The fate of mercury in fluidized beds under oxy-fuel combustion conditions

Loscertales, Margarita de Las Obras; Izquierdo, M.T.; Rufas, A.; Diego, Luis F. de; Garcı́a-Labiano, F.; Gayán, Pilar; Adánez, Juan

doi:10.1016/j.fuel.2015.11.045

Cited by 21 publications

(33 citation statements)

References 19 publications

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“…The experimental installation consists of a fluidized bed reactor, different auxiliary systems for gas supply (O 2 , CO 2 , H 2 O, NO and SO 2 ), solid feeding (coal, limestone and sand as inert solid) and gas analysis. The BFB combustor and the experimental method are described elsewhere [15,16].…”

Section: Bubling Fb Combustor Of 3 Kwth Working Under Oxy-coal Combusmentioning

confidence: 99%

Mercury capture by a structured Au/C regenerable sorbent under oxycoal combustion representative and real conditions

Gómez-Giménez

Izquierdo

Loscertales

et al. 2017

Fuel

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The environmental implications of mercury do not correspond only to the emissions to the atmosphere; the quality of the captured CO 2 to be transported and sequestered has been subject of research, concerning trace quantities of heavy metals participating in mineralization and precipitation reactions in sequestration conditions. For oxycoal combustion, mercury is not an environmental issue alone but also an operational issue, particularly about where mercury could accumulate within the CO 2 processing unit. Therefore, Hg removal is necessary to prevent its attack on the aluminium heat exchangers. In this work, a regenerable sorbent based on carbon supported Au nanoparticles (0.1%wt) has been used for Hg capture under oxycoal combustion atmosphere. The influence of the presence of O 2 , NO, SO 2 and HCl in a gas containing Hg and CO 2 on the sorbent as well as on the Hg oxidation (Au can act as an oxidation catalyst) has been evaluated under a simulated flue gas. The presence of either NO or HCl in the simulated flue gas led to mercury oxidation, with oxidized mercury not evolving in the gas, indicating that it is retained on the sorbent; the oxidized mercury is well stabilized on Au surfaces of the sorbent and favours the Hg-Au amalgam formation. This sorbent has been also evaluated in 3 kWth oxycoal bubling fluidized bed combustor. A lignite with high sulphur content was burned in presence of limestone. Despite high SO 2 concentration that reached the Au/C sorbent, high capture efficiency was achieved and breakthrough occurred after 3.5 h and 10% breakthrough is not reached during the experiments. Bearing in mind that regeneration time can be adjusted near 1 h, two swing sorbent beds could be used to control mercury emissions under oxycoal combustion conditions.

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Section: Bubling Fb Combustor Of 3 Kwth Working Under Oxy-coal Combusmentioning

confidence: 99%

Mercury capture by a structured Au/C regenerable sorbent under oxycoal combustion representative and real conditions

Gómez-Giménez

Izquierdo

Loscertales

et al. 2017

Fuel

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“…A summary of the experiments carried out in this study is depicted in Table 2. installation [15] showed that the increase of NO concentration from 768 ppm to 945 ppm had a negligible effect on Hg partitioning. However, the study of the effect of sulphur content of coals under the same reactor conditions is almost unexplored.…”

Section: Resultsmentioning

confidence: 98%

“…More details of the experimental installation can be found elsewhere [20]. Sampling of gaseous mercury, Hg(0) and Hg(II) in the gaseous outlet stream was performed at steady state operation [15,21]. Oxidized mercury was trapped in impingers containing 100 ml of KCl 1M.…”

Section: Methodsmentioning

confidence: 99%

“…The reaction of SO 2 with CaO may have created active sulphur sites on the bed solids which can chemisorb Hg(0) in the gas phase to produce sulphur-bound Hg on the BFB solid surface. In addition, the presence of CaO with SO 2 and H 2 O cause mercury oxidation, which can be more easily adsorbed by the ashes, even with low unburned carbon contents [15,27]. The increase of O 2 in the gas fed under oxy-combustion conditions seems to have little effect on Hg partitioning between particle-bound Hg and gas species.…”

Section: Effect Of Sorbent and Coal Characteristicsmentioning

confidence: 99%

“…The effect of combustion temperature and recycled gases (NO, SO 2 and H 2 O) on the fate of mercury emissions from coal combustion in fluidized beds (FB) has been previously studied [15]. In that study, it was concluded that the particle-bound mercury exhibited a maximum at a temperature about 925 ºC, with different Ca-sorbents and Ca/S ratios which coincided with the highest degree of the limestone sulphation and so the lowest SO 2 concentration.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Mercury emissions from coal combustion in fluidized beds under oxy-fuel and air conditions: Influence of coal characteristics and O2 concentration

Izquierdo

Loscertales

Diego

et al. 2017

Fuel Processing Technology

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In this work, the fate of mercury in a bubbling fluidized bed combustor working under oxy-combustion conditions has been studied and compared with air combustion. The influence of burning three different rank coals, with sulphur content ranging from 0.65 % to 5.17 %, on Hg partitioning has been studied. The presence of limestone as sorbent for SO 2 capture as well as the concentration of O 2 at the entrance of the combustor were also evaluated. Coal rank does not have a direct influence on coal partitioning. However, sulphur content of the coal is an important parameter to describe not only the high percentage of particle-bound mercury, up to 87 %, in presence of limestone but also the prevalence of Hg(0) as the main species in the gas phase when burning the lignite. The O 2 /CO 2 ratio has little effect on Hg partitioning in experiments carried out in presence of limestone at 925 ºC (the optimum temperature for sorbent sulphating under oxy-combustion conditions) and little differences are found with air combustion at 850 ºC (the optimum temperature for sorbent sulphating under air combustion conditions). Percentage of particle-bound mercury shows a maximum at 925 ºC independently of the coal studied, which it is related with the maximum sulphur retention for each coal at this temperature.

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