Sodium chloride
The process is conducted in a Mannheim furnace, a large cast iron kiln. Sodium chloride and sulfuric acid are first fed onto a stationary reaction plate where an initial reaction takes place. The stationary plate is up to in diameter. Rotating rabble arms constantly turn over the mixture and move the intermediate product to a lower plate. The kiln portion of the furnace is constructed with bricks that have high resistance to direct flame, temperature, and acid. The other parts of the furnace are heat and acid resistant. Hot flue gas passes up over the plates carrying out liberated hydrogen chloride gas. The intermediate product reacts with more sodium chloride in the lower, hotter section of the kiln producing sodium sulfate. This exits the furnace and passes through cooling drums before being milled, screened and sent to product storage facilities.