On-site demonstration of the Pansep Screen
Physical cleaning processes utilized in fine coal cleaning circuits are effective only over a specific particle size range. Beyond the optimum particle size range, the separation efficiency of these processes is significantly reduced, causing poor product quality and the loss of valuable clean coal to slurry ponds. Classifying cyclones are traditionally used to achieve fine particle size separation at particle size of 150 micron and finer primarily due to their high throughput capacity. However, their size separation inefficiency due to significant undersize misplacement and density effect on particle size classification is widely known. Thus, the main objective of this study was to demonstrate the size separation performance of the Pansep fine screening technology in an operating coal preparation plant in parallel with the plant cyclones. A slip-stream with a maximum flow rate of 350 L/min, obtained from the feed stream of the plant’s classifying cyclones, was sized using a Pansep screen having a projected surface area of 0.5 m2.
An optimization test program conducted with the Pansep screen not only confirmed previous findings obtained in a pilot-scale study (Mohanty, 2001), but also generated new technical information. Spray water pressure utilized for fluidizing and stratifying the solid material bed on the screen surface was found to play an important role in the size separation performance obtained from the Pansep screen. Samples taken while running the Pansep screen over one week showed minimal variability in the size separation performance of the Pansep screen. An average screening imperfection of 0.14 and undersize-bypass of 4.3% obtained from the Pansep screen compared favorably with the corresponding values of 0.43 and 33% for the 38-cm (15-inch) diameter classifying cyclones. The inferior size separation performance of the classifying cyclone was further compounded by the density effect on its classification process. More than 90% of the sulfur bearing minerals (pyrites) of ultrafine particle size (10 micron) and ash bearing minerals of 100 micron mean particle size were found to be concentrating in the cyclone underflow. No such density effect was apparent in the samples classified using the Pansep screen.
An economic analysis indicates an average size coal preparation plant in Illinois could recover an additional $2 million of fine coal by switching from classifying cyclones to Pansep screens. The revenue generated from recovery of fine coal would far offset the higher capital and operating costs required for the Pansep equipment.
The full report of this project is available by clicking on the link below:
