Together with the Institute of Non-Metallic Materials of the Clausthal University of Technology and the Chair of Environmental Process Engineering and Plant Design at the University of Duisburg-Essen, VDZ has recently started a research project to investigate the potential for the maximum recovery of electrical energy from cement clinker production.
The core concept of the research project is to generate the maximum amount of electrical energy from the process exhaust gas during the production of cement clinker without affecting its kiln capacity or clinker quality. The electricity generated should cover the base load requirements for the cement production.
Using a high-temperature heat exchange stage, the entire usable thermal energy remaining after heating and calcination in the calciner shall be used exclusively to generate electricity and not initially, as is usual in a conventional system, for pre-heating the raw material. This shall allow to generate electricity with the highest possible efficiency.
In the temperature range of 850 to 900 °C separating cyclones are the established dedusting devices so far. The dust properties under these process conditions is quite sticky, meaning that they would prevent a good heat transfer in a boiler by creating a coating layer on the surface. As cyclones do not achieve the high separation efficiency under these process conditions, two concepts will be investigated for the exchange stage in the adapted cement clinker burning process.
As a first option, a novel moving clinker bed filter shall be investigated regarding the high temperature dust from process gas without significant temperature reduction to be utilised in a subsequent heat exchanger. As a second option, a circulating fluid-ised bed, being an established high temperature process in a new application, will be investigated as integrated dust separator and heat recovery in a subsequent boiler.
To ensure a residue-free and environmentally compatible cement clinker production, all the dusts produced are to be returned to the process and the use of alternative fuels with a corresponding proportion of biomass will be considered. The research project involving both simulation and experimentation shall provide an evaluation of the concepts in terms of their technical feasibility, environmental and energy impacts and economic benefits.