The aim of the research project was to investigate the process of sorbent injection into the exhaust gas pipe of rotary cement kilns to reduce mercury loads. Whilst the process has proven to be effective in other industries, e.g. the power plant industry, no scientifically proven findings are available as yet for the cement industry. Individual tests with sorbents reveal some promising approaches, however generally applicable statements regarding how they will work under the specific exhaust gas conditions of rotary cement kilns and optimum operating conditions cannot be derived from these.
The research project was investigating the extent to which the different types of mercury bond, the alkaline atmosphere and high dust loading influence the effectiveness of possible additives such as activated charcoal, open-hearth coke or other calcium compounds and mixtures of these. The part of the exhaust gas pipe (temperature, required retention time) into which such sorbents have to be injected and the quantity required to achieve an optimum abatement rate with minimum use of sorbent are also still unknown. The effects which dusts doped with sorbents could have on product quality if used as so far in cement grinding likewise remain to be clarified. The cement industry must continue to satisfy the high quality requirements of the product. For this reason, consideration is to be given to the possible effects of residue-free, environmentally compatible utilisation of the dust occurring in the product. This is intended to permit assessment of the extent to which and the conditions under which sorbent-supported dust removal could be an ecologically and economically viable option for reducing mercury loads in the cement industry.