The raw material
Quartzite sand is mainly used in the construction industry. It consists of silicon dioxide (SiO2). The great hardness of the material (7 ° according to Mohs) is an advantage. The usual grain sizes in the building industry for coarse sand are 0.63 to 2.0 mm, for medium sand 0.2 to 0.63
In simple terms, sand is produced by the weathering of minerals. However, all rocks weather differently. A sand-lime brick weathers much faster than a hard quartz rock and subsequently rises again in superficial sediment. The proportion of sand here lies at around 10 %, while the proportion of gravel in these sediments amounts to 20 % . Unfortunately, the global demand cannot be covered by the sand deserts of our earth, as so often hoped for. It is too fine-grained and round, so it cannot be used as an aggregate for concrete. Usable sand is mainly found in rivers and on the coasts of emerging countries, where it is often extracted without regulation. For this reason, countries such as Malaysia, Cambodia, Vietnam and Indonesia have generally banned the export of sand.
In Germany, the construction industry is already warning about a sand shortage. Most buildings are made of concrete, which in turn consists of 60 % sand. Each medium-sized house requires around 200
The required particle sizes
The production of sands
The extraction of the resource sand is usually handled stationary. For this purpose, the sand is washed and classified into appropriate grain classes. If the resource sand is not available, gravel can be crushed and then classified.
The mobile screening of naturally moist sands
While mobile crushing and screening plants for processing coarser classifications over 2 mm have already proven their worth in road construction, this innovative concept has not yet been able to establish itself for finer separations. One problem in fine classification is the design of the screening machines used. The screening machines normally used, with a vibrating housing and amplitudes and frequencies unsuitable for fine screening, do not achieve the required screening qualities. Accordingly, the industry has not pursued this concept further, although it would offer massive advantages for the operator of such a plant. However, if a directly excited screening machine is placed on a conventional equipment carrier, fine sands can also be produced directly on site in the quarry. Without having to transport them over long distances before processing.
The semi-mobile production of moist sands
Thanks to the use of energy efficient machines, the sand processing plant can be operated energy self-sufficiently with the help of a power generator – an advantage in emerging countries with insecure power supply and in remote areas.
 Harder, Joachim: Rohstoff Sand – Eine Mangelware. AT MINERAL PROCESSING 01-02/2020, S. 48-60
 Ritter, Johannes: Warum Diebe einen Strand klauen. F.A.Z., 07.05.2019
 Charton, Cordelia u. Janczura, Sarah: Sandverbrauch führt zum Raubbau an der Natur. www.ingenieur.de, 03.03.2020
 Schütz, Sigurd: Erzeugung siebreiner Fraktionen bei naturfeuchten Körnungen mineralischer Rohstoffe. AT AufbereitungsTechnik, 07/2006, S. 28-34
 Planungsunterlagen der RHEWUM GmbH
Author: Dipl.-Ing. Sigurd Schuetz
RHEWUM GmbH, Remscheid/Germany
Dipl.-Ing. Sigurd Schuetz studied process engineering at Cologne University of Applied Sciences. He then worked in mechanical process engineering and mineral processing for globally operating companies. Here the focus was on development, design and sale of comminution and sizing equipment. Dipl.-Ing. Sigurd Schuetz has been working at RHEWUM GmbH since 2001 and widened his technical expertise in screening and sorting technologies. After being sales manager, he was appointed managing director of RHEWUM GmbH in April 2007.