1 Smash theory Overview The early pulverization theory research mostly reveals the relationship between the energy consumption of the pulverizing machine and the particle size reduction of the material to be crushed. In the late 19th century, some valuable energy consumption theories emerged. This is known as the surface area hypothesis, the volume hypothesis, the crack hypothesis, and the unified energy equation. However, these hypotheses are quite different from the actual situation and therefore cannot be used for the design of crushing machinery and actual crushing operations.
In fact, the method of using pulverization energy to study the degree of pulverization or solids fracture is not perfect. Because a large amount of energy is lost in the form of friction and sound during the mechanical transmission process, this loss can be measured; some energy losses within the pulverizing machine itself cannot be estimated, including the particles being rubbed without breaking. Energy loss due to cracking, loss of kinetic energy and potential energy, energy loss caused by particle elasticity and plastic deformation, energy loss caused by mechanochemical behavior during pulverization. Thus, the comminution can be the result of a pulverizing mechanical operation that consumes energy, while particle size reduction is only an indirect result of energy consumption.
Based on the above reasons, many scholars and experts in the world have begun extensive experimental research on material pulverization mechanism, energy balance and quantitative description of pulverization process, and put forward many valuable theories, and strive to be concrete and practical. Move in the direction. Based on the development of modern fracture mechanics and experimental techniques, the theory of high-pressure layer extrusion pulverization is proposed, that is, the stress concentration caused by the material under high pressure causes cracks and expansion, and then many micro-cracks are formed, and the surface cracks are formed to finally break the material. The crushing of the high-pressure layer avoids the waste of crushing energy taken by a large number of splash fragments generated during mechanical crushing, and the energy consumption is greatly reduced, thereby occupying the dominant position of the new-generation mill grinding theory.
2 Development trend of crushing technology and equipment——The emergence of energy-saving, consumption-reducing and environmentally-friendly ball mills has enabled the rapid development of metallurgy, electric power, mineral processing, chemical and other industries, due to its strong adaptability to various materials and high grinding capacity. Because of its simple manufacturing and adaptability to various production capacities, it has been favored by people for a long time. Only the cement industry's grinding operations, including raw material grinding and cement grinding, are basically applied by ball mills. The means of smashing. However, the ball mill is a kind of grinding equipment with low energy utilization rate. With the rapid development of the industry, the problem of over-exploitation of resources and insufficient energy has increasingly puzzled the scientific and technological personnel in various industries. In the cement industry, 60% to 70% of the total electricity consumption of cement production is used for grinding operations, while the effective work of grinding only accounts for about 3% of the total energy of the mill, and most of the input energy is converted into heat. Harmony with sound energy; and noise pollution is too serious to meet people's environmental requirements. Therefore, improving the grinding equipment is an important part of greatly reducing the energy consumption of the cement industry.
According to statistics, in 1990, the total energy consumption of building materials and other non-metallic mineral products processing industries accounted for 11.4% of the country's total energy consumption, accounting for 17.5% of the national industrial energy consumption, second only to the power industry, ranking second. . The energy consumption per 10,000 yuan of output value is 14.11t of standard coal, which is 3.8 times higher than the average energy consumption of the national industrial output value of 2.93t of standard coal. In the case of increasingly tight energy supplies, energy issues have become an important factor constraining the development of the building materials industry. In order to develop the building materials industry in a sustained, stable and coordinated manner and realize the transition from speed to efficiency, we must first realize the transition from high energy consumption to energy conservation.
Factors affecting the energy consumption of a product are multifaceted, both in terms of process (such as the selection and control of production processes and means), as well as in terms of equipment (such as the type of equipment and its performance), as well as operational and management aspects. s reason. Most of these factors are related to equipment. Energy conservation of equipment is an important area in energy conservation work, especially in the energy conservation of building materials industry.
The key to doing a good job in equipment energy conservation is to actively adopt new energy-saving equipment and technology to ensure that the equipment is in a good working condition, and to obtain the economic benefits of Zui with less energy consumption, which requires good equipment management and existing equipment. In particular, high-energy-consuming equipment carries out technological transformation centering on energy conservation and consumption reduction, and continuously develops, develops and promotes energy-saving equipment.
Since the 1980s, breakthroughs have been made in the extrusion and pulverization technology and equipment of the material layer, which is based on the theory of pulverization between particles under the action of large pressure. The vertical grinding and rolling press for grinding by extrusion has high energy efficiency, low energy consumption, compact structure and small floor space. The material layer extrusion pulverization technology and equipment are widely used in many industries such as cement, thermal power, mining and processing, and its development has been closely watched by various industries. However, the vertical grinding machine has a complicated structure and high system ventilation cost; the roller press has high roller pressure, complicated structure, large vibration, high maintenance cost, and low system drying ability. Therefore, the application of these mills has encountered certain difficulties.
In recent years, with the support of the European Community, the French FCB company has developed a compact structure with the reliability and product quality of the ball mill and the vertical mill on the basis of in-depth study of the grinding mechanism and various existing grinding equipment. The new low-energy, new-type grinding equipment of the roller press, the barrel roller mill, has the advantage of finding a new way to fully realize the energy-saving potential for the extrusion grinding process. The application of this technology can save 20% to 50% energy compared to the ordinary grinding system, and the output can be more than doubled.
3 Evaluation of the current situation of several layers of extrusion pulverization system The cement industry is committed to greatly reducing energy consumption is an important and long-term task, the main key is to improve the grinding efficiency and reduce the power consumption of grinding operations. Nowadays, cement raw meal grinding has been widely used in vertical grinding, and its superiority has been recognized, and its market share far exceeds that of traditional ball milling systems. However, in the field of cement grinding, whether it is a traditional ball milling system, a roller press, a vertical mill, a roller mill system, etc., they all have their own strengths, but they are insufficient.
3.1 Rolling press system material layer extrusion crushing technology and equipment, has been developed to a considerable extent abroad, Germany K. Professor Schî•nert has carried out pioneering research work in this area and achieved breakthrough achievements. In 1979 and 1984, he published an article on the experimental research and theoretical discussion of the traditional grinding method from the point of view of the energy of pulverizing materials. For the first time, "PressureComminutionintheMaterialBed" under high pressure was proposed. The new concept has triggered a revolution in the grinding industry.
The two companies in Germany quickly absorbed these technologies, and in 1985 they quickly introduced their respective roll presses, namely the HighPressure Grinding Roller from Polysius and The Pressed Roller from Humboldt. Then, the world's major cement machinery manufacturing companies, Danish Smith Company and American Fuller Company competed in the development of extrusion mills, and many cement manufacturers also rushed to apply, which caused the attention of relevant departments and cement industry workers in China.
China has also begun to introduce, develop and apply extrusion mills since the mid-1980s. Some research institutes and enterprises have introduced extrusion mills and their manufacturing technology from Humboldt, Germany, and have already developed large and medium-sized modern dry cement in China. The design and technical transformation projects of the production line have been promoted and applied. At the same time, the relevant design and scientific research units cooperated with the manufacturer to digest and transform the imported technical equipment, and on this basis, developed a series of small and medium-sized extrusion mills, and 1000t/d, 700t/d cement production lines. Matching, most of these equipments have adopted domestic materials and components, and have been applied in the production process, and achieved good economic benefits, which indicates that China's cement grinding technology application and equipment manufacturing has reached a new level.
According to relevant statistics, there are nearly 400 roller presses for cement crushing in the world, of which there are more than 90 in China, and the system has four kinds of pre-grinding, combined grinding, semi-final grinding and final grinding. The latter two are more advanced. The shortcomings of this system are the adjustment of system operating parameters and cement particle size composition. Because of the many influencing factors, the correlation is more complicated, the response time is slower, and each adjustment takes several hours to complete. Sometimes it may happen repeatedly, it is more laborious and time-consuming, not as simple and intuitive as the ball mill system, and the adjustment time is 30 minutes.
As for the semi-finish grinding system of the roller press, the situation is basically similar to that of the final grinding system, except that its grinding strength can also be lower, and the material circulation rate of the roller press can also be lower, so the inspection amount will be A little less, the annual utilization rate is higher. At the same time, the unit power consumption and investment of the system are slightly higher than the final grinding.
3.2 Vertical Grinding System In the early 1950s, Japan Tower Mill Co., Ltd. first developed a vertical mill. Sweden's Bryden Ellis Group Mineral Processing Systems (MPSI) has also developed vertical grinding. Countries such as the United States, Canada and Russia have been used in the field of fine grinding.
Vertical mills, also known as roller mills, have fundamental differences in terms of structure, grinding mechanism, system flow, process layout, automatic control, parameter determination, and energy consumption compared to ball mills. Some of its advantages are unmatched by the ball mill itself. The main performance is as follows: the vertical mill uses the thick bed principle to grind, the energy consumption is small, the grinding efficiency is high, and the power consumption of the whole grinding system is 10%-20 lower than that of the ball mill system. %; can make full use of the low temperature exhaust gas of the preheater. The hot air enters from the ring gap, and the wind speed is as high as 60-80 m/s, so the drying efficiency is high. If hot air furnace heat source is used, raw materials containing 15% to 20% moisture can be dried. Generally, the ball mill with drying chamber has a large drying moisture of 8%; the residence time of the material in the vertical mill is much shorter than that in the ball mill, which is convenient for measuring and adjusting the chemical composition of the material, and selecting the qualified fine powder in time. It is beneficial to realize the automatic control of the ingredients, and the chemical composition and particle gradation of the product are uniform; the particle size of the material can be from 50mm to 150mm, so the requirements for the crushing equipment can be generally relaxed.
The vertical mills currently used mainly include Loesche mills, MPS mills, Polysius mills, ring roll mills, Raymond mills and Atox mills. According to reports, the vertical mill is used for cement grinding, and the unit power consumption is 25-29 kWh/t cement.
The industrial practice of grinding cement with vertical mill has been used for more than 10 years. At the beginning, it has been hindering its promotion and application due to problems such as wear and vibration. In recent years, due to the breakthrough of raw mill grinding and the progress of materials science, it has made a good start in grinding cement and has become an eye-catching new army of cement grinding system.
The performance of vertical mill cement is the same as that of ball mill. It also has the following characteristics: simple system, flexible adjustment, fast response, easy to change the fineness and particle size distribution of cement, or change the production of different types of cement. It can be seen that its unit power consumption is also quite low and relatively advanced. The shortcoming is: if the moisture is too low, the thickness of the bed fluctuates greatly, affecting the smooth running of the mill, and properly spraying water into the grinding can solve the vibration problem. If the feed moisture is too high (eg > 15%), the hot blast stove must be activated to pass the hot air inside the mill. In the case of heavy rain during the rainy season, when the feed moisture is high, it can only be stopped.
At present, the CKP-FG vertical grinding system jointly developed by Japan's Chichibu Onoda and Kawasaki has great potential for grinding or ultra-fine grinding of cement and slag, which is characterized by selecting only the grinding part of the lower part of the vertical mill. The ground materials are all sent to a separate classifier by the hoist to sort and form a loop operating system with the vertical mill, aiming to save the power consumption of the wind mill-based vertical grinding pneumatic conveying materials. .
3.3 Can roller mill system In view of the high pressure of the roller press, the strict requirements of equipment manufacturing and the limitation of feed speed on the running speed, as well as the high manufacturing cost and low pressure of the vertical mill, the French FCB company launched in 1993. *Horomill, and successfully tested in Italy Buzzi Cement Co., Ltd., achieved a good effect of 18kWh per ton of cement grinding power. The barrel roller mill is a kind of extrusion grinding equipment for medium and high pressure, thin material layer and material circulation in the cylinder. In theory, it has both the energy saving effect of the roller press and the running reliability of the ball mill. It has a good application prospect and is received at home and abroad. Close attention has been paid to cement machinery manufacturers and cement plants in order to obtain greater benefits in terms of energy saving and consumption reduction of cement grinding. However, due to the fact that its structure and material selection still needs to be improved, there are still many problems in actual production, which need to be further studied by scientific and technical personnel to make it widely used in various grinding industries.
There are three kinds of roller mills in operation, commissioning, improvement or tackling stage, namely, Horomill of France FCB, Cemax mill of FLS of Denmark, and HXL barrel roller grinding of Huaxin Cement Company of China. Horomill has been plagued by mechanical and process operations in the actual operation of the cement grinding system, such as scraping plate fracture and wear, mill vibration, bearing heat leakage, roller surface damage. , material circulation fluctuations, transient peaks caused by system blockage. Under the strong support of Lafarge Cement Company of France, FCB has successively tried and tried in some cement plants, and is also constantly improving the design and seeking ways to solve the above drawbacks.
Cemax mills have three main differences in design compared to Horomill. Firstly, the grinding pressure is appropriately reduced. Under the premise of not significantly affecting the grinding effect, the load of the cylinder and the grinding roller is appropriately reduced, especially the strength is too concentrated; secondly, the mechanical two-end feeding and the wind are adopted. Sweeping both ends of the discharge mode, maintaining the balance of the two ends of the grinding roller to facilitate the elimination of many mechanical failures and smooth operation; the third is to increase the design temperature of the roller bearing to 130 ° C, appropriately increase the bearing specifications, so that It can withstand the temperature of the grinding material up to 100 °C, which is equivalent to the working condition of the ball mill, in order to dehydrate the part of the dihydrate gypsum and generate the hemihydrate gypsum to ensure the coagulation time of the finished cement is the same as that of the ball mill. It is understood that although the Cemax grinding system meets the design requirements, it is still not perfect and needs to be improved, mainly mechanical problems.
The HXL cylinder roller mill system developed by Huaxin Cement Company has been designed and commissioned to design a production OPC cement of about 100t/h, or a slag fineness of 450m 2 /kg of 45t/h. In the long-term operation in the future, if we can overcome some defects of the barrel roller mill, it will lead China's technological innovation in grinding.
4 Comprehensive comparison and evaluation of several material layer extrusion grinding systems Grinding systems can be roughly divided into three categories according to their technical maturity. * Classes are mature, such as: semi-final and final grinding of roller presses, and vertical grinding systems. Although they still have to be improved, people have basically found corresponding countermeasures and solutions to these shortcomings. The second category is largely mature, but there are still important deficiencies to be addressed, such as Horomill and Cemax mills. The third category is still to be verified by long-term practice, namely the newly developed system of Huaxin HXL cylinder roller mill.
According to the above pulverization theory and its development, in order to meet the needs of China's cement implementation of ISO international standards, the cement fineness and the efficiency of the grinding system need to be improved, and at the same time aiming at the development trend of international grinding technology, not only the material layer extrusion pulverization technology and The equipment is as energy-efficient as possible, reducing consumption, and it also puts forward higher requirements in terms of grinding effect, output, quality and environmental protection. This requires the scientific and technical personnel to focus on the development and promotion of the application of new grinding systems and corresponding measures, so that its grinding effect and efficiency are stable and efficient, and gradually become the leading machinery in the grinding industry. Such as: roller press, vertical mill, cylinder roller mill, ring roller mill and other grinding systems, although they are grinding speed, grinding strength in terms of material particle size distribution range and other process parameters of different forms of grinding system (see Table 1) But the common purpose is to save energy, reduce consumption, and protect the environment. Users can make correct evaluations and choices for various systems based on specific situations.
In fact, the method of using pulverization energy to study the degree of pulverization or solids fracture is not perfect. Because a large amount of energy is lost in the form of friction and sound during the mechanical transmission process, this loss can be measured; some energy losses within the pulverizing machine itself cannot be estimated, including the particles being rubbed without breaking. Energy loss due to cracking, loss of kinetic energy and potential energy, energy loss caused by particle elasticity and plastic deformation, energy loss caused by mechanochemical behavior during pulverization. Thus, the comminution can be the result of a pulverizing mechanical operation that consumes energy, while particle size reduction is only an indirect result of energy consumption.
Based on the above reasons, many scholars and experts in the world have begun extensive experimental research on material pulverization mechanism, energy balance and quantitative description of pulverization process, and put forward many valuable theories, and strive to be concrete and practical. Move in the direction. Based on the development of modern fracture mechanics and experimental techniques, the theory of high-pressure layer extrusion pulverization is proposed, that is, the stress concentration caused by the material under high pressure causes cracks and expansion, and then many micro-cracks are formed, and the surface cracks are formed to finally break the material. The crushing of the high-pressure layer avoids the waste of crushing energy taken by a large number of splash fragments generated during mechanical crushing, and the energy consumption is greatly reduced, thereby occupying the dominant position of the new-generation mill grinding theory.
2 Development trend of crushing technology and equipment——The emergence of energy-saving, consumption-reducing and environmentally-friendly ball mills has enabled the rapid development of metallurgy, electric power, mineral processing, chemical and other industries, due to its strong adaptability to various materials and high grinding capacity. Because of its simple manufacturing and adaptability to various production capacities, it has been favored by people for a long time. Only the cement industry's grinding operations, including raw material grinding and cement grinding, are basically applied by ball mills. The means of smashing. However, the ball mill is a kind of grinding equipment with low energy utilization rate. With the rapid development of the industry, the problem of over-exploitation of resources and insufficient energy has increasingly puzzled the scientific and technological personnel in various industries. In the cement industry, 60% to 70% of the total electricity consumption of cement production is used for grinding operations, while the effective work of grinding only accounts for about 3% of the total energy of the mill, and most of the input energy is converted into heat. Harmony with sound energy; and noise pollution is too serious to meet people's environmental requirements. Therefore, improving the grinding equipment is an important part of greatly reducing the energy consumption of the cement industry.
According to statistics, in 1990, the total energy consumption of building materials and other non-metallic mineral products processing industries accounted for 11.4% of the country's total energy consumption, accounting for 17.5% of the national industrial energy consumption, second only to the power industry, ranking second. . The energy consumption per 10,000 yuan of output value is 14.11t of standard coal, which is 3.8 times higher than the average energy consumption of the national industrial output value of 2.93t of standard coal. In the case of increasingly tight energy supplies, energy issues have become an important factor constraining the development of the building materials industry. In order to develop the building materials industry in a sustained, stable and coordinated manner and realize the transition from speed to efficiency, we must first realize the transition from high energy consumption to energy conservation.
Factors affecting the energy consumption of a product are multifaceted, both in terms of process (such as the selection and control of production processes and means), as well as in terms of equipment (such as the type of equipment and its performance), as well as operational and management aspects. s reason. Most of these factors are related to equipment. Energy conservation of equipment is an important area in energy conservation work, especially in the energy conservation of building materials industry.
The key to doing a good job in equipment energy conservation is to actively adopt new energy-saving equipment and technology to ensure that the equipment is in a good working condition, and to obtain the economic benefits of Zui with less energy consumption, which requires good equipment management and existing equipment. In particular, high-energy-consuming equipment carries out technological transformation centering on energy conservation and consumption reduction, and continuously develops, develops and promotes energy-saving equipment.
Since the 1980s, breakthroughs have been made in the extrusion and pulverization technology and equipment of the material layer, which is based on the theory of pulverization between particles under the action of large pressure. The vertical grinding and rolling press for grinding by extrusion has high energy efficiency, low energy consumption, compact structure and small floor space. The material layer extrusion pulverization technology and equipment are widely used in many industries such as cement, thermal power, mining and processing, and its development has been closely watched by various industries. However, the vertical grinding machine has a complicated structure and high system ventilation cost; the roller press has high roller pressure, complicated structure, large vibration, high maintenance cost, and low system drying ability. Therefore, the application of these mills has encountered certain difficulties.
In recent years, with the support of the European Community, the French FCB company has developed a compact structure with the reliability and product quality of the ball mill and the vertical mill on the basis of in-depth study of the grinding mechanism and various existing grinding equipment. The new low-energy, new-type grinding equipment of the roller press, the barrel roller mill, has the advantage of finding a new way to fully realize the energy-saving potential for the extrusion grinding process. The application of this technology can save 20% to 50% energy compared to the ordinary grinding system, and the output can be more than doubled.
3 Evaluation of the current situation of several layers of extrusion pulverization system The cement industry is committed to greatly reducing energy consumption is an important and long-term task, the main key is to improve the grinding efficiency and reduce the power consumption of grinding operations. Nowadays, cement raw meal grinding has been widely used in vertical grinding, and its superiority has been recognized, and its market share far exceeds that of traditional ball milling systems. However, in the field of cement grinding, whether it is a traditional ball milling system, a roller press, a vertical mill, a roller mill system, etc., they all have their own strengths, but they are insufficient.
3.1 Rolling press system material layer extrusion crushing technology and equipment, has been developed to a considerable extent abroad, Germany K. Professor Schî•nert has carried out pioneering research work in this area and achieved breakthrough achievements. In 1979 and 1984, he published an article on the experimental research and theoretical discussion of the traditional grinding method from the point of view of the energy of pulverizing materials. For the first time, "PressureComminutionintheMaterialBed" under high pressure was proposed. The new concept has triggered a revolution in the grinding industry.
The two companies in Germany quickly absorbed these technologies, and in 1985 they quickly introduced their respective roll presses, namely the HighPressure Grinding Roller from Polysius and The Pressed Roller from Humboldt. Then, the world's major cement machinery manufacturing companies, Danish Smith Company and American Fuller Company competed in the development of extrusion mills, and many cement manufacturers also rushed to apply, which caused the attention of relevant departments and cement industry workers in China.
China has also begun to introduce, develop and apply extrusion mills since the mid-1980s. Some research institutes and enterprises have introduced extrusion mills and their manufacturing technology from Humboldt, Germany, and have already developed large and medium-sized modern dry cement in China. The design and technical transformation projects of the production line have been promoted and applied. At the same time, the relevant design and scientific research units cooperated with the manufacturer to digest and transform the imported technical equipment, and on this basis, developed a series of small and medium-sized extrusion mills, and 1000t/d, 700t/d cement production lines. Matching, most of these equipments have adopted domestic materials and components, and have been applied in the production process, and achieved good economic benefits, which indicates that China's cement grinding technology application and equipment manufacturing has reached a new level.
According to relevant statistics, there are nearly 400 roller presses for cement crushing in the world, of which there are more than 90 in China, and the system has four kinds of pre-grinding, combined grinding, semi-final grinding and final grinding. The latter two are more advanced. The shortcomings of this system are the adjustment of system operating parameters and cement particle size composition. Because of the many influencing factors, the correlation is more complicated, the response time is slower, and each adjustment takes several hours to complete. Sometimes it may happen repeatedly, it is more laborious and time-consuming, not as simple and intuitive as the ball mill system, and the adjustment time is 30 minutes.
As for the semi-finish grinding system of the roller press, the situation is basically similar to that of the final grinding system, except that its grinding strength can also be lower, and the material circulation rate of the roller press can also be lower, so the inspection amount will be A little less, the annual utilization rate is higher. At the same time, the unit power consumption and investment of the system are slightly higher than the final grinding.
3.2 Vertical Grinding System In the early 1950s, Japan Tower Mill Co., Ltd. first developed a vertical mill. Sweden's Bryden Ellis Group Mineral Processing Systems (MPSI) has also developed vertical grinding. Countries such as the United States, Canada and Russia have been used in the field of fine grinding.
Vertical mills, also known as roller mills, have fundamental differences in terms of structure, grinding mechanism, system flow, process layout, automatic control, parameter determination, and energy consumption compared to ball mills. Some of its advantages are unmatched by the ball mill itself. The main performance is as follows: the vertical mill uses the thick bed principle to grind, the energy consumption is small, the grinding efficiency is high, and the power consumption of the whole grinding system is 10%-20 lower than that of the ball mill system. %; can make full use of the low temperature exhaust gas of the preheater. The hot air enters from the ring gap, and the wind speed is as high as 60-80 m/s, so the drying efficiency is high. If hot air furnace heat source is used, raw materials containing 15% to 20% moisture can be dried. Generally, the ball mill with drying chamber has a large drying moisture of 8%; the residence time of the material in the vertical mill is much shorter than that in the ball mill, which is convenient for measuring and adjusting the chemical composition of the material, and selecting the qualified fine powder in time. It is beneficial to realize the automatic control of the ingredients, and the chemical composition and particle gradation of the product are uniform; the particle size of the material can be from 50mm to 150mm, so the requirements for the crushing equipment can be generally relaxed.
The vertical mills currently used mainly include Loesche mills, MPS mills, Polysius mills, ring roll mills, Raymond mills and Atox mills. According to reports, the vertical mill is used for cement grinding, and the unit power consumption is 25-29 kWh/t cement.
The industrial practice of grinding cement with vertical mill has been used for more than 10 years. At the beginning, it has been hindering its promotion and application due to problems such as wear and vibration. In recent years, due to the breakthrough of raw mill grinding and the progress of materials science, it has made a good start in grinding cement and has become an eye-catching new army of cement grinding system.
The performance of vertical mill cement is the same as that of ball mill. It also has the following characteristics: simple system, flexible adjustment, fast response, easy to change the fineness and particle size distribution of cement, or change the production of different types of cement. It can be seen that its unit power consumption is also quite low and relatively advanced. The shortcoming is: if the moisture is too low, the thickness of the bed fluctuates greatly, affecting the smooth running of the mill, and properly spraying water into the grinding can solve the vibration problem. If the feed moisture is too high (eg > 15%), the hot blast stove must be activated to pass the hot air inside the mill. In the case of heavy rain during the rainy season, when the feed moisture is high, it can only be stopped.
At present, the CKP-FG vertical grinding system jointly developed by Japan's Chichibu Onoda and Kawasaki has great potential for grinding or ultra-fine grinding of cement and slag, which is characterized by selecting only the grinding part of the lower part of the vertical mill. The ground materials are all sent to a separate classifier by the hoist to sort and form a loop operating system with the vertical mill, aiming to save the power consumption of the wind mill-based vertical grinding pneumatic conveying materials. .
3.3 Can roller mill system In view of the high pressure of the roller press, the strict requirements of equipment manufacturing and the limitation of feed speed on the running speed, as well as the high manufacturing cost and low pressure of the vertical mill, the French FCB company launched in 1993. *Horomill, and successfully tested in Italy Buzzi Cement Co., Ltd., achieved a good effect of 18kWh per ton of cement grinding power. The barrel roller mill is a kind of extrusion grinding equipment for medium and high pressure, thin material layer and material circulation in the cylinder. In theory, it has both the energy saving effect of the roller press and the running reliability of the ball mill. It has a good application prospect and is received at home and abroad. Close attention has been paid to cement machinery manufacturers and cement plants in order to obtain greater benefits in terms of energy saving and consumption reduction of cement grinding. However, due to the fact that its structure and material selection still needs to be improved, there are still many problems in actual production, which need to be further studied by scientific and technical personnel to make it widely used in various grinding industries.
There are three kinds of roller mills in operation, commissioning, improvement or tackling stage, namely, Horomill of France FCB, Cemax mill of FLS of Denmark, and HXL barrel roller grinding of Huaxin Cement Company of China. Horomill has been plagued by mechanical and process operations in the actual operation of the cement grinding system, such as scraping plate fracture and wear, mill vibration, bearing heat leakage, roller surface damage. , material circulation fluctuations, transient peaks caused by system blockage. Under the strong support of Lafarge Cement Company of France, FCB has successively tried and tried in some cement plants, and is also constantly improving the design and seeking ways to solve the above drawbacks.
Cemax mills have three main differences in design compared to Horomill. Firstly, the grinding pressure is appropriately reduced. Under the premise of not significantly affecting the grinding effect, the load of the cylinder and the grinding roller is appropriately reduced, especially the strength is too concentrated; secondly, the mechanical two-end feeding and the wind are adopted. Sweeping both ends of the discharge mode, maintaining the balance of the two ends of the grinding roller to facilitate the elimination of many mechanical failures and smooth operation; the third is to increase the design temperature of the roller bearing to 130 ° C, appropriately increase the bearing specifications, so that It can withstand the temperature of the grinding material up to 100 °C, which is equivalent to the working condition of the ball mill, in order to dehydrate the part of the dihydrate gypsum and generate the hemihydrate gypsum to ensure the coagulation time of the finished cement is the same as that of the ball mill. It is understood that although the Cemax grinding system meets the design requirements, it is still not perfect and needs to be improved, mainly mechanical problems.
The HXL cylinder roller mill system developed by Huaxin Cement Company has been designed and commissioned to design a production OPC cement of about 100t/h, or a slag fineness of 450m 2 /kg of 45t/h. In the long-term operation in the future, if we can overcome some defects of the barrel roller mill, it will lead China's technological innovation in grinding.
4 Comprehensive comparison and evaluation of several material layer extrusion grinding systems Grinding systems can be roughly divided into three categories according to their technical maturity. * Classes are mature, such as: semi-final and final grinding of roller presses, and vertical grinding systems. Although they still have to be improved, people have basically found corresponding countermeasures and solutions to these shortcomings. The second category is largely mature, but there are still important deficiencies to be addressed, such as Horomill and Cemax mills. The third category is still to be verified by long-term practice, namely the newly developed system of Huaxin HXL cylinder roller mill.
According to the above pulverization theory and its development, in order to meet the needs of China's cement implementation of ISO international standards, the cement fineness and the efficiency of the grinding system need to be improved, and at the same time aiming at the development trend of international grinding technology, not only the material layer extrusion pulverization technology and The equipment is as energy-efficient as possible, reducing consumption, and it also puts forward higher requirements in terms of grinding effect, output, quality and environmental protection. This requires the scientific and technical personnel to focus on the development and promotion of the application of new grinding systems and corresponding measures, so that its grinding effect and efficiency are stable and efficient, and gradually become the leading machinery in the grinding industry. Such as: roller press, vertical mill, cylinder roller mill, ring roller mill and other grinding systems, although they are grinding speed, grinding strength in terms of material particle size distribution range and other process parameters of different forms of grinding system (see Table 1) But the common purpose is to save energy, reduce consumption, and protect the environment. Users can make correct evaluations and choices for various systems based on specific situations.
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