Pollutec Recycling

Survey Of Previous Work

Most work on plastics Feedstock Recycling" href="/plastics/plastics-pyrolysis-as-a-waste-management-option-status-in-the-eu.html">pyrolysis has been academic and directed at the analysis of polymers, their molecular structures and thermal stability, at the study of pyrolysis products, e.g. fire research, or at feedstock recycling at a laboratory or pilot scale. An early survey was given by Madorsky [4]. Given the large number of possible purposes, or different resins, additives, and operating conditions, the field is as wide as the sky!

Since the introduction of modern instruments (ca 1962) the thermal analysis of polymers as a research field has expanded very rapidly, encompassing specific techniques such as:

• differential scanning calorimetry (DSC), for measurements of specific heat and enthalpies of phase transition;
• differential thermal analysis (DTA), measuring the temperature difference between the sample and a reference and indicating the occurrence of any heat effect and of abrupt changes in heat capacity;
• thermogravimetric analysis (TGA), for assessing thermal stability and decomposition temperatures;
• thermomechanical analysis (TMA), for establishing the mechanical response of polymer systems to temperature changes. It includes dilatometry, penetration, torsion modulus, and stress/strain behaviour, as well as establishing the softening temperature, as determined by the Vicat penetration test, the deflection temperature or heat distortion test, the zero strength temperature test, the polymer melt or stick temperature test;
• flammability testing. Plastics used in furniture, mattresses, cars, electronics, etc. must satisfy specifications regarding fire behaviour and flame retardancy.

These techniques are often coupled with evolved gas analysis. TGA is a basic technique in studies on thermal decomposition. An excellent introduction is given in [5]. A systematic study of both physical and chemical aspects in plastics pyrolysis was launched in the E.U. Cycleplast project [6], aiming at a systematic scientific evaluation of various steps. The (German) Society for Thermal Testing listed methods relating to thermal testing [7]. Since 1965, prestigious, at present biannual meetings on Analytical and Applied Pyrolysis have been chaired by authoritative scientists such as G. Guiochon (1965), C.E.R. Jones (1972), J. Kistemaker (1976), T. Szekely (1979), K.J. Voorhees (1982), I. Luderwald & H.-R. Schulten (1984), C. Gutteridge (1986), I. Ericsson (1988), J.J. Boon (1990), W. Kaminsky (1992), S. Tsuge (1994), G. Audisio (1996), A. Kettrup (1998), F.J. Gonzalez-Vila (2000), J. Fink (2002), R. Font & A. Marcilla (2004), and M. Blaszo (2006). Themes such as instrumentation and analytical methods, elucidation of chemical structure, thermo-oxidation and photo-oxidation, mechanisms and kinetics are much more central in such work than is feedstock recycling.

On the industrial side, there has been a lively interest in plastics pyrolysis, since the breakthrough of mass production of plastics in the 1960s. A major tribute is to be paid to a first wave of Japanese enterprise, actively promoting plastics pyrolysis as a technical solution. New initiatives in Japan were launched in the 1980s and 1990s, such as the double fluid bed systems operated by Ebara Co. (Stardust Project, Yokohama), and, with less success, Tsukishima Kikai. At present these steady efforts are culminating in nationwide pyrolysis systems for converting waste plastics, separately collected from households, to yield liquid fuels and monomers, or used as a reducing agent in blast furnaces or as a coal substitute in coking plants. Plastics are converted in liquid phase, stirred tank reactors in plants at Niigata and Sapporo, PVC in rotary kiln units to coke and HCl by the former Nihon Kokan (at present JFE Holdings). Ube Industries jointly with Ebara Co. have developed an elevated pressure gasification process; the synthesis gas is cleaned and piped to a synthesis plant at the same site.

Japanese ventures were confronted with their counterparts in Europe and the USA during the International Symposia on Feedstock Recycling from Plastics, or ISFR, held at Sendai (1999), Ostend (2002) [8, 9] or at Karlsruhe (2005).