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124 Advances in Eco-Fuels for a Sustainable Environment

substance arrangement. Because of the high preference of water atoms with micro-
waves, humidity content inside a particular biomass molecule is focused explicitly
on accidental microwaves. Microwaves evaporate humidity in the deepness of the
molecule before volatilizing the natural substance. The produced mist is quickly
rejected into the surrounding area, thus eliminating the volatile substances and creat-
ing single deviations in the carbonaceous fort which increase its absorptivity. Thus,
that supports the arrival of volatile substances at low temperatures and, consequently,
its response to the emitted mist which supports partial oxidation and creation of per-
petual gases (CH 4 ,CO 2 ,H 2 , CO).
Microwave heating and conventional heating are distinguished based on differential
heating rates of the material being heated, as the microwave energy is directly delivered
into the material through molecular interaction with the electromagnetic field. Savings
of energy and time are attained in microwave pyrolysis due to higher heating rates
because of electromagnetic radiation. High heating rates improve the devolatilization
of material, which decreases the conversion time. The residence time of the volatile
matters is also controlled by the heating rate. The faster heating was decreased the vol-
atile residence time and obtained the more volatile substances that reach to the external
cold area or condenser, which reduces the activity of the products in the vapour phase in
the part of the secondary reactions. That gives high liquid yield and a reduction in the
deposit on char in the internal surface of the refractory material [32].

5.4 Factors affecting the pyrolysis process

The pyrolysis temperature, heating rate, and residence time majorly influence the
pyrolysis product and pyrolysis fuel quality. Morin et al. [33] investigated the effect
of the biomass nature and the pyrolysis conditions on the reactivity of char and the
physicochemical properties. Table 5.1 shows the effect of properties on the pyrolysis
product.
Pyrolysis processes were divided into three subgroups based on the operating
parameters. Each parameter resulted in a different product composition. These sub-
groups are slow pyrolysis, fast pyrolysis, and flash pyrolysis. The parameters that
describe slow pyrolysis are a temperature of 400°C with a residence time of more than
30min and a heating rate of (0.1–1°C/s). The product composition yield for slow
pyrolysis as explained by the investigators is 35% biochar (solid), 30% bio-oil (liq-
uid), and 35% syn-gas (gas) [34].
Slow pyrolysis has the lowest yield of liquid products that is the focus of most
experiments. Fast pyrolysis is the second type of pyrolysis that is explained. The oper-
ating parameters that describe fast pyrolysis are a temperature of 500°C with a resi-
dence time about 10–20s and a heating rate of (1–200°C/s). The product composition
yield for fast pyrolysis is 20% biochar (solid), 50% bio-oil (liquid), and 30% syn-gas
(gas) [34]. The yield for bio-oil under fast pyrolysis conditions is better than that of
slow pyrolysis. The third operating parameter is flash pyrolysis, which has operating
parameters that include a residence time of about 1s, a temperature of 500°C, and a
heating rate that is greater than 1000°C/s. The composition of product yield of flash