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An Investigation of the Effect of Input Air Upon Combustion

Performance and Emissions of Biodiesel and Diesel Fuel in an
Experimental Boiler

Article  in  Energy Sources Part A Recovery Utilization and Environmental Effects · February 2014
DOI: 10.1080/15567036.2010.538810

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Energy Sources, Part A: Recovery,

Utilization, and Environmental Effects
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An Investigation of the Effect of Input

Air Upon Combustion Performance and
Emissions of Biodiesel and Diesel Fuel in
an Experimental Boiler
a a a a
B. Bazooyar , N. Hallajbashi , A. Shariati & A. Ghorbani
a
Ahvaz Faculty of Petroleum Engineering , Petroleum University of
Technology (PUT) , Ahvaz , Iran
Published online: 23 Dec 2013.

To cite this article: B. Bazooyar , N. Hallajbashi , A. Shariati & A. Ghorbani (2014) An Investigation of
the Effect of Input Air Upon Combustion Performance and Emissions of Biodiesel and Diesel Fuel in an
Experimental Boiler, Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 36:4,
383-392, DOI: 10.1080/15567036.2010.538810

To link to this article: http://dx.doi.org/10.1080/15567036.2010.538810

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 Energy Sources, Part A, 36:383–392, 2014
Copyright © Taylor & Francis Group, LLC
ISSN: 1556-7036 print/1556-7230 online
DOI: 10.1080/15567036.2010.538810

An Investigation of the Effect of Input Air Upon

Combustion Performance and Emissions of Biodiesel
and Diesel Fuel in an Experimental Boiler
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B. Bazooyar,1 N. Hallajbashi,1 A. Shariati,1 and A. Ghorbani1

1
Ahvaz Faculty of Petroleum Engineering, Petroleum University of Technology (PUT),
Ahvaz, Iran

This article addresses effect of input air upon combustion performance and environmental pollution
of biodiesel and diesel in a semi industrial boiler. The thermal capacity and exhaust temperature as
the combustion performance and emissions like CO2 , SO2 , CO, and NOx are investigated and plotted
over a wide input air to the boiler at a constant fuel pressure of 160 psi and diffuser setting at 3
mm. Indeed, this article demonstrates, in a non-premixed combustion of biodiesel and diesel, how
performance of a boiler changes with increasing and decreasing of input air to the boiler. Afterwards,
the trend of emissions with change in the input air will be depicted as well.

Keywords: boiler, combustion, efficiency, emission, methyl ester

INTRODUCTION

The world, due to decreasing of limited petroleum reserves and increasing fuel demands owing
to development of urban population, is confronted with a crisis in this century. The scarcity of
petroleum reserves will make renewable energy resources more attractive to researchers (Barnwal
and Sharma, 2005). In addition, utilization of fossil fuels emits a large amount of greenhouse
and acid gases into the air, which causes global warming phenomenon and acid rains (Peterson
and Hustrulid, 1998; Warnatz et al., 2006). Meanwhile, fossil fuels turn back to dead biomass,
which lived several million years ago and have perished now. Consequently, produced CO2 in the
level of generating energy from fossil fuel does not absorb by an energy producing source and
accumulates in the atmosphere (Demirbas, 2008). Therefore, biofuels have lower emissions than
fossil fuels. It is also obvious that the large part of CO2 emitted in the level of generating energy
from these fuels will be consumed in photosynthesis process by the plants in which biofuels are
made of. Consequently, CO2 will pass through the producing-consuming cycle and not accumulate
in the atmosphere (Alonso et al., 2008).
Diesel is one of the main fossil fuels largely consumed in industrial sectors, agriculture,
commercial, and domestic with important roles in everyone’s life. Diesel fuel also could be used in
boilers for heating purposes and generating electricity (Barnwal and Sharma, 2005; Knothe, 2010).
Biodiesel is a type of biofuel that has the potential for total or partial replacement with diesel
fuel. Biodiesel could be made from vegetable oils and animal fats. Nowadays, more than 95% of

Address correspondence to Bahamin Bazooyar, Ahvaz Faculty of Petroleum Engineering, Petroleum University of
Technology (PUT), P.O. Box 63431, Ahvaz, Iran. E-mail: Bazooyar.bb@gmail.com

383
 384 B. BAZOOYAR ET AL.

produced biodiesel is made of pure edible vegetable oil (Ghorbani and Bazooyar, 2012). Biodiesel
is produced from the reaction of vegetable oil or animal fat with alcohol (especially methanol)
in the presence of a catalyst called transesterification. The alkali-catalyzed transesterification of
vegetable oils is currently the most commonly adopted method for biodiesel production (Leung
et al., 2010).
In many papers, biodiesel is defined as diesel replacement in diesel engines, and performance
of this renewable fuel in the other criteria is not examined (Gerpen, 2005). Tashtoush et al. (2003)
examined the combustion efficiency and emissions of the ethyl ester of used palm oil relative to
diesel fuel over a wide range of air/fuel ratios in a water-cooled furnace. Their findings show that
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at low energy input, biodiesel burned more efficiently with higher combustion efficiency. At higher
energy input, biodiesel combustion performance deteriorated and was inferior to diesel fuel due to
its high viscosity, density, and low volatility. As for emissions, biodiesel emitted lower pollutants
at both energy levels over the whole range of A/F ratio considered (Tashtoush, 2003). This study
investigates the effect of input air upon combustion performance and emissions of biodiesel and
diesel fuel compared with each other in a semi-industrial boiler.

MATERIAL

Two types of fuels are used in this study: Corn oil methyl ester and diesel. The used biodiesel is
made through alkali-based transesterification. Corn oil is purchased from Golden Maize Company
of Iran and diesel fuel is purchased from a gas station in Koot Abdollah of Ahvaz. Merck methanol
(chromatographic grade, 99.5%) and Merck KOH are used in the biodiesel production.

EQUIPMENT

The reactor employed for this study (biodiesel production) was a LR 2000 P modularly expandable
laboratory reactor designed for reproducing and optimizing chemical reaction processes as well
as mixing, dispersing, and homogenization processes at laboratory scale. This laboratory reactor
was double-walled, jacketed 2-liter vessels made of stainless steel, with a bottom discharge valve.
The unit used for burning fuels was a combustion laboratory unit C492 manufactured by P.A.
Hilton (England). Figure 1 depicts this combustion chamber and its main parts. The combustion
chamber was a steel-horizontal cylinder. A stainless steel water jacket was used to cool the
combustion chamber. A frame-mounted burner training unit was comprised of a cylindrical water-
cooled stainless steel chamber in which the flame was observed through four windows. The fuel
was forced from a pump at high pressure out of a nozzle within a tubular air director. A rotational
force was imparted to the fuel within the nozzle causing it to break up into small droplets as
it exits the nozzle to form a spray cone. Electrodes caused an ignition and were switched off
after the flame was self-sustaining. The instrumentation attached to the water heater allowed a
direct read-out of inlet and outlet cooling water temperatures, water mass flow rates, inlet air
temperature, air mass flow rate, exhaust gas temperature, and fuel flow rate.
The KM9106 analyzer was used to measure emissions from the boiler. It measured temperature
and O2 , CO, NO, NOx , and SO. Analyzer technical characteristics are indicated in Table 1.

Biodiesel Production
Figure 2 shows a simplified flow chart of the alkali-catalyst process, which was used in this survey.
Transesterification was done in the reactor, which was described before at 50ı C with an alcohol to
 INPUT AIR AND COMBUSTION PERFORMANCE 385
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FIGURE 1 C492 combustion chamber.

TABLE 1
Technical Characteristics of the Quintox KM9106 Gas Analyzer

Measuring
Parameter Range Precision Resolution

Temperature of smokes 0–1,100ıC 1.0ı C ˙ 0.3% of reading 0.1ı C

Oxygen (O2 ) 0–25% 0.1% C 2% 0.1%
Carbon oxide (CO) 0–10,000 ppm ˙20 ppm < 400 ppm 1 ppm
5% of reading < 2,000 ppm
˙10% of reading > 2,000 ppm
Nitric oxide (NO) 0–5,000 ppm ˙5% of reading > 100 ppm 1 ppm
˙5 ppm < 100 ppm
Sulfur dioxide (SO2 ) 0–5,000 ppm ˙5% of reading > 100 ppm 1 ppm
˙5 ppm < 100 ppm
 386 B. BAZOOYAR ET AL.
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FIGURE 2 Flow chart of biodiesel production.

oil ratio of 6:1 and 0.01 weight percent catalyst. First, the circular bath of the LP 2000 R is turned
on and set at 51ıC. Usually the temperature of the reactor is a little different than the setting
temperature of the heating circular bath and this is owing to the heat loss from the circular heating
water. Then vegetable oil is added to the reactor. When the temperature of the reactor reaches
the reaction temperature, methoxide solvent is added to the reactor carefully. After 45 min, two
major products exist: crude biodiesel and glycerol. Then, the reaction mixture is brought out from
the reactor to a separating vessel. The glycerol phase is much denser than the biodiesel phase
and settles at the bottom of the separating vessel, allowing it to be separated from the biodiesel
phase. Phase separation can be observed within 10 min and can be completed within several hours
of settling. Crude biodiesel needs to be purified before use. Since both glycerol and alcohol are
highly soluble in water, water washing is very effective for removing both contaminants. Water
also can remove potassium hydroxide and soap from crude biodiesel. After washing 10 times
with water at 60ıC, the water phase becomes clear, meaning that the contaminants have been
completely removed. After the water washing process, water may remain in the pure biodiesel.
To receive a better quality of this renewable fuel, drying is applied with the oven at 60ı C for 1 h.
 INPUT AIR AND COMBUSTION PERFORMANCE 387

TABLE 2
Quality and Properties of Methyl Ester and Unconventional Diesel Fuel

Property Diesel Biodiesel Standard

Flash point (ı C) 44 135 ASTM D93

Kinematic viscosity @ 20ı C (cSt) 3.9 6.2 ASTM D445
Cetane Number 45 41 ASTM D613
Specific gravity @ 60ı C 0.8367 0.8840 ASTM D1298
Cloud point (ı C) 6 1 ASTM D2500
Pour point (ı C)
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19 5 ASTM D97
Copper corrosion 1.5 2.1 ASTM D130
Carbon residues 0.01 0.04 ASTM D4530
Water and sediment Trace Trace ASTM D2709
Sulfated ash 0.001 0.009 ASTM D874
Acid number Trace 0.2
Total glycerol Trace 0.001 ASTM D6584
Free glycerol Trace 0.019 ASTM D6584
Gross caloric value (KJ/Kg) 43,640 40,900 ASTM D240

After this period of time, some water settles in the biodiesel’s vessels and the others are vaporized.
The biodiesel was then sent to Abadan refinery of Iran to measuring the diesel properties and
quality of the biodiesel. Diesel fuel was also sent to that refinery to determine its characteristics.
Table 2 represents the quality and properties of the biodiesel that was used in this study.

Operating Points
The operation was effective at the steady state condition that permitted good repeatability. In this
study, the effect of increasing air upon the combustion parameters and emissions of biodiesel and
diesel fuel were investigated. To do so, pressure and diffuser setting of the burner were set at the
constant values of 160 psi and 3 mm, respectively. In this state, the fan damper was set in 1, 3,
5, 7, and 9. Increasing of input air in non-premixed combustion would occur with increasing the
fan damper setting.
The study of emissions (O2 , CO, CO2 , NO, NOx , SO2 ), fuel consumption, as well as Text (the
temperature of outlet water) was done at the defined above operating points. The results presented
were obtained after a series of measurements of each fuel. Results were validated following
repetition of the tests carried out in the course of the study.

RESULT AND DISCUSSION

Exhaust Temperature and Thermal Efficiency

Trends of exhaust temperature Texh is depicted in Figure 3 in relation to the fan damper setting
of the boiler. In Figure 3, as expected, a decreasing trend of Texh with increasing input air was
observed. As can be observed in this figure, in a region of low input air to the boiler, heat transfer
to cooling water for both fuels are close to each other, till in the region of a high amount of input
air to the boiler, which leads to the close Texh of both diesel and biodiesel in a lower damper
setting and far in a high damper setting adjustment.
The thermal capacity of the boiler is obtained for both diesel and biodiesel at the same operating
conditions. Figure 4 shows the thermal efficiency in relation to fan damper setting of the boiler.
 388 B. BAZOOYAR ET AL.
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FIGURE 3 Texh in relation to fan damper condition.

As observed in this figure, the trend of thermal capacity with the fan damper adjustment is very
similar to the Texh . As shown in Figure 4, thermal capacity decreases with increasing the amount
of input air. Meanwhile, thermal efficiencies of the boiler in the region of low amount of input
air for both diesel and biodiesel fuels are close to each other, and in high fan damper setting
adjustment, thermal efficiencies of diesel and biodiesel have a significant deviation.

CO2 Emission
The CO2 value was calculated by the analyzer for biodiesel and diesel fuel based on the oxygen
measured by an analyzer. For this purpose, K2 of the analyzer, which is the maximum theoretical
CO2 roles in CO2 calculation, was defined. Figure 5 represents CO2 emissions in relation to fan
damper adjustment. Increasing the amount of input air or high fan damper adjustments results
in dilution of flue gas causing a reduced percent of CO2 in stock gas. Based on this finding,
biodiesel has a lower amount of CO2 in flue gas, which makes it more suitable as a burner fuel.
Therefore, CO2 is one of the important pollutions in the atmosphere that must be controlled. The
main disadvantage of this greenhouse gas is global warming.

CO Emission
Figure 6 shows a variation of CO in relation to damper setting of the boiler for two fuels. The
CO emission in flue gas of both biodiesel and diesel fuel has a similar behavior. Increasing input
air to the boiler results in poor spray characteristics of both fuels, which produces higher CO
emission. It could also be observed that at higher excess air, combustion of biodiesel emits higher
CO emissions than diesel fuel. Also, in low input air the amount of CO emission of both biodiesel
and diesel fuel are approaching each other.
 INPUT AIR AND COMBUSTION PERFORMANCE 389
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FIGURE 4 Thermal capacity in relation to damper setting.

FIGURE 5 CO2 emission in relation to fan damper setting.

 390 B. BAZOOYAR ET AL.
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FIGURE 6 CO in relation to damper setting.

NOx Emissions
NOx emission in relation to fan adjustment of the boiler is demonstrated in Figure 7. NOx actually
is a mixture of NO and NO2 . A Quintox analyzer KM9106 measures the NO emission and reports
NOx based on the fact that 5% of NO is composed of NO2 . Increasing the amount of input air
leads to lower combustion temperature of both diesel and biodiesel and decreases NOx emissions.
As observed in Figure 7, biodiesel emitted higher amounts of NOx than diesel fuel. Formation of
NOx depends mainly on oxygen availability and local combustion temperatures. Thus, the higher
exhaust temperature at a higher energy level for biodiesel explains, at least partially, the increase
of NOx compared with diesel fuel.

SO2 Emission
The source of SO2 in flue gas is from the sulfur of the fuel. Increasing the amount of input
air dilutes the flue gas with air and SO2 emission reduces for both fuels. The main point is
the significantly lower SO2 emission of biodiesel compared with the diesel fuel. Figure 8 shows
that biodiesel in all cases emitted apparently less amounts of sulfur pollutants, which is readily
explained by the fact that biomass-based fuels contain much less sulfur in comparison with fossil
fuels.

CONCLUSIONS

This article investigated the effect of increasing input air upon the combustion performance and
emissions of a boiler with biodiesel and diesel. Results clearly demonstrate that utilization of
methyl ester of pure vegetable oil (known as biodiesel) and diesel fuel challenges each other
 INPUT AIR AND COMBUSTION PERFORMANCE 391
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FIGURE 7 NOx in relation to damper setting.

FIGURE 8 SO2 emission in relation to fan damper setting.

 392 B. BAZOOYAR ET AL.

in terms of performance and emissions. Results show that at low excess air, performance of
both biodiesel and diesel fuel in the burners in terms of thermal capacity and Texh are close to
each other, and increasing input air makes diesel fuel appropriate as a fuel for burners compared
with biodiesel fuel. Emissions of CO2 , CO, and SO2 were reduced by utilization of biodiesel
in comparison with diesel fuel. Biodiesel, due to more double bound in their structure, emits a
higher amount of NOx than diesel fuel. Thus, investigating input air upon combustion of biodiesel
introduces the biodiesel as a good replacement of diesel fuel in burners (Bazooyar et al., 2011;
Bazooyar and Shariati, 2013).
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