Experimental Study of Defluidization by Continuous Water Injection into a Gas-Solid Fluidized Bed Using Pressure Fluctuation Measurements

2015 ◽  
Vol 798 ◽  
pp. 160-164 ◽  
Author(s):  
Flavia Tramontin Silveira Schaffka ◽  
Giulia Kaminski Tramontin ◽  
Maria Regina Parise
Keyword(s):  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Water Injection ◽  
Fixed Bed ◽  
Experimental Tests ◽  
Flow Rates ◽  
Bubbling Fluidized Bed ◽  
Inner Diameter ◽  
Bed Material

This work studies the induced defluidization condition of a gas-solid fluidized bed system when distilled water is continuously injected into the bed of particles. Experimental tests carried out to different water flow rates were analyzed through a technique based on pressure signals measurements. The bed material used was glass beads (Geldart D particles), with mean diameter of 1.55 mm. Experiments were performed in an acrylic Plexiglas tube with 0.11m in inner diameter and 1.0 m in height, with the bed led from an initially bubbling regime up to attain a fixed bed condition. Pressure fluctuations were acquired and processed using LabVIEW 10.0TMsoftware. Results showed that the defluidization condition promoted by water injection in a bubbling fluidized bed can be efficiently identified using pressure fluctuation measurements.

Horizontal Pressure Fluctuation in Bubbling Fluidized Bed

2003 ◽  
Author(s):  
Vesa V. Walle´n
Keyword(s):  
Pressure Gradient ◽  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Middle Part ◽  
Biomass Combustion ◽  
Bottom Part ◽  
Pressure Transducers ◽  
Bubbling Fluidized Bed ◽  
Horizontal Pressure

Pressure measurements were conducted in a two-dimensional hot atmospheric bubbling fluidized bed reactor in the laboratory of Energy and Process Engineering at Tampere University of Technology. A set of six fast pressure transducers was used to detect the rapid pressure fluctuations inside the bubbling bed of the reactor. These pressure transducers were placed both vertically and horizontally into the reactor. From these measurements it was found that the vertical pressure fluctuation took place at the same time at different levels of the bed. Also the same fluctuation could be seen under the air distributor. The horizontal pressure fluctuation was found to vary both by place and time. At the bottom part of the bed the highest pressure peaks was found at centre of the bed. Most of the time there was a pressure gradient the highest pressure being in the centre of the bed. This gradient creates horizontal flow of gases from middle to the sides. The velocity of this flow varies with the size of the pressure gradient. The opposite effect can be found in the upper part of the bed. The highest pressure was no more in the middle part of the bed. Instead, it was found to be between the centre of the bed and left and right walls. The pressure was low at the walls but also rather low at the middle of the bed. There must be flow towards the walls and to the centre axis. These pressure fluctuations can provide an explanation for the well-known “wandering plume” effect. They can also give a tool to better describe the mixing inside a bubbling fluidized bed. This kind of tool is needed when biomass combustion is modelled in bubbling fluidized bed.

Study of Defluidization Region of Large Particles in Fluidized Bed Using the Gaussian Spectral Pressure Distribution

2015 ◽  
Vol 1104 ◽  
pp. 69-74
Author(s):  
Flavia Tramontin Silveira ◽  
Frederic Conrad Janzen ◽  
Maria Regina Parise
Keyword(s):  
Pressure Distribution ◽  
Fluidized Bed ◽  
Pressure Fluctuations ◽  
Fixed Bed ◽  
Environment Temperature ◽  
Large Particles ◽  
Inner Diameter ◽  
Pressure Transmitter ◽  
Group D ◽  
Fluidization Condition

The present work aimed to identify the defluidization region of a gas-solid fluidized bed system composed by Geldart group D particles using the Gaussian spectral pressure distribution technique, which is based on pressure fluctuation measurements in the plenum. In experiments, the defluidization condition of glass beads with apparent density of 2,450 kg/m3 was induced in a plexiglas column of 0.11 m in inner diameter and 1.0 m in height. The gas-solid behavior close to the incipient fluidization condition was assessed for two fixed bed heights (0.10 and 0.20 m) and two mean sizes of particles (1.55 and 2.18 mm in diameter). The bed was fluidized with air at environment temperature. The experimental equipment was instrumented with a pressure transmitter connected to a data acquisition system in order to record the pressure fluctuations of the gas-solid flow. The results showed that the defluidization region can be detected efficiently by using the Gaussian spectral pressure distribution technique, which contributes for a better control of fluidized bed processes.

Experimental Investigation of Pressure Fluctuations on Inner Wall of a Centrifugal Pump

2019 ◽  
Vol 36 (4) ◽  
pp. 401-410 ◽  
Author(s):  
Xiao-Qi Jia ◽  
Bao-Ling Cui ◽  
Zu-Chao Zhu ◽  
Yu-Liang Zhang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
High Flow ◽  
Low Flow ◽  
Centrifugal Pumps ◽  
Flow Rates ◽  
Pressure Distributions ◽  
Blade Passing Frequency

Abstract Affected by rotor–stator interaction and unstable inner flow, asymmetric pressure distributions and pressure fluctuations cannot be avoided in centrifugal pumps. To study the pressure distributions on volute and front casing walls, dynamic pressure tests are carried out on a centrifugal pump. Frequency spectrum analysis of pressure fluctuation is presented based on Fast Fourier transform and steady pressure distribution is obtained based on time-average method. The results show that amplitudes of pressure fluctuation and blade-passing frequency are sensitive to the flow rate. At low flow rates, high-pressure region and large pressure gradients near the volute tongue are observed, and the main factors contributing to the pressure fluctuation are fluctuations in blade-passing frequency and high-frequency fluctuations. By contrast, at high flow rates, fluctuations of rotating-frequency and low frequencies are the main contributors to pressure fluctuation. Moreover, at low flow rates, pressure near volute tongue increases rapidly at first and thereafter increases slowly, whereas at high flow rates, pressure decreases sharply. Asymmetries are observed in the pressure distributions on both volute and front casing walls. With increasing of flow rate, both asymmetries in the pressure distributions and magnitude of the pressure decrease.

Enhancement of the Distribution of a Liquid Sprayed Into a Fluidized Bed

2004 ◽  
Vol 2 (1) ◽  
Author(s):  
David Zhou ◽  
Mohammad Saberian ◽  
Cedric Briens ◽  
Franco Berruti ◽  
Edward W Chan ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Evaporation Rate ◽  
Water Solution ◽  
Water Injection ◽  
Fixed Bed ◽  
Cylindrical Tube ◽  
Invasive Technique ◽  
Measured Concentration ◽  
Liquid Distribution ◽  
Wetted Area

In the fluid coking process, bitumen and steam are sprayed into a fluidized bed of coke particles. The liquid reacts on the surface of the hot particles to give distillate products, light gases and coke. A good primary particle/liquid mixing in the spray jet is required in order to achieve high yields of valuable products and minimize operability problems due to particles agglomeration or loss of bed fluidity.An Enhanced Solids Entrainment (ESE) device has been proposed to improve the mixing of droplets and particles during injection. It consists of a cylindrical tube mounted co-axially downstream of the spray nozzle. The objective of this study is to develop an effective and convenient non-invasive technique to quantify the improvements in liquid distribution on the particles that results from the use of ESE device.A slug of 30 vol% ethanol in water solution is sprayed into a fluidized bed of sand. The bed is defluidized shortly after the start of the ethanol water injection. Then, the gas-solid contacting pattern is changed to fixed bed, with downward airflow. The evaporation rate can be obtained from the measured concentration of ethanol in the gaseous effluent. The evaporation rate depends on the wetted area that is exposed to the gas. Good primary dispersion of the liquid on particles yields a large exposed wetted area and, hence, a high evaporation rate. A model is used to estimate the distribution of liquid on the particles from the measured evaporation rate.The experimental results show that the ESE device produces a more uniform primary liquid distribution on the particles, increasing by 7 to 21 % the mass of solids contacted by the injected liquid.

scholarly journals Experimental Investigation of Radial Gas Dispersion Coefficients in a Fluidized Bed

10.14311/1568 ◽  
2012 ◽  
Vol 52 (3) ◽  
Author(s):  
Jiří Štefanica ◽  
Jan Hrdlička
Keyword(s):  
Fluidized Bed ◽  
Formation Rate ◽  
Combustion Efficiency ◽  
Tracer Gas ◽  
Cold Model ◽  
Nox Formation ◽  
Gas Dispersion ◽  
Bed Height ◽  
Bubbling Fluidized Bed ◽  
Bed Material

In a fluidized bed boiler, the combustion efficiency, the NOX formation rate, flue gas desulphurization and fluidized bed heat transfer are all ruled by the gas distribution. In this investigation, the tracer gas method is used for evaluating the radial gas dispersion coefficient. CO2 is used as a tracer gas, and the experiment is carried out in a bubbling fluidized bed cold model. Ceramic balls are used as the bed material. The effect of gas velocity, radial position and bed height is investigated.

Investigating the flow structures in semi-cylindrical bubbling fluidized bed using pressure fluctuation signals

2019 ◽  
Vol 30 (6) ◽  
pp. 1247-1256
Author(s):  
Seyedeh Mahsa Okhovat-Alavian ◽  
Jamshid Behin ◽  
Navid Mostoufi
Keyword(s):  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Flow Structures ◽  
Bubbling Fluidized Bed

scholarly journals Systematic Study of Pressure Fluctuation in the Riser of a Dual Inter-Connected Circulating Fluidized Bed: Using Single and Binary Particle Species

Processes ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 890 ◽  
Author(s):  
Yusif A. Alghamdi ◽  
Zhengbiao Peng ◽  
Caimao Luo ◽  
Zeyad Almutairi ◽  
Behdad Moghtaderi ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Pressure Fluctuation ◽  
Circulating Fluidized Bed ◽  
Pressure Fluctuations ◽  
Single Species ◽  
Terminal Velocity ◽  
Operating Conditions ◽  
Cold Flow ◽  
Fluidization Regime ◽  
Spectrum Density

This study systematically investigates the pressure fluctuation in the riser of a dual interconnected circulating fluidized bed (CFB) representing a 10 kWth cold-flow model (CFM) of a chemical-looping combustion (CLC) system. Specifically, a single-species system (SSS) and a binary-mixtures system (BMS) of particles with different sizes and densities were utilized. The pressure fluctuation was analyzed using the fast Fourier transform (FFT) method. The effect of introducing a second particle, changing the inventory, composition (i.e., 5, 10 to 20 wt.%), particle size ratio, and fluidization velocity were investigated. For typical SSS experiments, the results were similar to those scarcely reported in the literature, where the pressure fluctuation intensity was influenced by varying the initial operating conditions. The pressure fluctuations of BMS were investigated in detail and compared with those obtained from SSS experiments. BMS exhibited different behaviour; it had intense pressure fluctuation in the air reactor and in the riser when compared to SSS experiments. The standard deviation (SD) of the pressure fluctuation was found to be influenced by the fluidization regime and initial operating conditions, while the power spectrum density (PSD) values were more sensitive to the presence of the particles with the higher terminal velocity in the binary mixture.

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