DE102005041519A1 - Treating foundry mold material containing core sand and binder, to regenerate the sand for reuse, by subdividing the sand while still hot into stream for wet regeneration and stream for use as drying heat source - Google Patents

Abstract

Treatment of foundry mold materials, containing core sand and binder involves subjecting the core sand (Sk) bonded with inorganic binder(s), while still hot after casting, to dry separation (A1) from the casting (M1), dry crushing (B1) and subdivision (E1) into two hot partial streams (T1, T2).

Description

The The invention relates to a method for treating core sand and Binder-containing foundry mold materials.

A method of mixing foundry sand containing core sand and foundries containing organic binders is described EP 0 445 436 B1 in which the mix is conveyed from a mixing space into a mixing space separated therefrom by an installation body, and the mixing got rotation is decelerated in the plane determined by the installation bodies; This achieves a high mixing intensity. It is also described that the mixing effect of mixers with rotating mixing tool can be increased by increasing the mixing tool speed until the friction of the mixture at the mixing container wall is no longer sufficient and the mix follows as a more or less compact mass of the rotary motion of the mixing tool. Thus, the friction, Zerteil- and Umschichtkräfte required for the mixing process are limited. This property is particularly disadvantageous when viscous components are present in the mix.

Of the Collective term "binder" includes a product which both similar and different substances with each other to connect. The setting process is carried out by physical Drying, by solidification or by a strong increase in viscosity - like a Melting process - or by chemical reactions. For example, bitumen is used in road construction and tar binder for Rock grains and in the field of refractories, aluminum phosphates may be used as Binders are used. With building materials turn become additives like sand and gravel through hardening tied and cemented with water-added binders.

The Allocation of binders has changed lately. For example is tried, so far common organic binders in the casting area for cores - and for Part also for Shapes - through to replace inorganic binders that are non-toxic and without Stench hardened by dehumidification. It acts for example, water glass, magnesium sulfate, sodium phosphate and similar Substances.

The Solidification of a sand-binder mixture enclosed in a core box of the casting industry happens through dehumidification; for example, it will be warm Core boxes, Microwaves or through the sand-binder mixture into the core box directed hot air used. For example, after casting the castings, the hard core may by shaking, removed in a water bath or by high-pressure water jets from the castings become.

from high importance is that the sand for economic reasons then must be reused to make new cores and molds, which led to a sand cycle Has. If the cores are dissolved by water, then the entire sand must subsequently be dried again so that it can be transported by pneumatic Advancement, for the Storage in silos and for dosing at the next Circulation is suitable - with In other words, he has to be free-flowing be, which requires a drying of the sand.

Known is the drying of sand by heat, thanks to which also the sand warms up. As with the types of binder used, the curing of the Sand by warming is done, warm sand remains for the production of cores i. w. not suitable. That's why the sand cooled after drying become. Because considerable amounts of sand are in circulation - it have to Amounts of more than 10 t / h can be processed - can be used for drying and cooling Energy expenditure and the equipment requirements the use of these environmentally friendly binders become uneconomic.

at dry gutting has been shown that the sand qualities after a few rounds through increasing binder content and influences of the casting process not are more sufficient.

In front the background of these considerations the inventor set the goal to develop a method that makes it possible Core sand to regenerate economically, with by moisture removal cured inorganic binders is provided. In particular, it should be possible to to regenerate the core sand after the casting, before the core sand cooling down could.

to solution performs this task the teaching of the independent claim; to give the dependent claims favorable Further education. In addition, all fall within the scope of the invention Combinations of at least two in the description, the drawing and / or the claims disclosed features. For specified naming ranges should also Values within limits are disclosed as limits and be used as desired.

According to the invention bound with inorganic / inorganic binder / n Core sand after a casting in still tempered state of thereby resulting castings dry separated, dry crushed and divided the tempered core sand into two streams. The one partial stream is buffered according to the invention and the other partial stream is regenerated. For this purpose, it has proven to be advantageous that, after the division process, the partial stream to be regenerated is fed to a liquid-containing reactor and the introduced sand is wet-regenerated until the grain surface has been sufficiently cleaned of binder residues and products of the casting process; then this partial stream is mixed with the other partial stream. In this case, the second partial flow is dried according to the invention by the heat of the first partial flow.

To Another feature of the method according to the invention is the first Partial flow through the heat of evaporation of the moisture of the second Partial flow cooled.

in the According to the invention, the first partial flow is due to the heating of the second partial flow to the mixing temperature of the merged sub-streams after cooling led the second part of the stream and the second substream by its introduction into the reactor is subjected to a wet regeneration. In addition, a cleaning the grain surface the introduced sand of binder residues and products of Casting done, this by means of a liquid, in particular by Water.

to support the dissolution process can the water additives be added in a suitable amount, for example sodium hydroxide with water glass binder.

Of the Cleaning process can be mechanically supported according to the invention, through agitators, Vibrations or ultrasonic radiators; through these stations triggered Operations can also be used in combination.

The with the tempered sand in the liquid introduced heat increases the cleaning intensity in the reactor. The bath temperature of the reactor should by means of a cooling device or with supplied Fresh water can be controlled.

honed Water can be cooled and after removing the substances dissolved in the water as the reactor Fresh water fed again become. Arising swaths are removed.

When Cheap it has been proven to treat the treatment batchwise or continuously perform.

The Amount of partial or sand flow taken for wet regeneration should be at least as big that after the union of the two streams after the wet regeneration of that partial stream results in a sufficiently high sand quality for new casts. The amount of partial flow is limited by the heat content the first subset through which - as described - the wet-regenerated Partial flow to be dried.

To further features of the invention has at a sand temperature from about 200 ° C the second partial flow - at a humidity of about 4% after wet regeneration - one Share of about 40% of the total amount of sand. Also intended to increase the second part of this current before adding to the first partial flow means Sieve, centrifuge or the like. Facilities are deprived of free water.

All in all results in an economically favorable Regeneration method for tempered inorganically bound foundry sands.

Further Advantages, features and details of the invention will become apparent the following description of preferred embodiments and by reference the drawing; show in it

1 . 4 in each case a schematized family tree for a sand preparation;

2 . 5 : Procedural steps to an area of the pedigree of 1 or the 4 ;

3 : further process steps in the field of 2 ,

• • Trockene Trennung in Station A gebundenen Sandes (Bezugszeichen S) von Gussstücken (Bezugszeichen M).
• • Trockenes Zerkleinern der stückigen Teile des Stromes S in Station B.
• • Einen Siebvorgang zum Sieben des Sandes auf die gewünschte Korngröße (Station C).
• • Das Entfernen von unerwünschten Feinteilen in Zone D.
• • Das Teilen der Sandmenge im Bereich der Zone E in zwei Sand- oder Teilströme, deren einer als Sandstrom S₁ einem Zwischenlager zugeführt wird, wohingegen der andere Sandstrom S₂ zu regenerieren ist.
• • Die Regenerierung des Sand- oder Teilstromes S₂ in Zone F.
• • Das Zusammenführen und Vermischen der beiden Sand- oder Teilströme S₁, S₂ in Zone G.

The 1 to 3 The drawing shows a process for the regeneration of cold sands, which are bound with inorganic binders; the regeneration of the core sand takes place in several steps:

• • Dry separation in station A bound sand (reference S) of castings (reference M).
• Dry comminution of the lumps of stream S in station B.
• • A sieving process to sieve the sand to the desired particle size (station C).
• • The removal of unwanted fines in Zone D.
• • The sharing of the amount of sand in the area of zone E in two sand or streams, one of which is fed as a stream S ₁ an intermediate storage, whereas the other stream S _{2 is} to be regenerated.
• • The regeneration of the sand or partial flow S ₂ in zone F.
• • The merging and mixing of the two sand or partial streams S ₁ , S ₂ in zone G.

In this case, the amount of withdrawn for the regeneration sub-stream S _{2 should} be selected so that after merging the two sand or streams S ₁ , S ₂ in the long-term cycle sufficiently good sand properties. Any resulting sand losses can be compensated with new sand and the regeneration effect can be supported.

• F₁: Das Einbringen des regenerierten Sandstromes S₂ in einen Reaktor mit Flüssigkeit.
• F₂: Das Behandeln des eingebrachten Sandes über einen bestimmten Zeitraum, der es ermöglicht, die Kornoberfläche ausreichend von Binderresten und Produkten des Gussvorganges zu reinigen.
• F₃: Das Abscheiden von freiem Wasser beispielsweise auf Schwingsieben oder in Siebtrommeln.
• F₄: Das Trocknen des Sandes.

The above-mentioned regeneration operation in zone F includes according to 2 the following sub-steps:

• F ₁ : The introduction of the regenerated sand stream S ₂ in a reactor with liquid.
• F ₂ : treating the introduced sand over a certain period of time, which makes it possible to sufficiently clean the grain surface of binder residues and products of the casting process.
• F ₃ : The separation of free water, for example on vibrating screens or in screening drums.
• Q ₄ : The drying of the sand.

As far as sub-step F ₂ is concerned, the cleaning of the introduced sand takes place in a liquid; as such, water is suitable. To assist the dissolution process, additives can be added to the water in a suitable amount, for example sodium hydroxide solution with waterglass binder. This cleaning process can be mechanically supported, for example, by stirrers, oscillations and ultrasonic radiators. The treatment may be batchwise or continuous.

During the drying process, the degree of drying is chosen so that the mixture of the completely dry sand or partial stream S _{1 of} the intermediate storage and the wet-regenerated sand or partial stream S _{2 is} free-flowing; Thus, the composite of two sand or streams S ₁ , S ₂ sand stream can be handled with the usual facilities of a foundry.

To 3 For the above-described process step F ₄ of sand drying, that is to say the treatment of the sand grains with moist surfaces in a drying reactor, a plurality of processes are alternatively used in which the sand grains do not or only very slightly heat up; on the one hand there is a flow through with dried cooler air in the fluidized bed or in the flow stream (step F _4.1 ), on the other hand a flow of slightly heated air with low relative humidity in the air flow or fluidized bed (step F _{4. 2} ). Or the sand is mixed with grains of a substance that absorbs the moisture from the surface of the sand grain (step Fa _4.3 ).

The sand is mixed with grains of a substance, which absorbs the moisture from the sand grain surface. For example, the grains consist of porous materials with a large internal surface area. After a sufficient reaction time, in which the mixture can be moved or rest, the grains of sand and the moisture-absorbing grains are separated, for example by sieving, if their dimension is greater than that of the grains of sand. So the drying takes place without heating the sand. The dried sand is added to the untreated sand or partial stream S ₁ . The residual moisture is distributed over the total sand amount.

The drying grains will be outside of the sand cycle deprived of absorbed moisture.

A another possibility shown by way of example the surface moisture the grains of sand Sufficient to lower is to use the wet grains of sand with contact fibrous substances. The fibers take the Moisture of the grains of sand on and when the sand is separated from the fibrous substances was dried, for example, by pressing, air purging or similar steps so far, that they can absorb moisture from sand grains again.

The pedigree of 4 illustrates another method, namely the regeneration of the core sand after the casting, before the core sand has cooled.

Thereto is separated into Station A _1, the sand S _k of the castings M ₁ and crushed into station _B1. For this purpose, the entire still temperate amount of sand in zone E _{1 is divided} into two partial streams T ₁ , T ₂ . The first partial flow T _{1 of} the sand S _k is temporarily buffered in zone K, the second partial flow T ₂ is wet-regenerated in a reactor NR, metered into zone Q and subsequently mixed again into the first partial flow T ₁ in zone G ₁ .

As a result, on the one hand, the drying of the second subset T ₂ by the heat of the first subset T ₁ and on the other cooling the first subset T ₁ by the heat of vaporization of the moisture of the second subset T ₂ and the heating of the sand of the second subset T ₂ the mixing temperature of the merged subsets T ₁ , T ₂ after cooling the second subset T ₂ by the regeneration process.

After combining the two subsets T ₁ , T ₂ , the sand in zone R is cooled to use temperature.

The screening and the removal of fines, so a sighting can be done before separation into two streams T ₁ , T ₂ in the region of the zone E ₁ or preferably after their combination or cooling, as the 4 with the stations C ₁ and Z indicates.

• NR 1: Einbringen des Teilstromes T₂ in einen Reaktor mit Flüssigkeit.
• NR 2: Behandeln des eingebrachten Sandes des Teilstroms T₂, bis dessen Kornoberfläche ausreichend von Bindemittelresten und Produkten vom Gussvorgang gereinigt ist.
• NR 2.1: Die Reinigung des eingebrachten Sandes des Teilstroms T₂ erfolgt in einer Flüssigkeit.

The wet regeneration of the second partial flow T ₂ is carried out according to 5 in the following process steps:

• NR 1: introduction of the partial flow T ₂ into a reactor with liquid.
• NR 2: treating the introduced sand of the partial stream T ₂ until its grain surface is sufficiently cleaned of binder residues and products from the casting process.
• No. 2.1: The cleaning of the introduced sand of the partial flow T ₂ takes place in a liquid.

When liquid in Zone NR 2.1, for example, water is suitable. In support of the releasing operation can the water additives be added in a suitable amount, for example sodium hydroxide with water glass binder.

Of the Cleaning process can be mechanically supported, e.g. by - also combined - use of agitators, Vibrations or ultrasonic radiators.

The tempered sand of the partial flow T _{2 introduced} into the liquid heat increases the cleaning intensity in the reactor NR. The bath temperature of the reactor NR can be controlled by means of a cooling device or with supplied fresh water.

honed Water can be cooled become. After removing the substances dissolved in the water, it can be added to the reactor NR returned as fresh water become. Arising swaths are removed.

The Treatment is carried out batchwise or continuously.

The amount of partial stream T ₂ taken for wet regeneration should be at least so great that after the combination of the two partial streams T ₁ , T ₂ or after the wet regeneration of partial stream T _{2, the} sand quality is sufficiently high for new casts.

The amount of the partial flow T ₂ is limited by the heat content of the amount of the first partial flow T ₁ , through which - - as described - the wet-regenerated substream T _{2 is to be} dried.

Thus, for example, at a sand temperature of 200 ° C, the partial flow T ₂ , which has a humidity of 4% after wet regeneration, have a share of about 40% of the total amount of sand.

To increase the partial flow T ₂ , the partial flow T ₂ by means of a sieve, a centrifuge or similar. Free water systems are withdrawn before the partial flow T _{2 is added to} the partial flow T ₁ again.

sand loss can balanced with new sand and so the regeneration effect can be supported.

Claims (14)

Process for treating foundry mold materials containing core sand and binders, characterized in that the core sand (S _k ) bonded to inorganic / inorganic binder / n is dry-separated, dry-comminuted and dry-crushed by castings (M ₁ ) produced in a still tempered state tempered core sand is divided into two partial streams (T ₁ , T ₂ ) (station E ₁ ). A method according to claim 1, characterized in that after the division process, a partial stream (T ₁ ) is buffered. A method according to claim 1 and 2, characterized in that after the division process to be regenerated partial stream (T ₂ ) a liquid-containing reactor (NR) supplied and the introduced sand is wet regenerated until the grain surface is sufficiently cleaned of binder residues and products of the casting process , after which this partial flow is mixed with the other partial flow (T ₁ ) (station G ₁ ). A method according to claim 3, characterized in that the second partial flow (T ₂ ) by the heat of the first partial flow (T ₁ ) is dried. A method according to claim 3 or 4, characterized in that the first partial flow (T ₁ ) is cooled by the heat of vaporization of the moisture of the second partial flow (T ₂ ). Method according to one of claims 3 to 5, characterized in that the first partial flow (T ₁ ) is carried out by heating the second partial flow (T ₂ ) to the mixing temperature of the merged partial flows after cooling of the second partial flow. Method according to one of claims 3 to 6, characterized by a wet regeneration of the second partial stream (T ₂ ) by its introduction into the reactor (NR). Method according to claim 7, characterized by Cleaning the grain surface the introduced sand of binder residues and products of Casting process. Method according to claim 8, characterized by Purification of the introduced sand by means of a liquid, especially by water. Method according to claim 9, characterized that of the liquid for support the dissolution process additions be added, for example, sodium hydroxide in water glass binder. Method according to one of claims 7 to 10, characterized that for the cleaning process at least one agitator and / or vibrations and / or ultrasonic beams used for mechanical support become. Method according to one of claims 7 to 11, characterized that the bath temperature of the reactor (NR) by at least one cooling device and / or supplied by Fresh water is controlled. Method according to one of claims 1 to 12, characterized in that at a sand temperature of about 200 ° C, the second partial stream (T ₂ ) at a humidity of about 4% after wet regeneration has a share of about 40% of the total amount of sand. Method according to one of claims 1 to 13, characterized in that the second partial stream (T ₂ ) before addition to the first partial stream (T ₁ ) by means of sieve, centrifuge or the like. Facilities free of water is withdrawn.