Effects Of Biomass Particle Size Research Articles

Evaluation of the Effect of Particle Size and Biomass-to-Water Ratio on the Hydrothermal Carbonization of Sugarcane Bagasse

The generation of platform chemicals and hydrochar is of great interest because they reduce dependence on fossil resources and contribute to climate change mitigation by reducing carbon emissions. The main objective of this study was to evaluate the effect of biomass particle size and biomass-to-water ratio in a hydrothermal conversion system for the generation of value-added products obtained from sugarcane bagasse. Biomass characterization was performed using proximal, elemental, and structural analysis; hydrothermal carbonization was carried out at 220 and 260 °C for one hour; and conversion was monitored using pH, conductivity, and IR spectroscopy. Platform chemicals were quantified using HPLC-IR. Hydrochars were characterized by using scanning electron microscopy and energy dispersive spectroscopy. Optimizing biomass particle size and water ratio is crucial for maximizing the yield of platform chemicals and hydrochar. The study’s outcomes revealed that specific combinations, such as a biomass-to-water ratio of 1:50 and a particle size of 212 μm at 220 °C, resulted in a substantial 31.07% yield of platform chemicals on a dry basis. This highlights the critical role these parameters play in influencing the production efficiency of valuable chemicals. Furthermore, variations in biomass particle size and water ratio also affect the characteristics of hydrochar. For instance, utilizing a biomass-to-water ratio of 1:50 and a larger particle size of 600 μm at 260 °C led to the production of hydrochar with higher carbon content and increased porosity. These findings underscore how adjustments in these factors can impact not only chemical yields, but also the properties and quality of the resulting hydrochar.

Quantitative measurement of sodium emissions during oxy-fuel combustion of a beech wood biomass particle using laser-induced breakdown spectroscopy

Oxy-fuel biomass combustion in a circulating fluidized bed is a clean and sustainable biomass utilization technology. Woody forest biomass is considered a promising source of renewable energy because of its widespread availability across the globe. However, effective biomass utilization in thermal power plants is largely limited by severe ash deposition and corrosion of heat transfer surfaces due to alkali metal and chlorine emissions during biomass combustion. In this study, laser-induced breakdown spectroscopy (LIBS) was applied to detect in-situ gas phase sodium (Na) emission during single particle combustion of widely available forest biomass, namely, beech wood. The operating conditions simulate the thermo-chemical conditions relevant to a fluidized bed combustor system, where the operating temperature varies between 1073K–1273K. This work aims to investigate the effect of O2 concentration, CO2 (oxyfuel environment), and particle size on the emission of sodium during the combustion of a single beech wood particle. The unresolved sodium doublet was used as the LIBS signal to quantify sodium emission concentration.Oxygen concentration is the most critical parameter affecting Na emissions, and an increase in O2 concentration led to higher Na emissions. It is observed that there is a significant reduction in the emission of Na in an O2/CO2 environment as compared to an O2/N2 environment. It is hypothesized that this drop in Na emissions in O2/CO2 environment could be due to lower particle temperatures caused by the lower diffusivity of O2 in CO2 as well as the endothermic gasification reaction in high CO2 environments. In addition, it is reported that the dissociation of sodium carboxylates and carbonates in the biomass matrix to release gaseous Na due to thermal decomposition is retarded at higher CO2 concentrations which could explain the drop in Na emissions. The effect of biomass particle size is pronounced mainly at lower concentration of O2 where, larger particles keep Na trapped in its matrix, however, at higher O2 concentrations (30%), the effect of particle size on Na emission is negligible.

Effect of Biomass Particle Size on the Torrefaction Characteristics in a Fixed-Bed Reactor

The aim of this study is to investigate the influence of biomass particle size on the torrefaction characteristics under different torrefaction temperatures and times. Paulownia wood with particle sizes ranging from 12 to <0.3 mm was selected. It was torrefied at 260 and 290 °C in a fixed-bed reactor for 30–90 min. The results showed that biomass particle size did affect the product’s evolution during biomass torrefaction. With the decrease in particle size from 12 to <0.3 mm, the yield of the solid product decreased by 5.41 and 3.54 wt.%, the yield of the liquid product increased by 5.87 and 3.25 wt.%, and the yield of the gas product changed insignificantly, at 260 and 290 °C, respectively. Comparatively, torrefaction temperature had a more significant effect on the composition of gas products than particle size and torrefaction time. At lower temperatures, decarboxylation reactions dominated in the torrefaction process with more CO2 produced. However, at higher temperatures, decarbonylation reactions were significantly strengthened with more CO generated. The contents of CO2 and CO could account for more than 98 vol% of the product gas. The influence of particle size on the chemical composition of the solid product was much smaller than that of torrefaction temperature and time, but the energy yield of the solid product decreased with the decrease in particle size. The increase in torrefaction temperature and time could significantly increase the C content in the solid product while reducing its O content. It is recommended to use a relatively higher temperature (e.g., 290 °C) for the torrefaction of large particle biomass, as it could significantly reduce the impact of particle size on the torrefaction process and reduce the torrefaction time.

In-depth numerical analysis of combustion and NOx emission characteristics in a 125 MWe biomass boiler

A 125MWe Yeongdong retrofit boiler burning 100 % biomass was adopted for electricity generation to achieve net zero energy emissions by 2050. However, the high volatile content of biomass affects temperature distribution and NOx mechanism compared to coal. Additionally, the wide range of particle size inlet results in large amounts of ash at the hopper and high unburned carbon of bottom ash. Here, an in-depth 3D numerical simulation was performed for the combustion and nitrogen oxides (NOx) emission behavior in the biomass boiler. The effect of biomass particle size, active burners on the char conversion at the boiler and bottom outlet, and particle residence time were assessed to determine the particle size range. The simulation results were validated by comparison with the actual data. The volatile burnout rate was significantly higher and faster than that of char burnout, and the burner throat exhibits the highest temperature range (approximately 1800–2100 K). Regarding NOx emission, the rate of thermal NOx was higher than that of total NOx, and the reduction of NOx was also significantly high to contribute the low NOx emission at boiler outlet. In addition, char conversion had significantly depended on the position of the active burner, and particle size below 665 μm can be entrained upward to the boiler outlet with char conversion over 96.85 % at boiler outlet and 100 % at bottom hopper. Therefore, analysis on each active burner can be used to find optimal standby burner while the particle size analysis suggested that percentage of particles larger than 665 μm should be reduced in the biomass boiler. The high-temperature propensity can aid in understanding the deposition behavior in biomass boilers.

Effect of Biomass Particle Size on the Adsorption of Phosphorus from Aqueous Solution by MgO-loaded Biochar

To study the effect of biomass particle size on the rate and ability of phosphorus removal from aqueous solution by MgO-loaded Phragmites australis biochar (MBC), MBC was prepared using 0.0-0.5, 1.0-2.0, and 6.0-8.0 mm Phragmites australis particles as the feedstock and MgCl2 as the modification material. The MBC was characterized using FTIR, XRD, and SEM techniques. Kinetic and isotherm experiments of phosphate (PO43--P) adsorption from aqueous solution by the MBC were conducted, and the experimental data were fitted with various kinetic and isotherm models. The results showed that the adsorption rate of PO43--P by the MBC increased with the increase in biomass particle size. The amount of PO43--P adsorbed by the MBC prepared from 0.0-0.5, 1.0-2.0, and 6.0-8.0 mm particles reached 15.4%, 25.8%, and 80.8%, respectively, within 2 h. The biomass particle size did not affect the maximum PO43--P adsorption capacity (249.0-254.7 mg·g-1) of the MBC. MBC prepared from the 6-8 mm particles retained the complete cell wall structure of the Phragmites australis, and a large number of micropores and mesopores were generated during pyrolysis, thereby forming a hierarchical, regular, and well-connected pore structure. MBC prepared from the 0.0-0.5 mm and 1.0-2.0 mm particles had inferior pore structures with inferior pore connectivity, which affected the diffusion rate of PO43- ions inside the MBC and limited the PO43--P adsorption rate. Therefore, when using waste Phragmites australis harvested from a constructed wetland to produce MBC and remove phosphorus from water, the Phragmites australis should be crushed into 6-8 mm particles. Over-crushing deteriorates the pore structure of the produced MBC and reduces the removal rate of phosphorus by the MBC.

Agri‐food waste valorisation

Agri‐food waste valorisation

Evaluation of Pore Size and Surface Morphology during Devolatilization of Coconut Fiber and Sugarcane Bagasse

ABSTRACT The prospect of exhaustion of fossil fuels and climate change caused due to the extreme use of fossil fuel consequence shifting energy supply from fossil energy to renewable energy. India ranks the second-largest producer of agricultural products and generates huge quantities of agricultural crop residues. These agricultural residues are a promising source of energy producing components. The goal of the present investigation is to study the effect of biomass particle size and devolatilization temperature varied from 500°C to 800°C on pore size distribution, pore volume, surface area, surface morphology, and a structural parameter of the biomass char. The Scanning Electron Microscope images results reveal the variations in the surface morphology of coconut fiber and sugarcane bagasse biomass chars and the decreases of pore fractions with an increase in temperature. Biomass char samples are mesoporous and microporous in nature confirmed by Barrett, Joyner, and Halenda (BJH) analysis, pore size ranging from 25 to 350 Å for mesoporous and 1.0 to 20 Å for microporous particles with open-ended adsorption-desorption isotherms and a substantial increase in BET surface area was observed at all the varied temperatures. A polynomial regression approach is adopted to find a relation between the pore volumes and pore size using thickness plot data to calculate the structural parameter. The structural parameter is a factor which predicts the behavior of Random Pore Model for char combustion kinetics. If the structural parameter is large then the model will result in a maximum reaction rate as the reaction proceeds, due to the growth of the size of the cylindrical pore causes an increase in the available surface area for reaction and results in an increase in the rate of reaction. Finally, as the reaction proceeds due to more pores interaction and pores overlapping, the available surface area decreases and therefore the rate decreases as the structural parameter value is smaller. The structural parameter estimated for mesopore size and micropore size ranges between 6.0 and 18.0 for Sugarcane Bagasse and 7.0 and 17.0 for coconut fiber particles.

The effect of biomass particle size and chemical structure on the enzymatic hydrolysis reaction of galactomannan from sugar palm fruit by β-mannanase from Kitasatospora sp. KY576672

Mannooligosaccharides is essential to support gut health. Unfortunately, obtaining these compounds by chemical synthesis is considered labor extensive. In contrast, production using enzymatic reaction is simpler. Mannan, one of lignocellulose fractions, is a suitable raw material for this purpose. Sugar palm fruit (kolang-kaling) contains a high level of galactomannan, which makes it potential to be used as a resource for MOS bio-production. Our previous work revealed that strain which showed highest mannan-degrading activity was Kitasatospora sp. KY576672. In this study, the use of β-mannanase enzyme produced by this strain to degrade galactomannan from sugar palm fruit was examined. The effect of biomass particle size and chemical structure of polymer towards reaction were studied by conducting reaction using biomass with three different particle sizes and comparing the hydrolysis profile of sugar palm fruit and locust bean gum. Reaction was performed at 40°C and 190 rpm in sodium phosphate buffer pH 6. Results suggested that reaction rate did not significantly change by altering biomass particle size from 150 μm to 75 μm, but it decreased by the use of 150-300 μm particle-size biomass. In addition, locust bean gum produced a more balanced ratio of hydrolysis products (M1-M6) compared to sugar palm fruit. Mannohaxaose (M6) was the main hydrolysis products from sugar palm fruit and locust bean gum.

Effect of Particle Size and Temperature on Pyrolysis of Palm Kernel Shell

Pyrolysis is a viable solution to curb the issue of growing lignocellulosic waste in the world through conversion to potential biofuel and bio-based chemicals. This study focused on the effect of biomass particle size on the feedstock characterisation, biomass ash content, thermal behaviour and pyrolysis products yield. The particle size ranges studied were <0.355, 0.355 to 0.710. 0.710 to 1.00 and 1.00 to 2.00 mm. Thermal behaviour was analysed using thermogravimetric analyser, and pyrolysis experiments were conducted in a fixed-bed pyrolyzer. TGA results show smaller particle size maximum temperature shifted to a lower temperature. From ashing, the results indicated that ash content is the highest at the smallest particle size, <0.355mm (2.8 wt.%). The gaseous yield was the highest in dpA (<0.355 mm) at a temperature of 600°C. The highest pyrolysis oil yield (50.1 wt.%) occurred at 400°C from dpA (<0.355mm). The highest char yield (33.70 wt.%) occurred at 400°C obtained from the largest particle size, dpD (1-2mm).

Ionic liquid pretreatment of yellow pine followed by enzymatic hydrolysis and fermentation.

In this study, it was aimed to enhance the enzymatic hydrolysis of recalcitrant yellow pine wood and subsequently to produce ethanol efficiently through the application of 1-ethyl-3-methylimidazolium acetate (EMIMAc) ionic liquid. The effect of biomass particle size (<2.5 mm, 500-850 μm, 363-500 μm, and <363 μm) prior to pretreatment and pretreatment time (15, 30, and 45 min) on the structural properties and enzymatic hydrolysis yield of EMIMAc pretreated pine wood were also investigated. In general, EMIMAc functioned more efficiently at larger biomass particle sizes compared to smaller ones. Dissolution of solids by pretreatment, amount of lignin extracted from biomass as well as biomass to glucose yield was increased with increasing pretreatment time. The conversion of biomass to glucose was 56% under the selected optimum conditions (500-850 μm particle size; 5% biomass concentration and 140°C-45 min EMIMAc pretreatment). The biomass samples pretreated at the optimal conditions were subjected to simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF) which resulted in ethanol yields of 86 and 96%, respectively. The results presented in this study give a general framework for reducing the recalcitrance of pine to enzymatic saccharification and microbial fermentation by EMIMAc pretreatment without need for long pretreatment times and size reduction. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018.

A Comprehensive Investigation on the Effects of Biomass Particle Size in Cellulosic Biofuel Production

Biofuels derived from cellulosic biomass offer one of the best near- to midterm alternatives to petroleum-based liquid transportation fuels. Biofuel conversion is mainly done through a biochemical pathway in which size reduction, pelleting, pretreatment, enzymatic hydrolysis, and fermentation are main processes. Many studies reveal that biomass particle size dictates the energy consumption in the size reduction. Biomass particle size also influences sugar yield in enzymatic hydrolysis, and biofuel yield in fermentation is approximately proportional to the former enzymatic hydrolysis sugar yield. Most reported studies focus on the effects of biomass particle size on a specific process; as a result, in the current literature, there is no commonly accepted guidance to select the overall optimum particle size in order to minimize the energy consumption and maximize sugar yield. This study presents a comprehensive experimental investigation converting three types of biomass (big bluestem, wheat straw, and corn stover) into fermentable sugars and studies the effects of biomass particle size throughout the multistep bioconversion. Three particle sizes (4 mm, 2 mm, and 1 mm) were produced by knife milling and were pelletized with an ultrasonic pelleting system. Dilute acid method was applied to pretreat biomass before enzymatic hydrolysis. Results suggested 2 mm is the optimum particle size to minimize energy consumption in size reduction and pelleting and to maximize sugar yield among the three particle sizes for big bluestem and wheat straw biomass. Nevertheless, there is no significant difference in sugar yield for corn stover for the three particle sizes.

Oxidative pyrolysis of mallee wood biomass, cellulose and lignin

The oxidative pyrolysis of mallee wood, cellulose and lignin was performed and the bio-oil products were analysed to understand how the externally added oxygen react with the pyrolysis products. Both wood cylinders of diameter 8 mm and fine particles (90–300 μm) were pyrolysed in this study to understand the combined effects of biomass particle size and the presence of oxygen. The results revealed that, at a low oxygen concentration, the gas-phase oxidation of volatiles would improve the yields of levoglucosan and syringaldehyde, as well as unsaturated hydroxyl ketones/aldehydes for small wood particles through the oxygen-induced radical reactions. Although oxygen could facilitate the production of some compounds in bio-oil through the gas-phase reactions, it did lead to decreases in the heavy bio-oil yield due to the over-oxidation of some pyrolysis products (e. g. aromatics, lactones, unconjugated alkyl aldehydes/esters and carboxylic acids). The effects of oxygen on the pyrolysis of wood cylinders were more complicated than mallee wood particles due to the secondary reactions of volatiles and the reactions involving the pyrolysing particle surface. The interactions between the polysaccharide-derived and lignin-derived products in gas phase might affect the oxidation of volatiles, changing the formation of pyrolytic products (e.g. levoglucosan and syringaldehyde).

Optimization of Dilute Acid Pretreatment and Enzymatic Hydrolysis of Phalaris aquatica L. Lignocellulosic Biomass in Batch and Fed-Batch Processes

Phalaris aquatica L., a rich in holocellulose (69.80 %) and deficient in lignin (6.70 %) herbaceous, perennial grass species, was utilized in a two-step (biomass pretreatment-enzymatic hydrolysis) saccharification process for sugars recovery. The Taguchi methodology was employed to determine the dilute acid pretreatment and enzymatic hydrolysis conditions that optimized hemicellulose conversion (75.04 %), minimized the production of inhibitory compounds (1.41 g/L), and maximized the cellulose to glucose yield (69.69 %) of mixed particulate biomass (particles <1000 μm) under batch conditions. The effect of biomass particle size on saccharification process efficiency was also investigated. It was found that small-size biomass particles (53–106 μm) resulted in maximum hemicellulose conversion (81.12 %) and cellulose to glucose yield (93.24 %). The determined optimal conditions were then applied to a combined batch pretreatment process followed by a fed-batch enzymatic hydrolysis process that maximized glucose concentration (62.24 g/L) and yield (92.48 %). The overall efficiency of the saccharification process was 88.13 %.

A Comparison of the Pyrolysis of Olive Kernel Biomass in Fluidised and Fixed Bed Conditions

The use of thermogravimetric analysis to describe biomass kinetics often uses bench top thermogravimetric analyser (TGA) analysers which are only capable of low heating rates. The aim of this research was to compare experimental fast pyrolysis of Olive kernels in a bespoke laboratory thermogravimetric fluidised bed reactor (TGFBR) characterised by rapid heating rates at high flow rates, compared to a smaller bench scale fixed bed TGA system. The pyrolysis in the TGFBR was analysed by using the isothermal kinetic approach and it was theorised that the pyrolysis decomposition reactions occurred by two mechanisms depending on the temperature, resulting in an activation energy of 67.4 kJ/mol at temperatures below <500 °C and 60.8 kJ/mol at temperatures >500 °C. For comparison, a bench scale TGA was used to look at the thermal behaviour in different fixed bed thermal conditions giving a higher activation energy of 74.4 kJ/mol due to the effect of external particle gas diffusion. The effect of biomass particle size (0.3–4.0 mm) on the conversion of biomass at different temperatures, was investigated between 300 and 660 °C in the TGFBR. The results suggested inhibition of internal gas diffusion was more important at lower temperatures, but in comparison had no significant effect when measured in the fixed bed TGA at lower heating rates. Bench top TGA analysis of pyrolysis is a rapid and valuable method, but is limited by smaller sample sizes and lower heating rates. In comparison, the conditions encountered with the laboratory scale TGFBR are more likely to be relevant to larger scale systems where heat distribution, heat transfer and mass diffusion effects play major roles in the reactivity of biomass.

Pretreatment methods to obtain pumpable high solid loading wood–water slurries for continuous hydrothermal liquefaction systems

Feedstock pretreatment is a prerequisite step for continuous processing of lignocellulosic biomass through HTL, in order to facilitate the pumpability of biomass aqueous slurries. Until now, HTL feedstock pumpability could only be achieved at solid mass content below 15%. In this work, two pretreatment methods to obtain wood-based slurries with more than 20% solid mass content, for continuous processing in HTL systems, are proposed. The effect of biomass particle size and pretreatment method on the feedstock pumpability is analyzed. The experimental results show that pumpable wood-based slurries containing 20% solids can be prepared using recycle HTL biocrude as carrier fluid, if particles smaller than 0.125 mm are used. The recycle biocrude concentration used for slurry make-up is strongly affected by the sawdust size distribution. A second pretreatment option is feedstock thermal treatment with alkalis. This method is less sensitive to particle size or wood type. 1 mm particles of either softwood or hardwood could be converted into pumpable liquid feedstock by thermal treatment with NaOH at 180 °C. Wood-water-biocrude slurries viscosity is reduced from 100 to 1000 Pa s to about 1 Pa s, when thermal treatment is applied.

Advanced reforming of agro-waste by modular gasifier for fuel generation

Cassava rhizome, a bulky residue from cassava plantation, was reformed using a modular downdraft gasifier in order to produce a high temperature fuel gas with low tar content. Effects of biomass particle size between 5 and 15mm, inlet air flow rate of 1.98–3.06m3/h and additional 5% Ni/char catalyst for secondary syngas cleanup were investigated. The air flow rate had integrated effects on product yield and composition; higher air flow rate resulted in higher gas yield with less tar and char. The conversion to H2 and CO increased with the biomass particle size, whereas the conversion to CH4 and CO2 decreased. The optimal operating conditions without catalyst addition were obtained with air flow rate of 2.5m3/h and particle size of 10mm where carbon and hydrogen conversions were 94.02% and 65.92%, respectively. In the presence of catalyst, the yield of CO2 was reduced whereas the CO increased. The carbon and hydrogen conversions were 92.87% and 55.69% with air flow rate of 1.98m3/h and particle size of 10mm, respectively. At this condition, tar formation was relatively low with gas heating value of 4.45MJ/m3 and H2/CO of 1.22. Obviously, prepared Ni/char catalyst enhanced condensable tar reforming to smaller gases resulting in increased gas heating value and cold gas efficiency with superior synthesis gas yield. The produced gas contained quality combustible gases, which can be readily used in heat and power applications.

Effects of biomass particle size on yield and composition of pyrolysis bio-oil derived from Chinese tallow tree (&lt;i&gt;Triadica Sebifera L.&lt;/i&gt;) and energy cane (&lt;i&gt;Saccharum&lt;/i&gt; &lt;i&gt;complex&lt;/i&gt;) in an inductively heated reactor

In the face of fluctuating petroleum costs and a growing demand for energy, the need for an alternative and sustainable energy source has increased. A viable solution for this problem can be attained by using thermochemical conversion, pyrolysis, of existing biomass sources for the production of liquid fuels. This study focuses on the effect that biomass particle size has on the conversion of biomass into liquid pyrolysis oil. Energy cane and Chinese tallow tree biomass were pyrolyzed at 550 ℃. The particle size ranges studied were < 0.5, 0.5 to 1.4, 1.4 to 2.4 and, 2.4 to 4.4 mm. The results indicate that the range from 0.5-1.4 mm is a better range for optimizing bio-oil production while keeping water content low.

Combustion Modelling of Pulverized Biomass Particles at High Temperatures

Biomass co-firing is becoming a promising solution to reduce CO2 emissions, due to its renewability and carbon neutrality. Biomass normally has high moisture and volatile contents, complicating its combustion behaviour, which is significantly different from that of coal. A computational fluid dynamics (CFD) combustion model of a single biomass particle is developed in this work, to predict the mass loss properties and temperature profile during the biomass devolatilization and combustion processes, by solving the energy and mass transport equations. The biomass devolatilization reaction was simulated by a two-competing-rate model and the biomass char burnout rate was controlled by both kinetics and diffusion to predict the particle size changes. The resulting predicted temperature profiles show good agreement with experimental data. The results also shed light on the effects of biomass particle size, air temperature and oxygen concentrations on biomass particle combustion behaviour.

Combustion of palm kernel shell in a fluidized bed: Optimization of biomass particle size and operating conditions

This work presents a study on the combustion of palm kernel shell (PKS) in a conical fluidized-bed combustor (FBC) using alumina sand as the bed material to prevent bed agglomeration. Prior to combustion experiments, a thermogravimetric analysis was performed in nitrogen and dry air to investigate the effects of biomass particle size on thermal and combustion reactivity of PKS. During the combustion tests, the biomass with different mean particle sizes (1.5mm, 4.5mm, 7.5mm, and 10.5mm) was burned at a 45kg/h feed rate, while excess air was varied from 20% to 80%. Temperature and gas concentrations (O2, CO, CxHy as CH4, and NO) were recorded along the axial direction in the reactor as well as at stack. The experimental results indicated that the biomass particle size and excess air had substantial effects on the behavior of gaseous pollutants (CO, CxHy, and NO) in different regions inside the reactor, as well as on combustion efficiency and emissions of the conical FBC. The CO and CxHy emissions can be effectively controlled by decreasing the feedstock particle size and/or increasing excess air, whereas the NO emission can be mitigated using coarser biomass particles and/or lower excess air. A cost-based approach was applied to determine the optimal values of biomass particle size and excess air, ensuring minimum emission costs of burning the biomass in the proposed combustor. From the optimization analysis, the best combustion and emission performance of the conical FBC is achievable when burning PKS with a mean particle size of about 5mm at excess air of 40–50%. Under these conditions, the combustor can be operated with high (99.4–99.7%) combustion efficiency, while controlling the gaseous emissions at acceptable levels. No evidence of bed agglomeration was found in this conical FBC using alumina as the bed material for the entire time period of experimental tests.

Biomass co-firing trials on a down-fired utility boiler

This paper describes the practical combustion issues encountered with biomass co-firing on a large scale trial in a 500MW down fired utility boiler at Aberthaw power station. It also investigates and discusses the effect of biomass particle size and physical properties on devolatilisation; flame stability; and slagging by using the biomass energy crop miscanthus.During large scale biomass co-firing, the air flow around the injectors plays an important part in the fuel combustion and stable boiler operation. Secondary air flow at the point of biomass injection was adjusted during the experiments to provide higher airflows around the biomass injectors, hence the mixing, and air available for biomass combustion, was improved producing less unburnt material in the ash and reducing potential filter blockages. However, higher biomass air flows disrupt the temperature distribution in the boiler causing a wider variation of superheater temperatures compared to the baseline condition firing coal only. This reduces the combustion efficiency and can lead to localised hot spots, in the superheaters, with the potential to cause equipment damage. The trials indicated during the experiments that a secondary biomass air flow of 50% of its maximum, gave an optimum balance between air/biomass mixing and variations in the superheater temperatures.