Gas chromatographic study of the volatile products from co-pyrolysis of coal and polyethylene wastes

The aim of this study was to determine the volatile products distribution of co-processing of coal with two plastic wastes, low-density polyethylene from agriculture greenhouses and high-density polyethylene from domestic uses, in order to explain the observed decrease in coal fluidity caused by polyethylene waste addition. Polymeric materials, although they are not volatile themselves, may be analysed by gas chromatography through the use of pyrolysis experiments. In this way, a series of pyrolysis tests were performed at 400 and 500 degrees C in a Gray-King oven with each of the two plastic wastes, one high-volatile bituminous coal and blends made up of coal and plastic waste (9:1, w/w, ratio). The pyrolysis temperatures, 400 and 500 degrees C, were selected on the basis of the beginning and the end of the coal plastic stage. The organic products evolved from the oven were collected, dissolved in pyridine and analysed by capillary gas chromatography using a flame ionization detector. The analysis of the primary tars indicated that the amount of n-alkanes is always higher than that of n-alkenes and the formation of the alkenes is favoured by increasing the pyrolysis temperature. However, this effect may be influenced by the size of the hydrocarbon. Thus, the fraction C17-C31 showed a higher increase of n-alkenes/n-alkanes ratio than other fractions. On the other hand, the difference between the experimental and estimated values from tars produced from single components was positive for n-alkanes and n-alkenes, indicating that co-pyrolysis of the two materials enhanced the chemical reactivity during pyrolysis and produced a higher conversion than that from individual components.     

烟煤与生物质快速共热解产物特性分析

研究了烟煤(YL)分别与富含半纤维素的玉米芯(CB)和富含木质素的松木屑(SD)快速共热解产物产率和气体组成的变化规律。结果表明,烟煤与生物质共热解组分互相作用,造成共热解气、液、固相产率和气体组成的明显变化,且与生物质种类有关。相对于独立热解过程,玉米芯丰富的半纤维素造成热解水蒸气和CO₂浓度较高,且玉米芯中富含的K元素挥发迁移至煤焦表面,对热解半焦与水蒸气、CO₂的气化反应起到催化作用,反应生成的H₂和富氢组分易与热解生成的自由基结合,抑制自由基之间的缩聚反应,使得共热解气体和液体产率增加,而半焦产率减小。烟煤/松木屑共热解过程中,松木屑中富含的Ca元素在煤焦表面迁移,促进了松木屑热解液体在半焦表面裂解反应,生成CO₂、CO和富氢自由基等轻质组分,造成共热解半焦和液体产率降低而气体产率增加。热解产物半焦、焦油、水蒸气、CO₂之间的气化和裂解反应均产生富氢的次生组分,从而提高了共热解气体中CO和烃类气体产率,降低了H₂产率。     

Fast co-pyrolysis of coal and biomass in a fluidized-bed reactor

Co-pyrolysis is one of the most promising options for the utilization of coal and biomass. Coal/biomass blends were prepared using Yilan subbituminous (YL) and corncob and the mass ratios of coal in mixtures varied between 0 and 100 %. Co-pyrolysis characteristics were investigated in a thermogravimetric analyzer from 303 to 973 K under the nitrogen flow of 100 mL min^?1. The co-pyrolysis residues were less than the sum simply added of the solid yields of individuals. With heating rate increased from 10 to 40 K min^?1, the residues decreased more severely compared to the expected under various blending ratios. For fast pyrolysis in fluidized-bed reactor, gas volumes and char yields of co-pyrolysis showed a significant linearity. But pyrolysis-oil yields were higher than the expected from the additive model when the YL blending ratios were less than 60 %. The co-pyrolysis evolved more H₂, CH₄, C₂ + C₃, and less CO than an additive pyrolysis process of individual fuel. The GC/MS results indicated that co-pyrolysis-oil contained more alcohols, ketones, aldehydes, or acids than that of individual fuel. All of that suggested the H/OH in volatiles produced from rapid pyrolysis of biomass transferred to the radicals of coal pyrolysis. The possible reaction mechanism also was provided in the paper.     

自由落下床中生物质与煤共热解的协同效应对焦油组成的影响

利用溶剂萃取-柱层析方法,将自由落下床中豆秸与大雁褐煤共热解以及单种原料热解的液体产品分为沥青烯、酚类、脂肪烃类、芳香烃类和极性物等组分。结果表明,共热解的沥青烯产率为11.4%,低于根据煤和生物质单独热解的质量加权平均计算值19.0%,且芳香性增大;与计算值相比,低分子量的酚类、甲基苯酚、二甲基苯酚及其衍生物的含量提高了5%;而且长侧链的脂肪烃含量减少。共热解焦油的芳香类组分中十氢萘的质量分数是43.37%,但其在单一原料热解焦油中并没有被检测到。热解油分析结果表明,自由落下床生物质与煤快速共热解过程中存在协同效应,其主要原因是,发生氢解和加氢反应。煤与生物质共热解有利于产生低分子量的化合物,改善油品的质量。     

稻草与煤固定床共热解特性的研究

选取稻草为生物质原料,将其与两种不同煤阶的煤(内蒙褐煤和神府烟煤)分别以0∶100、20∶80、40∶60、60∶40、80∶20、100∶0的干基质量比均匀混合.借助固定床反应器,研究了稻草与两种煤的共热解特性,探讨了共热解过程中可能存在的协同作用.结果表明,稻草添加有利于共热解气体产物的生成,且对神府煤作用更明显;稻草含量越高,热解气体产量的实验值与加权平均计算值的偏差也越大,说明稻草与煤共热解过程发生了协同作用.而共热解所得焦产量的实验值与加权平均计算值基本一致.热解焦傅里叶红外光谱分析结果表明,稻草添加对热解焦的官能团未造成显著影响.     

原料对自由落下床中生物质与煤共热解行为的影响

在500～700℃和生物质混合比0～100％(质量分数)条件下,利用自由落下床反应器考察原料对生物质与煤共热解行为的影响.所用煤原料为大雁褐煤(DY)和铁法烟煤(TF),而生物质原料为农业废弃物秸秆(LS)和木材加工余料白松木屑(SD).结果表明,即使在自由落下床中停留时间短的条件下,生物质与煤共热解的协同效应仍然发生...     

Mechanisms of aliphatic hydrocarbon formation during co-pyrolysis of coal and cotton stalk

Pyrolysis experiments were carried out in a tubular furnace. The characteristics of pyrolysis tar were analyzed by GC/MS. The results indicated that the aliphatic hydrocarbon yield derived from co-pyrolysis tar of cotton stalk and Shenmu coal was obviously higher than that of Shenmu coal pyrolysis under optimum condition. Moreover, microcrystalline cellulose was selected as a model compound and the copyrolysis tar of microcrystalline cellulose and Shenmu coal was analyzed for comparison. Base on the experimental results, it was indicated that the alkyl radicals generated from pyrolysis were converted to aliphatic hydrocarbons by radical reactions. Furthermore, the mechanisms of aliphatic hydrocarbon formation were discussed during co-pyrolysis of cotton stalk and Shenmu coal.     

Synergistic effects on co-pyrolysis of lignite and high-sulfur swelling coal

Co-pyrolysis of a lignite coal and a bituminous coal was carried out on a fixed-bed reactor. The lignite was enriched with calcium, and the bituminous coal featured in high sulfur and strong swelling. Experiments were also conducted for the blends using the acid-washed lignite and/or the acid washed bituminous coal to address the influences of calcium in the lignite on the synergistic behaviors. Calcium in the lignite exhibited some aspects of synergy including the catalytic cracking reactions of tar, the retention of sulfur in the char, and the catalyzed polyaromatization and gasification of char. These synergies impacted the differences in the product distribution and gas composition between the co-pyrolytic results and the additive ones. Moreover, there appeared to be a synergistic effect on the cross-linking reaction of volatile matter, resulting in an increase in the char yield irrespective of coal demineralization. The co-pyrolysis was also observed to destroy the swelling of coal. This synergistically increased the tar yield due to less resistant escaping of tar from the intra-particles of coal.     

重油残渣与不同煤阶煤共热解/气化实验研究

采用快速热解固定床在恒温热解条件下研究了不同混合比例不同煤阶煤与重油残渣共热解焦的形貌和焦产率的规律,进而在热重分析仪上采用非等温气化方法研究了煤焦、重油残渣焦及混合焦的气化反应性。结果表明,煤与重油残渣共热解焦有明显的结块现象,但焦产率与理论值一致,表明共热解过程中两者没有相互作用。重油残渣焦的气化反应性较褐煤和烟煤的低,比无烟煤活性略高,重油残渣与褐煤和烟煤混合焦气化反应速率比计算值高,表明气化过程有促进作用存在,进一步分析表明,煤中的矿物质如Ca、Fe,对重油残渣气化有一定的催化作用。     

富氢气氛下煤热解脱硫脱氮的研究

本文对兖州高硫煤在１０ｍｌ固定床反应器中分别与相当条件下的焦炉煤气、合成气、氢气共热解所得半焦及焦油元素进行系统的分析比较。结果表明,在压力为３ＭＰａ,温度为６５０℃,升温速率为１０℃／ｍｉｎ相对温和的热解条件下,兖州高硫煤与焦炉气、合成气、氢气共热解脱氮率分别为３０１％、３５７％、４４０％（ｗ％,ａｄ）,脱硫率基本相当约为８０％（ｗ％,ａｄ）,且在此三种热解气氛下煤中硫在热解固、液、气产物中的分布极为相似,分别约为２０％、１０％、７０％。与相当氢分压下的纯氢加氢热解相比,５ＭＰａ焦炉气气氛下兖州煤热解脱硫率增加约４５％,脱氮率降低约３５％。用焦炉气顶替纯氢气进行煤加氢热解具有较大的脱硫优势,这不失为我国高硫煤洁净利用的新途径     

A TG/DTA study on the effect of coal blending on ignition behaviour

Understanding the ignition behaviour of coal is of utmost importance for the design of boilers and control of the combustion process. In recent years there has been an increasing utilisation of coal blends for combustion, but information on the possible interactive effects during ignition of the individual components is scarce. In this work the ignition behaviour of a series of coal blends, made up from three coals of different rank, sub-bituminous, high volatile and low volatile bituminous, was studied. To this end a thermogravimetric analyser linked to a mass spectrometer for evolved gas analysis was used. Different ignition behaviour was observed for the coals studied; the sub-bituminous and low volatile bituminous coals ignited heterogeneously, while homogeneous ignition occurred for the high volatile bituminous coal. In the case of blends of the low and high volatile bituminous coals, different mechanisms of ignition were observed depending on the blends composition. This revised version was published online in July 2006 with corrections to the Cover Date.     

Structural properties of non-combustion-derived refractory organic matter which interfere with BC quantification

Black carbon (BC), presenting the residue from incomplete combustion processes of fossil fuels and vegetation, has received special interest as a possible carbon sink in soils and sediments. In spite of this, there is still a need to develop accurate and comparable analytical protocols to determine the amount of BC stored in different environmental matrices and to characterise potentially interfering materials in the analysis of BC. Therefore in this study a melanoidin, a sample from the Green River Shale, a lignite and a bituminous coal were characterised by means of elemental analysis, thermogravimetry–differential scanning calorimetry (TG–DSC), pyrolysis coupled with gas chromatography–mass spectrometry (Py-GC/MS) and ¹³C NMR spectroscopy. Thermal analysis (TG–DSC) indicated larger contributions of labile OM in the melanoidin and in the shale samples than in the lignite and the bituminous coal, although the coals showed an intense exothermal peak at temperatures higher than 550 °C. This behaviour is in agreement with high thermal recalcitrance of the latter and was also found in earlier studies of BC-rich material. Comparable to the latter, Py-GC/MS of the coals reveals considerable amounts of lignin-derived products. This and the similar thermal behaviour of both refractory materials aggravate their discrimination during BC-analysis. The pyrogram of the melanoidin reveals an important contribution of furanes and pyrane-like structures that derive from carbohydrates. NMR spectroscopy supports that those compounds are original constituents of the melanoidin rather than solely pyrolysis products. Considering that those compounds are typically formed during charring of N-containing biomass, their contribution to the BC structure should not be neglected if one seeks for a better understanding of BC structural properties. For the shale sample, both analytical pyrolysis and ¹³C NMR spectroscopy confirm a high contribution of long alkyl-C chains. Due to their high hydrophobicity such structures can stand chemical oxidation and their presence in soil and sediment samples can obscure BC quantification by those methods. This study indicates that present approaches for BC-identification that are based on the assumption of BC being mostly a highly condensed polyaromatic network, have to be taken with caution and modified in accordance with a more heterogeneous composition of BC containing considerable fractions of only partly charred biopolymers.     

HCN and NH3 (NOx precursors) released under rapid pyrolysis of biomass/coal blends

Rapid pyrolysis of 6 biomass/coal blends (1:4, wt) including rice straw + bituminous (RS + B), rice straw + anthracite (RS + A), chinar leaves + bituminous (CL + B), chinar leaves + anthracite (CL + A), pine sawdust + bituminous (PS + B), and pine sawdust + anthracite (PS + A) was carried out in a high-frequency magnetic field based furnace at 600-1200 °C. The reactor could not only achieve high heating rates of fuel samples but also make biomass and coal particles contact well; secondary reactions of primary products during rapid pyrolysis can also be efficiently reduced. By comparing nitrogen distributions in products of blends (experimental values) with those of the sums of individual biomass and coal (weighted values), nitrogen conversion characteristics under rapid pyrolysis of biomass/coal blends were investigated. Results show that, biomass particles in blends lead to higher experimental char-N yields than the weighted values during rapid pyrolysis of biomass/anthracite blends. The decreased heating rates of both biomass and coal particles caused by the low packing densities of biomass may be the reason. For blends of CL + B in which packing density of chinar leaves is high, and for PS + B during pyrolysis of which melting and shrinkage happen to pine sawdust, both biomass and coal particles can obtain high heating rates, synergies can be found to promote nitrogen release from fuel samples and decrease char-N yields under all the conditions. But the low fluidity and not easily collapsed carbon skeletons of rice straw make the heating rates of rice straw and bituminous particles in RS + B lower than those of CL + B and PS + B, and weaker synergies can be found from char-N yields of RS + B. The synergies can obviously be found to decrease the (NH₃ + HCN)-N yields and make more nitrogen convert to N₂ except for those of several low-temperature conditions (600-700 °C). Under the low-temperature (600-700 °C) condition, synergies make molar ratios of HCN-N/NH₃-N higher than those of the weighted values.     

The co-pyrolysis of flame retarded high impact polystyrene and polyolefins

The co-pyrolysis of brominated high impact polystyrene (Br-HIPS) with polyolefins using a fixed bed reactor has been investigated, in particular, the effect that different types of brominated aryl compounds and antimony trioxide have on the pyrolysis products. The pyrolysis products were analysed using FT-IR, GC–FID, GC–MS, and GC–ECD. Liquid chromatography was used to separate the oils/waxes so that a more detailed analysis of the aliphatic, aromatic, and polar fractions could be carried out. It was found that interaction occurs between Br-HIPS and polyolefins during co-pyrolysis and that the presence of antimony trioxide influences the pyrolysis mass balance. Analysis of the Br-HIPS + polyolefin co-pyrolysis products showed that the presence of polyolefins led to an increase in the concentration of alkyl and vinyl mono-substituted benzene rings in the pyrolysis oil/wax resulting from Br-HIPS pyrolysis. The presence of Br-HIPS also had an impact on the oil/wax products of polyolefin pyrolysis, particularly on the polyethylene oil/wax composition which converted from being a mixture of 1-alkenes and n-alkanes to mostly n-alkanes. Antimony trioxide had very little impact on the polyolefin wax/oil composition but it did suppress the formation of styrene and alpha-methyl styrene and increase the formation of ethylbenzene and cumene during the pyrolysis of the Br-HIPS.     

Co-primary thermolysis molecular modeling simulation of lignin and subbituminous coal via a reactive coarse-grained simplification

Co-pyrolysis of coal and biomass is one immediate approach to reduce net carbon dioxide emissions from heat and power generation. Interestingly there is often co-pyrolysis synergy, commonly enhancing tar and gas yields. To explore the synergy mechanisms requires the ability to predict yields and explore thermolysis of coal and biomass chemistry. The current state-of-knowledge allows individual yield predictions through mathematical modeling, and creation of large-scale molecular representations of lignin (as a biomass simplification) and coal. Yet there is no means of coupling these molecular representations and predicted yields. Here a reactive coarse-grained simulation is used to generate 2D lattice representations from complex large-scale subbituminous coal and generic hardwood lignin structural representations. The chemical percolation devolatilization (CPD) model was used to predict yields of chars and tars/gases during pyrolysis. Scripting within a molecular modeling environment generates the reactive 2D lattice in molecular modeling space and also simulates the primary thermolysis within the lattice to achieve the desired yields through a breaking of labile cross-links between “un-reactive” structural nodes. The approach is used to visualize the dynamic yield differentials between lignin and a subbituminous coal and to generate radical fragments that can be used to explore synergistic interactions. In this paper the coarse-graining and thermolysis processes are described.     

Analysis of products from the pyrolysis of plastics recovered from the commercial scale recycling of waste electrical and electronic equipment

Three plastic fractions from a commercial waste electrical and electronic equipment (WEEE) processing plant were collected and investigated for the possibility of recycling them by batch pyrolysis. The first plastic was from equipment containing cathode ray tubes (CRTs), the second plastic was from refrigeration equipment, and the third plastic was from mixed WEEE. Initially, the decomposition of each of the plastics was investigated using a TGA linked to a FT-ir spectrometer which showed that the CRT plastic decomposed to form aliphatic and aromatic compounds, the refrigerator plastic decomposed to form aldehydes, CO₂, aromatic, and aliphatic compounds, and the mixed WEEE plastic decomposed to form aromatic and aliphatic compounds, CO₂, and CO. Each plastic mixture was also pyrolysed in a batch reactor to determine the halogen and metal content of the pyrolysis products, additionally, characterisation of the pyrolysis oils was carried out by GC–MS and the pyrolysis gases by GC–FID and GC–TCD. It was found that the halogen content of the oils was relatively low but the halogen and metal content of the chars was high. The pyrolysis oils were found to contain valuable chemical products and the pyrolysis gases were mainly halogen free, making them suitable as a fuel.     

伊敏煤田伍牧场矿区煤中多环芳烃分布特征

伊敏煤田伍牧场矿区储藏着丰富的煤层，有从褐煤至瘦煤连续变化的系列煤样。对该煤系样品索氏抽提物中芳烃馏分进行ＧＣ／ＭＳ分析，取得从萘系至ｍ／ｅ４９６分子量的一个系列的芳烃分布数据。煤中多环芳 鉴定是通过气相色谱的保留指数，质量色变和质谱多个方面考证而定出本系列样品中５７个化合物的同系物。     

XAS combined with TG–DTG study on synergic effect on sulfur transformation during co-pyrolysis of sawdust and lignite

The synergic effect of sawdust (SD) and a lignite can be observed by analyzing their co-pyrolysis behavior. The co-pyrolysis behavior of SD and lignite mixtures was investigated by thermo-gravimetric analysis, and their sulfur transformation was measured by X-ray absorption spectroscopy (XAS). The pyrolysis process can be divided into three stages for SD and lignite, while four their mixtures. The experimental mass loss of SD and lignite mixture during co-pyrolysis is higher than its theoretically calculated mass loss, especially at the mixing ratio of 1:1. This indicates that synergy occurs during SD and lignite co-pyrolysis process. XAS spectra of sulfur show that SD can promote FeS to decompose before 900 °C during co-pyrolysis, as the peak of FeS decreases in the mixture’s char. However, the experimental sulfur removal of mixtures is lower than the theoretically calculated one. This indicates that synergic effect has no effect on sulfur removal, which is very corresponding to more thiophenes gathering in the mixture’s char, because the peak of thiophenes is very steep for the mixture after pyrolysis. And other sulfurs transformation in the mixture is very similar to that of CF coal. For CF coal and its mixture, sulfate peak increases obviously after pyrolysis, which is mostly caused by absorbing SO₂ of alkaline minerals during pyrolysis. This also suggests SD cannot prevent sulfate from forming during co-pyrolysis. Therefore, SD can be added to promote high-pyrite coal to increase sulfur removal, since the decomposition of FeS needs higher temperatures.

     

Study of the thermal decomposition of flame-retarded unsaturated polyester resins by thermogravimetric analysis and Py-GC/MS

The thermal degradation behaviours of flame-retarded unsaturated polyester resin formulations containing ammonium polyphosphate (APP), Cloisite 25A nanoclay and zinc based smoke suppressants have been studied using thermogravimetric analysis (TGA) combined with infrared analysis of the evolved gases (EGA) and pyrolysis/gas chromatography-mass spectrometry (GC/MS). In TGA-EGA experiments, the mass loss as a function of temperature has been correlated with the evolution of carbon monoxide (CO) and carbon dioxide (CO₂) and oxygen (O₂) consumption as measured by an oxygen analyser. The effect of APP, Cloisite 25A and the smoke suppressants on the evolution of CO and CO₂ has been examined. The decomposition behaviour of flame-retarded polyester resins under isothermal pyrolytic conditions was investigated and the evolved gaseous products were collected and qualitatively and semi-quantitatively analysed via GC/MS. The addition of APP does not yield many new gaseous products relative to the unmodified polyester resin neither does the presence of zinc borate (ZB) and zinc stannate (ZS) together with APP. Possible chemical interactions are discussed in an attempt to explain the observed results.     

Chemical composition of bio-oil produced by co-pyrolysis of biopolymer/polypropylene mixtures with K2CO3 and ZnCl2 addition

The chemical composition of liquid products of cellulose and lignin co-pyrolysis with polypropylene at 450 °C with and without the potassium carbonate or zinc chloride as an catalyst was investigated. The yield of liquid products of pyrolysis was in the range of 26–45 wt% and their form was liquid or semi-solid highly depending on the composition of sample and pyrolysis conditions. The potassium carbonate and zinc chloride addition to blends has also influenced the range of samples decomposition as well as the chemical composition of resulted bio-oils. All bio-oils from biopolymer and polypropylene mixtures were three-phase (water, oil and solid). While zinc chloride acted as catalyst, all bio-oils obtained from biopolymer and polypropylene mixtures were yellow liquids with well-separated water and oil phases. All analyses proved that the structure and quality of bio-oil strongly depends on both the composition of the blend and the presence of the additive. The FT-IR and GC–MS analyses of oils showed that oxygen functionalities and hydrocarbons contents highly depend on the composition of biomass/polypropylene mixture. Results confirmed the significant removal and/or transformation of oxygen containing organic compounds, i.e. levoglucosan, 1,6-anhydro-β-d-glucofuranose and phenol derivatives due to the zinc chloride presence during pyrolysis process. All analyses showed that zinc chloride as catalyst was generally much more effective for removal of hydroxyl and methoxy groups than was potassium carbonate. It was demonstrated in this study that catalysts used in present work lead to the increased char yield and improved the fuel quality of bio-oil.