Design, Fabrication, and Performance Evaluation of a Double Effect Evaporator

This project study was aimed at designing, fabricating, and evaluating the performance of a double effect evaporator, which was used to evaporate sugar syrup to be used for students’ demonstration. During the course of the study, the methods that were used comprised of the material balances, energy balances, and determination of the component parts of the evaporator. The results from the study included the overall material in the evaporator’s system, the material balance for each effect, the effect heat duties and required heat transfer areas, the temperatures for each effect, and the equipment specifications. A feed flow rate of 0.63kg/s was used which produced a product having a flow rate of 0.593kg/s with the total water evaporated as 0.037kg/s. It was discovered that the solid compositions of feed increased across each effect, from 0.725 to 0.745 to 0.77 solid composition, while the feed flow rate across each effect reduced from 0.63 kg/s to 0.613 kg/s to 0.593kg/s. Reduction in heat duties from 79.3KW to 37.8KW were obtained across each effect, which subsequently gave a reduction of heat transfer areas across each effect as 0.005m2 and 0.003m2. The temperatures of the products, exiting effects 1 and 2 were given as 112°C and 98.22°C respectively, which lead to a decrease in steam saturation temperatures from its initial temperature at 120°C to 107.22 to 93.16°C. This also lead to an increase in boiling points of the products from 4.78°C to 5.06°C. An overall steam economy of 1.03kg of water vaporized per kg of steam consumed was obtained, as well as the capacity which was obtained as 133.2kg of water vaporized per hour. From the study, it was concluded that the equipment was capable of utilizing the steam that is being fed into the double effect evaporator, thereby managing cost and time. At the end of the experiment, it is advised that more effects should be added to the system, other types of feed arrangements should be tested to determine its efficiency.

Keywords: double effect evaporator, sugar slurry, sugar

TABLE OF CONTENTS

Dedication                                                                                                                       ii

Acknowledgement                                                                                                     iii

Abstract                                                                                                                           iv

Table of ContentS                                                                                                       v

LIST OF TABLES                                                                                                                 ix

LIST OF FIGURES                                                                                                               x

NOMENCLATURE                                                                                                              xi

CHAPTER ONE

1.0       Introduction                                                                                                               1

1.1         Background of the Study                                                                                            1

1.2       Statement of the Problem                                                                                            3

1.3       Aim and Objectives                                                                                                    4

1.4       Scope of Study                                                                                                           4

1.5       Significance of the Study                                                                                           5

CHAPTER TWO

2.0       Literature Review                                                                                                     6

2.1       Design                                                                                                                         6

2.1.1    Design as a Process                                                                                                     6

2.1.1.1The Rational Model                                                                                                     7

2.1.1.2The Action-Centric Model                                                                                          9

2.1.2    Descriptions of Design Activities                                                                               9

2.1.3    Methods of Designing                                                                                                 10

2.1.4    Design and Engineering                                                                                              11

2.1.5    Design and Production                                                                                               11

2.1.6    Process Design                                                                                                            12

2.2       Metal Fabrication                                                                                                        13

2.2.1    Processes                                                                                                                     13

2.2.2    Raw Materials                                                                                                             15

2.2.3    Cutting and Burning                                                                                                   15

2.2.4    Forming                                                                                                                       16

2.2.5    Machining                                                                                                                   16

2.2.6    Welding                                                                                                                      16

2.2.7    Final Assembly                                                                                                           17

2.3       Performance Evaluation                                                                                             17

2.3.1    Performance Evaluation Process                                                                                18

2.3.2    Performance Evaluation Methods                                                                              19

2.4       Theory of Evaporation                                                                                                21

2.4.1    Factors Affecting Evaporation                                                                                   23

2.5       Evaporators                                                                                                                 23

2.5.1    How an Evaporator Works                                                                                         23

2.5.2    Evaporator Operation                                                                                                 24

2.5.3    Uses of Evaporators                                                                                                    25

2.5.4    Energetics of Evaporators                                                                                           27

2.5.5    Selection of Evaporators                                                                                             28

2.5.6    Types of Evaporators                                                                                                  29

2.5.6.1Short-Tube Vertical Evaporator                                                                                  30

2.6.6.2Basket-type Vertical Evaporator                                                                                 30

2.5.6.3Long-Tube Vertical Evaporator                                                                                  31

2.5.6.4Falling Film Evaporator                                                                                              31

2.5.6.5Rising or Climbing Film Evaporator                                                                           31

2.5.6.6Forced Circulation Evaporator                                                                                    32

2.5.6.7Agitated Thin Film Evaporator                                                                                   33

2.5.6.8Gasketed-Plate Evaporator                                                                                          33

2.5.7    Performance of Steam Heated Tubular Evaporators                                                  33

2.5.7.1Capacity and Economy                                                                                                33

2.5.8    Boiling Point Elevation                                                                                              34

2.6       Single and Multiple Effect Evaporators                                                                     35

2.6.1    Multiple-Effect Evaporator                                                                                        38

2.6.1.1Thermal Design Calculations for the Design of                                                          40

a Multiple-Effect Evaporator

2.7       The Use of Stainless Steel in the Design of Evaporators                                           45

2.7.1    Identification                                                                                                              45

2.7.2    General-Purpose Stainless Steels                                                                               47

2.7.3    Guidelines for Selection                                                                                             48

CHAPTER THREE

3.0       Materials and Methods                                                                                            49

3.1       Materials                                                                                                                     49

3.2       Methods                                                                                                                      49

3.2.1    Mathematical Methods                                                                                               49

3.2.2    Design of Components of the Machine                                                                      57

3.2.3    Mechanical Methods                                                                                                  61

3.3       Safety Consideration                                                                                                  63

CHAPTER FOUR

4.0       Result and Discussion                                                                                               64

4.1       Result                                                                                                                          64

4.1.1    Result of the Material Balance Summary of the Evaporator                                      64

4.1.2    Result of the Energy Balance Summary of the Evaporator                                        64

4.1.3    Result of the Equipment Specifications Summary                                                     65

4.2       Discussion                                                                                                                   65

CHAPTER FIVE

5.0       Conclusion and recommendation                                                                            69

5.1       Conclusion                                                                                                                  69

5.2       Recommendation                                                                                                        69       

References

APPENDIX

Appendix 1: Material Balance Calculations

Appendix 2: Energy Balance Calculations

Appendix 3: Equipment Specifications Calculations

Appendix 4: Cost of Materials