Wonderful Journey in a Mill

             Less than a week after joining into the industry, I was sent into the orientation program to get acquainted with the workings in the various locations of the industry. My first location was a newly developed mine that facilitated high mechanization with expansions in progress and having the beneficiation plant matching the production capacity of the mine. The mine head addressed us giving the brief introduction about the mine workings and handed us the schedule to pursue our objective. We being the mining people looked out the days of visits to the mines but we were astonished to find only two days to mine and lone day to mill. We weren’t expecting the mill visit thinking what is there in it for mining people.

Mill otherwise known as the beneficiation plant, where the extracted ore from the mines is separated into mineral and gangue while the former is advanced to further handling or direct use and the later for back-filling or left it in the form of dumps. The process commences from crushing of the extracted ore accompanied by the grinding of the sized product then separation of mineral in the froth flotation tanks for sulfide ores and concluding with separation of solids from liquids in the thickeners. Froth Flotation is the cardinal process used for the recovery of valuable minerals especially of the copper, zinc and lead bearing minerals.

As scheduled on the second day of the orientation program we were reluctant to have an insight on the working of the mill. The teachings of my mining machinery professor flashed through my mind about the various machines used in the mill and the way he taught, he crystallized the basic concepts of the machines. These thoughts made me to have the practical knowledge of the machines and we headed towards the mill. The first glimpse of the mill made me to think about the ribbons lurking in the circus watching the various conveyors coming out from top a building and landing at the bottom of another building.

Primary crusher was constructed in the mountain alongside the entrance of the mine to which we traveled from bottom through the tunnel and spiraling staircase to reach at the top to experience the gyratory crusher breaking down the ore. The sized product was carried by the conveyor located at the bottom of the crusher to make a stockpile for further crushing. To reach the stockpile we again needed to go through the swirling stairs and through the tunnel alongside conveyor to reach the top of that building. Stockpile was then carried by another conveyor to secondary and tertiary crushers i.e. the cone crusher to further reduce the size. If we would have taken the path of the conveyors we would have stuck in never ending circuits to which the material made its way through conveyor and we made through road to grinding section.

In the grinding section, to have clear view we had to climb up and we noticed the remarkable size of the rod mill and ball mill. The processes were crystal clear that material first entered into the rod mill followed by ball mill and then into hydro cyclone that whirls around the material to separate the heavier particles from lighter particles. Heavier particles are again sent to ball mill and the lighter particles to the froth flotation tank. One half of the tour made all the members in our group vexed and decided to discontinue but the spark of acquiring the full-fledged knowledge lit between us and we headed towards froth flotation plant.

The board outside the plant showed the safety equipment's we should be having on. We had all the equipment's except a mask which we managed through our handkerchiefs. The person explained the complex process of froth flotation in a very interesting manner. He elucidated the three stages in froth flotation i.e. roughing, scavenging & cleaning and the steps where reagents are mixed. It became a practical class of half an hour which we have never attended that attentively in our engineering life. The hot gases were flowing from beneath our feet that made us drench in our sweat and the never ending steps in the mill made the wonderful journey in the mill to a halt. When we were heading back to the office we were discussing about the whole trip in which we realized the journey being incomplete without the thickeners section. The lazy attitude that comes from our engineering life made us restrain from going back to the plant thus concluding the journey.

Milling is the integrated part of the mining industry as without the mill the extracted ore can’t be traded at high profits. Mining engineers should possess the idea of the primary crusher that makes them to comply with the size of the blasted ore. They should be well aware of the concentrate of mineral present in the ore for blending purposes. Mining engineers being the future General Manager’s and CEO’s need to have the basic idea of the workings in the every sector of the industry.