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 (<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]

[Display omitted] • The heat source in the self-heating torrefaction of dairy manure was determined. • A mathematical model for self-heating torrefaction was developed. • The conditions that induce self-heating of manure up to 300 °C were determined. • Higher pressure and lower ventilation induce self-heating at lower temperatures. A self-heating torrefaction system was developed to overcome the difficulties in converting high-moisture biomass to biochar. In self-heating torrefaction, the ventilation rate and ambient pressure must be set properly to initiate the process. However, the minimum temperature at which self-heating begins is unclear because the effects of these operating variables on the heat balance are not theoretically understood. The present report presents a mathematical model for the self-heating of dairy manure based on the heat balance equation. The first step was to estimate the heat source; experimental data showed that the activation energy for the chemical oxidation of dairy manure is 67.5 kJ/mol. Next, the heat balance of feedstock in the process was analyzed. Results revealed that the higher the ambient pressure and the lower the ventilation rate at any given pressure, the lower the temperature at which self-heating is induced. The lowest induction temperature was 71 °C at a ventilation rate of 0.05 L min−1 kg-AFS−1 (AFS: ash-free solid). The model also revealed that the ventilation rate significantly affects the heat balance of feedstock and drying rate, suggesting an optimal range for ventilation. [ABSTRACT FROM AUTHOR]

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]

The use of coal for energy generation is facing serious scrutiny because of environmental concerns. As a result, there is a growing global interest in biomass, a renewable and readily available energy source. However, the utilization of biomass comes with significant drawbacks, including its heterogeneity, low bulk density, and calorific value. Biomass also has a low energy content, high moisture, poor grindability, and high volatile matter, which affect its handling, bulk transportation, and storage. Torrefaction technology has been employed in previous works to improve the properties of biomass for subsequent handling and transportation and for low-cost energy generation. Since coal is a promising precursor for energy generation, it is imperative to compare the physicochemical properties of coal with that of torrefied biomass. Therefore, this study aims to conduct a comprehensive comparison between various grades of coal and torrefied biomass. The review revealed that torrefied biomass could replace coal, as its properties are similar to those of coal, except for high-grade coals. The proximate and ultimate analyses of coals (lignite and bituminous) were found to be comparable to various torrefied biomass materials. The fuel ratio (0.5–2.0), and higher heating values (16,100–19,000 kJ/kg) of coal and torrefied biomass were within the range useful for coal-fired plants. Additionally, ash analyses, ash fusion temperature, hygroscopic tendency, functional group study, and microstructural comparison were reviewed in this study. The results from various studies have shown close similarities with only small disimilarities in the fuel properties between coal and torrefied biomass. Therefore, torrefied biomass is proposed as a complimentary feedstock to coal in various applications. [Display omitted] • The similarity and disparity between torrefied biomass and coal are discussed. • Proximate, ultimate, calorific, and FTIR analyses of torrefied biomass and coal were discussed. • Fuel ratio, ash content, and grindability values of torrefied biomass and coal were discussed. • Present grade of coal with similar properties to torrefied biomass and application in thermal plants. • Recommend partial or total replacement of coal with torrefied biomass in co-fired plants. [ABSTRACT FROM AUTHOR]

Chemical looping gasification is an efficient technology to convert biomass into valuable syngas. The iron-based oxygen carriers are a promising option for large-scale commercial applications due to their low cost and environmentally-friendly properties. The present study aims at evaluating the performance of the syngas production from the chemical looping gasification of torrefied woodchips in a pilot-scale bubbling fluidized bed reactor using iron ore and ilmenite as oxygen carriers. The effects of the operating parameters were investigated in this study. The results show that an increase in operating parameters could favor the process performance. Carbon conversion efficiency and the yields accelerate at high operating conditions. Carbon conversion efficiency showed a maximum value of 91.42% for iron ore at the ratio of oxygen carrier-to-biomass of 6, while the gas yield reaches the peak at SBR of 1.4 for ilmenite. The addition of steam in biomass chemical looping gasification improves hydrogen production and syngas quality in the product gas. Despite ilmenite provides better performance for hydrogen production, it characterizes by a lower reactivity compared to iron ore. It is also found that iron ore performs better at lower values of steam-to-biomass ratios and temperatures, while ilmenite shows good results at higher those parameters. • Chemical looping gasification of torrefied woodchips using iron-based oxygen carriers was investigated experimentally. • Higher ratios of oxygen carrier-to-biomass do not favor syngas production. • Higher gasification temperatures significantly enhance the process performance. • The content and yield of H 2 in the product gas are proportional to the ratio of steam-to-biomas. • Superficial velocity considerably affects the performance of chemical looping gasification. [ABSTRACT FROM AUTHOR]

Combustion and oxy-fuel combustion characteristics of torrefied pine wood chips were investigated by Thermogravimetric Analysis (TGA). Three torrefaction temperatures (250, 300, and 350 °C) and two residence times (15 and 30 min) were considered. Experiments were carried out at three heating rates of 10, 20, and 40 °C/min. The isoconversional kinetic methods of FWO, KAS, and Friedman were employed to estimate the activation energies. The assessment of uncertainty in obtaining the activation energy values was also considered. The obtained results indicated that due to torrefaction, the O/C and H/C atomic ratios decreased, resulting the 300ºC-30 min and 350ºC-15 min torrefied biomass to be completely embedded in lignite region in van-Krevelen's diagram. Oxy-fuel combustion affected the decomposition of cellulose and lignin components of biomass while the impact on the hemicellulose component was negligible. The kinetic analysis revealed that with the evolution of conversion degree, the activation energy values increased during hemicellulose degradation, remained approximately constant during cellulose decomposition and showed a sharp decrease for lignin decomposition. The activation energy trends were comparable in both air and oxy-fuel combustion conditions, however slight changes in activation energy values were noticed. The highest activation energy value was obtained for 250ºC-30 min torrefied biomass at 183.40 kJ/mol and the lowest value was 72.93 kJ/mol for 350ºC-15 min biomass. The uncertainty values related to FWO method were lower than KAS and Friedman methods. The uncertainty values for FWO and KAS methods were at the range of 5–15%. • The torrefaction temperature effect was more significant than residence time. • Torrefaction resulted in decreased O/C and H/C atomic ratios. • Oxy-fuel combustion affected the decomposition of cellulose and lignin. • Activation energy values increased during the degradation of hemicellulose. • Activation energy values showed a sharp decrease during the decomposition of lignin. [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]

• Power level was a major parameter in affecting performance of torrefied products. • Dielectric materials and particle size affect significantly heating rate. • 150 to 250 W was sufficient to produce a good quality torrefied products. • Clean-products derived from microwave heating technique can be obtained. • Dedicated operating conditions in MW heating resulted in high EROI (6.1 to 34). Microwave (MW) heating offers numerous advantages over conventional heating. Its characteristics of fast internal heating, volumetric heating, and low energy consumption enable microwave torrefaction (MWT) of biomass to be performed. The purpose of this article is to review the current state of MWT of biomass. A brief explanation of MWT, including experimental setups and the effects of several important parameters, are reviewed and discussed. Potential future directions and challenges regarding MWT are also discussed. It is known that the MW power level, types of MW absorbers (catalyst), and particle size can significantly influence the performance of torrefied biomass in terms of energy and mass yields, mass loss, H/C and O/C ratios, fuel ratio, and high heating value. The effect of operating condition on products derived from MWT needs to be further investigated in order to make the technology feasible and reliable. Overall, MWT has the potential to serve as energy-efficient method to improve the performance of biomass. [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]

The combined use of bio-fuels along with CO 2 capture techniques is the basis for the so-called negative emissions energy systems. In this paper, oxy-fuel combustion of two torrefied biomasses is experimentally investigated in a lab-scale entrained flow reactor. The torrefied biomasses are fired alone, and co-fired with coal (50%). Two oxygen concentrations (21% and 35%) and four steam concentrations are tested: 0% (dry recycle oxy-combustion), 10% (wet recycle oxy-combustion), 25% and 40% (towards the concept of oxy-steam combustion). The tests are designed to get the same mean residence time for all the fuels and conditions. Burnout degrees are significantly increased (up to 9 and 16 percentage points) when the share of torrefied biomass is raised, with a slightly better behavior of the torrefied pine in comparison to the torrefied agro-biomass. C-fuel conversion to CO 2 follows a similar trend to the observed for the burnout degrees. NO formation rates are reduced when oxy-firing torrefied biomass alone in comparison to the blends, with maximum diminutions of 16.9% (torrefied pine) and 8.5% (torrefied agro-biomass). As regards the effect of steam, the best results are found for the 25% H 2 O atmospheres in most of the cases, yielding maximum conversions along with minimum NO levels. • New oxy-combustion results for two torrefied biomasses (up to 35% O 2 and 40% H 2 O). • Replacements of coal by torrefied biomasses improve fuel conversion and reduce NO. • Torrefied pine wood shows better behaviour than torrefied agro-biomass. • Best results are detected in most cases when 25% CO 2 is replaced by H 2 O. • The extent of NO reduction caused by H 2 O significantly depends on the fuel rank. [ABSTRACT FROM AUTHOR]

Abstract A synergistic scheme of co-gasification of wet sewage sludge and torrefied biomass was proposed in order to get the hydrogen-rich syngas, which could avoid the dual energy input for drying of wet sewage sludge and steam generation. Co-gasification behavior of wet sewage sludge and torrefied biomass was evaluated by using a general non-stoichiometric thermodynamic equilibrium model developed based upon the Gibbs free energy minimization. The tenary plot of C H O system was used to evaluate the theoretical carbon formation performance at thermodynamic equilibrium state. The effects of mixing ratio and torrefaction severity on carbon conversion ratio, compositions of dry syngas, and H 2 yield were also addressed. High mixing ratio of wet sewage sludge and high gasification temperature were required for the high carbon conversion ratio. The gasification temperature of 1100 K was a favorable level for the H 2 yield and energy input. The optimal mixing ratio range of wet sewage sludge for low and middle temperatures torrefied biomass samples was between 30% and 40%, while that for high temperature ones was approximately 55%. This work could provide a feasible technical route and basic data for the resource and energy utilization of sewage sludge and biomass. Highlights • Co-gasification of wet sewage sludge and torrefied biomass was proposed. • A thermodynamic equilibrium model for co-gasification process was established. • Effect of torrefaction severity on co-gasification behavior was identified. • Mixing ratio of wet sewage sludge was between 30 and 55% for high hydrogen yield. • 1100 K was determined as a suitable temperature for high hydrogen yield. [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]

Torrefaction improves energy density, grindability, and hydrophobicity of raw biomass for gasification and combustion. While literature focuses on single biomass torrefaction, industrial production is likely to be from biomass mixtures. To address this knowledge gap, we torrefied three raw biomasses (pistachio nutshells, feed corn stover, cherry pits) at 250 °C, as “pure” biomasses and in multiple component mixtures to understand if synergistic interactions during torrefaction impact oxidation behavior of resulting solid fuels. The combustion enthalpies of blended biomasses were well predicted by an additive function, whereby a blend's property was the mass-weighted average of each biomass' torrefied property. However, synergistic effects that enhanced devolatilization when biomasses were comingled during torrefaction led to systemically lower volatile matter contents and higher surface areas of resulting solid fuels. This synergistic behavior continues in terms of activation energy of oxidation of the torrefied samples. Co-torrefaction of biomass may lead to a solid fuel with predictable heat content, but synergistic effects lead to oxidation of blended streams at different rates and activation energies, with blends often having lower reactivities and higher activation energies than an “additive” prediction of pure fuel components. This is attributed to enhanced devolatilization among biomasses, leading to more condensed carbonaceous solids. [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 use of solid renewable fuels in domestic-scale boilers, DSB is especially common in places where the distribution of other renewable energy sources is strongly limited (mountain and foothill regions). High moisture content and limited ventilation have a destructive impact on wood pellets' stability. Torrefaction of biomass is recognized as a possible way to enhance the wood pellets' hardness under wet conditions. It was found that the maximal water uptake for torrefied biomass after its water immersion was only 18.7 wt%. In this work, the combustion performance and emission of main pollutants during the combustion of thermally–treated biomass are analyzed using two types of boilers: coal-fired 25 kW th (retort burner) and biomass-fired 10 kW th (pellets burner). The best results were obtained during the combustion of torrefied biomass in a 10 kW th DSB, i.e. emission of CO 218 g/GJ, SO 2 2.5 g/GJ, NO x 111 g/GJ, and particulates 10.5 g/GJ, boiler efficiency of 90.23%. The combustion of torrefied biomass met the requirement of a 5th-class boiler according to the PN-EN 303-5 standard. Thermally–treated biomass can be used as a substitute fuel in DSB. Nevertheless, the boiler construction can be improved to obtain lower emissions of CO. • Combustion of thermally-treated biomass in commercial-scale domestic boilers. • Combustion tests were carried out in 25 kWth (coal) and 10 kWth (biomass) boilers. • Coal and biomass can be substituted by thermally-treated biomass in domestic boilers. • The maximal water uptake of torrefied biomass (water immersion test) was only 18.7 wt%. • Torrefied biomass presented higher durability and hydrophobicity. [ABSTRACT FROM AUTHOR]

The effects of adding ash-free coal (AFC) as a binder on the physical and chemical properties of coke were investigated to understand the mechanism of coke strength increase and to measure CO conversion reactivity. Two AFC samples (AFC_P and AFC_E) were first extracted from Indonesian low-rank coal. Torrefied biomass was also produced from woody biomass for use as an additive to AFC samples. Coke samples were then prepared by adding 3% AFC and 3% AFC + torrefied fuel. The coke strength was investigated by performing indirect tensile tests and 13 C NMR analyses. Coke reactivity was examined using thermogravimetric analysis and a coke reactivity test apparatus. The use of AFC as a binder increased the tensile strength of coke between 39% and 48%. Specifically, coke tensile strength was 2.32 MPa with AFC_P and 2.16 MPa with AFC_P + torrefied fuel; and 2.17 MPa with AFC_E and 2.10 MPa with AFC_E + torrefied fuel. The reactivity of the coke containing AFC + torrefied fuel was higher than that of the coke containing AFC alone. The coke produced with AFC_E + torrefied fuel had the highest reaction rate and average CO emission of 257,543 ppm. [ABSTRACT FROM AUTHOR]

This study examined the torrefaction performance of Jatropha-seed residue after mechanical screw-press extraction of oil (denoted as JME) at fixed torrefaction temperature (T r ) of 533, 553 and 573 K in the torrefaction time (t r ) range of 10–60 min. The characteristics results of torrefied JME (JME T ) indicated that the mass yield decreases while dry-basis high heating value (H HD ) increases with increasing T r and t r . At t r = 20 min or longer and T r of 533–573 K, the H HD of obtained JME T is suitable for B1/B2/D Taiwan power industry fuel requirement. In addition, the H/C and O/C atomic ratios of JME T are better (i.e., lower) than those of torrefied wood and close to those of lignite and sub-bituminous coal. The satisfactory energy densification (E D ) of about 1.3 can be achieved for Case 1 at higher T r of 573 K and shorter t r of 30 min with log severity factor (logSF) of 7.37 or Case 2 at lower T r of 553 K and longer t r of 50 min with logSF of 7.00. The results indicated that Case 2 exhibits a lower value of SF than Case 1 at the same level of satisfactory E D , which is more beneficial for the torrefaction of JME. [ABSTRACT FROM AUTHOR]

Chemical looping combustion (CLC) is an emerging CO 2 capture technology utilizing two interconnected circulating fluidized beds (CFB). An oxygen carrier is oxidized in the air reactor and reduced in the fuel reactor. In comparison to a classic oxyfuel process, no air separation unit is required to provide the oxygen needed to burn the fuel. The solid fuel, such as coal or biomass, is gasified in the fuel reactor, and the products from gasification are oxidized by the oxygen carrier. This work presents results of 110 h autothermal and partial autothermal CLC operation with ilmenite and iron ore as oxygen carriers. Hard coal and a fuel blend of hard coal and torrefied biomass were used as fuels. The results show that the oxygen demand of the fuel reactor required for a complete conversion of unconverted gases was in the range of 27%. At the same time, the carbon capture efficiency was low in the present configuration of the 1 MW th pilot. This means that unconverted char left the fuel reactor and burned in the air reactor. The reason for this is that no carbon stripper unit was used during these investigations. Some possible modifications like an oxygen carrier with oxygen uncoupling, a lower fuel feeding point or a secondary fluidization of the fuel reactor could significantly enhance the carbon capture efficiency. [ABSTRACT FROM AUTHOR]

Recently, there has been growing interest in co-liquefaction of coal with biomass because biomass has potential to substitute as a cheap hydrogen-donor and enhance liquid yields during direct coal liquefaction. In addition, inclusion of biomass can reduce greenhouse gas emission compared to solely coal-based processes. This paper presents characterization of coal, biomass, torrefied biomass and mixtures of coal with biomass and torrefied biomass to be used for direct liquefaction for the production of liquid fuels. Samples of yellow-poplar (YP) and red maple (RM) biomass collected from Appalachian logging residue and West Virginia Kingwood bituminous coal (C) were used in this study. The red maple and yellow-poplar samples were torrefied at 300 °C to produce torrefied red maple (TRM) and torrefied yellow-poplar (TYP), respectively. The untorrefied and torrefied samples were mixed with coal in a 1:1 ratio (by weight) creating coal-biomass and coal-torrefied biomass mixtures to be used as feed for co-liquefaction. In addition, untreated yellow-poplar and coal samples were tested as controls. All samples and mixtures were characterized for calorific value and underwent proximate, ultimate, and thermo-gravimetric analyses. The volatiles produced during thermo-gravimetric analysis were tested for chemical functional groups present in the products. [ABSTRACT FROM AUTHOR]

Elevated emissions of hydrogen chloride (HCl) from combustion of biomass in utility boilers is a major issue as it can cause corrosion and, in combination with the high alkali content often encountered in these fuels, it can also deposit molten alkali chloride salts on the boiler’s water tubes. Such deposition can impede heat transfer and cause further corrosion. This work torrefied and then burned herbaceous biomass (corn straw) as well as crop-derived biomass (olive residue and corn-based Distillers Dried Grains with Solubles, DDGS), all pulverized in the size range of 75–150 µm. It monitored the HCl emissions from torrefaction of biomass and, subsequently, the comparative HCl emissions from combustion of both raw and torrefied biomass. Results showed that during torrefaction most of the chlorine of biomass was released in the gas phase, predominately as HCl. Consequentially, combustion of torrefied biomass, which contained less chlorine than raw biomass, generated significantly lower HCl emissions than raw biomass, particularly so for biomass of low alkali content. This observation complements previous findings in this laboratory that torrefied biomass also generated lower SO 2 emissions than raw biomass, albeit by a smaller factor. Both of these findings enhance the appeal of torrefied biomass as a substitute fuel in utility boilers. [ABSTRACT FROM AUTHOR]

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]

Flash pyrolysis gas yields from bituminous coal and torrefied biomass have been investigated in the temperature range between 873 and 1273 K for 22 different gas species simultaneously. Recording a larger number of species gives a more detailed insight into pyrolysis of solid fuels than it is provided by other studies in literature, where typically smaller numbers of species are tracked. As processes utilizing biomass are designed for lower process temperatures, literature data for biomass pyrolysis are scarce in the temperature range between 1023 and 1273 K. This work, aiming at investigating potential fuels for pulverized solid fuel combustion, approximates pyrolysis conditions in the ignition zone of actual power plant boilers, where possible. Thus, based on results of a literature review, an experiment was designed using a small-scale fluidized bed reactor (FBR) to simultaneously analyze the pyrolysis gas yields for 22 species and to close the temperature gap found for biomass. Small batches of pulverized torrefied biomass from poplar wood and pulverized Colombian bituminous coal (Mina Norte) were rapidly pyrolyzed in the reactor. The two fuels were chosen as exemplary conventional and alternative energy sources for pulverized fuel fired power plants. Experiments have been carried out under atmospheric pressure in pure nitrogen atmosphere. Product gas analysis was carried out by Fourier transform infrared spectroscopy (FTIR) including two different sampling techniques. As a novelty, offline measurements have been used exclusively to improve the gas species selection procedure and reliability of detection. In case of offline measurements, the gas flow to the FTIR gas cell is stopped and the gas is enclosed in the cell allowing longer scan times of the captured gas mixture and thereby enlarging the signal-to-noise ratio (SNR). In succession, regular measurements with continuous flow (online) were performed for the simultaneous quantitative analysis of total pyrolysis yields for 22 selected gas species. Obtained pyrolysis yields show good agreement with available literature data. The larger number of investigated species provides an extended data set also covering minor pyrolysis species, for which quantitative data are scarce. Additionally, trends in the gas yields for biomass agree well with those found by other authors outside the mentioned temperature gap between 1023 and 1273 K. [ABSTRACT FROM AUTHOR]

This work contrasted gaseous emissions of carbon, sulfur and nitrogen oxides from combustion of several types of biomass including woody, herbaceous and crop-derived wastes, pulverized in the size range of 75–150 μm. Both raw and torrefied biomass were exposed to high heating rates (10 4 –10 5 K/s) in a laboratory-scale electrically-heated drop-tube furnace, operated at 1400 K. Combustion occurred under fuel-lean conditions. Torrefied biomass has lower volatile matter content, higher fixed carbon content and higher heating value than raw biomass. Results revealed that (a) CO 2 emission factors from torrefied biomass were higher than those from raw biomass, reflecting the higher carbon content of the former, however there was no uniform trend in emission factors (kg/GJ); (b) SO 2 emission factors of torrefied biomass were lower than those from raw biomass, even if some torrefied biomass types contained higher sulfur mass fractions than their raw biomass precursors. All raw and torrefied biomass, with one exemption, generated lower SO 2 emission factors than a typical sub-bituminous coal; (c) torrefied biomass has higher fuel-nitrogen mass fractions than their raw biomass precursors; however, there was no clear trend in NO x emission factors between raw and torrefied biomass, as torrefied herbaceous and woody biomass types generated higher while torrefied crop biomass types generated lower emission factors than their raw biomass precursors. Comparing with the sub-bituminous coal, some raw and torrefied biomass types generated lower and some higher NO x emission factors. Overall, combustion of most types of biomass, either in raw or torrefied state, can result in lower SO 2 and NO x emissions factors than those of typical western US sub-bituminous coals while, in principle, generating minimal net emissions of carbon. [ABSTRACT FROM AUTHOR]

The adverse nature of biomass requires specific pretreatment processes to better utilize it in bioenergy applications, and torrefaction is one of the most recognized thermal pretreatment methods. In this regard, we studied the effect of torrefaction pretreatment on kinetics, reaction mechanism and heat flow during the pyrolysis of biomass by making a comparative analysis between the pyrolysis of dried and torrefied Eucalyptus wood. Torrefied biomass was produced at three temperatures, namely 250, 275 and 300 °C. Pyrolysis was performed at 700 °C. The char yield during pyrolysis increased from 22.39 percent to 36.34 percent when the torrefaction temperature was increased from 250 to 300 °C. Kinetic analysis showed that torrefied biomass has higher activation energy values than dried biomass. The reported activation energy values for dried biomass were within the range of 165–185 kJ/mol, and for the biomass torrefied at 300 °C they were within the range of 180–245 kJ/mol. We used two different approaches, namely master plots and kinetic compensation parameters, to identify the reaction mechanism. The results showed that torrefaction treatment had an effect on the reaction mechanism of the biomass pyrolysis. The reason could be the degradation of hemicellulose during torrefaction, and thereby the formation of smaller molecules during the pyrolysis of torrefied biomass. The heat flow data from differential scanning calorimetry (DSC) showed that pyrolysis started with exothermic reactions for dried samples, and endothermic reactions for torrefied samples. The results presented provide valuable insights into increasing the understanding of the pyrolysis of torrefied biomass. [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]

This study developed a clean hybrid power plant using a combination of integrated torrefied biomass co-gasification (TBCG), solid oxide fuel cell (SOFC), and calcium looping (CaL) CO 2 capture. Based on pre-SOFC (Design I) and post-SOFC (Design II) configurations, thermodynamic analysis is adopted to examine the performance of hybrid power generation plants. The carbon boundary points (CBPs) for different torrefied biomass blending ratios (TBBRs) are found using specific optimization algorithms to maximize the syngas yield. From the viewpoint of energy utilization, the simulation results show that Design I is superior to Design II. However, the CO 2 emissions of Design II are lower than those of Design I by 94.19%, although it has an accompanying energy penalty of 4.17%. Due to its use of the internal heat recovery approach, the energy penalty of Design II falls to 1.09%. As a whole, Design II with the heat integration design is recommended for use in hybrid power plants. [ABSTRACT FROM AUTHOR]

The objective of this experimental study consists in investigating the effects of torrefaction treatment on two different woody biomass chosen from softwood as spruce pine and annual grass lignocellulosic hardwood as reed . This thermal pre-treatment has been conducted in a small batch reactor directly fluxed by a controlled nitrogen flow. Tests have been carried out at different temperatures, ranging from 250 °C to 310 °C, and reaction time from few minutes to 1 h. Properties involved in this investigation are ultimate analysis, thermal quantities among which caloric value (HHV), fibers distribution and equilibrium moisture content. The obtained results confirm that torrefaction is a viable thermal pre-treatment to upgrade biomass and looks promising for a new generation of biomass derived fuel. As main topic, this research focuses on evaluating the role of the Mass Yield (MY) as synthetic parameter of the process. In particular it is made evidence that the properties of the torrefied samples can be led back to the MY without making reference to their thermal-time pathway. As example, considering two samples presenting the same MY of 80%, the former torrefied at 280 °C for 76 min, the second at 310 °C for 17 min, it is verified that the values of the aforementioned properties are very similar for both the samples even if submitted to different thermal pathways. The potentiality of the MY has been enhanced by extending this investigation to additional species of biomass pertaining to two groups, woody biomass and non-woody biomass. Inside the conditions ranges of the proposed experimental tests and for each of the indicated biomass type, an accurate linear correlation is obtained between MY and Energy Yield (EY) with a determination coefficient of ( R 2 ) 0.98 and 0.97 for woody and non-woody biomass respectively. Besides confirming the benefit of the torrefaction in enhancing the quality of the treated biomass, the use of the MY as synthetic parameter can be exploited to improve the torrefaction modeling schemes and to optimize the selection of the process working conditions. The proposed approach can therefore be useful to examine the relevant amount experimental data till now produced on this issue in view of exploiting and orienting their use towards real scale plant design. [ABSTRACT FROM AUTHOR]

Torrefaction process is a promising technology for changing the chemical and physical properties of biomass so, that it can be used in existing pulverized fuel firing systems. A numerical 3-D simulation to study the combustion behaviour of torrefied biomass in a pulverized-fired furnace has been carried out. In the model different reaction kinetics for devolatilization and char oxidation of three biomass components, namely hemicellulose, cellulose and lignin, have been applied. The reaction kinetic parameters for pyrolysis and char oxidation were determined by experimental work using thermogravimetric analysis (TGA). In numerical studies three different fuel blends were examined, which include pure coal, ∼9% and ∼17% (thermal basis) torrefied sawdust in coal. Gas concentrations, temperature distribution, pyrolysis and char reactions were analyzed along the 1 MW th combustion chamber. The numerical investigation suggests that the torrefied biomass can be used as a substitute fuel for coal without modifications in the co-firing system. However, the case-study with the highest biomass substitute leads to an incomplete decomposition of the lignin component, due to coarser biomass particles and decreased char reaction rates. [ABSTRACT FROM AUTHOR]

• An experimental design was used to investigate the effects of different torrefaction conditions on the properties of biomass. • Two spectrometers were simultaneously used to capture high SNR signals of continuous spectrum and characteristic spectrum. • In-situ detection of the temperature and K release concentration of torrefied biomass pellet combustion was achieved. • Changes in combustion characteristics and K release characteristics of torrefied biomass were evaluated. The orthogonal experiment designed in this paper investigated the effect of changes in experimental parameters such as biomass species, torrefaction temperature, torrefaction time, torrefaction oxygen concentration on the physicochemical properties and combustion characteristics of the torrefaction products. Two optical fiber spectrometers were used to capture the spontaneous emission spectra of the combustion flame of compressed pellets of torrefied biomass, and the in-situ measurement of pellet combustion temperature and K release concentration at high heating rate was realized by multi-spectral analysis algorithm. The experimental results indicate that for biomass, torrefaction will lead to a decrease of volatile and moisture content and an increase of fixed carbon and ash content in components, a decrease of O and H and an increase of C content in elements, a certain loss of biomass quality, an increase of high heat value, and each indicator move closer to coal. The effects of various experimental parameters on the volatile content, mass yield, high heat value increase rate and energy yield in biomass torrefaction products have similar laws, i.e., biomass species / torrefaction oxygen concentration > torrefaction temperature > torrefaction time. The mild torrefaction product pellets have a shorter ignition delay, increased volatile combustion flame height and peak temperature, longer volatile and char combustion duration, but lower peak char combustion temperature, among which the selected torrefaction products of rice straw and pine wood showed an increase in peak temperature of 0.56 % (11 K) and 0.61 % (12 K) for the volatile stage respectively, and a decrease of and 1.29 % (20 K) and 1.29 % (21 K) for the char stage respectively. In addition, the peak K release concentration during combustion of the mild torrefaction product pellets was reduced, among which the peak K release concentrations during the volatile and char stage were reduced by 43.22 % (3.89 ppm) and 52.93 % (51.55 ppm) of the rice straw torrefaction product respectively, and by 73.14 % (1.28 ppm) and 62.08 % (15.01 ppm) for the pine wood torrefaction product respectively. Biomass torrefaction products have fuel properties closer to coal, less K released from the combustion process, which have the potential to become an alternative to coal. [ABSTRACT FROM AUTHOR]

In order to explore the oxidation and reduction properties of the LaFe 0.5 M 0.5 O 3 (M = Mn, Co, Ni, Cu) perovskites, torrefied biomass (TB) gasification and CO 2 splitting were coupled as a whole chemical looping reaction, while the doped LaFe 0.5 M 0.5 O 3 were prepared and employed as oxygen carriers(OCs) in the chemical looping. An proper torrefaction temperature was screened first for producing more syngas, then the effect of doped perovskites on the chemical looping reaction were evaluated via thermogravimetric analyzer and fixed-bed reactor in terms of the syngas yield and CO formation rate. The results showed that the doped perovskites exhibited higher activity in the gasification process, which promoted the conversion of TB and improved the yield of H 2 and CO. Specifically, the CO yield of LaFe 0.5 Co 0.5 O 3 and the H 2 yield of LaFe 0.5 Ni 0.5 O 3 was improved by about 4 times and 1.3 times respectively compared with original LaFeO 3. Moreover, LaFe 0.5 Ni 0.5 O 3 exhibited better performance in both TB gasification and the CO 2 splitting reaction, and the yield of H 2 and CO reached 3.71 mmol·g−1 and 1.80 mmol·g−1, respectively. Furthermore, the composition and surface topography evolution of doped perovskite were analyzed via TEM, SEM and XRD, and the results of XPS, EPR and TGA were combined to reveal the reaction mechanism. In the gasification stage, the half doped perovskite converts biomass sample into syngas. In the CO 2 reduction stage, CO 2 is adsorbed and activated by oxygen vacancies and basic sites, and it reacts with the carbon and reduced perovskite to produce CO. [Display omitted] • Mn, Co, Ni and Cu were doped into LaFeO 3 to enhance the redox properties. • LaFe 0.5 Ni 0.5 O 3 showed good oxygen migration property in the coupled chemical looping. • Doped perovskites exhibited both catalyst and oxygen carrier properties in reactions. • Doping metals enhanced perovskites' adsorption and activation of CO 2. • Torrefaction biomass showed higher syngas yield in the chemical looping gasification. [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]

Highlights: [•] Biomasses were devolatilized at high temperatures and high heating rates. [•] Biomass decreases its reactivity after torrefaction. [•] The kinetic parameters of torrefied biomasses were determined. [•] CO and H2 are main released volatiles during devolatilization of torrefied biomass. [ABSTRACT FROM AUTHOR]

• A new integrated CFBG/ Steam Turbine / PEM fuel cell model for torrefied biomass. • The effect of gasifier operating parameters and torrefied biomass properties on PEM fuel cell. • Energy and exergy analysis for the CFBG/ Steam Turbine / PEM fuel cell combine system. • An artificial intelligence approach for the CFBG/ Steam Turbine / PEM fuel cell combine system. In this study, the Aspen Plus simulator was used to develop a circulating fluidized bed (CFB) gasifier/steam turbine/proton-exchange membrane (PEM) fuel cell integrated system. Since integrated systems comprise many thermochemical, biochemical, and physical processes, equipment, chemicals, etc., determining output parameters is challenging and important. In this context, twenty torrefied biomass samples were parametrically analyzed for syngas properties and H 2 production rates. So, using solid fuel characteristics and gasifier operating parameters, a data set including PEM fuel cell module outputs was created. Thereafter, the created data set was utilized to train the artificial neural network (ANN) model. This paper, as far as we know, examines the impacts of different torrefied biomass samples on PEM fuel cell outputs for a sophisticated integrated system dependent on gasification conditions, and provides a more generalized and rapid prediction model for the integrated system with complicated equations. Additionally, parametric studies assist in determining the proposed new integrated system's minimal operating condition, which is highly dependent on the fuel characteristic. High steam/fuel ratio, high carbonization degree, and low pressure lowered PEM efficiency while increasing power and voltage outputs. The ANN model also accurately forecasts PEM fuel cell output parameters (R2 greater than 0.99 and MAPE less than 1%) based on torrefied biomass proximate analysis data and gasification process operating parameters. As a consequence, a CFB gasifier/steam turbine/PEM fuel cell system, which contains diverse modules and thermochemical processes, can be examined using ANN models trained on a large and high-quality dataset. [ABSTRACT FROM AUTHOR]

Highlights: [•] Peak mass loss rate linearly proportional to torrefied biomass present in blend. [•] Activation energy to start decomposition decreases as torrefied biomass increases. [•] Combustion enthalpies linearly related to percent torrefied biomass present. [•] Percent torrefied biomass has no noticeable impact on extent of char oxidation. [ABSTRACT FROM AUTHOR]

Abstract: Microwave pyrolysis of torrefied Douglas fir sawdust pellet was investigated to determine the effects of torrefaction on the biofuel production. Compared to the pyrolysis of raw biomass, the increased concentrations of phenols and sugars and reduced concentrations of guaiacols and furans were obtained from pyrolysis of torrefied biomass, indicating that torrefaction as a pretreatment favored the phenols and sugars production. Additionally, about 3.21–7.50area% hydrocarbons and the reduced concentration of organic acids were obtained from pyrolysis of torrefied biomass. Torrefaction also altered the compositions of syngas by reducing CO2 and increasing H2 and CH4. The syngas was rich in H2, CH4, and CO implying that the syngas quality was significantly improved by torrefaction process. [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]

Abstract: Microwave torrefaction of rice straw and pennisetum was researched in this article. Higher microwave power levels contributed to higher heating rate and reaction temperature, and thus produced the torrefied biomass with higher heating value and lower H/C and O/C ratios. Kinetic parameters were determined with good coefficients of determination, so the microwave torrefaction of biomass might be very close to first-order reaction. Only 150W microwave power levels and 10min processing time were needed to meet about 70% mass yield and 80% energy yield for torrefied biomass. The energy density of torrefied biomass was about 14% higher than that of raw biomass. The byproducts (liquid and gas) possessed about 30% mass and 20% energy of raw biomass, and they can be seen as energy sources for heat or electricity. Microwave torrefaction of biomass could be a competitive technology to employ the least energy and to retain the most bioenergy. [Copyright &y& Elsevier]

The combustion of torrefied biomass under oxy-fuel conditions is a promising technological alternative, which has the potential to transform electric and heat generation systems into more sustainable and carbon-neutral forms. This combustion approach combines two complex processes, oxy-fuel and biomass combustion, which still require significant understanding. For this, an experimental study has been conducted considering a series of 40 kW th aerodynamically stabilized pulverized torrefied biomass and coal flames. Given the increasing interest and advantages of substituting coal by biomass in different thermal industrial processes, a set of four experimental conditions was studied and compared. Two torrefied biomass flames, under conventional and oxy-fuel combustion atmospheres, are compared to two similar coal (lignite) operating conditions. The combustion behavior of the flames is assessed by conducting detailed measurements of flow fields, gas compositions, and radiative heat fluxes. Experiments are performed employing a combustion chamber with a simplified configuration. Combined results from the different measurements show that the overall combustion characteristics of torrefied biomass under the two atmospheres are fairly similar. Also, they do not significantly differ from the combustion characteristics observed for the coal flames. Comparatively, the radiative heat fluxes produced by the torrefied biomass flames were higher than those produced by coal. In addition, oxy-fuel flames produced 15–20% lower radiative heat fluxes than the air counterparts. Gas concentration measurements near the flames showed diverse results attributed to small differences in the turbulent flow fields and fuel composition. The presented analysis of results can also contribute to the retrofitting of conventional pulverized coal firing systems for operation under oxy-fuel conditions with torrefied biomass. • An experimental comparison of torrefied biomass and lignite flames was made. • Detailed flow field, gas composition, and radiative flux measurements are presented. • Radiative heat flux profiles between coal and torrefied biomass flames are similar. • Torrefied biomass produced higher radiative heat fluxes than lignite. • Smaller inner recirculation zone and lower turbulence observed in oxy-fuel cases. [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]

The influence of two different biomass pre-treatment methods (torrefaction and combined treatment of washing and torrefaction) on the formation of NO and its precursors, NH 3 and HCN, during combustion has been studied. Experiments were conducted in an electrically heated single particle reactor under well-controlled conditions in N 2 and O 2 /N 2 at 850 °C. NO concentrations of the product gases were measured during devolatilization and char oxidation, and the total amounts of released NH 3 and HCN were determined during devolatilization. The results show that the conversion of vol-N and char-N to NO changed due to the pre-treatments, influencing the NO emission factor (released NO/energy content) of the fuel. For torrefied straw, the NO emission factor was significantly higher than for raw straw. The change in NO formation can partly be explained by how the nitrogen contents change due to the pre-treatments: both for bark and straw, around 20% of the initial fuel-N was removed during the torrefaction; for straw, 50% of the initial fuel-N was removed during the combined torrefaction and washing. In addition, the changes in the NO formation can be explained by the release of NH 3 and HCN during devolatilization. The HCN/NH 3 ratio increased with increasing N content and decreasing H/N ratio due to the pre-treatments. The conversion of vol-N to NH 3 increased with increasing Ca content and decreasing K content. In general, the devolatilization of the pre-treated biomass samples resulted in a higher conversion of vol-N to NH 3 and HCN as compared to the raw biomasses. [ABSTRACT FROM AUTHOR]

Pyrolysis of torrefied Acacia nilotica was investigated in a tubular fixed-bed reactor under nitrogen environment. The process was optimized using response surface methodology coupled with central composite design, in order to obtain the maximum yield of pyrolysis oil. The maximum yield of pyrolysis oil (33.59 wt %) was obtained at 507.04 °C , retention time of 58.25 min, heating rate of 38.00 °C /min, and sweeping gas flow rate of 40.52 mL/min. Analysis of variance confirmed that pyrolysis of torrefied biomass for maximum pyrolysis oil yield highly depended on temperature followed by heating rate, retention time, and sweeping gas flow rate, respectively. Pyrolysis of raw biomass was also carried out at the optimum condition for comparing the quality of both pyrolysis oils. The pyrolysis oil samples were subjected to FTIR, GC-MS, and 13C NMR analyses along with estimation of water content, pH, viscosity, HHV, etc., for comparing the physicochemical characteristics. Results showed that total aromatic carbon, carbonyl carbon, and primary alkyl carbon of pyrolysis oil from torrefied biomass increased by 40.28, 51.36, and 6.34%, respectively, as compared to pyrolysis oil from raw biomass. The phenol derivative compounds are increased by 18.91%. The HHV and pH of pyrolysis oil from torrefied biomass increased by 23.53, 42.15%, respectively, while water content decreased by 34.37% as compared to pyrolysis oil from raw biomass. Thus, with rapid advancement in pyrolysis process, the integrated approach of torrefaction-pyrolysis process may be beneficial to produce cleaner pyrolysis oil as compare to raw biomass. Image 1 • Process variables for pyrolysis of torrefied biomass were optimized using RSM. • Torrefaction as pretreatment before pyrolysis can improve quality of pyrolysis oil. • Temperature had most significant effect on yield of pyrolysis oil. • Sweeping gas flow rate had least significant effect on yield of pyrolysis oil. • Cross-linking and devolatilization of biomass causes lower pyrolysis oil yield. [ABSTRACT FROM AUTHOR]

• Plasma gasification performances of various raw and torrefied biomass are evaluated. • The developed plasma gasifier is reliable to predict gasification behavior. • Syngas yield, LHV of the product gas, PSR, and PGE can be improved by torrefaction. • Torrefied grape marc and macroalgae reduce the release of sulfur impurities under steam and CO 2 environments. • Highest plasma gasification efficiency is achieved with CO 2 as the gasifying agent. Plasma gasification of raw and torrefied woody, non-woody, and algal biomass using three different gasifying agents (air, steam, and CO 2) is conducted through a thermodynamic analysis. The impacts of feedstock and reaction atmosphere on various performance indices such as syngas yield, pollutant emissions, plasma energy to syngas production ratio (PSR), and plasma gasification efficiency (PGE) are studied. Results show that CO 2 plasma gasification gives the lowest PSR, thereby leading to the highest PGE among the three reaction atmospheres. Torrefied biomass displays increased syngas yield and PGE, but is more likely to have a negative environmental impact of N/S pollutants in comparison with raw one, especially for rice straw. However, the exception is for torrefied grape marc and macroalgae which produce lower amounts of S-species under steam and CO 2 atmospheres. Overall, torrefied pine wood has the best performance for producing high quality syngas containing low impurities among the investigated feedstocks. [ABSTRACT FROM AUTHOR]

Biomass-based fuel is a potential renewable energy source despite its low energy density, high moisture content, and complex ash components due to its carbon-neutral nature. Torrefaction process, a promising biomass pretreatment method for upgrading biomass properties, is effective to generate fuel with higher calorific value and energy density. Torrefied biomass performs higher energy density and improved grindability characteristics as well as lower ratios of O/C and H/C compared to its raw source. This study presents an evaluation of the hydrogen production from steam gasification using torrefied woodchips as a feedstock in a pilot-scale bubbling fluidized bed reactor. The feedstock used is torrefied woodchips, which were treated at 250 °C in the N 2 atmosphere. The experiments were conducted under isothermal and negative gauge pressure conditions in a pilot-scale bubbling fluidized bed reactor at different operating conditions such as gasification temperatures, steam-to-biomass ratio (SBR), and equivalence ratio (ER). Experimental results show that the high temperature and SBR are more favorable for hydrogen production and improve carbon conversion efficiency, while higher ER lowered content and yield of hydrogen. The optimal value of the steam-to-biomass ratio at 850 °C is 1.2 with the hydrogen content of 48.41% and the hydrogen yield of 0.039 Nm3/h. • Steam gasification experiments carried out for torrefied woodchips using bubbling bed reactor. • Higher gasification temperatures result in hydrogen-enriched product gas. • The content and yield of H 2 in the product gas are proportional to steam-to-biomass ratio. • The equivalence ratio considerably affects the composition of the product gas. [ABSTRACT FROM AUTHOR]

Empty fruit bunches (EFBs) in the current bulky form are low in energy density and highly moist making them an unattractive option as a solid fuel for producing steam and electricity in palm oil mill biomass boilers. Pre-treatment of EFBs using torrefaction is required in order to improve its energy density via reduction of moisture and oxygen contents, which eventually will lead to an increased high heating value (HHV). In this study, the experiments were conducted in a fixed bed reactor at different feedstock moisture contents (10–67 wt%), residence times (30 and 60 min), and a torrefaction temperature of 270 °C. The distribution of torrefaction products, structural and fuel properties of the torrefied EFBs were investigated with multiple techniques. The results showed that the decrease in the moisture content of feedstock led to a significant increase in the yield of torrefied EFBs. The decrease in moisture content also resulted in increased energy yield and HHV of torrefied EFBs from 52.2% to 99.3% and 18.2–19.2 MJ/kg, respectively. The obtained results were then fitted to a power model to estimate the mass and energy yields of torrefied EFBs at different moisture contents and residence times by using the least squares method. Empirical equations generated by the developed model were accurate and can obtain a satisfactory fit to the experimental data, with the coefficient of determination values higher than 0.96. The calculated energy and carbon stored from the torrefied EFBs offer additional income, clean power, and less pollution in palm oil milling. • The effect of the moisture content of EFBs on products and fuel properties was investigated. • A power model was developed to estimate mass and energy yields. • Estimation was easy because it requires only moisture content data as input. • The produced torrefied EFBs can be used as fuel in palm oil mill boilers. • This option could provide extra power to palm oil millers up to 41,782 kW per day. [ABSTRACT FROM AUTHOR]

Biomass (pellets, briquettes, logs) are a key contributor to many countries' strategies for decarbonising heat, particularly in domestic applications. The emissions from these small devices can be high and severely impact air quality, but their levels depend on the design, control, abatement and fuel options. This paper is concerned with the last case. A comparative study shows the emissions from a domestic wood stove for three biomass fuels and their torrefied counterparts. The fuels were burned in a multi-fuel stove along with two reload batches creating continuous combustion cycles: the initial cold start data is presented but not included in averaging and calculation of emission factors. Measurements were made using an FTIR instrument for carbon and nitrogen based gaseous emissions, particulates were measured using a smoke meter with micro-quartz filters as well as a size-selective impactor to obtain the particle size distribution. Particulate emissions were significantly reduced from the torrefied fuels and this is thought to be related to their pyrolysis fingerprint, which was investigated by pyrolysis-GC–MS. NOx was slightly reduced, despite increased fuel-N after torrefaction. In addition, the reduced moisture in the torrefied fuels decreases emissions of CO and CH 4 because of increased time of flaming combustion. • Compares emissions from combustion of raw and torrefied fuels in a domestic multi-fuel stove • Torrefied fuels emit significantly less particulate matter, and slightly less NOx/GJ energy. • CO and CH 4 emissions are reduced for the torrefied fuels. • Changes in pyrolysis products by PY-GC–MS can explain changes in particulate emission. [ABSTRACT FROM AUTHOR]