Search

Densification techniques allow biomass to be used in the energy mix with coal or as a direct replacement for coal as it is a renewable resource. Typically, biomass is bulky, so thermochemical methods, like torrefaction, reduce volatiles and moisture, leaving a higher composition of fixed carbon. After the torrefaction process, the torrefied biomass poses problems during handling, transportation, and storage because it consists of small (

This research addresses the urgent need for sustainable bioenergy alternatives, specifically evaluating betel nutshells as potential replacements for conventional biomass materials like coconut and palm fibers. The objective of the study was to gauge the inherent bioenergy potential of betel nutshells through an investigation of torrefaction under varying conditions, specifically temperatures ranging from 200-300 °C and residence times between 20-60 minutes in an inert environment. In this study, proximate analyses were utilized to investigate essential characteristics including moisture content, volatile matter, ash content, and fixed carbon, while a bomb calorimeter was used to determine their higher heating values. Initial results indicated that untreated betel nutshells had higher heating values and compositional similarities to coconut and palm fibers, highlighting their potential as a bioenergy source. Advanced torrefaction processes, involving increased temperatures and extended residence times, raised the fixed carbon content and reduced moisture in betel nutshells, thereby optimizing their higher heating value. This improvement is attributed to the decomposition of covalent bonds in the biomass structures, leading to the release of volatile compounds and consequent reductions in both oxygen-to-carbon and hydrogen-to-carbon ratios. Remarkably, at an operating temperature of 300 °C and a residence time of 60 minutes, torrefied betel nutshells reached a higher heating value of 25.20 MJ/kg, marking a substantial 31.39 % increase compared to untreated specimens. This study conclusively positions betel nutshells, typically considered agricultural waste, as competitive alternatives to traditional biomass resources in the biofuel industry.

Densification techniques allow biomass to be used in the energy mix with coal or as a direct replacement for coal as it is a renewable resource. Typically, biomass is bulky, so thermochemical methods, like torrefaction, reduce volatiles and moisture, leaving a higher composition of fixed carbon. After the torrefaction process, the torrefied biomass poses problems during handling, transportation, and storage because it consists of small (<100 μm) disintegrated particles. Densification minimizes these problems through thermal compaction which produces integrated and larger (4 mm – 200 mm diameter) solid particles. This process can be done naturally (without any additives) or by adding binders which improve the torrefied biomass's physical, chemical, mechanical, and heating properties. This in turn reduces any costs associated with handling/transportation and storage of the biomass before it is used for energy generation. Densification increases the biomass's energy content per unit volume thereby enabling coal substitution. Recent reviews on densification have mainly focused on the binding of coal fines, raw biomass, and some torrefied biomass. Reviews on the binding theories are also available. This current review focuses solely on the aspect of torrefied biomass densification and the factors associated with the process. Insights and recommendations for the possible application of an integrated biomass torrefaction and densification process were provided herein. In addition, the gaps in literature were identified to enable future research on the application of the process to realize innovative renewable energy production in industry. [ABSTRACT FROM AUTHOR]

This research addresses the urgent need for sustainable bioenergy alternatives, specifically evaluating betel nutshells as potential replacements for conventional biomass materials like coconut and palm fibers. The objective of the study was to gauge the inherent bioenergy potential of betel nutshells through an investigation of torrefaction under varying conditions, specifically temperatures ranging from 200-300 °C and residence times between 20-60 minutes in an inert environment. In this study, proximate analyses were utilized to investigate essential characteristics including moisture content, volatile matter, ash content, and fixed carbon, while a bomb calorimeter was used to determine their higher heating values. Initial results indicated that untreated betel nutshells had higher heating values and compositional similarities to coconut and palm fibers, highlighting their potential as a bioenergy source. Advanced torrefaction processes, involving increased temperatures and extended residence times, raised the fixed carbon content and reduced moisture in betel nutshells, thereby optimizing their higher heating value. This improvement is attributed to the decomposition of covalent bonds in the biomass structures, leading to the release of volatile compounds and consequent reductions in both oxygen-to-carbon and hydrogen-to-carbon ratios. Remarkably, at an operating temperature of 300 °C and a residence time of 60 minutes, torrefied betel nutshells reached a higher heating value of 25.20 MJ/kg, marking a substantial 31.39 % increase compared to untreated specimens. This study conclusively positions betel nutshells, typically considered agricultural waste, as competitive alternatives to traditional biomass resources in the biofuel industry. [ABSTRACT FROM AUTHOR]

This study aimed to enhance the thermal characteristics of rice husk biomass through torrefaction conducted in a fixed-bed reactor. A novel approach was employed by circulating the gas produced within the system, instead of using traditional nitrogen. The torrefaction process took place at temperatures ranging from 200 to 320 °C, with different residence times of 10, 20, and 30 min for heat exchange. Quantitative analysis of the torrefied biomass revealed several notable improvements. The higher heating value of the biomass increased significantly, reaching 23.69 MJ/kg at a temperature of 320 °C and a residence time of 30 min. This enhancement indicates the effectiveness of torrefaction in increasing the energy content of the biomass. Furthermore, the torrefied biomass exhibited a remarkable reduction in hygroscopicity, with reduction by as much as 92 wt% compared to raw rice husk biomass. This reduction implies that the torrefied biomass is more resistant to moisture absorption, making it more stable and suitable for various applications. The torrefaction process in the fixed-bed reactor yielded a torrefied biomass with a production yield of 76 wt% (RH-320, RT30). This yield showcases the potential of the employed technique for producing a substantial amount of high-quality torrefied biomass. The resulting biomass holds great promise for diverse applications. It can be utilized for industrial steam production, contributing to the efficient use of biomass resources. Moreover, it could serve as an alternative fuel source for biomass power plants, offering a sustainable energy solution. Overall, this study demonstrates the effectiveness of the proposed torrefaction method in enhancing the thermal characteristics of rice husk biomass. The improved energy content and reduced hygroscopicity make torrefied biomass a valuable resource for various industries, promoting the utilization of biomass as a renewable energy source. [ABSTRACT FROM AUTHOR]

The pretreatment of biomass through torrefaction is an effective means of improving the fuel quality of woody biomass and its suitability for use in existing facilities burning thermal coal. Densification of torrefied biomass produces a fuel of similar energy density, moisture content, and fixed carbon content to low-grade coals. Additionally, if the torrefaction conditions are optimized, the produced torrefied pellet will be resistant to weathering and biological degradation, allowing for outdoor storage and transport in a manner similar to coal. In untreated biomass, lignin is the primary binding agent for biomass pellets and is activated by the heat and pressures of the pellet extrusion process. The thermal degradation of lignin during torrefaction reduces its binding ability, resulting in pellets of low durability not suitable for transportation. The use of a binding agent can increase the durability of torrefied pellets/briquettes through a number of different binding mechanisms depending on the binder used. This study gives a review of granular binding mechanisms, as they apply to torrefied biomass and assesses a variety of organic and inorganic binding agents, ranking them on their applicability to torrefied pellets based on a number of criteria, including durability, hydrophobicity, and cost. The best binders were found to be solid lignin by-product derived from pulp and paper processing, biomass tar derived from biomass pyrolysis, tall oil pitch, and lime. [ABSTRACT FROM AUTHOR]

Conversion of low value agricultural residues to better-quality products e.g. biofuel, bioproducts can solve the issues related to energy crisis as well as environmental challenges. Torrefaction, a thermochemical pretreatment was employed on canola residue (CR) to augment the physicochemical properties of biomass for heat and energy applications. In the present study, the effects of microwave torrefaction on canola residue have been investigated for the following operating parameters: microwave power (250–450 W), residence time (10–20 min), and feeding load (70–110 g). Box Behnken design method was used to design the experiments and find the interaction between process parameters. Both mass and energy yields diminished with rise in microwave power and torrefaction reaction time. The results show that the carbon content significantly increased with degree of torrefaction while oxygen content had a reverse trend, therefore the atomic ratio of torrefied biomass reduced remarkably. Torrefied biomass shows higher carbon percentages than that for the bituminous coal. In addition, a noticeable decrease in volatile matter was observed with growth in torrefaction severity and thus increased fixed carbon content. The higher heating value (HHV) was boosted up by 26% (promoted from 17.8 MJ/kg to 22.4 MJ/kg). HHV of highly torrefied canola residue is very close to bituminous coal. Fourier transform infrared spectroscopy (FTIR) analysis showed that surface functional groups for example OH, CH, and CO decreased with torrefaction severity indicating the improvement of hydrophobicity of torrefied biomass. Scanning electron microscopy (SEM) results represent a more porous structure at highest torrefaction conditions which happened due to thermal cracking and decomposition of lignin and decreased the grinding energy by 89% compared to that for raw biomass. Moreover, inductively coupled plasma-mass spectrometry (ICP) analysis data showed that concentrations of minerals, alkaline and other essential element amplified with degree of torrefaction. The influence of microwave power was the highest on properties of torrefied biomass, followed by residence time and feeding load. The optimum torrefaction conditions were found at 450W with 90 g feeding load for residence time of 20 min.

Torrefaction is commonly used to improve biomass properties, applications, and economy. The characteristics and subsequent applications of torrefied biomass are largely contingent on the organic compounds in parent biomass and their evolution during torrefaction. Yet, the evolution of organic compounds in biomass particularly minor components (e.g., polyphenols) is far less investigated for torrefaction. To address such issues, a superheated steam (SHS) boosted torrefaction process at different temperatures (200, 250, and 300 °C) and residence times (15, 30, and 60 min) was performed on spent coffee ground (SCG), which is an emerging biowaste and is rich in various organic compounds. Results found that both temperature and residence time determine SHS torrefaction performance. SHS torrefaction could effectively remove volatile matters to upgrade SCG for solid fuel. The relatively high content of N and S in torrefied SCG may negatively affect fuel quality but may benefit its adsorption of environmental pollutants. SHS boosted torrefaction could facilitate cellulose and lipids degradation compared to conventional torrefaction. Efficient reduction/removal of labile carbon and ecotoxic chemicals (e.g., phenols and caffeine) in SCG was successfully achieved with SHS torrefaction. As a result, SHS-torrefied SCG with higher biostability and lower phytotoxicity was evaluated as soil amendments and additives to soilless growing substrate. Implications for subsequent application by revealing the evolution of organic compounds during SHS torrefaction were discussed. This study highlighted the potentiality of SHS torrefaction as a pretreatment of biomass for versatile applications. [Display omitted] • The maximal HHV of SHS-torrefied SCG reached 29.68 MJ/kg. • Cellulose and hemicellulose are greatly decomposed by SHS torrefaction. • Crude protein and lipids are less affected during SHS torrefaction. • Polyphenols, flavonoids, and caffeine are efficiently removed during SHS torrefaction. • SHS-torrefied SCG may be utilized as fuel, soil amendment, or biosorbent. [ABSTRACT FROM AUTHOR]

Because of different heat mechanism, the temperature distribution inside a reactor has its own characteristic. This is the limitation to increase the capacity of the reactor. This idea led to modify fixed-bed reactor that has a limitation on nonuniform temperature distribution inside a reactor with increasing heat transfer area by setting thermosyphon tube since fixed-bed reactor has another limitation in capacity and heat loss. Therefore, modifying fixed-bed reactor to operate as semi-batch can fix the limitation and improve thermal efficiency of a reactor as well. In order to study the performance of the reactor for torrefaction process, analyzing the fuel properties of each torrefied biomass batch is necessary. The controlled variables of this research are the temperature of heating chamber, which are 350, 400 and 400°C with an allotted torrefaction time of 35 minutes per batch that is close to research condition of thermosyphon reactor fixed-bed type. Fuel properties analyzed in this research are high heating value (HHV), bulk density, and energy density. This research also recorded the temperature inside the reactor to determine the temperature distribution when operated as a semibatch reactor. From the results gathered, it was discovered that when the operating reactor reached a steady behavior, the torrefaction process increased to a high level. As seen in energy density ratio, it reached a high level because of the increase of HHV ratio, that is 1.182 - 1.412 for 350 - 450°C. The bulk density ratio is also very low, and the value is close to a herbaceous biomass type that is usually seen in woody samples. These factors cause such energy density ratio in high levels and intensity of such process inside the reactor. [ABSTRACT FROM AUTHOR]

A model-fitting method at a single heating rate (10 °C·min-1 ) was used to investigate the thermal kinetic characteristics of torrefied woody biomass. The kinetic parameters were examined for pine, oak, and bamboo samples with the order of the reaction set ranging from 0.1 to 0.5 and 1.0. Based on the thermogravimetric, derivative thermogravimetric, and derivative2 thermogravimetric curves obtained, the ranges at which substantial hemicellulose and cellulose pyrolysis occurs were set as the analysis range, and the kinetic parameters of each species were analyzed. The activation energy and pre-exponential factor were obtained at these analytical ranges using two differential methods (Friedman and Chatterjee-Conard) and an integral method (Coats-Redfern). Although there were numerical differences between the results of the differential and integral methods, the thermal properties of each sample exhibited a consistent trend. Softwood was found to have the highest reactivity and intermolecular collisions per unit weight during thermal decomposition. In the case of the torrefied oak and torrefied bamboo, considering that the carbon content and fixed carbon content were approximately 24% to 25% higher than the softwood, it is appropriate to consider the thermal characteristics of each species for producing a solid fuel based on the application. [ABSTRACT FROM AUTHOR]

Melina wood torrefied at 260 °C for 60 min was agglomerated with lean grade coal fines into composite briquettes using pitch as binder. Torrefied biomass (3%–20%) and coal fines (80%–97%) were blended together to produce the composite briquettes under a hydraulic press (28 MPa). The briquettes were cured at 300 °C. Density, water resistance, drop to fracture, impact resistance, and cold crushing strength were evaluated for the composite briquettes. The proximate, ultimate, and calorific value analyses were carried out according to different ASTM standards. Microstructural studies were carried out using scanning electron microscope and electron probe microanalyzer equipped with energy dispersive x-ray. Fourier Transform Infrared Spectrophotometer (FTIR) was used to obtain the functional groups in the raw materials and briquettes. The density of the composite briquettes ranged from 0.92 to 1.31 g/cm3 after curing. Briquettes with < 10% torrefied biomass has good water resistance index (> 95%). The highest cold crushing strength of 4 MPa was obtained for briquettes produced from 97% coal fines and 3% torrefied biomass. The highest drop to fracture (54 times/2 m) and impact resistance index (1350) were obtained for the sample produced from 97% coal and 3% torrefied biomass. The fixed and elemental carbons of the briquettes showed a mild improvement compared to the raw coal. The peaks from FTIR spectra for the briquettes shows the presence of aromatic C=C bonds and phenolic OH group. The composite briquettes with up to 20% torrefied biomass can all be useful as fuel for various applications. [ABSTRACT FROM AUTHOR]

The aim of this research was to evaluate the changes in physico-chemical properties of agricultural residues (corn-cobs and rice husks) during torrefaction. Physical properties of the torrefied biomass pellets were analysed. The results showed that increasing the torrefaction temperature and time resulted in reduced moisture and volatile matter content of corn-cobs and rice husks. At the same time, fixed carbon, ash content and heating values were increased. The heating values of both torrefied fuels were in the range of 14.9-16.9 MJ kg-1, increased by about 16% to 21% from the raw biomass. The optimum treatment conditions were found to be in the range 200°C-250° C and 20 min. Physical properties of both torrefied pellet fuels were found to be enhanced, and closer to those required by the associated standard. The average bulk density and durability of torrefied pellets were between 1112 and 1226 kg m-3 and 91% and 94%, respectively. The water resistance and compressive strength were in the range 89%-92% and 140-156 kg m-3, respectively. The energy densities of corn-cob and rice husk torrefiled fuels were increased by 20.8% and 15.8% with compared to their original biomass inputs. [ABSTRACT FROM AUTHOR]

Dependence on inert gas such as nitrogen during torrefaction is not favourable due to the burden in terms of operational costs. Therefore, various alternatives have been introduced to reduce or eliminate the dependence on inert gas. The present article seeks to review the various alternatives to inert torrefaction for viable solid fuel production. The details on non-inert torrefaction, including experimental setup, effect of various essential parameters, and major findings, are reviewed and discussed. The primary trends in the torrefaction field were extracted from previous studies, were compiled and presented in several tables and graphs. The review findings showed that temperature, residence time, gas type, gas velocity, heating rate, and particle size can affect the performance, physicochemical, and combustion properties of torrefied biomass. The degree of the effectiveness of each parameter also depends on the biomass type and shape. Based on the van Krevelen diagram, the various alternative techniques can produce competitive torrefied solid products with viable fuel properties compared to commercial coals and products torrefied under inert torrefaction conditions. Overall, it is expected that the number of alternative techniques can be implemented on a larger scale after certain modifications are performed. • Physical, chemical, combination of physical and chemical approaches are available. • Effect of temperature and residence time were frequently investigated. • Various alternative approaches can produce very competitive solid fuels. • Temperature of 270–300 °C and holding time of 30–120 min are preferred. • Several alternatives can be implemented on a larger scale after modifications. [ABSTRACT FROM AUTHOR]

Peat is the main type of peloid used in Polish cosmetic/healing spa facilities. Depending on treatment and origin, peat waste can be contaminated microbiologically, and as a result, it must be incinerated in medical waste incineration plants without energy recovery (local law). Such a situation leads to peat waste management costs increase. Therefore, in this work, we checked the possibility of peat waste upcycling to carbonized solid fuel (CSF) using torrefaction. Torrefaction is a thermal treatment process that removes microbiological contamination and improves the fuel properties of peat waste. In this work, the torrefaction conditions (temperature and time) on CSF quality were tested. Parallelly, peat decomposition kinetics using TGA and torrefaction kinetics with lifetime prediction using macro-TGA were determined. Furthermore, torrefaction theoretical mass and energy balance were determined. The results were compared with reference material (wood), and as a result, obtained data can be used to adjust currently used wood torrefaction technologies for peat torrefaction. The results show that torrefaction improves the high heating value of peat waste from 19.0 to 21.3 MJ × kg−1, peat main decomposition takes place at 200–550 °C following second reaction order (n = 2), with an activation energy of 33.34 kJ × mol−1, and pre-exponential factor of 4.40 × 10−1 s−1. Moreover, differential scanning calorimetry analysis revealed that peat torrefaction required slightly more energy than wood torrefaction, and macro-TGA showed that peat torrefaction has lower torrefaction constant reaction rates (k) than wood 1.05 × 10−5–3.15 × 10−5 vs. 1.43 × 10−5–7.25 × 10−5 s−1.

In this article, four types of agricultural waste with different amounts of each lignocellulosic type, including rice husk (RH), coconut husk (CH), cassava rhizome (CR), and corncob (CC) were torrefied under inert environment at 200 - 300°C for 30 min. Biochar properties were characterized by various techniques in order to investigate their yield, physicochemical properties, higher heating value (HHV), thermal decomposition behavior, and surface functional group. The experimental results show that yield, HHV, and energy yield (Ey) of biochar were depended significantly on both types of agricultural waste and treatment temperature. The values of those parameters ranged from 81.75 - 35.59%, 19.06 - 28.29 MJ/kg, and 51.34 - 86.22%, respectively. Fuel properties of agricultural waste were greatly enhanced by torrefaction at 300°C. Biochar from torrefied CC provides the highest fuel ratio (2.18) with lowest atomic ratios of O/C and H/C (0.18 and 0.67, respectively) and this is comparative with bituminous coal. The changes of these properties were mainly due to dehydration and deoxygenation reactions. Interestingly, agricultural wastes with high cellulose content (44.41%) could produce biochar with the maximum energy yield (86.22%). These results indicated that torrefaction was a promising technology for conversion of agricultural wastes to biochar as coal substitute material. [ABSTRACT FROM AUTHOR]

Abstract The utilization of biomass has been increasing in recent years, how to achieve successful feeding of biomass into the different utilization systems is a common problem. Reliable information on flow properties are required for the design of storage, processing and handling equipment. In this paper, the flow properties of four representative agricultural biomass powders (soybean straw, corn straw, rice straw and rice husk) and their torrefied powders were investigated experimentally by two different testing methods (angle of repose test and packing properties test) with a powder synthetic characteristic tester. The effects of mean particle size, particle shape, biomass species and their interaction on different characterization parameters (angle of repose, bulk density, tapped density, Hausner ratio and compressibility index) were investigated. The results of the two different testing methods were compared, and it was found that Hausner ratio and compressibility index cannot always accurately characterize the flowability of biomass powders compared with angle of repose. Meanwhile, the effect of torrefaction pretreatment on the flowability of biomass powders was discussed. The results showed that torrefaction pretreatment can improve biomass powder flowability, however, it cannot change the relative relationship between the flowability of different biomass powders. Highlights • Flow properties of biomass powders useful for design and control were determined. • The results of two different testing methods were analyzed and compared. • Effects of main physical properties on biomass powders' flowability were discussed. • Effect of torrefaction on the flowability of biomass powders was studied. [ABSTRACT FROM AUTHOR]

Highlights • Biomass torrefied via microwave heating enhanced both the quantity and quality of bio-oil. • Parameters optimization of catalytic microwave co-pyrolysis of biomass and LDPE for bio-oil. • Temperature and catalyst dosage were key factors influencing both bio-oil yield and selectivity. • The proportion of hydrocarbons was the highest (about 40%) in the bio-oils. Abstract This study aims to produce high quality bio-oil by microwave co-pyrolysis of torrefied biomass (rice straw) and low density polyethylene (LDPE) using ZSM-5 as a catalyst. A central composite experimental design was used to optimize the reaction condition by response surface methodology analysis. The effects of reaction temperatures and catalyst dosages on the product yield and chemical selectivity of bio-oil were investigated. Results suggested that bio-oil obtained from torrefied biomass contained a lower water content compared with the control.The major chemical compounds of bio-oil were hydrocarbons, ketones, phenols, esters and alcohols (∼80%).Bio-oils with high hydrocarbon content (∼40% in the bio-oil) were obtained in the development of this experiment. Quadratic models were used to predict the bio-oil yield and chemical selectivity of the bio-oil obtained during the reactions. [ABSTRACT FROM AUTHOR]

In biomass harvesting and fuel preparation processes, grinding causes a prominent energy consumption penalty, which results in an analogous cost impact. This is due to the fibrous and tenacious nature of biomass. Torrefaction of biomass makes it brittle, as it diminishes its fibrous nature and, hence, it enhances its grindability. Nevertheless, grinding costs are still important and increase with decreasing targeted particle size. Therefore, this study introduces a methodology for assessing the torrefied biomass grind size that is suitable for firing or co-firing with coal in existing pulverized fuel boilers. It examines combustion of biomass of different origins, herbaceous, woody, or crop-related. Biomass was torrefied for 30 min at 275 °C in nitrogen. It was subsequently ground and sieved to various size cuts, which reflect the mean widths rather than the lengths of these typically elongated particles. Subsequently, the particles were burned, one at a time, in a drop tube furnace (DTF) under high temperature and high heating rate conditions. Luminous burnout times were observed pyrometrically and cinematographically for a number of single particles from various size cuts. Such burnout times were then contrasted with those of individual coal particles in the size range of 75–90 µm, i.e., at the upper end of particle sizes burned in coal-fired boilers. Based on this comparison, the nominal sieve size of the examined torrefied biomass particles whose overall observed burnout times matched those of the 75–90 µm coal particles was determined to be 212–300 µm. Hence, to minimize the grinding cost of co-firing such torrefied biomass with coal in existing boilers, its finer pulverization may not be necessary. [ABSTRACT FROM AUTHOR]

To develop a new integrated system for co-production of electricity and hydrogen with CO 2 capture, a biomass steam gasification (BSG) process integrated with an iron-based chemical looping hydrogen production (CLHP) system and a combined heat and power (CHP) system is presented and simulated using Matlab and Aspen Plus. The raw wood (RW) and torrefied wood (TW) are used as the feedstock of the BSG process to produce RW- and TW-derived syngas, respectively. The CLHP system operates with solid circulation and adopts two countercurrent moving bed reactors where detailed kinetic models are validated by experimental data from the literature. The CHP system uses a combination of a heat recovery steam generator (HRSG) and a series of steam turbine (ST) cycles to enhance the electricity efficiency and the overall system efficiency. To address the maximum syngas conversion and hydrogen yield of the BSG-CLHP-CHP system, the optimal results show that steam velocity of the moving bed oxidizer is a crucial parameter, which should be operated at less than 15 cm s −1 for RW-derived syngas and 8.7 cm s −1 for TW-derived syngas. Overall, based on a comparison of the BSG-CLHP-CHP system performance in terms of hydrogen thermal efficiency, overall system efficiency, and hydrogen yield between RW and TW, the predictions suggest that TW is obviously superior to RW. [ABSTRACT FROM AUTHOR]

The utilization of CO2 neutral carbon instead of fossil carbon is one way to mitigate CO2 emissions in the steel industry. Using reactive reducing agent, e.g., bio-coal (pre-treated biomass) in iron ore composites for the blast furnace can also enhance the self-reduction. The current study aims at investigating the self-reduction behavior of bio-coal containing iron ore composites under inert conditions and simulated blast furnace thermal profile. Composites with and without 10% bio-coal and sufficient amount of coke breeze to keep the C/O molar ratio equal to one were mixed and Portland cement was used as a binder. The self-reduction of composites was investigated by thermogravimetric analyses under inert atmosphere. To explore the reduction progress in each type of composite vertical tube furnace tests were conducted in nitrogen atmosphere up to temperatures selected based on thermogravimetric results. Bio-coal properties as fixed carbon, volatile matter content and ash composition influence the reduction of iron oxide. The reduction of the bio-coal containing composites begins at about 500 °C, a lower temperature compared to that for the composite with coke as only carbon source. The hematite was successfully reduced to metallic iron at 850 °C by using bio-coal, whereas with coke as a reducing agent temperature up to 1100 °C was required.

In this study, waste bamboo chopsticks (WBC) were upgraded as solid bio-fuel by torrefaction using a tubular furnace with nitrogen as carrier gas. In order to fulfill the quality specifications of coal and industrial wood pellets, the effects of temperature and time of torrefaction on proximate and ultimate compositions and its dry-basis heating value (H HD ) were studied and elucidated. The results showed that the mass yield of WBC is 69% at 563 K and 40 min, while H HD of WBC is increased from 19.31 to 23.04 MJ kg −1 with an energy densification factor of 1.19, which satisfy the specification of quality D of Taiwan Power Co. and I3 industrial quality of Initiative Wood Pellets Buyers. Further, the torrefied WBC (WBC T ) pellets become convenient to store, transport and processing and hard to be rotten because of the modification of surface hydrophobicity. The ash content of WBC T is only 2.19 wt.% in wet basis, which is beneficial in practical boiler. Further, the energies needed for drying, heating and torrefaction is 2.31 MJ for processing 1 kg WBC with CO 2 emission of 0.339 kg. Therefore, WBC T would be practical alternative as solid bio-fuel for cofiring with coal. [ABSTRACT FROM AUTHOR]

The interest of the steel industry in utilizing bio-coal (pre-treated biomass) as CO2-neutral carbon in iron-making is increasing due to the need to reduce fossil CO2 emission. In order to select a suitable bio-coal to be contained in agglomerates with iron oxide, the current study aims at investigating the thermal devolatilization of different bio-coals. A thermogravimetric analyzer (TGA) equipped with a quadrupole mass spectrometer (QMS) was used to monitor the weight loss and off-gases during non-isothermal tests with bio-coals having different contents of volatile matter. The samples were heated in an inert atmosphere to 1200 °C at three different heating rates: 5, 10, and 15 °C/min. H2, CO, and hydrocarbons that may contribute to the reduction of iron oxide if contained in the self-reducing composite were detected by QMS. To explore the devolatilization behavior for different materials, the thermogravimetric data were evaluated by using the Kissinger⁻ Akahira⁻Sonuse (KAS) iso-conversional model. The activation energy was determined as a function of the conversion degree. Bio-coals with both low and high volatile content could produce reducing gases that can contribute to the reduction of iron oxide in bio-agglomerates and hot metal quality in the sustained blast furnace process. However, bio-coals containing significant amounts of CaO and K2O enhanced the devolatilization and released the volatiles at lower temperature.

Measurements reported in the literature on ultimate analysis of various types of torrefied woody biomass, comprising 152 data points, have been compiled and empirical correlations are developed to predict the carbon content, hydrogen content, and heating value of a torrefied wood as a function of solid mass yield. The range of torrefaction temperature, residence time and solid yield of the collected data is 200–300 °C, 5–60 min and 58–97%, respectively. Two correlations are proposed for carbon content with a coefficient of determination ( R 2 ) of 81.52% and 89.86%, two for hydrogen content with R 2 of 79.01% and 88.45%, and one for higher heating value with R 2 of 92.80%. The root mean square error (RMSE) values of the proposed correlations are 0.037, 0.028, 0.059, 0.043 and 0.023, respectively. The predictability of the proposed relations is examined with an additional set of experimental data and compared with the existing correlations in the literature. The new correlations can be used as a useful tool when designing torrefaction plants, furnaces, or gasifiers operating on torrefied wood.

The firing and co-firing of biomass in pulverized coal fired power plants around the world is expected to increase in the coming years. Torrefaction may prove to be a suitable way of upgrading biomass for such an application. For transport and storage purposes, the torrefied biomass will tend to be in pellet form. Whilst standard methods for the assessment of the milling characteristics of coal exist, this is not the case for torrefied materials--whether in pellet form or not. The grindability of the fuel directly impacts the overall efficiency of the combustion process and as such it is an important parameter. In the present study, the grindability of different torrefied biomass pellets was tested in three different laboratory mill types; cutting mill (CM), hammer mill (HM) and impact mill (IM). The specific grinding energy (SGE) required for a defined mass throughput of pellets in each mill was measured and results were compared to other pellet characterization methods (e.g., durability, and hardness) as well as the modified Hardgrove Index. Seven different torrefied biomass pellets including willow, pine, beech, poplar, spruce, forest residue and straw were used as feedstock. On average, the particle-size distribution width (across all feedstock) was narrowest for the IM (0.41 mm), followed by the HM (0.51 mm) and widest for the CM (0.62 mm). Regarding the SGE, the IM consumed on average 8.23 Wh/kg while CM and HM consumed 5.15 and 5.24 Wh/kg, respectively. From the three mills compared in this study, the IM seems better fit for being used in a standardized method that could be developed in the future, e.g., as an ISO standard. [ABSTRACT FROM AUTHOR]

In this article, a co-gasification system blending coal and biomass is examined in the Aspen Plus environment in terms of energy conversion efficiency (ECE) and exergy efficiency (EE). Although the percentage of raw wood (RW), torrefied wood (TW) and coal in steam co-gasification is one of the most important parameters that affect the gasification process, the addition of CO 2 could effectively improve ECE and EE while the steam-to-carbon ratio ( S / C ) is adjusted at the carbon boundary point (CBP). The optimum operating conditions such as S / C and CO 2 supply ratio, are determined by solving a series of constrained optimization algorithms for maximizing ECE and EE. A combined heat and power (CHP) system using the maximum waste heat recovery and Rankine cycle is illustrated to assess performance in terms of power generation and CO 2 utilization. The results show that the total power generation by feeding the TW-based fuel blend of 40 wt% TW and 60 wt% coal is increased by 8.43%, as compared to that of the RW-based fuel blend of 40 wt% RW and 60 wt% coal. Compared with 100 wt% coal fuel, the TW-based fuel can significantly reduce CO 2 specific emission by 38.23%. [ABSTRACT FROM AUTHOR]

The pyrolysis of native and torrefied stump materials was studied in the kinetic regime by means of a thermogravimetric analyzer operated in the non-isothermal fashion. Three different kinetic models applicable to biomass pyrolysis were evaluated for the collected data, which include a single-reaction model, two three pseudo-components models, and a distributed activation energy model (DAEM). It was shown that the single-reaction model was not suitable to simulating stump biomass pyrolysis. The other models including the three pseudo-components model with n = 1 and n ≠ 1, and the DAEM demonstrated very good fits between simulated and experimental curves. However, the three pseudo-components model with n ≠ 1 is recommended as the most suitable for simulation and prediction of kinetic behaviour of slow pyrolysis for both untreated and torrefied stump, considering that it offers the best fits to the experimental data and that the generated reaction orders are realistic, being slightly higher than unity. It appears that the torrefied stump has higher activation energy than its native material. The activation energy predicted for the native stump pyrolysis is in the range of 105.2–108.9 kJ/mol, 183.5–183.6 kJ/mol, and 40.3–48.01 kJ/mol for hemicelluloses, celluloses, and lignin, respectively. That for pyrolysis of the stump torrefied at 200 °C is 105.13–111.19 kJ/mol, 183.68–185.79 kJ/mol, and 40.49–50.70 kJ/mol, respectively. [ABSTRACT FROM AUTHOR]

The char oxidation of a torrefied biomass and its parent material was carried out in an isothermal plug flow reactor (IPFR), which is able to rapidly heat the biomass particles to a maximum temperature of 1400 °C at a heating rate of 10 4 °C/s, similar to the real conditions found in power plant furnaces. During each char oxidation test, the residues of biomass particles were collected and analyzed to determine the weight loss based on the ash tracer method. According to the experimental results, it can be concluded that chars produced from a torrefied biomass are less reactive than the ones produced, under the same conditions, from its raw material. The apparent kinetics of the torrefied biomass and its parent material are determined by minimizing the difference between the modeled and the experimental results. The predicted weight loss during char oxidation, using the determined kinetics, agrees well with experimental results. [ABSTRACT FROM AUTHOR]

We apply a biomass pyrolysis model, based on the model developed by Haseli et al. [4] , which can be used in combination with Direct Numerical Simulation. The pyrolysis model is combined with a model for particle tracking to simulate 3D turbulent particle-laden channel flow with biomass particles undergoing pyrolysis in nitrogen. Transfer of momentum, heat and mass between gas and particles are fully taken into account. The effects of this transfer are analyzed and quantified in terms of the delay in the conversion or pyrolysis time. The delay is shown to depend on the initial volume fraction (number of particles) and on the size of the particles. The two-way coupling effects are relevant at volume fractions >10 −5 . For a fixed volume fraction, gas–particle interaction induces a delay in the devolatilization, decreasing with increasing particle size. Using this model, we also performed simulations of realistic biomass particle size distributions in order to compare two-way and one-way coupling. [ABSTRACT FROM AUTHOR]

Highlights: [•] The first study of integrated microwave torrefaction and pyrolysis of corn stover. [•] Microwave torrefied pyrolysis favored phenols and hydrocarbons production. [•] Organic acids were significantly reduced in bio-oils. [•] Up to 26.7 area% hydrocarbons in the bio-oil were produced. [ABSTRACT FROM AUTHOR]

Abstract: The combustion behaviors of four different pulverized biomasses were evaluated in the laboratory. Single particles of sugarcane bagasse, pine sawdust, torrefied pine sawdust and olive residue were burned in a drop-tube furnace, set at 1400 K, in both air and O2/CO2 atmospheres containing 21, 30, 35, and 50% oxygen mole fractions. High-speed and high-resolution images of single particles were recorded cinematographically and temperature–time histories were obtained pyrometrically. Combustion of these particles took place in two phases. Initially, volatiles evolved and burned in spherical envelope flames of low-luminosity; then, upon extinction of these flames, char residues ignited and burned in brief periods of time. This behavior was shared by all four biomasses of this study, and only small differences among them were evident based on their origin, type and pre-treatment. Volatile flames of biomass particles were much less sooty than those of previously burned coal particles of analogous size and char combustion durations were briefer. Replacing the background N2 gas with CO2, i.e., changing from air to an oxy-fuel atmosphere, at 21% O2 impaired the intensity of combustion; reduced the combustion temperatures and lengthened the burnout times of the biomass particles. Increasing the oxygen mole fraction in CO2 to 28–35% restored the combustion intensity of the single biomass particles to that in air. [Copyright &y& Elsevier]

Abstract: Pilot scale pelletizing of torrefied Norway spruce was performed in a factorial design with controlled factors at two levels: material moisture content (11% and 15%) and torrefaction temperature (270 and 300°C), and die temperature as an uncontrolled factor (60–105°C). Compared to commercial wood pellets, produced pellets had comparable bulk densities (630–710kg/m3) but lower pellet durability (80–90%). Energy consumption for pelletizing of torrefied materials was approximately 100% higher than for softwood pelletizing, despite using a much shorter die channel length (35 vs. 55mm:s), and the amounts of fines were high (10–30%). Die temperature showed a strong positive correlation with pellet production rate. Material moisture content had little influence on pellet quality and production rate, but addition of water created handling problems due to bad flow behavior. [Copyright &y& Elsevier]

Peat is the main type of peloid used in Polish cosmetic/healing spa facilities. Depending on treatment and origin, peat waste can be contaminated microbiologically, and as a result, it must be incinerated in medical waste incineration plants without energy recovery (local law). Such a situation leads to peat waste management costs increase. Therefore, in this work, we checked the possibility of peat waste upcycling to carbonized solid fuel (CSF) using torrefaction. Torrefaction is a thermal treatment process that removes microbiological contamination and improves the fuel properties of peat waste. In this work, the torrefaction conditions (temperature and time) on CSF quality were tested. Parallelly, peat decomposition kinetics using TGA and torrefaction kinetics with lifetime prediction using macro-TGA were determined. Furthermore, torrefaction theoretical mass and energy balance were determined. The results were compared with reference material (wood), and as a result, obtained data can be used to adjust currently used wood torrefaction technologies for peat torrefaction. The results show that torrefaction improves the high heating value of peat waste from 19.0 to 21.3 MJ × kg−1, peat main decomposition takes place at 200–550 °C following second reaction order (n = 2), with an activation energy of 33.34 kJ × mol−1, and pre-exponential factor of 4.40 × 10−1 s−1. Moreover, differential scanning calorimetry analysis revealed that peat torrefaction required slightly more energy than wood torrefaction, and macro-TGA showed that peat torrefaction has lower torrefaction constant reaction rates (k) than wood 1.05 × 10−5–3.15 × 10−5 vs. 1.43 × 10−5–7.25 × 10−5 s−1. [ABSTRACT FROM AUTHOR]

The oxidative torrefaction of rice straw polluted by heavy metals was carried out in a tube reactor (atmospheric pressure, AP) and an autoclave (gas-pressurized, GP), in order to compare the effects of the torrefaction temperature, carrier gas composition, and reactor type on torrefied products' properties. Compared with the AP, the GP-torrefied rice straw had a lower solid yield, volatile matter, fixed carbon, hydrogen and oxygen contents, lower overall colour change (Δ E), combustion characteristic factor (S N), but a higher bulk density, higher heating value, ash and carbon content, higher combustion temperatures (T i and T f) and fuel ratio. The weight loss, volatile matter, element, higher heating values and combustion characteristics of the AP-torrefied rice straw showed good correlations with its colour parameters, which indicating that it is technically feasible to identification and prediction by the human eye of AP-torrefied RS at the industrial level. However, higher amount of typical heavy metals remained in the GP-torrefied solid products with lower biological availability, indicating that GP torrefaction can be utilized as a low-cost and safe pre-treatment for heavy-metal-polluted rice straw at the industrial scale. Image 1 • RS subjected to GP torrefaction had higher weight loss, HHV and ash content. • The O 2 content of the carrier gas affected the product properties slightly. • Weight loss, HHV and ignition showed good correlation with the colour coordinates. • GP-torrefied RS had a higher ignition temperature in combustion. • The heavy metal yield in the solid fraction obtained using GP was much lower. [ABSTRACT FROM AUTHOR]