THERMOCHEMICAL CONVERSION: AN INTRODUCTION TO FAST PYROLYSIS - Biomass as a Sustainable Energy Source for the Future - page 380

achieved by removing the chemical functionality from the oil that is responsible
for coke. Oxygen removal is required to enhance the miscibility with refinery
streams and to (already) approach the composition of the target products. The
remaining part of the oxygen is removed in the refinery. The upgrading process
is a catalytic one and is operated at 250 400 C and 100 250 bar. For this proc-

ess, (more stable) catalysts are being developed and tested, and the first stages of
process development are in progress.

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For more information, see Elliott (2007), de Miguel Mercader et al. (2010), and
Venderbosch et al. (2010).

11.10 OUTLOOK

Liquefaction is an interesting thermochemical process for converting bulky inhomo-
geneous biomass into a liquid, which is easier to store, transport, and process. At the
time of writing, only one commercial pyrolysis process was in operation. However,
research is making good progress, and several demonstration plants are scheduled to
come on stream in the near future. In the years to come, companies should mature the
liquefaction technologies and develop the first large-scale applications of pyrolysis
oil. The scientific community should advance at a higher level of integration of the
different levels described in this chapter, allowing a much better control of the pro-
cesses occurring in reactors and consequently of the composition of the oils produced.
Improving the quality of the oils will be of paramount importance for the introduction
of this technology in the market. Many applications of the oils are envisaged; in the
authors view, refinery feeds, precursors for chemicals, and pyrolytic sugars are the

most promising.

'

APPENDIX 11.1 SINGLE-PARTICLE MODEL (BASED ON THE
MODEL BY DI BLASI, 1997)

The single-particle model uses the Broido - Shafizadeh pyrolysis scheme (see

Figure 11.13).
In this model, the biomass particle is described as an anisotropic, porous medium
with different properties along the grain (permeability to gas flow and thermal con-
ductivity are larger along the grain).

k 3 Vapors

k l

Biomass Active biomass

k 2 v c char + v g gas

FIGURE 11.13 Broido-Shafizadeh scheme for biomass pyrolysis as presented by Bradbury
and Allan (1979).