Process for thermal treatment, in particular low-temperature carbonisation, of organic wastes, and plant for carrying out the process

摘要

In the process for thermal treatment, preferably low-temperature carbonisation, of organic wastes, for example simply treated domestic refuse (for example removal of iron and inert materials) and pre-dehydrated sewage sludge are mixed and coarsely comminuted in a bowl mill, dried in an indirectly heated inert atmosphere and directly, together with the drying vapours, fused and/or degassed in a reactor heated indirectly by liquid heat carriers and adjusted to a uniform treatment temperature. The low-temperature carbonisation gas/vapour mixture is then separated by condensation into at least the three fractions water, liquid hydrocarbons and gaseous hydrocarbons, and the low-temperature carbonisation coke is processed to give a solid fuel. Preferably, the drying and low-temperature carbonisation are carried out in one apparatus, in which the drying zone merges into the low-temperature carbonisation zone. Preferably, a preclassification of large mesh width should be provided upstream of the bowl mill, and the iron from the screen oversize should be separated out upstream of the bowl mill, and the iron from the screen undersize downstream of the bowl mill. In the installation, a combined rotary drum reactor should be used which is indirectly heated by flue gases in the drying zone and by liquid heat carriers in the low-temperature carbonisation zone. To cool the low-temperature carbonisation coke, a heat exchanger should be used for simultaneous cooling of the coke and predrying of the sewage sludge. For this purpose, a rotary pipe can be used, for example, through the interior of which the hot low-temperature carbonisation coke is passed by means of suitable conveying elements or by inclination, while the rotary pipe has wings or screw flights on the outside which turn over and convey the sewage sludge in a closed housing and thus predry it by indirect heating.