Novel metal mesh filter using water-based regeneration for small-scale biomass boilers
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ORIGINAL ARTICLE
Novel metal mesh filter using water-based regeneration for small-scale biomass boilers Björn Baumgarten 1 & Peter Grammer 1 & Ferdinand Ehard 2 & Oskar Winkel 3 & Ulrich Vogt 4 & Günter Baumbach 4 & Günter Scheffknecht 4 & Harald Thorwarth 1 Received: 15 April 2020 / Revised: 11 August 2020 / Accepted: 13 August 2020 # The Author(s) 2020
Abstract 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. Keywords Biomass combustion . Particulate matter . Particulate matter filter . Ultrasound cleaning . Emission control . Baghouse filter . Ultrafine dust
1 Introduction Electronic supplementary material The online version of this article (https://doi.org/10.1007/s13399-020-00959-9) contains supplementary material, which is available to authorized users. * Björn Baumgarten [email protected] 1
University of Applied Sciences Rottenburg, Schadenweilerhof, 72 108 Rottenburg am Neckar, Germany
2
LK Metallwaren GmbH, Am Falbenholzweg 36, 91126 Schwabach, Germany
3
Oskar Winkel Filtertechnik, Kaiser-Wilhelm-Ring 30, 92224 Amberg, Germany
4
University of Stuttgart, Pfaffenwaldring 23, 70569 Stuttgart, Germany
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