Air swept coal mill Introduction

Air swept coal mill structure

The main components of the air swept ball mill include the mill shell, trunnion, slide shoe bearing, liners, diaphragm, grinding media, transmission device and so on. Depends on the transmission method, if the air swept ball mill is edge drive, then it will have girth gear and pinion.

Mill Shell: The foundation of the air swept ball mill, the mill shell, is a sturdy cylindrical structure crafted from premium-grade steel. This robust shell encases the grinding process, confining it within a controlled environment. Tongli heavy machinery is equipped with a large annealing furnace of 6.5x6.5x20m and a 6.5x6.5x20m large sandblasting room, which can conduct overall heat treatment and sandblasting on the ball mill to ensure the service life and appearance of the ball mill.

Transmission connection: Tongli air swept ball mill is equipped with a transmission connection, which is welded on the cylinder and machined together with the ball mill shell to avoid assembly errors and ensure the concentricity of the air swept ball mill.

Hood Cover: The discharge hood of the air swept ball mill is installed at the discharge end of the ball mill, and there is a screen inside. After grinding, the material with a qualified size will enter the discharge hood through the screen and enter the next process. There is a vent on the upper part of the discharge hood, and a discharge funnel on the lower part.

Diaphragm: The air swept ball mill diaphragm (compartment plate) is fan-shaped plate or bow-shaped grate plate fixed in the ball mill with bolts. Its function is to divide the ball mill into two or more chambers, the material moves to the next compartment through the holes on the grate plate. The function of the compartment plate is to prevent the grinding media running from one compartment to another compartment, so that the materials can be reasonably finely ground.

Liner: The function of the liner is to protect the shell of the air swept ball mill and the trunnion, some special-shaped liners can also design to lift the grinding media to a certain position. According to the shape of the liner, it can be divided into flat liner, beaded liner, corrugated liner, ribbed liner, stepped liner, etc.

Air swept ball mill transmission: Central drive ball mill refers to the arrangement of the driving mechanism for the mill. In a central drive configuration, the motor and gearbox are positioned at the center of the mill, usually between the grinding chamber and the mill shell. This design is in contrast to an edge or end drive configuration where the motor and gearbox are situated at one of the ends of the mill. Central drive transmission systems typically involve a motor that powers a gearbox, which then transfers the rotational energy to the mill's main shaft. The central drive design can provide advantages in terms of power distribution and efficiency compared to other drive arrangements. It can also offer better control over the mill's operation.

PLC control system: A PLC is a digital computer-based system that is designed to control various industrial processes automatically. In the context of a ball mill, a PLC is used to monitor and control parameters such as temperature, rotation speed, air flow, fuel flow, and other critical variables that affect the performance of the ball mill and the quality of the products being processed. 

Design principles of air-swept coal mill

Energy Efficient: The air-swept coal mill adopts an air-swept structure with a drying chamber, utilize the exhaust gas from the kiln which makes the air-swept coal mill more adaptable to the moisture of the raw coal., at the bottom of the mill, there are air inlets that allow the primary air to enter.

Structural design: The grinding chamber adopts stepped linings, double-stepped linings, corrugated the combined arrangement of lining boards improves the grinding capacity of the air-swept coal mill. The feeding device adopts a shutter-type structure with oblique air intake, which enhances the heat exchange capacity of the air-swept coal mill and can effectively prevent material blocking at the entrance of the coal mill.

Discharging device: It adopts curved pipe structure, and the air pipe is equipped with a liner to prevent wear and tear. It can use the return spiral barrel to push the unqualified coarse powder back to the grinding chamber for grinding, avoiding the slag discharge of the mill. and dust accumulation, ensuring safe production, reducing environmental pollution and labor intensity of workers.

Flexible Operation: Tongli air-swept coal mill can handle a wide range of coal types and moisture levels, making them versatile for different coal specifications. By adjusting parameters such as the size of the grinding ball, the rotation speed of the grinding body, and the amount of feed, the fineness of the fly ash can be controlled to meet different production requirements.

Efficient Grinding: The air-swept coal mill provides efficient grinding of coal, resulting in a fine powder suitable for efficient combustion in industrial furnaces and power plants.

Classifier: The classifier is located at the top of the air swept ball mill and is responsible for separating the fine coal particles from the coarser particles. The finer particles are carried away by the primary air, while the coarser particles are returned to the grinding zone for further grinding.

Lubrication system: Tongli air swept ball mill is equipped with force lubrication system, there is an oil station equipped for the transmission part, another oil station for the gearbox to ensure smooth operation and prolong service life of the ball mill.

Cooling system: The main bearing bush of air swept ball mill is equipped with a water-cooling system, and a cooler is also installed in the lubrication system to forcibly cool the lubricating oil.

Advanced manufacturing Equipment: Tongli has over 100 set of large-scale mechanical processing equipment, especially a 5.3x18-meter fully numerically controlled horizontal lathe to ensure the processing accuracy and concentricity of the ball mill.

Heat treatment: Tongli Heavy Machinery is equipped with a large annealing furnace of 6.5x6.5x20m and a large sandblasting room, which can conduct overall heat treatment and sandblasting on the ball mill to ensure the service life and appearance of the ball mill.

Transmission connection: Tongli’s ball mill is equipped with a transmission connection, which is welded on the cylinder and machined together with the ball mill shell to avoid assembly errors and ensure the concentricity of the ball mill.

Specifications of cement vertical roller mill

Note: * Mill diameter refers to the inner diameter, while the mill length refers to the effective grinding length.

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Industry Knowledge extension

What are the types of ball mill?

Tongli ball mill has following categories: according to the product material can be divided into cement ball mill, mineral ball mill, limestone ball mill, gypsum ball mill, slag ball mill, ore ball mill, raw material ball mill, coal mill, etc; according to the size of the crushed material can be divided into: coarse ball mill, high-fine powder ball mill, ultra-fine powder ball mill; according to the transmission mode, it can be divided into edge transmission ball mill and center transmission ball mill(Gear-less Motor Drive); according to the transmission method, it can be divided into sliding shoe ball mill, bearing bush ball mill and bearing ball mill;

What is the difference between central drive ball mill and edge drive ball mill?

Central Drive Ball Mill and Edge Drive Ball Mill are two common types of grinding mills used in various industrial applications. 

Central Drive Ball Mill: In this configuration, the motor is positioned in the center of the mill, and the shaft is driven directly through the central axis. The motor's power is transmitted to the mill via a gear unit, resulting in a balanced and efficient power distribution.

Edge Drive Ball Mill: In contrast, the edge drive mill utilizes a gearbox located on the periphery of the mill. The motor's power is transmitted to the mill through the gears, which are positioned around the shell. This design offers certain advantages in terms of installation and maintenance.

What is the difference between ball mill and vertical roller mill?

Both ball mills and vertical roller mills plays a vital role in the coal grinding plant. Ball mills are versatile and cost-effective, suitable for various materials and simple to maintain. On the other hand, vertical roller mills offer superior energy efficiency and particle size control, making them ideal for coal and raw material grinding applications. The choice between the two depends on specific requirements, budget constraints, and technical expertise.