Accelerating wet torrefaction rate and ash removal by carbon dioxide addition

Bach, Quang‐Vu; Tran, Khanh-Quang; Skreiberg, Øyvind

doi:10.1016/j.fuproc.2015.09.013

Cited by 38 publications

(10 citation statements)

References 19 publications

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“…Different published papers were reviewed to gather the information on proximate, ultimate and heating value analyses of both the raw and torrefied biomass materials. The collected information (in dry basis) from the literature for torrefied and raw biomass materials are summarized in Table S1 [ 12 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 ] and Table S2 [ 2 , 7 , 9 , 12 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 30 , 31 , 32 ,…”

Section: Methodsmentioning

confidence: 99%

HHV Predicting Correlations for Torrefied Biomass Using Proximate and Ultimate Analyses

2017

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Many correlations are available in the literature to predict the higher heating value (HHV) of raw biomass using the proximate and ultimate analyses. Studies on biomass torrefaction are growing tremendously, which suggest that the fuel characteristics, such as HHV, proximate analysis and ultimate analysis, have changed significantly after torrefaction. Such changes may cause high estimation errors if the existing HHV correlations were to be used in predicting the HHV of torrefied biomass. No study has been carried out so far to verify this. Therefore, this study seeks answers to the question: “Can the existing correlations be used to determine the HHV of the torrefied biomass”? To answer this, the existing HHV predicting correlations were tested using torrefied biomass data points. Estimation errors were found to be significantly high for the existing HHV correlations, and thus, they are not suitable for predicting the HHV of the torrefied biomass. New correlations were then developed using data points of torrefied biomass. The ranges of reported data for HHV, volatile matter (VM), fixed carbon (FC), ash (ASH), carbon (C), hydrogen (H) and oxygen (O) contents were 14.90 MJ/kg–33.30 MJ/kg, 13.30%–88.57%, 11.25%–82.74%, 0.08%–47.62%, 35.08%–86.28%, 0.53%–7.46% and 4.31%–44.70%, respectively. Correlations with the minimum mean absolute errors and having all components of proximate and ultimate analyses were selected for future use. The selected new correlations have a good accuracy of prediction when they are validated using another set of data (26 samples). Thus, these new and more accurate correlations can be useful in modeling different thermochemical processes, including combustion, pyrolysis and gasification processes of torrefied biomass.

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Section: Methodsmentioning

confidence: 99%

HHV Predicting Correlations for Torrefied Biomass Using Proximate and Ultimate Analyses

2017

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“…In the case of hydrochar, the mentioned increase in ash content is associated with the destruction of the VM and migration to the liquid phase (e.g., organic acids, furans) [36]. Additionally, the changes in pH during the HTC lead to the precipitation of inorganic compounds as salts on the surface of the hydrochar [27,37]. This is also in agreement with a previous study from Ovsyannikova et al [38] that shows that digested SSL contains many different salts, which usually precipitate in HTC conditions.…”

Section: Proximate and Ultimate Analysesmentioning

confidence: 99%

Combustion Characteristics of Hydrochar and Pyrochar Derived from Digested Sewage Sludge

et al. 2020

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In this paper, hydrochars and pyrochars were produced at 260 °C under different residence times (2 and 4 h) using anaerobic digested sewage sludge (SSL) as initial feedstock. The effect of reaction time on the fuel properties of hydrochars and pyrochars was evaluated. Moreover, the combustion kinetics of raw SSL and the derived pyrochars and hydrochars without coal blending were determined at two different air flows (20 and 90 mL/min) and compared. In the same conditions, the yield of hydrochar was significantly lower than that of pyrochar, confirming the different reaction pathways followed in each process. The results showed hydrochars have lower carbon recovery and energy yield than pyrochars, making the latter more suitable for energy purposes. The thermogravimetric combustion study showed that both thermochemical treatments increased the ignition temperature but decreased the burnout temperature, which results in higher stability during handling and storage. However, raw SSL is better for combustion than hydrochar according to the combustibility index. In addition, the kinetic study showed that the activation energy of the combustion of biochars, especially pyrochar, is lower than that of raw SSL, which is advantageous for their combustion.

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“…In the case of WT, the integration of CO 2 not only improved the conversion of biomass to volatiles but the resulting solids also showed an increase in heating value of up to 0.54 MJ kg À1 and a reduction of 72 However, the same research group also reported that the CO 2 -enriched WT produced similar hydrochar yields with less heating value compared to N 2 -WT, but with a significant increase in ash removal. 73 Similar to the impacts of CO 2 in biomass gasification, CO 2 -assisted pyrolysis showed an enhancement in the production of CO as a result of reactions between CO 2 and other gases, tar and char. 74 The resulting char presented a six-fold increase in surface area with a different chemical composition than chars produced with a N 2 environment.…”

Section: Thermochemical Processesmentioning

confidence: 85%

Introduction to High Pressure CO2 and H2O Technologies in Sustainable Biomass Processing

Questell‐Santiago

Luterbacher

2017

High Pressure Technologies in Biomass Conversion

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Biomass is an attractive source of renewable carbon-based fuels and chemicals and their production is envisaged within the framework of integrated biorefineries. Multiple research efforts to make biorefineries more economically competitive and sustainable are ongoing. In this context the use of high-pressure CO2 and CO2/H2O mixtures for biomass conversion is especially attractive. These mixtures are cheap, renewable, environmentally benign and allow tuning of various processing parameters by varying temperature, pressure and CO2 loading. This chapter presents a broad introduction of the principal processes and conversion routes being considered within biorefineries, and how high-pressure CO2 and CO2/H2O mixtures could help address certain challenges associated with biomass conversion. Some of the principle advantages associated with high-pressure CO2 and CO2/H2O mixtures that we highlight here are their abilities to act as green substitutes for unsustainable solvents, to enhance acid-catalysed reaction rates by in situ carbonic acid formation, to reduce mass transfer-limitations, and to increase access to substrates and catalysts. We discuss these advantages in the context of the trade-offs associated with implementing large-scale high-pressure systems including safety concerns and increased capital costs. With this introduction, we highlight both the principal benefits and challenges associated with the use of high-pressure CO2 and CO2/H2O mixtures, which are further detailed in subsequent chapters.

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Accelerating wet torrefaction rate and ash removal by carbon dioxide addition

Cited by 38 publications

References 19 publications

HHV Predicting Correlations for Torrefied Biomass Using Proximate and Ultimate Analyses

HHV Predicting Correlations for Torrefied Biomass Using Proximate and Ultimate Analyses

Combustion Characteristics of Hydrochar and Pyrochar Derived from Digested Sewage Sludge

Introduction to High Pressure CO2 and H2O Technologies in Sustainable Biomass Processing

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