Coal Preparation » Fine Coal
The objective of this project was to carry out coal preparation plant based trials of the performance enhanced diesel collector for increasing the combustibles recovery of both coarse and fine coal particles and/or reducing the consumption of diesel oil while maintaining good flotation performance. The project has successfully completed the following tasks:
- Visiting CHPP sites to collect information and coal slurry samples for planning plant-based trials;
- Assessing the effectiveness of the performance enhanced collector for the flotation of collected coal samples at the laboratory scale and optimising the dosage;
- Developing a collector addition system for plant based trials;
- Carrying out detailed preparation plant based investigations at selected CHPP sites.
Plant based trials of the performance enhanced diesel collector were carried out at three mine sites using Microcel columns or Jameson cells. The combustibles recovery obtained for thermal coals with the performance enhanced diesel collector was 5 to 10 % higher than that with the same dosage of normal diesel oil. The combustibles recovery obtained for coking coals with the use of the performance enhanced diesel was up to 6.6% higher than that for normal diesel oil at the same collector dosage. For highly hydrophobic coals, the combustibles recovery obtained with the performance enhanced diesel was comparable to that obtained with the same dosage of normal diesel oil. The use of the performance enhanced diesel collector increased the combustibles recovery of a low rank coal by up to 5% even at half the dosage normally used for diesel. Results from size-by-size recovery analysis indicated that the improved combustibles recovery increased with increasing particle size and the use of the performance enhanced diesel reduced the loss of recoverable combustible material in the coarse size fraction range of 0.25 to 0.5 mm. The use of the performance enhanced diesel collector reduced the ash values of flotation concentrates by 0.5 to 1.2% when the improved combustibles recovery was less than 75%. If the improved combustibles recovery was higher than 80%, the ash values of concentrate were slightly higher or comparable to those obtained by diesel oil. These observations from plant based trials were similar to those obtained from laboratory tests.
The performance enhanced diesel collector was effective in both Microcel columns and Jameson cells. It was also demonstrated that spraying collectors into the desliming cyclone overflows at multiple points gave a better combustibles recovery when compared with methods used by CHPPs, such as pumping collectors into a feed distributor or dripping into desliming cyclone overflow at a single point. Moisture contents of filter cake showed no significant negative effects of the performance enhanced collector on the dewatering of flotation concentrate.