Why does increasing the furnace height increase the reaction time in blast furnace ironmaking?

The reason why the height of blast furnace increases the reaction time is that increasing the height of blast furnace can improve the conversion rate of CO, so the reaction time can be increased according to relevant public information. Blast furnace ironmaking is the continuous production of liquid pig iron in vertical reactor blast furnace by using coke, iron-bearing ore (natural rich lump ore, sinter and pellets) and flux (limestone and dolomite).