by: Alexis Belonio, Daniel Belonio, Franciscus Tria Garleman, and Djoewito
Atmowidjojo
The cost of frying food products for small-scale
industry bake shop is now becoming expensive
brought about by the ever-increasing cost of LPG
fuel. Based on the experience of Sakura Ampan
Bakeshop in Jakarta Pusat, Indonesia, a singleburner gas stove consumes about 2.2 kilogram of
LPG per hour. With the present cost of LPG of
IDR 350,000.00 per 50-kg tank, the bakeshop is
spending around IDR 15,400.00 per hour for
cooking and/or frying food products. For 8 hours
operation per day, around IDR 123,200.00 is spent
for its cooking/frying activities using LPG.
Coal, which is abundant in supply and so far the
cheapest of the fuels available in Indonesia, is the
only alternative fuel to LPG that is considered
economical and feasible for small-scale industry
use. However, the emission of sulfur dioxide
(SO2), which is the predominant reason for the
unacceptability of this fuel among households, makes the use of coal unpopular for
industry application. Nevertheless, this problem is now resolved by gasification.
Injecting lesser amount of air to the coal bed during gasification in the stove greatly
reduced the amount of SO2emission as compared with the conventional direct
combustion burning of fuel. By
gasification, coal can be
conveniently used with almost no
SO2 emission during cooking.
In the month of September 2008,
the PTMJ Approtech in Jakarta
Selatan has designed and
developed a top-lit-updraft
(TLUD) gasifier stove for Sakura
Ampan Bakeshop using raw coal
as fuel. This project was carried
out as part of the research and
development program of MJ
Approtech on biomass energy that
is geared toward the production of appropriate technologies for thermal application,
particularly for small-scale industry sector.
As shown above, the stove is a large version of the top-lit-updraft type gasifier stove,
which was recently developed by MJ Approtech for carbonized coal. It has a reactor
having a diameter of 20 cm and a height of 50 cm. It is made of 3/16-in. thick
stainless steel plate to minimize oxidation of heat on the metal. The reactor is
surrounded by two concentric cylinders (inner and outer) of the same height having a
diameter of 28 cm and 30 cm, respectively. The reactor and the heat shield are
encased by a 1.2-mm thick metal with a diameter of 50 cm ad a height of 60 cm. A
12cm, 16-watt computer fan is used to supply the air required to gasify the fuel. It is
provided with a switch to control the speed of the fan thereby providing a control
mechanism to increase or decrease the intensity of the flame. The temperature of the
stove is cooled down by allowing ambient air to pass through the inner wall of the
stove casing. The heat produced
inside the gasifier is released
through the 16 holes on top of the
stove casing having a diameter of 20
mm. The fuel is held in place by a
grate made of 10-mm diameter
stainless steel rod with 10-mm
spacing. Ashes are discharged from
the grate using a sliding rake.
Combustible gases are burned in the
plate burner consisting of 40 and 45
holes at the inner and the outer
circles, respectively, with 10-mm
diameter
The stove was tested in terms of
water boiling and kitchen
performance tests. The water
boiling test was done at the PTMJ
Approtech R&D Unit at Taman
Tekno, BSD City, Serpong,
Tangerang, Banten, Indonesia. The
performance of the stove was
evaluated by measuring the
following parameters: fuel
consumption rate, thermal efficiency, power output, and others. Kitchen performance
tests were carried out at the Sakura Ampan Bakeshop in their actual frying of food
products. The food products, specifically egg rolls, were fried in the stove in batches.
Comparison of the quality of food
products fried in the coal gas stove
and those fried in their existing
industrial LPG stoves was done by
the Chef of Sakura Ampan
Bakeshop.
Results showed that the coal gas
stove operates at an average of 2.97
kg of raw coal per hour. One fullload of fuel in the stove requires 8 to
9 kg of coal fuel. It was observed
further that the fuel is ignited using
few pieces of wood charcoal or chunk wood plus drops of kerosene and produce
spontaneous combustion within 3 to 5 minutes thereafter. Fifteen liters of water is
boiled in the stove within 30 minutes from the start of firing. The computed power
output of the stove is 3.8 kW with specific gasification rate of 85 kg/hr-m
2
. The
thermal efficiency was computed based on the data obtained at 27%. The temperature
of the flame was measured from the bottom of the pot and ranges 500 to 750°C.
Actual frying test at the bakeshop revealed that 35 pieces of egg rolls can be cooked
in the stove in 3 to 5 minutes at an oil temperature of 140°C.
Gasifying raw coal in the stove was observed to produce smokeless burning and
almost no odor of sulfur dioxide during operation. The presence of fly ash was
observed to be negligible. More importantly, the Chef of the bakeshop confirmed that
the quality of fried products is the same with that of the LPG stove.
The total cost in fabricating a unit of the coal gas stove is IDR 5,000,000.00. At IDR
1,200.00 per kg of raw coal, the cost of fuel in operating the stove is IDR 3,564.00 per
hour. A saving of IDR 11,836.00 per hour can be derived in using the coal gas stove
over LPG stove, or a total of IDR 94,688.00 per 8-hour/day operation. In this case,
the owner of the bakeshop can recover his investment for the stove within 3 months of
use (at 20 days per month utilization).
For further information, please contact Mr. Djoewito Atmowidjojo, President
Director, PT. Minang Jordanindo Approtech, Jakarta Selatan, Indonesia
(mjapprotech@yahoo.com) website: http://www.minangjordanindo.com.
MJ Approtech would like to acknowledge Pak Mario of Sakura Ampan Bakeshop for
trusting us this project.
1 US$ = IDR 9,300.00
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