What is Acetylene Gas?
Acetylene is one of the most popular gases used as fuel in oxy-fuel cutting and welding processes, but what exactly is acetylene? It is known for its volatility and high flame temperature, but where do these qualities come from? To understand the traits that make acetylene a useful fuel and chemical building block in the production of other hydrocarbons, it is important to study the structure and behavior of acetylene gas.
Almost all the signature of characteristics of acetylene can be attributed to its unique chemical structure. Acetylene has the chemical formula C2H2 and is the simplest hydrocarbon in the family of alkynes.
Also, there is a triple bond between the two carbon atoms which is important because it stores a substantial amount of potential energy but is also inherently unstable. Due to its unique structure, acetylene is extremely flammable and burns with the hottest flame of all the common oxy-fuel gases, about 3,100 degrees C in O2. Conversely, the instability of the gas means that it must be stored and handled with extreme care to prevent an accident.
Challenges of Storing and Transporting Acetylene
In order to store and ship acetylene safely, producers dissolve it in liquid acetone and put it in thick-walled tanks filled with a porous material.
This is necessary because acetylene itself is too explosive to be sold as a liquid. Consequently, because of the explosive potential of acetylene, the regulator pressure is limited to 15 psi. Furthermore, acetylene forms dangerously explosive chemicals when it reacts with copper, silver, and mercury. Therefore, copper alloys must contain less than 65% Cu to be welded or cut with an oxyacetylene torch.
Uses of Acetylene Gas
Acetylene is noted in the welding industry for its ability to cut thin metals quickly and efficiently with little distortion.
However, outside of the welding industry, acetylene is used as a building block to create other chemicals. Aside from combustion, the most important chemical reaction of acetylene is its conversion to ethylene which is the precursor to polyethylene, a common type of plastic. Additionally, acetylene is used by chemists to produce a number of chemicals for industrial use including benzene, various vinyl compounds, and more.
Acetylene Safety Concerns
The primary safety concern with acetylene is its instability and flammability. Even a shock from static electrify is enough to ignite acetylene gas, so it is paramount that acetylene tanks be stored outdoors, away from electrical and heat sources. Like the other common fuel gases, acetylene gas is not toxic if inhaled but can displace oxygen in confined spaces. Luckily, commercial acetylene gas carries a pungent odor because of the presence of impurities such as hydrogen sulphide so it is easy to detect an unsafe concentration.
Acetylene is the smallest alkyne that packs a big punch when burned in oxygen to weld and cut metal. Although it is unstable and more expensive than propane or propylene, for many jobs, only acetylene will do.
