How does the Bolzano process differ from the Pidgeon process?

The primary difference between the Pidgeon process and the Bolzano process lies in their methods of supplying heat to the thermal reduction of calcined dolomite and ferrosilicon.1

• Pidgeon Process: This method utilizes cylindrical nickel-chromium-steel retorts placed horizontally within an oil- or gas-fired furnace. The heat is applied externally to the retorts, which operate at 1,200 °C under a vacuum of 13 pascals.1
• Bolzano Process: In this approach, the briquettes are stacked on a specialized charge support system. Heat is supplied internally via electric heating conducted directly to the charge. The reaction occurs at 1,200 °C under a vacuum of less than 400 pascals and typically requires 20 to 24 hours to complete.1

Both processes are forms of thermal reduction used to extract magnesium, differing fundamentally in their engineering design for heat transfer and reactor configuration.1