FI110607B - Process for the manufacture of briquettes and mineral wool - Google Patents

Description

Process for the manufacture of briquettes and mineral wool • 'j 1 O 6 O 7

The invention relates to a process for the manufacture of briquettes and to a process for the production of mineral 5 wool.

Many industrial processes use a source of mineral raw material in the form of briquettes than in the natural state. In particular, when the composition of the final briquette is subject to specific restrictions, the use of natural minerals is not always satisfactory, since the composition of natural minerals varies at least to some extent. By using prefabricated mineral briquettes rather than natural materials, it is thus possible to improve control over the chemical composition of the batch. Another reason to use briquettes rather than natural materials is the ability to optimize the particle size of the feedstock relative to the planned industrial process.

The particle size of the charge is a problem especially in mineral wool manufacturing. Mineral wool is made by melting a mineral raw material in a melting furnace, either in a traditional cupola furnace, a gas cupola furnace or an electric furnace.

20 In different types of furnaces, thermal energy is conducted to the mineral raw material in different ways: * «* • * * In a traditional dome furnace, the mineral raw material is charged together with fuel,« · «• V, usually coke, in the gas dome furnace heat is conducted by burning * or other running fuel, and electrodes extending into the electric furnace are used.

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One problem with cupola furnaces is that only: '·: relatively coarse material can be used, since the finely ground material tends to form a compact mass in the furnace, which makes it difficult to pass air: and gas through the batch. In addition, the finely ground material: * '': 30 is more difficult to handle and causes difficult dust formation, which • * ♦. ·: \ The use of finely ground material is also problematic in electric furnaces.

»;: Thus, it is not possible to use all the sources of raw materials that would otherwise be available, such as waste, ie extra fibers and non-fibrous material, so-called beads formed during mineral wool production, certain types of slag, industrial waste from flotation processes, or for example, the finest fractions obtained from the crushing of coarser material. This naturally means economic loss, but also limits available raw material compositions.

Attempts have been made to make finer mineral raw materials into briquettes. For this purpose, it is known to use hydraulic binders as binders in raw material briquettes, in particular Portland cement and clay and water glass (SE 205 247). The disadvantage of using Port Landsement is that the briquette has poor heat resistance and loses its strength and becomes brittle even at relatively low temperatures of 400-500 ° C. EP B 546 000 describes the use of an alkaline-activated slag binder in briquettes used for the production of mi-15 mineral wool. Such slag has a glassy structure and is in granular form which is easily activated by an alkaline agent. According to this patent, raw material briquettes are formed which after manufacture have good strength properties, especially against moisture and good behavior in the melting process itself.

It is an object of the present invention to provide further improvement of briquettes which | I t "V contains a particulate mineral raw material for the manufacture. Such« · · briquettes are particularly suitable for mineral wool production, although other uses of briquettes are imaginable, just like any use with excellent binder I · * 25 binding properties can be utilized, such use being, for example, iron ore briquettes for iron making.

Accordingly, the present invention relates to a process for the manufacture of briquettes comprising a particulate or finely divided mineral raw material and a mineral binder of the raw material. According to the invention, the binder contains a silicate-based. ·: *. a binder containing silicon and aluminum as their respective oxides, i.e. silica, calculated as silica and alumina, wherein the molar ratio of silica to alumina is in the range of 2 to 12. Preferably said range is 2.5-8, especially 3.5-6.

The invention thus relates to a process for the preparation of briquettes comprising a mineral raw material and a binder in particulate form, the process comprising the following steps: - taking the mineral raw material in particulate form, - mixing the mineral raw material with the binder and, where appropriate, water; the mixture is formed into briquettes, and the briquettes thus formed are cured using a binder comprising a colloidal silicate dispersion of silica and alumina in a molar ratio of from 2 to 12.

The invention also relates to a process for the production of mineral wool, wherein the method comprises adding a mineral raw material, in the form of briquettes containing a finely divided mineral raw material and a binder, to a melting furnace, removing the formed melt and forming it into fibers.

Briquettes produced according to the invention show improved properties, *. due to the increased alumina content of the binder. Such properties exhibit, among other things, improved strength and stability.

• · · i ·. · · ·. The silicate-based binder used in the briquettes according to the invention has an excellent binding, strength and refractory properties, and is acceptable.

Must also be considered for use or occupational hygiene. In addition, the binder may be made from inexpensive and readily available raw materials, or by-products of industrial processes, in a simple manner, enabling the binder to be: ': *: tailor-made or designed for the composition:': 30 . An important advantage is that the binder according to the invention does not cause min. '·': Inverse ecological burden on the environment, but only contains: '* *: components that are naturally present in nature.

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According to a preferred embodiment of the invention, the binder used has, contrary to the conventional water glass used e.g. In order to bind briquettes, for example, in mineral wool production, low alkali content, i.e. low alkali oxide content, especially sodium and potassium oxides. According to another preferred embodiment, the dispersion also contains alkaline earth metal oxides, such as calcium and / or magnesium oxides. Such an embodiment gives briquettes, among other things, improved water resistance properties due to the lower water solubility of alkaline earth metals than, for example, alkali metals.

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According to one embodiment of the invention, the binder contains silica and alkali metal in a molar ratio, which is the ratio of moles of silica to the sum of moles of alkali metal, i.e. mainly to the sum of moles of sodium oxide and / or moles of potassium oxide, which is from 10 to 350, preferably from 15 to 150. The desired molar ratio can be obtained by selecting the appropriate starting material for preparing the binder dispersion.

According to another embodiment of the invention, the binder comprises calcium and / or magnesium oxide and / or iron oxide, wherein the molar ratio between silica and the sum of calcium oxide, magnesium oxide and iron oxide is 0.5 to 2, preferably 0.6 to 1.5. Iron oxide is calculated in the form of FeO.

• ♦ .. ”: The binder used in briquettes is obtained by dissolving the particulate mineral. a solids containing silica and alumina in a molar ratio of 2 to 12 in an aqueous solution of I to form a solution containing nucleated (nucleated) re-precipitated particles, the solution thus obtained is stabilized in a colloidal dispersion, i.e.

* · • · to form a silicate containing sol having the desired particle size and optionally. . additionally, the solids content of the dispersion is adjusted and / or the dispersion coagulants · · · · · · are created to form a gel.

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According to a preferred embodiment, the primary particle size of the dispersion in sol form is 1 to 1000 nm, preferably 10 to 100 nm.

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The dry solids content of the dispersion used to make the binder may vary depending on the intended use, but for most purposes a solids content of more than 1%, such as between 5 and 60% by weight, is suitable. The solids content of the dispersion can be adjusted by removing water, for example by evaporation, or by adding water 5 in a suitable manner.

As described in more detail below, the dispersion can be readily converted into a gel, for example, by physico-chemical means, such as removing the sol-particle electrostatic repulsion by changing the pH, or by adding electro-lithium or surfactant. Gel formation can also be accomplished by drying the dispersion. As stated above, the colloidal binder dispersion can be used as such, whereby the binder can be converted into a gel, typically immediately before it is added to the binder minerals, or it is converted into a gel only in the final product, i.e. briquette.

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Preferably, the particulate mineral used as a starting material for the preparation of the binder has a glassy amorphous structure. Such a glassy structure has better dissolution properties than the crystalline structure and is formed when the mineral raw materials are melted and made into fibers at a high temperature. A suitable raw material is therefore mineral wool material or mineral · 'fiber product, for example waste or by-product from mineral fiber production, t · ·' '1, such as spinning waste, unused fibers or products and discarded mines.

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'\ combal fiber products. Of course, a material having an optimum or desired *, · · ·, composition for making a binder is selected.

• i • t 1, · · '. 25 t · · · ·

The mineral suitable for use as a starting material contains SiCl 2 in an amount of 35-45% by weight and AhCb in an amount of 8-25% by weight.

• · • · 1 ♦ · ·. According to a preferred embodiment, the low-alkali particulate mineral i ·> * t • '': 3o contains by weight, f% ». ···. S1O2 35-45 I <· 1 · I · I> * 1 · R 110607 6 Al2O3 10-25 R2O 0.2-3 where R represents Na or K. In addition, such a substance may contain 5% CaO 12-35 by weight

MgO 6-20

FeO (total iron) 2-10.

Another suitable mineral is a substance having the following composition, by weight, 10%, S1O2 35-45 Al2O3 8-13 R2O 0.2-1, wherein R represents Na or K. In addition, such material may contain% by weight calculated

CaO 30-40

MgO 5-11

FeO (total iron) 0.1-1.

This composition is a typical composition, for example, of a slag wool product. In this case, the preferred starting material for the preparation of the dispersion may be a product or by-product of the manufacture of slag wool.

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The addition of alkaline earth metal oxides also has the advantage of providing materials suitable for waterproof binders. Such an addition is of particular importance, for example, when used in briquettes, such as raw materials for mineral: wool production, or in ore briquettes.

• t · • · '! Preferably, the starting material used to form the binder dispersion is in the form of mineral wool, in particular as a by-product or waste product from mineral wool production, as stated above. This allows you to select the material with the optimum or desired *. '' Composition for preparing the dispersions of the invention. These types of waste materials • «·

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'· · ·' Are formed in large quantities, usually up to 20-30% by weight, of the 7 110607 feedstocks used as starting material, as spinning waste, pearls and as unused fibers in discarded fibrous products (pre-consumer products). One useful source of material is also various structures which are dismantled and which use mineral wool material, for example as thermal insulation (discarded products). Such a waste material 5 is already in a finely divided, usually fibrous, form and can thus be used as such or alternatively be further subdivided into a product having a large surface area, such as 0.4 m 2 / g or more, up to 25 m 2. / g, which gives it good solubility in aqueous solution. Fibers from mineral wool production typically have a diameter of 0.5 to 20 µm, usually 2 to 15 µm, such as 3 to 5 µm as measured by OM or SEM using a suitable method (e.g., Koenig et al., Analytica Chimica Acta 1993, 280, 289 -298; Christensen et al., AM IND HYG ASSOC (54) May 1993) and have a length of 0.5 to 50, usually 2 to 20 mm, such as 3 to 10 mm.

The aqueous solution is an acidic solution such as an aqueous solution acidified by the addition of an inorganic or organic acid such as HCl, HNO 3, KbSO 4, H 3 PO 4, formic, acetic, propionic or any other suitable mineral acid or organic acid. Adjust the pH of the solution to the appropriate level. A low pH results in a rapid dissolution of the mineral as the gel forms, with a gelation time dependent on pH, and a lower pH results in a faster gelation. * than at higher pH. Good solubility of a large number of minerals: · · is achieved at pH 0-6. The strength of the acid may be, depending on the acid, from 0.1 to 10 M, such as 0.5 to 5 M.

The aqueous solution may also be an alkaline solution such as an alkali metal or alkaline earth metal hydroxide, carbonate or hydrogen carbonate solution, especially sodium, potassium or lithium hydroxide solution or ammonium hydroxide solution. Such a solution is preferably 0.1-2 molar to the alkaline agent or has a pH of 10-14 to also readily dissolve the mineral raw materials having poor solubility in neutral solutions.

: ': At alkaline pH, the dispersion tends to be stable and particle size: #: growth can be observed. By keeping the dispersion pH alkaline for a suitable period of time or by raising the pH from about 8 to 110607 neutral to a pH of 10, the particle size will be increased, the growth being less clear if the solution further contains salts. In the presence of sufficient amounts of salts such as inorganic salts, e.g. sodium chloride, the particles tend to aggregate to form gels which precipitate. The same gel formation also occurs when the pH of the 5 solution is acidified, with a pH of about 2 to less than 7 being suitable for gel formation.

By controlling the pH in this way, the dispersion state can be maintained or the dispersion can be converted to a gel. The gel can be dispersed and stabilized using high shear mixing and raising the pH, after which it can be re-gelled by re-adjusting (lowering) the pH or adding an electrolyte.

Aluminum-containing particulate minerals, particularly those containing from about 10% to about 25% by weight of alumina, generally have relatively poor solubility in neutral solutions, but exhibit better solubility in acidic and alkaline media to give aqueous dispersions, containing dissolved silica and dissolved alumina in the desired proportions. When dissolved in an acidic solution, organic acids are more preferred than inorganic acids. This is because inorganic acids can form insoluble salt precipitates such as calcium and magnesium in the starting material. *. min. Some inorganic acids are also very corrosive and hence ''; 'Cause obvious disadvantages.

• »·. '; According to a preferred embodiment, the dissolution of the mineral material is preferably carried out at an elevated temperature such as 80-100 ° C, preferably with stirring, to facilitate the dissolution process. Dissolution:. The time is from 1-2 hours to 20 hours depending on the solubilizing medium used and the solids content of the solution.

Preferably, the mineral used as starting material is dissolved in the solution to give a metal oxide solution having a dry matter content preferably above 1%: preferably 5 to 60% by weight, which is a suitable concentration for later use si- 9 110607 as a substance. After complete dissolution, the substance is nucleated to form a dispersion of the desired particle size. Post-stabilization of the dispersion is accomplished by creating an electrostatic repulsion between the particles in the solution. Electrostatic repulsion between the particles can be achieved, for example, by adding suitable ions to the solution, or by changing the pH of the solution. If necessary, additional water may be added or the water may be removed, e.g. by evaporation, if necessary to control the viscosity of the resulting solution.

Stabilization may also be achieved using suitable surfactants and / or polyolymers, in particular non-ionizing agents. In some cases, nonionic surfactants and polymers may be advantageous because they are not very sensitive to environments containing high electrolyte concentrations and other chemicals, particularly at high ionic strength. Examples of suitable polymers are polyethylene oxide and polyethylene glycol. Examples of suitable surfactants are nonylphenols, Tween and is Span. Typically, such surfactants and polymers are used in an amount of 0.5 to 2.5% by weight based on the total solids in the solution. As stated above, the particle size of the dispersion can be adjusted by adjusting the pH.

The process thus makes it possible to obtain binder dispersions which primarily contain silica together with other metals from the starting material. *. oxides such as calcium oxide, magnesium oxide, alumina and possibly other metal oxides in smaller amounts. It is also possible. '': Adjusts the reaction conditions to obtain dispersions of the desired particle size. Here are 9 ·. · · ·. the resulting dispersions can be converted to a gel either directly after formation or; : 25 immediately prior to use, for example before dispersion of the dispersion as a binder on a mineral raw material. The dispersion can also be converted into a gel by heating or: · evaporation of the water to form the final product.

The composition of the particulate mineral raw material used as a raw material for the production of briquettes naturally varies depending on the intended use of the briquettes: '; Tosta. When briquettes are to be used in mineral wool production, the mineral substance in the particulate form: "": is selected according to the desired chemical composition of the fibers to be produced 10 110607. , waste material from mineral wool production, limestone, dolomite, wollastonite, etc. Briquettes are prepared simply by mixing mineral-5 lithic raw material with a binder dispersion and, if necessary, adding water to form a rigid mixture. it is cured during or after the manufacturing process, for example by heating.

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The amount of dispersion used as a binder can be readily determined by one skilled in the art. By way of example, when used as a binder in mineral wool briquettes, the amount of binder is generally from about 1% to about 15% by weight based on the dry weight of the product, but higher or lower amounts are naturally possible depending on the desired product and binder reactivity. When used as a binder in foundry metal briquettes, a typical amount would be about 1-15%, such as 1-5% by weight of the total weight of the batch.

In accordance with the invention, briquettes having good strength properties, including good raw strength properties, are obtained.

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EXAMPLE

• * t ..,.: Briquettes for mineral wool production can be prepared as follows.

2.1 g of fiber containing 42.1% S1O2, 17.4% Al2O3, 17.3% CaO, 13.7%

MgO, 5.8% FeO, 1.6% Na2O, 0.6% K2O, the remainder being impurities, dissolved in. I · 100 ml of 1 M formic acid. After dissolving the fibers, nucleation and stabilization of the solution can be accomplished by raising the pH to near neutral by adding a suitable: Y: alkaline agent such as sodium hydroxide. The water is evaporated to give a dispersion of / / 30 pigs with a solids content of e.g. 5%.

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A certain amount of this dispersion thus obtained is mixed with the dry components of the briquette raw material, whereby a typical composition of the raw material may be glass waste, basalt and sand in a ratio of 25:15:60. The dispersion is added in an amount such that the binder dry matter corresponds to 10% by weight of the total solids. If necessary, additional water may be added to obtain a rigid mixture. The pulp is then formed by compression or compression vibration into briquettes of suitable size, typically in a volume of about 0.5 to 1.0 dm 3.

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Claims (12)

1. A process for preparing a briquette containing particulate mineral raw material and binder comprising the following step 5. providing a particulate mineral raw material, - mixing the mineral raw material with the binder, and, if necessary, with water, - the mixture formed is formed into briquettes, and - the briquettes thus formed are cured, characterized in that adhesives comprising an aqueous colloidal silicate dispersion containing silica and alumina are present in a molar ratio which is in the range 2-12. The process of claim 1, wherein the colloidal silicate dispersion is prepared by dissolving a particulate mineral material containing silica and alumina in a molar ratio of 2-12 in an aqueous solution to form a solution containing nucleated ether precipitated particles. of the material, the so obtained solution is stabilized to form a dispersion and optionally the dry content of the dispersion is adjusted. ·; ·. 20 A method according to claim 1 or 2, in which the molar ratio of silica. and alumina is 2.5-8, preferably 3.5-6. I | "III" The process according to claim 1, 2 or 3, wherein the silicate dispersion contains alkali dioxide or alkali oxides, and the molar ratio of silica to the sum of the alkali oxides is 10-350, preferably 15-150. A process according to any one of claims 1-4, wherein the colloidal dispersion contains calcium and / or magnesium oxide and / or iron oxide and the molar ratio between the silica and the sum. of calcium oxide, magnesium oxide and iron oxide (such as V: FeO) is 0.2-2, preferably 0.6-1.5. is 110607 A method according to any one of the preceding claims 1-5, in which the dry content of the binder dispersion is adjusted to 5-60% by weight. 7. A process according to any one of the preceding claims 1-6, wherein the dispersion is used in the form of a gel or it is converted to a gel immediately before mixing with the particulate mineral raw material. A method according to any of the preceding claims 1-6, in which the binder dispersion is converted into a gel after briquetting. 10 A method according to any of the previous claims, in which the binder content of the briquette, calculated on the dry content, is 1-15% by weight of the briquette. A method according to any of the previous claims, in which the particulate mineral raw material is a raw material for mineral wool production. Method according to claim 10, in which the particulate mineral raw material contains etherally circulated mineral material, such as waste material for mineral wool production, post-consumer products, flotation waste and glass waste. : ·. 20 • · 2 Process for making mineral wool, in which mineral raw material, in shape! · · · Of briquettes containing particulate mineral raw materials and binders, a melting furnace is added, the resulting melt is extracted and converted into fibers, whereby; '': The line for making the briquette comprises the following steps: · providing a particulate mineral raw material, - mixing the mineral raw material with the binder, and if necessary,. ·: With water; The mixture thus formed is formed into briquettes, and: - the briquettes formed are cured, characterized in that ...: 3o use binder comprising an aqueous colloidal silicate dispersion,:: containing silica and alumina in a mole ratio that is within the interval 2-12.