Fuel and Feedstock Recovery

The raw materials of the polymer industry are obtained by pyrolysis (or cracking ) of oil. In earlier times, they were similarly obtained by pyrolysis of coal, which leads to the formation of coke, tars and town gas . Waste hydrocarbon polymers are similar in chemical structure to mineral oil and on heating to high temperatures they crack to give a mixture of lower molecular weight hydrocarbons (see, for example. Table 4,4), some of which have utility both as chemical feedstocks e.g. the olefins) and the rest as fuels. Pyrolysis can be carried out successfully 

From mixed plastics, the formation of ethene, methane and hydrogen increase with temperature but the formation of propene and higher hydrocarbons decreases. Whether the isolation of olefins can compete economically with the oil cracking process remains to be seen, but the total hydrocarbon pyrolysate is similar to naphtha, the feedstock for petrochemicals production. It should be noted that because pyrolysis is primarily a non-oxidative process carried out under carefully controlled conditions, the possibility of dioxin formation is much reduced. In 1995 about 100 kT of mixed plastics wastes were converted into chemical feedstocks in Europe by pyrolysis, and this is expected to increase at the expense of incineration over the next ten years. 

The hetero-chain polymers, notably the polyesters, polyamides and polyurethanes, can also act as a source of new monomers or oligomers by hydrolysis and alcoholysis. This recycling process (sometimes called 

---