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• The optimum pelletization conditions for pine sawdust were determined by RSM. • The best pellet quality was obtained with biomass moisture content of 16.6% at 80 °C. • Industrial quality pellets can be obtained from wood and residual biomass blends. • Contents of 30 wt% of almond shells and olive stones yield high quality pellets. Pellets for industrial use were produced from blends of pine sawdust (PIN) and alternative residual biomasses in a pilot-scale pelletizer. The effect of the pelletization temperature (T = 50–80 °C) and biomass moisture content (MC = 14–20%) on pine sawdust pellet quality was studied by using response surface methodology (RSM). Pelletization performance was evaluated on the basis of the durability, bulk density, moisture content, lower heating value (LHV), energy density, diameter, length and density of the pellets. From the RSM analysis, a maximum durability value of 99.4% was obtained at T = 80 °C and MC = 16.6%. Under these conditions, all the parameters showed values within the required range of industrial pellet qualities, i.e., a bulk density of 616 kg/m3, a pellet moisture content of 7.6%, a lower heating value (as received) of 18 MJ/kg, a diameter of 6.2 mm and a length of 23.4 mm. Blends of pine sawdust with eleven unconventional biomass samples were then pelletized under the optimum conditions to obtain pellets for industrial use according to the categories of quality defined by ISO 17225-2. Blends of pine sawdust with almond shells (AS) and olive stones (OS) contents of up to 30 wt%, as well as with pine cone leafs (PCL) contents of up to 15 wt%, produced I1 pellets. Blends of pine sawdust with coffee dregs (CD), coffee husks (CH) and grape pomace (GP) proportions of up to 10 wt%, as well as with hazelnut shells (HS), miscanthus (MIS), pine kernel shells (PKS) and switchgrass (SG) contents of up to 15 wt%, and also with a PCL content of between 15 and 30 wt%, generated I3 class pellets. Classification was not possible for cocoa shells (CS) mixed with pine sawdust due to the low bulk density of the pellets. Energy consumption resulting from the pelletization of the blends was evaluated with values ranging from 0.09 to 0.33 kWh/kg, while the pelletization of pine sawdust required 0.18 kWh/kg. The addition of alternative biomass feedstocks to pine sawdust may therefore serve to reduce energy consumption in industrial pelletization. [ABSTRACT FROM AUTHOR]

• For most scenarios, densifying biomass does not improve the economics. • Densification is economically advantageous when there is a high feedstock competition. • The plant size of a densification facility has a minimal impact on the overall economics. Biomass such as switchgrass can be converted to renewable gasoline and diesel (RGD) fuels via integrated fast pyrolysis and hydrodeoxygenation. However, the low bulk density of biomass feedstocks produces relatively high transportation costs, driven by the large volumes needed to supply biorefineries. Densification can reduce transportation volumes, and therefore transportation costs for bioenergy production. However, the additional costs of biomass densification, along with decreases in overall mass and energy yields, influence the overall economic performance of RGD production. This study investigated the techno-economic impacts of pelletizing, torrefying, or pyrolyzing the biomass at distributed facilities prior to upgrading the intermediates to RGD at a centralized facility. Eight scenarios were considered. When there is no feedstock competition, biomass densification at the distributed facility was shown to reduce the transportation cost by 20%–50%. However, the capital and operating costs required for densifying biomass increased the total cost of RGD production by 3%–35% compared to RGD made from non-densified biomass. The cost of making RGD from densified biomass was only reduced below the cost of making RGD from non-densified biomass for the case when the fraction of land surrounding the biorefinery facility allocated to the biomass cultivation is less than 0.25. This finding is attributed to the high cost of transporting non-densified biomass from a larger procurement radius. Sensitivity analysis indicated that RGD fuel yield, densification costs, project investment, and the rate of return all have significant impacts on the overall economics of RGD production. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The hydrothermal carbonization of cotton stalk process was developed. • Effects of HTC temperature and reaction time on product characteristics were studied. • Hydrochar pellets had better relaxation density and compressive strength than cotton stalk pellets. • Isoconversional KAS and FWO methods were applied for determining combustion kinetic parameter. Abstract The characteristics of hydrochars of cotton stalk (CS) and hydrochar pellets were investigated in this paper to obtain high quality biomass fuel. The differences between the characteristics of hydrochars at different temperatures (180–300 °C) and reaction times (1–8 h) were analysed by mass yield, energy yield, proximate analysis, element analysis and higher heating value (HHV). The content of carbon and HHV of the hydrocars reached 51.18–73.94 wt% and 19.66–25.68 MJ/kg. FTIR and XPS indicated dehydration and condensation exist in HTC. SEM showed the generation of carbon microspheres. There was a higher energy consumption of hydrochars during pelletization, but the pellets formed from hydrochar had a higher relaxation density (1.06–1.21 g/cm3) and compressive strength (6.84–8.90 Mpa) than the CS pellets. The integrated combustion characteristics index (Sn) of 180-4 hydrochar pellets were better due to the higher (dm/dt) max value. The combustion kinetic parameters were determined by the Kissenger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods. The results showed that the change tendency of the Eα values was consistent, the average activation energy (Eα) was very similar, and the average correlation coefficient (R2) was higher than 0.9 in all samples. [ABSTRACT FROM AUTHOR]

Biomass shows characteristics that makes it a promising feedstock for complementing traditional fossil fuels as main energy source. It is somewhat limited by its generally poor physical properties, but these can be enhanced by densification processes like torrefaction and pelletization. The aim of the present work is to evaluate the influence of different solid biomass additives (almond shell, cocoa shell, grape pomace, Miscanthus , olive pomace and olive stone), and parameters such as temperature, moisture content and glycerol addition upon pine sawdust, PIN, and its torrefied counterpart, PINT, pelletization performance, paying special attention to their abrasion index, higher heating value and energy density. It was observed that the addition of small quantities of lignin-rich solid additives, like grape pomace, enhances the natural binding properties of both PIN and PINT during pelletization using a bench-scale device. It was also found that a 13% overall moisture content and a glycerol addition of between 10 and 20% improve the pelletization properties of PIN and PINT, respectively, and increase their energy density when compared to the raw samples. [ABSTRACT FROM AUTHOR]

Small-scale, distributed and low cost biomass power generation technologies are highly required in the modern society. The biomass pretreatment process, that is, a combination of carbonization and pelletization processes of cedar wood were explored in this study. For the carbonization process, a novel carbonizer composed of one carbonization chamber and one combustion chamber was tested, and the mass and energy balances during cedar wood carbonization at 400–500 °C were analyzed, respectively. During the initial heating stage, about 22 kg of wood with dry basis should be supplied into the combustion chamber through several batches. When the temperature in the carbonization chamber reached to the range of 200–220 °C, the combustion chamber could be self-heated by burning the pyrolysis gas (tar vapor, CH 4 , H 2 , CO) sent from the carbonization chamber. The specific wood consumption for producing 1 kg of wood char was within 3.6–4.4 kg, which presented an increase trend with increasing the carbonization temperature. Moreover, this carbonization system can deal with different kinds of biomass with various water contents and shapes. For the pelletization process, effects of adding amount of the binder (poval solution), water and the carbonization temperature on the pellet quality were studied so as to explore the optimal condition for making high quality pellets from the crushed wood char. The results indicated that there was an optimal ratio among char, added water, and the binder for making high quality pellets. Considering the energy transfer efficiency and pellet quality, the mass ratio of 0.93:0.32:0.10 for 450 °C-char in the dry basis: added water plus water in char: poval solution was the optimal condition for making high quality pellets. [ABSTRACT FROM AUTHOR]

This study was conducted to verify the potential application of carbohydrates with low molecular weight (MW) as ash-free as well as nitrogen- and sulfur-free binders in biomass densification for solid biofuels. In the first step, different kinds of carbohydrates including molasses (industrial byproduct), fructose, maltodextrin, sucrose, and glucose alongside lignosulfonate (phenolic byproduct from pulp and paper industry) were employed as binders in two sources of cellulosic biomass, namely spruce wood shavings and wheat straw. The results indicated that irrespective of the interaction of the factors, fructose and molasses worked as the best binders for spruce wood shavings and wheat straw biomass, respectively. In the second stage where interaction of the two selected binders with lubricants were studied, results showed that canola oil worked as the best lubricant for spruce wood shavings with the least negative effect on the impact resistance (durability) of the pelletized biomass. However, no lubricant resulted in a superior result with the least negative effect for wheat straw. Also, results in this stage indicated that pure glycerol, in contrast to crude glycerol, works as a binder rather than as a lubricant. In the third stage, the densification process at pilot-scale indicated that combination of molasses with crude glycerol worked as the best binder and lubricant for wheat straw biomass, while, a combination of fructose and canola oil worked as the best binder and lubricant for spruce wood shavings. In contrast to crude glycerol, pure glycerol proved to increase the friction in the pelletization unit and would not be an effective lubricant. [ABSTRACT FROM AUTHOR]

The pelletization of MgO-based sorbents is necessary before implementing intermediate temperature CO 2 capture for industrial applications. In the current work, MgO-based sorbent pellets were prepared using an extrusion–spheronization method, with the aim of achieving an effective granulation method for MgO sorbents. Another objective of this investigation is attempting to find out the differences between the sorbents in pelleted and powdered forms. The compression and friability tests have proved that the prepared pellets have outstanding mechanical properties, which are of significant importance for the fluidization in CFBC for the practical applications. N 2 adsorption-desorption results have shown obvious variations in the surface areas and pore size distributions of the sorbents before and after granulation. These variations further result in different carbonation/regeneration rates and cyclic CO 2 capture performance for the powdered and pelleted sorbents. All these differences in the physicochemical properties between the sorbents pellets and corresponding powders indicate that the results derived from the powdered sorbents in previous studies should be re-examined before the practical application for the realization of highly-efficient CO 2 capture. [ABSTRACT FROM AUTHOR]

Highlights: [•] CaO-based pellet sorbents were tested for 31 carbonation–calcination cycles. [•] Pellet surface characterization was investigated using BET/BJH, XRD, and SEM tests. [•] Pellet sorbents exhibit lower activity loss than natural limestone. [•] Binders decreased the negative effect of sintering. [•] The core/shell pellets had the highest stability among the sorbents. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ginkgo leaf residue (GLR) has the potential to produce carbon-rich solid fuel. • The heating value of hydrochar pellets improved by 18.8% and the durability increased by 38.1% at 220 °C. • Hydrochar pellets had superior hydrophobicity, enhanced pyrolysis and combustion performance. This study explored the potential of hydrothermal carbonization (HTC) for the production of a carbon-rich solid fuel from Ginkgo leaf residues (GLRs). Density, durability, hardness, hydrophobicity, and energy input estimates for HTC treated and untreated GLRs pellets were determined. Results showed that hydrothermal treatment significantly improved the physical properties of pellets made from GLRs, especially, at the temperature treatment of 220 °C. Pellet durability and hardness from samples treated at 220 °C (HT 220) increased from 70.1% and 0.8 N/mm2 to 96.8% and 2.1 N/mm2 when compared to those made from untreated GLR (control). Hydrochar pellets had higher fixed carbon contents, elevated heating values, and enhanced energy densification ratio in comparison to the control pellets. The equilibrium moisture content decreased from 13.9% to 4.8% for HT 220 pellets. The activation energy of HT 220 pellets decreased from 44.6 to 26.8 kJ/mol in the first order reaction model and from 93.9 to 61.2 kJ/mol in the 3D diffusion model compared to the control pellets. The comprehensive combustibility index S was enhanced twice for HT 220 pellets. The high durability, low moisture uptake, and improved pyrolysis property indicated that combining hydrothermal carbonization with pelletization is an efficient way for GLRs utilization as solid biofuel. [ABSTRACT FROM AUTHOR]

[Display omitted] • Canola residue pellets were gasified at 650–850 °C with an equivalence ratio of 0.2–0.4. • Highest syngas yields were obtained from gasification at optimal temperature (800 °C) and equivalence ratio (0.4). • Torrefaction and densification significantly improved the gas yields and quality. • Syngas from torrefied pellets had a greater lower heating value (1828–2396 kJ/Nm3). • Tar content from gasification reduced remarkably due to torrefaction of pellets. In this study, steam gasification of pellets prepared from canola residue was carried out at varying temperatures (650–850 °C) and equivalence ratio (0.2–0.4). The optimal gasification temperature and equivalence ratio, based on syngas yield and its fuel quality, were found to be 800 °C and 0.4, respectively. Torrefaction and densification of canola residue significantly improved syngas yield. Torrefied pellets were obtained from torrefaction of canola residue at a microwave power, residence time and feeding load of 250 W, 10 min and 90 g, respectively. Pellets prepared with different bio-based additives were gasified to compare the effects of binder in gas compositions. The highest total gas yield (24.4 mol/kg), syngas yield (22.1 mol/kg), carbon conversion efficiency (85.1%), lower heating value of gases (2396 kJ/Nm3) and gas energy recovery (29.2%) were reported from the gasification of torrefied canola residue pellet at optimal conditions. Tar yield decreased significantly when torrefied pellets were gasified. A comprehensive characterization of biochar and tar produced from gasification of raw and torrefied canola residue pellets was performed to determine their potential applications. The formation of aromatic carbon structures in biochar produced at higher gasification temperatures was noticed through FTIR spectroscopy. The aromaticity of biochar also resulted in its greater carbon content, heating value and thermal stability as evident from ultimate and thermogravimetric analyses. Tar obtained from gasification of canola residue pellets contained depolymerized products such as organic acids, phenolics, aldehydes, ketones, ethers and esters. [ABSTRACT FROM AUTHOR]

Abstract: CaO-based pellets supported with aluminate cements show superior performance in carbonation/calcination cycles for high-temperature CO2 capture. However, like other CaO-based sorbents, their CO2 carrying activity is reduced after increasing numbers of cycles under high-temperature, high-CO2 concentration conditions. In this work the feasibility of their reactivation by steam or water and remaking (reshaping) was investigated. The pellets, prepared from three limestones, Cadomin and Havelock (Canada) and Katowice (Poland, Upper Silesia), were tested in a thermogravimetric analyzer (TGA). The cycles were performed under realistic CO2 capture conditions, which included calcination in 100% CO2 at temperatures up to 950°C. Typically, after 30 cycles, samples were hydrated for 5min with saturated steam at 100°C in a laboratory steam reactor (SR). Moreover, larger amounts of pellets were cycled in a tube furnace (TF), hydrated with water and reshaped, and tested to determine their CO2 capture activity in the TGA. It was found that, after the hydration stage, pellets recovered their activity, and more interestingly, pellets that had experienced a longer series of cycles responded more favorably to reactivation. Moreover, it was found that conversion of pellets increased after about 70 cycles (23%), reaching 33% by about cycle 210, with no reactivation step. Scanning electron microscope (SEM) analyses showed that the morphology of the low-porosity shell formed at the pellet surface during cycles, which limits conversion, was eliminated after a short period (5min) of steam hydration. The nitrogen physisorption analyses (BET, BJH) of reshaped spent pellets from cycles in the TF confirmed that sorbent surface area and pore size distribution were similar to those of the original pellets. The main alumina compound in remade pellets as determined by XRD was mayenite (Ca12Al14O33). These results showed that, with periodic hydration/remaking steps, pellets can be used for extended times in CO2 looping cycles, regardless of capture/regeneration conditions. [Copyright &y& Elsevier]

• Thermo–chemical process of municipal solid waste (MSW). • Devolatilization properties of pelletized municipal solid waste were investigated. • Substantial reduction of condensable hydrocarbons (tar) in CO 2 atmosphere. The pyrolysis characteristics of cylindrical municipal solid waste (MSW) pellets were studied in N 2 /CO 2 atmospheres with different proportion in fixed bed reactor. Gas release property, tar composition and char structure were analyzed and discussed. Results showed that the addition of CO 2 in the pyrolysis atmosphere increased the yields of char and gas, and decreased the tar yield significantly. For the gas components, the CO yield increased noticeably as CO 2 present, while the contents of light hydrocarbon and H 2 decreased. The volume fraction of CO increased from 15% (100% N 2) to 22% (10% CO 2) and 34% (20% CO 2) at 700 °C. The volume fraction of H 2 decreased from 21% (100% N 2) to 10% (10% CO 2) and 7% (20% CO 2) at 700 °C. In addition, the CH 4 yield increased with the proportion of CO 2. For the tar components, external CO 2 contributed to eliminate asymmetric substitutions and dearomatization. In addition, the aromatic rings, polycyclic aromatic hydrocarbons, and asymmetric aliphatic hydrocarbon structures were reduced in the N 2 /CO 2 atmosphere. At the temperature above 600 °C, CO 2 was favorable to the cracking of the small ring structures, which led to collapse the micro-pores and resulted in the lower accumulative pore volume of the char. At 700 °C, the specific surface area of pyrolytic char was 14.32 m2/g in N 2 , when CO 2 added, this value increased by 35%, which was further enlarged as the proportion of CO 2 increasing. [ABSTRACT FROM AUTHOR]

[Display omitted] • Torrefaction significantly improved the energy content and hydrophobicity of pellets. • Density and mechanical strength of pellet decreased with torrefaction severity. • Torrefaction optimized at 250 W microwave power with 90 g feed loading in 10 min. • Mustard meal acted as a binder in improving pellet quality. • Lignin, mustard meal and pyrolysis oil produced high-quality torrefied fuel pellets. This study involves a sequential torrefaction and pelletization process to produce high-quality fuel pellets from canola residue. Firstly, canola residue was torrefied via microwave irradiation at 250–450 W for 10–20 min with 70–110 g feed load and further pelletized under 3500 N load for a relaxation time of 15 s. The Box-Behnken design was employed to understand the interactions between torrefaction operating conditions for optimal relaxed density, durability, and hardness of the pellets. The optimal torrefaction as determined at 250 W for 10 min with 90 g feed load having the highest relaxed density (1090 kg/m3), durability (83%) and mechanical strength (0.55 MPa) of fuel pellets. The results show that torrefaction significantly improved the energy content as well as hydrophobicity due to the degradation of the lignocellulosic structure. The goal of this study was to investigate the effects of bio-additives (i.e., lignin, sawdust, mustard meal and pyrolysis-derived bio-oil) to further improve the relaxed density, durability, tensile strength, energy density and hydrophobicity of fuel pellets. The combination of the mustard meal, lignin with bio-oil improved the density, durability, tensile strength by 21%, 20% and 123%, respectively. The energy densities of raw, torrefied pellets and torrefied pellets with additives were found to be 15.6, 19.4 and 21.2 GJ/m3, respectively. [ABSTRACT FROM AUTHOR]