CH688543A5 - Regeneration of old foundry sand with magnetic constituents - Google Patents

Abstract

Regeneration of old foundry sand with magnetic constituents comprises the following: (a) the sand stream (1) is separated by means of a high-performance magnet (2) into two partial streams (3,4); one (3) with a large proportion of sand with magnetic iron oxide and the other (4) with none or only a small proportion of sand with magnetic iron oxide; (b) one of the partial sand streams is subjected to further mechanical or thermal treatment.

Description

       

  
 



  The invention relates to a method as described in the preamble of claim 1.



  DE 3 642 916 C2 has disclosed a method for regenerating chromium sands containing concrete, in which a magnetic separation treatment is carried out after the old sand mixture has been annealed and subjected to mechanical treatment in an impact jet mill.



  The entire process sequence and the equipment required for it are very complex and have a high energy consumption due to the additional thermal treatment.



  Furthermore, DE 2 909 408 C2 has disclosed a batch-wise drum for the regeneration of used sand, by means of which however used sand with magnetic components cannot be completely regenerated accordingly.



  The object of the present invention is to provide a method of the type mentioned at the outset by means of which used sands containing magnetic components, such as Chromite sand and bentonite-containing sands can also be regenerated to a usable molding sand and / or core sand without great energy expenditure.



  According to the invention, this object is achieved by the characterizing features of claim 1.



  Advantageous developments of the method are characterized in the dependent claims.



  Several versions of the method are shown schematically in the accompanying drawing and described below. Show it:
 
   Fig. 1 is a schematic representation of the method in a first embodiment
   Fig. 2 shows a second embodiment of the method and
   Fig. 3 shows a third embodiment of the method.
 



  1, used foundry sand 1 with portions of magnetic iron or iron oxides is fed to a high-performance magnet 2. The high-performance magnet 2 separates into a partial flow 3 with a high proportion of sands with magnetic iron oxide and into a partial flow 4 with no or a small proportion with magnetic iron oxide.



  Iron oxide additives are added to the quartz sand in order to avoid expansion errors in the casting caused by the quartz. This may be reduced in the casting process. As additives, they remain fixed on the quartz grain.



  If this sand is to be returned as core sand, the iron oxide still present can accelerate the resin hardening reaction and considerably reduce the processing time of the core sand.



  By using the high-performance magnet 2, the regenerate produced by the partial flow 4 can then be used directly as core sand 5 and / or as molding sand 6.



  In one process variant, the partial stream 4 is fed to a mechanical or pneumatic regeneration system 7. This can e.g. a scrubbing drum with short treatment times or one of the known pneumatic sand processing systems working in a continuous process. The regenerate 8 is then fed back to the molding sand of the casting process. The easily cleanable active bentonite is separated in the regeneration system and excreted as dust.



  The partial stream 3 with a high proportion of magnetic iron oxide is fed to a mechanical regeneration 9, which preferably consists of a scrubbing drum which has become known from DE 2 909 408 C2.



  The cleaned regrind 10 is recycled as molding sand and / or core sand.



  2 shows a variant of the method for the regeneration of old foundry sand 11, which at least partially has chromite sand or chromium-containing molding sand.



  The chromite sands 11 are freed of their surface contaminants by a mechanical regeneration 9 in a scrubbing drum, so that the regenerate 12 is subsequently separated via a high-performance magnet 2 into a partial flow 13 with chromite sand and into a partial flow 14 with non-chromite sand.



   With this described process, purities of the chromite sand can be achieved with over 95%. If the proportion of impurities in the chromite sand such as clay residues, quartz or metallic oxides is too large, this leads to casting defects in the casting process, e.g. Burning symptoms.



  3 shows a further method variant for regenerating bentonite-containing foundry sands 15 first by means of a mechanical regeneration 9 described above, the regenerate 16 in the high-performance magnet 2 being subsequently divided into two partial streams 17 and 18.



  The partial stream 17 has magnetic components such as e.g. Bentonite residues, pellets (pelleted clay residues) and e.g. also magnetic iron oxides. The partial stream 18 has no magnetic components and is recycled as recycled molding sand.


    

Claims (5)

      1. A method for the regeneration of foundry sand with portions of magnetic substances, characterized in that the waste sand stream is separated via a high-performance magnet with which magnetic substances can be attracted in such a way that a partial stream with a high proportion of sands with magnetic iron oxide and a partial stream with no or a small proportion with magnetic iron oxide and at least a partial stream of mechanical post-treatment is supplied. 2. The method according to claim 1, characterized in that the partial stream with no or a small proportion with magnetic iron oxide is used directly as molding sand and / or core sand. 3rd A method according to claim 1, characterized in that the partial flow with no or a small proportion with magnetic iron oxide of a regeneration treatment e.g. in a scrubbing drum or in a pneumatic regeneration system for the separation of cleanable active bentonite and the regenerate is used as molding sand or core sand. 4. The method according to claim 1, characterized in that the old foundry sand consists of a chromite sand previously cleaned in a scrubbing drum and a chromite sand with a purity of at least 93% of a new chromite sand can be discharged and the residual quartz content is less than 7%. 5.  A method according to claim 1, characterized in that the foundry used sand consists of a used sand previously mechanically regenerated in a scrubbing drum and a separation into a partial flow with magnetic components such as e.g. Bentonite residues, pelletized clayey dust residues and magnetic iron oxides and in a partial stream with a recyclable regenerate.