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Oxy-acetylene kits are heavy and expensive; oxy-propane is rather cheaper, but doesn't get so hot.
But for the small scale user, having a cylinder of oxygen around can be burdensome, and propane/air doesn't get very hot - certainly not hot enough to weld.
A low-rate oxygen generator/concentrator
provides oxygen, but at too low a pressure for serious welding.
Thus, behold the BorgCo electrolytic/mechanical oxygen concentrator.
The device consists of a high pressure electrolysis cell containing water and an electrolyte. Applying a DC voltage derived from mains power pressurizes one half of the cell with hydrogen and the other with oxygen.
The pure oxygen is led away to the primary collector reservoir through a pressure regulator.
The hydrogen is tapped off, mixed with atmospheric air, and fed to a small 4-stroke single cylinder internal combustion engine, where it is burned. The mechanical energy drives an oil-free compressor which transfers oxygen from the initial oxygen collection reservoir into the main oxygen reservoir, and also drives an injector pump which pumps more distilled water into the electrolysis cell as required..
This system generates high pressure pure oxygen on demand, and recovers energy from the otherwise "waste" hydrogen stream.
No cryogenic separation/distillation of air is required; the equipment operates at ambient temperature.
Unlike PSA systems, the output pressure can be arbitrarily high, depending on the compressor and the integrity of the secondary reservoir.
Startup time from cold is short compared to other such systems.
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As an alternative, consider feeding the hydrogen to a small fuel cell, and use it to generate more electricity to make more oxygen. |
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Obviously if that were done, the O2 compressor and the feedwater pump would be powered by electrical motors, instead of a hydrogen internal combustion engine, resulting in a simpler, more reliable setup, which would start up from cold just as quickly as your idea. |
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Of course, this being the HB, simpler might not be better... do halfbakers prefer internal combustion engines or fuel cells? |
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The entropic losses through the fuel cell/motor/compressor system would be higher (electric motors aren't that efficient) than from the mechanical system, which is direct thermo-mechanical. Fuel cells tend to use expensive noble metals or rare earths, and they poison easily. |
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IC engines have a better power to weight ratio than most equivalent electric motors. |
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IC engines are a simple, well understood and rugged technology. Adding extra electronics would probably decrease ruggedness and reliability. |
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1) Electrolysis cells can operate at high temperature and pressure; I seem to recall that it can even make them more efficient. The feed water would have to be pressurised, of course, but if you were happy to have a reservoir that is filled with the unit turned off, there might be no need for a pump at all. |
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2) Why not use an oxy-hydrogen torch? |
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Partly because "Water Welders" have been Baked, but mostly because the high calorific value of Propane makes for superior cutting, although not so good for welding. |
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