Page 21 - HUB-4 Magazine Issue 79
P. 21

Washing & Screening
     the loading shovel and removes oversized stones (larger than 150mm) from the material, which is achieved by the 150mm gaps in the finger bars installed. These oversized stones are stockpiled for later use. Medium size 150/80 mm are sent via a side chute into a feed hopper, feeding the Terex MPS crusher, a Horizontal Shaft Impactor, HIS 3434. Since occasional pieces of metal were present within the feed material, an over-band magnet has been installed after each of the feed hoppers.
Out of the Terex MPS HSI impact crusher, the crushed stones are either passed to a dedicated stockpile, a dry 0-40 mm, or onto the main conveyor sending the raw material to the washing plant.
Screening, Scrubbing and Classifying
After oversized stone and any metals are removed from the feed material, it makes it’s way up the main conveyor and enters into a Terex 20 x 6 (6m x 1.80m) 3 Deck Rinsing Screen. This 20 x 6 “Pre-screen” Rinser gives the material an initial wash before the various fractions is split with different apertures on the screen mats. The sand (0-4mm) and water from the rinsing screen passes to the “Prewash” tank. The Terex Washing Pre Wash has a unique design features which allows the operator to process difficult or dirty material and ensures production of sand products that confirm to strict specifications.
The 4 aggregrate fractions passes (4-80 mm) into the new Terex patented “HydroScrub” logwasher.
This HydroScrub is a unique design logwasher for aggregate scrubbing, patented by Terex which allows operators to hydraulically adjust the hull angle from 9° to 16°, depending
on the raw material to be treated. This gives the operator the ability to process a wider range of feed materials and is ideally suited for recycling applications.
Whether the raw material is containing a lot of “light density” contaminants like wood, roots, plastics etc, then the angle is set up “high”, and floating elements are easily removed. Likewise, if the raw material is containing more clay conglomerates, then the angle is set “low”, which results in a better ‘stone on stone’ scrubbing giving better throughputs and a cleaner aggregate product and eliminates the need for secondary scrubbing on high clay bound or dirty material.
The post-screen of the HydroScrub classifies the material into two different sizes - 4-40 mm and 40-80 mm. The 40 -80 mm can be sent back to the crusher, or it can be sent to the dry classifying screen. The 4-40 mm is also conveyed to the set of dry screens (see below).
Fine Sand Cleaning
The water that has washed the aggregates up until this point in the process along with the sand, is collected in the Terex Washing Systems PreWash tank. This unique solution is receiving all of the process water from the upstream process, with the sand, and the extra fines, clay, and contaminants, and light density particles:
 7 fractions are created, falling into underground bays fitted with automatic weighing scales and individual conveyors: a main conveyor is gathering each delivery according to client’s request for their recipes, automatically loaded in the clients trucks. March/April - Issue 79
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