Smelting early technology

As of this writing (ca 1994) none of the newer lead smelting technologies has been adopted in the United States. Also, no new lead mine has opened in the United States since the early 1980s. Most of the known U.S. reserves for lead are located in federally owned land in Missouri future mine development depends on the outcome of the U.S. government s intent to reform the Mining Law of 1872. 

The smelting process seems to have been independently discovered in the Middle East, China, and Southeast Asia. The chronological sequence in which the different metals were brought into use was probably determined by the difficulty in winning them from their ores. Copper, for example, which melts at just above 1000°C, a temperature within reach in a vented wood or charcoal fire, was separated from its ores quite early. Iron, which melts at above 1500°C, a temperature that for a long period of human technological development was out of reach, was first produced at a much later time. 

It seems that making arsenical copper was characteristic of a transitional stage of technological development, the alloy apparently first replacing pure copper and then eventually being supplanted by bronze. It is possible that during the early Bronze Age it was realized that the use of arsenic-rich copper ores, or the incorporation of arsenic ores into copper ores smelting... 

Among the technologies in existence by ca 4000 bc, which included the manufacture of synthetic lapis lazuli, the development of the first true pottery kilns must rate as a significant achievement (1). For polychrome pottery to be successfully manufactured, it was essential to separate the fire (fuel) from the work (clay pottery). The excavations performed in the near east (Mesopotamia in antiquity) indicate that these early kilns were probably of beehive construction. Subsequent Egyptian pottery kilns of the period ca 3000 BC were the familiar chimney shape. With the smelting of copper in pit hearths predating by perhaps a millenium millennium the start of the Bronze Age at ca 3000 BC, another important advance was the invention of the bellows at ca 2000 BC. Bellows supply combustion air where it is needed and are used as a means of raising furnace temperature. 

Zinc oxide is a very old technological material. Already in the Bronze Age it was produced as a byproduct of copper ore smelting and used for healing of wounds. Early in history it was also used for the production of brass (Cu-Zn alloy). This was the major application of ZnO for many centuries before metallic zinc replaced the oxide [149]. With the start of the industrial age in the middle of the nineteenth century, ZnO was used in white paints (chinese white), in rubber for the activation of the vulcanization process and in porcelain enamels. In the following a number of existing and emerging electronic applications of ZnO are briefly described. 

Our knowledge of the early chemical technologies is inevitably scanty. Some evidence is provided by the archaeologist. Sometimes an excavation may reveal the actual location at which pottery was made or a metal was smelted, but more often evidence of these processes is provided by the end-products that are unearthed. Chemical technologies had been practised for thousands of years before any written accounts were produced that have survived. The Roman writers Vitruvius (fl, first century BC) and Pliny the Elder (AD 23-79) describe many contemporary processes, but we believe that some of these had been carried out virtually unchanged for a very long time. 

The QSL process has significant advantages over sinter plant-blast furnace technologies. It is a single step smelting process, is well contained with low emissions and can accept a wide range of feed materials. It does not require dry feed as with the Kivcet process however, in its early stages it did not prove to be as robust or as flexible as the Kivcet process, particularly with attempts to use natural gas for reduction and in its ability to handle quantities of zinc plant residues. 

Some major developments in lead smelting technology have occurred in the last thirty years, with the pace of change accelerating since the mid-1980s, primarily in response to intensifying environmental pressures. Until the early 1960s, fundamental techniques of primary lead production... 

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