© Applied Science Innovations Pvt. Ltd., India
ASI
Carbon – Sci. Tech. 6/4(2014)15-22
Carbon – Science and Technology
ISSN 0974 – 0546
http://www.applied-science-innovations.com
ARTICLE
Received : 18/12/2014; Accepted :25/12/2014
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Efficiency enhancement of wood stove integrated with catalytic combustor and
modified chimney
G. Murali (*), P. Goutham, I. Enamul Hasan, P. Anbarasan, G. Ashok
Department of Mechanical Engineering, Adhiyamaan College of Engineering, Hosur - 635109, Tamil
Nadu, India.
Domestic wood combustion produces smoke that is harmful to human health and increases fine particle
level in the atmosphere. Some necessary changes in the design are essential in the domestic wood stove
in order to improve the performance and scale down the emission. In this work, an improved wood
stove integrated with the catalytic combustor and modified chimney that uses wood as fuel has been
experimentally evaluated. Water boiling test, cooking test and emission test have been conducted to
evaluate the performance of the stove. It was observed that emission has been considerably controlled
because of the incorporation of catalytic combustor. The heat losses through the walls of stove decresed
by providing ceramic insulation. The thermal efficiency value of an improved wood stove obtained was
41.18% and this is 31.52% higher than traditional stove. The improved wood stove results better
performance than a traditional wood stove.
Key words: Wood stove, Catalytic combustor, Emission, Cooking, Water boiling
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1. Introduction: Wood stove is widely used for
cooking and room heating. Still more people in
the rural and urban area uses firewood for
cooking. Electric stoves and boiling rings have
been rendered useless as a result of improper
power supplies. Usage of wood stove causes
discomfort owing to heavy smoke. According to
the U.S. Environmental Protection Agency, the
use of wood for residential heating contributes up
to 50 percent of the polynuclear organic air
pollutants, some of which may be carcinogenic.
During winter, in areas where wood is the
principal heating fuel, wood stoves produce as
much as 80 percent of these kind of pollutants.
Cooking over an open fire with solid fuels has
been recognised as causing a serious health
problem. Currently, most developed and
developing countries are heavily dependent on
fossil fuels. solid fuels are used for cooking
particularly in rural areas.
Fossil based technology is the primary source in
India to meet the energy requirement in small as
well as large industrial applications. Still 2.5
billion people around the world do not have
access to modern fuels [1]. Alphonse Nahayo et
al. [2] evaluated that the thermal efficiencies of
traditional stoves are relatively less. Yutana
Sriudom [3] stated that thermal efficiency also
decreases due to heat loss through walls, which
encouraged to insulate the walls in this paper. The
inverted siphon was used to draw the fire’s hot
fumes up the front and down the back of the
Franklin stove’s hollow baffle, in order to extract
as much heat as possible from the fumes which
made to redesign the chimney in this improved
wood stove. Smoke from biomass combustion
produces a large number of health-damaging air
pollutants including respirable particulate matter,
carbon monoxide (CO), nitrogen oxides,
formaldehyde, benzene, 1,3 butadiene, polycyclic
aromatic hydrocarbons (such as benzo[a]pyrene),
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and many other toxic organic compounds. West S
et al. [4, 5] stated that annually about 2 million
people become blind worldwide and cataractrelated blindness accounts for half of these cases.
Three epidemiological studies have provided
some evidence of an association between cataract
or blindness and exposure to indoor smoke from
household use of solid biomass fuels, such as
animal dung, wood, and crop residues [6-8].
Indoor air pollution (IAP) from traditional
biomass burning contributes to serious health
problems, particularly cancer and respiratory
infections that cause an estimated 1.6 million
premature deaths annually [9-11] which made to
incorporate this improved wood stove with
catalytic combustor.
2. Experimental Study: The wood stove consists
of Combustion Chamber, Air Vent 1 & 2, Ash
tray 1 & 2, Wood Holder, Chimney, Pot seat 1
and Pot seat 2. Combustion chamber is the place
where wood is burnt to produce useful heat.
Schematic diagram of wood stove with catalytic
combustor and modified chimney are shown in
Figure (1). The casing of the stove has three
layers. The walls of the combustion chamber and
remaining part of the stove is equipped with
50mm ceramic Insulation (Thermal conductivity
is 1.06 W/mK). The Catalytic combustor is placed
in between pot seat 2 and chimney. The inner and
outer layer of the stove is made of mild steel and
the chimney is made of galvanized iron pipe as
shown in the photographic view figure (2). Ash
tray is placed in stove which collects the burnt out
wood ash. Chimney is designed in such a way that
it restricts the flow of excess gas to the
atmosphere so as to enhance the heat transfer to
the both pots. Also two pots play a vital role in
improving efficiency. One pot is used to absorb
the energy from main source and another one is
used to utilize the excess energy from the gases
passing towards the chimney.
Christoph schmidl et al. [12] designed a sampling
device and compared the chemical profiles of fine
particle emissions from wood stove combustion
with various common woods. Murari Mohan
Roy et al. [13] investigated the potential use of
hay and switch grass briquettes and studied the
combustion and emission of biomass briquettes
and observed that CO emission has a strong
correlation with excess air factor, the higher the
excess air factor the lower the CO emissions.
NOx and SO2 emissions are proportional to fuel
N2 and S content respectively. Lars Kare
Grimsby et al. [14] studied the fuelling of jatropha
fruit coats in a sawdust stove with controlled
water boiling test. E.Pieratti et al. [15]
characterized the gaseous emission of spruce tree
using two staged high efficiency-air gasifying
woodstove. This experiment resulted in limitation
of emission of unburned components. Julie F.Hart
et al. [16] understood the reduction of particle
count
concentration
and
evaluated
the
effectiveness of an electrostatic filter portable air
purifier. Emma Hedberg et al. [17] characterized
the emissions of chemical compounds emitted
from birch wood combustion in a wood stove.
Komolafe [18] studied the design and fabrication
of improved charcoal cooking stove and evaluated
their performance under different test conditions.
This paper discusses the observation of the study
on an improved wood stove incorporated with
catalytic combustor and evaluation done on their
performance and efficiency.
Keeping the air flowing correctly through a woodburning stove is essential for safe and efficient
operation of the stove. Fresh air needs to enter the
wood compartment to provide oxygen fuel for the
fire; as the fire burns, the smoke must be allowed
to rise through the stove pipes, and exit through
the chimney. To regulate air flow, there
are damper devices built into the stove, flue, and
stove pipes. By opening or closing the dampers,
air flow can be increased or decreased, which can
fan the fire in the wood compartment, or
"dampen" it by restricting airflow and reducing
the flames. The dampers can usually be accessed
by turning a knob or a handle attached to the
damper, found outside the stove or stovepipe. One
of the uses of the dampers is to increase airflow
into the wood compartment to raise flames and
thus, the temperature of the stove, temporarily
create a high heat for cooking. It is ash handling
device in which burnt ash will be collected. After
, it can be removed. It is a cavity provided inside
the combustion chamber for placing the wood
inside the combustion chamber.
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creating the catalytic reaction. Ash, particulates,
and harmful gas exhausts are converted into water
vapor and carbon dioxide, which safely exit
chimney without polluting the atmospheric air.
Significant heat is released as a result of chemical
reaction occurred in the catalytic combustor. The
advantage of maintaining combustor is extracting
the excess heat that lost through the chimney. 'U'
shaped chimney is used in the stove to slow down
the flow gases, producing effective catalytic
reaction. Also it decreases the wood
consumptions with improved productivity. This
chimney provides good ventilation and creates
smooth flow to the flue gases from combustor.
Figure (1): Schematic diagram of wood stove with
catalytic combustor and Modified chimney
Figure (3) : Catalytic combustor used in the
improved stove
2.2 Water Boiling Test: The three trails of water
boiling test were carried out to evaluate the
improved cooking stove. The performance of the
improved stove with catalytic combustor was
evaluated and compared using wood as fuel
material. The woods are dried such that to burn
efficiently. The apparatus were two big size
aluminium pots, a weighing balance, an infrared
thermometer two mercury-in-glass thermometers,
a stopwatch, water and matches. The stoves were
tested in the open air with the atmosphere
conditions being 28ºC dry bulb and relative
humidity of 65%. These tests were carried out in
such a way to match the cooking method
commonly adopted in rural committees in India.
Figure (2) : Photographic view of wood stove
with catalytic combustor and Modified chimney
2.1 Catalytic combustor and Modified
chimney: Catalytic combustor is made of ceramic
honey comb structure coated with reactants like
platinum, palladium or rhodium. A typical
catalytic combustor used in this improved wood
stove is shown in Figure (3). Wood smoke gases
coming in contact with the catalyst, causes
chemical changes to take place. This will then
allow the smoke to ignite at temperatures around
260o C. The catalytic combustor not only removes
pollution from the exhaust, it also creates usable
heat and a safer chimney. Wood smoke flows
through the honeycomb of the combustor,
The improved wood stove was loaded with equal
amounts of fuel (wood). In improved wood stove
two pre-weighed aluminum pots designated as pot
A and B were filled with the same quantity of
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Carbon – Sci. Tech. 6/4(2014)15-22
𝑇𝑓𝑖𝑛𝑎𝑙 = final water temperature (oC)
𝐶𝑒 = water specific heat (0.00418 kJ/g/oC)
water. The initial temperature of the water was
recorded using a mercury-in-glass thermometer
before the pots were placed on the stove. The
wood was sprayed with 30 ml of kerosene and
then ignited. The change in temperature up to the
boiling point was recorded at two minutes
intervals with the two thermometers permanently
inserted in the two opened pots. At boiling
temperature the pots were removed from the
stoves
and
weighed.
The
temperature
measurements of different locations of wood
stove during the test are shown in figure (7). Also
the fire was put out immediately and the
remaining fuel was weighed. The traditional wood
stove was loaded with equal amounts of fuel as of
improved wood stove. In this stove, one preweighed aluminium pot filled with the same
quantity of water was placed and other process
were done as same as water boiling test done in
improved wood stove.
2.5 Emission Test: The emission test has been
carried out using Crypton D 680 4 gas analyzer to
measure CO & CO2 Indian Govt. ApprovedARAI Approved-TNPCB Approved). Test results
are presented in table (2). Emission measurements
were made on the both improved wood stove and
the traditional wood stove. Concentrations of CO
and CO2 were measured and emission factors
were calculated.
3. Results and Discussion: The water boiling test
results are specified in table (1) which gives the
information about the data used for thermal
efficiency calculation. Figure (4) illustrates time
vide temperature history of both improved wood
stove and traditional stove during water boiling
test. It can be seen from the figure that water boils
at pot A of improved wood stove within 19
minutes. But traditional wood stove takes 34
minutes to boil water. When water starts boiling
in pot A, the temperature of water in pot B
reaches 62oC, that is better than temperature of
water in traditional stove. The unburned gases
from pot A can be burnt due to the presence of
catalytic combustor near by the pot B.
2.3 Cooking test: One kg of rice with two litres
of water was cooked using improved wood stove,
as well as traditional stove. The cooking test
results are shown in table (2).
2.4 Thermal efficiency: Efficiency, which is a
measure of the proportion of the total energy
which is usefully employed in a thermodynamic
system. The burn rate and the net calorific value
of the fuel were used in the calculation of this
parameter as stated
Thermal Efficiency =
𝑆𝑢𝑚 𝑜𝑓 𝑄𝑈 𝑓𝑜𝑟 𝑎𝑙𝑙 𝑝𝑜𝑡𝑠
𝑄𝑎
𝑄𝑎 = 𝑊 × 𝐶
where
𝑄𝑎 = heat generated by the wood (dry weight)
W = Weight of the wood burnt during the trail
C = Calorific content of the wood is 17.39 kJ/g.
Figure (4): Time wide temperature variation
during water boiling test
𝑄𝑢 = (𝑊𝑖 − 𝑊𝑓 ) × 𝐶𝑣 + (𝑇𝑓 − 𝑇𝑖 ) × 𝑊𝑓 × 𝐶𝑒
where,
𝑄𝑢 = heat utilized (kJ),
𝑊𝑖𝑛𝑖𝑡𝑖𝑎𝑙 = initial weight of water (g),
𝑊𝑓𝑖𝑛𝑎𝑙 = final weight of water (g),
𝐶𝑣 = water vaporization heat (2.253 kJ/g),
𝑇𝑖𝑛𝑖𝑡𝑖𝑎𝑙 = initial water temperature (oC )
Figure (5) shows the fuel consumption of wood
stoves to boil the water during the cooking test. It
is absorbed from the figure that the improved
wood stove save firewood more than traditional
one. For cooking rice improved wood stove
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Carbon – Sci. Tech. 6/4(2014)15-22
consumed low quantity of firewood 0.53 kg and
the cooking time of 18 minutes but traditional
firewood stove consumed high quantity of
firewood like 2.43 kg and uses 37 minutes.
Table (2) Cooking Test Results of stoves.
Fire wood consumed (kg)
Time (minutes)
Improved
wood stove
Traditional
stove
1
2
3
Mean
0.5
0.6
0.5
0.53
2.4
2.5
2.4
2.43
Improved
wood
stove
18
19
19
18.66
Wood consumption (kg)
The performance of wood stoves by comparing
the thermal efficiency is shown in figure (6). The
efficiency obtained by improved and traditional
stove is 40.18% and 8.66% respectively. The
improved stove produces better efficiency
because of the design and modification such as
ceramic insulation of walls, incorporation of
catalytic combustor and "U" bend of chimney,
ceramic insulation. Ceramic insulation reduces
the considerable heat loss to the surrounding.
Catalytic combustor decreases the emission of CO
and CO2. The emission test results has been listed
in Table (3) for both stoves. The design
modification of chimney slows down the exhaust
gas flow in such a way that the catalytic
combustor can burn the unburned gases. These
things lead the improved performance of
improved wood stove than traditional stove.
No
of
test
Initial mass of the
water (Kg)
Water evaporated
(Kg)
Initial water
temperature (°C)
Final water
temperature (ºC)
Latent heat of
vaporization of
water (J/kg)
Fire wood used
(Kg)
Calorific value of
fire wood (J/K)
Specific heat
capacity of water
(J/kg)
2
2
0.8
0.4
0.6
20
20
20
98
62
98
0.5
2
1.5
1
0.5
45
40
35
30
25
20
15
10
5
0
Traditional stove
40.18
8.66
Improved wood stove
Traditional stove
Figure (6): Efficiency comparison of improved
wood stove with traditional stove
2.25 x 106
0.5
2.5
Figure (5): Wood consumption for
cooking rice (Kg)
Traditional
Stove
POT
C
2
3
Improved wood stove
Efficiency (%)
Parameter
38
38
37
37.66
0
Table (1) Water boiling test results of both stoves
Improved
wood Stove
POT
POT
A
B
Traditional
Stove
1.1
Table (3) Emission Test Results of stoves.
7
1.68 x 10
Name of the wood stove
4.2 x 103
19
Emission factors
(g/kg fuel used)
CO
CO2
Traditional wood stove
38.7
1607
Improved wood stove
22.2
1584
© Applied Science Innovations Pvt. Ltd., India
Carbon – Sci. Tech. 6/4(2014)15-22
[3]
[4]
[5]
[6]
[7]
f
Figure (7): Temperature measurements at
different locations of the wood stove during the
tests
[8]
4. Conclusion: The primary objective of the
study was to assess how improved firewood
stoves contribute to forest protection during the
time that increasing the household’s income. The
methodology used to test the improved wood
stove and traditional stove was water boiling test,
cooking test and emission test. The boiling time
and firewood consumption have been determined.
An improved wood stove was fabricated and
compared with a traditional stove. The
performances of the two stoves were evaluated. It
is observed from the experimental study that the
improved wood stove has an efficiency of 41.18%
and the thermal efficiency of traditional firewood
stove is 8.66%. Also the results that the improved
stove yields less fire wood consumption, time
consumption with controlled emission.
[9]
[10]
[11]
[12]
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Carbon – Sci. Tech. 6/4(2014)15-22
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G.Murali is presently an Associate Professor in
the Department of Mechanical Engineering,
Adhiyamaan college of engineering, Hosur, Tamil
Nadu, India. He has published 3 papers in the
International Journals and presented 2 papers in
the International Conferences
P.Goutham is currently an Under Graduate
Scholar at the Department of Mechanical
Engineering,
Adhiyamaan
College
of
Engineering, Hosur, Tamil Nadu, India.
I.Enamul Hasan is currently an Under Graduate
Scholar at the Department of Mechanical
Engineering,
Adhiyamaan
College
of
Engineering, Hosur, Tamil Nadu, India.
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© Applied Science Innovations Pvt. Ltd., India
Carbon – Sci. Tech. 6/4(2014)15-22
G. Ashok is currently an Under Graduate Scholar
at the Department of Mechanical Engineering,
Adhiyamaan College of Engineering, Hosur,
Tamil Nadu, India.
P.Anbarasan is currently an Under Graduate
Scholar at the Department of Mechanical
Engineering,
Adhiyamaan
College
of
Engineering, Hosur, Tamil Nadu, India.
***
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