Method for preparing raw materials for glass production

Description of the invention

The present invention relates to a process for the preparation of compounds based on one or more alkali metal silicates and the use of compounds based on one or more alkali metal silicates for the preparation of a set of components for the production of glass.

In the context of the present invention, the term ingredient kit means all materials, vitrifiable materials, natural ores or synthetic products, recycled cullet materials, etc. that may be included in the glass furnace feed composition. Likewise, the term glass means glass in a broad sense, i.e. it includes any material including glass, glass-ceramics or a ceramic matrix. The term production includes the necessary step of melting the batch of ingredients and possibly all subsequent / additional steps to clarify / condition the molten glass for the final forming operation, especially in the form of flat glass (glass windows), hollow products (flasks and bottles), in the form of slag wool (glass wool or slag wool) used for its thermal or acoustic insulating properties, or even optionally glass in the form of yarns defined as textile yarns used in reinforcement.

The set of ingredients necessary for the production of glass has a significant content of alkali metals, especially sodium, for example, soda-lime-quartz glass used in the manufacture of flat glass. The most common ingredient currently used to provide sodium or potassium is sodium carbonate Na2CO3 or potassium carbonate K2CO3, the choice of which is not without disadvantages, because, on the one hand, such a compound provides only sodium as a glass component, and the entire carbonate part is decomposed by precipitation CO2 during melting. On the other hand, compared to another set of ingredients, it is expensive because it is a synthetic product obtained by the Solvay method from sodium chloride and lime, which method requires many production steps and is rather expensive for energy reasons.

For this reason it has been proposed to use as a sodium source not a carbonate but a silicate, possibly in the form of a mixed alkali metal (Na) / alkaline earth metal (Ca) silicate prepared previously. Using this type of intermediate has the advantage of providing several glass components together, eliminating the decarbonisation phase and reducing CO2 emissions from the melting furnace. It also makes it possible to accelerate the melting of the batch of components as a whole and to contribute to their homogeneity during melting, as shown, for example, in French patents FR 1 211 098 and FR 2 469 109. However, this approach poses a problem in the production of this silicate.

The first method of synthesis is described in the international patent application WO 00/46161. It involves the conversion of a halide, for example NaCl, and silica to silicate at high temperature, with heat being supplied by immersion burners. Combustion using submerged burners is already known, for example, from US patents. US 3,627,504, US 3,260,587 or US 4,539,034 relating to the melting of vitrifiable materials for the manufacture of glass. The use of this technique in a context other than silicate synthesis, and therefore against the current of glass production, actually offers many advantages: this method of combustion causes, within the materials to be reacted, strong turbulence and vigorous convection motion around gas jets or flames from submerged burners. This promotes very efficient mixing of the reactants. In addition, submerged burners provide heat directly where it is needed to the mass of the reacted products. It is also an environmentally friendly combustion method.

For additional details on the various reactions involved, reference can be made to the above-mentioned publication of International Patent Application WO 00/46161.

The direct conversion of NaCl and silica in this way is therefore very attractive for more than one reason. However, this direct conversion has not been found to be well suited to large-scale implementation.

The object of the invention is therefore to develop a different type of silicate production that can retain the advantages of the technique outlined above while being easier to use on an industrial scale. Secondly, an attempt will be made to make this new type of production as environmentally friendly as possible and to make best use / use of all other reaction products other than silicates, with the production of silicates remaining the main objective of the present invention.

PL 200 156 B1

The invention relates to a process for the preparation of compounds based on one or more silicates of alkali metals such as Na, K and / or alkaline earth metals such as Ca, Mg and / or rare earth metals such as Ce, optionally in the form of mixed silicates, which combine at least two of these elements, characterized in that the process comprises a conversion reaction in which sulphates of alkali metals and / or rare earth metals and / or alkaline earth metals, together with the silica are converted to the corresponding silicates, the heat required for this conversion is provided at least in part by a combustion reaction using a submerged burner or a plurality of submersible burners.

Preferably, it also comprises a conversion reaction in which the halides, especially chlorides, of alkali metals and / or rare earth metals and / or alkaline earth metals are converted into the corresponding sulphates, which are then used in the conversion reaction to the corresponding silicates.

Preferably, the submerged burner or burners are fed with at least one gaseous fuel, including a sulfur-based compound, to carry out the combustion reaction.

Preferably, during the combustion reaction, at least one type of fuel in liquid or solid form based on a sulfur-based compound is brought in the vicinity of the above-mentioned submersible burner or burners.

Preferably, the sulfur oxides possibly obtained by the oxidation of sulfur-based compounds during the combustion reaction are recovered and then subjected to a conversion reaction to sulfuric acid.

Preferably, the sulfur oxides obtained during the reaction to convert sulphates to silicates are recovered and then they are converted to sulfuric acid.

Preferably, the sulfur oxides possibly obtained by the oxidation of sulfur-based compounds during the combustion reaction as well as the sulfur oxides obtained during the sulfate to silicate conversion reaction are recovered and then converted to sulfuric acid.

Preferably, the reaction to convert the halides to sulfates is carried out with sulfuric acid, all or part of this sulfuric acid coming from the conversion of sulfur oxides from the combustion reaction to sulfuric acid and / or from the reaction to convert sulfur oxides to sulfuric acid from the sulfate conversion reaction. into silicates.

Preferably, the sulfur oxides to sulfuric acid reactions produce more sulfuric acid in total than is needed for the halide to sulfate reaction.

Preferably, sodium silicate is produced by converting NaCl with H2SO4 to Na2SO4, together with HCl, which can be used, and then converting Na2SO4 to (SiO2) x-Na2O with silica while supplying heat from the combustion reaction using submerged burners.

Preferably, heat is recovered from the smoke from the submersible burner reactor used in the sulfate to silicate reaction and is used as an input to provide the heat needed for the halide to sulfate reaction.

The reaction to convert the halides to sulfate is preferably carried out in a Mannheimer reactor.

Preferably, the sulfur oxides obtained from the fumes are recovered and converted into sulfuric acid.

Preferably the recovered sulfuric acid is used to convert the halides to sulfates.

Preferably, the glass-making ingredients, detergent raw materials or precipitated silica raw materials are prepared.

Preferably, sulfur derivatives and / or hydrocarbons and / or coal of the industrial intermediates type are used as fuels in the combustion reaction using a single submersible burner or multiple submersible burners.

The invention also relates to the use of compounds based on one or more alkali metal silicates such as Na, K and / or alkaline earth metals such as Ca, Mg and / or rare earth metals such as Ce, optionally in the form of mixed silicates, which combine at least two of these elements for the manufacture of a glassmaking set of ingredients, a detergent raw material or a precipitated silica raw material.

A method for the preparation of compounds based on one or more alkali metal silicates such as Na, K and / or alkaline earth metals such as Ca, Mg and / or rare earth metals such as Ce, optionally in the form of mixed silicates which combine at least two of these elements consist of the transformation reaction (1) in which the halides, especially chlorides, the above-mentioned alkali metals and / or the above-mentioned alkaline earth metals and / or the above-mentioned rare earth metals are converted into the corresponding sulphates, and a conversion reaction (2) in which the above

The said sulphates are converted together with the silica into the corresponding silicates, and the heat required for this conversion is provided at least in part by a combustion reaction (3) using an immersion burner or a plurality of submerged burners.

The method may also only comprise a step in accordance with the reaction (2).

The term silica here means any compound containing mainly silica (silicon dioxide) SiO2, even though it may also contain other elements and other by-products, especially when natural sand-like materials are used.

The term submersible burners as used herein means burners configured so that the flames they generate or the flue gases emitted from these flames are formed in the reactor where the conversion takes place in the mass of materials undergoing transformation itself. Generally, the burners are placed so that they lie flush with the surface of the side walls or the floor of the reactor used, or protrude slightly (for ease of use, the term flames are used here, even though they are not strictly speaking the same flames as the flames produced from the top burners. kowe).

The process described above is an improvement over the process described in WO 00/46161 in that it divides the entire reaction involving a halide (such as NaCl) and silica into separate steps to produce a silicate. There is thus an intermediate step in the production of the sulphate in the process according to the invention. In this way, the industrial feasibility is greatly improved: the thermal decomposition of the NaCl-type halide at very high temperatures, which would cause some NaCl volatilization in the furnace where the reaction with the silica takes place, is thus avoided. In contrast, in the process according to the invention, step (1) of converting the halide to sulfate is easier to carry out and can take place at relatively lower temperatures and under operating conditions already well established in the chemical industry. Step (2) of converting sulphate to silicate using submerged burners makes it possible to obtain the desired product with all the advantages of the submersible burners mentioned in the introductory part of this application.

To illustrate these two steps for the production of sodium silicate, the following two successive steps are proposed:

NaCl + H.₂SO₄ On₂SO₄ + 2 HCl

On₂SO4 + x SiO2 (SiO2)_x - Na2O + SO2 / SO3

For this second reaction, the value of x may change, an example is especially x = 2.

The preferred uses / uses of the reactants / products present in these reactions, other than NaCl, SiO2 and silicate (SiO2) x-Na2O, are discussed later.

The efficiency of the burners in all aspects (mixing quality, excellent heat transfer) means that the conversion according to reaction (2) is greatly favored, without the need for extremely high temperatures.

Another advantage of submersible burners is as follows.

They allow the incorporation of liquid / solid fuels in the same way as a vitrifiable composition. This therefore results in high redox levels in the silicate molten being achieved, and this is favorable for the sulfate decomposition reaction.

The selected oxidizing agent to feed the submersible burner (s) in reaction (2) may simply be air. However, it is preferable to use the oxidizing agent in the form of oxygen-enriched air, or even the oxidizing agent actually in the form of oxygen alone. A high concentration of oxygen is advantageous for a variety of reasons, and thus the exhaust smoke volume is reduced, which is beneficial for energetic reasons and avoids the risk of over-fluidization of the reacted materials which can cause spattering on the surfaces and roof of the reactor where the transformation takes place. Moreover, the obtained flames are short and more emissive, thus enabling their energy to be transferred more quickly to the melted / transformed materials.

Regarding the choice of fuel for the submersible burner (s), there are three possible alternatives or a combination of alternatives: a choice of liquid fuel, gaseous fuel or solid fuel.

If it is at least partially gaseous, it can feed the immersion burners directly. If it is in liquid or solid form, it can be brought close to the immersion burners.

PL 200 156 B1

As the gaseous fuel, mention may be made of natural gas (mainly methane), propane, hydrogen or any other hydrocarbon-based and / or sulfur-based compound.

Any compound primarily based on carbon and / or hydrocarbons and / or sulfur (including sulfur or carbon) may be mentioned as a solid or liquid fuel. As in the previous case, these may be by-products from the petroleum industry (heavy fuel oil, asphalt). These can be polymer-based materials that can thus be recycled (plastics, tires, etc.), or even sand contaminated with hydrocarbons, which also supplies both silica and fuel, which is an innovative way to solve the problem of sand decontamination. , for example, after an oil spill.

In the process according to the invention, it is possible to use, if desired, sulfur-containing fuels and even pure sulfur. Traces of sulfur are present in all vulcanized polymers (tires), sulfur has also been found in by-products from the petroleum industry, and the process according to the invention makes it possible to use them advantageously. This is because the sulfur contained in the fuel supplied for the combustion reaction (3) will be oxidized. Nowadays, as used in the chemical / petroleum industry, these sulfur oxides (SO2 and / or SO3) can be converted to sulfuric acid by recovering them from the smoke and subjecting them to appropriate treatment. Therefore, there are two possibilities (alternative or actually combined use, especially depending on the amount of H2SO4 produced, which in fact depends on the selected S content in the fuel), namely either H2SO4 is used as a reactant widely used in the chemical industry, regardless of the method according to the invention, or it is reused in the process of the invention. This is due to the fact that sulfuric acid is preferably used in reaction (1) to convert the halides to sulfates. It is therefore a feedback process in which the combustion product of reaction (2), once it has been transformed, is used as a substrate in reaction (1).

There is another method, alternative or used in conjunction with the previous method, for the production of H2SO4 based on the method of the invention: reaction (2) of the conversion of sulfate to silicate itself produces sulfur oxides SO2 and / or SO3. Here again, sulfur oxides can be obtained and converted into sulfuric acid. As in the previous case, this sulfuric acid can be reused as a reactant in reaction (1) and / or as a reactant for the chemical industry.

Hence, if the fuel contains a significant amount of sulfur, these two sulfur oxides to sulfuric acid reactions may produce more, or even much more, sulfuric acid than is needed for the halide to sulfate reaction (1), resulting in the preferred application of the process of the invention as a whole. .

There is another reaction product in the process of the invention that can be used, particularly in the chemical industry. It is an acid, hydrochlorides, HCl, produced during reaction (1) of the transformation of halides into sulfates, when the halide in question is a chloride of the NaCl type.

Of course, it can be treated as waste water that can be neutralized with CaCO3 calcium carbonate, which means the production of CaCl2, which can be used, for example, to clear snow from roads. HCl can also be considered a basic chemical widely used in the chemical industry (so is H2SO4) and can be obtained from smoke to create an industrial HCl production line. Therefore, it is advantageous to install the reaction device (1) in an industrial chemical site where this type of chlorinated product is needed.

The first market for the silicates produced by the process according to the invention is the glass industry: they can replace, at least in part, the commonly used set of components that provides alkali or rare earth metals, especially with regard to sodium, they can at least partially replace Na2CO3 by Na2O- (SiO2). x. The silicates obtained by the process according to the invention can therefore be used to feed a glass furnace.

Before introducing the silicate formed by the process according to the invention into a glass furnace, it may be necessary to undergo a granulation-type treatment. The glass furnace may be of standard design (e.g., an electric melting furnace using immersion electrodes, a tip-flame furnace operating with side regenerators, a horseshoe-flame furnace, and any type of furnace known in the glass industry, thus including submerged-burner furnaces), optionally structure and function, which are slightly modified6

They are designed to conform to the melting process without carbonate or with less carbonate than commonly used melting operations.

It should be noted that certain silicates other than sodium silicate are also very useful in the process of the invention. Thus, the process according to the invention makes it possible to produce potassium silicate from KCl, which is at least economically very advantageous as a component containing Si and K for the production of what is referred to as mixed alkali glass, i.e. glass containing both Na and K. which glass is used particularly in the manufacture of touch screens, glass for television screens and glass for plasma monitor panels.

Moreover, the method according to the invention allows a more economical production of special glasses containing additives for which chlorides are cheaper than oxides. This is the case of rare earth metals such as cerium, where the presence of cerium oxide gives the glass UV shielding properties, and rare earth metals of this type are also found in the high modulus special glass composition for hard discs. Thus, the process according to the invention makes it possible to obtain a component containing Si and Ce, namely cerium silicate, at moderate cost.

A second market for the silicates produced by the process of the invention (in addition to the silicates used as an ingredient pack for a glass furnace), more particularly sodium silicate, is the detergent industry, sodium silicate being frequently included in washing powder / detergent compositions.

A third market for the silicates (and possibly chlorinated derivatives) according to the invention is the production of particular silicas, usually called precipitated silicas, which are incorporated, for example, in concrete compositions, since the silicates according to the invention can be treated with acid, preferably acid. sulfuric acid so as to precipitate the silica in the form of particles of the specified size. The planned particle size is generally nanomeric (for example 1 to 100 nm).

To carry out the reaction (1) for converting the halide to sulfate, a reactor known in the chemical industry as a Mannheimer kiln can be used.

In order to carry out the reaction (2) for the conversion of sulphates into silicates, it is possible to use, as described in the international patent application WO-00/46161, a reactor provided with one or more submerged burners and at least one agent introducing silica and / or sulphates. below the level of the molten materials, particularly in the form of one or more charging batch screw feeders. Preferably the same applies to the solid or liquid fuels optionally used, such as the compounds based on carbon or hydrocarbons and / or sulfur (including sulfur and carbon) mentioned above. It is therefore possible to introduce, directly into the mass of the melt / reaction products, at least those of the starting reactants which may evaporate before having time to react.

In order to optimize the overall process from an energetic point of view, heat can be recovered from the smoke produced by the submerged burner reactor used in reaction (2) and used as input to supply the heat needed for reaction (1) in a Mannheimer-type furnace.

The process according to the invention described above thus has many advantages, namely to reduce CO2 emissions in glass furnaces in which sodium carbonate has been completely or partially replaced by sodium silicate, these furnaces consume less energy because decarbonization reactions are reduced or eliminated; preferably using halogen from the starting halide, especially in the form of HCl when it is chloride; the possibility of changing the process to a feedback process with the produced by-product H2SO4, which is reused; possibility of using sulfur-based derivatives as fuel.

A detailed explanation of the subject matter of the invention is provided below by means of examples and Fig. 1.

Figure 1: Diagram of a preferred method of implementing the inventive method operating in reverse mode.

Both examples relate to the production of sodium silicate from sodium chloride and sulfuric acid according to the implementation method illustrated in Fig. 1.

We will now explain the details of the reaction process as three main steps, each shown as a feedback loop in fig. 1: the purpose of the two examples is to produce

PL 200 156 B1

1000 kg of sodium silicate of formula Na2O- (SiO2) 2, ie 5489 mol. The yields of the reactions that occur are believed to be 100%.

Synthesis of sodium sulfate (1) NaCl

Quantity in moles 2 x 5489 Quantity in kg 642 + H₂SO₄ - On₂SO₄ + 2 HCl

5489 5489 2 x 5489

538 779 401

This step is carried out in a Mannheimer kiln in a manner known per se. Sodium silicate synthesis with immersion burner (2)

On₂SO₄+

Amount in moles 5489

Quantity in kg 779

This synthesis is performed

SO₂/ SO₃

5489

SiO2 —— Na2- (SiO2) 2 + x 5489 5489

660 1000 in a submerged burner furnace, such as the furnace described in WO 00/46161.

Combustion reaction providing the energy needed to synthesize the silicate (estimated here at 2042 kWh / ton of silicate) (3)

For a fuel containing carbon chains of the standard formula CHx and sulfur, the combustion reactions are as follows:

CHx + (1 + x / 4) O2 - CO2 + x / 2 H2O S + O₂ - SO₂

Depending on the sulfur content of the fuel, the combustion reaction releases more or less SO2 into the smoke, which is added to the SOx produced by the silicate synthesis itself. The number of moles of SO2 produced by combustion is y.

Conversion of sulfur oxides (4 and 4 ') into sulfuric acid

SO₂/ SO₃ - H.₂SO₄

Number of moles 5489 + y 5489 + y

5489 mol of H2SO4 is fed to the synthesis of sodium sulfate (1). y moles remaining can be used outside of this synthesis loop.

Example 1

This example uses 100% sulfur fuel for step (3) (especially from the desulfurization of refined petroleum products).

Its lower heating value (NCV) is 2584 kWh / ton of sulfur.

Reaction (2) requires 2042 kWh, ie 790 kg of sulfur (24688 mol S).

Combustion of this sulfur produces y (= 24688) mole of SO2.

In addition to self-feeding of the 5489 mol feedback loop with H2SO4, thus an additional 24688 mol of H2SO4, i.e. 2420 kg, is obtained which can be used outside the feedback loop.

Example 2

This example uses heavy fuel oil fuel No. 2 with 4% sulfur for step (3).

Its NCV is approximately 10,930 kWh / t. Therefore, 187 kg of fuel oil are needed to produce one ton of silicate.

7.5 kg of sulfur from this fuel oil, ie 234 moles, will therefore be burnt, releasing y (= 234) moles of SO2.

Thus, 234 mol, ie 23 kg of H2SO4 are obtained, which can be used outside the feedback loop.

Thus, it can be seen that the excess sulfuric acid that can be obtained in an amount greater than that needed for the reaction (1) varies significantly depending on the choice of fuel. All intermediate solutions with a combination of fuel oil and sulfur or other than the use of vulcanized tires are possible, which allows the best adjustment of combustion (3), depending on the type of fuel most available and / or the amount of sulfuric acid to be produced.