Thermal Reduction of NO^sub x^ with Recycled Plastics

This study develops technology for mitigation of NO^sub x^ formed in thermal processes using recycled plastics such as polyethylene (PE). Experiments involve sample characterization, and thermogravimetric decomposition of PE under controlled atmospheres, with NO^sub x^ concentration relevant to indu...

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Bibliographic Details
Published in:Environmental science & technology 2017-07, Vol.51 (13), p.7714
Main Authors: Oluwoye, Ibukun, Dlugogorski, Bogdan Z, Gore, Jeff, Vyazovkin, Sergey, Boyron, Olivier, Altarawneh, Mohammednoor
Format: Article
Language:English
Subjects:
Activation analysis
Activation energy
Atmospheric models
Chemical compounds
Chemiluminescence
Compensation
Controlled atmospheres
Decomposition
Experiments
Fourier transforms
Fragments
Industrial applications
Infrared spectroscopy
Kinetics
Mass transfer
Mitigation
Nitrogen
Plastics
Polyethylene
Polyethylenes
Polymers
Reburning
Recycled materials
Recycled products
Thermal reduction
Viscosity
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Summary:This study develops technology for mitigation of NO^sub x^ formed in thermal processes using recycled plastics such as polyethylene (PE). Experiments involve sample characterization, and thermogravimetric decomposition of PE under controlled atmospheres, with NO^sub x^ concentration relevant to industrial applications. TGA-Fourier transform infrared (FTIR) spectroscopy and NO^sub x^ chemiluminescence serve to obtain the removal efficiency of NO^sub x^ by fragments of pyrolyzing PE. Typical NO^sub x^ removal efficiency amounts to 80%. We apply the isoconversional method to derive the kinetic parameters, and observe an increasing dependency of activation energy on the reaction progress. The activation energies of the process span 135 kJ/mol to 226 kJ/mol, and 188 kJ/mol to 268 kJ/mol, for neat and recycled PE, respectively, and the so-called compensation effect accounts for the natural logarithmic pre-exponential ln (A/min^sup -1^) factors of ca. 19-35 and 28-41, in the same order, depending on the PE conversion in the experimental interval of between 5 and 95%. The observed delay in thermal events of recycled PE reflects different types of PE in the plastic, as measurements of intrinsic viscosity indicate that, the recycled PE comprises longer linear chains. The present evaluation of isoconversional activation energies affords accurate kinetic modeling of both isothermal and nonisothermal decomposition of PE in NO^sub x^-doped atmosphere. Subsequent investigations will focus on the effect of mass transfer and the presence of oxygen, as reburning of NO^sub x^ in large-scale combustors take place at higher temperatures than those included in the current study.
ISSN:0013-936X