| 1. |
- Wu, Peng, et al.
(författare)
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A novel methodology for synthesizing crystalline metallosilicates with expanded pore windows through molecular alkoxysilylation of zeolitic lamellar precursor
- 2008
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society. - 0002-7863 .- 1520-5126. ; 130:26, s. 8178-8187
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Tidskriftsartikel (refereegranskat)abstract
- Postalkoxysilylation with diethoxydimethylsilane has been carried out on the zeolitic lamellar precursors of various topologies such as MWW, FER, CDO and MCM-47 aiming to construct new crystalline structures with expanded pore apertures between the layers. The silylation process and the crystalline and pore structures of the resulting materials have been investigated with the techniques of XRD, IR, 13C and 29Si MAS NMR, ICP, SEM, HRTEM, elemental analyses, and N2 adsorption. In contrast to forming known three-dimensional zeolite structures after direct calcination of the lamellar precursors, the silylation led to new crystalline structures with opener pores, as evidenced by the shift of layer-related diffractions to the lower-angle region in XRD patterns and the enlarged interlayer pores found by HRTEM images. After optimizing the treatment conditions, particularly the amount of silane agent, a maximum and homogeneous silylation was realized, which guaranteed the phase purity in interlayer expanded zeolites. The expanded structures were well preserved after calcination at 823 K or reflux in water for 1 to 2 weeks, indicating a high thermal stability and also a hydrothermal stability. The interlayer expanded zeolites prepared from the metallosilicate precursors of MWW topology exhibited higher catalytic activities in the redox and solid acid-catalyzed reactions of bulky molecules than that of their counterparts with conventional MWW topology.
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| 2. |
- Allgurén, Thomas, 1986, et al.
(författare)
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Alkali sulfation during combustion of coal in a pilot scale facility using additives to alter the global sulfur to potassium and chlorine to potassium ratios
- 2021
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 38:3, s. 4171-4178
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Tidskriftsartikel (refereegranskat)abstract
- Due to the urgent needs to reduce anthropogenic carbon dioxide emissions there is an increasing interest in the use of alternative fuels. For this reason, there is a need for new knowledge on how to design and adapt existing heat and power plants to biogenic and waste-derived fuels. This work relates to co-firing of biomass and coal and the sulfation of alkali chlorides in coal-fired flames doped with chemical additives. We aim to examine the global time scales of alkali sulfation and chlorination based on combustion experiments that were conducted in a 30-kW coal flame. Temperature, gas and particle composition measurements were conducted. Both experiments and modelling support that the apparent alkali sulfation kinetics are fast in a coal-fired flame and that it is dominated entirely by the presence of SO 2. The availability of oxygen and carbon monoxide, or hydrocarbons, is also critical to sustain the sulfation reaction cycle; low concentrations are sufficient. For industrial boilers this implies that sulfur addition, in combination with reburning, should constitute an efficient strategy to mitigate alkali-chlorination and the related high temperature corrosion.
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| 3. |
- Allgurén, Thomas, 1986, et al.
(författare)
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The Influence of Alkali, Chlorine and Sulfur on Aerosol Formation
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The use of low-quality fuels in power generation is typically motivated by a potential reduction in fuel costs or CO2 emissions, the latter in case the fuel is based on biomass. These features make low quality fuels attractive at the same time as such fuels are usually problematic to use in power generation due to fuel composition. One of the main issues is deposition of aerosols upon heating surfaces reducing heat transfer and causing high-temperature corrosion (HTC). The later most often related to alkali chlorides, and these are formed from alkali species and chlorine when released during the combustion process. The present work aims to investigate how the gas phase chemistry are connected to the formation aerosols and their characteristics. This is an ongoing work why only part of the preliminary results is presented focusing on the interaction between alkali, sulfur and chlorine in the gas phase. The results presented here indicate a clear correlation between the S/Cl ratio and the formation of alkali sulfates over chlorides. It is also indicated that the local conditions at which the species are released and available in the gas phase is important for the resulting formation of alkali sulfates.
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| 4. |
- Fry, Andrew, et al.
(författare)
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The influence of fuel composition on sulfation and deposition rates of alkali salts
- 2018
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Ingår i: CLEARWATER CLEAN ENERGY CONFERENCE 2018. - 9781510867666
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Konferensbidrag (refereegranskat)abstract
- The present work is based on recent pilot-scale experiments that examines the behavior of alkali, chlorine and sulfur containing aerosols during both air- and oxy-combustion conditions. The experiments have been performed at University of Utah where solid fuel experiments were performed in a 100kW combustion unit. The experiments focus on the formation of depositing ash particulates. The results from these experiments are then compared to chemical reaction kinetics simulations that allows for a more detailed investigation of the gas phase chemistry and its influence on the ash composition. The work aims to improve the understanding of how the ash composition and its deposit rate depends on the fuel composition and combustion conditions. The results show that the temperature is an important parameter for the aerosol formation influencing both composition and particle size distribution. The simulations also indicate that the amount of sulfur and chlorine in relation to potassium is important for the sulfation of potassium.
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| 5. |
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| 6. |
- Li, Xiaolong, et al.
(författare)
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The roles of added chlorine and sulfur on ash deposition mechanisms during solid fuel combustion
- 2021
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 38:3, s. 4309-4316
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Tidskriftsartikel (refereegranskat)abstract
- The focus of this paper is on effects of chlorine and sulfur on coal ash deposition rates, under practically relevant but systematically controlled combustion conditions. This problem is important, not so much for coal, but to understand and predict deposition rates for biomass combustion where chlorine contents can be high. To this end, ash deposition rates on a controlled temperature surface were measured for controlled amounts of chlorine and sulfur added to a pulverized coal, doped with potassium and burned in a 100 kW rated combustion rig. Previous work with 35 tests on 11 coal, biomass and petroleum coke fuels burned under a range of operating conditions had strongly suggested that the deposition rate of the tightly bound inside deposits was independent of the ash aerosol composition, and depended only on PM1 in the flue gas. The loosely bound outside deposition rate was dependent primarily on the total alkali content in the flue gas. The new results using chlorine added to the fuel (in the form of ammonium chloride) required these previous conclusions to be drastically revised. They showed that chlorine, not alkali alone, had large effects on the deposition rate of the inside deposits, which now were orders of magnitude higher than without chlorine addition, and did not fit previous (multi-fuel) correlations with PM1. Sulfur addition, together with chlorine, did not affect deposition rates much, although it did lower the chlorine content of the deposit. These results are interpreted in terms of the ash aerosol size segregated composition, which was also measured, and potential sulfation reactions within the deposit.
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| 7. |
- Niu, Jiqiang, et al.
(författare)
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Aerodynamic simulation of effects of one- and two-side windbreak walls on a moving train running on a double track railway line subjected to strong crosswind
- 2022
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Ingår i: Journal of Wind Engineering and Industrial Aerodynamics. - : Elsevier BV. - 0167-6105. ; 221
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Tidskriftsartikel (refereegranskat)abstract
- High-speed railway lines are widely distributed worldwide. The surrounding wind environment of such railway lines is complex, which significantly affects the safety of high-speed train operations. Using a combination of the computational fluid dynamics method of improved delayed detached eddy simulation and sliding grid technology, the effects of one- and two-side windbreak walls on the unsteady aerodynamic performance of a high-speed train running under a crosswind on a double-track railway line with an embankment and the flow-field characteristics around the train were systematically studied. The grid independence and numerical methods used in this study were verified. The results showed that when the windbreak wall was absent, the aerodynamic performance of the train running on the upstream railway line was the poorest, while the train running on the downstream railway line exhibited large aerodynamic fluctuations. The windbreak wall significantly reduced the aerodynamic force and its fluctuation; the one- and two-side windbreak walls had different effects on the unsteady aerodynamic performance of trains running on the upstream and downstream railway lines under a crosswind. The one-side windbreak wall could restrain the aerodynamic fluctuation of the train more and is thus preferred from the perspective of construction effort and cost.
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| 8. |
- Niu, Jiqiang, et al.
(författare)
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Numerical investigation on application of train body airflow diversion device to suppress pressure waves in railway high-speed train/tunnel system
- 2023
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Ingår i: International Journal of Rail Transportation. - : Informa UK Limited. - 2324-8386 .- 2324-8378. ; 11:4, s. 490-507
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Tidskriftsartikel (refereegranskat)abstract
- The development of the high-speed maglev train (HSMT) is important for the future of high-speed rail transit. A pressure wave (PW) is a common aerodynamic effect in high-speed railway tunnels. For HSMTs with a speed of 600 km/h, the amplitude of PW in the tunnel can be very big, which maybe far exceed the current design strength standard of the train body structure and seriously threatens the safety of the railway train/tunnel structure and passenger ear comfort. Therefore, aerodynamic PWs caused by a two-dimensional axisymmetric model with an ellipsoidal nose passing through a tunnel was investigate, and the numerical method adopted in this study was validated by two scaled moving model tests. The PWs caused by trains in four cases and the effects of train speed and tunnel length were analysed and compared. Some results show that diversion device significantly reduces the amplitude of the PWs (Delta C-p) on the train surface and tunnel wall. The diversion device on the train tail (C4) not only changes Delta C-p, but also changes the waveform. The diversion device on the train tail (C3) and diversion device on both train head and tail which are connecting each other (C2) mainly reduced the Delta C-p. When the decrease in both PWs on the train surface and tunnel wall is considered, C2 has the best effect. With an increase in the train speed, the effect of C2 on restraining the PW on the train surface and tunnel wall increases to a certain extent. However, the restraining effect on the micro-pressure wave (MPW) at the tunnel exit does not exceed 5%. The suppression effect of C2 on Delta C-p on the train surface and tunnel wall decreases with an increase in the tunnel length. However, it does not change the distribution law of Delta C-p along the train and tunnel. This study can provide a reference for the design of the body of HSMTs and the suppression of PW in tunnels.
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| 9. |
- Viljanen, Jan, 1990, et al.
(författare)
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In-situ monitoring of transient gas phase K-Cl-S chemistry in a pilot-scale combustor
- 2021
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 38:1, s. 1823-1831
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Tidskriftsartikel (refereegranskat)abstract
- Biomass and waste derived fuels contain large amounts of sodium, potassium, and chlorine that form NaCl and KCl, that is, compounds that cause operational problems, such as slagging, fouling, and high-temperature corrosion. Therefore, alkali chlorides are the main reasons that explain why steam parameters are less advanced and efficient in biomass and waste-based power generation when compared to coal. These problems can be mitigated by introducing sulphur into the system to form alkali sulphates that are not as problematic on steel surfaces as alkali chlorides. However, the alkali sulphation process in realistic combustion environments needs further exploration. Thus, new diagnostic methods for in-situ monitoring of alkali sulphation kinetics in combustion systems are required. In this work, the simultaneous monitoring of KCl and KOH concentrations in a pilot-scale combustor using Collinear Photofragmentation and Atomic Absorption Spectroscopy (CPFAAS) during stationary and transient operation of the combustor, is introduced. The CPFAAS information is complemented by monitoring SO2 and HCl concentrations using Fourier-transform infrared spectroscopy (FTIR). The temporal performance of the system is demonstrated by measuring the temporal combustor response curves for KCl sulphation for different Cl/K ratios during rapid changes in gaseous SO2 concentrations. The temporal concentration curves obtained imply that the Cl/K ratio has a significant impact on the temporal alkali sulphation behaviour. The measurement system described enables further exploration of K-Cl-S chemistry in realistic large-scale power plant environments.
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| 10. |
- Zhang, Lin, et al.
(författare)
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Characteristics of pressure waves along high-speed Maglev trains in railway tunnels and comparison of fatigue strength requirements according to different standards
- 2023
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Ingår i: International Journal of Vehicle Design. - 0143-3369. ; 93:4, s. 293-309
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Tidskriftsartikel (refereegranskat)abstract
- The aerodynamics of railway trains and tunnels were studied by using N-S equations and SST k-ω turbulence model. The results indicate that the train surface pressure amplitudes when high-speed trains are travelling at 500-800 km/h in a tunnel show a tendency to increase along the train, while the amplitudes intersecting in a tunnel were relatively close at the front and rear of the train, with fluctuations in the uniform section. When a train passed through the tunnel, the negative peak value and amplitude of the pressure wave acting on the train body exhibited linear relationship with the train speed, whereas when two trains met in the tunnel, the positive peak value, negative peak value, and amplitude were proportional to the 2.8, 2.5, and 2.6 power of the train speed. Finally, the characteristics of the International Union of Railways (UIC) and Japanese Industrial Standards (JIS) were compared and studied.
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| 11. |
- Zhou, Xiaohong, et al.
(författare)
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Global Analysis of Differentially Expressed Genes and Proteins in the Wheat Callus Infected by Agrobacterium tumefaciens
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:11, s. e79390-
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Tidskriftsartikel (refereegranskat)abstract
- Agrobacterium-mediated plant transformation is an extremely complex and evolved process involving genetic determinants of both the bacteria and the host plant cells. However, the mechanism of the determinants remains obscure, especially in some cereal crops such as wheat, which is recalcitrant for Agrobacterium-mediated transformation. In this study, differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) were analyzed in wheat callus cells co-cultured with Agrobacterium by using RNA sequencing (RNA-seq) and two-dimensional electrophoresis (2-DE) in conjunction with mass spectrometry (MS). A set of 4,889 DEGs and 90 DEPs were identified, respectively. Most of them are related to metabolism, chromatin assembly or disassembly and immune defense. After comparative analysis, 24 of the 90 DEPs were detected in RNA-seq and proteomics datasets simultaneously. In addition, real-time RT-PCR experiments were performed to check the differential expression of the 24 genes, and the results were consistent with the RNA-seq data. According to gene ontology (GO) analysis, we found that a big part of these differentially expressed genes were related to the process of stress or immunity response. Several putative determinants and candidate effectors responsive to Agrobacterium mediated transformation of wheat cells were discussed. We speculate that some of these genes are possibly related to Agrobacterium infection. Our results will help to understand the interaction between Agrobacterium and host cells, and may facilitate developing efficient transformation strategies in cereal crops.
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