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CHE4162 – PARTICLE TECHNOLOGY

EXPERIMENT 2: FIXED AND FLUIDISED BEDS FOR WATER

SYSTEMS

Preparation:

Revise the Fluidization Chapter of Rhodes, “Introduction to Particle Technology”, with

particular attention to non-bubbling fluidization, determination of Umf, expansion of a non-

bubbling fluidized bed and the Richardson-Zaki Equation.

Objectives:

1. To reinforce knowledge of particulate fluidization.

2. To determine experimentally the relationships between superficial velocity of the fluid

and pressure drop for flow through particulate fluidization bed, minimum fluidization

velocity and bed expansion and to compare the measure values with predictions.

Apparatus:

The apparatus is designed for the demonstration of pressure drop of fluid flow across fixed and

fluidized bed of solid particles. Two independent circuits are provided for the experiment on

water and air flow. The system is bench top unit mounted on a sturdy coated steel frame and

front panel with flow diagram and measuring instruments.

The air circuit comprises of an air pressure regulator connected to the compressed air line for

supply to the bottom of the second packed column. The column is also made of transparent

plexi-glass fitted with sintered bronze base support plate to hold the solid particles of the packed

bed. Flow rates going into the column are controlled via an air control valve fitted on the front

control panel. The differential pressure across the column is measured with a differential

pressure sensor and displayed on a panel digital meter. Air flow rate is measured with an air flow

sensor and displayed on a panel digital meter.

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The water circuit comprises of a re-circulating water pump fitted to deliver water from the sump

tank into the bottom of the first packed column. The column is made of transparent plexi-glass

fitted with a sintered bronze base support plate. Flow rates going into the column are controlled

via a hand valve fitted on the control panel. Water flow rate is measured with a flow sensor and

displayed on a panel digital meter

Technical Details

1. Two cylindrical acrylic columns, one each for air and water circuits (50 mm diameter × 550

mm height)

2. Two units of digital flow meter for air (0 - 30 LPM) and water circuit (0 - 12 LPM)

3. Each column has tapping points and a digital manometer for measurement of the bed

pressure drop (0-38 mbar differential)

4. Bronze impeller and casing centrifugal pump - 0.5 hp

5. Stainless steel water tank - 25 liters

6. Air pressure regulator for compressed air supply (compressor optional)

Safety & Precaution:

1. Do not attempt change the setting of the digital meters.

2. Do not start the water pump if there is no water in the water tank.

3. Do not allow water pump to run for long period of time if all the valves are fully closed.

4. Do not fill the test material more than half of the column height.

Data

Air Circuit

1. Material properties: sand

2. Mass of particles in the bed: 263.07 g

3. Density of particle: 2256.5 kg/m3

4. Inner diameter of column: 46 mm

5. 1 liters = 0.001 m3

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Water Circuit

1. Material properties: 6-mm diameter ceramic ball

2. Mass of particles in the bed: 280 g

3. Inner diameter of column: 46 mm

4. 1 liters = 0.001 m3

Experimental unit

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Experimental procedure

Air circuit

1. Ensure the tubing for the pressure drop points are connected properly for the air column.

2. Switch ON the main power supply and the apparatus main switch. Ensure the MCB/ELCB is

switched on. Check all the digital meters. Ensure all are working properly.

3. Open main control valve for entry of air into the equipment. Ensure valve is only half-open.

4. Study the pressure drop as a function of air flow rate over the range 1 – 30 liters/minute,

starting at the low flow rate.

5. Regulate the air flow rate by regulating the air flow control valve. Stop increasing the air

flow rate if some particles reach the top of the column (to avoid loss of bed particles).

6. Repeat the measurements with decreasing air flow rate.

Water circuit

1. Fill the water tank (located at the back of the apparatus) with water up to 3/4 height.

2. Ensure the tubing is connected properly for the water column.

3. Switch ON the main power supply and the apparatus main switch. Ensure the MCB/ELCB is

switched ON.

4. Check all the digital meters. Ensure all are working properly.

5. Ensure water control valve is closed.

6. Switch ON the water pump switch.

7. Study the bed height as a function of water flow rate over the range 1 – 12 liters/minute,

starting at the low flow rate.

8. Regulate the water flow rate by regulating the water flow control valve. Stop increasing the

water flow rate when the fluidized bed surface comes near to the column top (to avoid loss of

bed particles).

9. Repeat the measurements with decreasing water flow rate.

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Report

For the packed bed region compare the experimental data with that predicted by the Ergun

equation.

Compare the experimental and predicted fluidized bed pressure drop.

Compare the incipient fluidization velocity Umf with the value predicted by the Wen and Yu

equation.

Plot your results for fluidized bed expansion in such a way that they can be compared with

the expansion predicted by the Richardson-Zaki equation.

Sample calculation must be provided in the report, stating the assumptions made in

calculations for both air and water circuit.

Team self-assessment required includes the following:

a. The roles played by each team member in carrying out this assignment.

b. Summary of team meeting outcomes.

c. How well did you work together?

d. What would you do differently next time?