| 摘要 |
<p>1297734 Recovery of silver BATTELLE DEVELOPMENT CORP 19 April 1971 [9 March 1970] 22809/71 Heading C7D A process for recovering silver from a silvercontaining manufactured organic material such as photographic film, printed circuit boards, or photographic paper, comprises pyrolizing the material in a hot non-oxidizing gas to form a silver-containing carbon residue and a pyrolitic off-gas mixture, burning the carbon residue in an oxidizing atmosphere to form a silver-containing ash and a non-oxidizing gas, and separating the silver from the ash. The material is fed to the rotary air lock valve 15 of a retort 10, by a conveyer 17. The chamber 11 of the retort has an oxidizing zone 20, and a contiguous reduction zone 21, gas is supplied to the chamber above or below a grate 12 by a line 22, and gas is removed from the retort by a line 23. Air and water vapour are supplied to line 22 via valves 33, 38, and are preheated by the off-gas mixture passing through line 23 and into a heat exchanger 30. Thermocouples 35, 36, 37, are provided for indicating the working temperatures at the different stages of the process. In operation, the process is started by placing a carbonaceous material on the grate 12, loading film on top of this material, passing natural gas into a chamber 30 through line 40 and igniting with air from line 28, so that the heat from air and water vapour passing through line 22 burns the carbonaceous material. Hot gases from the latter pyrolyze the film so as to reduce the film to a silver-bearing carbon residue and produce the desired off-gases. Valve 40 is now closed enabling the process to be self-sustaining with the addition of air through line 28. Grate 12 may be vibrated, or opened and closed periodically or continuously. The ash mixture is removed for subsequent separation of the silver from the ash, by a valve 14 and falls into a container 26.</p> |
