Fuel gas mixture for oxy-fuel processing of metals

Abstract

A fuel gas mixture for oxy-fuel processing of metals consists of 0.01 vol.-% to 1 vol.% acetylene, 0 to 20 vol.-% ethane and / or methane, remainder hydrogen. The fuel gas mixture is characterized by high stability and good visibility of the primary flame, is suitable for all types of oxy-fuel metal processing techniques and is preferably provided in the form of a mixture ready for use.

Description

[0001] Fuel gas mixture for the autogenous processing of metals

[0002] The invention relates to a fuel gas mixture for the autogenous processing of metals. The invention further relates to a method for the autogenous processing of metals using this fuel gas mixture.

[0003] For the autogenous processing of metals, such as flame cutting, flame straightening, gouging or oxyacetylene welding, hydrocarbon-based fuel gases such as propane, acetylene, propene, ethylene, etc. are currently predominantly used, as described, for example, in DE 2 823 305 A1 or EP 0 812 898 A2. Due to the carbon dioxide emissions produced during the combustion of these gases, these very fuel gases and fuel gas mixtures will be subject to a CO2 tax in the near future through legislation that is already being prepared. Regardless of the cost aspect, the avoidance of climate-damaging carbon dioxide and other emissions, such as carbon monoxide or microparticles (carbon), which are produced as reaction products of combustion, is of great importance for increasing occupational safety and environmental protection.

[0004] A key aspect of using hydrocarbon-based fuel gases is the highly visible primary flame. This is where any multiple bonds are broken and carbon is burned to form carbon monoxide, resulting in a clear visual perception of the primary flame. This also allows the practitioner to determine the respective mixture ratio of fuel gas to oxygen based on the geometry and shape of the primary flame. Depending on the application and material, different mixture ratios are advantageous. These can range from an excess of oxygen to "neutral" (stoichiometric ratio) to an excess of fuel gas. These can be easily visually monitored and, if necessary, readjusted by an experienced practitioner.

[0005] Instead of carbon-based fuel gases, hydrogen, which has been used as a fuel gas in oxyfuel technology for over 100 years, offers an environmentally friendly alternative. In oxyfuel technology, the use of

[0006] REPLACEMENT SHEET (RULE 26) Hydrogen, however, has the disadvantage that when it burns with oxygen, no visible primary flame is formed. Instead, it burns with oxygen in a bluish, transparent flame that is almost invisible, especially in brighter surroundings. The poor visibility of the flame makes it difficult or even impossible to accurately align the primary flame cone, as well as to maintain a defined distance between the flame cone(s) and the surface of a workpiece being machined. Furthermore, the above-described control of setting an optimum fuel gas-oxygen mixture for the respective task is difficult or even impossible to carry out visually. For these reasons, the satisfactory use of pure hydrogen as a fuel gas for manual work is only possible in exceptional cases. In automated operation, suitable control technology using flow meters or the like could be used.However, this requires additional equipment, which in turn increases the susceptibility to errors.

[0007] To increase the visibility of the flame, EP 0 952 205 A1 proposes a combustion gas mixture consisting of two gases, which contains acetylene in addition to hydrogen or natural gas. In the case of hydrogen, the acetylene content in the gas mixture is between 1 and 10%.

[0008] JP 61083292 A describes a ternary combustion gas mixture of 10-50 mol% natural gas, 5-70 mol% hydrogen and 20-85 mol% acetylene, which is said to have almost the same heat energy as acetylene and at the same time forms a clearly visible primary flame cone during combustion.

[0009] Such gas mixtures, which contain a comparatively high proportion of acetylene, cannot easily be filled as a ready-mix and stored for extended periods due to the instability of acetylene. For this reason, they are generally only mixed together immediately before use, for example in a gas mixer. Accordingly, the individual gases must be provided separately at the site of use, requiring complex mixing equipment that must be operated with great care. The associated logistical and equipment costs make the use of such gas mixtures uneconomical in many cases. The object of the present invention is therefore to provide a hydrogen-containing gas mixture with the option of primary flame adjustment, which can be provided on-site as a ready-mix without additional mixing technology and stored in containers such as compressed gas cylinders or compressed gas cylinder bundles.

[0010] This object is achieved with a fuel gas according to patent claim 1 and by a method having the features of claim 5. Advantageous embodiments of the invention are claimed in the subclaims.

[0011] The fuel gas mixture according to the invention is a gas mixture consisting of a proportion of 0 to 20 vol.% ethene (C2H4) and / or methane (CH4), 0.01 vol.% to 1 vol.% acetylene (C2H2), the remainder hydrogen.

[0012] The actual fuel gas for autogenous processing is the hydrogen predominantly contained in the fuel gas mixture according to the invention. Acetylene and, if present, ethene, when combined with oxygen as oxidants, support the formation of a clearly visible primary flame in the hydrogen matrix and thus allow, in particular, visual monitoring of a set ratio of fuel gas to oxygen before or during autogenous processing. Acetylene has excellent properties for primary flame formation, but due to its low partial pressure and tendency to spontaneous decomposition, it can only be added in very small amounts (up to 1 vol.%). Ethene also promotes the formation of a clearly visible primary flame when combined with oxygen and is therefore the preferred third component alongside hydrogen and acetylene in a ternary mixture.The optionally included portion of ethene and / or methane also stabilizes the fuel gas mixture and prevents the spontaneous decomposition of the acetylene in the container. Methane has a similar effect to ethene, but does not provide as strong a primary flame improvement. However, it particularly promotes the stabilization of the mixture. The fuel gas according to the invention is therefore comparatively stable and can be stored in containers, preferably in compressed gas cylinders or compressed gas cylinder bundles, for extended periods. The fuel gas mixture according to the invention is particularly user-friendly. The parameters important for autogenous processing, such as flame temperature, ignition speed, or flame power, are not affected, or only slightly affected, or even positively affected by the gases added to the hydrogen, since they are themselves highly combustible gases.The aforementioned disadvantages of using pure hydrogen as a fuel gas can thus be overcome. The fuel gas mixture according to the invention achieves similar performance characteristics to those achieved with pure acetylene as the fuel gas, particularly with regard to an adjustable flame pattern with primary flame formation. Furthermore, the fuel gas mixture according to the invention meets stringent safety requirements due to its low acetylene content and is comparatively low in emissions due to its high hydrogen content of at least 79 vol.%.

[0013] The acetylene content in the fuel gas mixture according to the invention is preferably, for example, between 0.01 vol.% and 1 vol.%, between 0.01 vol.% and 0.5 vol.%, between 0.1 and 0.5 vol.%, or between 0.1 and 0.3 vol.% acetylene. Other preferred acetylene content in the fuel gas mixture according to the invention is between 0.1 vol.% and 0.99 vol.%, between 0.2 vol.% and 0.9 vol.%, or between 0.5 vol.% and 0.8 vol.%.

[0014] Furthermore, the fuel gas mixture according to the invention can contain a proportion of - in total - less than 20 vol.%, preferably between 5 vol.% and 20 vol.%, of ethene and / or methane, wherein the ratio of methane to ethene can be chosen as desired; for example, the mixture contains between 0 and 20 vol.%, between 10 vol.% and 20 vol.% or between 15 vol.% and 20 vol.% ethene, and between 0 and 20 vol.%, between 0 and 10 vol.% or between 0 and 5 vol.% methane.

[0015] Preferably, it is a binary gas mixture of hydrogen and acetylene with the preferred acetylene proportions specified above, or a ternary gas mixture of hydrogen, acetylene, and one of the gases ethene or methane. The object of the invention is also achieved by a process having the features of patent claim 7.

[0016] According to the method according to the invention, the fuel gas mixture according to the invention is used as a fuel gas in a known method for the autogenous machining of a workpiece. A stream of a fuel gas mixture according to the invention and a stream of an oxidizing agent are fed to an autogenous machining tool, which may be, for example, an oxyacetylene cutting machine, a flame spraying device, a gouging device, or an oxyacetylene welding device.

[0017] The fuel gas mixture and the oxidizing agent are brought together in the machining tool or in front of a nozzle opening of the machining tool and caused to react with each other, whereby a flame used for the autogenous machining of a workpiece is generated in front of the nozzle opening of the machining tool.

[0018] By using a fuel gas mixture according to the invention (as described above) as fuel gas in the autogenous machining of a workpiece, a clearly visible primary flame is generated, which in particular allows the setting of a desired ratio of fuel gas mixture and oxidant to be visually controlled before or during the autogenous machining in order to be able to work with an excess of oxidant, an excess of fuel gas or a stoichiometric ratio if necessary.

[0019] An oxygen-containing gas is preferably used as the oxidizing agent. A gas with an oxygen content of more than 99 vol.% is preferred, and a gas with an oxygen content of more than 99.9 vol.% is particularly preferred.

[0020] In order to reduce the logistical effort for a user in particular, the fuel gas mixture according to the invention is expediently provided as a ready-mixed mixture in a preferably transportable container, for example a compressed gas cylinder or a compressed gas cylinder bundle, from which it is removed during the autogenous machining of the workpiece and fed to the machining tool.

[0021] The fuel gas mixture according to the invention is suitable for all types of autogenous metal processing, such as, in particular, autogenous flame cutting, flame spraying, gouging, or welding. It is particularly suitable for manual autogenous processing.

[0022] The fuel gas mixture according to the invention can be used to process all workpieces and materials that can usually be processed using oxyacetylene technology, in particular unalloyed or low-alloyed steels or aluminum materials. The method according to the invention is particularly suitable for flame cutting unalloyed or low-alloyed steels, especially those with a sheet thickness of over 10 mm.

Claims

Patent claims 1. Fuel gas mixture for the autogenous processing of metals, consisting of a proportion of between 0 and 20 vol.% ethene and / or methane, 0.01 vol.% to 1 vol.% acetylene, the remainder hydrogen.

2. Fuel gas mixture according to claim 1, characterized in that the proportion of acetylene is between 0.01 vol.% and 0.5 vol.%, preferably between 0.1 and 0.5 vol.%, particularly preferably between 0.1 and 0.3 vol.%.

3. Fuel gas mixture according to claim 1, characterized in that the proportion of acetylene is between 0.1 and 0.99 vol.%, preferably between 0.2 and 0.9 vol.%, particularly preferably between 0.5 and 0.8 vol.%.

4. Fuel gas mixture according to claim 1 or 2, characterized in that the proportion of ethene is between 0 and 20 vol.%, preferably between 10 vol.% and 20 vol.%, particularly preferably between 15 vol.% and 20 vol.% and the proportion of methane is between 0 and 20 vol.%, preferably between 0 and 10 vol.%, particularly preferably between 0 and 5 vol.%.

5. Fuel gas mixture according to one of the preceding claims, characterized in that the proportion of ethene and methane is between 5 vol.% and 20 vol.% in total.

6. Fuel gas mixture according to one of the preceding claims, characterized by the formation as a ternary mixture consisting of hydrogen, acetylene and one of the gases ethene or methane.

7. A process for the autogenous machining of metals, in which a fuel gas and an oxidizing agent are brought together in or on an autogenous machining tool and reacted with each other, wherein a flame used for the autogenous machining of a workpiece is generated at an orifice of the machining tool, characterized in that a fuel gas mixture according to one of the preceding claims is used as the fuel gas.

8. Method according to claim 7, characterized in that the fuel gas mixture is provided as a ready mixture.

9. Method according to claim 7 or 8, characterized in that the autogenous machining of the workpiece consists in welding, flame cutting, flame straightening or gouging.

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