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.     

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.     

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.     

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.     

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。     

Kinetic analyses of biomass pyrolysis using the distributed activation energy model

The pyrolysis behaviors of several agricultural residues have been investigated by using thermogravimetric analysis. The evolving rates of the gaseous products during the pyrolysis such as H₂, CH₄, H₂O, CO and CO₂ were also measured by the TG-MS techniques. Without any assumption and mathematical fitting, we could obtain the very proper kinetic parameters (the distribution curve of activation energy, f(E), and the activation energy dependent frequency factor, k₀(E)) of biomass pyrolysis by utilizing the distributed activation energy model (DAEM) proposed by Miura and Maki [Miura K, Maki T. Energ Fuel 1998;12:864]. The peaks of f(E) curve for rice straw, rice husk, corncob and cellulose were found to be 170, 174, 183, and 185 kJ/mol, respectively. The k₀ value increased from an order of 10¹¹ to an order of 10¹⁸ s⁻¹, while E increased from 120 to 250 kJ/mol. The catalytic effects of alkali and alkaline earth metals during the pyrolysis play a major role in the variation of f(E) curve among the different biomass species.     

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.     

Kinetic study of Chinese biomass slow pyrolysis: Comparison of different kinetic models

The slow pyrolysis of six Chinese biomasses was studied by thermogravimetric experiments. Non-linear square fitting method is used to calculate DTG data. The analysis results show that it is not possible to exactly represent the biomass pyrolysis by a one-step model with different mechanisms. Thus, three-pseudocomponent models were used to simulate the biomass pyrolysis. It was found that the three-pseudocomponent model with n-order kinetics (model II) is more accurate than the model with first-order kinetics (model I). Activation energies of three-pseudocomponents in model II are bigger than the values in model I. It is shown that model II yields the best simulation results, especially with respect to describe accurately the pyrolysis of the first pseudocomponent (hemicellulose) and the last one (lignin). Nevertheless, with regard to a practical utilization, the three-pseudocomponent model with a reaction order of one could be used, because the accuracy to represent biomass pyrolysis is high enough. Unrealistic high values of the reaction order are avoided, and thus this model is more realistic with respect to the chemical interpretation of the reaction order.     

Simultaneous catalytic esterification of carboxylic acids and acetalisation of aldehydes in a fast pyrolysis bio-oil from mallee biomass

This paper reports the simultaneous catalytic esterification and acetalisation of a bio-oil with methanol using a commercial Amberlyst-70 catalyst at temperatures between 70 and 170 °C. The bio-oil was prepared from the pyrolysis of mallee woody biomass in a fluidised-bed pyrolysis reactor under the fast heating rate conditions. Our results show that the conversion of light organic acids and aldehydes to esters and acetals rises significantly with increasing temperature, reaction time and catalysts loading. However, some acetals (e.g. dimethoxymethane) could decompose at higher operating temperatures (>110 °C) and catalyst loadings (>6 wt.%). The medium and heavy fractions of bio-oil also reacted with methanol to result in increases in their volatility (or decreases in boiling points) when their reactive O-containing functional groups were stabilised. The acid-catalysed reactions between bio-oil and methanol also decreased the coking propensity of the bio-oil reaction products.     

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.     

Catalytic pyrolysis of biomass for biofuels production

Fast pyrolysis bio-oils currently produced in demonstration and semi-commercial plants have potential as a fuel for stationary power production using boilers or turbines but they require significant modification to become an acceptable transportation fuel. Catalytic upgrading of pyrolysis vapors using zeolites is a potentially promising method for removing oxygen from organic compounds and converting them to hydrocarbons. This work evaluated a set of commercial and laboratory-synthesized catalysts for their hydrocarbon production performance via the pyrolysis/catalytic cracking route. Three types of biomass feedstocks; cellulose, lignin, and wood were pyrolyzed (batch experiments) in quartz boats in physical contact with the catalysts at temperature ranging from 400 °C to 600 °C and catalyst-to-biomass ratios of 5-10 by weight. Molecular-beam mass spectrometry (MBMS) was used to analyze the product vapor and gas composition. The highest yield of hydrocarbons (approximately 16 wt.%, including 3.5 wt.% of toluene) was achieved using nickel, cobalt, iron, and gallium-substituted ZSM-5. Tests performed using a semi-continuous flow reactor allowed us to observe the change in the composition of the volatiles produced by the pyrolysis/catalytic vapor cracking reactions as a function of the catalyst time-on-stream. The deoxygenation activity decreased with time because of coke deposits formed on the catalyst.     

Structural evolution of chars from biomass components pyrolysis in a xenon lamp radiation reactor

The structural evolution of the chars from pyrolysis of biomass components(cellulose, hemicellulose and lignin)in a xenon lamp radiation reactor was investigated. The elemental composition analysis showed that the C content increased at the expense of H and O contents during the chars formation. The values of ΔH/C/ΔO/Cfor the formation of cellulose and hemicellulose chars were close to 2, indicating that dehydration was the dominant reaction. Meanwhile, the value was more than 3 for lignin char formation, suggesting that the occurrence of demethoxylation was prevalent. FTIR and XRD analyses further disclosed that the cellulose pyrolysis needed to break down the stable crystal structure prior to the severe depolymerization. As for hemicellulose and lignin pyrolysis, the weak branches and linkages decomposed firstly, followed by the major decomposition. After the devolatilization at the main pyrolysis stage, the three components encountered a slow carbonization process to form condensed aromatic chars. The SEM results showed that the three components underwent different devolatilization behaviors, which induced various surface morphologies of the chars.     

Production and characterization of bio-oil and biochar from ablative pyrolysis of lignocellulosic biomass residues

Abstract

Agricultural residues are one of the large untapped sources of bio-energy in Thailand, with over 30 million tons available per year. They may be utilized to generate renewable liquid and solid fuels. In this work, pyrolysis of lignocellulosic biomass residues (corncobs, coconut shells, and bamboo residue) was carried out in an ablative pyrolysis reactor with rotating blades. Influences of inert carrier gas flows (5–15?L/min) and rotating frequency (4–8?Hz) at a fixed hot plate temperature of 500?°C on generating bio-oil were investigated. Characterization of bio-oil as well as biochar products was performed. Maximum bio-oil yield was found to be about 50% w/w for coconut shell at 5?L/min of flowrate and 8?Hz of the rotating frequency, and 45% w/w for bamboo residues at the same condition. For corncob, the highest bio-oil yield was 72% w/w at 5?L/min of flowrate and 6?Hz of the rotating frequency. Solid char yields were around 23–28% w/w. The heating values of the liquid oil and solid char were about 20–25 and 23–30?MJ/kg, respectively. Rotating blade ablative reactor was able to generate high yields of bio-oil for agricultural residues. The main compounds of the bio-oil obtained were phenolics, including furfuran, organic acids, aldehydes, alcohols, ethers, and ketones.     

Prediction of pyrolysis kinetic parameters from biomass constituents based on simplex-lattice mixture design

The aim of this study is to determine the effect of the main chemical components of biomass:cel ulose, hemicel-lulose and lignin, on chemical kinetics of biomass pyrolysis. The experiments were designed based on a simplex-lattice mixture design. The pyrolysis was observed by using a thermogravimetric analyzer. The curves obtained from the employed analytical method fit the experimental data (R2 N 0.9). This indicated that this method has the potential to determine the kinetic parameters such as the activation energy (Ea), frequency factor (A) and re-action order (n) for each point of the experimental design. The results obtained from the simplex-lattice mixture design indicated that cellulose had a significant effect on Ea and A, and the interaction between cellulose and lignin had an important effect on the reaction order, n. The proposed models were then proved to be useful for predicting pyrolysis behavior in real biomass and so could be used as a simple approximation for predicting the overall trend of chemical reaction kinetics.     

Modelling intra-particle phenomena of biomass pyrolysis

The characteristic times of the main intra particle phenomena of wood pyrolysis are discussed to develop a new model of biomass pyrolysis. The model accounts for a simplified multi-step chemical decomposition with the formation of tars at liquid phase inside the particle. The tars at liquid phase are then competitively converted into a secondary char and gases and evaporated following a Clausius–Clapeyron law. To our knowledge, a tar evaporation law had so far never been coupled with cellulose pyrolysis kinetics. The convective mass transport of all the volatile species through the porous particle is modelled by a Darcy's law. This model offers a first approach to simulate the tar (at liquid phase) life time and its intra-particle conversion. The Clausius–Clapeyron evaporation parameters are reviewed and modified if levoglucosan or cellobiosan are supposed as the main tar compounds at liquid phase. The effects of these parameters on cellulose pyrolysis mass loss rate are modelled and discussed. Mass transfer limitations can lead to a high intra-particle over-pressure and can control the life time of tar at liquid phase and the subsequent “secondary” char formation from the liquid tar conversion.     

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 unified lumped approach in kinetic modeling of biomass pyrolysis

Thermogravimetry analysis and gas chromatography techniques are used at different heating rates (from 5 to 50 K/min) to map all the products and to develop suitable kinetic models of biomass pyrolysis. A three-independent-parallel-reactions model is used to model kinetic of total devolatilization. This part accounts for the total char yield and devolatilization time. The evolutions of condensable vapors (tar and H₂O) and non-condensable gases (H₂, CH₄, CO and CO₂) are also studied using gas chromatography technique. It is shown that the final total yield of gases increases by increasing the heating rate, whereas those of tar decrease by increasing heating rate. A kinetic model was then proposed and the parameters for that were calculated, which can predict the change of the gases yields at different heating rates. The performance of the kinetic models was evaluated for other experimental works available in the literature or by exposing the biomass to different heating program.     

The influence of temperature on the yields of compounds existing in bio-oils obtained from biomass samples via pyrolysis

The influence of temperature on the compounds existing in liquid products obtained from biomass samples via pyrolysis were examined in relation to the yield and composition of the product bio-oils. The product liquids were analysed by a gas chromatography mass spectrometry combined system. The bio-oils were composed of a range of cyclopentanone, methoxyphenol, acetic acid, methanol, acetone, furfural, phenol, formic acid, levoglucosan, guaiacol and their alkylated phenol derivatives. Thermal depolymerization and decomposition of biomass structural components, such as cellulose, hemicelluloses, lignin form liquids and gas products as well as a solid residue of charcoal. The structural components of the biomass samples mainly affect the pyrolytic degradation products. A reaction mechanism is proposed which describes a possible reaction route for the formation of the characteristic compounds found in the oils. The supercritical water extraction and liquefaction partial reactions also occur during the pyrolysis. Acetic acid is formed in the thermal decomposition of all three main components of biomass. In the pyrolysis reactions of biomass: water is formed by dehydration; acetic acid comes from the elimination of acetyl groups originally linked to the xylose unit; furfural is formed by dehydration of the xylose unit; formic acid proceeds from carboxylic groups of uronic acid; and methanol arises from methoxyl groups of uronic acid     

Kinetics of pyrolysis,combustion and gasification of three biomass fuels

The paper compares the microstructural properties and the intrinsic reactivity of pine seed shells, olive husk and wood chips upon pyrolysis, combustion and gasification (with CO₂ and H₂O). Such biomasses, all of interest in energy production, are quite different from one another in terms of O/C and H/C content, of porosimetric structure and of ash content.