Fast Pyrolysis Conditions Research Articles

Measuring biomass fast pyrolysis kinetics: State of the art

Fast pyrolysis of lignocellulosic biomass is considered to be a promising thermochemical route for the production of drop‐in fuels and valuable chemicals. During the past decades, a comprehensive understanding of feedstock structure, fast pyrolysis kinetics, product distribution, and transport effects that govern the process has allowed to design better pyrolysis reactors and/or catalysts. A variety of lignocellulosic biomass feedstocks, like corn stover, pinewood, poplar, and model compounds like glucose, xylan, monolignols have been utilized to study the thermal decomposition at or close to fast pyrolysis conditions. Significant progress has been made in understanding the kinetics by developing unique setups such as drop‐tube, PHASR, and micropyrolyzer reactors in combination with the use of advanced analytical techniques such as comprehensive gas and liquid chromatography (GC, LC) with time‐of‐flight mass spectrometer (TOF‐MS). This has led to initial intrinsic kinetic models for biomass and its main components, namely cellulose, hemicellulose, and lignin, validated using experimental setups where the effects of heat and mass transfer on the performance of the process, expressed using Biot and pyrolysis numbers, are adequately negligible. Yet, not all aspects of fast pyrolysis kinetics of biomass components are equally well understood. The use of time‐resolved or multiplexed experimental techniques can further improve our understanding of reaction intermediates and their corresponding kinetic mechanisms. The novel experimental data combined with first principles based multiscale models can reshape biomass pyrolysis models and transform biomass fast pyrolysis to a more selective and energy efficient process.This article is categorized under: Energy and Climate > Climate and Environment Energy Research & Innovation > Science and Materials Bioenergy > Science and Materials

Modelling and improvement of heat transfer coefficient in auger type reactors for fast pyrolysis application

Simulations of auger type reactors are conducted with the aim of assessing the rate of heat transfer between heat carrier and biomass particles to achieve fast pyrolysis conditions. It is shown that the heat transfer coefficient can be comparably high as in fluidized bed reactors due to the dense packing of particles that is kept by mechanical agitation under certain conditions. This holds specifically true if the system is designed such that heat dissipation through the packed bed is avoided.An auger reactor design featuring twin screws that is under operation in pilot scale since several years at KIT has been investigated in more detail. Inefficiencies in the initial mixing section have been identified that lead to the fact that most of the heat is transferred under suboptimal conditions. By investigating three design changes by simulation some of these inefficiencies could be removed and the relevant initial mean heat transfer coefficient increased significantly as compared to the original design. Additionally, this changed design has further potential for process intensification due to a decrease in the mean residence time of biomass particles in the reactor by 50%.

High-grade activated carbon from pyrolytic biochar of Jatropha and Karanja oil seed cakes—Indian biodiesel industry wastes

Most of the commercially available pyrolysis plants use fluidized bed technologies where bio-oil is the major product and the biochar produced is combusted for process heat. However, auger-based technologies are now gaining importance because of their small to medium scale of operation and decentralized nature where biochar is obtained as a by-product. One of the factors which may greatly influence the techno-economic viability of such decentralized plants is making high-grade carbon from pyrolytic biochar. In the present study, Jatropha and Karanja oil seed cake-based biochar is obtained as a by-product in a pilot-scale (20 kg/h) direct gas-fired auger pyrolysis process at 500 °C under fast pyrolysis conditions that is originally aimed at maximizing the bio-oil yield. The biochar has low surface area and porosity. To value add to this carbon, downstream physical and chemical activation are carried out in an externally heated laboratory-scale reactor. CO2 activation resulted in the formation of activated carbon with BET surface area up to ~ 200 m2/g with marginal improvement in porosity, while K2CO3 activation enhanced the surface area to as high as 2400 m2/g along with substantial enhancement of porosity.

Application of Py-GC/MS coupled with PARAFAC2 and PLS-DA to study fast pyrolysis of genetically engineered poplars

Field-grown genetically engineered and wild-type poplars were pyrolyzed in a micro-pyrolysis (Py-GC/MS) setup under fast pyrolysis conditions. Poplars (Populus tremula x P. alba) down-regulated for cinnamoyl-CoA reductase (CCR), which catalyzes the first step of the monolignol-specific branch of the phenylpropanoid biosynthetic pathway, were grown in field trials in France and harvested after a full rotation of 2 years. The effect of small compositional differences, specifically small shifts in lignin composition and their impact on the bio-oil composition, could not be identified using principal component analysis (PCA), necessitating the use of more advanced analysis techniques. The combination of parallel factor analysis 2 (PARAFAC2) and partial least squares-discriminant analysis (PLS-DA) for detailed characterization and classification of the pyrolysis data enabled the classification of the poplars with a success rate above 99% using the PARAFAC2 scores. This methodology proved to be extremely valuable to identify subtle information in complex datasets, such as the one used in this study. The obtained PLS-DA models were validated by cross-validation, jackknifing and permutation tests in order to ensure that the model was not overfitting the data. PLS-DA showed that down-regulation of CCR disfavored the relative amount of both guaiacyl and syringyl lignin-derived compounds. This study shows that lignin engineering can be a promising strategy to alter the lignin composition of the biomass for the production of high value-added phenolic compounds.

Late-Transition-Metal-Modified β-Mo2C Catalysts for Enhanced Hydrogenation during Guaiacol Deoxygenation

Molybdenum carbide has been identified as a promising bifunctional catalyst in the deoxygenation of a variety of pyrolysis vapor model compounds. Although high deoxygenation activity has been demonstrated, complementary hydrogenation activity has been limited, especially for lignin-derived, aromatic model compounds. The ability to control the relative site densities of acidic and hydrogenation functionalities represents a catalyst design challenge for these materials with the goal to improve hydrogenation activity under ex situ catalytic fast pyrolysis (CFP) conditions. Here we demonstrate that the addition of Pt and Ni to β-Mo2C resulted in an increase in the H*-site density with only a minor decrease in the acid-site density. In contrast, the addition of Pd did not significantly alter the H*- or acid-site densities. High conversions (>94%) and high selectivities to 0-oxygen products (>80%) were observed in guaiacol deoxygenation under ex situ CFP conditions (350 °C and 0.44 MPa H2) for all catalysts. Pt...

Apparent Kinetics of Fast Pyrolysis of Four Different Microalgae and Product Analyses Using Pyrolysis-FTIR and Pyrolysis-GC/MS

This study reports an experimental technique to obtain the isothermal mass loss profiles of four different microalgae (Chlorella vulgaris, Nannochlorpsis oculata, Schizochytrium limacinum, and Arthrospira platensis) under fast pyrolysis conditions in the temperature range of 400–700 °C at short residence times of 2–60 s using an analytical pyrolyzer. The microalgae investigated in this study vary significantly, based on elemental and biochemical composition. The apparent kinetic parameters of fast pyrolysis of the algae were evaluated using first-order and multidimensional diffusion models. The apparent activation energy and pre-exponential factor evaluated under fast heating rate conditions were lower compared to those reported under slow pyrolysis conditions, which is attributed to the diffusion effects. The rate parameters were validated by constructing a kinetic compensation plot, which showed that ln(A) = 0.19Ea + 0.43. The product time evolution at short time scales was studied using in situ Fourier...

Bioproducts from the Slow and Fast Pyrolysis of Sugar Cane Bagasse

In this work, it was done a series of analysis in different conditions of the pyrolysis process to verify the difference of the composition in each one of the final products. In the case of the slow pyrolysis the heating ratio varied among 1.5, 20, 40 e 50 °C/min, and analyzed for each of these rates the composition of the final product. For the case of the fast pyrolysis, the temperature varied among 350, 400, 450, 500, 550 °C, maintaining the other conditions of the process constant, in the end of the process analyzed the composition of the final product for each temperature. For the verification of the composition of these products, they were classified and separate in categories according to the functional group, and after that, the ones who had the most relevant quantities were more deeply analyses to verify some important characteristics and the main industry applications. After this, it was determined the ideals conditions of slow and fast pyrolysis. The resulting products were analyzed by gas chromatography/mass spectrometry. For slow pyrolysis, the heating rate of 40°C/min produced a diversified product, composed by the heterocyclics, levoglucosan, phenols and hydrocarbons. The fast pyrolysis produced mainly the heterocyclic compounds, levoglucosan, phenols and carboxylic acids, in temperatures between 450°C and 500°C.

Design and cold flow testing of a Gas-Solid Vortex Reactor demonstration unit for biomass fast pyrolysis

Innovative gas-solid fluidized beds with process intensification capabilities are among the most promising alternatives for the current state of the art in the chemical industry. In the present work the advantages of such a reactor that sustains a rotating fluidized bed with gas-solid slip velocities much higher than those in conventional fluidized beds are illustrated computationally and experimentally. A Gas-Solid Vortex Reactor (GSVR) demonstration unit is designed to operate at typical biomass fast pyrolysis conditions targeting the production of chemicals and fuels from renewable feedstocks. For the demonstration unit preheated N2 supplies the thermal energy required by the fast pyrolysis process but alternative sources can also be evaluated. A broad range of operation conditions in the 80mm diameter and 15mm height GSVR can be evaluated: N2 mass flow rates of 5–10gs−1 and biomass feed mass flow rates of 0.14–1.4gs−1. Particle-free and particulate flow experiments confirmed that the carrier gas is evenly distributed around the GSVR cylindrical chamber as anticipated by computational fluid dynamic simulations. The latter also supported the inclusion of a profiled bottom end wall and a diverging exhaust. Cold flow experiments with biomass confirmed that the GSVR sustains a rotating fluidized bed with average bed height of 10mm and solids azimuthal velocities of 6–7ms−1.

Analysis of Residual Biomass Fast Pyrolysis at Laboratory Scale: Experimental and Numerical Evaluation of Spent Coffee Powders Energy Content

Abstract The thermochemical pyrolysis process is one of the key intermediate processes to flexibly produce electric/thermal power output. In this paper, experimental results of a small externally heated biomass screw reactor are presented. This paper aims at validating a 1D-DAEM model with experimental data collected by varying maximum temperature in fast pyrolysis conditions. The experimental system, here used for the spent coffee conversion, has been specifically designed for allothermic processes, allowing for controlling heating and mass flow rates. A comparison with pellet has been performed to refer the observed yields to literature available data. The implemented four parallel reaction framework coupled with a DAEM model, is able to give results in very good agreement with the bio-oil experimental data yields, showing in any case prediction errors lower than 4.5%. The maximum bio-oil production has been observed at 500°C, both for the pellet and the spent coffee with yields respectively of 66% and 56%.

Thermal decomposition of pyrolytic lignin under inert conditions at low temperatures

A pyrolytic lignin, separated from the bio-oil generated from biomass fast pyrolysis bio-oil at 500°C via cold-water extraction, was thermally decomposed in a drop-tube/fixed-bed reactor under inert conditions at 100–350°C. It is found that the char yield of the pyrolytic lignin under such fast pyrolysis conditions decreases rapidly from ∼82% at 100°C to ∼23% at 350°C. The majority of the weight loss is contributed by the significant reduction in the fraction of light aromatic oligomers (i.e., the CH2Cl2-soluble fraction) retained in the pyrolytic lignin chars, with such reductions increasing with temperature. On the contrary, there is insignificant change in the fraction of heavy aromatic oligomers (i.e., the CH2Cl2-insoluble fraction) retained in the pyrolytic lignin chars during pyrolysis at such low temperatures. It is evident that there are strong interactions between the light and heavy aromatic oligomers during thermal decomposition of the pyrolytic lignin, leading to the observed additional char formation. The main reactions during thermal decomposition of the pyrolytic lignin are the release of aliphatic and small phenolic compounds (i.e., via demethylation and decarbonylation reactions), mainly due to the breaking of ether bonds in the pyrolytic lignin structure. The char structure becomes more aromatic as temperature increases, due to the enhanced polymerization reactions at high temperatures (>250°C).

Bio-oil production from fast pyrolysis of maple fruit (acer platanoides samaras): product yields

PurposeThe purpose of this paper is to investigate fast pyrolysis of maple fruit as an energy sources. This could serve as a solution to the energy sources problem.Design/methodology/approachFast pyrolysis of maple fruit (samara) was achieved in a fixed bed reactor. The pyrolysis experiments have been conducted on the sample of maple seeds to particularly determine the effects of pyrolysis temperature, particle size and sweep gas flow rate on the pyrolysis product yields.FindingsThe oil of maple fruit from fast pyrolysis has good properties to be a potential candidate as a biofuel or as a source of chemicals. In addition to being environmentally desirable, it can reduce the energy cost, e.g. that Turkey imports a majority of its energy.Originality/valueThe use of maple fruit for fast pyrolysis and pyrolysis conditions impact on the yields of pyrolysis liquid can be considered as novel aspects of this paper.

Simulation of biomass particle evolution under pyrolysis conditions using lattice Boltzmann method

To accurately characterize biomass fast pyrolysis at the particle scale, intra-particle transport phenomena needs to be considered together with the gas flow surrounding the particle. In this study, a detailed numerical method was used to simulate the evolution of biomass particles under fast pyrolysis conditions. To conduct particle-scale simulations, the lattice Boltzmann method (LBM) was employed to solve the conservation equations, and pyrolysis kinetics were implemented to describe the chemical reactions. The present model was validated by comparing the numerical results with experimental data for a single biomass particle under pyrolysis conditions. The predicted temperature and conversion history agree with the experimental data. The temperature and density fields in the particle were found to be anisotropic due to the effect of the gas flow surrounding the particle, which was ignored by the 1D model. The non-uniform distributions of surface temperature indicate that using a constant temperature or heat flux as boundary conditions may cause numerical errors. Sensitivity analysis shows that density is the most influential parameter while porosity is the least. The heat of reaction converting the intermediate solid to char is more dominant than those of the three primary reactions. A parametric study was conducted to investigate the effect of particle shape on conversion time and final product yields. The simulation results show that the conversion time decreased when using the elliptic particle instead of the regular (circular) particle. The model also shows that more tar and syngas were produced, while less char was generated from an elliptic particle. The effect of particle shape on the center temperature of the biomass particle can be explained by comparing the heat transfer conditions at the front of the particle and the convective heat transfer at the top and bottom of the particle. The results demonstrated that the current LBM framework has the ability to reveal the detailed conversion process of biomass particles under various pyrolysis conditions, which can then be used to improve engineering models for reactor-scale simulation.

An investigation into support cooperativity for the deoxygenation of guaiacol over nanoparticle Ni and Rh2P

For guaiacol deoxygenation under catalytic fast pyrolysis conditions, support acidity increases catalytic activity while support reducibility enhances selectivity to deoxygenated products.

Thermal decomposition pathways of 4-ethylguaiacol under fast pyrolysis and gasification conditions

Thermal decomposition pathways for the vapor-phase, homogeneous pyrolysis of 4-ethylguaiacol were examined. Experiments were conducted using a laminar-flow reactor operated at atmospheric pressure, temperatures in the range 300–900°C, and a residence time of one second. Analysis of the products by gas chromatography shows that they can be categorized as light gases, oxygen-containing compounds, and aromatic hydrocarbons. The major products observed were: methane, ethane, ethylene, acetylene, and carbon monoxide for the light gases; 4-ethylcatechol, 5-ethyl-2-hydroxybenzaldehdye, and 4-ethylphenol for the oxygen-containing products; benzene, indene, and naphthalene for the aromatic hydrocarbons. The product distribution was strongly influenced by temperature, with the oxygen-containing compounds dominating at temperatures below 700°C, while light gases and aromatic hydrocarbons dominated above 700°C. By consideration of the product distributions and analogous reactions based on established thermal decomposition mechanisms of structurally-similar compounds, reaction pathways leading to the generation of major products are proposed and discussed. Computational chemistry calculations at the B3LYP/6-311G+(2d,p) level of theory were performed to complement the proposed pathways. The results presented in this study would be of relevance to lignin fast pyrolysis and gasification processes.

High-Throughput Continuous Flow Synthesis of Nickel Nanoparticles for the Catalytic Hydrodeoxygenation of Guaiacol

The translation of batch chemistries to high-throughput flow methods addresses scaling concerns associated with the implementation of colloidal nanoparticle (NP) catalysts for industrial processes. A literature procedure for the synthesis of Ni-NPs was adapted to a continuous millifluidic (mF) flow method, achieving yields >60%. Conversely, NPs prepared in a batch (B) reaction under conditions analogous to the continuous flow conditions gave only a 45% yield. Both mF- and B-Ni-NP catalysts were supported on SiO2 and compared to a Ni/SiO2 catalyst prepared by traditional incipient wetness (IW) impregnation for the hydrodeoxygenation (HDO) of guaiacol under ex situ catalytic fast pyrolysis conditions (350 °C, 0.5 MPa). Compared to the IW method, both colloidal NPs displayed increased morphological control and narrowed size distributions, and the NPs prepared by both methods showed similar size, shape, and crystallinity. The Ni-NP catalyst synthesized by the continuous flow method exhibited similar H-adsorpt...

Prospects and Challenges of Pyrolysis Technologies for Biomass Conversion

Prospects and Challenges of Pyrolysis Technologies for Biomass Conversion

Furan Production from Glycoaldehyde over HZSM-5

Catalytic fast pyrolysis of biomass over zeolite catalysts results primarily in aromatic (e.g., benzene, toluene, xylene) and olefin products. However, furans are a higher value intermediate for their ability to be readily transformed into gasoline, diesel, and chemicals. Here we investigate possible mechanisms for the coupling of glycoaldehyde, a common product of cellulose pyrolysis, over HZSM-5 for the formation of furans. Experimental measurements of neat glycoaldehyde over a fixed bed of HZSM-5 confirm furans (e.g., furanone) are products of this reaction at temperatures below 300 °C with several aldol condensation products as coproducts (e.g., benzoquinone). However, under typical catalytic fast pyrolysis conditions (>400 °C), further reactions occur that lead to the usual aromatic product slate. ONIOM calculations were utilized to identify the pathway for glycoaldehyde coupling toward furanone and hydroxyfuranone products with dehydration reactions serving as the rate-determining steps with typical...

Effect of fast pyrolysis conditions on biomass solid residues at high temperatures

Fast pyrolysis of wood and straw was conducted in a drop tube furnace (DTF) and compared with corresponding data from a wire mesh reactor (WMR) to study the influence of temperature (1000–1400)°C, biomass origin (pinewood, beechwood, wheat straw, alfalfa straw), and heating rate (103°C/s, 104°C/s) on the char yield and morphology. Scanning electron microscopy (SEM), elemental analysis, and ash compositional analysis were applied to characterize the effect of operational conditions on the solid residues (char, soot) and gaseous products. The char yield from fast pyrolysis in the DTF setup was 3 to 7% (daf) points lower than in the WMR. During fast pyrolysis pinewood underwent drastic morphological transformations, whereas beechwood and straw samples retained the original porous structure of the parental fuel with slight melting on the surface. The particle size of Danish wheat straw char decreased in its half-width with respect to the parental fuel, whereas the alfalfa straw char particle size remained unaltered at higher temperatures. Soot particles in a range from 60 to 300nm were obtained during fast pyrolysis. The soot yield from herbaceous fuels was lower than from wood samples, possibly due to differences in the content of lignin and resin acids.

Pyrolysis of eastern redcedar: Distribution and characteristics of fast and slow pyrolysis products

Eastern redcedar is a problematic plant in Oklahoma due to its extinguished environmental flexibility and rapid expansion. Thermally converting solid biomass polymers into liquid fuel intermediate, solid char and gaseous products through pyrolysis is one promising approach to use redcedar for the production of sustainable fuels. The objective of this study was to investigate effects of eastern redcedar wood zones (heartwood and sapwood), pyrolysis temperature (450 and 500°C) and pyrolysis types (slow at lab-scale and fast at micro-scale) on the distribution and composition of the pyrolysis products. In fast pyrolysis conditions, the products were dominated by anhydrous sugars, phenols and guaiacols. The total yield of lignin-derived compounds from heartwood was higher than that from sapwood at 500°C but the total yields were not significantly different at 450°C. In slow pyrolysis conditions, acetic acid and furfural were the two most abundant species in bio-oil. Slow pyrolysis products consisted of less branched compounds of phenols and guaiacols as compared to fast pyrolysis products. Cedar oil components (alpha/beta-cedrene) were only produced at slow pyrolysis conditions and its maximum yield (21.04±1.08area%) of was obtained from heartwood at 500°C. Heartwood produced significantly more cedrenes than sapwood.

Evaluation of Silica-Supported Metal and Metal Phosphide Nanoparticle Catalysts for the Hydrodeoxygenation of Guaiacol Under Ex Situ Catalytic Fast Pyrolysis Conditions

A series of metal and metal phosphide catalysts were investigated for the hydrodeoxygenation of guaiacol under ex situ catalytic fast pyrolysis conditions (350 °C, 0.5 MPa, 12 H2:1 guaiacol, weight hourly space velocity 5 h−1). Ligand-capped Ni, Pt, Rh, Ni2P, and Rh2P nanoparticles (NPs) were prepared using solution-phase synthesis techniques and dispersed on a silica support. For the metal phosphide NP-catalysts, a synthetic route that relies on the decomposition of a single molecular precursor was employed. The reactivity of the NP-catalysts was compared to a series of reference materials including Ni/SiO2 and Pt/SiO2 prepared using incipient wetness (IW) impregnation and a commercial (com) Pt/SiO2 catalyst. The NP-Ni/SiO2 catalyst exhibited the largest reduction in the oxygen mol% of the organic phase and outperformed the IW-Ni/SiO2 material. Although it was less active for guaiacol conversion than NP-Ni/SiO2, NP-Rh2P/SiO2 demonstrated the largest production of completely deoxygenated products and the highest selectivity to anisole, benzene, and cyclohexane, suggesting that it is a promising catalyst for deoxygenation of aryl-OH bonds. The com-Pt/SiO2 and IW-Pt/SiO2 catalyst exhibited the highest normalized rate of guaiacol conversion per m2 and per gram of active phase, respectively, but did not produce any completely deoxygenated products.