Fast Pyrolysis Of Biomass Research Articles

Prediction of NH3 and HCN yield from biomass fast pyrolysis: Machine learning modeling and evaluation

Rapid pyrolysis is a promising technique to convert biomass into fuel oil, where NOX emission remains a substantial environmental risk. NH3 and HCN are top precursors for NOX emission. In order to clarify their migration path and provide appropriate strategies for their controlling, six up-to-date machine learning (ML) models were established to predict the NH3 and HCN yield during rapid pyrolysis of 26 biomass feedstocks. Cross-validation and grid search methods were used to determine the optimal hyperparameters for these ML models. The support vector regression (SVR) model achieved optimal accuracy among them. The optimal root means square error (%), mean absolute error (%), and R2 of test set for NH3/HCN yield were 1.2901/1.1531, 1.0501/0.84712, and 0.98253/0.96152, respectively. In addition, based on the results of Pearson correlation analysis, the input variables with a weak linear correlation with the target product were eliminated, which was found capable of improving the prediction accuracy of almost all ML models except SVR. While after input variables elimination, the SVR model still showed the optimal NH3 and HCN yield prediction accuracy. It reflects SVR's great significance and potential for predicting the yield of NOX precursors during rapid biomass pyrolysis.

Syngas production by bio-oil steam gasification in a fountain confined conical spouted bed reactor

The combination of delocalized units for the fast pyrolysis of biomass to produce bio-oil followed by centralized units for the gasification of bio-oil appears as an economically attractive option for the full-scale production of syngas because transportation of bio-oil is less costly than that of biomass. First goal of this study lies in the validation of a bio-oil feeding device made up of a line-thermostated at 60–80 °C and a non-atomizing injector cooled by water. This injector allows feeding the crude bio-oil in continuous mode into the conical spouted bed reactor without being clogged by the pyrolytic lignin in the bio-oil. The effect of gasification temperature on gas properties, tar composition, and carbon conversion efficiency were assessed in the 800–900 °C range. The results show that temperature promotes tar reduction (from 40.7 to 12.5 g/Nm3), carbon conversion efficiency (from 91.2 to 96.3 %) and gas yield (from 1.37 to 1.85 Nm3/kg on a dry basis) as temperature is increased from 800 to 900 °C. A novel aspect of this study is the detailed characterization of the tar evolution with temperature, which, to our knowledge, is an aspect that has not been approached in the literature related to raw bio-oil gasification.

Effect of Acid Pretreatment on the Primary Products of Biomass Fast Pyrolysis

A high load of inorganics in raw lignocellulosic biomass is known to inhibit the yield of bio-oil and alter the chemical reactions during fast pyrolysis of biomass. In this study, palm kernel shell (PKS), an agricultural residue from palm oil production, and two other woody biomass samples (mahogany (MAH) sawdust and iroko (IRO) sawdust) were pretreated with distilled water or an acidic solution (either acetic, formic, hydrochloric (HCl) or sulfuric acid (H2SO4)) before fast pyrolysis in order to investigate its effect on the primary products and pyrolysis reaction pathways. The raw and pretreated PKS, MAH and IRO were pyrolysed at 600 °C and 5 s with a micro-pyrolyser connected to a gas chromatograph–mass spectrometer/flame ionisation detector (GC-MS/FID). Of the leaching solutions, HCl was the most effective in removing inorganics from the biomass and enhancing the primary pyrolysis product formed compared to the organic acids (acetic and formic acid). The production of levoglucosan was greatly improved for all pretreated biomasses when compared to the original biomass but especially after HCl pretreatment. Additionally, the relative content of the saccharides was maximised after pretreatment with H2SO4, which was due to the increased production of levoglucosenone. The relative content of the saccharides increased by over 70%. This increase may have occurred due to a possible reaction catalysed by the remaining acid in the biomass. The production of furans, especially furfural, was increased for all pretreatments but most noticeable when H2SO4 was used. However, the relative content of acids and ketones was generally reduced for PKS, MAH and IRO across all leaching solutions. The relative content of the phenol-type compound decreased to a large extent during pyrolysis after acid pretreatment, which may be attributed to dehydration and demethoxylation reactions. This study shows that the production of valuable chemicals could be promoted by pretreatment with different acid solutions.

Prediction of instantaneous yield of bio-oil in fluidized biomass pyrolysis using long short-term memory network based on computational fluid dynamics data

Computational fluid dynamics (CFD) is an effective tool to investigate biomass fast pyrolysis in fluidized bed reactor for bio-oil production, while it requires huge computational time when optimizing operating conditions or simulating large/industrial units. Machine learning (ML) is a promising approach to achieving both accuracy and efficiency. In this work, a reduced-order model including long short-term memory (LSTM) layer, pooling layer, and fully connected layer was established to predict future mass flow rates by training the historical CFD data. Unsteady mass flow rates, which are normally used to determine product yields, were treated as data of time series in ML. Influencing factors, such as sequence length, number of neurons, learning rate, subsequences order (shuffle or not), number of LSTM layers, and ratio of testing set, were evaluated to obtain their optimal values. The developed LSTM model framework and training process showed good applicability for the dataset of different species and temperatures. Product yields predicted by the derived LSTM were in good agreement with those obtained by CFD, while nearly 30% computational effort was saved. Thus, it is clearly seen that the well-predicted fluctuating characteristics and final product yields are helpful to improve accuracy of process simulation for digitalizing key reactors and building smart factories.

Combustion and emission characterization of upgraded biomass fast pyrolysis oil in a swirl burner

Fast pyrolysis oil (FPO, also called bio-oil) is a biofuel made from thermal decomposition of renewable or waste biomass. However, the physiochemical properties of FPO have limited its widespread use in combustion applications. In this study, the impacts of FPO upgrading with multi-stage condensation, catalytic pyrolysis with ZSM-5, and ethanol blending were studied through characterization of physiochemical properties and combustion in a swirl burner. A commercially available FPO sample (COMM) and diesel were used to benchmark the upgraded FPO samples. The non-catalytic FPO (NC) sample produced with multi-stage condensation had 9.0wt% less oxygen and an HHV 2.2 MJ/kg higher than COMM. The FPO produced using ZSM-5 catalyst (CAT) had 19.0wt% less oxygen, an HHV greater by 7.4 MJ/kg, and lower viscosity than COMM. The CAT sample also had fewer low-molecular-weight compounds, showing a peak mass loss rate 70 °C higher than NC. The NC and CAT samples were also blended with 10vol% ethanol, which had minor effects on the measured physiochemical properties aside from improving volatility. Combustion was evaluated by measuring unburned hydrocarbon, CO, NOx, and particulate matter exhaust concentrations from a swirl burner as well as through flame visualization. Combustion of neat NC was stable, although compared to COMM, CO was ∼2-times higher and NOx was ∼2-times lower. In contrast, the CAT flame was unstable, resulting in the highest CO concentrations overall. Blending NC and CAT with 10vol% ethanol resulted in lower CO concentrations (NC: 88% less, CAT: 96% less) and higher NOx (NC: 2-times, CAT: 1.4-times) compared to neat FPO. Although catalytic upgrading and multi-stage condensation improved HHV, oxygen content, and viscosity, changes to these properties did not improve combustion performance. Ethanol blending emphasized the outsize role of volatility in improving furnace combustion relative to other measured physiochemical properties as reflected by the improved flame stability and exhaust composition.

Comparative life cycle assessment of corn stover conversion by decentralized biomass pyrolysis-electrocatalytic hydrogenation versus ethanol fermentation

Biomass fast pyrolysis followed by electrocatalytic hydrogenation (Py-ECH) with renewable electricity outperforms cellulosic ethanol in three environmental impact categories.

Advancements and challenges in the production of low-carbon fuels via catalytic fast pyrolysis of biomass through refinery integration and co-product generation

Creating pathways to renewable fuels, chemicals, and materials through improved catalyst formulations and integrated process development.

At-Line Sampling and Characterization of Pyrolytic Vapors from Biomass Feedstock Blends Using SPME-GC/MS-PCA: Influence of Char on Fast Pyrolysis.

Solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) analysis was used for the at-line sampling of pyrolytic vapors produced during the fast pyrolysis of biomass. The pure and binary blends of switchgrass (SWG) and pine harvest residues (PT6) were used as biomass feedstocks. Sequential SPME sampling allowed for monitoring of changes in the pyrolysis vapors as char accumulated in the fluid bed. The relative concentration and composition of the pyrolysis vapors desorbed from the SPME fibers were investigated using GC-MS, and the resulting chromatograms were analyzed using principal component analysis (PCA) to compare the composition of the pyrolysis vapors over the course of the pyrolysis run. The chemical compositions of both carbohydrate and lignin fragments varied as the char builds up in the reactor bed. Fragments derived from cellulose and hemicelluloses included anhydrosugars, furans, and light-oxygenated compounds. Lignin fragments included methoxyphenols, phenolic ketones, aldehydes, and low-molecular-weight aromatics. The composition of the carbohydrate fragments changed more than those of the lignin fragments as the char built up in the fluid bed. This combination of SPME-GC/MS-PCA was a novel, easy, and effective method for measuring the composition and changes in the composition of pyrolysis vapors during the fast pyrolysis process. This work also highlighted the effect of char build-up on the composition of the overall pyrolysis vapors.

Numerical simulation and multi-process coupling analysis for biomass pyrolysis fluidized bed reactor based on synergistic effects between biomass and nitrogen inlet modes

Biomass fast pyrolysis fluidized bed reactor is regarded as one of the most promising technologies for high value utilization of biomass. In this work, one two-dimensional fluidized bed reactor model was established, coupling with multiphase CFD simulation method and pyrolysis reaction kinetics, and further verified by the experimental data. This work mainly investigated the effects of biomass inlet and nitrogen inlet modes on multi-process characteristics, such as flow behavior, heat transfer and pyrolysis reaction. The synergistic effects between the two inlet modes were further explored and thus would affect the three-phase pyrolysis product distribution. The results showed that the spatial particle distribution and temperature distribution in the dense phase zone were becoming more uniform and the tar yield increased when the biomass inlet mode changed from single nozzle to double nozzles jetting opposite. Besides, when the nitrogen nozzle number was set as one and the auxiliary gas velocity was set as 0.15 m/s, much larger local circulation formed in the dense phase zone, meanwhile the particle volume fraction and temperature became more evenly distributed, which was conducive to the biomass pyrolysis process. The nitrogen inlet mode was found to show a greater impact on the tar yield compared to the biomass inlet mode. For single gas inlet mode, one biomass nozzle should be preferred for lower auxiliary gas velocity and the opposite double nozzle would be better for higher auxiliary gas velocity. The synergistic effects between biomass and nitrogen inlet modes were further summarized, which were found to have a positive impact on the biomass pyrolysis reaction characteristics. Based on the above conclusions, this work could provide a feasible theoretical guidance for designing fluidized bed pyrolysis reactor and optimizing the biomass pyrolysis process.

Process Model-Based Validation of the Intensification of Biomass Fast Pyrolysis in a Fluidized Bed via Autothermal Operation

Process Model-Based Validation of the Intensification of Biomass Fast Pyrolysis in a Fluidized Bed via Autothermal Operation

Effect of particle characteristics, kinetics and transport phenomena on the prediction of particle mass loss and products yields during biomass fast pyrolysis

A low computational cost model for the pyrolysis of biomass anisotropic particles was used to study the effect of thermal conductivity of the particle, CRECK kinetic scheme implementation, intraparticle secondary reactions, heats of reaction, and advection on particle conversion prediction. The model considers a shrinking anisotropic cylindrical particle with biomass pseudo-components, the appearance of liquid intermediates, intra-particle mass and heat transport and secondary reactions of volatiles. The model was validated against oak and birchwood single particle experiments. More accurate predictions for mass loss evolution are found when considering the change of the particle thermal conductivity anisotropy with conversion and the temperature dependency of the thermal conductivities of the biomass and the gas phase, compared to ignoring these phenomena. The CRECK biomass pyrolysis reaction scheme provides insights into the effect of biomass composition on the evolution of the liquid intermediate phase allowing future studies about the presence of heavy compounds in the bio-oil and other phenomena such as aerosol ejection. Secondary intraparticle vapor phase reactions showed a negligible effect in volatiles conversion while heterogeneous reactions slightly overestimate its conversion. Heats of reaction and product advection are important for accurate prediction of particle mass loss.

Synergistic enhancement of bio-oil quality through hydrochloric or acetic acid-washing pretreatment and catalytic fast pyrolysis of biomass

Peanut shells were used as raw materials, and the synergistic effects of various acid pretreatments and catalytic pyrolysis for biomass were comprehensively studied. The results showed that the oil yield of 0.5 mol/L hydrochloric acid treatment was 44.75 wt%, and that of 0.5 mol/L acetic acid treatment was 43.40 wt%. The solid products decreased apparently after pretreatment. Acid-washing pretreatment and the subsequent catalytic pyrolysis of the pretreated biomass promoted the yield of aromatic in bio-oil. The yield of bio-oil gradually decreased while the gas yield increased with the increase of catalytic pyrolysis temperature. Ketones and anhydrosugars were also reduced in the bio-oil, while aromatics increased significantly, reaching the highest value of 19.62 wt% (0.5 mol/L hydrochloric acid treatment) and 19.30 wt% (0.5 mol/L acetic acid treatment) respectively at 600 ℃. Synergy effect facilitated the conversion of pyrolytic intermediates to gas and aromatics. Besides, the possible formation mechanism of bio-oil under different pyrolysis conditions is proposed. The study indicates the optimized combination could effectively improve the quality of bio-oil.

Study on biomass fast pyrolysis kinetics in an isothermal spouted-bed thermogravimetric analyzer and its application to CFD

In this study, a spouted-bed thermogravimetric analyzer (SB-TGA) was developed to accurately investigate the reaction models and kinetic parameters of the spouted beds. In addition, the analyzer overcomes the disadvantages of conventional thermogravimetric analyzers that arise from different hydrodynamics. The spouted-bed reactor used in the SB-TGA was scaled down to a small size using dimensional scaling laws, and the hydrodynamic similarity of the reactor to a large-scale reactor was validated. Isothermal experiments using the SB-TGA were performed from 673.15 to 823.15 K. The contracting volume model (R2) was found to suitably represent the pyrolysis reaction of sawdust in a spouted-bed reactor. The activation energy and pre-exponential factor of the global degradation reaction, and the formation rate constants in the same temperature range for tar, char, and gas were determined. The experimental results demonstrated that the SB-TGA provides more reliable results for predicting the pyrolysis reaction by computational fluid dynamic (CFD) in a spouted-bed.

Rate constants for H-atom abstraction reactions from mono-aromatic hydrocarbons by H, CH3, OH and 3O2: A systematic theoretical investigation

Mono-aromatic hydrocarbons (MAHs) are key components in surrogate fuels formulation (e.g. toluene), as well as the initial building blocks of PAHs growth (e.g. benzene). Moreover, the viability and sustainability of biomass fast pyrolysis processes increased the interest in oxygenated aromatic hydrocarbons (e.g. anisole, phenol) as anti-knocking additives for gasoline fuels and reference components for bio-oils surrogates. Differently from other classes of compounds (e.g. n-alkanes, iso-alkanes) a systematic approach to build kinetic mechanisms based on reaction classes and rate rules is still lacking for MAHs. Taking advantage of automated tools to perform state-of-the-art theoretical calculations, this work provides a consistent set of 52 accurate rate constants for H-atom abstraction reactions from benzene, toluene, phenol, and anisole by H, CH3, OH, and 3O2 for direct implementation in existing kinetic models. New insights about the accuracy of the theoretical methodology are presented, assessing the impact of the level of theory used for electronic structure calculations, of the treatment of hindered rotors, and of the implementation of variational transition state theory in both Cartesian and internal coordinates. This investigation provides guidelines to develop appropriate theoretical protocols for the treatment of MAHs reactivity and for the quantification of the associated uncertainty, with the final aim of building fundamentally-based sets of reaction classes of relevance for the pyrolysis and oxidation of MAHs.

Cellulose Fast Pyrolysis Activated by Intramolecular Hydrogen Bonds.

The conversion of inedible biomass by fast pyrolysis is a promising route for sustainable production of renewable fuels and value-added chemicals, but low selectivity toward desired products hampers its economic viability. Understanding the molecular-level reaction pathways of biomass fast pyrolysis could be the key to overcoming this challenge. However, the effects of intramolecular and interchain hydrogen bonds near the reaction center have not been thoroughly explored. In this work, the reaction pathways and kinetics of fast pyrolysis of cellulose, a major component of biomass, were investigated using the density functional theory. A new intramolecular hydroxyl-activated mechanism is presented for cellulose activation. Our calculations incorporating noncovalent interactions accurately captured the activation energy of 50.8 kcal mol-1, agreeable with the apparent activation energy measured experimentally. The findings of cellulose pyrolysis provide insights into the investigation of interactions during real-life biomass pyrolysis.

Fast estimation of reaction rates in spherical and non-spherical porous catalysts

We present a methodology for modeling multi-step reaction rates in porous catalyst particles for use in CFD–DEM and two fluid models. Single-step effectiveness factors based on a Thiele modulus, while useful, cannot accurately capture the cascading reaction systems common in high temperature vapor-phase chemical reactors like fluidized catalytic cracking units and catalytic biomass fast pyrolysis systems. Instead, multi-step effectiveness vectors derived from steady-state solutions to the governing reaction–diffusion equations are needed. Solutions for various catalyst shapes are presented, including spheres, cylinders, and prisms. Computational challenges inherent in repeated evaluation of reaction rates with diffusion limitations are discussed, and an efficient implementation based on pre-computed lookup tables is proposed and demonstrated on a simulation of a fluidized bed reactor. Open-source code is provided for the compilation of reaction rate tables for use in ODE, DEM, and two-fluid models.

Hydrogenation of biomass pyrolysis oil using enhanced reduction catalytic capacity cellular by expressing excavated carbonyl reductase

A biocatalytic method to achieve the hydromodification of biomass fast pyrolysis oil was implemented. Two carbonyl reductases SDR-1 and SDR-8 were excavated in the genome of Bacillus coagulans NL01, enhanced Escherichia coli ability to tolerate and reduce various toxic ketone aldehydes. 10 g/L furfural and 8 g/L acetoin as bio-oil model compounds could be transformed by the recombinant E. coli SDR-1 and E. coli SDR-8 respectively. The biphasic catalysis system was constructed to convert the keto-aldehyde compounds in bio-oil to the corresponding alcohol at 30 °C. Recombinant E. coli SDR-8 could completely consume 20 g/L glucose and consume 60% 20 g/L glucose in the diluted 50-fold and 30-fold bio-oil catalytic system, respectively. This provided a new pathway for the hydrogenation of bio-oil by biocatalytic method and laid the foundation for the low-temperature esterification in the later stage.

Product regulation and catalyst deactivation during ex-situ catalytic fast pyrolysis of biomass over Nickel-Molybdenum bimetallic modified micro-mesoporous zeolites and clays

Ni-Mo bimetallic modified micro-mesoporous zeolite catalysts were prepared and employed in the process of ex-situ catalytic fast pyrolysis (CFP) of poplar to produce liquid fuel. Clay catalysts were incorporated to further improve the products quality. The mass yield of monocyclic aromatic hydrocarbons (MAHs) increased under the catalysis of composite catalysts AZM and NiMo/AZM. HAP&Zeolite dual catalyst system reduced coke yield of NiMo/AZM to 5.01 wt%. Through real-time monitoring of gas products, the catalytic performance of zeolites began to decrease after the ratio of biomass and catalyst was more than 1. A series of characterization results futher demonstrated that AZM and NiMo/AZM possessed more stable catalytic ability and higher catalytic activity during the whole CFP process. N2 adsorption–desorption measurement and Raman characterization illustrated the formation and structure of coke, catalyst deactivation and the protective mechanism of mesopores on micropores.

Coprocessing Biomass Fast Pyrolysis and Catalytic Fast Pyrolysis Oils with Vacuum Gas Oil in Refinery Hydroprocessing

Coprocessing Biomass Fast Pyrolysis and Catalytic Fast Pyrolysis Oils with Vacuum Gas Oil in Refinery Hydroprocessing

Modelling fast pyrolysis of biomass in a fluidized bed reactor

AbstractA compartmental one‐dimensional model of a fluidized bed pyrolytic converter of biomass is presented. Reference conditions are those of non‐catalytic fast pyrolysis of biomass in a shallow fluidized bed with external regeneration of the bed material. The fate of biomass and of the resulting char has been modelled by considering elutriation of biomass and char particles, char attrition as well as bed drain/regeneration. The course of primary and secondary pyrolitic reactions is modelled according to a semi‐lumped reaction network using well‐established kinetic parameters taken from the literature. A specific focus of the present study is the role of the heterogeneous volatile–char secondary reactions, whose rate has been modelled by borrowing a kinetic expression from the neighbouring area of tar adsorption/decomposition over char. The results of computations highlight the relevance of heterogeneous volatile–char secondary reactions and of the closely associated control of char loading in the bed. The sensitivity of the reactor performance to char elutriation and attrition, to proper management of bed drain/regeneration, and to control of gas phase backmixing is demonstrated. Model results provide useful guidelines for optimal design and control of fluidized bed pyrolyzers and pinpoint future research priorities.