| 1. |
- Ge, Yaxin, 1992, et al.
(författare)
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Emission Characteristics of NOx and SO2 during the Combustion of Antibiotic Mycelial Residue
- 2022
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Ingår i: International Journal of Environmental Research and Public Health. - : MDPI AG. - 1661-7827 .- 1660-4601. ; 19:3
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Tidskriftsartikel (refereegranskat)abstract
- The antibiotic mycelial residue (AMR) generated from cephalosporin C production is a haz-ardous organic waste, which is usually disposed of by landfilling that causes potential secondary environmental pollution. AMR combustion can be an effective method to treat AMR. In order to develop clean combustion technologies for safe disposal and energy recovery from various AMRs, the emission characteristics of NOx and SO2 from AMR combustion were studied experimentally in this work. It was found that the fuel-N is constituted by 85% protein nitrogen and 15% inorganic nitrogen, and the fuel-S by 78% inorganic sulfur and 22% organic sulfur. Nitrogen oxide emissions mainly occur at the volatile combustion stage when the temperature rises to 400◦C, while the primary sulfur oxide emission appears at the char combustion stage above 400◦C. Increasing the combustion temperature and airflow cause higher NOx emissions. High moisture content in AMR can significantly reduce the NOx emission by lowering the combustion temperature and generating more reducing gases such as CO. For the SO2 emission, the combustion temperature (700 to 900◦C), airflow and AMR water content do not seem to exhibit obvious effects. The presence of CaO significantly inhibits SO2 emission, especially for the SO2 produced during the AMR char combustion because of the good control effect on the direct emission of inorganic SO2. Employing air/fuel staging technologies in combination with in-situ desulfurization by calcium oxide/salts added in the combustor with operation temperatures lower than 900◦C should be a potential technology for the clean disposal of AMRs. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
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| 2. |
- Cheng, W., et al.
(författare)
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Effect of oxidative torrefaction on particulate matter emission from agricultural biomass pellet combustion in comparison with non-oxidative torrefaction
- 2022
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Ingår i: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 189, s. 39-51
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Tidskriftsartikel (refereegranskat)abstract
- Torrefaction could improve the fuel properties and reduce the operating costs. However, the particulate matter (PM) emission behavior during the torrefied pellet combustion remains unknown. In this work, cotton stalk was torrefied at a temperature of 220–300 °C with a O2 concentration of 0–21%. The torrefied pellet was burned out and PM emission behavior was investigated using a Dekati low-pressure impactor. The results show that oxidative torrefaction leads to notable decreases of H/C and O/C ratios, which makes the fuel properties similar to coals. The heating value is significantly improved and sensitive to the torrefaction temperature. Both non-oxidative and oxidative torrefaction give rise to considerable increase in the yield of PM10. The main composition of PM1 changed from KCl to K2SO4 due to the substantial release of Cl during torrefaction. Meanwhile, Ca and K contents in PM1-10 are generally high, implying that the presence of oxygen can facilitate the transformation of alkali and alkaline-earth metals into coarse particles. The torrefaction temperature at around 260 °C with a low O2 concentration of 0–6% are the optimal torrefaction operation conditions to produce good quality torrefied cotton stalk pellet with respect to high heating value and low PM emission in later combustion application.
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| 3. |
- Ding, C., et al.
(författare)
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The research on anaerobic digestion conditions of biomethanation using low-temperature pyrolysis oil
- 2021
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Ingår i: Zhongguo Huanjing Kexue/China Environmental Science. - 1000-6923. ; 41:8, s. 3676-3683
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Tidskriftsartikel (refereegranskat)abstract
- This article focused on the research of anaerobic digestion conditions using low-temperature pyrolysis oil, including the fresh inoculum acclimatization, the operation conditions of pyrolysis oil (PO) digestion and the influence of biomass pyrolysis parameters. The coupling process was studied by controlling different pyrolysis parameters and anaerobic digestion parameters. It can be concluded that the fresh sludge inoculum acclimatization can significantly improve the tolerance to the inhibitors contained in the PO, thus, the methane production from the PO digestion to a great degree. The mesophilic condition was favorable to the biooil biomethanation for the low POs under 4% as used in the experiment, whereas the thermophilic condition was favorable for the high PO concentration of 10%. Besides, more methane production can be given by 0.85mm biomass particle size, 300℃ pyrolysis temperature in the downstream step of PO digestion.
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| 4. |
- Jiang, Bingyi, et al.
(författare)
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Low-Grade Syngas Biomethanation in Continuous Reactors with Respect to Gas–Liquid Mass Transfer and Reactor Start-Up Strategy
- 2023
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Ingår i: Fermentation. - : MDPI AG. - 2311-5637. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- In order to utilize a wider range of low-grade syngas, the syngas biomethanation was studied in this work with respect to the gas–liquid mass transfer and the reactor start-up strategy. Two reactors, a continuous stirred tank (CSTR) and a bubble column with gas recirculation (BCR-C), were used in the experiment by feeding an artificial syngas of 20% H2, 50% CO, and 30% CO2 into the reactors at 55 °C. The results showed that the CH4 productivity was slightly increased by reducing the gas retention time (GRT), but was significantly improved by increasing the stirring speed in the CSTR and the gas circulation rate in the BCR-C. The best syngas biomethanation performance of the CSTR with a CH4 productivity of 22.20 mmol·Lr−1·day−1 and a yield of 49.01% was achieved at a GRT of 0.833 h and a stirring speed of 300 rpm, while for the BCR-C, the best performance with a CH4 productivity of 61.96 mmol·Lr−1·day−1 and a yield of 87.57% was achieved at a GRT of 0.625 h and a gas circulation rate of 40 L·Lr−1·h−1. The gas–liquid mass transfer capability provided by gas circulation is far superior to mechanical stirring, leading to a much better performance of low-grade syngas biomethanation in the BCR-C. Feeding H2/CO2 during the startup stage of the reactor can effectively stimulate the growth and metabolism of microorganisms, and create a better metabolic environment for subsequent low-grade syngas biomethanation. In addition, during the thermophilic biomethanation of syngas, Methanothermobacter is the dominant genus.
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| 5. |
- Zhang, Zhenwen, et al.
(författare)
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CO Biomethanation with Different Anaerobic Granular Sludges
- 2021
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Ingår i: Waste and Biomass Valorization. - : Springer Science and Business Media LLC. - 1877-2641 .- 1877-265X. ; 12:7, s. 3913-3925
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Biomethanation of the syngas from biomass gasification provides an alternative method for production of biofuel and chemicals. CO in syngas plays a key role in biomethanation of syngas, as it is both a substrate and an inhibitor of certain methanogenesis processes. In this study, CO biomethanation by using a mixture of N2 and CO as the gas substrate, was investigated with the help of 5 adapted anaerobic granular sludges under thermophilic and mesophilic conditions. The results show that CO biomethanation by the adapted inocula is omnipresent. The sludge from the juice plant has a methane yield more than 80% of the theoretical value both at 37 °C and 55 °C. Increasing the temperature from 37 °C to 55 °C has a slight effect on the final methane production, but can significantly increase the CO consumption rate and shorten the time for CO biomethanation. Graphic Abstract: [Figure not available: see fulltext.].
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| 6. |
- Chansa, Oris, et al.
(författare)
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Behavior of alkali minerals in oxyfuel co-combustion of biomass and coal at elevated pressure
- 2021
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Ingår i: Journal of Zhejiang University: Science A. - 1673-565X. ; 22:2, s. 116-129
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Tidskriftsartikel (refereegranskat)abstract
- Combustion of biomass or coal is known to yield aerosols and condensed alkali minerals that affect boiler heat transfer performance. In this work, alkali behavior in the pressurized oxyfuel co-combustion of coal and biomass is predicted by thermodynamic and chemical kinetic calculations. Existence of solid minerals is evaluated by X-ray diffraction (XRD) analysis of ashes from pressure thermogravimetric combustion. Results indicate that a rise in pressure affects solid alkali minerals negligibly, but increases their contents in the liquid phase and decreases them in the gas phase, especially below 900 °C. Thus, less KCl will condense on the boiler heat transfer surfaces leading to reduced corrosion. Increasing the blend ratio of biomass to coal will raise the content of potassium-based minerals but reduce the sodium-based ones. The alkali-associated slagging in the boiler can be minimized by the synergistic effect of co-combustion of sulphur-rich coal and potassium-rich biomass, forming stable solid K2SO4 at typical fluidized bed combustion temperatures. Kinetics modelling based on reaction mechanisms shows that oxidation of SO2 to SO3 plays a major role in K2SO4 formation but that the contribution of this oxidation decreases with increase in pressure.
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| 7. |
- Cheng, W., et al.
(författare)
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Mitigation of ultrafine particulate matter emission from agricultural biomass pellet combustion by the additive of phosphoric acid modified kaolin
- 2021
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Ingår i: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 172, s. 177-187
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Tidskriftsartikel (refereegranskat)abstract
- The emission of ultrafine particulate matter (PM0.2) originated from the agricultural biomass pellet combustion poses great threat to atmospheric environment and human health, which restricts its large-scale utilization. In this study, a new phosphoric acid modification method is proposed to improve the PM0.2 reduction efficiency by kaolin additive. The effects of phosphoric acid concentration and treatment time on the physicochemical properties of kaolin and on the mitigation of PM0.2 emission from the pellet combustion are investigated. Results indicate that phosphoric acid modification destroy the internal structure of kaolin by the leaching of Al cations and the formation of active free silica. Meanwhile, the pore structure increases after modification with residual P deposited on the surface, which results in better alkali capture ability of modified kaolin. With the addition of phosphoric acid modified kaolin, significant reduction of PM0.2 emission can be achieved and the reduction ratio is proportional to the acid concentration. The maximum PM0.2 emission reduction ratio reaches 64.5% for the kaolin additive modified by 12 mol/L phosphoric acid for 6 hours. Finally, the PM0.2 reduction mechanism is proposed based on the analysis results, which provides technical knowhow for the industrial application of agricultural biomass pellet combustion.
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| 8. |
- Fallahjoybari, Nima, et al.
(författare)
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A comparative study of different heat transfer enhancement mechanisms in a partially porous pipe
- 2021
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Ingår i: SN Applied Sciences. - : Springer Science and Business Media LLC. - 2523-3963 .- 2523-3971. ; 3:10
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Tidskriftsartikel (refereegranskat)abstract
- The effect of porous material position on the heat transfer inside a pipe working in a turbulent regime is studied here to obtain a detailed understanding of the heat transfer enchantment mechanisms in different porous substrate positions. To this end, an in-house Fortran code is developed to solve the governing equations using the finite volume method and SIMPLE algorithm. Turbulent flow in porous media is modeled using a modified version of k–ε model. The flow field and heat transfer inside the partially filled pipe are investigated for the two cases of central and boundary configurations. The porous and flow characteristics including Reynolds number, Darcy number, the conductivity ratios of solid to fluid and the thickness of inserted porous layer are varied and the heat transfer performance is studied in different cases. It is observed that two entirely different phenomena enhance the heat transfer in central and boundary configurations. While the channeling of fluid between the porous media and the pipe wall highly affects the heat transfer performance in the former, the thermal conductivity of porous media plays a highly critical role in the latter configuration. It is shown that, for the same filling ratio, inserting the porous layer at the core of the pipe is more effective than placing it at the wall. Investigating porous materials with different solid conductivities revealed that covering the pipe wall with a porous material is justified only for solid matrixes with high thermal conductivities.
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| 9. |
- Fatahian, Hossein, et al.
(författare)
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Improving the flow uniformity in compact parallel-flow heat exchangers manifold using porous distributors
- 2022
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Ingår i: Journal of thermal analysis and calorimetry (Print). - : Springer Science and Business Media LLC. - 1388-6150 .- 1588-2926. ; 147:22, s. 12919-12931
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Tidskriftsartikel (refereegranskat)abstract
- The present study deals with the numerical simulation of turbulent flow in a Z-type manifold in which the fluid is distributed via nine distribution tubes. One of the major drawbacks of such devices is the mal-distribution of flow within these tubes. The flow rates are usually low in the first tubes close to the header entrance and increase in the other tubes. To address this problem and achieve a more uniform flow distribution inside the manifold, a novel solution is introduced in the present study, which includes the insertion of thin layers of porous media at the inlet of distribution tubes. In addition, a parametric study is conducted to evaluate the effect of porous media geometrical parameters such as pore diameter, porosity, and porous layer thickness on flow distributions among the tubes. The results demonstrate that the proposed approach increases the uniformity of flow distribution specifically when a porous media with higher resistance against the fluid flow is inserted uniformly within the manifold. In this case, a standard deviation as small as Phi=0.0067 could be reached showing the high level of flow uniformity within the manifold. Also, a maximum pressure drop of 12.557 kPa is observed which is approximately 38% larger than that calculated in the manifold without porous insertions. Moreover, several non-uniform distributions of porous media are also investigated to further improve the flow uniformity and decrease the pressure drop. An improvement in the standard deviation of Phi=0.0043 is obtained in the case of #E3 with a non-uniform porous distribution with a 5% reduction in pressure drop compared to the pressure drop calculated in the corresponding uniform case #E1. The results reveal the effectiveness of the approach presented here to reach a more uniform flow distribution within the manifold without the need for re-designing and altering the manifold geometry which is usually proposed in the literature.
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| 10. |
- Ge, Yaxin, 1992, et al.
(författare)
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Effect of fresh bed materials on alkali release and thermogravimetric behavior during straw gasification
- 2023
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361 .- 1873-7153. ; 336
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Tidskriftsartikel (refereegranskat)abstract
- Alkali-associated problems are key issues for the efficient use of straw that is available as a major renewable energy resource worldwide. The effects of six bed materials commonly used in fluidized bed reactors on straw pyrolysis and char gasification were evaluated using online monitoring of alkali release and thermogravimetric analysis. Scanning electron microscopy with energy dispersive spectroscopy was used to determine the elemental composition of the char surface. In the straw pyrolysis stage, alkali release is reduced by the addition of dolomite and silica due to alkali adsorption on the bed materials, and enhanced by the addition of alumina because of its high sodium content. In the char gasification stage, silica, sea sand, olivine, and ilmenite reduce the char reactivity and alkali release, which is attributed to transfer of Si and Ti from the bed materials to the char and reaction with alkali to form stable and catalytically inactive compounds. Alumina also reduces the char conversion rate by transfer of Al to the char and formation of K-Al-Si and Ca-Al-Si compounds, while alkali release from the straw and alumina blend remains high due to the high Na content in alumina. Dolomite initially appears to increase the char gasification reactivity, but the results are affected by conversion of volatile matter that deposited on the dolomite in the straw pyrolysis stage. Dolomite also significantly increases the alkali release, which is attributed to Ca reactions with aluminosilicate compounds that allow potassium to remain in volatile form. Fresh bed materials are concluded to have significant effects on straw conversion depending on their chemical composition, and the results can contribute to the understanding required for efficient use of straw in commercial applications of biomass thermochemical conversion.
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