Initial Stage Of Pyrolysis Research Articles

One-Stage Synthesis of Microporous Carbon Adsorbents from Walnut Shells—Evolution of Porosity and Structure

One-stage synthesis technology for preparing carbon adsorbents with tailored porosity from agricultural waste is worthwhile due to their extensive application value. Thermal gravimetric analysis, low-temperature N2 adsorption, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), and Raman spectroscopy were used to record the structure transformations of carbon materials, namely pore development, proceeding in the course of the step-wise pyrolysis of renewable and low-cost raw materials such as walnut shells (WNSs), which was carried out within a temperature range of 240–950 °C in a CO2 flow. The minimum threshold carbonization temperature for preparing nanoporous carbon materials from WNSs, determined by the examination of the N2 adsorption data, was 500 °C. The maximum specific micropore volume and BET surface achieved in the process without holding a material at a specified temperature were only 0.19 cm3/g and 440 m2/g, respectively. The pyrolysis at 400–600 °C produced amorphous sp2 carbon. At a temperature as high as 750 °C, an increase in the X-ray reflection intensity indicated the ordering of graphite-like crystallites. At high burn-off degrees, the size of coherently scattering domains becomes smaller, and an increased background in X-ray patterns indicates the destruction of cellulose nanofibrils, the disordering of graphene stacks, and an increase in the amount of disordered carbon. At this stage, pores develop in the crystallites. They are tentatively assigned to crystallites with sizes of 15–20 nm and to micropores. According to the Raman spectra combined with the XRD and SAXS data, the structure of all the pyrolysis products is influenced by the complex structure of the walnut shell precursor, which comprises cellulose nanofibrils embedded in lignin. This structure was preserved in the initial stage of pyrolysis, and the graphitization of cellulose fibrils and lignin proceeds at different rates. Most of the pores accessible for gas molecules in the resulting carbon materials are associated with former cellulose fibrils.

Thermochemical Valorization of Plastic Waste Containing Low Density Polyethylene, Polyvinyl Chloride and Polyvinyl Butyral into Thermal and Fuel Energy

Pyrolysis is a promising technology for transforming waste plastics (WPs) into high-value products. In the near future it will play a key role in the circular economy, as a sustainable and environmentally friendly method of managing this waste. Although the literature reports on the pyrolysis of plastics, it is focused on pure polymers. On the other hand, the state-of-the-art knowledge about the pyrolysis of mixed and contaminated WPs is still scarce. Industrial waste processing usually uses polymer mixtures containing various impurities that influence the pyrolysis process during chemical WPs recycling. In the paper the pyrolysis of three types of WPs: low density polyethylene (LDPE), polyvinyl chloride (PVC) and polyvinyl butyral (PVB) from repeated mechanical recycling of plastics, as well as their binary and ternary mixtures, is considered. The influence of particular components on the pyrolysis process is analyzed. The aim is to determine synergistic behavior of the mixtures during the pyrolysis process, which is important for increasing the efficiency and quality of the obtained bioproducts. Methods such as thermogravimetric (TG/DTG) analysis coupled with Fourier transform infrared spectroscopy (FTIR) and mass spectroscopy (MS) are used. The variations in the initial and final temperature of pyrolysis, mass loss and mass loss rate are determined. The content of PVC significantly lowers the initial temperature and mass loss and increases the final temperature. The pyrolysis of the considered mixtures shows a noticeable synergism—in the initial stage of pyrolysis up to a temperature around 450 °C, the mass loss is accelerated compared to what is predicted by simple superposition. The inhomogeneity of the mixtures as well as the waste origin causes a significant variation in the activation energy. Three main conclusions are obtained: (i) if the waste does not contain PVC, the pyrolysis is nearly complete at a temperature around 500 °C at a heating rate of 10 °C/min, whereas PVC is not fully processed even at 995 °C; (ii) the synergistic effects affect significantly the pyrolysis process by accelerating some steps and lowering the activation energy; and (iii) the presence of PVC noticeably lowers the temperature of the first stage of PVB pyrolysis. The investigation results prove that chemical recycling of mixed LDPE, PVC and PVB waste can be an effective method of plastic waste management.

Investigation of the co-pyrolysis characteristics and gas emission properties of spent bleaching earth and biomass in a thermogravimetric analyser and a fixed bed reactor

The co-pyrolysis of spent bleaching earth (SBE) for adsorption decolorization and biomass can promote the resource utilization of industrial waste. The thermal behaviour and kinetics during the co-pyrolysis of SBE with sawdust (SD) were comparatively evaluated with thermogravimetric analysis at different mixing ratios and heat rates. Activation energies corresponding to the different conversion rates were determined by the distributed activation energy model (DAEM). The pyrolysis yield and evolved gases were measured by a fixed bed pyrolysis system. The results demonstrated that as SBE increased, the activation energy during the initial stage of pyrolysis clearly decreased. The fixed bed isothermal pyrolysis experiment showed that the increase in SBE had a significant effect on the gas production components, resulting in a decrease in CO and CO2 yields and an increase in alkane content. At 800°C, the addition of 30 % SBE had the highest H2 yield, indicating that SBE is a valuable additive.

Pyrolysis of Solid Recovered Fuel Using Fixed and Fluidized Bed Reactors

Currently, most plastic waste stems from packaging materials, with a large proportion of this waste either discarded by incineration or used to derive fuel. Accordingly, there is growing interest in the use of pyrolysis to chemically recycle non-recyclable (i.e., via mechanical means) plastic waste into petrochemical feedstock. This comparative study compared pyrolysis characteristics of two types of reactors, namely fixed and fluidized bed reactors. Kinetic analysis for pyrolysis of SRF was also performed. Based on the kinetic analysis of the pyrolytic reactions using differential and integral methods applied to the TGA results, it was seen that the activation energy was lower in the initial stage of pyrolysis. This trend can be mainly attributed to the initial decomposition of PP components, which was subsequently followed by the decomposition of PE. From the kinetic analysis, the activation energy corresponding to the rate of pyrolysis reaction conversion was obtained. In conclusion, pyrolysis carried out using the fluidized bed reactor resulted in a more active decomposition of SRF. The relatively superior performance of this reactor can be attributed to the increased mass and heat transfer effects caused by fluidizing gases, which result in greater gas yields. Regarding the characteristics of liquid products generated during pyrolysis, it was seen that the hydrogen content in the liquid products obtained from the fluidized bed reactor decreased, leading to the formation of oils with higher molecular weights and higher C/H ratios, because the pyrolysis of SRF in the fluidized bed reactor progressed more rapidly than that in the fixed bed reactor.

Investigation on the Edge Doping Process of Nitrogen-Doped Carbon Materials by In Situ Pyrolysis Mass Spectrometry and Laser-Induced Acoustic Desorption Mass Spectrometry

Nitrogen-doped carbon materials demonstrate high performance as electrodes in fuel cells and higher oxygen reduction reactivity than traditional Pt-based electrodes. However, the formation process of nitrogen-doped carbon materials has long been a mystery. In this study, the formation mechanism of nitrogen-doped carbon materials from polyaniline (PANI) pyrolysis was studied by the combination of in situ pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry (Py-VUVPI-TOF MS) and substrate-enhanced, laser-induced acoustic desorption source time-of-flight mass spectrometry (SE-LIAD-TOF MS). The initial pyrolysis species, including free radicals and intermediates, were investigated via in situ Py-VUVPI-TOF MS during the temperature-programmed desorption process (within tens of microseconds). The pyrolysis residues were collected and further investigated via SE-LIAD-TOF MS, revealing the product information of the initial pyrolysis products. The results show that the edge doping of carbon materials depends on free radical reactions rather than the direct substitution of carbon atoms by nitrogen atoms. Meanwhile, pyrrole nitrogen and pyridine nitrogen are formed by the free radical cyclization reaction and the amino aromatization reaction at the initial stage of pyrolysis, while the formation of graphitic nitrogen depends on the further polymerization reaction of pyrrole nitrogen and pyridine nitrogen.

High-temperature pyrolysis modeling of a thermally thick biomass particle based on an MD-derived tar cracking model

• New tar cracking model developed with ReaxFF molecular dynamics method. • Thermally thick modelling based on multistep kinetic scheme and MD tar cracking model. • Particle-resolved pyrolysis simulation of a single biomass particle over 800 °C. • Tar evolution inside and outside porous biomass particle. Biomass pyrolysis in the thermally thick regime is an important thermochemical phenomenon encountered in many different types of reactors. In this paper, a particle-resolved algorithm for thermally thick biomass particle during high-temperature pyrolysis is established by using reactive molecular dynamics (MD) and computational fluid dynamics (CFD) methods. The temperature gradient inside the particle is computed with a heat transfer equation, and a multiphase flow algorithm is used to simulate the advection/diffusion both inside and outside the particle. Besides, to simulate the influence of intraparticle temperature gradient on the primary pyrolysis yields, a multistep kinetic scheme is used. Moreover, a new tar decomposition model is developed by reactive molecular dynamic simulations where every primary tar species in the multistep kinetic scheme cracks under high temperature. The integrated pyrolysis model is evaluated against a pyrolysis experiment of a centimeter-sized beech wood particle at 800–1050 °C. The simulation results show a remarkable improvement in both light gas and tar yields compared with a simplified tar cracking model. Meanwhile, the MD tar cracking model also gives a more reasonable prediction of the species yield history, which avoids the appearance of unrealistically high peak values at the initial stage of pyrolysis. Based on the new results, the different roles of secondary tar cracking inside and outside the particle are studied. Finally, the model is also used to assess the influence of tar residence time and several other factors impacting the pyrolysis.

Research of the thermal decomposition mechanism and pyrolysis pathways from macromonomer to small molecule of waste printed circuit board

Pyrolysis is an important pre-treatment technology for pyrometallurgy, which could reduce pollution and recover materials from waste printed circuit boards (WPCBs). However, present studies on mechanism of pyrolysis were insufficient, which results in the unclear of controlling reaction rate and inhibiting side reaction. To further develop pyrolysis technology, the in-depth research on the pyrolysis mechanism is necessary. In this study, we investigated the thermal decomposition process and pyrolysis pathways from macromonomers to products of WPCBs. The results showed that HBr was produced at the initial stage of pyrolysis. Then, the resin body depolymerized into macromonomers, followed by random rupture and free radical reactions to form pyrolysis products. Besides, possible mechanism for bisphenol A thermal decomposing was analyzed by bond energy. The results suggested that methyl groups in bisphenol A would be preferentially removed because of low bond energy. The six possible pathways may occur simultaneously when energy sufficient. Moreover, the mechanism function was determined by Škvára-Šesták method as: G(α)=-ln 1-α2, which indicated pyrolysis reaction agreed with the model of random nucleation followed by random growth. This study provided the theoretical basis for pollution control, process optimization and reactor design of WPCBs pyrolysis.

Thermogravimetric and mass spectrometry analyses of cellulose pyrolysis under the synergistic effect of CaO and K2HPO4∙3H2O

ABSTRACTThe cellulose pyrolysis processes under the individual and synergistic effects of CaO and K2HPO4∙3H2O were studied by the thermogravimetric-mass spectrometric analysis (TG-MS) technique, mainly focusing on the changes of some important products such as CH4 during the pyrolysis process under different conditions. The experimental results showed that after the addition of CaO, the amounts of CO, CH4, and other species decreased. CaO could fix the “CO2-like reactive intermediate” produced during the cellulose pyrolysis process, thus reducing the evolution of CO2 in the temperature range of 300–440°C and continuing the CO2 evolution in the temperature range of 520–710°C. When K2HPO4∙3H2O was added, the amounts of CO, CH4, CO2, and other gaseous species increased, indicating that K2HPO4∙3H2O could significantly change the pyrolysis reaction process, such as promoting the benzene ring formation reactions involving small molecules such as toluene. When the mixture of CaO and K2HPO4∙3H2O was added, the weight loss at the initial stage of pyrolysis was relatively moderate compared to that adding K2HPO4∙3H2O alone. At the same time, an obvious weight loss appears in the pyrolysis process in the temperature range of 600–770°C, and the amounts of various species generated increased compared to those generated in the single catalytic pyrolysis. Therefore, CaO and K2HPO4∙3H2O exhibited a strong synergistic effect in the pyrolysis process.

Studies on a Thermal Fault Simulation Device and the Pyrolysis Process of Insulating Oil

In order to analyze the composition of pyrolysis products of insulating oil at different thermal fault levels, this paper proposes a thermal fault simulator device for oil-filled equipment. This device simulates different thermal fault levels by changing the heat source temperature, provides the real pressure environment by using a closed container and analyzes the composition of the insulation products by chromatographic analysis methods. By analyzing the temperature and velocity of flow distributions, it is proved that the fault simulator results are consistent with the actual results. The influence of heat source energy on the pyrolysis reaction of insulating oil is also discussed. The obtained results show that the correlation coefficient between pyrolysis product and heat source energy reaches 0.978. As a result, a multivariate nonlinear energy calculation model is presented to establish the relationship between the complete reaction process and energy. By calculating the energy absorbed by different products during the reaction, it can be found that the decomposition of alkanes absorbs a large amount of energy at the initial stage of pyrolysis, which corresponds to low temperature overheating fault. When the pyrolysis reaction continues, dehydrogenation occupies the leading role, which corresponds to high temperature overheating fault. This can be used as an effective basis for distinguishing fault levels according to the corresponding relationship between energy and fault level.

The primary products of cellulose pyrolysis in the absence of extraparticle reactions

Cellulose pyrolysis leads to formation of char, gases and condensable species, with levoglucosan being one of the main components among the latter. However, the literature is not conclusive regarding which of these pyrolysis products are primary as opposed to form through reactions of volatiles in the pyrolyser once they have been released from the cellulose particle. To understand these cellulose pyrolysis pathways, cellulose, levoglucosan and cellulose/levoglucosan mixtures were pyrolyzed in a wire mesh reactor, which suppresses interactions between volatiles released from one particle and other particles. The product distribution and levoglucosan yield were compared at different temperatures in slow and fast heating rate. Above 60% levoglucosan was obtained at low temperature and in slow pyrolysis. Fast pyrolysis produced a large amount of small particles/aerosols in liquid phase. Gas was mainly formed in the initial stage of pyrolysis possibly due to the amorphous cellulose decomposition. The levoglucosan did not undergo secondary reactions. For cellulose/levoglucosan mixture, the vaporization of levoglucosan was not affected by cellulose pyrolysis. These results showed that levoglucosan and low molecular weight species are both formed directly from cellulose in reactions taking place in parallel. The alternative sequential pathway where levoglucosan is produced initially and then reacts to form low molecular weight species was not observed in these conditions.

Relation between char structures and formation of volatiles during the pyrolysis of Shenfu coal: Further understanding on the effects of mobile phase and fixed phase

The formation of resultant volatiles is closely related with chemical structure of char during the pyrolysis process. In this study, all-components, that are semi-char, tar and gas product obtained by Shenfu coal pyrolyzed under various residence time at 435 °C were comprehensively analyzed at molecular level, aiming to reveal the reaction pathways responsible for the evolution of chemical structure of coal/char. The results showed that CO2 and CO were the predominant pyrolysis gas product which inferred high content of organic oxygen species in low-rank Shenfu coal. At the initial stage of pyrolysis, cracking of bridged bonds, especially heteroatom bridged bonds, such as O, N and S, would produce relatively stable radicals in semi-char. Phase change of light components and decomposition of asphaltene in mobile phase can be strongly related with light tar aliphatic compounds formation. At the middle and later stage of pyrolysis, thermal cracking of polar radicals and decomposition of solvent extracted metaplast materials made predominant contribution to tar formation. In addition, the cracking of peripheral aromatic structures of coal/char skeleton structure, through which secondary reaction (such as methylation and dehydrogenation reaction) took place, would result in tar (light tar and heavy tar) and H2 formation.

Study on the structural evolution of semi-chars and their solvent extracted materials during pyrolysis process of a Chinese low-rank coal

The structural evolution of coal during pyrolysis process has been studied for a long time but remains unclear, mainly due to the extraordinary complexity of coal structure. The present study aimed to further identify the chemical structural evolution of different parts in the semi-chars obtained by low-temperature pyrolysis of a Chinese low-rank coal (Shenfu coal). Semi-chars and their solvent extracted materials (oil, resin, asphaltene and preasphaltene) were analyzed by 13C nuclear magnetic resonance (NMR) mass spectrometry, diffuse reflectance Fourier transform-infrared spectroscopy (DRIFTs) and ultraviolet (UV) fluorescence spectroscopy, separately. The results showed that 23.8% weight loss occurred during the whole pyrolysis process at 435 °C and half of the weight loss was achieved in the initial five minutes. By contrast, amount of the extracts in semi-chars (solvent extracted metaplast materials) decreased more dramatically in the initial stage of the pyrolysis, and 51.8% of the extracts disappeared in the initial one minute. Oil and preasphaltene showed higher thermal sensitivity than asphaltene and resin. Considerable content of metaplast materials with 1–2 rings (especially in oil and/or asphaltene) were produced along with the pyrolysis process. Condensed aromatic structures in semi-chars were relatively stable and mainly decomposed in the initial stage of pyrolysis which could be attributed to the dramatically decomposition of some active aromatic structures with ≥ 4 rings (especially the components in extracts such as preasphaltene). The results provided a new insight into the structural evolution of coal during low-temperature pyrolysis process, which specially considered the detailed information of the solvent extractable metaplast materials in semi-chars.

Preparation and characterization of Poly(vinyl alcohol)/graphene nanocomposite with enhanced thermal stability using PEtVIm-Br as stabilizer and compatibilizer

Poor thermal stability and thermoplastic processability are the main obstacles for wide application of polyvinyl alcohol, which is a typically water-soluble polymer with excellent mechanical properties, biocompatibility, barrier properties and biodegradability. In this work, a novel method was demonstrated for preparing PVA based material with improved thermal stability, low additive loading, and without impairing the inherent good properties of PVA. Poly (1-vinyl-3-ethyl-imidazolium bromide) (PEtVIm-Br) was synthesized and used as both a thermal stabilizer for PVA and a compatibilizer for PVA/graphene nanocomposites. A 49% improvement in tensile strength and 65% improvement in the elongation at break were achieved by incorporating 2.5 wt% of PEtVIm-Br and 0.5 wt% of graphene into PVA matrix. The thermal stability of the PVA/PEtVIm-Br-graphene composite has been investigated by thermogravimetric analysis (TGA), TGA-DSC simultaneous thermal analysis, and TGA coupled with FTIR. With the addition of PEtVIm-Br-graphene, the elimination reaction of PVA at the initial stage of pyrolysis was suppressed remarkably, while the activation energy for pyrolysis of the nanocomposite increased obviously, resulted in a much improved thermal stability, comparing to pure PVA. The volatile products of pure PVA and PVA composites were detected by TGA/FTIR and Py-GC/MS. The improvement in thermal stability of PVA/PEtVIm-Br and PVA/PEtVIm-Br-graphene composite comparing to pure PVA may attribute to the ability of capturing free radicals of PEtVIm-Br and the barrier effect of well-dispersed graphene.

Release and Transformation of Sodium during Pyrolysis of Zhundong Coals

Zhundong coalfield is one of the superhuge coalfields newly discovered in Xinjiang Autonomous Region of China. While many studies on alkali metals in coal/biomass have been reported previously, few efforts were conducted on Zhundong coals which are characterized by a high content of sodium. It is challenging to explore the ash deposition problems related to Zhundong coals directly using existing findings on the behavior of alkali metals. The occurrence mode and transformation of alkali metals during thermal conversion of Zhundong coals could be quite different. Specific investigation on sodium transformation during pyrolysis of Zhundong coals will make a contribution to our understanding on the fate and behavior of alkali metals involved in high-sodium coals. Here, the release and transformation fundamentals of sodium during pyrolysis of two Zhundong bituminous coals were investigated using an experimental approach of sequential chemical extraction. The sodium volatilization and evolution of occurrence modes in chars of Zhundong coal were probed in a laboratory-scale reactor. The occurrence of alkali metals in Zhundong coals greatly differs from those in other coals of China. Water-soluble sodium is the predominant chemical form in Zhundong coals. Most of the water-soluble sodium is released into gas phase as a volatile during pyrolysis and part of the remainder is converted into an insoluble form, but the release of sodium is not always synchronous with volatility. The release behavior of sodium demonstrates a nonmonotonic variation with the particle size of the coal while the effect of particle size includes many factors resulting in the challenge of demonstrating its individual contribution to sodium release. The duration time has an insignificant effect on volatile release and sodium transformation at low temperature, while it has an obvious influence at high temperature or in the initial stage of pyrolysis. With the extension of duration time at high temperature, no more sodium is obviously released from the residual chars of Zhundong coal but more water-soluble sodium will still transform into insoluble form. During the devolatilization of Zhundong coals under CO2 atmosphere, the release of sodium and its conversion into insoluble form will be inhibited compared to that under N2 condition.

Experimental Study of Gas-Phase Pyrolysis Reaction of Benzene to Investigate the Early Stage of Coke Formation

Gas phase pyrolysis of benzene was performed at 1,123, 1,173, and 1,223 K using a flow type reactor to examine the mechanism of the initial stage of coke (poly-aromatic hydrocarbons; PAHs) formation. The pyrolysis products including hydrogen, tar, and coke were quantified as the function of benzene residence time using gas chromatography, gas chromatography-mass spectrometry, LDI-TOFMS, and elemental analysis to establish the carbon balance within 95 to 105% for all of the experiments. Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) was applied to determine individual components in coke. Main tar components quantified were biphenyl (C12H10), terphenyl isomers (C18H14), quaterphenyl isomers (C24H18), phenanthrene (C14H10), and triphenylene (C18H12). Phenanthrene was found to be formed by the H-abstraction-C2H2-addition (HACA) mechanism and the other components were judged to be formed by the phenyl addition (PA) and the phenyl addition/cyclization (PAC) mechanisms. One of the smallest molecules identified within the coke was dibenzo[fg,op]naphthacene (C24H14) that is formed from triphenylene by the PAC mechanism. Larger molecules formed by the PAC mechanism and the HACA mechanism were also identified as coke components at the initial stage of pyrolysis. The phenyl addition to PAHs by the PAC mechanism and the HACA mechanism were judged to be main pathways to form larger PAHs. Main reaction mechanisms at the early stage of coke formation were suggested based on the detailed experimental data.

Fuel Particle Conversion of Pulverized Biomass during Pyrolysis in an Entrained Flow Reactor

This study addresses the change of char morphology and fuel conversion during pyrolysis in a laminar entrained flow reactor by experiments and particle simulation. Three experimental parameters were examined: reaction temperature (1073 and 1273 K); particle size (125–250, 250–500, and 500–1000 μm); and the length of reaction zone (650 and 1885 mm). The scanning electron microscopic (SEM) images showed that biomass swelled during heating and shrank during initial stage of pyrolysis. Then, char morphology transformed to cenospheres after the plastic stage. The yields of solid residue from the experiments were reasonably predicted by particle simulation. To give a guideline for the design of laminar entrained flow pyrolysis reactors, the required reactor length for complete conversion of biomass was also calculated for the pyrolysis. High reaction temperature, small particles, and slower gas flow were favorable for high fuel conversion.

Modeling initial stage of phenolic pyrolysis: Graphitic precursor formation and interfacial effects

Reactive molecular dynamics simulations are used to study the initial stage of pyrolysis of phenolic polymers with carbon nanotube and carbon fiber. The products formed are characterized and water is found to be the primary product in all cases. The water formation mechanisms are analyzed and the value of the activation energy for water formation is estimated. A detailed study of graphitic precursor formation reveals the presence of two temperature zones. In the lower temperature zone (<2000 K) polymerization occurs resulting in the formation of large, stable graphitic precursors, while in the high temperature zone (>2000 K) polymer scission results in formation of short polymer chains/molecules. Simulations performed in the high temperature zone of the phenolic resin (with carbon nanotubes and carbon fibers) show that the presence of interfaces does not have a substantial effect on the chain scission rate or the activation energy value for water formation.

Influence of biopretreatment on the character of corn stover lignin as shown by thermogravimetric and chemical structural analyses

The effect of corn stover lignin structure alteration caused by white-rot fungi pretreatment on the pyrolysis kinetics was studied by FTIR and TG/DTA. Results showed that biopretreatment had a remarkable effect on lignin pyrolysis. Biopretreatment can decrease the activation energy and increase the pre-exponential factor in the initial stage of pyrolysis, which makes it possible to start the lignin pyrolysis at a relatively gentle condition and improve the availability of biomass pyrolysis as a renewable energy. Analysis by FTIR showed that white-rot fungi destroyed the aromatic skeletal carbons, which are the main ether and carbon linkages of lignin, converting lignin into compounds having relatively simple structures. The relationship between the pyrolysis characteristics and the structure alteration pretreated by white rot fungi showed that the deconstruction and depolymerization of recalcitrant linkages of lignin could accelerate the reaction and lignin pyrolysis with lower energy consumption.

A new structural model of glass-like carbon

The results of an experimental study of X-ray diffraction, diamagnetic susceptibility, thermoelectricity and electron emission are presented for glass-like carbons. They lead to a new model of glass-like carbon structure and its modification due to heat treatment. At the initial stage of pyrolysis the stacks of narrow graphite-like sheets are formed being surrounded by a chain-like matrix. The main factor determining such system behavior under heat treatment is mutual parallelism of layer borders and adjacent chains. The most important feature of the model is the destruction of chain-like fragments with simultaneous formation of interstitials above 2000°C. The proposed model is consistent with many other properties of the material.

The effects of an inert central core on the thermal pyrolysis of an electrical cable

A mathematical model is formulated to simulate pyrolysis of the insulation layer of an electrical cable. The cable is vertically orientated and the model resembles a cable flammability test similar to IEC 60332-1 (Test on Electrical Cables Under Fire Conditions). Only non-flaming pyrolysis is investigated in this paper. The composition of the cable is idealised such that it consists of an inert central core and an insulation layer. The configuration of the external heat source is also simplified such that only the truncated end of the cable sample receives heat. Pyrolysis is modelled as ablation which assumes a single constant critical pyrolysis temperature. Investigations are concentrated on the effect of the thermal properties of the central core on the pre-heating time and the initial stage of pyrolysis.