etay hailu sugar power point

7/26/2019 ETAY HAILU Sugar Power Point

http://slidepdf.com/reader/full/etay-hailu-sugar-power-point 1/64

Sugar processing



Cane supply

Cane transportation starts immediately after cutting

Therefore cane transportation and storage time should always be

kept to a minimum

Deterioration is accelerated by high temperature, light, loss of

moisture, all of which factors are greater under tropical

conditions.

To minimize the delay time a close cooperation between

harvesting crew and factory people is essential



Raw materials and its accessories

• The raw materials used in the every sugar factory is

sugar cane.Howeverthere are accessories material

used for dierent purpases

• For instance Sulphur dioxide-used in clarication

process to make

- rapid setting of uice

- fast !oiling of massecuite- fast crystali"ation of sucrose

- market improvement of suger colour

- !etter elimination of phosphates and waxes



• #ime$%a&'-also used during clarication to(

neuterili"e the free organic acids present in a uice

for the pricipitation of colouring matters

• )ater-used for

*m!i!ition(process in which water is applied to the crushed

cane to enhance the extraction of the uice at the next mill!

Steam generation

Sugar wash . . .etc



Cane cutting method

• "and cutting

• #echanical cutting

1. Hand Cutting$

. %ndoubtedly, hand cut cane is better suited for factory processing

than mechanically harvested cane

. &ecause a hand cut cane is cleaner and its purities are higher

since in general cane is cut lower to the ground by hand than by

machine



The highest sugar content is known to be in the lowest part of the

cane stalk, the poorest part being the top.

The cane toping is also properly done by hand cutting

2. Mechanical Cutting$

#echanically cutting and loading is a faster process.

The main problem with machine handling of cane is usually

damage to the field, harming future cane crop

particularly this occurs when harvesting is done during the rainy

season in which damage to the next years cane can be appreciable.



• 'hen the cane is cut, rapid deterioration of the cane begins.

• Therefore, unlike sugar beets, sugarcane cannot be stored for later

processing without excessive deterioration of the sucrose content.



Cane preparation

The preparation of the cane is accomplished by several ways.

&y revolving cane knives that cut the cane into chips but extracts

no uice.

&y shredders that tears the cane into shreds, but extract no uice.

&y crusher that break and crush the structure of the cane

extracting a large proportion of the uice.

&y combination of any or all of the means ust enumerated. we use

combination of and )



• *reparation of the cane has three main obectives.

To increase capacity by increase of bulk density of the feed.

To assist extraction at the mills by breaking down the structure of

the cane.

To render the uice more readily available for the action of

+mbibition by breaking and opening cane cells



Separation of Juice from Cane

The sugar content of cane is dissolved in uice contained in millions

of plant cells.

There are two different systems of extracting the sugar containing

uice from the cane. uch methods of extraction are$ -

a. &y means of pressure in a number of mills provided with three

rollers through which the cane is forced

b. &y means of diffusion, extracting uice by applying heat and

immersion in water and sueezing of the baggasse



Milling process

• The classical combination of three rollers arranged in a triangular

form is the standard milling unit for industry

• The milling process may be separated into two steps

The preparation of cane by breaking down the hard structure and

rupturing the cells

The actual grinding of the cane



+illing ,iagram



• /or the grinding, or milling, of the crushed cane, multiple sets of

three-roller mills are most commonly used although some mills

consist of four, five, or six rollers in multiple sets

• Conveyors transport the crushed cane from one mill to the next.

• +mbibition is the process in which water or uice is applied to the

crushed cane to enhance the extraction of the uice at the next mill

• The crushed cane exiting the last mill is called bagasse



elt conveyor



Screw conveyor



0ir unit (pump!



Juice Screening

• #ixed uice from the milling tandem contains a large amount

of cane fiber that falls out with the uice between the rollers

of the mills.

• The process in which the fiber is separated from the uice is

called uice screening

Juice Screening Equipments

• 0 stationary and vibrating or rotating wire mesh screen.

• 0n inclined wedge-wire screen (D#!

• 0 rubber-lined Dorr clone (cyclone! system



Extraction

• The term extraction is generally used to mean total sugar extracted

by the milling tandem, a percent of sugar in cane

Juice Weighing

• +n a sugar mill, the main material whose weight must be determined

is cane.

• The weight of cane is the most important information, since other

materials are always related to cane weigh



• #ixed uice is normally weighed or measured.

• +f the uice is measured samples of each measuring tank is taken to

obtain an average density of the measured uice and find the

correct specific gravity.

• The volume of the uice is converted to weight by multiplying it by

its specific gravity



• 1enerally, mixed uice weighing is the starting point for control of

the whole factory.

• 0ccurate weighing, sampling and analysis of uice for sucrose is

essential for determination of extraction, boiling house recovery

and boiling house efficiency

Juice Heating

• 2uice heating is excited in a number of vessels called uice heaters

or preheaters



Heat Transfer Rate

• The fundamental heat transfer euation describes how heat is

transferred across the heating surface.

• The total heat flux across the heating surface of a heater is given by

a usual formula.

3 4 %0 ∆t

'here 3 4 Total heat flux, heat transferred, in ' or, 5Cal6hr!

% 4 7verall heat transfer coefficient in (5Cal6hr6m869C!

0 4 0rea of heating surface (ft8, m8!

∆t 4 Temperature drop of condensing steam to boiling uice. +n 5, oC.



• The main purpose of such heating is the following.

Due to application of heat to the 2uice, certain organic constituents

like proteins are coagulated

"eat destroys microorganisms and enzymes preventing loss of

sucrose by microbiological activity

"eat accelerates the reaction rate between the uice acids and the

lime, which will be subseuently added

types of Juice Heaters

There are two main types of heaters.

• The *late "eat :xchangers

• 0 hell and Tube Type (;ertical and "orizontal!



a. The Plate Heat Exchangers

. These types heaters are made up of a number of thin corrugated

or dimpled sheets separated by gaskets and held in place by an

adustable framework

. They are widely used for heating and cooling liuid sugars

(sucrose syrup and invert sugar solutions!

. The unit provides counter current or concurrent liuid-liuid heat

exchange, or vapor to liuid heat exchange or combined heatingand regenerative cooling in the same heat frame



b. Shell and Tube T!pe "#erticaland Hori$ontal%-

+t is a uice heater consists of a cylindrical mild steel shell with a

heating tube, tube plate and header at each end.

The tube plates are perforated to receive the tubes, which are

expanded into them.

The shell is extended at both ends beyond the tube plates into

heaters, which are divided by baffles into compartments



Juice clari&cation

• +n uice clarification process the elimination of non-sugars has to

be done in such a way that

• +norganic non-sugars are removed and not produced afresh when

the clarifying agents are used

• +f agents are not used under proper condition, color and ash are

produced afresh

•

<either sucrose nor reducing sugars are destroyed in considerableuantity



• The main obects of cane uice clarification are$-

To separate soluble and insoluble matter that can precipitate

To reduce color and turbidity of the uice

To produce clear uice of correct p" (=.>!

To kill or inactivate microorganisms in the uice by heat treatment



Methods of Juice Clarification

• Depending on the type of final product to be produced, there are

different methods of uice clarification

Carbonation process

Defecation *rocess

ulfitation *rocess



Caronation !rocess$ The main clarifying agents in the carbonation

process are lime and C78 gas. The process consists of precipitating

calcium carbonate.

Ca (7"!8 ? C78 @ CaC7) ? "87

• The precipitate (Calcium Carbonate! adsorbs coloring matter and

gums

• +t is easily filterable. The raw uice is heated to a temperature A> B

AA>

C and pumped into the carbonation tank where lime is addedand mixed thoroughly.

• The uice is neutralized with C78 gas



'efecation Process

Clarification by heat and lime is known as a simple defecation

process. ufficient lime is added to neutralize the organic acids

present in the uice, after which the temperature is raised >C

(boiling point!.

The treatment causes formation of heavy precipitate of complex

composition.

The flocculent precipitate carries with it most of the finely

suspended material of the uice that has escaped mechanical

screening.

0 uice clarified does the separation of this precipitate from the uice



Sul&tation Process

• +n the sulfitation system clarification is done by heat lime and

sulphurdioxide gas

• The mixed uice is heated to =A >C, more lime slurry is added to the

raw uice and the excess of lime is neutralized by 78 gas.

• The process is called after the name of the acid used for

neutralization of excess lime EsulphitationF

• The treated uice is heated to >

C and separation of flocculated

non-sugars takes place in a continuous settler.



• /rom the settler the clear uice continues in the process and the

underflow mud is a filtered on continuous drum filter and the

filtrate is recycled to the measured raw uice



Juice (lashing

• The treated uice delivered by one of the suited pump and heated at

a temperature of about >8 9C - >A 9C

• contain air bubbles which retard setting in the further process.

• 'hile the under pressure uice enter tangentially in to cylindrical

(vertical! tank which has a large vent to the atmosphere called flash

tank, the bubbles attached to the suspended particles of the uice is

flash out.

• Tangential entrance of the uice used to give a circular movement of

the uice inside the flash tank and this benefit the separation of air

and this avoid the loss of uice through the escaping air



(locculent

/locculent is materials of high molecular weight purchased in

powder form and it acts as abridge between two or more particles

present in the uice to unit the solid particles in to a loose porous

state

/locculent must be free flowing (solution! for mixing with the

uice

There are two flocculent tanks each has a capacity of G m) for

preparation of flocculent solution and to store the prepared one

The normal dosage in uice clarification is 8 B G ppm on weight of

uice



Juice Setting

+n the clarifier, the suspended solids are allowed to settle out from

the uice

The uice flows upward at a velocity low enough to allow the

precipitate to settle

The precipitate are falling down against rising streams if uice

going to the overflow point

7bviously, for effective separation, the settling rate must be faster

than all of the up-flow streams of uice so that net direction of

particle movement is downward

f i i d f l f h l ifi



• +f uice is drawn from only one compartment of the clarifier, a

very high upward velocities of uice exists which restricts the

falling rate of the precipitate or particles entertainment to the over

flow clear uice occurs

• clarifiers have a settling tray, which are supposed to segregate the

setting uice into compartments

• Hiuid-solid separation occurs utilizing the cross sectional area of

each tray

• This system reduces the overall up-flow velocity dividing it by the

number of settling trays



'here$ ; - falling velocity of the particle (m6sec!

D - diameter of the particles (Cm!

d - density of the solid particle (gm6Cm)!

d8 - density of the liuid (gm6Cm)!

g - gravity constant Cm6sec8

u - viscosity of the liuid (poises!

The above euation is for a particle of spherical shape.

This is expressed by stokesI Haw

The settling rate of the particles depends on the size and density

of the particles as well as density and viscosity of the uice

u

g d d DV

D

!( 8

8−

=

E ti



E)aporation

The evaporation process is the process of concentration of the

solids in uice with removed of the water, without substantial

changes in the composition or character of the solids in the

solution

+n the clarification, process impurities are removed from uice as

far as possible

The clarified uice contains about ) B J solids, depending on

the concentration of the original uice in the cane and the

imbibition practice employed

T d h f l i h b



• To produce sugar, the water content of clear uice has to be

removed almost entirely

•

This is the obective of evaporation

• "ence the evaporation process is separated into two phases

a. :vaporation so called, which proceeds from clear uice to syrup,

and during which only liuid material is handled.

b. The sugar boiling (pan boiling!, in which further concentration is

carried out so that crystals form and are grown under controlled

conditions to the desired size

i ff i



multiple Effect E"aporation

:vaporation in open pots over a fire had already been

abandoned and evaporation of uice by heating with steam

had been commenced

team is used for heating uice to evaporate the water which it

contains.

'ith steam at >>C, pressure >.G 5g6Cm8 uice at

atmospheric pressure may be heated and evaporated



• the vapor of uice so boiling at atmospheric pressure is at >> >C.

&ut, with vapor at that temperature it is not possible to boil uice

at the same temperature

• 0 temperature difference is necessary between the heating fluid

and the fluid to be heated

• +t thus became possible to create the necessary temperature

difference and utilize the vapor arising from the uice in the st

vessel to heat the uice in the 8nd vessel, the vapor produce in the

8nd vessel to heat the uice in the )rd vessel, etc



#apor *leeding"steam econom!%

• +n a multiple effect evaporators, it is possible to enlarge the st

vessel, tap off some of the vapor boiled there (instead of sending

all vapor to the next vessel!, and use that vapor for heating at other

stations like uice heating, pan boiling.

• This practice is called vapor bleeding and it results in further

saving of steam.

• &ut the exhaust steam saved is not eual to the exhaust steam that

would otherwise have had to be used to heat the mixed uice, but

to some fraction of it



condenser

• 0 condenser is a tank in which the vapor enters near the bottom

and rises to condense on a shower of water droplets falling

through the tank.

• The water containing the condensed vapor leaves the condenser

by displacement through its barometric leg about >.G meter long

pipe

• 0bout G> B A> tons of water is needed to condense ton of vapor.

• The barometric leg of the condenser deeps into a sealing well that

is always filled with water

• +n condensers the total heat contained in vapor is transferred to the



• +n condensers, the total heat contained in vapor is transferred to the

cooling water or inection water.

•

The inection water reuired per unit vapor can be calculated by theeuation

'here - Total heat in Cal65g of vapor

- Temperature of the in let water (>C!

- Temperature of the discharge water (>C'



#acuums Pans

The operation known in the sugar factory, as sugar boiling is

essentially the process of crystallization, which is carried out in

single effect vacuum evaporators designed for handling viscous

materials and known as vacuum pans

Thus, the vacuum pan is an evaporative crystallizer in which

degree of super saturation is controlled by evaporating solvent as

the solute crystallizes out

T f #



Types of #acuum pan

• There are two types of vacuum pans used in sugar boiling, namely

a.The Coil !ans

• The heating surface consists of a series of coils, ) − A in number

placed one upon the other.

• The coils occupy a large position of the cylindrical height.

• :ach coil set has a separate steam trap, a steam inlet and exhaust

value.

• The heating coils are made of copper tubing which are securely

held in position by tie rods.



. calanderia pans

• +n calanderia pans the tubes are shorter and of larger diameter than

in evaporators.

• 'hether the pan is of coil or calanderia type, the massecuite rises

through the heating surface, between the turns of the coils or

through the tubes of the calanderia



'etermination of Critical Points

• The different zones of super saturations are determined and

identified by experience.

• The sugar boilers learns by experience and observation to know

when a solution was the right degree of super saturation for

graining or growth of existing grain, though they didnKt think in

terms of super saturation.

• +n modern practice instruments are used which give an indication

of super saturation coefficient

+ i i , th d " i t%



+raining ,ethods"assignment%

• There are two different techniues for establishing grain.

! 'aiting of pontaneous 1raining #ethod

8! eeding #ethod

a! hock eeding #ethod (Dry ugar Dust eeding #ethod!

b! The lurry #ethod

Crystalli$ation



Crystalli$ation

Crystallization is a process which consists of mixing the massecuite

for certain time after dropping from the pans, and before passing tothe centrifugals.

The process is with the aim of completing the formation of crystals

and forcing further exhaustion of the mother liuor

The massecuite when discharged from the pan is at a high super

saturation.

+f it is allowed to stand, the sugar still contained in the mother

liuor will continue to be deposited as a crystal, but this masscuite

is very viscous

• Th f th it t b k t i ti i d t h



• Therefore the masscuite must be kept in motion in order to change

constantly the relative positions of the particles of mother liuor

and crystals until the mother liuor becomes a substantiallyexhausted molasses

T!pes of Cr!stalli$ers

•

There are crystallizer of batch and continuous operation.Depending on the system of cooling there are-

. 0ir Cooled Crystallizers

8. 'ater Cooled Crystallizers



-. irCooled Cr!stalli$ers

• The massecuite is cooled by the circulation of air from the walls

of crystallizers and from the surface of the massecuite.

• The cooling effect is slow. <owadays the air cooled crystallizers

are commonly used for storing high grade massecuite and their

use for cooling low grade massecuite is not favored

/ Water Cooled Cr!stalli$ers



/.Water Cooled Cr!stalli$ers

These crystallizers have three arrangements$-

'ater acketed

Cooling coil of rotating type

• 'ater acketed crystallizers are not found very

satisfactory, recently they are not used.

•

The cooling coil of stationary type is less efficient due to

poor contact of the massecuite with the cooling surface.

• They are only used because of lower cost

Centrifugal Separation



Centrifugal Separation

• The final stage of the process of sugar making has now been

peached.

• The sugar crystals mixed with the mother liuor has been obtained.

• 'hat remains is to separate them by the centrifugal force in proper

marketable form.

• uch separation is known as curing, purging by a centrifugal

machine

sugar con"eyor



sugar con"eyor

ugar conveyors are of three designs

crew or scroll conveyor

1rass-hopper conveyor (shaker conveyor!

&elt or slat conveyor

. Scre% Con"eyors

• are not favored for carrying dry white sugar as crystals are liable to be

grounded there in.

•

crew conveyors are generally used to convey massecuite in horizontaltrough

• 0 full screw may be used, but more often the screw consists of a simple

metal ribbon held in place by steel strips

&elt Con"eyor



&elt Con"eyor

• The dry sugar is conveyed horizontally by means of a belt conveyor

of 8 B )L inch width which saves the crystals from being rubbed

• The belt conveyor has the lowest power consumption and is only

used for moisture free sugar

Sugar Ele"ator

• The sugar elevator is used for lifting the sugar to a higher level.

• +t consists of a number of buckets attached to the endless

detachable chain

Sugar dr!er



Sugar dr!er

• The sugar leaving the centrifugals is hot at L> B =>> C and moist >.A

B .AJ moisture and as such it canKt be bagged for sale.

• There are two ways of sugar drying in practice

» Drying sugar in rotary drying

» Drying sugar is centrifugal machines

• 7f the two, drying sugar in centrifugal machines is considered

superior, since in the rotary dryers the crystals lose their moisture

by rubbing action against each other

• /urther, the sugar dust formed means loss of sugar and reuires

additional euipment to recover it

T!pes of 'r!ers



T!pes of 'r!ers

There are three principle types of sugar dryers

/luidized &ed Dryers

Motating Drum Dryers

'luidi$ed(&ed )ryer$

• The sugar is distributed on the perforated plate. "ot air passes

through this plate and through the sugar layer

• The transmission of heat is very rapid, permitting a very brief time

in the dryer

• "owever the fluidization and the air flow involve abrasion of the

crystal

! Rotary )rum )ryer$



!. Rotary()rum )ryer$

+t is the most widely used.

+t is cylindrical and set at a slope of A> to the horizontal, which

facilitates the movement of the sugar from end and end of the

drum.

The revolving motion of the drum causes to lift the sugar and fall

from one sloop to other through a countercurrent hot air flow and

reaches the discharge end of the drum.

The drum is often arranged to act as both dryer and cooler.

The cold air enters at the lower end and leaves near the middle of

the drum

Sie"ing and *rading of Sugars



Sie"ing and *rading of Sugars

• The sugar obtained after drying and cooling consists of a mixture of

heterogeneous crystals and needs to be well sieved and graded

before it is marketed.

• The sieving is done through sifters which are of the following.

Motary Type

#agnetic or ;ibrating Type

a Rotar! T!pe



a. Rotar! T!pe

• This type of screen is attached to a rigid cylindrical frame carried

on a rollers or control shaft

• The axis of the cylinder is usually inclined to the horizontal, so

that the material is carried forward while rolling over the screen

• usually each screen is bounded with several rings of plates having

different perforations arranged in order of sizes, the smallest being

in the beginning

• The whole arrangement is simple.

b #ibrating T!pe



b. #ibrating T!pe

• The vibrating movement reduces chocking of screens and works

for a longer period without cleaning.

• creens of various mesh sizes are fixed in frames and arranged one

over the other in order to facilitate grading of sugars

• The frames are vibrated at a very high speed by means of an

eccentric having a small throw >.A B .> inch and are belt driven by

a motor

• The mechanism is placed under the upper part of the box free for

access to the screen

etay hailu sugar power point

Documents