Biomass Blends Research Articles

Pelletization of eucalyptus wood and coffee growing wastes: Strategies for biomass valorization and sustainable bioenergy production

The global energy matrix is based on the use of fossil fuels, which are the main contributors of the greenhouse effect. There are several different alternatives to minimize this problem, such as the pelletization of agroforestry wastes for bioenergy purposes. The aim of this research was to evaluate the potential of forest biomass (eucalyptus wood [E]) and agricultural residues of coffee processing (parchment [P], silver skin [S] and coffee husk [CH]) for pellets production focusing on the generation of energy and to classify them according to commercialization standards. Different proportions of forest biomass mixed with coffee residues were evaluated and used for the production of the pellets with six compositions (EPCH and EPS). Additionally, three coffee processing residues were individually pelleted (100% pure). The pellets with the composition eucalyptus-parchment-coffee husk (ECPCH) had greater durability (98.17%), hardness (37.12 kg) and net energy density (11.60 GJ m−3), and are eligible for commercialization and export according to European standards (type B). The pellets produced with biomass blends provide better energy results (16.51–17.08 MJ kg−1), compared to pellets produced only with CH (15.76 MJ kg−1) and S (16.26 MJ kg−1). The biomass blends positively influenced the bulk density, mechanical durability, and combustibility of pellets.

Co-gasification of biomass blends: Performance evaluation in circulating fluidized bed gasifier

An important aspect of the commercialization of biomass gasifiers is feedstock flexibility. The present study has dealt with performance assessment of a circulating fluidized bed gasifier (50 kWth) with binary blends of three biomasses, sawdust (SD), rice husk (RH) and bamboo dust (BD), as feedstock. The performance of gasification was assessed in respect of the specific yield of producer gas, its LHV, and tar content in addition to gasification efficiencies. Experiments were conducted with varying equivalence ratio (ER) from 0.19 to 0.35, and temperatures of 800°–900 °C. The blending of biomasses resulted in the enhancement of gasification performance due to synergistic effects. Minerals in the ash of RH catalyzed char and tar conversion leading to higher efficiencies. At ER = 0.35, maximum CGE = 62% and CCE = 98% were obtained for RH + BD blend. With increasing temperature, H2, CO content and net yield of producer gas increased with concurrent decreasing in tar. The highest LHV of producer gas (5.05 MJ/Nm3) was obtained for the RH + BD blend at ER = 0.19 and 800 °C. Maximum gas yield (1.72 Nm3/kg dry biomass) and minimum tar content (2.01 g/kg dry biomass) were obtained for SD + BD and RH + BD blends, respectively, at 800 °C and ER = 0.35.

Research of co-combustion of solid biofuel with lean and bituminous coal

The object of research is the processes of thermal conversion of steam coal and biomass, with the aim of creating highly efficient environmentally friendly technologies for its joint combustion into fuel boiler units.One of the important problems that impede the introduction of co-combustion of biomass with coal is the insufficient knowledge of the interaction of two very different solid fuels. The characteristics of grinding, particle aerodynamics, kinetics of all stages of combustion during the joint combustion of two solid fuels remain unexplored. Co-combustion of biomass with coal allows partially replacing scarce grades of steam coal, as well as reducing emissions of harmful gases and dust.To study the peculiarities of co-combustion of coal and biomass, experimental and computational research methods are used, including combustion in a continuous installation designed to study the combustion characteristics of pulverized fuels.Experiments on the combined combustion of lean and bituminous coal with various types of solid biomass showed an improvement in the ignition conditions of coal, with the addition of biomass from 5 to 15 % by heat. The effect of biomass impurities on coal on the temperature distribution along the length of the plume is shown. The paper presents the dependences of the conversion degree of bituminous coal and its blends with crushed pellets of pine, wheat straw and sunflower husk, and also explains the nature of this dependence. The gas analysis of the combustion products shows the effect of biomass blending in bituminous coals on the formation of nitrogen oxides.The findings and dependencies justify the environmental feasibility and efficiency of co-combustion and allow to proceed to the development of a pilot project for partial replacement of coal with various types of solid biofuel.

Application of response surface methodology in catalytic co-gasification of palm wastes for bioenergy conversion using mineral catalysts

Biomass gasification is a promising approach for bioenergy conversion. Usually, biomass gasification is facing interruption in feedstock supply due to seasonal availability of biomass. In biomass gasification, formation of tar also affects the gasification efficiency. Therefore, in this study, catalytic air co-gasification of two palm wastes (coconut shells; CS, oil palm fronds; OPF) was investigated for syngas (H2+CO) and methane production in downdraft gasifier using three mineral catalysts such as Portland cement, dolomite, and limestone to address the issues. The three main process variables were investigated within the specific range, the temperature of 700–900 °C, catalyst loading of 0–30 wt%, and the biomass blending ratio of 20–80 wt%. Response Surface Methodology, Box-Behnken Design was used for process optimization. The results showed that temperature was the most influencing parameter for syngas production, followed by catalyst loading and blending ratio. The maximum methane produced from Portland cement catalyst followed by limestone and dolomite. The syngas and methane yield was obtained 38.81 vol% and 19.96 vol% respectively at optimized conditions of catalyst loading of 20 wt%, temperature of 900 °C, and blending ratio of CS20:OPF80 using Portland cement as a catalyst. The higher syngas and methane yields from catalytic co-gasification as compared to non-catalyst co-gasification was due to the catalytic effect of Ca, Fe, Mg, K, P, and Al oxides present in catalysts and biomass materials.

Characterization of Pure and Blended Pellets Made from Norway Spruce and Pea Starch: A Comparative Study of Bonding Mechanism Relevant to Quality

The mechanism of bonding in biomass pellets is such a complex event to comprehend, as the nature of the bonds formed between combining particles and their relevance to pellet quality are not completely understood. In this study, pure and blended biomass pellets made from Norway spruce and pea starch were characterized using advanced analytical instruments able to provide information beyond what is visible to the human eye, with intent to investigate differences in bonding mechanism relevant to quality. The results, which were comprehensively interpreted from a structural chemistry perspective, indicated that, at a molecular level, the major disparity in bonding mechanism between particles of the pellets and the quality of the pellets, defined in terms of strength and burning efficiency, were determined by variation in the concentration of polar functional groups emanating from the major organic and elemental components of the pellets, as well as the strength of the bonds between atoms of these groups. Microscopic-level analysis, which did not provide any clear morphological features that could be linked to incongruity in quality, showed fracture surfaces of the pellets and patterns of surface roughness, as well as the mode of interconnectivity of particles, which were evidence of the production of pellets with dissimilarities in particle bonding mechanism and visual appearance.

Co-pyrolysis of Miscanthus Sacchariflorus and coals: A systematic study on the synergies in thermal decomposition, kinetics and vapour phase products

In this work, co-pyrolysis of Miscanthus Sacchariflorus (MS) and three ranks of coal, namely lignite (LC), bituminous coal (BC), and anthracite (AC), was performed at the analytical scale. The co-pyrolysis kinetic and products were analysed and compared theoretically and experimentally. The results revealed the synergistic effects of the coal characterstics and biomass blend ratio (BBR) on the thermal decomposition and the products in gaseous phase.The co-pyrolysis of MS-LC and MS-BC samples was characterised by three distinct stages, which were sequentially dominated by moisture removal, decomposition of MS and decomposition of coal. The activation energies of the co-pyrolysis process were different from the activation energies of the pyrolysis of individual MS and coal samples. The kinetics analysis showed that increasing the BBR increased the activation energies of the MS-coal blends up to 25% at the temperatures below 350 °C. However, at the higher temperature range, it decreased the activation energies of MS-LC and MS-BC blends but increased those of MS-AC blends. Both of the coal rank and BBR had noticeable impacts on the thermal behaviour during co-pyrolysis. The optimum positive synergistic effects were obtained on MS-LC blend with a BBR of 1:1. The FTIR analysis results showed the evolution profiles of CH4, CO, CO2, water, formic acid, phenol and xylene. All the products analysed showed L-peaks (250–400 °C) corresponding to MS decomposition. Increasing the BBR promoted the release of all the analysed products from MS-LC and MS-BC, indicating the synergistic effect of the co-pyrolysis.

Methods to improve properties of fuel pellets obtained from different biomass sources: Effect of biomass blends and binders

This study evaluates the effect biomass blending and binder addition on the strength, calorific value (CV), and durability by biomass pellets. Blended biomass materials (0 to 60 wt% additive) and three binders (2 to 6 wt%) (i.e.) recovered polyvinyl alcohol (rPVA); waste cooking oil (WCO) and waste lubricating oil (WLO) were used to make biomass pellets. Ground nut shell (GNS) pellets exhibited the highest CV but lowest strength which was improved by the addition of saw dust (SWD) and Leaf litter waste (LLW) additives. Contrarily, LLW pellets exhibited good strength but the minimum CV which was improved by GNS audition. The LLW biomass contributed as strength improver and GNS served as CV enhancer. The SWD biomass provided both strength and CV to the pellets. In case of binders, a significant increase in the strength of GNS pellets was observed on rPVA addition in comparison to LLW pellets and SWD pellets, whereas WCO and WLO showed a marginal reduction in strength of all the biomass pellets. The rPVA material worked as strength improving binder whereas WCO and WLO were responsible to increase the CV of the pellets.

Effects of biomass blending, ashing temperature and potassium addition on ash sintering behaviour during co-firing of pine sawdust with a Chinese anthracite

When biomass and coal are co-combusted, the ash sintering behaviour cannot be directly predicted on the basis of the properties of individual fuel ash. Knowledge of the ash sintering behaviour can help understanding the subsequent ash fouling and slagging. Herein, the ash sintering characteristics during co-combustion of Jincheng coal (JC) and pine sawdust (PS), together with the effects of biomass blending ratio, ashing temperature and K2CO3 catalyst addition were investigated in depth. The results indicated that for a given JC/PS blend, the ash slagging degree expressed by different decision indices was different, but the tendency was consistent. No obvious fusion phenomenon was observed among the individual particles from the blends without K2CO3 addition. Both types of the particles from individual fuel could be separately identified with obvious difference from their respective particles. When K2CO3 was added to the blends, the ash surface structure varied from unmelted to slightly adhesion. The formation of potassium silicates made great contributions to slagging. The molten and solidified zone on the agglomerate surface featured high contents of K, Si, O and Al, and the coating on the melting surface was composed of the mixture of K-bearing aluminosilicates, potassium chloride and smaller amounts of Ca-bearing aluminosilicates.

Investigation of Ash-Related Issues During Combustion of Maize Straw and Wood Biomass Blends in Lab-Scale Bubbling Fluidized Bed Reactor

Abstract During the combustion of solid fuels, the undesired effects of ash transformation include bed agglomeration, slagging, and fouling processes. In particular, a problematic consequence of bed agglomeration is the defluidization process, resulting from the disappearance of gaseous bubbles that are created behind air distributors. Different solutions can be applied against the agglomeration process. One possible method is to apply some additives that influence the ash behavior, thus inhibiting the agglomeration process. This paper presents the results of investigations into ash-related issues in a laboratory-scale bubbling fluidized bed (BFB) reactor. In particular, the impact of additives (kaolin, halloysite, fly ash, and the residuals from wet desulfurization system (IMOS)) on bed agglomeration was investigated. It was found that the addition of these compounds increased the defluidization time from ∼109 min (without additive) to ∼285 min in the BFB (with the addition of 0.1 g/min of kaolin). The morphology of additive (kaolin and halloysite) transformation after their addition into the combustion chamber was discussed. Another interesting phenomenon is that residuals from the IMOS exhibited the ability to be an additive against the agglomeration process. The defluidization time can be also significantly increased by the simultaneous application of the additive and the control of fluidization air velocity. The procedure of periodical bed moving by impulse primary air feeding against defluidization (PADM) is suggested and discussed. The PADM procedure resulted in a 36% reduction of additive, thus reducing the cost of measures against ash-related issues.

Influence of physical and chemical compositions on the properties and energy use of lignocellulosic biomass pellets in Brazil

Lignocellulosic residues are potential sources of renewable energy, but these materials have low energy density and undesirable properties for energy use. For this reason, pelleting is a viable alternative for the biomass energy valorization because it produces high-energy-density solid biofuels. The aim of this research is to evaluate the physical, chemical, and energetic characteristics of pellets produced with lignocellulosic biomass blends (elephant grass [EG], eucalyptus wood [EW], and sugarcane bagasse [SB]) for bioenergy generation. For biomass and pellets, bulk and energy densities, chemical compositions, and heating values, were determined. For pellets, the mechanical durability, fines content, diametrical compression, diameter, length, and unit density were measured. Pellets presented increased heating value, bulk and energetic density, and reduced moisture content. The highest absolute ash contents were found in the compositions and pellets produced with high amounts of EG (2.89%–6.48%). The reduction of EG in the blends has improved the energy properties of pellets. A 55% reduction of ash content was observed in the pellets produced with 50% EG and 50% EW compared with the pellets produced with 100% EG. The pellets produced with biomass blends obtained better energy and mechanical performances when compared with those produced with only one biomass.

Co-combustion characteristics of lignite/woody biomass blends. Reactivity and fusibility assessment

ABSTRACT Present work aimed at investigating the combustion behavior of lignite/woody biomass blends, in terms of ignition, reactivity, burnout temperature and time and at evaluating any synergy effects, by carrying out thermogravimetric analysis tests. Furthermore, it aimed, by applying a simple method for removing problematic ash elements, to examine their role on the combustion behavior of blends, as well as on mitigation of deposition problems in boilers co-firing such fuels, through mineralogical and fusibility analyzes. Fuels ignition occurred between 205 and 215°C, whereas the thermochemical reactivity followed the order: wheat straw>acacia pruning>cotton residue>lignite. The combustion performance and fusibility behavior of lignite were improved by blending it with the woody fuels. Some synergistic interactions occurred between component fuels. Alkali minerals increased the reactivity of acacia pruning and wheat straw in air and corresponding mixtures with lignite, while acted as diluents in cotton residue combustion. The slagging/fouling propensity of lignite/leached biomass mixtures was reduced.

Rapid co-pyrolysis of lignite and biomass blends: Analysis of synergy and gasification reactivity of residue char

This work investigated the structural evolution of rapid co-pyrolysis char and its influence on co-gasification characteristics. The chars were prepared in a high frequency furnace at 900 °C with the heating rate of 300 °C/min, using Xinjiang lignite and cotton straw as raw materials. Blends of coal and biomass were prepared in proportions of 25:75, 50:50 and 75:25 wt.%. Compared to the individual pyrolysis, co-pyrolysis enhanced the transformation of ion-exchanged alkali and alkaline-earth metals (AAEMs). Moreover, the surface area of co-pyrolysis chars were enhanced, and the carbon structure of biomass char in mixtures became more ordered. The gasification reactivity of co-pyrolysis char was evaluated by thermogravimetric analyzer (TGA), including isothermal (800, 850 and 900 °C) and non-isothermal (5 °C/min) gasification using CO2 as agent. For isothermal gasification, the synergistic effect of reactivity changed from inhibition to promotion with the increasing conversion. The synergy index changed obviously at 800 °C. For non-isothermal gasification, the maximum reaction rate was increased. The blends with 75% biomass had the minimum activation energy. The co-gasification reactivity varied with the temperatures, biomass blending ratios and conversions, which were well related to the char structural evolution caused by rapid co-pyrolysis.

Life Cycle Analysis of Decentralized Preprocessing Systems for Fast Pyrolysis Biorefineries with Blended Feedstocks in the Southeastern United States

Blending biomass feedstock is a promising approach to mitigate supply chain risks that are common challenges for large‐scale biomass utilization. Understanding the potential environmental benefits of biofuels produced from blended biomass and identifying driving parameters are critical for the supply chain design. Herein, a cradle‐to‐gate life cycle analysis model for fast pyrolysis biorefineries converting blended feedstocks (pine residues and switchgrass) with traditional centralized and alternative decentralized preprocessing sites, so‐called depots, is explained. Different scenarios are developed to investigate the impacts of parameters such as feedstock blending ratios, biorefinery and depot capacities, preprocessing technologies, and allocation methods. The life‐cycle energy consumption and global warming potential (GWP) of biofuel production with depots vary between 0.7–1.1 MJ MJ−1 and 43.2–76.6 g CO2 eq. MJ−1, respectively. The results are driven by biorefinery processes and depot preprocesses. A decentralized design reduces the energy consumption of the biorefinery but increases the overall life‐cycle energy and GWP. Such increases can be significantly mitigated by increasing switchgrass content as the energy consumption at the depot is driven largely by the higher moisture content of pine feedstocks. Allocation methods also have a large impact on the results but do not change the major trends and overall conclusions.

Model Validation of Biomass-Coal Blends Co-Pyrolysis to Produce Hybrid Coal

Co-pyrolysis of coal and biomass blend to produce hybrid coal has recently been experimentally studied by some previous researchers. For similar generated energy, a newly developed hybrid coal is claimed to be more environmentally friendly compared to the coal only due to the release of neutral CO2. To acquire a better understanding of co-pyrolysis of coal and biomass blend, an experiment had been carried out in a tubular furnace reactor. For this purpose, the blends of constant mass composition of 20 wt% sawdust and 80 wt% low-rank coal were used throughout the study. It was found from the experiment that approximately 42.1% carbon, and 1.6% of ash were produced from the co-pyrolysis blend. Then, a steady state simulation of co-pyrolysis was developed using Aspen Plus v8.8 to predict the hybrid coal carbon content and required heat to perform the co-pyrolysis. The model simulation showed that hybrid coal yielded 44.0% carbon, which was at 4.5% deviation from the experimental study. The model had also been successfully used to estimate heat required to produce hybrid coal. It predicted that the equivalent heat of 336.2 kW was required to produce hybrid coal from 1,000 kg/h blend feed. The heat generated by the modeling of sawdust biomass combustion for fuel purposes was also estimated to supply heat for endothermic co-pyrolysis. It was found that 1,000 kg/h sawdust was predicted to be equivalent to 371.4 kW. This suggests that for scaling up purpose, ratio of sawdust fuel to blend feed of 1:1.1 is sufficient for this process.
 Keywords: co-pyrolysis, hybrid coal, low-rank coal, sawdust, Aspen Plus

Performance evaluation of gasification system efficiency using artificial neural network

Gasification is one of the thermo-chemical energy conversion processes with energy self-sufficiency, recoverability and controllable efficiency when compared to combustion and pyrolysis. Gasification process is carried out using different systems (gasifiers), different types of fuels and process conditions, and these factors determine the efficiency of the overall process. The performance of a gasifier is evaluated by some parameters such as Cold Gas Efficiency (CGE), Carbon Conversion Efficiency (CCE), gas yield, gas composition, and lower heating value (LHV) of gas. To understand how efficient a gasifier is, several experiments are needed, but conducting these experiments is time consuming and capital intensive, and the information is vital in energy production plants. Meanwhile, a model that could accurately predict the aforementioned parameters irrespective of the type of gasifier, fuel, and operating conditions is imperative for some time conditions. In this study, Levenberg-Marquardt (LM) back-propagation and Bayesian Regularisation (BR) training algorithms for an Artificial Neural Networks (ANN) were used to study a dataset containing 315 experimental data of biomass, coal, and blends of biomass and coal from various gasifiers and process conditions. Eleven input variables were used in the study, and the result shows that the Mean Square Error (MSE) of the BR algorithm was higher than that of the L-M algorithm. To reduce the MSE, techniques called Input Variables Representation Technique with Visual Inspection method (IVRT-VIM) and Output Variables Representation Technique with Visual Inspection Method (OVRT-VIM) were developed, and their applications produced smaller MSE and an R2 of between 79 – 98% and 95–96%, respectively. Further, the results of the sensitivity analysis revealed that carbon (% amount) is the most important input parameter affecting the outputs, and with sum of the Squares of the Partial Derivatives (SSD) value of 1.18 for the CGE prediction.

Evaluation of the fusion and agglomeration properties of ashes from combustion of biomass, coal and their mixtures and the effects of K2CO3 additives

This study investigated the ash fusion and agglomeration characteristics of a Chinese bituminous, “Neimongol” (NM) coal, soybean straw (SS) material and their blends, as well as the effects of high biomass blending ratio (20–80 wt%) and the addition of K2CO3 (0–20 wt%) on the ash agglomeration propensity of the mixtures in a muffle furnace at 815 °C. The ash fusion and agglomeration characteristics of the fuel blends and their modified behaviours based on the blending ratio and flux were examined using ash fusion temperature (AFT) analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). The results indicated that, compared to Neimongol coal ash (NMA), the contents of SiO2 and Al2O3 in soybean straw ash (SSA) were lower, and the contents of basic oxides were higher, which was the main reason for the lower AFT of SSA. The AFT curves for the NM/SS blends showed a “bathtub” shaped trend with increasing SS mass ratios. For a given coal/biomass blend, XRD analysis indicated that for blends without added K2CO3, mineral phases were dominated by arcanite and quartz; with increasing SS mass ratios, the diffraction intensity of quartz decreased obviously. With increasing the K2CO3 additions, the content of potassium feldspars and sylvine in ash increased, and the quartz content decreased. The EDX analysis confirmed that the K2CO3 addition made it possible for kyanite and mullite to react with K-bearing minerals and form low melting point eutectics. The SEM images revealed that the fused particles in SSA were coated with KCl, whereas the NMA particles mostly contained aluminosilicate minerals. As the K2CO3 addition increased, the morphologies of the ashes from blends changed from slightly agglomerated to seriously slagged, and the molten and solidified zone on the slag surface featured high contents of sylvine, quartz, and potassium aluminosilicates.

Biomass co-pyrolysis: Effects of blending three different biomasses on oil yield and quality.

In the present study, pyrolysis and co-pyrolysis of sugarcane bagasse, poppy capsule pulp, and rice husk were conducted in a fixed bed reactor at 550⁰C in nitrogen atmosphere. The moisture (5%-8%), ash (4%-17%), volatile matter (60%-76%), and fixed carbon analyses (11%-24%) of the utilized biomass were conducted. The decomposition behavior of biomasses due to the heat effect was investigated by thermogravimetric analysis/differential thermal analysis . In the pyrolysis of biomasses separately, the highest bio-oil yield was obtained with sugarcane bagasse (27.4%). In the co-pyrolysis of the binary blends of biomass, the highest bio-oil yield was obtained with the rice husk and sugarcane bagasse blends. While the mean bio-oil yield obtained with the separate pyrolysis of these two biomasses was 23.9%, it was observed that the bio-oil yield obtained with the co-pyrolysis of biomass blends was 28.4%. This suggested a synergistic interaction between the two biomasses during pyrolysis. It was observed that as the total ash content in the biomasses used in the pyrolysis increased, the bio-oil yield decreased, and the solid product content increased. Characterization studies of bio-oils were conducted by Fourier-transform infrared spectroscopy, gas chromatography-mass spectrometry (GC-MS), and hydrogen-1 nuclear magnetic resonance analyses. Results of these studies revealed that, all bio-oils were mainly composed of aliphatic and oxygenated compounds. The calorific values of bio-oils were determined by calorimeter bomb. Based on the GC-MS, the bio-oils with high fatty acid and its ester content also had high calorific values. The highest calorific value was 29.68 MJ kg-1, and this was obtained by pyrolysis of poppy capsule and sugarcane bagasse blend.

Catalytic gasification of biomass and coal blend with Fe2O3/olivine in a decoupled triple bed

Steam co-gasification of pine sawdust and bituminous coal blend was performed in a pyrolysis-reforming-combustion decoupled triple bed gasification (DTBG) system with Fe2O3/olivine as both solid heat carrier and in-situ tar cracking/reforming catalyst. The effects of reformer temperature (RT) and circulation rate (CR) of catalyst on gasification performance were investigated. Besides, X-ray diffraction (XRD) and temperature programmed reduction (TPR) are employed to reveal the properties of Fe2O3/olivine catalyst during the continuous redox cycle between those decoupled reactors. The results indicated that, the configuration of the DTBG system favor tar cracking/reforming reaction to enhance H2 yield. Higher RT promotes the gas yield, H2 content in product gas, carbon conversion and cold gas efficiency of the process. Specifically, a gas yield of 0.66 Nm3/kg, tar content as low as 4.87 g/Nm3 with the H2 content of 42.2 vol% has been obtained at the RT of 850 °C. Lower CR of catalyst leads further reduction of Fe2O3 that allows increment on the gas yield and H2 content. The H2 content reduced from 44.5 vol% to 40.8 vol% and CO2 increased from 37.3 vol% to 41.4 vol% with increasing catalyst CR from 1.9 kg/h to 4.5 kg/h. Reduction level of Fe2O3/olivine increased with decreasing catalyst CR. Fe2O3/olivine not only has catalytic effect on tar cracking/reforming but also acts as an oxygen carrier transports oxygen from the combustor to the reformer.

A Multi-Objective Optimization Model for the Design of Biomass Co-Firing Networks Integrating Feedstock Quality Considerations

The growth in energy demand, coupled with declining fossil fuel resources and the onset of climate change, has resulted in increased interest in renewable energy, particularly from biomass. Co-firing, which is the joint use of coal and biomass to generate electricity, is seen to be a practical immediate solution for reducing coal use and the associated emissions. However, biomass is difficult to manage because of its seasonal availability and variable quality. This study proposes a biomass co-firing supply chain optimization model that simultaneously minimizes costs and environmental emissions through goal programming. The economic costs considered include retrofitting investment costs, together with fuel, transport, and processing costs, while environmental emissions may come from transport, treatment, and combustion activities. This model incorporates the consideration of feedstock quality and its impact on storage, transportation, and pre-treatment requirements, as well as conversion yield and equipment efficiency. These considerations are shown to be important drivers of network decisions, emphasizing the importance of managing biomass and coal blend ratios to ensure that acceptable fuel properties are obtained.

Experimental Investigation of Ash Deposit Behavior during Co-Combustion of Bituminous Coal with Wood Pellets and Empty Fruit Bunches

In Korea, oil-palm empty fruit bunches (EFBs), which are byproducts of the crude palm-oil milling process, are among the most promising potential energy sources for power plants. However, the slagging and fouling characteristics of EFBs during combustion have not yet been fully studied. Accordingly, in this study, we investigated the fundamental ash behavior of EFBs in comparison to that of wood pellets (WPs) using a thermomechanical analyzer (TMA) and a drop-tube furnace (DTF). Ash melting and the deposition of ash particles were investigated with traditional prediction indices at several biomass blending ratios. The results demonstrated that, as the ratio of WPs to EFBs increases, the melting temperature decreases and the slagging propensity increases because of the increased biomass alkali content. Moreover, the penetration derived using the TMA shows a higher melting peak at which rapid melting occurs, and the melting temperature distribution is decreased with increased biomass blending. Conversely, the DTF results show different phenomena for ash deposition under the same blending conditions. Blend ratios approaching 10% WP and 15% EFB result in gradual decreases in ash deposition tendencies because of the lower ash contents of the co-combusted mass compared to that of the single coal ash. Further biomass addition increases ash deposition, which is attributable to ash agglomeration from the biomass. Thus, this study demonstrates that blending ratios of 10% WP and 15% EFB provide optimal conditions for co-combustion with the selected bituminous coal. In addition, it is shown that the slagging propensity of EFB is higher than that of WP owing to its ash content and simultaneous agglomeration.