EP1053292A1

EP1053292A1 - Fuel gas mixture, in particular for cutting torch

Info

Publication number: EP1053292A1
Application number: EP99901642A
Authority: EP
Inventors: Gilles Cannet; Jean-Christophe Charbonnel; Gervais Lemesle
Original assignee: Air Liquide SA; LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Current assignee: LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date: 1998-02-12
Filing date: 1999-01-28
Publication date: 2000-11-22
Also published as: AU2167899A; FR2774693A1; FR2774693B1; WO1999041340A1

Abstract

The invention concerns a fuel mixture containing acetylene, propane and propylene, such that the ratio Qp/Qa of the proportion (Qp) of propane and propylene to the proportion (Qa) of acetylene is such that: 1.1</=Qp/Qa</=4. Preferably, the propane/propylene proportion in the gas mixture ranges between 50:50 and 99:1. Advantageously, the gas mixture contains 15 % to 50 % by volume of acetylene, the remainder being propane and propylene. The invention is applicable to a fuel mixture for oxyacetylene cutting of metals, the fuel mixture being produced on the site of operation, in particular in a gas mixer.

Description

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The present invention relates, on the one hand, to a combustible gas mixture containing propane, propylene and acetylene, and, on the other hand, to a method of flame cutting a metal or a metal alloy by heating. using a flame and supply of a cutting oxygen flow.

Conventionally, flame cutting uses, on the one hand, a flame of. heats and, on the other hand, a jet or flow of cutting oxygen.

The heating flame, usually fed by a mixture of combustible gas and heating oxygen, largely conditions the efficiency and quality of the flame cutting. Currently, the known combustible gases for feeding the heating flame are acetylene, propane, methane, hydrogen and other liquefied petroleum gases (LPG), ethylene, propylene optionally mixed with methylacetylene, or mixtures of gases such as CRYLENE ™ (mixture comprising approximately 73% ethylene, 22% acetylene and 5% propylene), TETRENE ™ (MAPP type mixture containing approximately 39% methylacetylene and propadiene, 44% propylene and 17% of a mixture of butane, propane and their unsaturated derivatives); TETRENE ™ and CRYLENE ™ are marketed by the company L'AIR LIQUIDE.

In addition, mixtures of liquefied petroleum gas (G. P. L.), some of the constituents of which contain -OH radicals, are also used to feed an oxy-fuel flame. Mention may be made, for example, of the following combustible mixtures which are commercially available: FLAMEX ™, CHEMTANE II ™, HGX ™, OR EXCELLENE ™. However, the aforementioned sophisticated mixtures and the specific gases derived from hydrocarbons have relatively high costs, in particular of implementation, since they consume a lot of oxygen. In addition, they are often sensitive to cold and are conditioned under low pressure. Acetylene, although making it possible to obtain high cutting speeds with good qualities of cutting edges, is poorly adapted to cuts of large thicknesses and is sensitive to flashback.

Research aimed at improving the heating flame of an oxygen cutting process has led to the various gases above being mixed together and has made it possible to obtain gas mixtures having variable properties for the application considered.

As such, mention may be made of document EP-A-0313176 describing a flame plating process using a detonation gun using a combustible-oxidant gas mixture consisting of oxygen or nitrogen oxide , as an oxidizer, and a premix of acetylene and propylene, methane, ethylene, methylacetylene, propane, pentane, butadiene, butylene, butane, ethylene oxide, ethane, cyclopropane, propadiene and / or cyclobutane, as fuel.

In addition, document US-A-3982883 teaches a flame cutting process using a combustion gas consisting, on the one hand, of propane, butane, natural gas, acetylene and their mixtures and, on the other hand, a hydrocarbon additive, such as 1-pentene, cyclopentane, 1-octene ...

The document JP-A-61042592 describes, for its part, a gas mixture of combustion for welding, heating or cutting by fusion consisting of 20 to 70% of natural gas, 10 to 60% of hydrogen and 20 to 70% acetylene.

Furthermore, the document JP-A-50006003 teaches a liquid mixture for welding, heating or cutting metal consisting of 64 to 95% of methane and from 5 to 35% of ¹ ethylene.

Likewise, document JP-A-530065303 describes a gas mixture for fusion cutting containing methane, ethylene and liquefied petroleum gas (G. P. L.), for example propane or propylene.

In addition, document FR-A-2099217 relates to a combustible gas mixture intended for heating, melting, welding or cutting metals, containing 1 to 77% of methylacetylene and / or propadiene, methane, ethane, ethylene, propane and / or propylene.

In some cases, flame cutting is carried out by supplying the heating flame with natural gas, essentially formed of methane. Indeed, the use of natural gas for flame cutting has the advantage of using a gas whose cost is low, while making it possible to cut metallic elements over a wide range of thicknesses. However, it has been observed that natural gas only provides a low flame temperature, requires long preheating times and, moreover, leads to poor quality of the cutting edges.

The object of the present invention is therefore to propose a combustible mixture, in particular for flame cutting, which does not have the drawbacks of conventional gas mixtures, which makes it possible to replace the mixtures currently used, such as CRYLENE ™ and TETRENE ™, which leads to good performance, which is easy and safe to use and of reasonable cost.

The present invention therefore relates to a combustible gas mixture containing acetylene, propane and propylene, characterized in that the ratio Qp / Qa of the proportion (Qp) of propane and propylene to the proportion (Qa) of acetylene of said mixture is such that:

1.1 <Qp / Qa <4. Preferably, the Qp / Qa ratio is between

1.5 and 3 approximately, preferably between 1.9 and 2.6 approximately.

Advantageously, the combustible mixture according to

1 invention is a ternary mixture consisting of acetylene, propane and propylene and optionally containing impurities.

Preferably, the propane / propylene proportion is between 50:50 and 99: 1, preferably between 60:40 and 98: 2 preferably between 70:30 and 95: 5.

Depending on the case, the combustible mixture according to the invention may comprise at least one other compound chosen from nitrogen, oxygen, methane or another hydrocarbon and their mixtures.

Advantageously, the combustible mixture of the invention contains from 15% to 50% by volume of acetylene, the remainder being essentially propane and / or propylene, preferably from 20 to 45% of acetylene, preferably approximately 25% to 40% acetylene.

The fuel mixture according to the invention is preferably in gaseous form. According to another aspect, the invention also relates to a welding process chosen from flame cutting, drilling in full sheet metal, brazing, heating, heat treatment and flame treatment, in particular of granites and marbles, characterized in that it uses a combustible gas mixture according to the invention. In the context of the invention, the term “welding process” is understood to mean a process for working with materials requiring an addition of heat delivered by a torch.

Preferably, the pressure of the combustible mixture sent to the torch is between 0.1.10 ⁵ Pa and 5.10 ⁵ Pa, preferably between 0.5.10 ⁵ Pa and 2.5.10 ⁵ Pa.

Preferably, the flow rate of said combustible mixture is between 20 lh ^"1 to 2000 lh ^{" 1} , preferably 150 lh ^"1 to 1000 lh ^{" 1} . As for the pressure and the flow rate of heating oxygen, they are adjusted, in a known manner, according to the type of torch used and the desired consumption ratio.

According to yet another aspect, the invention relates to a process for manufacturing a combustible mixture containing propane, propylene and acetylene, characterized in that given proportions of acetylene, propane and of propylene, preferably mixed together, on the one hand, acetylene and, on the other hand, a propane / propylene premix, and in that one obtains a combustible mixture having the aforementioned Qp / Qa ratio .

Advantageously, the combustible mixture is produced directly at the site of use, for example, by means of a mixer comprising a flow meter measuring the flow of propane and / or propylene (Qp), controlling, from this measurement of Qp, a acetylene flow regulator (Qa) and also ensuring the maintenance and / or obtaining of the desired Qp / Qa value; the mixture thus obtained is then sent to a torch.

As detailed in the following examples, given by way of illustration, but not limiting of the invention, a combustible mixture according to the invention containing a proportion (Qa) of acetylene and a proportion (Qp) of propane and propylene such as Qp / Qa ratio is preferably equal to about 1.9 to 2.6, and containing at least 25% (by volume) of acetylene, the remainder being mainly propane and propylene, makes it possible to obtain, when it is used in an oxycut sheet process, results equivalent to those obtained with a TETRENE ™ type gases and significantly better than those obtained with propane alone.

In fact, if the combustible mixture according to the invention leads to a preheating time, before cutting the sheet by adding cutting oxygen, substantially identical to that obtained with TETRENE ™, it turns out that the cutting quality is , meanwhile, significantly better than that resulting from cutting with a heating flame supplied with TETRENE ™, thanks to the presence of acetylene in high proportion compared to propane and propylene, which acetylene probably increases the heat exchange. taking place at the bottom of the groove between the flame and the workpiece.

Examples

The following tests aim to determine the evolution of the priming time in full sheet metal for a cutting torch as a function of the proportion of acetylene in the fuel supply mixture; the remainder of the mixture being propane and propylene, and possibly common impurities.

In the context of these tests, the propane used contains a few% of propylene, typically about 1 to 5%, but, for the sake of simplification, we speak below only of propane while bearing in mind that it it is in fact a propane / propylene mixture, the proportion of propane being much higher in this case than that of propylene.

The tests were carried out with a torch fitted with a 10/10 "Mach 3S" cutting head. marketed by LA SOUDURE AUTOGENE FRANÇAISE.

In addition, the appropriate operating parameters are as follows: - test pieces: steel plates 100 mm x 100 mm and 20 mm thick, which are subjected to surface sanding beforehand;

- nature of the steel of the test pieces: type A42;

- cutting oxygen: purity of at least 99.9% (here oxygen marketed under the name LASAL 2003 ™ by the company L'AIR LIQUIDE, S. A.);

- cutting oxygen pressure: 5.10 ⁵ Pa;

- total flow of combustible gas (acetylene + propane mixture): 300 lh ^"1 ; - temperature of the test pieces: approximately 15 to 20 ° C;

- other conventional equipment: regulators, mixer, mass flow regulator (15 1 / h) for acetylene, mass flow meter (35 1 / h) for propane, adapters ... As mentioned above, the measurement on the priming time, that is to say the time necessary to bring the sheet to the cutting temperature (about 1,300 ° C.) from ambient temperature, the priming time being defined experimentally as being the time minimum heating which allowed to obtain a cutting initiation of the sheet during the supply of cutting oxygen.

In order to determine the priming time, a series of tests is in fact carried out, during which the test pieces are initially heated with the same gas mixture at room temperature for different periods of time.

Then, immediately after heating, each time cutting oxygen is supplied.

From there, the priming time is determined which is the minimum period of time which gave rise to a priming, that is to say at the beginning of combustion of the test piece in the oxygen jet.

The results obtained are recorded in Tables I to III below and in the attached single figure.

TABLE II Mixture C ₃ H ₈ + C ₂ H ₂ at the practical consumption ratio

% Debit Debit Debit A Report Time Gain

C2H2 C3H8 C2H2 02 Priming Qp / Qa time (1 / h) (1 / h) (1 / h) (sec.) ()

0 300 - 1,125 3.75 - 24 -

10,270 30 1,045 3.49 9 22 8.3

20 240 60 966 3.22 4 20 16.7

30 210 90 886 2.96 2.33 14 41.7

40 180 120 807 2.69 1.50 14 41.7

50 150 150 727 2.43 1 13 54.2

TABLE 11 Î Mixture C ₃ H ₈ to the stoichiometric consumption ratio

% Flow Flow Flow A Time Ratio Gain of C2H2 C3H8 C2H2 0 ₂ Priming Qp / Qa time (1 / h) (1 / h) (1 / h) (sec.) (%)

0 300 - 1 500 5 - 15 -

10,270 30 1,425 4.75 9 14 6.7

20 240 60 1 350 4.50 4 12 20

30 210 90 1 275 4.25 2.33 9 40

50 150 150 1 125 3.75 1 7 53.3 TABLE ini Mixture C ₃ H ₈ + C ₂ H ₂ with practical consumption ratio

% Debit Debit Debit A Report Time Gain

C2H2 C3H8 C2H2 02 Priming Qp / Qa time (1 / h) (1 / h) (1 / h) (sec.) (%)

0 300 - 1,125 3.75 - 37 -

10,270 30 1,045 3.49 9 32 13.5

20 240 60 966 3.22 4 30 18.9

30 210 90 886 2.96 2.33 26 29.7

40 180 120 807 2.69 1.5 24 35.1 The quantity A corresponds to the consumption ratio, that is to say the flow rate of heating oxygen reduced to the flow rate of fuel, and is determined as follows: A (mixture) =% A (propane) +% A (acetylene ) It follows that we then obtain: - for a practical consumption ratio: A (propane) = 3.75 A (acetylene) = 1.10

- for a stoichiometric consumption ratio: A (propane) = 5 A (acetylene) = 2.50.

In addition, it should be noted that, according to the tests in Tables I (curve PP in the figure) and II (curve PS), the cutting head is of the MACH 3S PROPANE type, whereas, according to the tests in Table III (curve TP on figure), the cutting head is of type MACH 3S TETRENE.

It is noted, in the light of Tables I to III, that the priming time is an inverse function of the acetylene content of the mixture. In particular, a time saving of 30 to 42% is obtained for a mixture composed of 70% propane and 30% acetylene, which increases with the content 10

in acetylene, up to 54% for a mixture of 50% acetylene.

More precisely, as it appears on the appended figure, one observes an inflection of the curve of priming time (in sec.) Compared to the quantity of acetylene (in%) in the combustible mixture from approximately 25 % ± 5% acetylene with a Qa / Qp of approximately equal to 2.3 ± 0.3.

This inflection is observed whatever the cutting head used (TP, PP and PS curves in the figure), but is more marked in the case of tests carried out with the MACH 3S PROPANE type cutting head with stoichiometric ratio (PS curve on figure and Table II).

Furthermore, it is observed that if the gain in priming time is significant when the concentration of the combustible mixture of acetylene (C ₂ H ₂ ) is increased, it increases even more when the convergence of the darts is increased by using heads different cutting: MACH 3S PROPANE or TETRENE type heads. However, this increase in the convergence of the darts is harmful for edge fusion and therefore for the quality of cut.

In addition, the presence of acetylene in the combustible mixture makes it possible to obtain a luminous flame and the morphology of the dart and the plume facilitates the adjustment of the consumption ratio of the torch compared to its use powered only by propane and propylene. .

In addition, acetylene added to propane and propylene increases the flame temperature and improves the quality of the cutting edges.

Conversely, while acetylene has a high deflagration speed, the present combustible mixture has a reduced deflagration speed thus requiring reduced precision of the torch settings. 11

In addition, while acetylene provides only a short flame length, the mixture of acetylene and propane and propylene makes it possible to obtain a flame having a longer length, which makes it possible to cut out elements of strong thickness.

Furthermore, the mixture of propane, propylene and acetylene with Qa / Qp ≥ 2.30 approximately and containing approximately 30% acetylene is advantageously usable in applications of welding, surface quenching, heating, shrinking or thermal spraying. Thus, this mixture is versatile and can be used for all of the applications implemented, for example, by a boilermaker or a metal carpenter. However, it should be noted that for acetylene percentages greater than 50%, the cost of mixing becomes too high and it is necessary to use specific torch nozzles, which tends to conclude ^" that the range 30% to 50 % acetylene is preferred It should be noted that tests aiming to compare the effect of propane N25 (purity of approximately 99.5%) with industrial propane (propane / propylene mixture 70/30) have not shown any notable differences in priming times; the purity of propane therefore a priori has little or no importance.

The combustible mixture according to the present invention is particularly well suited for use in an oxycutting process of metals, such as steels, in particular non-alloyed or low-alloyed steels, as defined in particular in the document AFNOR N ° FD CR 12187.1995. F; April 1996.

Claims

12 CLAIMS

1. Combustible gas mixture containing acetylene, propane and propylene, characterized in that the ratio Qp / Qa of the proportion (Qp) of propane and propylene to the proportion (Qa) of acetylene of said mixture is such that: 1.1 <Qp / Qa <4.

2. Combustible gas mixture according to claim 1, characterized in that the ratio Qp / Qa is between 1.5 and 3 approximately, preferably between 1.9 and 2.6 approximately.

3. Combustible gas mixture according to one of claims 1 to 2, characterized in that it consists of acetylene, propane and propylene.

4. Combustible gas mixture according to one of claims 1 to 3, characterized in that it contains from 15% to 50% by volume of acetylene, the remainder being propane and propylene, preferably about 20% to 45% acetylene, more preferably still from 25% to about 40% acetylene.

5. Combustible gas mixture according to one of claims 1 to 4, characterized in that the ratio of the proportion of propane to the proportion of propylene in the gas mixture is between 50:50 and 99: 1, preferably between 60 : 40 and 98: 2, preferably between 70:30 and 95: 5.

6. Welding method chosen from flame cutting, full sheet drilling, heating, heat treatment, brazing and flame treatment, in particular of granites and marbles, using a torch characterized in that it implements , in addition, a combustible gas mixture according to one of claims 1 to 5.

7. Use of a combustible gas mixture according to one of claims 1 to 5 in a process 13

oxycutting of steels, preferably non-alloyed or low-alloyed steels.

8. Method of manufacturing a combustible mixture containing propane, propylene and acetylene, characterized in that given proportions of acetylene, propane and propylene are mixed, preferably acetylene is mixed with a propane / propylene premix, and in that a combustible mixture having a Qp / Qa ratio according to one of claims 1 to 5 is obtained.

9. The manufacturing method according to claim 8, characterized in that the combustible mixture is produced on site of use.

10. The manufacturing method according to claim 9, characterized in that it is carried out in a mixer.