Grid ball mill Introduction

Grid type ball mill is a kind of ball mill. Its function is an important equipment for further crushing materials after they are crushed. Lattice ball mill is widely used in cement industry, building material industry, refractory material industry, ore industry, etc. It is often used to grind ore with coarse particle size. The grid type ball mill is composed of feeding part, discharging part, rotary part, transmission part (reducer, small transmission gear, motor, electric control) and other main parts. The trunnion is made of cast steel, and the lining can be replaced. The girth gear is processed by casting and hobbing. The shell is inlaid with a wear-resistant liner, which has good wear resistance.

Grid ball mill structure

Mill Shell: The foundation of the Grid ball mill, the mill shell, is a cylindrical structure made of premium-grade steel. 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.

Trunnion: The trunnion (hollow shaft) of the Grid ball mill is a steel casting manufactured in our metal casting workshop. It mainly plays the role of supporting and connecting the shell, it is the passage for the material to enter and exit. When the ball mill is operating, the trunnion is floating on the bearing bush with the aid of the forced high pressure lubrication system.

Bearing Bush: Grid ball mill bearing bush ensures the smooth rotation of the ball mill and empowers the ball mill to maintain optimal grinding conditions. It is equipped with a forced lubrication system and also cooling system. It has alloy surface and 3 rolling rods on the bottom to make sure when the ball mill trunnion moves, the position of the bearing bush can be adjustable.

Hood Cover: The discharge hood of the Grid 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 ball mill Diaphragm (compartment plate) is fan-shaped plate or bow-shaped grate plate fixed in the Grid 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 openings 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 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.

Over-flow 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 grid ball mill

The structure of the grid ball mill is similar to that of the over-flow ball mill, the only difference is the ore discharge grid plate is installed at the ore discharge end. The grid ball mill has a trunnion at the ore discharge end, there are bearing inner sleeves and ore discharge grids. 

The ore row grid is composed of a central lining board, a grid lining board and a dustpan-shaped lining board. Eight radial ribs are cast on the inner wall of the end cover, and the end cover is divided into eight fan-shaped chambers. A dustpan-shaped liner is installed in each fan-shaped chamber and fixed on the end cover with screws. Each fan-shaped chamber formed by the dustpan liner. 

There are two structural forms of the grid liner: one is composed of two pieces, which are pressed by wedge iron, and the wedge iron is fastened on the end cover with screws through the ribs, and the central part is supported by the center liner. to prevent them from tilting and falling off; the other is to combine the two pieces into one and fix them directly with screws.

The holes on the liner of the grid ball mill are arranged obliquely, and the width of the holes gradually expands toward the ore discharge end, which can prevent the backflow of ore slurry and blockage of coarse particles. The ore slurry flows into the fan-shaped chamber through the pores on the grid liner at the lower part of the ore discharge end, and then turns to the upper part with the cylinder and is discharged along the channel. The trunnion is inlaid with a wear-resistant inner sleeve, and one end is made into a trumpet-shaped blade, so as to guide the pulp to flow out of the mill along the blade. Because the ore pulp of this kind of grinding machine is discharged through the grid plate discharge device, it is called a grid type ball mill.

 The rotation motion of the Grid ball mill drives the internal steel balls or rods to squeeze the material to produce fine powder that meets the process requirements. The ball mill is composed of feeding part, discharging part, rotary part, transmission part and others.

The Grid ball mill is equipped with a jacking device, which is convenient for maintenance and can be used for dry grinding or wet grinding with high efficiency. The inner lining of the Grid ball mill shell is made of wear-resistant materials, so as to enhance the wear resistance and prolong the service life. The Grid ball mill replaces the bush sliding bearing with rolling bearing, which not only saves energy but also reduces consumption.

Grid type wet ball mill: Lattice ball mill is equipped with a forced discharge device at the discharge end, the grinding efficiency is high, and the residence time of the material in the mill is relatively short.

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

Process Control: Tongli has its own metal casting foundry, starting from the raw material to the finished product, Quality in every detail, from start to finish.

Lubrication system: Tongli 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 is equipped with a water cooling system, and a cooler is also installed in the lubrication system to forcibly cool the lubricating oil.

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 grid ball 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 is the advantage of grid ball mill?

Due to the unique grid plate and the lifting bucket in the fan-shaped room, the grid type ball mill realizes low-level forced ore discharge. The finely ground ore particles will not stay in the ball mill for too long, and can be discharged in time, and the phenomenon of over-crushing is prevented, features fast grinding speed and high efficiency.

Due to the low pulp level and less mineral material in the grid type ball mill, a higher grinding media filling rate can be used to increase the number of balls loaded, and an appropriate number of small balls can be added, the grinding ball has a greater falling height. Therefore, the impact of the grinding ball is strong, which has a great effect on crushing the mineral material.

Due to the high speed of the discharge spiral classifier and the short retention time of the mineral material, the ground ore can be quickly discharged from the mill into the classifier for subsequent operations, so that the mill can replenish more raw ore, and at the same time, the denser ore Particles will not gather in the grinding machine, thereby reducing over-grinding and improving productivity. Compared with the overflow type of the same specification, the productivity is 10% to 25% higher. This kind of mill is suitable for one-stage coarse grinding or the first stage of two-stage grinding, and can also be used to grind easily crushed and soft ores.

What is the difference between Open-circuit and closed-circuit ball mill?

Closed-circuit grinding refers to that in the grinding operation, the material is fed into the mill and then classified after one grinding, the ore with unqualified particle size is returned to the mill for regrinding, and the ore with qualified particle size is sent to the next stage. The closed-circuit mill has a high crushing rate, and the quality of the obtained product is high. At the same time, the output of the closed-circuit production is relatively large, but its disadvantage is that the production process is relatively complicated and the input cost is high.The production process of the open circuit mill is relatively simple, and the input cost is low. And its disadvantage is that it has low production efficiency, because the qualified fine powder cannot be removed in time, so it produces a large energy consumption during production.

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

Both ball mills and vertical roller mills plays a vital role in the cement 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 cement and ore grinding applications. The choice between the two depends on specific requirements, budget constraints, and technical expertise.

How to install A Ball mill?

The first step of ball mill installation is to Install the base frame of the ball mill. The base installation uses a large number of metal partitions as base pads, prepare metal partitions with different thicknesses in advance for backup. After the base is installed, the worker can adjust the position of the base and the number of partitions according to the actual situation, the width of the partition cannot be less than 80mm, and the external exposed part should exceed at least 10mm In order to move the baffle, after the location of the baffle is determined, a welding operation is required. After the ball mill chassis is installed, it is necessary to accurately measure the levelness and level of the chassis with a spirit level and a tracking instrument.