Paul David (metalúrgico)

Paul David (full name Marie Paul Eugène David; January 29, 1842 – June 26, 1923; also known as Paul David du Jonquier), This appearance of nobility refers to a small hamlet.</ref> was a French metallurgical engineer who, in 1880 with his employer Pierre Manhès, adapted the principle of the Bessemer converter to copper pyrometallurgy, thus inventing the Manhès–David process. He continued optimizing his converter throughout his career, and it was widely adopted in the United States.

Biography

Little is known about his personal life beyond his birth in Nîmes in 1842, his marriage to Marguerite Jacobé de Haut de Sigy in Paris on November 7, 1877 (with whom he had four children), and his death in Lyon at the age of 81.

Invention of the Manhès–David Process

Process Improvement

The 1855 invention of the Bessemer converter sparked great interest among metallurgists. However, its limitations became apparent, and it was not until 1877 that Sidney Thomas perfected it for steel production. Almost immediately, metallurgists considered applying it to copper smelting:

> The similarities between the two processes are substantial. Just as in a blast furnace iron ore is reduced to pig iron, copper ore by simple fusion becomes a sulphide of copper, iron, and sulphur. In both operations, gangue is separated and similar intermediate products are obtained. Through air injection, silicon, manganese, and carbon are removed in the Bessemer process; likewise, sulphur and iron—both more oxidizable than copper—are removed from copper matte. > However, treating copper matte poses far greater challenges than pig iron, which contains only 9–10 % oxidizable elements by weight. Matte usually contains only about 20 % copper, so 80 % of the material must be oxidized. Iron, silicon, and carbon generate significant heat upon combustion; sulphur and iron yield only 2200 and 1500 calories per kilogram, respectively.

British metallurgist John M. Hollway’s 1878 experiments failed due to intermittent air flow, rapid refractory wear, tuyere clogging, premature solidification, and lengthy operation times compared to steel processes. Although Hollway managed to convert “bronze matte” to “white matte,” he could not advance further.

When Pierre Manhès began trials at his Vedène works, he encountered the same tuyere clogging by dense copper that solidified at the converter’s bottom. Manhès patented additives whose oxidation released sufficient heat to prevent blockages. Finally, in 1880, engineer Paul David proposed horizontally mounted tuyeres positioned just above the converter’s bottom, keeping copper below them and ensuring constant air contact with the matte. Trials in 1880–1881 confirmed this eliminated clogging.

For low-copper mattes, the process required draining the converter after iron oxidation and then refining the “white matte” in a second stage. In 1883–1884, Manhès and David introduced a cylindrical converter, allowing adjustable tuyere immersion by aligning all nozzles along the cylinder’s generatrix—another decisive improvement.

The invention was credited equally to both:

> From the standpoint of inventing the apparatus for air injection into copper mattes, it is clear that Mr. Manhès’ name should be associated with Mr. Paul David’s.

Invention of the Selector

As developed, the Manhès–David process removes elements more oxidizable than copper. For gold recovery:

> The earlier Welsh process included a “selection” variant: forming a copper-rich “bottom” at the operation’s start that concentrates foreign metals and gold, yielding a small mass of impure, gold-rich copper and a large mass of copper stripped of gold and many impurities.

While managing the Société des Brasses de France works near Avignon, Paul David independently designed a spherical converter with tuyeres inclined along a hyperboloid to induce bath rotation. Its pivot axis was tilted about 30° so the nozzle stayed outside the support frame, preventing spills. A small side chamber (“selector”) collected the copper-rich bottom by rotating the converter.

Although successfully used at Éguilles, the selector arrived after the rise of electrolytic refining—now the standard for 99.95 % pure copper. American works preferred large, basic-lined horizontal converters coupled with electrolysis. Nevertheless, the selector presaged the side tap hole now ubiquitous in modern steel converters.

The Jonquier Castle

Around 1899, Paul David began building a neo-medieval castle in Saint-Étienne-des-Sorts, Gard. Construction on a rocky promontory above the Rhône Valley was so challenging that, after the owner refused to sell adjacent land, materials were lifted in a suspended tub on a cable supported by pylons—an engineering feat of its time.

See Also

• Manhès–David process
• History of copper production
• Pierre Manhès