lab manual for various experiments in chemical engineering

Chemical Engineering Department, Birla Institute of Technology & Science Pilani, Pilani Campus

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A LABORATORY MANUAL

FOR

Chemical Engineering

Laboratory I

Edited By

Dr Suresh Gupta & Dr Hare Krishna Mohanta

Department of Chemical Engineering,

Birla Institute of Technology & Science (BITS), Pilani

September 2014

Chemical Engineering Department, Birla Institute of Technology & Science Pilani, Pilani Campus

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CONTENTS

CYCLE - I

S. No. Experiment Page No.

1. a. Flow through Fluidized Bed (Gas and Water) b. Flow through Packed Bed (Gas and Water)

3

2 . a. Losses due to pipe fittings b. Losses due to friction in pipes c. Drag Coefficient determination

10

3. a. Bernoullis Theorem verification b. Discharge through venturi, orifice and rotameter c. Flow through tubular pipe

22

4. a. Pitot tube experiment (Air and Water) b. Reynolds Apparatus

34

5. a. Centrifugal pump characteristics b. Reciprocating pump characteristics

42

6. a. Heat Pipe demonstrator b. Thermal Conductivity of solids c. Thermal conductivity of liquids

52

7. a. Drop wise and film wise condensation b. Unsteady state heat transfer unit

61

8. a. Heat Transfer in agitated vessel b. Fluidized bed heat transfer unit

76

9. a. Parallel flow & Counter flow heat exchanger b. Shell and Tube heat exchanger

83

10. a. Plate type Heat Exchanger b. Finned tube heat exchanger

92

CYCLE - II

S. No. Experiment Page No.

11. Stefan-Boltzmann Apparatus

151

12. Cross-circulation drying apparatus 110

13. a. Vapour in air diffusion b. Open pan evaporator

114

14. Simple/Differential distillation setup 120

15. Batch crystallizer 125

16. a. Steam distillation setup

b. Vapor liquid equilibrium setup

128

17. Two phase flow 136

18. Mass transfer with chemical reaction 141

19. Adsorption in packed bed 144

20. Humidification in wetted wall column 148

Chemical Engineering Department, Birla Institute of Technology & Science Pilani, Pilani Campus

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EXPERIMENT NO. 1(a)

FLOW THROUGH FLUIDIZED BED (AIR & WATER)

1. Aim Study of hydrodynamic and bed characteristics for flow through fluidized beds.

2. Objective

To determine the minimum fluidization velocity experimentally as well as theoretically.

To study the bed expansion characteristics of the fluidized bed (plot log NRe vs. porosity and pressure drop vs. NRe).

3. Apparatus Stop watch, graduated cylinders, beakers

4. Theory When a liquid or a gas is passed at very low velocity up through a bed of solid particles, the

particles do not move, and the pressure drop is given by the Ergun equation. If the fluid

velocity is steadily increased, the pressure drop and the drag on individual particles increase,

and eventually the particles start to move and become suspended in the fluid. The terms

fluidization and fluidized bed are used to describe the condition of fully suspended particles, since the suspension behaves like a dense fluid.

Fluidized beds are used extensively in the chemical process industries, particularly for the

cracking of high-molecular-weight petroleum fractions. Such beds inherently possess

excellent heat transfer and mixing characteristics. These are devices in which a large surface

area of contact between a liquid and a gas, or a solid and a gas or liquid is obtained for

achieving rapid mass and heat transfer and for chemical reactions.

The fluidized bed is one of the best known contacting methods used in the processing

industry, for instance in oil refinery plants. Among its chief advantages are that the particles

are well mixed leading to low temperature gradients, they are suitable for both small and

large scale operations and they allow continuous processing. There are many well established

operations that utilize this technology, including cracking and reforming of hydrocarbons,

coal carbonization and gasification, ore roasting, Fisher-Tropsch synthesis, coking,

aluminium production, melamine production, and coating preparations. Nowadays, you will

find fluidized beds used in catalyst regeneration, solid-gas reactors, combustion of coal,

roasting of ores, drying, and gas adsorption operations. The application of fluidization is also

well recognized in nuclear engineering as a unit operation for example, in uranium extraction,

nuclear fuel fabrication, reprocessing of fuel and waste disposal.

When a fluid is admitted at the bottom of a packed bed of solids at a low flow rate, it passes

upward through bed without causing any particle motion. If the particles are quite small, flow

in the channels between the particles will be laminar and the pressure drop across the bed will

be proportional to the superficial velocity (Vo) and for turbulent situations, pressure drop

across the bed increase nonlinearly with the increase in the superficial velocity. As the

velocity is gradually increased, the pressure drop increases, but particles do not move and the

bed height remains the same. At a certain velocity, the pressure drop across the bed

counterbalances the force of gravity on the particles or the weight of the bed, and any other

further increase in velocity causes the particles to move and the true fluidization begins. For a

Chemical Engineering Department, Birla Institute of Technology & Science Pilani, Pilani Campus

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high enough fluid velocity, the friction force is large enough to lift the particles. This

represents the onset of fluidization once the bed is fluidized pressure drop across the bed

remains constant, but the bed height continues to increase with increasing flow.

Figure 1 Fluidization regimes

In order to determine the pressure drop through a fixed bed for any flow condition, the Ergun

equation (1952) can be used:

dp is the size of particles (m)

L is the height of the bed (m)

is the viscosity of sir (N/m2.s)

U is the average superficial velocity (m/s)

is the bed voidage or porosity is the density of air/water (kg/m3) P is the pressure drop across the bed (N/m2)

The average Reynolds number based on superficial velocity which is given by,

If the Reynolds number is less than 10 then it is laminar flow and is greater than 2000 it is

turbulent flow. The rest of the values lie in the transition regime. If the flow rate of air/water

Q is measured in litres, A is the bed cross-sectional area and U is the superficial velocity in

m/s, then

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Theoretically at incipient fluidization (the stage in the fluidized bed where the force on the

solid is enough to balance the weight of the solid material),

P is in mm of manometer

The pressure drop at fluidization can also be predicted by the equation,

p is the particle density (kg/m3)

is the fluid density (kg/m3) g is the gravitational force (m/s

2)

Minimum fluidization velocity

Umf, the minimum fluidizing velocity, is frequently used in fluid-bed calculations and in

quantifying one of the particle properties. This parameter is best measured in small-scale

equipment at ambient conditions. The correlation given below can then be used to back

calculate dp. This gives a particle size that takes into account effects of size distribution and

sphericity. The correlation can then be used to estimate Umf at process conditions. If Umf

cannot be determined experimentally, use the expression below directly.

Assumption: - Consider the uniform particle size.

Remf = (1135.7 +0.0408Ar) 0.5

- 33.7 (Wen and Yu correlation for particles dp> 100 m)

/Re mffpmf Ud

23 / gdAr fsfp (Ar is the Archimedes Number)

For particles of dp < 100 m, Baeyens and Geldart (1977) can be used,

5. Experimental procedure

1. The height of the static bed Z1 i.e. when there is no flow of water/air (porosity 1) was noted.

2. The flow of air/water in the column is started and the flow rates from the rotameter were noted.

3. The corresponding bed heights and pressure drop values were noted. 4. The flow rates were increased steadily and similar data were collected at different intervals.

5. 6 to 8 readings of flow rates were varied and reading were taken. 6. Steady state flow rate of water was ensured at each point.

Chemical Engineering Department, Birla Institute of Technology & Science Pilani, Pilani Campus

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6. Observations and calculations

Particle size = 8 mm

Porosity = 0.6

Inside diameter of the column (D) = 0.055m

Cross-sectional area of fluidized column

= 0.002375 m

Density of water (at T0C) = 1000 kg/m3 Viscosity of water (at T

0C) = 0.798*10

-3 kg/m-s

Density of air = 1.1687 kg/m3

Viscosity of air = 1.8633x10-5

Pa.s

Velocity V (m/s) = volumetric flow rate of water / cross section area of column

Initial height of static bed in the column (Z1)

Porosity of the fluidized Bed: If Z1 and 1 are the height and porosity of the static bed and Z2