FR3078963A1 - IMMERSE BURNER - Google Patents

Abstract

The invention relates to a submerged burner for a glass or rock melting furnace, said burner being at least partly, and preferably wholly, made of an alloy having the following composition, in weight percent of the alloy: Cr at 25% Ni 5 to 20% Mo less than 6%, preferably less than 5% Mn less than 3%, preferably less than 2% If less than 2%, preferably less than 1% N less than 0.2 %, preferably less than 0.1% P less than 0.1%, preferably less than 0.05% S less than 0.05%, the remainder being iron, carbon and unavoidable impurities, said alloy being characterized in that the mass ratio Cr / C in said alloy is greater than 500, and preferably is greater than 530.

Description

The present invention relates to a burner intended for use as a burner submerged in a glass or rock melting furnace, in particular at temperatures sufficiently high to allow the melting of rock.

Rock melting is traditionally done in cupola type ovens heated with coke. The melting of rock requires significantly higher temperatures than the melting of glass, which can go up to 1550 ° C.

In recent years, however, the composition of the rock used has been modified in the direction of a decrease in the melting temperature as described in publication WO2017 / 060637. However temperatures of the order of 1450 ° C to 1500Ό at the outlet of the furnace are still necessary to ensure the melting of such rocks.

At such temperatures, premature wear of the refractory ceramics generally used in ovens is observed. This wear can be avoided by using an oven with bare metal walls, continuously cooled by a system for circulating a coolant (water jacket, in English waterjacket).

More particularly, a conventional submerged burner consists of a system of pipes allowing a coolant, generally water, to circulate inside the burner, so as to significantly reduce the corrosion of the metal constituting it. this. The consequence of cooling is the formation of a layer of glass or rock between the molten layer and the metal walls, a layer which seems to act as a protective layer against metal oxidation.

An example of this burner is described in particular in application WO2013 / 117851. In this publication of the applicant, a burner for an oven is described comprising a plurality of aligned injectors, each injector comprising a mixing chamber in the form of a cylinder, with an ejection orifice, a fuel supply line and a line of oxidant supply opening into the mixing chamber at

-2 level of the cylinder casing in a direction causing a tangential flow of the fuel and of the oxidant with respect to the cylinder casing, and a system of pipes making it possible to circulate a cooling fluid inside the burner. Such a burner is typically, but not solely, of the type of those capable of being used according to the present invention. For more details, reference is made to FIGS. 1 to 3 described in this publication and to the associated description of publication WO2013 / 117851A1.

According to another particular embodiment of a burner according to the invention, it can also be cylindrical, in particular of the type of that described for example in the publication US2005236747.

Despite significant advances in terms of burner durability, linked to such an architecture, there is always a need to extend the life of the burners to avoid costly phases of change requiring the shutdown of the installation, in addition the cost of the burner itself.

The object of the present invention is therefore to propose a submerged burner which can be used in a glass or rock melting furnace. The burner according to the invention is characterized in that it is made of a specific alloy allowing it to increase its service life under its usual conditions of use. More specifically, the present invention relates according to a first aspect to a burner for glass or rock melting furnace, said burner being at least partly, and preferably entirely, made of an alloy having the following composition, in weight percentage of the alloy:

-3Cr

Neither 25% to 20%

MB

mn

If less than 6%, preferably less than 5% less than 3%, preferably less than 2% less than 2%, preferably less than 1% less than 0.2%, preferably less than 0.1% less 0.1%, preferably less than 0.05% less than 0.05%, the remainder consisting of iron and carbon and unavoidable impurities, said alloy being characterized in that the Cr / C mass ratio in said alloy is greater than 500, preferably greater than 530, more preferably still greater than 550, or even very preferably greater than 600.

According to an advantageous embodiment, the Cr / C mass ratio and less than 850.

Thus, while conventionally in the field, it is considered that the quantity of carbon in a steel must be sufficient to promote the formation of a sufficient quantity of chromium carbides, the applicant company has found that an alloy relatively depleted in carbon in relation to its overall chromium content could be advantageously used in the constitution of burners for glass or rock melting furnaces. Such use advantageously results in a significant increase in the life of such burners.

According to other advantageous embodiments of the invention:

- the alloy comprises less than 0.045% by weight of carbon;

- the alloy comprises less than 0.040% by weight of carbon;

- the alloy comprises less than 0.035% by weight of carbon;

- the alloy comprises less than 0.030% by weight of carbon;

- the alloy comprises between 7 and 16% by weight of nickel; more preferably between 8 and 15% nickel;

- the alloy comprises between 15 and 22% by weight of chromium; more preferably between 17 and 20% chromium;

- the alloy comprises between 60 and 75% by weight of iron;

- the alloy comprises less than 5% by weight of molybdenum;

- the alloy comprises between 1 and 5% by weight of molybdenum;

- The alloy has the following composition, in percentage by weight of

the alloy: Cr 17 to 20% Or 8 to 10% MB less than 1%, preferably less than 0.1% mn less than 3% Yes less than 2% NOT less than 0.2% Zr less than 0.1%, P less than 0.1%

the rest being iron and unavoidable impurities. Such an alloy may comprise less than 0.045% by weight of carbon, or even less than 0.040% by weight of carbon or even less than 0.035% by weight of carbon.

- The alloy has the following composition, in percentage by weight of

the alloy: Cr 17 to 20% Or 10 to 15% MB between 2 and 4% mn less than 3% Yes less than 2%, preferably less than 1% NOT less than 0.2%

-5Zr less than 0.1%,

P less than 0.1%, the remainder consisting of iron and unavoidable impurities. Such an alloy can comprise less than 0.035% by weight of carbon, or even less than 0.030% by weight of carbon.

The invention also relates to a submerged burner as described above, comprising:

a plurality of aligned injectors, each injector comprising a mixing chamber in the form of a cylinder, with an ejection orifice, a fuel supply line and a fuel supply line opening into the mixing chamber at the level the envelope of the cylinder in a direction causing a tangential flow of the fuel and of the oxidant relative to the envelope of the cylinder, and

- a system of pipes allowing a coolant to circulate inside the burner.

The burner is used as a submerged burner, so that it is preferably installed at the level of the hearth of the furnace, more preferably so that the ejection orifices are approximately at the same level as the oven bottom surface. For example, the metal sides and partitions can be raised in relation to the surface of the sole.

Other configurations of the burner can be envisaged and the person skilled in the art can choose them anyway allowing him to obtain the homogeneous fusion of the batch materials, for example according to the principles described in application US2005236747.

Furthermore, the present invention relates to a glass melting furnace with a zone for introducing vitrifiable materials, a zone for leaving the molten material and, between these zones, a zone for flow of the molten material, said furnace. comprising in the flow zone of the molten material at least one submerged burner as described above.

As explained in the introduction, the furnace of the present invention is preferably used for melting rock at high temperatures, of the order of 1400 to 1600 ° C., higher than those necessary for melting glass. At these temperatures, refractory ceramics conventionally used as thermal insulation materials in glass furnaces are subject to excessive wear.

Although nothing in principle precludes the use of the burners of the present invention in conventional ovens comprising refractory insulating materials, these burners are particularly useful in ovens operating at high temperature. In a preferred embodiment, the furnace of the present invention therefore comprises bare metal walls, for example made of A42CP boiler steel, directly in contact with the molten material and is essentially devoid of insulating materials made of refractory ceramic, at least in the submerged areas of the oven that are in contact with the glass or rock bath. The roof of the oven of the present invention can optionally be insulated by means of refractory materials, although this is not a preferred embodiment.

The oven, like the burner, preferably has at least one system of internal conduits for circulating a cooling fluid inside the walls of the oven. These pipes advantageously cool all of the zones in contact with the bath of molten materials, devoid of refractory insulating materials.

Finally, the present invention relates to a process for melting vitrifiable materials using a burner as described above, said process comprising,

- the introduction of vitrifiable materials into the vitrifiable materials introduction zone of the oven,

- supplying the submerged burner (s) with a gaseous fuel, preferably natural gas, and with a gaseous oxidant, preferably oxygen,

- the withdrawal of the molten material in the outlet zone of the molten materials, and

- the circulation of a coolant, preferably water, in the pipe systems provided for this purpose in the walls of the oven and / or in the burner.

In such a process, the vitrifiable materials generally comprise rock, preferably basalt rock.

In general, the temperature of the molten rock, immediately upstream from the exit zone of the molten glass, is between 1400 ° C and 1600 ° C.

The batch materials advantageously comprise a certain fraction of rock, preferably basalt rock. This fraction is advantageously at least equal to 40%.

Basalt rock requires in particular melting temperatures higher than those of silica-based glass, the temperature of the molten rock (immediately upstream from the exit zone of the furnace) is preferably between 1400 ° C and 1600 ° C, in particular between 1450 ° C and 1550 ° C.

The invention and its advantages are illustrated by the following examples.

Examples:

In these examples, burners were synthesized in accordance with the teaching of the publication WO2013 / 117851.

According to a first comparative example 1, an alloy as described in publication WO2013 / 117851 in which the Cr / C mass ratio is equal to 208 was used for the manufacture of a first burner.

According to a second example 2, an alloy having a composition of a refractory steel in which the Cr / C mass ratio is equal to 566 was used for the manufacture of a second burner according to the present invention.

The compositions of the alloys constituting the two burners are given in Table 1 below:

Composition Example 1 (prior art) Example 2 (invention) VS 0.12% 0.03% Cr 25% 17% Or 19% 12% Yes 0.5% 0.5% MB - 2.0% mn 2.0% 2.0% P 0.04% 0.04% S 0.03% 0.03% Fe rest rest

Table 1

The two burners were used in a submerged burner of the type described in application WO2013 / 117851, for the melting of a rock composition.

The melted composition is based on basalt, bauxite, diabase, dolomite and devoid of slag was melted in a submerged burner oven. The molten bath was fiberized by external centrifugation to obtain mineral fibers having a chemical composition comprising the following constituents, in weight percentages:

SiO ₂ about 40% ai ₂ o ₃ about 15% CaO about 15% MgO around 10 % Fe ₂ O ₃ around 10 % Na ₂ O less than 4%% K ₂ O less than 2% TiO ₂ less than 2%%

The melting is carried out under conditions such that the molten liquid has a temperature of 1450 ° C. at the outlet of the oven.

For each of the alloy compositions, the burners have been tested under industrial conditions. The life of the burners used is reported in Table 2 below. It is considered that a burner is no longer usable under industrial conditions when there is a leak at the injectors.

Example 1 Example 2 Average burner life (days) 138 > 314

îo Table 2

The examples reported above show that the burner according to the invention, in which the Cr / C ratio is maximized, has a life much longer than the other two examples.

Claims (14)

1. Submerged burner for a glass or rock melting furnace, said burner being at least partly, and preferably entirely, made of an alloy having the following composition, as a percentage by weight of the alloy: Cr Or MB mn Yes NOT P S 11 to 25% 5 to 20% less than 6%, preferably less than 5% less than 3%, preferably less than 2% less than 2%, preferably less than 1% less than 0.2%, preferably less than 0, 1% less than 0.1%, preferably less than 0.05% less than 0.05%, the remainder consisting of iron, carbon and unavoidable impurities, said alloy being characterized by the Cr / C mass ratio in said alloy is greater than 500. 2. Submerged burner according to claim 1, in which the Cr / C mass ratio in said alloy is greater than 530. 3. Submerged burner according to one of the preceding claims, in which the alloy comprises less than 0.040% by weight of carbon. 4. submerged burner according to one of the preceding claims, in which the alloy comprises between 7 and 16% by weight of nickel. 5. Submerged burner according to one of the preceding claims, in which the alloy comprises between 15 and 22% by weight of chromium. 6. submerged burner according to one of the preceding claims, in which the alloy comprises between 60 and 75% by weight of iron. 7. submerged burner according to one of the preceding claims, in which the alloy comprises less than 5% by weight of molybdenum. 8. submerged burner according to one of the preceding claims, in which the alloy comprises between 1 and 5% by weight of molybdenum. 9. submerged burner according to one of the preceding claims, in which the alloy has the following composition, in percentage weight of the alloy: Cr 17 to 20% Or 8 to 10% MB less than 1%, preferably less than 0.1% mn less than 3% Yes less than 2% NOT less than 0.2% Zr less than 0.1%, P less than 0.1% the rest being iron and unavoidable impurities. 10. Burner submerged according to one of the preceding claims, in which the alloy has the following composition, as a percentage weight of the alloy: Cr 17 to 20% Or 10 to 15% MB between 2 and 4% mn less than 3% Yes less than 2%, preferably less than 1% NOT less than 0.2% Zr less than 0.1%, P less than 0.1% the rest being iron and unavoidable impurities. 11. Submerged burner according to one of the preceding claims, comprising: a plurality of aligned injectors, each injector comprising a mixing chamber in the form of a cylinder, with an ejection orifice, a fuel supply line and a fuel supply line opening into the mixing chamber at the level the envelope of the cylinder in a direction causing a tangential flow of the fuel and of the oxidant relative to the envelope of the cylinder, and - a system of pipes allowing a coolant to circulate inside the burner. 12. Glass melting furnace with a zone for introducing vitrifiable materials, an outlet zone for the molten material and, between these zones, a zone for flow of the molten material, said furnace comprising in the flow zone of the molten material at least one submerged burner according to any one of the preceding claims. 13. A method of melting vitrifiable materials using a burner according to any one of claims 1 to 10, said method comprising, - the introduction of vitrifiable materials into the vitrifiable materials introduction zone of the oven, - supplying the submerged burner (s) with a gaseous fuel, preferably natural gas, and with a gaseous oxidant, preferably oxygen, - the withdrawal of the molten material in the outlet zone of the molten materials, and - the circulation of a coolant, preferably water, in the pipe systems provided for this purpose in the walls of the oven and / or in the burner. 14. A method of melting vitrifiable materials according to claim 12, characterized in that the vitrifiable materials comprise rock, preferably basaltic rock. 15. A method of melting vitrifiable materials according to claim 12 or 13, characterized in that the temperature of the molten rock, immediately upstream of the exit zone of the molten glass, is between 1400 ° C and 1600 ° C.