Combustion behavior of different kinds of torrefied biomass and their blends with lignite

Key fuel characteristics and techno-economic aspects of torrefied rubberwood biomass pellets produced by incorporating various cassava-based binders at varied doses

Improving energy content and hydrophobic nature of woody biomass can be pursued through torrefaction. This gives torrefied biomass with a low bulk density, potentially increasing storage and transport costs. To overcome this issue, densifying the torrefied biomass is necessary. However, poor binding of particles makes densification challenging without using a binder. Therefore, the aim of this study was to investigate the physicochemical characteristics and techno-economic aspects of torrefied rubberwood biomass (TRWB) when pelletized using various cassava-based binders at different blending ratios. The selected binders included cassava starch (CS), cassava pulp (CP), and cassava chip (CC). Each binder at 5%, 10%, or 15% (wt.) was mixed with TRWB and water before pelletizing using a flat die machine. The results revealed that pelletizing TRWB with different cassava-based binders at various blending ratios influenced the physicochemical characteristics of the TRWB pellets, particularly dimensions, bulk density, fuel and atomic ratios, and energy content. The TRWB pellets demonstrated energy densities in the range of 7.95-11.39 GJ/m3, and their mechanical durability and fine content fell within acceptable ranges. The TRWB pellets maintained their shape during 120 min of water soaking, with water absorption levels varying by binder dose. The pelletizing ability, material, and energy costs of TRWB pellets depend on binder type and dose. CP can be applied as a binder for pelletizing torrefied rubberwood biomass. However, the mechanical durability of the product needs to be above the user requirement or standard.

Fuel properties and incineration behavior of poultry litter blended with sweet sorghum bagasse and pyrolysis oil

The incineration of poultry litter (PL) effectively reduces the volume of waste in line with the United Nations Sustainable Development Goal of "affordable and clean energy". However, mono-incineration is associated with considerable challenges due to the varying moisture, structural and chemical composition and low energy yield. The aim of the present work was to investigate the influence of sweet sorghum bagasse (SS) and pyrolysis oil (PO) on improving the fuel properties of PL and mitigating ash related burdens during incineration. The different biomass feedstocks were produced by combining PL with SS at 0.0% (T0), 25% (T1), 50% (T2), 75% (T3) and compared with 100% SS (T4). In order to achieve high energy potential and low ash deposition, the parallel samples were additionally mixed with 10% PO to improve the energy value. The experimental results show that increasing the proportion of SS and adding PO to the mixtures increases the volatile matter and decreases the moisture and ash content. The addition of PO also increases the carbon and hydrogen content. The use of SS and PO thus increased the values of the ignitability index and apparently also the flammability by 30.0%-49.4% compared to pure PL. SS and PO shifted the HHV of the starting material from 16.90 to 18.78 MJ kg-1. In addition, SS + PO improved the flame volume and red color intensity of the PL blends based on the image analysis method. However, the presence of SS and PO did not sufficiently improve the ash-related index values, which requires further investigation.

Effect of torrefaction on fuel properties of biopellets

The study aimed to determine the effects of torrefaction on the fuel properties of pellets. Therefore, firstly, torrefaction parameters of rose (Rosa Damascena Mill.) oil distillation solid waste and red pine sawdust were determined through the torrefaction optimization process in terms of temperature and holding time. Then, using the selected torrefaction parameters, 14 different raw and torrefied pellets containing RP, PS, and Turkish Elbistan Lignite were prepared in different weight ratios. Finally, the fuel properties of the prepared raw and torrefied pellets, namely dimensions, proximate analyses, higher heating values, tensile strength, durability, abrasive resistance, and water uptake resistances, were investigated. The findings demonstrated that the higher heating values and carbon content of raw biomass samples increased while their volatile matter content decreased. The use of lignite at high concentrations led to an increase in ash content and a decrease in the strength and durability of pellets, which should be emphasized. In addition, red pine sawdust was used in place of solid waste from rose oil distillation solid waste to produce pellets with greater strength. All pellet mixtures with torrefaction had higher heating values and energy densities despite the fact that their mass and energy efficiency had decreased. It was determined that torrefaction increased the pellets' resistance to absorbing water and gave them a more hydrophobic structure. Thus, it was determined that torrefaction could enhance the crucial fuel parameters of the biomass samples.

Catalytic Performance Investigation of Alkali and Bifunctional Catalysts Derived from Lignocellulosic Biomasses for Biodiesel Synthesis from Waste Frying Oil

In this study, alkali and bifunctional catalysts were synthesized for waste frying oil methyl ester (WFOME) synthesis. Coffee husk (CH) and CH blended with Eragrostis tef straw (TS) (CH-TS) lignocellulosic biomasses (LBs) were utilized during the catalysts' synthesis. The alkali catalysts were CH and CH-TS ashes, both modified by KNO3 impregnation. They are designated as C-45 and C-Mix, respectively. Zirconia (ZrO2) promoted CH ash catalysts via precipitation followed by impregnation (Bic-PP) and in situ precipitation-impregnation (Bic-Dm) were the bifunctional ones. CH and CH-TS chars were the supporting frameworks during the catalysts' composite materials (CCMs) preparation. The combustion performance of LBs and CCMs was evaluated and associated with the catalysts' physicochemical properties. Using XRD, SEM, FTIR, alkalinity, TOF, and BET surface area analysis, catalysts were characterized. The combustion performance of the LBs was in the order of TS > CH-TS > CH. Among CCMs, the highest combustion performance was for CCM-Mix (KNO3/(CH-TS char)) and the lowest was for CCM-45 (KNO3/ CH char). The C-Mix catalyst was a light green powder due to the reaction between inorganic components, whereas C-45 was dark gray due to the presence of unburned char. The CCMs for bifunctional catalysts had moderate combustion performance and yielded light gray powdered catalysts containing tetragonal ZrO2. The optimum WFOME yields were 98.08, 97, 92.69, and 93.05 wt % for C-Mix, C-45, Bic-Dm, and Bic-PP assisted WFO transesterification, respectively. The results were obtained at a reaction temperature of 65 °C, time of 1 h, and methanol to WFO molar ratio of 15:1 using catalyst amounts of 5 and 7 wt % for the alkali and bifunctional catalysts, respectively. The greatest moisture resistance was offered by the C-Mix catalyst. The best reusability was for the C-45 catalyst. Catalysts' deactivation modes include active site leaching and poisoning.

Thermochemical behavior of agricultural and industrial sugarcane residues for bioenergy applications

The Colombian sugarcane industry yields significant residues, categorized as agricultural and industrial. While bagasse, a widely studied industrial residue, is employed for energy recovery through combustion, agricultural residues are often left in fields. This study assesses the combustion behavior of these residues in typical collection scenarios. Additionally, it encompasses the characterization of residues from genetically modified sugarcane varieties in Colombia, potentially exhibiting distinct properties not previously documented. Non-isothermal thermogravimetrical analysis was employed to study the thermal behavior of sugarcane industrial residues (bagasse and pith) alongside agricultural residues from two different sugarcane varieties. This facilitated the determination of combustion reactivity through characteristic combustion process temperatures and technical parameters like ignition and combustion indexes. Proximate, elemental, and biochemical analyses revealed slight compositional differences. Agricultural residues demonstrated higher ash content (up to 34%) due to foreign matter adhering during harvesting, as well as soil and mud attachment during collection. Lignin content also varied, being lower for bagasse and pith, attributed to the juice extraction and milling processes that remove soluble lignin. Thermogravimetric analysis unveiled a two-stage burning process in all samples: devolatilization and char formation (~170°C), followed by char combustion (~310°C). Characteristic temperatures displayed subtle differences, with agricultural residues exhibiting lower temperatures and decomposition rates, resulting in reduced ignition and combustion indexes. This indicates heightened combustion reactivity in industrial residues, attributed to their elevated oxygen percentage, leading to more reactive functional groups and greater combustion stability compared to agricultural residues. This information is pertinent for optimizing sugarcane residues utilization in energy applications.

Machine learning in the evaluation and prediction models of biochar application: A review

This article reviews recent studies applying machine learning (ML) approaches to biochar applications. We first briefly introduce the general biochar production process. Various aspects are contained, including the biochar application in the elimination of heavy metals and/or organic compounds and the biochar application in environmental and economic scopes, for instance, food security, energy, and carbon emission. The utilization of ML methods, including ANN, RF, and NN, plays a vital role in evaluating and predicting the efficiency of biochar absorption. It has been proved that ML methods can validly predict the adsorption effectiveness of biochar for water heavy metals with higher accuracy. Moreover, the literature proposed a comprehensive data-driven model to forecast biochar yield and compositions under various biomass input feedstock and different pyrolysis criteria. They said a 12.7% improvement in prediction accuracy compared to the existing literature. However, it might need further optimization in this direction. In summary, this review concludes increasing studies that a well-trained ML method can sufficiently reduce the number of experiment trials and working times associated with higher prediction accuracy. Moreover, further studies on ML applications are needed to optimize the trade-off between biochar yield and its composition.

Kinetic Mechanisms and Emissions Investigation of Torrefied Pine Sawdust Utilized as Solid Fuel by Isothermal and Non-Isothermal Experiments

This study comprehensively investigated the utilization of torrefied pine sawdust (PS) as solid fuels, involving the characterization of torrefied PS properties, the investigation of combustion behaviors and kinetic mechanisms by non-isothermal experiments, and the evaluation of emissions during isothermal experiments. Results show that torrefaction significantly improved the quality of the solids. The upgradation of torrefied PS properties then further enhanced its combustion performance. For the kinetics mechanisms, degradation mechanisms and diffusion mechanisms were respectively determined for the volatile combustion and the char combustion by using both Coats-Redfern (CR) and Freeman-Carroll (FC) methods. Further, after torrefaction, the emission of NO for volatile combustion reduced while it increased for char combustion. An inverse relationship was found between the conversion of fuel-N to NO and the nitrogen content in the torrefied samples. This study provided comprehensive insights for considering torrefaction as a pretreatment technique for PS utilization as a solid fuel.

Co-Combustion of Food Solid Wastes and Pulverized Coal for Blast Furnace Injection: Characteristics, Kinetics, and Superiority

The combustion characteristics and kinetics of food solid wastes (FSW), pulverized coal (PC), and their mixtures were studied by a non-isothermal thermogravimetric method. In the co-combustion of FSW and PC, with the increase in FSW content in the mixture, the initial decomposition temperature, burnout temperature, and ignition temperature of the mixture decreased, and the flammability index and comprehensive combustion characteristic index gradually increased. The co-combustion of FSW and PC showed an inhibitory effect in the devolatilization stage but exhibited a combustion-promoting effect in the fixed carbon combustion stage. The interaction between FSW and PC while co-combusting them appeared to be dominated by thermal effects. On one hand, FSW combusted first and released heat that was partially absorbed by the PC, which hence suppressed the devolatilization stage of the co-combustion process. On the other hand, the PC absorbed the heat released by the combustion of the FSW, which increased the combustion rate of the PC in the fixed carbon combustion stage of the co-combustion process. The activation energy of the devolatilization stage and the fixed carbon combustion stage of the co-combustion process was calculated to be 34.16–74.52 kJ/mol and 15.04–36.15 kJ/mol, respectively. In general, the combustion performance of FSW is better than that of PC. The mixed injection of FSW and PC can improve the overall combustion efficiency and reduce CO2 emissions in the iron-making process.

Effects of potassium additives on the combustion behavior of chrysanthemum biochar blended with graphite carbon as a heating source for heat-not-burn tobacco

The minimum ignition temperature of the carbon mixture is decreased by only 2–17 °C and the burnout temperature can be reduced by 30–60 °C with 1.00 wt% of K2CO3.

Chlorine Release from Co-Pyrolysis of Corn Straw and Lignite in Nitrogen and Oxidative Pyrolysis

Elevated emissions of hydrogen chloride (HCl) from the combustion of biomass in utility boilers are a major issue because they can cause corrosion problems and deposit molten alkali chloride salts on boilers’ water tubes, resulting in further corrosion. Pyrolysis is a good pre-treatment for solving this problem. This work conducted pyrolysis and co-pyrolysis of pulverized corn straw and lignite coal in a horizontal muffle furnace, with compositions typical of power plant combustion effluents (5% O2, 15% CO2, 80% N2) at different temperatures. Cl compounds were monitored in fuel, flue gas, and solid production of pyrolysis. The co-pyrolysis significantly affected Cl release from fuel. Cl release from corn straw into fuel gas was reduced during biomass co-pyrolysis with lignite. Co-pyrolysis had little influence on the release of organic Cl and KCl. Furthermore, at moderate-temperature pyrolysis, O2 promoted HCl release, when compared with pyrolysis under a N2 atmosphere.

Torrefied herb residues in nitrogen, air and oxygen atmosphere: Thermal decomposition behavior and pyrolytic products characters

The thermal decomposition behavior and pyrolytic products characters of herb residue (HR) torrefied in N₂, air and O₂ were investigated in present work. The clear gradual regularity of samples in Van Krevelen diagram exhibited the severity and some similarities of torrefaction. The activation energy (E) calculated by distributed activation energy model (DAEM) found that the E values of torrefied samples was higher than raw HR if the conversion is below 0.8. Torrefaction treatment would beneficial to increase the yield of gas but inhibit the formation of oil, and the compounds of gas and bio-oil under different torrefaction conditions are also quite different. It should be noticed that the presence of oxygen in the torrefaction atmosphere would reduce the torrefaction temperature significantly, while maintaining the severity of torrefaction and pyrolytic products distribution.

Investigation on thermal degradation kinetics and mechanisms of chicken manure, lignite, and their blends by TGA

In this study, thermogravimetric analysis (TGA) was performed under the air environment for four different heating rates (10, 20, 30, and 40 °C min^-1) in order to find out thermal degradation and mechanisms of the chicken manure, a Turkish lignite, and their blends (25 lignite + 75 manure, 50 lignite + 50 manure, and 75 lignite + 25 manure). To calculate thermal kinetics and responsible solid-state mechanisms of the samples, the Flynn-Wall-Ozawa and Coats-Redfern methods were applied. Significant differences between Turkish lignite and chicken manure samples were observed in terms of thermal kinetics and mechanisms. D1 and D4 mechanisms were found to be the responsible mechanisms for the main oxidation region of the lignite and chicken manure/blends, respectively. A similar decreasing trend for the calculated activation energies and pre-exponential constants was observed with increasing biomass content in the manure blends from 25 to 75% by both Flynn-Wall-Ozawa and Coats-Redfern methods. Furthermore, biomass content has an effect on the mechanisms of chicken manure blends during the combustion. D3 was found to be the responsible solid-state mechanism for the third regions (pre-combustion of the manure) of the chicken manure samples. However, D1 and D2 mechanisms were found to be responsible mechanisms for the blends.

Visualization of Combustion Phases of Biomass Particles: Effects of Fuel Properties

This work established a high-speed camera-assisted visualization system that investigated the effect of volatile matter and fixed carbon content in biomass particles on single-particle combustion phases and their luminous properties. Three types of biomass particles, namely, sawdust (a mixture of pine and willow), corncob, and rice husk, were examined on a Hencken flat-flame burner. The luminous region and intensity of single biomass particles were closely related to the flammability and calorific value of biomass fuel and derived by analyzing a sequence of images captured using a high-speed camera. The combustion temperature was determined through analysis of its radiant energy. The results showed that the ignition mechanisms of volatile matter and fixed carbon corresponded to homogeneous and heterogeneous reactions, respectively. The maximum luminous region values of 1.75 × 10⁶, 2.1 × 10⁶, and 1.0 × 10⁶ μm² for sawdust (SD), corncob (CC), and rice husk (RH) correlated to the volatile matter content of each biomass sample, which was 69.38, 74.15, and 64.56%, respectively. Because of the high fixed carbon content, the peak temperature of the SD particles could reach 1549 °C. The luminous region and intensity of the combusting particles were significantly affected by the volatile matter and fixed carbon, respectively.

Evaluation on nitrogen conversion during biomass torrefaction and its blend co-combustion with coal

In this work, biomass torrefaction was combined with coal co-combustion to illustrate the differences in biomass performance and the mechanisms of migration and transformation of nitrogen over the entire course of thermal treatments. XPS analysis illustrated that torrefaction in CO₂ suppressed the conversion of pyrrole-N (N-5) to quaternary-N (N-Q), whereas the trend for an O₂ atmosphere moved in the opposite direction. During co-combustion, the impact on NO emission reduction shifted from positive to negative as the pretreatment temperature was raised, which is closely related to the six elementary reactions involving the intermediacy of NCO and NH, as well as to heterogeneous reduction of NO with char. In addition, torrefaction in a N₂/O₂ atmosphere at a lower temperature of 250 °C improved the properties of biomass and achieved the lowest NO emission during co-combustion, which provides the supporting theory needed for using effluent in power plants as a torrefaction medium.

Combustion behavior and mechanical properties of pellets derived from blends of animal manure and lignocellulosic biomass

This paper presents the possibility of valorization of animal manure (camel and cow) by mixing it with agro-industrial biomass (cotton stalk and rapeseed oil cake) to produce pellets for use in power generation processes. Feedstocks were mixed in specific proportions based on certain assumptions concerning the energy and mechanical parameters of pellets. The assessment concerned both the combustion behavior as well as mechanical properties of four types of pellets derived from blends of animal manure and agro-industrial biomass. Thermogravimetry (TGA) and Differential Scanning Calorimetry (DSC) techniques are applied to analyze the reaction areas, characteristic temperatures as well as heat flow rates of raw materials and their blends. Results showed that addition of agro-industrial biomass (even 10%) to animal manure changed the specific combustion parameters: initiation and burn-out temperature and combustion time. For blends of cow manure (COM) and rapeseed oil cake (ROC), a reduction in the initiation temperature was achieved compared to the combustion of raw cow manure, and the combustion time increased by 1/3. In the case of camel manure (CAM) with the addition of cotton stalk (CS) the burn-out temperature and combustion time decreased. The addition of agro-biomass also causes a change in the heat release profiles, for the blends no pronounced DSC peaks are obtained in the area of devolatilization as it happens animal manure alone and in the area of fixed carbon combustion as for cotton stalk and rapeseed oil cake. The heat released from camel manure blends was 9.2-9.3 kJ/kg and from cow manure blends 10.2-10.4 kJ/kg. An evaluation of the physical and mechanical properties showed that all types of pellets at a moisture content of 10-15% have a similar drop strength in the range of 80-85%, while this strength decreases to 40-60% after the pellets have absorbed water.

Study of Combustion Characteristics and Kinetics of Agriculture Briquette Using Thermogravimetric Analysis

The present paper was aimed to investigate the physicochemical properties and combustion characteristics of corn straw briquette as a fuel energy. The results of physicochemical properties displayed that corn straw briquette has higher volatile matter, lower ash content, and higher heating value. Combustion characteristics and kinetic analysis were investigated using thermogravimetry analysis at various heating rates of 10, 15, and 20 °C/min. It was observed that the maximum burning rate shifted to a higher temperature as the heating rate increased. In addition, a lower heating rate would help in better heat transfer, leading to less mass residual. In contrast, the combustion characteristic index showed a nearly 2-fold increase under a higher heating rate, indicating a good combustion performance. The combustion kinetics were expressed using isoconversional methods with Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall methods, which authenticated the average activation energy at 108.85 and 114.42 kJ/mol, respectively. These results can provide a theoretical basis and data support for further utilization of agriculture biomass briquette.

Co-combustion performance analysis of a Fujian anthracite with Cunninghamia lanceolate and Mycorrhizal plants

The co-combustion characteristics of Fujian anthracite with two biomasses (i.e. Cunninghamia lanceolata) and Mycorrhizal plants in different proportions were investigated using thermogravimetric analysis. The result showed that first, the co-combustion processes of Fujian anthracite with the two biomasses ( Cunninghamia lanceolata and Mycorrhizal plants) proceeded in three stages, separation and combustion of volatiles, combustion of fixed carbon in the biomass, and combustion of fixed carbon in Fujian anthracite. Secondly with increasing proportion of biomass, the co-combustion of Fujian anthracite with Cunninghamia lanceolata and Mycorrhizal plants shifted to a low-temperature zone, with a lower ignition temperature, shortened burnout time, and growth of both combustibility index ( Ci) and comprehensive combustion index S. Finally, at different mixing proportions, the comprehensive combustion index S during co-combustion of FW with Mycorrhizal plants is always larger than that during co-combustion with Cunninghamia lanceolata; therefore, FW and Mycorrhizal plants exhibit superior comprehensive co-combustion performance to FW and Cunninghamia lanceolata. Analysis of various parameters pertaining to combustion performance shows that the ignition and combustion performance of Fujian anthracite was improved as long as the Fujian anthracite was mixed with around 20% biomass.

Evolution of chemical functional groups during torrefaction of rice straw

The evolution of CHON functional groups during torrefaction of rice straw at 200-300 °C were investigated. The results showed that 300 °C was more suitable for rice straw torrefaction due to the ideal fuel ratio, energy densification, energy-mass co-benefit index and the significantly improved HHV of the torrefied products. The functional groups such as O-H, N-H, C-H, C = O in the solids decreased with rising temperature accompanied by the releases of H₂O, CH₄, CO₂, CO and NH₃, et al. At 300 °C, 40.04% of fuel-N was released in the form of NH₃, HCN, HNCO et al. due to the decomposition of N-A which was the overall N-functionality in the raw rice straw. It is worth noting that the absorbance of NH₃ and HCN has the same order of magnitude as CO. Therefore, the releases of N-containing gases should be highly concerned for the application of torrefaction technology from the environmental perspective.

Experimental study on co-combustion of low rank coal semicoke and oil sludge by TG-FTIR

Co-combustion was proposed as an effective and complementary means for the co-treatment of low rank coal semicoke (LRCS) and oil sludge. The combustion, kinetics and gaseous pollutants emission characteristics during co-combustion of LRCS and oil sludge were investigated by thermogravimetric analyzer coupled with Fourier transform infrared spectrometer (TG-FTIR). Results showed oil sludge had more complex weight loss characteristics than LRCS. Proper addition of oil sludge could effectively improve the ignition, burnout and comprehensive combustion performance of blends and 60% was a recommended oil sludge blend ratio. High heating rates could also enhance the combustion performance of blends. The activation energy determined by Coats-Redfern method gradually decreased with the increase of oil sludge blend ratio. DAEM kinetic analysis results showed the maximum activation energy of 113.4 kJ/mol was obtained when conversion rate was 0.4 due to the poor ignition performance of LRCS. All of the CO, CO₂, NOx and SO₂ emission gradually decreased with the increasing oil sludge blend ratio. LRCS had suppression effect on NOx emission during co-combustion while oil sludge was just the opposite. The low sulfur release rate of oil sludge resulted in the decreasing SO₂ emission of blends although oil sludge had promotion effect on SO₂ emission.

Effects of gaseous agents on the evolution of char physical and chemical structures during biomass gasification

Bio-char samples were prepared from gasification of corn straw under N₂, CO₂ and H₂O conditions, and systematically characterized to reveal the effects of gaseous agents on the evolution of char structural features during the gasification process. The results showed that the increase of reacting temperature had positive effects on the gasification of char in both H₂O and CO₂ atmospheres. The evolution of char pore structures under H₂O and CO₂ was quite different. The formation of micropores was facilitated by CO₂, while mesopores and macropores were developed more in H₂O condition. Besides, char structures obtained at 800 °C were more ordered than those obtained at 600 °C. Compared with the longitudinal merging, the aromatic layers preferred to grow laterally. Moreover, the mechanisms of gasification between char and gaseous agents were different. CO₂ preferred to react with amorphous carbon, while the cross-linked carbon was more likely to be consumed during char gasification with H₂O.

Experiment and expectation: Co-combustion behavior of anthracite and biomass char

The combustion behavior of anthracite, biomass (Ficus virens) char and their blends were investigated by thermogravimetry analysis (TGA). The combustion process mainly focused on the volatile combustion and char combustion. The addition of char reduced the initial temperature and final temperature of fuels. The interactions firstly inhibited and then facilitated. When the blending ratio was 70AN30FV, the antagonism was the minimum, and synergism was the strongest at 830 K for the random ratio. The kinetic models of Coats-Redfern (CR), Doyle equation (Doyle), Friedman (FR), Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO) and distributed activation energy model (DAEM) were used to calculate the kinetic parameters. The average values of activation energy for CR and Doyle were close and that of KAS, FWO and DAEM were near. Based on these six models, the corresponding expectation equations of activation energy and pre-exponential factor were proposed and the best predicted results was CR model for 60AN40FV.

Assessment of the Energy Potential of Chicken Manure in Poland

Animal waste, including chicken manure, is a category of biomass considered for application in the energy industry. Poland is leading poultry producer in Europe, with a chicken population assessed at over 176 million animals. This paper aims to determine the theoretical and technical energy potential of chicken manure in Poland. The volume of chicken manure was assessed as 4.49 million tons per year considering three particular poultry rearing systems. The physicochemical properties of examined manure specimens indicate considerable conformity with the data reported in the literature. The results of proximate and ultimate analyses confirm a considerable effect of the rearing system on the energy parameters of the manure. The heating value of the chicken manure was calculated for the high moisture material in the condition as received from the farms. The value of annual theoretical energy potential in Poland was found to be equal to around 40.38 PJ. Annual technical potential of chicken biomass determined for four different energy conversion paths occurred significantly smaller then theoretical and has the value from 9.01 PJ to 27.3 PJ. The bigger energy degradation was found for heat and electricity production via anaerobic digestion path, while fluidized bed combustion occurred the most efficient scenario.

Effect of torrefaction conditions on the physicochemical characterization of agricultural waste (sugarcane bagasse)

Pakistan is an agricultural country whose agricultural sector employs 43% of the labour force. However, a substantial amount of agricultural waste contributes little economic benefit to the farmers. The annual production of agricultural waste studied in this work, i.e., sugarcane bagasse, is approximately 12 million tonnes per year, and most of that is burned inefficiently. The present work shows that agricultural waste is a significant energy resource that could be used to generate electricity after the application of a simple thermal processing technique (i.e., torrefaction). Torrefaction is a mild pyrolysis treatment in an inert atmosphere that is carried out to improve the physical and chemical properties of biomass. In this study, sugarcane bagasse was torrefied at five different temperatures (200 °C, 225 °C, 250 °C, 275 °C and 300 °C) for four different residence times (15, 30, 45 and 60 min). The physical and chemical properties, such as proximate and ultimate analysis, true density, grindability and hydrophobicity, of the raw and torrefied sugarcane bagasse were investigated. No significant improvement in the characteristics of torrefied waste was found at low torrefaction temperatures (200 °C and 225 °C). However, with the increase in the temperature and residence time torrefaction conditions to 300 °C and 60 min, respectively, a significant improvement was found. The Fourier transform infrared spectroscopy (FTIR) analysis showed that owing to torrefaction, the hydroxyl group content is decreased and carbonyl group content is increased within the fuel. Moreover, a scanning electron microscopy (SEM) study indicated that tiny dispersed particles in the raw sample fused together at a higher torrefaction temperature of 300 °C, forming a tubular structure due to lignin degradation, and the biomass became easy to grind. Thus, torrefaction is an effective approach for improving the characteristics of sugarcane bagasse.

NO and SO2 emissions from combustion of raw and torrefied biomasses and their blends with lignite

The impact of torrefaction on the NO and SO₂ emissions from combustion of biomass was investigated. Combustion experiments were carried out with two torrefied biomass fuels, i.e., poultry litter and olive tree pruning and their blends with lignite using a bench scale single particle reactor. For comparison, NO and SO₂ emissions from tests with untorrefied biomasses and their blends with lignite were also investigated. The total release of SO₂ and NO for each fuel was determined at three different temperatures: 900, 1000, and 1100 °C. The NO release from the untorrefied biomasses was found to be lower than those from torrefied biomasses, despite their higher fuel- N content. In case of co-combustion of both raw and torrefied biomass with lignite, the NO release was lower than the anticipated one. On the other hand, in the co-combustion experiments, blends with torrefied biomass showed a larger reduction in SO₂ release than the blends with raw biomass. The study revealed that the SO₂ emissions from blends are not proportional to the mixing ratio of the fuels and to the emissions properties of the respective fuels. No clear correlation was detected between the NO_x emissions and fuel-N content. In addition to the NO and SO₂ emissions, the sintering propensity of the ash residue were investigated using scanning electron microscopy (SEM).

Effects of alkali and alkaline earth metal species on the combustion characteristics of single particles from pine sawdust and bituminous coal

Alkali and alkaline earth metal (AAEM) species are the main components of the ash of biomass, and which would influence the combustion of biomass and coal during the co-firing process. The aim of this paper is to investigate the effects of potassium (K), sodium (Na), calcium (Ca), and magnesium (Mg) on the combustion characteristics of pine sawdust (PS) and bituminous coal (BC) by a single particle combustion method. The raw, ash-free and impregnated samples were prepared, and their combustion processes were recorded by a high speed camera. Based on the recorded flame images, the effects of K, Na, Ca and Mg on the combustion characteristics (ignition, volatiles combustion, char combustion) of PS and BC were analyzed. The results reveal that the demineralization treatment brings negative effects on the combustion of PS, which reflects in longer ignition delay time, volatiles and char burnout time, and lower combustion temperature, while the effects on the combustion of BC are opposite. The impregnated samples exhibit shorter ignition delay time, volatiles and char burnout time, and higher combustion temperature than the ash-free samples. In the entire combustion process of PS and BC, K exhibits the strongest promotion effect. When the concentration of K increases from 0 to 2 wt%, the ignition delay time of PS and BC decreases about 5.5 ms and 16.4 ms respectively, the volatiles combustion temperature increases about 41 °C and 77 °C respectively, and the char combustion temperature increases about 226 °C and 141 °C respectively.

Characteristics and synergistic effects of co-combustion of carbonaceous wastes with coal

This study presents combustion behavior and emission results obtained for different fuels: poultry litter (PL) and its char (PLC), scrap tires (ST) and its char (STC) and blends of char/lignite (PLC/LIG and STC/LIG). The combustion parameters and emissions were investigated via a non-isothermal thermogravimetric method and experiments in a lab-scale reactor. Fuel indexes were used for the prediction of high temperature corrosion risks and slagging potentials of the fuels used. The addition of chars to lignite caused a lowering of the combustion reactivity (anti-synergistic effect). There was a linear correlation between the NO_x emissions and the N content of the fuel. The form of S and the concentrations of alkali metals in the fuel had a strong effect on the extent of SO₂ emissions. The use of PL and PLC in blends reduced SO₂ emissions and sulphur compounds in the fly ash. The 2S/Cl ratio in the fuel showed that only PLC and STC/PLC would show a risk of corrosion during combustion. The ratio of basic to acidic oxides in fuel indicated that ST, STC and STC/LIG have low slagging potential. The molar (Si+P+K)/(Ca+Mg) ratio, which was used for PL, PLC and PLC containing blends, showed that the ash melting temperatures of these fuels would be higher than 1000 °C.

Combustion characteristics and retention-emission of selenium during co-firing of torrefied biomass and its blends with high ash coal

The combustion characteristics, kinetic analysis and selenium retention-emission behavior during co-combustion of high ash coal (HAC) with pine wood (PW) biomass and torrefied pine wood (TPW) were investigated through a combination of thermogravimetric analysis (TGA) and laboratory-based circulating fluidized bed combustion experiment. Improved ignition behavior and thermal reactivity of HAC were observed through the addition of a suitable proportion of biomass and torrefied. During combustion of blends, higher values of relative enrichment factors in fly ash revealed the maximum content of condensing volatile selenium on fly ash particles, and depleted level in bottom ash. Selenium emission in blends decreased by the increasing ratio of both PW and TPW. Higher reductions in the total Se volatilization were found for HAC/TPW than individual HAC sample, recommending that TPW have the best potential of selenium retention. The interaction amongst selenium and fly ash particles may cause the retention of selenium.

Evaluation of different water-washing treatments effects on wheat straw combustion properties

A series of experiments was conducted to explore the effects of various water-washing solid-liquid ratios (1:50 and 1:10) and the stirring on wheat straw (WS) combustion properties. Comparing different solid-liquid ratio groups, a 16% increment in the higher heating value was obtained for 1:50 groups and only 5% for 1:10 groups relative to the raw material. Moreover, energy was lost 4-26 times greater in 1:10 groups than 1:50 groups. While water-washing reduced the comprehensive combustibility index by 14.89%-32.09%, the index values of washed WS were all higher than 2, indicating good combustion performance. The combustion activation energy of four washed WS were 175, 172, 186, and 176kJ/mol, which were all higher than the 160kJ/mol of WS. The fouling/slagging propensity of washed WS reduced to a lower possibility compared to medium of untreated WS. Overall, the recommended condition for washing WS before combustion is 1:50 ratio without stirring.

Investigating co-combustion characteristics of bamboo and wood

To investigate co-combustion characteristics of bamboo and wood, moso bamboo and masson pine were torrefied and mixed with different blend ratios. The combustion process was examined by thermogravimetric analyzer (TGA). The results showed the combustion process of samples included volatile emission and oxidation combustion as well as char combustion. The main mass loss of biomass blends occurred at volatile emission and oxidation combustion stage, while that of torrefied biomass occurred at char combustion stage. With the increase of bamboo content, characteristic temperatures decreased. Compared with untreated biomass, torrefied biomass had a higher initial and burnout temperature. With the increase of heating rates, combustion process of samples shifted to higher temperatures. Compared with non-isothermal models, activation energy obtained from isothermal model was lower. The result is helpful to promote development of co-combustion of bamboo and masson pine wastes.

Combustion of thermochemically torrefied sugar cane bagasse

This study compared the upgrading of sugar bagasse by thermochemical and dry torrefaction methods and their corresponding combustion behavior relative to raw bagasse. The combustion reactivities were examined by non-isothermal thermogravimetric analysis. Thermochemical torrefaction was carried out by chemical pre-treatment of bagasse with acid followed by heating at 160-300°C in nitrogen environment, while dry torrefaction followed the same heating treatment without the chemical pretreatment. The results showed thermochemical torrefaction generated chars with combustion properties that are closer to various ranks of coal, thus making it more suitable for co-firing applications. Thermochemical torrefaction also induced greater densification of bagasse with a 335% rise in bulk density to 340kg/m³, increased HHV_mass and HHV_volume, greater charring and aromatization and storage stability. These features demonstrate the potential of thermochemical torrefaction in addressing the practical challenges in using biomass such as bagasse as fuel.

Thermogravimetric investigation of the co-combustion between the pyrolysis oil distillation residue and lignite

Co-combustion of lignite with distillation residue derived from rice straw pyrolysis oil was investigated by non-isothermal thermogravimetric analysis (TGA). The addition of distillation residue improved the reactivity and combustion efficiency of lignite, such as increasing the weight loss rate at peak temperature and decreasing the burnout temperature and the total burnout. With increasing distillation residue content in the blended fuels, the synergistic interactions between distillation residue and lignite firstly increased and then decreased during co-combustion stage. Results of XRF, FTIR, (13)C NMR and SEM analysis indicated that chemical structure, mineral components and morphology of samples have great influence on the synergistic interactions. The combustion mechanisms and kinetic parameters were calculated by the Coats Redfern model, suggesting that the lowest apparent activation energy (120.19kJ/mol) for the blended fuels was obtained by blending 60wt.% distillation residue during main co-combustion stage.

Torrefaction of cultivation residue of Auricularia auricula-judae to obtain biochar with enhanced fuel properties

Auricularia auricula-judae, commonly known as the wood ear, is a species of edible Auriculariales fungus. Torrefactions of cultivation residues of A. auricula-judae (CRAA) at different temperatures and residence times are carried out. Effect of different torrefaction conditions on the mass and energy yields, elemental composition, heating value, thermal properties; and chemical, crystal and morphological structures of biochars are analyzed. Low torrefaction temperatures could not enhance the fuel properties as expected. Crystallinities of biochars derived from mild torrefaction conditions do not have a suitable variation trend because of the unstable degrees between degradation and recrystallization. Torrefaction of CRAA should be processed under severe conditions, such as 320 °C for 60 min and 280 °C for 120 min, in order to obtain enhanced biochar properties with DTGmax at low peak temperatures of 367 and 361 °C, as well high burnout temperatures of 528 and 530 °C, respectively.

A thermogravimetric analysis of the combustion kinetics of karanja (Pongamia pinnata) fruit hulls char

The combustion characteristics of Karanj fruit hulls char (KFH-char) was investigated with thermogravimetry analysis (TGA). The TGA outlined the char combustion thermographs at a different heating rate and isoconversional methods expressed the combustion kinetics. The Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods authenticated the char average activation energy at 62.13 and 68.53kJ/mol respectively, enough to derive the char to burnout. However, the Coats-Redfern method verified the char combustion via complex multi-step mechanism; the second stage mechanism has 135kJ/mol average activation energy. The TGA thermographs and kinetic parameters revealed the adequacy of the KFH-char as fuel substrate than its precursor, Karanj fruit hulls (KFH).

Application of artificial neural networks to co-combustion of hazelnut husk-lignite coal blends

The artificial neural network (ANN) theory is applied to thermal data obtained by non-isothermal thermogravimetric analysis (TGA) from room temperature to 1000°C at different heating rates in air to study co-combustion of hazelnut husk (HH)-lignite coal (LC) blends of various composition. The heating rate, blend ratio and temperature were used in the ANN analysis to predict the TG curves of the blends as parameters that affect the thermal behavior during combustion. The ANN model provides a good prediction of the TG curves for co-combustion with a coefficient of determination for the developed model of 0.9995. The agreement between the experimental data and the predicted values substantiated the accuracy of the ANN calculation.

Grindability and combustion behavior of coal and torrefied biomass blends

Biomass samples (pine, black poplar and chestnut woodchips) were torrefied to improve their grindability before being combusted in blends with coal. Torrefaction temperatures between 240 and 300 °C and residence times between 11 and 43 min were studied. The grindability of the torrefied biomass, evaluated from the particle size distribution of the ground sample, significantly improved compared to raw biomass. Higher temperatures increased the proportion of smaller-sized particles after grinding. Torrefied chestnut woodchips (280 °C, 22 min) showed the best grinding properties. This sample was blended with coal (5-55 wt.% biomass). The addition of torrefied biomass to coal up to 15 wt.% did not significantly increase the proportion of large-sized particles after grinding. No relevant differences in the burnout value were detected between the coal and coal/torrefied biomass blends due to the high reactivity of the coal. NO and SO2 emissions decreased as the percentage of torrefied biomass in the blend with coal increased.