Application of Sunwoele VFD (Variable-frequency Drive) in ball mill of fertilizer plant

I. Introduction

As the global "energy saving and emission reduction" industrial transformation plan is being implemented on a large scale, advanced energy saving technology has gradually become a bright spot in society. However, in many energy-saving enterprises, especially in the fertilizer industry, it is generally believed that ball mills are difficult to control, because the amount of electricity consumed by electrical equipment is determined by its electromechanical characteristics, and subjective control is powerless. Obviously, this concept is wrong. In the face of the severe electricity consumption situation across the country, Sunwoele adopted the latest HSF600 series VFD (Variable-frequency Drive) and advanced frequency conversion energy-saving technology to implement energy-saving transformation of the ball mill at the Qingcun Phosphate Fertilizer Factory, the largest phosphate fertilizer manufacturer in the country in Fengxian, Shanghai. Practice has proved that through a series of technical and management measures to reduce the energy consumption of ball mills to a minimum, which not only protects the environment but also creates economic benefits for enterprises, enterprises can reduce operating costs by at least 5 to 10%.

2. Working principle of ball mill

In fertilizer production companies, ball mills account for more than 80% of the company's total electricity consumption due to their relatively large power. The basic structures of various types of ball mills are generally the same, but some of their components are different. Mills generally They are composed of cylinder, lining plate, feeder, discharger, aerial shaft, bearings, transmission device, and lubrication system.

3. Problems existing in the ball mill system of the phosphate fertilizer plant

This ball mill is a 130KW 2-pole electrode. It adopts a simple auto-coupling voltage reduction to start. The starting current is particularly large, which can reach 370A. The working current is about 240A. It has a great impact on the equipment and power grid, and can easily cause excessive grinding of materials. , the required grinding cycle is long, the grinding efficiency is low, and the power consumption per unit product is large. The production and maintenance of mechanical equipment is also large, and the loss of electricity is quite alarming, which will inevitably bring a lot of unnecessary trouble and trouble to the factory. It is a serious waste of resources. Therefore, with the development of social economy and the expansion of government energy conservation and emission reduction projects, the shortcomings of the original startup method of ball mills have undoubtedly been exposed. Frequent maintenance has seriously hindered the production efficiency of the enterprise. This prompted people to develop a ball mill with smooth start-up, high grinding efficiency, large output and low energy consumption - Sunwoele frequency conversion control ball mill.

4. Working principle of ball mill frequency conversion speed regulation energy-saving control system.

System performance requirements

Based on the problems existing in the original working conditions and combined with the production process requirements of the phosphate fertilizer plant, the modified ball mill system should meet the following requirements:

1: The modified equipment must have sufficient starting torque to meet the requirements of a large load capacity of the ball mill, and ensure that the equipment can make the motor run smoothly under variable frequency operation and ensure that the motor has constant power characteristics;

2: Use the frequency conversion speed control system to transform the original ball mill drag system to meet the normal operation of the ball mill at low speed, ensure normal process control requirements, extend the service life of the ball mill and motor, and reduce maintenance.

VFD (Variable-frequency Drive) selection

Based on the above principles, the HSF600 vector VFD (Variable-frequency Drive) from Chengdu Sunwoele Co.,led. was selected. This series of VFD (Variable-frequency Drive) has the following characteristics:

This series is a VFD (Variable-frequency Drive) that adopts a new generation of SVPWM waveform generation technology. It has low-speed rated torque output and strong load capacity. It can reach 180% of the rated distance output at low speed and has a variety of torque boosts and V/F. The curve can be set, a variety of acceleration and deceleration modes can be selected, the PID function is built-in, and many parameters can be adjusted online.

It has a variety of complete protection functions and fault diagnosis systems, with over-voltage, over-current and stall protection functions. It has advanced technology, complete functions, and is easy to use. It can meet the needs of electrical energy saving and various production process requirements.

With various voltage levels and complete power specifications, the performance can reach the level of similar foreign products.

High frequency accuracy ensures smooth operation and meets design requirements;

The system circuit is as follows:

Application effect

After installing the frequency conversion energy-saving control system on the ball mill, the following results have been achieved:

The modified equipment can realize automatic control and overcome the rebound voltage caused by the large inertia of the ball mill, effectively ensuring the normal operation of the equipment.

Utilizing the VFD (Variable-frequency Drive) automatic voltage adjustment function, the motor can be maintained at its highest efficiency regardless of the load. By eliminating the impact during starting, the service life of mechanical parts such as the crankshaft, transmission gear, and belts is extended, and maintenance costs are reduced.

The ball mill’s drag system has been modified using variable frequency speed regulation technology, which satisfies the ball mill’s characteristics of low-speed operation and large starting torque, and enables the ball mill’s operating speed to be continuously adjustable. There is no inrush current when the motor starts, the starting torque is sufficient, and the protection function is perfect. It ensures the quality of process control and saves maintenance costs.

After the VFD (Variable-frequency Drive) ball mill uses variable frequency speed regulation, the starting current can be more than 5 times smaller than the original one (for example, the original starting current of the 132kW motor is more than 1000A, and the starting current of the variable frequency energy-saving control system is between 180A and 200A). It achieves true soft start and also achieves energy saving effect. Since the starting current is greatly reduced, there will be no impact on the grid and a drop in grid voltage, eliminating