Pyrolysis In Fluidized Bed Reactor Research Articles

Techno-Economic Analysis of Thermochemical Conversion of Waste Masks Generated in the EU during COVID-19 Pandemic into Energy Products

During the COVID-19 pandemic, more than 24 billion pieces of surgical mask waste (WM) were generated in the EU region, with an acute shortage of their management and recycling. Pyrolysis and gasification are among the most promising treatments that were proposed to dispose of WMs and convert them into pyrolysis oil and hydrogen-rich syngas. This work aimed to investigate the techno-economic analysis (TEA) of both treatments in order to assess the feasibility of scaling up. The TEA was carried out using a discounted cash flow model and its data were collected from practical experiments conducted using a fluidised bed pyrolysis reactor and bubbling fluidised bed gasifier system with a capacity of 0.2 kg/h and 1 kg/h, respectively, then upscaling to one tonne/h. The technological evaluation was made based on the optimal conditions that could produce the maximum amount of pyrolysis oil (42.3%) and hydrogen-rich syngas (89.7%). These treatments were also compared to the incineration of WMs as a commercial solution. The discounted payback, simple payback, net present value (NPV), production cost, and internal rate of return (IRR) were the main indicators used in the economic feasibility analysis. Sensitivity analysis was performed using SimLab software with the help of Monte Carlo simulations. The results showed that the production cost of the main variables was estimated at 45.4 EUR/t (gate fee), 71.7 EUR/MWh (electricity), 30.5 EUR/MWh (heat), 356 EUR/t (oil), 221 EUR/t (gaseous), 237 EUR/t (char), and 257 EUR/t (syngas). Meanwhile, the IRR results showed that gasification (12.51%) and incineration (7.56%) have better economic performance, while pyrolysis can produce less revenue (1.73%). Based on the TEA results, it is highly recommended to use the gasification process to treat WMs, yielding higher revenue.

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.

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 study and CO2 emission reduction analysis of coal liquefaction residue fluidized bed pyrolysis

The direct coal liquefaction process usually produces a liquefaction residue of about 30% of its coal feed. The effective utilization of the coal liquefaction residue (CLR), which contains about 80% organic matter, is of great significance for improving the oil yield of the direct liquefaction process and reducing the amount of pollution emitted from this oil-containing organic solid waste. In this study, the CLR fluidized bed pyrolysis process was studied through a fluidized bed reactor pyrolysis experiment and steady-state thermal analysis. The characteristics of CLR were first analyzed, and then the pyrolysis experiment was conducted in a fluidized bed reactor system. The experiment results show that the oil yield is 34.81% at 540°C for an ash-free feedstock using a fluidized bed pyrolysis reactor. Based on the pyrolysis experimental data and the Aspen Plus software platform, the fluidized bed pyrolysis reactor, fractionation column, coke burner, gasifier, and other equipment were modeled to compare four different process schemes. CLR pyrolysis is an endothermic reaction, and its heat is usually supplied by coke combustion, which produces significant CO2 emissions. Case studies of the pyrolysis process were performed in detail in order to reduce CO2 emissions. Thermal efficiency, carbon efficiency, solid waste discharge, and CO2 emissions of the different schemes were compared, and a flexible fluidized pyrolysis (FFP) process coupled with water electrolysis was proposed. The introduction of green hydrogen and green oxygen to the process can realize near-complete utilization of carbon and hydrogen elements in the CLR and produce high-quality liquid fuels and syngas (for further chemical synthesis), and this new process can achieve almost near-zero CO2 emission in the entire unit. This process principle can also be applied to the CO2 emission reduction of organic solid waste pyrolysis, catalytic fluid cracking, fluid coking, and so on.

Valorization potential of technical lignins from Norway spruce (Picea abies) via pyrolysis

Analytical pyrolysis (Py-GC/MS) on mg-scale of Norway spruce (Picea abies)-derived kraft lignin, ethanosolv lignin, and dried lignin-rich soda-anthraquinone (AQ) black liquors was studied at 500 °C to compare the valorization potential of these materials, focusing on the type and yield of condensable pyrolysis products. Of particular interest was the relatively selective formation of guaiacol (2-methoxyphenol) from the dried soda-AQ black liquors in contrast to the formation of complex phenolic product mixtures from the pyrolysis of the kraft and ethanosolv lignins. It was shown that this finding could be attributed to differences in composition and structure as was assessed by various NMR and 2D-GC/FID analyses. From a comparison between the analytical pyrolysis results and the results of Norway spruce-derived pyrolysis oils that were produced in earlier research with a state-of-the-art kg-scale bubbling fluidized bed pyrolysis reactor, it was concluded that analytical pyrolysis is suitable to predict the pyrolysis behavior of lignin also on a larger scale. However, it was found that the prediction of reliable product yields for larger-scale pyrolysis from the semi-quantitative analytical pyrolysis yield results was less accurate, mainly due to differences in process conditions, such as heating rate and hot-vapor-residence times leading to secondary degradation reaction of the individual monomers.

A review on CFD simulation of biomass pyrolysis in fluidized bed reactors with emphasis on particle-scale models

This paper reviews the recent advances in multi-scale computational fluid dynamics (CFD) simulations of biomass pyrolysis in fluidized bed reactors. The interconnection among molecular-scale, particle-scale, CFD cell-scale, and reactor-scale are first introduced, together with the Eulerian-Lagrangian (E-L) and Eulerian multi-fluid model (MFM) frameworks. Then an overview of the theoretical basis and practical applications of four main particle-scale models, i.e, uniform conversion model, progressive conversion model, interface-based model, and corrected uniform conversion model, are highlighted. The coupling of particle-scale models with CFD cell-scale models is discussed, as well as with molecular-scale models. Finally, the perspective of future work to develop reliable and efficient CFD models for simulating biomass pyrolysis in fluidized bed reactors is outlined.

Selective catalytic conversion of tea waste biomass into phenolic-rich bio-oil and subsequent extraction

Fast pyrolysis has appeared as a promising technology for bio-fuels and bio-based chemicals production. This paper reports tea waste (TW) as a promising source of phenolic-rich bio-oil production via catalytic fast pyrolysis in fluidized bed reactor. TG-FTIR analysis is applied to optimize pyrolysis temperature for phenolic-rich bio-oil production and maximum phenols yield (17.3 %) was obtained at 500 °C. Meanwhile, bio-oils are produced at each corresponding temperatures of TG-FTIR analysis and GC–MS analysis is performed to examine consistency and authenticity of TG-FTIR results. Moreover, catalytic effect of activated carbon + KOH (AC-K) with different biomass-to-catalyst ratio was examined to optimize most efficient ratio at 500 °C and maximum phenol contents (39.72 %) were obtained at 1:6 ratio of biomass-to-catalyst as compared to non-catalytic pyrolysis (23.85 %). Moreover, effect of temperature on product distribution was examined and maximum liquid yield (40.7 %) was obtained at 500 °C. Furthermore, switchable hydrophilic solvents (SHS) were used to isolate phenols from bio-oil with 95.02 % yield calculated by GC–MS analysis. The elemental analysis and high heating value (HHV) of the crude and residue bio-oil were determined. The carbon contents and HHV of residue bio-oil were increased to 67.3 % and 13.7 MJ/Kg from 46.2 % and 10.38 MJ/Kg respectively while; oxygen contents were decreased to 19.7 from 45.3 % demonstrating its potential for fuel application.

Impact of the Reactor Structure on Biomass Pyrolysis in Fluidized-Bed Reactors: A Coarse-Grained CFD-DEM Study

Impact of the Reactor Structure on Biomass Pyrolysis in Fluidized-Bed Reactors: A Coarse-Grained CFD-DEM Study

CFD-DEM Simulation of Biomass Pyrolysis in Fluidized-Bed Reactor with a Multistep Kinetic Scheme

The pyrolysis of biomass in a fluidized-bed reactor is studied by a combination of a CFD-DEM algorithm and a multistep kinetic scheme, where fluid dynamics, heat and mass transfer, particle collisions, and the detailed thermochemical conversion of biomass are all resolved. The integrated method is validated by experimental results available in literature and a considerable improvement in predicting the pyrolysis product yields is obtained as compared to previous works using a two-fluid model, especially the relative error in the predicted tar yield is reduced by more than 50%. Furthermore, the evolution of light gas, char and tar, as well as the particle conversion, which cannot easily be measured in experiments, are also revealed. Based on the proposed model, the influences of pyrolysis temperature and biomass particle size on the pyrolysis behavior in a fluidized-bed reactor are comprehensively studied. Numerical results show that the new algorithm clearly captures the dependence of char yield on pyrolysis temperature and the influence of heating rate on light gas and tar yields, which is not possible in simulations based on a simplified global pyrolysis model. It is found that, as the temperature rises from 500 to 700 °C, the light gas yield increases from 17% to 25% and char yield decreases from 22% to 14%. In addition, within the tested range of particle sizes (<1 mm), the impact on pyrolysis products from particle size is relatively small compared with that of the operating temperature. The simulations demonstrate the ability of a combined Lagrangian description of biomass particles and a multistep kinetic scheme to improve the prediction accuracy of fluidized-bed pyrolysis.

Production of bio-oils enriched with aroma compounds from tobacco waste fast pyrolysis in a fluidized bed reactor

As tobacco waste production from tobacco industry increases, it becomes important to convert tobacco waste into high value-added products. In this paper, the production of aroma compounds from the fast pyrolysis of tobacco waste was investigated, two kinds of tobacco waste—tobacco leaf fragments (TF), tobacco stems (TS)—and Modeng-brand cigarette tobacco (MT) were used as raw materials in a fluidized bed pyrolysis reactor. Tobacco types, pyrolysis temperatures, and bio-oil separation methods were assigned as influence factors, and the type and content of bio-oil-containing aroma compounds were defined as evaluation standards. Our results indicate that (i) the bio-oil yield under the same pyrolysis temperature (350 °C) is TS > MT > TF; (ii) when TF and MT are used as raw materials, low-temperature (about 350 °C) pyrolysis is beneficial for the production of aroma compounds, whereas TS requires higher temperature (more than 380 °C) pyrolysis; and (iii) bio-oils obtained from different separation methods contain different kinds of aroma compounds, with some compounds requiring certain separation methods. The formation and pyrolysis mechanism of nitrogen (N)-containing compounds in tobacco was also studied. The study demonstrated that nicotine converts to N-containing heterocycles because of secondary decomposition under high temperature.

A hybrid SVR-PSO model to predict a CFD-based optimised bubbling fluidised bed pyrolysis reactor

Comprehensive scrutiny is necessary to achieve an optimised set of operating conditions for a pyrolysis reactor to attain the maximum amount of the desired product. To reach this goal, a computational fluid dynamic (CFD) model is developed for biomass fast pyrolysis process and then validated using the experiment of a standard lab-scale bubbling fluidised bed reactor. This is followed by a detailed CFD parametric study. Key influencing parameters investigated are operating temperature, biomass flow rate, biomass and sand particle sizes, carrier gas velocity, biomass injector location, and pre-treatment temperature. Machine learning algorithms (MLAs) are then employed to predict the optimised conditions that lead to the maximum bio-oil yield. For this purpose, support vector regression with particle swarm optimisation algorithm (SVR-PSO) is developed and applied to the CFD datasets to predict the optimum values of parameters. The maximum bio-oil yield is then computed using the optimum values of the parameters. The CFD simulation is also performed using the optimum parameters obtained by the SVR-PSO. The CFD results and the values predicted by the MLA for the product yields are finally compared where a good agreement is achieved.

Blended Feedstocks for Thermochemical Conversion: Biomass Characterization and Bio-Oil Production From Switchgrass-Pine Residues Blends

An abundant, low-cost, and high-quality supply of lignocellulosic feedstock is necessary to realize the large-scale implementation of biomass conversion technologies capable of producing renewable fuels, chemicals, and products. Barriers to this goal include the variability in the chemical and physical properties of available biomass, and the seasonal and geographic availability of biomass. Blending several different types of biomass to produce consistent feedstocks offers a solution to these problems and allows for control over the specifications of the feedstocks. For thermochemical conversion processes, attributes of interest include carbon content, total ash, specific inorganics, density, particle size, and moisture content. In this work, a series of switchgrass and pine residues blends with varying physical and chemical properties were evaluated. Physical and chemical properties of the pure and blended materials were measured, including compositional analysis, elemental analysis, compressibility, flowability, density, and particle size distribution. To screen blends for thermochemical conversion behavior, the analytical technique, pyrolysis gas chromatography mass spectrometry (Py-GC/MS), was used to analyze the vapor-phase pyrolysis products of the various switchgrass/pine residues blends. The py-GC/MS findings were validated by investigating the bio-oils produced from the selected blends using a lab-scale fluidized-bed pyrolysis reactor system. Results indicate that the physical properties of blended materials are proportional to the blend ratio of pure feedstocks. In addition, pyrolysis of pine residues resulted in bio-oils with higher carbon content and lower oxygen content, while switchgrass derived pyrolysis products contained relatively greater amount of anhydrosugars and organic acids. The distribution of the pyrolysis vapors and isolated bio-oils appear to be a simple linear combination of the two feedstocks. The concentration of alkali and alkaline earth metals (Ca, K, Mg, and Na) in the blended feedstocks were confirmed to be a critical parameter due to their negative effects on the bio-oil yield. This work demonstrates that blending different sources of biomass can be an effective strategy to produce a consistent feedstock for thermochemical conversion.

Computational Study of Sugarcane Bagasse Pyrolysis Modeling in a Bubbling Fluidized Bed Reactor

This work investigates computationally the modeling of sugarcane bagasse pyrolysis in a bubbling fluidized bed reactor. An Euler-Euler multiphase approach, as invoked by the open code MFIX (Multiphase Flow with Interphase eXchanges), is adopted, and the simulations are carried out in a two-dimensional Cartesian domain. While several pyrolysis kinetic models have been developed for wood, coal, and generic biomass, generally using TGA analysis, no such model has been specifically tested or adapted to simulate sugarcane bagasse pyrolysis in fluidized bed reactors through CFD. In the present study, seven pyrolysis kinetic models available in the literature are implemented as MFIX user-supplied routines, and evaluated within given operational temperature ranges. Initially, well established wood pyrolysis results are used to validate the implementations. Following validation, six kinetic schemes are employed to simulate sugarcane bagasse pyrolysis. Results for the products distribution, formation reaction rate ...

Characterization of fast pyrolysis oil from short-rotation willow by high-resolution Fourier transform ion cyclotron resonance mass spectrometry

Fast pyrolysis oil (FPO) produced from short-rotation willow was characterized by using high-resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry and various bulk chemical analyses. The pyrolysis experiments were carried out on a bench-scale bubbling fluidized bed pyrolysis reactor operating at the temperature of 500°C. The resulting pyrolysis oil was a single-phase liquid with relatively low oxygen content and had pH and total acid number values of 3.0 and 129mg/g, respectively. A wealth of compositional information of the willow FPO was obtained using FT-ICR MS in combination with electrospray ionization (ESI) and atmospheric-pressure photoionization (APPI) techniques. While ESI preferentially ionized acidic extractives, small phenolics and anhydrosugars, APPI ionized clearly larger compounds, including neutral lipophilic extractives, triterpenoids and high molecular mass pyrolytic lignin, most of which are beyond conventional gas chromatography–mass spectrometry analyses.

Numerical simulations on the effect of potassium on the biomass fast pyrolysis in fluidized bed reactor

In this study, the effect of potassium on the cellulose fast pyrolysis in a fluidized bed reactor has been studied using Computational Fluid Dynamics (CFD). A multiphase pyrolysis model of cellulose has been implemented by integrating the hydrodynamics of the fluidized bed with an adjusted cellulose pyrolysis mechanism that accounts for the effect of potassium. The model has been validated with the reported experimental data. The simulation results show that potassium concentration and reactor temperature have a significant effect on the yield and component of cellulose pyrolysis products. The product yields fluctuate is caused by the unstable flow in the fluidized bed. The result shows that the increased potassium concentration in the cellulose causes a significant increase of the gas and char yields and reduction in the bio-oil. Also, the dramatic composition variations in bio-oil and gas were observed due to the inhibition of fragmentation, and the depolymerization reaction of activated cellulose, and the catalysis of the depolymerization reaction of cellulose. It is also found that the increase in reactor temperature greatly enhances the endothermic pyrolysis reaction, which leads to the significant changes in the yield and composition of cellulose pyrolysis products.

Bio-oil production from dry sewage sludge by fast pyrolysis in an electrically-heated fluidized bed reactor

Abstract The optimization of bio-oil produced from sewage sludge using fast pyrolysis in a fluidized bed reactor was investigated. Effects of temperature, sludge particle size and vapor residence time on bio-oil properties, such as yield, high heating value (HHV) and moisture content were evaluated through experimental and statistical analyses. Characterization of the pyrolysis products (bio-oil and biogas) was also done. Optimum conditions produced a bio-oil product with an HHV that is nearly twice as much as lignocellulosic-derived bio-oil, and with properties comparable to heavy fuel oil. Contrary to generally acidic bio-oil, the sludge-derived bio-oil has almost neutral pH which could minimize the pipeline and engine corrosions. The Fourier Transform Infrared and gas-chromatography and mass spectrometry analyses of bio-oil showed a dominant presence of gasoline-like compounds. These results demonstrate that fast pyrolysis of sewage sludge from domestic wastewater treatment plant is a favorable technology to produce biofuels for various applications.

Enhancing biogas production of corn stover by fast pyrolysis pretreatment

A new thermo-chemical pretreatment by a lower temperature fast pyrolysis (LTFP) was applied to promote anaerobic digestion (AD) efficiency of corn stover (CS). The pretreatment experiment was performed by a fluidized bed pyrolysis reactor at 180, 200 and 220°C with a carrier gas flow rate of 4 and 3m3/h. The components characteristics, Scanning Electron Microscope (SEM) images and Crystal Intensity (CrI) of the pretreated CS were tested to explore effectiveness of the pretreatment. The results showed that the cumulative methane production at 180°C for 4 and 3m3/h were 199.8 and 200.3mL/g TS, respectively. As compared to the untreated CS, the LTFP pretreatment significantly (a<0.05) increased the methane production by 18.07% and 18.33%, respectively. Methane production was well fitted by the Gompertz models, and the maximum methane potential and AD efficiency was obtained at 180°C for 3m3/h.

Formate assisted pyrolysis of pine sawdust for in-situ oxygen removal and stabilization of bio-oil

Pine sawdust was pretreated with several calcium compounds and then pyrolyzed in a fluidized bed pyrolysis reactor at 500°C. The catalytic action of the calcium compounds varies depending on the anion. Analysis of pyrolysis gas, liquid and char yields and compositions demonstrates that calcium sulfate is inert during pyrolysis while calcium formate, carbonate, hydroxide and oxide show significant deoxygenation activity. Of the salts which showed deoxygenation activity, calcium formate had the highest relative yield. This effect is likely attributable to the activity of calcium formate as a hydrogen donor at the pyrolysis temperature.

Fast co-pyrolysis of coal and biomass in a fluidized-bed reactor

Co-pyrolysis is one of the most promising options for the utilization of coal and biomass. Coal/biomass blends were prepared using Yilan subbituminous (YL) and corncob and the mass ratios of coal in mixtures varied between 0 and 100 %. Co-pyrolysis characteristics were investigated in a thermogravimetric analyzer from 303 to 973 K under the nitrogen flow of 100 mL min−1. The co-pyrolysis residues were less than the sum simply added of the solid yields of individuals. With heating rate increased from 10 to 40 K min−1, the residues decreased more severely compared to the expected under various blending ratios. For fast pyrolysis in fluidized-bed reactor, gas volumes and char yields of co-pyrolysis showed a significant linearity. But pyrolysis-oil yields were higher than the expected from the additive model when the YL blending ratios were less than 60 %. The co-pyrolysis evolved more H2, CH4, C2 + C3, and less CO than an additive pyrolysis process of individual fuel. The GC/MS results indicated that co-pyrolysis-oil contained more alcohols, ketones, aldehydes, or acids than that of individual fuel. All of that suggested the H/OH in volatiles produced from rapid pyrolysis of biomass transferred to the radicals of coal pyrolysis. The possible reaction mechanism also was provided in the paper.

The Investigation on Fragmentation Behavior of Lignite Coal during Fluidized Bed Pyrolysis

This paper reported the fragmentation behavior of lignite coal particles during coal pyrolysis in fluidized bed reactor at temperature of 300°C,350°C,600°C,650°C. The particles with size of 2-4mm,4-6mm and 7-10mm pyrolyzed under N2 atmosphere. The fragments were recovered by hopper, cooled to the ambient temperature and sieved in different ranks. Experimental results show that with the increasing of temperature and initial coal size due to internal overpressure induced by volatiles releasing and thermal stress caused by thermal gradient of coal intra-particles the intensity of fragmentation was enhanced monotonously, the number of fragments increased sharply and the average size of fragments declined.