Method and apparatus for the autogenous processing of metals with an odorized fuel gas

Abstract

A method for the autogenous processing of metals, in which a fuel gas, in particular hydrogen, is taken from a fuel gas source and combined with an oxidizing agent on an autogenous processing tool and reacted therewith, is characterized according to the invention in that the fuel gas is mixed with a parent gas mixture in the flow path between the fuel gas source and the processing tool in order to form a fuel gas mixture, said parent gas mixture being formed from a carrier gas consisting of fuel gas and / or hydrocarbon as well as an odorant.

Description

[0001] Method and apparatus for the autogenous machining of metals with an odorized fuel gas

[0002] The invention relates to a method for the autogenous machining of metals using an odorized fuel gas, in which a fuel gas is taken from a gas supply system, mixed with an odorant, and the odorized fuel gas is combined with an oxidizing agent at an autogenous machining tool and reacted with it. The invention further relates to a corresponding apparatus.

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

[0004] Instead of carbon-based fuel gases, hydrogen, which has been used as a fuel gas in oxy-fuel technology for over 100 years, offers an alternative. Hydrogen is now used in both industrial and manual oxy-fuel cutting processes. However, the use of hydrogen in oxy-fuel technology is not without its problems, as its diffusion properties mean that hydrogen can easily escape into the environment through even the smallest leaks in improperly installed or frequently used lines or fittings, such as hose connections or rotating seals. This creates the risk of a flammable mixture forming in the vicinity of the work area over time. This risk is further exacerbated by the fact that hydrogen is a completely odorless gas, meaning that its leakage is not easily noticed by the user.

[0005] From a safety perspective, it would therefore be advisable to label odorless fuel gases, especially hydrogen, with an odorant when used in oxy-fuel technology, as has long been the practice with gases supplied by public gases, such as natural gas. These gases are treated with an odorant, for example, organic sulfur compounds like thioethers or mercaptans, to make the gases detectable in the event of leaks. Suitable odorants for this purpose are described, for example, in DVGW (German Technical and Scientific Association for Gas and Water) worksheet G 280, "Gas Odorization," ISSN 0176-3490.

[0006] It is already known from DE 197 45 851 A1 to add an odorant to the fuel gas acetylene used for autogenous machining.

[0007] WO 90 / 06170 A1 discloses the odorization of oxygen used for welding or cutting with an odorant, for example dimethyl sulfite. The odorized oxygen is produced by first mixing the odorant with a non-flammable gas, for example carbon dioxide, in a pressure vessel to form a mother mixture, which is then introduced into the gaseous oxygen.

[0008] A major challenge in oxy-fuel welding is the correct dosage of the odorant. Especially in manual applications, the concentration must not be too high to avoid health risks to the user from odorants, some of which are classified as carcinogenic. Furthermore, odorants can be corrosive to pipes and fittings, shortening their lifespan and / or causing leaks. Conversely, the concentration must not be too low to ensure the user can reliably detect the gas mixture. Therefore, the odorant must be added reliably at a low concentration within a narrow tolerance range. Commercially available odorization systems inject a small amount of odorant into the gas to be odorized at regular intervals using a metering pump.A minimum flow rate is required for reliable operation. This is often not the case with small-scale consumers, such as those using bundled torches in oxy-fuel technology. As a result, the required tolerance range for the mixture composition cannot always be reliably maintained.

[0009] The object of the present invention is therefore to provide a method for the autogenous processing of metals with an odorized fuel gas, in which the user is reliably warned by olfactory means and at the same time the risk to the user or plant technology from an excessively high or low concentration of odorant is largely excluded.

[0010] This problem is solved by a method with the features of claim 1 and by a device with the features of claim 8. Advantageous embodiments of the invention are claimed in the dependent claims.

[0011] A method according to the invention of the type and purpose mentioned at the outset is therefore characterized in that the odorant is contained in a mother gas mixture which, in addition to the odorant, contains a carrier gas consisting of hydrocarbon and / or fuel gas and which is supplied upstream to the processing tool with the fuel gas taken from the gas supply system and mixed with it to form a fuel gas mixture.

[0012] For the purposes of this definition, "hydrocarbon" means a liquid or gaseous hydrocarbon or a mixture of such hydrocarbons.

[0013] The term "gas supply system" here refers to a system consisting of one or more pressure vessels, such as compressed gas cylinders, cylinder bundles, or pressure tanks, in which the fuel gas is stored, and in which the pressure vessel(s) is / are equipped with a gas extraction port. A pressure reducing valve is preferably connected to the gas extraction port, reducing the fuel gas pressure from the filling pressure of the pressure vessel(s) to a pressure suitable for the intended autogenous machining process.

[0014] The term "machining tool" here refers to any standard tool used for oxy-fuel machining, such as an oxy-fuel cutting machine, a flame spraying device, a gouging device, or an oxy-fuel welding machine.

[0015] The term "fuel gas" refers to the gas stored in the gas supply system, which is reacted with the oxidizing agent in the machining tool.

[0016] The term "fuel gas mixture" shall be understood to mean the gas mixture after the mixing of the parent gas mixture and the fuel gas, in which the fuel gas is present as the main component preferably at least 80 vol.%, preferably at least 90 vol.%, and particularly preferably at least 95 vol.%.

[0017] The fuel gas in the fuel gas mixture originates predominantly from the gas supply system; however, a portion of it may also be a component of the carrier gas. In this case, the carrier gas contains the same fuel gas stored in the gas supply system, for example, hydrogen. Alternatively, or as a further option, the carrier gas consists of a highly flammable hydrocarbon. Therefore, the carrier gas always consists of a highly flammable gas or gas mixture and thus does not impair the fuel properties of the fuel gas used.

[0018] Especially when using hydrogen as a fuel gas, the presence of a hydrocarbon component in the carrier gas is preferable, as it improves flame visibility. Examples of hydrocarbons used in the carrier gas include methane, ethane, ethene, propane, propene, butane, acetylene, or mixtures of two or more of these gases. Preferably, the carrier gas consists of or contains ethene or propane, or a mixture of ethene and propane. Mixtures of hydrogen with ethene and / or propane are very stable and can easily be stored in pressure vessels for extended periods. The carrier gas is usually gaseous, but can also be liquid, for example, in the case of propane stored under pressure.

[0019] To produce the mother gas mixture, the carrier gas is mixed with a small amount, for example between 10 ppm (v / v) and 10000 ppm (v / v), of an odorant.

[0020] Hydrogen is used as the preferred fuel gas. For the purposes of this invention, "hydrogen" is understood to mean a gas with a hydrogen content of at least 99.5% by volume, preferably at least 99.99% by volume. Another oxygen-containing gas is preferably used as the oxidizing agent. A gas with an oxygen content of over 99% by volume is preferred, and particularly preferably with an oxygen content of over 99.9% by volume.

[0021] After mixing with the fuel gas, the supplied mother gas mixture preferably has a volume fraction of 0.1% to 20% in the fuel gas mixture.

[0022] The odorant preferably has a volume fraction of between 100 ppb and 50 ppm, preferably between 1 ppm and 25 ppm, and particularly preferably between 5 ppm and 15 ppm, in the fuel gas mixture after mixing the parent gas mixture with the fuel gas. The volume fraction of the odorant in the finished fuel gas mixture should be above 100 ppb (0.1 ppm) to ensure reliable olfactory detection of the fuel gas mixture even under unfavorable flow conditions in the ambient atmosphere, but should not exceed 50 ppm if there is a risk of people coming into direct contact with the fuel gas mixture escaping from a leak.This comparatively small amount of odorant ensures that the fuel gas mixture remains easily detectable due to its noticeable odor, while simultaneously posing no health risk to the user, having no or negligible corrosion effects on the system, and decomposing odorlessly during the autogenous combustion process. In a particularly preferred embodiment of the invention, the parent gas mixture has a composition such that the fuel gas mixture contains a hydrocarbon volume fraction of between 0.1% and 20%, preferably between 1% and 10%, and most preferably between 1% and 5% or between 1% and 3%. A volume fraction of less than 5% is preferred. The preferred fuel gas in this fuel gas mixture is hydrogen.

[0023] Preferably the carrier gas contains ethene and / or propane or consists of ethene and / or propane; in this case, the fuel gas mixture contains, in addition to the fuel gas, preferably hydrogen, and the odorant, only ethene or propane as a hydrocarbon component with a volume fraction of, for example, between 1% and 10%.

[0024] A sulfur-containing odorant, such as THT (tetrahydrothiophene), TBM (2-methyl-2-propanethiol, tert-butyl mercaptan), or DMS (N,N-dimethylsulfamide), is used as the preferred odorant in the mother gas mixture according to the invention. However, sulfur-free odorants can also be used according to the invention.

[0025] The object of the invention is also solved by a device with the features of claim 8.

[0026] An apparatus for the autogenous machining of metals using an odorized fuel gas comprises an autogenous machining tool which is connected via a fuel gas line to a gas supply system for supplying the machining tool with fuel gas and via an oxidant line to a source of an oxidant, wherein the fuel gas line is equipped with an odorizing insert for odorizing the fuel gas. The apparatus is characterized according to the invention in that the odorizing insert is equipped with a container for storing a mother gas mixture and a gas supply line connected to the container and opening into the fuel gas line, wherein the container is filled with a mother gas mixture consisting of a carrier gas comprising fuel gas and / or hydrocarbons and an odorizing agent.A small pressure vessel with a volume of, for example, between 0.51 and 51 liters or a gas cartridge, preferably refillable or available as an exchange bottle in the odorization application, is preferably used as a container for the mother gas mixture.

[0027] The mother gas mixture is preferably the mother gas mixture described above, with a proportion of between 10 ppm (v / v) and 10000 ppm (v / v) of an odorant, for example THT, TBM or DMS, in a carrier gas which is formed from a fuel gas, for example hydrogen, and / or a hydrocarbon, for example ethene and / or propane.

[0028] The mother gas mixture is preferably supplied under an overpressure in the container relative to the pressure in the fuel gas line, either via a continuously operating mixer or a metering unit, in the form of successive doses at regular intervals. In the latter case, diluting the odorant in the mother gas mixture allows for very rapid cycle times and thus comparatively stable odorant concentrations in the fuel gas mixture. In the case of a liquid carrier gas, such as propane, a metering pump can also be used.

[0029] To monitor the concentration of the odorant in the fuel gas mixture, an advantageous embodiment of the invention provides that a device for detecting gas flow is / are arranged in the gas supply line and / or in the fuel gas line. This device is / are operatively connected to a control device, for example, an electronically operated control unit, and to a valve for controlling the volume flow of the mother gas mixture through the gas supply line. With this arrangement, the ratio of the volume flows of fuel gas and / or mother gas mixture can be regulated so that a predetermined target range for the volume fraction of the odorant contained in the fuel gas mixture can be reliably maintained. To achieve rapid and thorough mixing of the fuel gas and mother gas mixture, a mixer, for example, a static mixer, is preferably arranged at the junction of the gas supply line and the fuel gas line.

[0030] A further advantageous embodiment of the device according to the invention provides that the odorizing insert can be detachably connected to the fuel gas line and is designed as a mobile unit. If necessary, the odorizing device can therefore be detached and connected to a different gas supply system.

[0031] The inventive method and device make it possible to ensure a predetermined volume fraction of the odorant with comparatively little effort within a narrow tolerance range of, for example, ±10%. They are suitable for all known oxy-fuel machining processes, such as oxy-fuel welding, flame cutting, flame shearing, or gouging.

[0032] Furthermore, according to the invention, all materials commonly machinable by oxyfuel technology can be processed, in particular unalloyed or low-alloy steels or aluminum alloys. The inventive method is particularly suitable for flame cutting of unalloyed or low-alloy steels, especially those with a sheet thickness of over 10 mm.

[0033] An embodiment of the invention will be explained in more detail with reference to the drawing. The single drawing (Fig. 1) schematically shows a device according to the invention.

[0034] The device 1 comprises a gas supply system in the form of a pressurized gas cylinder 2 for storing a fuel gas, for example, hydrogen, which is equipped in the usual manner with a shut-off valve 3. Instead of a pressurized gas cylinder 2, other containers can also be used, for example, a bundle of pressurized gas cylinders, an arrangement of several bundles of pressurized gas cylinders, or a pressure tank. A pressure reducing valve 4 is connected to the shut-off valve 3 in a known manner. This valve reduces the pressure of the fuel gas from the filling pressure of the pressurized gas cylinder 2, for example, 200 bar or 300 bar, to a working pressure of, for example, 3 bar to 5 bar, which can be set on a regulator 5.The pressure-reduced fuel gas is supplied via a fuel gas line 6 to an oxy-fuel processing tool 7, in the embodiment shown here an oxy-fuel welding torch, where it is reacted with an oxidizing agent, for example pure oxygen, in a manner known per se. The oxidizing agent is supplied to the processing tool 7 from an oxidation source (not shown here) via an oxidizing agent supply line 8.

[0035] Downstream of the pressure reducing valve 4, i.e., on its low-pressure side, an odorizing insert 10 is arranged in the fuel gas line 6. The odorizing insert

[0036] 10 has a pipe section 11 with an inlet connection 12 for detachable connection to the pressure reducing valve 4 and an outlet connection 13 for connecting a downstream section of the fuel gas line 6. In the pipe section

[0037] A static mixer 14 is arranged in section 11, to which a gas supply line 15 opens into the pipe section 11. The gas supply line 15 is connected to a pressure vessel 16, for example a gas cartridge, in which an odorized mother gas mixture is stored. The pressure vessel 16 is preferably detachably connected to the gas supply line 15 and can be replaced with another pressure vessel of the same type if necessary, for example after emptying. A flow meter 17 and a flow valve 18 are also arranged in the gas supply line 15. Another flow meter 19 is located on the pipe section 11, upstream of the inlet of the gas supply line 11. The flow meters 17, 19 and the flow valve 18 are in data communication with an electronic control unit 20.For easier handling of the odorizing insert 10, the fittings 17, 18, 19, 20 and the pressure vessel 16 are arranged in a housing 21 - which is only indicated here by a dashed line.

[0038] In the operation of the device 1, the pressure vessel 16 is filled with a mother gas mixture of a predetermined composition, which consists, for example, of hydrocarbons, such as ethene and / or propane, and a small proportion, e.g., 1000 ppm, of an odorant. Fuel gas (the same fuel gas as that stored in the pressure gas container 2) can also be used instead of or in addition to the hydrocarbon. After the shut-off valve 3 is opened, fuel gas flows from the pressure gas container 2 via the pressure reducing valve 4, the line section 11 of the odorant insert 10, and the fuel gas line 6 to the processing tool 7. Simultaneously, an oxidizer, for example, oxygen, is supplied via the oxidizer supply line 8. The fuel gas and oxidizer are reacted at a burner nozzle 22 of the processing tool 7, whereby a flame (not shown here) forms in front of the nozzle opening.

[0039] To odorize the fuel gas supplied to the machining tool 7, the mother gas mixture is drawn from the pressure vessel 16 and fed into the fuel gas via the gas supply line 15, where it mixes thoroughly with the fuel gas in the mixer 14 to form a fuel gas mixture. The odorant decomposes odorlessly in the flame in front of the burner nozzle 22. The proportion of the odorant in the fuel gas mixture can be very precisely adjusted via the flow valve 18, depending on the volume flows of the fuel gas and mother gas mixture measured at the flow meters 17, 19. The concentration of the odorant in the fuel gas mixture should not exceed 50 ppm (v / v) to prevent any health risks to the user from the odorant.

[0040] The odorization reliably warns the user of any leaks that may be present in the fuel gas line 6 or in any fittings connected therein downstream of the odorization insert 10.

[0041] List of reference signs

[0042] 1 Device

[0043] 2 pressurized gas containers

[0044] 3 shut-off valves

[0045] 4 Pressure reducing valve

[0046] 5 regulators

[0047] 6 Fuel gas line

[0048] 7 Machining tool

[0049] 8 Oxidizing agent supply

[0050] 9

[0051] 10 Odorizing Use

[0052] 11 cable section

[0053] 12 Input connection

[0054] 13 Output port

[0055] 14 mixers

[0056] 15 Gas supply line

[0057] 16 pressure vessels

[0058] 17 flow meters

[0059] 18 Flow valve

[0060] 19 flow meters

[0061] 20 Control unit

[0062] 21 cases

[0063] 22 Burner nozzle

Claims

Patent claims 1. A method for the autogenous machining of metals using an odorized fuel gas, in which a fuel gas is taken from a gas supply system, mixed with an odorizing agent, and the odorized fuel gas is combined with an oxidizing agent at an autogenous machining tool (7) and reacted with it, characterized in that the odorizing agent is contained in a mother gas mixture which, in addition to the odorizing agent, contains a carrier gas consisting of hydrocarbons and / or fuel gas and which is supplied to the fuel gas, fluidically between the gas supply system and the machining tool (7), and mixed with it to form a fuel gas mixture.

2. Method according to claim 1, characterized in that hydrogen is used as the fuel gas.

3. Method according to claim 1 or 2 characterized in that the supplied mother gas mixture has a volume fraction of 0.1% to 20% in the fuel gas mixture.

4. Method according to one of the preceding claims, characterized in that the fuel gas mixture, after addition of the mother gas mixture, has a volume fraction of between 100 ppb and 50 ppm, preferably between 1 ppm and 25 ppm, particularly preferably between 5 ppm and 15 ppm, of odorant.

5. Method according to one of the preceding claims, characterized in that the fuel gas mixture, after addition of the mother gas mixture, has a volume fraction of carbon between 0.1% and 20%, preferably between 1% and 10%, particularly preferably between 1% and 5%.

6. Method according to one of the preceding claims, characterized in that the carrier gas contains ethene and / or propane or consists of ethene and / or propane.

7. Method according to one of the preceding claims, characterized in that a sulfur-containing odorant, for example a thiol or a mercaptan, is used as the odorant.

8. Device for the autogenous machining of metals using an odorized fuel gas, comprising an autogenous machining tool (7) which is connected via a fuel gas line (6) to a gas supply system for supplying the machining tool (7) with a fuel gas and via an oxidant line (8) to a source of an oxidant, and in which the fuel gas line (6) is equipped with an odorizing insert (10) for odorizing the fuel gas, characterized in that the odorizing insert (10) is equipped with a container (16) for storing a mother gas mixture and a gas supply line (15) connected to the container (16) and opening into the fuel gas line (6), and the container (16) is filled with a mother gas mixture consisting of a carrier gas consisting of hydrocarbons and / or fuel gas and an odorizing agent.

9. Device according to claim 8, characterized in that a device (17, 19) for detecting a gas flow through the gas supply line (15) and / or through the fuel gas line (6) is / are arranged in the gas supply line (15) and / or in the fuel gas line (6), which is / are operatively connected with a control device (20) and with a valve (18) for controlling the volume flow of the mother gas mixture through the gas supply line (15).

10. Device according to claim 8 or 9, characterized in that a mixer (14) is provided at the junction of the gas supply line (15) with the fuel gas line (6).

11. Device according to one of claims 8 to 10, characterized in that the odorizing insert (10) is detachably connected to the fuel gas line (6) and is designed as a mobile unit.

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