Experimental Study on Fluidization Characteristics of an Air-Sand Bed inside a Rectangular Fluidized Bed

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Delft University of Technology

FACULTY MECHANICAL, MARITIME AND MATERIALS ENGINEERING

Department Maritime and Transport Technology Mekelweg 2 2628 CD Delft the Netherlands Phone +31 (0)15-2782889 Fax +31 (0)15-2781397 www.mtt.tudelft.nl

This report consists of 34 pages and 2 appendices. It may only be reproduced literally and as a whole. For commercial purposes only with written authorization of Delft University of Technology. Requests for consult are

Specialization: Transport Engineering and Logistics Report number: 2014.TEL.7907

Title: Experimental Study on

Fluidization Characteristics of an Air-Sand Bed inside a Rectangular Fluidized Bed

Author: S. Kraijema

Assignment: Research assignment

Confidential: No

Initiator (university): S.M. Derakhshani, M.Sc. Dr.Ir. D.L. Schott Supervisor: S.M. Derakhshani, M.Sc.

Dr.Ir. D.L. Schott

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Delft University of Technology

FACULTY OF MECHANICAL, MARITIME AND MATERIALS ENGINEERING

Department of Marine and Transport Technology Mekelweg 2 2628 CD Delft the Netherlands Phone +31 (0)15-2782889 Fax +31 (0)15-2781397 www.mtt.tudelft.nl

Student: S. Kraijema Assignment type: Research assignment

Supervisor (TUD): S.M. Derakhshani, M.Sc. Creditpoints (EC): 15 Dr.Ir. D.L. Schott Specialization: TEL

Report number: 2014.TEL.7907 Confidential: No

Subject: Experimental Study on Fluidization

A fluidized bed is formed when a granular material is converted from a static solid-like state to a dynamic fluid-like state. This process occurs when a pressurized fluid (liquid or gas) is passed up through the granular material. Recently, there has been interest in the application of fluidized bed technology in the industrial production and process. Therefore, a good knowledge of gas and particle dynamics is essential for evaluating the important characteristics of a fluidized bed [1].

In a liquid-fluidized bed, the upward liquid velocity is in between the minimum fluidization velocity and the terminal settling velocity of a single particle [2]. The single particle terminal settling velocity is key parameter in fluidization, as it is the highest superficial liquid velocity attainable in a fluidized bed. The macroscopic parameters that describe the behaviour of the fluidized bed in the bubbling regime are: minimum fluidization velocity, pressure drop across the bed, bed height increase, porosity and particle elutriation.

In this research assignment the macroscopic properties of a fluidized bed will be determined by performing a series of laboratory experiments.

 Essential steps

 A literature review of fluidized bed systems

 Measuring the macroscopic properties of a fluidized bed throughout the experiments

1. Deb, S. and D. Tafti, Investigation of flat bottomed spouted bed with multiple jets using DEM– CFD framework. Powder Technology, 2014. 254: p. 387-402.

2. Van Zessen, E., et al., Fluidized-bed and packed-bed characteristics of gel beads. Chemical Engineering Journal, 2005. 115(1): p. 103-111.

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Summary

Fluidized beds are widely used in chemical processing industries where a large contact area is required between a fluid and solid particles. Examples can be found in various applications, such as reactors or separation, combustion, and drying processes. In order to design such a chemical process, a thorough understanding of the fluid and particle behaviour in fluidized state is required. Hence a large amount of research is conducted to describe this behaviour and capture it in models. Recently hybrid models are successfully used to simulate the behaviour of fluidized beds in the bubbling phase. These models require experimental data to check their validity.

The goal of this research is to experimentally determine the key parameters used to describe the behaviour - on a macroscopic level - of a fluidized bed system containing dried Dorsilit type 8 sand particles, fluidized by air in a rectangular shaped vessel. These parameters are: the minimum fluidization velocity, the pressure drop over the bed, the bed height increase, and the bed void fraction.

The measurements were performed on a small and a medium sized rectangular fluidized bed vessels. The cross sectional area was 8 x 90 mm and 15 x 200 mm respectively. The pressure drop over the bed, bed height and fluid flow rate were measured directly. The minimum fluidization velocity and bed void fraction were derived from the measured values. The most important key parameter to describe the behaviour of a fluidized bed system is the minimum fluidization velocity. of which the results are given in Table 1.

Table 1: Summary of experimental minimum fluidization velocities Fluidization velocity Umf [m/min]

Solid bed height [mm]

Small vessel, derived from:

Medium vessel, derived from:

Pressure drop Bed height Pressure drop Bed height

100 19,5 19,5 18,6 16,4

150 23,1 20,0 18,5 15,7

200 22,8 18,9 18,2 16,3

250 24,6 20,7 18,6 15,7

The measurements with a solid bed height of 250mm in the small sized vessel had a bed height to width ratio of 0,032 and showed a two-phase bed at the minimum fluidization velocity of 18,6 m/min. None of the experiments with a higher ratio showed this

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phenomenon. It is opted that this behaviour can be explained by the dampening effects that may occur with high bed height to width ratio’s. It is recommended to perform further research to investigate the validity of this hypothesis and to understand the mechanics behind this behaviour.

Measurements using the small sized vessel had a solid particle diameter to hydraulic bed diameter ratio of 0,027. All measurements with a ratio higher then 0,027 showed an increased minimum fluidization velocity due to wall effects. It is recommended to perform further experimental research to find the relations between the dimensions of a rectangular vessel and material properties of both bed and vessel.

The results and data provided by this experimental research is intended to be used to validate simulation models of fluidized bed setups in rectangular vessels. The data should be sufficient to validate models using the same bed material and vessel dimensions. This research also provides some insight to the relevance of the ratio’s between vessel dimensions and bed properties, such as bed height and particle diameter. For best results it is recommended to perform future measurements using a fluidization vessel with known distributor internals. The following parameters should be known; (1) dimensions of the screen, (2) absence of flow diverters, (3) inner dimensions of the distributor chamber and inlet pipe.

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List of symbols

Symbol Unit Property

a m length of the bed

b m width of the bed

l/min volumetric flow rate of fluid

∆P bar pressure drop over the bed

∆Ptot bar pressure drop over the bed and distributor

U m/s fluid velocity

Umf m/s minimum fluidization velocity

H m height of the bed - void fraction of the bed

µ Pa.s viscosity of the fluid

Dp m solid particle diameter

Vt m3 total volume of the bed

Vp m3 volume occupied by particles

ρp kg/m3 particle density W kg weight of the bed

A m2 cross sectional area of the bed

DH m hydraulic diameter of the vessel

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1 Introduction

Background

Fluidized beds are mostly used in chemical processing industries where a large contact area is required between a fluid and solid particles. Figure 1 gives a schematic overview of a fluidized bed setup. Examples of applications can be found in reactors of all sizes where the solid particles contain a catalyst. The advantage of a fluidized bed reactor is the increased reaction rate, which is directly proportional to the contact area. Other applications are for example found in separation processes, like the preparation of coal. In a fluidized bed particles of smaller specific gravity will float on top of particles with a greater specific gravity and vice versa. This causes the particles to be distributed according to their specific gravity and allows for separation. Yoshida, et al. [3] describe this application in more detail. Fluidized beds are also used for both batch sized and continuous drying of solids with particle size ranging from 50µm to 5000 µm [4]. The advantage over other drying techniques like spray drying or flash drying, is the reduced drying time. This is due to uniform temperature distribution and high heat and mass transfer rates in the fluidized bed. Fluidized beds are used in various combustion processes as well. Lyngfelt, Leckner, and Mattisson [5] present a proposal to use a chemical looping combustion system using two fluidized beds in order to separate CO2 from fuel gasses. In chemical looping combustion

systems, metal oxide particles are used as bed material. They serve as oxygen carrier for the combustion of fuel in the first bed and re-oxidize in air in the second bed. The big advantage of such a combustion process is that the combustion air and the fuel are separated from each other and the chemical reactions are greatly simplified. Also, due to the absence of nitrogen, no harmful NOX gasses are formed. In some combustion processes, sand is added

as primary bed material on which the combustible particles are fed in to the furnace, see Figure 1 for a schematic representation.

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1 Introduction

This setup is for example used to increase the heat transfer rate for the devolatilization of coal. In a fluidized sand bed furnace, the coal is rapidly heated to a temperature in excess of 350°C [7]. This causes thermal decomposition of the coal and a fraction of the volatile content is released. Fluidized sand beds are also used in biological filtering systems for circulating water applications, such as aquaculture systems. Summerfelt [8] describes the various design aspects of such a filter.

In order to design the earlier mentioned chemical processes, a thorough understanding of the fluid and particle behaviour in fluidized state is required. Hence a large amount of research is conducted to describe this behaviour and capture it in models. Most of the recent models are based on Computational Fluid Dynamics (CFD) modelling [9]. Recently hybrid models are successfully used to simulate the behaviour of fluidized beds in the bubbling phase using Distinct Element Modelling (DEM) coupled with CFD [10]. These models require experimental data to check their validity.

Goal of the research

The goal of this research is to experimentally determine the key parameters used to describe the behaviour - on a macroscopic level - of a fluidized bed system containing dried Dorsilit type 8 sand particles, fluidized by air in a rectangular shaped vessel.

Outline

First the theoretical fundamentals of fluidized bed systems are explained in chapter 2. Then the methodology and experimental setup used to perform the measurement are described in chapter 3. The results of the experiments are given and discussed in chapter 4. Finally, the conclusions and recommendations are given in chapter 5.

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2 Theory of fluidized beds

This section will give a brief overview of the relevant theoretical background needed to understand and perform the experimental research on fluidized beds, reported in this work. The key parameters used to describe the fluidization mechanics are introduced in section 2.1. Then the flow regimes in which the fluidized bed can operate are illustrated in section 2.2.

2.1 Macroscopic parameters

The parameters that describe the behaviour of the fluidized bed on macroscopic level are the minimum fluidization velocity, particle elutriation, bed height, pressure drop over the bed, and the void fraction of the bed [2].

Minimum fluidization velocity

Assume a fluid travels upwards through the voids in a bed of solid particles, refer to Figure 2 for a visual representation. When the fluid velocity is low, the particles are not disturbed by the fluid flow. In literature this is referred to as a packed bed. When the fluid velocity increases, the hydrodynamic drag forces on the particles also increase and can exceed the particles gravitational force. In literature this fluid velocity is referred to as the single particle terminal settling velocity. Beyond this fluid velocity, the particles will be elevated by the fluid and the bed will start to expand. At this stage the voids between the particles in the bed will increase which causes the drag force to drop again due to reduced fluid velocity and vice versa. The fluid velocity at which a state of pseudo equilibrium is reached is referred to as the minimum fluidization velocity.

Figure 2: Schematic representation of a fluidized bed of solid particles, with increased fluid velocity from left to right [11].

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The minimum fluidization velocity is the superficial fluid velocity at which the packed bed becomes a fluidized bed [12]. At this velocity, the forces of gravity, buoyancy, and hydrodynamic drag on all particles in the bed are in a state of quasi equilibrium. In fact this is a highly dynamic state caused by differences in particle size, shape, and orientation [12].

Particle elutriation

Particle elutriation is a term used to describe the separation of particles of different sizes and shapes in a fluidized bed. In literature this process is also called entrainment or carryover [12]. This process is caused by differences in terminal settling velocity of different sized and shaped particles. The terminal settling velocity of a particle is reached when the forces of gravity, buoyancy, and drag are in a state of equilibrium and is therefore size and shape dependant. Also the orientation of a particle in relation to the fluid velocity influences the terminal settling velocity. This phenomenon causes the smaller particles to float to the upper region of the bed and even eject from the surface of the bed when the fluid velocity almost reaches the minimum fluidization velocity. Significantly smaller particles like dust will completely leave the vessel.

Pressure drop over the bed

Friction between the fluid and the particles in the bed will cause a pressure drop over the bed. In the packed bed stage, the pressure drop will increase with increased fluid velocity. Once the bed begins to expand and enters the fluidized stage, the pressure drop will remain constant. Figure 3 shows a diagram of the pressure drop over the bed as a function of the fluid velocity.

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Bed void fraction

The void fraction of the bed is the ratio between the volume occupied by the solid particles over the total bed volume. This parameter can used to describe the theoretical relation between the pressure drop over the bed and the fluid velocity [12]. This relation is given by the Carman - Kozney equation (2), where ∆P is the pressure drop over the bed, U is the fluid velocity, µ is the viscosity of the fluid, Dp is the solid particle diameter, and is the void

fraction of the bed.

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Bed height

As the fluid velocity increases beyond the minimum fluidization velocity, the bed will start to expand. The bed height increase is needed to experimentally determine the average bed void fraction.

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Figure 4: Flow regimes of fluidized beds [13]

2.2 Flow regimes

A fluidized bed can operate in various flow regimes, much like pipe flow can operate in turbulent or laminar flow regime depending on the Reynolds number. The Reynolds number in pipe flow depends on the material properties of the fluid, the pipe dimensions, and the fluid velocity. The flow regime in a fluidized bed is dictated by the material properties of both fluid and solid, dimensions of the vessel, and the fluid velocity [14].

When the fluid velocity is increased through a given bed, the system will pass through up to seven different flow regimes, depending on the material properties of the solid and the dimensions of the vessel. Figure 4 gives a visual representation of the seven flow regimes of fluidized beds. Initially the fluid velocity is too small to disturb the particles in the bed. This first regime is called the fixed bed regime. The second regime is entered when the fluid velocity is increased beyond the minimum fluidization velocity. The bed expands as the particles are lifted by the fluid. This non-bubbling fluidization is often referred to as the homogeneous or particulate regime. Some solids skip this phase and bubbles will be formed directly beyond the minimum fluidization velocity, i.e. it enters the bubbling regime. Whether or not a solid will fluidize without forming bubbles depends on the particle size, the density of the solid, and the density of the fluid [14]. If the fluid velocity is increased further still, the bubbles will increase in size as they raise up through the bed. In relatively small vessels, the diameter of the bubbles will match the width of the vessel before collapsing. This is referred to as slugging. As the fluid velocity is increased even further, the bed will successively enter the turbulent flow regime, fast fluidization regime, and pneumatic transport regime.

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Figure 5: Geldart's powder classifications [14]

It was mentioned earlier that the observed sequence of flow regimes can vary with different solids. In [14], Geldart describes four classifications of powders based on the particle size, the density of the solid, and the density of the fluid in order to predict their fluidization behaviour in air under ambient conditions. Figure 5 shows the relation between group classifications and material properties.

 Powders that will smoothly fluidize at a relatively low fluid velocity without bubbling are classified as Group A. Group A powders will show a homogeneous regime at fluid velocities at and little beyond the minimum fluidization velocity before entering the bubbling regime. In the bubbling regime they tend to have a maximum bubble size [13].

 Group B powders can be fluidized as well, but bubbles will be formed directly after the fluid velocity reaches the minimum fluidization velocity. The bubble size will keep increasing with increasing velocity [13]. Group B powders are typically sand-like materials. Figure 6 shows the typical behaviour of a fluidized sand bed at increasing air velocity settings.

 Very fine and cohesive powders are designated as Group C powders. Due to relatively large cohesive forces, these powders are extremely difficult to fluidize. Channelling is one of the main problems that arise when trying to fluidize Group C powders [12].

 Large particle powders are categorized as Group D powders. When fluid velocity is increased, a Group D powder will form a jet in the bed from which particles will be ejected in a spouting motion.

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3 Methodology

This section gives a detailed description of the methodology followed in order to obtain the required experimental data. Note that only the macroscopic parameters are measured during these experiments. The macroscopic parameters used to describe fluidized bed behaviour are the minimum fluidization velocity, the pressure drop over the bed, the bed height increase, the bed void fraction, and the particle elutriation. Microscopic parameters such as particle velocity, solid circulation rate, and granular temperature are not covered in this work.

3.1 Material properties

The solid material used in this experiments is dried Dorsilit sand of type 8-1: 2010. The material properties are given in Table 2. Figure 7 shows the particle size distribution of Dorsilit 8-1: 2010 as experimentally determined by Derakhshani [15]. According to Geldart's classification this material belongs to powder Group B, also refer to Figure 5. Air was used as fluid material.

Table 2: Material properties of Dorsilit 8-1: 2010 [15] Dorsilit 8-1: 2010

Particle shape Rounded Particle diameter 300-600µm Particle density 2,653 kg/dm3 Bulk density 1,530 kg/dm3

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3 Methodology

3.2 Experimental setup

The layout of the experimental setup1 is visualized in Figure 8. The experimental setup consists of a rectangular fluidization vessel (8) containing a bed (7) of Dorsilit type 8 sand. The top of the fluidization vessel is open to ambient air. The bottom of the vessel contains a distributor (5), where air enters on the side and has to pass through a fine screen (6) before flowing up through the bed. Air entering the system is pressurized by a compressor (1) to 8 bar and pressure relieved to 4 bar by a hand operated pressure regulator valve (2). This is necessary to ensure proper operation of the flow regulator (3). The airflow is measured and controlled using a flow regulator in conjunction with a PI controller (4). The pressure in the distributor is measured by means of a pressure transducer (9) connected to the distributor. The transducer is read out by a digital multi meter (10), set to measure volts DC. The vessel has measuring tape applied at both sides in order to monitor and measure the bed height.

Figure 8: Schematic layout of experimental setup.

Figure 9: Schematic representation of the bottom side and distributor of the vessel.

1

All experiments were performed in the O&O group laboratory of the Chemical Engineering department of the Technical University of Delft under the supervision of Dr. Ir. J.R. van Ommen.

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3 Methodology

3.3 Equipment

The specifications for all of the equipment used during the experiments are given in this part.

Pressure regulator

The pressure of the supplied air is reduced from approximately 8 bar to 4 bar using a hand operated pressure regulator. The pressure is read from a analogue gauge with a scale showing tenths of a bar. The pressure is set to 4 bar with an approximate accuracy of 1 percent. This setting is not of great significance since the flow controller will operate correctly in a wider range of feed pressure.

Flow regulator

The volume flow rate of air is controlled by Bronkhorst EL-FLOW flow controller. The flow rate for air is adjustable in the range 0 - 100L/min. It has an accuracy of 0,5% on the reading [16].

PI controller

The flow regulator is controlled by a HI-TEC Model E-5514-5A PI controller. The controller displays the percentage of the maximum flow rate of the flow controller. The display shows the percentage with 1 decimal accuracy.

Fluidization vessel

Measurements were performed using two different sized vessels. The reason for this is to be able to compare both results and evaluate the influence of wall friction. The small vessel has a cross sectional area a x b of 90 mm x 8 mm. The wall material is glass on the front and back and brass on the sides. The medium sized vessel has a cross sectional area a x b of 200 mm x 15 mm. The wall material is Perspex. The vessel has measuring tape applied to both sides of the bed, with a scale of 1mm accuracy.

Pressure transducer

The pressure in the distributor is measured by a FSM Elektronik Type DPS. The transducer has a measuring range of 0 - 200mBar and gives an output signal ranging from 0 - 10V.

Digital multi meter

The output signal of the pressure transducer is read using an Elro M970 set to the 20V DC range. The voltage is displayed with 2 decimals accuracy.

HD Camera

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3 Methodology

3.4 Measurements

The parameters that need to be determined during the experiments can be divided into three groups. Table 3 gives an overview of these parameter groups. The first group consists of input parameters, the second group are the parameters that can be measured directly, and the third group are the parameters that have to be derived from directly measured parameters. The method of determination of each parameter is given in this section.

Table 3: Parameter groups Parameters

Input Measured Derived

Fluid volumetric flow rate Fluid velocity U

Total pressure drop ∆Ptot Pressure drop over bed ∆P

Minimum fluidization velocity Umf

Bed height H Bed void fraction

Due to fluctuations of pressure and bed height with increasing fluid velocity, it is necessary to average the readings. The averages are estimated over 10 seconds. Each measurement session is recorded on video.

Fluid volumetric flow rate

The volumetric flow rate of the fluid is an input parameter and is set and regulated by the PI controller that is connected to the flow regulator. The range of settings is given in Table 4. Note that actually the volumetric flow rate is set and therefore fluid velocity in the bed has to be derived using the cross sectional area of the vessel.

Table 4: Fluid volumetric flow rate settings Fluid volumetric flow rate settings

Vessel size Range Increment size Small 0 - 26 L/min 1 L/min

26 - 0 L/min 1 L/min Medium 0 - 100 L/min 5 L/min 100 - 0 L/min 5 L/min

These settings are found by filling the vessel to an initial bed height of 200mm. Next, the fluid velocity is increased to well within the bubbling regime. This setting is reached when large bubbles are formed in the bed and the pressure reading heavily fluctuates. The

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3 Methodology

appropriate range of fluid volumetric flow rates is chosen so that it includes measurements starting in the fixed bed regime to well within the bubbling regime. The increment size is chosen so that at least 10 measurements are performed both before and after passing the minimum fluidization velocity.

Pressure drop

The pressure drop over the bed cannot be measured directly, due to restrictions of the available equipment. The pressure transducer can only be connected to the fluidization vessel in such a way that the pressure in the distributor chamber is measured. This means that the pressure drop over the distributor screen is also included in the measurement and needs to be subtracted to determine the pressure drop over the bed. The pressure drop over the distributor screen is measured with an empty vessel for all volumetric flow rate settings of the fluid, given in Table 4.

Bed height

The fluidized bed vessel has measuring tape applied on both sides of the bed, so the bed height can be measured directly. Due to the highly dynamic behaviour in the bubbling regime, the average bed height will be registered. The settings for initial bed height are given in Table 5. The minimum initial bed height is chosen to be 100mm because of expected erratic behaviour of the bed with lower settings. This is due to the lack of dampening effects in the bed [17].

The vessel is filled with the specified material to the desired initial bed height, according to Table 5. Due to consolidation of the material during filling it is difficult to set the initial bed height precisely to the desired height. The weight of the material is measured on a scale for each bed height setting. This is done before the material is filled into the vessel. In order to minimize the effect of consolidation stresses between the particles in the bed on the measurements, the fluid velocity is set to the upper bound of the range for at least 1 minute. From there, it is slowly reduced to the lower bound of the range. Fresh material is used for every new setting to minimize moisture build up in the bed.

Table 5: Initial bed height settings Initial bed height

100 mm 150 mm 200 mm 250 mm

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3 Methodology

The minimum fluidization velocity is derived from the relation between the pressure drop over the bed and the fluid velocity. The fluid velocity at which the pressure drop remains constant, is the minimum fluidization velocity. Figure 3 gives a visual representation of the relation between the pressure drop as a function of the fluid velocity and the minimum fluidization velocity. It is considered best practice to measure the pressure drop for at least 10 fluid velocity settings on both sides of the knee in the graph, with both increasing and decreasing velocity settings [17]. The latter will give a slightly different graph, due to the absence of consolidation stresses in the bed material.

Bed void fraction

There are two methods available to derive the void fraction of the bed. One method is using the Carman - Kozney equation (2) in the region where the relation between the fluid velocity and the pressure drop is linear and use the slope to calculate the void fraction. In the Carman - Kozney equation µ is the fluid viscosity and Dp is the solid particle diameter.

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The second method is directly based on the bed void fraction definition: the fraction of the total volume of the bed, not occupied by particles. This can be calculated using equation (3), where Vt is the total volume of the bed andVp is the volume occupied by particles.

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The total bed volume is determined by the product of the bed height and the cross sectional area of the bed A. The volume of the particles is determined by the weight of the bed W, divided by the particle density ρp. The bed void fraction can now be calculated using

equation (4).

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Note that air is compressible and therefore the air density varies over the bed height. Both segregation and particle elutriation will cause the density of the bed to vary over the bed height. It is also important to measure the ambient air temperature in order to be able to calculate the air density.

Also note that bed void fraction calculations will probably vary between different measurements, because of differences in particle orientation in the initial packed bed.

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3 Methodology

Experimental plan

All measurements are performed according to the procedures described in the previous section and repeated three times for each vessel. The number of repetitions is limited to three times, due to the fact that high consistency of the measurements is observed in the initial stage of the experiment. This is consistent with the experience of J.R. van Ommen [17]. An overview of all measurements is given in the experimental plan in Table 6.

Table 6: Experimental plan, repeated 3 times Experimental plan

ID Vessel size Initial bed height

Fluid volumetric flow rate settings Range Increment size 1 Small Empty vessel 0 - 26 L/min 1 L/min

2 Small 100 mm 0 - 26 L/min 1 L/min 3 Small 100 mm 26 - 0 L/min 1 L/min 4 Small 150 mm 0 - 26 L/min 1 L/min 5 Small 150 mm 26 - 0 L/min 1 L/min 6 Small 200 mm 0 - 26 L/min 1 L/min 7 Small 200 mm 26 - 0 L/min 1 L/min 8 Small 250 mm 0 - 26 L/min 1 L/min 9 Small 250 mm 26 - 0 L/min 1 L/min 10 Medium Empty vessel 0 - 100 L/min 5 L/min 11 Medium 100 mm 0 - 100 L/min 5 L/min 12 Medium 100 mm 100 - 0 L/min 5 L/min 13 Medium 150 mm 0 - 100 L/min 5 L/min 14 Medium 150 mm 100 - 0 L/min 5 L/min 15 Medium 200 mm 0 - 100 L/min 5 L/min 16 Medium 200 mm 100 - 0 L/min 5 L/min 17 Medium 250 mm 0 - 100 L/min 5 L/min 18 Medium 250 mm 100 - 0 L/min 5 L/min

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4 Results and discussion

4 Results

and discussion

The results of the fluidization experiments are presented in this section, categorised by parameter and vessel size. The raw experimental data, is given in Appendix A: Data.

The minimum fluidization velocity is derived from the bed pressure drop versus fluid velocity plots. This is done according to the methods described in section 3. The minimum fluidization velocity is also derived from the bed height increase plotted against the fluid velocity. The fluid velocity at which the bed height starts to increase significantly - i.e. the intersection between the horizontal and diagonal lines - is assumed to be the minimum fluidization velocity.

Table 7 gives a summary of all experimental minimum fluidization velocities, categorised by vessel size and solid bed height. The plots that are used to derive these values are given in Appendix B: Minimum fluidization velocity derivation plots.

Table 7: Summary of experimental minimum fluidization velocities Fluidization velocity Umf [m/min]

Solid bed height [mm]

Small vessel, derived from:

Medium vessel, derived from:

Pressure drop Bed height Pressure drop Bed height

100 19,5 19,5 18,6 16,4

150 23,1 20,0 18,5 15,7

200 22,8 18,9 18,2 16,3

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Pressure drop

Figure 10 shows the pressure drop over the bed versus the fluid velocity for the small vessel. The results of measurement ID 2 to 9 (according to Table 6) are visible in the plot, i.e. 100mm, 150mm, 200mm, and 250mm solid bed height.

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Figure 11 shows the pressure drop over the bed versus the fluid velocity for the medium sized vessel. The results of measurement ID 11 to 18 (according to Table 6) are visible in the plot, i.e. 100mm, 150mm, 200mm, and 250mm solid bed height.

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When the results of Figure 10 and Figure 11 are compared, it is clear to see the difference in system behaviour between the small sized vessel and the medium sized vessel. The latter gives a classic example of the expected relation between the pressure drop over the bed and the fluid velocity. Whereas Figure 10 shows that the pressure drop keeps increasing at fluid velocities well beyond the minimum fluidization velocity. Moreover, the minimum fluidization velocity is higher in the small sized vessel, with same solid bed height. Refer to Figure 12 for a typical plot comparing the results of both vessels, using 200mm solid bed height. This phenomenon can be subscribed to an increased influence of wall friction inside the small vessel, in literature called the wall effect. The solid particles near the wall of the vessel experience an increased drag force that effects the single particle terminal settling velocity. According to Richardson and Zaki this wall effect can be described by the ratio between the hydraulic diameter of the vessel DH and the particle diameter dp [2]. In [18],

Richardson and Zaki propose a correction of the terminal settling velocity v∞:

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Figure 12: Pressure drop versus fluid velocity, with 200mm solid bed height comparing both vessels.

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Both vessels used in this experiments are rectangular shaped, so the hydraulic diameter DH is

used to calculate the correction factors, where a is the vessel length and b is the vessel width:

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Using both equation (5) and (6) results in a correction factor of 0,94 for the small sized vessel and 0,97 for the medium sized vessel. The correction factor is used here to quantify the relevance of the wall effect on the behaviour of the bed. The lower the correction factor, the higher the impact of wall effects on the single particle terminal velocity and therefore the minimum fluidization velocity of the bed. Between the small and medium sized vessels, there is a significant difference in wall effect relevance and this could explain the observed behaviour. To find the relation between the hydraulic diameter of a rectangular vessel and the wall effect on the minimum fluidization velocity is a recommended topic for future research. One should include a series of experiments in order to the quantify the parameters that describe the friction between the wall and bed particles, e.g. the wall friction angle. The same effects can be found in Figure 11 with increasing solid bed height. The wall effect correction factor is relatively small for the medium sized vessel and can therefore not explain this phenomenon. Moreover, it only appears at solid bed heights of 200mm and more. However, referring to Table 7, it does not seem to have a significant effect on the minimum fluidization velocity.

A difference is observed between the minimum fluidization velocity derived from the pressure drop over the bed and the one derived from the bed height. An explanation can be found in the way the minimum fluidization velocity is obtained from both measurements. The derivation from the bed height uses the increasing fluidization plot. Whereas the derivation from the bed pressure drop uses the de-fluidization plot. In this case the derivation from the increasing fluidization plot results in a lower fluidization velocity. The difference seems more pronounced using the small sized vessel.

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Bed height

Figure 13 shows the bed height versus the fluid velocity for the small sized vessel. The results of measurement ID 2 to 9 (according to Table 6) are visible in the plot, i.e. 100mm, 150mm, 200mm, and 250mm solid bed height.

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Figure 14 shows the bed height versus the fluid velocity for the medium sized vessel. The results of measurement ID 11 to 18 (according to Table 6) are visible in the plot, i.e. 100mm, 150mm, 200mm, and 250mm solid bed height.

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Bed void fraction

The void fraction of the bed is derived from the bed height using Equation (4). Note that this method gives an average void fraction over the complete height of the bed.

Figure 15 shows the void fraction of the bed versus the fluid velocity for the small sized vessel. The results of measurement ID 2 to 9 (according to Table 6) are visible in the plot, i.e. 100mm, 150mm, 200mm, and 250mm solid bed height.

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Figure 16 shows the void fraction of the bed versus the fluid velocity for the medium sized vessel. The results of measurement ID 11 to 18 (according to Table 6) are visible in the plot, i.e. 100mm, 150mm, 200mm, and 250mm solid bed height.

When comparing the results of the average void fraction of the small vessel (plotted in Figure 15) with the results of the medium sized vessel (plotted in Figure 16), one can see the influence of increased bed weight. The void fraction calculated from increasing fluidization is smaller than the void fraction calculated from de-fluidization. This effect is more pronounced when using the medium sized vessel. This is due to increased consolidation stress caused by the weight of the bed on de-fluidization.

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During the experiments it was observed that the material behaves like a Geldart Group B powder as expected. However, an interesting phenomenon was experienced during the measurements using a 250mm solid bed height in the small sized vessel (measurement ID 8, 9). At the minimum fluidization velocity the system started to behave like a 2 phase system where the upper part was operating in the homogeneous regime and the lower part in the bubbling regime. Figure 17 gives a screenshot to visualize this two-phase system behaviour. This might be explained by dampening effects occurring when the bed height to width ratio is high. In this case the bed height to width ratio was 0,032. None of the measurements with a higher ratio showed this behaviour. Further investigation would be necessary to confirm this hypothesis.

Figure 17: Two-phase system at minimum fluidization velocity, using small sized vessel with 250mm solid bed height

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Error analysis

This section gives an objective assessment of the possible errors in the data and results presented in this work. According to [19], there are three types of experimental error sources, causing deviation between model predictions and experimental data: (1) wrong properties, (2) random errors of measurement, and (3) bias errors.

The solid material is not sieved to before conducting the experiments. However the exact distribution of particle sizes is known and given in Figure 7. The bed void fraction calculations are based on the particle density of Dorsolit 8 which is experimentally determined in [15].

Readings of the bed pressure drop and bed height start to fluctuate with increasing fluid velocity. The fluctuation ranges from about 1% at fluid velocities little over the minimum fluidization velocity up to 10% in the upper range of the fluid velocities used during the experiments. In order to get more reliable results in the upper regions of the bubbling regime, it is recommended to record the data from the pressure transducer against time using a computer. Using this method, the data can be processed using statistics software in order to determine the average with a high level of accuracy. However, the effect on the derived minimum fluidization velocities is expected to be insignificantly small. In this research, the error is minimized by performing all measurements three times and use the averaged results. This assumption is supported by the flat part of the plots in Figure 11 where the average pressure drop over the bed remains constant. The standard deviation of all measurements are give in the tables of Appendix A: Data.

The effect of possible bias or calibration errors are considered to be insignificant in comparison with the possible errors of measurement reading described above.

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5 Conclusions and recommendations

5 Conclusions

and recommendations

Four key parameters were experimentally determined in order to describe the behaviour of an air fluidized bed of Dorsilit type 8 sand particles on macroscopic level. These parameters are: the minimum fluidization velocity, the pressure drop over the bed, the bed height increase, and the bed void fraction.

It is concluded that the results of the experiments follow the theoretical behaviour as expected from literature research. With the exception of some special cases, where either the bed height to width ratio or the solid particle diameter to hydraulic bed diameter ratio were out of proportion. Both ratios are important factors that have a significant impact on the system behaviour.

The measurements with a solid bed height of 250mm in the small sized vessel had a bed height to width ratio of 0,032 and showed a two-phase bed at the minimum fluidization velocity of 18,6 m/min. None of the experiments with a higher ratio showed this phenomenon. It is opted that this behaviour can be explained by the dampening effects that may occur with high bed height to width ratio’s. It is recommended to perform further research to investigate the validity of this hypothesis and to understand the mechanics behind this behaviour.

Measurements using the small sized vessel had a solid particle diameter to hydraulic bed diameter ratio of 0,027. All measurements with a ratio higher then 0,027 showed an increased minimum fluidization velocity due to wall effects. It is recommended to perform further experimental research to find the relations between the dimensions of a rectangular vessel and material properties of both bed and vessel.

The results and data provided by this experimental research is intended to be used to validate simulation models of fluidized bed setups in rectangular vessels. The data should be sufficient to validate models using the same bed material and vessel dimensions. This research also provides some insight to the relevance of the ratio’s between vessel dimensions and bed properties, such as bed height and particle diameter. For best results it is recommended to perform future measurements using a fluidization vessel with known distributor internals. The following parameters should be known; (1) dimensions of the screen, (2) absence of flow diverters, (3) inner dimensions of the distributor chamber and inlet pipe.

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References

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http://www.bronkhorst.com/files/downloads/brochures/folder-el-flow.pdf. 17. Ommen, J.R.v. 2014.

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Appendix A: Data

This section gives all raw data of the experiments. ID 1: Small sized vessel, empty vessel

Values are averaged over 3 measurements air flow rate air velocity pressure SD pressure [l/min] [m/min] [mbar] [mbar]

0,0 0,0 0,0 0,0 1,8 2,5 2,1 0,1 3,0 4,1 3,5 0,1 3,9 5,4 5,1 0,1 4,9 6,8 6,9 0,1 5,9 8,2 8,7 0,1 7,0 9,7 10,8 0,0 7,9 11,0 12,8 0,0 9,0 12,5 15,1 0,2 9,9 13,8 17,2 0,0 11,0 15,3 19,7 0,1 12,0 16,7 21,9 0,1 13,0 18,1 24,5 0,1 14,0 19,4 26,9 0,1 15,0 20,9 29,5 0,1 16,0 22,2 32,0 0,2 17,0 23,7 34,8 0,2 18,0 25,0 37,3 0,1 19,1 26,5 40,3 0,1 20,1 27,9 43,0 0,2 21,0 29,2 45,9 0,1 22,1 30,7 48,8 0,0 23,1 32,0 51,7 0,2 24,1 33,4 54,5 0,2 25,1 34,8 57,9 0,2 26,1 36,2 60,7 0,2

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Appendix A: Data

ID 2, 3: Small sized vessel, 100mm solid bed height (100,433g bed weight)

Values are averaged over 3 measurements air flow rate air velocity pressure corrected pressure height void fraction SD pressure SD height [l/min] [m/min] [mbar] [mbar] [mm] [mbar] [mm]

0,0 0,0 0,0 0,0 100 0,474 0,0 0 1,8 2,5 3,5 1,4 100 0,474 0,1 0 2,9 4,0 6,0 2,5 100 0,474 0,2 0 3,9 5,4 8,8 3,7 100 0,474 0,2 0 4,9 6,8 11,9 4,9 100 0,474 0,1 0 5,9 8,2 15,1 6,4 100 0,474 0,1 0 6,9 9,6 18,1 7,3 100 0,474 0,1 0 7,9 11,0 21,6 8,8 100 0,474 0,0 0 8,9 12,3 25,1 10,0 100 0,474 0,1 0 9,9 13,8 28,9 11,7 100 0,474 0,1 0 10,9 15,1 32,2 12,5 100 0,474 0,2 0 11,9 16,6 36,3 14,3 100 0,475 0,1 0 13,0 18,0 40,1 15,7 101 0,479 0,2 1 14,0 19,4 43,6 16,7 101 0,481 0,3 1 15,0 20,9 47,1 17,6 103 0,489 0,5 1 16,0 22,3 50,1 18,1 108 0,513 0,4 0 17,0 23,7 53,5 18,7 110 0,520 0,1 0 18,0 25,0 56,7 19,4 111 0,526 0,2 1 19,1 26,5 60,3 20,1 115 0,541 0,2 0 20,1 27,9 63,7 20,7 118 0,554 0,2 0 21,0 29,2 67,1 21,2 120 0,561 0,4 0 22,1 30,6 70,7 21,9 124 0,577 0,2 1 23,1 32,1 74,2 22,5 127 0,584 0,2 1 24,0 33,4 77,2 22,7 128 0,589 0,9 0 25,1 34,9 81,2 23,3 132 0,602 0,9 0 26,1 36,3 85,9 25,2 136 0,613 0,2 1 24,9 34,6 80,9 23,0 131 0,599 0,7 1 23,9 33,2 76,7 22,2 128 0,589 0,8 0 22,9 31,9 73,5 21,8 125 0,579 0,1 0 21,9 30,5 70,1 21,3 121 0,565 0,2 1 20,9 29,0 66,7 20,8 120 0,560 0,3 0 19,9 27,7 63,3 20,3 118 0,554 0,3 0 18,9 26,3 59,9 19,6 114 0,540 0,1 0 17,9 24,8 56,3 19,0 111 0,526 0,2 0 16,8 23,3 52,7 17,9 109 0,516 0,2 0 15,8 22,0 49,3 17,3 108 0,511 0,4 0 14,8 20,6 45,8 16,3 105 0,497 0,3 0 13,8 19,2 42,1 15,2 104 0,494 0,2 0 12,8 17,8 38,4 13,9 103 0,489 0,3 0 11,8 16,4 34,7 12,7 102 0,486 0,2 0 10,8 15,0 31,1 11,4 102 0,484 0,3 0

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Appendix A: Data 9,9 13,7 27,9 10,7 102 0,484 0,1 0 8,9 12,4 24,7 9,6 102 0,484 0,2 0 7,9 10,9 21,0 8,2 101 0,479 0,2 0 6,8 9,5 17,6 6,8 101 0,479 0,2 0 5,9 8,2 14,7 6,1 101 0,479 0,1 0 4,9 6,8 11,7 4,7 101 0,477 0,2 0 3,8 5,3 8,6 3,5 100 0,474 0,0 0 2,9 4,1 6,0 2,5 100 0,474 0,0 0 1,8 2,5 3,5 1,4 100 0,474 0,1 0 0,0 0,0 0,0 0,0 100 0,474 0,0 0

Table 9: Data from measurement ID 2, 3.

0,0 0,0 0,0 0,0 149 0,471 0,0 0 1,9 2,6 4,1 2,0 149 0,471 0,1 0 2,9 4,1 7,1 3,6 149 0,471 0,1 0 3,9 5,4 10,3 5,1 149 0,471 0,1 0 4,9 6,8 13,8 6,9 149 0,471 0,2 0 5,9 8,2 17,4 8,7 149 0,471 0,2 0 6,9 9,6 21,2 10,4 149 0,471 0,2 0 7,9 11,0 25,1 12,3 149 0,471 0,1 0 8,9 12,4 29,1 14,1 149 0,471 0,2 0 9,9 13,8 33,3 16,1 149 0,471 0,2 0 11,0 15,2 37,7 17,9 149 0,472 0,3 1 12,0 16,7 42,0 20,1 150 0,474 0,3 0 13,0 18,1 46,1 21,7 150 0,477 0,2 1 14,0 19,4 50,0 23,1 151 0,478 0,2 0 15,0 20,9 53,4 23,9 153 0,487 0,2 0 16,1 22,3 56,9 24,9 157 0,500 0,2 1 17,0 23,6 60,1 25,3 160 0,509 0,1 0 18,0 25,0 63,3 26,0 168 0,531 0,2 0 19,1 26,5 67,0 26,7 174 0,548 0,2 1 20,0 27,8 70,7 27,7 178 0,557 0,5 0 21,0 29,2 73,5 27,7 181 0,565 0,4 1 22,1 30,6 77,7 28,9 188 0,581 0,5 0 23,1 32,0 81,7 29,9 191 0,587 0,5 1 24,0 33,4 85,0 30,5 197 0,600 0,8 2 25,1 34,8 88,0 30,1 203 0,612 0,0 2 26,1 36,3 92,0 31,3 208 0,622 0,0 2

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Appendix A: Data 23,9 33,2 84,7 30,1 199 0,605 0,5 1 23,0 31,9 81,0 29,3 193 0,592 0,0 1 22,0 30,5 76,5 27,7 189 0,583 0,4 1 20,9 29,1 73,5 27,7 184 0,572 0,4 1 19,9 27,6 70,4 27,4 178 0,557 0,0 2 19,0 26,3 66,8 26,5 173 0,544 0,2 2 17,8 24,8 62,9 25,6 167 0,529 0,2 1 16,9 23,5 59,5 24,7 162 0,515 0,1 1 15,9 22,1 55,7 23,7 159 0,505 0,2 0 14,9 20,7 51,7 22,3 157 0,498 0,2 0 13,9 19,3 47,6 20,7 155 0,494 0,2 0 12,9 17,9 43,5 19,0 155 0,493 0,1 0 11,9 16,5 39,5 17,6 154 0,488 0,1 0 10,9 15,1 35,4 15,7 152 0,484 0,2 0 9,9 13,7 31,9 14,7 152 0,483 0,1 0 8,8 12,2 27,9 12,8 151 0,480 0,1 0 7,8 10,8 24,1 11,3 151 0,478 0,1 0 6,8 9,5 20,4 9,6 150 0,476 0,2 0 5,8 8,1 16,9 8,2 150 0,476 0,1 0 4,9 6,8 13,5 6,5 150 0,476 0,2 0 3,8 5,3 10,0 4,9 150 0,474 0,0 0 2,9 4,1 7,1 3,5 149 0,473 0,1 0 1,8 2,5 4,1 2,0 149 0,472 0,1 0 0,0 0,0 0,0 0,0 149 0,472 0,0 0

0,0 0,0 0,0 0,0 195 0,463 0,0 0 1,8 2,5 4,4 2,3 195 0,463 0,0 0 2,9 4,0 7,8 4,3 195 0,463 0,0 0 3,8 5,3 11,5 6,4 195 0,463 0,1 0 4,9 6,8 15,5 8,5 195 0,463 0,1 0 5,9 8,2 19,5 10,9 195 0,463 0,1 0 6,9 9,6 23,7 12,9 195 0,463 0,1 0 7,9 11,0 28,3 15,5 195 0,463 0,1 0 8,9 12,4 32,7 17,7 195 0,463 0,2 0 9,9 13,8 37,4 20,2 195 0,463 0,2 0 10,9 15,2 42,1 22,4 195 0,463 0,2 0 12,0 16,6 46,7 24,8 196 0,465 0,1 0 13,0 18,0 51,5 27,1 198 0,469 0,3 0

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Appendix A: Data 13,9 19,4 55,5 28,6 199 0,473 0,5 1 15,0 20,8 58,3 28,8 204 0,485 0,5 1 16,1 22,3 62,4 30,4 209 0,499 0,2 1 17,0 23,6 65,5 30,7 217 0,516 0,1 2 18,0 25,0 69,2 31,9 221 0,525 0,3 1 19,0 26,4 73,0 32,7 227 0,539 0,0 2 20,1 27,9 76,2 33,2 233 0,551 0,3 1 21,0 29,2 79,3 33,5 238 0,559 0,5 2 22,1 30,6 83,3 34,5 244 0,571 0,5 3 23,1 32,1 88,0 36,3 252 0,583 0,0 2 24,0 33,4 91,3 36,8 258 0,594 0,9 2 25,1 34,8 94,7 36,8 265 0,604 0,9 0 26,1 36,2 98,7 38,0 270 0,612 0,9 0 24,9 34,5 95,3 37,5 265 0,604 0,9 0 23,9 33,2 90,7 36,1 260 0,597 0,9 0 22,9 31,8 86,0 34,3 253 0,585 0,0 4 21,9 30,4 83,0 34,2 246 0,574 0,8 1 20,9 29,0 79,0 33,1 241 0,564 0,8 1 19,9 27,6 76,3 33,3 235 0,554 0,5 0 18,9 26,3 72,3 32,0 229 0,543 0,4 1 17,9 24,9 69,1 31,7 224 0,533 0,1 1 16,8 23,3 65,3 30,5 215 0,512 0,1 0 15,8 22,0 61,1 29,1 209 0,499 0,1 0 14,9 20,7 56,5 27,1 206 0,490 0,2 0 13,8 19,2 51,9 25,1 204 0,487 0,2 0 12,8 17,8 47,7 23,3 203 0,483 0,1 0 11,8 16,4 43,5 21,6 202 0,481 0,1 0 10,8 15,0 39,3 19,5 200 0,476 0,1 0 9,8 13,6 35,2 18,0 199 0,474 0,2 0 8,8 12,2 31,1 16,1 198 0,471 0,1 0 7,8 10,8 26,9 14,1 198 0,469 0,2 0 6,8 9,4 22,8 12,0 197 0,468 0,0 0 5,8 8,1 18,9 10,2 197 0,467 0,1 0 4,8 6,7 15,1 8,1 196 0,465 0,2 0 3,8 5,3 11,3 6,2 196 0,465 0,2 0 2,8 3,9 7,7 4,1 196 0,465 0,1 0 1,9 2,6 4,6 2,5 196 0,465 0,0 0 0,0 0,0 0,0 0,0 195 0,462 0,0 0

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Appendix A: Data

0,0 0,0 0,0 0,0 245 0,464 0,0 0 1,8 2,5 4,9 2,8 245 0,464 0,1 0 2,9 4,0 8,5 5,0 245 0,464 0,2 0 3,9 5,4 12,4 7,3 245 0,464 0,2 0 4,9 6,8 16,6 9,7 245 0,464 0,2 0 5,9 8,2 21,1 12,5 245 0,464 0,2 0 6,9 9,6 25,5 14,7 245 0,464 0,3 0 7,9 11,0 30,2 17,4 245 0,464 0,2 0 8,9 12,4 35,1 20,1 245 0,464 0,2 0 9,9 13,8 40,1 22,9 245 0,464 0,4 0 10,9 15,1 44,9 25,2 245 0,464 0,2 0 12,0 16,6 50,7 28,8 245 0,464 0,2 0 13,0 18,1 56,1 31,7 245 0,465 0,4 0 14,0 19,4 61,2 34,3 246 0,468 0,2 0 15,0 20,9 66,3 36,8 251 0,478 0,1 4 16,1 22,3 68,9 36,9 254 0,485 1,2 3 17,0 23,6 72,3 37,5 258 0,493 1,2 1 18,0 25,0 76,6 39,3 267 0,508 1,6 3 19,1 26,5 79,0 38,7 274 0,522 0,8 1 20,1 27,9 83,3 40,3 282 0,535 0,9 1 21,0 29,2 86,0 40,1 289 0,547 0,0 1 22,0 30,6 90,0 41,2 298 0,560 0,0 3 23,1 32,0 94,0 42,3 306 0,571 0,0 1 24,0 33,4 98,0 43,5 311 0,579 0,0 2 25,1 34,8 101,3 43,5 317 0,586 0,9 3 26,1 36,3 105,3 44,7 323 0,594 0,9 2 24,8 34,5 102,0 44,1 319 0,590 0,0 1 24,0 33,3 97,3 42,8 311 0,578 0,9 1 23,0 31,9 92,7 40,9 303 0,567 0,9 0 22,0 30,5 90,0 41,2 296 0,557 0,0 1 20,9 29,0 86,0 40,1 289 0,547 0,0 1 19,9 27,6 83,3 40,3 283 0,537 0,9 1 18,9 26,3 80,0 39,7 274 0,522 0,0 2 17,8 24,8 76,7 39,3 266 0,507 0,9 4 16,8 23,3 72,6 37,8 259 0,495 0,2 1 15,8 22,0 66,4 34,4 258 0,491 0,7 0 14,9 20,7 61,0 31,5 256 0,489 0,4 0 13,9 19,3 56,2 29,3 256 0,487 0,3 0 12,8 17,8 51,6 27,1 254 0,485 0,3 0 11,8 16,4 47,2 25,3 253 0,482 0,3 0 10,9 15,1 42,8 23,1 250 0,476 0,3 0

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Appendix A: Data 9,9 13,7 38,4 21,2 250 0,475 0,3 0 8,9 12,4 33,9 18,9 248 0,471 0,2 0 7,8 10,9 29,1 16,3 247 0,469 0,2 0 6,8 9,4 24,6 13,8 246 0,467 0,3 0 5,8 8,1 20,6 11,9 246 0,467 0,4 0 4,8 6,7 16,4 9,5 246 0,466 0,3 0 3,9 5,4 12,5 7,3 245 0,466 0,3 0 2,9 4,0 8,4 4,9 245 0,466 0,3 0 1,9 2,6 5,1 3,0 245 0,465 0,1 0 0,0 0,0 0,0 0,0 244 0,464 0,0 0

ID 10: Medium sized vessel, empty vessel Values are averaged over 3

measurements air flow rate air velocity pressure SD pressure [l/min] [m/min] [mbar] [mbar]

0,0 0,0 0,0 0,0 4,9 1,6 2,6 0,0 9,9 3,3 5,3 0,1 14,9 5,0 8,0 0,0 20,0 6,7 10,6 0,0 25,0 8,3 13,4 0,0 30,0 10,0 16,0 0,0 35,1 11,7 18,8 0,0 40,1 13,4 21,6 0,0 45,1 15,0 24,5 0,1 50,1 16,7 27,3 0,1 55,1 18,4 30,4 0,0 60,0 20,0 33,4 0,0 65,0 21,7 36,6 0,0 70,1 23,4 39,9 0,1 75,0 25,0 43,2 0,0 80,0 26,7 46,7 0,1 85,0 28,3 50,3 0,1 90,1 30,0 54,1 0,1 95,3 31,8 58,3 0,1 100,2 33,4 62,3 0,1

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Appendix A: Data

ID 11, 12: Medium sized vessel, 100mm solid bed height (480,88g bed weight)

0,0 0,0 0,0 0,0 105 0,422 0,0 0 5,0 1,7 4,1 1,5 105 0,422 0,1 0 9,9 3,3 8,2 2,9 105 0,422 0,0 0 15,1 5,0 12,4 4,4 105 0,422 0,2 0 20,0 6,7 16,6 6,0 105 0,422 0,2 0 24,9 8,3 20,7 7,3 105 0,422 0,2 0 29,9 10,0 24,9 8,9 105 0,422 0,3 0 34,9 11,6 29,3 10,5 105 0,422 0,4 0 39,9 13,3 33,7 12,1 105 0,422 0,5 0 45,0 15,0 38,1 13,6 105 0,422 0,6 0 50,0 16,7 41,8 14,5 106 0,428 0,4 0 55,0 18,3 45,3 14,9 109 0,447 0,2 0 60,0 20,0 48,7 15,3 112 0,460 0,1 2 65,1 21,7 52,0 15,4 116 0,480 0,0 1 70,0 23,3 55,3 15,4 120 0,496 0,1 0 75,1 25,0 58,8 15,6 125 0,515 0,2 0 80,0 26,7 61,9 15,3 129 0,532 0,1 1 85,1 28,4 65,7 15,4 133 0,546 0,2 1 90,1 30,0 69,6 15,5 139 0,564 0,0 1 95,2 31,7 73,7 15,3 141 0,570 0,1 1 100,2 33,4 77,1 14,7 143 0,578 0,4 1 95,0 31,7 73,3 14,9 141 0,570 0,2 1 90,0 30,0 69,4 15,3 136 0,555 0,3 1 84,9 28,3 65,7 15,4 133 0,545 0,2 1 79,9 26,6 61,9 15,2 129 0,530 0,1 1 74,8 24,9 58,2 15,0 124 0,514 0,2 1 69,7 23,2 54,7 14,9 120 0,496 0,2 0 64,7 21,6 51,5 14,9 117 0,484 0,1 1 59,8 19,9 48,3 14,9 112 0,462 0,1 0 54,8 18,3 44,7 14,3 109 0,447 0,1 0 49,9 16,6 40,8 13,5 107 0,435 0,2 0 45,0 15,0 36,7 12,1 106 0,429 0,2 0 40,0 13,3 32,5 10,9 106 0,429 0,2 0 35,0 11,7 28,3 9,5 106 0,429 0,2 0 30,1 10,0 24,2 8,2 106 0,429 0,0 0 25,0 8,3 20,1 6,7 105 0,426 0,1 0 20,0 6,7 16,0 5,4 105 0,424 0,0 0 15,0 5,0 12,0 4,0 105 0,424 0,0 0 10,0 3,3 7,9 2,7 105 0,424 0,1 0 4,8 1,6 3,8 1,2 105 0,424 0,0 0

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Appendix A: Data

0,0 0,0 0,0 0,0 105 0,424 0,0 0

0,0 0,0 0,0 0,0 150 0,444 0,0 0 5,0 1,7 4,7 2,1 150 0,444 0,1 0 10,0 3,3 9,5 4,2 150 0,444 0,1 0 15,1 5,0 14,3 6,3 150 0,444 0,1 0 19,9 6,6 19,0 8,4 150 0,444 0,2 0 25,0 8,3 24,0 10,6 150 0,444 0,2 0 29,9 10,0 28,9 12,9 150 0,444 0,2 0 35,1 11,7 33,9 15,1 150 0,444 0,2 0 39,9 13,3 38,8 17,2 151 0,446 0,4 0 45,0 15,0 43,9 19,3 151 0,448 0,5 0 50,0 16,7 48,3 21,0 154 0,458 0,9 1 55,1 18,4 51,7 21,3 159 0,475 0,2 0 60,0 20,0 56,0 22,6 163 0,489 1,1 1 65,2 21,7 59,1 22,5 169 0,505 0,2 1 70,2 23,4 62,3 22,5 175 0,524 0,1 2 75,1 25,0 65,3 22,1 180 0,536 0,1 2 80,0 26,7 69,0 22,3 183 0,543 0,2 0 85,0 28,3 73,0 22,7 190 0,561 0,0 0 90,1 30,0 76,7 22,6 199 0,581 0,2 1 95,1 31,7 80,6 22,3 203 0,589 0,3 1 100,2 33,4 85,1 22,8 205 0,593 0,7 0 95,0 31,7 80,5 22,2 201 0,584 0,1 1 89,9 30,0 76,3 22,2 198 0,579 0,4 0 84,9 28,3 73,0 22,7 191 0,563 0,2 1 79,8 26,6 69,5 22,8 187 0,553 0,2 2 74,9 25,0 65,7 22,5 179 0,535 0,2 1 69,9 23,3 61,9 22,0 174 0,519 0,1 1 64,9 21,6 58,5 21,9 169 0,505 0,1 1 60,0 20,0 55,1 21,7 162 0,486 0,1 0 55,1 18,4 51,5 21,1 159 0,475 0,2 1 50,1 16,7 46,9 19,6 155 0,461 0,1 0 45,1 15,0 42,2 17,7 154 0,458 0,2 0 40,1 13,4 37,4 15,8 153 0,454 0,2 0 35,2 11,7 32,7 13,9 152 0,452 0,2 0 30,1 10,0 28,0 12,0 152 0,451 0,2 0

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Appendix A: Data 20,0 6,7 18,6 8,0 151 0,448 0,2 0 14,9 5,0 13,9 5,9 151 0,446 0,1 0 9,9 3,3 9,1 3,9 150 0,445 0,1 0 4,9 1,6 4,5 1,9 150 0,444 0,1 0 0,0 0,0 0,0 0,0 150 0,444 0,0 0

0,0 0,0 0,0 0,0 203 0,452 0,0 1 5,0 1,7 5,7 3,1 203 0,452 0,2 1 10,0 3,3 11,4 6,1 203 0,452 0,4 1 15,0 5,0 17,0 9,0 203 0,452 0,6 1 19,9 6,6 22,7 12,1 203 0,452 0,7 1 24,9 8,3 28,5 15,1 203 0,452 0,5 1 29,8 9,9 34,1 18,1 203 0,452 0,8 1 34,9 11,6 40,1 21,3 203 0,452 0,9 1 40,0 13,3 46,2 24,6 203 0,452 1,0 1 44,9 15,0 51,7 27,1 204 0,455 1,1 1 49,9 16,6 55,7 28,4 208 0,463 0,8 2 55,0 18,3 59,8 29,4 213 0,478 0,3 1 59,9 20,0 63,5 30,1 220 0,493 0,2 0 65,1 21,7 67,2 30,6 228 0,512 0,2 1 69,9 23,3 70,6 30,7 235 0,526 0,3 2 75,0 25,0 73,6 30,4 241 0,538 0,0 3 80,0 26,7 77,6 30,9 250 0,554 0,2 2 85,0 28,3 80,7 30,4 258 0,568 0,4 2 90,0 30,0 85,3 31,2 266 0,581 0,5 1 95,0 31,7 89,3 31,0 274 0,594 0,5 3 100,0 33,3 94,0 31,7 285 0,609 0,0 4 94,9 31,6 89,4 31,1 276 0,596 0,3 5 90,0 30,0 85,5 31,4 264 0,577 0,4 4 85,1 28,4 81,8 31,5 255 0,563 0,2 0 80,1 26,7 77,4 30,7 251 0,556 0,3 1 75,0 25,0 73,7 30,5 245 0,545 0,2 0 70,0 23,3 70,2 30,3 236 0,528 0,3 1 64,9 21,6 66,7 30,1 229 0,513 0,2 1 60,0 20,0 63,1 29,7 222 0,497 0,1 1 55,0 18,3 59,1 28,7 216 0,483 0,1 0 50,0 16,7 54,1 26,8 210 0,470 0,2 0 45,0 15,0 48,8 24,3 209 0,467 0,2 0

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Appendix A: Data 40,0 13,3 43,3 21,7 208 0,464 0,2 0 35,0 11,7 37,9 19,1 208 0,463 0,1 0 29,9 10,0 32,6 16,6 207 0,461 0,2 0 25,0 8,3 27,2 13,8 206 0,459 0,0 0 20,0 6,7 21,8 11,2 205 0,457 0,0 0 15,0 5,0 16,2 8,2 205 0,457 0,0 0 10,0 3,3 10,7 5,5 205 0,456 0,2 0 5,1 1,7 5,4 2,8 205 0,456 0,2 0 0,0 0,0 0,0 0,0 204 0,454 0,0 0

0,0 0,0 0,0 0,0 249 0,458 0,0 1 4,8 1,6 5,7 3,1 249 0,458 0,2 1 9,9 3,3 12,2 6,9 249 0,458 0,6 1 15,0 5,0 18,8 10,8 249 0,458 0,6 1 20,0 6,7 25,2 14,6 249 0,458 0,7 1 25,0 8,3 31,7 18,3 249 0,458 0,9 1 29,9 10,0 38,1 22,1 249 0,458 0,9 1 35,0 11,7 44,8 26,0 249 0,458 1,2 1 39,9 13,3 51,3 29,7 249 0,459 1,2 1 44,9 15,0 57,2 32,7 250 0,461 1,1 1 49,9 16,6 61,4 34,1 257 0,475 0,8 1 55,0 18,3 65,7 35,3 263 0,488 0,5 1 60,0 20,0 69,3 35,9 271 0,503 0,2 1 65,0 21,7 72,9 36,3 280 0,519 0,1 0 70,0 23,3 76,7 36,8 290 0,535 0,2 0 75,1 25,0 80,0 36,8 299 0,550 0,3 1 80,0 26,7 84,9 38,2 308 0,562 0,7 2 85,1 28,4 87,9 37,6 314 0,571 0,2 1 90,2 30,1 92,0 37,9 322 0,581 0,3 1 95,1 31,7 97,2 38,9 333 0,595 0,3 5 100,1 33,4 100,9 38,5 349 0,614 1,0 3 95,0 31,7 96,3 38,0 334 0,597 0,5 1 90,0 30,0 91,7 37,6 324 0,584 0,5 1 85,0 28,3 87,8 37,5 313 0,569 0,3 2 80,0 26,7 84,4 37,7 306 0,559 0,9 1 75,0 25,0 80,2 37,0 298 0,548 0,6 2 69,9 23,3 75,7 35,8 289 0,534 0,2 2

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Appendix A: Data 59,9 20,0 68,7 35,3 272 0,504 0,1 1 54,9 18,3 64,7 34,3 263 0,487 0,1 1 49,9 16,6 59,7 32,4 258 0,478 0,3 0 44,9 15,0 53,5 29,0 256 0,474 0,3 0 39,8 13,3 47,4 25,8 255 0,472 0,4 0 34,9 11,6 41,6 22,8 254 0,469 0,3 0 29,8 9,9 35,7 19,7 253 0,468 0,4 0 24,8 8,3 29,7 16,3 252 0,466 0,4 0 19,9 6,6 23,7 13,1 252 0,466 0,2 0 14,8 4,9 17,6 9,6 251 0,464 0,2 0 10,4 3,5 12,2 6,9 251 0,464 1,3 0 4,8 1,6 5,3 2,7 251 0,463 0,2 0 0,0 0,0 0,0 0,0 250 0,462 0,0 0

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Appendix B: Minimum fluidization velocity derivation plots

This section gives all plots that are used to derive the minimum fluidization velocities found in Table 7.

Figure 18: Derivation of minimum fluidization velocity from bed pressure drop and bed height measurement ID 2, 3.

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Experimental Study on Fluidization Characteristics of an Air-Sand Bed inside a Rectangular Fluidized Bed

Summary

List of symbols

Contents

1 Introduction

2 Theory of fluidized beds

3 Methodology

4 Results

and discussion

5 Conclusions

and recommendations

References

Appendix A: Data

Appendix B: Minimum fluidization velocity derivation plots