Materials handling and processing system company Claudius Peters (CP), in collaboration with Germany-based Steag Power Minerals (SPM), was developing a fly ash classifier and separator to alter the carbon content and fineness of fly ash to create a higher-quality product, CP sales manager for Africa Jens Garbe said at bulk materials handling solutions provider ELB Engineering Services’ Bulk Materials Handling Technology Day, held in Sandton, Johan-nesburg, last week.
Fly ash is a residue of coal-fired power plants, which can be used in several applications, such as cement, as a raw material.
However, Garbe noted that fly ash often had a high content of unknown material that made it unsuitable for use.
“For this reason, CP was approached by a power plant operator to develop a machine for the separation and classification of fly ash. We have started with the process and have an established test facility,” he explained.
The current test machine at CP’s test centre had a capacity of 850 kg/h of fly ash, with the duration of testing lasting up to 30 minutes.
The main factor with regard to fly ash was its carbon content, garbe said.
“According to European standards, the carbon content in fly ash has to be less than 5%, while in the US it has to be less than 6%.”
Fly ash requires a certain fineness to make it suitable for most applications.
“The CP system works on the principle of the varying resistance of the materials in fly ash,” Garbe said, adding that “the resistance of coal is low, as opposed to the other materials in fly ash which have a high resistance”.
The separation and classification machine charges the particles with a corona and disperses the particles using air. The electrical charge, owing to its different conductivity level, will be transferred to the surface of a roller. Positive carbon particles will be rejected from the roller, while coarser particles will also be rejected owing to the centrifugal force.
The target loss of ignition, which consists of contaminant unburnt fuel, was reached for most of the fly ash tested to date, while the fineness targets were nearly reached within the actual parameters, Garbe said.
However, he pointed out that the main focus of the study, until recently, was not on the fineness target.
The next steps in this project enatil the testing of the last optimisations and completing the detailed design, which will result in the installation of a pilot plant, with a 10 t/h capacity for continuous operation.
“We hope that this will be executed by the end of 2013,” Garbe concluded.