Kinetics of pyrolysis of sugarcane bagasse: effect of catalyst on activation energy and yield of pyrolysis products

Cellulose - In this work we have attempted to use biomass as energy source which is abundantly available throughout the world. The work is focused on pyrolysis of sugarcane bagasse in a...     

蔗渣的热解与燃烧动力学特性研究

利用热重分析仪对蔗渣在不同升温速率下的热解、燃烧失重特性进行了研究。采用Friedman法对反应过程中可能存在的反应机理进行初步判断，蔗渣热解过程由其主要组分半纤维素、纤维素和木质素热解的三个独立的平行反应来描述，相应的反应活化能分别为203.92 kJ·mol-1、238.50 kJ·mol-1和77.11 kJ·mol-1； 蔗渣燃烧过程分为两段，第一段类似于其热解过程，第二段由木质素热解和残焦燃烧共同组成的连续反应，反应活化能为255.57 kJ·mol-1和159.11 kJ·mol-1。通过非线性回归法拟合获得的曲线与实验曲线基本一致，证实了蔗渣的热解、燃烧过程中存在着上述假定的反应机理。     

Production of hydrogen and syngas via pyrolysis of bagasse in a dual bed reactor

Pyrolysis of bagasse followed by thermal cracking of tar was carried out at atmospheric pressure using a dual bed reactor. The first bed was used for the pyrolysis and the second bed was used for thermal cracking of tar. Iron fillings were used as the packed bed material in the second bed. The effects of reaction time (20 to 40 min), reactor temperature (600 to 900℃) and packed bed height (40-100 mm) on the product (char, tar and gas) yield and gas (H2 , CO, CO2 , CH4 , CnHm ) composition were studied. Over the ranges of the experimental conditions used, the operating conditions were optimized for pyrolysis temperature around 850℃, a reaction time of 30 min and packed bed height of 100 mm, thus we could obtain a gas richer in hydrogen and carbon monoxide and poorer in carbon dioxide and hydrocarbons. It was observed that compared with single bed process, dual bed process increased the gas yield from 0.397 to 0.750 m3 /kg and decreased the tar yield from 0.445 to 0.268 g/g while the heating value of the product gas remained almost constant (10-11 MJ/m3 ).     

Determination of kinetic parameters and analytical pyrolysis of tobacco waste and sorghum bagasse

The thermal decomposition of tobacco waste and sorghum bagasse was investigated by non-isothermal thermogravimetric analyses, applying slow heating rates and well-defined conditions. The purpose of evaluating the decomposition was to estimate the kinetic parameters of the analyzed materials. Activation energies and Arrhenius exponential factors were inferred by different estimation methods: the classical methods of Ozawa and Starink and the independent parallel reactions model. The analytical pyrolysis was performed in a micro-pyrolyzer coupled to a gas chromatographer/mass spectrometer. Values of activation energy obtained with single step reaction models by the Ozawa method were: 103.94 kJ/mol for tobacco waste and 120.01 kJ/mol for sorghum bagasse, and by the Starink method - 135.95 kJ/mol for tobacco waste and 148.91 kJ/mol for sorghum bagasse. The independent parallel reaction model presented energy activation values of 39.7-272.0 kJ/mol for tobacco waste and 35.7-220.0 kJ/mol for sorghum bagasse. In analytical slow and fast pyrolysis of tobacco residue and sorghum bagasse, holocellulose and lignin-derived compounds were identified, as well as hydrocarbons and aromatic hydrocarbons. The kinetic behavior of the materials are presented and discussed. Our findings may be helpful in evaluating other types of lignocellulosic biomass.     

Chlorinated products of plastic pyrolysis

The formation of various chlorinated products in pyrolysis of polymers and plastics additives was studied. Formation of chlorobenzenes (in addition to the monomers) from poly(chlorostyrene) and poly(vinylbenzyl chloride) was observed. Hydrogen chloride is only produced from these polymers at above 600 °C when the chlorine atoms are cleaved off and abstract hydrogen. A similar process takes place in aromatic chlorine-containing dyes, in which the strong aromatic molecular structure prevents the thermal cleavage of chloroaromatic volatile products. We have observed that cupric and ferric chlorides chlorinate phenolic thermal decomposition products of plastic materials which originate either from the polymer or from the stabilizer. The highest yields of chlorophenols are obtained in pyrolysis at around 700 °C.     

Empirical model of slow pyrolysis of hardwood chips

Applied Biochemistry and Biotechnology - The thermal decomposition of mixed hardwood chips was investigated by pyrolyzing 1-kg samples at atmospheric pressure in an electrically-heated batch...     

Thermal characterisation of microalgae under slow pyrolysis conditions

Aquatic microalgae have high potential for production of bio-chemicals, liquid transport fuels and charcoal. Their main advantage over existing energy crops is that they have faster growth rates and do not compete with food production. In this study six species of microalgae (Tetraselmis chui, Chlorella like, Chlorella vulgaris, Chaetocerous muelleri, Dunaliella tertiolecta and Synechococcus) were selected, presenting a broad cross-section of physical characteristics and known behaviour under cultivation. The objective of this work was to ascertain differences in thermal conversion behaviour between the microalgae species under slow pyrolysis conditions.The samples were first analysed with a Computer Aided Thermal Analysis (CATA) technique at a standard heating rate of 10 °C/min. For all species, the energy required to achieve thermal conversion was found to be approximately 1 MJ/kg. Gas chromatography was then applied to measure the evolution of biogas compounds with temperature. The heat of combustion of the biogas compounds was estimated to vary significantly between species, ranging from 1.2 to 4.8 MJ/kg.Pyrolysis oil product yields were also estimated at 500 °C. The oils produced at this temperature were collected and their molecular weight distribution assessed by Matrix Assisted Laser Desorption/Ionisation (MALDI). The species were found to produce up to 43% by volume of bio-oils. In all samples the char fraction remained above one third of total sample weight.     

Pyrolysis of sorghum bagasse biomass into bio-char and bio-oil products

The transformation of renewable biomass into valuable products as alternatives to fossil fuels is essential for sustainable energy in sustainable society. This work systematically investigates the pyrolysis of sorghum bagasse biomass into bio-char and bio-oil products and studies the effect of temperature (623–823 K) on the conversion of sorghum bagasse and products yields. The physicochemical properties of bio-char were thoroughly studied using powder X-ray diffraction, elemental analysis (CHNSO), scanning electronic microscope, calorific value (CV), and Fourier transform infrared (FTIR) spectroscopy techniques. Also, gas chromatography–mass spectrometry (GC–MS), CV, and FTIR were used to understand the properties of bio-oil. The results obtained indicate that an increase in the pyrolysis temperature from 623 to 823 K leads to a decrease in the bio-char yield from 42.55 to 30.38%. On the other hand, the maximum bio-oil yield of 15.94% was obtained at 723 K. The bio-char obtained at 673 and 773 K was found by FTIR analysis to be composed of a highly ordered aromatic carbon structure. The calorific value of bio-oil, which contains a greater amount of acidic compounds, was found to be 6740 kcal/kg. The GC–MS analyses revealed the presence of octadecenoic acid, p-cresol, 2,6-dimethoxy phenol, 4-ethyl 2-methoxy phenol, phenol, o-guaiacol, and octadecanoic acid in the bio-oil obtained from the pyrolysis of sorghum bagasse biomass. The present study provides useful information for understanding the quality of bio-oil and bio-char obtained from high biomass sorghum bagasse.     

Study of the slow batch pyrolysis of mixtures of plastics,tyres and forestry biomass wastes

This work aimed to study the recovery of three types of waste by the process of pyrolysis: biomass, plastics and used tyres. The effects of experimental conditions in products yield and composition were studied. The increase of reaction time increased alkane content both in gas phase from 53% to 70% v/v and in liquid fraction from 48% to 60% w/w. The rise of reaction temperature led to a decrease of liquid yield (from 82% to 73% w/w), which was followed by the increase of solids and gases. The increase of reaction temperature also allowed the increase of the alkane content in gas phase from 39% to 70% v/v. The parameter that most affected products yield and composition was plastics content on the wastes initial mixture. The enhancement of this parameter increased liquid yield from 33% to 92% w/w, at the expense of solids and gases contents and also decreased aromatic contents from 52% to 28% w/w.     

Fast pyrolysis of rice straw,sugarcane bagasse and coconut shell in an induction-heating reactor

With the application of induction heating, a fast pyrolysis was used for producing valuable products from rice straw, sugarcane bagasse and coconut shell in an externally heated fixed-bed reactor. The effect of process parameters such as pyrolysis temperature, heating rate and holding time on the yields of pyrolysis products and their chemical compositions were investigated. The maximum yield of ca. 50% on the pyrolysis liquid product could be obtained at the proper process conditions. The chemical characterization by elemental (CHNO), calorific, Fourier transform infrared (FT-IR) spectroscopy and gas chromatography/mass spectrometry (GC–MS) showed that the pyrolysis liquid products contain large amounts of water (>65 wt.%), and fewer contents of oxygenated hydrocarbons composing of carbonyl groups, resulting in low pH and low heating values. The results were very similar to bio-oils obtained from other biomass materials. The residual solid (char or charcoal) was also characterized in the present study.     

Catalytic effects of eight inorganic additives on pyrolysis of pine wood sawdust by microwave heating

In this paper, pyrolysis of pine wood sawdust was carried out by microwave heating at ca. 470 °C under dynamic nitrogen atmosphere. Eight inorganic additives (NaOH, Na₂CO₃, Na₂SiO₃, NaCl, TiO₂, HZSM-5, H₃PO₄, Fe₂(SO₄)₃) were investigated in terms of their catalytic effects on the pyrolysis. All of the eight additives have increased yields of solid products greatly and decreased yields of gaseous products more or less. Yields of liquid products have not subjected to dramatic change. The incondensable gases produced from pyrolysis consist mainly of H₂, CH₄, CO and CO₂. All of the eight additives have made these gases evolve earlier, among which the four sodium additives have the most marked effect. All the additives have made the amount of CH₄ and CO₂ decrease, while all of them except NaCl, TiO₂ and Fe₂(SO₄)₃ have made that of H₂ increase and all of them except Na₂SiO₃ and HZSM-5 have made that of CO decrease. Alkaline sodium compounds NaOH, Na₂CO₃ and Na₂SiO₃ favor H₂ formation most. The most abundant organic component in the liquid products from pyrolysis of untreated sample and samples treated by all the additives except H₃PO₄ and Fe₂(SO₄)₃ is acetol. All the four sodium compounds favor acetol formation reaction and the selection increasing effect follows the order of NaOH > Na₂CO₃ ≈ Na₂SiO₃ > NaCl. TiO₂ goes against the formation of acetol, HZSM-5 has no marked effect on acetol formation. The two dominant organic components identified in the liquid products from pyrolysis of H₃PO₄ and Fe₂(SO₄)₃ treated samples are both fufural and 4-methyl-2-methoxy-phenol. A possible pathway for acetol formation is tentatively proposed.     

Isomeric structure of styrene-acrylonitrile and styrene-methylcrylate copolymer pyrolysis products

Summary Gas chromatographic retention indices of pyrolysis products of styrene-acrylonitrile and styrene-methylacrylate copolymers were measured on two columns prepared with different stationary phases. A retention index against retention index diagram proved to be useful to define the composition of product molecules, as the points of homologous series form straight lines. We identified the isomeric structure of dimers and trimers consisting of two kind of monomer units by comparing their retention indices. This comparison was based on the determination of the retention index increments of cyano, methoxy-carbonyl and phenyl groups bounded to primary, secondary or olefinic carbon atom. The isomeric structures of styrene-acrylonitrile dimers and trimers were confirmed by mass spectroscopy.     

Parallels between slow pyrolysis of Estonian oil shale and forest biomass residues

Different types of forest residual biomass, including pine wood, pine bark and spruce needles, and Estonian Kukersite oil shale, were parallelly subjected to the slow pyrolysis in similar conditions. A Fischer assay, modeling industrial semi-coking retorts, was used. Both the yield and the composition of liquid, gaseous and solid products of pyrolysis were determined. FTIR-spectroscopic and chromatographic methods were used to study products group and individual composition. Common and specific features in biomass and oil shale semi-coking have been described. In comparison with oil shale, the biomass yielded less oil and more gas. Specifically large amounts of reaction water and carbon dioxide were obtained in biomass pyrolysis resulting in formation of significantly deoxygenated liquid and solid products. Bio-oils can be distinguished by the solubility in conventional solvents. Kukersite shale oil and the benzene-soluble fractions of different bio-oils were characterized by similar group composition.     

Characterization of liquid products of automobile tire pyrolysis

The liquid product of automobile tire pyrolysis and its fractions were studied. The amount of the liquid hydrocarbon fraction is 40–45% of the total weight of pyrolysis products. The hydrocarbon fraction is similar in its characteristics to low-sulfur heavy crude oil. Fractionation of the hydrocarbon fuel was performed. The maximal yield of the light distillation fraction is 39% (temperature interval 180–340°C). The extent to which the characteristics of the light fraction obtained meet the regulations was evaluated. The light fraction of hydrocarbon fuel produced by pyrolysis is recommended for use as a component of diesel motor fuel after additional purification.     

温度对松木屑气化液体产物组成的影响

利用傅里叶变换红外光谱(FT-IR)和气质联用(GC/MS)技术,研究了松木屑在400~900℃气化液体产物的主要组成成分和液体产物主要化学组成的来源与转化随气化温度变化的规律。结果表明,松木屑低温气化液体产物主要为酮、呋喃和愈创木酚等含氧化合物。随气化温度升高,液体产物的组成发生显著变化,400~ 500℃主要发生愈创木酚向酚类化合物的转变,500~600℃主要发生酮、呋喃向酚类化合物的转变,600~700℃主要发生酚类向茚和PAHs (多环芳烃)的转变,700~900℃主要发生酚类化合物向PAHs的转变,900℃液体产物的组成为大分子量的PAHs。     

Catalytic pyrolysis of oak via pyroprobe and bench scale, packed bed pyrolysis reactors

The pyrolytic conversion of oak sawdust at 500 °C in flowing He over eight proprietary catalysts is described and compared to the control bed material, quartz sand. The reactions were conducted and compared in two reactors, an analytical, μg-scale pyroprobe reactor and a bench, g-scale packed bed reactor. The catalysts examined were modified acid catalysts, dealuminated-zeolite Y, β-zeolite, a naturally occurring metal hydroxide containing mineral, mordenite, and a mesoporous aluminosilicate molecular sieve. The packed bed reactor allowed the collection of three bulk product fractions, char, liquid, and gas, all of which could not be obtained from the μg-scale pyroprobe reactions. The catalysts effect on the mass balance of the bulk fractions tended toward more chars and less liquid compared to the sand control. The catalysts’ effects on the liquid products obtained in both reactors shifted away from acetic acid, furfural and higher molecular weight phenolics obtained with sand to lower molecular weight aromatics. This halved the total acid number of the liquid fraction and raised the pH by up to 1.4 units. The modified catalysts’ effects on the gas products from both reactors did not follow a specific trend. Instead, specific catalysts were able to enrich specific gas species up to a factor of 15 while suppressing the formation of others compared to the sand control. Two catalysts, β-zeolite and a naturally occurring metal hydroxide containing mineral, were regenerated and recycled up to five times with no loss of activity.     

Study of the pyrolysis of municipal solid waste for the production of valuable products

To obtain information on the potential of thermal conversion (pyrolysis) of municipal solid waste (MSW), a thermogravimetric study (TGA) is performed in a stream of nitrogen. Based on TGA results, pyrolysis experiments are carried out in a semi-batch reactor under inert nitrogen atmosphere. Slow pyrolysis is performed up to 550 °C (heating rate of 4 °C/min). Fast pyrolysis is performed at 450, 480, 510 and 550 °C and different input transfer rates (12 or 24 g material/min). The pyrolysis products are studied on composition and yield/distribution and investigated for their use as valuable product.The liquid obtained by slow pyrolysis separates spontaneously in a water rich product and an oily product. For all fast pyrolysis conditions, a viscous, brown oil which contains a poly(ethylene-co-propylene) wax is obtained. Composition analyses by GC/MS of the oil products (slow/fast pyrolysis) show that aliphatic hydrocarbons are the major compounds. The pyrolysis oils have high calorific value (between 35 and 44 MJ/kg), low wt% of water (around 6 wt%) and a low O/C value (between 0.2 and 0.3). The presence of waxy material is probably due to incomplete breakdown of poly(ethylene-co-propylene) present in MSW under study. The optimal pyrolysis conditions, regarding to oil yield, fuel properties, and wax yield is fast pyrolysis at 510 °C with 24 g material/min input transfer rate. The fast pyrolysis gases contain mainly hydrocarbons and have an averaged LHV around 20 MJ/Nm³. ICP-AES analyses of pyrolysis products reveal that almost none of the metals present in MSW are distributed within the liquid fractions.     

Producing fuel and specialty chemicals from the slow pyrolysis of poultry DAF skimmings

The production of bio-oil via the slow pyrolysis of dissolved air flotation (DAF) skimmings from poultry processing is described. The raw DAF skimmings were characterized for physicochemical properties and for thermal behavior (TGA). The bio-oil was produced in a batch pyrolysis system at varying temperatures between 400 and 700 °C to study the effect of temperature on product yield. The fatty acids in the bio-oil produced displayed a high degree of saturation that caused the bio-oil to have poor cold flow properties (high cloud point and viscosity) so a solvent extraction scheme was devised to extract a bio-oil fraction rich in unsaturated fatty acids that could be further esterified into a bio-diesel and fatty nitriles that could be further processed into surfactants. This ethyl acetate-soluble fraction demonstrated much improved cold flow properties as well as lower water content and a higher HHV. The esterification of this soluble fraction was performed using methanol and sulfuric acid as an acid catalyst and the formation of fatty acid methyl esters was verified using GC/MS and FT-IR.