CH685293A5 - Lightweight aggregate manufacturing procedure - Google Patents

Abstract

The procedure consists of using recycled expanded polystyrene waste material as one ingredient of an aggregate e.g. for making lightweight concrete or plaster. The polystyrene goes through two shredding processes after first being sorted and graded by specific weight and having such contaminants as paper and adhesive strips removed form it by hand. In between the shredding processes any ferrous metal particles are extracted by an electromagnet. After the second shredding, which avoids heating the polystyrene, the particles pass through a 6 mm riddle, and those of a suitable size are used for mixing with sand and cement or with plaster.

Description

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CH 685 293 A5

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Description

The object of the present invention is a process for obtaining light aggregates.

The process relates to the recycling of expanded polystyrene waste into light aggregates (density from 20 to 30 kg / m3) in order to be used for obtaining, for example, light concretes whose density can be determined between 300 and 1800 kg / m3.

Lightweight concrete aggregates have the property of being impregnated on the surface with an admixture which suppresses electrostatic repulsion as well as the hydrophobicity of expanded polystyrene. This impregnation guarantees a homogeneous distribution of the light aggregates and solves the problem of wetting when mixing with concrete.

The following description will be better understood with reference to the drawings showing an embodiment of the method according to the invention in which:

Fig. 1 shows the steps of the process, as well as possibilities for using the aggregates.

Fig. 2 is a schematic view of the arrangement of the various machines for obtaining light aggregates.

As can be seen in fig. 2:

On arrival, the EPS waste is sorted by specific weight category 1 and manually cleared of its contaminants (paper, adhesive tapes, etc.) then transported 2 to the primary shredder 3 by gravity.

The primary grinding is ensured by a hammer type impact crusher 3 equipped with a pneumatic stuffer, the EPS waste is subjected to the impact of hammers which rotate at high speed until their dimensions allow them to pass through of a grid calibrated from 10 to 30 mm.

From the primary crusher, the waste is extracted and transported to a buffer silo 5 by a pneumatic conveyor 4.

From the buffer silo, the waste is transported to the secondary shredder 8 by means of a belt conveyor 7, equipped with an electromagnetic separator 6 (Overband). Ferrous particles are extracted and put in a tank.

Secondary grinding is ensured by a rotary knife grinder 8 whose knife geometry has been studied in order to ensure continuous fine grinding and to avoid excessive heating of the expanded polystyrene, the grinder is equipped with a grid calibrated to 6 mm.

The waste is taken up at the outlet of the grid by a pneumatic system 9 and conveyed to a separator 10, the fine particles and the dust are extracted and stored in a bucket 14.

After mechanical reduction and dedusting, the waste is conveyed 11 to a silo 12 and from there, introduced 13 into a horizontal mixer 15 where it is homogenized and impregnated.

The impregnating agent (or adjuvant) is dosed by a storage cell and its extraction system.

The mixture is equipped with a weighing system using an electronic strain gauge to ensure correct filling according to variations in the specific weight of the waste and the dosage of the impregnant.

After a mixing time of approximately 16 minutes, the mixer empties automatically into a diverter silo 16, 17 whose function is on the one hand to ensure a continuous supply of the rotary screen, and on the other hand to supply 22 the bagger 23 of non-screened waste.

At the outlet of the diverter silo, the waste is conveyed 18 to a rotary screen 19 by a pneumatic hot air system in order to dry it.

The screen is equipped with perforated seals with a diameter of 6 mm. Brushes clean the screening cylinder over the entire length of the screen.

Refusals of size larger than the mesh are conveyed by a conveyor belt to reception and again follow the grinding cycle until they are reduced to the desired size.

The impregnated, screened product is then transported to bagging silos 20, 21.

The following example is given as an illustration of the invention:

250 kg of cement 100 kg of sand 0.4 100 liters of water

1000 liters of light aggregates (25 kg)

give 1 m3 of concrete with density 400

kg / m3

The various expanded polystyrene waste consists of generally very elaborate materials which present a precious raw material. This is destroyed by incineration, landfill, or partially reused.

The solution defined by the invention allows ecological management of PSE waste, since no pollution is generated during treatment.

Claims (5)

Claims 1. A process for obtaining light aggregates, characterized in that it consists in recycling waste expanded polystyrene in order to obtain light aggregates. 2. Light aggregates for the building and public works sector, characterized in that they are obtained using the method according to claim 1. 3. Use of light aggregates according to claim 2, characterized in that they allow, by mixing with sands, cements and lime, to obtain light insulating mortars and concretes. 4. Use of light aggregates according to claim 2, characterized in that they allow, by a mixture with gypsum and its derivatives, to obtain plasters or insulating light plaster elements. 5. Use of light aggregates according to claim 2, characterized in that they make it possible to obtain prefabricated insulating light elements. 5 10 15 20 25 30 35 40 45 50 55 60 65 2