THERMOCHEMICAL CONVERSION: AN INTRODUCTION TO FAST PYROLYSIS - Biomass as a Sustainable Energy Source for the Future - page 383

At the particle-surrounding boundary,

−

: λ x ∂

T
∂ x =

T 4 T r For x − σ − h c T ð − T r Þ p = p 0 ð Eq : 11 : 24 Þ

−

: λ y ∂

T
∂ y =

T 4 T r

− σ − h c T ð − T r Þ p = p 0 ð Eq : 11 : 25 Þ

For y

At the center of the particle, there are no gradients due to symmetry.

CHAPTER SUMMARY AND STUDY GUIDE

This chapter describes the processes to generate bio-oil from biomass. Bio-oil can be
used as a fuel in combustion or further upgraded for more sophisticated applications.
For dry biomass, the process is termed pyrolysis; in case of wet biomass, reactions are
carried out at subcritical liquid (water or solvent) conditions, and the process is called
hydrothermal liquefaction or solvolysis. The kinetic background of biomass conver-
sion for this process type is presented as well as reactor engineering fundamentals to
obtain a better understanding of the process.

KEY CONCEPTS

Difference between pyrolysis and hydrothermal liquefaction/solvolysis

Chemistry
Reaction kinetics

Heat, mass, and momentum balances for the process
Different reactor configurations

SHORT-ANSWER QUESTIONS

11.1 a. Explain why the observation of larger oligomers during the pyrolysis of a

cellulose particle contradicts an unzipping mechanism.
b. Argue how these large oligomer anhydrosugars (DP = 9) leave the particle.

11.2 The Biot number is the ratio of the resistance of internal heat transfer to external
heat transfer. Which processes do the Py and Py 0 numbers compare?

11.3 The concentration of acetic acid in pyrolysis oil varies between 1 and the 8 wt%.
HAc is the most abundant acid in the oil. Can you explain the low (2 - 3) but

hardly varying pH of the oil?