Plastics Process Analysis, Instrumentation, and Control. Группа авторов

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Figure 1.6 Steam cracking process (93).

This is, on the one hand, returned directly to the cracker and, on the other hand, passed as heat transfer agent through the melt in the stirring container and through the heating jacket of the stirring container and finally returned to the cracker. Residues and solids 8 are removed, e.g., by means of a hydrocyclone 9, from the bottom product after it has left the column. The vapor mixture leaving the top of the column at about 240°C is fed, after a partial condensation, to another column 10, e.g., a packed column, at about 110°C. The liquid/gas mixture entering the packed column is washed with water or aqueous NaOH 11 in countercurrent; any HCl still present in the gas is removed as aqueous HCl or aqueous NaCl solution with the liquid mixture at the bottom. The liquid mixture emerging at the bottom (organic liquid/aqueous HCl or aqueous NaCl solution) is separated in a downstream phase separating vessel 12. The lighter organic phase is, on the one hand, removed from the process as feed material A for the steam cracker and, on the other hand, returned to the column. The heavier aqueous phase, possibly enriched with HCl or NaCl 13, is removed from the process. The HCl-free gas mixture emerging at the top of the packed column is likewise fed to the steam cracker as feed material B.

A blow molded fraction (from Duales System Deutschland GmbH, Bonn, Germany), whose plastic content essentially consists of poly(ethylene) (PE) and PP, including any adherent soiling, sticky label materials, fillers, residual contents, and other materials, was processed in a plant, as shown in Figure 1.6. The resulting feed materials A (liquid mixture) and B (gas mixture) for the steam cracker have the compositions shown in Tables 1.5 and 1.6. Here, the following abbreviations are used in the Tables: HC = hydrocarbons, NA = non-aromatics, and EB = ethylbenzene.

The cracked products obtainable from the steam cracking process have the compositions shown in Tables 1.7 and 1.8. Here, for comparison, also, the compositions of the cracked products if the steam cracker is operated with the traditional feed material naphtha are shown.

      A comparison of Tables 1.7 and 1.8 shows that the yield of ethylene and propylene is higher if the steam cracker is operated with the feed materials obtained from the blow molded fraction than if the steam cracker is operated with naphtha.

       1.15.3.4 Decomposition into Liquid Hydrocarbon Fuels

      Methods of producing high-quality liquid fuels from solid plastic waste or high-quality liquid fuels have been developed (94).

Table 1.5 Feed materials, liquid mixture (93).