Page 159 - Advances in Eco-Fuels for a Sustainable Environment

130 Advances in Eco-Fuels for a Sustainable Environment

From the previous research, nearly 40 million tires every year are scrapped in the
United Kingdom. Out of all the scrap tires, 74% by weight were recovered in 1997,
and about 20% of the recovered tires were recycled for reusable purposes; this can be
used for energy recovery. Waste and used tires can be converted into value-added
products such as olefins, chemicals, and surface-activated carbons through conven-
tional pyrolysis processes. They consist of compounds such as elastomers, vulcanizing
agents, reinforcing agents, and plastificants [37]. The main advantage of this process
is the recovery of material and structural damage reduction. Changes in pyrolysis tem-
perature can change the mass reduction percentage. Increases in pyrolysis temperature
will lead to a decrease in the solid char percentage [53]. Sulfur and nitrogen oxide
emissions can be reduced compared to conventional pyrolysis. High temperatures
can be achieved easily in microwave pyrolysis tires, which is a disadvantage of con-
ventional pyrolysis.

5.8 Experimental setup and procedure

The experiment was conducted by electrical and microwave heating mechanisms. Both
pyrolysis processes maintained an equal power-to-volume ratio for the comparison of
results. The electrical heating method is explained by the following steps. Heat is sup-
plied through the heating mantle, the power supplied is 450W, and 600mL of waste
lubricantoilistakeninsidethethree-neck,round-bottomreactor.Itisheatedatdifferent
temperatures (250°C, 300°C, and 350°C). The water-cooled condenser cools the vapor
that evolved from the waste lubricant oil. A k-type thermocouple was used in the pro-
cess to monitor and control the temperature. An ero-therm data acquisition system is
additionally attached to collect temperature and time data in the microwave process.
The microwave pyrolysis quartz vessel is used as a reactor due to the favorable prop-
erties of this material. A 1.5-L vessel is placed in a microwave oven, and the power rat-
ingcan bevaried between 1.1and 2.2kW.In thisexperiment,1Lof waste engineoilhas
been used, and the heating is given through a pair of magnetrons to attain a temperature
range of 300–400°C. The oven has two pairs of magnetrons, and each pair is organized
by a distinct button, which controls the power supplied to the magnetron. Only one pair
ofmagnetronsispoweredatatimetosupplythenecessaryheat,andtheotherpairiskept
inactive. The power supply isexchanged betweenthe pair of magnetrons every3 min to
avoidoverheating. The susceptors are used in the microwave heating for a better energy
transformation and it is used to reach the maximum effectiveness of the pyrolysis pro-
cess because of the microwave absorbance. The susceptor used in this process is silicon
carbide (SiC). Alumina bricks were placed between silica carbide and the quartz to
avoid direct contact of susceptors on the quartz vessel, as direct contact may lead to
the thermal crack on the vessel. Pure nitrogen of 99.99% at a range of 2–5L/min is sup-
plied in both processes to maintain the inert atmosphere. The gas from the heated waste
engine oil was directed to the double tube lei bag condenser, which condenses the gases
at three stages. Water at room temperature circulates around the condenser, and the liq-
uidfuelisobtainedandcollectedinthevessels.Thechar(residue)insidethereactorwas
measured at the end of the pyrolysis process. The noncondensable gases left out were
passed into the water to reduce the release of the toxic gases into the atmosphere.