Direct recycling of waste plastics is not always possible, e.g. waste plastics can be contaminated; moreover, they often mixed with different sorts of materials such as paper, glass, metal, biowaste, etc. Food and beverage packaging is a typical example when plastic attached to other materials (aluminium/polymer laminate). It is impossible to separate this laminate from paper at the recycling facility.
Incinerators do not "welcome" large amount of plastics in the waste due to large quantity of the released heat as well as non-complete burning of plastics and associated with it clogging the equipment.
Pyrolysis of plastics can be used to dispose the waste and to recover synthetic fuel. Pyrolysis oil recovered from the process can be used as diesel generator fuel or fuel for burners.
After pyrolysis in the kiln at ~400 C the pyrolysis gases are cooled down. The recovered oil is fed into the distillation column and separated into three fractions; light oil from the top, medium oil from the middle and heavy oil from the bottom of the column. These three types of oils are stored in separate oil tanks and sent to the furnaces and cogeneration system in the plant as fuel through piping, or loaded onto a tank lorry for shipment to customers. The energy of hot off-gases is used to generate steam.
Plastics pyrolysis facility and oil recovery
Typical average composition of the initial mixed plastic waste: Polyethylene, polypropylene, polystyrene ~ 71 %; PVC's ~ 4.5%: PET ~ 12.5 %, Other plastics ~ 9.5%; Other materials (foil, etc) - 2.5%. Process Characteristics:
Easy operation and maintenance due to atmospheric pressure process
Energy recovery use of product oil, gas and residue
Chlorine recovery from PVC as hydrochloric acid
Heavy pyrolysis oil usage for furnaces in plant as well as co-generation as fuel
Full automatic operation, computer control system
Low environmental emissions
Low running cost of the pyrolysis facility since part of the recovered pyrolysis oil is used for self-supporting operations of the pyrolysis plant.
Plastics pyrolysis facility and electricity generation
Since the pyrolysis oil is used as fuel for diesel generators, pyrolysis of plastics can also occur in accordance with the MPSC technology. The pyrolysis facility efficiently handles mixed plastics, separating plastics from the laminates and generating vast quantities of renewable energy. The plastics pyrolysis facility inherits all the advantages of the MPSC plant described on the web page "Pyrolysis Technology"
Pyrolysis of Electronic Waste
E-waste is not biodegradable and represents a global problem of modern time. Electronic appliances bodies are made of different plastics and therefore represent a good raw material for the pyrolysis. Disposal of Printed Circuit Boards (PCB) is a separate issue. Electronic boards is a mixture of organic resins, fiberglass, and ceramics. Boards also contain valuable metals. During the pyrolysis the volatile portion of the board materials will be thermally decomposed, solids (including noble metals and fiberglass) will be recycled. Direct electricity generation in accordance with the general MPSC scheme is the efficient way to treat this e-waste.
Bromine flame retardants are widely used in the printed circuit boards. Therefore, technically the e-waste treatment pyrolysis facility will have extended gas cleaning capabilities due to bromine.