Effects of particle size on the fast pyrolysis of oil mallee woody biomass

This study aims to investigate the effects of biomass particle size (0.18-5.6 mm) on the yield and composition of bio-oil from the pyrolysis of Australian oil mallee woody biomass in a fluidised-bed reactor at 500 °C. The yield of bio-oil decreased as the average biomass particle size was increased from 0.3 to about 1.5 mm. Further increases in biomass particle size did not result in any further decreases in the bio-oil yield. These results are mainly due to the impact of particle size in the production of lignin-derived compounds. Possible inter-particle interactions between bio-oil vapour and char particles or homogeneous reactions in vapour phases were not responsible for the decreases in the bio-oil yield. The bio-oil samples were characterised with thermogravimetric analysis, UV-fluorescence spectroscopy, Karl-Fischer titration as well as precipitation in cold water. It was found that the yields of light bio-oil fractions increased and those of heavy bio-oil fractions decreased with increasing biomass particle size. The formation of pyrolytic water at low temperatures (<500 °C) is not greatly affected by temperature or particle size. It is believed that decreased heating rates experienced by large particles are a major factor responsible for the lower bio-oil yields from large particles and for the changes in the overall composition of resulting oils. Changes in biomass cell structure during grinding may also influence the yield and composition of bio-oil.     

Bio-coke from upgrading of pyrolysis bio-oil for co-firing

Bio-cokes were formed by upgrading pyrolysis oils from wheat spent grain and rapeseed meal biomasses using a thermo-t vis-breaking technology. The bio-cokes presented moisture levels below 2 wt.%, were virtually ash-free and had very low oxygen contents in the range of 10–14 wt.%. Their calorific values were in the range of 29–37 MJ/kg comparable to that of bituminous coal. About 15–25 wt.% of the original biomass on dry ash-free basis was converted into the ash-free bio-coke and about 20–40% of the heating value of the original biomass was retained in the bio-coke. From TGA analysis it was found that the fuel properties of the bio-coke from wheat spent grain were comparable to those of coal, where blends of up to 50 wt.% of WSG bio-coke with coal showed virtually similar oxidation behaviour to that of coal. This work shows that low-density biomass can be transformed into high density bio-coke that can logistically be treated like coal and indicates that co-firing with bio-coke can easily exceed current levels in the future.     

复合微波吸收剂辅助生物质裂解制取生物油研究

针对传统生物质微波热解体系单纯追求升温快而引起部分热点负效应,导致挥发分发生二次裂解的现象,使用复合微波吸收材料辅助生物质微波裂解制取生物油,并比较不同复合微波吸收材料的升温曲线及其对热解产物分布和生物油组成的影响。结果表明,复合微波吸收材料的加入能够改变生物质的微波升温行为,其中SiC/Fe3O4具有较高的炭化温度,保留了更多的中间产物。当SiC和Fe3O4以8∶2的比例混合、热解温度为650℃、加热功率为600 W的条件下,得到的生物油收率高达46.8%,而且生物油中呋喃类、醚类、酮类含量显著提升。     

Steam gasification reactivity of char from rapid pyrolysis of bio-oil/char slurry

A slurry of bio-oil and char originating from wood pyrolysis is a promising gasifier feed-stock because of its high energy density. When such a slurry is injected into a high temperature gasifier it undergoes a rapid pyrolysis yielding a char which then reacts with steam. The char produced by pyrolysis of an 80 wt% bio-oil/20 wt% char mixture at heating rates of 100-10,000 °C/s was subjected to steam gasification in a thermogravimetric analyzer. The original wood char from the bio-oil production was also tested. Gasification was conducted with 10-50 mol% steam at temperatures from 800 to 1200 °C. Reactivity of the slurry chars increased with pyrolysis heating rate, but was lower than that of the original chars. Kinetic parameters were established for a power-law rate model of the steam-char reaction, and compared to values from the literature. At temperatures over 1000 °C, the gasification rates appeared to be affected by diffusional resistance.     

Production of bio-oil from fixed bed pyrolysis of bagasse

The objective of this work was to produce renewable liquid fuel (bio-oil) from locally produced bagasse by pyrolysis in a batch feeding and fixed bed reactor. The experiments were performed at different temperatures ranging from 300 to 600 °C. The bio-oil was collected from two condensers of different temperatures and defined as oil-1 and oil-2. The maximum total yield of bio-oil was found to be 66.0 wt% based on bagasse. The carbon based non-condensable gases were CO, CO₂, methane, ethane, ethene, propane and propene. The density and viscosity of oil-1 were found to be 1130 kg/m³ and 19.32 centipoise and that were 1050 kg/m³ and 4.25 centipoise for oil-2, respectively. The higher heating values (HHV) of them were 17.25 and 19.91 MJ/kg, respectively. The pH of the bio-oils was found to be around 3.5 and 4.5 for oil-1 and oil-2, respectively. The water, solid and ash contents of oil-1 and oil-2 were determined and found to be around 15, 0.02 and 0.03 wt% and 11, 0.01 and 0.02 wt%, respectively based on bagasse.     

木块微波裂解及产物组成分析

使用2 450 MHz/12 kW微波裂解装置裂解木块并对不同裂解条件下气、液产物进行了分析.结果表明,木块微波裂解生成了极具价值的生物油、合成气等产品;裂解功率对液体产品收率及主要组分的种类产生影响;裂解温度对液态产品各组分相对含量及气态产品的成分构成产生影响.     

Devolatilization in the temperature range 300-600 K of liquids derived from wood pyrolysis and gasification

A thermogravimetric system, previously developed for solid fuel degradation, has been modified to examine liquids obtained from conventional pyrolysis and updraft gasification of beech wood. Thermogravimetric curves in air show two main reaction stages. The first (temperatures ≤600 K) concerns evaporation, formation and release of gases and formation of secondary char (coke). Then, at higher temperatures, heterogeneous combustion of secondary char takes place. A reliable procedure has been developed to carry out the first stage under assigned temperature using a PID controller and the applied heat flux as the manipulated variable. It has been found that the pyrolysis temperature does not affect significantly weight loss dynamics and amount of secondary char (approximately equal to 20% of the liquid on a dry basis). The thermogravimetric curves are well predicted by a global mechanism consisting of three parallel first-order reactions (activation energies of 66, 32 and 36 kJ/mol, respectively). Due to strong physico-chemical transformations (sample swelling and solidification) associated with secondary char formation, it is not possible to avoid ignition during heterogeneous combustion. Therefore, this reaction stage should be investigated separately after collection and adequate re-preparation of the charred sample.     

Catalytic pyrolysis of biomass in inert and steam atmospheres

The objective of this study was to investigate thermal conversion of a perennial shrub, Euphorbia rigida biomass sample with catalyst in inert (N₂) and steam atmospheres. Experimental studies were conducted in a well swept fixed bed reactor with a heating rate of 7 °C/min to a final pyrolysis temperature of 550 °C and with a mean particle size of 0.55 mm in order to determine the effect of different atmospheres with various catalyst ratios on pyrolysis yields and characteristics. The catalyst ratios were 5%, 10% and 20% (w/w) under nitrogen atmosphere with flow rates of 50, 100, 200 and 400 cm³/min and steam atmosphere with well-swept velocities of 12, 25 and 52 cm³/min. The optimum oil yield was obtained as 32.1% at the nitrogen flow rate of 200 cm³/min, while it was obtained as 38.6% at steam flow rate of 25 cm³/min when a 10% catalyst by weight according to the biomass was used. Higher oil yields were observed when biomass sample was treated in steam atmosphere than in inert (N₂) atmosphere. The oil composition was then analysed by elemental analyses techniques such as IR and GC-MS. The oil products were also fractionated by column chromatography. The bio-oils obtained at both atmospheres contain mainly n-alkanes and alkenes, aromatic compounds; mainly benzene and derivatives and PAHs, nitrogenated compounds and ketones, carboxylic acids, aldehydes, phenols and triterpenoid compounds. More oxygenated compounds and less substituted alkanes and alkenes were obtained in catalytic pyrolysis of E. rigida in the steam atmosphere. The experimental and chemical characterisation results showed that the oil obtained from perennial shrub, E. rigida can be used as a potential source of renewable fuel and chemical feedstock.     

Hydrogen from biomass-production by steam reforming of biomass pyrolysis oil

Thermo-conversion of biomass is one of the leading near-term options for renewable production of hydrogen and has the potential to provide a significant fraction of transportation fuel required in the future. We propose a two-step process that starts with fast pyrolysis of biomass, which generates high yields of a liquid product, bio-oil, followed by catalytic steam reforming of bio-oil to produce hydrogen. A major advantage of such a concept results from the fact that bio-oil is much easier and less expensive to transport than either biomass or hydrogen. Therefore, the processing of biomass and the production of hydrogen can be performed at separate locations, optimized with respect to feedstock supply and to hydrogen distribution infrastructure. This approach makes the process very well suited for both centralized and distributed hydrogen production. This work demonstrates reforming of bio-oil in a bench-scale fluidized bed system and provides hydrogen yields obtained using several commercial and custom-made catalysts.     

Production and fuel properties of fast pyrolysis oil/bio-diesel blends

This paper describes the production and fuel properties of fast pyrolysis oil/bio-diesel blends. The bio-oils used in this study were produced from the fast pyrolysis of woody biomasses, oil mallee and pine. The bio-diesel employed was derived from canola vegetable oil. The conditions used to prepare the bio-oil/bio-diesel blends, as well as some of the fuel properties of the resulting bio-diesel rich phase, are reported. The experimental results show that the solubility of fast pyrolysis oils in bio-diesel is not as high as was previously reported for decanted oils obtained by Auger pyrolysis. The carboxylic acids, mono-phenols, furans and lignin derived oligomers were the compounds most soluble in bio-diesel, while the sugars, on the other hand, showed poor solubility. Although the presence of phenols enhances the oxidation stability of the bio-diesel rich phases, other fuel properties deteriorate. For example, the content of solid residues increased primarily because of the solubilisation of lignin derived oligomers, which were quantified by UV-fluorescence. Concentrations as high as 3.5 mass % of these compounds were observed in the bio-diesel rich phase. The solubility of bio-oil in bio-diesel was enhanced by using ethyl acetate/bio-diesel blends. Some fuel properties of the bio-diesel rich phase, after the removal of ethyl acetate, are reported.     

生物质热解研究进展

当今社会面临着能源短缺和环境破坏日益严重等问题,生物质能源作为可再生绿色能源,大量开发利用对于工业和社会生活中具有重要的意义。生物质热解技术是将生物质转化成生物质能的有效可行方法之一。为实现生物质能源工业化、规模化生产,必须要完善热解反应技术及其核心热解反应器装置。在分析了生物质热解机理的基础上,着重介绍了热解反应器的类型以及其特点。     

An FT-IR spectroscopic study of carbonyl functionalities in bio-oils

Pyrolysis bio-oil contains abundant O-containing structures. Carbonyls are particularly important not only because they are abundant and exist in many forms (e.g. as acids, esters, ketones and aldehydes) but also because they are reactive and are a key consideration of bio-oil upgrading. This study aims to investigate the distribution of carbonyl groups in a variety of bio-oil samples prepared from the pyrolysis of mallee wood, bark and leaves in a fluidised-bed reactor. Some bio-oil samples also underwent esterification reactions with methanol in the presence of solid Amberlyst acid catalyst. The bio-oil samples were diluted with isopropanol prior to the acquisition of FT-IR spectra using a CaF₂ liquid cell. The FT-IR spectra of bio-oils in the range of 1490–1850 cm⁻¹ were deconvoluted with 9 Gaussian bands. Our results reveal that the bio-oils from the pyrolysis of wood, bark and leaves of the same mallee tree species had very different concentrations and types of carbonyls, which are related to the contents of hemicellulose, cellulose, lignin and extractives in the wood, bark and leaves. Our study also reveals that the carbonyls in the light and heavy fractions of a bio-oil may react differently during the reactions of bio-oil with methanol in the presence of the Amberlyst solid acid catalyst.     

Energy-dense liquid fuel intermediates by pyrolysis of guayule (Parthenium argentatum) shrub and bagasse

Guayule is a perennial shrub grown in the southwestern United States that is used to produce high quality, natural rubber latex. However, only about 10% of the plant material is used for latex production; the remaining biomass, called bagasse, can be used for renewable fuel production. Fast pyrolysis of guayule, both whole shrub and bagasse was performed. From both feedstocks a very viscous, high energy content (∼30 MJ/kg) pyrolysis liquid (bio-oil) was produced in yields averaging over 60% without any catalyst. The properties and compositions of the bio-oils were found to be similar in the two feedstocks. Co-products, charcoal (20-30 wt%) and non-condensable gas (5-15%), were also dense and had a high energy content. Of the two feedstocks, the whole shrub yielded higher quantities of charcoal that also had a higher energy content than the charcoal produced from bagasse. As a result, the energy recovery, estimated as the percentage of the energy products, to energy input into the reactor was lower (60%) for guayule bagasse than for the whole shrub (73%). This notwithstanding, the bagasse is a more attractive feedstock for thermochemical conversion, not only because it is a residue from a primary process (latex extraction) that is on-site, but also because it has a high energy content. Moreover, it produces high quality pyrolysis products. Co-production of latex rubber from the whole shrub and renewable fuels from the residual bagasse by pyrolysis should improve the already positive economics of the guayule latex rubber industry.     

生物质热解特性研究

以竹材、稻壳、木屑为原料,通过常规热解结合快速热解研究生物质热解特性。结果表明,生物质常规热解的液体得率较低,相比而言竹材最高,稻壳最低,且热解温度是影响竹材和木屑热解的主要因素,其液体得率随温度的升高呈先增后减的变化规律;快速热解方面,利用居里点裂解仪和GC—MS在线分析竹材热解的液相组成,其组成以糠醛和酚类物质为主,它们分别来源于纤维素、半纤维素和木质素的热解。     

Modeling the combined impact of moisture and char shrinkage on the pyrolysis of a biomass particle

A detailed computational model of pyrolysis of a moist, shrinking biomass particle is presented. This model is used to examine the effect of varying the moisture content for a single shrinking biomass particle subjected to a constant external temperature. Particle half-thicknesses ranging from 5 μm to 2 cm, temperatures from 800 to 2000 K, moisture contents from 0 to 30% (dry basis), and shrinkage factors from 1.0 to 0.4 are examined. The impact of moisture content and shrinkage was found to be a function of pyrolysis regime. In general, coupling between moisture content and shrinkage was found to result in longer pyrolysis times than if they were considered separately. Additionally, coupling between moisture content and shrinkage increased tar yield and decreased light hydrocarbon yield compared to considering moisture and shrinkage separately.     

A novel test method for catalysts in the treatment of biomass pyrolysis oil

A novel microscale test method was developed for testing catalysts. A pyrolyser connected to a gas chromatograph was used for pyrolysing the biomass sample and for leading the pyrolysis vapours through the catalyst for instant analysis. The injection port of the gas chromatograph was used as a fixed-bed catalyst reactor. Detection of reaction products was carried out with an atomic emission detector to quantify the various elements or with a mass selective detector to identify the compounds.

The test method was applied to treating pyrolysis vapours of Scots pine sawdust with ZnO, MgO, dolomite and limestone. Mass balances for carbon and hydrogen were determined with and without the catalyst. The carbon yields in liquid fraction decreased with all the catalysts studied. The highest yields were obtained with ZnO. Product distribution in pyrolysis vapours was rather similar with ZnO or without any catalyst. With MgO, dolomite and limestone, the compounds of pyrolysis vapours comprised mainly gases, water and degradation products of polysaccharides as well as some aromatic hydrocarbons.     

Characterization of a lab-scale platinum filament pyrolyzer for studying the fast devolatilization of solid fuels

Platinum filament pyrolyzers achieve very high temperature and heating rate and can provide useful parameters for practical applications in combustion, pyrolysis and gasification processes. The critical use of an experimental instrument is necessary to provide reliable data. In this work, a commercial pyrolyzer (CDS Pyroprobe 2000) is characterized to obtain a correspondence between the nominal and the effective operating conditions. This is the basis for the modeling estimation of the effective thermal history of the sample during each experimental run. The experimental results obtained performing the devolatilization of coals, biomass and waste fuels using the pyrolyzer are compared with those obtained in a conventional thermogravimetric balance, to evaluate the effects of extremely different operating conditions. The amount of volatile released programming the most severe thermal conditions using the pyrolyzer (thus in conditions more similar to large-scale plants) differs significantly from that of thermogravimetric runs. Global kinetics are obtained fitting the experimental results and using the thermal history of the sample from the model results. They depend strongly on the conditions used for the devolatilization. Global kinetics obtained in the thermogravimetric balance runs (low heating rate) overestimate the rate of devolatilization in the pyrolyzer (high heating rate).