Discovered in 1836 by Edmund Davy, acetylene gas is important in the making of numerous organic chemicals. The gas is combustible, colorless with garlic-like odor. On being liquefied, compressed, heated or mixed with air, the gas has a tendency to turn volatile and explosive. Obviously, handling of the gas requires expert handling to avoid fires and explosions. Apart from being used for making organic compounds, acetylene is also used as fuel gas in oxy-acetylene welding and metal cutting.
In fact, it is known as one of the most efficient fuel gases. The gas used for making 1, 4-butanediol which is an essential ingredient in the making polyurethane and polyester plastics. It finds application in the making of acetylenic alcohols and dry cell batteries as well. A German company developed a process in 1920s for making acetylene from natural gas and petroleum-based hydrocarbons. The process is still used in the making of the gas. Calcium carbide is another compound used for making acetylene.
Raw materials used in the making of acetylene gas
Represented by chemical symbols, C2 H2, acetylene gas is a hydrocarbon which is made up of two carbon atoms and two hydrogen atoms. There are numerous processes available for commercial production of acetylene using different raw materials. The most common process uses calcium carbide and water as raw materials for making of the fuel gas.
Natural gas is also used as a raw material which is mainly methane. Petroleum-based processes use crude oil and naphtha. However, making of acetylene using hydrocarbons require high temperature to turn the raw material into different gases like acetylene, carbon dioxide, carbon monoxide, hydrogen, etc. Chemical reaction for extracting acetylene from methane is written as 2CH4→ C 2 H 2 + 3 H 2. Acetylene is separated by dissolving it in acetone, water, methanol, or numerous other solvents available based on the process used in the manufacturing of acetylene gas.
Chemical reaction process
There are many processes for making of acetylene such as thermal cracking and chemical reaction. For our purposes, we will confine our discussion to chemical reaction process, being most commonly used for generation of acetylene gas. Chemical reaction process for generation acetylene gas involves reacting calcium carbide with water generating acetylene and a lot of heat, which needs to be moderated to stop the fuel gas from exploding.
Wet process for acetylene production involves either adding calcium carbide to water or water being added to calcium carbide. Dry process is also used where limited water utilized that evaporates with absorption of heat. However, we will limit our discussion to the wet process where calcium carbide is added to water for extracting acetylene and cooling of heat generated during the reaction.
Chemical reaction process description
Acetylene generator with a rotating conveyor is used for depositing calcium carbide granules into the reaction chamber, where water is added according to the requirements of the reaction. Granule size of 2 mm x 6 mm is used for the reaction to take place. Feed rate is used as per the chosen flow rate of gas which can be controlled from the chamber.
Mixture of calcium carbide and water is constantly stirred rotating paddles for getting a comprehensive reaction. It also stops granules from rising to the top and getting overheated risking ignition of acetylene.
Acetylene gas rises to the surface from where it is collected under low pressure. As the gas moves out of the reaction chamber, it is cooled with water. Reaction chamber is added with more water as new calcium carbide is added for continuation of the reaction. Subsequently, the gas is moved through a flash arrester for avoiding accidental fires.
On reacting calcium carbide with water, there forms slurry of calcium carbonate which drops to the bottom of the chamber. It is necessary to stop the reaction intermittently to clear slurry, which is moved out of the chamber and pumped into a holding pond where it separates into calcium carbonate and water, which is removed. Then, the calcium carbonate is dried and collected for sale. It has numerous applications including as an acid neutralizer, road construction, etc.