DE19651721A1 - Metal-containing waste conglomerate, e.g. mill scale, moulding production - Google Patents

Abstract

A process for producing a moulding of metal-containing waste conglomerate (MAK) with a certain particle size distribution involves making additions for adjustment to a certain viscosity and then moulding and firing. Preferably, viscosity adjustment is achieved by addition of viscosity controlling additives (preferably cellulose, gelatin, stearine, water-glass, sodium carbonate, soap, calcium or magnesium lignosulphonate, molasses and/or other similar starch and/or sugar containing components) and/or sintering aids (preferably clay, fireclay, volcanic rock powder, kieselguhr and/or aluminium and/or magnesium oxide and/or hydroxide).

Description

The invention relates to a method for manufacturing of a shaped body made of waste conglomerate containing metal.

Especially in the metalworking industry produce a large number of metal-containing waste materials that with comparatively energy-consuming and technically com processed procedures and another use be fed.

For example, hot rolling scale is formed during the hot rolling of steel sheets, which forms on the surface of the rolling stock. Such a mill scale ver stands for the iron oxide formed during the rolling process on the steel surface, which, when predetermined rolling temperatures are exceeded, a multilayer structure of iron oxide (Fe ₂ O ₃ ), iron oxide oxide (magnetite) (Fe ₃ O ₄ ) and iron oxide (FeO ) having. The thickness of the rolled scale layer increases with the rolling temperature and the rolling time, since this scale layer is permeable to oxygen, ie even if the scale layer is formed, oxygen can diffuse through the layer and react with the iron. The mill scale is a porous, brittle and not firmly adhering layer, which mostly falls off of the surface of the rolling stock on its own. For complete separation of the mill scale, the rolled products are subjected to a thermal or mechanical treatment during the rolling process, so that the lower rolling layer flakes off.

As mentioned above, these contain layers of mill scale a high Fe content and are therefore high quality Ab waste materials attributed to the manufacturing cycle are. A problem with the reprocessing of this roller  scale waste consists in the fact that it is not or granular waste, but with Water and especially mixed with rolling / pressing oil residues are, so that the waste material as gritty, cakey up muddy mass may be present, which is a significant concern part of the organic components (VOC - Volatile Organic Compounds).

So far, one has such mill scale waste with steel scrap mixed and in the blast furnace process as an addition to Pig iron added. Such a return of the roll tinder, however, has the problem that it is due to the undefined size and composition of the roller scale particles and the different proportions of organi components is very difficult, a predetermined one Adjust the mixing ratio with the steel scrap, see above that in unfavorable cases it is caused by the blast furnace process Steel quality to be manufactured fluctuates. Is problematic furthermore that for such a reuse at the Steel making only mill scale can be used has an oil content of less than 1% by mass, so that often costly post-treatment of the mill scale are required to get this to the predetermined Bring rolling oil content.

In order to ensure the steel quality, the steel industry has defined a number of criteria that aggregates must meet, which, in the interests of the circular economy, are returned to the product cycle through use in the blast furnace process. Examples of such criteria are:

• - The input material (mill scale) may have a maximum of 10 Mass% aggregates are offset;
• - The input material must be free from organic stock to be share;
• - The maximum volume is limited to 0.5 dm ³ ;
• - The bulk density should be about 2.0 g / cm ³ ;
• - The input material should be wear-resistant and frost-free be;
• - The input material must have a burst strength when immersed in the melt ze, the Platzfe strength must be guaranteed at least up to 800 ° C.
  This space stability ensures that no dust emissions occur when immersed in the melt and the melt is cooled by the sinking input material;
• - The input material should be as ferromagnetic as possible Have properties and a high proportion of "Magnetite" (artificial iron ore) included.

These criteria can be used with the previously known Process for recycling mill scale or other me waste conglomerates containing metal (e.g. with cooling lubricating dust or chips machining processes) were not met will.

In German patent application 196 39 443 there is a Process for the production of a molded body from MAK wrote in which the MAK with an acid, preferably Phosphoric acid, oxalic acid, acetic acid or a phosphorver bond offset, then molded body who formed the and the curing of the moldings on chemoreactive We ge is done. This means that there is no sine in this process tion of the formed body but a curing by chemical reaction of the acid with the solid.

Such a method has the disadvantage that the Ver use of phosphorus compounds or acids considerable process engineering required and around extensive measures for processing and recycling the chemical aggregate and for the hydrogenation of Exhaust air must be taken.

In contrast, the invention is based on the object a process for producing a molded body from MAK create, with the minimal procedural Auf wall moldings can be created that meet the requirements industry.

This task is accomplished through a procedure with the characteristics len of claim 1 solved.

Through the measure, the waste conglomerate that - depending by origin - from a pouring or a muddy Mass can exist before the formation of a shaped body first by adding suitable additives to one before set certain viscosity, then the shape training body and then this molded body by a Binding the sintering reaction can depend on the addition of acids or other chemically reactive additives be largely avoided, so that the process proceeded is technically easier to master.

During the burning process, which can take place, for example, at temperatures of about 1000 ° C, the organic components of the MAK are driven out, the water part of the MAK evaporates and the oil components (cooling lubricant, rolling oil) burned, so that the "internal energy" of the MAK can be used for the burning process. Surprisingly, it has been shown that a significant reduction in the proportion of iron oxide (Fe ₂ O ₃ ) is possible due to the reducing combustion operation. This iron oxide is non-magnetic, while the other iron oxides (FeO, Fe ₃ O ₄ ) can be magnetized. By reducing the proportion of Fe ₂ O ₃ , a magnetic molded body is obtained, so that the sintered material obtained after the firing process can be handled, for example, by magnets.

Through the additives, the viscosity in the desired Be set so that, for example, a pourable or a tough plastic, inherently stable "Plastomasse" can be set, which a variety of poss Opportunities for the formation of the molded body opens.

The viscosity of the molding compound can be increased by adding viscosity-controlling additives and / or addition of as Adjust sintering agents.

Materia comes as viscosity-controlling substances lien from the group cellulose, gelatin, stearins, water glass, sodium carbonate, soaps, calcium, magnesium lignosul fonat, molasses and similar starchy / sugary components ten in question.

Minera materials such as clays, clay chamotte, volcanic ge stone powder, diatomaceous earth or aluminum / magnesium oxides or -hydroxides are used.

The viscosity-controlling additives are preferred wise with a share of 0.5 to 2 mass% and the plastifi decorative substances with a share of 5 to 10% by mass added.

When setting to a comparatively low Viscosity (pourable mass) can shape the mold body by using a form or formwork.

A particularly simple procedure can be obtained if the Formwork is designed as lost formwork, which during of the firing process or when used in the steel mill is decomposed or melted.  

Formwork that is decomposed during the firing process can NEN for example made of cardboard, wood fibers, plastics, Pa pier etc. exist.

For formwork that is not during the firing process are decomposed and introduced into the molten steel materials containing clay are preferred. In the In these cases, care must be taken to ensure that the additional the sound component still meets the criteria mentioned at the beginning be filled. It is particularly advantageous if the Clay has a predetermined iron content, so that this Criteria (aggregate ≦ 10 mass%) easier to meet are.

As an alternative to using formwork, the Vis the mass of the mass is also set comparatively high be, so that a stable, kneadable mass places, for example, on a surface brought.

Preliminary tests have shown that egg A layer thickness of 60 to 150 mm is a particularly good result let it be achieved.

The final shape can then by Ausste Chen, punching, cutting, etc. of the molded body from the flat mass.

The mass can be fully exploited if the Shaped bodies are formed in a honeycomb structure, so that each molded body has a large hexagonal surface.

The method according to the invention is self-evident not on the use of Fe-containing waste conglomerates limited, but other metal or ore-containing waste materials are used.  

Particularly high-quality moldings are obtained when the Molding compound evacuated before the molding is formed (vented).

Caking the molded articles becomes more advantageous prevented by applying a release agent.

Other advantageous developments of the invention are the subject of further subclaims.

Preferred embodiments of the Invention explained with reference to schematic drawings. Show it:

Fig. 1 is a flowchart of a procedural invention;

Fig. 2-5 formwork, which are decomposed during the firing process;

FIGS. 6 and 7 temperature-resistant molds; and

Fig. 8 shows an embodiment for Herge without formwork molded body.

The processing of hot rolling scale cases is discussed using the process diagram according to FIG. 1. This hot rolling scale waste is produced in large quantities as a waste product in a steel hot rolling process. This is often a muddy mass that has a relatively large water / oil content. The solids content of this waste product mainly consists of different iron oxides (hammer blow, magnetite), the further processing of which was previously only possible after a comparatively complex treatment of the waste material. The mill scale formed during the rolling process is replaced by a process of removal. Descaling is carried out using various methods, mechanical, chemical or thermal methods or combinations of these methods being used. Processes are frequently used in which blasting media made of ferrous materials are thrown onto the scaled rolling stock. Accordingly, in the case of such mechanical processes, in addition to water and rolling oil, the mill scale that has been blasted or reduced can also be mixed with blasting media made of iron materials. The proportion of hydrocarbon in mill scale is approximately 6 to 7 percent by mass.

As mentioned at the beginning, the process according to the invention is but also with waste materials from metal cutting metal processing methods applicable in which dusts, Chips or other material abrasion occur. These substances are often mixed with cooling lubricant and so lie with also in muddy form. The following This muddy waste, the Fe, Cr-Ni or other metals or fractions containing ore holds together under the term metal waste conglomerate (MAK) quantified.

The hot rolling mill delivered by the rolling mill with the above-described composition and consistency usually has solid fractions with different size dimensions, so that a size reduction step can first be provided in order to set a predetermined grain size distribution of the solid components. Such comminution can be carried out using suitable mills. As indicated in Fig. 1, this crushing step is only provided as an option and can be omitted if the solid components are already supplied with sufficiently small particle diameters.

Frequently, the hot rolling scale - or generally speaking, the MAK - are odor-laden, so that an odor neutralization step can be provided before or after the comminution process according to FIG. 1. This odor neutralization can be done, for example, by the addition of hydrogen peroxide, so that an odorless starting product is present.

After this mechanical preparation of the MAK is then in a subsequent process step agreed viscosity of the conglomerate. The Vis The viscosity is adjusted so that there is a consistency spectrum of the resulting molding compound results from a flowable casting compound up to a viscous, own dimensionally stable mass, a so-called "plastomass", is sufficient. Depending on the set viscosity or consistency of the shape This can be achieved through a variety of well-known apparatuses portioned and shaped.

The viscosity is set depending on on the consistency of the delivered hot rolling scale for example by adding viscosity-controlling substances sets from the group with the fabrics, cellulose, gelatin, Stearine, water glass, sodium carbonate, soaps, calcium or Magnesium lignosulfonate, molasses and similar starch / components containing sugar. By encore Such substances can increase the viscosity or he can be lowered. As a rule, the MAK is covered with screed moist to free-flowing input consistency delivered, so that a liquefaction of the MAK takes place.

The viscosity-controlling substances are included in the for example 0.1 to 2 mass percent added (based on the total mass). It is essential that the substance addition ze and the MAK are mixed intensively, these ver Mixing can be done for example by kneaders, etc.  

If the viscosity of the MAK supplied is already sufficient, the above step can be skipped (dashed line in Fig. 1).

In a further step we are used as sintering agents added substances that are practical as binders act in the later sintering or firing process. This as Sintering agents also influence the Viscosity of the MAK, so that the addition of these substances with the Addition of the viscosity-controlling substance additives coordinated must become. In addition, those that act as sintering agents Substances have a water and oil absorbing effect, so that the viscosity is usually increased. As special Fabrics such as for are suitable for this function for example clays, clay flours, clay refractory flours, vulkaniti stone powder, diatomaceous earth and oxides / hydroxides of aluminum miniums and magnesium. The share of this substances acting as sintering agent is 5 to 10 mass percent, so that the aforementioned, from the Stahlindu The required limits for the maximum proportion of Zu impact materials (≦ 10 mass percent) is observed.

After intensive mixing of the visco sity-controlling additives and as sintering agents acting substances can be the resulting consistency still fine-tuned by adding or removing water will.

During the first test attempts, it turned out to be special turned out to be advantageous if after the default the viscosity by adding the aforementioned additives an evacuation of the prepared MAK in a vacuum reorganization takes place. This will evacuate adhering water removed and the mass over it vented from, so that the MAK is compressed. The mass is further homogenized by this compression and increases the molding quality.  

Depending on the type and amount of additives and, if applicable, the amount of set vacuum, a molding compound is obtained, which either which has a certain inherent shape stability or else is pourable. This wide range of viscosities allows es, a variety of apparatus for portioning and Use mold filling. Can be used in principle for example slurry pumps, baked goods blank portioning machines, Soft stone molding machines, Piston presses, semi-moist to dry molding compound rotary presses, Screw presses, etc.

A number of al alternative procedures are available.

A variant consists in adjusting the viscosity of the MAK in such a way that a pourable molding compound is made available. This casting compound is not inherently stable, so that no direct, kneading formation of a shaped body is possible. In order to set a predetermined shaped body geometry, native circuits such as are shown in FIGS . 2 to 7 are used at this age. These formworks act practically like casting molds into which the casting compound is poured. The formwork (casting molds) can have practically any geometry. In Fig. 2 shows a simple cassette 1 is shown having a rectangular shape. This cassette 1 can be filled directly with casting compound, so that a quaderför shaped casting is obtained which, for example, has external dimensions of 60 × 40 × 20 cm. Such a shaped body could, for example, be used as a floor covering. In the event that the molded body in the steel industry should be used as an additive in the blast furnace process, however - as mentioned at the beginning - smaller dimensions are required. For this purpose, formwork is used, which is formed by a formwork grid 2 . This means that the formwork has a large number of adjacent form nests, each with the same geometry. FIG. 3 shows a circuit grid with rectangular fields, while FIG. 4 shows a honeycomb-shaped formwork grid 2 with hexagonal fields. As indicated in Fig. 5, the formwork grid 2 can be provided with a bottom 5 ; However, it is also conceivable that only the peripheral walls are formed in the Schalungsra ster 2 and the bearing surface is so precisely made that it can be placed sealingly on a base so that a cross flow between the individual fields or nests is prevented. The circumferential walls 6 of the nests do not have to run vertically to the base, but can - as indicated in FIG. 5 - also taper conically towards the bottom 5 , so that demolding is made easier with reusable formwork.

It is also conceivable that the formwork grid ( 2 ) according to FIGS. 3 to 5 is inserted into the cassette ( 1 ) according to FIG. 2, so that different shaped bodies can be formed with a standard cassette by changing the formwork grid geometry.

The cassette 1 and the formwork grid 2 can optionally be made of refractory material, which can be used again after the mold has been removed from the mold (after the firing process). As an alternative to this, the formwork grid 2 can also be produced as lost formwork which is decomposed or burned during the firing process. As materials for the formwork grid, for example, paper, pressed cardboard, wood fibers, plastics, cardboard or corrugated cardboard can be used.

Instead of the formwork or fan grid 2 shown in FIGS . 3 to 5, of course, other formwork forms and arrangements (for example molded tray trays, etc.) can also be used.

In Figs. 6 and 7 show a further variant of a mold or a casting mold is shown. In this variant, the formwork is made of clay or clay-like material that is shaped into hollow bodies. These Hohlkör by can - as indicated in Fig. 6, have the shape of a hollow brick 2 , in the cavities, the casting compound (MAK) is filled. The hollow body 2 is, however, not fired clay but only made from preformed and dried material. This material is preferably mixed with iron or with the metal contained in the MAK, so that the total mass fraction of iron (or the corresponding metal) in the hollow body 2 filled with the MAK meets the criteria set by the steel industry (see previous statements) he fills. The formwork (hollow brick) 2 , as indicated in FIG. 6, can be without a floor - similar to a hollow brick - or, according to FIG. 7, which shows a section through a hollow brick 2 , in turn has a floor 5 . In the case in which the formwork 2 is carried out without a floor, it is advantageous if the MAK is set with a higher viscosity, so that a cross flow along the contact surface between the individual cavities is avoided. In the design of the formwork 2 according to FIG. 7 (with floor 5 ), a lower viscosity setting of the MAK can be provided.

In the variant shown in FIGS. 6 and 7, in which the formwork consists predominantly of clay, the MAK is sintered during the firing process with the formwork, so that a molded body with a MAK filling and a clay shell staggered with egg arises. This "compound" molded body is then further processed in the blast furnace process.

While a pourable mass was used in the formwork shown in FIGS. 1 to 7, in a further alternative method the MAK is set to a higher viscosity, so that a viscoplastic inherently stable mass is obtained. This inherently stable "plastic mass" is then applied to a suitable refractory base. This application can be done by spraying or rolling, the layer thickness preferably being 60 to 150 mm.

This layer of inherently stable MAK is then subdivided into a plurality of moldings by a suitable cutting / punching device, such as a lattice knife. This subdivision can have the honeycomb structure shown in FIG. 8 with hexagonal plates (shaped body 8 ). By the cutting / punching process, the layer is completely severed, so that a gap 10 is formed between the shaped bodies 8 , which is indicated in detail X in FIG. 8. That is, after the cutting / punching process, the planar layer is subdivided into a multiplicity of shaped bodies 8 arranged at a distance from one another. Of course, the shaped bodies are not limited to the hexagon shape shown, but any other geometries can also be selected.

The width of the gap 10 is selected so that the shaped bodies 8 no longer connect in a subsequent firing process.

In the preliminary tests, it has been shown that this gap width can be chosen to be relatively small, since the oil / water emulsate contained in the MAK wets the peripheral edges of the shaped bodies 8 after the cutting / punching process and prevents caking during the firing process, so that the flat layer disintegrates into a large number of shaped bodies 8 after firing.

The "caking" of the molded body 8 on the base or the caking of adjacent molded bodies 8 can be prevented by additionally treating them with a non-sintering material. Such a material can be quartz sand or the like, for example, which practically forms a release agent.

The shape formed in the manner described above bodies are then burned to about Heated from 1000 to 1100 ° C. This burning process can be done in an egg NEN furnace, which is designed as a tunnel or ring furnace is to be carried out. This kiln is as through running furnace, which usually has a heating zone slowly rising temperature, a burning zone with con constant high temperature and a cooling zone with sink the temperature has.

A new, universally applicable converter furnace developed to The subject of a separate patent application was made.

In principle, however, Brennaggre are for this application gate can also be used, as used for example in drawing gel production can be used.

The molded body provided with the formwork ( Fig. 2-7) or the molded body applied to a fireproof base ( Fig. 8) passes through the kiln, and it is heated to the aforementioned temperature of approx. 1000 to 1100 ° C. The "heating materials" in the MAK, ie the oil content and the total carbon content, can also be used for this heating process. Theoretically, 80% of this internal energy can be used for heating and for endothermic processes when heating to the firing temperature. However, since the firing process has to be heated to regulate, only 1100 kJ / kg of the theoretically available 2100 kJ / kg MAK can be used for the firing process, while around 1000 kJ / kg escape unburned. To remove these "excess" hydrocarbons and the escaping organic constituents, the furnace must be equipped with an exhaust gas purification system, which enables the unused hydrocarbons to be returned to the combustion chamber. The exhaust gas cleaning required for plant operation is comparable to cleaning in other thermal processes in which fractions containing oil are thermally treated. According to current knowledge, exhaust gas afterburning with subsequent separation of the acidic exhaust gas components should be sufficient, either using the entrained flow process or by exhaust gas scrubbing.

During the firing process, the MAK is reduced using the substances that act as sintering agents, so that after the firing process, a dimensionally stable molded body with a comparatively high iron content is present. During the firing operation, the iron oxides (Fe ₂ O ₃ ) contained in the mill scale (MAK) are reduced, similar to the blast furnace process. This reduction may be due to the same mechanisms as the reduction of Fe ₂ O ₃ in the blast furnace process by the addition of coke, which is burned to carbon monoxide CO. It is assumed that the hydrocarbon mixture, which is finely distributed in the molding composition, has a small-scale effect similar to that of the coke in the blast furnace process.

By reducing Fe ₂ O ₃ , a magnetic sintered product is obtained which can be referred to as "artificial ore". The magnetic properties of this synthetic ore make it possible to remove and handle the shaped body by means of electromagnets.

The material properties of the molded body can be through targeted temperature control during heating and cooling vary, with it being preferred that the Heating with a steep temperature gradient, while the body cooling after a comparatively fla Chen temperature gradient is extremely slow.  

As already mentioned above, the lost formwork according to FIGS . 3 to 5 are burned during the firing process, while the formwork according to FIGS. 6 to 7 sinter with the MAK.

The resulting sintered bodies meet the requirements at the beginning mentioned criteria set by the steel industry and can therefore be used as a high-quality aggregate in high oven process can be used.

Claims (19)

1. A method for producing a shaped body from metal-containing waste conglomerate (MAK), which is present with a particle size distribution, with the steps:

• Addition of additives to set a predetermined viscosity,
• - Form a shaped body and
• - Burning the molded body.

2. Process for producing a molded article according to An saying 1, characterized in that the viscosity by Addition of viscosity-controlling substances and / or additives substances that act as sintering agents. 3. Process for the production of a shaped body according to An saying 2, characterized in that the viscosity tax substance additives from the group cellulose, gelatin, Stearine, water glass, sodium carbonate, soaps, calcium or Magnesium lignosulfonate, molasses and similar starchy / sugary ones Components are selected. 4. Process for the production of a shaped body according to claim chen 1 to 3, characterized in that the sintered medium-acting substances from the group clays and clay flour, Clay chamotte, volcanic stone powder, diatomaceous earth and Al / Mg oxides, hydroxides are selected. 5. Process for the production of a shaped body according to claim chen 3 and 4, characterized in that the viscosity controlling substance additives with 0.01 to 5 mass%, preferably 0.1 to 2 mass% and the substances acting as sintering agents  with 1-20 mass%, preferably 5-10 mass% based on the total mass can be added. 6. A method for producing a shaped body according to any one of the preceding claims, characterized in that the mass set to the predetermined viscosity for forming the shaped body is introduced into a formwork ( 2 ). 7. A method for producing a shaped body according to claim 6, characterized in that the formwork is a lost formwork ( 2 ). 8. A method for producing a shaped body according to claim 7, characterized in that the lost Scha development ( 2 ) consists of a material that is decomposed during the burning process. 9. A method for producing a shaped body according to claim 7, characterized in that the formwork ( 2 ) consists of a clay-containing material. 10. A method for producing a molded article according to claim 9, characterized in that the formwork ( 2 ) has an iron content. 11. A method for producing a molded body according to one of claims 6 to 10, characterized in that the formwork ( 2 ) has a plurality of mold nests. 12. A method for producing a shaped body according to one of claims 1 to 5, characterized in that the mass set to the predetermined viscosity is applied flatly to a base and divided into shaped body sections ( 8 ). 13. A method for producing a molded article according to An award 12, characterized in that the layer thickness 30th up to 200 mm, preferably 60 to 150 mm. 14. A process for producing a molded article according to An saying 11 or 12, characterized in that the Auftei by cutting, punching or cutting. 15. A process for producing a shaped body according to a of claims 12 to 14, characterized in that the Shaped body has a hexagonal outline shape. 16. A method for producing a shaped body according to a of claims 12 to 15, characterized in that on the peripheral edges and / or between the underlay and the support Do not sinter the surfaces of the molded body before firing of the material is introduced, which is preferably made of sand consists. 17. A method for producing a shaped body according to a of the preceding claims, characterized in that firing at about 900 to 1200 ° C, preferably 1000 ° C.   18. A method for producing a shaped body according to a of the preceding claims, characterized in that that contains MAK Fe, Cr / Ni or ore-containing fractions. 19. A method for producing a shaped body according to a of the preceding claims, characterized in that the MAK after the viscosity has been adjusted by evacuation tion is compressed.