Chemistry Reference
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Figure 3.2
Principles of microwave biorefinery.
source of chemicals, they have also successfully been tested in stationary
engines and boilers, and have been shown to be suitable for upgrading into
high-quality hydrocarbon fuels for road and aviation uses.
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An ideal
conversion process would combine the advantages of both biochemical and
thermochemical treatments, operating continuously, at low temperatures and
producing a narrow product range on a reasonable timescale.
Here, we show that energy-ecient, low-temperature specific microwave
activation of key plant structural components can be used to substantially
enhance the energy value of biomass. The process converts biomass into an
energy concentrated solid fuel, along with oils with properties superior to those
achievable with conventional methods. This research demonstrates and delivers
enormous economic and environmental benefits associated with the utilisation
of biomass for a variety of higher-value energy products with flexible and
controllable technologies which can be installed close to source (see Figure 3.2).
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.
3.2
Introduction to Microwaves
3.2.1 Background
Microwaves lie in the electromagnetic spectrum between infrared waves and
radio waves. This microwave region corresponds to wavelengths of 1 cm to 1 m
(30GHz to 300 MHz) (Figure 3.3).
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The wavelengths 12.2 cm (2.45GHz) or
33.3 cm (900 MHz) only are allowed to be used by international agreement for
dielectric heating (unless thorough shielding precautions are taken) as the other
frequencies are used for radar and telecommunications. The majority
of domestic and commercially available microwave applications operate at
2.45GHz as this frequency has the right penetration depth for heating food
and also chemical reactions. In addition, the energy in a microwave photon
(ca. 1 kJ mol
-1
) is very low, relative to the typical energy required to break not
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