The Siemens Thermal Waste Recycling Process — a modern technology for converting waste into usable products

Abstract

Thermal waste recycling technology was developed for the thermal treatment of domestic refuse, municipal waste and sewage sludge. The main objectives in the development of this technology were to ensure good environmental compatibility and to achieve complete recycling of the residual materials wherever possible. Good environmental compatibility was achieved by treating the waste in a carbonization drum at about 450°C to produce carbonization gas and a solid residue which is removed from the carbonization drum in a dry form. After cooling, the solid residue is separated into the usable fractions of ferrous metals, non-ferrous metals, glass and ceramic substances, and a fine solid residue containing about 30% carbon. Subsequently, this fine residue and the carbonization gas are combusted in a high-temperature combustion stage which ensures destruction of the organic pollutants. After smelting and quenching in a water bath, the mineral component of the fuel forms high-grade granulated slag. Waste heat from the combustion process is used in a steam generator. A two-stage wet flue-gas scrubber with downstream DENOX catalytic converter and a fabric filter stage results in a very low environmental impact. As a result thermal waste recycling technology converts waste into products which can be recycled directly without further processing (except for a small amount of the flue-gas scrubbing residues). The process does not produce any waste water. The gaseous emissions meet the requirements of the latest German regulations. Finally the process provides usable energy, for example electric current and/or district heat or steam. The described process has been implemented on a practical scale in a demonstration plant, which has to date been in operation for about 8000 h.