High Efficiency VRM Cement Mill for Raw Material Grinding
Description
Which is better cement vertical roller mill or ball mill?
1. Comparison of Ball Mill and Vertical Mill Pulverization Schemes
1.1 Comparison of Process Plans for Ball Mill Pulverization and Vertical Mill Pulverization
Limestone grinding can be done using a vertical mill or ball mill. The top of the vertical mill comes with a separator. By adjusting the air ring valve, the product fineness can be changed, and the load of the material bed inside the mill can be uniform and stable. After the powder is discharged from the mill, it enters the pulse bag dust collector with the exhaust fan airflow for collection, and then enters the limestone powder silo for storage through horizontal and vertical conveying equipment, as shown in Figure 4. If it is a ball mill, after the powder is discharged, it first passes through an efficient powder concentrator for sorting. The powder concentrator has a rotor driven by a variable frequency motor and rotating vertically. By adjusting the speed of the rotor and the ventilation rate of the powder concentrator, the fineness of the finished product is adjusted. The sorted coarse material is sent back to the inlet of the mill through a screw conveyor for further grinding. The powder with the required fineness enters the pulse bag dust collector along with the exhaust fan airflow for collection, and then enters the limestone powder silo for storage through horizontal and vertical conveying equipment, as shown in Figure 1.
Figure 1: Process Flow Diagram of Ball Mill Pulverizing System
Figure 2: Process Flow Diagram of Vertical Grinding Powder System
The process flow shown in Figure 3 is a "two-stage dust collection system". The process is complex, there are many system equipment, and there are many system failure points. The system is characterized by difficult operation, multiple constraints on process layout, and a large footprint. Although high concentration dust collectors are not required, the relative investment is also significant.
The process flow shown in Figure 4 is a "primary dust collection system". It has the advantages of simple process flow, fewer system equipment, fewer system failure points, convenient system operation, flexible process layout, and no wear on the main fan impeller of the system. But it requires the configuration of a high concentration dust collector, which is relatively expensive.
Through comparison, it can be found that the vertical grinding process is simple, occupies a small area and space. The vertical grinding itself has a powder concentrator, and does not require additional powder concentrators and lifting equipment, resulting in fewer system equipment. The system has few fault points, convenient operation, and flexible process layout. The process is simple, the layout is compact, and can be arranged outdoors. The building area is about 70% of the ball mill system, and the building space is about 50-60% of the ball mill pulverizing system.
1.2 Comparison of Ball Mill Pulverizing and Vertical Mill Pulverizing System Schemes
The HVM type vertical mill pulverizing system used in a Fossil fuel power station is compared with the original ball mill pulverizing system of the plant.
Table 1: Comparison of Limestone Powder Preparation System Schemes
| Programme Project | Scheme 1 | Scheme 2 |
| Production Capacity(t/h) | ≥40 | ≥35 |
| Product Fineness | 325 mesh 90% pass | 250 mesh 90% pass |
| Product Power Consumption(kWh/t) | ~35 | ~60 |
| Allowed to Enter the Grinding Moisture(%) | ≤15 | ≤5 |
| Allowable grain size of grinding materials(mm) | ≤40 | ≤25 |
| Mill Main Motor Power(kW) | 560～630 | 1500 |
| Powder Separator | Bring Your Own | The system is reconfigured |
| System Installed Capacity(kW) | 920 | ～2200 |
| Equipment Price (Ten Thousand) | Mill | 500 | 380 |
| System Device | ≤700 | ≤750 |
| Construction Cost(Ten Thousand) | ≤30 | ≤85 |
| Installation Cost(Ten Thousand) | ≤15 | ≤42 |
| Total Investment(Ten Thousand) | ≤805 | ≤877 |
| Noise(dB) | ≤85 | ≥100 |
| Drying Capacity | Big | Small |
| System Ventilation Volume | Big | Small |
| System Equipment Maintenance Volume | Small | Big |
| System Process | Simple | Complex |
| System Host Process Layout | Indoor | Indoor |
From Table 1, it can be seen that using a ball mill milling system incurs nearly 10% more investment than using a vertical milling system. However, all technical and economic indicators are lower than those of the vertical grinding powder system. Especially for the power consumption per unit product, the vertical milling system is 30% to 40% lower than the ball milling system. It can be seen that the vertical grinding powder system is far superior to the ball mill powder system in terms of technical and economic indicators. In terms of other technical indicators, the vertical grinding powder system is also much more advanced.
3, Conclusion analysis
Through a comprehensive comparison between the ball mill milling system and the vertical milling system, it can be seen that the advantages of the vertical milling system over the ball mill milling system are:
(1) Significant reduction in production investment costs
The vertical grinding powder system has a simple process flow, compact layout, and small footprint. The vertical mill itself comes with a powder concentrator, without the need for additional powder concentrators and lifting equipment. The dust containing gas from the mill can be directly collected by a high concentration bag dust collector, so the process is simple, the layout is compact, and can be arranged outdoors. The building area is about 70% of the ball milling system, and the building space is about 50-60% of the ball milling system.
(2) High production efficiency, energy conservation and environmental protection
The vertical mill adopts the principle of bed material layer grinding to grind materials, with low energy consumption. The power consumption of the pulverizing system is 30%~40% lower than that of the ball mill pulverizing system. Moreover, with the increase of raw material moisture, the energy-saving effect is more obvious, and there is no phenomenon of ball pasting. The vertical mill does not have the metal impact sound of steel balls colliding with each other or colliding with the lining plate in the ball mill, so the noise is low, which is 20-25dB lower than that of the ball mill. In addition, the vertical mill adopts a full Closed system, and the system works under negative pressure, so there is no dust and the environment is clean.
(3)Easy operation and maintenance, convenient maintenance
The vertical mill is equipped with an automatic control system, which can achieve remote control and is easy to operate; By repairing the oil cylinder and flipping the rocker arm, it is convenient and quick to replace the roller sleeve and lining plate, reducing the loss of enterprise downtime. Due to the fact that the main grinding components are made of wear-resistant materials, the wear is not as fast as that of a ball mill. Frequent replacement of the grinding body can be achieved even if maintenance of the grinding components is required for a short period of time
(4) Stable product quality and easy detection
The chemical composition of the product is stable and the particle size distribution is uniform, which is beneficial for subsequent product performance. The material stays in the vertical mill for only 2-3 minutes, while in the ball mill it takes 15-20 minutes. So the chemical composition and fineness of vertical mill products can be quickly measured and corrected.
(5)The grinding body has low wear, high utilization rate, and low wear
The grinding body has low wear and high utilization rate. Due to the lack of direct metal contact between the grinding roller and the grinding disc during the operation of the vertical mill, the wear is small, and the metal consumption per unit product is generally 5-10 grams/ton; The service life of wear-resistant components is around 10000 hours.
(6)High drying capacity
Vertical mills use hot air to transport materials. When grinding materials with high moisture content, the inlet air temperature can be controlled to ensure that the product meets the required final moisture content. In a vertical mill, materials with up to 20% moisture content can be dried.
(7)Low noise, less dust, and clean operating environment
In the operation of a vertical mill, the grinding roller and grinding disc do not directly contact each other, and there is no metal impact sound of steel balls colliding with each other or hitting the lining plate in the ball mill. Therefore, the noise is low, which is 20-25 decibels lower than that of a ball mill. In addition, the vertical mill adopts a fully sealed system, which operates under negative pressure, without dust, and the environment is clean.
Specifications And Technical Parameters Of Cement Vertical Mill
| Model | HVM2500 | HVM2800 | HVM3400 | HVM3700 | HVM4200 | HVM4500 | HVM4800 | HVM5100 | HVM5600 |
| Grinding Table median Diameter(mm) | 2500 | 2800 | 3400 | 3700 | 4200 | 4500 | 4800 | 5100 | 5600 |
| Capacity(t/h) | 30-35 | 70-80 | 96-110 | 130-150 | 150-170 | 150-170 | 200-230 | 240-270 | 250-290 |
| Rough Material Moisture | ＜3% |
| Product specific surface area | ≥350㎡/kg |
| Product Moistrue | ≤1% |
| Main Motor Power(kW) | 900 | 1800 | 2500 | 3350 | 3800 | 4500 | 5300 | 6150 | 6450/6700 |
| Illustrate | Re:Raw materials bond index≤18kwh/t |
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