Trace Element Concentrations in Firewood and Corresponding Stove Ashes

Wood combustion is a major part of the current efforts to reduce CO2 emissions. However, wood combustion leads to emissions of other pollutants like fine particulate matter. A new option to reduce particulate matter emissions is a metal mesh filter with counter current flushing. An automatic prototype was tested under realistic conditions including starts and stops of the boiler. For regeneration, the filter was flushed using water in opposite flow direction. The water was recycled multiple times to limit water consumption. The results are very promising. Regeneration was successful and no signs of decay could be observed over 419.5 h of operation and 234 regenerations. The filter can be operated during all phases of boiler operation, which is a major step forward compared to alternative secondary measures. Separation efficiency was high with 80–86%, even though the filter showed internal leakage, which reduced the separation efficiency. Additionally, waste products were examined. About 1000 l wastewater can be expected to be produced every month, which could be disposed using the communal waste water system, given the low heavy metal loading. A part of the fine particulate matter is unsoluble and has to be removed from the regeneration water before reuse. The unsoluble fraction contains the majority of heavy metals and has to be disposed as fly ash or used for urban mining. Generally spoken, the metal mesh filter is a new, promising option which can overcome limitations of current secondary measures without increasing costs given its simple and robust construction.

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“…Spectroblue FMX 26, Spectro) after microwave digestion using HCl, HNO 3 and H 2 O 2 as described by Tejada et al in [44].…”

Section: Regeneraɵon Watermentioning

confidence: 99%

Evaluation of a metal mesh filter prototype with wet regeneration

Baumgarten

Grammer

Ehard³

et al. 2021

Biomass Conv. Bioref.

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“…Further chemical analysis was performed using an ICP-OES (Spectroblue FMX 26, Spectro) after microwave digestion using HCl, HNO 3 , and H 2 O 2 following a routine developed by Tejada et al [38].…”

Section: Pellet and Ash Analysismentioning

confidence: 99%

“…The main mode of cleaning is the formation of jets directed at the surface of objects emerged in the ultrasonic bath, which effectively removes particles [36]. Further contributing to a good cleaning result is the solubility of the main ash compounds in waterchloride and sulfate salts of potassium, sodium, calcium, and zinc [37][38][39].…”

Section: Introductionmentioning

confidence: 99%

Novel metal mesh filter using water-based regeneration for small-scale biomass boilers

Baumgarten

Grammer

Ehard³

et al. 2020

Biomass Conv. Bioref.

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Particulate matter emissions are a key issue of modern biomass boilers. A novel gas cleaning method using a metal mesh filter combined with water-based cleaning was developed and tested. The filter was tested batch-wise. Flue gas of a commercial 50-kW boiler was filtered until a pressure drop of 2000 Pa was reached. Afterwards, the filter was regenerated. The initial prototype used ultrasound in order to remove the filter cake from the filter candles. Regeneration was complete and, even after boiler malfunctions producing tar, the filter cake could still be removed. Given the good results, a second cleaning mode, flushing the filter candles with water, was tested. The results were as good as with ultrasonic cleaning. Peak mass collection efficiency was very high with 98 ± 2% (burning wood pellets). However, directly after cleaning, the first layer of filter cake has to be developed. In this initial phase, collection efficiency is low. Service time until maximum pressure drop was reached depended on the gas velocity. Using pellets as fuel, at a gas velocity of 66.6 m/h, 12-h service time was reached and 4.1 g dust was collected per square meter filter surface, while at 33.3 m/h, service time increased to 55 h and collected dust to 13.9 g/m2. Using low-quality wood chips, the raw gas dust loading was much higher but also the maximum loading of the filter was higher with 13.3 to 28.9 g dust separated per square meter. Still, the service time decreased to 3.4 respective 38 h. Peak collection efficiency increased to 99.5 ± 0.8%. The overall collection efficiency including the buildup of the filter cake depends on the gas velocity and fuel. It ranges from 74 ± 4 to 91 ± 1%. The feasibility of the filter concept could be proven, and further development towards a commercial application is in progress. Metal mesh filters with countercurrent cleaning showed a high potential given their simple and robust design, as well as high collection efficiency.

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“…The use of ashes in road construction has successfully been tested in research projects in Austria and Finland [22,32,33]. Tejada et al (2019) [34] investigated wood ashes as a source of raw materials in urban mining.…”

Section: Introductionmentioning

confidence: 99%

Valorization of Residues from Energy Conversion of Biomass for Advanced and Sustainable Material Applications

2022

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Trace Element Concentrations in Firewood and Corresponding Stove Ashes

Cited by 12 publications

References 33 publications

Evaluation of a metal mesh filter prototype with wet regeneration

Evaluation of a metal mesh filter prototype with wet regeneration

Novel metal mesh filter using water-based regeneration for small-scale biomass boilers

Valorization of Residues from Energy Conversion of Biomass for Advanced and Sustainable Material Applications

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