IMPROVED VERSIONS OF THE CONTINUOUS-TYPE RICE HUSK GAS STOVE FOR HOUSEHOLD-USE

by
Alexis Belonio and Elmer Castillo
Glory to God!!
An improved version of the continuous-type rice husk
gas stove was developed to provide rural households a
technology for cooking not requiring frequent
unloading of char and refueling of rice husk fuel. The
improved version of the stove comes in two different
models, these are:   (a) The single-burner stove, with
12cm-diameter reactor and (b) The double-burner
stove, with 14cm-diameter reactor.  To ensure safe
operation, both models are powered by a 12-volt DC
fan making it more adaptable to available power source
- may it be a grid, a battery, or a solar panel.  This
development is another breakthrough by the Center for
Rice Husk Energy Technology (CRHET) with funding
support from the Rolex Awards for Enterprise 2008 and
The Tech Awards 2010. CRHET aims to broaden the
adoptability of the rice husk gasifier stove as a cooking
device for households as well as for home-based
industry.
The stove, shown at the right,
basically consists of the following
parts:  a fuel hopper where rice
husks are fed; a fan which
supplies the air needed for
gasification; a reactor where rice
husks are gasified using limited
amount of air; a gas burner where
combustible gases generated are
ignited; a gas duct where gas
produced is channeled from the
reactor to the burner; an ignition
port where rice husk fuel is
ignited; an adoptor which is used
to regulate the intensity of the flame; a char sweeper which facilitates the removal of burnt rice
husks; a pan which makes the collection of char easy; and support legs which support the entire
structure.  A continuous and easy operation is
achieved in these improved models of the stove
where a smokeless blue flame, which is similar to
that of an LPG- fueled burner, is obtained.  The
salient feature of these improved models is that
there is no need of reloading and igniting rice husk
fuel just to prolong the operation of the stove. The
intensity of fire can be controlled either by adjusting
the opening of the gas burner or by changing the
input voltage of the adoptor selector switch.  With
the two-burner stove, households can finish cooking
in a shorter period of time since they, for instance,
can cook rice and cook dish or boil water
simultaneously.
During the performance testing of the stove, it was
observed that the single-burner has a bit longer
start-up time to generate gas than the doubleburner which is 5 to 10 minutes and 4 to 7 minutes,
respectively. This difference in start-up time may be attributed to the size of the ignition port,
which is smaller for the single-burner stove.  Rice husk consumption of the single-burner stove
is 1.1 kg per hour while
that of the two-burner is
1.6 kg per hour.  Results of
performance tests further
revealed that the gas
temperature at the duct is
hotter for the two-burner,
which is around 110C,
than the single-burner,
which is around 90C. The
temperature beneath the
pot is measured at 410
and 460C for the singleand double- burner,
respectively.  In terms of
boiling test, two liters of
water takes 17 minutes to
boil in the single burner
while 8 and 9 minutes in
the double burner, with 1
liter on each burner.  The
computed specific gasification rate is 94 kg/hr-m
2
for the single-burner and 102 kg/hr-m
2
for
the double-burner stoves. The power input and output for the single- burner are 3.7 and 1.0
kWt and for the double-burner are 5.6 and 1.8 kWt, respectively.  The char obtained per hour
of operation is 0.33 and 0.48 kg from the single- and from the double-burner stoves,
respectively.
These stove designs were simplified versions of the continuous-type rice husk gasifier stove
prototype model.  Local materials can be used in the construction of these stoves employing
local labor in the rural areas.  One person can build a unit of the single-burner stove in less than
2 days while the same number of labor can build a unit of the double-burner in not more than 3
days.  The stoves as of July 2013 are available at P5,000.00 per unit of the single-burner and at
P7,500.00 per unit of the double-burner stove.  Comparing it with the LPG-fueled stove, users
of these improved-version stoves can recover their investment cost in 4 months.  These
improved-version stoves have the advantages over the conventional direct combustion stoves
in terms of reduced greenhouse gas emission (CO
2 and black carbon) and of savings on fuel.
Further development on the stove is underway applying the steam injection principle to further
enhance its performance.
For further information, kindly contact:
The Project Director
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
atbelonio@yahoo.com
Released: July2013
Acknowledgement:
Thanks for 6m’s Ag Biosystem Engineering Enterprise and Consultancy Corporation for the
support during the development of this improved continuous-type rice husk gas stove and for
the dissemination of this technology nationwide.