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Second, the principle of ball mill In the fertilizer production enterprises, the ball mill because of the relatively large power, accounting for more than 80% of the total electricity consumption of the company, the basic structure of all types of ball mills is generally the same, but some of their parts have Differently, mills are generally composed of cylinders, liners, feeders, dischargers, air shafts, bearings, transmissions, and lubrication systems.
Third, the phosphate fertilizer plant ball system problems The ball mill is a 130KW 2-pole electrode, using a simple auto-buck start, the starting current is particularly large can reach 370A, working current is about 240A, for the equipment and power grid The impact is very large, which can easily cause excessive grinding of materials, requiring a long grinding cycle, low grinding efficiency, and high power consumption per unit of product. The production and maintenance of mechanical equipment is also large, and the amount of electric power loss is astonishing, which is bound to give The plant brought a lot of unnecessary trouble and serious waste of resources, so with the development of the social economy and the expansion of the government's energy saving and emission reduction projects, the original startup mode of the ball mill has exposed the ills, and frequent maintenance has seriously hindered the The company's production efficiency. This prompted people to develop a smooth, high grinding efficiency, high output, low energy consumption of the ball mill - Weikai frequency control ball mill.
Third, the ball mill frequency control energy-saving speed control system works.
System performance requirements According to the problems existing in the original working conditions and combined with the requirements of the phosphate fertilizer plant production process, the modified ball mill system should meet the following requirements:
1: The transformed equipment must have sufficient starting torque to meet the requirements of large ball mill load, and ensure that the equipment runs smoothly under variable frequency operation to ensure that the motor has constant power characteristics;
2: The use of frequency control system to transform the original ball mill drive system to meet the normal operation of the ball mill at low speed, ensure the normal process control requirements, extend the life of the ball mill and motor, reduce maintenance.
Inverter selection Based on the above principles, select the WKS vector inverter from Welch Electric (Shanghai) Co., Ltd. The inverter has the following features:
This series is a frequency converter using the new generation of SVPWM waveform generation technology, low speed rated torque output, strong load capacity, 180% rated torque output at low speed with a variety of torque boost and V / F curve can be set , A variety of acceleration and deceleration modes can be selected, built-in PID function, many parameters can be adjusted online.
With a variety of perfect protection functions and fault diagnosis systems, with over-voltage, over-current and stall protection functions and other advanced technology, complete functions, easy to use, can meet the needs of electrical energy-saving and various production processes.
The voltage level has multiple power specifications and the performance can reach the level of similar foreign products.
High frequency accuracy, stable operation and meeting design requirements
The system circuit is as follows:
Application effect After installing the frequency conversion energy-saving control system, the ball mill achieves the following effects:
The transformed equipment can realize automatic control, and can overcome the rebound voltage caused by the large inertia of the ball mill and effectively ensure the normal operation of the equipment.
Using the automatic voltage regulation function of the inverter, it can maintain the highest efficiency of the motor under conditions independent of the load. Because the impact at start-up is eliminated, the service life of the mechanical parts such as crankshaft, gearbox gear, and belt is prolonged, and the maintenance cost is reduced.
The use of frequency control technology to transform the ball mill's drive system to meet the ball mill low-speed operation, the characteristics of a large starting torque, to achieve the ball mill operating speed is continuously adjustable. There is no inrush current when starting the motor, enough starting power, perfect protection function. It ensures the quality of process control and saves maintenance costs.
After the inverter ball mill uses frequency conversion speed regulation, the starting current can be more than 5 times smaller than the original (such as 132kW motor original starting current above 1000A, frequency conversion energy-saving control system starting current is between 180A~200A), realizing soft Start, also received the effect of energy conservation. Since the starting current is greatly reduced, it will not cause impact on the grid and the grid voltage will drop, eliminating the tripping or failure of other electrical equipment caused by the start of the ball mill. Under the same grid capacity, the number of installed machines may be increased.
Built-in PLC multi-speed automatic operation function can conveniently set the grinding time, plus grinding time and automatic stop function through the inverter, making the operation more intelligent and user-friendly.
The energy-saving effect of ball mill frequency conversion speed-regulation energy-saving system is generally about 12% to 15%.
IV. Investment and Returns The plant has installed 16 high-power inverters from Welchall. Take one of the 40-ton ball mills as an example. The motor power is 132 kW, the actual power is 115 KW. It works 18 hours a day and works 30 days a month. The monthly power consumption of the original ball mill is: 115 kW × 16 hours × 30 days = 55200 kW.h (degrees). After the ball mill's special frequency conversion energy-saving control system is installed, the energy saving rate can reach 15.6%, and the monthly electricity savings can be: 55200 x 14.6% x 0.65 yuan/degree = 5238.48 yuan. If the investment per inverter is calculated as 55,000 yuan, the payback period for investment is 55000÷5238.48=10.5 months. In less than a year, you can recover all your investments. The service life of the inverter is generally 10 to 15 years. After one year, it is a pure payback period, which means that the annual power saving income is about 5.5 million yuan.
7. Concluding remarks In China's fertilizer industry, ball mills are used in large quantities and are an indispensable and important production equipment for material crushing. Practice has proved that the WKS series frequency converters produced by Welke Electric (Shanghai) Co., Ltd. are used for energy-saving driving of ball mills in the fertilizer industry. They have been very successful and have achieved good economic benefits. For China's proposed construction of a conservation-minded society, reducing environmental pollution has major economic and social significance!
I. INTRODUCTION With the global "energy saving and emission reduction" industrial transformation plan being implemented on a large scale, advanced energy conservation technologies have gradually become a bright spot in society. However, in many energy-saving companies, especially for the fertilizer industry, it is generally believed that the ball mill is difficult to control because the electricity consumed by the electricity equipment is determined by its electromechanical characteristics, and subjective control is powerless. Obviously, this concept is wrong. Under the severe situation of electricity consumption across the country, Weike Electric adopts the latest WKS series inverters and utilizes advanced frequency conversion energy-saving technology to implement ball mill energy-saving transformation at the Qingcun Phosphate Fertilizer Plant, the 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 enterprises, companies can at least reduce the operating costs of 5-10%.