INTRODUCTION
Many plants have installed a system to reduce the circulating chlorine volatiles from a clinker producing preheater type kiln system by way of extracting a small percentage of the kiln inlet dust-laden gas. The hot gases are quenched to solidify chlorine compounds onto the lime dust. The bypass dust is then available for extraction from the gas using a filter. The system thus generates an exhaust gas similar to that of the kiln and a stream of high chlorine content dust. Some plants in the USA have installed larger kiln gas bypass systems for the purposes of reducing sulphur volatiles with a view to producing low-alkali cement. In these cases the amount of dust extracted is considerable relative to the raw materials fed to the kiln system inlet.