Influence of the Feedstock on the Process Parameters, Product Composition and Pilot-Scale Cracking of Plastics

Abstract

Chemical recycling of polymers can lead to many different products and play a significant role in the circular economy through the use of plastic waste as a feedstock in the production of valuable materials. The polyolefins: polyethylene (PE) and polypropylene (PP), together with polystyrene (PS), can be chemically recycled by the thermal cracking (pyrolysis) process. In this study, continuous cracking of polyolefins and polystyrene in different proportions and with the addition of other polymers, like polyethylene terephthalate (PET) and polyvinyl chloride (PVC), was investigated at the pilot scale in terms of the process parameters and product yields. Gas chromatography with mass spectrometry (GC-MS) was used for the detailed analysis of the products’ compositions. The boiling temperature distribution and the bromine number were used for additional characterization of products. It was found that an increase of PP share caused a decrease in the process temperature, an increase of the product yield and a shift of the boiling range towards lighter products, increasing the content levels for unsaturates and branched hydrocarbons. It was observed that the addition of 5% PS, PET and PVC reduced the overall product yield, resulting in the creation of a lower-boiling product and increasing the conversion of polyethylene. An addition of 10% polystyrene increased the PP conversion and resulted in a higher product yield, without significant change in the boiling temperatures distribution.

Utilization of polymeric wastes in steel refining process: Carbon dissolution into liquid steel at high temperature

“…Many previous studies [ [6] , [7] , [8] , [9] , [10] , [11] ] converted plastics into various forms of solid carbon, such as carbon sphere and carbon nanorod, by pyrolysis at temperatures from 300 to 900 °C. However, effect of plastics fillers had not been reported.…”

“…The PS used in the present study contains Ca(OH) 2 as a filler, which might affect the carbon dissolution into liquid steel. According to previous studies [ [6] , [7] , [8] , [9] , [10] , [11] ], we have pyrolyzed PS and Blend#1 – Blend#6 with iron catalyst at 800 °C for 15 min under argon atmosphere. XRD patterns of the chars derived are presented in Fig.…”

“…The obtained product was 22.63–35.92% of the pyrolysis oil, consisting of 80–90% aromatic hydrocarbons. Fraczak et al [ 11 ] investigated continuous pyrolysis of polyolefins and PS in different proportions and with the addition of PET and polyvinyl chloride (PVC), at the pilot scale. It was reported that the overall product yield had decreased with the addition of 5% PS, PET and PVC.…”

“…These result in the formation of a lower-boiling product and the increase in amount of polyethylene conversion. By adding 10% of PS, the conversion of PP had increased, leading to a higher product yield and no significant change in the distribution of boiling temperatures [ 11 ].…”

Chemical recycling: A critical assessment of potential process approaches

“…Aguado et al, 2006) and the treatment of the low-grade gaseous and/or liquid products obtained from it (e.g. Fraçzak et al, 2021). In combination, this has apparently been a high obstacle and only a few (half-) industrial pyrolysis processes for plastics exist to date (e.g.…”