Method and plant for processing waste

A method for processing a humid solid waste material, comprising the steps of:

• (a) removing larger objects that cannot be ground from the solid waste material;
• (b) optionally removing any ferrous metals, aluminum or glass from the solid waste material;
• (c) following steps (a) and (b), mixing the humid solid waste material with limestone powder in an amount sufficient to react with chlorine, present in the waste material, and grinding the mixture to a particle size no greater than 10 to 15 mm to form a pyrolyzable refuse product;
• (d) drying the pyrolyzable refuse product in two drying stages, wherein in the first drying stage, the pyrolyzable refuse product is dried with hot air, at a temperature of 250 to 260° C., and at an underpressure of 2 to 10 mm of water, and removing water vapor from the first drying stage, and after moving the pyrolyzable refuse product from the first drying stage to the second drying stage, drying the pyrolyzable refuse product at a temperature of 450 to 500° C., to fully remove water vapor;
• (e) pyrolyzing the dried pyrolyzable refuse product, following step (d), in two pyrolysis stages, wherein in the first pyrolysis stage, the pyrolyzable refuse product is pyrolyzed with the exclusion of air, at a temperature of 220 to 250° C., to convert the chlorine in the pyrolyzable refuse product to hydrogen chloride, which reacts with the ground limestone to form calcium chloride, and a dechlorinated pyrolysis gas, and wherein in the second pyrolysis stage, the dechlorinated pyrolysis gas is pyrolyzed at 450 to 500° C., at an overpressure of 5 to 15 mm of water, with the exclusion of air, to obtain a pyrolysis gas and a solid pyrolysis residue containing calcium chloride, heavy metal salts, and slag, and optionally calcium sulfate when acid tars containing sulfuric acid are initially present in the solid waste material;
• (f) condensing the pyrolysis gas to obtain both a condensed pyrolysis gas and a non-condensed pyrolysis gas, recovering a portion of the condensed pyrolysis gas as a separate liquid fuel, and combusting the non-condensed pyrolysis gas and any condensed pyrolysis gas not separated as a liquid fuel, to produce hot chimney gases providing heat for the two-stage drying and two-stage pyrolyzing steps (d) and (e);
• and a hot slag product useful in the manufacture of concrete, and cooling down the hot slag product initially to a temperature of 200° C. and then to a temperature of 65 to 70° C. through contact with circulating cooling water;
• (g) washing the solid pyrolysis residue obtained according to step (e), with an aqueous washing liquid, to dissolve the calcium chloride and heavy metal salts therein, and to obtain a washed solid pyrolysis residue, and extracting the calcium chloride and the heavy metal salts in aqueous solution from the solid pyrolysis residue, centrifuging the aqueous solution containing the calcium chloride and the heavy metal salts to separate out solid particles of pyrolysis residue from the aqueous solution, separating the heavy metal salts from the aqueous solution and recovering the heavy metal salts as a product, spray-drying the aqueous solution containing calcium chloride with a portion of the hot chimney gases produced according to step (f) to recover the calcium chloride as a product, desorbing carbon dioxide from the portion of the hot chimney gases used to spray-dry the calcium chloride, and recovering carbon dioxide as a product, separate from the heavy metal salts;
• and
• (h) channeling the washed solid pyrolysis residue to the combustion carried out according to step (f) so that the washed solid pyrolysis residue is combusted together with the non-condensed pyrolysis gas and any condensed pyrolysis gas not separated as a liquid fuel, to produce the hot chimney gases and the hot slag product.