Method and device for compaction of porous substrate by the gaseous phase chemical infiltration

FIELD: chemical industry; other industries; methods and devices for compaction of porous substrates by- the gaseous phase chemical infiltration.

SUBSTANCE: invention is pertaining to the field of compaction of porous substrates by- the gaseous phase chemical infiltration. Exercise loading of substrates exposed to compaction- into the furnace loading area; heat up substrates in the furnace up to their temperature, at which the required substance of the mold will be formed from the gaseous source or sources contained in the gas-reactant. Then- on the one hand of the furnace inject gas-reagent and heat it up after injection- during its transit in the furnace through the gas heating area located- in the direction of the gas-reagent travel through the furnace in front of the loading area. Gas-reactant is exposed to preheating before its injection in the furnace for reaching prior its injection in the furnace of the temperature intermediate -between the environment temperature and the substrates preheating temperature. Installation includes the furnace, the area of substrates loading in the furnace, the means of heating of substrates in the loading area, at least, one hole for the gas-reagent injection in the furnace and, at least, one heating area of the gas-reagent disposed in the furnace between the hole of the gas-reagent injection and the loading area. Installation also contains, at least, one gas preheating device disposed out of the furnace and connected, at least, with one hole used for injection of the gas-reagentin the furnace and ensuring- preliminary heating up of the gas-reagent before its injection in the furnace. The presented method and the device allow to reduce significantly the temperature gradient in the whole area of loading without usage of the large the volume of the gas-reagent heating area.

EFFECT: invention allows to reduce significantly the temperature gradient in the whole area of loading without usage of the large the volume of the gas-reagent heating area.

24 cl, 7 dwg

The technical FIELD

The present invention relates to the field of seals porous substrates by infiltration of the gas phase.

The invention is applicable in the field of manufacture of parts of thermostructural composite materials, i.e. composite materials with simultaneous mechanical properties that make them suitable for the manufacture of structural parts, and the ability to retain these properties at high temperatures. A typical example thermostructural composite materials are composite materials like carbon/carbon (C/C, a contraction of the French "carbone/carbone"), having a reinforcing texture of carbon fiber, reinforced by a matrix of pyrolytic carbon, and composite materials with a ceramic matrix (CMC, an acronym for the French "les composites à matrice céramique"), having a reinforcing texture of refractory fibers (carbon or ceramic), reinforced ceramic matrix.

PRIOR art

A well-known method of sealing a porous substrate for the production of parts made of composite materials of the type/S or CMC by chemical infiltration in the gas phase. The sealing substrate is placed into the loading zone of the furnace and is heated. The furnace is gas-reagent containing one or more sources comprising the substances of the matrix. The temperature and pressure inside the furnace is adjusted in such a way as to ensure the diffusion of a reagent gas into the porous structure of the substrate and the formation of sediments constituting the substance of the matrix in the decomposition of one or more components of a reagent gas, which constitutes the substance of the matrix. This process is carried out at reduced pressure, contributing to the diffusion of a reagent gas into the substrate. Temperature conversion source or sources, which is formed comprising a substance matrix, such as pyrolytic carbon or ceramic material, in most cases exceeds 900°and, as a rule, is approximately 1000°C.

To obtain the most uniform compaction of the substrate across the loading area of the furnace, both from the point of view of increasing density, and from the point of view of the microstructure of the resulting material matrix, it is necessary that the temperature was essentially the same throughout the download area.

In addition, the furnace usually contains a zone of heating of a reagent gas, located between the insertion point of a reagent gas into the furnace and loading area. Usually the loading area contains several perforated plates through which the gas-reactant.

As a result of finding in the oven plate heat gas heat as well as the substrate is. The furnace heating is usually provided by means of a current collector made of, for example, of graphite, which forms the side wall of the furnace and connected to a coil surrounding the furnace.

The inventors have observed that the presence of a reagent gas in district heating does not always lead to the desired result. An illustrative example is the seal of substrates consisting of an annular billet, carbon fiber or pre-compacted ring blanks for the manufacture of brake discs composite type With a/C. the Substrates are formed in one or more vertical stacks placed in the loading area, above the zone of heating of a reagent gas, located in the lower part of the furnace.

Despite the heat of a reagent gas between the lower part of the loading zone and the rest of the observed temperature gradient, and the temperature in the zone of location of the substrates placed in the bottom of the stack, can be several tens of degrees lower than the temperature in the area of finding other substrates that are in the stack. The result is a significant gradient in the degree of sealing of substrates depending on their position in the stack.

To eliminate this drawback can be proposed increasing the efficiency of heating of a reagent gas by increasing the of zone heating. However, while maintaining a constant volume of the furnace it will reduce the useful volume of the loading zone. In addition, the processes of chemical infiltration in the gas phase is carried out on an industrial scale, expensive and take a significant amount of time. Therefore, it is highly desirable that the furnace had a high performance, whether we are talking about the use of old stoves or the creation of new, and therefore that the ratio of the useful volume, intended for loading substrates, and useful volume, intended for heating of a reagent gas was as high as possible.

The INVENTION

The invention is directed to a method of sealing a porous substrate by chemical infiltration in the gas phase, which would result in the entire loading area significantly reduced the temperature gradient of the cost volume of zone heating of a reagent gas, thus not decreasing or even increasing the productivity of the furnace.

To solve this problem, we propose a method that contains:

- download the sealing substrate in the loading area of the furnace,

- heating of the substrate in a furnace with a view to bringing them to a temperature at which the gaseous source or source contained in the gas-reactant is formed to the desired matrix material,

introduction one is part of the furnace gas-reagent

- as well as a heated gas-reagent after its introduction into the furnace due to the passage through the zone heating the gas located in the direction of passage of a reagent gas through the furnace before loading area,

moreover, according to the invention in this way

- gas-reagent is pre-heated prior to its introduction into the furnace to achieve by the time of its introduction into the furnace temperature between ambient temperature and the temperature of the heating substrates.

Pre-heating of a reagent gas outside the furnace improves the performance zone heating the inside of the furnace, when making of a reagent gas to the time of its introduction in the loading area of the substrate to the desired temperature.

Since the temperature at which infiltration exceeds 900°C, gas-reagent prior to its introduction into the oven pre-heated to a temperature, preferably equal to at least 200°C. At the same time, the temperature of the preheating gas preferably should not exceed 800°or even 600°To avoid danger of formation of foreign deposits in the transformation of the source or sources prior to the introduction of gas into the furnace, and also to allow the use of standard materials made for the Sabbath.I input channels in an oven pre-heated gas-reagent and elements, for example, valves and connections on these channels.

Pre-heating may be carried out at a gas pressure essentially equal to the pressure existing within the furnace or exceeding it. In the latter case, before the introduction of the preheated gas into the furnace pressure lower.

The invention also aims to create a setup that allows you to apply this method.

To solve this problem is proposed installation comprising a furnace, the loading area of substrates into a furnace, means for heating the substrate in the loading area, at least one insertion in the furnace of a reagent gas and at least one zone of heating of a reagent gas, located in the furnace between the insertion of a reagent gas and the loading area, and according to the invention in this set is additionally provided at least one device that preheats gas located outside the furnace, United, at least one insertion of a reagent gas into the furnace and provide pre-heating of a reagent gas prior to its entry into the oven.

In accordance with one embodiment of the invention, the device preheats contains a flow pipe installed in the feed channel of a reagent gas to the insertion of a reagent gas into the oven.

In accordance with the other variants of the invention, the device preheats contains a gas burner or electric heating furnace, through which passes at least one channel or bundle of tubes through which flows a pre-heated gas-reactant.

A BRIEF DESCRIPTION of GRAPHIC MATERIALS

Other features and advantages of the present invention will be clear from the following detailed description, given with reference to the accompanying drawings that do not impose any restrictions on the scope of the invention. In the drawings:

1 very schematically shows in the context of the first variant of the installation for sealing according to the invention;

figure 2 presents curves illustrating the temperature change of a reagent gas from a point prior to its entry into the oven, until the time after it is entered in the download area of the substrate, with preliminary heating of a reagent gas and without preheating;

3 very schematically shows in section a second variant implementation of the installation for sealing according to the invention;

Figure 4 illustrates another method for loading substrates in the installation for sealing;

Figure 5 schematically illustrates another method for loading substrates in the installation for sealing;

figure 6 very schematically presents a view of figure 5 in section along the plane VI-VI;

7 depicts a part in the system to seal illustrating one of the embodiments of the kiln feed of a reagent gas in the furnace in the form of several stacks of substrates.

INFORMATION CONFIRMING the POSSIBILITY of carrying out the INVENTION

The following describes embodiments of the method and installation according to the invention within the scope of their application to seal the annular porous substrate consisting of a billet, carbon fiber or pre-compacted billets and intended for the manufacture of brake discs composite type With a/C. they are commonly used in aircraft landing gear, and sports cars.

1 schematically shows a furnace 10, bounded by side wall 12, bottom wall 14 and top wall 16. The wall 12 includes an inductor, e.g. made of graphite, which is connected with the coil 18 of the inductance, which is located outside of the furnace, with an insulating gasket 20. The heating furnace is provided with an inductor 12 using a power supply coil 18 inductance.

Gas-reagent is introduced into the furnace through an opening 22 provided in the bottom wall 14, and exhaust gases are expelled through hole 24 provided in the upper wall 16, and the hole 24 are connected by a channel 26 with the pumping equipment (not shown).

The sealing substrate 32 is placed in a vertical annular stack, close the top cover 34. Thus, folded in a stack of substrates divide the internal volume of the loading zone on volume 36, located inside the stack and formed by the Central openings of the substrates, and volume 38 located outside of the stack.

The stack of substrates is located on the lower carrier plate 40 and can be divided into several vertically stacked tiers separated by intermediate plates 42 and plate 40, 42 include Central openings 41, 43, aligned with the Central openings of the substrates 32. Although figure 1 shows only one stack, multiple stacks can be placed in the oven next to each other, as described below.

As shown in detail in the sidebar on the Figure 1, each substrate 32 is separated from adjacent the substrate, the plates 40, 42 or from the lid 34 of the dividing strips 44, forming gaps 46. Strip 44 or, at least, some of them are so as to provide a passage of gas between the volumes 36 and 38 through the gap 46. This passage can be ensured by the approximate pressure equalization in volumes 36 and 38, as described in U.S. patent No. 5904957, or by creating a simple discharge passages supporting the pressure gradient between the volumes 36 and 38, as described in the application for French patent No. 0103004.

Area 50 of the heating gas is located between the bottom of the furnace 14 and the lower support plate 40. On the all right well-known solution, area 50 heating has several perforated plates 52 made, for example, of graphite, which are located one above the other and at some distance from each other. Plate 52 may be located in the casing containing the bottom 54 and the side wall 56 and the limiting zone heating. Through the bottom 54 is channel 58, the connecting hole 22 of the input of a reagent gas with a heating zone 30.

Cover and heat plates 40, 42 are supported by beams and columns 28. All of these elements can be manufactured, for example, of graphite.

Gas-reactant flowing into the furnace through the inlet 22, passes through the zone 50 of the heat and into the volume 36 through the Central hole 41 of the plate 40. Gas-reagent passes from volume 36 volume 38 through the porous structure of the substrates 32 and through the passages in the gaps 46. The exhaust gases are discharged from volume 38 through the outlet 24.

One of the embodiments of the invention, the volume 36 may be closed at the bottom, and its upper part is communicated with the outlet 24. Gas-reagent coming from the zone 30 of the heat, in this case falls in volume 38 of the loading zone and passes into this zone from volume 38 volume 36, because the amount of 38 top is closed.

According to another variant of the invention, the input reagent gas can be carried out through the upper wall 16 of the furnace, and the area is agrimonia in this case is located in the upper part of the furnace. The volume 36, 38 which communicates with the area of heating, closed bottom, and the second of these two volumes is communicated with the hole of the gas outlet provided in the bottom wall of the oven.

For the formation of a matrix of pyrolytic carbon gas-reagent contains one or more carbon sources, for example, hydrocarbons. As carbon sources often use methane, propane or their mixtures. Chemical infiltration in the gas phase is carried out usually at a temperature exceeding 900°With, for example component from 950°1100°and under reduced pressure, for example at a pressure of less than 0.1 kPa.

According to the invention the gas-reagent before putting into the oven pre-heated by the passage through the device 60 pre-heating, coupled with the inlet 22 of the furnace channel 62 of the gas supply. On channel 62, directly in front of the entrance hole 22, is the shutoff valve 64, which allows, if necessary, to isolate the furnace from the supply circuit of a reagent gas.

In the embodiment shown in figure 1, the device preheats contains a flow pipe 66 connected to the channel 62, which forms a gas-reagent supplied from a source 68.

The flow tube is used in the known solutions for heating circulara the appropriate liquids. The heat release occurs due to the Joule effect during the flow along the pipe section of the electric current. The pipe is simultaneously an electric resistance, channel flow and surface heat transfer.

Electric current is supplied by the circuit 70 power supply providing the voltage U and connected to the ends of the pipe section. The circuit 70 receives information from the sensor 72, for example, thermocouples, located at the output of the device that preheats. Setting a predetermined temperature of the preliminary heating is carried out by automatic change of the voltage U, depending on the temperature values measured by the sensor 72.

Heating of a reagent gas can be carried out under reduced pressure existing in the furnace, through a reduction gear 74, which is located at the exit of the source 68 of the gas.

In another embodiment, the heating of a reagent gas can be carried out at a pressure greater than the pressure existing in the furnace, and it is smaller than the pressure source 68, but greater than the pressure existing in the furnace. In this case, the pressure of a reagent gas is reduced before it is input into the furnace, for example, by passing it through a calibrated orifice provided in the channel 62 of the gas supply.

The purpose of pre-heating of a reagent gas is h the ordinary gas after additional heating during the passage through the zone 50 of the heat fell into the loading area at a temperature equal or close to the temperature necessary to prevent a significant temperature gradient between the bottom of the loading zone and the rest of her space.

To pre-heating gas-reagent was effective, it must ensure that the gas supply to the inlet of the furnace at a temperature of not less than 200°C.

The temperature of pre-heating, i.e. the temperature at the outlet of the device pre-heating should, however, be limited to avoid the formation in the channel 62 of the gas supply foreign deposits (soot), as well as technological constraints.

Thus, to avoid the formation of extraneous sediment choose the temperature of pre-heating not exceeding 800°and in the preferred embodiment, to allow the use of materials acceptable cost for manufacturing the channel 62 (e.g., steel), valve 64, and possibly other elements exposed to gas-reagent, such as gaskets, temperature not exceeding 600°C.

Depending on the length and insulation of the channel 62, after the release of the pre-heated gas from the pre-heating and prior to its entry into the furnace may more or less significant decrease his pace is atmospheric temperature. So, when pre-heated to 600°With the temperature of the gas prior to its entry into the furnace can be reduced in size from a few degrees to a few tens of degrees, and then, when the input gas into the furnace or even shortly before entering the furnace (under the influence of the atmosphere of the furnace), again to rise.

Trials were conducted, during which the furnace similar to that shown in figure 1, was supplied to the gas-reactant is preheated up to 600°C. the gas Temperature was measured at the exit of the pre-heating in the feed channel, at the entrance to the furnace and at the exit of the heating zone 50, which is located in the furnace. The measured temperature change is depicted in figure 2, curve A.

Two similar tests were carried out at a temperature of pre-heating equal to 500°S, with the same consumption of a reagent gas and increases its consumption by approximately 42%. Measured in these two cases, the temperature changes shown in figure 2, respectively, curves b and C.

For comparison, the test was performed without pre-heating, in which the gas-reagent was received in the channel 62 at a temperature equal to 20°C, and the gas flow rate was the same as in the preliminary heating up to 600°C. changing the temperature of a reagent gas in this case, measured up to its entrance to the loading area of the furnace, shown on IG curve D.

At the same flow rate of a reagent gas and the use of the same zone heating pre-heating the gas to a temperature equal to 600°500°With (curves a and b), allows you to deliver it to the entrance to the loading area at a temperature approximately equal to 993°and 975°With, while without pre-heating (curve D) this temperature is clearly less than 850°C.

Thus, any temperature gradient that can cause a significant temperature gradient seal between the substrates located at the bottom of the stack, and others, are avoided because of pre-heated gas.

The authors of the invention improve the performance of the zone 50 heat for pre-heating the gas to achieve results similar to the obtained with the use of pre-heating of gas requires the use of at least 5% of the volume of the loading zone. Pre-heating of a reagent gas outside the furnace provides, therefore, a reasonable method of improving its performance.

Pre-heat up to 500°additionally retains its effectiveness in a significant increase in the gas flow, since the temperature at the entrance to the loading area is approximately 950°With (curve C). Pre-heating of a reagent gas, t is thus, provides the possibility of increasing the consumption of a reagent gas, which helps to reduce the total duration of the process seal.

Figure 3 shows an implementation option installation for sealing, which differs from that shown in figure 1. the device 80 preheating formed not running pipe and the gas column.

Water heater 80 includes a burner 82, in which the channel 75 is installed on the regulating valve 76, fed fuel gas such as a gaseous hydrocarbon, such as natural gas. Channel 78 that has a compressor 79 and the regulating valve 84, the burner 82 is served conveying air. The resulting combustion gases pass through the heat exchanger 86, and then excreted through the pipe 88. Gas-reagent supplied from a source 68, passes through the channel 87 through the heat exchanger 86 and then through the loop 62 of the feed gas is fed into the furnace.

Control valves 76 and 84 are controlled by the circuit 90 controls in accordance with signals from the temperature sensor 72 located at the outlet of the gas column 80, and the support given temperature of a reagent gas.

Part of the exhaust gases can be withdrawn from the channel 26, to mix with fuel gas and burned in the burner.

Of course, for pre-heating of a reagent gas can is be used and other types of devices for heating liquids.

Thus, the gas-reagent can be pre-heated in the circulation in the tube or bundle of tubes, heated by electric resistance, and the temperature of a reagent gas at the outlet of the heating device is adjusted by controlling power supplied to the electric resistance.

Figure 4 shows a variant of the loading of the substrates 32. As shown in the inset of Fig.4, the gaps 46 between adjacent substrate or between substrates and plates 40, 42 or cover 34 provided with an annular dividing strips 44', hermetically closing the gaps 46. Thus, the passage of a reagent gas from volume 36 volume 38 is carried out exclusively through the porous structure of the substrate, which creates a significant pressure gradient between these two amounts.

Figure 5 and 6 show the option of loading substrates that differ from version download of the substrate of figure 1 so that the substrates 32 are composed of several annular stacks 31A, 31b, s, 31d, 31E, 31f, 31g, located on the carrier plate 40. This plate contains several openings similar to the openings 41A, aligned with the internal volume 36A-36g, and each of the stacks is closed on top by a cover similar to the cover 34a. Circulation of a reagent gas through the zone 50 of the heat, and then into the internal volume of the piles, to the x gas passes into external relative to the stacked volume 38, located within the zone 30 of the boot. Although figure 6 shows 7 stacks, their number may be different, in particular greater than 7.

7 shows another variant of implementation of the kiln feed of a reagent gas in the case of a load formed by several annular stacks. This implementation differs from that shown in Figure 5 so that the supply of a reagent gas in the stack is made individually.

In this case, the bottom 14 of the furnace is provided by the openings essentially aligned with the internal volume of the piles. 7 shows three such openings 22A, 22s and 22f, aligned with the internal volume 36A, 36C, 36f stacks 32A, 32C and 32f. Individual gas supply channels, such channels a, s, 62f, are connected with the openings provided in the bottom of the furnace.

Stack supported by the support plate 40, are located above the individual heating zones, such zones 50A, 50C, 50f. Each of the heating zones is restricted to a vertical cylindrical wall, such walls 56a, s, 56f, total bottom 54 and plate 40. Channels similar to the channels 58A, s, 58f, connect the openings provided in the bottom of the furnace, with different zones of heat through the holes provided in the bottom 54. Each zone heating has several perforated plates 52, which are located one above the other.

At the individual channels of the gas supply installed valves similar to the valves 64A, S, 64f.

In the depicted example, the gas-reagent coming from the device that preheats (not presented on Fig.7), passes through the common channel 62, which are connected to individual channels, such channels a, s, 62f. Thus, in the stack gas arrives-reagent, heated to the same temperature.

In one embodiment, the individual channels, such channels a, s, 62f, can be connected to individual devices pre-heating to account for possible differences of temperature in the heating zones and the bottom of the piles depending on their placement in the oven. Thus, the temperature of the preliminary heating of a reagent gas can be set individually depending on the position in the furnace stack of substrates, which is sent to the gas-reactant.

Finally, it should be noted that the scope of the invention is not limited to the manufacture of brake discs made of composite material type, but also covers the manufacture of other parts from composite material such as, for example diffuser pipes rocket engines, as shown, in particular, in the aforementioned U.S. patent No. 5904957. More generally the invention may be applied to the manufacture of parts from all types thermostructural composite materials, i.e. composite materials not only type C/S, but the type of CMC. In the latter case, the composition of a reagent gas is selected in accordance with the specific properties of ceramic matrix. Gaseous sources of ceramic matrices are well known, for example, methyltrichlorosilane (MTS) and gaseous hydrogen (H₂)forming a matrix of silicon carbide. Additional information can be found in French patent No. 2401888 that describe how the formation of various ceramic matrix.

1. Method of sealing porous substrate matrix obtained by chemical infiltration in the gas phase with the use of a reagent gas containing at least one gaseous source material of the matrix, including the loading of the sealing substrate in the loading area of the furnace; heating the substrate in an oven to bring them to a temperature at which the gaseous source or source contained in the gas-reactant is formed to the desired matrix material; introduction to one side of the furnace of a reagent gas; natural gas heating-reagent after its introduction into the furnace due to the passage through the zone heating the gas located in the direction of passage of a reagent gas through the furnace before loading area, characterized in that the gas-reactant is subjected to preliminary heating prior to its introduction into the furnace to achieve by the time of its introduction to the furnace temperature, the intermediate is between ambient temperature and the temperature of the heating substrates.

2. The method according to claim 1, characterized in that the substrate is brought to a temperature exceeding 900°and the gas-reactant is subjected to preliminary heating prior to its introduction into the furnace before reaching the moment of introduction into the oven temperature equal to at least about 200°C.

3. The method according to claim 2, characterized in that the gas-reactant is subjected to preliminary heating to a temperature not exceeding 800°C.

4. The method according to claim 2, characterized in that the gas-reactant is subjected to preliminary heating to a temperature not exceeding 600°C.

5. The method according to claim 1, characterized in that the gas-reagent outside the furnace is heated by passing it through a heat exchanger.

6. The method according to claim 1, characterized in that the gas-reactant is heated outside the furnace under pressure essentially equal to the pressure existing inside the oven.

7. The method according to claim 1, characterized in that the gas-reactant is heated outside the furnace under pressure higher than the pressure existing within the furnace, and before entering the gas in the furnace pressure is reduced.

8. The method according to claim 1, characterized in that it is used for sealing the annular porous substrates for brake discs made of composite material such as carbon/carbon.

9. The method according to claim 8, characterized in that the substrates are loaded into the furnace in the form of one or more annular stacks, and gas-reagent coming from the zone is agrimonia gas, send in one of the two volumes, educated internal volume or the internal volume of the ring stack or ring stacks and space loading zone outside of the ring stack or ring stacks, and exhaust gases are collected in the second of two volumes and is removed from the oven.

10. The method according to claim 9, characterized in that the substrates are put in a stack in such a way that between them are formed openings for the passage of gas, providing the message of these amounts with each other.

11. The method according to claim 9, characterized in that the substrates stacked in piles without forming between them openings for the passage of gas so that the passage of a reagent gas from one volume to another is carried out exclusively through the porous structure of the substrate.

12. The method according to claim 9, characterized in that the gas-reagent enters the ring stack individually, through their respective channels in one of the walls of the furnace.

13. The method according to item 12, characterized in that the temperature of the preliminary heating of a reagent gas flowing in the stack of substrates, set individually for each stack.

14. Installation for sealing porous substrate by chemical infiltration steam phase containing a furnace (10), (30) loading substrates into a furnace, means (12) heating the substrate in the loading area, at least one CTE is rstj (22; 22A, 22s, 22f) input into the furnace of a reagent gas and at least one zone (50, 50A, 50C, 50f) heating of a reagent gas, located in the furnace between the insertion of a reagent gas and the loading area, characterized in that the said installation further comprises at least one device (60; 80) pre-heating of gas located outside the furnace (10), United, at least one insertion of a reagent gas into the furnace and providing a pre-heating gas-reagent before putting in oven.

15. Installation according to 14, characterized in that the device preheats contains a flow pipe (66), installed in the feed channel of a reagent gas to the insertion of a reagent gas into the oven.

16. Installation according to 14, characterized in that the device is pre-heating gas contains a column (80)through which passes at least one circulation channel pre-heated gas.

17. Installation according to item 16, characterized in that the gas column is connected with a hole (24) output from the furnace off-gases to use at least part of the exhaust gases as a fuel gas for gas burners.

18. Installation according to 14, characterized in that the device preheats contains electric heating furnace, through which passes at least one circulation channel pre-heated gas.

19. Installation according to 14, characterized in that it contains a gearbox located between the pre-heating and insertion of a reagent gas into the oven.

20. Installation according to 14, characterized in that the device is pre-heating includes means for temperature control.

21. Installation according to 14, characterized in that the sealing ring of the substrates stacked in several piles, it contains several zones (50A, 50C, 50f) heating, each of which is located between the corresponding hole (22A, 22s, 22f) input of a reagent gas into the furnace and the location of the respective stacks of annular substrates in the download area.

22. Installation according to item 21, characterized in that it contains several individual channels (a, s, 62f) feeding the preheated gas-reagent, United with holes input of a reagent gas into the oven.

23. Installation according to item 22, wherein the individual channels (a, s, 62f) gas supply connected by a common channel with one device that preheats.

24. Installation according to item 22, wherein the individual channels of the gas supply connected to respective devices pre-heating of a reagent gas.