Combustion Of Polyethylene Research Articles

Combustion of polyethylene and polypropylene in the fluidized bed with a variable vertical density profile

A new type of fluidized bed with a variable vertical density profile was developed. A mixture of sand (Ønominal = 100–140 μm, 2.6 g/cm3) and cenospheres (Ønominal = 140–160 μm, 0.85 g/cm3) was used to form a binary fluidized bed. The minimum fluidization velocity of the binary fluidized bed was determined experimentally. Two points of inflection on the fluidization curve were observed. Additionally, a measurement of the pressure as a function of height was used to determine the profile of fluidized bed density. It was proven that the fluidized bed made out of cenospheres and sand can be characterized by a variable vertical density profile. The binary fluidized bed was used for the combustion of polyolefins. The results were compared to combustion in a conventional fluidized bed made out of sand. The surface of the fluidized bed was video recorded and the changes in the image brightness were used to identify diffusion combustion in the freeboard. A Fourier Transform Infrared (FTIR) analyzer with high spectral resolution (1 cm−1) was used to record the IR spectra of flue gases. In-house software was used to deconvolve complex IR spectra. In the process performed in the fluidized bed made out of sand, regardless of temperature, around 30 % of the polymeric carbon left the reactor in the form of soot. The lack of dependence on the temperature results from the fact that in such an organized process combustion did not take place inside the fluidized bed but on its surface. The binary fluidized bed eliminated the problem of the presence of diffusion flames and soot formation. High fuel conversion to CO2 (above 90 %) was observed at temperatures above over 800 °C during polyolefin combustion in the binary fluidized bed.

Combustion of Polyethylene and Polypropylene in the Fluidized Bed with a Variable Vertical Density Profile

Combustion of Polyethylene and Polypropylene in the Fluidized Bed with a Variable Vertical Density Profile

Dataset on flue gas composition during combustion in the fluidised bed reactor. Polyethylene combustion.

The dataset presented in this article is the supplementary data for the research article titled “The combustion of polyolefins in the inert and catalytic fluidised beds”, in which polyethylene combustion in the cenosphere fluidised bed were investigated. The use of cenospheres as a bed material made it possible to free sink of PE particles in the bed and rule out its combustion in freeboard. It also lead to elimination of soot formation. The quantitative and qualitative analysis of flue gases were performed by Fourier Transform Infrared Spectroscopy (FTIR, Gasmet DX-4000). This data article provides detailed information on changes in product concentration at intervals of a few seconds.

Self-propagating high-temperature synthesis of silicon carbide nanofibers

The article presents the results of studies into the gas-phase synthesis of silicon carbide fibers using silicon powder, polytetrafluoroethylene (PTFE) energy additive and polyethylene (PE) powder by self-propagating high-temperature synthesis (SHS). Stoichiometric mixtures were used for experiments. Green mixture components were mixed in a 3 liter drum with tungsten carbide balls for 30 min. The green mixture weight was 500 g. Experiments were conducted in the SHS-30 industrial reactor. Silicon + PTFE mixture combustion was accompanied by a rapid increase in pressure from 0.5 to 4.0 MPa in less than 1 s, and a relatively rapid pressure drop to 1.5 MPa in 1.5 min. The combustion rate was more than 50 cm/s. It was established that there was a spread of the mixture components during the combustion due to the high combustion rate and intense gas emission. A cottonlike material of light blue color was obtained; it consisted of 100-500 nm thick silicon carbide fibers. The maximum pressure in the reactor reached 3.1 MPa in 1 s during the silicon + PTFE + PE combustion and then decreased to 1.5 MPa in 3 min. The combustion rate was about 40 cm/s. The entire volume of the reactor was filled with blue-grey cotton-like silicon carbide and SiC powder with equiaxed 0.5-3,0 μ m particles merged into conglomerates. Needle-like silicon crystals were formed in the transition layer between the powder and silicon carbide fibers. The results of experiments proved the possibility of obtaining silicon carbide nanofibers in relatively large quantities during the combustion of exothermic mixtures.

Enhanced flame retardancy of polyethylene/magnesium hydroxide with polycarbosilane

Polycarbosilane (PCS) was used for surface modification of magnesium hydroxide (MNH) to enhance the flame retardant effectiveness by forming cohesive binding between MgO particles with ceramic adhesive. Chemical interaction and ceramic reaction were revealed between PCS and MNH, which made for a compact, thermal stable and ceramic-like barrier during the combustion of polyethylene (PE). The flame retardancy of PE/MNH/PCS composites was greatly enhanced and a limiting oxygen index (LOI) of 35.0 was achieved at the PCS/MNH ratio of 4/26 in the composite with 30 wt.% PCS modified MNH. Such results were superior in terms of high LOI value at low global content of MNH. Thanks to the better shielding effect of the integrated and self-supporting ceramic char, the peak heat release rate (p-HRR) and the total heat release (THR) of PE/MNH/PCS composites with 50 wt.% PCS modified MNH were remarkably decreased by 36% and 25% in comparison with PE/MNH with 50 wt.% MNH, respectively. The ceramic reaction between PCS and MNH, the superior thermal stability due to crosslinked PCS and the good barrier function of cohesive ceramic layer play important roles in the effective flame retardant mechanism.

The effect of graphite nanoplates on the thermal degradation and combustion of polyethylene

Studies of thermal and fire-resistant properties of the polyethylene/graphite nanoplates (PE-GNP) nanocomposites prepared by means of in situ polymerization are discussed.The key factor of influence of graphite nanoplates on the thermal degradation and combustion of PE-GNP nanocomposites is analyzed using the sets of the data acquired with the aid of thermogravimetry (TG) and gas chromatography − mass spectrometry (GC–MS) experiments. It has been found that the addition of graphite nanoplates changes the composition of polyethylene pyrolysis products resulting in dramatically increase the fraction of heavy hydrocarbons.The results of cone calorimetric tests lead to traditional conclusion that formation of GNP protective shield plays a key role in the mechanism of flame retardation for PE-GNP nanocomposites. On the other hand, the decrease in PE-GNP nanocomposites combustibility can also be a result of the reduction in the diffusion rate of the degradation products in the liquid pyrolysis phase and gaseous phase of combustion.

Agglomeration and Deposition Behavior of Solid Recovered Fuel

Waste-derived fuels, such as solid recovered fuel (SRF), are increasingly being used in, e.g., the cement industry as a means to reduce cost. The inhomogeneous nature of SRF makes it difficult to combust, and many problems may arise within, e.g., combustion control, feeding of fuel, deposit formation, or accumulation of impurities. The combustion of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), wood, and SRF were studied in a rotary drum furnace. The combustion was recorded on a camera (60 frames per second), so that any agglomeration or deposition of fuel or ash could be monitored. PE and PP pose no significant risk of forming deposits in a combustion environment (T > 800 °C) as a result of a rapid devolatilization, while PET may cause deposits as a result of a sticky char residue. The deposition tendency of the investigated SRF is low, and it may be managed by a careful combustion control. The ash from SRF or wood does not pose a significant risk of melting and deposits at tem...

Effects of sorbents on the heavy metals control during tire rubber and polyethylene combustion in CO2/O2 and N2/O2 atmospheres

This paper investigated the capture behavior for three heavy metals (Cu, Ni and Zn) during the waste tire rubber (TR) and high density polyethylene (HDPE) combustion in N2/O2 and CO2/O2 atmospheres in a lab-scale tubular furnace. Both the replacement of N2 by CO2 and addition of limestone decreased the evaporation of Ni, Cu and Zn during TR and HDPE combustion. Replacement of N2 by CO2 increased the capture efficiency of limestone for Zn, Cu and Ni from TR combustion (except for Ni at 700°C), but decreased for capturing Zn, Cu and Ni from HDPE combustion. The waste composition highly influenced the capture efficiency of limestone for Zn, Cu and Ni, but theamount of sorbent only significantly affected the capture efficiency of limestone for Ni. The increment of the furnace temperature increased the capture efficiency of limestone for Zn but decreased for Ni. The sorption efficiency of limestone was worse than CaO. This work contributes to the control of heavy metals during municipal solid waste (MSW) incineration and management of MSW oxy-fuel combustion.

Firing tests of hybrid engine with varying oxidiser nature and operating conditions

Hybrid combustors are of increasing interest for space and civilian propulsion. A test facility has been settled to investigate high-density polyethylene combustion (propellant of length 0.15 m). A parametric study has been conducted on the oxidiser nature (gaseous oxygen diluted in nitrogen, from 31.4 vol.% to 69.2 vol.% of O2), on the oxidiser flow rate (from 28.6 g/s to 53.1 g/s), on the combustor pressure (from 11.4 bar to 25 bar) and on the nozzle diameter (from 6.4 mm to 12.9 mm). The regression rate has been estimated by weight loss (mean value of 0.207 mg/s) and by thermocouples (0.198 mg/s). Its values are compared to existing data through the Marxman law; this enlarges the range of validity of this law. The conduction heat flux in the solid reducer is estimated around 6000–8000 W; which is related to the low regression rate of the solid fuel. The axial thrust has been measured in addition to other parameters (pressures, temperatures and mass flow rates). Solid particles have been gathered at the combustor outlet to conduct additional chemical analyses. These particles were formed at the surface of the reducer and extracted by the oxidiser from the solid surface.

Synthesis of carbon nanotubes by sequential pyrolysis and combustion of polyethylene

Carbon nanotubes (CNTs) were synthesized from polyethylene using a pyrolysis–combustion technique. Pre- or post-consumer polyethylene (in strips, pellets or ground particles) was pyrolyzed to gaseous products, which were then combined with an oxygen-containing gas and auto-ignited to create a fuel-rich flame. The combustion effluent was used to synthesize multi-wall CNTs using stainless-steel wire mesh as both catalyst and substrate. An overall CNT yield in the order of 10%, by mass relative to the initial carbon in the fuel, was typically achieved before purification. The viability of partial conversion of a readily-available waste stream to the value-added product of CNTs was demonstrated, combining the economy and process safety aspects of flame synthesis with the control of synthesis temperature that chemical vapor deposition methods typically afford.

Toxicity of smoke extracts towards A549 lung cells: Role of acrolein and suppression by carbonyl scavengers

The noxious 3-carbon electrophile acrolein forms on combustion of diverse organic matter including synthetic polymers such as polyethylene. While known to play a key role in smoke inhalation injury (SII), the molecular basis for the pulmonary toxicity of high dose acrolein-containing smoke is unclear. As a result, drug interventions in SII are poorly directed against pathogenetic smoke toxicants such as acrolein. The first aim of this study was to confirm a role for acrolein in the acute toxicity of smoke extracts towards A549 lung cells by monitoring adduction of known acrolein targets and the expression of acrolein-inducible genes. A second aim was to evaluate carbonyl scavengers for their abilities to protect cell targets and block smoke extract toxicity. Extracts were prepared by bubbling smoke released by smouldering polyethylene through a buffered saline-trap. Acrolein levels in the extracts were estimated via HPLC after derivatisation with 2,4-dinitrophenylhydrazine. Extracts were highly toxic towards A549 cells, eliciting greater ATP depletion than an equivalent concentration of acrolein alone. The toxicity was accompanied by pronounced carbonylation of several cytoskeletal targets, namely vimentin and keratins-7, -8 and -18. Western blotting revealed that polyethylene combustion products also upregulated several acrolein-responsive protein markers, including GADD45β, NQO1, HMOX, Hsp70, Nur77 and Egr1. Several carbonyl scavengers (bisulfite, d-penicillamine, hydralazine and 1-hydrazinoisoquinoline) strongly attenuated smoke extract toxicity, with bisulfite suppressing both the adduction and cross-linking of intermediate filament targets. Bisulfite also suppressed the cytotoxicity of smoke extracts when detected using real-time monitoring of cellular impedance. These findings confirm a key role for acrolein in smoke cytotoxicity and suggest drugs that block acrolein toxicity deserve further investigation as possible interventions against SII.

Scission Products and Molecular Weight Effects on the Combustion of Polyethylene

The mutual relations between the flame positions during the vertical combustion test and the thermal degradation of polyethylene (PE), polypropylene (PP) and polybutene (PB) as polyolefin and polystyrene (PS) were studied. The flame developed downward for PE and upward for PS. The flames of PP and PB remained in the middle. The combustion of polymer materials has been thought to occur on the surface of the material after having been ignited. However, from the result of the vertical combustion test, it was understood that a flame exists on the surface of the material that drips from PE. The vaporization of the sample is not thought to occur in the primary degradation, but in the secondary degradation phase, when it reacts with oxygen. In order to analyze the phenomena, the scission products of those polymers were measured by Py-GC-MS. When the combustibility of PE of different molecular weight was evaluated by the vertical combustion test, PE of lower molecular weight did not burn where as PE of higher molecular weight did. PE of the lower molecular weight only melted without ignition. Even if the Bunsen flame of the burner was applied to the thinly dripping melted material, it would not ignite. It was then concluded that PE with lower molecular weight does not degrade and vaporize in the secondary degradation.

Emissions from the Premixed Combustion of Gasified Polyethylene

An investigation was conducted on pollutants emitted from steady-state, steady-flow gasification and combustion of polyethylene (PE) in a two-stage furnace. The polymer, in pulverized form, was first pyrolyzed at 1000 °C, and subsequently, its gaseous pyrolyzates were burned, upon mixing with air at high temperatures (900–1100 °C). The motivation for this indirect type of burning PE was to attain nominally premixed combustion of the pyrolyzate gases with air, thereby achieving lower pollutant emissions than those emanating from the direct burning of the solid PE polymer. This work assessed the effluents of the two-stage furnace and examined the effects of the combustion temperature, as well as the polymer feed rate and the associated fuel/air equivalence ratio (0.3 < φ < 1.4). It was found that, whereas the yield of pyrolysis gas decreased with an increasing polymer feed rate, its composition was nearly independent of the feed rate. CO2 emissions peaked at an equivalence ratio near unity, while the CO emi...

Semivolatile and volatile compounds in combustion of polyethylene

The evolution of semivolatile and volatile compounds in the combustion of polyethylene (PE) was studied at different operating conditions in a horizontal quartz reactor. Four combustion runs at 500 and 850 °C with two different sample mass/air flow ratios and two pyrolytic runs at the same temperatures were carried out. Thermal behavior of different compounds was analyzed and the data obtained were compared with those of literature. It was observed that α,ω-olefins, α-olefins and n-paraffins were formed from the pyrolytic decomposition at low temperatures. On the other hand, oxygenated compounds such as aldehydes were also formed in the presence of oxygen. High yields were obtained of carbon oxides and light hydrocarbons, too. At high temperatures, the formation of polycyclic aromatic hydrocarbons (PAHs) took place. These compounds are harmful and their presence in the combustion processes is related with the evolution of pyrolytic puffs inside the combustion chamber with a poor mixture of semivolatile compounds evolved with oxygen. Altogether, the yields of more than 200 compounds were determined. The collection of the semivolatile compounds was carried out with XAD-2 adsorbent and were analyzed by GC–MS, whereas volatile compounds and gases were collected in a Tedlar bag and analyzed by GC with thermal conductivity and flame ionization detectors.

Comparative Study on Polycyclic Aromatic Hydrocarbons, Light Hydrocarbons, Carbon Monoxide, and Particulate Emissions from the Combustion of Polyethylene, Polystyrene, and Poly(vinyl chloride)

A laboratory-scale study was performed to compare the emissions of pollutants from the batch combustion of polystyrene (PS), polyethylene (PE), and poly(vinyl chloride) (PVC) and to examine the conditions that minimize them. Fixed beds of polymer particles were burned in a two-stage, preheated muffle furnace, using air at atmospheric pressure. The temperature of the primary furnace was varied over a range of 500−1000 °C, to identify its influence on the emission of pollutants. The combustion effluent was mixed with additional preheated air, channeled to a secondary muffle furnace (afterburner), which was operated at 1000 °C. Emissions of CO, CO2, light hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), and particulates were monitored either on-line or by sample collection, followed by gas chromatographic analysis. Emission magnitudes and trends were found to be dependent on the type of the polymer burned. The combustion of PS produced the largest yields of PAHs and, especially, soot; PE produced the n...

Design, construction and testing of a low‐cost hybrid rocket motor

Small hybrid rocket motors using solid propellant and gaseous oxidizer are becoming increasingly popular as a propulsion device. This paper describes the development of a one‐dimensional flow model for the design of a small rocket motor. Combustion of polyethylene as solid propellant with oxygen is used as a candidate hybrid fuel to test and evaluate the performance of this hybrid system. To assess the performance under different operating conditions, a computer program has been developed, which facilitates inputs to be varied and effects assessed. A system of governing equations is summarized in the main body of this paper and is numerically solved by the computer program. The results of the modelling are then used to design and build a small low‐cost rocket motor for experimental verification. Therefore, the materials presented herein could be used in the future design of hybrid rocket motors.

Role of inorganic chlorides in formation of PCDDs, PCDFs, and coplanar PCBs from combustion of plastics, newspaper, and pulp in an incinerator.

The total amounts of dioxins found in exhaust gases from combustion of polyethylene (PE), polystyrene (PS), and poly(ethylene terephthalate) (PET) with approximately 3% (w/ w) NaCl were 6.07, 17.7, and 28.9 ng/g, respectively. Plastics containing benzene rings produced more dioxins than plastic containing no benzene ring. The amounts of dioxin formed in the exhaust gases from the combustion of newspapers impregnated with CaCl2, KCl, and NaCl were 18.6, 28.6, and 49.0 ng/g, respectively. Dioxin formation was associated with the bond energy between metal atom and chlorine atom. When newspapers impregnated with four different amounts of NaCl were combusted, the highest NaCl content newspaper (chlorine content 4.08%, w/w; lignin content 19.8%, w/w) produced the greatest amount of dioxins (174 ng/g). Pulp with NaCl (chlorine content 4.25%, w/w; lignin content 0.69%, w/w) produced more dioxins (6.71 ng/g) than pulp alone (0.799 ng/g) did upon combustion. The lignin content in a combustion sample correlated with the amount of dioxin formation. The results exhibited that combustion conditions with low CO concentration (<2 ppm) produced much less dioxins than conditions with high CO concentration (159 ppm).

Oxidation catalyst of iron oxide suppressing dioxin formation in polyethylene combustion

A new iron oxide catalyst, which has a superior oxidation activity in carbon monoxide and polyethylene (PE) combustion, was synthesized by an aqueous solution reaction. Catalytic oxidation of carbon monoxide over six kinds of hematite obtained from the goethite was done using a microcatalytic pulse reactor, and the composition of the hematite with the highest oxidation activity was determined. With the aim of suppressing dioxin formation on combustion, incineration tests of solid wastes in PE refuse bags with and without the goethite were carried out using a commercial semibatch-type incinerator with a combustion chamber of 6.2 m3. The result confirmed that the concentration of dioxins in the flue gas decreased considerably when the refuse was incinerated in PE bags manufactured with goethite.

Performance of an experimental polyethylene solid fuel ramjet

An experimental investigation on the characteristics of polyethylene combustion in a solid fuel ramjet is reported. An experimental expression for the fuel regression rate is presented for the conditions of the tests: r=2.78×10 −3 p 0.8 c G 0.35 air T 0.36 air, where the units of ṙ are mm s −1, p c is the chamber pressure (atm), G air is the air mass flux (g cm −2 s −1) and T air is the air inlet temperature (K). Additionally, the effects of the introduction of an intermediate mixing chamber and of the increase in the post mixing chamber length over the combustion efficiency are studied. Radiation loss transfer rates are also analysed and discussed. The parameter was obtained by the use of a translucid polyethylene grain, which was first operated bare and later covered with an insulation aluminium sheet. Experimental results trends agree with those of previous works conducted with systems of similar geometry and different fuels.

Examination of the additivity assumption using the spiral and standard Salmonella assays to evaluate binary combinations of mutagens

Binary combinations of pure chemicals and complex mixtures were evaluated for their ability to produce additive mutagenicity responses in the spiral and standard Salmonella mutagenicity assays. Single chemicals were selected that were representative of the primary chemical class responsible for much of the mutagenic activity of each complex mixture. The following agents were evaluated in the absence of S9: 1-nitropyrene, diesel exhaust extract, and the chlorinated drinking water mutagen 3-chloro-4-dichloromethyl-5-hydroxy-2-[5 H]-furanone (MX). In the presence of S9, the following agents were evaluated: 4-aminobiphenyl, benzo[ a]pyrene, and an organic extract from the particulate emissions resulting from the combustion of polyethylene in a rotary kiln incinerator. Binary combinations of the agents within each S9 group were tested. The results were analyzed for additivity by determining whether the difference between the expected response of the binary mixture was significantly different from the observed response. In general, the combinations of mutagens produced additive responses at low doses in both assays. However, at high doses, the results generally departed from additivity, especially for combinations of indirect-acting mutagens. A requirement for exogenous metabolic activation imposes conditions, such as different S9 optima for each mutagen, that complicate the application of the additivity assumption to binary combinations of indirect-acting mutagens. Although the two bioassays generally gave similar results for each binary combination of mutagens, the spiral assay permitted a gradient of mutagen and/or S9 concentrations to be evaluated, and it allowed the mutagens to be evaluated in the absence of solvents, eliminating any potential solvent-mutagen interactions. These features of the spiral assay may be advantageous when studying chemical interactions.