A liquid-solid circulating fluidized bed boiler is designed and built for visualization research by applying the fluidized bed heat transfer and fouling prevention technology to the water side of the boiler. Four type...A liquid-solid circulating fluidized bed boiler is designed and built for visualization research by applying the fluidized bed heat transfer and fouling prevention technology to the water side of the boiler. Four types of engineering plastic particles with different physical properties are selected as the solid working media. The effect of particle types on the fluidization and distribution of particles in the boiler is investigated under different feedwater flow rates and amount of added particles by using the charge couple device image measurement and acquisition system. The results show that all kinds of particles can't be normally fluidized and accumulate in the drum at low amount of added particles and feedwater flow rate. The particles with great density and low sphericity are more likely to accumulate. The average solid holdup in the riser tubes increases with the increase in feedwater flow rate and the amount of added particles. The non-uniform degree of particle distribution in the riser tubes generally decreases with the increase in feedwater flow rate and the amount of added particles. The particles with small density and settling velocity have high average solid holdup in the riser tubes under close sphericity. In generally,the smaller the density and settling velocity, the more uniform the particle distribution in the riser tubes.Three-dimensional diagrams of the non-uniform degree of particle distribution in the riser tubes of the boiler are established.展开更多
This article introduces the present status anddevelopment of 600 MW class boilers in China. The statisticaldata indicate that most 600 MW generating units experiencedrelatively length" growing up" period. In...This article introduces the present status anddevelopment of 600 MW class boilers in China. The statisticaldata indicate that most 600 MW generating units experiencedrelatively length" growing up" period. In this period, unitscould not operate stably , their unplanned outage times weremany and durations long, and availabilities low. On the basis oftesting and research and the summing-up of practice, it wasindicated slagging in the furnace, deviation of tine gas energy atthe exit of furnace, and overheating bursting of superheater andreheater etc, endangering the safety and economics ofoperation,main problems could be completely alleviated oravoided through design and type selection of boiler furnace andburners, coal characteristics and coal handling management,and optimization management of operation conditions etc.展开更多
In this paper, we present an investigation of type-II ＇W＇ quantum wells for the InAs/Ga1-xInxSb/A1Sb family, where ＇W＇ denotes the conduction profile of the material. We focus our attention on using the eight-band...In this paper, we present an investigation of type-II ＇W＇ quantum wells for the InAs/Ga1-xInxSb/A1Sb family, where ＇W＇ denotes the conduction profile of the material. We focus our attention on using the eight-band k. p model to calculate the band structures within the framework of finite element method. For the sake of clarity, the simulation in this paper is simplified and based on only one period--A1Sb/InAs/Ga1-xInxSb/InAs/A1Sb. The obtained numerical results include the energy levels and wavefunctions of carriers. We discuss the variations of the electronic properties by changing several important parameters, such as the thickness of either InAs or Cal_xInxSb layer and the alloy composition in Ga1-xInxSb separately. In the last part, in order to compare the eight-band k·p model, we recalculate the conduction bands of the ＇W＇ structure using the one-band k·p model and then discuss the difference between the two results, showing that conduction bands are strongly coupled with valence bands in the narrow band gap structure. The in-plane energy dispersions, which illustrate the suppression of the Auger recombination process, are also obtained.展开更多
MnZn-doped W-type barium cobalt ferrite powder composites of Ba(MnZn)xCo2(1-x)Fe16O27 (x = 0.1, 0.2, 0.3, 0.4, and 0.5) were prepared in a sol-gel process. The microwave absorbing properties of the composites in the r...MnZn-doped W-type barium cobalt ferrite powder composites of Ba(MnZn)xCo2(1-x)Fe16O27 (x = 0.1, 0.2, 0.3, 0.4, and 0.5) were prepared in a sol-gel process. The microwave absorbing properties of the composites in the range of 2 - 18 GHz and their electromagnetic loss mechanisms were studied. The results demonstrated that the synthesized Ba(MnZn)xCo2(1-x)Fe16O27 samples possess a W-type phase of the crystal structure with a hexagonal flaky shape in micro-morphology, and the samples exhibited a soft magnetic trait that enables improving their microwave absorption properties through suitable MnZn doping. For Ba(MnZn)0.4Co1.2Fe16O27 with a thickness of 2.8 mm, the reflection loss peak was -40.7 dB at a frequency of 7.3 GHz, with a bandwidth of 6.6 GHz at a loss of less than -10 dB. The microwave absorption primarily resulted from magnetic losses caused by magnetization relaxation, domain wall resonance, and natural resonance.展开更多
基金supported by the open foundation of State Key Laboratory of Chemical Engineering (SKL–ChE–18B03)the Municipal Science and Technology Commission of Tianjin, China (2009ZCKFGX01900)。
文摘A liquid-solid circulating fluidized bed boiler is designed and built for visualization research by applying the fluidized bed heat transfer and fouling prevention technology to the water side of the boiler. Four types of engineering plastic particles with different physical properties are selected as the solid working media. The effect of particle types on the fluidization and distribution of particles in the boiler is investigated under different feedwater flow rates and amount of added particles by using the charge couple device image measurement and acquisition system. The results show that all kinds of particles can't be normally fluidized and accumulate in the drum at low amount of added particles and feedwater flow rate. The particles with great density and low sphericity are more likely to accumulate. The average solid holdup in the riser tubes increases with the increase in feedwater flow rate and the amount of added particles. The non-uniform degree of particle distribution in the riser tubes generally decreases with the increase in feedwater flow rate and the amount of added particles. The particles with small density and settling velocity have high average solid holdup in the riser tubes under close sphericity. In generally,the smaller the density and settling velocity, the more uniform the particle distribution in the riser tubes.Three-dimensional diagrams of the non-uniform degree of particle distribution in the riser tubes of the boiler are established.
文摘This article introduces the present status anddevelopment of 600 MW class boilers in China. The statisticaldata indicate that most 600 MW generating units experiencedrelatively length" growing up" period. In this period, unitscould not operate stably , their unplanned outage times weremany and durations long, and availabilities low. On the basis oftesting and research and the summing-up of practice, it wasindicated slagging in the furnace, deviation of tine gas energy atthe exit of furnace, and overheating bursting of superheater andreheater etc, endangering the safety and economics ofoperation,main problems could be completely alleviated oravoided through design and type selection of boiler furnace andburners, coal characteristics and coal handling management,and optimization management of operation conditions etc.
基金supported by the National Natural Science Foundation of China (Grant No. 60636030)
文摘In this paper, we present an investigation of type-II ＇W＇ quantum wells for the InAs/Ga1-xInxSb/A1Sb family, where ＇W＇ denotes the conduction profile of the material. We focus our attention on using the eight-band k. p model to calculate the band structures within the framework of finite element method. For the sake of clarity, the simulation in this paper is simplified and based on only one period--A1Sb/InAs/Ga1-xInxSb/InAs/A1Sb. The obtained numerical results include the energy levels and wavefunctions of carriers. We discuss the variations of the electronic properties by changing several important parameters, such as the thickness of either InAs or Cal_xInxSb layer and the alloy composition in Ga1-xInxSb separately. In the last part, in order to compare the eight-band k·p model, we recalculate the conduction bands of the ＇W＇ structure using the one-band k·p model and then discuss the difference between the two results, showing that conduction bands are strongly coupled with valence bands in the narrow band gap structure. The in-plane energy dispersions, which illustrate the suppression of the Auger recombination process, are also obtained.
文摘MnZn-doped W-type barium cobalt ferrite powder composites of Ba(MnZn)xCo2(1-x)Fe16O27 (x = 0.1, 0.2, 0.3, 0.4, and 0.5) were prepared in a sol-gel process. The microwave absorbing properties of the composites in the range of 2 - 18 GHz and their electromagnetic loss mechanisms were studied. The results demonstrated that the synthesized Ba(MnZn)xCo2(1-x)Fe16O27 samples possess a W-type phase of the crystal structure with a hexagonal flaky shape in micro-morphology, and the samples exhibited a soft magnetic trait that enables improving their microwave absorption properties through suitable MnZn doping. For Ba(MnZn)0.4Co1.2Fe16O27 with a thickness of 2.8 mm, the reflection loss peak was -40.7 dB at a frequency of 7.3 GHz, with a bandwidth of 6.6 GHz at a loss of less than -10 dB. The microwave absorption primarily resulted from magnetic losses caused by magnetization relaxation, domain wall resonance, and natural resonance.
