As we have
already mentioned, bio-oil is a mixture of various compounds, its properties
have proved to be a collective of them all. Following is a detailed account of
the physical properties and other characteristics of the crude bio-oil that has
been derived from the wood.
Pyrolysis oil is a dark brown free flowing liquid. Depending upon the
initial feedstock and the mode of fast pyrolysis, the color can be almost black
through dark reddish brown to dark green, being influenced by the presence of
micro-carbon in the liquid and by the chemical composition. Hot vapors
filtration gives a more translucent reddish brown appearance due to the absence
of char. High nitrogen contents in the liquid can give it a dark green tinge.
liquid has a distinctive odor, an acrid smoky smell, which can irritate the
eyes if exposed for a prolonged period to the liquids. The cause of this smell
is due to molecular weight aldehydes and acids. The liquid contains several
hundred different chemicals in widely varying proportions, ranging from
formaldehyde and acetic acid to complex high molecular weight phenols, a hydro
sugars and other oligosaccharides.
refer to the char produced during the process of pyrolysis. Their typical
amount retained in the liquid oil is 0.2% by weight. However, 0.1 weight % is a
good level and 1% is often consumed.
practically no ash to be separately identified from the char. All of it is
associated with the char and is assumed to be 0%.
184.108.40.206 Moisture Content
average value is 25% by weight, but the values can range from 15 to 35%. The
water in the bio-oil comes from the moisture in feed and from the reaction. It
cannot be separated from the liquid oil.
density of the liquid is very high at around 1.2 kg/L, compared to the light
fuel oil at around 0.85Kg/L. This means that the liquid has about 42% of the
energy content of fuel oil on a weight basis, but 61% on a volumetric basis.
This has implications on the design and specification of the equipment as
viscosity of the bio-oil is measured at 40C and with 25% water. The viscosity
of the bio-oil as produced can vary from as low as 25 grapes to as high as 1000
grapes more, depending on the feedstock, water content of the oil, the amount
of light ends that have been collected and the extent to which the oil has
aged. Viscosity is important in many fuel applications.
liquid contains varying quantities of water which forms a stable single phase
mixture, ranging from about 15%by weight to an upper limit of about 30-50% by
weight of water, depending on how it was produced and subsequently collected.
Pyrolysis liquids can tolerate the addition of some water, but there is a limit
to the amount of water, which can be added to the liquid before phase separation
occurs. In other words, the liquid cannot be dissolved in water. It is miscible
with polar solvents such as methanol, acetone, e, but totally immiscible with
220.127.116.11 Higher Heating Value
stands for the Higher Heating Value and depends on water. Bio-oil has a higher
heating value of about 18 MJ/Kg as produced with about 25% by weight of water
that cannot be separated.
of the bio-oil is 2.5 and this low pH comes from the presence of organic acids.
18.104.22.168 Elemental Analysis
bio-oil gives the following elemental analysis, typically:
Carbon C 57%
Hydrogen H 6%
Oxygen O 37%
Nitrogen N trace
trace (depends on char content)
Pyrolysis liquids cannot be completely vaporized once they have been
recovered from the vapor phase. If the liquid is heated to 100C or more to try
to remove water or distil off lighter fractions, it rapidly reacts and
eventually produces a solid residue of around 50% by weight of the original
liquid and some distillate containing volatile organic compounds and water. The
liquid is, grapestherefore, chemically unstable, and the instability increases
with heating, so it is preferable to store the liquid at room temperature.
These changes do also occur at room temperature, but much more slowly and can
be accommodated in a commercial application.
22.214.171.124 Aging of Pyrolysis liquid
complexity and nature of bio-oil causes some unusual behavior, specifically in
a manner that the following properties tend to change with time:
Volatility decreases, and
Phase separation and deposition of gums can occur.
Any form of biomass can be
considered for fast pyrolysis. While most work has been carried out on wood due
to its consistency, and comparability between tests, nearly 100 different
biomass types have been tested by many laboratories ranging from agricultural wastes
such as straw, olive pits and shells to energy crops such as miss- canthus,
sorghum, and solid wastes.
3.1 Biomass Resources
resources are classified into following main categories:
gives higher yield than herbaceous and fruit biomass,
3.1.1 Woody Biomass
the names of some commonly used woody biomass materials:
10. Bark fir
Hard wood pellets 11. Bamboo
12. Guayule bagasse
13. Chicken litter
14. Alfalfa stem
Hgrapes- Mat sector 15.
3.1.2 Herbaceous Biomass
Wheat straw 5. Switch grass
3.1.3 Fruit Biomass
Some of the
common fruit biomass materials are:
Empty fruit bunches
10. Orange peels
Peas shells 11.
Dry fruit shells (e.g. peanuts, walnuts) 12.
13. Sugar beets top
3.1.4 Miscellaneous Materials
which can be used as biomass are:
Construction and demolition debris 5. Manure
6. Sewage sludge
Slaughter-house wastes 7. Household organic wastes
8. Cotton rags
3.2 Biomass Constituents
constituents in biomass are the following:
carbohydrates found in biomass include starch, cellulose, hemi-cellulose and
are the high molecular-weight and branched poly-aromatic structures (cell walls).
included are oils, fats and waxes (e.g. triglycerides, cholesterol).
the amino acid chains found in organic and life matter.
The operation of pyrolysis in our experiment is carried out in a
batch system. A small amount of the biomass is taken in a small stainless steel
autoclave. The autoclave is closed tightly to avoid any unwanted escape of the
gases to be produced and the entry of air. The autoclave is heated by the help
of burners. The numbers of burners used depends on the temperature required.
The temperature of the pyrolytic chamber is kept between 450-5200C
and the pressure atmospheric, although the pressure increases when the vapors
start to generate.
The temperature is maintained into the process up to 450 c.
The water tank is placed the equipment in order to cool down or
condense the produced vapors.
4.2 Equipment and Installation
The equipment used is mostly from the pulp and paper laboratory of
our department. The temperature gauge was bought and the condensers were
borrowed from the process technology lab. The various parts of the
experimentation system are explained in the following sub-sections
The autoclave is a stainless steel vessel. It has basically two
parts. The upper one is a pipe shaped so as to facilitate the application of
any equipment, measurement device and any other auxiliary; and to provide a
controlled passage for the gases, whose flow is controlled with the help of a
The temperature gauge used
is automatic type showing the temperature inside the au.
The transportation tube is
a pipe made of copper. It is used normally in refrigeration system. It is used
to transfer the vapors formed in the to
the condenser section. The metallic tube can be of various shapes depending on
the ambient temperature, in order to provide heat transfer with the
surroundings. It can be straight or can be coiled (Figure 4.2-5), immersed in
with condensation assembly are used in this experimentation. The coolers are
made of glass
The coolers are
basically cylindrical pipes with a helical glass tube inside it, which has its
own isolated path. The condenser is a type of heat transfer equipment that is
enhanced with an outer jacket (Figure 4.2-7) made of plastic (polyethylene
terephthalate) bottle. In the jacket, salted ice is filled to provide
condensation of the Vapors and cooling of the gases inside the cooler tube. Tap
water flows through the inner helical tube to provide cooling.
4.2.5 Glass Tube for Liquids
liquids obtained from pyrolysis. These liquids may not sometimes condense due
to high temperature developed in the condensation section.
4.3.1 Wheat straw
Wheat straw is obtained from agricultural farms. It is used in the
countryside as fodder for cattle. Pakistan has an abundant quantity of it
produced each year. But its other use is only as a raw material in the
manufacture of paper and board.
5.1Testing of biomass materials
The testing of biomass
materials was carried out in order to evaluate that which type of these wastes
has the highest potential of having a bio-fuel. This testing was carried out in
the fuel testing laboratory of our department.
5.1.1 Biomass material
The biomass material we used is wheat straw.
5.2 Testing procedure
A known weight of crushed biomass sample is placed in a crucible
that has already been antested its weight. The crucible is then covered to
avoid its direct contact with air, which will otherwise its direct contact with
air, which will otherwise lead to combustion of material.
The covered crucible is
then heated in Muffle furnace at temperature of about 400 °C, for 7 minutes.
After completion of the heating process, the remained ash or char left from the
biomass is weighted to find the percentage loss in weight. Thus, the percentage
of volatile compounds, which would surely contain pyrolyzed chemicals from the
biomass, is known through this method.