Cement is produced in three main steps: grinding of a mixture of raw materials, sintering of the raw meal to form clinker, and grinding and mixing of clinker, gypsum and additives to make cement. Slag from steel manufacturing can be used to replace some of the raw material, but since slag is a carrier of some unwanted compounds, problems arise. Excess sulphur circulating in the system during clinker production can cause various problems such as clogging. In this report, the circulation of sulphur and other volatile compounds as well as the composition of gaseous and solid materials in the cyclone tower has been studied using old data from 2014 and new measurements. No sulphuric gases were found in the cyclones, so it was concluded that most of the sulphur condenses at the bypass at the inlet to the cyclone closest to the kiln. Condensation is assumed to occur early in the pre-heating tower because of air leaking in. Sulphur balances from 2014 and 2020 showed that usage of slag increases the amount of sulphur that circulates in the system and that the critical amount has been exceeded as of the measurements taken 2020. It is recommended that further measurements are performed, such as qualitative analysis of the solid material to distinguish the different sulphuric compounds, as well as more experiments with varied parameters such as the amount of slag and kiln fuel used.