The CO2 Gasification Kinetic Study of WEEE Plastic Char Derived from Medium Temperature pyrolysis

Abstract

The isothermal CO 2 gasification characteristics of three chars derived from medium temperature pyrolysis of waste electrical and electronic equipment (WEEE) plastics were studied by using a thermogravimetric analyzer (TGA) within the temperature range of 850−1050°C. Phenolic board (PB), brominated high impact polystyrene (HIPS) and acrylonitrile butadiene styrene (ABS) plastics are widely used for the electric and electronic equipment and were employed as model WEEE plastics for the char sample production in this study. The effects of their physicochemical properties and gasification temperature on the WEEE plastic chars conversion rate, the reactivity indexes and the gasification rate were investigated in detail. The random pore model (RPM), the extended random pore model (eRPM) and the shifted extended random pore model (s-eRPM) have been employed to fit the CO 2 gasification rate curve of WEEE plastic chars, respectively. The kinetic parameters and the correlation coefficients (R 2 ) were evaluated by RPM, eRPM and s-eRPM, respectively. It was found that the CO 2 gasification reactivity of PB char was the highest, followed by that of HIPS char and the gasification reactivity of ABS char was the lowest, which have a close relationship with their pore and carbon crystal structure properties. In addition, it was found that RMP could fit the gasification reaction rate of HIPS char well whose maximum reaction rate appeared at the char conversion of approximate 0.4. Nevertheless, as for PB char and ABS char, their maximum gasification rate presented at char conversion of around 0.8 and 0.2, respectively. And it was observed that eRMP and s-eRPM could predict their gasification rate of PB char and ABS char very well with higher R 2 , respectively.

Alternative Reducing Agents in Metallurgical Processes: Gasification of Shredder Residue Material

“…The position of the peak in the angle region of 27-29°, corresponds to the (002) peak of graphite, which is generally attributed to the stacking of the graphitic basal plans of chars [29]. The disordering of carbon crystalline structure results in the broadening of the (002) diffraction peak: the more disordering of carbon crystalline structure, the wider the diffraction peak of (002) [9]. The char produced at slow devolatilization heating rate shows more order in the structure, indicated by carbon (002) peak accompanied by an overlapping peak of silica, compared with the char produced at fast devolatilization heating rate, which explains the lower reactivity observed for the this char.…”

“…The gasification rate of SRM char was higher than that of coal char; and the estimated activation energy for its gasification was lower than coal char. This difference could be due to different physical properties of material, such as surface area, morphology of char, and the pore distribution, which are known to play a vital role on gasification reactivity [9]. In addition, the ash content, especially alkali and alkaline earth metals (AAEM) and iron, are known to act as catalysts in the gasification reactions.…”

“…Carbon in char can react with CO 2 , H 2 O, or O 2 , where reaction of O 2 is very fast and reaction with H 2 O is insignificant. Therefore, the rate of CO 2 gasification of chars is the lowest and the most significant, and consequently, it is considered as the rate-determining step during thermal decomposition [9].…”

“…In addition, in the literature, there is a lack of study of a complex material such as SRM, which is a mixture of plastics alongside inorganic materials. Most studies deal with the gasification of char produced from individual plastics [9,12,13]. As an example, Wu et al [9] studied the effect of physiochemical properties and gasification temperature on the conversion rate of char derived from three common plastics in electronic scrap at 873 K. Results showed that as the gasification temperature increases, the conversion time decreases, and the gasification reactivity was the highest for char with the highest surface area and the lowest carbon crystalline degree.…”