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Title: Simultaneous combustion of waste plastics with coal for pulverized coal injection application

Abstract

A bench-scale study was conducted to investigate the effect of simultaneous cofiring of waste plastic with coal on the combustion behavior of coals for PCI (pulverized coal injection) application in a blast furnace. Two Australian coals, premixed with low- and high-density polyethylene, were combusted in a drop tube furnace at 1473 K under a range of combustion conditions. In all the tested conditions, most of the coal blends including up to 30% plastic indicated similar or marginally higher combustion efficiency compared to those of the constituent coals even though plastics were not completely combusted. In a size range up to 600 {mu}m, the combustion efficiency of coal and polyethylene blends was found be independent of the particle size of plastic used. Both linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE) are shown to display similar influence on the combustion efficiency of coal blends. The effect of plastic appeared to display greater improvement on the combustion efficiency of low volatile coal compared to that of a high volatile coal blend. The study further suggested that the effect of oxygen levels of the injected air in improving the combustion efficiency of a coal-plastic blend could be more effective under fuel rich conditions.more » The study demonstrates that waste plastic can be successfully coinjected with PCI without having any adverse effect on the combustion efficiency particularly under the tested conditions. 22 refs., 12 figs., 2 tabs.« less

Authors:
; ;  [1]
  1. University of New South Wales, Sydney, NSW (Australia). Cooperative Research Centre for Coal in Sustainable Development, School of Materials Science and Engineering
Publication Date:
OSTI Identifier:
20838262
Resource Type:
Journal Article
Resource Relation:
Journal Name: Energy and Fuels; Journal Volume: 20; Journal Issue: 6; Other Information: sushil@materials.unsw.edu.au
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; COCOMBUSTION; PLASTICS; SOLID WASTES; COAL; PULVERIZED FUELS; INJECTION; BLAST FURNACES; BENCH-SCALE EXPERIMENTS; COMBUSTION PROPERTIES; POLYETHYLENES

Citation Formats

Sushil Gupta, Veena Sahajwalla, and Jacob Wood. Simultaneous combustion of waste plastics with coal for pulverized coal injection application. United States: N. p., 2006. Web. doi:10.1021/ef060271g.
Sushil Gupta, Veena Sahajwalla, & Jacob Wood. Simultaneous combustion of waste plastics with coal for pulverized coal injection application. United States. doi:10.1021/ef060271g.
Sushil Gupta, Veena Sahajwalla, and Jacob Wood. Fri . "Simultaneous combustion of waste plastics with coal for pulverized coal injection application". United States. doi:10.1021/ef060271g.
@article{osti_20838262,
title = {Simultaneous combustion of waste plastics with coal for pulverized coal injection application},
author = {Sushil Gupta and Veena Sahajwalla and Jacob Wood},
abstractNote = {A bench-scale study was conducted to investigate the effect of simultaneous cofiring of waste plastic with coal on the combustion behavior of coals for PCI (pulverized coal injection) application in a blast furnace. Two Australian coals, premixed with low- and high-density polyethylene, were combusted in a drop tube furnace at 1473 K under a range of combustion conditions. In all the tested conditions, most of the coal blends including up to 30% plastic indicated similar or marginally higher combustion efficiency compared to those of the constituent coals even though plastics were not completely combusted. In a size range up to 600 {mu}m, the combustion efficiency of coal and polyethylene blends was found be independent of the particle size of plastic used. Both linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE) are shown to display similar influence on the combustion efficiency of coal blends. The effect of plastic appeared to display greater improvement on the combustion efficiency of low volatile coal compared to that of a high volatile coal blend. The study further suggested that the effect of oxygen levels of the injected air in improving the combustion efficiency of a coal-plastic blend could be more effective under fuel rich conditions. The study demonstrates that waste plastic can be successfully coinjected with PCI without having any adverse effect on the combustion efficiency particularly under the tested conditions. 22 refs., 12 figs., 2 tabs.},
doi = {10.1021/ef060271g},
journal = {Energy and Fuels},
number = 6,
volume = 20,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}
  • The influence of carbon structure and mineral matter of three pulverized coals on their char characteristics including reactivity was studied under a range of combustion conditions in a drop tube furnace (DTF) and thermogravimetric (TGA) furnace for PCI application. Physical and chemical properties of coals and their combustion derivatives were characterized by automated reflectogram. X-ray diffraction, scanning electron microscope, and BET N{sub 2} adsorption. The QEMSCAN{asterisk} technique was used to characterize the heterogeneous nature of minerals of discrete coal particles. The TGA char reactivity was related to the proportion of coal particles displaying strong association of calcium/sulfur phases with carbonmore » matrix to highlight the catalytic influence of minerals on char reactivity at low temperatures. The study suggested that during DTF combustion tests at 1200{sup o}C, char reaction rates might have been catalyzed by coal minerals, particularly due to illite and its association with carbon. Under the same combustion conditions, most of the coal minerals did not transform significantly to slag phases. Coal burnout was found to improve significantly in a combustion temperature range of 1200 to 1500{sup o}C. The improvement of coal burnout with temperature appeared to be influenced by coal properties, particularly as a function of the chemical nature of minerals, as well as the degree of associations with other minerals. The study implies that coals with similar mineral compositions might not necessarily reflect similar combustion behavior due to the differences in their associations with other phases.« less
  • This paper presents results on the gas phase emissions from the combustion of coal and alternative waste fuels (plastics and automobile tires). The plastics examined were poly(ethylene) and poly(styrene). All fuels were burned in powder form. Mixtures (50- 50 by weight) of the above waste fuels with coal were also burned. Results are reported on the SO{sub 2}, NO{sub x}, CO and CO{sub 2} emissions. For a limited number of cases results are also presented on the release of organic air toxics, in particular the polynuclear aromatic hydrocarbons (PAHs). Experiments were conducted under well-controlled conditions in bench-scale laboratory facilities. Coalmore » particles, {approx}100 {mu}m, and particles of pulverized alternative fuels, {approx}200 {mu}m, were injected and burned in an electrically-heated droptube furnace. The furnace temperature was set to 1250{degrees}C. The residence time of the gas was 1 s. Experiments spanned a range of fuel-lean ({phi} < 1), stoichiometric ({phi} = 1) and fuel-rich ({phi} > 1) conditions. Results showed that (a) the NO{sub x} emissions of tires were a few times lower than those of coal and those of plastics were even lower. Thus, blending these alterative fuels with coal drastically reduced NO{sub x} emissions.« less
  • Combustion of pulverized coal in CO/sub 2//O/sub 2/ as well as in air atmospheres is studied. Predictions using a one-dimensional computer code were compared with actual experimental data from tests conducted by Battelle Columbus Laboratories. The comparison of predicted and measured data for all test cases show that the observed trends of distributions of temperature and of species concentrations are generally predictable. The study confirms that the combustion of pulverized coal can be completed in a CO/sub 2//O/sub /2 atmosphere over a range of CO/sub 2/-toO/sub 2/ mole ratios between 2.23 and 3.65.
  • Pyrolysis of waste plastics is one of the routes to waste minimization that has been gaining in interest in recent times. A compact unit is designed that can pyrolyze a mixture of waste plastics and used oil. The product of the process is a liquid oil that has considerably reduced viscosity and which can be either used as fuel directly or as a feedstock for refineries. Pyrolysis was carried out for the waste oil alone and for its mixture with plastics of one type (HDPE). Different temperatures of reaction and the product viscosities related to the temperatures of operation. Residencemore » times were as low as 2-8s. The reactor was divided into two parts, the first part at the inlet was deliberately kept at a lower temperature to first bring up the Reynolds numbers (> 15,000) to high values before introduction to the high temperature second section. The liquid product of pyrolysis can be used for the co-liquefaction of coal. Several coal liquefaction studies were carried out to determine the effect of the use of the waste plastic-used oil product of pyrolysis as solvent. The result indicate considerable enhancements of the conversions and selectivities of coal for such prepyrolyzed liquid.« less