As the global “energy-saving and emission-reduction” industrial transformation plan is being implemented on a large scale, advanced energy-saving technologies have gradually become a bright spot in society. However, in many energy-saving companies, especially in the chemical 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. Under the severe situation of the country’s upper and lower power consumption, Wilka Electric adopts the latest WKS series inverters and advanced frequency conversion energy-saving technology to implement energy-saving ball mills in Qingcun Phosphate Fertilizer Plant, the country’s largest phosphate fertilizer manufacturer in Fengxian, Shanghai. Practice has proved that through a series of technical and management measures to minimize the energy consumption of the ball mill, that is, to protect the environment and create economic benefits for the enterprise, the enterprise can reduce operating costs by at least 5-10%.
Second, the working principle of the ball mill
In fertilizer production enterprises, ball mills account for more than 80% of the total electricity consumption of the enterprise due to their relatively large power. The basic structure of all types of ball mills is roughly the same, except that some of their components are different. All are composed of a cylinder, a liner, a feeder, a discharger, an aerial shaft, a bearing, a transmission device, and a lubrication system.
3. Problems in the ball mill system of the phosphate fertilizer plant
The ball mill is a 130KW 2-pole electrode. It adopts a simple auto-coupling step-down start. The starting current is particularly large and can reach 370A. The working current is about 240A, which has a great impact on the equipment and the power grid, and it is easy to cause excessive grinding of materials. , The required grinding cycle is long, the grinding efficiency is low, and the unit product power consumption is relatively large. The production and maintenance of mechanical equipment is also large, and the amount of electricity consumption is quite alarming, which will inevitably bring a lot of unnecessary troubles and troubles to the factory. Serious waste of resources, so with the development of social economy and the expansion of government energy saving and emission reduction projects, the defects of the original starting method of ball mills have been exposed undoubtedly, and frequent maintenance has seriously hindered the production efficiency of the enterprise. This urges people to develop a ball mill with smooth start-up, high grinding efficiency, large output and low energy consumption-Wilka frequency conversion control ball mill.
3. The working principle of the energy-saving control system of the ball mill frequency conversion speed regulation.
System performance requirements
According to the existing problems of the original working conditions and combined with the production process requirements of the phosphate fertilizer plant, the reformed ball mill system should meet the following requirements:
1: The modified equipment must have enough starting torque to meet the large load requirement of the ball mill, and ensure that the equipment runs smoothly under the variable frequency operation state to ensure that the motor has constant power characteristics;
2: Use the frequency conversion speed regulation control system to transform the original ball mill drive 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 the motor, and reduce maintenance.
According to the above-mentioned principles, the WKS vector inverter of Wilka Electric (Shanghai) Co., Ltd. is selected. This series of inverters has the following characteristics:
This series is a frequency converter using a new generation of SVPWM waveform generation technology, with low-speed rated torque output, strong load capacity, and 180% rated torque output at low speed
It has a variety of torque boost and V/F curve can be set, multiple acceleration and deceleration modes can be selected, built-in PID function, 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, advanced technology, complete functions, easy to use, and can meet the needs of electrical energy saving and various production process requirements.
Various voltage grades and complete power specifications are complete, and the performance can reach the level of similar foreign products.
The frequency accuracy is high, which can make the operation stable and meet the design requirements;
The system circuit is as follows:
After the ball mill is installed with a frequency conversion energy-saving control system, the following effects have been achieved:
The modified equipment can realize automatic control, and can overcome the rebound voltage caused by the large inertia of the ball mill, effectively ensuring the normal operation of the equipment.
With the automatic voltage adjustment function of the inverter, the motor efficiency can be maintained at the highest level under conditions irrelevant to the load. Because the shock during starting is eliminated, the service life of mechanical parts such as the crankshaft, gearbox gears, and belts is prolonged, and maintenance costs are reduced.
The drive system of the ball mill is transformed by the frequency conversion speed regulation technology, which meets the characteristics of low-speed operation and large starting torque of the ball mill, and realizes the continuous adjustment of the operating speed of the ball mill. There is no impact current when the motor starts, the starting distance is sufficient, and the protection function is perfect. Ensure the quality of process control and save maintenance costs.
After the frequency converter ball mill uses frequency conversion speed regulation, the starting current can be more than 5 times smaller than the original. The start-up has also received energy-saving effects. Since the starting current is greatly reduced, it will not cause an impact on the grid and a drop in grid voltage, eliminating the trip or failure of other electrical equipment caused by the starting of the ball mill. Under the same grid capacity, the number of installed machines can be increased.
Built-in PLC multi-speed automatic operation function, you can conveniently set the grinding time, grinding time and automatic stop function through the inverter, making the operation more intelligent and humane.
The energy-saving effect of the frequency conversion speed regulation energy-saving system of the ball mill is generally about 12% to 15%.
4. Investment and return
The factory has installed 16 high-power inverters from Wilka. Take one of the 40-ton ball mills as an example, the motor power is 132 kW, the actual power used is 115 kW, working 18 hours a day, and working 30 days a month, so the monthly electricity consumption of the original ball mill is: 115 kW×16 hours× 30 days = 55200 kW.h (degrees). After the ball mill special frequency conversion energy-saving control system is installed, the power saving rate can reach 15.6%, and the monthly electricity savings can be: 55200×14.6%×0.65 yuan/kWh = 5,238.48 yuan. If the investment for each inverter is 55,000 yuan, the payback period is 55,000÷5238.48=10.5 months. That is, the entire investment can be recovered in less than a year. The service life of the frequency converter is generally 10 to 15 years, and the net payback period is one year later, that is, the annual electricity saving income is about 55,000 yuan.
Seven, concluding remarks
In my country’s fertilizer industry, ball mills are used in large quantities, and they are indispensable and important production equipment for material crushing. Practice has proved that the WKS series inverter produced by Wilka Electric (Shanghai) Co., Ltd. is very successful in the energy-saving drive of ball mills in the fertilizer industry and has achieved good economic benefits. For the construction of a conservation-oriented society proposed by our country, reducing environmental pollution has great economic and social significance!