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 |
