Fast pyrolysis of biomass

The development of viable fast pyrolysis processes for biomass and other carbonaceous feedstocks will offer significant advantages over conventional pyrolysis, flash pyrolysis and gasification processes with respect to product yield quality and flexibility. Fast pyrolysis is defined and related to other biomass thermochemical conversion processes in some detail. Brief references are made to corresponding coal, hydrocarbon and oil conversion research and development. Proposed mechanisms and chemical pathways are reviewed, potential products. product upgrading and product applications are identified. Fast pyrolysis research is reviewed on both the fundamental bench-scale level and the applied process development level.     

Microwave pyrolysis of biomass

Because of the inherent moisture and large particle size of wood used in the Forest Products Industry, there has been regional interest in exploring the feasibility of processing wood, cellulose, and other such related materials using microwave dielectric-loss heating. A research project was undertaken in the late 1970’s to determine the important variables altering the rate of microwave-induced reactions of this polymeric material. The research presented dates from that period. Reaction proudcts were measured in detail and some optimization of the coupling of the microwave energy to the large particles was studied. Results and principal findings at the time of the study are presented in this paper as well as two papers by the author in the cited literature. Suggestions for future directions for this type of study are also presented.     

热裂解气相色谱法测定动物源性食品中敌百虫残留量

通过对热裂解气相色谱及气-质联用技术测定动物源性食品中敌百虫的探讨,建立了气相色谱进样口裂解产物的检测方法,并确定了气相色谱的主要分析条件(进样口280℃,DB-225毛细管色谱柱及FPD检测器)。样品前处理结合动物源性食品的特点,采用V(乙腈)∶V(水)=9∶1提取,乙酸锌水解除酯,并利用三氯化碳相转移的方式,建立了一套前处理方法。检测方法的回收率在80.7%~96.5%之间,RSD<5.5%,线性相关系数为0.9991,检出限为0.02mg/kg。该方法是按照我国关于兽药残留分析方法要求建立的,适合进出口及日常动物源性食品中敌百虫残留量的检测。     

Introduction to pyrolysis of biomass

The pyrolytic properties of biomass are controlled by the chemical composition of its major components, namely cellulose, hemicelluloses and lignin and their minor components including extractives and inorganic materials. Pyrolysis of these materials proceeds through a series of complex, concurrent and consecutive reactions and provides a variety of products.Pyrolysis cellulose at lower temperatures below 300° C involves reduction in molecular weight, evolution of water, carbon dioxide and carbon monoxide and formation of char. On heating at higher temperature 300–500° C, the molecule is rapidly depolymerized to anhydroglucose units that further reacts to provide a XXXX pyrolyXXXXA: still higher temperatures, the anhydrosugar compounds undergo fussion, dehydration disproportionation and decarboxylation reaction to provide a mixture of low molecular weight gaseous and volatile produces. The composition of these produces and mechanism and kinetics of their production are reported.     

Determination of ergosterol as an indicator of fungal biomass in various samples using non-discriminating flash pyrolysis

Ergosterol is the major sterol constituent of most fungi. Since it is present in negligible amounts in higher plants, it can be used as a chemical marker for the presence of fungal contamination. A number of different ergosterol assays have been developed for the quantification of fungi in various samples. The paper presents the development of a new method for ergosterol detection based on the combination of non-discriminating flash pyrolysis with gas chromatography/mass spectrometry (Py-GC/MS). The design of the non-discriminating Py-GC/MS systems assures efficient transfer of high-molecular-weight pyrolysis products to the GC column for separation, followed by analyte detection by MS. The method was tested on different types of samples, including baker's yeast (Saccharomyces cerevisiae), moldy bread, indoor dust, and a leaf infected with powdery mildew. Ergosterol was detected in all these samples at levels ranging from approximately 4mg/g for the baker's yeast to approximately 6mug/g for household dust. The main benefits of non-discriminating pyrolysis over other techniques include elimination of the need for sample preparation, small sample size required and short analysis time.     

A pyrolysis/gas chromatographic method for the determination of hydrogen in solid samples

A method is described for the determination of hydrogen in solid samples. The sample is heated under vacuum after which the evolved gases are separated by gas chromatography with a helium ionization detector. The system is calibrated by injecting known amounts of hydrogen, as determined manometrically. The method, which is rapid and reliable, was checked for a variety of lunar soils; the limit of detection is about 10 ng of hydrogen.     

High-temperature gasification kinetics of biomass pyrolysis

The rate of gas formation from wood pyrolysis has been experimentally measured at temperatures from 300°C to 1000°C. The formation rate of specific product gases has been measured rather than the rate of solid weight loss. Even for very fine particles, the rate becomes heat transfer limited a: high temperatures. The product gases also approach thermodynamic equilibrium rapidly at high temperatures. The results are corrected using the experimental residence time distribution.     

Inorganics distribution in bio oils and char produced by biomass fast pyrolysis: The key role of aerosols

Fast pyrolysis of biomass is a promising process for the preparation of bio-oil dedicated to energy production. Inorganic species originally present in biomass are known to induce problems such as bio-oil instability or deposits and fouling. However the mechanisms of inorganic species release during biomass pyrolysis into the raw bio-oils still remain unclear. The present work focuses on the determination of inorganic distribution in the products from wheat straw and beech wood fast pyrolysis performed in a fluidized bed. More specifically, the bio-oils are fractionated by using a series of condensers. The results show that more than 60 wt.% of the inorganic content of the overall bio-oil is contained in the aerosols. Several possible interpretations for this observation are discussed. It is likely that the inorganics are transported within the aerosols droplets and solid particles which are recovered in the bio-oils, either by mechano-chemical processes, or by entrainment of submicron intermediate liquid compound formed in the first steps of biomass fast pyrolysis.     

Comparison of contact and radiant ablative pyrolysis of biomass

Ablation characterizes the phenomena occurring when a solid, submitted to a high external heat flux density, gives rise to solids, liquids and/or gases that can be rapidly and continuously eliminated. Ablation can be exploited for carrying out the fast pyrolysis of materials such as biomass. This paper describes and compares, on a fundamental point of view, two methods of biomass ablative pyrolysis. In the first one, biomass is pressed against a hot surface (contact ablative pyrolysis). In the second one, biomass intercepts a concentrated radiation (radiant ablative pyrolysis). The comparison is made on the basis of the values of ablation thickness and velocity (derived from experiments and modelling), and of product fractions and compositions. The results can be very different in spite of the fact that biomass may be subjected to similar heat flux densities in both cases. The paper shows the advantages, drawbacks and complementarities of each technology.     

Gasification and catalytic conversion of biomass by flash pyrolysis

The influence of the water content, the gasification atmosphere and the action of inorganic catalysts on biomass pyrolysis is discussed. The pyrolysis conditions are characterized by a heating rate of a wood sample of 250–300°C/s and a residence time of the gas in the hot zone of the reactor of less than 1 s. Volumes, carbon contents, weights and energy balances at different temperatures (600–1000°C) are tabulated. The total volume of pyrolysis gas and the yields increase with increasing temperature and water content. This increase is especially due to the production of hydrogen. A large part of the gasified hydrogen comes from water. Water that has not been driven off from green wood is more gasifiable than water that is re-added or from the atmosphere. Three types of catalysts were tested: alumina, aluminosilicate material and nickel-supported catalyst. The results show that it is possible to control the distribution of gas species by controlling the water content of the biomass and selecting the catalyst on which the wood is pyrolysed. A nickel catalyst on mordenite seems to be very efficient in directing pyrolysis gas production towards synthesis gas.     

Chemometric detection of thermally degraded samples in the analysis of drugs of abuse with gas chromatography-Fourier-transform infrared spectroscopy

We present a chemometric procedure for the identification of the reference standard chromatographic peak in cases where the GC-FTIR analysis of commercial standards results in the appearance of more than one peak in the GC chromatogram. The procedure has been designed for phenethylamines, which represent the class with the largest number of individual molecules on the illicit drug market, and which are abused for their stimulant and/or hallucinogenic effects. The similarity between their vapor-phase FTIR spectra was modeled using principal component analysis (PCA), and class identity was assigned on the basis of soft independent modeling of class analogy (SIMCA). Additional peaks could be assigned to impurities in the standards, but most often they were artifacts formed during the GC-FTIR analysis of thermolabile or chemically unstable compounds. The latter case is illustrated by the identification of the reference standard chromatographic peak and FTIR spectrum of the potent psychotropic amphetamine derivative N-methyl-1-(3,4-methylenedioxyphenyl)-2-butanamine (MBDB), and by the elucidation of the chemical changes that occur in the molecule of MBDB due to thermal degradation.     

High temperature pyrolysis of novolac resin biomass composites

Composites of novolac resin (N.R.) and biomass derived from olive stones (OL.B.), in various proportions, were cured with hexamethylenetetramine (HTA) and pyrolyzed up to 900°C. The pyrolysis mechanism was monitored using TGA and gas chromatography. The pyrolysis regions, as well as important pyrolysis parameters of the materials used, were determined. Cured and pyrolyzed composites of N.R./OL.B. varied from 20/80 to 75/25, exhibiting at temperatures up to approx. 600°C lower weight losses than expected by the rule of mixtures, owing to additional cross linkages of lignin with HTA. This stabilization effect vanished during pyrolysis at higher temperatures because of the breaking of other chemical bonds, e.g. cross linkages. The release of CH₄ during the pyrolysis of OL.B. is derived from the lignin contained in OL.B. The other gases, CO, CO₂ and H₂, could be formed from celluose, hemicellulose and lignin which are the main components of OL.B. The use of N.R. in the initial mixture with OL.B. reduces the weight losses during pyrolysis compared with OL.B. alone. A heating rate of 10°C/min was necessary for the carbonization processes of OL.B. and its mixtures with N.R. in order to promote minimum weight loss of material and minimum pyrolysis time.     

Relevance of analytical pyrolysis studies to biomass conversion

The principles and methods of soft ionization mass spectrometry in combination with pyrolysis of macromolecules are outlined. Essential features of the newly developed techniques are the extension of the recorded mass range and the almost exclusive formation of molecular ions of the pyrolyzates. Using field ionization and field desorption mass spectrometry at low and high mass resolution, with electrical and photographic detection, pyrolysis products of biomass were analyzed for the first time. The results of flash pyrolysis by Curie-point heating and thermally programmed degradation of biopolymers are compared.The main topic is the evaluation of the methodology for time- and temperature-resolved pyrolysis. The thermograms and pyrolysis mass spectra obtained enable the study of pyrolysis reactions and the chemical fingerprinting of complex biological matter. The kinetics for the devolatilization of individual chemical species or classes of compounds can be monitored. Curie-point pyrolysis of biopolymers such as kappa-carrageenan and time-programmed degradation of cellulose and lignin are reported. Furthermore, preliminary investigations of pine wood and coal illustrate the potential of the introduced methods.     

两种食用菌菌糠的化学成分分析及热解液化研究

目前,由于煤、石油和天然气等不可再生的化石资源日益枯竭,将可再生的生物质资源转化为能源和化学品受到越来越多的关注[1],其中,热解液化作为独立的热化学转化技术在近年得到了很好的发展[2].     

High resolution gas phase chromatography-mass spectrometry of polychlorinated biphenyl congener residues in samples of biologic origin

A study is performed on polychlorinated biphenyl (PCB) congener residues in samples of human blood and milk as well as in falcon and pigeon eggs. Most of the PCB congeners found in these biological samples were quantified by high-resolution gas chromatography (HRGC). A PCB technical mixture--namely, DP6 (Phenochlor)--was used for the calibration as its composition was previously determined by HRGC-mass spectrometry. The usefulness of such a congener analysis is outlined. It is the first time to the best of our knowledge that a Phenochlor mixture is used for standardization.     

NOx and N2O precursors from biomass pyrolysis

Chlorine content in agricultural straw is high, and HCl formation during straw combustion is a challenging problem. The relationship between HCl and the formation of NO_x and N₂O is important and unclear. Effect of HCl in atmosphere on nitrogen transfer during wheat straw and cotton stalk pyrolysis was performed using a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer. Pyrolysis of polyvinyl chloride supplies HCl. The pathway of nitrogen transfer in the presence of HCl was studied. The results show that in the presence of HCl, the temperature corresponding to NH₃ starting release during wheat straw pyrolysis increases, and those of HCN and HNCO reduce. HCl inhibits the conversion of straw–N into NH₃, however, favors the transformation of straw nitrogen into HCN and HNCO.     

Calculation of kinetic parameters and sequence distribution from pyrolysis gas chromatographic data of styrene-methyl acrylate copolymers

Styrene-methyl acrylate copolymers have been investigated by pyrolysis gas chromatography. The pyrolysis product distribution, ranging from methyl acrylate monomer to styrene trimer, was measured and introduced into a mathematical model described previously. Applying this model, the sequence distribution and the rate constants of the degradation reactions were obtained. The results show that the sequential arrangement is important in the thermal decomposition of styrene-methyl acrylate copolymers. In most cases the rate constant of a product release reaction depends considerably on the nature and sequence of the monomer units in the product molecule, as well as on the nature of the monomer unit remaining on the macroradical end, from which the molecule was released.     

Devolatilization behaviour and pyrolysis kinetic modelling of Spanish biomass fuels

The basic pyrolysis behaviour of eight different biomass fuels has been tested in a thermogravimetric analyser under dynamic conditions (5, 20 and 50 °C min^?1 heating rates) from room temperature up to 1,000 °C. Their decomposition was successfully modelled by three first-order independent parallel reactions, describing the degradation of hemicellulose, cellulose and lignin. Hemicellulose would be the easiest one to pyrolyse, while lignin would be the most difficult one. Experimental and calculated results show good agreement. The reactivity of the different biomass type functions of various thermal, kinetic and composition parameters are discussed. The effect of the heating rate on pyrolysis behaviour was studied, and a comparison between slow and fast heating rate reveals a small displacement of the DTG profiles to higher temperatures. The heating rate not only affects the highest mass loss rate temperature but also influences the mass loss rate value.