INVERTED-DOWNDRAFT COAL GASIFIER FOR SMALLSCALE INDUSTRY THERMAL APPLICATION

by
Alexis Belonio, Daniel Belonio, Fraciscus Tria Garleman, Bima Tahar, and Djoewito
Atmowidjojo
Fuel source for small-scale
industry heating application is
becoming expensive. This is
more so for food, grain, and
other processing industries in
Indonesia where the energy
sources for various processes
are highly dependent on
conventional fuel. At present,
the cost of LPG went up to
IDR 7,000 per kg while
kerosene and diesel to as high
as IDR 12,000 and IDR 5,500
per liter, respectively.
Coal, which is one of the
abundant fuel resources in the
country, is a potential
alternative to address energy crisis. As of
2006, Indonesia has about 4,968 millions tons
of coal reserves. With the present market
prices of coal at IDR 400 to IDR 1,500 per kg
and with the application of the method of
extracting heat energy from coal by
gasification, a clean and convenient method
of utilizing coal can be done as compared
with the traditional burning devices where
sulfur oxides and smoke emissions are
common problems.
In September 2008, the PT Minang
Jordanindo Approtech designed and
developed a coal gasifier to serve as
alternative to conventional burners using
LPG, kerosene, and diesel fuel burners. By
gasification process, coal can be conveniently
burned with almost no smoke and no sulfur
odor at all. Combustible gases generated
from the reactor can be piped-in to a burner
for heating stoves, mechanical dryers, kilns,
and even boilers.
The Gasifier with Drum‐Type Burner
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Temperature ( C )
Time (10 x min)
Gas
Flame
As shown in the first two photos above, the gasifier is a
fixed-bed type operating inan inverted downdraft
mode. It has a fuel feed tray for manual loading of coal
into the reactor. The fuel reactor where the coal is
gasified by burning it with limited amount of air, is
made of 3-mm thick stainless steel plate having a
diameter of 0.35 m. Burnt ash or slag obtained from
the reactor is temporarily collected in the chamber
before they are discharged through the ash outlet. The
gas, before it is conveyedto the burner, passes through
a 0.6-m diameter separator to remove fly ashes. Two
types of gas burners are usedfor the gasifier: One is a
jet-type burner (0.15-m φ) for heating dryer or for
firing kiln or other similar devices, and the other is a
drum-type burner (0.40-m φ) for cooking, boiling,
steaming, and/or frying. Pressure relief devices are
coupled into the reactor and into the separator for
safety purposes in discharging build-up pressure in case
there is pre- ignition of gases. Three 2-1/2-in. electric
blowers (1/4 hp, 220 V) provide the air needed for
gasification and for cooling the reactor. The entire
construction of the gasifier is made of mild steel as
primary materials except for the reactor cylinders
where stainless steel is used to minimize heat corrosion problem.
The gasifier was tested using crushed and briquetted coals as fuel at 1 to 3-cm sizes.
Charcoal fuel was used as igniter to conveniently set the fuel into firing with almost no
smoke emission. At the start of ignition, valves are regulated to exhaust premature gases into
the chimney and to divert quality gas into the burners when fully developed. The gasifier is
operated by one person who
needs to ensure of the proper
operation and at the same time
to load fuel and discharge
ashes.
Performance tests of the
gasifier showed that it requires
22 to 35 minutes to generate
combustible gases, from the
start of ignition of fuel. After
10 to 25 minutes of operation,
high quality gas is obtained
from the gasifier. Coal
consumption is minimum at
12 kg per hour and maximum
at 20 kg per hour when the
blower is fully opened. The
computed specific gasification
rate ranged from 125 to 208
Crushed Coal
Briquetted Coal
kg/hr-m
2
. During the tests, the temperature of the gas leaving the reactor was measured at
200 to 320 C, while the temperature of the flame varied from 400 to 510 C. Based on the
data gathered, the average computed gasifier efficiency is 68 percent while the overall
thermal efficiency using the water boiling test is, 15%. Water boiling test indicated that 40
liters of water can be boiled within 30 to 42 minutes, depending on the degree of firing the
fuel. The percentage amount of ash, including the slag obtained in each operation, varied
from 6 to 10%. The computed heat output of the gasifer, based on combustible gases
produced, ranged from 40,800 to 68,000 kcal per hrwith an average power output of 65.3
kW.
The gasifier total investment cost is IDR 15,000,000.00. Using crushed coal as fuel, the
gasifier requires an operating cost of IDR 4,288.71 per hour. Considering a 10-hour per day
and 20 days per month operation, the investment cost for the gasifier canbe recovered within
0.3, 0.9, and 1.4 years against kerosene, diesel, and LPG burners, respectively.
For further information, contact: Djoewito Atmowidjojo, President Director, PT Minang
Jordanindo Approtech, K2-7 Techno Park, BSD City, Serpong, Tangerang, Banten,
Indonesia. Email: djoewito@yahoo.co.id. Website: www.minangjordanindo.com.
Released: November 2008
1 USD = 11,600 IDR