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Øyvind Skreiberg - One of the best experts on this subject based on the ideXlab platform.
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Drying of Thermally Thick Wood Particles: A Study of the Numerical Efficiency, Accuracy, and Stability of Common Drying Models
Energy & Fuels, 2017Co-Authors: Inge Haberle, Nils Erland L. Haugen, Øyvind SkreibergAbstract:The primary focus of this paper is on studying different numerical models for Drying of wet wood particles. More specifically, the advantages and disadvantages of the models, with respect to numerical efficiency, stability, and accuracy, are investigated. The two basic models that are studied in detail are the Thermal Drying model and the kinetic rate Drying model. The Drying models have been implemented in an in-house simulation tool that solves for Drying and devolatilization of a one-dimensional cylindrical wood log. It is found that the choice of Drying model can significantly influence the computational time associated with the Thermal conversion. Furthermore, the occurrence of numerical pressure oscillations in the Thermal Drying model has been found and investigated. The numerical oscillations are reduced by introducing an evaporation fraction, fevap. When the Thermal Drying model is applied, the Drying zone is very thin, commonly only including one grid point, which can result in numerical instabi...
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Comparison of numerical efficiency of the Thermal and the kinetic rate Drying model applied to a Thermally thick wood particle
Energy Procedia, 2017Co-Authors: Inge Haberle, Nils Erland L. Haugen, Øyvind SkreibergAbstract:Abstract In this work, the Drying and devolatilization of a Thermally thick wood particle were modeled. The work was validated against experiments and good agreement was found. The work compared the numerical efficiency and accuracy of the Thermal Drying model and the kinetic rate Drying model. The Thermal Drying model was used with a fixed boiling temperature (373 K). The kinetic data for the kinetic rate Drying model was taken from an earlier work by Di Blasi [1] and additionally one set of kinetic data that was also tested, was assumed by the authors, with the main purpose of reducing the stiffness of the evaporation equation. The numerical efficiency was compared by comparing the CPU times associated with the different Drying models. It was found that the Thermal Drying model is the most efficient Drying model at both high and low moisture contents. Soft Drying kinetics resulted in intermediate CPU times, while very stiff kinetics yielded the lowest numerical efficiency. No trend was observed regarding how CPU times of the different Drying models behave with respect to increasing or decreasing moisture contents.
Inge Haberle - One of the best experts on this subject based on the ideXlab platform.
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Drying of Thermally Thick Wood Particles: A Study of the Numerical Efficiency, Accuracy, and Stability of Common Drying Models
Energy & Fuels, 2017Co-Authors: Inge Haberle, Nils Erland L. Haugen, Øyvind SkreibergAbstract:The primary focus of this paper is on studying different numerical models for Drying of wet wood particles. More specifically, the advantages and disadvantages of the models, with respect to numerical efficiency, stability, and accuracy, are investigated. The two basic models that are studied in detail are the Thermal Drying model and the kinetic rate Drying model. The Drying models have been implemented in an in-house simulation tool that solves for Drying and devolatilization of a one-dimensional cylindrical wood log. It is found that the choice of Drying model can significantly influence the computational time associated with the Thermal conversion. Furthermore, the occurrence of numerical pressure oscillations in the Thermal Drying model has been found and investigated. The numerical oscillations are reduced by introducing an evaporation fraction, fevap. When the Thermal Drying model is applied, the Drying zone is very thin, commonly only including one grid point, which can result in numerical instabi...
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Comparison of numerical efficiency of the Thermal and the kinetic rate Drying model applied to a Thermally thick wood particle
Energy Procedia, 2017Co-Authors: Inge Haberle, Nils Erland L. Haugen, Øyvind SkreibergAbstract:Abstract In this work, the Drying and devolatilization of a Thermally thick wood particle were modeled. The work was validated against experiments and good agreement was found. The work compared the numerical efficiency and accuracy of the Thermal Drying model and the kinetic rate Drying model. The Thermal Drying model was used with a fixed boiling temperature (373 K). The kinetic data for the kinetic rate Drying model was taken from an earlier work by Di Blasi [1] and additionally one set of kinetic data that was also tested, was assumed by the authors, with the main purpose of reducing the stiffness of the evaporation equation. The numerical efficiency was compared by comparing the CPU times associated with the different Drying models. It was found that the Thermal Drying model is the most efficient Drying model at both high and low moisture contents. Soft Drying kinetics resulted in intermediate CPU times, while very stiff kinetics yielded the lowest numerical efficiency. No trend was observed regarding how CPU times of the different Drying models behave with respect to increasing or decreasing moisture contents.
Athanasios A Koutinas - One of the best experts on this subject based on the ideXlab platform.
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Novel Technology Development through Thermal Drying of Encapsulated Kluyveromyces marxianus in Micro- and Nano-tubular Cellulose in Lactose Fermentation and Its Evaluation for Food Production
Applied Biochemistry and Biotechnology, 2012Co-Authors: Harris Papapostolou, Yiannis Servetas, Loulouda A. Bosnea, Maria Kanellaki, Athanasios A KoutinasAbstract:A novel technology development based on the production of a low-cost starter culture for ripening of cheeses and baking is reported in the present study. The starter culture comprises Thermally dried cells of Kluyveromyces marxianus encapsulated in micro- and nano-tubular cellulose. For production of a low-cost and effective biocatalyst, whey was used as raw material for biomass production and Thermal Drying methods (convective, conventional, and vacuum) were applied and evaluated at Drying temperatures ranging from 35 to 60 °C. The effect of Drying temperature of biocatalysts on fermentability of lactose and whey was evaluated. Storage stability and suitability of biocatalysts as a commercial starter cultures was also assessed and evaluated. All Thermally dried biocatalysts were found to be active in lactose and whey fermentation. In all cases, there was sugar conversion ranging from 92 to 100 %, ethanol concentration of up to 1.47 % ( v / v ), and lactic acid concentrations ranged from 4.1 to 5.5 g/l. However, convective Drying of the encapsulated cells of K. marxianus in micro- and nano-tubular cellulose was faster and a more effective Drying method while Drying at 42 °C appear to be the best Drying temperature in terms of cell activity, ethanol, and lactic acid formation. Storage of the biocatalysts for 3 months at 4 °C proved maintenance of its activity even though fermentation times increased by 50–100 % compared with the fresh dried ones.
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Thermal Drying of Lactobacillus delbrueckii subsp. bulgaricus and its Efficient Use as Starter for Whey Fermentation and Unsalted Cheese Making
Applied Biochemistry and Biotechnology, 2010Co-Authors: Eleftheria Katechaki, Argyro Bekatorou, Theodoros Solomonidis, Athanasios A KoutinasAbstract:Lactobacillus bulgaricus grown on whey was dried by a simple Thermal Drying method at the range 35–55°C and its efficiency for lactic acid fermentation of whey was evaluated. Drying of cells in whey suspension in the examined temperature range did not affect significantly their viability (82–87% survival), indicating a protective effect of whey as both growth and Drying medium. The kinetics of fermentation of whey and mixtures of whey/molasses using the dried culture were comparable to those of non-dried cells, and only low pH had a detrimental effect on the fermentation ability of the dried cells. Furthermore, dried L. bulgaricus , free or immobilized on casein coagulates, was used as starter for the production of unsalted hard-type cheese. The effects of the amount of starter culture and the immobilization technique, the evolution of microbial counts, and the sensory properties of the produced cheeses were evaluated during ripening at various temperatures.
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fermentation efficiency of cells immobilized on delignified brewers spent grains after low and high temperature thin layer Thermal Drying
Applied Biochemistry and Biotechnology, 2010Co-Authors: Konstantina Tsaousi, Argyro Bekatorou, Athanasios A Koutinas, Paul LoukatosAbstract:Low-cost dried yeasts immobilized on delignified brewers' spent grains for use in wine making and brewing were produced by simple Thermal Drying techniques. To optimize the Thermal Drying process, vacuum and air stream conditions were examined. Drying of thin layers of the biocatalysts was performed at low (30–38 °C) and high temperatures (40–70 °C). The fermentation efficiency of the Thermally dried biocatalysts was acceptable, with immobilized cells showing a significantly higher thermotolerance compared with free cells. Immobilized cells dried at high temperatures presented slightly improved glucose fermentation efficiency compared with the low-temperature dried biocatalysts. Gas chromatography–mass spectrometry analysis of aroma volatiles of the fermented products revealed an increase of esters, lower higher alcohol formation, and significantly lower concentration of carbonylic compounds.
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Evaluation of the Thermally Dried Immobilized Cells of Lactobacillus delbrueckii subsp. bulgaricus on Apple Pieces as a Potent Starter Culture
Journal of agricultural and food chemistry, 2007Co-Authors: Nikolaos Kopsahelis, Panayiotis Panas, Yiannis Kourkoutas, Athanasios A KoutinasAbstract:The aim of the present study was to evaluate the impact of Thermal Drying of immobilized Lactobacillus delbrueckii subsp. bulgaricus on apple pieces on the use of the derived biocatalyst in whey fermentation. The Thermally dried immobilized biocatalyst was compared to wet and freeze-dried immobilized cells, in respect to maintenance of cell viability and fermentation efficiency. The Thermal Drying process appeared to be more efficient on survival rate as an 84% of the cells used for immobilization survived the process, while the freeze-Drying process led to a 78% rate. The Thermally dried immobilized biocatalyst was used in 12 repeated batch fermentations of synthetic lactose medium and whey at 37, 45, and 50 °C in order to evaluate its metabolic activity. The high number of repeated batch fermentations showed a tendency for high operational stability. Fermentations continued for up to 2 months without any significant loss of metabolic activity. SPME GC/MS analysis of aroma-related compounds revealed the ...
Lars Stoumann Jensen - One of the best experts on this subject based on the ideXlab platform.
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Increased retention of available nitrogen during Thermal Drying of solids of digested sewage sludge and manure by acid and zeolite addition.
Waste management (New York N.Y.), 2019Co-Authors: Jingna Liu, Andreas De Neergaard, Lars Stoumann JensenAbstract:Abstract Thermal Drying is an increasingly common post-treatment for digestate-solids, but prone to N losses via ammonia (NH3) volatilization. Acidification with strong acids prior to Drying may retain ammonium (NH4+) in the solids. Natural zeolites can provide adsorption sites for exchangeable cations as ammonium and porosity for free ammonia, which has the potential to contribute to higher N retention in the dried solids. The present study investigated whether the zeolite addition increases NH4+-N retention during Thermal Drying of two digestate solids (manure based, MDS; sewage sludge based, SDS), and whether any synergistic effects of combining acidification with sulfuric acid and the addition of zeolite exist. Operating conditions included four pH levels (non-acidified control, adjusted to 8.0, 7.5, 6.5 with concentrated sulfuric acid), four zeolite addition rates (0%, 1%, 5% and 10%), fixed Drying temperature (130 °C) and fixed air ventilation rate (headspace exchange rate of 286 times hour−1). Zeolite addition significantly increased NH4+-N retention from 18.0% of initial NH4+-N in the non-acidified control up to a maximum of 57.4% for MDS, and from 76.6% to 94.5% for SDS. No positive synergistic effect between acidification and zeolite addition was observed, with acidification being the dominant. Nevertheless, zeolite has the potential to be a safe and easy-to-handle alternative to concentrated sulfuric acid.
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Effects of Thermal Drying on phosphorus availability from iron-precipitated sewage sludge
Journal of Plant Nutrition and Soil Science, 2017Co-Authors: Camilla Lemming, Charlotte Scheutz, Sander Bruun, Lars Stoumann Jensen, Jakob MagidAbstract:Thermal Drying of sewage sludge implies sanitation and improves practical handling options of the sludge prior to land application. However, it may also affect its value as a fertilizer. The objective of this study was to assess whether Thermal Drying of sewage sludge, as well as Drying temperature, affects plant P availability after application to soil. The experiment included dewatered sewage sludge (20% DM) and Thermally dried sewage sludge (95% DM) collected at a Danish wastewater treatment plant, as well as laboratory oven-dried (70, 130, 190, and 250°C; DM > 95%) subsamples of the dewatered sludge, and a triple superphosphate as a reference. Plant P availability was studied in a 197 d soil incubation experiment, with sampling for Diffusive Gradients in Thin films (DGT) and water extractable P (WEP) analyses over time, and in a pot experiment with spring barley (Hordeum vulgare L.). In both experiments, Thermal Drying reduced P availability, as shown by 37 and 23% lower DGT and WEP values, respectively, and a 16% lower P uptake by barley in the pot experiment. The specific Drying temperature did not appear to have much effect. Overall, our results suggest that Thermal Drying of iron-precipitated sewage sludge is not an optimal treatment option if the aim is to optimize plant P availability.
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Increasing Thermal Drying temperature of biosolids reduced nitrogen mineralisation and soil N_2O emissions
Environmental Science and Pollution Research, 2016Co-Authors: Sean D. C. Case, Jakob Magid, Beatriz Gómez-muñoz, Lars Stoumann JensenAbstract:Previous studies found that Thermally dried biosolids contained more mineralisable organic nitrogen (N) than the raw or anaerobically digested (AD) biosolids they were derived from. However, the effect of Thermal Drying temperature on biosolid N availability is not well understood. This will be of importance for the value of the biosolids when used to fertilise crops. We sourced AD biosolids from a Danish waste water treatment plant (WWTP) and dried it in the laboratory at 70, 130, 190 or 250 °C to >95 % dry matter content. Also, we sourced biosolids from the WWTP dried using its in-house Thermal Drying process (input temperature 95 °C, Thermal fluid circuit temperature 200 °C, 95 % dry matter content). The Drying process reduced the ammonium content of the biosolids and reduced it further at higher Drying temperatures. These findings were attributed to ammonia volatilisation. The percentage of mineralisable organic N fraction (min-N) in the biosolids, and nitrous oxide (N_2O) and carbon dioxide (CO_2) production were analysed 120 days after addition to soil. When incubated at soil field capacity (pF 2), none of the dried biosolids had a greater min-N than the AD biosolids (46.4 %). Min-N was lowest in biosolids dried at higher temperatures (e.g. 19.3 % at 250 °C vs 35.4 % at 70 °C). Considering only the dried biosolids, min-N was greater in WWTP-dried biosolids (50.5 %) than all of the laboratory-dried biosolids with the exception of the 70 °C-dried biosolids. Biosolid carbon mineralisation (CO_2 release) and N_2O production was also the lowest in treatments of the highest Drying temperature, suggesting that this material was more recalcitrant. Overall, Thermal Drying temperature had a significant influence on N availability from the AD biosolids, but Drying did not improve the N availability of these biosolids in any case.
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Increasing Thermal Drying temperature of biosolids reduced nitrogen mineralisation and soil N2O emissions
Environmental science and pollution research international, 2016Co-Authors: Sean D. C. Case, Jakob Magid, Beatriz Gómez-muñoz, Lars Stoumann JensenAbstract:Previous studies found that Thermally dried biosolids contained more mineralisable organic nitrogen (N) than the raw or anaerobically digested (AD) biosolids they were derived from. However, the effect of Thermal Drying temperature on biosolid N availability is not well understood. This will be of importance for the value of the biosolids when used to fertilise crops. We sourced AD biosolids from a Danish waste water treatment plant (WWTP) and dried it in the laboratory at 70, 130, 190 or 250 °C to >95 % dry matter content. Also, we sourced biosolids from the WWTP dried using its in-house Thermal Drying process (input temperature 95 °C, Thermal fluid circuit temperature 200 °C, 95 % dry matter content). The Drying process reduced the ammonium content of the biosolids and reduced it further at higher Drying temperatures. These findings were attributed to ammonia volatilisation. The percentage of mineralisable organic N fraction (min-N) in the biosolids, and nitrous oxide (N2O) and carbon dioxide (CO2) production were analysed 120 days after addition to soil. When incubated at soil field capacity (pF 2), none of the dried biosolids had a greater min-N than the AD biosolids (46.4 %). Min-N was lowest in biosolids dried at higher temperatures (e.g. 19.3 % at 250 °C vs 35.4 % at 70 °C). Considering only the dried biosolids, min-N was greater in WWTP-dried biosolids (50.5 %) than all of the laboratory-dried biosolids with the exception of the 70 °C-dried biosolids. Biosolid carbon mineralisation (CO2 release) and N2O production was also the lowest in treatments of the highest Drying temperature, suggesting that this material was more recalcitrant. Overall, Thermal Drying temperature had a significant influence on N availability from the AD biosolids, but Drying did not improve the N availability of these biosolids in any case.
Xiaohu Dai - One of the best experts on this subject based on the ideXlab platform.
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Change of Thermal Drying characteristics for dewatered sewage sludge based on anaerobic digestion
Journal of Thermal Analysis and Calorimetry, 2012Co-Authors: Fan Luo, Bin Dong, Lingling Dai, Xiaohu DaiAbstract:The moisture distribution and Thermal Drying characteristics of dewatered sludge in anaerobic digestion were investigated by a thermo-gravimetric analyzer (TG) and the isoThermal kinetic characteristics during the Drying were developed by an unreacted core model. The TG results showed that the bound water was partly converted to the free water with the invariant interstitial water and surface water after anaerobic digestion, which enhanced the Drying performance of sludge. The time required for the complete Drying of digestate was less than that of the raw sludge in the same temperature. The moisture evaporative efficiency of digestate was related to the vapor diffusion rate of the outer surface, and the Drying efficiency of digested sludge cannot be enhanced by increased temperatures.