Charcoal from agricultural residues as alternative reducing agent in metal recycling

Typical carbonization units have the target to produce a charcoal which is in nearly all cases used as energy carrier for the production of heat in different forms. These often very old and not efficient processes are in most cases operated at temperatures between 350 and 500 °C and generate a charcoal with only medium quality. To realize an application of charcoals as CO2-neutral reducing agent in metallurgical processes special high quality charcoals are needed, which meet metallurgical requirements - fixed carbon content of more than 85%, low ash amount and low content of volatiles. Therefore carbonization processes at higher temperature are required. The performed carbonization experiments with agricultural residues at temperatures up to 1000 °C show the possibility of the production of a charcoal which meets the requirements of various metallurgical processes and can act in these industry sector as reducing agent and substitute the so far used fossil coals and cokes. This was realized with some first reduction tests of heavy metal containing residues where charcoals showed a better performance than petroleum coke typically used in such reduction processes. The charcoal application in metal production and recycling processes as substitute of fossil carbon carriers leads to an enormous potential of saved fossil based CO2-emissions because of the high energy and reducing agent demands in these industry sector. So the metal industry has the opportunity to fulfill environmental regulations and restrictions to reduce their CO2-footprint and guarantee the supply of metals in Central Europe in future.