# Development of Active CO2 Emission Control for Diesel Engine Exhaust Using Amine-Based Adsorption and Absorption Technique

Authors: Solomon Jenoris Muthiya; L. Natrayan; L. Yuvaraj; Mohankumar Subramaniam; Joshuva Arockia Dhanraj; Wubishet Degife Mammo
Journal: Adsorption Science & Technology
 (2022)

---

## Abstract

Diesel-powered transportation is considered an efficient method of transportation; this sees the increase in the demand for the diesel engine. But diesel engines are considered to be one of the largest contributors to environmental pollution. The automobile sector accounts for the second-largest source for increasing CO2 emission globally. In this experiment, a suitable postcombustion treatment to control CO2 emission from IC engine exhaust is developed and tested. This work focuses to control CO2 emission by using the chemical adsorbent technique in diesel engine exhaust. An amine-based liquid is used to adsorb the CO2 molecules first and absorb over the amines from the diesel engine exhaust. Three types of amino solutions (L-alanine, L-aspartic acid, and L-arginine) were prepared for 0.3 mole concentrations, and the CO2 absorption investigation is performed in each solution by passing the diesel exhaust. A suitable CO2 adsorption trap is developed and tested for CO2 absorption. The experiments were performed in a single-cylinder diesel engine under variable load conditions. The eddy current dynamometer is used to apply appropriate loads on the engine based on the settings. The AVL DIGAS analyzer was used to measure the CO2, HC, and CO emissions. An uncertainty analysis is carried out on the experimental results to minimize the errors in the results. The effective CO2 reduction was achieved up to 85%, and simultaneous reduction of HC and CO was also observed.


---

## Body

## 1. Introduction

Global climate change is one of the main problems addressed by many researchers. The increase of greenhouse gases such as carbon dioxide (CO2), methane, and nitrous oxide [1] has raised the global earth temperatures by around 2° since the preindustrial revolution [2]. Globally, humans are the main contributors to emitting 36 billion tonnes of CO2 per year, and this trend continues to increase every year [3, 4]. The world’s largest CO2-emitting countries are China, the USA, Russia, Japan, and India. India contributes 7% of global CO2 rise; a definitive method to control the CO2 emission should be in place, or by the year 2030, it is expected to increase the global earth temperature to 3.1°C-3.7°C [5]. CO2 emissions are considered to be a dangerous pollutant liberated from the internal combustion engines (ICE). The combustion of any fuel in an IC engine produces CO2 emission as a byproduct. In an IC engine, complete combustion leads to higher power and also reduced HC, CO, and smoke in the exhaust [6]. But the CO2 emission increases when the fuel is completely burnt [7]. The main technologies for postcombustion CO2 capture are membrane separation, amine absorption, cryogenic separation, and physical adsorption. These are the technologies followed by the industry or power plant to control CO2 emission [8]. Amine absorption and physical absorption techniques are the most effective methods followed in the industry for postcombustion treatment of flue gases [9]. In this work, an novel attempt is made to utilize an amine-based solution to trap the CO2 gas directly from the tailpipe of the diesel engine exhaust.The adsorption and absorption technique is considered as one of the alternatives because of the wide range of operating temperatures, pressure, low energy consumption, and cost-effectiveness [10]. The experimental work conducted by Jenoris et al. states that the usage of solid adsorbent can reduce CO2 emission when the exhaust gas is maintained at less than 100°C [2]. At higher temperature, the solid adsorbent does not effectively capture CO2 less than 30% reduction as possible. For the effective CO2 reduction, the adsorbent material should have the durability with high CO2 selectivity, good regeneration, adsorption capacity, and adsorption/desorption kinetics for CO2 [11]. The predominantly available method to capture CO2 is amine-based processes and amine scrubbing [12, 13]. Amine scrubbing is the process of capturing CO2 by passing the gases over the amine solution [14, 15].In this work, an attempt has been made to control CO2 emissions from diesel engine using an amine scrubbing method. In this research, three different amine solutions are prepared with different concentrations to identify its CO2 trapping efficiency with real diesel exhaust. The amines used are L-arginine, L-alanine, and L-aspartic acid. The prepaid amine solution is tested for CO2 reduction by passing the diesel exhaust in to the solution. In this research, a suitable CO2 trap was designed, fabricated, and retrofitted in the tailpipe of the single-cylinder diesel engine. The experimental test was carried out by varying the loads from 0 to 100%. And mission testing was carried out for the CO2 trap.


## 2. Materials and Methods

### 2.1. Amine Solution Preparation

In this work, the investigation is carried out to find an effective amine solution to effectively trap the CO2 molecule. The amino slats used L-Arginine, L-alanine, and L-aspartic acid. Figure 1 shows the amine salts used in preparing amine solution. Initially, various trial experiments are made in preparing the amine solution with various concentrations varying from 0.01 to 0.3. It was observed at initial experiments that 0.3 mole concentration of amino salt solution has a good tendency to trap the CO2 molecule [15]. So, with L-arginine, L-alanine, and L-aspartic acid amino salts, 0.3 mole concentration is fixed to prepare an amino salt solution to test in diesel exhaust. The amine solution is to be prepared by mixing the amino salt and sodium hydroxide in the deionized water as per the mole solubility and molecular weight of the chemicals. At first, 0.01 m of concentration has been mixed in the 4 lit of deionized water based upon the molecular weight of the chemical. And further, the mole concentration of amino salt has been increased from 0.01 m to 0.3 m. By increasing the mole concentration, the amino acid concentration level is increased which can be effective to absorb more CO2 molecules. For example, to prepare amine solution as per the mole concentration and molar mass, the mole concentration of 0.01 and the molar mass 174.2 is dissolved in the 4 lit of deionized water; 0.01×174.2×4=6.96gm of amino salt has to be dissolved in the 4 lit of deionized water. This is for arginine amino salt for 0.01 m concentration. For 0.3 m mole concentration, 209 gm of amino salt is added to prepare the solvent solution [16]. Sodium hydroxide (NaOH) of 1.6 gm has been added to the chemical solution as per the mole concentration in the amino solution for better and efficient absorption. Similarly, for L-arginine, L-alanine, and L-aspartic acid, 0.3 mole concentrations of amine solution are prepared and tested for CO2 emissions trapping in the diesel engine exhaust.Figure 1
Amine salts.Amine solutions are prepared as per the mole concentration and molar mass. Figure2 shows prepared amine solution. Table 1 shows the physical and chemical properties of amines used.Figure 2
Preparation of amine solution.Table 1
Important properties of amines used.
PropertiesSodium hydroxideL-AlanineL-Aspartic acidL-ArginineMolecular formulaNaOHC3H7NO2C4H7NO4C6H14N4O2Molecular weight (g/Mol)40.0089.09133.1174.2AppearancePowderCrystallinePowderPowderColourWhiteWhiteWhiteColourlesspH at 25°C12 - 135.62.711.24pKa13.72.35, 9.861.88, 9.612.18, 9.08Melting point (°C)315314260240Boiling point (°C)140188323365Density (g/cm3)2.111.4221.6621.662The CO2 absorption mechanism in the amine solution is given in the below reaction.
(1)2‐OOC‐R‐NH2+CO2⟶ABSORPTION‐COO‐R‐NH‐COO‐+‐OOC‐R‐NH3+⟶0‐COO‐R‐NH2+‐HCO3‐+‐OOC‐R‐NH3⟶DESORPTION2‐OOC‐R‐NH2+CO2


### 2.2. CO2 Reduction Trap

CO2 reduction trap is designed in such a way that the exhaust gas can easily pass over the amine solution and react for trapping the CO2 molecules. Figure 3 shows the line diagram of the CO2 reduction trap. The CO2 trap has an inlet pipe that is extended to the bottom of the reactor. The exhaust gas enters into the inlet pipe and mixes into the amine solution which is filled inside the reactor. Finally, exhaust gas bubbles out of the solution at the outlet pipe which is fixed at the top of the reactor section. A stack of the perforated sheet is placed in the reactor to arrest the return flow solution leak in the holes of the pipes. The designing of a CO2 trap is carried out to eliminate the backpressure by reducing the obstacles in the flow of exhaust. Figure 4 shows the design model of the CO2 reduction trap. The design plays a key role in the CO2 trap, in which the exact components like inlet and outlet pipes and also the inbuilt perforated metal sheets all are been fabricated and placed as per the design. CO2 trap is fabricated using stainless steel material. It is corrosion-resistant and light in weight. Figure 5 shows the image of the fabricated CO2 reduction trap. The layout of the CO2 reduction trap is shown in Figure 6.Figure 3
The line diagram of CO2 reduction trap with dimensions.Figure 4
The design model of CO2 reduction trap.Figure 5
The image of fabricated of CO2 reduction trap.Figure 6
Layout of CO2 reduction trap.


## 2.1. Amine Solution Preparation

In this work, the investigation is carried out to find an effective amine solution to effectively trap the CO2 molecule. The amino slats used L-Arginine, L-alanine, and L-aspartic acid. Figure 1 shows the amine salts used in preparing amine solution. Initially, various trial experiments are made in preparing the amine solution with various concentrations varying from 0.01 to 0.3. It was observed at initial experiments that 0.3 mole concentration of amino salt solution has a good tendency to trap the CO2 molecule [15]. So, with L-arginine, L-alanine, and L-aspartic acid amino salts, 0.3 mole concentration is fixed to prepare an amino salt solution to test in diesel exhaust. The amine solution is to be prepared by mixing the amino salt and sodium hydroxide in the deionized water as per the mole solubility and molecular weight of the chemicals. At first, 0.01 m of concentration has been mixed in the 4 lit of deionized water based upon the molecular weight of the chemical. And further, the mole concentration of amino salt has been increased from 0.01 m to 0.3 m. By increasing the mole concentration, the amino acid concentration level is increased which can be effective to absorb more CO2 molecules. For example, to prepare amine solution as per the mole concentration and molar mass, the mole concentration of 0.01 and the molar mass 174.2 is dissolved in the 4 lit of deionized water; 0.01×174.2×4=6.96gm of amino salt has to be dissolved in the 4 lit of deionized water. This is for arginine amino salt for 0.01 m concentration. For 0.3 m mole concentration, 209 gm of amino salt is added to prepare the solvent solution [16]. Sodium hydroxide (NaOH) of 1.6 gm has been added to the chemical solution as per the mole concentration in the amino solution for better and efficient absorption. Similarly, for L-arginine, L-alanine, and L-aspartic acid, 0.3 mole concentrations of amine solution are prepared and tested for CO2 emissions trapping in the diesel engine exhaust.Figure 1
Amine salts.Amine solutions are prepared as per the mole concentration and molar mass. Figure2 shows prepared amine solution. Table 1 shows the physical and chemical properties of amines used.Figure 2
Preparation of amine solution.Table 1
Important properties of amines used.
PropertiesSodium hydroxideL-AlanineL-Aspartic acidL-ArginineMolecular formulaNaOHC3H7NO2C4H7NO4C6H14N4O2Molecular weight (g/Mol)40.0089.09133.1174.2AppearancePowderCrystallinePowderPowderColourWhiteWhiteWhiteColourlesspH at 25°C12 - 135.62.711.24pKa13.72.35, 9.861.88, 9.612.18, 9.08Melting point (°C)315314260240Boiling point (°C)140188323365Density (g/cm3)2.111.4221.6621.662The CO2 absorption mechanism in the amine solution is given in the below reaction.
(1)2‐OOC‐R‐NH2+CO2⟶ABSORPTION‐COO‐R‐NH‐COO‐+‐OOC‐R‐NH3+⟶0‐COO‐R‐NH2+‐HCO3‐+‐OOC‐R‐NH3⟶DESORPTION2‐OOC‐R‐NH2+CO2


## 2.2. CO2 Reduction Trap

CO2 reduction trap is designed in such a way that the exhaust gas can easily pass over the amine solution and react for trapping the CO2 molecules. Figure 3 shows the line diagram of the CO2 reduction trap. The CO2 trap has an inlet pipe that is extended to the bottom of the reactor. The exhaust gas enters into the inlet pipe and mixes into the amine solution which is filled inside the reactor. Finally, exhaust gas bubbles out of the solution at the outlet pipe which is fixed at the top of the reactor section. A stack of the perforated sheet is placed in the reactor to arrest the return flow solution leak in the holes of the pipes. The designing of a CO2 trap is carried out to eliminate the backpressure by reducing the obstacles in the flow of exhaust. Figure 4 shows the design model of the CO2 reduction trap. The design plays a key role in the CO2 trap, in which the exact components like inlet and outlet pipes and also the inbuilt perforated metal sheets all are been fabricated and placed as per the design. CO2 trap is fabricated using stainless steel material. It is corrosion-resistant and light in weight. Figure 5 shows the image of the fabricated CO2 reduction trap. The layout of the CO2 reduction trap is shown in Figure 6.Figure 3
The line diagram of CO2 reduction trap with dimensions.Figure 4
The design model of CO2 reduction trap.Figure 5
The image of fabricated of CO2 reduction trap.Figure 6
Layout of CO2 reduction trap.


## 3. Experimental Methods and Testing

### 3.1. Experimental Setup

To analyze the emission characteristic of the CO2 trap, a single-cylinder four-stroke direct injection diesel engine is coupled with eddy current dynamometer to power take-off shaft. The coolant used in the engine is water, and it is recirculated using a conventional pump. To compare the emission characteristics, an AVL Digas analyzer and an AVL smoke meter are connected to the tailpipe. Figure 7 shows the layout of the experimental setup.Figure 7
Layout of experimental setup.


### 3.2. Experimental Procedure

The initial condition such as engine oil level and the condition, coolant water feed rate, and its overhead tank capacity is tested at engine rest position to confirm normal working throughout the experiment. To avoid any variance, the experimental setup is started and run on neat diesel for about 10 to 15 minutes at the idle condition to reach the nominal operating temperature. During this phase, the calibration is executed on the dynamometer to eliminate loading error. After the warm-up, the exhaust emission measurement is done by running the engine for 15-20 minutes at each load condition. The emission concentration is noted by installing the emission analyzer probe in the tailpipe. Figure8 shows the image of the experimental setup. Then, the engine is run at various load instances (0%, 25%, 50%, 75%, and 100%), and the results are obtained. The experiment is conducted in two phases, one without connecting the CO2 trap and one with connecting the CO2 trap in the tailpipe of the engine. Initially, a baseline reading is taken without connecting the CO2 trap. Next, the CO2 trap is connected to the tailpipe of the engine, and readings are taken to evaluate its performance and emission characteristics.Figure 8
The image of experimental setup.


## 3.1. Experimental Setup

To analyze the emission characteristic of the CO2 trap, a single-cylinder four-stroke direct injection diesel engine is coupled with eddy current dynamometer to power take-off shaft. The coolant used in the engine is water, and it is recirculated using a conventional pump. To compare the emission characteristics, an AVL Digas analyzer and an AVL smoke meter are connected to the tailpipe. Figure 7 shows the layout of the experimental setup.Figure 7
Layout of experimental setup.


## 3.2. Experimental Procedure

The initial condition such as engine oil level and the condition, coolant water feed rate, and its overhead tank capacity is tested at engine rest position to confirm normal working throughout the experiment. To avoid any variance, the experimental setup is started and run on neat diesel for about 10 to 15 minutes at the idle condition to reach the nominal operating temperature. During this phase, the calibration is executed on the dynamometer to eliminate loading error. After the warm-up, the exhaust emission measurement is done by running the engine for 15-20 minutes at each load condition. The emission concentration is noted by installing the emission analyzer probe in the tailpipe. Figure8 shows the image of the experimental setup. Then, the engine is run at various load instances (0%, 25%, 50%, 75%, and 100%), and the results are obtained. The experiment is conducted in two phases, one without connecting the CO2 trap and one with connecting the CO2 trap in the tailpipe of the engine. Initially, a baseline reading is taken without connecting the CO2 trap. Next, the CO2 trap is connected to the tailpipe of the engine, and readings are taken to evaluate its performance and emission characteristics.Figure 8
The image of experimental setup.


## 4. Results and Discussion

In this work, CO2 reduction trap is designed and tested for its performance and emission reduction characteristics in a single-cylinder diesel engine. The experiment is conducted by retrofitting the CO2 reduction trap in the tailpipe of the diesel engine.


### 4.1. Performance Characteristics

The performance of the engine after fixing the CO2 reduction trap can be analyzed by evaluating the Brake thermal efficiency and brake-specific fuel consumption. In this experiment, the baseline reading was taken without connecting the CO2 reduction trap in the engine tailpipe, and readings were taken after connecting the CO2 trap in the engine tailpipe. Figure 9 shows the variation of brake thermal efficiency with respect to engine load. It is observed that the brake thermal efficiency of the engine was not much affected after connecting the CO2 trap. This is because the back pressure is not increased after connecting the trap and the design is safe.Figure 9
Variation of brake thermal efficiency with respect to engine load.Figure10 shows the deviation of specific fuel consumption with respect to engine load. It is observed from the graph that specific fuel consumption for baseline does not vary after connecting the CO2 reduction device. This is because the CO2 reduction trap does not impact any load to the engine, and the fuel consumption range does not increase. And with the CO2 reduction trap, the backpressure does not affect the engine performance.Figure 10
Effect of CO2 reduction trap on specific fuel consumption.


### 4.2. Emission Characteristics

The emission testing is carried out for an amine solution of 0.3 mole concentration. At 0.3 moles, the CO2 absorption was observed effectively. So, for all different amine solutions, 0.3 is fixed as an effective absorption concentration. The prepared solution is filled inside the CO2 reduction trap, and it is checked for the maximum level of filling the solution. The exhaust flow inside the CO2 reduction trap is designed in such ways that exhaust gas passes over the amine solution and gets scrubbed. The diesel exhaust continuously passes over the CO2 reduction trap and reacted with the amine solution for emission reduction. The experiment is conducted by varying the load. The concentration of exhaust is also varied by switching the load. The graphs are plotted with respect to various emissions for the given engine load and explained below.Figure11 shows the variation of CO2 emission with respect to engine load. It is observed from the graph that the CO2 emission concentration varies with respect to supplied engine load. The CO2 emission increases due to the complete combustion of fuel [17]. The maximum level of CO2 emission from the exhaust was 6.4% which is liberated at the full load condition of the engine. After in connection with the CO2 reduction trap, the CO2 level was dramatically reduced. It is due to the effective wet scrubbing of exhaust gas over the amine solution.Figure 11
Variation of carbon dioxide with respect to engine load.The double-bond CO2 molecules get adsorbed and absorbed over the amine solution. L-Alanine and L-arginine absorbent shows moderated reduction of 27% and 55% in CO2 emission. It is due to poor absorption of CO2 with respect to L-alanine and L-arginine. Compared with baseline reading, L-aspartic acid shows a maximum reduction of 85% in CO2 emission. It is due to the suitable amine properties of L-aspartic acid in absorbing the CO2 molecules.Figure12 shows the variation of HC emission with respect to engine load. In a diesel engine, HC emission rises due to the incomplete combustion of fuel [18]. The maximum concentration of 48 PPM was liberated from the diesel engine at full load conditions. After in connection with the CO2 reduction trap, the HC emission also tends to be reduced. It is due to the absorbent reaction of amine solution with the HC molecules. L-Alanine and L-arginine have 7% and 25% CO2 reduction. L-Aspartic acid shows a maximum reduction of 37% HC emission. It is due to the suitable amine properties of L-aspartic acid in absorbing the HC molecules.Figure 12
Variation of hydrocarbon with respect to engine load.Figure13 shows the variation of CO emission with respect to engine load. In the diesel engine; CO emission increases due to less oxygen concentration during combustion [19, 20]. Also, the CO emission increases with a rich mixture [21]. After in connection with the CO2 reduction trap, the CO emission slightly decreases. It is due to the reaction of amine solution with the CO molecules. L-Alanine and L-arginine absorbent shows slight reduction in CO. L-Aspartic acid shows maximum reduction of CO emission when compared with L-alanine and L-arginine absorbents. It is due to the suitable amine properties of L-aspartic acid in absorbing CO molecules.Figure 13
Variation of carbon monoxide with respect to engine load.NOx emission increases in diesel engines due to high peak cycle temperature. At high combustion temperatures, NO and O2 undergo endothermic reactions to form NOx [22]. Figure 14 shows the variation of NOx emission with respect to engine load for three different amine solutions. It is observed that only slight NOx reductions of 5-10% were observed with respect to amines. It is due to the poor reduction ability of amines over the NOx molecule. The amines could not be able to trap the double-bond nitrogen molecules over it. The exhaust NOx does not cause any effect on CO2 reduction.Figure 14
Variation of NOx concentration with respect to engine load.Figure15 shows the variation of O2 concentration with respect to load. O2 concentration of the diesel engine exhaust is varied with respect to load [23]. The exhaust oxygen concentration shows how efficient is combustion [24]. With respect to O2 concentration, there is not much change with the CO2 reduction trap. With L-aspartic acid, slight variation in O2 concentration was observed. It is due to the effective reduction of CO2 and CO molecules over the amine solution.Figure 15
Variation of O2 concentration with respect to engine load.


## 4.1. Performance Characteristics

The performance of the engine after fixing the CO2 reduction trap can be analyzed by evaluating the Brake thermal efficiency and brake-specific fuel consumption. In this experiment, the baseline reading was taken without connecting the CO2 reduction trap in the engine tailpipe, and readings were taken after connecting the CO2 trap in the engine tailpipe. Figure 9 shows the variation of brake thermal efficiency with respect to engine load. It is observed that the brake thermal efficiency of the engine was not much affected after connecting the CO2 trap. This is because the back pressure is not increased after connecting the trap and the design is safe.Figure 9
Variation of brake thermal efficiency with respect to engine load.Figure10 shows the deviation of specific fuel consumption with respect to engine load. It is observed from the graph that specific fuel consumption for baseline does not vary after connecting the CO2 reduction device. This is because the CO2 reduction trap does not impact any load to the engine, and the fuel consumption range does not increase. And with the CO2 reduction trap, the backpressure does not affect the engine performance.Figure 10
Effect of CO2 reduction trap on specific fuel consumption.


## 4.2. Emission Characteristics

The emission testing is carried out for an amine solution of 0.3 mole concentration. At 0.3 moles, the CO2 absorption was observed effectively. So, for all different amine solutions, 0.3 is fixed as an effective absorption concentration. The prepared solution is filled inside the CO2 reduction trap, and it is checked for the maximum level of filling the solution. The exhaust flow inside the CO2 reduction trap is designed in such ways that exhaust gas passes over the amine solution and gets scrubbed. The diesel exhaust continuously passes over the CO2 reduction trap and reacted with the amine solution for emission reduction. The experiment is conducted by varying the load. The concentration of exhaust is also varied by switching the load. The graphs are plotted with respect to various emissions for the given engine load and explained below.Figure11 shows the variation of CO2 emission with respect to engine load. It is observed from the graph that the CO2 emission concentration varies with respect to supplied engine load. The CO2 emission increases due to the complete combustion of fuel [17]. The maximum level of CO2 emission from the exhaust was 6.4% which is liberated at the full load condition of the engine. After in connection with the CO2 reduction trap, the CO2 level was dramatically reduced. It is due to the effective wet scrubbing of exhaust gas over the amine solution.Figure 11
Variation of carbon dioxide with respect to engine load.The double-bond CO2 molecules get adsorbed and absorbed over the amine solution. L-Alanine and L-arginine absorbent shows moderated reduction of 27% and 55% in CO2 emission. It is due to poor absorption of CO2 with respect to L-alanine and L-arginine. Compared with baseline reading, L-aspartic acid shows a maximum reduction of 85% in CO2 emission. It is due to the suitable amine properties of L-aspartic acid in absorbing the CO2 molecules.Figure12 shows the variation of HC emission with respect to engine load. In a diesel engine, HC emission rises due to the incomplete combustion of fuel [18]. The maximum concentration of 48 PPM was liberated from the diesel engine at full load conditions. After in connection with the CO2 reduction trap, the HC emission also tends to be reduced. It is due to the absorbent reaction of amine solution with the HC molecules. L-Alanine and L-arginine have 7% and 25% CO2 reduction. L-Aspartic acid shows a maximum reduction of 37% HC emission. It is due to the suitable amine properties of L-aspartic acid in absorbing the HC molecules.Figure 12
Variation of hydrocarbon with respect to engine load.Figure13 shows the variation of CO emission with respect to engine load. In the diesel engine; CO emission increases due to less oxygen concentration during combustion [19, 20]. Also, the CO emission increases with a rich mixture [21]. After in connection with the CO2 reduction trap, the CO emission slightly decreases. It is due to the reaction of amine solution with the CO molecules. L-Alanine and L-arginine absorbent shows slight reduction in CO. L-Aspartic acid shows maximum reduction of CO emission when compared with L-alanine and L-arginine absorbents. It is due to the suitable amine properties of L-aspartic acid in absorbing CO molecules.Figure 13
Variation of carbon monoxide with respect to engine load.NOx emission increases in diesel engines due to high peak cycle temperature. At high combustion temperatures, NO and O2 undergo endothermic reactions to form NOx [22]. Figure 14 shows the variation of NOx emission with respect to engine load for three different amine solutions. It is observed that only slight NOx reductions of 5-10% were observed with respect to amines. It is due to the poor reduction ability of amines over the NOx molecule. The amines could not be able to trap the double-bond nitrogen molecules over it. The exhaust NOx does not cause any effect on CO2 reduction.Figure 14
Variation of NOx concentration with respect to engine load.Figure15 shows the variation of O2 concentration with respect to load. O2 concentration of the diesel engine exhaust is varied with respect to load [23]. The exhaust oxygen concentration shows how efficient is combustion [24]. With respect to O2 concentration, there is not much change with the CO2 reduction trap. With L-aspartic acid, slight variation in O2 concentration was observed. It is due to the effective reduction of CO2 and CO molecules over the amine solution.Figure 15
Variation of O2 concentration with respect to engine load.


## 5. Conclusion

In this experimental testing, emission investigation test of the engine has been done with and without connecting the trap. The difference in emission percentage levels of HC, CO, CO2, and O2 from the diesel engine is analyzed for emission reduction. The preparation of amino solution has been done as per molar solubility and molar concentration; the L-arginine and sodium hydroxide has been mixed with the deionised water as per concentration and solubility quantity; the amino solution has been prepared. Similarly, for L-alanine and L-aspartic acid are used to make an amino solution, the CO2 reduction trap has been designed, and as per the design and dimensions, the fabrication has also been done. The emission testing is carried out in the experimental setup by connecting the trap in the diesel exhaust. The experiment has been done successfully and the emission reading has been taken by using the AVL di gas analyser. The following results have been obtained from the experiments:
(i)
It is observed from the results that L-aspartic acid has a high level of 85% CO2 reduction rate(ii)
L-Alanine has 27%, and L-arginine has 55% CO2 reduction(iii)
L-Aspartic acid has a maximum HC reduction of 37% and CO reduction of 45%, and NOx reduction up to 5-10% was achieved in this workForm this work, it is recommended that L-aspartic acid is effective in controlling CO2 emissions. The CO2 control by a postcombustion method was successfully demonstrated in this work. It is concluded that CO2 reduction by wet scrubbing can be an effective method to reduce CO2 over the amine solutions. In future work, the CO2 reduction tarp will be evaluated for back pressure analysis in CFD. And in experimental, many different biodiesels will be used in diesel engines, and their emission concentrations will be tested with the CO2 reduction trap.



---

*Source: 8803585-2022-02-14.xml*