Thermodynamic calculations have shown that chlorine can accumulate and cycle in the shaft of the blast furnace in the form of alkalis chlorides. Cycling of chlorine and alkalis in the upper part of the shaft was simulated at laboratory scale with a countercurrent reduction furnace (BORIS furnace) and also directly investigated at an industrial blast furnace. Experiments and calculations have shown the superposition of two cycles: one “pure” alkalis cycle in a large temperature domain, and a KCl cycle in a narrower range (600-1,000°C). According to the trials, effects of KCl on reduction and disintegration behaviour of sinter are similar to those of “pure” alkalis.