Across Europe, natural gas is usually seen as the energy carrier of choice for the firing of heavy clay products, while in Asia most firing is done with coal. Due to the high proportional cost of energy in the production of heavy clay products, potential alternative fuels are being sought. Their use can also help reduce the harmful emissions associated with the burning of coal. To date, however, the use of alternative fuels has been thwarted by a lack of availability, inconvenience of use as solid fuel, or simply the price.

The use of synthesis gas (syngas) is therefore considered a possible alternative. Syngas can be obtained by pyrolytic treatment of any arbitrary substance containing organic constituents (biomass, garbage, ...) and therefore counts as a suitable “renewable source of energy”. Gasification processes are generally well-established technology. To date, the use of synthesis gas obtained via thermal decomposition of waste material or residue for firing heavy clay products has not been tested to any major extent. Contrary to conventional forms of gasification, however, it offers the advantage of producing gas with a significantly higher heat of combustion (fuel value), because the process requires no air supply, so the otherwise attendant, energetically inert nitrogen load does not occur. Under certain circumstances, the altered composition of the fuel can exert an influence on the quality of the finished heavy clay product. This applies in particular to roof tiles, because the quality and colour of glazed roof tiles are heavily dependent on the kiln atmosphere.

The paper presents the results of a research project, including both the technical findings and the regulatory situation.

Eckhard Rimpel, IZF Brick and Tile Research Institute Essen Regd,
Essen, Germany