| 1. |
- Mellin, Pelle, 1985-, et al.
(författare)
-
Accuracy and Potential Use of a Developed CFD-pyrolysis Model for Simulating Lab-scale Bio Oil Production
- 2012
-
Ingår i: The 20th EU BC&E Online Proceedings 2012. - 9788889407547 ; , s. 953-959
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The paper describes development of a CFD¬pyrolysis model using an Eularian-Eularian framework with an implemented pyrolysis reaction model. The CFD¬pyrolysis model is used to simulate the bubbling fluidized bed reactor integrated in a new experimental fast pyrolysis process for bio oil production. The model is compared to experiments in aspect of outlet gas composition, temperature and bed height. Tar behavior and yield of bio oil are illustrated and a parametric study investigates impact of flow rate and temperature on bio oil yield. The results show a tolerable fit compared to measurements and reasonable tendencies in the parametric study.
|
|
| 2. |
- Mellin, Pelle, et al.
(författare)
-
Simulation of Bed Dynamics and Primary Products from Fast Pyrolysis of Biomass : Steam Compared to Nitrogen as a Fluidizing Agent
- 2014
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 53:30, s. 12129-12142
-
Tidskriftsartikel (refereegranskat)abstract
- Fast pyrolysis of biomass, using steam as a fluidizing agent, provides several benefits. In this paper, an unsteady multiphase computational fluid dynamics (CFD) model coupled with a comprehensive kinetic scheme for primary pyrolysis is used to obtain the formation rates of primary products and compare the profiles when operating with steam and nitrogen. The model only considers the physical effects of the fluidizing gas at the moment, although a literature review indicates the existence of various chemical and surface-interacting effects. At stabilized pyrolysis reaction rates, the product yields were compared to data found in the literature, which indicated similar yields; this supports the correct implementation of the kinetic model. However, the difference in overall rate and composition is very small when steam is compared to nitrogen. The simultaneous simulation of bed dynamics indicate a shifted formation rate of primary products toward the lower part of the fluidized bed, with an increase in solid vapor contact time and better temperature distribution as a result. More specifically, total heat flux to the biomass increased by 1396 in the lowest part of the reactor. In addition, more heat from the sand is carried through the gas phase when using steam: an increase by 9% in the overall reactor (25% in the lowest part), as indicated by the results. Finally, since no substantial differences in overall product formation rate and composition were found, the considerable effect of steam found in experiments and the literature is mainly (not exclusively) attributed to the chemical and surface-interacting mechanisms. Because of the complex nature of secondary pyrolysis in this process, a comprehensive gas-phase kinetic model is needed to investigate the effects of steam further. Coupling of both is difficult, because of computational constraints, as the present model already is very demanding. The obtained profiles of formation rate of primary products can however be used as an input to another model specifically made for studying homogeneous secondary pyrolysis reactions.
|
|
| 3. |
- Peng, Ningxin, et al.
(författare)
-
Platelet mitochondrial DNA methylation : A novel biomarker for myocardial infarction – A preliminary study
- 2023
-
Ingår i: International Journal of Cardiology. - 0167-5273.
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Platelet activation and thrombus formation play critical roles in the pathogenesis of myocardial infarction (MI). In addition to their role in energy production, platelet mitochondria also regulate cellular functions related to apoptosis, oxidative stress, and inflammation. Epigenetic modifications of platelet mitochondrial DNA (mtDNA) may influence platelet function and are believed to be an important factor in MI. Therefore, the aim of this study was to investigate the differences in platelet mtDNA methylation levels between MI patients and controls. Methods: The present study utilized propensity score matching to generate 45 multivariate matched apparently healthy controls for 45 patients with newly-onset acute MI. Platelet mtDNA methylation levels were assessed through bisulfite-PCR pyrosequencing and compared between the two groups, with further adjustments made in the sensitivity analysis. Results: Among the measured mitochondrial genes (MT-COX1, MT-COX2, MT-COX3, MT-ND5, MT-ATP6 and tRNA_Leu), patients with MI exhibited statistically significant differences in mtDNA methylation levels as compared to matched controls. Specifically, higher levels of mtDNA methylation were observed in MT-COX1, MT-COX3, and tRNA_Leu, while a lower level was observed in MT-ATP6 (all p < 0.0001). These results remained robust in the sensitivity analysis. Conclusion: Our study demonstrated significant variations in platelet mtDNA methylation levels between patients with MI and controls. Platelet mtDNA methylation may serve as a novel biomarker for MI. This observation also provided some insights into the etiology of MI.
|
|
| 4. |
- Zhou, Chunguang, et al.
(författare)
-
A study of the pyrolysis behaviors of pelletized recovered municipal solid waste fuels
- 2013
-
Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 107, s. 173-182
-
Tidskriftsartikel (refereegranskat)abstract
- Pelletized recovered solid waste fuel is often applied in gasification systems to provide feedstock with a stabilized quality and high heating value and to avoid the bridging behavior caused by high moisture content, low particle density, and irregular particle size. However, the swelling properties and the sticky material generated from pyrolysis of the plastic group components also tend to trigger bridging in the retorting zone. It is well known that the plastic group materials, which occupy a considerable proportion of municipal solid waste, can melt together easily even under low temperature. This study investigates the pyrolysis behaviors of typical recovered solid waste pellets, including the devolatilization rate, heat transfer properties, char properties, and swelling/shrinkage properties, in a small fixed-bed facility over a wide temperature range, from 900 degrees C to 450 degrees C. The results are also compared with those from wheat straw pellets, a typical cellulosic fuel. Moreover, the SEM images and BET analysis of the char structure are further analyzed to provide additional explanation for the mechanisms of swelling/shrinkage phenomena observed during heating.
|
|
| 5. |
- Zhou, Chunguang, et al.
(författare)
-
Characteristics of waste printing paper and cardboard in a reactor pyrolyzed by preheated agents
- 2013
-
Ingår i: Fuel processing technology. - : Elsevier BV. - 0378-3820 .- 1873-7188. ; 116, s. 63-71
-
Tidskriftsartikel (refereegranskat)abstract
- We studied the characteristics of waste printing paper and cardboard particles in a reactor pyrolyzed by preheated agents with the aim of simulating a real case in a fixed-bed gasifier. A TGA/DSC was first used to study of the kinetics and enthalpy change of the printing paper and cardboard pyrolysis. Pyrolitic conversion was further carried out in a batch-type reactor with non-electrical heating. Syngas, tar and char were produced and characterized from printing paper and cardboard pyrolysis at 400 degrees C, 500 degrees C and 600 degrees C. Different flow rates of carrier gas were applied to study the effect of residence time on the products distribution. When the flow rate increased, the relative mass change of gas agrees with that of tar. With increase in temperature, the yield of furfural, olefins and other non-aromatic compounds in tar decreased, while phenols and heavier aromatic hydrocarbons increased. The evolution of CO2, CO and other gas species in the syngas was presented. Van Krevelan diagram of chars was also presented in the paper.
|
|
| 6. |
- Zhou, Chunguang, et al.
(författare)
-
Characterization of the Products from Spruce and Pine Sawdust Pyrolysis at Various Temperatures
- 2013
-
Ingår i: Proceedings of the 21st EU BC&E - Copenhagen 2013. - : EU BC&E. - 9788889407530 ; , s. 968-973
-
Konferensbidrag (refereegranskat)abstract
- Pyrolitic conversion of lignocellulosic biomass is a promising field to achieve the energy utilization and the significant reduction in CO2 emission. Both the spruce and pine are the main species in Swedish forests. During gasification process, water scrubbing system is widely adopted due to its simple and economical structure. The understanding of the releasing of tar components is quite important for the operation and gas cleaning system. Thus, pyrolysis study of spruce and pine sawdust was conducted in a batch-type reactor at 400°C, 500°C and 600°C. Yields of pyrolytic liquid, gas, and char were calculated. Pyrolytic liquids were characterized by GC-MS. Kinetic study of individual gas component was carried out. The element analysis of chars was conducted. And the energy distribution in the char, gas, and liquid, were also presented in the paper. The optimized pyrolysis conditions will achieve the oil upgrading and improve the energy utilization efficiency.
|
|
| 7. |
- Zhou, Chunguang, et al.
(författare)
-
Effect of calcium oxide on high-temperature steam gasification of municipal solid waste
- 2014
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 122, s. 36-46
-
Tidskriftsartikel (refereegranskat)abstract
- Steam gasification of municipal solid waste (MSW) using a CaO additive was investigated in a batch-type fixed bed, to examine the effects of CaO addition on the heat transfer properties, the devolatilization characteristics of MSW, CO2 adsorption capacities of CaO, and char gasification in the presence of steam. Evolutionary behaviors of syngas molar compositions and individual gas flow rates at both MSW devolatilization and char gasification stages were examined at different CaO/MSW mass ratios with a fixed MSW mass. The effect of temperature varying from 700 to 900 C was also considered in this test. In both stages, hydrogen concentrations were found to increase and CaO was found to have a catalytic effect. Finally, using from the experimental observations and the results of SEM/EDS analyses of the obtained residues, the mechanism underlying the catalytic effects of calcium species in both reaction stages was discussed.
|
|
| 8. |
|
|
| 9. |
- Zhou, Chunguang, et al.
(författare)
-
Effect of heat transfer model on the prediction of refuse-derived fuel pyrolysis process
- 2015
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 142, s. 46-57
-
Tidskriftsartikel (refereegranskat)abstract
- Heat transfer models using to estimate the effective thermal conductivity have been developed and included in a model for the pyrolysis of refuse-derived fuel or solid recovered fuel particles composed of cardboard and polyethylene. Both the predictions from the Kunii and Smith model and the Breitbach and Barthels model were presented and compared with the experimental data. The possible mechanisms of heat transfer in the porous solid particles were discussed. Compared to the conduction mode by solid matrix and gas phase, radiation heat flux between the neighboring voids and from particle surface and neighboring particle surface are considered as the main mechanisms at the temperatures presented in this paper. The porosity has been reported to serve as an important role in the accurate estimation of the radiation exchange factor for the radiation term in heat transfer model in a highly porous medium. Refuse-derived fuel particle with a high plastic concentration exhibits a rapid increase of porosity with the continuous thermal conversion of plastic. Thus, a coefficient as a function of porosity was applied to the radiation exchange factor in the Kunii and Smith model, which was constructed and based on a simplified model of heat transfer in packed bed. Moreover, the effect of the contact surface area between solid particles on the heat transfer of conduction mode was also considered in the Breitbach and Barthels model. Both modified models were further validated with experimental results obtained at different temperature, with different PE content and initial porosity.
|
|
| 10. |
- Zhou, Chunguang, 1986-
(författare)
-
Gasification and Pyrolysis Characterization and Heat Transfer Phenomena During Thermal Conversion of Municipal Solid Waste
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The significant generation of municipal solid waste (MSW) has become a controversial global issue. Pyrolysis and gasification technologies for treating rejects from solid waste disposal sites (SWDSs), for which over 50 % of MSW is attributed to combustible species, have attracted considerable attention. MSW is an alternative energy source that can partly replace fossil resources; there is an increasing awareness that global warming caused by the utilization of fossil resources is occurring.The goal of this thesis is to realize the efficient and rational utilization of MSW and decrease the harmful impact of pollutants, such as dioxin, HCl, and CO2, on the environment. To achieve this goal, some fundamental studies have been experimentally and numerically conducted to enhance the understanding of the properties of municipal solid waste thermal conversion.In this thesis, the pyrolysis behaviors of single pelletized recovered fuel were tested. A detailed comparison of the pyrolysis behaviors of typical recovered solid waste and biomass particles was conducted. A swelling phenomenon with a swelling ratio of approximately 1.6 was observed on the surface of pelletized recovered fuels. Subsequently, a particle model was constructed to describe the thermal conversion process for large recovered fuel particles that are composed of a high fraction of polyethylene (PE) and a comparable low fraction of cardboard. The results indicate that an understanding of the heat transfer mechanism in highly porous and molten structures and the selection of a heat transfer model are crucial for accurate prediction of the conversion process.MSW pyrolysis is a promising method for producing liquid products. With the exception of lignocellulosic materials, such as printing paper and cardboard, PE, polystyrene (PS), polypropylene (PP), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) are the six main polymers in domestic waste in Europe. Characterization studies of the products obtained from these individual components, such as PE, PET, PVC, printing paper, and cardboard, have been conducted on a pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) system and a fixed-bed reactor. The possible pathways for the formation of the main primary/secondary products in rapid and conventional pyrolysis were also discussed.MSW steam gasification with CaO was performed in a batch-type fixed-bed gasifier to examine the effect of CaO addition on the heat transfer properties, pollutant removal, and devolatilization and char gasification behaviors in the presence of steam.A new carbon capture and recycle (CCR) system combined with an integrated municipal solid waste system was proposed. The foundation of the system is the development of a novel method to remediate CO2 using a high-temperature process of reforming CH4 and/or O2 and/or H2O without catalysts. Thermodynamic and experimental studies were performed. High temperatures significantly promoted the multi-reforming process while preventing the problem of catalyst deactivation. Potential improvements in the efficiency of the novel technology can be achieved by optimizing the reforming reactants. Landfill gas (LFG) and fuel gas from bio-waste treatment contain a considerable fraction of CH4, which may be a source of CH4 for this process.
|
|
