DD297087A5 - PROCESS FOR RECONSTRUCTING FOUNDRY SAND - Google Patents

Abstract

The invention relates to a method for recycling of organic and / or inorganic binder containing mono- / Mischgieszereisand, wherein the organic binder-containing sand after a thermal regeneration or the inorganic binder-containing sand after a thermal and mechanical regeneration depending on its after regeneration by a measuring operation of certain p H value is neutralized with a suitable base or acid so that it finally has a p value between 6 and 8. Figure {treatment; Gieszereisand; thermal regeneration; mechanical regeneration; Neutralization}

Description

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The invention relates to a method for reprocessing foundry sand. It is known, foundry sand such as quartz sand, olivine, zirconium, Chromiterzsand and the like with organic or

regenerate inorganic binders wet, mechanically, thermally or in combination. Goal of such

Regeneration process is to create a reclaimed sand, which is used instead of or wio new sand

can. With the regeneration at the same time the environmentally hazardous substances of the foundry sand should be eliminated.

Organic bound sand usually only needs to be thermally regenerated, unless it is alkaline, acid or alkaline

contains other interfering components that neither burn nor volatilize.

Inorganically bound mono or mixed sand, in particular sand originally treated with bentonite, must be thermal

and mechanically regenerated to produce a reusable sand.

A disadvantage of these known methods is that, for example, be! organic binder with bad or bad

non-eliminable basic or acidic components and especially in the case of mono or mixed sand with inorganic binders, the regenerate differs from virgin sand in properties such as, for example, in the pH, in the electrical conductivity, in the

Oolithisierungsgrad, in Schlämmstoffgehalt and the like. Thus, properties of such regenerates are above all

when reused in core production more or less impaired. Decreased use properties of such regenerants are especially when used as a resin-bonded core sand and have a reduced strength, reduced

Processing time of the sand mixtures, increased binder consumption and the like. The object underlying the invention is to provide a method of the above umrissonon type, with which

thermally and / or mechanically regenerated sand is treated so that it is then similar or as new sand.

This charge is inventively achieved in that the organic binder contained sand after a theoretical Regenerate or the inorganic binder-containing sand after a thermal and mechanical regeneration in Dependence of his determined after the regeneration by a measuring operation such as titration pH

a suitable base or acid is neutralized so that it finally has a pH between 6 and 8.

Advantageous embodiments of the method emerge from the subclaims.

The essence of erfindungsgomtlßon proposal is therefore in particular, belsplolswolso dig originally with organic and / or inorganic Blndor (Bontonlt) boaufschlagton sand grains wlo üuarzkörnor after einor thermlsclien treatment and mechanical Nachreinigen additionally wet iu nouualieloron and nachzuroinigon to his particular pH and his electrical conductivity to match the corresponding Neusandwerten.

Due to the thermal and mechanical treatment z. For example, the organic bond burns to a great extent or has offered inorganic bonding, e.g. the clay or bentolite was petroleum-borne and, by means of the mechanical rolling, it was carefully detached from the grain of sand and excreted. According to the invention, the thus obtained Regenerato anschlioßond are wet-neutralized and purified in Dohällorn. To support and accelerate the process, stirring or circulation of the mixture takes place in the treatment vessel.

With particular advantage, the necessary mongon can be determined by addition of neutralization additives to titration on 60 × to 100 g sand samples, specifically when the sand is in its thermal and possibly mechanical regeneration state.

Experiments have surprisingly shown that e.g. upon addition of a suitable acid as a neutralizer to Regeneraton with inorganic binding, a sudden turbidity of the aqueous solution is used. Obviously, the neutralization causes a slight detachment of dust or slurry liquor or binder adhering to the sand grains; This also eliminates any electrostatic bonding between grains and buildup.

After neutralization and, if appropriate, washing and final drying, the sand thus treated already shows a clearly clean appearance and properties in front of dom binoculars; which are the same or similar to Nousand, this results from the following examples I and II.

Example I Quartz sand rogenorate: AFS CO, 3

feature Output source Neutralization with 10ml conc. H ₁ SO ₄ per kg Comparable new sand PH value 9.6 7.4 about 7.0 Electr. Conductivity in pS / cm 172 4 ca.O Loss on ignition (%) 0.17 0.14 co. O Slurry content (%) 1.04 0.34 about 0.3 oolitization 0.93 0.79 ca.O Example II Quartz sand-Regenorate: AFS 45 feature Output · regenerat Neutralization with 12 ml NH ₄ OH (25%) per kg sand PH value 3.6 7.2 Electr. Conductivity in pS / crn 189 12

In the attached drawing is shown schematically a neutralization of regenerated sand. The already regenerated sand is led by a sanding task 1 for the purpose of weight adjustment per batch via a belt weigher 2 Ir neutralization tank 3. With the sand job a neutralization solution is pumped from a reservoir 4 via a pump 5 in the neutralization tank 3, controlled by a level indicator (not shown). During the filling process and the Neutralisiorungsdauer takes place in the container 3 with a stirrer shown schematically, a stirring or circulating the goods. After neutralization dia solution is sucked through a filter plate 6, a pump 7 and oin filter 8 and returned to the reservoir 4. A refreshment of the spent neutralization solution by means of rinsing or fresh water and addition of new acid or base takes place with the interposition of a container 16. After neutralizing, a washing and cleaning of the neutralized Regenerates by introducing rinse solution from a reservoir 13 into the container 3 in a continuous stirring process. Thereafter, the sand-rinsing water mixture is pumped from the container 3 via a pump 9 in a cyclone 10. In the Zyklon 10, sand and slaked water settle. The sludge water is purified via a pump 11 i.i a filter 12 and then returned to the reservoir 13. This consumed rinse water is filled with fresh water. The settled, cleaned and neutralized sand from the cyclone 10 is dried by means of a vibratory dryer 14 and then transported to a storage bunker 15. The neutralization and rinsing or cleaning takes place alternately in two closed circuits. For neutral setting of the rinsing solution, bases can be added, for example, when neutralizing by means of acid, and vice versa. The belt weigher can also fill several neutralization tanks via a distributor belt, whereby several cyclones can also be used.

For environmental reasons, the neutralization and purification process takes place in a closed circuit with the lowest possible water consumption. After the reaction is complete, the neutralization solution is withdrawn from the container together with the detached sludge constituents and then passed through a filter to separate the sludge

cleverly. If necessary, the filtered neutralisutlone solution filtered with fresh acid b2v. Jane and fresh water or rinse water refreshed and only next treatment z, ti. about ZwiacliVibehBlicr always returned to the circulation process.

In the following, another example of an inorganic bonded mixed sand, represented by initial salt content, thermally and mechanically produced regenerate and its subsequent neutralization and purification is indicated. To wild a strength comparison made on particularly sensitive reacting cold-box Kernsandmiechungon the different Behanalungsetufen compared to new sand.

Example III

Sieve Analysis Bentonite used sand 0.2 Therm.-mech, rain. 0 Neutral, with 0.5 Sand of I 0.7 10 ml conc. 3.6 6.1 HjSO ₄ per kg 25.1 22.3 Sand of I I 52.8 Il 48.0 III 0,71mm 14.2 21.0 0.1 0,5mm 3.3 1.8 0.9 0,355mm 0.3 0.1 5.7 0.25mm 0 0 21.5 0.18 0 0 50.2 0.125 mm 9.8 9.7 20.0 0.09 mm 1.5 0.063 mm 976 165 0.1 0.02mm 8.26 0.93 0 20.02 mm 2.57 0.17 0 PH value 2.3 0.89 7.1 Elektr.Leitf. in pS / cm 3 % Schlämmst. 0.32 % Glühverl. 0.14 Oolith. Degree 0.77

Compensation of flexural strength in N / cm ³ on cold-box Sand samples: Sand mixture: 30% new sand, AFSca. 60

70% therm. Mech. Regenerate 0.8% synthetic resin 352T14 0.8% synthetic resin 652 TEA 700

Test time Sand Il Sand III 100 new sand immediately 150 260 230 Vih 185 390 340 1h 190 420 410 2h 192 440 420 24 hours 225 450 460

Claims (11)

1. A process for the recycling of organic and / or inorganic binder containing mono / mixed foundry sand, characterized in that the organic binder-containing sand after a thermal regeneration or the inorganic binder-containing sand after a thermal and mechanical regeneration depending on after regeneration by a measurement of certain pH with a suitable base or acid is neutralized so that it finally has a pH between 6 and 8. 2. The method according to claim 1, characterized in that the pH word of the sand after neutralization is between 6.8 and 7.5. 3. The method according to claim 1, characterized in that the sand is neutralized after darkening a wet cleaning and subsequent drying. 4. The method according to claim 1, characterized in that are used for neutralizing NH ₄ OH as the base or sulfuric acid or hydrofluoric acid. 5. The method according to claim 1, characterized in that after neutralizing the regenerating sand for neutralization concentrated sulfuric acid in an amount of 3 to 50 ml per kg of sand is added. 6. The method according to claim 1, characterized in that after the basic regeneration sand for neutralizing concentrated sulfuric acid in an amount of 8 to 12 ml per kg of sand is added. 7. The method according to claim 1, characterized in that the acidic after the regeneration of sand to neutralize 3 to 40ml 25% NH ₄ OH per kg of sand is added. 8. The method according to claim 1, characterized in that the after acidic regeneration of sand to neutralize 12 ml of 25% NH ₄ OH per kg of sand is added. 9. The method according to claim 1, characterized in that the neutralizing and cleaning is carried out in a closed loop system and alternately in a single container. 10. The method according to claim 1 or 6, characterized in that the neutralizing solution is cleaned after use by filtration and reused after being refreshed with rinse water in the neutralization process. 11. Recycled foundry sand which is obtainable by thermally and / or mechanically treating it, depending on the binder contained, and then neutralizing it so that its pH is between 6.8 and 7.5.