# Characterization and Use of Char Produced from Pyrolysis of Post-Consumer Mixed Plastic Waste
## 3 Results and Discussion
### Effect of the Operating Temperature on the Properties of the Produced Solids
#### 3.3.1 Elemental Analysis, Thermal Decomposition, Immediate Analysis, HHV and Surface Properties
Figure 1 shows the thermogravimetric curve for the different solid materials. Figure 1: Thermogravimetric curves of the solids obtained by pyrolysis of the non-recyclable mixed plastics from municipal solid waste at different temperatures. There are evident differences between the curves of the solids subjected to different temperatures, especially for the solid obtained at 450 \({}^{\circ}\)C. This solid starts to degrade significantly at a lower temperature than the rest, around 350 \({}^{\circ}\)C, losing practically 20% of its weight in a temperature range of approximately 100 \({}^{\circ}\)C; from 460 \({}^{\circ}\)C to 730 \({}^{\circ}\)C the degradation phase is slightly slower. In this phase, the solid loses 20% of its weight, and again enters a more pronounced degradation phase until it reaches 807 \({}^{\circ}\)C where it loses 15% of its weight. The last section of the curve corresponds to the amount of fixed carbon present in the sample, since at 850 \({}^{\circ}\)C thermal degradation occurs in the presence of oxygen. The solid obtained at 450 \({}^{\circ}\)C is the one that loses the most mass during the thermogravimetric test, reaching a final mass fraction of 0.3, which indicates that it is the one with the lowest amount of ash and the most volatile matter. The pyrolyzed sample at 500 \({}^{\circ}\)C presents a more constant degradation from 400 \({}^{\circ}\)C to 730 \({}^{\circ}\)C, losing only 10% of its weight. From 730 \({}^{\circ}\)C to 820 \({}^{\circ}\)C a more pronounced degradation occurs, with a weight loss of 16%. Finally, the curve corresponding to fixed carbon is the longest of all, which reveals that it is the sample with the highest fixed carbon content, reducing from 71% to 50%. With respect to the sample pyrolyzed at 550 \({}^{\circ}\)C, it shows a similar trend to the sample pyrolyzed at 500 \({}^{\circ}\)C, although the degradation between 400 and 730 \({}^{\circ}\)C is higher, losing 15% of weight. A more pronounced degradation occurs until 820 \({}^{\circ}\)C, with a weight loss of 16%. Fixed carbon curve clearly differs from the two previous samples, being the shortest indicating the lowest fixed carbon content. In addition, this sample is the one that has the highest ash content (around 60%). Table 4 also presents the results of the average immediate analysis obtained on the basis of the thermogravimetric curves. The results reveal that both the ash content and the volatile content are related to the pyrolysis temperature. This relationship is direct for the ashes content, since at higher the temperature the ash content is higher, due to the higher thermal degradation suffered by the samples. For the volatile matter content, as expected, it presents an inverse relationship with the temperature since, as the temperature increases, solid residues with a lower volatile content are obtained. This is due to the fact that the higher the temperature, the more volatile compounds contained in the solid waste are released. However, the fixed carbon content remains practically constant at temperatures of 450 and 500 \({}^{\circ}\)C, decreasing significantly when the temperature rises up to 550\({}^{\circ}\)C, which is again related to the higher decomposition of the solid at this temperature. The results are similar to those reported by [PERSON] et al. [45], who performed pyrolysis on municipal waste, varying the temperature between 400 and 700 \({}^{\circ}\)C. The immediate analysis of the solid products revealed a very similar moisture content (between 0.25 and 2.25%), ash content (between 26.73 and 42.19%) and volatile material (between 13.73 and 42%), with the fixed carbon content being slightly higher (between 26.17 and 41.57%). The trend for carbon content was also similar, with a large increase from 400 to 500 \({}^{\circ}\)C and then remaining more or less constant up to 700 \({}^{\circ}\)C. [PERSON] et al.