Incineration with energy recovery and material recovery
Normal solid-waste incinerators with energy recovery can usually tolerate up to 3% chlorine. However, such processes are not accepted as recycling by waste regulation. If HCl and/or its neutralised salts are recovered and used, then partial recycling may be claimed.
MVR: MVR (Müllverwertungsanlage Rugenberger Damm) is an advanced 320,000 tonnes per year energy-recovery plant owned by the City of Hamburg. It is designed to handle much higher hydrochloric-acid levels in its raw gas than most conventional plants which provides more flexibility in waste treatment. The hydrochloric acid is recovered as a 30% aqueous solution, the purity of which makes it suitable for the chemical sector.
Trials with the addition of PVC waste (500 tonnes over five weeks) were extremely successful. No modifications were observed in the composition of the slag or the fly ash, and steam generation was not affected. Hydrochloric acid production increased in proportion to the added PVC waste and the level of dioxins in the gaseous effluent remained extremely low – well below mandatory limits.
The SOLVAir® Solution: PVC waste is thermally decomposed in a modern waste-to-energy plant which enables efficient neutralization of the resulting higher volumes of hydrochloric acid gas by sodium bicarbonate. The fly ash and the residual sodium chemicals are combined and treated in solution, yielding a small amount of solid residue and a purified brine which supplies the soda ash plants. The recovered brine replaces the mined salt in the so-called ammonia-soda process (also known as Solvay process) to produce both sodium bicarbonate and sodium carbonate. The carbon dioxide needed for the production of soda ash is obtained by the decomposition of calcium carbonate, with calcium chloride being at the end the only major by-product. The calcium chloride is sold on the market and used for example in food industry, waste water treatment or as a road salt. The recovery operation from solid flue gas treatment residues is recognized as a recycling operation in “The Best Available Techniques Reference Document for the Waste Treatment”.