A TWO-BURNER RICE HUSK GASIFIER STOVE FOR BOILING COCOSAP

by
Alexis Belonio, Alvin Guadalupe, Hermes Aguila, and Francisco Cuaresma
Glory to God!!
Amid the ever increasing prices of
conventional fuel sources like kerosene, LPG,
and wood, a two-burner rice husk gasifier
stove that can effectively boil cocosap and
convert it to syrup was recently developed.
This technology is another breakthrough
project of the Center for Rice Husk Energy
Technology (CRHET) under the CLSUCRHET Rice Husk Project at the College of
Engineering, Central Luzon State University
at the Science City of Munoz, Nueva Ecija.
This project aimed to provide a cheaper way
of boiling coconut sap and converting it to
syrup by using gasified agricultural waste as
fuel, like rice husks.  By gasifying rice husks,
a combustible clean gaseous and low-cost
fuel can be generated to economically heat
and boil cocosap and convert it to syrup.
Converting cocosap to syrup would basically
require about 2 hours of boiling.  Doing this activity using
conventional fuel, about 1.1 kg of LPG is needed to
convert a liter of cocosap to syrup.  Alternatively, around
44 kg of LPG is needed to convert 40 liters of cocosap to
syrup, which costs a lot to the processors consequently
reducing the income that they can derive from cocosugar
production. On the other hand, using wood in boiling
cocosap often results in overheating the syrup which
subsequently produces crystallized sugar and darkens the
color of the finished product. Smoke emission, moreover,
contributes to unhealthy operation and results in producing
low-quality products.
The Rice Husk Gasifier for Boiling Cocosap
Burning Gas from the Stove
Basically, the
rice husk
gasifier stove is
a larger version
of the
continuous-type
stove previously
designed for
domestic use. It
also follows the
principle of a
moving-bed
downdraft
gasifier that
produces
combustible
gases by burning
rice husks in an
oxygen-starve
environment.
The gasifier basically consists of a 35-cm diameter reactor where rice husk is gasified, a char box
where char is temporarily held and gradually discharged to ensure continuous operation, a gas
pipe that delivers the gas from the reactor to the gas burners, a two-burner assembly where 20-liter capacity kettles are heated to boil cocosap on a drum-type burners, and a 2½-in. electric
blower that supplies the air needed for combustion of rice husks and forces the gas generated to
the burners.
Forty (40) liters of fresh cocosap
can be boiled continuously in the
stove turning it to syrup in 2
hours. The start-up time in
operating the stove is 5 to 10
minutes before combustible
gases reach the burner.  Rice
husks are consumed at a rate of
12 kg per hour, with specific
gasification rate of 125 kg/hr-m
2
.
About 4 kg of rice husks is
needed to replace a kilogram of
LPG.  The gas temperature
ranges from 209° to 258°C.  The
Boiling of Cocosap in the Gasifier Stove
computed heat output is 9,020 kcal/hr.  It takes around 15 to 20 minutes to boil 40 liters of
water/cocosap, sustain the boiling until the sap turns to syrup. The gasifier is manually operated
by loading rice husks into the reactor through a feed hopper and by removing gradually the char
with the use of a sweeper.  About 3.6 kg of char is produced per hour.  One person can attend
four units of the gasifier at a time.
Pictorial of the Conversion of Cocosap to Syrup Using the Rice Husk Gasifier Stove
The advantage features of the gasifier stove
are: (1) It is a good alternative to LPG-fueled
stoves since the intensity of firing is also easily
controlled; (2) Almost no smoke during
operation thus providing a clean environment
while boiling the sap; (3) Rice husks are
available and hauling cost is very minimal or
sometimes free at all; and (4) The by-product
of the stove, which is char, can be used to
improve the soil condition in the coconut tree
plantation which subsequently improves the
production of sap in terms of quantity.  Just
like any other equipment, however, the use of
this two-burner rice husk gas stove has also
limitations which include the following: (1) A
power supply line is needed to energize the
blower; and (2) Training on the operation and
maintenance of the stove is required to fully
understand its proper operation and to lengthen
its service life.
The total investment for the gasifier stove, as
Series of Fabricated Rice Husk Gasifier Stove
for Boiling Cocosap
of July 2012, varies from P70,000.00 to P150,000.00 (excluding freight and transport cost)
depending on the type of accessories needed and degree of automation.  The operating cost of the
stove is computed at a maximum of P30.17 per hour. In terms of the quantity of coco sap and of
sugar, the operating cost of the stove is P2.01 per liter of coco sap and P14.08 per kg of sugar.
The investment cost for the stove can be recovered within 5 months, against the use of an
industrial-size LPG stove.
Further development is being done with regard to the use of the gasifier for jacketed kettle, for
crystallization of sugar, for steamer/dryer, and for micro gasifier for power supply particularly
for areas where the processing plant is located far from the grid.
For further information, please contact:
The Project Director (atbelonio@yahoo.com)
CLSU-CRHET Rice Husk Project
Room 201, PHILSCAT, Central Luzon State University
Science City of Munoz, Nueva Ecija, Philippines
Released:  August 2012