# Thermogravimetric Study of Refuse Derived Fuel Produced from Municipal Solid Waste of Kazakhstan
## 3 Results and Discussions  
### Thermogravimetry (TG) and Differential Thermogravimetry (DTG) Curves of RDF Samples  
The weight loss curves (TG curve) of RDF and its compounds at 10 \({}^{\circ}\)C/min were shown in Figure 4. As seen from the figure, the initial weight loss of samples occurred at the temperature of 100 \({}^{\circ}\)C, which can be attributed to the release of moisture. The moisture release for samples were in the following order, plastic (0.4-1.5%) < textile (1.5-2.0%) < paper (4.0-4.5%) and for the RDF varied in the 2.0-2.5% range. In the temperature range of 370 and 400 \({}^{\circ}\)C, the weight loss was greater for the paper samples, followed by mixed RDF, plastic and textile fractions. In addition, more than 80% of samples were decomposed when the temperature reached 500 \({}^{\circ}\)C (see Figure 4). However, when the temperature exceeded 550 \({}^{\circ}\)C, the weight loss of textile was higher in comparison to the plastic, paper, and mixed RDF. Furthermore, minor weight losses were observed for all samples at temperatures more than 600 \({}^{\circ}\)C and these losses can be attributed to the end of conversion stage. The residual weight for plastic and paper samples were roughly 8-10% and only around 4.3% for textile. Similar low residual weight of cotton samples were also observed by Font [43] through their TGA analysis.  
In the temperature range of 200 and 600 \({}^{\circ}\)C, three main decomposition peaks were observed for textile and mixed RDF samples, while this was different for mixed plastic and mixed paper samples. Such differences in the DTG curves for plastic can be explained by the presence of several types of plastic materials, which may lead to several peaks [8; 13]. The first decomposition interval of samples takes place between 180 \({}^{\circ}\)C and 370 \({}^{\circ}\)C, with peaks being at 330 \({}^{\circ}\)C. Similar temperature range for RDF decomposition were observed by [PERSON] et al. [44], [PERSON] et al. [8], and [PERSON] et al. [38]. As also noted by [PERSON] et al. [44], the decomposition of RDF samples at these temperature range mainly occurs due to the release of volatiles, followed by the gas phase reactions between the volatiles and oxygen. Mixed paper and plastic, on the other hand, shows the highest and lowest decomposition rate in the first peak, respectively (Figure 4). According to [PERSON] [6], [PERSON] et.al [45], the first peak represents mostly the degradation of hemicellulose and cellulose, while the second peak attributes to the degradation of plastics such as PE and PP.  
In other studies, the paper and plastic samples had only one peak, except PVC which produced two peaks [8; 13]. [PERSON] et al. [8] have reported that the total conversion of several plastic samples were practically 100%, except for PVC which accounted for 91.7%. A higher residual mass in plastic, that we observed in our experiments, could be due to the presence of PVC in the mixed plastic. Several DTG peaks between 400 and 600 \({}^{\circ}\)C in plastic samples clearly indicates the presence of different types of plastics. It is also worth noting herein that the mixed paper can contain impurities, including tetra pack. It is well known that tetra pack is made of wood-based material coated with PE and aluminum. The DTG curve for mixed paper in Figure 4 shows two peaks that correspond to degradation of cellulose followed by decomposition of plastic based materials, respectively.