Working up residues and dust from pyrolysis of spent, recycled domestic batteries includes adding hydrogen peroxide solution to water used for scrubber pyrolysis waste gas containing mercury and compounds

摘要

In working up residues and dust from pyrolysis of spent, recycled domestic batteries, in which mercury and mercury compounds, in pyrolysis waste gas preferably are absorbed in water in a scrubber fitted with inclined clarifier and tower for reducing mercury (II) with tin (II) chloride, as described in AT 40P 201, hydrogen peroxide solution is added, to eliminate precipitate, sludge etc. Process for working up residues/dust (I) from thermal or pyrolytic treatment of spent, recycled domestic batteries, especially zinc (Zn)/carbon and alkali/manganese (Mn) batteries, involves separating environmentally harmful and/or re-usable metals, especially iron (Fe), Zn and Mn, and wet chemical precipitation of mercury (Hg). (I) contain reaction products of the metals/compounds, especially Zn, Fe, Mn, with pyrolysis gases, e.g. hydrogen chloride, and atmospheric oxygen. After separating a magnetic coarse fraction containing especially Fe and crushing and/or grinding and suspending in water, (I) are treated with hydrochloric acid at pH 1-3, without releasing any gas, especially hydrogen, and subjected to wet oxidation with Mn (III,IV) oxide to convert metallic Fe and Zn and the Mn (III,IV) oxide into the corresponding 3- or 2-valent salts and bring them into solution. Then aqueous caustic alkali, especially sodium hydroxide solution is added in stages to adjust the solution to (1) pH 3.4-4 to precipitate Fe as Fe (III) hydroxide; (2) pH 5-6 to precipitate Zn as Zn hydroxide, preferably 95-98% pure; and (3) pH 6.5-8, with introduction of oxygen, especially air, to precipitate Mn as Mn (III,IV) hydroxide(s), preferably 95-98% pure. Each precipitate is separated in turn. Hg and its compounds, especially Hg (II) chloride, present in the waste gases from pyrolysis are absorbed in a scrubber, preferably in water in a scrubber fitted with an inclined clarifier for separating the slurry from the waste liquor and a reduction tower for reducing Hg(II) with Sn(II) chloride, as described in AT 40P 201. The novelty is that to eliminate, especially dissolve, precipitates, sludge etc. present or formed in the water from the scrubber or to free it from sludge, hydrogen peroxide solution is added in the sludge separator or water flowing through this, preferably in the inclined clarifier. An Independent claim is also included for the plant used in this process.