BORODAI Valery, NESTEROVA Olha, SHYKHOV Stanislav & KHALAYIMOV Taras
Study the possibilities to increase the efficiency and decrease energy consumption of powerful tumbling mills.
The studies were carried out through the justification of operating modes of tumbling mills and determination the methods of reaching their maximum efficiency by adjusting the operating mode.
One of the ways of efficiency increasing of powerful tumbling mills is to improve the technology of grinding, as well as the use of more modern systems of electric drive.
The grinding technology involves the following methods of minerals destruction [1]: by friction, impact, and in a combined way. The implementation of these methods in tumbling mills is created by operating modes: cascade, cataract or combined.
The cascade mode of operation has the highest power consumption, followed by a combined, and the last in this list is a cataract operating mode. To increase the efficiency of the mill means to create conditions that allow achieving the maximum productivity with minimal energy consumption of the mill. It is clear that for different types of input grinding material it is necessary to adjust the operating modes of the mill, which depend on the speed of rotation of the drum.
The second way to improve the efficiency of grinding machines is to use a class of drive with better energy performance in the mechanism. Such type of drive is synchronous one. Its advantages, such as increased efficiency, the ability to compensate reactive power, a significant air gap, which reduces the requirements for the accuracy of the manufacturing and low speed of the shaft, thus no gearbox is needed
Traditionally, the synchronous drive of tumbling mills is set up at a rational speed for grinding minerals of a concrete deposit. As a consequence, there is no speed adjusting throughout the entire duration of the work, regardless of the changes in the properties of the input product that occur in different areas of extraction.
Taking into account the current economic challenges and requirements for increasing mills’ efficiency, the relevance of creating automatic speed control systems for synchronous drive of tumbling mills cannot be called into question.
Thus, the required range of velocity control does not exceed 50 % of its the maximum value, so for such a case the frequency control fully meets the requirements of the technological process. In addition, the use of a modern frequency converter’s control strategy can allow energy savings together with other methods that are mentioned above.
According to the last conclusion and using the original model of the synchronous drive [2, 3], the preliminary structural scheme of the mill drive model is shown, where the parameters of the quadrature and direct armature current and speed regulators are calculated according to the classical methods of the theory of automatic control.
Keywords: grinding, tumbling mills, operating modes, synchronous drive