Electrothermal furnace

ELECTROTHERMAL (FURNACE) ATOMIC ABSORPTION, ARGON INDUCTION COUPLED PLASMA, AND PLASMA ATOMIC FLUORESCENCE... 

At first, batchwise horizontal retorts were used for smelting, and later continuous vertical retorts, both externally fired. Continuous, internally heated furnaces such as the electrothermic furnace followed, and the last important development was the Imperal Smelting blast furnace. 

The Weaton-Najarian zinc condenser was commercialized in 1936. The condenser and cooling well of the electrothermic furnace hold 48 t of molten zinc. Hot zinc-laden gases bubble through the zinc in the condenser and cause rapid circulation through the cooling well which is kept at 480—500°C by water coils. The off-gases are scmbbed and burned for fuel value. Scmbber water is ponded to recover blue powder. 

A highly advanced continuous electrothermal furnace process was developed by The Superior Graphite Company for production of Desulco, Commercial operation was first begun in 1977 at Hopkinsville, Kentucky, Plants with total capacity ol 0,000 metric tons are in operation in the U.S. and Europe. 

Achieving the required degree of desulfurization dictated electrothermal heating. Fixed-bed electrothermal furnaces of the Acheson type were initially considered for use directly with granular coke but the test results were disappointing. The product of the Acheson furnace was not uniform in its sulfur content. Adaptation of the Acheson Process, which is a batch process, presented problems in materials handling that were considered very difficult to resolve at the 10,000 tons per year capacity determined to be the... 

The most widely used process employs a short electrothermal furnace. Electrical energy is supplied via electrodes, which causes the lime and carbon to react, forming molten calcium carbide, which then acts as a reaction medium. An alternative process uses a shaft furnace, which is charged with a mixture of lime and coke/anthracite [31.4]. The temperatures required for the reaction to proceed are generated by the partial combustion of the carbonaceous matter in oxygen, or oxygen-enriched air. The residual carbonaceous matter then reacts with the lime to produce calcium carbide. 

Most of the quicklime used is in the size range 6 to 50 mm to provide the necessary voidage for the gases produced in the reaction to escape. However, modern electrothermal furnaces have hollow electrodes through which fine material (less than 6 mm) can be blown. This enables less expensive fine fractions of coke and quicklime (including any recycled lime) to be introduced. Up to 25 % of the charge to the furnace may be added in this way. 

The atomizer is the sample cell of the AAS system. The atomizer must produce the ground state free gas phase atoms necessary for the AAS process to occur. The analyte atoms are generally present in the sample as salts, molecular compounds, or complexes. The atomizer must convert these species to the reduced, free gas phase atomic state. The atomizer generally does this via thermal energy and some chemistry. The two most common atomizers are flame atomizers and electrothermal (furnace) atomizers. 

The determinations of gold are made by an atomic absorption spectrophotometer (Zeeman 5000, Perkin-Elmer) equipped with an electrothermal furnace atomizer (HGA-400) and with Zeeman effect background corrector. The operating conditions and the atomizer program for the spectrometer are listed in Table 3. 

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