The Thermochemical Conversion of Biomass into High-Value Products: Microwave Pyrolysis - The Economic Utilisation of Food Co-Products - page 57

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Figure 3.8 Polypropylene used as an in situ temperature verification experiment. Left,
polypropylene bead during various stages of melting. Right, an STA trace
showing the melting point of polypropylene.

To further add confidence to the hypothesis that temperature measurement
by external temperature probes were correct, experiments were carried out
using a novel technique of adding nonmicrowave adsorbing polymer beads of
known melting point to the reaction mixture. Reactions are carried out at a
range of temperatures - as observed by the external infra-red probe. The results
are shown in Figure 3.8.
As can be seen in the photographs of the melted polypropylene bead the
probe-measured temperature follows the melting trend of the polymer bead (as
shown in the STA trace), which gives confidence in the infrared temperature
measurement technique as providing a fair and reliable representation of the
temperature of the bulk material during microwave pyrolysis of biomass.

3 .

3.5.3 Pyrolysis Oil Requirements - Chemical or Fuel Replacement
3.5.3.1 Fuel Replacement
High-grade pyrolysis oil is oil that has both physical and chemical properties
that are dramatically improved in comparison to those of conventional biomass
pyrolysis oil, and are closer to the properties of crude oil itself. It has been
demonstrated that bio-oil produced via microwave pyrolysis has great
potential, in that the water content and total acid number are exceptionally low
for pyrolysis oil types.
Key parameters that need to be assessed in order to quantify the ''grade'' of
oil are outlined in Table 3.6.

3.5.3.2 Chemical Source
Wheat straw is an agricultural residue high in the main plant nutrients,
especially potassium that is a well-known catalytic metal for biomass pyrolysis.