DUAL-REACTOR RICE HUSK GASIFIER WITH GAS-PIPE BURNER

by

AlexisT. Belonio, BSAE, MSc,PAE
Appropriate Technology Center
College of Agriculture
Central Philippine University
Iloilo City, Philippines
cpu_aprotech@yahoo.com
Fuelling LPG oven with biomass
fuel is quite difficultto achieve. With
the dual reactor rice husk gasifier,
however, LPG oven can now be
retrofitted with gasburner using
biomass rice husk as fuel. This
technology was developed at the
Department of Agricultural
Engineering and Environmental
Management, College of
Agriculture, Central Philippine
University, Iloilo City, Philippines.
Test runs on the performance of this
rice husk gasifier were conducted
with the assistance from the following
T-Chimney
GasPipe
Burner
FuelReactor
Char
Collector
CharGrate
Lever
Gas
Pipe
CharChamber
Schematic Drawing ofthe Dual Reactor
Rice husk Gasifier
agricultural engineering students
Jason Gem Villaruel, Lucio Larano, Daniel Belonio, Yvone Herbo, and Jeffrey
Cocjin . The rice husk gasifier adopts two top-lit updraft (t-lud) type reactors so
as to allow continuous supply of combustible gases into the gas-pipe burner that
is suitable for LPG bakery ovens.
Each reactor,
right photos, has
a diameter of
0.25 m and a
height of 1.05 m.
It is here in the
reactor where rice
husk is gasified
by burning it with
limited amount of
air (equivalence
ratio = 0.27). In
order to prevent
the heat from
The Dual Reactor Rice Husk Gasifiers with Gas-Pipe Burner
radiating from the reactor, a 5-cm ricehusk ash insulation was provided between
the inner and the outer cylinders. Beneath the reactor isa char chamber to hold
burnt rice husk discharged after each operation. A flat grate made of 6-mm
diameter plain round bar, with ¼-in. spacing, is used to hold rice husk during
operation. This grate can be released manually to discharge the char from the
reactor. A 2-in. diameterelectric blower is used to push the ambient air into the
fuel bed to gasify rice husks at a rate of 34.4m
3
per hour. The reactor is
provided with a lid to facilitate loading and igniting of fuel. The gas produced
during gasification is diverted out of the reactor through a cylindrical-momentum
type separator that is made of 3-inch GI pipe. A 1¼-in. diameter chimney is used
to divert unwanted gases at the initial stage of firing the fuel. When quality gas is
produced, it is diverted out to a 1-1/4 in. diameter gas-pipe burnerfor subsequent
burning. The gas burner is made of GI pipe with series of 3/16-in. holes spaced
at ¼ in.
Performance tests of the gasifier
were carried out thru series of runs
using freshly obtained rice husk
from a rice mill. The weight of rice
husk fuel and of char was
recorded using a 10-kg spring
scale. The temperature of the gas
leaving the reactor and the gas
entering the gas-pipe burner were
taken using a type K thermocouple
wire thermometer. The pressure
draft in the fuel bed inside the
reactor was also measured during
the tests using a U-tube manometer.
BurningGases fromthe Gas Pipe Burner
Results showed that firing of rice husk fuel can
be easily done and spontaneous combustion
is achieved within a minute. Each reactor
contains an average of 4.96 kg of rice husk
per load and producesa char of 1.25 kg after
each operation. Tests also showed that a fully
loaded reactor with rice husk fuel can be
operated within 29.50 minutes with specific
draft of 25.73 mm of water per meter depth of
fuel . The computed rice husk consumption is
10.18 kg per hour while the specific
gasification rate is 191.77 kg/m
2
-hr. The rate
of movement of the fire zone is 3.42 cm/min
with superficial gas velocity of 5.41 cm/sec.
The temperature of gas leaving the reactor
varies from 270 to 320ºC. The gas enters the
Close-Up View of the Burning
Gases
gas-pipe burner at a temperature of 152 to 170ºC. The thermal efficiency of the
gasifier, based on the amountof combustible gases produced from the burner
and the fuel used, is 41.11%. The computed power output ofthe gasifier is
14.89 kW. The gas burnerwas found to have satisfactory performance
producing a bluish to pinkish flame color at a gas velocity of 1.22 meter per
second. The power input of the electric blower is 0.04 kW-hour.
The reactors are operated in sequential mode to provide a continuous supply of
combustible gases into the gas-pipe burner. In order to attain uninterrupted
operation, the second reactor must be ready at least 3 minutes before the fuel in
first reactor is fully consumed. One person is needed to attend the operation of
the gasifier for sequential loading ofrice husk and unloading of char.
The total cost to produce the gasifier at current prices is P35,000.00. Production
period takes at least 2 weeks employing two skilled workers. When used in a 24-plate bakery oven, the computed payback period is less than one year compared
with LPG fuel.
Based on the results of the study the following are concluded and recommended:
(a) The gasifier is a simple and a low-costtechnology that can be effectively used
as replacement for LPG fuel;
(b) It can be fabricated in a small fabricating shop using local materials;
(c) The gas produced from the gasifier can be successfully burned in a gas-pipe
burner and is suitable for use in an LPG-type bakery oven; and
(d) There is a need to consider the kind of materials to be used for the inner
cylinder of the reactor to prolong its useful life.
Inquiry regarding this technology can be coursed through the Project Director,
AppropriateTechnology Center, Department of Agricultural Engineering,
Environmental Management, College of Agriculture, Central Philippine University,
Iloilo City, Philippines.You may contact us through phone (063-033-3291971 loc
1071) and/or email (cpu_aprotech@yahoo.com).
1 US$ = 55 PHP