Design and Development of a Low Cost SCR

System for NOx Reduction in a Diesel Engine

Shamil Backer O Akshay B.P. Shameem K
B. Tech student in Mechanical B. Tech student in Mechanical B. Tech student in Mechanical
Engineering. Engineering. Engineering.
Government Engineering College, Government Engineering College, Government Engineering College,
Kozhikode Kerala. Kozhikode Kerala. Kozhikode Kerala.
Kozhikode, India. Kozhikode, India. Kozhikode, India.
shamilbackero@gmail.com akshayjanard@gmail.com shameem4k@gmail.com

Sharun K.K. Pradeep V

B. Tech student in Mechanical Associate Professor in Mechanical
Engineering Engineering
Government Engineering College, Government Engineering College,
Kozhikode Kerala. Kozhikode Kerala.
Kozhikode, India. Kozhikode, India.
sharunkk1997@gmail.com pradeepv25@gmail.com

Abstract—After-treatment of exhaust gases are generally influence of injected quantity of reducing agent and use of
preferred to control engine emissions since engine hardware appropriate low cost catalyst, which can work efficiently
demands no significant modification. Selective Catalytic at low temperatures, need to be explored. Koebel et al.
Reduction (SCR) is a promising after-treatment method for (2000) studied fundamental challenges of Urea-SCR for
NOx reduction in Diesel engines. In the present work an mobile applications viz. reduction of required catalyst
exhaust gas treatment system, involving Urea injection and
volume, minimization of residence time of the exhaust gas
an activated carbon catalyst chamber were designed and
fabricated, for NOx control, in a Diesel engine. Activated in the catalyst, the risk for secondary pollution such as
carbon catalyst, which can perform at low temperatures, was NH3 slip, freezing point of Urea solution [1]. Solaimuthu
expected to make the system cost-effective. Experiments and Ganesan (2015) reported the experimental results on a
were conducted at 60 percentage and 80 percentage of the single cylinder Diesel engine regarding performance,
maximum engine load. Apart from Diesel, engine was also combustion and emission characteristics using Bio-Diesel
fuelled with Bio-Diesel developed from chicken slaughter and its blends in different volumetric proportions with
waste. The results demonstrated the capability of developed petrol Diesel [2]. The SCR could produce up to 20.
SCR system in reducing NOx emissions. The Nitric Oxide Praveena et al. (2018) reviewed various after-treatment
(NO) emission was reduced by 47 percentage 29 percentage methods for NOx reduction viz. SCR, Lean NOx Trap and
for Bio-Diesel and Diesel respectively, at a brake power of SCR Filter [4]. The study revealed the benefits and
3kW, without increasing HC emission and sacrificing
constraints of different types of SCR. It was observed that
efficiency. Significant reduction in NO was also obtained at
2kW.
Urea-SCR produced 96 - 99 percentage conversion
efficiency with NH3 as a reducing agent. They could also
Keywords—Diesel Engine, Selective Catalytic Reduction find improvement in SCR activity, at low temperature,
(SCR), Urea injection, Oxides of Nitrogen, Biodiesel with the increase in NO2/NOx ratio and the adsorption rate
of NH3. Ayodhya et al. (2019) used rhodium coated
I. INTRODUCTION AND BACKGROUND ceramic SCR catalyst to mitigate vehicular NOx emissions
Air pollution created by Diesel vehicles being a on a CRDI engine fuelled with the waste plastic oil blend
serious concern demands increased attention. Oxides of [7]. NOx reduction up to 36.8 percentage was observed.
Nitrogen (NOx,) are one of the dominant pollutants from Mehregan et al. (2018) studied the influence of Mn2O3
highly efficient Diesel engines. Approaches considered and Co3O4 nano-additives on a Bio-Diesel fuelled engine
for pollution abatement from such power plants include equipped with a Urea-SCR system [5]. Both strategies
engine modifications, changes in fuel properties and were successful in reducing NOx. However, with cobalt
exhaust after-treatment methods. Exhaust gas treatment is oxide, higher NOx reduction could be achieved. Zhang et
comparatively easier method to control engine exhaust al. (2018) studied a combination of Diesel Oxidation
emissions since engine hardware demands no significant Catalyst, Catalytic Diesel Particulate Filter and SCR on a
modification. Selective Catalytic Reduction (SCR) is an heavy-duty Diesel engine [6]. The NOx reduction
exhaust after-treatment technology that injects a reducing efficiency was improved with the Urea injection quantity.
agent through a catalyst into the exhaust stream of a However, higher Urea injection quantity led to severe
Diesel engine. Liquid Urea and precious metals are widely ammonia slip and demanded the need for optimizing the
used as a reducing agent and catalyst respectively. Even injection quantity.
though SCR has been a proven method for NOx control,

Electronic copy available at: https://ssrn.com/abstract=3445998

 II. EXPERIMENTAL SETUP AND E XPERIMENTATION injection duration and mass flow rate of AdBlue.
A four stroke, single cylinder, 5HP, 661cm3, water Electronic circuitry and control unit (ECU) utilized
cooled engine was used in the present study. A rope brake L293D motor module and programmable Arduino UNO
dynamometer was coupled to the engine. A Non- board. Injection duration was optimized at 60 percentage
Dispersive Infrared (NDIR) based AVL Gas Analyzer was of rated power and this quantity was used for all further
used to measure Nitric Oxide (NO), CO, HC and CO2 experiments involving Diesel and Bio-Diesel. Injection of
emissions. Exhaust Gas Temperature was measured using AdBlue was in the direction of the flow of exhaust gases
a K-type thermocouple. All experiments were conducted and the Injector was oriented at an angle of 60° w.r.t
at a rated speed of 1500 rpm. After calculating the vertical so as to promote uniform droplet distribution.
maximum load for the engine, a baseline experiment was (Xian Shi et al. 2013).
conducted initially, with Diesel fuel only, to obtain the
performance and emission characteristics of engine.
Subsequently all experiments were conducted at 60
percentage and 80 percentage of maximum load. Exhaust
gas temperatures were higher than 200°C at these load
conditions and found suitable for efficient working of
SCR catalyst (Qiu et al. 2014). Also NO emissions were
expected to be higher at these higher torque conditions
where combustion temperatures are generally higher.
Investigations were done using Diesel and Bio-Diesel.
Bio-Diesel has been identified as an alternative to Diesel
fuel. Engines fueled with Bio-Diesel fuels generally emit
more NOx due to inherent Oxygen in their structure. Bio-
Diesel fuel developed from chicken slaughter waste, by
the Kerala Veterinary Animal Sciences University was
used in the present experimentation. Influence of SCR
system on performance and emission characteristics of
Bio-Diesel blend B20 was also explored. Fig.1 and fig.2
demonstrate the details of experimental setup. Fig.2. Experimental setup
1. Single cylinder four stroke diesel engine, 2. Catalytic
chamber, 3.Injector, 4. Pump, 5. ECU, 6.Ad Blue Tank,
7. 12V Battery

III. RESULTS AND DISCUSSIONS

Engine performance and emissions obtained at 60
percentage and 80 percentage of maximum engine load is
as shown in Fig. 3-5.

Fig.1. Schematic of the experimental setup

In this work AdBlue, an aqueous Urea solution made
with 32.5 percentage Urea and 67.5 percentage deionized
water has been used a reducing agent whereas low cost
activated carbon was used as a catalyst. The catalytic
chamber was designed and fabricated considering
corrosive environment, strength, easy maintenance and
residence time.
Electronic injection was employed to inject AdBlue in
the exhaust duct ahead of catalytic chamber. A small Fig.3. Variation of Brake thermal efficiency
plunger pump-was used to inject AdBlue in the exhaust
duct. NO emission measured from preliminary baseline Brake thermal efficiency (BTE) was comparable for diesel
experiments was used to estimate the AdBlue quantity. and Biodiesel (B20 as shown in Fig.3. Brake specific fuel
Subsequently the electronic injector was calibrated at a consumption (bsfc) obtained in both cases were 0.31 and
pressure of 1.5 bar (abs) to establish relation between 0.34 kg/kWhr respectively.

Electronic copy available at: https://ssrn.com/abstract=3445998

 employed. With urea–activated carbon combination also
HC emissions were lower than baseline values. However,
in the case of bio-diesel B20, with activated carbon
catalyst, HC emissions increased compared to the case
where urea was injected. This trend was visible, at both
loads, in the case of bio-diesel. However, with diesel fuel
urea-activated carbon combination, HC emissions showed
a decreasing trend. This is probably due to the differences
in the fuel structures of B20, influence of activated carbon
and lower temperatures at the catalytic chamber.
IV. CONCLUSIONS
In this detailed experimental study, the exhaust pipe of a
Fig.4. Variation of NO emission single cylinder, four stroke diesel engine was modified to
facilitate injection of a liquid reducing agent AdBlue. A
Figure 4 shows the influence of AdBlue injection and catalytic chamber incorporating low cost activated carbon
activated carbon catalyst on Oxides of Nitrogen (NO) was designed and fabricated. The developed SCR system
emissions, for both diesel and biodiesel fuels. It can be was employed for NOx control from the engine fuelled
observed that NO emissions reduced significantly at both with biodiesel (B20) and diesel. Major conclusions from
load conditions demonstrating the potential of developed the experimental study are as follows:
SCR system. Due to inherent oxygen in their structure NO • The brake thermal efficiency of the engine while
emissions are generally seen higher in the case of bio- using Biodiesel (B20) and diesel fuel was
diesel fuels. In the present study, at 2kW, bio-diesel (B20) comparable.
emissions were higher by 35 percentage compared to • NO emission from baseline biodiesel (B20) fuel was
baseline diesel fuel experiments. At 3kW also NO higher compared to that of diesel fuel, without any
emissions were higher for B20 compared to that of Diesel
SCR system.
fuel. At 2kW, about 18 percentage reduction in NO could
be obtained, in the case of B20, when urea solution was • In the case of biodiesel (B20), at higher power of
injected. Further reduction in NO emissions were 3kW, the developed SCR system could reduce oxides
observed, when activated carbon was used as a catalyst. of nitrogen (NO) by 47 percentage.
Compared to B20 baseline, about 40 percentage reduction • In the case of Diesel fuel, at higher power of 3kW,
in NO could be obtained with Urea-activated carbon the developed SCR system could reduce NO by 29
combined strategy. Similar trends were seen in the case of percentage.
diesel fuel at 2 kW. Upto 35 percentage reduction in NO • In the case of biodiesel (B20), unburned hydrocarbon
was obtained with urea- catalyst combination. (HC) emission was observed to be increasing, when
activated car-bon catalyst was used, in addition to the
AdBlue Injection. However, this trend was not visible
for diesel fuel.
FUNDING AND ACKNOWLEDGEMENTS
Authors thank Dr. John Abraham, Professor, Kerala
Veterinary and Animal Sciences University, Wayanad for
the supply of Biodiesel fuel for experimentation. Financial
assistance provided by the TEQIP II cell at Government
Engineering College Kozhikode is gratefully
acknowledged.

REFERENCES
[1] M. Koebel, M. Elsener and M. Kleemann, “Urea-SCR: A
Fig.5. Variation of HC emission Promising Technique to Reduce NOx Emissions from Automotive
Diesel Engines,” Catalysis Today, vol.59, June 2000, pp. 335–345.
At higher power of 3kW, in the case of B20, NO
[2] C. Solaimuthu, V. Ganesan, D. Senthilkumar and K.K.
reductions were about 47 percentage whereas NO reduced Ramasamy, “Emission Reductions Studies of a Biodiesel Engine
by 29 percentage for diesel fuel with urea-catalyst using EGR and SCR for Agriculture Operations in Developing
combination. Hydrocarbon (HC) emissions obtained at the Countries,” Applied Energy, vol.138, January 2015, pp. 91–98.
above conditions are as shown in Fig.5. It can be seen that [3] D. Ravi , “Selective Catalytic Reduction-An Effective Emission
Controller in CI Engines,” Middle-East Journal of Scientific
compared to baseline readings of B20 and diesel, HC Research, vol. 20, 2014, pp.1379-1385.
emissions were always lower when urea injections was

Electronic copy available at: https://ssrn.com/abstract=3445998

[4] M. Leenus Jesu Martin and V. Praveena, “A Review on Various [6] Diming Lou, Piqiang Tan, Yunhua Zhang and Zhiyuan Hu,
After Treatment Techniques to Reduce NOx emissions in a CI “Experimental Study on the Particulate Matter and Nitrogenous
Engine,” Journal of the Energy Institute, vol.91, October 2018, Compounds from Diesel Engine Retrofitted with
pp.704-720. DOC+CDPF+SCR,” Atmospheric Environment, vol.177, March
[5] Mina Mehregan and Mohammad Moghiman, “Effects of Nano- 2018, pp.45–53.
additives on Pollutants Emission and Engine Performance in a [7] A.S. Ayodhya, V.T. Lamani, M Thirumoorthi, G. Kumar, “NO x
Urea-SCR Equipped Diesel Engine Fueled with Blended- Reduction Studies on a Diesel Engine Operating on Waste Plastic
Biodiesel,” Fuel, vol.222, June 2018, pp. 402–406. Oil Blend Using Selective Catalytic Reduction Technique,” Journal
of the Energy Institute, vol.92, April 2019, pp.341–350 .

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