Possibilities of fine material removal

Summary of bachelor study on "Possibilities of fine material removal". Author: Erki Närep

Limestone is one of the most common minerals in Estonia. It is mainly used as raw material for the production of splinters and cement. The limestone bed consists of upper layers with high quality limestone and lower layers with clay-rich limestone. Producing splinters and cement with a clay-rich limestone requires additional processing, in order to reduce clay content using fine material removal.

The aim of this study was to test and evaluate three different methods for fine material removal – jigging, pressure washing and dry sieving, and research the appropriate equipment. As a reference method, washing by hand was also carried out which represented the ideal subsample. In this study, fine material is defined as material sized 0-4 mm. The clay-rich limestone sample material used in the experimental work was taken from Väo IV open cast. The sample material was first homogenized and distributed into subsamples. The subsamples were then processed using the mentioned methods. Finally, sieve analysis was carried out with the processed subsamples in order to evaluate the effectiveness of these methods.

The results showed that the most effective method is dry sieving, which removed the full percentage of fine material. Jigging removed 70% and pressure washing removed 29% of the 0-4 mm sized material. The appropriate equipment for fine material removal is McLanahan’s Rotary Scrubber, McLanahan’s Log Washer and Haver & Boecker’s Hydro Clean Washing System.

Dry sieving proved to be the most effective method. However, it is not industrially applicable due to high time expenditure and energy consumption. Pressure washing as an independent method is also not applicable due to low percentage of fine material removal. Therefore, the most effective industrially applicable method is jigging. The highest effectiveness would be achieved by combining both, jigging and high pressure washing (as additional processing), which theoretically should remove all fine material. Hydro Clean Washing System has the lowest water consumption, appropriate productivity, low upkeep, it is environment friendly and it uses the previously mentioned combined method which makes it the best choice for fine material removal today.

The best method for fine material removal on the basis of Väo IV open cast:

- Extraction with hydraulic hammer

- Preliminary crushing with jaw crusher

- Fine material removal with Hydro Clean Washing System

- Producing splinters with a crusing complex

- Processing removed fine material with CDE equipment