Characterization of the devolatilization rate of solid fuels in fluidized beds by time‐resolved pressure measurements

Solimene, Roberto; Chirone, Riccardo; Salatino, Piero

doi:10.1002/aic.12607

Cited by 15 publications

(7 citation statements)

References 59 publications

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“…For conventional combustion, the correlation provided in the literature − relates devolatilization time as a function of only the particle size. Pragadeesh and co-workers proposed a new correlation that embodies the effects of other parameters such as temperature and particle shape: where A is the proportionality constant which takes into account the effects of transient mass and heat transfer within the particles and the devolatilization kinetics, d p is the particle diameter in millimeters, T is the operating FR temperature, and φ is the sphericity of particles. i , j , k are the empirical exponents of the respective parameters.…”

Section: Effect Of Volatiles On Bio-clcmentioning

confidence: 99%

Chemical Looping for Combustion of Solid Biomass: A Review

Coppola¹,

Scala

2021

Energy Fuels

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Chemical looping combustion of solid biomass has the unique potential to generate energy with negative carbon emissions, while entailing an energy penalty compared to traditional combustion that is lower than that of the competing carbon capture technologies. In spite of these attractive features, research is still needed to bring the technology to a fully commercial level. The reason relies on a number of technological challenges mostly related to the oxygen carrier performance, its possible detrimental interaction with the biomass ash components, and the efficiency of the gas–solid contact with the biomass volatiles. This review is focused on these specific challenges which are particularly relevant when firing biomass rather than coal in a solid-based chemical looping combustion process. Special attention will be given to the most recent findings published on these aspects. Related performance evaluation by modeling, system integration, and techno-economic analysis will also be briefly reviewed.

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Section: Effect Of Volatiles On Bio-clcmentioning

confidence: 99%

Chemical Looping for Combustion of Solid Biomass: A Review

Coppola¹,

Scala

2021

Energy Fuels

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“…There are several methods available for the determination of devolatilization time of solid fuels in a fluidized bed, as detailed by Solimene et al . Visual techniques − include the flame period technique (which considers the time period of flame visibility) and the flame extinction technique (which considers time period between fuel introduction and flame disappearance).…”

Section: Introductionmentioning

confidence: 99%

“…Visual techniques − include the flame period technique (which considers the time period of flame visibility) and the flame extinction technique (which considers time period between fuel introduction and flame disappearance). The instrumental techniques include mass loss history and thermogravimetric analysis of residual volatiles , in fuel particles sampled at regular time intervals during devolatilization, time-resolved exhaust gas concentration of methane , (in pyrolysis conditions) or carbon dioxide/oxygen (in oxidizing conditions), ,,− particle center temperature history, ,− where the time at which the center of the fuel particle reaches the bed temperature is calculated as the devolatilization time, time-resolved overboard pressure measurements to determine the devolatilization rates and correspondingly the devolatilization time. …”

Section: Introductionmentioning

confidence: 99%

Color Indistinction Method for the Determination of Devolatilization Time of Large Fuel Particles in Chemical Looping Combustion

Pragadeesh

Sudhakar

2019

Energy Fuels

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Chemical looping combustion (CLC) is one of the promising fuel conversion technologies for carbon capture with low energy penalty. Devolatilization is an important physical phenomenon occurring during solid fuel CLC. Devolatilization behavior influences fragmentation, combustion rate, emission, and particulates generation in fluidized bed CLC (FB-CLC), thus a critical input for its design. Existing visual techniques for determining devolatilization time cannot be applied in CLC conditions because of its flameless combustion nature. In the present study, a new, simple, and quick technique called “color indistinction method” (CIM) is proposed for the determination of devolatilization time (τd) in FB-CLC, where the end of devolatilization is inferred from the disappearance of fuel particle in a hot fluidized bed. Single-particle devolatilization studies in FB-CLC are conducted to determine the devolatilization time using CIM for two types of fuels, viz., coal and biomass (Casuarina equisetifolia wood), of size range 8–25 and 10–20 mm, respectively, at three different fuel reactor bed temperatures (800, 875, and 950 °C) and one fluidization velocity. The proposed technique is validated in three ways: (i) the measurement of residual volatiles present in char by thermogravimetric analysis; (ii) mass loss history of the fuel during devolatilization; and (iii) diagnostics using particle center temperature measurements. The results of CIM experiments, in terms of degree of error involved, are compared with an established flame extinction technique (FET) and a more accurate particle center temperature (PCT) method. The amount of volatiles released during devolatilization, as determined by CIM, is 91.3% for coal and 98.9% for biomass. These values compare very well with the results of the established FET, in which the volatile release is 90.7% for coal and 99.1% for biomass samples. The devolatilization times determined using CIM are in line with particle center temperature measurements with an acceptable error range of −7.57 to +3.70%. The proposed CIM is successful in establishing the devolatilization time of different fuels in CLC conditions and can also be applied in other flameless combustion conditions.

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“…The 'flotsam' behaviour of the lighter fuel particles in a fluidized bed is accentuated in fuels with high volatile content, such as biomass and low-rank coal. The release of volatiles in hot conditions results in the formation of bubbles, which tend to lift the fuel particles to the surface of the bed [4][5][6]. These bubbles are commonly known as endogenous bubbles to differentiate them from those generated by the fluidization gas, which are denominated exogenous bubbles.…”

Section: Introductionmentioning

confidence: 99%

“…These bubbles are commonly known as endogenous bubbles to differentiate them from those generated by the fluidization gas, which are denominated exogenous bubbles. Previous research on segregation of gas emitting particles has focused on quantifying the lifting time and/or lifting force due to the formation of endogenous bubbles [4][5][6][7]. The experiments were performed in small reactors with a single fuel particle and at incipient fluidization velocity [4][5][6][7] or fluidization velocities up to 2•umf [7].…”

Section: Introductionmentioning

confidence: 99%

Behaviour of biomass particles in a large scale (2–4MWth) bubbling bed reactor

Vilches¹,

Sette²,

Thunman³

2015

Computational Methods in Multiphase Flow VIII

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Biomass is regarded as an interesting fuel for energy-related processes owing to its renewable nature. However, the high volatile content of biomass adds a number of difficulties to the fuel conversion and process operation. In the context of fluidized bed reactors, several authors have observed that devolatilizing fuel particles tend to float on the surface of a gas-fluidized bed of finer solids. This behaviour, known as segregation, leads to undesired effects such as poor contact between volatiles and bed material. Previous investigations on segregation of gas-emitting particles in fluidized beds are conducted in small units and they are often operated at rather low gas velocities, typically between the minimum fluidization velocity (umf) and 2•umf. Therefore, it is not known to what extent such results are of relevance for industrial scale units and for higher fluidization velocities that are commonly used in large bubbling beds. In this paper the behaviour of biomass particles in a large scale bubbling bed reactor is investigated. Tests were conducted at a wide range of fluidization velocities with three different bed materials of varying particle size and density. The fuel was wood pellets and the fluidization medium was steam, which makes the findings relevant for indirect gasification, chemical looping combustion (CLC) and bubbling bed combustion applications. The experiments were recorded by means of a digital video camera and the digital images were subsequently analysed qualitatively. The results show high level of segregation at fluidization velocity up to 3.5 umf. Beyond this point fuel mixing was significantly enhanced by increasing fluidization velocities. At the highest fluidization velocity tested (i.e. >8 umf), a maximum degree of mixing was achieved.

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Characterization of the devolatilization rate of solid fuels in fluidized beds by time‐resolved pressure measurements

Cited by 15 publications

References 59 publications

Chemical Looping for Combustion of Solid Biomass: A Review

Chemical Looping for Combustion of Solid Biomass: A Review

Color Indistinction Method for the Determination of Devolatilization Time of Large Fuel Particles in Chemical Looping Combustion

Behaviour of biomass particles in a large scale (2–4MWth) bubbling bed reactor

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