Thermal Refining

Marchandise H, Vandendriessche S (1985) The Certification of the Impurity Contents (Ag, As, Bi, Cd, Ni, Sb, Se, Sn, Te, T1 and Zn) in Three Grades of Lead, Electrolytically Refined Lead BCR No 286, Thermally Refined Lead BCR No 287, Lead with Added Impurities BCR No 288. European Commission Report EUR 9665 EN. Community Bmeau of Reference, Brussels. Merry f (1995) Reference materials for monitoring nutrients in sea water environment, approach, preparation, certification and their use in environmental laboratories. Fresenius J Anal Chem 352 148-151. 

The quality of tar sand bitumen is low compared to that of conventional crude oil and heavy oil. The high carbon residue of bitumen dictates that considerable amounts of coke will be produced during thermal refining (Table 3). 

Thermal refining of the crudes consists of two basic operations i.e. atmospheric and subsequent vacuum distillation. The boiling range of the atmospheric distillates extends to approximately 370 °C and yields the fractions ... 

Chapter 12-Thermal Refining of Primary Lead Bullion.197... 

Details of thermal refining practices are covered in Chapter 12 and electrolytic refining in Chapter 13. 

Removal of impurities or refining is mainly carried out by thermal refining methods, which are commonly conducted by batch processing in open pots or kettles . Impurities are generally removed individually or in groups in a series of steps. The usual refining steps are made in the following order ... 

Figure 12.1 illustrates a generalised flow sheet of the thermal refining sequence. 

The alternative approach for lead refining is the electrolytic refining process, which is covered in Chapter 13, but this must be preceded by copper removal and usually by some softening. It also requires a final caustic refining stage and is not a full replacement of thermal refining. 

The silver dore is separated and refined following the same procedures outlined in Chapter 12 for thermal refining. 

The bismuth-rich slags from the converter operation and from dord cupellation can be reduced in a short rotary furnace with coal and some sulfur addition to give a bismuth-lead alloy and a copper matte. The bismuth-lead alloy can be refined by a similar sequence as used for the thermal refining of lead, as follows ... 

The production of lead metal can be divided into two broad areas - the basic smelting operation to produce a crude lead bullion, and the refining operation. Since the sinter plant-blast furnace method of smelting coupled with thermal refining has been the workhorse of the industry they are examined in greater detail herein as a benchmark for other processes. 

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