PROCESS FOR THE CAPTURE OF CO2 INTEGRATED INTO THE MELTING OF GLASS

Abstract

Glass melting process including the introduction of a vitrifiable solid charge into a furnace, heating and melting of charge thereby obtaining molten glass. Discharging the molten glass from the furnace and discharging a CO.sub.2-containing gaseous effluent from the furnace. The charge having at least one carbonate undergoing a dissociation reaction and releasing gaseous CO.sub.2 when heated and melted. The gaseous effluent discharged from the furnace being used to produce, at least one additive in the form of an alkali metal or alkaline earth metal carbonate, at least a part of which is incorporated in the charge which is introduced into the furnace.

Claims

1. A glass-melting process comprising: a. introducing a vitrifiable solid charge into a furnace, the vitrifiable solid charge comprising at least one carbonate, b. heating and melting the charge in the furnace, thereby obtaining molten glass, the at least one carbonate undergoing a dissociation reaction and releasing gaseous CO.sub.2, c. discharging the molten glass from the furnace, d. discharging a CO.sub.2-containing gaseous effluent from the furnace, and e. utilizing the gaseous effluent discharged from the furnace to produce, by carbonation with the CO.sub.2 present in the gaseous effluent, at least one additive in the form of an alkali-metal or alkaline-earth-metal carbonate, wherein at least a part of said additive produced in stage e. is incorporated in the vitrifiable solid charge which is introduced into the furnace in stage a., wherein the heat for heating the charge in stage b. is provided: by electric heating, by combustion of a non-carbon-based fuel with an oxidant, and/or both by combustion of a non-carbon-based fuel with an oxidant and by combustion of a carbon-based fuel with an oxidant.

2. The process according to claim 1, wherein at least a part of the heat for heating the charge in stage b. is provided by combustion of a non-carbon-based fuel selected among hydrogen and ammonia.

3. The process according to claim 1, wherein at least a part of the heat for heating the charge in stage b. is provided by combustion, the oxidant being chosen from air or oxygen-enriched air.

4. The process according to claim 1, wherein, for the carbonation in stage e., the gaseous effluent is brought into contact in a carbonator with the oxide and/or the hydroxide of the alkali metal or alkaline-earth metal corresponding to the carbonate to be produced in stage e.

5. The process according to claim 4, wherein the carbonator is a batch carbonator, a fluidized bed carbonator or an entrained bed carbonator.

6. The process according to claim 4, wherein the carbonation is carried out in the carbonator at a temperature between 500? C. and 950? C.

7. The process according to claim 4, wherein the gaseous effluent is cooled down to a predetermined temperature or range of temperatures before being introduced into the carbonator, said predetermined temperature or said predetermined range of temperatures being between 600? C. and 1000? C.

8. The process according to claim 4, wherein the gaseous effluent is cooled in one or more heat exchangers before being introduced into the carbonator.

9. The process according to claim 8, wherein, during the cooling of the gaseous effluent, thermal energy extracted from the gaseous effluent is used to heat an oxidant and/or a non-carbon-based fuel, in which at least a part of the heat for heating the charge in stage b. is provided by combustion and in which oxidant and/or fuel heated during the cooling of the gaseous effluent is/are used to heat the charge in the furnace by combustion with the heated oxidant and/or the heated fuel.

10. The process according to claim 1, wherein the furnace is a batch furnace, a semi-batch furnace or a continuous furnace.

11. The process according to claim 1, wherein, during stage e., at least one additive chosen from sodium carbonate, calcium carbonate, potassium carbonate, magnesium carbonate, lithium carbonate or barium carbonate is produced.

12. The process according to claim 11, wherein, during stage e., at least one additive chosen from sodium carbonate, calcium carbonate and potassium carbonate is produced.

13. The process according to claim 1, wherein the glass is chosen from soda-lime glasses and borosilicate glasses.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0120] For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

[0121] FIG. 1 illustrates a schematic representation of one embodiment of the present invention.

[0122] FIG. 2 illustrates a schematic representation of another embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0123] As illustrated in FIG. 1, a charge 11 containing vitrifiable material and/or cullet, and also functional additives, including in particular the stabilizer CaCO.sub.3, is introduced into a melting furnace 1.

[0124] Inside the furnace 1, the charge 11 is melted and forms a glass bath 15. Above the bath 15 is a gaseous atmosphere 16.

[0125] The molten glass present in the bath 15 is refined before being discharged from the furnace 1 in the form of a flow of liquid glass 17 and being directed to a forming installation (not illustrated in the figures) for the manufacture of the final product.

[0126] The furnace 1 is heated by combustion of a fuel 12 with an oxidizer 13. The gases 14 generated by the combustion are discharged from the furnace 1 in the form of a gaseous effluent 20.

[0127] The fuel 12 can be a combination of a carbon-based fuel and a non-carbon-based fuel. However, in the embodiment illustrated, all of the fuel 12 is green hydrogen, thus reducing the emissions of CO.sub.2 per tonne of glass from the melting furnace by avoiding the generation of CO.sub.2 by combustion.

[0128] Despite this measure, CO.sub.2 is indeed present in the gaseous effluent 20 discharged from the furnace 1, more particularly because of the decarbonation, during the melting of the charge 11 and the refining of the molten glass in the glass bath 15, of the carbonate(s) present in the charge 11, in particular calcium carbonate. This decarbonation generates gaseous CO.sub.2, at least a part 18 of which passes into the gaseous atmosphere 16 and is thus discharged from the furnace 1 by the gaseous effluent 20.

[0129] In order to reduce even more the emissions of CO.sub.2 to the atmosphere without having to resort to expensive processes, such as CCS or CCU, the gaseous effluent 20 discharged from the furnace 1 is used to produce, by carbonation with the CO.sub.2 present in the gaseous effluent 20, at least one additive in the form of an alkali-metal or alkaline-earth-metal carbonate, at least a part of which is introduced into the furnace 1 with the charge 11.

[0130] For this purpose, the CO.sub.2-containing gaseous effluent 20 is introduced into a carbonator 30, in which the gaseous effluent 20 is brought into contact with CaO 31 under conditions, and in particular conditions of temperature and of residence time, such that at least 50%, preferably at least 60% and more preferably at least 70% of the CO.sub.2 present in said effluent 20 reacts with the CaO 31 with formation of CaCO.sub.3.

[0131] A single carbonator 30 is shown in FIG. 1. The use of several carbonators, operating simultaneously or alternately, is also possible, whereby operating refers to the chemical process of carbonation, i.e. the formation of carbonate. In the figure, the sole carbonate formed by carbonation with the CO.sub.2 present in the gaseous effluent 20 is CaCO.sub.3. The CO.sub.2 present in the gaseous effluent 20 can similarly be used for the production of another alkali-metal or alkaline-earth-metal carbonate, which can be used as a functional additive in the glass melting furnace 1, indeed even for the production of a combination of such carbonates.

[0132] The CO.sub.2-depleted residue 32 of the gaseous effluent is discharged from the carbonator 30, as is the carbonated product 33.

[0133] The conditions, and in particular the conditions of temperature and of residence time, in the carbonator 30 are chosen so that at least 50%, preferably at least 60% and more preferably at least 70% of the CO.sub.2 present in said effluent 20 reacts with the ground CaO 31 with formation of CaCO.sub.3.

[0134] The amount of CaO 31 introduced into the carbonator 30 and its surface area of contact with the gaseous effluent 20 are chosen so as to maximize the conversion of CaO into CaCO.sub.3.

[0135] In order to increase this contact surface area, porous CaO in the form of particles is advantageously chosen.

[0136] Thus, in the embodiment illustrated in FIG. 1, porous CaO having a pore volume of greater than 0.078 cm.sup.3/?/g, also called quicklime and commercially available. This porous CaO is ground to a particle size of less than 1 mm, preferably of about 137 ?m, so as to obtain a specific surface (BET) greater than 17. This ground CaO 31 is subsequently introduced into the carbonator 30. Inside said carbonator 30.

[0137] In the embodiment illustrated in FIG. 1, the carbonator 30 is a batch carbonator. The duration of the contact between the gaseous effluent 20 and the ground CaO 31 is greater than 4 minutes. The temperature in the carbonator 30 is between 500? C. and 650? C.

[0138] At least a part of the carbonated product 33 discharged from the carbonator 30 is incorporated in the charge 11 which is introduced into the furnace 1, if necessary with a supplement 34 of CaCO.sub.3. A large part of the CO.sub.2 of the gaseous effluent 20 is thus trapped and the CaCO.sub.3 obtained will be used as a starting material in the furnace 1.

[0139] In so far as the carbonation of the CaO is not complete and it turns out to be necessary to limit the amount of unconverted CaO which is added to the charge 11 and/or that the amount of carbonate formed in the carbonator 30 exceeds the amount to be added to the charge 11, a part 35 of the carbonated product 33 is extracted from the recycle and is not added to the charge 11.

[0140] As indicated above, the temperature in the carbonator 30 is chosen so as to promote the reaction of the CO.sub.2 present in the effluent 20 with the CaO, this temperature lying, for example, between 500? C. and 650? C. The gaseous effluent 20 is discharged from the furnace 1 at a temperature (typically between 1400? C. and 1550? C., indeed even more) which promotes decarbonation rather than carbonation.

[0141] The temperature in the carbonator 30 is largely determined by the temperature of the gaseous effluent 20 at the inlet of the carbonator 30.

[0142] In order to ensure an appropriate temperature in the carbonator 30, it is proposed to cool the gaseous effluent 20 between its exit from the furnace 1 and its entry into the carbonator 30.

[0143] In the embodiment illustrated in FIG. 1, to this end, the gaseous effluent 20 passes through a heat exchanger 40 located on the flow path of the gaseous effluent 20 between the furnace 1 and the carbonator 30. The operation of said heat exchanger 40 is regulated so that the gaseous effluent 20 enters the carbonator 30 at an appropriate temperature.

[0144] FIG. 2 shows an advantageous embodiment in which the thermal energy extracted from the gaseous effluent 20 in the heat exchanger 40 is used to preheat at least a portion of the fuel 12 and/or at least a portion of the oxidizer 13 upstream of the furnace 1.

[0145] In order to regulate the portion 12a of the fuel 12 and/or the portion 13a of the oxidizer 13 sent to the heat exchanger, a distribution valve 52 is installed on the flow path of the fuel 12 to the furnace 1 and/or a distribution valve 53 is installed on the flow path of the oxidizer 13 to the furnace 1. The part 12b of the fuel 12 and the part 13b of the oxidizer 13 which is thus not directed towards the heat exchanger 40 is introduced into the furnace 1 without passing through the exchanger 40.

[0146] By thus regulating the portion 12a of the fuel 12 and/or the portion 13a of the oxidizer 13 introduced into the exchanger 40, it is possible to regulate the level of cooling of the gaseous effluent 20 in the exchanger 40 while reusing the thermal energy extracted from the gaseous effluent 20 in the glass melting furnace 1.

[0147] The distribution between the portions 12a and 12b and/or between the portions 13a and 13b can be regulated automatically, for example as a function of the temperature of the gaseous effluent 20 at the outlet of the exchanger 40 or at the inlet of the carbonator 30.

[0148] It is possible to thus preheat both fuel 12a and oxidizer 13a, for example in a single exchanger 40 or in two separate exchangers 40, or to preheat only fuel 12a or only oxidizer 13a.

[0149] It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.