hydration water demand, low wet curing requirements, and high expansion efficiency, making them a future development direction for the expansive agent industry (Chinese journal article (Current Status and Development Direction of Concrete Expansive Agent Industry, Zhao Shunzeng, You Baokun, Liu Li, Concrete and Cement Products, 2009, No. 3)). Therefore, the industrial production of high-calcium expansive clinker, necessary for preparing calcium oxide expansive agents, has become the main direction in the current field of expansive clinker production and preparation technology.

[0003] Currently, there are two main production processes for high-calcium expanded clinker: one process, represented by Denka Corporation of Japan, involves mixing limestone, gypsum, and bauxite in a certain proportion to form raw materials, which are then melted and calcined in an electric furnace to produce expanded clinker. The calcined expanded clinker is then ground into an expansion agent product of a specified fineness (the commercial name of the product is CSA expansion agent). This expansion agent has excellent performance and can be called a full clinker expansion agent, but the production process is difficult and costly. Another production process, represented by domestic research institutes such as the China Building Materials Academy, involves preparing raw materials by mixing limestone, gypsum, bauxite, and iron powder in a certain proportion, then calcining them in a hollow rotary kiln to obtain expanded clinker. This clinker is then ground together with a certain amount of gypsum and auxiliary materials to a specified fineness. Examples of patents include CN103951302A (A multi-purpose high-calcium expanded clinker and its preparation method), CN101333083A (A high-performance expanded cement clinker and a series of expanding agents prepared therefrom), CN103130437A (Gypsum and calcium oxide molten inclusion expanded clinker, concrete expanding agent and its preparation method and application), CN102838308A (An expanded clinker, expanding agent and its preparation method), and CN102162244A (Expanded concrete cast-in-place pile and its manufacturing method and a concrete expanding agent). Overall, high-calcium expanded clinker has a narrow sintering temperature range, a large liquid phase content, and extremely difficult-to-control sintering process, making continuous industrial production in rotary kilns impossible. It often requires a four-day kiln shutdown after three days of calcination to address the issue of ring formation within the kiln, resulting in a "three days fishing, two days drying nets" situation. To address the problem of ring formation in high-calcium expanded clinker, which prevents continuous industrial production in rotary kilns, some high-calcium expanded clinker producers have developed targeted equipment such as rotary kiln head bridging carts (publication number CN205138180U), rotary kiln bridging devices (publication number CN205138181U), and rotary kiln bridging machines (publication number CN205138183U). However, these efforts have yielded limited results and have failed to fundamentally solve the problem of continuous production of high-calcium expanded clinker in rotary kilns. Summary of the Invention

[0004] To address the shortcomings of existing traditional expanded clinker in industrial production on rotary kilns, such as high viscosity of the calcined liquid phase, easy ring formation, and short continuous production time, this invention provides a high-calcium expanded clinker that can be continuously produced on a rotary kiln and its preparation method.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention provides a high-calcium expanded clinker that can be continuously produced on a rotary kiln. The high-calcium expanded clinker uses limestone as a calcium raw material, celestite as a sulfur raw material, and aluminum fluoride as a mineralizing raw material. The raw meal powder obtained from the above three raw materials is calcined on a rotary kiln at a temperature of 1200℃-1300℃ to obtain the high-calcium expanded clinker.

[0007] The above three raw material components are as follows by weight:

[0008] 70-90 parts limestone

[0009] Celestite, 8-24 parts

[0010] 2-6 parts aluminum fluoride;

[0011] The limestone contains ≥95wt% CaCO3;

[0012] The celestite contains ≥90wt% SrSO4;

[0013] The aluminum fluoride contains ≥80wt% AlF3.

[0014] The present invention also provides a method for preparing the above-mentioned high-calcium expanded clinker, comprising the following steps:

[0015] S1. Mix the following components by weight: 70-90 parts limestone, 8-24 parts celestite, and 2-6 parts aluminum fluoride to obtain a mixture;

[0016] S2. Grind the mixture together to a specific surface area of ​​350 m². 2 / kg~400m 2 / kg, and the residue on an 80μm square hole sieve is no more than 5%, to obtain the raw meal powder used for producing high-calcium expanded clinker;

[0017] S3. Feed the raw meal powder into the rotary kiln through an automatic conveying and metering device. By adjusting the burner position and fuel consumption, maintain the temperature of the rotary kiln calcination zone at 1200℃-1300℃ to ensure that the raw meal powder is slowly burned at a low temperature in the rotary kiln.

[0018] S4. The expanded clinker, after being slowly calcined at low temperature in the rotary kiln, is discharged from the kiln head and enters a single-cylinder cooler with lifting plates for cooling.

[0019] S5. Grind the cooled calcined clinker powder into clinker powder with a residue of ≤10% on a 0.08mm sieve to obtain the high-calcium expanded clinker of the present invention.

[0020] Furthermore, the rotary kiln speed is 1.0 rpm to 1.5 rpm.

[0021] Furthermore, in step S4, the granulation diameter of the expanded clinker exiting the kiln is controlled to be 5-20 mm, and the vertical weight per liter of the expanded clinker sampled at the kiln head cooler outlet is controlled to be 1100 g / L-1200 g / L. Sampling and measuring the vertical weight per liter of clinker particles at the cooler outlet can help understand the quality stability of the calcined clinker.

[0022] Furthermore, the rotary kiln is preferably a rotary kiln with a five-stage preheater, and the kiln diameter is preferably 2.5m-3.2m.

[0023] Furthermore, when an annular sintering ring forms inside the rotary kiln due to abnormal operation, the highest temperature point inside the rotary kiln should be adjusted by moving the burner position, and the flame shape should be controlled in combination with the secondary air volume of the pulverized coal injection pipe. This allows the sintering ring to self-collapse and disintegrate during the process of rapid heating and cooling, thus solving the problem of ring formation inside the kiln without stopping the kiln.

[0024] Compared with the prior art, the present invention has the following characteristics and beneficial effects:

[0025] (1) The traditional high-calcium expanded clinker batching scheme is based on limestone, gypsum, and bauxite as the three main raw materials, with limestone as the main component and gypsum and bauxite as auxiliary components. Occasionally, some enterprises use iron powder instead of bauxite as the mineralizing component for raw material batching. In this batching scheme, while ensuring the Ca / S ratio, the large amount of gypsum introduced results in a high viscosity of the calcined liquid phase during the decomposition and recrystallization process at high temperatures. This easily leads to the formation of sintering rings in the rotary kiln, and the escaped SO3 can also cause the SO2 emission concentration at the kiln tail to exceed the standard, resulting in failure to meet environmental protection online monitoring standards. Both the formation of rings in the kiln and failure to meet environmental protection online monitoring standards at the kiln tail will interrupt the continuity of rotary kiln production, resulting in forced kiln shutdown. Through years of practical exploration, this invention creatively utilizes the characteristic of celestite being rich in SO3 and not easily decomposed at high temperatures. Celestite is used to replace gypsum as the sulfur-containing component. While ensuring the Ca / S ratio, the amount of gypsum in the raw material that is easily decomposed at high temperatures is eliminated, thereby reducing the amount of sintering liquid phase and the amount of SO2 released from the kiln tail, thus improving the continuity of industrial production of expanded clinker in rotary kilns.

[0026] (2) By introducing celestite, which is not easily decomposed at high temperatures, the present celestite can not only reduce the amount of calcined liquid phase during the calcination production process of high calcium expanded clinker in a rotary kiln, but its non-decomposition inertness can also play a barrier effect on the binding liquid phase, effectively reducing the viscosity of the liquid phase and playing the role of sulfur fixation and viscosity reduction. This makes it easy to process the sintering ring formed due to human operation errors during the rotary kiln production process without stopping the kiln, further improving the continuity of industrial production of high calcium expanded clinker in a rotary kiln.

[0027] (3) Compared with the traditional high-calcium expanded clinker, which has poor firing continuity in rotary kilns and requires constant kiln shutdowns and ringing to ensure industrial production, this invention can improve the firing continuity of expanded clinker from 5-7 days in the traditional process to about 150 days through the combined control of raw material batching scheme and clinker calcination process. This significantly extends the continuous industrial production time of high-calcium expanded clinker in rotary kilns, avoids labor-intensive and time-consuming process operations such as kiln shutdowns and ringing, increases the average monthly output of expanded clinker, reduces the firing heat consumption of expanded clinker, saves the production cost of expanded clinker, and improves the market competitiveness of expanded clinker.

[0028] (4) Compared with the traditional three-component feeding scheme of limestone, anhydrite, and bauxite, this invention uses limestone as the calcareous raw material, celestite as the sulfurous raw material, and aluminum fluoride as the mineralizing raw material, through the F in aluminum fluoride... - And Al 3+ The composite mineralization process allows the active SrSO4 in celestite to enter the f-CaO lattice produced by the high-temperature decomposition of limestone, forming a continuous solid solution. This effectively promotes the sintering and densification of the core mineral component, free calcium oxide, in the high-calcium expanded clinker, optimizes the expansion process of the expanded clinker, and significantly improves the expansion efficiency of the expanded clinker. With low compounding dosage, an expansion agent product that meets the requirements of the national standard first-class product (type II) can be formulated, saving the cost ratio of the core raw materials of the expansion agent product, improving the cost-effectiveness advantage of the expansion agent product, and facilitating the market promotion of the expansion agent product. Detailed Implementation

[0029] The technical features of the high-calcium expanded clinker and its preparation method, which can be continuously produced in a rotary kiln according to the present invention, are further described below with reference to specific embodiments. The limestone and celestite used in the following embodiments of the present invention are obtained from factory mines, and the aluminum fluoride is a commercially available industrial-grade sample.

[0030] A high-calcium expanded clinker that can be continuously produced in a rotary kiln is prepared by calcining the following raw materials in parts by weight in a rotary kiln at a temperature of 1200℃-1300℃: 70-90 parts limestone, 8-24 parts celestite and 2-6 parts aluminum fluoride.

[0031] This invention also provides a method for preparing high-calcium expanded clinker that can be continuously produced on a rotary kiln. Preferably, the rotary kiln is equipped with a five-stage preheater as an industrial production equipment, and the preferred diameter of the rotary kiln is 2.5m-3.2m. The preferred rotary kiln production operation process is low-temperature slow firing, and the preferred rotary kiln speed is 1.0-1.5 rpm. The calcination temperature of the rotary kiln firing zone is controlled between 1200℃ and 1300℃. The granulation diameter of the expanded clinker exiting the kiln is controlled to be 5-20mm, and the vertical weight per liter is controlled to be 1100-1200g / L.

[0032] The embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. The embodiments will help to understand the present invention, but the protection scope of the present invention is not limited to the following embodiments.

[0033] Example 1

[0034] Example 1 of the present invention, high-calcium expanded clinker, is composed of the following raw materials in parts by weight:

[0035] 70 parts limestone

[0036] 24 samples of celestite

[0037] 6 parts aluminum fluoride;

[0038] In this embodiment 1, the industrial production equipment for high-calcium expanded clinker is a rotary kiln with a five-stage preheater and a kiln diameter of 3.0m. The production and preparation method on the rotary kiln includes the following steps:

[0039] (1) First, mix 70 parts limestone, 24 parts celestite, and 6 parts aluminum fluoride according to the specified ratio, and then send them to a common mill with a specific surface area of ​​350 m². 2 / kg, which is processed into raw meal powder and temporarily stored in the raw meal warehouse;

[0040] (2) The raw meal powder in the raw meal silo is conveyed to the feeding port of the fifth-stage preheater through the bottom unloading device and automatic conveying and metering equipment. After being fully preheated, it enters the rotary kiln from the kiln tail for high-temperature calcination. By adjusting the burner position and fuel consumption, the temperature of the rotary kiln calcination zone is maintained at 1200℃-1300℃, and the kiln speed is controlled to be stable at 1.5 rpm to ensure that the raw meal powder is slowly calcined at low temperature in the rotary kiln.

[0041] (3) The expanded clinker after being calcined at low temperature and slow speed in the rotary kiln is discharged from the kiln head and enters a single-cylinder cooler with lifting plates for cooling. The weight of the expanded clinker measured at the outlet of the cooler is 1100 g / L. The cooled expanded clinker particles are transported to the clinker silo for temporary storage by the conveying equipment.

[0042] (4) The expanded clinker particles in the clinker silo are ground into expanded clinker powder with a thickness of 0.08 mm and a sieve residue of ≤10%, which is the high-calcium expanded clinker that can be continuously produced on a rotary kiln according to the present invention.

[0043] Example 2

[0044] Example 2 of the present invention, the high-calcium expanded clinker, is composed of the following raw materials in parts by weight:

[0045] 76 portions of limestone

[0046] 20 portions of celestite

[0047] 4 parts aluminum fluoride;

[0048] In this embodiment 2, the industrial production equipment for high-calcium expanded clinker is a rotary kiln with a five-stage preheater and a kiln diameter of 3.0m. The production and preparation method on the rotary kiln includes the following steps:

[0049] (1) First, mix 76 parts limestone, 20 parts celestite, and 4 parts aluminum fluoride according to the specified ratio, and then send them to a common mill to achieve a specific surface area of ​​380 m². 2 / kg, which is processed into raw meal powder and temporarily stored in the raw meal warehouse;

[0050] (2) The raw meal powder in the raw meal silo is conveyed to the feeding port of the fifth-stage preheater through the bottom unloading device and automatic conveying and metering equipment. After being fully preheated, it enters the rotary kiln from the kiln tail for high-temperature calcination. By adjusting the burner position and fuel consumption, the temperature of the rotary kiln calcination zone is maintained at 1200℃-1300℃, and the kiln speed is controlled to be stable at 1.2 rpm to ensure that the raw meal powder is slowly calcined at low temperature in the rotary kiln.

[0051] (3) The expanded clinker after being calcined at low temperature and slow speed in the rotary kiln is discharged from the kiln head and enters a single-cylinder cooler with lifting plates for cooling. The weight of the expanded clinker measured at the outlet of the cooler is 1150 g / L. The cooled expanded clinker particles are transported to the clinker silo for temporary storage by the conveying equipment.

[0052] (4) The expanded clinker particles in the clinker silo are ground into expanded clinker powder with a thickness of 0.08 mm and a sieve residue of ≤10%, which is the high-calcium expanded clinker that can be continuously produced on a rotary kiln according to the present invention.

[0053] Example 3

[0054] Example 3 of the present invention, the high-calcium expanded clinker, is composed of the following raw materials in parts by weight:

[0055] 80 parts of limestone

[0056] 15 portions of celestite

[0057] 5 parts aluminum fluoride;

[0058] In this embodiment 3, the industrial production equipment for high-calcium expanded clinker is a rotary kiln with a five-stage preheater and a kiln diameter of 3.0m. The production and preparation method on the rotary kiln includes the following steps:

[0059] (1) First, mix 80 parts limestone, 15 parts celestite, and 5 parts aluminum fluoride according to the specified ratio, and then send them to a common mill with a specific surface area of ​​400 m². 2 / kg, which is processed into raw meal powder and temporarily stored in the raw meal warehouse;

[0060] (2) The raw meal powder in the raw meal silo is conveyed to the feeding port of the fifth-stage preheater through the bottom unloading device and automatic conveying and metering equipment. After being fully preheated, it enters the rotary kiln from the kiln tail for high-temperature calcination. By adjusting the burner position and fuel consumption, the temperature of the rotary kiln calcination zone is maintained at 1200℃-1300℃, and the kiln speed is controlled to be stable at 1.0 rpm to ensure that the raw meal powder is slowly calcined at low temperature in the rotary kiln.

[0061] (3) The expanded clinker after being calcined at low temperature and slow speed in the rotary kiln is discharged from the kiln head and enters a single-cylinder cooler with lifting plates for cooling. The weight of the expanded clinker measured at the outlet of the cooler is 1180 g / L. The cooled expanded clinker particles are transported to the clinker silo for temporary storage by the conveying equipment.

[0062] (4) The expanded clinker particles in the clinker silo are ground into expanded clinker powder with a thickness of 0.08 mm and a sieve residue of ≤10%, which is the high-calcium expanded clinker that can be continuously produced on a rotary kiln according to the present invention.

[0063] Example 4

[0064] Example 4 of this invention, the high-calcium expanded clinker, is composed of the following raw materials in parts by weight:

[0065] 85 parts limestone

[0066] 12 portions of celestite

[0067] 3 parts aluminum fluoride;

[0068] In this embodiment 4, the industrial production equipment for high-calcium expanded clinker is a rotary kiln with a five-stage preheater and a kiln diameter of 3.0m. The production and preparation method on the rotary kiln includes the following steps:

[0069] (1) First, mix 85 parts limestone, 12 parts celestite, and 3 parts aluminum fluoride according to the specified ratio, and then send them to a common mill to achieve a specific surface area of ​​360 m². 2 / kg, which is processed into raw meal powder and temporarily stored in the raw meal warehouse;

[0070] (2) The raw meal powder in the raw meal silo is conveyed to the feeding port of the fifth-stage preheater through the bottom unloading device and automatic conveying and metering equipment. After being fully preheated, it enters the rotary kiln from the kiln tail for high-temperature calcination. By adjusting the burner position and fuel consumption, the temperature of the rotary kiln calcination zone is maintained at 1200℃-1300℃, and the kiln speed is controlled to be stable at 1.1 rpm to ensure that the raw meal powder is slowly calcined at low temperature in the rotary kiln.

[0071] (3) The expanded clinker after being calcined at low temperature and slow speed in the rotary kiln is discharged from the kiln head and enters a single-cylinder cooler with lifting plates for cooling. The weight of the expanded clinker measured at the outlet of the cooler is 1200 g / L. The cooled expanded clinker particles are transported to the clinker silo for temporary storage by the conveying equipment.

[0072] (4) The expanded clinker particles in the clinker silo are ground into expanded clinker powder with a thickness of 0.08 mm and a sieve residue of ≤10%, which is the high-calcium expanded clinker that can be continuously produced on a rotary kiln according to the present invention.

[0073] Example 5

[0074] Example 5 of the present invention, the high-calcium expanded clinker, is composed of the following raw materials in parts by weight:

[0075] 90 parts limestone

[0076] Eight portions of celestite

[0077] 2 parts aluminum fluoride

[0078] In this embodiment 5, the industrial production equipment for high-calcium expanded clinker is a rotary kiln with a five-stage preheater and a kiln diameter of 3.0m. The production and preparation method on the rotary kiln includes the following steps:

[0079] (1) First, mix 90 parts limestone, 8 parts celestite, and 2 parts aluminum fluoride according to the specified ratio, and then grind them together to achieve a specific surface area of ​​370 m². 2 / kg, which is processed into raw meal powder and temporarily stored in the raw meal warehouse;

[0080] (2) The raw meal powder in the raw meal silo is conveyed to the feeding port of the fifth-stage preheater through the bottom unloading device and automatic conveying and metering equipment. After being fully preheated, it enters the rotary kiln from the kiln tail for high-temperature calcination. By adjusting the burner position and fuel consumption, the temperature of the rotary kiln calcination zone is maintained at 1200℃-1300℃, and the kiln speed is controlled to be stable at 1.4 rpm to ensure that the raw meal powder is slowly calcined at low temperature in the rotary kiln.

[0081] (3) The expanded clinker after being calcined at low temperature and slow speed in the rotary kiln is discharged from the kiln head and enters a single-cylinder cooler with lifting plates for cooling. The weight of the expanded clinker measured at the outlet of the cooler is 1100 g / L. The cooled expanded clinker particles are transported to the clinker silo for temporary storage by the conveying equipment.

[0082] (4) The expanded clinker particles in the clinker silo are ground into expanded clinker powder with a thickness of 0.08 mm and a sieve residue of ≤10%, which is the high-calcium expanded clinker that can be continuously produced on a rotary kiln according to the present invention.

[0083] Comparative Example 1

[0084] The limestone used is the same as in Example 1, except that an equal amount of anhydrite is used instead of celestite, and an equal amount of bauxite is used instead of aluminum fluoride. Similar to Example 1, industrial production is also carried out in a rotary kiln with a five-stage preheater and a kiln diameter of 3.0 meters. The production process is as follows: first, 70 parts by weight of limestone, 24 parts by weight of anhydrite, and 6 parts by weight of bauxite are mixed in proportion and then sent to a common mill with a specific surface area of ​​350 m². 2 / kg, to be made into raw meal powder and sent to the raw meal warehouse for temporary storage; then the raw meal powder is conveyed to the feeding port of the five-stage preheater through an automatic conveying and metering device. After being fully preheated, it enters the rotary kiln from the kiln tail for high-temperature calcination. By adjusting the burner position and fuel consumption, the temperature of the rotary kiln calcination zone is maintained at 1200℃-1300℃, and the kiln speed is controlled to be stable at 1.5 rpm to ensure that the raw meal powder is slowly calcined at low temperature in the rotary kiln; after calcination, the expanded clinker is discharged from the kiln head, cooled by the cooler, and sampled and measured. The vertical weight of the expanded clinker is 1100g / L. Finally, the expanded clinker particles are ground into expanded clinker powder of 0.08mm with a sieve residue of ≤10%, which is the comparative clinker 1 prepared by the same calcination process as in Example 1 of this invention.

[0085] Comparative Example 2

[0086] The raw materials and formula composition were identical to those in Comparative Example 1, the only difference being the calcination process. The production process was as follows: 70 parts by weight of limestone, 24 parts by weight of anhydrite, and 6 parts by weight of bauxite were mixed in a specific ratio and then ground together to a powder with a specific surface area of ​​350 m². 2 / kg, to be made into raw meal powder and sent to the raw meal warehouse for temporary storage; then the raw meal powder is conveyed to the feeding port of the five-stage preheater through an automatic conveying and metering device. After being fully preheated, it enters the rotary kiln from the kiln tail for high-temperature calcination. By adjusting the burner position and fuel consumption, the temperature of the rotary kiln calcination zone is maintained at 1350℃-1450℃, and the kiln speed is controlled to be stable at 1.8 rpm to ensure that the raw meal powder is fully calcined in the rotary kiln; after calcination, the expanded clinker is discharged from the kiln head, cooled by the cooler, and sampled. The vertical weight of the expanded clinker is measured to be 1400g / L. Finally, the expanded clinker particles are ground into expanded clinker powder of 0.08mm with a sieve residue of ≤10%, which is the comparative clinker 2 prepared by a different calcination process than that of Example 1 of this invention.

[0087] Performance testing

[0088] Table 1 shows a comparative analysis of the rotary kiln firing process between the examples and the comparative examples.

[0089] Table 1. Performance Comparison Analysis of Examples and Comparative Examples in Industrial Production Process on Rotary Kilns

[0090] Calcination process Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 kiln ring formation No knot No knot No knot No knot No knot Slightly coiled Severe ringing Continuous production time / d 150 160 140 155 145 40 5 Clinker sintering state dense particles dense particles dense particles dense particles dense particles Loose particles dense particles Clinker weight per liter (g / L) 1100 1150 1180 1200 1100 1100 1400

[0091] As shown in Table 1, when Examples 1-5 were industrialized on a rotary kiln with a preheater and a kiln diameter of 3.0 meters, a certain thickness of kiln skin existed inside the kiln, but there was no obvious ring formation. After ignition and heating, the continuous production time was long, up to about 150 days. The continuous operation of the rotary kiln was generally stopped only during the normal kiln shutdown and maintenance period. Moreover, the expanded clinker particles produced had good sintering density when the vertical weight was 1100g / L to 1200g / L.

[0092] Compared with Example 1, Comparative Example 1, which was prepared using the same calcination process, formed a sulfur-fixing zone in the rotary kiln during industrial production due to the calcination, decomposition, volatilization, and recrystallization of gypsum in the batching scheme. When the temperature of the calcination zone in the kiln was controlled at 1200℃-1300℃, it could be continuously produced for up to 40 days after ignition and heating. However, the expanded clinker particles produced were relatively loose and had poor sintering density. This indicates that the traditional three-component batching scheme of limestone, anhydrite, and bauxite used in Comparative Example 1 could not be effectively sintered under the low-temperature slow-fire production process of the present invention, resulting in poor performance of the expanded clinker produced.

[0093] Comparative Example 2 used the same raw materials and formula as Comparative Example 1. The difference was that during industrial production in a rotary kiln, the temperature of the calcination zone was increased from 1200℃-1300℃ to 1350℃-1450℃. The resulting expanded clinker particles had a weight per liter as high as 1400 g / L, exhibiting good sintering density. However, due to the high calcination temperature, the amount of liquid phase in the clinker increased, and the decomposition, volatilization, and recrystallization of gypsum increased. This quickly led to the formation of three or four sintering rings in the rotary kiln. After about 5 days of continuous firing, the kiln had to be shut down manually to remove the rings, as the severe ring formation affected ventilation and material movement. The firing continuity was very poor. It can be seen that the embodiments of the present invention can achieve continuous industrial production of high-calcium expanded clinker in a rotary kiln through the combined control of the batching scheme and firing process. In contrast, the comparative example using the traditional batching scheme could not achieve clinker sintering density during low-temperature calcination, and the high-temperature calcination resulted in a large amount of liquid phase, easy ring formation, and poor firing continuity.

[0094] Application Examples

[0095] Application Example 1

[0096] Using the reference cement specified in GB8076 and referring to the provisions of GB / T23439-2017 "Concrete Expansion Agents", the expanded clinker prepared in the examples and comparative examples was used to conduct a cement-admixed mortar restricted expansion test. The results are shown in Table 2. As can be seen from Table 2, under the same admixture dosage, the restricted expansion rate of the expanded clinker sample prepared in the examples of this invention is significantly greater than the corresponding value of the expanded clinker sample prepared in the comparative examples. Furthermore, the expansion efficiency of the sample with 7% admixture is slightly better than that of the sample with 10% admixture in the comparative examples. This indicates that the expanded clinker prepared in the examples of this invention has superior expansion efficiency.

[0097] Table 2 Comparative analysis of the restricted expansion rate of expanded clinker mortar prepared in the examples and comparative examples.

[0098]

[0099]

[0100] Application Example 2

[0101] Using the expanded clinker samples prepared in Example 1 and Comparative Example 2 as research objects, an expansive agent product was prepared by compounding the expanded clinker with a certain amount of gypsum. The performance of the expansive agent product was evaluated according to the requirements and mix proportions specified in GB / T23439-2017 "Concrete Expansive Agents". The test results are shown in Table 3. The results in the table show that, compared with Comparative Example 2, the expansive agent product prepared in Example 1 has better expansion performance at the same compounding ratio. The performance of the expansive agent product prepared with 35% of Example 1 meets the requirements of the national standard for Type II expansive agents, and is comparable to that of the expansive agent product prepared with 50% of Comparative Example 2. Therefore, the expanded clinker prepared in the embodiments of this invention has effective expansion efficiency, and an expansive agent product with excellent expansion performance can be compounded with low dosage, which can significantly reduce the production cost of expansive agent products and improve the market competitiveness of expansive agents.

[0102] Table 3 Comparison of the expansion performance of the expansion agent products prepared by compounding in Example 1 and Comparative Example 2

[0103]

Claims

1. A high-calcium expanded clinker that can be continuously produced on a rotary kiln, characterized in that, The high-calcium expanded clinker is prepared by calcining raw meal powder made from limestone as calcium raw material, celestite as sulfur raw material, and aluminum fluoride as mineral raw material in a rotary kiln at a temperature of 1200℃-1300℃. The above three raw material components are as follows by weight: 70-90 parts limestone Celestite, 8-24 parts 2-6 parts aluminum fluoride; The limestone contains ≥95 wt% CaCO3. The SrSO4 content in the celestite is ≥90 wt%; The aluminum fluoride contains ≥80wt% AlF3.

2. A method for preparing the high-calcium expanded clinker according to claim 1, characterized in that, Includes the following steps: S1. Mix the following components by weight: 70-90 parts limestone, 8-24 parts celestite, and 2-6 parts aluminum fluoride to obtain a mixture; S2. Grind the mixture together to a specific surface area of ​​350 m². 2 / kg~400 m 2 / kg, and the residue on an 80μm square hole sieve is no more than 5%, to obtain raw meal powder for the production of high-calcium expanded clinker. S3. Feed the raw meal powder into the rotary kiln through an automatic conveying and metering device. By adjusting the burner position and fuel consumption, maintain the temperature of the rotary kiln calcination zone at 1200℃-1300℃ and the kiln speed at 1.0 rpm to 1.5 rpm to ensure that the raw meal powder is slowly burned at a low temperature in the rotary kiln. S4. The expanded clinker, after being slowly calcined at low temperature in the rotary kiln, is discharged from the kiln head and enters a single-cylinder cooler with lifting plates for cooling. S5. Grind the cooled calcined clinker powder into clinker powder with a residue of ≤10% on a 0.08mm sieve to obtain the high-calcium expanded clinker.

3. The preparation method according to claim 2, characterized in that, In step S4, the granulation diameter of the expanded clinker exiting the kiln is controlled to be 5-20mm, and the vertical weight control index of the expanded clinker sampled at the kiln head cooler outlet is 1100g / L-1200g / L.

4. The preparation method according to claim 2, characterized in that, The rotary kiln is a rotary kiln with a five-stage preheater, and the kiln diameter is 2.5m-3.2m.

5. The preparation method according to claim 2, characterized in that, When an annular sintering ring forms inside the rotary kiln due to abnormal operation, the highest temperature point inside the rotary kiln is adjusted by moving the burner position, and the flame shape is controlled by combining the secondary air volume of the pulverized coal injection pipe.

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