From 1981 Veba Oil AG operated a coal-to-oil hydrogenation plant at Kohleol Anlage Bottrop (KAB) in Germany, using the Bergius Pier coal liquefaction technology to convert coal into naphtha and gas oil. In 1987 the plant was modified, applying Veba Combi Cracking (VCC) technology to convert crude oil vacuum distillation residues into synthetic crude. Since 1988 a share of the petroleum residue feedstock was substituted by chlorine-containing waste (containing, e.g. PCBs). In 1992/1993 a depolymerization unit was added in front, to process exclusively mixed plastics waste from packaging, as collected by DSD. In 1998 some 87 000 tonnes were treated. DSD and Veba both agreed to terminate their contract in 1999, instead of in 2003: hydrogenation was unable to compete economically with treatment in blast furnaces and with the SVZ process at Schwarze Pumpe.
The plant includes first a depolymerization section and then the VCC section (Figure 1.3). In the first section, the agglomerated plastic waste is depolymerized and dechlorinated at 350-400°C. The overhead product is partly condensed. The main part (80%) of the chlorine introduced evolves as gaseous HCl in the light gases and is washed out, yielding technical HCl. The condensate, still containing some 18% of the chlorine input, is fed to a hydrotreater where the chlorine is eliminated together with the water formed. The resulting chlorine-free condensate and gas are again mixed with the depolymerizate for further treatment in the VCC section.
There, the depolymerizate is hydrogenated under high pressure (about 10 MPa) at some 400-450°C, using a liquid phase reactor without internals. Separation yields a synthetic crude oil, which may be processed in any oil refinery. Light cracking products end up in the off-gas and are sent to a treatment section, for removal of ammonia and hydrogen sulphide. A hydrogenated bituminous residue comprises heavy hydrocarbons, still contaminated with ashes, metals and salts. It is blended with coal for coke production (2 wt%). The input specifications for the plastic waste are:
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