300,000TPY Clean Coal Grinding Plant

Design Scheme

In 2016, a state-owned energy company in Gansu, China 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 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

Since 2015, the air pollution has been a headache in northern China. Coal combustion aggravates environmental pollution and damages ecosystems due to massive emissions of dust, SO₂ and nitrogen oxides. For coal combustion, both the thermal power plants and industrial coal-fired boilers 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, the release and revision of some other related policies stipulated the government’s responsibility for environmental protection and punishments for any company that attempts to discharge pollutants randomly.

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

The efficient industrial coal powder boiler is a new energy-saving technology strongly supported 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 recycled 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, an 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 the production plant along the underground hopper, vibrating feeder, conveyor belt and elevator. Beneath the coal storage bin, there is a weighing coal feeder and plunger valves. The raw coal is sent to mills after being weighed.

• 3) Grinding System

  When raw coal enters the vertical mill, hot air also enters the mill. The material falls onto the center of the grinding plate and, under the action of eccentric force, the material starts to move towards the edge of the grinding plate evenly. When moving to the grinding roller bed, the bulky coal is crushed by the grinding roller, while the fine coal forms a material bed where particles crush one another. 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 material in the airflow is divided into two parts by the rotor blade: coarse particles falling to the grinding plate, and qualified fine material discharged from the 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 fuel, the hot air system can achieve high thermal efficiency and low operating costs, meeting customers’ demand for energy conservation and environmental protection.

• 6) 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 and O₂ are beyond the set value, the fire extinguishing system works automatically to dilute the content and lower the 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 a special explosion-proof bag filter.

Advantages of Vertical Mill

The 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 grinding efficiency is quite high while the energy consumption is quite low.
  • b) Little abrasion: No direct contact between the roller and the grinding plate, and excellent materials used in the roller and lining plates extend the service life.

• 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 residence time of materials inside the mill makes the monitoring and control of particle size and chemical composition easier.

• 6) Easy maintenance

  The maintenance tasks including checking oil cylinder, overturning the movable arms, replacing the roller covers and plates are 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 for coal powder products shows a year-by-year increasing trend. 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.