Optimization and renovation of the coarse coal slime separation system at Yangjiaqu Coal Preparation Pant

To address issues of low separation efficiency in the coarse coal slime system—which led to easily exceeding the target ash content of clean coal and insufficient production, and to ensure clean coal quality (ash content ≤ 8.5%) while enhancing the economic performance of the plant, Yangjiaqu Coal Preparation Plant optimized the system through a "problem diagnosis–stepwise renovation" approach. Specific measures included: conducting particle size distribution, infrared spectroscopy, and XRD analysis of the hydroclassification feed; replacing damaged screen plates on the desliming screen and modifying the pneumatic agitation system of the cyclone feed tank to reduce contamination by greater than 1 mm coarse particles; implementing a closed-loop intelligent control system for the hydrocyclone based on "density–pressure" (target density 250 ± 10 g/L, pressure 0.15 ± 0.02 MPa) to minimize fine coal loss in the underflow; and equipping the spiral concentrator with an automatic water replenishment device for the underflow box while adjusting the cutter position to 300 mm from the central axis to reduce misplacement rates. Production practice shows that: the yield of > 1 mm particles in the hydroclassification feed decreased from 13.99% to 3.06%; the proportion of < 0.25 mm particles in the cyclone underflow dropped by 12.16 percentage points; the clean coal yield of the spiral concentrator increased from 45.84% to 70.54%, a gain of 24.7 percentage points, with ash content consistently meeting standards. Economically, the renovation added annual benefits of 91.46 million yuan compared to a middlings-dominated product scenario and 54.70 million yuan compared to the existing blending method. The renovation effectively resolved core issues in the coarse coal slime separation system, ensuring both quality and yield of clean coal. The technical approach offers a reliable reference for optimizing similar coarse coal slime systems in low-rank thermal coal preparation plants.