Exp. 7 Study of Evaporation Process Using Climbing Film Evaporator

Mass & Heat Transfer Lab

BKF3721

Faculty of Chemical & Natural Resources Engineering

Experiment 7 STUDY OF EVAPORATION PROCESS USING CLIMBING FILM EVAPORATOR

Name Matric No. Group Program Section Date

Semester II - Session 2013/2014

Mass & Heat Transfer Lab

BKF3721

EXPERIMENT 7: STUDY ON EVAPORATION PROSESS USING CLIMBING FILM EVAPORATOR OBJECTIVE

1. To analyze the influence of the steam pressure on the evaporation process at a constant inlet flow rate. 2. To explain the effect of evaporation process on the product characteristics in terms of composition, viscosity and heat-transfer coefficients.

INTRODUCTION

The objective of evaporation is to concentrate a solution consisting of a nonvolatile solute and a volatile solvent. Evaporation is conducted by vaporizing a portion of the solvent to produce a concentrated solution of thick liquor. Normally, in evaporation, the thick liquor is the valuable product and the vapor is condensed and discarded. Most evaporators are heated by steam condensing on metal tubes. When a single evaporator is used, the vapor from the boiling liquid is condensed and discarded. This method is so- called single-effect evaporation.

EQUIPMENT/APPARATUS/MATERIAL 1. CTS4 Climbing Film Evaporator 2. Steam supply 3. Vacuum pump 4. Stop watch 5. Digital balance 6. Beakers 7. Glass rod 8. Portable conductivity meter 9. Water supply 10. Salt

Mass & Heat Transfer Lab

BKF3721

EXPERIMENTAL PROCEDURES

1. Prepare the standard salt solution and its conductivity using the conductivity meter. (the standard curve data must covers the experimental sample data). 2. Prepare 20 L salt solution with concentration of 22.5 g/L and feed in the feed vessel. 3. Switch ON the vacuum pump so that the liquid from the feed vessel can be transferred into the vessel column. 4. Run the cooling water to cool down the steam in the condenser. 5. Set the feed flow rate FI 1 at 0.3 L/min and vacuum pressure at 0.4 bar. 6. Set the steam pressure at 0.5 bar. 7. Record the temperature change at the top and bottom of the evaporator column for every 5 minutes until 30 minutes. Then, stop the operation by closing the vacuum valve and steam pressure valve. 8. Repeat steps 6 to 7 for steam pressure 1 bar (g). 9. Shutdown the equipment.

RESULT Table 1: Standard curve data for sodium chloride NaCl concentration (g/L) 0 5 10 15 20 25 30 40 50

Conductivity

Mass & Heat Transfer Lab

BKF3721 Table 2: Experimental Data

Steam

Time

T1

T2

Volume

Conductivity

Pressure

(min)

(0C)

(0C)

(mL)

(mS)

V3

(Bar)

V5

V3

V5

5 10 15

0.5

20 25 30 5 10 15

1.0

20 25 30

DISCUSSION

Discuss all your results. The question below only serves as a guideline. Your discussion should not only limit to these questions. 1. Give two reasons why we must operate the column pressure under 1 atm or at vacuum condition. 2. For standard solution, plot a graph for conductivity versus concentration of salt solution and give your explanation of the relationship between concentration and conductivity. 3. Plot three graphs for different steam pressure where the time versus concentration of salt solution taken from valve, V3. 4. Explain the effect of steam pressure and column pressure (fixed) of constant inlet feed flow to

the evaporation rate.

5. Compare the salt solution concentration taken from valve V3 and valve V5, and give the relationship between composition, viscosity and heat-transfer coefficients. 6. Give all safety precautions that need to be taken before, during, and after running this experiment.