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Ashes from biomass heat (and power) plants that apply untreated woody biofuels may be suitable for use as fertilizers if certain requirements regarding pollutant and nutrient contents are met. The aim of this study was to examine if both bottom and cyclone ashes from 17 Bavarian heating plants and one ash collection depot are suitable as fertilizers (n = 50). The range and average values of relevant nutrients and pollutants in the ashes were analyzed and evaluated for conformity with the German Fertilizer Ordinance (DüMV). Approximately 30% of the bottom ashes directly complied with the heavy metal limits of the Fertilizer Ordinance. The limits were exceeded for chromium(VI) (62%), cadmium (12%) and lead (4%). If chromium(VI) could be reduced by suitable treatment, 85% of the bottom ashes would comply with the required limit values. Cyclone ashes were high in cadmium, lead, and zinc. The analysis of the main nutrients showed high values for potassium and calcium in bottom ashes, but also relevant amounts of phosphorus, making them suitable as fertilizers if pollutant limits are met. Quality assurance systems should be applied at biomass heating plants to improve ash quality if wood ashes are used as fertilizers in agriculture.
Hans Bachmaier; Daniel Kuptz; Hans Hartmann. Wood Ashes from Grate-Fired Heat and Power Plants: Evaluation of Nutrient and Heavy Metal Contents. Sustainability 2021, 13, 5482 .
AMA StyleHans Bachmaier, Daniel Kuptz, Hans Hartmann. Wood Ashes from Grate-Fired Heat and Power Plants: Evaluation of Nutrient and Heavy Metal Contents. Sustainability. 2021; 13 (10):5482.
Chicago/Turabian StyleHans Bachmaier; Daniel Kuptz; Hans Hartmann. 2021. "Wood Ashes from Grate-Fired Heat and Power Plants: Evaluation of Nutrient and Heavy Metal Contents." Sustainability 13, no. 10: 5482.
Air pressure resistance during ventilation was measured experimentally for a high variety of conventional wood chip samples that had been produced using various raw materials, chippers and chipper settings (n = 95). Physical fuel properties such as bulk density or particle size distribution were determined according to international standards for solid biofuels. In addition, particle length and particle shape were determined using a continuously measuring image analysis device. Pressure resistance (in Pa m−1) was determined using a custom-built flow cylinder (2 m height, 0.4 m3 filling volume) and related to air flow rate. Pressure resistance increased exponentially with air flow rate for all samples. Thereby, pressure resistance was highly variable among wood chip samples, ranging from 10 to 107 Pa m−1 at low air flow rates (0.1 m3 s−1 m−2) and from 197 to 1240 Pa m−1 at higher air flow rates (0.5 m3 s−1 m−2). Four common equations to describe pressure resistance (Ramsin, Shedd, Hukill & Ives, Ergun) were compared. Multiple linear regression analysis was applied to express pressure resistance as a function of selected fuel quality parameters. Sensitivity analyses of the resulting equations were performed. Results indicate that pressure resistance strongly depends on bulk density, particle size and particle shape as these parameters determine the number, size and shape of free air voids within wood chip fillings.
Daniel Kuptz; Hans Hartmann. Prediction of air pressure resistance during the ventilation of wood chips as a function of multiple physical fuel parameters. Biomass and Bioenergy 2021, 145, 105948 .
AMA StyleDaniel Kuptz, Hans Hartmann. Prediction of air pressure resistance during the ventilation of wood chips as a function of multiple physical fuel parameters. Biomass and Bioenergy. 2021; 145 ():105948.
Chicago/Turabian StyleDaniel Kuptz; Hans Hartmann. 2021. "Prediction of air pressure resistance during the ventilation of wood chips as a function of multiple physical fuel parameters." Biomass and Bioenergy 145, no. : 105948.
Aerobic and anaerobic storage of wood chips from coniferous forest residues, coniferous energy roundwood and short rotation coppice were investigated regarding dry matter losses, energy losses and changes in fuel properties using several approaches, i.e. a field trial with 90 m3 wood chip piles, small-scale storage containers (0.5 m3) incl. greenhouse gas measurements and miniature bunker silos (1.5–2 m3). After storage, selected fuels were combusted in a 30 kW wood chip boiler and emissions (CO, NOX, TPM) were measured. Dry matter losses in fleece-covered piles were 7%–9% after 153 days of storage. Drying compensated for energy losses. Container trials achieved full anaerobic conditions in the lab reducing dry matter losses to 0.4–2% while preserving fuel properties. Methane emissions during anaerobic storage in containers were low. Anaerobic conditions could not be achieved in outdoor bunker silos due to insufficient airtightness. The mass fraction of H2O in fuels increased in bunker silos by 4.2–10.4% due to precipitation and dry matter losses up to 22% were recorded. During combustion, CO and TPM emissions were often increased significantly with materials that were stored in silos or piles compared to technically dried fuels, most likely due to changes in their woody or physical-mechanical structure and their mass fraction of H2O. Anaerobic storage might in theory be an interesting option to reduce dry matter losses but could not sufficiently be realized during this study using miniature bunker silos. For many applications, aerobic storage in fleece-covered piles seems preferable to anaerobic storage.
Daniel Kuptz; Simon Lesche; Theresa Mendel; Robert Mack; Elisabeth Rist; Claudia Schön; Hans Hartmann. Fuel properties, dry matter losses and combustion behavior of wood chips stored at aerobic and anaerobic conditions. Biomass and Bioenergy 2020, 142, 105745 .
AMA StyleDaniel Kuptz, Simon Lesche, Theresa Mendel, Robert Mack, Elisabeth Rist, Claudia Schön, Hans Hartmann. Fuel properties, dry matter losses and combustion behavior of wood chips stored at aerobic and anaerobic conditions. Biomass and Bioenergy. 2020; 142 ():105745.
Chicago/Turabian StyleDaniel Kuptz; Simon Lesche; Theresa Mendel; Robert Mack; Elisabeth Rist; Claudia Schön; Hans Hartmann. 2020. "Fuel properties, dry matter losses and combustion behavior of wood chips stored at aerobic and anaerobic conditions." Biomass and Bioenergy 142, no. : 105745.
Wood chip quality is essential for failure-free and low-emission combustion in automatically stoked small-scale biomass boilers (< 100 kW). Screening and drying of wood chips might be suitable to reduce fuel heterogeneity and to guarantee defined qualities according to ISO 17225-4. Six case studies on screening and drying of forest residue wood chips were performed at German biomass terminals. Screening was done using drum, star, or jigger screens. Drying was done in storage piles and in rolling bed, walking floor, belt, and batch container dryer. Throughput rate was assessed on-site. Fuel properties were analyzed according to international standards. Moisture content of fresh wood chips was too high for small-scale biomass boilers (up to 51 w-%). Raw materials did not comply with specifications of ISO 17225-4 (i.e., ash content, particle size) while fuel indices (Fe/Mn, Al/200) implied contamination with soil material. Technical drying provided moisture contents ≤ 15 w-% while natural drying in piles resulted in values often exceeding 35 w-%. Screening reduced ash content, fines, oversized particles, and the share of N, S, Cl, K, and Si. Screening of pre-dried fuels seems to be beneficial compared to screening of fresh wood chips. After processing, chips could usually be classified as specification A2 to B1 according to ISO 17225-4.
Daniel Kuptz; Kathrin Schreiber; Fabian Schulmeyer; Simon Lesche; Thomas Zeng; Finn Ahrens; Volker Zelinski; Claudia Schön; Annett Pollex; Herbert Borchert; Volker Lenz; Achim Loewen; Michael Nelles; Hans Hartmann. Evaluation of combined screening and drying steps for the improvement of the fuel quality of forest residue wood chips—results from six case studies. Biomass Conversion and Biorefinery 2019, 9, 83 -98.
AMA StyleDaniel Kuptz, Kathrin Schreiber, Fabian Schulmeyer, Simon Lesche, Thomas Zeng, Finn Ahrens, Volker Zelinski, Claudia Schön, Annett Pollex, Herbert Borchert, Volker Lenz, Achim Loewen, Michael Nelles, Hans Hartmann. Evaluation of combined screening and drying steps for the improvement of the fuel quality of forest residue wood chips—results from six case studies. Biomass Conversion and Biorefinery. 2019; 9 (1):83-98.
Chicago/Turabian StyleDaniel Kuptz; Kathrin Schreiber; Fabian Schulmeyer; Simon Lesche; Thomas Zeng; Finn Ahrens; Volker Zelinski; Claudia Schön; Annett Pollex; Herbert Borchert; Volker Lenz; Achim Loewen; Michael Nelles; Hans Hartmann. 2019. "Evaluation of combined screening and drying steps for the improvement of the fuel quality of forest residue wood chips—results from six case studies." Biomass Conversion and Biorefinery 9, no. 1: 83-98.
Nicolas Hofmann; Theresa Mendel; Fabian Schulmeyer; Daniel Kuptz; Herbert Borchert; Hans Hartmann. Drying effects and dry matter losses during seasonal storage of spruce wood chips under practical conditions. Biomass and Bioenergy 2018, 111, 196 -205.
AMA StyleNicolas Hofmann, Theresa Mendel, Fabian Schulmeyer, Daniel Kuptz, Herbert Borchert, Hans Hartmann. Drying effects and dry matter losses during seasonal storage of spruce wood chips under practical conditions. Biomass and Bioenergy. 2018; 111 ():196-205.
Chicago/Turabian StyleNicolas Hofmann; Theresa Mendel; Fabian Schulmeyer; Daniel Kuptz; Herbert Borchert; Hans Hartmann. 2018. "Drying effects and dry matter losses during seasonal storage of spruce wood chips under practical conditions." Biomass and Bioenergy 111, no. : 196-205.
Fuel qualities of wood chips and energy consumption during their production vary depending on raw materials and machine settings. Thereby, requirements for small combustion units <1 MW are rarely met. Therefore, the effects of raw material and machine settings on chipping performance were investigated in numerous field trials (n = 34). Raw materials were derived from different tree parts of various species (forest residues and “energy round wood,” i.e. small-sized delimbed stem wood). Chipper settings varied in knife sharpness, screen size and discharge systems. All samples were analyzed following European standards. In addition, particle size distribution and particle shape were analyzed using a continuously measuring image analysis device. Classification followed ISO standards 17225-1 and 17225-4. Fuel consumption during chipping was measured and related to volume and weight of the bulk material. Ash content of wood chips ranged from 0.4–1.7 weight.-% (w.-% dry basis) for energy round wood and from 1.0–5.4 w.-% for forest residues. Particle size distribution of all samples could be classified according to ISO 17225-1 but only 30% could be classified according to ISO 17225-4. These requirements were often met when using energy round wood and sharp knives. Moreover, particle shape strongly related to knife sharpness. Specific fuel consumption during chipping ranged from 0.17–0.70 litres per m3 bulk volume and was high for forest residues, small screen sizes or blunt knives. Overall energy consumption of the chipping process was <1% of the energy stored within the produced bulk material.
Daniel Kuptz; Hans Hartmann. The effect of raw material and machine setting on chipping performance and fuel quality – a German case study. International Journal of Forest Engineering 2015, 26, 60 -70.
AMA StyleDaniel Kuptz, Hans Hartmann. The effect of raw material and machine setting on chipping performance and fuel quality – a German case study. International Journal of Forest Engineering. 2015; 26 (1):60-70.
Chicago/Turabian StyleDaniel Kuptz; Hans Hartmann. 2015. "The effect of raw material and machine setting on chipping performance and fuel quality – a German case study." International Journal of Forest Engineering 26, no. 1: 60-70.