Simulation of waste plastic gasification and thermogravimetric analysis of waste plastic in CO2 atmosphere

  • Ruth D. Alli

Student thesis: Master's Thesis

Abstract

Waste plastic gasification is a means of maximizing resources as well as an economic waste handling system using CO2 as the gasifying agent and consequentially satisfying the heightened energy demands of the world. CO2 is anticipated to proffer a better opportunity of generating Syngas with higher proportion of CO. Various challenges towards CO2 separation, mitigation, utilization are of current research focus due to its effect of global warming and stringent regulations. The project is concerned with the simulation of fluidized bed gasification of waste plastics in ASPEN plus using CO2 as the gasifying agent. CO2 as the gasifying agent would engender a higher CO generation than the use of steam or air as gasifying agents. The modeling process involves four major stages: reduction of moisture content in a drier, the decomposition of plastic feed in a pyrolyzer reactor modeled as RYIELD reactor, devolatilization stage modeled as RGIBBS reactor and the gasification process modeled as fluidized bed reactor. The hydrodynamics of the reactor and the kinetics were considered in order to comprehend the feasibility of using CO2 in a fluidized bed reactor to simulate a more realistic process that could be scaled up for industrial applications. Gasification temperature, CO2 flowrate, reactor height, orifice diameter, number of orifices, plate free area, fluidized bed diameter and solid flowrate were all varied in order to observe how these parameters affect syngas distribution and carbon conversion. The maximum carbon conversion of 99.5% could be achieved at a reactor temperature of 1100°C, with a reactor of diameter of 3.2m, orifice of diameter 2mm, reactor of height 19m, superficial gas velocity of 0.44m/s and CO2 and carbon flow rate of 70 and 40kmol/hr respectively. The syngas composition at the maximum carbon conversion correspond to H2, CO, CH4, and CO 2 flow rates of 3, 57, 26 and 14mol% respectively. The high proportion of CO/H2 validate the benefits CO2 gasification as compared to other gasifying methods. In addition, the kinetic parameters of CO2 gasification of Polyethylene was determined by using the Thermogravimetric analysis. The kinetic data was tested with different models such as Differential, Friedman and Coats-Redfern models to identify the appropriate kinetic model. Based on the fit of data with model (R2), Friedman model was identified as the most appropriate. The activation energy was found to be 328kJ/mol.
Date of AwardDec 2016
Original languageAmerican English
SupervisorAhmed Al Shoaibi (Supervisor)

Keywords

  • Applied sciences; CO2; Gasification; Plastics; Simulation

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