New Reasons for Installing a Chloride By-Pass. Interaction Between Chloride and Sulphur

The growing use of alternative fuels and raw materials are increasing the input of chloride to many kiln systems. Too high chloride is influencing economy in clinker production by causing kiln stoppages, corrosion, and uneven clinker quality. The effects of chloride are strongly influenced by the sulphur load in the kiln. This paper presents a modelling of the chloride circulation in the kiln and how this is influenced by the sulphur load, deduced from simple thermodynamic considerations, and supported by statistical treatment of data collected from more than 50 modern kiln systems. A new reason for installing a by-pass is introduced: The use of the by-pass to counteract SO₂ emissions caused by pyrite containing raw materials is documented. Simple calculation rules are presented showing the basic differences in design of small (1- 3%) and large (>10%) by-passes. Differences in chloride sensitivity between pre-heater and pre-calciner kilns are explained and illustrated. Finally some modern by-pass designs are presented.