MXPA00009751A - Method for preparing raw materials for glass-making - Google Patents

Abstract

The invention concerns a method for making compounds based on silicate(s) of alkaline such as Na, K and/or of alkaline-earth such as MgO, CaO and/or of rare earths such as Ce, optionally in the form of mixed silicates combining those, by converting silica and halides, in particular chloride(s), or sulphates or nitrates of said alkalis and/or said rare earths and/or said alkaline-earths, such as NaCl, KCl, CeCl4. The thermal input required for the conversion is supplied, at least partly, by an immersed burner or burners. The invention also concerns an implementing device and the use thereof.

Description

METHOD FOR PREPARING RAW MATERIALS TO MANUFACTURE GLASS DESCRIPTION OF THE INVENTION The invention relates to a process for preparing certain materials that can be used for the manufacture of glass. In the context of the present invention, "raw material" should be understood as all the materials, flexible materials, natural minerals or synthesized products, materials that come from the recycling of waste glass, which can be used in the composition to feed an oven to make glass. Likewise, "glass" should be taken as glass in its broadest sense, that is, any glass matrix, glass ceramic or ceramic material. The term "manufacture" shall be understood as the indispensable step for melting the raw materials and possibly all subsequent complementary steps aimed at refining / conditioning the molten glass for the purpose of giving it a fine configuration, especially the form of flat glass (glaze) , hollow articles (flasks and bottles), glass in the form of fiberglass, (fiberglass or mineral wool used for its acoustic or thermal insulation properties or possibly a glass in the form of the so-called textile yarns used The invention relates more particularly to the raw materials required to manufacture glass having a significant content of alkali metals, especially sodium, for example silica-soda-lime types used for the manufacture of flat glass. raw material most frequently currently used to provide sodium is Na2Co3 sodium carbonate, or An option that is not free of disadvantages. This is because, on the one hand, this compound provides only sodium as a constituent element of the glass, the entire coal-containing part decomposes and breaks off in the form of C02 during melting. On the other hand, it is a costly raw material compared to others because it is a synthetic product obtained by the Solvay process of sodium chloride and lime, whose process involves a number of manufacturing steps and does not save much energy. For this reason, several solutions have already been proposed to use, as a source of sodium, not a carbonate but a silicate, possibly in the form of mixed silicate of alkali metals (Na) and alkaline earth metals (Ca) to be prepared in advance. The use of this type of intermediate product has the advantage of jointly providing several of the constituents of the glass and eliminating the decarbonisation phase. It also makes it possible to accelerate the melting of the raw material in its entirety and to favor its homogenization during melting, as indicated, for example, in patents FR-1,211,098 and FR-1, 69, 109. However, this approach it has problems to manufacture this silicate and does not propose a completely satisfactory method of synthesis. The object of the invention is therefore to develop a novel process for f abr icar. It is the kind of silicate, which is especially suited to provide industrial production with a reliability, an efficiency and a cost that are all acceptable. The object of the invention is, first, a process to manufacture compounds based on alkali metal silicates such as Na, K and / or on the basis of alkaline earth metals such as Mg or Ca and / or on the basis of rare earths such as cerium Ce, optionally the form of mixed silicates that combine at least two elements between the alkali metals, alkaline earth metals and rare earths, notably the silicates that combine the alkali metals with the metals of alkaline earths or rare earths. This process consists of synthesizing these compounds through the conversion of silica and one or more halides (especially chlorides), alkali metals and / or alkaline earth metals and / or rare earths of the NaCl, KCl or CeCl 4 type., (and optionally halides, especially alkali earth metal chlorides, in case of mixed silicates comprising some thereof), the heat necessary for this conversion is supplied, at least partially, by one or more submerged burners. Within the framework of the invention part or all of the halides can be substituted by sulphate or even by nitrates, as a source of alkali metals / alkaline earth or earth. It can be notably Na2S0 sodium sulfate. Thus, those different initial materials (solids, nitrates, sulfates) should in the invention be considered as equi-alents.

The term "silica" should be understood as any compound containing mainly silica (silicon oxide) Si02 even if it can contain other elements or other minor components, this being more particularly the case when using natural sand-like materials. The expression "submerged burners" should be understood as burners configured in such a way that the "flames" they generate or the combustion gases that result from these flames develop inside the reactor where the conversion takes place, within the current mass of the materials that undergo conversion. Generally, they are placed to be light with or slightly projecting from the side walls or bottom of the reactor used (reference is made herein to flames, even if they are not strictly speaking the same "flames" as those produced by the overhead burners for greater simplicity). The invention in this way results in a particularly sensible technological solution to be able to exploit, on an industrial scale, a chemical transformation already proposed by Gay-Lussac and Thenard, principally the direct conversion of NaCl into soda, implying the NaCl reaction with silica at high temperature in the presence of water according to the following reaction: 2 NaCl + Si02 + H20? Na Si03 + 2 HCl the principle consists of extracting the soda forming the silicate, the equilibrium is always changed in the direction of NaCl decomposition due to. that the two phases are immiscible. When sodium sulfate is used instead of NaCl, the reaction is as follows: Na2S04 + Si02 + H20? Na2Si03 + 2 H2S04 In fact, S03 is first formed and then transformed into sulfuric acid due to the heat and water produced by combustion with the burners. So far, this reaction has caused considerable processing problems associated with the difficulties in producing an intimate mixture of reagents and ensuring that they are replenished during manufacture, also associated with difficulties in discharging HCl (or H2SO4) without reacting Once again with the silicate formed, extract the silicate and be able to supply enough thermal energy.

The use of submerged burners to supply this thermal energy solves most of these difficulties at the same time. In fact, the use of heating by submerged burners has already been proposed for melting vitreous materials to make glass. For example, patents US-3,627,504, US-3,260,587 or US-4, 539, 03 may be referred to. However, the use of such burners in the specific context of the invention, mainly the synthesis of salts of silicates, is extremely advantageous: - this is because this mode of combustion generates water, whose water, as mentioned above, is indispensable in the desired conversion. By virtue of the submerged burners, it is thus possible to manufacture at the same site the water necessary for the conversion, at least partially (even if, in some cases, it may be necessary to supply additional water). It is also true that water is introduced into other initial substances, mainly silica and salts (for the sake of brevity, the term "salts" will be used as meaning of the chloride-like halides of the alkali metals, earth rare and, optionally, alkaline earth metals, used as initial reagents), are, of course, prone to promote the reaction; on the other hand, the combustion produced by the submerged burners causes, within the materials that suffer the reaction, strong turbulence and convention movements around each "flame" or "flames" and / or each of the gas jets that enter from each of the burners. Consequently, up to now, at least partially, a vigorous agitation between the reagents will be ensured, whose agitation is necessary to guarantee the intimate mixing between the various reagents., more particularly those introduced in their solid (powdery) form such as silica and salts. Submerged burners are also particularly advantageous from the strictly thermal point of view, since they supply heat directly to the point where it is necessary, ie in the mass of the products that undergo the reaction, therefore minimizing any loss of energy, and to which they are sufficiently powerful and effective for the reactants to be able to reach relatively high temperatures necessary for their melting / conversion, ie temperatures of at least 1000 ° C, especially around 1200 ° C; in addition, they are a particularly environmentally friendly heating mode, in a special way reducing as much as possible any gas emission type N0X. Therefore it can be concluded that the effectiveness of these burners at any level (quality of mix, excellent heat transfer and one of the reactants being generated insitu), means that the conversion is favored highly, this being true without necessarily having a requirement to achieve extremely high temperatures. The oxidizing element chosen to feed the submerged burners can simply be air. However, an oxidizing element is preferred in the form of air enriched with oxygen, and still substantially in the form of oxygen on its own. A high concentration of oxygen is advantageous for several reasons: the volume of combustion gases is reduced, this is favorable from an energy point of view and avoids any risk of excessive fluidization of materials that suffer the reaction that may cause them to be projected against the superstructure of the roof of the reactor where the conversion takes place. In addition, the "flames" obtained are shorter and with a higher emission capacity, with this allowing a faster transfer of their energy to the materials that undergo fusion / conve r s ion. With respect to the choice of fuel for submerged burners, two approaches are possible, which are alternative or can be combined: - it is possible to choose a liquid fuel, of the fuel oil type, or a gaseous fuel, of the natural gas type (mainly methane) ), propane or hydrogen; it is also possible to use a fuel in its solid form, containing carbon, for example coal, or other material containing hydrocarbons, optionally chlorinated polymers. The option of the oxidizing agent and the option of the fuel for the submerged burners influences the nature of the obtained products, besides the silicates, in this way, when the burners are fed with oxygen and with natural gas, the following two reactions occur schematically: (starting from the simplest situation in which it is desired to make the Na silicate from NaCl, but that it is possible to transpose it to all other cases, either by making K silicate, Ce silicate or silicates containing Ca or Mg, etc. ): (a) 2 NaCl + Si02 + H20 - > Na2Si03 + 2 HCl (b) CH4 + 2 02 - > C02 + 2 H20 These two reactions can be combined in a single reaction: (c) 4 NaCl + 2 Si02 + CH4 + 2 02 - »2 Na2Si03 + 4 HCl + C02. When hydrogen is used as a fuel instead of natural gas, there is no longer an emission of C02 and the total reaction can be written as: (d) 4 NaCl + 2 Si0 + 2 H2 + 02 - > 2 Na2Si03 + 4 HCl When using a fuel of the solid type containing carbon, always with an oxygen-like oxidizing agent, the following reaction can be written: (e) 2 NaCl + 3/2 02 + C + Si02 - > Na2Si03 + Cl2 + C02 This time, therefore, what is produced is not HCl but chlorine Cl2 as a secondary product of the conversion. It is therefore clear from these reaction balances that the reaction imagined by the invention also generates halogen-containing derivatives more particularly chlorine-containing derivatives usable as HCl or Cl 2 (or H 2 SO), which are found in the combustion gases. Two ways of operation are possible: - one is to treat them again as effluents. In this way, it is possible to neutralize the HCl with calcium carbonates CaC02 that ends up producing CaCl2 which is usable in a possible way (for example, to remove snow from the roads); the other way is to consider the conversion according to the invention as a means to manufacture HCl or Cl2 on an industrial scale, these are chemical bases widely used in the chemical industry. (It is possible, especially, for chlorine obtained electrolytically, which is necessary for the manufacture of chlorinated polymers of the PVC or polyvinyl chloride type to be substituted with the HCl or Cl2 manufactured according to the invention). In this case, then it would be necessary to extract them from the combustion gases and thus establish an industrial production line for the HCl or the Cl2, for example by incorporating the apparatus to carry out the process according to the invention directly on a site. of chemical industry needing these types of chlorinated products. Thus, the use of the formed chlorinated derivatives further makes it possible to lower the costs of the alkali metal-containing raw materials necessary for the manufacture of glass. A first market for the silicates manufactured according to the invention is related to the glass manufacturing industry: They can replace, at least partially, the metals or the rare earths, more particularly with respect to the sodium, at least partially replacing CaCO3 with Na2Si3. The silicates of the invention can therefore be used to feed a furnace to make glass, this being done in two different ways in particular: the first way is to treat the silicates formed to make them compatible with the use as raw materials vi trifi cable for furnaces of glassmaking: therefore, this involves extracting them from the reactor and generally converting them "cold" to a powdery solid phase, especially through a granulation step using techniques known in the glassmaking industry. Therefore there is a complete separation between silicate manufacturing processes and glass manufacturing processes, with adequate formation, and possible storage / transport, the silicate formed before it is fed into the glass manufacturing furnace; - the second way consists in using the silicates formed according to the invention "hot", ie using a glass manufacturing process that incorporates a previous step of manufacturing the silicate to be fed, while it is still molten to the glass making furnace. In this way, the silicate can be manufactured in a reactor connected to the glassmaking furnace, which constitutes one of the "upstream" compartments, as compared to the possible "downstream" compartments intended to refine / condition the glass once and for all. melted In both situations, the glassmaking furnace may have a conventional design (e.g., an electric melting furnace using submerged electrodes, a corona-ignited furnace operating with side generators, a furnace ignited at one end, or any type of oven known in the glassmaking industry, thus including ovens with submerged burners, optionally with a design and mode of operation that are slightly modified to be suitable for a melting process that does not involve carbonates or with fewer carbonates than the case of standard melting processes It should be noted that various silicates other than sodium silicates are also highly advantageous to manufacture according to the invention Thus, the invention makes it possible to manufacture potassium silicate from KCl, this being, at least economically, highly advantageous as raw material containing Si and K to manufacture glass They are called "mixed alkalis", that is to say those containing both Na and K. These glasses are used especially to be touch screens, glass for television screens, leaded, and glasses for display panels of Pia SMA. Likewise, the invention allows a more economical manufacture of special glasses containing additives for which fluoride is less expensive than oxides. This is the case of rare earths, such as cerium, the presence of cerium oxide provides UV filtration properties to the glasses, and rare earths of this type are also included in the composition of special glasses that have a high elastic modulus for hard drives. The invention in this way makes it possible to have a raw material containing Si and Ce-silicate of cerium - ,. for a moderate cost. Another additional advantage of the invention is that the silica introduced at the beginning suffers during the conversion to silicate a certain loss of iron, since the iron chloride is volatile: the glass produced from this silicate, using at least some amount of this silicate, therefore will have a tendency to be more transparent than a glass that does not use this type of silicate at all. This is advantageous from an aesthetic point of view and tends to increase the solar factor of the glass (in a "flat glass" application). A second market for the silicates manufactured according to the invention, (in addition to those used as raw material for glassmaking ovens), more particularly sodium silicate, is in the detergent industry, the sodium silicates Na2Si03 frequently they are used in powder-detergent washing compositions. The third market for the silicates (and optionally the chlorinated derivatives) formed according to the invention is in the preparation of special silicas, commonly called "precipitated silicas" used, for example, in the composition of concretes. The silicas formed according to the invention can, in fact, be subjected to attack by acid, sold by hydrochloric acid HCl which has also been formed by the conversion according to the invention, to precipitate the silica in the form of particles having a particular particle size: the intended particle size is generally in the order of one nanometer (1 to 100 nm, for example) . The sodium chloride also formed during the precipitation of the silica can advantageously be recycled, again serving more particularly as a raw material for the manufacture of silicates according to the invention. This is an extension of the invention in which, starting from a In particles of a "coarse" particle size (about 1 miera or thicker, for example), a particulate silica is obtained once more, but the particle size is much smaller, this control and this particle size They open the way to a wide variety of uses of materials used in the industry. For this third market, more particularly, it is interesting to choose an alkaline sulfate instead of a chloride: H2S04 is obtained, instead of HCl which serves for the attack by acid, of the sodium silicate formed. It is this type of acid that is used in the chemical industry to prepare the precipitated silicas. It is more advantageous than HCl in this particular case, because it avoids any- presence of residual chlorides in the silica, which are potentially a source of corrosion for this product. A process for producing the precipitated silicas according to the invention can schematically show the following steps: reaction in a furnace equipped with submerged burners (notably oxy-gas or oxy-hydrogen), between a silica area with the appropriate purity and sodium sulfate, with an amount of water to be added in a controlled manner depending on the amount of water generated by combustion. In this way, the sodium silicate is formed with the reaction mentioned above. It is evacuated continuously, so that the S03 formed is transformed into H2S0, which is recovered downstream, - >; Sodium sulfate produced with the appropriate Si02 / Na20 module, then bound by the recovered H2SO4. The silica, is precipitated, and is treated to confer it to the appropriate properties according to its uses "rubber additives, ...), - during this reaction, sodium sulfate is formed once more, which can concentrate and recycle in ovens equipped with submerged burners as a source of sodium.It can be seen that this process works continuously in a "closed circuit" in terms of acid and sodium source, it makes it possible to modify the granulometry of the The heat from the exhaust fumes and from the condensation of SO3 can be recovered to produce, for example, the steam needed to concentrate the aqueous solutions.This type of process is applied in a very similar way when They use other alkalis than sodium or other three points as a sulphate, or any other element whose sulphate is thermally stable and can undergo the same type of reaction. The process is related to the treatment of chlorine-containing wastes, more particularly carbon-containing and chlorine-containing wastes such as chlorinated polymers (PVC, etc.); the fusion by the submerged burners, according to the invention, can pyrolyze this waste with, as final combustion products, C02 and HCl, the HC'l can possibly, as previously seen, neutralize or use as such. It can also be noted that such a waste can therefore also serve as a solid fuel containing carbon, which in fact allows the amount of fuel to be injected into the burners to be decreased (other types of waste, such as sand). of casting, may be involved). The pyrolysis of these various types of waste once again here is advantageous from an economic point of view since their cost of treatment which is otherwise necessary is deducted from the cost of producing the silicates according to the invention. Instead of currently pyrolying the waste it can also be vitrified. Those wastes containing both chlorine and organic materials can be considered as inert in a chemical point of view according to the process of the invention. To the sand and chlorine (or its equivalent), liquid or solid waste can be added. Some additives may also be included, such as CaO. aluminum oxide, or other oxides. To be a real vitrification, the vitrified material obtained must be able to stabilize the possible mineral materials contained in those wastes. The acid produced can be recovered in an absorption volume that filters the fumes, and can be recycled. This process is very advantageous from an economic point of view. On the one hand, the main fusion component used is provided by the salt and at least part of the energy necessary for vitrification is provided by the waste itself. On the other hand, it is possible to recycle the acid formed. Different types of combustible waste can be mixed. For this application, it is more appropriate to make a silicate rich in alkaline earth metals, or made only of alkaline earth silicates: The objective is to make the waste inert, and not make a high quality glass, it is advantageous to use mainly earth silicates alkaline because the raw material that these alkaline earth metals carry is less cost than those that carry alkaline metals. The object of the invention is also the apparatus for carrying out the process according to the invention, the apret of which preferably comprises a reactor equipped with one or more submerged burners and with at least one means for introducing silica and / or halides (or equivalents such as sulfates or nitrates) below the level of molten materials, especially in the form of one or more loaders per batch with feed screw. Preferably, solid or liquid fuels such as the aforementioned wastes can be introduced into the kiln in the same way. In this way it is possible to introduce directly into the mass of products undergoing fusion / reaction, at least those initial reactants capable of vaporizing before having time to react: one thinks here more particularly about sodium chloride NaCl. In this way it is possible to ensure a sufficient time of stay of the liquid or solid fuels to achieve complete combustion. Preferably, the walls of the reactor, especially those intended to be in contact with the different reaction / reaction products involved in the conversion, are provided with refractory materials lined with a metal liner. The metal must be able to withstand the different types of corrosive attacks, especially those caused by HCl. Titanium, a metal of the same family or a titanium-containing alloy is preferred. Advantageously, all the elements within the reactor, which emerge in the latter, can be disposed as based on this type of metal or protected on the surface by a coating of this metal (the loaders per batch and the submerged burners). It is preferred that the walls of the reactor, and also especially all the metal parts within the latter, be associated with a fluid circulation cooling system of the water box type. The walls can also be made entirely of metal, without or by far very few standard refractories used for the construction of glassmaking ovens.

The walls of the reactor define, for example, an approximately cubic cylindrical or parallelepiped cavity (having a round rectangular or square base). Advantageously, several introduction points of initial reagents can be provided, for example distributed in a regular manner in the side walls of the reactor, especially in the form of a certain number of loaders per batch. This multiplicity of supply points allows the amount of reagents in each of them to be limited and a more homogeneous mixture to be obtained in the reactor. The reactor according to the invention can also be equipped with various means for treating the chlorinated effluents, especially for recovering or neutralizing the effluents of the type Cl 2 or HCl, or H 2 SO 4, and / or with means for separating the solid particles, especially those based on in metal chlorides, from gaseous effluents. These means are advantageously placed in the smoke ducts that extract the combustion gases from the reactor. Finally, the subject of the invention is also a process for producing glass containing silica and alkali metal oxides of the Na20 or K20 type, or rare materials in which the heat necessary to melt them comes at least partially from the submerged burners . In this case, the invention resides in the fact that the raw material containing alkali metals of the Na or K type, or rare earths of the Ce type, are partially in the form of halides, especially chlorides, of such elements, such as -NaCl , KCl or CeCl4. This is the second main aspect of the invention in which, as such, everything is carried out as if the silicate previously described "in situ", was manufactured during the current processing of the fusion of the trifiable materials to be able to produce glass. The economic advantage of replacing all or part of, especially, sodium carbonate with NaCl is clear. In this case, there are the same advantages as those mentioned above, related to the manufacture of silicate independently of glass manufacturing, mainly the lower iron content in. the glass, the possible use of the chlorinated (halogenated) derivatives produced, the pyrolysis or the vitrification of the waste, the latter being, moreover, possibly suitable for acting as a solid fuel, etc. The invention will be explained in detail with the aid of a modality illustrated by the following Figure 1: D Figure 1 is a schematic plan view for manufacturing sodium silicate according to the invention. This figure is not necessarily to scale and has been extremely simplified for the sake of clarity. A reactor 1 is shown comprising a rectangular-shaped bottom 2 which is regularly tapped to be equipped with rows of burners 3 which pass through it and penetrate slightly into the reactor. The burners are preferably covered with titanium and are cooled with water. The side walls are also cooled with water and comprise a refractory lining 5 melted in an electric furnace or are completely made of titanium-based metal. The material level 5 undergone by the melting / mixing is such that the loaders 6 per batch with feeding screw introduce the reagents through the side wall below this level. The bottom comprising the burners can have a greater thickness of melted refractories in electric furnace than the side walls. It is also pierced with a threaded hole 10 to extract the silicate. The roof 8 can be a flat suspended ceiling made of refractory materials of the type AZS (to lumi ni oir conio s 1 i ce), zir coni a-mu 1 itao mulita or of any ceramic material resistant to HCl and / or NaCl. It is designed to be impermeable to combustion gases containing HCl: a non-limiting solution to ensure this impermeability consists of using a honeycomb ceramic structure consisting of hollow hexagonal pieces in which an insulation is placed. The impermeability therefore, it is achieved between the pieces on the back surface by means of a low temperature mastic resistant to HCl. In this way the structure supporting the metal is protected. The bottom 9 is also constructed of materials resistant to HCl and NaCl (oxide refractories, silicon carbides, graphite). It is provided with a system for separating the solid particles that can be condensed (metal chlorides) and with an HCl recovery tower, the latter not illustrated.

Once the silica has been removed from the reactor via the threaded hole 10, it is transported to a granulator (not shown) of the type used in the glass manufacturing industry or in the sodium silicate detergent industry. The purpose of the process is to manufacture a silicate that is highly concentrated in terms of sodium, the latter being quantified in a known manner by a molar ratio of Na20 with respect to the total (SiO2 + Na20) in the 50% region, and In the reactor, by means of batch loaders, a mixture of sand (silica) and NaCl These two reagents can also be introduced separately and may have been optionally pre-extended before being introduced into the reactor. Preferably, the burners 3 are fed with oxygen and with natural gas or hydrogen. The viscosity of the raw material during the fusion / reaction and the high reaction rate obtained by virtue of the submerged burner technology makes it possible to achieve high speci fi c suctions - to provide an order of magnitude of, for example, at least 10 tons / day a.

In conclusion, the process of the invention provides a new way to manufacture silicates, more particularly cerium, potassium and sodium silicates at a moderate cost. It also falls within the context of the present invention to use m u t di di m m e t in the same process to make not only alkali metal silicates or rare earth silicates but also titanates, zirconates and aluminates of these elements (optionally mixed with silicates). Thus, a metal can be at least partially replaced by silicon, especially a metal belonging to the transition metals and more particularly those of column IVB of the Periodic Table, such as Ti or Zr or the metals of the IIIA column. of the Periodic Table co or Al. The advantage of such substitution is that the product obtained is soluble in water. The selective attack of these products in an aqueous solution, especially using hydrochloric acid formed during the conversion, results in the precipitation of non-silica particles, as mentioned above in the text, but the corresponding metal oxide particles. as Ti02, Zr02 and A12Ü3, whose particles are generally nanosized in size, as when starting with silica, and which may have different applications in the industry. It is therefore possible to use them as fillers in polymers and concretes, and incorporate them into ceramic or glass-ceramic materials. It is also possible to exploit its photocatalytic properties: particularly intended are the Ti02 particles (which can be incorporated in photometric refractories having properties against dirt for any architectural material, glazing, etc.). In order to manufacture these titanates, zirconates or aluminates according to the invention, the process described above for obtaining the silicates is transposed, starting from the halides of the NaCl type and the metal oxides of the metals involved (Ti02, Zr02, Al2? 3, etc.) Alternatively, it is possible to use directly, as the initial product containing a metal for the conversion, the halides of the metal and no more its oxide. This can be especially a chloride, such as TiCl 4, ZrCl 4 or AICI 3 (it is also possible to choose as initial metal-containing products a mixture of an oxide and a metal chloride). In this case, the alkali metal containing material may be the same type of halide NaCl used to make silicates, this salt may be supplemented with or replaced with soda when the alkali metal sodium is involved. As in the case of "precipitated silica", this extension of the process according to the invention can thus be seen as a means to modify, in particular reduce, the size of the particles of a metal oxide to provide it with other applications. in industrial materials. It should also be noted that the invention makes it possible to recycle waste. It can be used, remarkably, to prevent impurities in oil-contaminated sands, the collection of this sand contaminates to use it as an initial material for silica within the framework of this invention provides two main advantages: - >; First, the sand is already included with the organic fuel waste (fuel, hydrocarbon compounds), - > second, it is a simple way to clean the coasts and beaches of this contaminated sand 'when any other method to clean them is too long or too expensive. The process according to the invention in this way allows the fuel to be completely eliminated. It is advantageous, for this type of application, to make alkaline earth silicates or silicates comprising mainly alkaline earth metals: as for the application to make the chlorine / organic waste inert mentioned above it is economically more interesting to use raw materials that carry metals from alkaline earths that come with alkaline metals.

Claims (18)

1. Process for manufacturing 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 earths such as Ce, optionally in the form of mixed silicates that combine at least two of these elements, by the conversion of silica and halides or sulfates or nitrates, especially of one or more chlorides of the alkali metals and / or rare earths and / or alkaline earth metals, such as NaCl, KCl or CeCl 4 characterized in which the heat necessary for this conversion is supplied, at least partially, by one or more. submerged burners.

2. Process according to claim 1, characterized in that the submerged burners are fed with an oxidizing agent in the form of air, air enriched with oxygen or oxygen.

3. Process according to any of the preceding claims, characterized in that the submerged burners are fueled with a fuel in the form of natural gas, fuel oil or hydrogen and / or because the solid or liquid type fuel, especially the fuel containing carbon materials based on polymers, possibly chlorinated polymers, or based on carbon, are supplied near the burner.

4. Process according to some of the preceding claims, characterized in that the combustion created by the submerged burners at least partially ensures the agitation of the silica and the halides.

5. Process according to any of the preceding claims, characterized in that the combustion created by the submerged burners at least partially generates the water necessary for the conversion.

6. Process according to any of the preceding claims, characterized in that the conversion also generates halogenated derivatives, especially chlorinated derivatives usable as HCl or Cl2 or H2S04.

7. Process according to any of the preceding claims, characterized in that the formed silicates are treated to be compatible with the use as one or more raw materials for a glass manufacturing furnace, the treatment comprises, in particular, a step of granulation.

8. Process according to any of claims 1 to 6, characterized in that the formed silicates are hot fed into the glassmaking furnace.

9. Apparatus for carrying out the process according to one of the preceding claims, characterized in that it comprises at least one reactor equipped with one or more submerged burners and at least one means for introducing silica and / or halides or nitrates or sulfates and optionally solid type or liquid type fuels, below the level of materials undergoing melting, especially in the form of one or more loaders per batch with feed screw.

10. Apparatus according to claim 9, characterized in that the. The walls of the reactor, especially those intended to be in contact with the different products: the reactants / reactions involved in the conversion, are provided with refractory materials, for example of the type melted in an electric furnace or with refractory materials coated with a metal lining of the titanium or zirconium type or based on this type of metal, and preferably combined, at least in the case of the side walls, with a cooling system using the circulation of water-type fluids.

11. Apparatus according to the claim 9 or 10, characterized in that the walls of the reactor define a cylindrical cavity or approximately cubic parallelepiped.

12. Apparatus according to one of claims 9 to 11, characterized in that the reactor is equipped with means for treating the chlorinated effluents, especially means for recovering Cl2 or H2S0 or for neutralizing the HCl and / or means for separating the solid particles for example those based on a metal chloride, the gaseous effluents.

13. Use of the process according to one of claims 1 to 8, or of the apparatus according to one of claims 9 to 12 for preparing tri-ficable raw materials for the manufacture of glass.

14. Use of the process according to one of claims 1 to 8, or of the apparatus according to one of claims 9 to 12 for preparing raw materials, especially sodium silicate Na2Si? 3 for the manufacture of detergents.

15. Use of the process according to one of claims 1 to 8, or of the apparatus according to > one of the above indications 9 to 12 for preparing raw material, especially sodium silicate Na2S? Ü3 for the manufacture of precipitated silica, more particularly to form sodium sulfate and silica.

16. Use of the process according to one of claims 1 to 8, or of the apparatus according to one of claims 9 to 12 for the vitrification of waste, notably of the organochloride type, preferably by the conversion of silica and of the raw material that carries alkaline earth metals at least.

17. Use of the process according to any of claims 1 to 8, or of the apparatus according to any of claims 9 to 12 for the treatment of sand contaminated by fuel or similar hydrocarbon compounds, preferably by the conversion of silica and of the raw material that carries at least alkaline earth metals.

18. Process for obtaining glass containing silica and alkali metal oxides of the Na20 or K20 type and / or oxides of alkaline earth metals of the CaO or MgO type and / or rare earth oxides of the Ce02 type, melting the materials vi trifi cabl es en which the heat necessary for the melting comes at least partially from the submerged burners, characterized in that the tri-ficable materials containing alkali metals, of the Na or K type, or rare earths, of the Ce type or of alkaline earth metals, they are at least partially in the form of halides, especially chlorides of such elements, such as NaCl, KCl or CeCl