by: Alexis Belonio and Billy Belonio
Drying paddy is one of the major problems of
seed growers in Nueva Ecija. Oftentimes when
drying coincides with rainy periods, seed grains
become deteriorated because of the inability to
dry them which results in a poor germinability.
The use of mechanical drying is the alternative
method to dry seed grains in order to assure
good quality, especially during rainy periods. The
use a flatbed dryer has been proven to be the
simplest method of drying grains since almost no
moving parts in it, except the fan. Additionally,
using rice husks as fuel is the cheapest energy
source for heating the dryer. However, the use
of traditional rice husk furnaces as a source of
heat for the flatbed dryer has brought lots of
problems. The major problems or feedbacks
about the use of traditional rice husk furnaces
for the dryer are: (1) investment cost per power
output is high; (2) inconvenient to use, requiring
lots of attendance during operation; (3) smoke
emission is excessive, especially at the start up; (4) difficult to maintain the right temperature
for drying; (5) life span
is short, since parts
easily get corroded
brought about by the
intense heat; and (6)
char and ash
particulates go with the
drying air.
Schematic Drawing the Continuous‐Flow
Rice Husk Gasifier
The Gasifier as Coupled to the Flatbed Paddy Dryer
In order to overcome
these problems, a
recently developed
moving‐bed inverted
downdraft rice husk
gasifier was tested and
evaluated for the
flatbed dryer in drying
rice seeds in
Mapangpang, Munoz, Nueva Ecija. Instead of using the traditional rice husk furnace, a rice husk
gasifier was used. The gasifier produces combustible gases from rice husks as contrasted with
direct combustion of rice husks in the traditional rice husk furnace. The gasifier, as shown
above, basically consists of a feed hopper, a reactor, a char chamber, a gas burner, a ladder,
and a support leg. Rice husks are fed at the reactor through a feed hopper. With limited
amount of air (1.25 m
3
per kg of fuel), rice husks are burned which produces carbon. When the
carbon gas produced reacts with air, it produces combustible gases that are rich in carbon
monoxide and hydrogen. Burning of rice husks starts from the bottom and it moves vertically
upward along the reactor. Hot air is introduced from the top and leaves through the char
chamber’s annular space. The gases are allowed to pass through the particle separator before
they are burned in the gas burner. The char is discharged by swinging the scraper at the
bottom of the char chamber.
The Burning Gas Coming Out of the Gasifier Burner
Entering the Dryer Fan
The gasifier is coupled to the
flatbed dryer by positioning its
burner 30‐cm apart from the
dryer fan inlet in offset position.
Combustible gases are
produced from the gasifier
within 15 to 20 minutes after
ignition of fuel. Burning gas
provides the required heat for
drying seed grains at a
temperature of 39 to 43°C. The
0.4‐meter diameter gasifier
reactor can sufficiently provide
the heat energy needed by a 4‐
ton capacity flatbed dryer;
whereas, the 0.5‐meter
diameter gasifier reactor suits
perfectly for a 6‐ton capacity
dryer. Only one person is
needed to attend the operation
of the gasifier, that is, to load
fuel and to discharge char. Seed
grains are dried in the flatbe
dryer using the gasifier within
12 to 14 hours consum
kg of rice husks per hour per
The Paddy Seeds Being Dried in Flatbed Dryer
Using the Gasifier.
d
ing 5 to 6
ton
of rice seeds. Results of tests conducted revealed that rice seeds dried in the flatbed dryer
using the gasifier has higher germination percentage of 85% and above.
The advantages of the use of gasifier for the flatbed dryer are: (1) It is convenient to use ‐ the
ignition time to produce gaseous fuel is very short also the loading of rice husks and the
removal of char are simple; (2) No smoke emission is observed during operation – the smoke
produced are combustible and are efficiently burned in the burner; (3) Easy to control and
provides uniform temperature for drying – the amount of heat can be easily increased or
decreased with the use of a rheostat switch or a gas valve and no wider fluctuation in the
drying temperature during operation that can be observed; and (4) Low electrical consumption
per power output – only 0.01 kWe per kWt is needed to run the gasifier.
The gasifier cost P90,000.00 which includes the reactor and the two units 2½‐in. electric
blowers. The electric consumption of the two blowers is 32 watts. The investment for the
gasifier can be recovered within a year provided that drying operation will be done 20 days per
month and 9 months per year.
For further information, contact: The Project Director, Center for Rice Husk Energy Technology,
College of Agriculture, Resources and Environmental Sciences, Central Philippine University,
Iloilo City, Philippines. Email: atbelonio@yahoo.com and website: www.crhet.org. You can
also contact Engr. Billy Belonio for the technical aspect of the gasifier and the dryer at
btbelonio@yahoo.com or at +639167173476. Interested seed processors who would like to
see the technology can contact Ms. Divina Gracia Boydon (+639164219007) at Mapangpang,
Science City of Munoz, Nueva Ecija.
Released: November 2009
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