Question

Explain manufacturing of Acetylene using Calcium carbide as a raw material. 

Answer 1

Acetylene from CaC2

Raw materials: lime stone, coke, water

Chemical reactions:

CaO + 3C CaC2 + CO

CaC2 + H2O Ca(OH)2 + CH≡CH

Process Description:

Calcium carbide is produced by heating lime and coke in an electric furnace at 2100 ˚C . Molten CaC2 is solidified and cooled and ground under nitrogen In the wet process the pulverized carbide is fed through a gas tight hopper to a C2H2 generator in which the quality of water used is sufficient to discharge Ca(OH)2. The carbide is fed to water at a measured rate until exhausted. Calcium hydroxide slurry containing 90% water is discharged. The gas is passes through a scrubber to remove impurities like NH3, sulphides, phosgene and finally through a purifier containing iron oxide and alumina or silica gel. The temperature in the gas generator is kept below 90˚C and a pressure of 2 atm. In a dry process equal weights of the quantities H2O and CaC2 are used in the generator to eliminate waste disposal problem of lime slurry. The heat of reaction is largely dissipated by water vaporization leaving by product lime in dry state. The dry process is more dangerous because of the temperature control in the generator. Acetylene polymerizes at 250˚C and above and decomposes violently at 650˚C . Hence temperature is maintained below 150˚C and 30 cm of water pressure.