Abstract: Based on the introduction of the wet permanent magnet roller strong magnetic separation method for iron ore beneficiation, this paper elaborates on the principle and composition of the constant flow and limited liquid odor frequency conversion control system for the slurry pump in the concentrate tank. I. Overview A certain iron ore company uses a wet permanent magnet roller high-intensity magnetic separation method for mineral processing. The principle is as follows: the ore slurry flows into the rotating magnetic roller from the upper feed box. The magnetic tiny mineral particles are immediately attracted by the strong magnetic field to the outer surface of the magnetic roller and are carried into the upper unloading area along with the rotating magnetic roller. In this area, a high-pressure water jet is sprayed directly onto the outer surface of the magnetic roller. Under the washing of the high-pressure water, the magnetic concentrate adsorbed on the surface of the magnetic roller is washed off and falls into the concentrate tank, and is carried into the concentrate pool with the water flow to become concentrate powder. Meanwhile, gangue particles such as gravel and soil, as well as weakly magnetic mineral particles that were not attracted by the first magnetic roller, flow directly into the next magnetic roller with the slurry for scavenging again. The concentrate enriched by magnetic separation is discharged into the concentrate pool. The concentrate after multiple scavenging separations is all discharged into the concentrate pool, while the tailings slurry with extremely low grade is discharged into the tailings pool. The raw ore slurry continuously flows into a wet permanent magnet roller separator. After multiple scavenging processes, the concentrate and tailings are continuously introduced into the concentrate pool and tailings pool, respectively, ensuring a continuous and uninterrupted beneficiation process. The concentrate powder after scavenging by the wet permanent magnet roller separator can have a grade more than 20 degrees higher than that of the raw ore, and the tailings contain virtually no magnetic minerals. The economic benefits of the wet beneficiation method are considerable and worthy of promotion. The concentrate slurry flows into the concentrate pool and is pumped by a slurry pump to the next stage of refining into concentrate powder, which is an important process step. II. System Process Flow Due to the inherent unevenness of ore sources and the high wear and tear of mining and beneficiation equipment, the supply of raw slurry varies, resulting in variations in concentrate slurry volume. However, the volume of the concentrate pool is fixed once constructed, and the maximum output flow rate of the slurry pump transporting the concentrate slurry is also fixed. If the slurry pump is undersized, overflow will occur when the maximum beneficiation capacity is required. Therefore, the slurry pump is generally designed based on the maximum production capacity of the beneficiation process. This means that when the concentrate slurry flow rate is low, the slurry pump will run dry, and manual water replenishment will lag behind changes in flow rate. Furthermore, the slurry pump operates continuously at industrial frequency, leading to significant wear and tear; on average, the pump body needs replacement every 3-6 months. Simultaneously, downstream processes require a highly stable concentrate slurry supply flow rate. Therefore, using variable frequency control (VFD) for the slurry pump is currently the optimal choice. The system process principle diagram is as follows: [align=center] Figure 1, System Process Principle Diagram[/align] III. System Control Scheme [align=center] Figure 2, System Electrical Principle Diagram[/align] The system adopts advanced automated control equipment such as frequency converters, PLCs, and touch screens to achieve constant flow control of concentrate slurry. One operating and one standby slurry pump ensures reliable system operation. The system has three control modes: fully automatic, semi-automatic, and manual, which are switched via knobs on the on-site control box. In manual mode, the slurry pump is controlled by the power frequency cabinet, starting in a star-delta configuration and running at power frequency without speed adjustment, and water is manually added. In semi-automatic mode, the slurry pump is controlled by the power frequency cabinet, starting in a star-delta configuration and running at power frequency without speed adjustment. An ultrasonic level gauge detects the concentrate tank level, and based on the change in the concentrate tank level, the PLC outputs a water addition signal to control the amount of water added, ensuring that the concentrate tank level does not fall below the calibrated lower limit level. In fully automatic mode, the slurry pump is controlled by a frequency converter cabinet, featuring frequency converter soft start and frequency converter operation. Based on the flow signal detected by the flow sensor, the PID module inside the PLC controls the PLC output, adjusting the slurry pump speed to achieve a constant flow rate. Based on changes in the concentrate tank level, the PLC outputs a water replenishment signal to control the amount of water replenished, ensuring the concentrate tank level does not fall below the calibrated lower limit. IV. PLC Flowchart V. System Summary Practice has proven that the constant flow and level limiting frequency converter speed control scheme for the concentrate tank slurry pump can effectively meet the control requirements of iron ore production. Due to the use of a high-performance frequency converter, the system features high starting torque, strong overload capacity, fast dynamic response, and constant flow rate. It provides a perfect solution for iron ore production, reducing energy consumption, extending the service life of the slurry pump, improving production efficiency, saving users more costs, and is increasingly widely used in the mineral processing industry. Author Introductions: Chen Yongdong, Hometown: Chaohu, Date of Birth: July 1970, Henan Xinlong Mining Co., Ltd.; Li Fangjin, Hometown: Huainan, Date of Birth: August 1981, Hefei Zhanchi Technology Development Co., Ltd.