Acetylene gas, renowned for its ease of production, transportation, and ability to reach exceptionally high temperatures (around 5,000°F) during combustion, is a staple in gas welding. However, acetylene poses inherent risks due to its highly unstable and flammable nature. In the presence of elevated pressure and oxygen, it can explosively decompose. Therefore, storing acetylene gas under pressure in conventional cylinders is inherently dangerous.
To address this hazard, acetylene used for welding is stored in cylinders containing liquid acetone absorbed in a porous material, such as firebrick. This ingenious solution serves several crucial purposes:
Elimination of Free Space: By filling the cylinder with the acetone-saturated porous material, there is no void space left for free acetylene gas to accumulate. This prevents the formation of high-pressure pockets that could trigger explosive decomposition.
Cooling Mechanism: In the event of thermal decomposition, the acetone and porous material act as a heat sink, absorbing and dissipating the heat generated. This cooling effect further inhibits the escalation of decomposition reactions and reduces the risk of explosion.
Stabilization: Acetylene dissolved in acetone is no longer in direct contact with oxygen, effectively preventing its decomposition. Acetone is chosen for this purpose due to its ability to dissolve large quantities of acetylene under pressure without altering the gas’s chemical properties.
In summary, the use of acetone-saturated porous material in acetylene cylinders is a critical safety measure. By eliminating free space, providing a cooling mechanism, and stabilizing the acetylene gas, this approach significantly reduces the risk of explosions, making acetylene a safer and more reliable fuel source for welding applications.