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HUSSEIN SUGAR MILLS LIMITED INTERNSHIP REPORT
ANEES AHMAD
CIIT/SP11-BEC-015/LHR
A report submitted in partial fulfillment ...
ii
iii
TABLE OF CONTENTS
List of Figures vii
Acknowledgments ix
Vision and Mission Statement of Industry x
Executive Summary ...
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  1. 1. HUSSEIN SUGAR MILLS LIMITED INTERNSHIP REPORT ANEES AHMAD CIIT/SP11-BEC-015/LHR A report submitted in partial fulfillment of the requirements for the award of the degree of Bachelor of Science (Chemical Engineering) Department of Chemical Engineering COMSATS Institute of Information Technology AUGUST 2014
  2. 2. ii
  3. 3. iii TABLE OF CONTENTS List of Figures vii Acknowledgments ix Vision and Mission Statement of Industry x Executive Summary xi Chapter-1 Introduction 1 1.1 What is sugar? ...............................................................................................................1 1.2 Properties of Sucrose (Sugar)........................................................................................1 1.2.1 Physical Properties of Sucrose .....................................................................1 1.2.2 Chemical Properties of Sucrose....................................................................2 a) Oxidation of Sucrose...............................................................................2 b) Hydrolysis of Sucrose.............................................................................2 c) Alkaline Degradation..............................................................................2 d) Thermal Degradation ..............................................................................2 1.3 Uses of Sucrose .............................................................................................................3 a) Food Applications ....................................................................................................3 b) Feedstock for Chemical Synthesis............................................................................3 c) Fermentation Feedstock............................................................................................3 d) Pharmaceutical Applications....................................................................................3 1.4 Nutrition and Health Aspects of Sucrose ......................................................................3 Chapter-2 Sugar Mill Feed Section Specifications & Details 5 2.1 Feed Section (Delivery, Unloading, Weighing & Handling of Cane)… ......................5 2.2 Feed Table… .................................................................................................................5 2.3 Cane Carrier…...............................................................................................................5 2.4 Leveller…......................................................................................................................6 2.5 Cutters… .......................................................................................................................6 2.6 Magnetic Separator........................................................................................................7 2.7 Shredder….....................................................................................................................8 2.8 Shredded Cane Elevator… ............................................................................................9 2.9 Turbines….....................................................................................................................9
  4. 4. iv Chapter-3 Mill House 10 3.1 Block Flow Diagram… .................................................................................................10 3.2 Mills…...........................................................................................................................10 3.2.1 Mills Configuration… .................................................................................12 3.2.2 Trash Plate...................................................................................................12 3.2.3 Characteristics of a Mill ..............................................................................12 3.3 Imbibition… ..................................................................................................................13 3.4 Bagasse Elevator… .......................................................................................................13 3.5 Stationary Screen and Rotary Screen… ........................................................................13 3.6 Mixed Juice Tank… ......................................................................................................13 3.7 Juice Supply Configuration to Process House...............................................................14 Chapter-4 Mill Drive by Steam Turbine 15 4.1 Steam Turbine ...............................................................................................................15 4.2 Gears…..........................................................................................................................15 Chapter-5 Boiler House 17 5.1 Boiler Feed Water Treatment........................................................................................17 5.1.1 Ion Exchange Process (A special type of Adsorption)….............................17 5.1.2 Sodium Zeolite Softening.............................................................................17 5.1.3 Zeolites… .....................................................................................................18 5.1.4 Boiler Feed Water Specifications….............................................................18 5.2 Boiler….........................................................................................................................18 5.2.1 Types of Boiler.............................................................................................18 5.3 Water Tube Boiler… .....................................................................................................19 5.4 Configuration of Boilers…............................................................................................21 Chapter-6 Power House 22 6.1 Turbines (Expanders) ....................................................................................................22 6.2 Steam Turbine ...............................................................................................................22 6.2.1 Way of Working............................................................................................22 6.3 Types of Blades… .........................................................................................................24 6.4 Defects of Steam Turbine…..........................................................................................24
  5. 5. v 6.5 Calculation of Shaft Work Produced by Turbine..........................................................24 6.6 Electric Generator…......................................................................................................25 6.6.1 Working Principal… ....................................................................................25 6.7 Synchronization….........................................................................................................25 Chapter-7 Process House 27 7.1 Vapor Line Juice Heaters… ..........................................................................................27 7.2 Primary Heaters….........................................................................................................27 7.3 Defecation… .................................................................................................................29 7.4 Retention Tanks….........................................................................................................29 7.5 Secondary Heaters….....................................................................................................30 7.6 Flash Tank… .................................................................................................................30 7.7 Distributor… .................................................................................................................31 7.8 Clarifier (Sedimentation)…...........................................................................................31 7.9 Mud Mixer….................................................................................................................32 7.10 Rotary Vacuum Filter..................................................................................................32 7.11 Evaporators…..............................................................................................................33 7.12 Falling Film Evaporator ..............................................................................................33 7.13 Multiple Effect Evaporator…......................................................................................34 7.14 Calculation of Amount of Vapors Generated..............................................................36 7.15 Syrup Tank ..................................................................................................................36 7.16 Batch Pans… ...............................................................................................................36 7.17 Continuous Pans…......................................................................................................39 7.18 Crystallizers….............................................................................................................39 7.19 Horizontal Crystallizer… ............................................................................................39 7.20 Vertical Crystallizer.....................................................................................................40 7.21 Pug Mills… .................................................................................................................42 7.22 Centrifugal Separators (Machines)..............................................................................42 7.23 Remelter ......................................................................................................................42 7.24 Buffer Tank… .............................................................................................................43 7.25 Baby Heater….............................................................................................................43
  6. 6. vi 7.26 Talo Clarifier… ...........................................................................................................43 7.27 Sugar Grader…............................................................................................................44 7.28 Dryer…........................................................................................................................44 7.29 Hopper….....................................................................................................................44 7.30 Packaging ....................................................................................................................44 7.31 Brix and Purity Data....................................................................................................46 Chapter-8 Chemical Laboratory 47 8.1 Brix Test........................................................................................................................47 8.2 Bagasse Test… ..............................................................................................................48 SWOT Analysis of Hussein Sugar Mills Limited 49 References 50
  7. 7. vii LIST OF FIGURES Figure-1 ……………………………………………………………………………... 1 Figure-2 ……………………………………………………………………………... 5 Figure-3 ……………………………………………………………………………... 5 Figure-4 ……………………………………………………………………………... 6 Figure-5 ……………………………………………………………………………... 7 Figure-6 ……………………………………………………………………………... 7 Figure-7 ……………………………………………………………………………... 7 Figure-8 ……………………………………………………………………………... 8 Figure-9 ……………………………………………………………………………... 8 Figure-10 ……………………………………………………………………………... 10 Figure-11 ……………………………………………………………………………... 11 Figure-12 ……………………………………………………………………………... 11 Figure-13 ……………………………………………………………………………... 12 Figure-14 ……………………………………………………………………………... 12 Figure-15 ……………………………………………………………………………... 13 Figure-16 ……………………………………………………………………………... 13 Figure-17 ……………………………………………………………………………... 14 Figure-18 ……………………………………………………………………………... 15 Figure-19 ……………………………………………………………………………... 16 Figure-20 ……………………………………………………………………………... 16 Figure-21 ……………………………………………………………………………... 18 Figure-22 ……………………………………………………………………………... 20 Figure-23 ……………………………………………………………………………... 21 Figure-24 ……………………………………………………………………………... 22 Figure-25 ……………………………………………………………………………... 24 Figure-26 ……………………………………………………………………………... 25 Figure-27 ……………………………………………………………………………... 26 Figure-28 ……………………………………………………………………………... 27 Figure-29 ……………………………………………………………………………... 27 Figure-30 ……………………………………………………………………………... 28 Figure-31 ……………………………………………………………………………... 29 Figure-32 ……………………………………………………………………………... 30
  8. 8. viii Figure-33 ……………………………………………………………………………... 31 Figure-34 ……………………………………………………………………………... 33 Figure-35 ……………………………………………………………………………... 34 Figure-36 ……………………………………………………………………………... 35 Figure-37 ……………………………………………………………………………... 36 Figure-38 ……………………………………………………………………………... 37 Figure-39 ……………………………………………………………………………... 38 Figure-40 ……………………………………………………………………………... 39 Figure-41 ……………………………………………………………………………... 40 Figure-42 ……………………………………………………………………………... 40 Figure-43 ……………………………………………………………………………... 41 Figure-44 ……………………………………………………………………………... 42 Figure-45 ……………………………………………………………………………... 42 Figure-46 ……………………………………………………………………………... 42 Figure-47 ……………………………………………………………………………... 43 Figure-48 ……………………………………………………………………………... 44 Figure-49 ……………………………………………………………………………... 44 Figure-50 ……………………………………………………………………………... 45 Figure-51 ……………………………………………………………………………... 45 Figure-52 ……………………………………………………………………………... 45 Figure-53 ……………………………………………………………………………... 45 Figure-54 ……………………………………………………………………………... 45 Figure-55 ……………………………………………………………………………... 47 Figure-56 ……………………………………………………………………………... 48 Figure-57 ……………………………………………………………………………... 48
  9. 9. ix ACKNOWLDGEMENTS A great many people have helped us in this internship training. First of all we thanks respected Mr.Tariq Mahmood (A.G.M.) for giving us chance in Husein Sugar Mills (PVT) Ltd. for internship program. Engr.Sohail Akbar’s (P.M.) recommendations to this report have been invaluable. We thank mechanical staff and electrical staff for giving us support during maintenance work in the power house, in the mill house; with mechanical and electrical engineering point of views. In the process house we got support from Mr.Shahzad (Chief Chemist), Mr.Kashif Imran (Senior Chemist), Mr.Nadeem Wali (Senior Chemist), Mr.Khizar Aziz (Shift Chemist), and Mr.Abdul Wahid (Shift Chemist). We also thanks Mr.Almas Arshad (Trainee Engineer), for his efforts to complie this report. We thanks to Mr.Azhar Fazal (G.M.T), Mr.Tariq (A.G.M.) for providing us so valuable environment, in which our practical growth occured. We are also thankful to Mr.Gulzameer who have entertained us in this sugar mill for our practical growth. We are also thankful to Dr.Engr.Moin-ud-Din Gahuri for providing us a such type of opportunity in which our theoratical approach is integrated with practical knowledge; in order to grasp chemical engineering concepts in a more favorable and pratical way.
  10. 10. x VISION & MISSION STATEMENT OF INDUSTRY Our Vision  A leading producer of sugar and its by-products by providing the highest quality of products and services to its customers.  Lowest cost supplier with assured access to long-term supplies.  Sustained growth in earning in real terms.  Highly ethical company and the respected corporate citizen to continue playing the role in the social and environmental sectors of the company.  To develop an extremely motivated and professional trained work force, which would drive growth through innovation and renovation.  To strive for excellence through commitment, honest and team work. Our Mission Our mission is to be a dynamic, profitable and growth oriented company by providing good return on investment to its shareholders and investors, quality products to its customers, promote agriculture sector secured and friendly environment place of work to its employees and present the company as a reliable partner to all sugarcane growth and other business associates.
  11. 11. xi EXECUTIVE SUMMARY Husein sugar mill is located in the Jaranwala city which is the district of Faisalabad. It is located on the jaranwala road lahore near lahore moor. Husein Sugar Mills (PVT) Ltd. is one of the pioneers of the sugar industry in punjab. Main product of company is white refined sugar. The working capacity of Husein Sugar Mills is 5500 ~ 6000 tons crushing of cane per day. It has maximum capacity of 8500 tons crushing of cane per day. The organization believes in strict adherence to commitment, discipline and fair business principles. The operation activities of the mill revolve on its departments. There are different types of employees which are hired at need basis, some employees are permanent who work for whole year and some are temporary (seasonal employees). Husein sugar mill is giving different incentives or benefits to employees to improve the production. The management is quite successful in providing a congenital and co-opperative atmosphere to its employees. The organization provides all the basic facilities to the employees. From the processing point of view the operation can be summarised in the following way: Sugar cane is purchased from farmers and is supplied to the mill where it is weighed conveyed, cutted, and shredded. The juice is then extracted from the shredded cane by milling operation and the waste bagasse is used in the boilers as a fuel for the production of steam, in order to meet industrial requirements. Additional bagasse is sailed to the paper and board making industries. The steam produced is used to drive milling operation by turbines as well as it is supplied to power house to generate electricity. This sugar mill generates so much electricity that it can meet the energy requirements of the whole jaranwala city if it is provided to them. The extracted juice is then heated and clarified by different equipments to form concentrated solution. The syrup is then decolorized by chemical treatment in order to produce refined sugar by different operations. Other by products are also of importance because they are utilized as the feed stock for other process. Mud, which is the by product; is utilized to fertilizer field. While molasses are supplied to ethyl alcohol production plant.
  12. 12. xii The final production of refined sugar is 3500 bags per shift. Where as shift is of 8 hours. And each bag is of 50kg. So final production is of 525 tons/day.
  13. 13. 1 CHAPTER-1 INTRODUCTION 1.1 What is sugar? Sucrose in common language is known as sugar (table sugar). Sucrose having chemical formula 𝐶12𝐻22𝑂11 is also known by its structural name (β-D-fructofuranosyl-α-D- glucopyranoside). Its molecular weight is 342.3 g/gmole. It belongs to the family of disaccharides composed of glucose and fructose joined by an α,β-glycosidic bond.[1] 1.2 Properties of Sucrose (Sugar) 1.2.1 Physical Properties of Sucrose a) Its physical properties are shown in Table-1[1] Property Value Density, kg/m3 1587.9 Melting point, °C 160~186 Solubility in H2O at 20 °C, g/g 2 Specific Heat, J/gmole Crystalline at 20°C Amorphous at 22°C 415.8 90.2 Heat of solution, kJ/gmole 4.75±0.26 Enthalpy of crystallization at 30°C, kJ/gmole 10.5 b) Relative sweetness of sucrose and other sweet substances are shown in Table-2[1] Sweetener Relative Sweetness Sweetener Relative Sweetness Fructose 1.2~1.8 Saccharin 250~550
  14. 14. 2 Sucrose 1.00 Aspartame 120~200 Glucose 0.60 Sucralose 550~750 Maltose ~0.5 Cyclamate 30~50 Lactose 0.15~0.3 Acesulfame K ~200 Galactose 0.32 Alitame 2000 1.2.2 Chemical Properties of Sucrose [1] a) Oxidation of Sucrose Sucrose can be oxidized by HNO3, KMnO4, and H2O2. Under selected conditions using oxygen with palladium or platinum to form sucronic acid derivatives. b) Hydrolysis of Sucrose Sucrose can be enzymatically hydrolyzed to glucose and fructose by invertase. 𝐶12𝐻22𝑂11 + 𝐻 2 𝑂 𝑦e𝑙𝑑𝑠 →−−−→ 𝐶6𝐻12𝑂6(𝐺𝑙𝑢𝑐o𝑠e) + 𝐶6𝐻12𝑂6(𝐹𝑟𝑢𝑐𝑡o𝑠e) The reversal is called inversion and the resulting glucose-fructose mixture is called invert. Sugar is destroyed by Ph extremes, and inadequate Ph control can cause significant sucrose losses in sugar mills. c) Alkaline Degradation At high Ph, sucrose is relatively stable; however, prolonged exposure to strong alkali and heat converts sucrose to a mixture of organic acids (mainly lactate), ketones, and cyclic condensation products. In aqueous solutions, sucrose is most stable at ~Ph 9.0. d) Thermal Degradation At high temperatures (160-180°C), sucrose decomposes with charring, emitting an odor of caramel. Acid catalyzed thermolysis causes decomposition to glucose and fructofuranosyl cation. The latter reacts with sucrose to form a complex mixture of products, including fructoglucan and several ketoses. These substances are examples of
  15. 15. 3 fructooligosaccharides (FOS) and are known to promote the growth of beneficial intestinal microorganisms. 1.3 Uses of Sucrose a) Food Applications Its principle contribution to food is sweetness. However it provides many other functionalities, e.g. mouth feel and moisture retention. Cereals and backed goods are the leading consumers of sucrose, followed closely by confectionary products. It is used as a preservative in jam and jelly. It lowers the freezing point of ice cream and other frozen desserts to improve product mouth feel and texture.[1] b) Feedstock for Chemical Synthesis Sucrose reacts with fatty acids to produce esters with degrees of esterification (DE) from 1 to 8.[1] c) Fermentation Feedstock Sucrose, in the form of beet or cane molasses, is a fermentation feedstock for production of a variety of organic compounds, including lactic, glutamic, and citric acids, glycerol, and some antibiotics. Rum is made by fermentation of cane molasses. Beet and cane molasses are used for production of baker’s and brewer’s yeast. A more abundantly produced substance is ethanol for use in alcoholic beverages, and as a fuel, solvent, and feedstock for organic synthesis.[1] d) Pharmaceutical Applications Sucralfate, an aluminum salt of sucrose octasulfate, is used as an antacid and antiulcer medication. Bis- and tris-platinum complexes of sucrose show promise as an anti-tumor agents. Sucrose monoesters are used in some pharmaceutical preparations. A sucrose polyester is under evaluation as a contrast agent for magnetic resonance imaging (MRI). Oral administration of this substance opacifies gastrointestinal tract and eliminates the need for purging prior to MRI.[1] 1.4 Nutrition and Health Aspects of Sucrose For many years, there has been concern by medical professionals and nutritionists over the effects of dietary sugar on human health. Sucrose has been
  16. 16. 4 implicated as a cause of juvenile hyperactivity, tooth decay, diabetes mellitus, obesity, atherosclerosis, hypoglycemia and nutrient deficiencies. The sugar task force’s select committee on Nutrition and Human Needs recommended a daily consumption of sugars at 10% of total calories.[1]
  17. 17. 5 CHAPTER-2 SUGAR MILL FEED SECTION SPECIFICATION AND DETAILS 2.1 Feed Section (Delivery, Unloading, Weighing & Handling of Cane) Raw material (sugar cane) is imported and weighed on weight balance. Then it isintroduced onto the feeding table by elevating the trawler through jack.[2] 2.2 Feed table There are four (4) Feed tables in the industry. The purpose of feed table is to transfer the sugar cane on the cane carrier. Conveyer belts and impellers are mounted on the feed table. They helps in transportation of cane from feed point to cane carrier.[2] 2.3 Cane Carrier The Cane Carrier is a moving apron. Cane carrier is a type of conveyer belt which carries cane from feed table and transport it towards leveler, cutters, leveler, magnetic separator, shredder, mills, boilers, and finally to bagasse storage point.[2] It consists majorly of two portion stated as following:
  18. 18. 6 a) The horizontal portion It is used for horizontal transportation of cane. b) The inclined portion It conveys cane horizontally as well as vertically simultaneously.
  19. 19. 7 Cane carrier is driven through electric motor. As this is essentially a constant-speed machine, and the carrier speed must be frequently varied, the drive is effected by a variable speed coupler. 2.4 Leveller Leveller is a set of knives which evens out the layer of cane, so that other size reductionoperations can easily be performed. The leveler blades, which are coated with specific materialwhich are inert to cane juice, mounted on the shaft which rotates at a specific rpm. The shaft is driven through electric motor. After passing through the leveler the cane would be at such a level that can easily be handled in cutters without jamming it. There are two (2) levelers in thesugar industry one is used before cutters and other one is used after cutters.[2] 2.5 Cutters Cutters are used to cut the cane into small pieces. Three (3) cutters are installed over the feed carrier. Two of the cutters are motor driven and third one is driven through steam turbine. The knives are mounted on the shaft spindle. Different number of knives are used to make the cutting more effective.[2] Cutters Specification
  20. 20. 8 Cutter No. Knives Drive Type Cutter-1 72 Motor Driven Cutter-2 84 Motor Driven Cutter-3 96 Steam Turbine Driven
  21. 21. 9 Knives Types 2.6 Magnetic Separator Magnetic separator is used to remove the iron particles or pieces which become the partof cutted cane or other iron particles which are already present. The commonest objects are: pieces of knife blades, sling hooks, broken pieces of slings,monkey wrenches, horse shoes, bolts and nuts. If iron pieces are not removed then they jam the mills and pressure feeder, and so it is required to remove them before cane feeding to mills. Mills are very expensive due to the millrollers.[2]
  22. 22. 10 Shredder Specifications No. of Hammers 76 Weight of Each Hammer 22 kg No. of Rods 8 No. of Disks 20 2.7 Shredder The objective of shredder is to complete the preparation and disintegration of the cane,so as to facilitate the extraction of juice by the mills. Shredder is a type of hammer mill whichis used to disintegrate the cane. It is driven by steam turbine imported from Germany. It receives the cane from the leveler, which is placed after the third cutter and sends it to the milling house. The cane is hammered by the hammers mounted on the rod, which is inserted into the disk holes. These hammers are mounted alternatively. These hammersdisintegrate the cane against a curved metal plate. After shredding this cane is passed to the milling section by shredded cane elevator.[2]
  23. 23. 11 2.8 Shredded Cane Elevator It is basically inclined cane carrier which transports shredded cane horizontally as wellas vertically simultaneously to the pressure feeder of mill 1. [2] 2.9 Turbines It is a device which is used to convert the pressure energy of the superheated steam intomechanical work. It is basically a type of prime mover. Its further details are given in power house chapter. In the feed section two turbines are used. One is used to drive cutter-3 and other one is used to drive shredder. The turbine specifications are stated below: Turbine Specifications Turbine for Cutter-3 Turbine for Shredder Power 650 kW Power 1800 kW Inlet Steam Temperature 330°C Inlet Steam Temperature 330°C Inlet Steam Pressure 22 kgf/cm2 Inlet Steam Pressure 22 kgf/cm2 Outlet Steam Pressure 1.15 kgf/cm2 Outlet Steam Pressure 1.15 kgf/cm2 No. of Rotations Produced 6500 rpm No. of Rotations Produced 5400 rpm Steam Used 7 tons/hr Steam Used 12 tons/hr
  24. 24. 12 Cane H2O Bagasse to Boiler House Baga Cillo Juice to Process House Rotary Screen / Stationary Screen + Mixed Juice Tank Extracted Juice Tank Mills (5) + Elevators Bagasse Elevator Shredded Cane Elevator Shredder Magnetic Separator Leveller Cutters (3) Leveller Cane Carrier Feed Table Weight Balance CHAPTER-3 MILL HOUSE 3.1 Block Flow Diagram The feed handling and juice extraction steps are shown in the diagram below: Block Flow Diagram [Feed Section + Milling House] 3.2 Mills Mill is a machine which is used to extract the juice from shredded cane. It consist of two major parts: 1- Pressure Feeder 2- Mill Pressure feeder consists of three rolls stacked together to form a shape of triangle and its lower roller is driven through steam turbine. Objective of pressure feeder is to feed the shredded cane at high pressure to the mill inlet in order to facilitate the cane milling operation for proper juice extraction and in order to avoid shredded cane back coming effect. Mill itself also consists of three rolls for juice extraction. The rolls of a mill are stacked together to form a triangle shape and its upper roller is driven through steam turbine. Objective of a mill is to extract the juice from shredded cane. In reality pressure feeder and mill both are integrated to each other in order to form a six roll stack for easier cane handling. There are five mills are used in series, each mill have a pressure feeder associated with it. About 80% juice is extracted in mill-1. Feed to each pressure
  25. 25. 13 feeder is introduced by inclined cane carrier. So every mill’s pressure feeder has an inclined cane carrier associated with it and it precedes to mill. [2] Mills Specifications Mill Inlet Clearance Outlet Clearance No. of Rotations Mill-1 60 mm 30 mm 5 ~ 6.7 rpm Mill-2 50 mm 25 mm 5 ~ 6.7 rpm Mill-3 40 mm 20 mm 5 ~ 6.7 rpm Mill-4 30 mm 15 mm 5 ~ 6.7 rpm Mill-5 20 mm 10 mm 5 ~ 6.7 rpm Mill Rollers
  26. 26. 14 3.2.1 Mills Configuration 3.2.2 Trash Plate Trash plate is a plate with teethes on both sides and it is used among mill rollers. It fulfills two basic functions: 1- It provides a tight fitting between rollers which improves the crushing and so juice recovery is improved. 2- Its teeth clarify the space between roller disks to some extant which prevent mill choking. [2] Trash Plate Specifications No of Teethes 40, 50, or 60 mm Length 1700 mm 3.2.3 Characteristics of a Mill 1- It possess a surface especially constructed to permit it to grip the cane or pieces of cane which are fed to it, in the best possible conditions.
  27. 27. 15 2- This surface must at the same time be designed in such a way as to break, tear up, and crush the cane, in order to permit the mills to get to work immediately and effectively on the broken up material, which is already of the nature of bagasse rather than cane.[2] 3.3 Imbibition Even when bagasse is subjected to high and repeated pressures, it never gives up all the juice which it contains. It approaches to a minimum moisture in the most favorable cases: that is, it retains a high proportion of juice, amounting roughly to half its weight. In order to extract as much as possible of the sugar which it retains, it is therefore necessary to move to some mechanism of more juice removal known as imbibition. Since this moisture content cannot be reduced, the effort will be made to replace by water the juice comprising it. In this process the bagasse is sprayed with water, this water spreads in the bagasse and dilutes the juice which it contains. The next mill will then recover bagasse at limiting moisture. But this moisture will consist, no longer of absolute juice, but of diluted juice. Hence sugar will have been extracted; and the operation may be repeated. [2] 3.4 Bagasse Elevator Bagasse elevator is a type of inclined carrier which transports the bagasse from last mill outlet to all boilers inlet as well as towards the additional bagasse storage point. [2] 3.5 Stationary Screen and Rotary Screen It is a stationary screen filter/rotary screen filter used for the separation of suspended bagasse particles from extracted juice. Rotary screen size is 0.5 ~ 0.7 mm. Note: Only one filter operates at a time.[2] 3.6 Mixed Juice Tank It is a tank which stores extracted juice for further processing in process house.
  28. 28. 16 Extracted Juice Tank Rotary Sceen DSM Juice to Process House Juice from Mills 3.7 Juice Supply Configuration to Process House Mixed Juice Tank
  29. 29. 17 CHAPTER-4 MILL DRIVE BY STEAM TURBINE 4.1 Steam Turbine Mills are driven by steam turbines. There are five mills in the industry so there are five steam turbines installed for each mill. A figure of a typical steam turbine is shown below: Turbine Specifications Turbine Steam Used Power Inlet T Inlet P Outlet P No. of Rotations Turbine-1 of Mill-1 10 tons/hr 850 kW 330°C 22 kgf/cm2 1.15 kgf/cm2 7500 rpm Turbine-2 of Mill-2 9 tons/hr 850 kW 330°C 22 kgf/cm2 1.15 kgf/cm2 3200 rpm Turbine-3 of Mill-3 10 tons/hr 850 kW 330°C 22 kgf/cm2 1.15 kgf/cm2 1200 rpm Turbine-4 of Mill-4 9 tons/hr 850 kW 330°C 22 kgf/cm2 1.15 kgf/cm2 3200 rpm Turbine-5 of Mill-5 9 tons/hr 850 kW 330°C 22 kgf/cm2 1.15 kgf/cm2 3200 rpm 4.2 Gears From turbine specification table it is clear that each turbine operates at very high rpm and the requirement for milling is 5 to 6.7 rpm so turbine rpm should have to be reduced in
  30. 30. 18 order to meet the requirements of mills. For this purpose large size reduction gears are used. In order to reduce so high rpm to very low rpm very large size single gear is required. If so large size reduction gear is used then its installation and maintenance requires so much effort that difficulties will arise during these tasks. Second option of rpm reduction is used practically in the sugar mill which is that rpm are reduced in a stage wise operation by using many different sizes gears. The rpm of turbine is reduced up to 5 rpm in stage wise speed reduction operation. This rpm reduction operation is of mechanical concern so more details are eliminated for the sake of convenience.[2] A typical stage wise rpm reduction gear assembly is shown in the figure below:
  31. 31. 19 CHAPTER-5 BOILER HOUSE 5.1 Boiler Feed Water Treatment It is necessary to treat boiler feed water to remove scale forming ions for proper boiler operation. Ca2+ and Mg2+ are scale forming ions. Many process have been developed for this purpose but most economical is the ion exchange process. After water treatment its hardness is removed and soft water can be used for boiler feed and for other purposes where ever it is required. [3] 5.1.1 Ion Exchange Process (A special type of Adsorption) Ion exchangers exchange one ion for another, hold it temporarily, and then release it to a regenerant solution. In an ion exchange system, undesirable ions in the water supply are replaced with more acceptable ions. Ionizable groups attached to the resin bed determine functional capability of the resin. Industrial water treatment resins are classified into four basic categories: 1- Strong Acid Cation (SAC) 2- Weak Acid Cation (WAC) 3- Strong Base Anion (SBA) 4- Weak Base Anion (WBA) SAC resins can neutralize strong bases and convert neutral salts into their corresponding acids. SBA resins can neutralize strong acids and convert neutral salts into their corresponding bases. These resins are used in most softening and full demineralization applications. WAC and WBA resins are able to neutralize strong bases and acids, respectively. These resins are used in dealkalization, partial demineralization, or (in combination with strong resins) full demineralization. [3] 5.1.2 Sodium Zeolite Softening Sodium zeolite softening is the most widely applied use of ion exchange. In zeolite softening, water containing scale-forming ions, such as Ca2+ and Mg2+, passes through a resin bed containing SAC resin in the sodium form. In the resin, the hardness ions are exchanged with the sodium, and the sodium diffuses into the bulk water solution. The hardness-free water, termed soft water, can then be used for low to medium pressure boiler feed water, reverse osmosis system makeup, some chemical processes, and commercial
  32. 32. 20 applications, such as laundries. The resin is then regenerated with sodium chloride (NaCl) brine solution in a zeolite softener. [3] 5.1.3 Zeolites Zeolites are micro porous, aluminosilicate minerals commonly used as commercial adsorbents and catalysts. Zeolites occur naturally but are also produced industrially on a large scale. [4] 5.1.4 Boiler Feed Water Specifications Boiler feed water should have to meet following specifications in order to minimize scaling and to maximize efficiency. Property Value TDS (Total Dissolved Solids) 1400 ~ 1700 ppm Hardness 0 % pH 8.5 ~ 10 5.2 Boiler Boiler is an equipment which is used to convert water into steam. 5.2.1 Types of Boilers There are two main types of boilers: 1- Water Tube Boiler A water tube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. 2- Fire Tube Boiler A fire-tube boiler is a type of boiler in which hot gases from a fire, pass through tubes running through a sealed container of water.
  33. 33. 21 In Husein Sugar Mill there are three water tube boilers are installed to generate steam from water at different capacities. So further discussion will be related to water tube boiler only. [4] 5.3 Water Tube Boiler According to configuration there are three types of water tube boiler: 1- A-Type 2- O-Type 3- D-Type (It is used in the sugar mill) A water tube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gases which heats water in the steam- generating tubes. In the industry there are three water tube D-type boilers are working with the following specifications: [4] Boilers Specifications Boiler Capacit y Furnace Area Inlet Water T Inlet Water P Outlet Steam T Outlet Steam P Furnace T Outlet Flue gases T Boiler-1 35 tons/hr 16ft by 17ft 95°C 38 kgf/cm2 360°C 24 kgf/cm2 1100 ~ 1200 °C 180°C Boiler-2 40 tons/hr 16ft by 16ft 95°C 38 kgf/cm2 360°C 24 kgf/cm2 1100 ~ 1200 °C 180°C Boiler-3 80 tons/hr 18ft by 22ft 95°C 38 kgf/cm2 360°C 24 kgf/cm2 1100 ~ 1200 °C 180°C
  34. 34. Furnace material is cast iron. Furnace inside layer is made of refractory bricks, middle is of insulating bricks and outer is of cast iron. Furnace tube material is Mild Steel (M.S.). Tubes are of M.S. No. A192/A520 ASME (American Standard for Mechanical Engineers). Bagasse is used as a fuel for boiler furnaces. Bagasse having 52% moisture is burned. Bagasse is the final solid product of mill section. Bagasse from the last mill is sent to the boilers by bagasse elevator. Air is supplied to furnace by Forced Draft Fan, Secondary Fan, and Induced Draft Fan. The furnace is operated under negative draft. To produce negative draft Speed Ratio of (F.D. Fan) : (I.D. Fan) is kept to 1:1.2 ~ 1.5. A steam super heater is integrated with boiler and in this saturated steam is converted to superheated steam by exchanging heat with flue gases. An air pre-heater is also integrated with boiler. Flue gases enter the air pre- heater at 250°C and leave at 180°C. 2 tons of steam is produced per ton of bagasse combusted. 20
  35. 35. 21 Ash 5.4 Configuration of Boilers Extra Bagasse to Storage Air Steam Flue Gases Steam to Power House Water Showering Water Bagasse from Mill House Air Steam Flue Gases Air Steam Flue Gases Steam Header Steam to Milling House Power House Milling House Steam Desuperheater Steam to Process House Steam from all three boilers combine in the steam header at 360°C temperature and 24 kgf/cm2 pressure, and then this steam is transferred to milling house, feed section, and power house to run turbines. When steam reaches the milling house and power house its temperature becomes 325 ~ 330°C due to heat losses to environment. While the pressure of the steam reduces to 22 kgf/cm2 due to pressure drop in pipes and valves. After steam turbines its temperature becomes near about 180°C and then it goes to steam desuperheater, where its temperature is reduced to 125°C which is the requirement of process house. Boiler-1 -2 -3 Water Boiler Ash Water Boiler Ash
  36. 36. 22 CHAPTER-6 POWER HOUSE 6.1 Turbines (Expanders) Turbine is a device which converts internal energy of the fluid to mechanical work. There are two fundamental types of turbine: 1- Hydraulic Turbine (Turbine driven by incompressible fluid) a) Water Turbine (Turbine driven by water) 2- Pneumatic Turbine (Turbine driven by compressible fluid) a) Steam Turbine (Turbine driven by superheated steam) b) Gas Turbine (Turbine driven by any other dry gas) In industrial power house steam turbine is used, so major focus of attention will be steam turbine. 6.2 Steam Turbine Steam turbine is a device which converts pressure energy of the superheated steam into useful work. Note: It is only a prime mover like as an electric motor. 6.2.1 Way of Working: The expansion of a gas in a nozzle to produce a high velocity stream is a process which converts internal energy into kinetic energy, which in turn is converted into shaft work when the stream impinges on blades attached to a rotating shaft. Thus a turbine (or expander) consists of alternate sets of nozzles and rotating blades through which vapor or gas flows in a steady state expansion process. The overall result is the conversion of internal energy of a high pressure stream into shaft work. When steam provides the motive force as in a power plant the device is called a turbine; when it is a high pressure gas, such as ammonia or ethylene in a chemical or petrochemical plant, the device is called an expander. [5]
  37. 37. 23 Turbine consists of a casing in which a turbine router is fitted in such a way that it can rotate about its axis of rotation. Turbine router has blades on its surface. Superheated steam is introduced from the inlet pipe line at high pressure and temperature which strikes the router blades and imparts its pressure energy to it. This pressure energy rotates the turbine router which generated shaft work. The shaft work produced by the turbine router is then used to rotate shaft of any equipment. Turbine’s other rotational parts have oil assembly which decreases friction in order to improve the efficiency. The oil by circulating continuously inside the equipment got heated during operation. So, an oil cooling mechanism is required. With the turbine a shell & tube heat exchanger is used as cooler, for cooling the hot oil; with water as coolant in the shell side. There are four turbines used in power house. One of them is made by Peter Brother Hood Company (England), which generates 4MW of work power, and remaining are imported from Czechoslovakia and each generate 1.25MW work power. Turbines Specifications Turbines Steam Used Power Inlet T Inlet P Outlet T Outlet P No. of Rotations before reduction No. of Rotations after reduction Turbine-1 Peter Brotherhood 33 tons/hr 4 MW 330°C 22 kgf/cm2 180°C 1.15 kgf/cm2 9067 rpm 1500 rpm Turbine-2 11 tons/hr 1.25 MW 330°C 22 kgf/cm2 130°C 1.15 kgf/cm2 7500 rpm 1500 rpm Turbine-3 11 tons/hr 1.25 MW 330°C 22 kgf/cm2 130°C 1.15 kgf/cm2 7500 rpm 1500 rpm Turbine-4 11 tons/hr 1.25 MW 330°C 22 kgf/cm2 130°C 1.15 kgf/cm2 7500 rpm 1500 rpm
  38. 38. 24 6.3 Types of Blades 6.4 Defects of Steam Turbine In the steam turbine defects arise when saturated steam is used instead of superheated steam. As from the knowledge it is clear that saturated steam have water droplets in it. When saturated steam is used in the turbine, its water droplets causes pitting to turbine blades. This pitting phenomenon is the process, in which very small liquid particles at high pressure and temperature strikes to a surface, causes its momentum transfer to it in such a way that; this momentum transfer is only to certain points of the blades, instead of even momentum transfer to turbine blades, so the turbine blades got damage from improper momentum distribution on blades. In order to save blades and other turbine inside parts from this type of mechanical damages, it is strongly recommended that superheated steam is used instead of saturated steam. 6.5 Calculation of Shaft Work Produced by Turbine [5] = 𝑚f𝑙o𝑟𝑎𝑡e(𝐻2 − 𝐻1) (𝑠e𝑛𝑡𝑟o𝑝𝑐) = (∆𝐻)𝑠 (𝐸ff𝑐e𝑛𝑐𝑦) = 𝑠 = (∆𝐻) (𝑠e𝑛𝑡𝑟o𝑝𝑐) (∆𝐻)𝑠 𝑠 = 𝑆ℎ𝑎f𝑡 o𝑟𝑘 𝑃𝑟o𝑑𝑢𝑐e𝑑 (𝑘) 𝑚 𝑘𝑔 f𝑙o𝑟𝑎𝑡e = 𝑀𝑎𝑠𝑠 f𝑙ow𝑟𝑎𝑡e of 𝑠𝑡e𝑎𝑚 ( 𝑠 ) 𝐻 = 𝑆𝑝e𝑐f𝑐 e𝑛𝑡ℎ𝑎𝑙𝑝𝑦 of 𝑠𝑡e𝑎𝑚 𝑛𝑙e𝑡 ( 𝐽 ) 1 𝑘𝑔
  39. 39. 25 6.6 Electric Generator 𝐻2 = 𝑆𝑝e𝑐f𝑐 e𝑛𝑡ℎ𝑎𝑙𝑝𝑦 of 𝑠𝑡e𝑎𝑚 o𝑢𝑡𝑙e( 𝑘𝐽 ) 𝑘𝑔 Electric generator is a device which is used to convert mechanical energy into electrical energy. 6.6.1 Working Principal It produces electricity by electromagnetic induction. Four generators are used to produce electricity in power house. Electric Generators Specifications Generator Output Voltages Produced Generator-1 11000 Volts Generator-2 440 Volts Generator-3 440 Volts Generator-4 440 Volts Step down transformers are used to reduce 11000 V to 440 V. Generators are derived by steam turbine like shown in figure below: Synchronization In an alternating current electric power system, synchronization is the process of matching the speed and frequency of a generator or other source to a running network. An AC generator cannot deliver power to an electrical grid unless it is running at the same frequency as the network. If two segments of a grid are disconnected, they cannot exchange AC
  40. 40. 26 power again until they are brought back into exact synchronization. In the power house of the sugar mill, synchronization is used to match the frequency of 50 Hz of electricity which is produced by four generators.[4]
  41. 41. 27 Specifications Inlet Juice Temperature 35 ~ 40°C Outlet Juice Temperature Heating Surface Area 72°C 160 ~ 400 m2 pH of Juice 4.5 ~ 5.5 CHAPTER-7 PROCESS HOUSE 7.1 Vapor Line Juice Heaters After juice accumulator tank, juice comes to the tubes of vapor line juice heater and where it is heated. Vapor line juice heater is the shell and tube heat exchanger in which heating media is vapors which are generated by multiple effect evaporators. Vapor flows in shell side. There are two vapor line juice heaters are installed in the industry. Only one of them is operated in season. Specifications Inlet Juice Temperature 25°C Outlet Juice Temperature Heating Surface Area 35 ~ 40°C 400 m2 ,400 m2 7.2 Primary Heaters After passing through the vapor line juice heater, the juice goes to the primary heaters. Primary heaters are actually shell and tube heat exchangers. Vapors from the multiple effect evaporator are the heating media used in the shell side. Juice from vapor line juice heater is fed to the tube side of the primary heaters. There are five primary heaters are installed in the industry. Only two heaters operate during production.
  42. 42. 28
  43. 43. 29 7.3 Defecation Lime (CaO) has remained the universal basic defecant from the beginning. The treatment of juice with lime is called defecation. [2] Defecation is carried out in order to raise the Ph value of the juice. It is necessary to raise the Ph value because at low Ph and high temperature juice decomposes which causes sucrose losses and it is not feasible for industry. Inversion losses can also take place. In the industry there are three tanks used in which this operation is carried out. First and last tank acts as holding tanks while in the second tank milk of lime Ca(OH)2 is added to carry out the defecation process. 1st Defecation Tank: In the 1st Defecation Tank there is only mixing by stirrer to make the mixture homogeneous. 2nd Defecation Tank: In the 2nd Defecation Tank, milk of lime is added to the mixed juice to increase the Ph from 4.5 ~ 5.5 to 6.8 ~ 7.2 3rd Defecation Tank: In the 3rd Defecation Tank, holding time is given as retention time in the vessel to maintain the Ph value at specified point. 7.4 Retention Tanks After defecation tank, juice enters into retention tank where two other streams also enters. One of them comes from entrainment separator (Liquid) while other one is scum from
  44. 44. 30 talo clarifier. 7.5 Secondary Heaters After passing through the retention tanks, the juice goes to the secondary heaters. Secondary heaters are shell and tube heat exchangers. Juice from retention tanks is fed to the tube side of the secondary heaters. Vapors from the multiple effect evaporator are the heating media used in the shell side. There are four secondary heaters are installed in the industry. Only two heaters operate during production. Specifications Inlet Juice Temperature 70°C Outlet Juice Temperature Heating Surface Area 105°C 280 ~ 350 m2 7.6 Flash Tank After secondary heater the hot juice goes to the flash tank. The main purpose of flash tank is to remove the water vapors (Partial Vaporization) from the hot juice. For this purpose the hot juice is introduced into the flash vessel by a diffuser onto the flat plate, where its pressure is sudden decreased which causes partial vaporization. Removal of vapors prior to clarification (sedimentation) is necessary otherwise mud rising phenomenon will take place in the clarification vessel, which causes deficiency in the clarification operation. [4]
  45. 45. 31 When the juice is introduced into the flash vessel by diffuser, then pressure reduction causes partial vaporization of the juice and vapors are produced. These vapors contain some juice particles in it. In order to recover these juice particle de-entrainment mesh pad is used some times in the top of the flash vessel. The liquid juice droplets in the vapors strikes the pad and return to liquid stream back, while remaining vapors are escaped from the vessel. The total capacity of the flash tank used in the industry is 31m3 . 7.7 Distributor After flash tank, the hot juice goes to the distributor vessel. The main purpose of distributor is to distribute the juice in the each clarifier by four different ways. The advantage of the distributer is to avoid channeling in the clarifier. 7.8 Clarifier (Sedimentation) The main purpose of the clarifier is to clarify the juice by removing impurities in the form of mud. Hot juice enters into the clarifier by four paths that combines in the feed launder. Then after the filling of the feed launder it falls inside the channel to deplection plate. The purpose of the deplection plate is to minimize the splashing effect which causes mud disturbance. Splashing causes to break the mud cake at the bottom of the clarifier due to this mud disturbance it may come in the juice again and so clarification will not give clarified juice, so we have to prevent splashing by deplection plate. Impurities are converted into mud by the addition of a suitable polyelectrolyte. This polyelectrolyte having high molecular weight attaches impurities with it and form strong bond with them which causes the formation of mud. This mud having high density starts to fall under the action of gravity to the bottom of the clarifier which is known as sedimentation, and this is the basic concept which governs this type of clarification. The polyelectrolyte in the form of solution is supplied to four juice supply
  46. 46. 32 distribution drums, where it is mixed in a certain proportion with hot juice feed which goes into feed launder. This polyelectrolyte solution in water is made prior to clarification in a vessel by simple mixing effect. The level of juice raises in the clarification tank and reaches to the inside and outside launders. Juice enters into these two launders and then with the help of their separate outlet pipes combine into a compartment of the outlet supply drum. It attains a level in the compartment and then enters into the second compartment of the outlet supply drum from which it is supplied to the DSM screens. There are three DSM screens used in the industry with 0.35mm screen size. The juice is then sent to juice pre heater where its temperature is increased to 110°C ~ 115°C. The mud is removed from the bottom of the clarifier tank with the help of the scraper and is sent to the Mud mixer. There are two clarifiers used in the sugar mill. In first clarifier the deplection plate has conical upper surface. The height and diameter of first clarifier are 6m and 9.15m respectively. Second clarifier is of SRI type. In the second clarifier the upper surface of deplection plate is flat. And in the second clarifier mud scraper also translate itself for better mud removal. The length and diameter of second clarifier are 3m and 8m respectively. Only one clarifier operates in the season during production. The temperature inside the clarification tank is kept to 105°C. 7.9 Mud Mixer Mud from the clarifier goes into the Mud Mixer. The main purpose of mud mixer is to form the thick (viscous) mud, by adding the milk of lime, polyelectrolyte, and bagacillo into it. Addition of bagacillo to the mud, is necessary, otherwise vacuum filter will not furnish a satisfactory filtration. It is estimated that 3-6 kg bagacillo per ton cane should be introduced. Usually 8 and 12 mesh screens are used to obtain bagacillo from mill house. Capacity of mud mixer is 7m3 . 7.10 Rotary Vacuum Filter After the mud mixer the thick mud goes into the vacuum filter. In vacuum filter the juice is extracted from the mud by suction with the help of vacuum pump. The suction divider plate is used in suction head. There are two vacuum zones in the vacuum filter. The first one is high vacuum zone and second is low vacuum zone. In high vacuum zone the vacuum is of 18 to 20 in of Hg due to more number of visible tubes and in low vacuum zone the vacuum is of 8 to 10 in of Hg due to the less number of visible tubes. In no vacuum zone the mud scrapping by scrapper from the rotating drum will be more. Mud is scrapped from the drum and with the
  47. 47. 33 help of chute and conveyor it is conveyed to the mud disposal hopper. Mud is used as a fertilizer in the fields. The suction product goes into the vacuum receiver tanks. From vacuum receiver tanks liquid portion goes to clear cloudy juice tanks, and then it is recycled to defecation tank. In the vacuum receiver tank some juice vapors are present due to suction effect. From the vacuum receiver tank the juice vapor portion is supplied to entrainment separator. In the entrainment separator juice droplets will separate from vapors portion. The liquid portion goes to the retention tank, while the vapor portion will condense during passing through cascade condenser. There are four vacuum filters are installed in the industry. 1 ton/hr crushing requires 0.45m2 area of filtration. Filtering area of each vacuum filter is 56m2 . 7.11 Evaporators Evaporator is an equipment that is used to concentrate the solution by evaporating the solvent (water). There are two types of evaporators are used in the industry. Which are following: 1- Falling Film Evaporator (FFE) 2- Multiple Effect Evaporator (MEE) 7.12 Falling Film Evaporator These are, like long vertical columns. It is a special type of shell and tube heat exchanger. The process fluid to be evaporated, flows downward from the FFE top side by gravity as a continuous film through tubes. The fluid creates a film along the tube walls, progressing downwards (falling). The fluid distributor has to be designed carefully in order to maintain an even liquid distribution for all tubes along which the solution falls. Heating medium is placed on the outside of the tubes so it acts like a shell and tube heat exchanger. Condensing steam is used as a heating medium which flows in the shell side.
  48. 48. 34 Steam consumption is lower in the falling film evaporator than a simple cylindrical evaporator, because the juice flows in the form of film. In this way the heat transfer coefficient is enhanced, so more evaporation occurs hence the load on the boiler is decreased. So it is an energy efficient evaporator. [4] 7.13 Multiple Effect Evaporator It is also a type of shell and tube heat exchanger. In this evaporator vapors or steam which is used for first effect as a heating media will condense and the vapors produced by evaporation of solution will be used in next effect as heating media, while the same solution is evaporated in multiple effects. This Process repeats in the remaining effects. Such type of ten effects are installed in the industry while five of them works for the produced capacity. [6] There is a gap between the half bundles of tubes which is known as central well. The width of the central well is ¼ times of the diameter of the evaporator. Juice enters from the bottom of calandria and after heat exchange it comes back from central well. Water present in the juice is evaporated and collected from the top and is further utilized as heating media to the next evaporator. Concentrated juice is collected from the bottom and it is sent to the next body. Juice discharges as concentrated juice termed as syrup is collected from last body (evaporator).
  49. 49. 35 Juice enters the FFE from juice preheater at 110°C ~ 115°C, and after passing through FFE it enters into MEE which increase the Brix and converts juice to syrup. There are two FFE’s are installed in the industry, one of them is in working condition. There are ten evaporators other than FFE’s. These evaporators are used in multi effect. No of effects required depends upon the required heat transfer area. In usual production, five effects are used in order to get the required evaporation. At the entrance of 1st effect brix is 15, while at the outlet of 5th effect brix is 65. Precautions: i. Shut down condition: In shut down condition the water should circulate in the evaporator tubes. Otherwise the tubes would collapse and the tubes are the heart of the evaporator. So it should be handled carefully. ii. Scale formation: This is the salting out of materials. The salted out materials are deposited on the walls of heating tubes. This causes clogging of tubes and thus reduce the heat transfer coefficient. Then sodium hydroxide is circulated during heat exchanger cleaning to remove the scaling. iii. Corrosion: Many solutions attack ferrous metals thus causing damage to evaporators and contamination of products. It is therefore important to use evaporators whose material of construction is compatible with the solution being evaporated. Evaporator Heating Surface Area (m2) F.F.E. 1 3500
  50. 50. 36 F.F.E. 2 3500 Evaporator 1 3000 Evaporator 2 1800 Evaporator 3 2450 Evaporator 4 880 Evaporator 5 500 Evaporator 6 1250 Evaporator 7 900 Evaporator 8 900 Evaporator 9 500 Evaporator 10 500 7.14 Calculation of Amount of Vapors Generated Amount of vapors generated in these multiple effect evaporators is given by the following formula: 𝐸 = (1 − 𝑟𝑥𝑛 ) 𝑚 𝐵𝑟𝑥o𝑢𝑡 f E = Mass of water evaporated Brix in = Brix into the evaporator Brix out = Brix out of the evaporator m f = Mass flow rate of juice at inlet 7.15 Syrup Tank After multiple effect evaporators the syrup goes to the syrup tank through pump. The main purpose of the syrup tank is to store the syrup and to give some residence time to the syrup to become homogeneous. 7.16 Batch Pans Batch pan is an equipment in which syrup concentration is increased by heating it under vacuum. By increasing temperature vacuum decreases, while by decreasing temperature
  51. 51. 37 vacuum increases. The syrup is sent to A-Batch Pan (No.4 or 5). A1-Molasses and B-Sugar is added into it which improves the rate of nucleation. In the pan the mixture is boiled through vapors under vacuum. In the similar way A-Heavy after dilution is sent to the B-Batch pan where it is mixed with c-seed and the mixture is heated with vapors under vacuum. B-Heavy after dilution is sent to the C-Batch pan where it is mixed with c-light and the mixture is heated with vapors under vacuum. Vacuum of 25 ~ 26 in of Hg is created. Vapors from 2nd effect are used for heating purposes.
  52. 52. 38
  53. 53. 39 NOTE: The process is clearly shown in the block flow diagram and it is self-explanatory so only general details are explained. 7.17 Continuous Pans Continuous pans are used in which further syrup vaporization is achieved by heating with vapors under vacuum. Syrups after batch pans are sent to their corresponding continuous pans for further vaporization. 7.18 Crystallizers There are two main types of crystallizers: 1- Horizontal crystallizer 2- Vertical crystallizer 7.19 Horizontal Crystallizer The crystallizer, horizontal in shape with open top side is called horizontal crystallizer. The crystallization process consists of two major events, nucleation and crystal growth. Nucleation is the step where the solute molecules dispersed in the solvent start to gather into clusters that become stable under the current operating conditions.
  54. 54. 40 The crystal growth is the subsequent growth of the nuclei that succeed in achieving the critical cluster size. Nucleation and growth continue to occur simultaneously while the supersaturation exists. Supersaturation is the driving force of the crystallization hence the rate of nucleation and growth is driven by the existing supersaturation in the solution. There are 12 horizontal open crystallizers in the process house. Crystallizers Used for Crystallizer 1 Refine sugar Crystallizer 2 Refine sugar Crystallizer 3 Refine sugar Crystallizer 4 A-1 sugar Crystallizer 5 A-grain Crystallizer 6 A-massecuite Crystallizer 7 A/B-massecuite Crystallizer 8 B-massecuite Crystallizer 9 B-grain Crystallizer 10 B-massecuite Crystallizer 11 C- massecuite Crystallizer 12 C-grain 7.20 Vertical Crystallizer Vertical crystallizer is used in cane sugar industry for efficient sugar crystallization from low-purity crystal suspensions.
  55. 55. 41 There are four vertical crystallizers used in the industry. First crystallizer is used for crystallizing the B-massecuites and the remaining three are used for crystallizing C- massecuites. The brix achieved is nearly 98°. The temperature is decreased to 40ᴼC. Vertical Crystallizer Massecuite No. of Coils Volume (m3) Capacity (kg) (volume*density) Brix out Crystallizer 1 B-massecuite 18 175 262 98ᴼ Crystallizer 2 C-massecuite 18 175 262 101ᴼ Crystallizer 3 C-massecuite 18 175 262 101ᴼ Crystallizer 4 C-massecuite 18 175 262 101ᴼ Vertical cooling crystallizer concept is based on a vertical unit with cooling tube bundles. The aim is to remove as much sucrose as possible from the mother liquor by continuing the crystallization of crystals that have already formed. Benefits and features: [2]  Easy operation also with highly viscous massecuites  Vertical design requires only little floor space, outdoor installation is possible (no building costs). Shape of Sugar Crystal (Sucrose)
  56. 56. 42 7.21 Pug Mills After crystallizers their respective massecuites are sent to the respective pug mills. The main purpose of pug mill is to prevent the massecuite from solidifying by the mixing process, through rotating shaft on which the rods are fixed. 7.22 Centrifugal Separators (Machines) They separate the phases by filtration using centrifugation process. The walls of the centrifuge basket are porous, and the liquid filters through the deposited cake of solids and is removed. After pug mill massecuites are sent to centrifugal machines for separation of crystals from mother liquor. 7.23 Remelter After A-centrifuge, A-sugar is sent to the remelter and wasted sugar is also added in the
  57. 57. 43 remelter. This remelter melts both sugars and makes a homogeneous mixture. This mixture is sent to the buffer tank. 7.24 Buffer Tank The main purpose of the buffer tank is to give the residence time to make the mixture homogeneous. The entering temperature to the buffer tank is 70°C. 7.25 Baby Heater After buffer tank the mixture goes to the baby heater. The main purpose of the heater is to heat up the mixture. The entering temperature of the mixture is 68°C and the outer temperature is approximately 80 to 85°C. 7.26 Talo Clarifier The fundamental operation in this clarifier is the separation of scum from liquor by froth floatation method with the addition of additive chemicals. Additives: 1- Talo Float (Used to decrease the density of scum in order to start floatation) 2- Talo Floc (Used to clarify the juice) 3- Phosphoric Acid (Used to maintain the pH level) 4- Lime Sucrate (Fine Liquor + Milk of Lime + Hot water) (Used to maintain the pH level)
  58. 58. 44 Temperature Condition: 80 ~ 85°C, pH Condition: 6.4 ~ 6.5 7.27 Sugar Grader Sugar grader is used to separate the different sizes sugar crystals for market and industrial operation demands. Particle Size of Sugar grain 4, 8, 12, 16, 20 mesh is produced as per market requirement. 7.28 Dryer Drier is used to dry the final product sugar crystals with the help of steam. 7.29 Hopper Hopper is used to supply the final sugar to packaging section. 7.30 Packaging After hopper sugar is packed into 50 kg bags. Manual packaging is used and it is closed by sewing machine. In 8 hr shift 3500 bags are produced.
  59. 59. 45
  60. 60. 46 7.31 Brix and Purity Data Material Brix Purity % Clear J 15 80 Syrup 64 81 A-Grain 94 87 A-Mass 95 84 A-Heavy 82 65 A-Sugar 97 97 B-Heavy 90 45 B-Light 75 90 B-Grain 93 72 B-Mass 98 68 B-Sugar 98 96 B-Seed 96 96 C-Grain 80 72 C-Mass 101 51 C-Light 81 65 C-Sugar 98 81 C-Seed 95 94 Fine Liquor 65 97 A1-Mass 91 92
  61. 61. 47 CHAPTER-8 CHEMICAL LABORATORY In chemical laboratory there are two major tests that often performed three times in a shift (8 hours period). 1- Brix Test 2- Bagasse Test 8.1 Brix Test This test is performed by the instrument known as hydrometer. A hydrometer is an instrument used to measure the specific gravity of liquids; that is, the ratio of the density of the liquid to the density of water. A hydrometer is made of glass and consists of a cylindrical stem and a bulb weighted with mercury or lead shot to make it float upright. To get the reading from the hydrometer following steps are performed. 1. Fill the glass cylinder with sample. 2. Put the hydrometer with the bulb end down. It will bob up and down in the sample. Note that; the sample may overflow from the cylinder. 3. Assure that the hydrometer is not in contact with the sides of the cylinder and take the reading.
  62. 62. 48 8.2 Bagasse Test Pol in the bagasse is tested by polarimeter, after the extraction of pol by pol extractor. a- Pol Extractor The pol extractor is a mixer developed for the quick determination of pol% in cane and mill bagasse and fiber% in the cane and bagasse. Cold water is used for the extraction of pol and for the determination of fiber, hence the method is called as cold water dissection method. For finding pol in cane or bagasse a weighed quantity of the sample along with the predetermined quantity of water is mixed in the vessel for a set time. The homogeneous liquid thus formed is filtered by adding lead sub acetate in it and it is polarized for the pol reading. b- Polarimeter The polarimeter is an instrument used for determining the optical rotation of substances. In this way, the concentration, content and purity of certain substances can be found. Therefore, the polarimeter has become one of the most useful Instruments in laboratories of sugar industry.
  63. 63. 49 SWOT ANALYSIS OF HUSSEIN SUGAR MILLS LIMITED  STRENGTHS  Husein Sugar Mills has hardworking, cooperative and trained staff. As well as very friendly environment.  The turnover ratio is very low because it is offering best packages to its employees.  ISO certified  The HR department is working for the increasing communication and computer skills of lower staff.  Ease of access to the top management.  WEAKNESS  No integrated control system to control the plant.  The packaging is manually controlled causing more men power.  Operation of plant below its capacity due to low demand  OPPORTUNITY  The demand of sugar is increasing with the passage of time therefore the importance of this sugar plant has much increased.  Generation of electricity from bagasse (waste) for use in process.  THREATS  Availability of raw material (cane) only in three months in year  Due to political and safety condition of Pakistan, there are security threads to Husein Sugar Mills.
  64. 64. 50 REFERENCES 1. Kirk Othmer, “Encyclopedia of Chemical Technology”, Vol.23, Ed.4th . 2. E.Hugot, “Handbook of Cane Sugar Engineering”, Ed.3rd . 3. Kirk Othmer, “Encyclopedia of Chemical Technology”, Vol.25, Ed.4th . 4. Wikipedia a free Encyclopedia 5. J.M.Smith, “Introduction to Chemical Engineering Thermodynamics”, Ed.7th . 6. Coulson & Richardson’s, “Chemical Engineering”, Volume-2.

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