Bubbling Fluidized Bed Reactor Research Articles

An experimental investigation into the characteristics of ammonia dissociation in a Bubbling Fluidised Bed

Ammonia (NH3) dissociation is of an initial and very important step during its combustion process. This study therefore systematically investigates the effect of reaction temperature (650–950 °C), fluidisation number (0.83–2.50) and static bed depth (0–25 mm) on NH3 dissociation in a laboratory-scale Bubbling Fluidised Bed (BFB). By analysing the concentrations of H2 and N2 in the effluent using gas chromatography, results show that the conversion ratio of NH3 in BFB was merely 0.26%–0.29% at 650 °C but increased significantly to 18.1%–25.3% at 950 °C. This highlights the importance of temperature in promoting NH3 dissociation. However, as fluidisation number increased from 1.0 to 2.5, attributing to a decrease in gas – solid contact time, the conversion ratio of NH3 decreased correspondingly from the highest 20.7%–5.7%. Moreover, as static bed depth increased from 15 mm to 25 mm, the conversion ratio of NH3 increased slightly from 21.5% to 26.8%, both of which were found to be higher than that without bed particles. Clearly, NH3 dissociation is enhanced by the bed material depth but is also dependent on the gas – solid contact time. In addition, by measuring the temperature distribution in the BFB reactor, a temperature drop of ca. 20 °C near the distributor was confirmed, showing a strong effect of endothermicity during NH3 dissociation. These would provide an improved comprehension on the mechanisms of NH3 dissociation and offer theoretical guidance for optimising the combustion processes in BFB burning NH3.

Reaction Characteristics of Calcination and Decomposition of Phosphogypsum in a Bubbling Fluidized Bed.

A bubbling fluidized bed reactor is designed to investigate the high-temperature calcination and decomposition characteristics of phosphogypsum (PG). The reactor employs electric heating, and a lifting discharge tube is installed in the middle of the air distributor to allow flexible switching between batch and continuous feeding modes. The batch test results show that the solid-phase bed materials with a PG particle size of 0.27-0.55 mm and a coal particle size of 0.55-0.83 mm are found to have uniformly mixed at a PG/coal mass ratio of 5:1 and calcined at a high temperature of 1100 °C for 30 min. PG completely decomposes to yield mainly CaS and a small amount of Ca2(SiO4) as the solid-phase products. For the above-mentioned optimal process parameters, a 120 min thermal-state continuous test is conducted. Feeding and discharging are performed at intervals of 30 min to maintain the stability of the static bed height inside the reactor. The results indicate that the PG decomposition rate is higher than 92% in the batch and continuous tests. However, the continuous decomposition of PG has significant process advantages, such as a higher CaS yield (71.20%) compared to that in the batch mode (64.49%). Furthermore, PG undergoes agglomeration and bonding within the particles when heated, intensifying the formation of a Ca2(SiO4) eutectic.

Experimental and numerical investigation on the pyrolysis of oil shale particles in a bubbling fluidized bed

The efficient utilization of oil shale resource is beneficial to environment and the resource diversity. In this work, a bubbling fluidized bed (BFB) reactor was first used to pyrolyze Huadian oil shale experimentally, mainly focusing on the influence of fluidization flow rates. The yield of shale oil, char and non-condensable gas varies little at different fluidization flow rates, but the components in shale oil are different due to the secondary cracking, such as the fractions and species of aliphatic hydrocarbons, aromatic hydrocarbons and non-hydrocarbons. Then, the dense discrete phase model (DDPM) was used to track the trajectories of oil shale particles with different diameters in a bubbling fluidized bed. Population balance model (PBM) coupled Eulerian model was used to well describe the bubbling status of bed materials to characterize the hydrodynamic behaviors. Furthermore, a segmented kinetic model was compiled by UDF module to illuminate the pyrolysis of oil shale particles. The multi-phase reactive flow modeling clearly indicated the distribution of oil shale particles and gaseous products in BFB reactor, as well as pyrolysis time and the secondary cracking at different fluidization flow rates. In summary, this work provides a reference basis for complete pyrolysis of oil shale particles in a bubbling fluidized bed and generating shale oil with high yield and good quality.

Hydrodynamics and OCM reaction performance in a bubbling fluidized bed reactor and a riser reactor

The reasonable reactor design is of great importance for increasing the C2 yield (C2H4 and C2H6) of the oxidative coupling of methane (OCM), and the OCM reactor should remove the heat released in reactions quickly and efficiently and minimize the consecutive reaction of ethylene to carbon oxides. The fluidized bed reactor is characterized by excellent heat transfer, superior mass transport, and large handling capacity, while fewer studies focused on large-scale fluidized bed reactors for the OCM reaction. Therefore, large cold-model experiments and computational fluid dynamics simulations were conducted to investigate hydrodynamics and the OCM reaction performance in a large-scale bubbling fluidized bed (BFB) and a large-scale riser. In the BFB reactor, consecutive reactions of ethylene are acute because of the strong gas back-mixing, high solids holdup, and non-uniform solids distribution. While the consecutive reactions of ethylene are negligible due to the plug flow structure and low solids holdup in the riser reactor. Further, both reactors can achieve isothermal operation for the OCM process. The C2 selectivity of 45.4% and C2 yield of 21.1% are obtained in the riser reactor, increasing by 20.3% and 5.8% individually than that in the BFB reactor. This study provides useful information and reference to the OCM reactor design and commercialization.

Numerical simulation method of a circulating fluidized bed reactor using a modified MP-PIC solver of OpenFOAM

There are some previous works for simulating a bubbling fluidized bed (BFB) reactor using OpenFOAM's MPPICFoam solver, but those for circulating fluidized bed (CFB) reactors are few. In this study, the MPPICFoam solver was verified with a BFB reactor by comparing the solver's simulation results with the experiment and simulation results from the literature. By introducing the inter-boundary particle circulation function and a new module for setting sand particle size distribution, simulations were performed for a 0.1 MW th pilot-scale CFB combustor under isothermal conditions. The modified solver for the CFB reactor gives similar results as the experiment and commercial computational fluid dynamics (CFD) tool, well-predicting the pressure distribution and solid volume fraction in the riser. • MPPICFoam solver reliability for lab-scale bubbling fluidized-bed reactor verified. • Accurate solver prediction of solid volume fraction (horizontal) distribution. • Model used for numerical simulation to study riser hydrodynamics of a CFB combustor. • Particle size distribution module and new circulating boundary conditions added. • Improved solver shows superior predicted experimental results in dense bed region.

Design guideline for CO2 to methanol conversion process supported by generic model of various bed reactors

This study developed a novel design guideline for CO2 to methanol (CTM) conversion process supported by a generic model for various types of bed reactors (BRs) as the process economics depends on BR selection. Using commercially feasible BRs, such as fixed bed (FxB), bubbling fluidized bed (BFB), turbulent fluidized bed (TFB), and fast fluidized bed (FFB), we analyzed the CTM process to determine the optimum recycle ratio, gas velocity over the minimum fluidization velocity (GV/MFV) ratio, inlet reactor pressure, and inlet reactor temperature. At full recycle of unconverted gas, the optimum GV/MFV ratio was 0.1 for the process using an FxB reactor, while conversion using a TFB reactor was a better option than those using BFB and FFB reactors at the GV/MFV ratio of 7.03. Meanwhile, the CTM process using various types of BRs performed the minimum cost at 55 bar for reactor pressure and 498 K for reactor temperature. Owing to the competitiveness of the FxB and TFB reactors at small and large CO2 source rates, respectively, further analysis of the optimal conditions was conducted for these reactors, and a design guideline for the CTM process using these reactors was developed. The effect of the uncertainty parameters on the process design was analyzed to determine the CO2 source rate, green H2 cost, and CO2 cost. The design guideline was suggested for proper CTM process at different uncertainty values of CO2 source rate and material costs under a vision up to 2050 (for net-zero emissions). Finally, the design guideline integrated with methanol purifiers highlighted its reliability for high-purity methanol production. The production cost (∼340 $/tMeOH at 2050) for green methanol (mitigated −0.78 to −0.83 kgCO2/kgMeOH) was highly competitive with the cost (310 to 520 $/tMeOH) of traditional methanol production emitted 1.6 to 2.971 kgCO2/kgMeOH. The developed guidelines are useful for the design, operation, and decision-making of the CTM process. In addition, the developed models for BRs can contribute to other CO2 utilization processes.

Detailed biomass fast pyrolysis kinetics integrated to computational fluid dynamic (CFD) and discrete element modeling framework: Predicting product yields at the bench-scale

Fast pyrolysis is an intricate process due to the variability and anisotropy of lignocellulosic biomass and the complicated chemistry and physics during conversion in a bubbling fluidized bed reactor (BFBR). The complexity of biomass fast pyrolysis lends itself well to computational fluid dynamics (CFD) and discrete element (DEM) analysis, which promises to reduce experimental time and its associated cost. This study investigated switchgrass fast pyrolysis simulated by computational fluid dynamics coupled with a discrete element method to track individual reacting biomass particles throughout a bench-scale BFBR reactor. We accounted for the fast pyrolysis chemistry through a comprehensive reaction scheme with secondary cracking reactions. We performed a three-step reduction for secondary cracking reactions to convert the full cracking scheme into a reduced scheme easily incorporated into our model. We assessed the impact of operational conditions on the steady-state yields of liquid bio-oil, non-condensable gases (NCG), at 550 °C over a range of fluidization numbers (2 – 6 Umf), reported as a ratio to the minimum fluidization velocity (Umf). At steady-state, the volatile bio-oil yield had a range of 49.3–50.4 wt%. Levoglucosan was the primary volatile component present with 21 wt% of the bio-oil while water was the second largest with 20 wt%. The reduction of the secondary reaction schemes did not appreciably affect the overall yields of switchgrass pyrolysis compared to the full secondary scheme.

An experimental investigation of high-ash coal gasification in a pilot-scale bubbling fluidized bed reactor

Gasification of low-grade, sub-bituminous coal with a high-ash content above 45% is carried out in a pilot-scale bubbling fluidized bed reactor using air and steam as the fluidizing gases. For a stable autothermal operation of the gasifier, the effects of equivalence ratio (φ) and steam/coal ratio (ψ) on syngas composition, carbon conversion, cold gas efficiency, and agglomeration behavior are investigated. The chemical composition of the ash samples is analyzed using X-ray fluorescence, whereas a scanning electron microscope, coupled with energy-dispersive spectroscopy, is utilized to inspect agglomerates formed during the gasification. The optimum range of φ is found in the range of 0.19–0.28, which maintains bed temperature in the range of 800−900°C. Steam injection increases heating value, carbon conversion, and gasification efficiency, however beyond a threshold value of ψ, no additional gain is observed. The highest heating value of the syngas obtained from the experiments is found to be 3 MJ/Nm3, whereas the corresponding carbon conversion and cold gas efficiency are found to be 85%, and 48%, respectively. At low fluidization numbers, agglomerates are formed due to local hotspots, as the collected ash sample has small alkali content.

3D Unsteady Simulation of a Scale-Up Methanation Reactor with Interconnected Cooling Unit

The production of synthetic natural gas (SNG) via methanation has been demonstrated by experiments in bench scale bubbling fluidized bed reactors. In the current work, we focus on the scale-up of the methanation reactor, and a circulating fluidized bed (CFB) is designed with variable diameter according to the characteristic of methanation. The critical issue is the removal of reaction heat during the strongly exothermic process of the methanation. As a result, an interconnected bubbling fluidized bed (BFB) is utilized and connected with the reactor in order to cool the particles and to maintain system temperature. A 3D model is built, and the influences of operating temperature on H2, CO conversion and CH4 yield are evaluated by numerical simulations. The instantaneous and time-averaged flow behaviors are obtained and analyzed. It turns out that the products with high concentrations of CH4 are received at the CFB reactor outlet. The temperature of the system is kept under control by using a cooling unit, and the steady state of thermal behavior is achieved under the cooling effect of BFB reactor. The circulating rate of particles and the cooling power of the BFB reactor significantly affect the performance of reactor. This investigation provides insight into the design and operation of a scale-up methanation reactor, and the feasibility of the CFB reactor for the methanation process is confirmed.

Catalytic pyrolysis of spent coffee waste for upgrading sustainable bio-oil in a bubbling fluidized-bed reactor: Experimental and techno-economic analysis

Spent coffee waste (SCW) is extremely attractive to be exploited and utilized as a material source for energy generation and chemical production. This study concerned bio-oil production via non-catalytic and catalytic fast pyrolysis using SCW in a bubbling fluidized-bed reactor (BFR). In particular, a comparative analysis of the quality of the bio-oil produced was conducted for non-catalytic (using silica sand as the bed material) and catalytic (using dolomite, HZSM-5, hematite, and magnetite as the catalyst) fast pyrolysis. Scale-up modeling confirmed using the experimental data was performed at a feed rate of 100 kg h−1 (1,000-fold capacity), which showed different orders in the quality of energy (hematite > magnetite > dolomite > HZSM-5 > silica, in order of energy from highest to lowest) owing to the realistic integration of the BFR with other components in plants, such as the combustor, compressor, and separator. Further, techno-economic analysis of scale-up system revealed that the unit production costs of bio-oil were 0.0151, 0.0034, 0.0143, 0.0095, and 0.0102 $ MJ−1 for silica, dolomite, HZSM-5, hematite, and magnetite, respectively (dolomite > hematite > magnetite > HZSM-5 > silica, in order of unit cost from lowest to highest). Among them, dolomite and hematite showed competitive unit production costs compared to the price of conventional crude oil (0.0098 $ MJ−1). The importance of coupling laboratory-scale experimental results with scale-up modeling and economic analysis has thus been demonstrated for practical feasibility studies of the SCW pyrolysis for bio-oil production.

Dynamic model and performance of an integrated sorption-enhanced steam methane reforming process with separators for the simultaneous blue H2 production and CO2 capture

An integrated sorption-enhanced steam methane reforming (SESMR) process for simultaneous blue H2 production and CO2 capture is developed on the semi-central scale of ~ 48 ton H2/day. The developed SESMR process consists of a cyclic fluidized-bed (CFB) system, heating and pretreatment systems, CO2 capture system, a H2 pressure swing adsorption (PSA) system, compressors, and a combustor. To analyze the CFB system consisting of a bubbling fluidized-bed (BFB) reactor and fast fluidized-bed (FFB) regenerator, a dynamic model is formulated using the conservation equations combined with the Lagrange and Eulerian approaches and gas-velocity prediction. After a validation with reference, the developed CFB model is integrated with the dynamic model of the PSA and the algebraic equations for the other units to analyze the dynamic behavior and performance of the integrated SESMR process. The energy efficiency (82.2%) and H2 production cost of the SESMR process (12% reduction from that of the SMR process) are close to the prediction by the United States Department of Energy, let alone CO2 capture. According to the sensitivity analysis, the temperature of the BFB reactor is the most important factor because it considerably affects the production rate, product quality, CO2 capture, H2 cost, and energy efficiency. Since the CFB model has been shown to accurately predict the performance and reasonably explain the dynamic behaviors, it can be applied not only to the SESMR process but also to other CFB-related processes. The SESMR process contributes to the design, optimization, control, and decision-making processes relating to centralized or semi-central blue H2 production.

Simulation of biomass gasification in bubbling fluidized bed reactor using aspen plus®

The direct (with air) gasification process of biomass in bubbling fluidized bed reactor was simulated using Aspen Plus®. The reactor was divided in three parts: the pyrolysis zone, combustion zone and reduction zone. The pyrolysis process simulation was supported by an external MS-Excel® subroutine to define the yield and composition of the main components, namely, char, gas and tar. Whereas the combustion and reduction processes were simulated using a kinetic model. These models were calibrated and thereafter validated with a set of distinct results from gasification of four different types of biomass using a pilot-scale bubbling fluidized bed reactor, with different equivalence ratio (from 0.17 to 0.35) and temperature (from 709 °C to 859 °C). The results obtained from the simulation, namely the concentration of CO, CO2, H2, CH4, C2H4 in the producer gas, were in good agreement with the experimental ones for a set of biomass types and operating conditions. Amongst the gases analysed, H2 gas was predicted with the lowest accuracy, always being overestimated; despite that, the highest absolute error obtained for H2 was only 4.4%. Finally, the tar concentration predicted was between 20 and 42 g/Nm3 and it decreased with the increase of equivalence ratio, temperature and biomass particle size.

Chemical looping gasification of torrefied woodchips in a bubbling fluidized bed test rig using iron-based oxygen carriers

Chemical looping gasification is an efficient technology to convert biomass into valuable syngas. The iron-based oxygen carriers are a promising option for large-scale commercial applications due to their low cost and environmentally-friendly properties. The present study aims at evaluating the performance of the syngas production from the chemical looping gasification of torrefied woodchips in a pilot-scale bubbling fluidized bed reactor using iron ore and ilmenite as oxygen carriers. The effects of the operating parameters were investigated in this study. The results show that an increase in operating parameters could favor the process performance. Carbon conversion efficiency and the yields accelerate at high operating conditions. Carbon conversion efficiency showed a maximum value of 91.42% for iron ore at the ratio of oxygen carrier-to-biomass of 6, while the gas yield reaches the peak at SBR of 1.4 for ilmenite. The addition of steam in biomass chemical looping gasification improves hydrogen production and syngas quality in the product gas. Despite ilmenite provides better performance for hydrogen production, it characterizes by a lower reactivity compared to iron ore. It is also found that iron ore performs better at lower values of steam-to-biomass ratios and temperatures, while ilmenite shows good results at higher those parameters.

Bio-oil production from fast pyrolysis of furniture processing residue

The pyrolysis characteristic of furniture processing residue (FPR), which was analyzed by thermogravimetric analysis (TGA) under nitrogen atmosphere, mainly decomposed between 230 °C and 500 °C. The FPR was submitted to fast pyrolysis in a bubbling fluidized-bed reactor (BFR) for converting into bio-oil, bio-char. The product distribution and characteristics of bio-oil depend on the operating conditions (temperature, fluidizing flow rate, particle size of sample). The bio-oil yield showed the highest value (50.68 wt%) at the pyrolysis temperature of 450 °C with a biomass particle size of 1.0 mm and a fluidization velocity of 2.0×Umf. The bio-oil had high selectivity for dioctyl phthalate, levoglucosan, and phenolic derivatives. The carbon number proportions in bio-oils of FPR were 32.74 wt% for C5–C11 fraction, 47.60 wt% for C12–C18 fraction and 19.38 wt% of C25–C38 fraction, respectively. The gas product included CO, CO2, H2, and hydrocarbons (C1–C4), and the selectivity of CO2 was the highest. The high heating value (HHV) of gas products was between 4.60 and 12.90 MJ/m3. The bio-char shows high HHV (23.87 MJ/kg) and high C content (62.47 wt%) that can be applied as a solid fuel.

Reactive MP-PIC investigation of heat and mass transfer behaviors during the biomass pyrolysis in a fluidized bed reactor

Gas-solid reactive flows during the biomass fast pyrolysis in a three-dimensional bubbling fluidized bed (BFB) reactor are numerically modeled via the multiphase particle-in-cell approach. The model is comprehensively validated with the experimental data regarding the bubble dynamics and product yields. Subsequently, the physical and thermal dynamics of bubbles under the condition of high-temperature biomass pyrolysis in the BFB reactor are explored. The results indicate that the axial segregation induced by size and density difference between sand and biomass results in the occurrence of preferential distribution of biomass particles, which significantly affects the spatial distributions of hydrodynamics, temperature, and species of gas-solid flows. The presence of biomass inlet results in low temperature, large density, and large aspect ratio of rising bubbles around this region. Bubble pressure and bubble temperature increase and decrease along with bed height, respectively. Pyrolysis temperature obviously affects the temperature, pressure, density of bubbles. The results are expected to shed light on the gas-solid hydrodynamics and thermochemical characteristics, especially the dynamics of meso-scale bubble structures in the reactor.

Potential of Virginia Mallow as an Energy Feedstock

This study aims to compare the potential of Virginia mallow to other high yielding perennial grasses and hardwoods by characterising and comparing fast pyrolysis product yields. Feedstocks selected for this study include miscanthus (Miscanthus x giganteus), Virginia mallow (Sida hermaphrodita), willow short rotation coppice (SRC) (Salix viminalis) and oak (Quercus robur). The experimental work was split into two sections: analytical (Py–GC–MS) and laboratory-scale processing using a 300 g h−1 continuous bubbling fluidised bed reactor. Pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS) has been used to quantify pyrolysis products from these feedstocks by simulating fast pyrolysis heating rates using a CDS 5200 pyrolyser closed coupled to a PerkinElmer Clarus 680 GC–MS. High bio-oil yields were achieved for Virginia mallow, willow SRC and oak (65.36, 62.55 and 66.43 wt% respectively), but miscanthus only produced a yield of 53.46 wt% due to increased feedstock ash content. The water content in the bio-oil is highest from miscanthus (17.64 wt%) and relatively low in the Virginia mallow and hardwoods willow SRC and oak (12.49, 13.88 and 14.53 wt%). Similar high yields of bio-oil and low yields of char and non-condensable gas compared to willow SRC make Virginia mallow an attractive feedstock for fast pyrolysis processing.Graphic

Experimental study on steam gasification of torrefied woodchips in a bubbling fluidized bed reactor

Biomass-based fuel is a potential renewable energy source despite its low energy density, high moisture content, and complex ash components due to its carbon-neutral nature. Torrefaction process, a promising biomass pretreatment method for upgrading biomass properties, is effective to generate fuel with higher calorific value and energy density. Torrefied biomass performs higher energy density and improved grindability characteristics as well as lower ratios of O/C and H/C compared to its raw source. This study presents an evaluation of the hydrogen production from steam gasification using torrefied woodchips as a feedstock in a pilot-scale bubbling fluidized bed reactor. The feedstock used is torrefied woodchips, which were treated at 250 °C in the N2 atmosphere. The experiments were conducted under isothermal and negative gauge pressure conditions in a pilot-scale bubbling fluidized bed reactor at different operating conditions such as gasification temperatures, steam-to-biomass ratio (SBR), and equivalence ratio (ER). Experimental results show that the high temperature and SBR are more favorable for hydrogen production and improve carbon conversion efficiency, while higher ER lowered content and yield of hydrogen. The optimal value of the steam-to-biomass ratio at 850 °C is 1.2 with the hydrogen content of 48.41% and the hydrogen yield of 0.039 Nm3/h.

Energy recovery by fast pyrolysis of pre-treated trommel fines derived from a UK-based MSW material recycling facility

In this experimental study, a physically pre-treated trommel fines feedstock, containing 44 wt% non-volatiles (ash and fixed carbon) and 56 wt% volatile matter (dry basis), was subjected to fast pyrolysis to recover energy from its organic load, using a 300 g h−1 bubbling fluidized bed (BFB) fast pyrolysis rig. A physical pre-treatment method (including crushing, grinding and sieving) was used to prepare a 0.5–2 mm sized trommel fines feedstock to make it suitable for fast pyrolysis in the BFB reactor. Experimental results from the fast pyrolysis process showed that the highest yield of organic liquid was obtained at around a temperature of 500 °C. However, both char and gas yields increased dramatically at temperatures above 500 °C, as a result of enhanced cracking of organic vapours, which reduced the yield of liquid products. Overall, energy recovery from the pyrolysis products (liquid and gas products as well as char pot residues) ranged from 63 to 70%, generally increasing with temperature. A large proportion of the high ash content (36 wt%) of the feedstock was found in the char pot (>62%), while smaller proportions were found in the reactor bed and some liquid products. The char pot ash residues composed mostly of non-hazardous earth materials and may be applied in bulk construction materials e.g. cement manufacture. Although, there was no problem with the pyrolysis rig during 1 h of operation, longer periods of operation would require periodic removal of accumulated solid residues and/or char pot modification to ensure continuous rig operation and process safety.

Fluidisation characteristics and inter-phase heat transfer on product yields in bubbling fluidised bed reactor

Fluidisation and mixing of sand and biomass particles have significant effects on product yields in bubbling fluidised bed reactors (BFBR). There is a lower limit for the velocity of fluidising media known as minimum fluidisation velocity. Similarly, an upper limit is defined for velocity where the bio-oil production is maximised – known as the maximum effective velocity (MEV). A computational fluid dynamics (CFD) simulation for biomass fast pyrolysis process in a 2-D lab-scale BFBR is developed to analyse the variation of MEV as the sand particle size varies. The model is first validated using the experimental data. Then, a parametric study is conducted for the carrier gas velocities in a range of 0.3–1.1 m/s where the sand particle sizes vary from 0.4 to 1 mm, and the biomass particles are in a range of 0.2–0.5 mm. Effects of the packing limit are also analysed. For this purpose, the different sand particle sizes and their corresponding MEV are tested at the sand packing limits of 45, 55, 65, and 75 mm in which the optimal packing limit is found to be 55 mm. A detailed thermodynamic study is performed with the focus on the sand particle size and packing limit affecting the heat transfer rates between phases. A decrease in required heat transfer rates is directly linked to an increase in bio-oil yield. It is observed that heat transfer between sand-biomass is much more efficient than the heat transfer between nitrogen-biomass, confirming the importance of the sand particles as the heat carriers.

Co-gasification of refused derived fuel and biomass in a pilot-scale bubbling fluidized bed reactor

In this work, direct (air) co-gasification of refused derived fuel with biomass was demonstrated in an 80kWth pilot-scale bubbling fluidized bed reactor. The influence of the process operating parameters, namely average bed temperature between 785 and 829 °C, equivalence ratio between 0.21 and 0.36 and refused derived fuel weight percentage in the fuel mixture (0, 10, 20, 50 and 100 wt%) was analyzed. For the operating conditions used, the process was demonstrated as autothermal and operating under steady-state conditions, with no defluidization phenomena observed. The increase of the refused derived fuel weight percentage in the fuel mixture led to an increase of the methane and ethylene concentration in the producer gas and, consequently, an increase of the producer gas lower heating value, reaching a maximum value of 6.4 MJ/Nm3. In terms of efficiency parameters, cold gas efficiency was found between 32.6 and 53.5% and carbon conversion efficiency between 56.0 and 84.1%. A slight increase of the cold gas efficiency was observed with the increase of the refused derived fuel weight percentage in the fuel mixture. Thus, refused derived fuel co-gasification with biomass was shown as a highly promising process for the valorization of wastes as an energetic resource.