Using Stereo XPTV to determine Cylindrical Particle Distribution and Velocity in a Binary Fluidized Bed

Non‐spherical particles are commonly found when processing biomass or municipal solid waste (MSW). In this study, cylindrical particles are used as generic non‐spherical particles and are co‐fluidized with small spherical particles. X‐ray particle tracking velocimetry (XPTV) is used to track the 3D particle position and velocity of a single tagged cylindrical particle over a long time period in the binary fluidized bed. The effects of superficial gas velocity (uf), cylindrical particle mass fraction (α), particle sphericity (Φ), and bed material size on the cylindrical tracer particle location and velocity are investigated. Overall, the cylindrical particles are found in the near‐wall region more often than in the bed center region. Increasing the superficial gas velocity uf provide a slight improvement in the uniformity of the vertical and horizontal distributions. Increasing the cylindrical particle mass fraction α causes the bed mixing conditions to transition from complete mixing into partial mixing

Evaluation of mixing and mixing rate in a multiple spouted bed by image processing technique

Mixing efficiency is one of the most significant factors, affecting both performance and scale-up of a gas-solid reactor system. This paper presents an experimental investigation on the particle mixing in a multiple spouted bed. Image processing technique was used to extract the real-time information concerning the distribution of particle components (bed materials and tracer particles). A more accurate definition of the tracer concentration was developed to calculate the mixing index. According to the visual observation and image analysis, the mixing mechanism was revealed and the mixing rate was evaluated. Based on these results, the effects of operation parameters on the mixing rate were discussed in terms of the flow patterns. It is found that the detection of the pixel distribution of each component in RGB images is not affected by the interference of air void, thus maintaining good measurement accuracy. Convective transportation controls the particle mixing in the internal jet and spout, while shear dominants the particle mixing in the dense moving region. Global mixing takes place only when the path from one spout cell to the other is open. This path can be formed either by the bubbles or particle circulation flows. The mixing rate is linked to the bubble motion and particle circulation. Provided that there are interactions between the spout cells, any parameters promoting the bubble motion and circulation can increase the mixing rate. Finally, a mixing pattern diagram was constructed to establish the connection between the flow structure and mixing intensity

Strain-induced semiconductor to metal transition in MA2Z4 bilayers

Very recently, a new type of two-dimensional layered material MoSi2N4 has been fabricated, which is semiconducting with weak interlayer interaction, high strength, and excellent stability. We systematically investigate theoretically the effect of vertical strain on the electronic structure of MA2Z4 (M=Ti/Cr/Mo, A=Si, Z=N/P) bilayers. Taking bilayer MoSi2N4 as an example, our first principle calculations show that its indirect band gap decreases monotonically as the vertical compressive strain increases. Under a critical strain around 22%, it undergoes a transition from semiconductor to metal. We attribute this to the opposite energy shift of states in different layers, which originates from the built-in electric field induced by the asymmetric charge transfer between two inner sublayers near the interface. Similar semiconductor to metal transitions are observed in other strained MA2Z4 bilayers, and the estimated critical pressures to realize such transitions are within the same order as semiconducting transition metal dichalcogenides. The semiconductor to metal transitions observed in the family of MA2Z4 bilayers present interesting possibilities for strain-induced engineering of their electronic properties

Orientation of cylindrical particles in a fluidized bed based on stereo X-ray particle tracking velocimetry (XPTV)

Fluidization of non-spherical particles commonly exists in the biomass utilization and municipal solid waste (MSW) processing industries. In this study, cylindrical particles are used as a typical type of non-spherical particle and its orientation distribution is investigated when being co-fluidized with small spherical bed material. X-ray particle tracking velocimetry (XPTV), based on an X-ray stereography imaging system, is used to measure the 3D orientation of a single tracer particle over a long time period in the fluidized bed. The effects of gas velocity (uf), cylindrical particle mass fraction (ω), particle sphericity (Φ), and bed material size on the orientation distribution of the cylindrical particle are investigated and discussed in detail. An orientation distribution probability density function (PDF) model is proposed based on all experimental results. The distribution probability P of the angle between the cylindrical particle central axis and vertical direction λ across the bed shows two minima in the ranges 0° ≤ λ \u3c 10° and 40° ≤ λ \u3c 50°, and two maxima in the ranges 20° ≤ λ \u3c 30° and 70° ≤ λ \u3c 80°. Increasing uf reduces λ, while the effect of particle sphericity Φ and cylindrical particle mass fraction ω increases with increasing uf

Oxy-coal combustion in a 30kWth pressurized fluidized bed: Effect of combustion pressure on combustion performance, pollutant emissions and desulfurization

Oxy-coal combustion with pressurized fluidized beds has recently emerged as a promising carbon capture and storage (CCS) technology for coal-fired power plants. Although a large number of energy efficiency analyses have shown that an increase in combustion pressure can further increase the net plant efficiency, there are few experimental studies of pressurized oxy-coal combustion conducted on fluidized bed combustors/boilers with continuous coal feeding. In this study, oxy-coal combustion experiments with lignite and anthracite were conducted with a 30 kWth pressurized fluidized bed combustor within the pressure range of 0.1 MPa to 0.4 MPa. The investigation focused on the elucidation of the impacts of combustion pressure on the combustion performance, pollutant emissions and desulfurization of oxy-coal combustion in fluidized beds. The results showed that an increase in pressure increased the combustion efficiency and combustion rate of coal particles, and the promoting effect of pressure increase was more significant for the high rank coal with smaller particle size and the high O2 concentration atmosphere. For both coals, NOx emissions decreased with pressure but N2O emissions increased with pressure and accounted for a considerable part of the nitrogen oxide pollutants under high pressure oxy-coal combustion conditions. The pressure had insignificant impact on the SO2 emissions of oxy-coal combustion but an increase in pressure enhanced the direct desulfurization of limestone

Experimental study of NOx emissions in a 30 kWth pressurized oxy-coal fluidized bed combustor

© 2019 As one of the most promising carbon capture technologies for coal-fired power plants, oxy-coal combustion has attracted wide interests during the last two decades. In comparison to atmospheric oxy-fuel combustion, pressurized oxy-fuel combustion has the potential to further reduce the energy penalties caused by the carbon capture and storage and improve the net power plant efficiency. Although many researchers have investigated the NOx emissions of atmospheric oxy-coal combustion, the NOx emission behaviors under pressurized oxy-coal combustion conditions are much less understood and further comprehensive experimental investigations with continuous fuel-feeding pressurized oxy-coal combustion systems are needed in order to fill this knowledge gap. In the present study, a series of oxy-coal combustion experiments were conducted in a 30 kWth pressurized fluidized bed combustor. The effects of combustion pressure, bed temperature and excess oxygen on the NOx emissions were investigated systematically. The experimental results have shown that an increase in combustion pressure from 0.1 MPa to 0.4 MPa leads to a significant reduction in NOx emissions. An increase in bed temperature or excess oxygen results in higher NOx emissions under the higher combustion pressure conditions, which is consistent with what is observed under the atmospheric pressure combustion condition. Besides, it is found that the promoting effect of temperature increase on NOx emissions under the higher combustion pressures is weaker than that under the atmospheric pressure

Multi-stakeholder perspectives on the impacts of service robots in urban hotel rooms

The main purpose of this exploratory research was to determine city hotel guest, manager, and owner perspectives on the impacts in terms of costs and benefits of the introduction of artificial intelligence (AI) service robots. Hotel guests perceived more benefits than costs while management views were more focused on the costs involved. Owners mainly adopted a financial view of hotel robot use. The negative attitudes held by hotel managers toward AI service robots were related to costs of implementation and a concern that these costs could not be returned. The Technology Readiness Index (TRI) was applied to examine guest perceptions

Immune Protection Induced on Day 10 Following Administration of the 2009 A/H1N1 Pandemic Influenza Vaccine

BACKGROUND: The 2009 swine-origin influenza virus (S-OIV) H1N1 pandemic has caused more than 18,000 deaths worldwide. Vaccines against the 2009 A/H1N1 influenza virus are useful for preventing infection and controlling the pandemic. The kinetics of the immune response following vaccination with the 2009 A/H1N1 influenza vaccine need further investigation. METHODOLOGY/PRINCIPAL FINDINGS: 58 volunteers were vaccinated with a 2009 A/H1N1 pandemic influenza monovalent split-virus vaccine (15 µg, single-dose). The sera were collected before Day 0 (pre-vaccination) and on Days 3, 5, 10, 14, 21, 30, 45 and 60 post vaccination. Specific antibody responses induced by the vaccination were analyzed using hemagglutination inhibition (HI) assay and enzyme-linked immunosorbent assay (ELISA). After administration of the 2009 A/H1N1 influenza vaccine, specific and protective antibody response with a major subtype of IgG was sufficiently developed as early as Day 10 (seroprotection rate: 93%). This specific antibody response could maintain for at least 60 days without significant reduction. Antibody response induced by the 2009 A/H1N1 influenza vaccine could not render protection against seasonal H1N1 influenza (seroconversion rate: 3% on Day 21). However, volunteers with higher pre-existing seasonal influenza antibody levels (pre-vaccination HI titer ≥1∶40, Group 1) more easily developed a strong antibody protection effect against the 2009 A/H1N1 influenza vaccine as compared with those showing lower pre-existing seasonal influenza antibody levels (pre-vaccination HI titer <1∶40, Group 2). The titer of the specific antibody against the 2009 A/H1N1 influenza was much higher in Group 1 (geometric mean titer: 146 on Day 21) than that in Group 2 (geometric mean titer: 70 on Day 21). CONCLUSIONS/SIGNIFICANCE: Recipients could gain sufficient protection as early as 10 days after vaccine administration. The protection could last at least 60 days. Individuals with a stronger pre-existing seasonal influenza antibody response may have a relatively higher potential for developing a stronger humoral immune response after vaccination with the 2009 A/H1N1 pandemic influenza vaccine