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Lead chamber process


The lead chamber process was an industrial method used to produce sulfuric acid in large quantities. It has been largely supplanted by the contact process.

In 1746 in Birmingham, England, John Roebuck began producing sulfuric acid in lead-lined chambers, which were stronger, were less expensive, and could be made much larger than the glass containers which had been used previously. This allowed the effective industrialization of sulfuric acid production and, with several refinements, this process remained the standard method of production for almost two centuries. So robust was the process that as late as 1946, the chamber process still accounted for 25% of sulfuric acid manufactured.

Sulfur dioxide is introduced with steam and nitrogen oxide into large chambers lined with sheet lead where the gases are sprayed down with water and chamber acid. The sulfur dioxide and nitrogen dioxide dissolve and over a period of approximately 30 minutes the sulfur dioxide is oxidized to sulfuric acid. The presence of nitrogen dioxide is necessary for the reaction to proceed at a reasonable rate. The process is highly exothermic, and a major consideration of the design of the chambers was to provide a way to dissipate the heat formed in the reactions.

Early plants used very large lead-lined wooden rectangular chambers (Faulding box chambers) that were cooled by ambient air. The internal lead sheathing served to contain the corrosive sulfuric acid and to render the wooden chambers waterproof. Around the turn of the nineteenth century, such plants required about half a cubic meter of volume to process the sulfur dioxide equivalent of a kilogram of burned sulfur. In the mid-19th century, French chemist Gay-Lussac redesigned the chambers as stoneware packed masonry cylinders. In the 20th century, plants using Mills-Packard chambers supplanted the earlier designs. These chambers were tall tapered cylinders that were externally cooled by water flowing down the outside surface of the chamber.


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