Coal Preparation » Fine Coal
Methyl isobutyl carbinol (MIBC), an aliphatic alcohol frother, has been widely used in Australian coal flotation plants. However, MIBC can cause health, safety and environment problems due to its low flash point and high evaporation rate, and therefore it has been under safety alert from the Australian government. Coal preparation plants are keen to move away from MIBC. Test work has been conducted to identify a MIBC replacement before, but this type of work is based on a trial and error approach without considering the specific properties of frothers, coals and process water. In this project, a scientific approach was developed to help identify the optimal frother to replace MIBC.
The approach of this project was fourfold, as detailed in the report.
Based on the flotation results, it was found that:
- For Case 1 - slightly oxidatized coal with a low ash content in high salinity water, Interfloat F207 could be used to replace MIBC;
- For Case 2 - severely oxidized coal with a high ash content in medium salinity water, Interfloat F207, Nalco 9840+ and BASF FF1908 could be used to replace MIBC;
- For Case 3 - unoxidized coal with a low ash content coal in low salinity water, Interfloat F228, Nalco 9840+ and BASF FF1908 could be used to replace MIBC;
- For Case 4 - unoxidized coal with a high ash content in medium salinity water, BASF FF1908 could be used to replace MIBC.
In addition, to understand how the flotation cell type influenced the frothing power of the selected frothers, Jameson Cell and Microcel were employed to conduct flotation tests. The results showed that when Jameson Cell and Microcel were used, the solubility of the frothers significantly influenced the frothing power of the frothers due to their poor dispersion in the large pulp volume with less agitation. However, similar to the case in a mechanical cell, similar flotation performance as MIBC could be achieved by using a higher frother dosage for the selected frothers with poor solubility.
Two frother decision trees (A and B) were developed using CART decision tree algorithm from the experimental data obtained in this study. Frother decision tree A could help predicate if an existing or new type of frother could be used to replace MIBC based on the specific frother, coal and water characteristics. Frother decision tree B could help identify whether some potential frothers in the existing database could replace MIBC based on certain coal type and water type.
The effectiveness of the developed frother decision trees was validated, and a simplified and user friendly decision making support toolbox for frother selection was developed using the computer software MATLAB to guide the plant engineers to use the developed frother decision trees to fast identify the best frother for their coal preparation plants.
Both the support toolbox and a guide for its use are available to download as part of the final report.