Biomass torrefaction technology: Techno-economic status and future prospects
TL;DR: In this article, the authors focus on the current status of the compact moving bed torrefaction and identify process performance characteristics such as thermal efficiency and mass yield and discuss their determining factors through analysis of mass and energy balances, and show that woody biomass can be torrefied with a thermal and mass efficiency of 94% and 48% respectively.
About: This article is published in Energy.The article was published on 2013-12-01. It has received 288 citations till now. The article focuses on the topics: Torrefaction & Energy source.
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TL;DR: In this paper, an updated review on the fundamentals and reaction mechanisms of the slow-pyrolysis and hydrothermal carbonization (HTC) processes, identifies research gaps, and summarizes the physicochemical characteristics of chars for different applications in the industry.
Abstract: Slow-pyrolysis of biomass for the production of biochar, a stable carbon-rich solid by-product, has gained considerable interest due to its proven role and application in the multidisciplinary areas of science and engineering. An alternative to slow-pyrolysis is a relatively new process called hydrothermal carbonization (HTC) of biomass, where the biomass is treated with hot compressed water instead of drying, has shown promising results. The HTC process offers several advantages over conventional dry-thermal pre-treatments like slow-pyrolysis in terms of improvements in the process performances and economic efficiency, especially its ability to process wet feedstock without pre-drying requirement. Char produced from both the processes exhibits significantly different physiochemical properties that affect their potential applications, which includes but is not limited to carbon sequestration, soil amelioration, bioenergy production, and wastewater pollution remediation. This paper provides an updated review on the fundamentals and reaction mechanisms of the slow-pyrolysis and HTC processes, identifies research gaps, and summarizes the physicochemical characteristics of chars for different applications in the industry. The literature reviewed in this study suggests that hydrochar (HTC char) is a valuable resource and is superior to biochar in certain ways. For example, it contains a reduced alkali and alkaline earth and heavy metal content, and an increased higher heating value compared to the biochar produced at the same operating process temperature. However, its effective utilization would require further experimental research and investigations in terms of feeding of biomass against pressure; effects and relationships among feedstocks compositions, hydrochar characteristics and process conditions; advancement in the production technique(s) for improvement in the physicochemical behavior of hydrochar; and development of a diverse range of processing options to produce hydrochar with characteristics required for various industry applications.
1,061 citations
TL;DR: In this paper, the potential use of wood-based biochar (WB) for the removal of potentially toxic elements (PTEs) from water and wastewater has been discussed, and a review demonstrates the overarching scientific opportunities for a comprehensive understanding of using WB as an emerging biosorbent and a promising low-cost and effective material for the remediation of contaminated water.
Abstract: Recently, biochar has received significant attention, especially for the removal of potentially toxic elements (PTEs) from water and wastewater. No review has been focused on the potential use of wood-based biochar (WB) for the removal of PTEs in water and wastewater. Here, we have critically reviewed the (i) preparation and characterisation of WB; (ii) removal efficiency of WB for PTEs in water with respect to its physicochemical characteristics, biochar/water ratio, pH, and sorption system; (iii) removal mechanisms of PTEs by WB; (iv) fate of the sorbed PTEs onto WB; and (v) recovery of the sorbed PTEs from the resultant sludge of WB. We also discussed the removal of PTEs by engineered/designer WB as compared to pristine WB. This review demonstrates the overarching scientific opportunities for a comprehensive understanding of using WB as an emerging biosorbent and a promising low-cost and effective material for the remediation of PTEs contaminated water.
350 citations
TL;DR: In this paper, torrefaction of hemicellulose, cellulose, and lignin were studied at a series of torfaction temperatures (210, 240, 270, and 300°C) based on the properties of their three-phase products, namely solid, liquid (water and tar), and gaseous products.
312 citations
TL;DR: Torrefied biomass has several benefits, such as higher energy density, good grindability, higher flowability and uniformity as mentioned in this paper, such as high energy efficiency, high energy density and high grindability.
254 citations
TL;DR: Although the mass yield for the organic fraction was only about 25% above 500°C, biochar was the primary product of pyrolysis containing 40% of energy and 45% of carbon from the straw, since the sum of energy yield was about 60%.
238 citations
Cites background from "Biomass torrefaction technology: Te..."
...Pyrolysis at low temperatures (typically below 300 C), also referred to as torrefaction, is used to upgrade its fuel quality, such as the heating value (energy density) and grindability, as a pretreatment of biomass for pelletization, bio-oil production, gasification or combustion processes (Meng et al., 2012; Batidzirai et al., 2013)....
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References
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Book•
01 Jan 1958
TL;DR: Plant design and economics for chemical engineers, Plant design for chemical engineering, and plant design for plant design and economic analysis are discussed in this paper, where the authors propose a plant design approach based on chemical engineering.
Abstract: Plant design and economics for chemical engineers , Plant design and economics for chemical engineers , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
3,016 citations
Additional excerpts
...i e the discount rate (%) N e the lifetime of the facility (years) [117]...
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...Since torrefaction is an emerging technology, estimation of investment costs uses the factorial approach where cost components are estimated using factors and percentages on the basis of the purchased equipment cost (following [102,116,117])....
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TL;DR: An overview of the research on biomass upgrading by torrefaction for the production of biofuels is presented in this article, where the removal of oxygen from biomass aims to produce a fuel with increased energy density by decomposing the reactive hemicellulose fraction.
Abstract: An overview of the research on biomass upgrading by torrefaction for the production of biofuels is presented. Torrefaction is a thermal conversion method of biomass in the low temperature range of 200–300 °C. Biomass is pre-treated to produce a high quality solid biofuel that can be used for combustion and gasification. In this review the characteristics of torrefaction are described and a short history of torrefaction is given. Torrefaction is based on the removal of oxygen from biomass which aims to produce a fuel with increased energy density by decomposing the reactive hemicellulose fraction. Different reaction conditions (temperature, inert gas, reaction time) and biomass resources lead to various solid, liquid and gaseous products. A short overview of the different mass and energy balances is presented. Finally, the technology options and the most promising torrefaction applications and their economic potential are described.
1,125 citations
Additional excerpts
...pulverize [60,61] Improved grindability: torrefied biomass requires less electricity to grind compared to wood chips [62,63,13,64,22]....
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...[60,74]....
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TL;DR: In this article, the authors examined torrefaction in nitrogen of two energy crops, reed canary grass and short rotation willow coppice (SRC), and a residue, wheat straw.
822 citations
Additional excerpts
...Combustion properties: torrefied biomass takes less time for ignition due to less moisture [45]....
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...[45] and Chen et al....
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...burns longer due to larger percentage of fixed carbon [45]....
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TL;DR: Torrefaction of biomass clearly showed the improved fuel characteristics and grinding properties closer to coal.
755 citations
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...Torrefaction promises to deliver a solid biofuel which (when densified) has superior characteristics that are similar to coal in terms of handling, milling and transport [5,36,1,69,2,3]....
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...Biomass is the only renewable resource that can directly substitute coal in many applications [1,69,2,3]....
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...Biomass is highly heterogeneous in quality and nature, and is mostly available in low energy density form [36,37,3,38,39]....
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...Using a Retsch SM 2000 laboratory heavy duty knife mill Phanphanich and Mani [3] give grinding energy for pine chips of 103 kWh/t (at 225 C) and 24 kWh/t (300 C); for logging residues energy required is 114 kWh/t (at 225 C) and 38 kWh/t (300 C); Using a Retsch SM1 knife mill with a 8 mm grid, Repellin et al....
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...On grinding, the particle size distributions, sphericity, and particle surface areas become similar to coal [3]....
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TL;DR: In this paper, a questionnaire survey of European producers of densified biomass fuels was performed, where the authors evaluated the quality of their products in terms of the following parameters: the dimensions of the fuels, the bulk and the particle density, the water and the ash content, the gross and the net calorific value, the abrasion, the content of starch (as an indication for the use of biological binding agents), the concentrations of C, H, N, S, Cl, K as well as of the heavy metals Cd, Pb, Zn,
Abstract: With respect to the use of densified biomass fuels in fully automatic heating systems for the residential sector a high quality of these fuels is required. Several European countries already have implemented standards for such fuels. In other countries such standards are in preparation or planned. Furthermore, in some countries also standards from associations are existing (e.g. from the Austrian Pellets Association). In addition to these national standards, European standards for solid biomass fuels are under development. For producers of densified biomass fuels, especially for pellet producers, it is therefore very important to produce high-quality fuels keeping the limiting values of the standards addressed. However, in this context it has to be considered that as a high fuel quality as is necessary for the combustion of densified biomass fuels in automatic small-scale furnaces is not necessary if these fuels are used in larger industrial furnaces as they are equipped with more sophisticated flue gas cleaning, combustion and process control systems. Two pellet qualities, one for industrial and one for small-scale consumers seem to be more meaningful. Within the framework of the EU-ALTENER-project “An Integrated European Market for Densified Biomass Fuels (INDEBIF)” a questionnaire survey of European producers of densified biomass fuels was performed. In this connection the possibility was offered to the producers to participate in an analysis programme with their fuels. An overview was obtained of the qualities of densified biomass fuels offered in the European market, covering pellets and briquettes from Austria, Italy, Sweden, Spain, Norway and the Czech Republic. The parameters analysed were the dimensions of the fuels, the bulk and the particle density, the water and the ash content, the gross and the net calorific value, the abrasion, the content of starch (as an indication for the use of biological binding agents), the concentrations of C, H, N, S, Cl, K as well as of the heavy metals Cd, Pb, Zn, Cr, Cu, As and Hg. These parameters have been chosen following the Austrian, German, Swiss and Swedish standards for densified biomass fuels. The results showed that a majority of the participating producers produce fuels of high quality. However, wood pellets of some producers show a high abrasion, one of the most important quality parameters for pellets. An increased amount of fines often causes failures in the feeding systems used in the residential heating sector. In order to decrease abrasion, the addition of small amounts of biological binding agents (e.g. maize or rye) is possible. This kind of additive is most common in Austria. Moreover, some producers obviously use not only chemically untreated raw materials or additives, which increase the content of pollutants. Such fuels cause problems regarding emissions, deposit formation and corrosion. Emission problems are expected due to increased contents of N, Cl, S as well as heavy metals. Increased concentrations of heavy metals additionally contaminate the ash, increased Cl concentrations raise the risk of corrosion. Moreover, an increased content of K has a negative effect on the ash melting behaviour and causes higher aerosol formation, which enhances deposit formation and particulate emissions.
722 citations