DE102009053210A1 - Producing lime- or dolomite containing agglomerate, useful e.g. as a fertilizer, a supplement agent in metallurgy, comprises building-up agglomeration with finely divided solid starting materials and a liquid agglomeration medium - Google Patents

Abstract

Producing lime- or dolomite containing agglomerate, comprises building-up agglomeration with finely divided solid starting materials and a liquid agglomeration medium, which is anhydrous or exhibits a water content of up to 40 wt.%, and either has self-binding agent properties or an additional binding agent dissolved or dispersed, where the finely divided starting materials are made from lime and/or dolomite. An independent claim is also included for a granulate made from lime, dolomite, lime- or dolomite-containing mixtures, obtained by the above mentioned method, comprising a layer comprising the granulate particles of synthetic polymers or copolymers, preferably polyvinyl alcohol, natural polymers, polysaccharides, molasses, glue, resin, wax and/or linseed oil as a binding agent and optionally other additives placed at least externally.

Description

The invention relates to a process for the preparation of lime or dolomite agglomerates, which thereby newly accessible agglomerates or granules themselves and their uses.

Lime products are used in a variety of ways. There is a distinction between unburned and baked products. Limestone (calcite, calcium carbonate, CaCO ₃ ) belongs primarily to the green products. The fired products are based on lime (calcium oxide, CaO) and include those from it. Water added obtained slaked lime (hydrated lime, calcium hydroxide, Ca (OH) ₂ ). Lime / calcium oxide is produced by burning limestone / calcium carbonate at temperatures above 1000 ° C. Characteristic is the spontaneous exothermic and extremely violent reaction with water. Lime reacts strongly alkaline in water.

Due to the similarity in raw material and production, the analogous dolomitic products, in which calcium is partially replaced by magnesium, are also included here; H. counted to the lime products. Both lime and dolomite products have a variety of applications ranging from the building materials industry to steelmaking, flue gas cleaning, fertilizers and drinking water treatment.

In many applications it may be desired that other substances are associated with the lime or dolomite. In order to obtain from the pure lime or dolomite and the additives mixtures that can not demix, sometimes finely divided mixtures of lime / dolomite and the additives are pressed together. This production process is also referred to as press agglomeration.

Press agglomerates, however, have several disadvantages. They are sensitive to pressure during storage and can crumble, making them harder to handle. Also, they show quite high levels of abrasion when pouring and they dust. The dust pollutes the ambient air, or parts of the material can be lost through drift or suction.

Pure lime or dolomite is often lumpy, d. H. used broken. Again, similar disadvantages occur as the aforementioned. The irregular cracked surface gets caught easily, prevents even trickling and increases the abrasion and thus the amount of dust. The grain size is production-related uneven and can only be limited by sieving.

The invention has for its object to avoid the disadvantages of the prior art and lime products with more uniform, adjustable grain size and high resistance to breakage and abrasion available. In particular embodiments, the agglomerates should be readily water-soluble, in certain other embodiments, especially for steel processing, anhydrous.

The object is achieved by a process for producing lime- or dolomite-containing agglomerates in which a buildup agglomeration is carried out with finely divided solid starting materials and a liquid agglomeration medium which is anhydrous or has a water content of up to 40% by weight and either itself has binder properties or contains an additional binder dissolved or dispersed, and wherein the finely divided starting materials consist of lime and / or dolomite or contain these individually or in admixture.

The liquid agglomeration medium may be a more or less viscous liquid or a mixture of liquids and also includes solutions or dispersions. In particular, a binder may be dissolved or dispersed in the liquid agglomeration medium. The liquid agglomeration medium may be an organic solvent or a mixture of several solvents. A water content of up to 40 wt .-% is possible, but is excluded in the event that the solids content of the substrate to be agglomerated consists exclusively of lime. Pure lime agglomerates are produced with virtually anhydrous agglomeration media, but the binders may have water contents which should not exceed 50% by weight, based on the binder.

Preferably, the liquid phase portion of the liquid agglomeration medium is comprised of at least 60% by weight of one or more nonaqueous organic chemical liquids, especially oils, including curing or crosslinking oils, hydrocarbons, without any dissolved, suspended or dispersed solids content. Esters, such as As ethyl acetate or alcohols.

The content of liquid agglomeration medium, if appropriate with binder content, should be at most up to 50% by weight and in particular between 10 and 50% by weight, preferably between 20 and 40% by weight, more preferably between 25 and 35% by weight. -% based on the agglomeration mixture. The liquid phase fraction depends strongly on the particle size distribution and the porosity of the solid.

The invention uses the coarsening of finely divided calcined lime products by buildup agglomeration. As a result, fine fractions occurring in the lime process can be usefully used. The buildup agglomeration with binders and solvents leads to solid, loadable granules or agglomerates which show low abrasion, break little and dust little. Due to the targeted construction of finely divided material, the grain size is easily adjustable. Using conventional granulating or pelleting machines, granules / pellets of uniform shape and surface with well-tunable chemical composition result in application-optimized properties.

For the purposes of this invention lime and / or dolomite are not binders but the agglomeration substrate.

Since quicklime reacts violently with water, agglomeration of pure lime with water or aqueous solutions is not possible. Mostly, the simultaneous deletion of the lime is also undesirable. A product containing pure lime or a high proportion of lime (greater than 50% by weight CaO in annealed sample) should therefore not be agglomerated with water according to this invention but may instead be agglomerated with a mixture of water and alcohol or with alcohol alone , The person skilled in the art is able to select the right agglomeration medium on the basis of his expertise based on the composition of the starting material.

Under the processing conditions of the invention and typical ambient conditions (normal pressure and temperature), the magnesium component in the calcined dolomite does not react with water, i.e., in the calcined dolomite. H. there is only a proportionate hydration of the calcium oxide. Depending on the composition and in particular magnesium content of dolomite, the proportion of bound water can be more than halved in comparison with quicklime (calcium oxide).

In a construction agglomeration with water processed dolomitic products are intended primarily for use as fertilizers. The chemical composition of the agglomerates can be changed by adding further substances to the agglomeration mixture and thus the range of applications can be extended.

In contrast to fertilizer application, the water content in other lime products can be disturbing. This applies, for example, to metallurgical additives in the steel industry. The water content would explode explosively at the high operating temperatures of alloy surcharges. Also, the hydrogen contained is a generally undesirable element in metallurgy, which adversely affects the steel properties. For this application target direction, it is therefore preferable to work completely anhydrous or subsequently to dry / burn. As solvent (agglomeration medium), in these cases it is preferred to use at least one alcohol or an alcohol mixture.

The built-up agglomeration of calcined dolomite can be carried out as described above with water or aqueous mixtures, but also with anhydrous agglomeration medium. This results in particularly interesting products, eg. As for the "slagsplashing", as the specifically targeted decomposition of the agglomerates in the converter leads to a good distribution of the magnesium-containing components on the refractory lining.

The buildup agglomeration and wet agglomeration are known as such. "Agglomerate" serves as a generic term for the methods of mechanical grain enlargement and means the agglomeration of and bonding of finely dispersed solid primary particles to larger particle aggregates.

Agglomeration processes enable a targeted adjustment of the product properties of bulk solids. For example, the product handling can be significantly improved by a good flowability or a reduced dust content in the bulk material. The type and quality of the agglomerates also has an influence on properties such as dissolution behavior, granule size, shape and strength as well as storage stability or abrasion stability.

In the buildup agglomeration used in the invention, the powder to be agglomerated is mixed with a suitable liquid so that capillary bonds can form between the particles, thus producing a solid, mechanically loadable agglomerate. The strength is increased by the addition of binders.

Suitable laboratory and large-scale facilities for the assembly agglomeration are known and therefore need not be described separately here. Suitable are u. a. Granulating discs, granulating drums, granulating or fluidized bed granulators used in, among others, the ceramics, building materials and glass industries, metallurgy and the manufacture of feed and fertilizers.

For example, commercially available pelleting mixers which can be used under standard conditions without any special further precautions or structural changes are suitable. In addition, to obtain the desired grain band, it is possible that within the manufacturing process a separation of undersize and / or oversize is provided, preferably by sieving.

Desired particle sizes suitable for many applications for the finished granulate / agglomerate are preferably between 1 and 12 mm grain diameter (exclusion limits when screening against top grain and undersize, see also for diameter determination) DIN EN 933 ).

It may be helpful in agglomerating (granulating, pelleting) to add nucleating agents. It is therefore preferably provided that, in addition to the finely divided starting materials, coarse-grained material is added which can form agglomeration nuclei. The coarse-grained material is further preferably selected from the group lumped lime and / or dolomite material, separated undersize, separated broken oversize, coal, charcoal, wood chips and organic shredded material.

For use as a fertilizer, the use of charcoal is provided in a particularly preferred embodiment. The broken and thus rough surface of the charcoal acts as a good basis for the buildup agglomeration. In addition, the charcoal very well supports plant growth, as known from studies on the charcoal soil "Terra Preta do Indio" (Amazon). The charcoal germs may be impregnated with other fertilizer ingredients.

Preferably, the agglomeration is carried out at room temperature or generally at a working temperature of from 20 to 40 ° C, more preferably from 25 to 35 ° C. An elevated processing temperature above room temperature is especially recommended when processing with molasses and viscous oils.

Binders which can generally be used are binders such as are known for paints, lacquers, in the food industry or for cosmetic products. Preference is given to organic binders, in particular those selected from the group: synthetic polymers or copolymers, in particular in the form of polymer dispersions or solutions, natural polymers, in particular polysaccharides, or mixtures such as molasses, glue, resin, wax or varnish, which do not exist as natural multi-substance mixtures clearly to be categorized.

Preferred polymeric binders include polyvinyl alcohol (PVA, PVOH), polyvinyl esters, especially polyvinyl acetate (PVAc), including their copolymers, natural and synthetic polysaccharides, including carbohydrates such as alginates and starch, sugars, gelatin and other natural thickeners.

If the binders are used as i. a. powdery solids are present, they are first preferably dissolved, swollen or dispersed. The preferred polyvinylyl alcohol or the polyvinyl acetate for some applications is preferably dissolved in alcohol, more preferably in a polyhydric alcohol such as glycol and / or glycerol or in triethanolamine or these substances are used with their solvent as a liquid agglomeration medium. Alternatively, the binder is first dissolved, dispersed or swollen and then mixed with an additional liquid agglomeration medium.

According to the invention, it is also possible that the liquid agglomeration medium used is one which itself has binder properties, so that no separate binder has to be added any more. This is given, for example, when the liquid agglomeration medium cures or crosslinks. As liquid agglomeration media having binder properties, it is preferable to use: hardening (crosslinking) oils, natural or synthetic resins, varnish builders, waxes or fats. Particularly preferred is varnish, in particular linseed oil varnish. Further agglomerating agents of this group are resins, optionally diluted with solvents, and glue, for example cellulose glue.

The liquid agglomeration media, which themselves have binder properties, can additionally be mixed with a binder. The choice of the agglomeration medium and possibly the binder depends on the desired product properties.

In a particularly preferred embodiment for the production of fertilizer granules, the binder used is molasses in combination with thermosetting lacquer or oil, in particular in a mixture with linseed oil varnish. As a result, mechanically strong, abrasion-resistant, easily water-soluble agglomerates are available, which are environmentally friendly.

As alcohols which are used according to the invention individually or in admixture with water, it is generally possible to use the known representatives of the substance class, for example ethanol, propanol, isopropanol. Polyols are preferably used, in particular glycol (ethylene glycol, propylene glycol), glycerol or triethanolamine, in each case individually or mixed or else mixed with monohydric alcohols.

In a further particularly preferred embodiment, polyvinyl alcohol is used as a binder and dissolved in an alcohol or an alcohol mixture. This embodiment is particularly suitable as Ca-aggregate for steel processing.

The object of the invention is accordingly also achieved by granules of lime, dolomite, calcareous or dolomite-containing mixtures which are obtained, in particular, by the process according to the invention and which comprise synthetic polymers or copolymers, in particular polyvinyl alcohol, natural polymers, in particular in at least one outer layer of the granule particles Polysaccharides, molasses, glue, resin, wax and / or (cured) linseed oil varnish as a binder and optionally other additives.

The additives can be added to the granulation mixture and, insofar as they are soluble in the agglomeration medium or its liquid phase, advantageously dissolved in advance therein.

As additives, the particles may contain, for example, carbon, oil, resin, wax, lacquer, salts and / or oxidic minerals. For example, oils, resins and waxes make the granules tougher and more elastic. Paints give a solid smooth surface. Salts can be fertilizer salts used for plant nutrition, and oxidic minerals are both within fertilizers and for metallurgical additives in question.

Further preferably, the granules contain a core of lumpy lime or dolomite, lime or dolomite-containing material or coal or charcoal.

The preferred uses for the granules of this invention are in the fields of fertilizers, metallurgical additives, flue gas cleaning, and water purification or treatment.

In the following the invention will be described in more detail by means of exemplary embodiments which are given solely for the purpose of illustration and for a better practical understanding of the invention and which are not to be understood as limiting in any way.

EXAMPLES

All tests were carried out on a commercial pelletizer under standard conditions. It can pellets between 1 to 12 mm are produced, in some cases, depending on the starting material and coarser. Further agglomeration techniques and the possibilities for adjusting the grain size and the grain size distribution are known to the person skilled in the art and therefore need not be considered here in additional examples.

• 1.) 30 g Polyvinylalkohol wurden in 670 g Glycerin gelöst und mit 2000 g gebranntem Dolomit pelletiert. Die Pellets wurden bei der Stahlherstellung eingesetzt. Bindemittel ist Polyvinylalkohol, das flüssige Agglomerationsmedium Glycerin ist gleichzeitig das Lösungsmittel für das Bindemittel. Der Bindemittelgehalt beträgt in diesem Beispiel nur ca. 0,01 Gew.-%. Damit konnten feste Granulate erhalten werden. Der Feststoffgehalt beträgt in der Granuliermischung 76 Gew.-%.
• 2.) 300 g Melasse mit einem Wassergehalt von 28 Gew.-% und 300 g Leinölfirnis wurden gemischt und mit 2000 g gebranntem Dolomit pelletiert. Das erhaltene Granulat wurde als Dünger eingesetzt Der Bindemittelgehalt liegt mit etwa 8% allein für die Melasse deutlich höher als im ersten Beispiel.
• 3.) 500 g stückige Holzkohle, längste Ausdehnung der Stückchen 1 bis 3 mm, wurden mit 100 g kommerziellem Düngemittelsubstrat versetzt. Hinzu kamen 150 g Melasse, 150 g Leinölfirnis und 700 g Dolomit, gebrannt. Das Granulat wurde als Dünger mit Nährstoffspeicher eingesetzt.

The following mixtures were granulated / agglomerated:

• 1.) 30 g of polyvinyl alcohol were dissolved in 670 g of glycerol and pelleted with 2000 g of calcined dolomite. The pellets were used in steelmaking. Binder is polyvinyl alcohol, the liquid agglomeration medium glycerol is also the solvent for the binder. The binder content is in this example only about 0.01 wt .-%. Thus, solid granules could be obtained. The solids content in the granulation mixture is 76% by weight.
• 2.) 300 g of molasses with a water content of 28% by weight and 300 g of linseed oil varnish were mixed and pelleted with 2000 g of calcined dolomite. The resulting granules were used as fertilizer The binder content is about 8% for the molasses alone significantly higher than in the first example.
• 3.) 500 g lumpy charcoal, longest extension of the pieces 1 to 3 mm, were mixed with 100 g of commercial fertilizer substrate. In addition, 150 g of molasses, 150 g of linseed oil and 700 g of dolomite were burned. The granules were used as fertilizer with nutrient storage.

The built-up agglomeration resulted in a closed ceiling of dolomite, binder and additives around a core of charcoal.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• DIN EN 933 [0024]

Claims (13)

A process for the preparation of lime or dolomite agglomerates, characterized in that a buildup agglomeration is carried out with finely divided solid starting materials and a liquid agglomeration medium which is anhydrous or has a water content of up to 40 wt .-% and either itself has binder properties or an additional binder dissolved or dispersed contains, and wherein the finely divided starting materials of lime and / or dolomite or contain these individually or in admixture. A method according to claim 1, characterized in that the liquid agglomeration medium contains at least 60 wt .-% of one or more non-aqueous organic chemical liquids as liquid phase content, in particular oils, hydrocarbons, esters or alcohols. A method according to claim 1 or 2, characterized in that the content of liquid agglomeration medium, optionally with binder content, between 10 and 50 wt .-%, preferably between 20 and 40 wt .-%, more preferably between 25 and 35 wt. % based on the mixture to be agglomerated. Method according to one of claims 1 to 3, characterized in that organic binders are used as binders, in particular those selected from the group: synthetic polymers or copolymers, in particular in the form of polymer dispersions or solutions, natural polymers, especially polysaccharides, or mixtures such Molasses, glue, resin, wax or varnish. Method according to one of claims 1 to 4, characterized in that the liquid agglomeration medium with binder properties curing (crosslinking) oils, natural or synthetic resins, Lackbildner, waxes or fats. Method according to one of claims 1 to 5, characterized in that within the production process, a separation of undersize and / or oversize is provided, preferably by sieving. Method according to one of claims 1 to 6, characterized in that in addition to the finely divided starting materials coarser-grained material is added, which can form Agglomerationskeime. Method according to one of claims 1 to 7, characterized in that the coarse-grained material is selected from the group lumped lime and / or dolomite material, separated undersize, separated broken oversize, charcoal, wood chips, organic shredded material. Method according to one of claims 1 to 8, characterized in that it is carried out at a working temperature of 20 to 40 ° C, preferably from 25 to 35 ° C. Granules of lime, dolomite, calcareous or dolomite-containing mixtures, in particular obtained by a process according to any one of claims 1 to 7, characterized in that it comprises synthetic polymers or copolymers, in particular polyvinyl alcohol, natural polymers, in particular polysaccharides, at least in an outer layer of granules , Molasses, glue, resin, wax and / or linseed oil varnish as binder and optionally other additives. Granules according to claim 10, characterized in that the particles contain as additives carbon, oil, resin, wax, lacquer, salts and / or oxidic minerals. Granules according to claim 10 or 11, characterized in that they contain a core of lumped lime or dolomite, lime or dolomite-containing material or of coal or charcoal. Use of the process products according to any one of claims 1 to 9 and the granules according to any one of claims 10 to 12 as fertilizers, additives in metallurgy, for flue gas cleaning and for water purification or treatment.