Design Scheme
Project Site: Gansu, China
Equipment: 1 LM220 Vertical Mill, dust collector, fan, nitrogen protection system, fire extinguishing device and intelligent centralized control device
Material: Coal
Input Size: ≤40mm
Output Size: 200meshes （0.074mm）， D80
Capacity: 300,000TPY
In 2016, a state-owned energy company in Gansu, Chian entered business relationship with SBM to build an efficient and clean coal powder preparation production line. The annual output is 300,000 tons. Currently, the project becomes the model of efficient coal powder industrial boilers in local areas and surrounding areas. This energy-saving and environment-friendly project is deemed to have a promising future.
Project Profile
Through years of research, the new clean coal produced by this company is of low cost, low dust, low sulfur content but high heat efficiency. The target of product for this project is the power-supply companies in the city and neighboring towns.
Project Background
Support and Pressure from Policies
Since 2015, the air pollution has been a headache in northern China. Coal combustion deepens the environment pollution and damage of ecosystems because of a great deal of emission of dust, SO2 and nitric oxides. For coal combustion, both the thermal power plant and industrial coal-fired boiler are the two main application fields.
So, in 2015, China National Energy Bureau launched the Action Plan of Efficient& Clean Use of Coal (2015-2020) and required every province to boost the transformation and upgrading of industrial coal-fired boilers. Meanwhile, release and revise of some other related policies stipulated the responsibility of government on environment protection and punishments once there is some company trying to discharge pollutants at random.
In response to environmental protection, this customer has been adjusting its operation structure in recent years and started to march to the market of clean coal powder.
Technological Verification
Efficient industrial coal powder boiler is the new energy saving technology which supported strongly by China. Based on the absorption of advanced foreign technologies, the efficient coal powder boiler has been developed by China Coal Research Institute. The new boiler can save coal by 30% and reduce dust emission by 95%. The emission of SO2 is one ninth of the national standard. The coal ash formed can be cycled as building material so that the problems of waste gas and residues can be avoided.
Configuration of Production Line
Considering the actual situations, we recommended our vertical mill to the customer. And the efficient coal powder preparation system we customized mainly consists of coal pre-homogenization system, coal conveying system, grinding system, hot-air system and anti-explosion system, etc.
1) Coal Pre-homogenization System
To keep the quality of coal powder, the raw coal must be pre-homogenized first. When the raw coal is transported into the coal storage yard, earthmover is used to stratify the coal, achieving the effect of pre-homogenization.
2) Coal Conveying System
Raw coal at the storage yard is sent into the storage bin of production plant along the underground hopper, vibrating feeder, conveyor belt and elevator. Under the coal storage bin, there is a weighing coal feeder and plunger valves. The raw coal is send to mills after being weighed.
3) Grinding System
When the raw coal enters to the vertical mill, the hot air would enter into the mill, too. The material fall on to the center of grinding plate and under the action of eccentric force, the material starts to move towards the fringe of grinding plate evenly. When moving to the grinding roller bed, the bulky coal would be crushed by the grinding roller while the fine coal would form a material bed where fine coal crushes each other. The crushed material would move toward the fringe of the grinding plate continuously until it is blown away by the strong airflow. The larger particle falls to the grinding plate again for another grinding. The materials in the airflow would be divided into two parts under the rotor blade --- coarse particle falling to the grinding plate, the qualified fine material sent out from mill with the airflow.
4) Coal Conveying System
In light of the characteristics of coal powder, the coal conveying system takes the dense phase transportation by using fluidizing transporter which can help reduce energy. The inert gas (N2) used in this system guarantees the safe and reliable operation.
5)Hot Wind System
Using coal powder as the fuel, the hot wind system can generate high heat efficiency but low operation costs, meeting customer’s demand on energy reduction and environment protection.
Anti-explosive System
a) Online evaluation of CO, O2 and CO2 Fire Extinguishing System
Mill’s air inlet and outlet, body and ash bucket of dust collector are monitored dynamically. Once the content and temperature of CO, O2 is beyond the set value, the fire extinguishing system works automatically to dilute content and lower temperature. If smoke or fire occurs, the system can start to put out the fire. This system integrates the monitoring, dilution and fire-proof protection, keeping safe operation.
b) The system uses the special anti-explosive sack-duster.
Advantages of Vertical Mill
Vertical mill is the ideal mill integrating crushing, drying, grinding, classification and conveying.
The features are as follows:
1) Low investment cost
The mill is characterized by simple structure but compact layout. Thus, the investment costs are reduced greatly.
2) Low operation cost
a) High grinding efficiency: The roller grinds the materials on the grinding plate directly so the energy consumption is quite low.
b) Little abrasion: No direction touch between roller and grinding plate and qualitative materials used in roller and lining plates extend the life expectancy.
3) High drying efficiency
The hot wind mixes with the powdery materials in the mill fully and repeatedly. By adjusting the temperature of hot wind, the materials can meet different demands on humidity.
4) Easy and stable operation
The mill can be monitored and controlled remotely, which makes the operation easy.
5) Satisfying quality of finished product
The short longing time of materials inside the mill makes the monitoring and control of granularity and chemical components easier.
6) Easy maintenance
The maintenance including checking oil cylinder, overturning the movable arms, replacing the roller covers and plates is easy. So the unnecessary costs brought by downtime can be avoided.
7) Environmental protection
Slight vibration reduces noises; enclosed design ensures no fly powder.
Conclusion
With the rapid growth of coal powder boilers in Gansu province, the target market of coal powder products presents a tendency of increase by years. Because the quality of products is reliable and the future of this market is promising, the customer is confident to recover costs quickly and earn more money.
