Innovative measuring technology on the burner cuts operating costs when using liquid substitute fuels

The cement production process requires large quantities of energy. For this reason, the use of secondary fuels was studied intensively at an early stage, with the aim of reducing energy costs in the thermal zone of this process. The most diverse alternative fuels and raw materials, extending from coarse grained solids up to and including liquids, are used, depending on their market availability and their suitability for the combustion process, to heat the rotary kiln. A constant energy input rate is important in clinker production, to assure consistent and uniform clinker quality in the kiln. Monitoring of the diverse mass flows of combustion air, and the various fuels, at the burner is now standard technological practice. On-line mass flow meters applying the Coriolis principle are increasingly being installed to monitor liquid fuel flows. A frequently encountered characteristic of secondary fuels is the fact that their properties and parameters may change with every new delivery; in the case of liquid fuels, the variable factors may be composition or viscosity - or both, in some cases. The existing infrastructure is generally utilized to provide storage tanks for liquid secondary fuels, assuring adequate buffer capacity for accommodation of several batches or shipments. Segregation of the individual batches can occur during storage, however, with the consequence that any sample taken at a previous delivery has too little informative value concerning the quality of the liquid secondary fuel now metered at the burner. In the following, liquid alternative fuels like glycerin by-product from bio-diesel production and waste oil are looked at, and the use of online viscosity measurement to save costs and optimize the burner is described.