Evaluation of Plastic Waste Management in Thailand Using Material ...

Figure 2.24 Coke oven chemical feedstock recycling (Plastic Technology Center, 2008)
2.3.2.4 Blast furnace feedstock recycling: Plastics used as a reducing agent
The process by which plastics are used as a reducing agent is as follows. Plastic waste
collected from factories and homes is cleansed of non-combustible matter and other
impurities such as metals, then finely pulverized and packed to reduce its volume. Plastics
that do not contain PVC are granulated, and then fed into the blast furnace with coke.
Plastics that do contain PVC are fed into the blast furnace after first separating the
hydrogen chloride at a high temperature of around 350 ºC in the absence of oxygen, as the
emission of hydrogen chloride can damage a furnace. The hydrogen chloride thus extracted
is recovered as hydrochloric acid and put to other uses, such as acid scrubbing lines for hot
rolling at steel mills.
2.3.3 Material Recycling
There are many treatments and processes for plastic waste recycling such as washing to
remove dirt and contaminants, grinding and crushing to reduce the plastic particle size,
extrusion by heat and reprocessing into new plastic goods.
Mechanical recycling is limited by the non-compatibility between the different types of
polymers in the mix. A higher quality of recycled plastics is achieved when there is the
separation of recycled resins prior to the remolding process. Moreover, the color of
recycled resins is also the one important issue of material recycling, especially grey color
of recycled resins which is an undesirable color. Recycled plastics cannot be used in food
containers, unless direct content with the food can be avoided. The recycled products are
usually produced by two plastic resins such as recycled resin and virgin resin, and the
proportion of both resins is based on the demand of market. Some material recycling are
described as below:
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