Principles of Pidgeon Metallurgy and Arts and Crafts
The Pidgeon method to produce metal magnesium is based on calcined dolomite as raw material, ferrosilicon as reducing agent, and fluorite as catalyst, and the dosage is carried out. After grinding, it is pressed into balls, called pellets. Put the pellets into a reduction tank, heat to 1200°C, and evacuate the interior to 13.3Pa or higher, then generate magnesium vapor. Magnesium vapor forms crystalline magnesium, also known as crude magnesium, in the condenser at the front end of the reduction tank. Then it is refined by flux to produce commercial magnesium ingots, that is, refined magnesium.
The main chemical reaction formula of Pidgeon metallurgy is:
(1) Dolomite is fired in a rotary kiln or shaft kiln:
(2) Reduction reaction in the reduction tank
Magnesium production process by Pidgeon process
(1) Dolomite calcination: Dolomite is heated to 1100-1200°C in a rotary kiln or a shaft kiln, and calcined into calcined white (MgOCaO).
(2) Batching and making balls: Calcined white, ferrosilicon powder and fluorite powder are measured, batched, ground, and then pressed into balls.
(3) Reduction: Heat the pellets in a reduction tank to 1200+10°C, and keep it for 8-10 hours under a vacuum condition of 13.3 Pa or higher. Magnesium oxide will be reduced to magnesium vapor, which will become crude magnesium after condensation.
(4) Refining ingot casting: heating and melting crude magnesium, refining it with a solvent at a high temperature of about 710°C, and casting it into magnesium ingots, also known as refined magnesium.
(5) Pickling: Clean the surface of magnesium ingots with sulfuric acid or nitric acid to remove surface inclusions and make the surface beautiful.
(6) Gas workshop: convert raw coal into gas and use it as fuel. Magnesium plants that directly use raw coal do not have gas-making workshops.