**3. Results and discussion**

### **3.1. Solubility of polymers**

a mixture hexadecane (*CN*=100) and heptamethylnonane (CN=15). For practical purposes, the

0.69 <sup>1413</sup> *CN = t FIA*

1

<sup>×</sup> (3)

22 *CN = CN + CFR FIA* (4)


Furthermore, the relationship between *CN* of FAME using FIA and *CN* value using the CFR standard institutional organization engine test, *CNCFR*, is described by the following relation

One of the important characteristics of diesel fuel is the carbon residue (CR). The CR is a characteristic value related to the amount of carbon deposits stored inside the engine, carbon deposits for petroleum-based fuels in general are measured using a sample condensed to 10% in volume. For FAME, the high-temperature heating process under condensation results in thermal decomposition of FAME components. In addition, the chemical structure of the fatty acid methyl ester component is changed. For this reason, the CR value for FAME was measured

The heating value of fuel is related to fuel economy and engine power. In this study, the higher heating value of fuel was measured using an automatic bomb calorimeter (Shimadzu, CA-4PJ).

FIA cetane number(*CNFIA*) was determined by Eq.3.

using a sample without condensation in this study.

**Figure 2.** Configuration of fuel ignition quality analyzer (FIA).

where *τ* denotes the ignition delay [ms].

210 Biofuels - Status and Perspective

[18]:

Figure 4 represents data of the polymers as mesh spheres, and the solvents as dots. Figure 5 also represents the data as two-dimensional planes. Table 3 shows the results calculated from the HSP analysis. In Figures 4 and 5, the scale in coordinate of dispersion(*δ*D) is expressed in HSPiP as twice as large as those in coordinates of polarity(*δ*P) and hydrogen bonding(*δ*H), due to the coefficient "4" of dispersion component in Eq.1.

In Figures 4 and 5, it seems that the methyl oleate is inside of polystyrene (PS) and polypro‐ pylene(PP) spheres, methanol and oleate acid are outside of them. From *RED* value in Table 3, the combination of PS and methyl oleate had a *RED* value less than 1.0. The PP and poly‐ ethylene (PE) combinations with methyl oleate had *RED* values slightly higher than 1.0. This indicates that methyl oleate is significantly outside the PE and PP spheres. The *RED* value of methanol and oleic acid are significantly greater than 1.0. Therefore, only polystyrene can be considered to be sufficiently dissolved in methyl oleate. The results also show that FAME will selectively dissolve the polystyrene in the form of mixed waste plastic.


**Figure 4.** plot of the HSP sphere for polymers and solvents.

**Figure 5.** plot of the HSP for polymers and solvents.

#### **3.2. Characteristics of FAME-dissolved polystyrene**

To examine solubility, both the food trays (polystyrene paper; PSP) and the expanded polystyrene(EPS) were completely dissolved in FAME, which was completely transparent

**Figure 6.** Photos of FAME dissolved polystyrene.

**Polymer**

212 Biofuels - Status and Perspective

**Table 3.** RED numbers computed by HSPiP.

**Figure 4.** plot of the HSP sphere for polymers and solvents.

**Figure 5.** plot of the HSP for polymers and solvents.

**3.2. Characteristics of FAME-dissolved polystyrene**

To examine solubility, both the food trays (polystyrene paper; PSP) and the expanded polystyrene(EPS) were completely dissolved in FAME, which was completely transparent

**Solvent Methyl Oleate Oleic Acid Methanol**

PS 0.93 1.17 4.20 PE 1.08 1.23 7.12 PP 1.05 1.15 40.6

> after the dissolution, as shown in Figure 6. Figure 7 shows the relation between kinematic viscosity and mass concentration of PS dissolved in FAME. The figure also shows results obtained by another researcher [8] and the dissolved polystyrene standards (average molec‐ ular weight of 4000 and 50,000). Kinematic viscosity increased with increasing PSP and EPS concentrations. For EPS, kinematic viscosity increased exponentially, revealing a high kinematic viscosity such as that of heavy oil at a concentration of 9%(m/m) EPS in FAME. In contrast, the kinematic viscosity of the PS standard in FAME was less than those of EPS and PSP. In addition, the kinematic viscosity increased with an increase in average molecular weight, suggesting that an increase in kinematic viscosity is related to the degree of polymer‐ ization and molecular weight of the dissolved polystyrene.

**Figure 7.** Relationship between kinematic viscosity and mass concentration of the polystyrene dissolved in FAME.

The molecular weight distribution of polystyrene in FAME was measured by GPC. Figure 8 shows the experimental results for the polystyrene (PS) standard with an average molecular weight of 50,000 dissolved in FAME and 5%(m/m) EPS in FAME. The molecular weight peak was similar to that of the polystyrene standard; however, the EPS molecular weights in FAME were distributed across a wide range compared to the range of the PS standard, and indicated a compound with a molecular weight greater than 107 . These results suggest that the existence of a very large polymer causes an increase in kinematic viscosity.

Next, the rate of volume reduction of polystyrene and PSP caused by dissolution in FAME was investigated. The solvent *n*-hexane—a non-polar solvent—was added to crystallize the PS. The crystallized PS was filtered and the mass was measured to determine specific volume. The specific volume of PS in FAME was 1.38 × 10-3 m3 /kg, indicating that the specific volume of 82.6 × 10-3 m3 /kg for PS before dissolution was reduced. Therefore, dissolution of PSP in FAME can reduce the volume of waste plastic. Also, in case of EPS and XPS which show high expansion ratio, the volume will be extremely reduced by dissolution in FAME.

**Figure 8.** Distribution of polystyrene molecular weight in FAME.

### **3.3. Fuel characteristics**

Figure 9 shows a series of combustion pressures obtained by the FIA fuel ignitability tester. The cycle-to-cycle fluctuation in combustion pressure for EPS dissolved in FAME is less than that for neat FAME.

Figure 10 shows the changes in ignition delay and cetane number (*CNFIA*) against the dissolved EPS concentration. The ignition delay gradually increased with increasing EPS concentration. For this reason, the *CNFIA* value also decreases. This is caused by the increased kinematic viscosity and the suppression of fuel spray atomization upon dissolution of EPS. Furthermore, generally the petroleum-based fuels are known to possess poor ignitability at higher concen‐ trations of aromatic hydrocarbons. The raw material for styrene monomers is represented by the aromatic chemical formula of C8H8. For this reason, the ignition delay gradually increases with PS concentration.

**Figure 9.** Courses of combustion pressure obtained by FIA fuel ignitability tester.

The molecular weight distribution of polystyrene in FAME was measured by GPC. Figure 8 shows the experimental results for the polystyrene (PS) standard with an average molecular weight of 50,000 dissolved in FAME and 5%(m/m) EPS in FAME. The molecular weight peak was similar to that of the polystyrene standard; however, the EPS molecular weights in FAME were distributed across a wide range compared to the range of the PS standard, and indicated

Next, the rate of volume reduction of polystyrene and PSP caused by dissolution in FAME was investigated. The solvent *n*-hexane—a non-polar solvent—was added to crystallize the PS. The crystallized PS was filtered and the mass was measured to determine specific volume. The

can reduce the volume of waste plastic. Also, in case of EPS and XPS which show high

Figure 9 shows a series of combustion pressures obtained by the FIA fuel ignitability tester. The cycle-to-cycle fluctuation in combustion pressure for EPS dissolved in FAME is less than

Figure 10 shows the changes in ignition delay and cetane number (*CNFIA*) against the dissolved EPS concentration. The ignition delay gradually increased with increasing EPS concentration. For this reason, the *CNFIA* value also decreases. This is caused by the increased kinematic viscosity and the suppression of fuel spray atomization upon dissolution of EPS. Furthermore, generally the petroleum-based fuels are known to possess poor ignitability at higher concen‐ trations of aromatic hydrocarbons. The raw material for styrene monomers is represented by the aromatic chemical formula of C8H8. For this reason, the ignition delay gradually increases

expansion ratio, the volume will be extremely reduced by dissolution in FAME.

/kg for PS before dissolution was reduced. Therefore, dissolution of PSP in FAME

. These results suggest that the existence

/kg, indicating that the specific volume of

a compound with a molecular weight greater than 107

specific volume of PS in FAME was 1.38 × 10-3 m3

**Figure 8.** Distribution of polystyrene molecular weight in FAME.

**3.3. Fuel characteristics**

that for neat FAME.

with PS concentration.

82.6 × 10-3 m3

214 Biofuels - Status and Perspective

of a very large polymer causes an increase in kinematic viscosity.

**Figure 10.** Changes of ignition delay and cetane number (*CNFIA*) against the dissolved polystyrene (EPS) concentration.

Figure 11 shows the relation between calorific value and EPS concentration. Initially, the dissolution of EPS in FAME was expected to result in a sufficiently high heating value. However, the increase at a lower heating value was greater than that at the higher heating value, because the oxygen content in the original FAME of approximately 10%(m/m) is reduced by dissolution of EPS.

**Figure 11.** Effect of polystyrene (EPS) concentration in FAME on higher calorific value.


**Table 4.** Comparison of density, kinematic viscosity, higher heating value, cetane number(*CNFIA*), carbon residue.

Table 4 shows the density, kinematic viscosity, higher heating value, cetane number (*CNFIA*), and carbon residue without sample condensation. The carbon residue at 5%(m/m) dissolved EPS was twice that at 2%(m/m) dissolved EPS. When this was used as diesel fuel, the amount of carbon deposit in the combustion chamber increased. This deposit may affect the fuel injection system and fuel spray atomization.

Figures 12 and 13 show the effect of fatty acid components of FAME on kinematic viscosity and carbon residue. As shown in Figure 12, the kinematic viscosity increases with an increase in concentration of EPS, and the fatty acid methyl ester with higher carbon number shows higher kinematic viscosity. Also, the carbon residue at methyl oleate shows higher value than methyl palmitate and methyl laurate at all concentrations of EPS. From the results, fuel properties of FAME dissolved EPS may be improved by changing fatty acid composition in FAME. In other words, to use FAME dissolve EPS as fuel, FAMEs with short and middle length of carbon chains as fatty acid component will be better than fatty acid methyl ester with the long length chains.

### **3.4. Diesel engine performance**

This section describes the engine performance and problem of diesel generator fuelled with FAME dissolved EPS. The experiment was carried out by using small diesel engine generator. Fuel consumption was measured by a burette-installed fuel line at various engine loads. And the brake thermal efficiency was calculated. Table 5 shows the main specification of engine generator used in experiment. Figure 14 shows the result obtained by engine test. From Figure 14, the thermal efficiency at the FAME dissolved EPS-5% shows higher value than that at neat FAME at rated engine output. This might be caused by lower cycle-to-cycle fluctuation in combustion as shown in Figure 9 in case of EPS-5%.

In general, the lubricating oil in the diesel engine was mixed with some injected fuel, a process called "oil dilution by fuel." Then, a mixing test that involved mixing of regular diesel lubricant hydrocarbons and FAME-dissolved EPS was conducted. Figure 15 shows the photos of mixture with regular diesel lubricant hydrocarbon and with lubricant oil derived from castor oil. These photos show that, immediately after mixing, the dissolved EPS crystallizes in the gel and precipitates for both cases. Thus, the use of FAME- dissolved polystyrene as diesel fuel requires the prevention of precipitation and deposition of polystyrene.


**Table 5.** Main specification of diesel generator.

**Properties FAME(SME)**

injection system and fuel spray atomization.

Density kg/L@15o

216 Biofuels - Status and Perspective

Kinematic viscosity

long length chains.

**3.4. Diesel engine performance**

combustion as shown in Figure 9 in case of EPS-5%.

mm2 /s@40o C **EPS-2%(m/m) in FAME(SME)**

4.16 6.46 19.5

C 0.886 0.888 0.894

Higher heating value MJ/kg 39.6 40.8 39.8

Cetane Number CNFIA 28 27 23.5

100%-Carbon residue %(m/m) 0.012 0.042 0.078

**Table 4.** Comparison of density, kinematic viscosity, higher heating value, cetane number(*CNFIA*), carbon residue.

Table 4 shows the density, kinematic viscosity, higher heating value, cetane number (*CNFIA*), and carbon residue without sample condensation. The carbon residue at 5%(m/m) dissolved EPS was twice that at 2%(m/m) dissolved EPS. When this was used as diesel fuel, the amount of carbon deposit in the combustion chamber increased. This deposit may affect the fuel

Figures 12 and 13 show the effect of fatty acid components of FAME on kinematic viscosity and carbon residue. As shown in Figure 12, the kinematic viscosity increases with an increase in concentration of EPS, and the fatty acid methyl ester with higher carbon number shows higher kinematic viscosity. Also, the carbon residue at methyl oleate shows higher value than methyl palmitate and methyl laurate at all concentrations of EPS. From the results, fuel properties of FAME dissolved EPS may be improved by changing fatty acid composition in FAME. In other words, to use FAME dissolve EPS as fuel, FAMEs with short and middle length of carbon chains as fatty acid component will be better than fatty acid methyl ester with the

This section describes the engine performance and problem of diesel generator fuelled with FAME dissolved EPS. The experiment was carried out by using small diesel engine generator. Fuel consumption was measured by a burette-installed fuel line at various engine loads. And the brake thermal efficiency was calculated. Table 5 shows the main specification of engine generator used in experiment. Figure 14 shows the result obtained by engine test. From Figure 14, the thermal efficiency at the FAME dissolved EPS-5% shows higher value than that at neat FAME at rated engine output. This might be caused by lower cycle-to-cycle fluctuation in

In general, the lubricating oil in the diesel engine was mixed with some injected fuel, a process called "oil dilution by fuel." Then, a mixing test that involved mixing of regular diesel lubricant hydrocarbons and FAME-dissolved EPS was conducted. Figure 15 shows the photos of

**EPS-5%(m/m) in FAME(SME)**

**Figure 12.** Effect of polystyrene(EPS) concentration in FAME on kinematic viscosity.

**Figure 13.** Effect of polystyrene(EPS) concentration in FAME on carbon residue.

**Figure 14.** Brake thermal efficiency vs. engine load of diesel engine generator.

**Figure 15.** Photo of mixture of FAME-dissolved EPS and engine lubricant oil.
