Browsing by Author "Vogt, Ulrich"

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Open Access
Application of the urban climate model PALM-4U to investigate the effects of the diesel traffic ban on air quality in Stuttgart
(2024) Samad, Abdul; Caballero Arciénega, Ninoska Alejandra; Alabdallah, Talal; Vogt, Ulrich
The air pollution situation in the German city of Stuttgart is very important, as high pollutant concentrations are measured here compared to other German cities. This is mainly due to Stuttgart’s geographical location as it is in a basin covered by hills on three sides. This leads to reduced wind speeds that inhibit pollutant dispersion. One of the main contributors to the pollutant concentrations in Stuttgart is local traffic. To improve the air quality in Stuttgart, a diesel traffic ban was introduced on 1 January 2019, and is ongoing. In this study, the urban climate model PALM-4U was applied to obtain the pollutant distribution along the federal highways B14 and B27 of Stuttgart to evaluate the impact of the diesel traffic ban on air quality. The simulations were carried out in two areas of the city, namely the city center and Kaltental Valley, with domain sizes of 3.2 km × 2 km and 3.2 km × 1.6 km, respectively, and with a grid size of 10 m for each domain. The influence of traffic emissions on the air quality of Stuttgart was studied for a typical summer day. The results showed that air pollutant concentrations were highest near federal highways B14 and B27 (e.g., NO2 concentration peaks of around 200 µg/m3). Also, a significant reduction of around four times in air pollutant concentrations was observed in the study area after the diesel traffic ban was introduced.
Open Access
Assessment of coarse, fine, and ultrafine particles in S-Bahn trains and underground stations in Stuttgart
(2022) Samad, Abdul; Arango, Kathryn; Alvarez Florez, Diego; Chourdakis, Ioannis; Vogt, Ulrich
The Stuttgart S-Bahn network comprises six subway lines and is used by approximately 425,000 people on a daily basis. In previous studies in other cities, it was found that subways can be a source and collection point of particulate matter (PM), which is detrimental to human health. This study focused on making an initial assessment of the pollution situation inside the trains and on the underground platforms. Real-time measurements were performed with high time-resolution instruments inside the S-Bahn trains, two underground stations, and two outdoor stations in the Stuttgart subway network in November 2019. Firstly, the variation in concentration inside the train as it traveled through the tunnel was investigated, and it was recurrently observed that the pollutant concentration in the train increased while traveling through the tunnel and then decreased when nearing the tunnel exit. Secondly, the measurement location with the highest particulate matter concentrations was determined. The particulate matter concentrations on underground platforms were higher than those on the train and on the outdoor platforms. In addition, the dominant fraction of the particulate matter measured was in the range of ultrafine particles (UFP). Finally, the wind speed and wind direction data were analyzed in conjunction with specific locations along the platforms. From the wind measurement results, it was assumed that the combined airflows led to higher particle resuspension and particulate matter concentrations in these areas. In conclusion, it was determined that subway users were exposed to higher particle concentrations, particularly UFP (10-116 nm), while standing on underground platforms and when traveling through underground tunnels. It was found that the PNCs inside the train wagons as well as PM and BC mass concentrations increase when passing through the tunnel. Additionally, the average number concentration of UFPs on underground platforms was significantly higher than in other locations by factors of around 1.7 to 1.9 for UFPs and 1.6 to 2 for coarse and fine particles.
Open Access
Calibration method for particulate matter low-cost sensors used in ambient air quality monitoring and research
(2021) Venkatraman Jagatha, Janani; Klausnitzer, André; Chacón-Mateos, Miriam; Laquai, Bernd; Nieuwkoop, Evert; Mark, Peter van der; Vogt, Ulrich; Schneider, Christoph
Over the last decade, manufacturers have come forth with cost-effective sensors for measuring ambient and indoor particulate matter concentration. What these sensors make up for in cost efficiency, they lack in reliability of the measured data due to their sensitivities to temperature and relative humidity. These weaknesses are especially evident when it comes to portable or mobile measurement setups. In recent years many studies have been conducted to assess the possibilities and limitations of these sensors, however mostly restricted to stationary measurements. This study reviews the published literature until 2020 on cost-effective sensors, summarizes the recommendations of experts in the field based on their experiences, and outlines the quantile-mapping methodology to calibrate low-cost sensors in mobile applications. Compared to the commonly used linear regression method, quantile mapping retains the spatial characteristics of the measurements, although a common correction factor cannot be determined. We conclude that quantile mapping can be a useful calibration methodology for mobile measurements given a well-elaborated measurement plan assures providing the necessary data.
Open Access
Concept of using an Unmanned Aerial Vehicle (UAV) for 3D investigation of air quality in the atmosphere - example of measurements near a roadside
(2022) Samad, Abdul; Florez, Diego Alvarez; Chourdakis, Ioannis; Vogt, Ulrich
Open Access
Contribution of airplane engine emissions on the local air quality around Stuttgart airport during and after COVID-19 lockdown measures
(2022) Samad, Abdul; Arango, Kathryn; Chourdakis, Ioannis; Vogt, Ulrich
Air quality investigations at airports have shown that aircrafts cause a significant increase in air pollution at and around the vicinity of the airport, which can cause adverse effects on human health. The objective of this research was to investigate the aircraft-sourced pollutant levels at the Stuttgart airport and in the surrounding areas during and after COVID-19 lockdown measures. Three phases of stationary measurements of ultrafine particles (UFP), particulate matter (PM), black carbon (BC), CO2, O3, NO, and NO2 were made at various points on the east and west sides of the airport in the extension of the airport runway. In first phase of measurement, the airport was closed for construction, and no air traffic took place. In the second phase, the airport was reopened with limited operation due to a lockdown period at the beginning of the COVID-19 pandemic. Finally, in the third phase, measurements were performed during the peak summer holiday travel season to measure the air quality during maximum air traffic, after the end of the first lockdown period. While there were fewer notable changes in the BC concentrations, coarse PM fractions, and gases across the three phases, there were significant increases in the UFP concentrations from aircraft emissions. Throughout the three phases, the peak particle concentration decreased from between 27 and 86 nm in phase 1. to between 27 and 35 nm in phase 2, to finally 11 nm in phase 3 on all days in which the aircraft plumes were measured. During flight arrivals, definite increases in UFP particle number concentration (PNC) were observed, with the majority of the particles being in the 10 nm size class. These results were measured repeatedly on both sides of the airport in the direct prolongation of the runway and even at distances of up to 3 km away in nearby neighbouring communities. While the overall PM and UFP levels are affected by vehicular traffic, the freeway measurements showed particles from aircrafts and vehicles are distinguishable using the parameters PNC and Dp. The BC concentrations were rarely influenced by aircraft activity, while only some NO and NO2 peaks were measured depending on the consistency of the wind.
Open Access
Developing a cloud-based air quality monitoring platform using low-cost sensors
(2024) Samad, Abdul; Kieser, Joschka; Chourdakis, Ioannis; Vogt, Ulrich
Conventional air quality monitoring has been traditionally carried out in a few fixed places with expensive measuring equipment. This results in sparse spatial air quality data, which do not represent the real air quality of an entire area, e.g., when hot spots are missing. To obtain air quality data with higher spatial and temporal resolution, this research focused on developing a low-cost network of cloud-based air quality measurement platforms. These platforms should be able to measure air quality parameters including particulate matter (PM10, PM2.5, PM1) as well as gases like NO, NO2, O3, and CO, air temperature, and relative humidity. These parameters were measured every second and transmitted to a cloud server every minute on average. The platform developed during this research used one main computer to read the sensor data, process it, and store it in the cloud. Three prototypes were tested in the field: two of them at a busy traffic site in Stuttgart, Marienplatz and one at a remote site, Ötisheim, where measurements were performed near busy railroad tracks. The developed platform had around 1500 € in materials costs for one Air Quality Sensor Node and proved to be robust during the measurement phase. The notion of employing a Proportional-Integral-Derivative (PID) controller for the efficient working of a dryer that is used to reduce the negative effect of meteorological parameters such as air temperature and relative humidity on the measurement results was also pursued. This is seen as one way to improve the quality of data captured by low-cost sensors.
Open Access
Evaluation of a low-cost dryer for a low-cost optical particle counter
(2022) Chacón-Mateos, Miriam; Laquai, Bernd; Vogt, Ulrich; Stubenrauch, Cosima
The use of low-cost sensors for air quality measurements has become very popular in the last few decades. Due to the detrimental effects of particulate matter (PM) on human health, PM sensors like photometers and optical particle counters (OPCs) are widespread and have been widely investigated. The negative effects of high relative humidity (RH) and fog events in the mass concentration readings of these types of sensors are well documented. In the literature, different solutions to these problems - like correction models based on the Köhler theory or machine learning algorithms - have been applied. In this work, an air pre-conditioning method based on a low-cost thermal dryer for a low-cost OPC is presented. This study was done in two parts. The first part of the study was conducted in the laboratory to test the low-cost dryer under two different scenarios. In one scenario, the drying efficiency of the low-cost dryer was investigated in the presence of fog. In the second scenario, experiments with hygroscopic aerosols were done to determine to which extent the low-cost dryer reverts the growth of hygroscopic particles. In the second part of the study, the PM10 and PM2.5 mass concentrations of an OPC with dryer were compared with the gravimetric measurements and a continuous federal equivalent method (FEM) instrument in the field. The feasibility of using univariate linear regression (ULR) to correct the PM data of an OPC with dryer during field measurement was also evaluated. Finally, comparison measurements between an OPC with dryer, an OPC without dryer, and a FEM instrument during a real fog event are also presented. The laboratory results show that the sensor with the low-cost dryer at its inlet measured an average of 64 % and 59 % less PM2.5 concentration compared with a sensor without the low-cost dryer during the experiments with fog and with hygroscopic particles, respectively. The outcomes of the PM2.5 concentrations of the low-cost sensor with dryer in laboratory conditions reveal, however, an excess of heating compared with the FEM instrument. This excess of heating is also demonstrated in a more in-depth study on the temperature profile inside the dryer. The correction of the PM10 concentrations of the sensor with dryer during field measurements by using ULR showed a reduction of the maximum absolute error (MAE) from 4.3 µg m-3 (raw data) to 2.4 µg m-3 (after correction). The results for PM2.5 make evident an increase in the MAE after correction: from 1.9 µg m−3 in the raw data to 3.2 µg m−3. In light of these results, a low-cost thermal dryer could be a cost-effective add-on that could revert the effect of the hygroscopic growth and the fog in the PM readings. However, special care is needed when designing a low-cost dryer for a PM sensor to produce FEM similar PM readings, as high temperatures may irreversibly change the sampled air by evaporating the most volatile particulate species and thus deliver underestimated PM readings. New versions of a low-cost dryer aiming at FEM measurements should focus on maintaining the RH at the sensor inlet at 50 % and avoid reaching temperatures higher than 40 ∘C in the drying system. Finally, we believe that low-cost dryers have a very promising future for the application of sensors in citizen science, sensor networks for supplemental monitoring, and epidemiological studies.
Open Access
Evaluation of a metal mesh filter prototype with wet regeneration
(2021) Baumgarten, Björn; Grammer, Peter; Ehard, Ferdinand; Winkel, Oskar; Vogt, Ulrich; Baumbach, Günter; Scheffknecht, Günter; Thorwarth, Harald
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.
Open Access
Feasibility study on the use of NO2 and PM2.5 sensors for exposure assessment and indoor source apportionment at fixed locations
(2024) Chacón-Mateos, Miriam; Remy, Erika; Liebers, Uta; Heimann, Frank; Witt, Christian; Vogt, Ulrich
Recent advances in sensor technology for air pollution monitoring open new possibilities in the field of environmental epidemiology. The low spatial resolution of fixed outdoor measurement stations and modelling uncertainties currently limit the understanding of personal exposure. In this context, air quality sensor systems (AQSSs) offer significant potential to enhance personal exposure assessment. A pilot study was conducted to investigate the feasibility of the NO2 sensor model B43F and the particulate matter (PM) sensor model OPC-R1, both from Alphasense (UK), for use in epidemiological studies. Seven patients with chronic obstructive pulmonary disease (COPD) or asthma had built-for-purpose sensor systems placed inside and outside of their homes at fixed locations for one month. Participants documented their indoor activities, presence in the house, window status, and symptom severity and performed a peak expiratory flow test. The potential inhaled doses of PM2.5 and NO2 were calculated using different data sources such as outdoor data from air quality monitoring stations, indoor data from AQSSs, and generic inhalation rates (IR) or activity-specific IR. Moreover, the relation between indoor and outdoor air quality obtained with AQSSs, an indoor source apportionment study, and an evaluation of the suitability of the AQSS data for studying the relationship between air quality and health were investigated. The results highlight the value of the sensor data and the importance of monitoring indoor air quality and activity patterns to avoid exposure misclassification. The use of AQSSs at fixed locations shows promise for larger-scale and/or long-term epidemiological studies.
Open Access
Ganzheitliche Bewertung von Holzheizungen
(Stuttgart : Zentrum für Energieforschung Stuttgart, 2016) Huang, Ganlin; Schmid, Dorothea; Friedrich, Rainer; Vogt, Ulrich; Mahami, Golnoosh; Struschka, Michael; Juschka, Winfried
Holzfeuerungen emittieren nur wenige Treibhausgasemissionen, aber erhebliche Mengen an Feinstaub und Stickoxiden. Überwiegen die Vorteile des Klimaschutzes die Nachteile, nämlich die Gesundheitsrisiken durch die Luftschadstoffbelastung? Um dies zu klären, werden die sozialen Kosten, also die Summe aus Kosten, monetarisierten Klimaschäden und monetarisierten Gesundheitsschäden von Holzheizungen denen von Erdgas- und Ölheizungen gegenübergestellt. Es zeigt sich, dass in Stuttgart - als Beispiel für eine Großstadt -, Erdgas- und Ölheizungen niedrigere soziale Kosten aufweisen als Holz- und Pelletfeuerungen, selbst wenn diese mit Partikelfiltern versehen wären; in Städten sollten Holzfeuerungen daher nicht verwendet werden. Auf dem Land weisen dagegen mit Partikelfiltern versehene Holzheizungen günstigere soziale Kosten auf als Feuerungen für fossile Brennstoffe.
Open Access
Investigating a low-cost dryer designed for low-cost PM sensors measuring ambient air quality
(2021) Samad, Abdul; Melchor Mimiaga, Freddy Ernesto; Laquai, Bernd; Vogt, Ulrich
Air pollution in urban areas is a huge concern that demands an efficient air quality control to ensure health quality standards. The hotspots can be located by increasing spatial distribution of ambient air quality monitoring for which the low-cost sensors can be used. However, it is well-known that many factors influence their results. For low-cost Particulate Matter (PM) sensors, high relative humidity can have a significant impact on data quality. In order to eliminate or reduce the impact of high relative humidity on the results obtained from low-cost PM sensors, a low-cost dryer was developed and its effectiveness was investigated. For this purpose, a test chamber was designed, and low-cost PM sensors as well as professional reference devices were installed. A vaporizer regulated the humid conditions in the test chamber. The low-cost dryer heated the sample air with a manually adjustable intensity depending on the voltage. Different voltages were tested to find the optimum one with least energy consumption and maximum drying efficiency. The low-cost PM sensors with and without the low-cost dryer were compared. The experimental results verified that using the low-cost dryer reduced the influence of relative humidity on the low-cost PM sensor results.
Open Access
Messung und Bewertung der Schadstoffemissionen von Holzfeuerungen in Innenräumen
(Stuttgart : Universität Stuttgart, Institut für Energiewirtschaft und Rationelle Energieanwendung, 2019) Li, Naixin; Huang, Ganlin; Friedrich, Rainer; Vogt, Ulrich; Schürmann, Stefan; Straub, Dieter
Holzöfen in Wohnräumen verursachen nicht nur Emissionen von Schadstoffen über den Schornstein in die Außenluft, vielmehr tragen sie auch zur Schadstoffkonzentration in Innenräumen bei. Diese gelangen insbesondere beim Öffnen der Ofentür beim Anfeuern oder beim Nachlegen von Holzscheiten in die Innenraumluft. Allerdings liegen hierfür bisher noch keine Emissionsfaktoren vor. In diesem Bericht werden Ergebnisse von Messungen an einem modernen Holzofen vorgestellt, die die Emissionen von Feinstaub (PM1, PM2.5, PM10, UFP) und Stickoxiden für Prozesse wie Anfeuern und Nachlegen mit verschiedenen Türöffnungsgeschwindigkeiten repräsentieren. Mit den so gewonnenen Emissionsfaktoren werden dann die entstehenden Gesundheitsschäden ermittelt und monetarisiert. Wird nur mit Holzöfen geheizt, steigen die Gesundheitsrisiken durch Feinstaub um ca. 5%, bei gelegentlicher Nutzung des Holzofens ergibt sich ein um ca. 1% höheres Risiko.
Open Access
Meteorological and air quality measurements in a city region with complex terrain : influence of meteorological phenomena on urban climate
(2023) Samad, Abdul; Kiseleva, Olga; Holst, Christopher Claus; Wegener, Robert; Kossmann, Meinolf; Meusel, Gregor; Fiehn, Alina; Erbertseder, Thilo; Becker, Ralf; Roiger, Anke; Stanislawsky, Peter; Klemp, Dieter; Emeis, Stefan; Kalthoff, Norbert; Vogt, Ulrich
Open Access
Methode zur Bilanzierung von Luftverunreinigungen anhand von Vertikal- und Horizontalprofilmessungen
(2010) Vogt, Ulrich; Baumbach, Günter (Prof. Dr.-Ing. habil.)
Ziel dieser Arbeit ist es, eine Methode zu beschreiben, mit deren Hilfe die in einem Untersu-chungsgebiet freigesetzten Emissionen von Luftverunreinigungen durch Messungen in der Außenluft bestimmt werden können. Mit Hilfe von Vertikal- und Horizontalprofilmessungen konnten die Konzentrationsverteilungen im Luv und Lee von Emissionsquellen bestimmt werden. Die Messergebnisse wurden verwendet, um aus den Konzentrationsdifferenzen zu-sammen mit Messergebnissen von meteorologischen Parametern die Massenströme der be-trachteten Luftverunreinigungen zu berechnen und eine Massenbilanz für ein Untersuchungs-gebiet aufzustellen. Auf diese Weise konnten die in den Untersuchungsgebieten freigesetzten Emissionen messtechnisch bestimmt und gleichzeitig durchgeführte Emissionsmodellrech-nungen validiert werden. Die Validierung ist wichtig, da Emissionsmodellierungen in der Luftreinhaltung immer häufiger eingesetzt werden. Einerseits gehen die modellierten Emissi-onen als Eingangsdaten in die immer häufiger verwendeten Ausbreitungsmodellierungen ein, andererseits werden sie auch für Emissionsminderungsszenarien verwendet. Aufgrund der sehr weitreichenden politischen und finanziellen Folgen der Verwendung dieser Emissionsda-ten, ist eine Überprüfung der Richtigkeit der berechneten Emissionen unumgänglich. In dieser Arbeit wurden die Ergebnisse von zwei Experimenten zur Beschreibung der Bilan-zierungsmethode herangezogen. Im ersten Projekt wurde erstmals die Bilanzierung aller frei-gesetzten Luftverunreinigungen einer ganzen Stadt durchgeführt. Es wurden über mehrere Monate Konzentrationsmessungen in und um Augsburg vorgenommen. Die vertikale und ho-rizontale Verteilung der Luftverunreinigungen und der meteorologischen Parameter wurden im Luv und Lee der Stadt mit Hilfe von drei Fesselballonmesssystemen, einem ferngesteuer-ten Luftschiff, zwei Messflugzeugen und weiterer Messtechnik bestimmt. Für den gleichen Zeitraum wurde ein zeitlich, räumlich und stofflich hochaufgelöstes Emissionskataster für die Stadt erstellt. Anschließend wurden die gemessenen und bilanzierten Emissionen mit den mo-dellierten Emissionen verglichen und somit das Emissionsmodell validiert. Die Fesselballon- und Luftschiffmessungen wurden vom IFK bzw. mit Unterstützung des IFK durchgeführt. Die großen Vorteile von Fesselballon- und Luftschiffmessungen haben sich auch bei diesem Experiment bewährt. Allerdings hat sich im Projekt EVA auch herausgestellt, dass eine Stadt wie Augsburg mit ihren ca. 255.000 Einwohnern eine horizontal sehr ausgedehnte Abgasfahne besitzt, die es gilt messtechnisch möglichst komplett zu erfassen. Für eine Stadt dieser Größe reichten die Fesselballon- und Luftschiffmessungen alleine nicht aus, um die ca. 9 km breite Abgasfahne in ausreichender Messdichte zu erfassen. Die Kombination dieser beiden Messsysteme mit Flugzeugmessungen hat sich jedoch zur Erfassung der gesamten Abluftfahne sehr gut bewährt. Der Vergleich der messtechnisch bestimmten mit den model-lierten NOx-Emissionen ergab für die meisten Daten, die sich für eine Auswertung eigneten, eine Übereinstimmung, wenn auch die modellierten Emissionen stets über den auf Messungen beruhenden lagen. Allerdings waren die Unsicherheiten, die sowohl bei den Messungen als auch bei den Berechnungsmethoden und den Emissionsmodellierungen anzusetzen waren, teilweise hoch. Im zweiten Projekt fanden intensive Messungen und Untersuchungen an einer Autobahn statt. Der Vergleich der über die Vertikalprofilmessungen bestimmten NOx-Emissionsfaktoren mit den NOx-Emissionsfaktoren, die über das Emissionsmodell bestimmt wurden, ergab deutliche Abweichungen. Besonders für den Schwerverkehr (HDV) lagen die gemessenen Emissions-faktoren zwischen 20 und fast 100 % über den modellierten Emissionsfaktoren, die auf dem Handbuch für Emissionsfaktoren (HBEFA Version 1.2) basierten. Aufgrund dieser Erkennt-nisse wurden die Emissionsfaktoren für den Schwerverkehr (HDV) angepasst und liegen nun in der aktuellen Version 2.1 entsprechend höher. Der Vergleich der VOC-Emissionsfaktoren ergab sehr gute Übereinstimmung für die Komponenten BTX – Benzol, Toluol, Xylole - da für diese Komponenten den Emissionsmodellen genügend Messdaten zugrunde liegen. Für weitere VOC-Komponenten traten teilweise sehr große Abweichungen zwischen den gemes-senen und den modellierten Emissionsfaktoren auf, wobei die gemessenen Emissionsfaktoren grundsätzlich höher ausfielen als die modellierten. Die Abweichungen lagen für manche Komponenten im Bereich von Faktor sechs bis 20! Der Grund ist in der dünnen Datenlage für die für die Emissionsmodellierung zur Verfügung stehenden VOC-Emissionsfaktoren zu su-chen. Alle Partikel-Emissionsfaktoren, die im Projekt BAB II bestimmt wurden, lagen in der gleichen Größenordnung wie die zum Vergleich verfügbaren Literaturwerte. Für die aktive Partikeloberfläche lagen die im Projekt BAB II ermittelten Werte etwas über den Literatur-werten, für alle anderen berechneten und verglichenen Partikelparameter lagen die im Projekt BAB II ermittelten Emissionsfaktoren innerhalb der maximalen und minimalen Vergleichs-werte. Der Vergleich der Emissionsfaktoren von Rußpartikeln ergab eine sehr gute Übereinstimmung sowohl im direkten Vergleich der Messergebnisse mit den Ergebnissen der Emissions-modellierung im Projekt BAB II als auch im Vergleich mit Literaturwerten.
Open Access
Novel metal mesh filter using water-based regeneration for small-scale biomass boilers
(2020) Baumgarten, Björn; Grammer, Peter; Ehard, Ferdinand; Winkel, Oskar; Vogt, Ulrich; Baumbach, Günter; Scheffknecht, Günter; Thorwarth, Harald
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.
Open Access
Particulate matter profiles along the rack railway route using low-cost sensor
(2021) Samad, Abdul; Maali, Anas; Laquai, Bernd; Vogt, Ulrich
Air pollution due to Particulate Matter (PM) is an increasing concern of global extent. It has been the focus of many research projects worldwide and the latest low-cost technology is offering an ease and cheap way to monitor PM concentration. In this research, a low-cost PM monitoring platform was built with the objectives of evaluating its feasibility and its performance in mobile measurements, as well as characterizing the concentration profiles of PM along the measurement route. The rack railway in Stuttgart was utilized as means of transportation for this low-cost monitoring system with which the temporal and spatial distribution of the PM10, PM2.5 and PM1 concentration along the route was attained. The measurements were conducted for around two months from mid of January until mid of March 2019, during the operation hours of the rack railway. The results showed that the PM concentrations were dominated by fine particulate matter (PM2.5 and PM1) along the route of the rack railway. Higher PM concentrations were measured near the federal highway and high traffic area as compared to the residential area. An overestimation of PM concentration using low-cost sensor platform was observed during high relative humidity conditions as compared to the professional aerosol spectrometers.