IDEAL OPERATIONAL PARAMETERS OF TIN SMELTING FURNACES

IDEAL OPERATIONAL PARAMETERS OF TIN SMELTING FURNACES - J₁ FACTOR

L. R. Jaccard

ANTECEDENTS

We verified that the C₃ equations ( I = C₃ . P^2/3 and V = P^1/3 / C₃ ), commonly used to define the submerged arc ideal parameters, are wrong.

Based on theoretical principles, confirmed by experiences made in cassiterite reduction furnaces, we concluded that, for a determined electrode spacing, the voltage that promotes the electrode ideal position is a function of the electrodes diameter and the active power: V = J₀ . D / P^1/4, where D is the electrode diameter, P is the active power and J₀ is a factor dependent of the processed material and electrode space.

It was also suggested that, inside a certain range, the ideal voltage is proportional to the electrode spacing square root: V = J₁ . D . S^1/2 / P^1/4, in which S is the electrode spacing and J₁ is a factor proportional to the resistivity of the processed material ( J₁ = V . P^1/4 / D . S^1/2 ).

APPLICATION OF FACTOR J₁ TO TIN SMELTING ( CASSITERITE ) FURNACES

During 2005 and 2006 we conducted tests in tin smelting furnaces, varying the active powers between the limits of 400 kW and 1000 kW, changing electrode diameters and sizes. For each operational set of parameters it was verified the energy consumption and the productivity. Also, the factors C₃, J₀ and J₁ were calculated. The experiences showed that the factor C₃ equations did not match with reality.

We concluded that for cassiterite reduction furnaces the factor J₁ is equal to 0,607, using the following unities:

V ( Volts )

P ( 1 phase, Watts )

D ( cm )

S ( cm )

Practical application of J₁ for cassiterite furnaces

For the case of a furnace with certain electrode diameter and space, assuming operation with certain active power:

The ideal voltage between electrode and hearth is: V = 0,607 . D . S^1/2 / P^1/4

The ideal current is: I = P / V

The unload voltage V₀ at the transformer secondary is: V₀ = V / cos phi.

Cos phi can be calculated knowing the circuit reactance X and the load resistance R, being tan phi = X / R.

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