Tight furnace operation is a manifestation of abnormal furnace conditions during the blast furnace ironmaking process. If the difficult furnace condition cannot be eliminated in time, it will turn into hanging material due to the expansion of the blocked area of the furnace material (see hanging material and sitting material).

Symptoms of difficult furnace conditions are that the furnace charge slows down until it is close to stagnation or stagnates for a short period of time; the wind pressure rises and the air volume drops, and the two do not correspond, and the air permeability index drops significantly; the furnace top temperature rises and the temperature curve narrows .

The treatment method is to reduce the air volume (such as 5% to 10% or more) as appropriate, so that the pressure difference is lower than the normal value and the air volume corresponds to the wind pressure; if the furnace temperature is sufficient, the air temperature can be reduced (such as 50 to 100°C). Adopt an advanced charging system and reduce the load accordingly; strengthen the work in front of the furnace to remove clean slag and iron.