ENVIRONMENTAL BIOTECHNOLOGY

1. Production of oils and fuels from
wood waste
Dr. Esther Shoba R
Assistant Professor
Kristu Jayanti College

2. • In a continuing search for alternative supplementary energy
sources, wood wastes, bovine manure, and municipal organic
refuse have been successfully converted into oil
• This is an important technological development in view of the
energy shortage as well as the waste-disposal problems
• Wood chips are selected as feedstock

3. Process
Basically, the process involves reacting carbon monoxide with the wood
wastes in the presence of a sodium carbonate solution as a catalyst at up to a
temperature of 700 deg F (371 deg C) and up to 4000 psig.
Carbon monoxide reacts with sodium carbonate in the presence of water to
form sodium formate which, in turn, reacts with cellulose in the wood wastes
to form oil and regenerate sodium carbonate.

5. • Drying and Grinding
• Wood wastes have a high moisture content (up to 50 percent) and
practically no ash.
• drying the wood wastes to approximately 4 percent moisture
content because
• (1) excessive moisture going into the reactor with the wood
effectively reduces the reactor capacity, and
• (2) dry wood grinds much more easily than wood with a high
moisture content.
• Grinding dry wood to a fine powder is necessary to facilitate
pumping a wood-oil slurry.

6. Feed Systems
Wood-Oil Slurry Feed System
The dried and ground wood is continuously mixed with oil to form
a slurry with up to 30 percent solids content.
For initial start-up, anthracene oil is used; after the plant is in
operation, oil produced in the process is recycled for slurry
preparation.
This slurry is extremely thick and poses a problem in pumping at
4000 psig.
A plunger pump with special knife-edged spring-loaded cone
valves will be used to develop the required pressure.

7. • The catalyst used in this process is a 20
percent sodium carbonate solution.
• Carbon monoxide will be compressed in a
diaphragm compressor to a pressure of 4000
psig and introduced into the reactor through a
dip pipe.

8. • Solids Feed System
Two methods were considered for feeding solids directly into
the reactor: (1) pneumatic, and (2) mechanical feeding.

9. • Pretreated Wood-Oil Slurry System
• This is another alternative to feeding wood wastes into the
reactor. It is similar to the wood-oil slurry feed system except
that it involves pretreatment of wood wastes with water at up
to 500 deg F (260 deg C) and up to a pressure of 700 psig.
Under these conditions, wood is converted into material
similar to charcoal.
• A pretreater will be loaded with wood wastes and water and
heated up to 500 deg F.
• This will build up pressure to 700 psig because of the vapor
pressure of water.

10. • After maintaining the process conditions for the required length of
time, the pretreater and its contents, which comprise a 15 percent
slurry of pretreated wood in water, are cooled to 150 deg F (66
deg C) through an external pump-around loop, including an air-
cooled heat exchanger, and then transferred to a holding tank.
• The pretreated wood is filtered out, dried, ground, mixed with
either anthracene or recycle oil, and fed to the reactor as
previously described.
• The advantage of pretreating the wood wastes is that it can be
slurried in oil up to 50 percent.

12. • The reaction is carried out continuously in a
stirred pressure vessel at 4000 psig and 700
deg F (371 deg C).
• The process conditions will be optimized in
this pilot plant to achieve the lowest operating
pressure and temperature.
• The pressure in the reactor will be controlled
by the pressure-reducing valve in the reactor
off-gas line.

13. • Reactor Off-Gases
• After exchanging heat with the incoming carbon monoxide,
and after the pressure reduction, the reactor off-gases
(consisting primarily of carbon monoxide, carbon dioxide, and
water vapor) are cooled and flashed to recover light oils and
water.
• The non-condensible gases are burned in a flare stack. In a
commercial plant, it is anticipated that the non-condensible
gases will be purified to remove ammonia and hydrogen
sulfide and then burned along with a portion of the synthesis
gas in a Dowtherm system to provide approximately 90
percent of the heat requirements of the plant.
• The waste gases will then be vented to the atmosphere.

14. • Oil Recovery
• The liquid phase from the reactor is also flashed after it is cooled.
Light oils and water are removed from the flashed gases, and the
noncondensable gases are disposed of in the same way as the
reactor off-gases. The liquid consists mainly of the oil, water,
unconverted wood, and sodium salts of organic acids.
• The liquid phase is centrifuged to remove suspended solids and
water. The oil, thus recovered, is recycled back to the processes, as
needed, and the remainder is stored as product. The oil produced
has the following characteristics: