Grinding, incineration, and pyrolysis; these three methods are generally used for recycling fiberglass. In grinding, a material is reduced to little pieces or converted into a powdered form. This reducing material can be used in other products and almost without any unused waste. The reground materials are used as recyclate.
Incineration is a process of thermal oxidation in which a material is burnt to create heat. Though the by products of fiberglass incineration are useful for other products, but it is only the ashes which remain unused. The organic materials in the resin forms the heat content of fiberglass laminates. Here we can take the example of SMC on which most of the incineration studies have been carried out. About 25% to 30% organic material is there in SMC which is why it has a low heat content and high ash content. The ash is nothing but calcium oxide coming from boron, calcium carbonate and other oxides.
Composites can be a suitable fuel and feed-stock for cement kilns, revealed by the studies conducted in Scandinavia. Junk fiberglass laminate is burnt to create heat in the kiln (2, 5520F/1,4000C). This is the way for its complete combustion and the new cement is incorporated with the inorganic ash. A large and steady quantity of feedstock is supplied to the cement kilns as the kilns’ appetite may not be supported by the recovery processes for composites. But further developments can be made in this field. A material is chemically decomposed or transformed into one or more recoverable substances by pyrolysis. In this process, the material is heated to a very high temperature in an oxygen-depleted environment. Unlike incineration, an open atmosphere is required for carrying out this process. Pyro-gas, pyro-oil, and solid byproduct, these three recoverable substances are formed by the decomposition of pyrolyzed fiberglass. The interesting thing is that these substances can undergo a recycle process too. The tires of scrap automobiles are also disposed by pyrolysis.
Pyrolysis of SMC is done in various steps. It is transformed into 2” squares and fitted into the pyrolysis reactor. A vacuum assists it drawing most of the oxygen in the atmosphere. Around 1,4000F (7600C) amount of heat is given to the reactor and at about 5000F (2600G), gas formed due to the decomposition of hydrocarbons in the resin. A scrubber draws off the gas which is separated into pyro-gas and pyro-oil. The pyro gas has similarities to natural gas in terms of cleanness and energy content. It can replace the natural gas and the pyrolysis reactor is fueled by the pyro gas. Pyro oil shares similarities with crude oil, but is less valuable than the latter. It blends oil with other fuel oils. About 25% of the pyrolysis traction output is there in pyro gas and pyro oil.
They do not cause any environmental problems as they are free of halogens, phosphorous, sulfur and other heavy metals. The remaining inert solid by-product comprises of almost 75% and can be used in many products. The fluid potential from the glass fibers are resided more in the residue filler in the solid by-product. The residue filler is there for more SMG carbon char and coal, asphalt shingles and paving are formed from calcium carbonate by further processing. You can use the solid by-products in electric fences, gates, horse stalls, animal pens, barrier retainers and plastic lumber.
By going through the process of incineration and pyrolysis, the fiberglass waste gets dirty. Like metal bits and oil residues, there is no need to pure or cure it from impurities. In fact, you can mix it with other type of plastics and pass through the incineration and pyrolysis process at once. It is easier to remove impurities from ash or solid by-product than the scrap before hand.
This process is gaining popularity in junk yard recycling industry where auto salvage products are brought back to be scrapped. Today around 80% of the junk vehicles can be recycled. It not only saves our valuable resources it helps protect our environment too. Fiberglass recycling has in a way revolutionized boat making industry where cheaper alternatives from used boat auctions were clogging the new boat making market.
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