**4. Experimental results and discussion**

For comparative testing, the samples will be performed simultaneously under two different conditions.

Natural aging experiment: A set of 5 sheet samples and 2 kg of PP granules were placed on the sample tray in one of the pyramid skylight structure. Under natural conditions, they were directly exposed to solar radiation. Because the pyramid skylight structure is closed, the impact of moisture on the material is not considered. The experiment time is 12 consecutive days.

Ultraviolet aging experiment: Place another set of 5 sheet samples and 2 kg of PP granules on a sample tray inside of another pyramidal skylight structure, and place them in a dark environment at a controlled constant temperature of 22°C. Four ultraviolet lamps were placed outside the four inclined triangle sides of the pyramid skylight structure. The position of the UV light source is higher than the sample tray and the distance between the sample and the ultraviolet lamp is 10 cm, as shown in the **Figure 3**. The sample was receiving 100% UV light for 12 consecutive days.

The rest 2 kg of PP granules are without any aging treatment.

### **4.1 Aging test results and discussion**

The appearance changes of two groups of samples under different aging test conditions are shown in **Table 2**. In 12 days of natural aging, the color of PP sheet, EPS sheet, Natural rubber sheet and PP granules did not change. The PE sheet and PS sheet only turned yellow very slightly. It can be seen that the surface aging of the material is not obvious in the short-term irradiation of natural light. Normally, the aging test under natural conditions takes months up to years to see the obvious aging effect.

While under 12 consecutive days of UV light irradiation, PP granules very slightly turned yellow; PP sheet, EPS foam sheet turned light yellow; Natural rubber sheet turned yellow; PE sheet and PS sheet severely yellowed. Obviously, UV light has a significant influence on the aging of Natural rubber, PE and PS.

### **4.2 Pyrolysis test results and discussion**

The pyrolysis experiments were conducted in a fully automatic 5 kW electromagnetic induction heating pyrolysis system, which was manufactured by Greenlina SA, Switzerland as shown in **Figure 4**. Under exactly the same experimental conditions without using any catalysts, three pyrolysis experiments were carried out on 2 kg PP granules without any aging treatment, 2 kg PP granules that had undergone natural aging and 2 kg PP granules that had been aging by


### **Table 2.**

*Experimental results of two different aging methods.*

### **Figure 4.**

ultraviolet light respectively. The ambient temperature in the experiment was 27±0.5°C. The setting temperature of the chiller used for condensation was 3°C, and the start-up time of the chiller was completely the same in the two tests. The set temperature of the heating jacket on the separation tank was 120°C, and the heating jacket started to heat at the beginning of the experiment for both tests.

It is not difficult to see from the **Table 3** that without the aid of catalyst, under the same experimental conditions, there is not much difference in oil yield between the two different treatments of PP granules and the granules without any aging treatment. However, the PP granules that have undergone UV accelerated aging began to produce pyrolysis oil after about 17 minutes, and it took about 60 minutes to complete the entire pyrolysis process. The naturally aged PP granules started to produce pyrolysis oil after about 24 minutes, and it took about 77 minutes to complete the entire pyrolysis process. While the PP granules without aging treatment started to produce pyrolysis oil after about 25 minutes, and it took about 78 minutes to complete the entire pyrolysis process. Considering of reasonable deviation, short-term natural aging samples hardly improve the oil generation time and the time required to complete the entire pyrolysis process comparing with the sample without aging. Nevertheless, we have noticed that the pyrolysis (from long chains to short chains) of PP plastic granules after UV accelerated aging becomes much easier and faster. In other words, less energy was consumed to complete the entire pyrolysis process.

*Fully automatic electromagnetic heat induction pyrolysis system.*

*Accelerate the Aging of Polymer as Energy-Saving Method Prior to the Pyrolysis Process DOI: http://dx.doi.org/10.5772/intechopen.99995*


### **Table 3.**

*The comparison test of pyrolysis.*

### **Figure 5.**

*The pyrolysis oil of PP plastic granules.*


### **Table 4.**

*Component in liquid fraction obtained from pyrolysis of PP granules using GC–MS analysis.*

The pyrolysis-oil (**Figure 5**) from PP granules was analyzed by GC–MS (as shown in **Table 4**). The identified compounds were categorized according to the length of their carbon chain: C5–C9, C10–C13 and C>13. Those molecules with a chain length of C5–C9 represents to light hydrocarbons (gasoline fuel), which generally contain hydrocarbons between C5 and C9, while C>13 correspond to the heavy oils.

It was observed that pyrolysis of PP granules mainly yielded non-aromatic hydrocarbons with carbon number C>13 around 52.49% and aromatic hydrocarbons with carbon number C>13 around 13%. For PP granules, the resulting oils are mostly aliphatic hydrocarbons (alkanes and alkenes) with carbon number more than C13, which makes it suitable for use in diesel engines.


**Table 5.**

*The most abundant compounds present in oils from the pyrolysis of PP granules as detected by GC–MS analysis.*

The most abundant compounds present in oils from the pyrolysis of PP granules are present in **Table 5**. Pyrolysis of PP granules produced an oil containing C9H18 (15.35%), C23H46 (15.18%), C18H36 (8.84%), C15H30 (8.68%) and C12H24 (4.12%).

### **5. Conclusions**

Through review, we found that the heterogeneous nature of MSW is not well suited to gasfication/pyrolysis technology due to high energy consumption and low energy efficiency. Pyrolysis is suitable for homogeneous material streams (e.g., Waste plastics/rubber after sorting; numerous studies have shown that the shortterm accelerated aging of polymers under a specific wavelength of artificial ultraviolet light is equivalent to the results of long-term natural aging of polymers.

In this study, 12 days of natural aging has almost no effect on the appearance of the experimental samples. While the artificial accelerated aging by the aid of 340 nm ultraviolet light in 12 days has a significant effect on the appearance of the experimental samples.

In the comparative pyrolysis experiments of PP granules under the same experimental conditions, the pyrolysis results confirmed that the PP granules undergone UV accelerated aging were faster than the short-term natural aging PP granules in the time of oil producing and completing the entire pyrolysis. The time was reduced about 1/4, thereby reducing total energy consumption. The performance of the PP granules undergone short-term natural aging is consistent with the performance of the PP particles that have not undergone any aging treatment, which confirms the short-term natural aging does not help the energy consumption of thermal cracking.

Pyrolysis is a high energy-consuming treatment method. In addition to the use of catalysts to greatly reduce the cracking temperature, it is recommended to use ultraviolet light to artificially accelerate the aging of the raw materials at the same time when the raw materials are dried/dehydrated in the pretreatment stage.

This additional pretreatment step can speed up the thermal cracking reaction, reduce energy consumption and increase thermal efficiency which has been confirmed by lab-scale experiments. While in some remote or power-deficient areas, it is not realistic to implement UV light to artificially accelerate aging during the pretreatment of raw materials. Where conditions are available, for large-scale pyrolysis production, there are currently many unknown factors such as: how much additional investment is needed as an additional step of pretreatment; the optimal irradiation frequency and intensity of artificial UV light for universal/mixed polymers; the shortest and most effective aging time required for artificial aging; the overall energy consumption of artificially accelerated aging by UV light; the overall energy saving during the pyrolysis after this pretreatment; whether it is cost-effective if the *Accelerate the Aging of Polymer as Energy-Saving Method Prior to the Pyrolysis Process DOI: http://dx.doi.org/10.5772/intechopen.99995*

investment required for UV sped up aging compared with the benefits brought by energy-saving…all need to be further verified in the future study.
