Page 33 - Refining Biomass Residues for Sustainable Energy and Bioproducts

12 Refining Biomass Residues for Sustainable Energy and Bioproducts

shape selectivity,
pore size,
acidity,
activity,
selectivity to particular products,
catalyst deactivation,
catalyst regeneration, and
catalyst pretreatment and calcination.

1.5 Liquid yield: influence of various parameters

Through pyrolysis, large complex molecules could be converted into several smal-
ler molecules, and the products can be classified into three different types:
1. Solid (mostly char and carbon)
2. Liquid (tars, heavier hydrocarbons, and water)
3. Gas (CO 2 ,H 2 O, CO, C 2 H 2 ,C 2 H 4 ,C 2 H 6 , and C 6 H 6 )
Different liquid products are obtained from the SWs through pyrolysis, including
tar, bio-oil, or biocrude or pyrolytic oil. Tar is a black tarry fluid obtained from the
SWs containing up to 20% water and also it contains some homologous phenolic
compounds. Bio-oil consists of large amount of oxygen and water with complex
hydrocarbon mixtures. Four features are considered as essential for the fast pyroly-
sis process, because these factors could increase the yield of the liquid. They are as
follows:

Heating rate
Reaction temperature
Residence time of vapor in the reactor
Quenching of the product gas
For the high liquid yield the following factors should be maintained: very high

heating rate, range of reaction temperature should be within 425 C 600 C, mainte-
nance short residence time of vapor in the reactor, and rapid quenching of the prod-
uct gas. There are some factors that influence the liquid yield such as,
physicochemical properties of biomass and chemical composition of biomass and
its phases.

1.5.1 Physicochemical properties of biomass

Based on the physicochemical properties of the biomass, the liquid yield rate will
be varied. For example, lignocellulosic biomasses have greater potential in produc-
ing of fuels and several chemicals. These materials are present in worldwide but do
not compete with the food supply. Bio-oils were obtained from the lignocellulosic
biomasses through the degradation at higher temperatures with different heating
rates. The slow heating rate (SHR) pyrolysis or slow pyrolysis typically operates at