The cement roller press is a kind of cement equipment for brittle materials, apply for cement clinker, and cement raw material, gypsum, coal, quartz sand, iron ore, blast furnace slag, and other materials.
The cement roller press is generally applied to the cement grinding plant, according to the real working process, cement roller press works with cement ball mill or vertical cement mill, which helps cement grinding plant to works well.
As new-type and energy-efficient cement grinding machine, cement roller press has advantages of energy-saving, high efficiency, less steel consumption and less noise. Both apply for new cement plant building and old cement plant revamping. According to the data, roller press helps ball mill system to increase the output by 30-50%. The 0.08mm fine material in the extruded material cake accounts for 20-35%, and smaller than 2mm accounts for 65-85%.
install the roller press in the cement grinding plant, the high pressure load is transmitted to the layer of the grinded material through the diameter of the double roller, most of the energy is used for the mutual extrusion between the materials. The sound energy and thermal energy generated by the friction of the material are transformed into the deformation energy of the material, which causes deformation, tearing and pulverization and fully utilize the potential of the cement grinding equipment, increase the output by 50-100%, and reduce the total energy consumption by 20%-30%. Promote the production efficiency of the entire system.
The material after grinding is greatly reduced in both particle size and the Bond function index, thereby greatly improving the grinding condition of grinding machine, and the power consumption of the entire cement grinding system is significantly reduced. It can save25-50% energy compared to traditional grinding methods, and the annual electricity saving are considerable.
Compared with the tube mill, the roller press is simple in structure, small in size, light in weight, and takes up less space in the workshop. It can save civil construction investment and also facilitate the original investment. In addition, the operation and maintenance of the roller press is very simple.
The material is squeezed and smashed continuously in the roller cover, and the harmful dust is not easy to spread. At the same time, the noise of the roller press is much smaller than that of the tube mill because of no impact.
The traditional tube mill is limited by processing, transportation, heat treatment and other conditions, and the large-scale tube mill is greatly restricted. The roller press grinding system solves such problems well.
The roller press works according to the principle of high-pressure layer pulverization, and adopts the work mode of single-grain pulverization. The brittle material is subjected to high pressure extrusion (the pressure of the machine in the pressure zone is about 150 MPa), the particle size of the material is rapidly reduced, the fine powder content of less than 0.08 mm reaches 20-30%, and the material of less than 2 mm reaches 70% or more, and a large number of cracks are present in all extruded materials, so that the energy required for the material to be ground in the next process is greatly reduced.
The main body of the roller press is two rollers that rotate in opposite directions, one is a fixed roller and the other is a movable roller. The brittle material is fed into the weighing chamber with the load cell by the conveying device, and then passes through the feeding device of the roller press into two rolls of the same size and opposite to each other, and the material is pulled into the nip by one side of the roller. The material is pressed into a dense material cake with high pressure, and finally falls from the nip, and is discharged from the hopper by the conveying device. The cake is further dispersed or ground by the next process.
Both the cementball mill and the cement roller press have their own advantages and disadvantages, but in actual production, the cement roller press has the advantages that the ball mill does not have, mainly reflected in the following points.
Note: Due to the large force of the roller of the roller press, the roller press has some problems, such as the material and the wear of the roller surface, the bearing is easily damaged, and the gear of the reducer is prematurely broken. In addition, the process operation process is strict. For example, the feed material column is required to be dense and full, and a certain feed pressure is maintained. The feed amount control should be appropriate, and the grinding process system configuration should be appropriate, otherwise its superiority cannot be exerted.
Grinding machines are indispensable equipment in cement plants. In the process of cement production, the cement plant needs to complete the grinding of pulverized coal, raw meal powder, and cement products. The purpose of grinding is to increase the specific surface area of the material and reduce the particle size of the powder, so as to achieve the activity required by the next process.
Tube mill has been used as the main grinding equipment in the cement industry for a long time, and it is still widely used because of its simple structure, easy operation, and low price. However, the energy utilization rate of tube mills is only 2% ~ 20%, which is very low. With the continuous development of grinding technology, there are two kinds of cement grinding equipment with lower energy consumption, one is vertical roller mill, and the other is roller press.
Both the vertical roller mill and roller press apply the working principle of material bed milling. During the grinding process, only a small part of material particles directly contact with the grinding parts of the mill; but under the action of grinding parts, material particles form a material bed, and through the stress transmission and interaction between the particles, they are cracked, broken, and crushed.
For vertical roller mill, the grinding parts are rollers and grinding disc. The pressure required for grinding mainly comes from the rollers. At present, the loading force is mainly formed by hydraulic pressure. The material is fed into the grinding disc from the center or side of the upper housing, and the material layer is formed in the process of moving on the grinding disc. When the material passes between the roller and the grinding disc, the grinding is completed under the extrusion and shear force between them.
For roller press, the grinding parts are two rollers of the same size. The materials fall vertically from the top to the two rollers to form the material bed. Under the extrusion force of the two rollers, materials are ground to fine particles. There are two transmission modes of roller press, namely double drive, and single drive. The double drive roller press is the more popular type. The transmission device of a single drive roller press has only one set to drive one roller, and the other roller is driven by connecting with the former one with a gear train.
In a vertical roller mill, the material on the grinding disc is restricted by the air duct ring, but the side of the material between roller and disc is not restricted. In roller press, in addition to the restriction between the two rollers, side baffles will also be set on the sides of both ends of the roller, which will limit the side of the material bed of the roller press.
Because the grinding area of the roller press is restricted from all sides, the increase of applied energy will also increase the fine powder and specific surface area of material. But for vertical roller mills, the growth rate of that of material will gradually decrease. From this point of view, roller press is superior to vertical mill.
In a vertical mill, there generally are two or more grinding rollers. The contact area between the grinding roller and the grinding disc is large, and the energy utilization rate is higher than that of the roller press. Moreover, the materials are generally milled on the grinding disc by several grinding rolls repeatedly. From this point of view, the vertical mill is better than the roller press.
When grinding cement products, a grinding system composed of a roller press or an external circulation vertical mill + a powder concentrator + a tube mill is generally selected. Taking grinding P o42.5 cement as an example, the pre grinding closed-loop system composed of roller press or external circulation vertical mill and powder concentrator has a circulation load rate of 200% 300%, and the specific surface area of the selected materials is 180-280m2 / kg. The following table lists the main machine preparation and the product particle size of several cement grinding systems.
The particle shape of the materials from the roller press and the vertical roller mill is also different. The vertical mill grinds the material by two forces, the extrusion force and the shearing force between the roller and the grinding disc; the roller press grinds the material by only one force, the force between the two grinding rollers. When the material is ground to a certain fineness, most of the fine powders from the vertical mill are irregular and prismatic, and the fine powders from the roller press are mainly irregular flake and strip particles. From the particle shape, the fine powder from vertical mill is closer to that from tube mill, and the fine powder from vertical mill is more suitable for making cement products than that from roller press.
The grinding process consumes the most energy in the cement production, its energy consumption accounts for more than 70% of the total power consumption in the whole process of cement production. There are three main grinding processes in the cement production: raw meal grinding, cement grinding, and raw coal grinding. The power consumption of the cement grinding accounts for about 40% of the total power consumption of the cement production process. Therefore, the selection of a reasonable cement grinding system plays a key role in energy saving and consumption reduction of cement plants.
Nowadays, the cement grinding system has developed from the previous single ball mill system to ball mill + roller press system and vertical roller mill system. Today we will introduce three mainstream ball mill + roller press cement grinding processes that are often adopted in cement plants and cement grinding stations.
The cement grinding process in this system is rather simple with less equipment required. The finished product cement from this system has all been further ground in the ball mill, so it has wide particle size distribution and stable performance.
However, due to the fact that the materials rolled by the roller press are not sorted, a large amount of fine powder is returned to the roller press. If the return proportion is more than 60%, the roller press will not be able to operate stably, so the power saving range of the roller press is limited.
In this system, the ground materials from the roller press is first processed by the separator and divided into two parts: the coarse part and the fine part. The fine part is sent to the ball mill and ground to product cement, the coarse part is returned to the roller press to be ground again. The finished product cement from this system also has wide particle size distribution and stable performance.
But this system also has its weakness. The cyclone and the circulating fan in this system are easily worn, and there are a lot of qualified fine powers in the semi-finished products, which lowers the grinding efficiency of this system.
The two stage grinding system is developed from the combined grinding system of roller press and ball mill. This system performs even better on energy saving, and also solves the worn problem of the cyclone and the circulating fan.
In this system, the pressed materials from the roller press are divided into three parts by the separator: the coarse part, the fine part, and the medium-fine part. The coarse part is returned to the roller press for crushing once again; the medium fine part is sent to the ball mill for final grinding; and the fine part is discharged directly as the finished product cement.
Because the roller press and the ball mill are two separate circulate system, the whole cement grinding process is easy to operate and control. The grinding efficiency of the system is also enhanced because qualified fine powers from the roller press dont need to be ground again by the ball mill.
However, due to the fact that part of the finished cement produced by this system has not been ground by the ball mill, its particle uniformity and working performance may be slightly worse than those produced by the other two systems.
The three cement grinding systems are all formed mainly by a roller press and a cement ball mill, and each of them has its own advantages and disadvantages. The selection of the three systems mainly depends on the relative size of the roller press and the ball mill
As a professional contractor of cement plant, in the design process of cement plant, our team will select the most appropriate cement grinding system after fully considering the production condition and discussing with the client.
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The cement roller press is a kind of grinding equipment applied for brittle materials, such as cement clinker, granular blast furnace slag, cement raw materials (limestone, sandstone, shale, etc.), gypsum, coal, quartz sand, iron ore, etc. It is designed according to the principle of bed grinding, the high-pressure load directly acts on the material layer through double rollers, which causes internal stress in particles and leads to cracks to achieve the purpose of grinding.
The cement roller press has a high energy utilization rate and remarkable energy-saving effect in the material grinding process. In cement plant, cement roller press is a kind of important cement equipment used for clinker grinding. It is usually combined with a cement ball mill to form a high-efficiency cement grinding system because the practice shows that the grinding process with small grinding ratio and step-by-step completion is more energy-saving than that with large one-time completion.
Cement ball mill is a main cement grinding mill with a low energy utilization rate (only 3%-5%). Compared with the grinding energy consumption, most of its energy is consumed by collision heating and noise. Therefore, we usually adopt the cement roller press to replace the fine crushing and coarse grinding role of the ball mill. This increases the output of the ball mill system by 30-50%, and 20-35% of the extruded materials are smaller than 0.08mm, 65-85% are smaller than 2mm. Besides, a large number of cracks will be produced on all extruded materials, which will greatly reduce the energy consumption of materials in the next grinding process.
Pre-grinding system: after the material is pulverized by the roller press, all or part of them with a good extrusion effect will enter the subsequent ball mill for further grinding. This system has the advantages of simple processes, less equipment, wide particle size distribution, and stable cement performance. But because the ground material is not classified, a large number of fine powders are back to the roller press, the power saving range is limited.
Combined grinding system: materials ground by cement roller press are divided into two parts by air classifier: coarse part and fine part. The fine part will enter the ball mill to be further ground into the finished product, the coarse part will return to the roller press to be ground again. Because the cement finished products are all ground by the ball mill, the finished products have wide particle size distribution and the cement performance is stable.
Semi-finishing grinding system: after ground by cement roller press, materials are divided into three parts through an air classifier: coarse, medium and fine, in which the coarse material is returned to roller press for re-grinding, the medium material is put into ball mill for further grinding, and the fine material is directly discharged as the finished cement product. Because the roller press and the ball mill are two completely independent circulation systems, they are easier to operate and control and are more energy saving.
Finish grinding system: this system only includes a cement roller press to complete the grinding of cement clinker. Materials ground by cement roller press are divided into two parts by air classifier: coarse part and fine part. The coarse part will return to the roller press to be ground again and the fine part will be discharged as the cement product.
The cement roller press is composed of two rollers that rotate synchronously in the opposite direction and a set of a hydraulic system. Its main structure includes a press roller system, transmission device, mainframe, hydraulic system, feeding device, and so on.
The two rollers of cement roller press, one is fixed and the other is movable, which are driven by a motor and a reducer to rotate at a relatively low speed. The movable roller bearing seat is connected with the hydraulic system. It can be moved along a horizontal direction to control the gap between the two rollers, while the fixed roller is installed in the inner chamber of the mainframe. When materials enter between the two rollers from above, pressure (50-300Mpa) is transferred to materials by the hydraulic system through oil cylinder, bearing seat, and rollers so that material particle size can be reduced by means of extrusion. After grinding, the fine particles less than 90m account for about 20-30%. At the same time, there are many cracks in the coarse particles. In the process of further grinding, their energy consumption can be greatly reduced.
AGICO is a professional cement plant equipment supplier in China. The cement roller press is one of our hot-sales products in the cement grinding unit. Compared with other cement mills, the roller press produced by AGICO has the following advantages:
Cement ball mill and cement roller press are both the commonly used equipment for clinker grinding. But in the actual cement production process, the roller press has more advantages in different aspects, mainly reflected in the following points:
AGICO Group is an integrative enterprise group. It is a Chinese company that specialized in manufacturing and exporting cement plants and cement equipment, providing the turnkey project from project design, equipment installation and equipment commissioning to equipment maintenance.
India is the world's second largest producer of cement and produces more than 8 per cent of global capacity. Due to the rapidly growing demand in various sectors such as defense, housing, commercial and industrial construction, government initiative such as smart cities & PMAY, cement production in India is expected to touch 550600 million tones per annum (MTPA) by the end of year 2025.
With recent growth and success journey there is also a threat approaching to cement industry that its input cost is increasing. Power cost, fuel cost, raw material cost have doubled up in recent years whereas cement price has not hiked in that fashion. Also 40% of the cement production costs are energy costs out of which more than 60% of the total electricity is used in grinding circuits. In order to survive and sustain in the market they need to increase their profitability which can only be achieved by increasing productivity and reducing power consumption. High productivity and low power costs can be achieved by increasing output, lowering breakdowns and optimizing the energy consuming grinding process.
The objective of the study, is to draw attention to the need of Cement grinding process optimization to minimize power consumption and achieve higher productivity. In the study the advantages of vertical roller mill are discussed over ball mills. VRM construction, its process and parameters which affects the performance and productivity of vertical roller mill are discussed. Also the consequences of variations in parameter explained. With proper optimization of these parameters, the productivity of vertical roller mill can be improved and performance stability can be achieved by addressing root causes.. This study can benefit the organizations using VRM and are not able to utilize its full productivity due to some bottlenecks or constraints.