Activity of chars and activated carbons for removal and decomposition of tar model compounds – A review

Ravenni, Giulia; Sárossy, Zsuzsa; Ahrenfeldt, Jesper; Henriksen, Ulrik Birk

doi:10.1016/j.rser.2018.07.001

Cited by 100 publications

(41 citation statements)

References 64 publications

(121 reference statements)

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“…The valorisation of chars as catalysts for tar cracking appears as an attractive approach providing a solution to the main issues of the pyrogasification process development: (1) find new valorisation routes for the chars [26], and (2) develop an efficient and low-cost syngas cleaning process. Recently, chars from biomass were proved to be promising low-cost catalysts [27][28][29] or catalyst supports [30][31][32] for tar cracking. In most of the studies, the operating conditions are specifically selected to obtain chars with suitable characteristics.…”

Section: Introductionmentioning

confidence: 99%

Reactivity and deactivation mechanisms of pyrolysis chars from bio-waste during catalytic cracking of tar

et al. 2019

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Section: Introductionmentioning

confidence: 99%

Reactivity and deactivation mechanisms of pyrolysis chars from bio-waste during catalytic cracking of tar

et al. 2019

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“…This is a significant advantage when the aim is to reduce the tar dew point of the gas (so that it can be burned in an engine) as it is mainly determined by the concentration of polyaromatic compounds. However, char may deactivate rapidly due to coking under some operating conditions [10,[13][14][15].…”

mentioning

confidence: 99%

“…On the contrary, when gasification is faster than deposition, the char can maintain or even increase its initial activity. Therefore, the selection of experimental conditions ensuring a positive net rate of carbon conversion (gasification − deposition) is necessary to maintain the activity of the char [10,[13][14][15]30]. Figure 1: Tar conversion mechanism over char.…”

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confidence: 99%

Tar conversion of biomass syngas in a downstream char bed

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Dieguez-Alonso

et al. 2020

Fuel Processing Technology

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The catalytic conversion of biomass-derived tars over char during long tests (over 6 hours) is studied. The syngas is generated in a steam-blown fluidized-bed gasifier employing wood pellets and conducted to a second tubular reactor where non-activated char particles are fluidized. The gasifier operated at 750 °C whereas the temperature of the secondary reactor was varied between 750 °C and 875 °C. The evolution of the tar conversion, gas composition and internal structure of the used catalysts were studied. At 750 °C, the initial catalytic activity of the char was low and deactivation occurs rapidly. However, as the reactor temperature increased, the catalytic activity of the char improved significantly. At 875 °C, the initial conversion of tar was above 70 % and over 64 % after 5 h of operation. Moreover, the conversion of the heaviest tars was above 80 % during the entire test. At this temperature, the decrease in tar conversion is attributed to the consumption of the char by steam gasification since its catalytic activity increased during of the test. In these conditions the char bed with an initial weight of 32 g converted approximately 12 g of tars (benzene not included) after 5 h of operation. 1-IntroductionGasification is a thermo-chemical route for conversion of solid fuels, such as biomass and wastes, into a syngas that can be used in a variety of applications [1,2]. Fluidized bed (FB) gasification has several advantages over that in fixed/moving bed or entrained-flow for distributed energy production [3]. However, in all types of FB gasifiers the process temperature must be kept relatively low to prevent agglomeration and sintering of bed material. The low temperature results in incomplete carbon conversion and a high concentration of heavy tars in the gas. The condensation of heavy tars in downstream equipment is the main bottleneck for the use of the syngas in any application where the gas needs to be cooled down.

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“…An increase of the SSA leads to enhancement of adsorption of target compounds on the material surface that may further support their oxidation and formation of by-products [16]. This effect was also observed for naphthalene when it was adsorbed on materials of various SSAs [88,89]. Adsorption of target compounds may also be influenced by other textural properties of packing materials (e.g., pore size and volume).…”

Section: The Effect Of Packing Materials Properties (Ssa Shape and Smentioning

confidence: 83%

The Effect of Packing Material Properties on Tars Removal by Plasma Catalysis

et al. 2020

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Plasma catalysis has been utilized in many environmental applications for removal of various hydrocarbons including tars. The aim of this work was to study the tars removal process by atmospheric pressure DBD non-thermal plasma generated in combination with packing materials of various composition and catalytic activity (TiO2, Pt/γAl2O3, BaTiO3, γAl2O3, ZrO2, glass beads), dielectric constant (5–4000), shape (spherical and cylindrical pellets and beads), size (3–5 mm in diameter, 3–8 mm in length), and specific surface area (37–150 m2/g). Naphthalene was chosen as a model tar compound. The experiments were performed at a temperature of 100 °C and a naphthalene initial concentration of approx. 3000 ppm, i.e., under conditions that are usually less favorable to achieve high removal efficiencies. For a given specific input energy of 320 J/L, naphthalene removal efficiency followed a sequence: TiO2 > Pt/γAl2O3 > ZrO2 > γAl2O3 > glass beads > BaTiO3 > plasma only. The efficiency increased with the increasing specific surface area of a given packing material, while its shape and size were also found to be important. By-products of naphthalene decomposition were analyzed by means of FTIR spectrometry and surface of packing materials by SEM analysis.

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Activity of chars and activated carbons for removal and decomposition of tar model compounds – A review

Cited by 100 publications

References 64 publications

Reactivity and deactivation mechanisms of pyrolysis chars from bio-waste during catalytic cracking of tar

Reactivity and deactivation mechanisms of pyrolysis chars from bio-waste during catalytic cracking of tar

Tar conversion of biomass syngas in a downstream char bed

The Effect of Packing Material Properties on Tars Removal by Plasma Catalysis

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