300,000TPY Coal Powder Grinding Plant

Case Summary:

In 2016, a state-owned energy company in Gansu cooperated with SBM of an efficient clean coal powder grinding plant with the capacity of 300,000 tons/year. It has become an important supporting project of high-efficiency pulverized coal industrial boilers in the city and its surrounding areas. It has the function of energy saving and emission reduction and has a bright future.

Grinding Plant Equipment Allocation:

Based on the actual situation of customers, we recommended vertical mill grinding process for customers. The high efficiency coal powder preparation and production system designed for customers mainly includes the raw coal pre-homogenization system, the raw coal transportation system, the milling process system, the hot-blast system and the safety explosion-proof system etc.

1. 1) Raw Coal Pre-homogenization System

   In order to ensure the stability of coal quality, the raw coal entering the coal mill is firstly pre-homogenized in the coal storage yard. When the raw material coal which is transported into the plant is discharged into the coal storage yard, the bulldozer is used to carry out the layered stacking to achieve the pre-homogenization of raw coal.

2. 2) Raw Coal Transportation System

   The raw coal of the storage yard is fed into the original coal bunker in the production workshop through underground silo, silo vibrating feeder, raw material coal belt conveyor and bucket elevator. The lower part of the coal bunker is provided with an inserting rod valve and a weighing type coal feeder(pressure closed type), then the metered raw coal is fed into the mill.

3. 3) Vertical Mill Grinding Process System

   The raw coal enters into the vertical grinding mill through the weighing coal feeder under the original coal bunker, and the hot air from the hot blast furnace enters into the vertical mill body from the air inlet. The material falls from the blanking port to the center of the millstone. Under the influence of centrifugal force, the material moves evenly from the center of the millstone to the edge. When it passes through the grinding roller zone on the grinding disc, it is crushed by the mill roll, and the large piece of material is crushed directly. When the fine material is extruded, a bed is formed to comminute between particles. The crushed material continues to move toward the edge of the millstone until it is removed by strong winds from the wind ring, while the larger particles fall back to the grinding disc again and continue to comminute. When the material in the airflow passes through the upper separator, under the influence of rotor blades, the coarse particles return to the grinding plate to grind, and the qualified fine powder leaves together with the airflow.

4. 4) Pulverized Coal Delivery System

   The raw coal of the storage yard is fed into the original coal bunker in the production workshop through underground silo, silo vibrating feeder, raw material coal belt conveyor and bucket elevator. The lower part of the coal bunker is provided with an inserting rod valve and a weighing type coal feeder(pressure closed type), then the metered raw coal is fed into the mill.

   The finished pulverized coal collected by the dust collector is sent into the buffer hopper through the screw conveyor, then enters into the pneumatic conveying system consisting of a warehouse pump. This guarantees that the whole pulverized coal transportation will be continuously transported to the finished pulverized coal silo.

5. 5) Hot Air System

   The hot air system uses the coal powder as fuel, which has high thermal efficiency, low operation and management cost, and effectively meets the requirements of customers for energy saving and environmental protection.

    

6. 6) Safety Explosion-proof System

   1. 1. CO-O2 Online Gas Analysis and CO2 Automatic Dilution Extinguishing System We performed real-time monitoring of the mill inlet, outlet, dust box and bucket. Once the content and temperature of the CO and O2 exceed the standard in the system, the CO2 dilution extinguishing system will automatically start diluting and cooling. If smoke or fire occurs in the system, the CO2 fire extinguishing system will automatically start spraying, extinguishing, diluting and cooling. The system is interlocked with monitoring, dilution, cooling and fire protection to ensure the safe operation of the pulverized coal preparation system.

   2. 2. This system uses the explosion-proof high concentration bag dust collector which is specially used in the coal mill.

Vertical mill’s Advantage:

Vertical mill is a kind of ideal equipment for milling industry, which integrates crushing, drying, grinding, grading and conveying.

Its main features are:

1. 1) Low Investment Cost

   The system is simple and compact, so it can greatly reduce the cost of investment.

2. 2) Low Operating Cost

   1. 1. High milling efficiency: the roller is used to grind the materials directly on the grinding disc, and the energy consumption is low.

   2. 2. Less wear: because the roller is not in direct contact with the millstone, and the roller and lining plate are made of high quality material, the service life is long, and the abrasion is less.

3. 3) High Drying Efficiency

   The hot air from the outside to the mill is fully contacted with the powdery material directly and repeatedly in the mill. Therefore, the drying capacity is strong, which can save a drying machine for the mill system and save energy, and also meet the requirements of different humidity materials by adjusting the hot air temperature.

4. 4) Easy and Reliable Operation

   The equipment has automatic control system, so remote control can be achieved, and is easy to operate. It is equipped with a limiting device for preventing the roll sleeve and the lining plate of the grinding machine from contacting directly, so as to avoid damaging shock and violent shock.

5. 5) Stable Product Quality

   Because the material stays in the mill for a short time, it is easy to detect and control the particle size and chemical composition, reduce repeated grinding, and stabilize the quality of products.

6. 6) Convenient Maintenance

   By overhauling the oil cylinder and turning the movable arm, it is convenient and fast to replace the roller sleeve and the lining plate , and the downtime loss is reduced.

7. 7) Environmental Protection

   The system is small vibration, low noise, and is integrally sealed. It works under negative pressure without dust overflow, and the environment is clean, which meets the requirements of national environmental protection.