1. The need for purification

Dust is entrained to a greater or lesser extent by the gas, depending on its density, grain size and gas velocity. The amount of dust carried off therefore varies according to blast furnace operating conditions and material quality. It is usually in the range of 8 to 15 kg of dust per tonne of cast iron, which corresponds, roughly speaking, to a concentration of 5 to 10 g / Nm ³ of gas (volume measured under normal conditions of temperature, 0°C, and pressure, 1.013 x 10 ⁵ Pa).

The gas, which contains carbon monoxide and hydrogen, has a low calorific value (3,000 kJ / Nm ³ ) but represents a significant fraction ("30%) of the appliance's heat balance. This gas is therefore recovered for use as fuel, which presupposes sufficient...