Effect of Temperature and Vapor Residence Time on the Micropyrolysis Products of Waste High Density Polyethylene

Abstract

Thermal degradation of plastics is a promising technology for addressing the waste management issues of landfill disposal, while obtaining useful products. Primary thermal degradation of polymers usually yields a large quantity of high molecular weight compounds with a limited applicability, making necessary a secondary degradation to improve the product quality. In this study, pyrolysis vapors from waste high density polyethylene (HDPE) were subjected to secondary degradation by varying the temperature and vapor residence time (VRT) in the reaction zone of a new two-stage micropyrolysis reactor (TSMR) attached to a commercial micropyrolysis unit. Temperature and VRT variations showed a strong effect on the product distribution, with low temperature (625 °C) and short VRT (1.4 s) producing a wide range of gases and liquid products and with high temperature (675 °C) and long VRT (5.6 s) producing mostly hydrocarbon gases and mono- and polyaromatics. The results showed a good agreement with previously reported product distributions for larger-scale pyrolysis reactors and were well explained by known degradation mechanisms.

Degradation Mechanism of Nickel-Cobalt-Aluminum (NCA) Cathode Material from Spent Lithium-Ion Batteries in Microwave-Assisted Pyrolysis

“…This cracking is a function of microwave power and working temperature. It is understood that too high temperature, long residence time, and secondary cracking mechanisms will lead to the formation of aromatic compounds [37], which account for the generation of aromatic hydrocarbons, like toluene, ethylbenzene, and styrene. The aromatic hydrocarbons contain sigma bonds, which are difficult to break at lower temperatures.…”

Waste high‐density polyethylene recycling process systems for mitigating plastic pollution through a sustainable design and synthesis paradigm

“…All computational experiments are performed on a DELL OPTIPLEX 7040 desktop with Intel(R) Core (TM) i7‐6700 CPU @ 3.40 GHz and 32 GB RAM. The product distributions for HDPE pyrolysis are leveraged from relevant literature 30‐32 . The process simulation models for each technology alternative in HDPE pyrolysis, light component separation, heavy chemical component separation sections are developed in Aspen Plus V10.0 70 .…”

“…The proposed superstructure starts with the HDPE preprocessing section, where the waste HDPE is ground into small particles to be transported to the downstream pyrolizer. Four technology options with pressure swing‐adsorption (PSA) are considered: “FBR, SiO 2 , 675°C, with PSA,” “FBR, SiO 2 , 650°C, with PSA,” “FBR, HZSM‐5, 500°C, with PSA,” and “FBR, HZSM‐5, 600°C, with PSA.” 30‐32 The “FBR” denotes the fluidized bed reactor. The sand, which is approximated as SiO 2 , is circulated to maintain high‐temperature in the first two technology options, while the HZSM‐5 catalyst used in the last two technology options improves the yield of monomeric molecules 37 .…”

“…The proposed superstructure consists of 1,728 processing routes and nine sections, namely HDPE preprocessing, HDPE pyrolysis, light component separation, heavy chemical component separation, aromatic extraction, hydrogen production, hydrotreating, inner heat and electricity generation, and CO 2 separation. We leverage experimental data from various literature to determine the reaction conditions for HDPE pyrolysis 30‐32 . In addition, heat integration is implemented into each technology alternative involved in light component separation, heavy chemical component separation, and aromatic extraction sections to reduce utility usage.…”

“…We leverage experimental data from various literature to determine the reaction conditions for HDPE pyrolysis. [30][31][32] In addition, heat integration is implemented into each technology alternative involved in light component separation, heavy chemical component separation, and aromatic extraction sections to reduce utility usage.…”