Method for controlling the suspension in a suspension smelting furnace, a suspension smelting furnace, and a concentrate burner

A suspension smelting furnace for suspension smelting of pulverous solid matter, wherein the suspension smelting furnace comprises

• a reaction shaft having a top and a lower end,
• a concentrate burner that comprises a pulverous solid matter supply device for feeding pulverous solid matter and that comprises a gas supply device for feeding reaction gas into the reaction shaft to produce a suspension of pulverous solid matter and reaction gas in the reaction shaft, wherein the concentrate burner is located at the top of the reaction shaft,
• a lower furnace for collecting suspension in the lower furnace to form a melt having a surface, wherein the lower end of the reaction shaft ends in the lower furnace and wherein, when the suspension smelting furnace is in use, suspension that is produced in the reaction shaft and that lands on the surface of the melt in the lower furnace is configured to create a collection zone at the surface of the melt in the lower furnace, and
• a reducing agent feeding means for feeding additionally to pulverous solid matter and additionally to reaction gas reducing agent into the suspension smelting furnace,
• wherein the reducing agent feeding means is configured for feeding, when the suspension smelting furnace is in use, reducing agent in the form of a concentrated stream of reducing agent through the suspension that is produced in the reaction shaft onto the surface of the melt in the lower furnace to form a reducing zone containing reducing agent in the collection zone of the melt in the lower furnace,
• wherein the reducing agent feeding means is configured to feed reducing agent at an initial velocity that is at least the feeding velocity of the reaction gas,
• wherein the concentrate burner being configured to feed pulverous solid matter and reaction gas into the reaction shaft so that suspension produced by pulverous solid matter and reaction gas forms a suspension jet in the suspension shaft, wherein the suspension jet widens in the reaction shaft in the direction of the lower furnace and wherein the suspension jet has an imaginary vertical central axis, and
• wherein the reducing agent feeding means being configured to feed the concentrated stream of reducing agent essentially in the direction of the imaginary vertical central axis of the suspension jet and in the vicinity to the imaginary vertical central axis of the suspension jet to prevent reducing agent of the concentrated stream of reducing agent from reacting with reaction gas prior landing on the surface of the melt.