Stable operating range and solids residence time of fine fluorite particles in the two-stage fluidized bed

Advanced drying technology enables drying of rough rice and dedusting of rice husks to be carried out simultaneously in the same unit processor. This paper reports the efficiency of dedusting of rice husks in a two-stage inclined cross flow fluidized bed dryer and the drying kinetics of rough rice in a batch fluidized bed dryer as well as the conceptual design of a hybrid drying dedusting unit processor. Experimental works had been carried out using rough rice (a Group D particle according to Geldart classification of powders) in a 2.5 m height two-stage inclined fluidized bed column of cross sectional area of 0.61m x 0.15m and a 3 m high batch fluidized bed dryer. The objectives of the study was to investigate the separation efficiency of dedusting of rice husks in the two-stage cross flow fluidized bed dryer and to study the drying kinetics of rough rice drying in the batch fluidized bed dryer. The experimental results showed that the dedusting separation efficiency at low superficial gas velocity gave unsatisfactory separation of merely 40% of rice husks. At higher superficial gas velocity, separation efficiency of rice husks as high as 93% was achieved. In addition, higher distributor inclination angle gave slightly improved separation efficiency. The drying kinetics showed that the residence time that is required to reduce the moisture content of rough rice to 18% (intermediate storage moisture content for second stage drying) is 3 minutes whereas the residence time that is required to reduce the moisture content to 13% (desirable final moisture content) is approximately 10 minutes regardless of the effect of kernel cracking. It was also found that higher drying temperatures gave higher drying rate. A conceptual design has been developed based on the results obtained in the studies. In order to maximize the heat utilization and to carry out two processes viz. dedusting and drying in one unit processor, it is suggested that drying dedusting can be carried out in a multistage mode where drying is taken place at each stage while dedusting is taking place at the upper stage. This concept can be applied to a packed bed or a fluidized bed unit processor.

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An Investigation of the Stability Enhancement of a Centrifugal Compressor Stage Using a Porous Throat Diffuser

Journal of Turbomachinery ◽

10.1115/1.4038181 ◽

2017 ◽

Vol 140 (1) ◽

Cited By ~ 8

Author(s):

Lee Galloway ◽

Stephen Spence ◽

Sung In Kim ◽

Daniel Rusch ◽

Klemens Vogel ◽

...

Keyword(s):

Centrifugal Compressor ◽

Compressor Stage ◽

Vaned Diffuser ◽

Flow Rates ◽

Stall Inception ◽

Centrifugal Compressor Stage ◽

Operating Range ◽

Stable Operating ◽

The Stability ◽

Circumferential Pressure

The stable operating range of a centrifugal compressor stage of an engine turbocharger is limited at low mass flow rates by aerodynamic instabilities which can lead to the onset of rotating stall or surge. There have been many techniques employed to increase the stable operating range of centrifugal compressor stages. The literature demonstrates that there are various possibilities for adding special treatments to the nominal diffuser vane geometry, or including injection or bleed flows to modify the diffuser flow field in order to influence diffuser stability. One such treatment is the porous throat diffuser (PTD). Although the benefits of this technique have been proven in the existing literature, a comprehensive understanding of how this technique operates is not yet available. This paper uses experimental measurements from a high pressure ratio (PR) compressor stage to acquire a sound understanding of the flow features within the vaned diffuser which affect the stability of the overall compression system and investigate the stabilizing mechanism of the porous throat diffuser. The nonuniform circumferential pressure imposed by the asymmetric volute is experimentally and numerically examined to understand if this provides a preferential location for stall inception in the diffuser. The following hypothesis is confirmed: linking of the diffuser throats via the side cavity equalizes the diffuser throat pressure, thus creating a more homogeneous circumferential pressure distribution, which delays stall inception to lower flow rates. The results of the porous throat diffuser configuration are compared to a standard vaned diffuser compressor stage in terms of overall compressor performance parameters, circumferential pressure nonuniformity at various locations through the compressor stage and diffuser subcomponent analysis. The diffuser inlet region was found to be the element most influenced by the porous throat diffuser, and the stability limit is mainly governed by this element.

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Development of a novel two-stage fluidized bed incineration technology for the control of heavy metal emissions

Waste Management ◽

10.1016/0956-053x(93)90107-8 ◽

1993 ◽

Vol 13 (5-7) ◽

pp. 524-525

Author(s):

Thomas C. Ho

Keyword(s):

Heavy Metal ◽

Fluidized Bed ◽

Two Stage ◽

Fluidized Bed Incineration ◽

Heavy Metal Emissions

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A method for measuring the residence time distribution of particles in a fluidized bed based on digital image analysis

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2020-0177 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Jiamin Li ◽

Xiaoping Chen ◽

Jiliang Ma ◽

Cai Liang

Keyword(s):

Image Analysis ◽

Fluidized Bed ◽

Residence Time ◽

Digital Image ◽

Time Distribution ◽

Residence Time Distribution ◽

Digital Image Analysis ◽

Color Space ◽

The Difference ◽

Accuracy And Repeatability

AbstractTraditional methods for measuring the residence time distribution (RTD) of particles in a fluidized bed are complex and time-consuming. To this regard, the present work proposes a new measurement method with remarkable efficiency based on digital image analysis. The dyed tracers are recognized in the images of the samples due to the difference of colors from bed materials. The HSV and the well-known RGB color space were employed to distinguish the tracers. By enhancing the Saturation and the Value in HSV and adjusting the gray range of images, the recognition error is effectively reduced. Then the pixels representing the tracers are distinguished, based on which the concentration of the tracers and RTD are measured. The efficiency, accuracy and repeatability of the method were validated by RTD measurements experiments. The method is also fit for distinguishing the target particles from multi-component systems consisting of particles of different colors.

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Numerical Investigation of an Asymmetric Double Suction Centrifugal Compressor With Different Backswept Angle Matching for a Wide Operating Range

Volume 2C: Turbomachinery ◽

10.1115/gt2017-63372 ◽

2017 ◽

Author(s):

Hanzhi Zhang ◽

Dazhong Lao ◽

Longyu Wei ◽

Ce Yang ◽

Mingxu Qi

Keyword(s):

Mass Flow ◽

Centrifugal Compressor ◽

Flow Distribution ◽

Operating Mode ◽

Mode Transition ◽

Distribution Characteristics ◽

Operating Range ◽

Stable Operating ◽

Angle Difference ◽

Matching Models

The work presented here investigates the characteristics of the different impeller backswept angle matchings for a wide stable operating range in an asymmetric double suction centrifugal compressor. The numerical simulation was employed to investigate the influence of different backswept angle matchings on the stable operating range. The aim is to propose a proper change of the backswept angle matching between two impeller sides to improve the impeller power capability and mass flow distribution, furthermore, to delay the operating mode transition and widen the stable operating range of the compressor. Firstly, the method to determine the optimum backswept angle matching obtained by the theory calculation. Then, three matching models were proposed and analyzed in detail. In three matching models, the backswept angle differences between the front and rear impeller side are 0°, 10° and 20°, respectively. The analysis mainly focused on the influence of the different backswept angle matchings on the compressor flow field characteristics and the mass flow distribution characteristics. The results show that the change of the impeller backswept angle matching can improve the mass flow distribution characteristics for two impeller sides and further reduce the stall mass flow rate of the double suction compressor. The model that the backswept angle difference is 10° can delay the operating mode transition and reduce the stall mass flow of the double suction compressor. The model that the backswept angle difference is 20° can also reduce the stall mass flow and finally enable the front impeller into the stall condition. Therefore, the proper change of the backswept angle matching can achieve the purpose of reducing the stall mass flow and widening the operating range for the double suction centrifugal compressor.

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