A 5-KWE RICE HUSK GASIFIER POWER GENERATING PLANT

by
Alexis Belonio
Glory to God!!
A 5-kWe rice husk gasifier
power generating plant was
recently developed to provide
out-of-the-grid areas of a local
technology for generating
electricity using rice husks as
fuel.  By gasifying rice husks, a
clean fuel is produced which
can be used as replacement for
the conventional gasoline fuel
for a spark-ignition engine that
drives a generator to produce
electricity.  This technology is
another development by the
Center for Rice Husk Energy
Technology, in collaboration
with private entrepreneurs,
aimed to provide the rural
sector an appropriate
technology for generating
electricity using agricultural
wastes as fuel.
As shown at the right, the gasifier
generally consists of:  a reactor where
rice husks are converted to
combustible gas rich in carbon
monoxide, hydrogen, and a very little
of methane; a wet scrubber where the
gas, after leaving the reactor, is washed
by spraying with water; a packed-bed
filter which mechanically screens the
gas leaving the wet scrubber; and an
engine-generator set which produces
electricity using the gas generated.
Pictorial of the 5-kWe Rice Husk Gasifier
Power Generating Unit
The gasifier reactor is a moving-bed downdraft
type with 0.35-m diameter. The wet scrubber
is an impact-type with 10-cm diameter by 1.2-m high spray tower and a water tank made of
200-liter-capacity petrol drum. A 1/2-hp selfpriming pump is used to circulate the water
from the tower to the tank, and vice versa.  The
hot water is subsequently cooled in the pond
made of petrol drum which was cut into halves.
The packed-bed filter is also mad e of a petrol
drum with filter material made of 0.4-m thick
rice husks, wood chips, stone or anything that is
readily available in the farm.  After passing the
filter, the cleaned gas is directed to a 16- or 18 -hp gasoline engine to drive the 5-KW AC
synchronous generator.
Rice husks are manually fed into the gasifier reactor using a platform.  Char is discharged from
the bottom end of the reactor by swinging the lever and by rotating the scraper to eliminate
bridging. As rice husks burns
inside the reactor, the fire zone
moves upward producing
combustible gas which is
subsequently used as fuel for the
engine. The gas is cleaned and
cooled by allowing it to pass
through a series of washing and
filtering to remove particulates
and tars.  The water used in the
wet scrubber is cooled naturally in
a pond of water located next to
the scrubber. Accumulated
particulates and tars are allowed
to drip out of the tank and of the
pond from time to time. Water is
added or replaced in the cooling
pond when needed.  Filters are
backed-wash, when needed, to
clean.
The gasifier consumes 12 kg of rice husk per hour.  It requires 5 to 10 minutes from start-up to
produce combustible gases from the rice husk fuel.  The temperature of the gas leaving the
reactor ranges from 205° to 258°C. After passing the wet scrubber and the packed-bed filter,
The Gas Intake Port to the Engine
the gas temperature drops to around 38° to 43°C. The computed specific gasification rate of
the gasifier is 125 kg/hr-m
2
.   Water to gas ratio is 2.1 liters per m
3
of gas.  The total electrical
power produced is 4.9 kWe with parasitic load of 1.0 kWe.  Specific fuel consumption is 2.4
kg/hr-kWe.
The power generating device can provide electricity to remote places that are far from grid to
light group of houses, small community street lighting, and to energize  home-based industry.
Using this device, moreover, disposal of rice husks can be addressed and the problem on
greenhouse gas emission can be mitigated since gasifier, basically, has reduced CO2
and black
carbon emission during operation.
The gasifier power generating unit can be built locally using available local materials such as
petrol drums, steel bars, and metal sheets and plates.  Standard parts such as pump, blowers,
engine, and generator can be purchased from local suppliers.  Local skills can be utilized in
constructing the gasifer using commonly available tools and equipment.   Investment cost for
the plant, including the shed , is around P250,000.00. One person is needed to attend the
operation of the plant – i.e., to load fuel and to discharge char as well as to oversee the
operation of the different components of the power generating unit. Investment can be
recovered within a year, considering an 8-hour operation a day and the cost of rice husk of
P5.00 per bag, as compared when the engine driving the generator uses purely gasoline fuel.
For further information contact:
The Project Director (atbelonio@yahoo.com)
Center for Rice Husk Energy Technology
CLSU-CRHET Rice Husk Project
Room 201, PHILSCAT
College of Engineering, Central Luzon State University
Science City of Munoz, Nueva Ecija, Philippines
Acknowledgment:
CRHET acknowledges Pauchon Research Foundation of Morgan Hill California for the support in carrying out this
project to develop series of micro-gasifier power generating units to benefit the rural people, especially the
farmers. The Tech Awards 2010 and the Rolex Awards for Enterprise 2008 for the funding support in the early
development of rice husk gasifiers, particularly the moving-bed downdraft-type reactor.  To Edward Ligisan and
Charlie Buco of Biomass Energy System and Technology Enterprises (BEST-e) for fabricating the unit of the gasifier
as well as to Genesis Lazo and Roel Pranilla who assisted in the testing of the gasifier.
Updated:  January 2013