Pernot furnace

A Pernot furnace is a reverberatory melting vessel with a circular hearth that rotates beneath a stationary arched roof. The furnace body is cylindrical, typically 4 to 6 meters in diameter, with the rotating hearth mounted on a central vertical axis. Fuel burned in side arches or ports above the hearth radiates heat downward onto the charge; the slowly turning hearth ensures even heating of the metal and helps homogenize the melt.

The rotating hearth serves several practical purposes. It brings different portions of the charge into the hottest zones repeatedly, which accelerates melting and reduces temperature gradients. The rotation also aids in stirring the molten steel gently, promoting dissolution of oxides and improving metal quality. Scrap steel, pig iron, and other charge materials benefit from this passive mixing action without requiring mechanical stirring.

Variants and operational scope

Pernot furnaces were built in various sizes for small to medium steel production, from laboratory scales up to industrial works. Some designs incorporated tilting mechanisms alongside rotation, allowing controlled pouring without stopping the hearth. Variants differed in fuel type (coke, gas, oil) and in the positioning of burners or combustion chambers relative to the main vessel. The furnace fell from favor in the late twentieth century as electric arc furnaces and basic oxygen processes became dominant.

The furnace is named after its inventor, a French metallurgist, and gained adoption primarily in European steel mills during the late 1800s and early 1900s. It represented a practical middle ground between stationary reverberatory furnaces and fully mechanical stirring systems. Pernot furnaces were valued for their fuel efficiency and for producing consistent steel quality with minimal technical intervention during the melt cycle.

Maintenance challenges included refractory lining wear on the rotating hearth and bearing corrosion from heat and spillage. The rotating mechanism itself required skilled fitting to keep the hearth centered and running true. By the mid-twentieth century, the design had become labor-intensive relative to newer technologies, though some furnaces remained in service for specialty melting work in smaller foundries.