ssp pumps in sugar processing

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SSP Pumpsin

Sugar Processing


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The information provided in this document is given in good faith,

but Alfa Laval Ltd, SSP Pumps is not able to accept anyresponsibility for the accuracy of its content, or anyconsequences that may arise from the use of the

information supplied or materials described.

Inside View

This document has been produced to support pump users at all levels, providing an invaluablereference tool. It includes information on the Sugar processes and provides guidelines as to thecorrect selection and successful application of SSP Rotary Lobe Pumps.

Main sections are as follows:

1. Introduction

2. General Applications Guide

3. Cane Sugar Processing

4. Beet Sugar Processing

5. Refining

6. Pump Specification Options

7. The SSP Advantage

8. Pump Selection and Application Summary


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ContentsPage

Section 1.0: Introduction 3Introduction of SSP Pumps in Sugar Processing

Section 2.0: General Appl ications Guide 5 Overview of the pump ranges currently available from SSP Pumps

and which particular pumps to apply within various application areas

Section 3.0: Cane Sugar Processing 7 Description of how cane sugar is processed and where to find SSP rotary lobe pumps

3.1 Harvesting 73.2 Extraction 73.3 Evaporation 83.4 Crystallisation 93.5 Storage 10

Section 4.0: Beet Sugar Processing 13Description of how beet sugar is processed and where to find SSP rotary lobe pumps

4.1 Harvesting 134.2 Extraction 134.3 Purification 144.4 Evaporation 144.5 Crystallisation 15

Section 5.0: Refining 19Description of the sugar refining process and where to find SSP rotary lobe pumps

5.1 Affiniation 205.2 Carbonatation 21

5.3 Decolourisation 225.4 Evaporation/Crystallisation 235.5 Separation/Drying 24

Section 6.0: Pump Specification Options 27Description of various pump specification options available on SSP rotary lobe pumps

6.1 Mechanical Seals 276.2 Heating J ackets and Saddles 286.3 Wear Plates 296.4 Bi-lobe Rotors 30

Section 7.0: The SSP Advantage 31SSP Pumps comparison with other pump technologies

7.1 Other Technologies 337.1.1 Gear Pumps 337.1.2 Sliding Vane Pumps 337.1.3 Progressing Cavity Pumps 35

Section 8.0: Pump Selection and Appli cation Summary 39SSP Pump selection guidelines summary for the different pumpedmedia found in Sugar Processing


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1.0 Introduction

Sugar is currently produced in 121 countries and global production now exceeds 120 million tonnes ayear. Approximately 70% is produced from sugar cane, a very tall grass with large stems which ismostly grown in tropical countries. The remaining 30% is produced from sugar beet, a root cropresembling a large carrot grown mostly in the temperate zones of the northern hemisphere.

Historically, sugar was only produced from sugar cane and then only in relatively small quantities.This resulted in it being considered a great luxury, particularly in Europe where cane could not begrown. Even today, it is difficult to ship food quality sugar across the world so a high proportion ofcane sugar is made in two stages. Raw sugar is produced where the sugar cane grows and whitesugar is produced from the raw sugar in the country where it is required. Beet sugar is easier to purifyand most is grown where it is required so white sugar is produced in only one stage.

As a recognised market leader in pumping technology SSP Pumps has been at the forefront ofsupplying rotary lobe pumps to the sugar industry for over 50 years. SSP rotary lobe pumps are to befound in numerous sugar processes, where their reliable low shear flow characteristics are ideallysuited to the transfer of such wide-ranging media as magma, massecuite and thick juice.


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2.0 General Applications Guide

This section gives an overview of the pump ranges currently available from SSP Pumps and whichparticular pumps to apply within various application areas in the Sugar Industry.

Within the various sugar industry processes many opportunities exist for utilising SSP rotary lobepumps, not only for the final product but other processes such as by-products, sampling and waste.

Walk the Process

Opportunities

By-Products Sampling Waste

Raw Material Final Product

The Process

The Process

SamplingWaste

Raw Material Final Product

Services

B -Products


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Within the sugar industry typical application areas for SSP Pumps are to be found in:

Carbonation

Crystallisation Evaporation

Recovery

Separation

Storage

Tanker Loading

Transfer

The table below indicates the typical pumped media found and which pump series can be generallyapplied:

Pump SeriesMedia Handled S D G

Glucose - -

High / Low Green Syrup - -

Liquid Sugar - -

Magma -

Massecuite -

Molasses -

Sugar Syrup - -

Thick Juice - -

Treacle - -

General Requirements

S D G

Pumped Media

Max. Viscosity - cP 1000000 1000000 1000000

Max. Pumping Temperature 200C (392F) 200C (392F) 200C (392F)

Min. Pumping Temperature -20C (-4F) -20C (-4F) -20C (-4F)

Ability to pump abrasive products 8 9 9Ability to pump fluids containing air or gases 9 9 9Abilty to pump solids in suspension 9 9 9CIP capability 9 8 8Dry running capability (when fitted with flushed mechanical seals) 9 9 9Self draining capability 9 8 8Performance

Max. Capacity - m/h 106 120 680

Max. Capacity - US gall/min 466 528 2992

Max. Discharge Pressure - bar 20 15 10

Max. Discharge Pressure - psig 290 215 145

Pump Series

The table shown below gives a general guide as to the SSP pump series required to suit the application


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3.0 Cane Sugar Processing

The processing of sugar from sugar cane can be divided into the following steps:

Harvesting Extraction Evaporation Crystallisation Storage

3.1 Harvesting

3.2 Extraction

The cane must be processed as soon as possible after delivery to the sugar mill. Typically, cane isprocessed within 24 hours of cutting. Cane preparation is critical to good sugar extraction. This isachieved with rotating knives and hammer mills called shredders.

The extraction is conducted as a counter-current process using fresh hot water pumped through thechain of multiple roller mills or the continuous diffuser. The more water that is used, the more sugar isextracted but the more dilute the mixed juice is. In best milling practice more than 95% of the sugar inthe cane goes into the juice.

A typical mixed juice from extraction will contain 15% sugar. The residual fibre produced fromcrushing the cane is known as bagasse, which also contains the un-extracted sugar and 45-55%water. The bagasse is subsequently sent to the boilers to be used as fuel.

Cane grows very tall, up to 3 metres, in goodgrowing regions. Harvesting is done either by hand

or by machine.

Hand cut cane is cut about ground level andassembled in bundles. These bundles are thentransferred to a large vehicle and transported to themill.

Most machine-cut cane is chopped into short lengthsbut otherwise handled in a similar way.


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3.3 Evaporation

The dark-green mixed juice from the mills is acid and turbid. The clarification process uses heat andlime as clarifying agents. The mixed juice is preheated before milk of lime {calcium hydroxideCa(OH)2}, to approximately 0.5 kg per tonne of cane, is added to the juice. The lime neutralises thenatural acidity and insoluble lime salts, like calcium phosphate precipitate. Heating the limed juice toboiling coagulates the proteins and some of the fats, waxes and gums. The juice goes through agravitational settling tank, known as a clarifier, where the solids settle out and clear juice exits.

The mud from the clarifier still contains valuable raw sugar so it is filtered on rotary drum vacuumfilters where the residual juice is extracted and the mud can be washed before discharge, producing a

sweet water. The filtered juice and sweet water is returned to the clarified juice; the press cake isdiscarded or used as fertiliser.

The clear juice is heated in a number of juice heaters and concentrated in a multi-stage evaporator to60-75 Brix and is now called syrup or raw syrup.


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CO2

CO2

A direct consumption white sugar can be manufactured from concentrated cane juice if sulfur dioxide(SO2) or carbon dioxide (CO2) is used in conjunction with lime i.e. the sulphitation or carbonationprocess. The sulphitation process can be carried out either as an acid or alkaline sulphitation

depending on whether the sulfur dioxide (SO2) or lime is added first. In the carbonation process, firstquick lime and carbon dioxide (CO2) are produced in a limekiln. The quick lime is mixed with water toproduce lime milk and added to the juice. The lime is precipitated with carbon dioxide (CO2) in twosteps, 1st and 2nd carbonation. Before concentrating the juice it is often decolorized by adding (sulfurdioxide (SO2).

3.4 CrystallisationThe syrup is boiled in the vacuum pans, crystallised and separated into white sugar and remainingsugar syrup.

Physical chemistry assists with sugar purification during the crystallisation process as there is anatural tendency for the sugar crystals to form as pure sucrose, rejecting the non-sugars. Thus, whenthe sugar crystals are grown in the mother liquor they tend to be pure and the mother liquor becomesmore impure. Most remaining non-sugar in the product is contained in the coating of the mother liquorleft on the crystals. The mother liquor still contains valuable sugar, so the crystallisation is repeatedseveral times.

Cane Bagasse

2nd Carbonation

1st Carbonation

Cake Processing

SO2

ClarifiedJuice

Sulphitation

Filter

Purification

Screen

Liming

Milk ofLime

Lime Kiln

Pre-heating

SSP Pump Application


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The crystallisation step i.e. boiling, takes place in a vacuum pan: a large closed kettle with steamheated pipes. The mixture of crystals and mother liquor from a boiling, known as massecuite, isdropped into a receiving tank called a crystalliser where it is cooled down and the crystals continue to

grow. This also releases the pan for a new boiling. From the crystalliser the massecuite is fed to thecentrifuges.

In a raw sugar factory it is normal to conduct three boilings. The first or A boiling produces the bestsugar which is sent to storage. The second B boiling takes longer and the retention time in thecrystalliser is also longer if a reasonable crystal size is to be achieved. Some factories re-melt the Bsugar to provide part of the A boiling feedstock, others use the crystals as seed for the A boilingsand others mix the B sugar with the A sugar for sale. The C boiling takes proportionally longer thanthe B boiling and considerably longer to crystallise. The sugar is usually used as seed for B boilings

The diagram on the following page shows where typically SSP rotary lobe pumps can be found in thecane sugar process.

Location Application1 Thick J uice2 Thick J uice3 Massecuite A4 High Green Syrup5 High Green Syrup6 High Green Syrup7 Massecuite B8 Low Green Syrup9 Low Green Syrup10 Low Green Syrup

11 Low Green Syrup12 Massecuite C13 Molasses14 Affination Massecuite15 Affination Massecuite16 Magma17 Magma18 Clear J uice19 Clear J uice20 Massecuite21 Thick J uice

3.5 Storage

The final raw sugar forms a sticky brown mountain which is stored. Although the sugar could be usedat this stage it invariably becomes dirty in storage and has a distinctive taste. It is therefore refinedwhen it gets to the country where it will be used. Additionally, as all the sugar cannot be extracted outof the juice, a sweet by-product is formed known as molasses. The molasses is used extensively asa livestock feed or in distilleries as part of the fermentation process.


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4.0 Beet Sugar Processing

The processing of sugar from beets is traditionally a seasonal process. After harvesting the campaignlasts normally for 3 months, which is generally in Europe from middle of September until end ofDecember. Larger sugar mills introduce a second campaign, which is called thick juice campaign.With this campaign, they do not produce any beets, but refine the stored thick juice to sugar. The thick

juice being produced in the beet campaign is stored for the thick juice campaign. The extension of thecampaign gives a better use of the equipment in the sugar mill. As the thick juice campaign uses justthe later stages of the sugar process, there are no differences in the process.

The processing of sugar from sugar beet can be divided into the following stages:

Harvesting Extraction

Purification Evaporation Crystallisation

4.1 Harvesting

4.2 Extraction

After the removal of stones and dirt, the beets are conveyed to the slicers for cutting into very thin V-shaped slices, known as cossettes. This increases the surface area of the beet for easier extraction ofsugar. The sugar is removed from the beets by means of diffusion. During diffusion the sugar isextracted from the cossettes by hot water, leaving a pulp containing very little sugar but when mixedwith molasses and dried it is used as animal feed.

A typical raw juice from diffusion will contain perhaps 14% sugar and the residual pulp will contain 1 -2% and a total of 8 - 12% solids.

The beets are dug out of the ground andbeing dirtier than sugar cane have tothoroughly washed and separated from anyremaining beet leaves, stones and otherwaste material before processing.


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4.3 Purification

The raw juice contains proteins, pectins, inorganic salts and colouring substances. These impuritieshave to be removed before the evaporation.

Firstly, milk of lime {calcium hydroxide Ca(OH)2}, is added to the juice vessel and carbon dioxide(CO2) is bubbled through the liquor. This coagulates most of the colloidal matter which is precipitatedwith the lime as calcium carbonate.

The resultant juice is passed through a clarifier in which the solids are separated and scraped to theoutlet as mud and pumped away, generally to a press where the sweet water is returned to the milkof lime make-up tank. The juice from the clarifier is again treated with carbon dioxide (CO2) in thesecond carbonation vessel to precipitate more impurities and is the filtered by vacuum, bag or presstype system. The filtered juice now passes through a decalcification process (similar to watersoftening) and using ion exchange resins to remove calcium hardness, followed by sulphitation{sulphur dioxide (SO2) gas bubbled through the juice to remove colour and control acidity}. Any rejectmatter from the second carbonation filters is returned to the raw juice line.

The purified sugar solution has a sugar content of 14 - 16 Brix.

4.4 Evaporation

At this stage the juice is fairly thinand is pumped into a multi-stageevaporator which concentrates thesolution to 60 - 75 Brix.

It is subsequently pumped andstored as thick juice.

S6 pumps handling

Thick Juice in Denmark


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4.5 Crystallisation

This final stage involves boiling the thick juice in vacuum pans, crystallising and separating into white

sugar and remaining sugar syrup.

Three vacuum pans are used, A, B and C. Pan A concentrates the thick juice to a state wherecrystals start to form. The liquor is pumped to crystallisers in which further crystals form as it coolsand here it is known as massecuite. From the crystallisers the massecuite is pumped to a centrifugewhere the crystals are washed thoroughly to remove all adhering syrup.

The liquor spun from Pan A centrifuge is known as High Green Syrup and is pumped to Pan Bwhere second product crystals are formed. The mixture is again put through crystallisers and thesecond or B massecuite is then centrifuged. The resulting liquor now known as Low Green Syrupis passed on to Pan C and the crystals from B centrifuge are conveyed to a dissolver where theyare mixed with thick juice from storage. This mixture is known as magma and is then thinned by the

wash water from A centrifuge to lower its viscosity. The syrup is pumped through a filter and returnedto the thick juice tank to ultimately be reprocessed through Pan A.

The Low Green Syrup now in Pan C continues through the process as in B and after centrifugingthe crystals they are dissolved in A syrup to form the magma, diluted with centrifuge B wash waterand pumped to Pan B.

The liquor from centrifuge C is known as molasses and is pumped to storage or the pulp mixer.

The white sugar crystals produced from Pan A are dried, granulated and bagged.

G7 pump handling Molasses in Ukraine


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The diagram on the following page shows where typically SSP rotary lobe pumps can be found in thecane sugar process.

Location Application1 Thick J uice2 Thick J uice3 Massecuite A4 High Green Syrup5 High Green Syrup6 High Green Syrup7 Massecuite B8 Low Green Syrup9 Low Green Syrup10 Low Green Syrup

11 Low Green Syrup12 Massecuite C13 Molasses14 Affination Massecuite15 Affination Massecuite16 Magma17 Magma18 Clear J uice19 Clear J uice20 Massecuite21 Thick J uice

D6 pump handling Massecuite in USA


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5

6

8

7

9

10

11

12

13

14

15

16

17

18

19

C Boiler B Boiler A Boiler

C

Centrifuge

B Melter

C Melter

Affinat ion

Refined Sugar

WhiteSugar

Clear Juice

Clear Juice

Molasses

Crystallisation Process Diagram

SSP Pump Application


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5.0 Refining

Raw sugar is produced in tropical countries where sugar cane can be grown profitably. It is thenshipped in bulk to a refinery in the country where the sugar is required. It now has to be finallycleaned, purified and made ready consumer use.

The incoming raw sugar consists of 95 - 99% sucrose and the remainder is made up of impurities.The purpose of the refining process is to produce white sugar of approx. 99.95% sucrose withexcellent shelf life qualities and of food quality specification. In simple terms, the refining processconsists of a series of progressive separations of impurities from the sucrose.

Most of the impurities finish up in molasses, together with some sucrose that cannot be economicallyextracted. Some impurities also finish up in intermediate products such as brown sugars, goldensyrup and some liquid sugars where colour, taste and aroma are important.

Raw Sugar

Refined

Molasses Sugar

Mud

S6 pump handling Glucose in UK


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Melted Liquor

5.1 Affination

Affination orWashing is the first step in the sugar refinery. The raw sugar crystals have a thin film ofimpurities on the surface. This thin film is softened by mixing with hot impure sugar syrup (60C). Theresulting magma is fed to centrifuges, which spin off the syrup including the impurities. In the last stepof the centrifugal separation, water is sprayed on the crystals to remove the final traces of impurities.Leaving the affination process the sugar crystals have a purity between 98.5 - 99%. These crystalsare melted with sweet water of the same purity. This melted liquor is sent to further purification steps.

Raw syrup from the Affination process is sent to the Recovery House where a triple combination ofcrystallising and centrifuging is used. The recovered sucrose is returned to the Melting process whilstthe discarded impurities, still containing some sucrose, form Molasses.

SSP Pump

App licat ion

WeighScales

Raw SugarMinglers

MasseFeed Pipes

RawSyrup

FromRawSugarStore

Melters

Condensate

SweetLiquor

AffinedSugarConveyors

AffinationCentrifuges

To RecoveryHouse

RecoveredSugar fromRecoveryHouse

Steam

To Carbonatation


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5.2 Carbonatation

The melted liquor still includes some insoluble material as bagacillo (very fine bagasse), soil,suspended solids and colloids. There are different processes used for carbonatation e.g. pressurefiltration with inert filter aid or chemical treatment and filtration. The chemical treatment consists oftenof a liming step and a carbonisation or phosphatation step. Recovered carbon dioxide (CO2) gas fromthe boiler flue gas reacts with the lime and forms chalk. The impurities stick to the chalk and can beremoved in the filter presses downstream. The optimum liming and impurity absorption is at atemperature around 80C. Half of the colour is already removed in this step before the liquor is goingto the main decolourisation step. In the phosphatation process, phosphoric acid is used to formcalcium phosphate as the carrier for the impurities before filtration.

SSP Pump

App licat ion

SSP PumpApp licat ion

To Resin Plant

Vent

Flue GasMilk of Lime

CarbonatationTanks

PressMud

Filter Supply Tank

Filters

MelterLiquor

PressedLiquor


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5.3 Decolourisation

Sugar in itself is colourless. The non-sugar contaminants are responsible for the colour, which ismostly brown. These non-sugar contaminants are removed by adsorption in the decolourisation tanks.

The adsorption can be achieved by different materials and chemicals, with anionic resins and ion-exchange columns being commonly used today. In combination with these or as stand-alone bonechar columns being used as well. The total colour removal in these systems exceeds 90% and theliquor leaving is known as fine liquor.

SSP Pump

Appl ication

SSP PumpAppl ication

Acrylic 1Resin Cells

Acrylic 2Resin Cells

StyreneResin Cells

GranularCarbonCisterns

Pressed Liquor fromCarbonatation P lant

Fine Liquor

To Evaporators

To Liquid Sugar Plant


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5.4 Evaporation / Crystallisation

Fine Liquor leaving the decolourisation stage usually has a dry substance quantity of 60 - 67 Brix.

Before crystallisation in the vacuum pans it has to be further concentrated to 70 - 75 Brix in anevaporation system.

Evaporated fine liquor with 70 - 75 Brix is fed to vacuum pans. Pressurised steam provides indirectheat by means of coils inside the pans. The liquor itself is processed under reduced pressure so as tominimise colour formation. White sugar crystals are grown to the correct size and are dischargedtogether with the residual liquor into a mixing vessel.

The sugar crystal / liquor mixture known as massecuite is now centrifuged to separate the marketquality white sugar crystals from the liquor. Pure, hot condensate wash water is applied to removeresidual traces of liquor. The resultant liquor is then spun off and used again for further crystallisation.

The final liquor, containing some 88 - 91% sucrose, is now returned to the Recovery House.

Evaporator

Vapour

Vapour

CondensateSteam

Vacuum

Pans

Mixers

StorageTanks

Steam

Condensate

To Centrifuges

To LiquidSugar Plant

Fine Liquor fromDecolourisation

SSP PumpAppl ication

SSP Pump

Applicat ion



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5.5 Separation / Drying

The separated white sugar crystals discharged from the centrifuges still contain about 1% moisture.This is removed by passing the sugar into a rotating, two-stage, fluidised-bed dryer, through whichfiltered, heated air is passed.

The moisture level of the emerging sugar is about 0.04% but further drying occurs during conveying.Dry sugar from the Dryers discharges onto conveyor belt systems which take it to various storagesilos and packaging processes.

StorageSilos

RetailPackets

SpecialProcesses

Bulk White SugarRoad Tanker Deliveries

25/50 kg Bags and1 tonne Containers

Hot Air

Dryers

J et Liquor

Sugar Conveyors

Sugar Conveyors

From Mixers

White SugarCentrifuges

To Liquid Sugar PlantFurtherCrystallisationProcesses

Va our



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Approximately 15% of a refinerys output is sold as liquid sugar. This can be Dissolved GranulatedSugar, Fine Liquor or intermediate liquors from the various crystallising stages. All these products aremicrobiologically filtered before storage, prior to loading into road tankers for delivery to customers.

S5 pumps handling Molasses in Denmark


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6.0 Pump Specif ication Options

Dependent upon application, various pump specification options are available on the ranges of SSProtary lobe pumps as follows:

6.1 Mechanical SealsDue to the tendency for media containing sugar particulates to harden when in contact with theatmosphere, the standard mechanical seal specification is a single flushed mechanical seal with hardfaced tungsten carbide seal faces and FPM elastomers.

The presence of a flush media will act as a barrierbetween the pumped media and atmosphere(acting as an interface film between the sealfaces). This will inhibit drying out and hardening

of the media, so avoiding seal face stiction (sealfaces gluing together).

The flush should be a warm compatible fluid e.g.water at a pressure of 0.5 bar max.

Using a flushed mechanical seal will increaseoverall seal life and enable pumps to run drywithout pumphead component damage.

Rotorcase

Rotary seal faceStationary seal face

Shaft

Seal housing

Lip seal

Flush liquid

Shaft sleeve/spacer

Seal housing o ring

R90 Single Flushed Mechanical Seal


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6.2 Heating Jackets and SaddlesSSP Series S pumps have the option of being fitted with jackets to the rotorcase cover and/or saddlesto the rotorcase. These are used for heating the pumphead so as to maintain the pumped media

viscosity and reduce risk of any crystallisation / solidification.

The maximum pressure and temperature of the heating fluid is 3.5 bar and 150C respectively.Heating jackets and saddles should be in operation approximately 15 minutes prior to pump start-upand remain in operation 15 minutes after pump shut down.

Saddle

Jacket

Connections for steamor hot fluid


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6.3 Wear PlatesDue to the abrasive nature of massecuite and magma in particular, a degree of component wear willtake place over time, principally to the rotorcase and rotorcase cover. Pump rotational speed plays a

key role in determining the rate of component wear, where put simply the faster the speed, the greaterthe rate of wear. This factor must be taken into account at the time of pump selection, by applying amaximum speed limit dependent upon the pumped media. Assuming correct pump selection,rotational speed relating to pumped media, the rate of wear should be extremely low.

However, to increase abrasion resistance, SSP Series D and G pumps have the option of being fittedwith replaceable wear plates. These are manufactured from hardened steel and can be replaced insitu with minimal pump dismantling.

For all Series D pumps wear plates can be fitted to rotorcase only. For all Series G pumps wear platescan be fitted to rotorcase and for G9 pump models wear plates can also be fitted to rotorcase cover.Additionally rotorcase covers are hardened as standard on all Series D and G pumps.

If there is any doubt over the pumped media being handled at the time of pump selection, it isrecommended that wear plates are supplied on all massecuite, magma and molasses applications.

Wear Plate to be fit ted toback of rotorcase bore


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6.4 Bi-lobe RotorsOn applications where the preservation of sugar crystals is highly desired, Series S and D pumps canbe fitted with stainless steel bi-lobe rotors in place of the standard tri-lobe rotors to further minimise

any potential crystal damage due to crushing. Bi-lobe rotors are typically able to handle solids of asize 1.5 times that of the tri-lobe equivalent.

The majority of the small amount of crystal damage which does occur will take place either in the rotormesh (the clearance between the two rotors) or the radial clearance. With a tri-lobe form, the rotorswill come into mesh three times per pump revolution, whereas bi-lobe rotors only come into meshtwice per revolution.

The extent and degree of crystal damage in the pump will be dependent upon the actual size andvolume of the crystals in suspension. Should the crystal be significantly larger than the clearances, itwill not be able to pass between the clearances, thus little or no crush damage will occur to eithercrystal or pumphead component. Should the crystal be significantly smaller than the clearances, it will

pass between the clearances suffering little or no crush damage. Only when the crystal isapproximately the same size as the clearances will there be moderate damage to either pumpedmedia or pumphead component (dependent upon hardness of pumped media compared tocomponent material).

Fitting pumps with bi-lobe rotors should be considered on applications where the pumped media hasa high crystalline solids content i.e. massecuite and magma.

Stainless Steel Bi-lobe Rotor


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7.0 The SSP Advantage

SSP Rotary Lobe Pumps offers significant advantages over other pump technologies as follows:

Volumetric efficiencySSP rotary lobe pumps have a high volumetric efficiency typically in excess of 95% onapplications where the product viscosity within the pump is 250 cP or greater. With most pumptechnologies as product viscosity increases, the volumetric efficiency decreases. However thisis not the case with rotary lobe pumps, as efficiency increases with increasing viscosity, up toaround 500 cP, thereafter efficiency remains constant at around 98%. As many sugarapplications are related to media with a high viscosity, this means that to counter the loss ofefficiency, competitors offering alternative technologies either have to increase their operatingspeed (if possible), which in turn increases pump wear rate, or more usually select largerpump units. The selection of a larger pump unit increases cost itself and also means more

space required, plus an increase in absorbed power requirement, which results in larger moreexpensive drives and higher energy costs.

Solids handlingThe main factors contributing to rotary lobe pumps being able to handle solids are:

o Cavity size within pump head.Rotor rotation produces a series of distinct cavities, which act to carry media fromsuction to discharge. The SSP rotary lobe pump design and principle of operationmeans the nature of these cavities are such that their size is constant throughout eachrotor revolution and do not compress the product.

o

No rotor to rotor, or rotor to rotorcase / cover contact.See section 6.4 Bi-lobe Rotors.

o Pump port geometry (size)Design of inlet port optimised to allow direct entry of media into rotorcase withoutsudden restriction, which would otherwise contribute to adverse pump hydraulicoperation, leading to increased noise, possible NPSH/cavitation problems.

No contact between ro tating elementsBenefits include:

o Reduced crystal damage, thus optimising pumped media quality and therefore value.

o Reduced media wetted component wear (rotors, rotorcase, rotorcase cover).

o Reduced power consumption due to low friction/break out torque.

Dry running capabilityAs there is no contact between rotating elements, the possibility of heat build up due to friction,which would otherwise lead to rapid component failure, is avoided. Provided the option of aflushed seal is selected, to ensure seal face/seat lubrication, the pump is able to run dryindefinitely. This in turn gives the advantage of increased process flexibility.


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Slow start-up speed capabilityBenefits include:

o Ability to overcome pumped media yield stress in long pipe runs, thus providing greatersystem design flexibility.

o Ability to handle high viscosity media, where there would otherwise be a significant riskof drive train overload, resulting in damage to pump shafts, bearings, drive/motorgearbox, and/or flexible coupling.

Operating pressures up to 20 bar (range dependent)Ability to handle high viscosity media over long pipe runs, thus providing greater systemdesign flexibility and being able to use one pump technology (supplier) over a wide range ofdifferent media/applications, meaning a potential reduction in key supplier numbers andspares inventory.

Operating flow rates up to 400 m/hBenefits include:

o Increased process flexibility.

o Optimised pump/speed selection, when considering pumped media integrity versuspump component wear.

o Wide range of flow rate options from a single pump technology, meaning a potentialreduction in key supplier numbers, leading to increased purchasing strength.

Compact sizeBenefits include:

o Optimisation of available space, providing potential for reduced costs.

o Easy maintenance through easy access.

Ease of servicingSSP rotary lobe pumps are designed to be maintenance friendly by trained personnel.

Low overall cost of ownershipThe combination of all the above provides a pump solution with low overall cost of ownership,

relative to other competing pump technologies.


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7.1 Other Technologies

There are several pump technologies which could compete with SSP rotary lobe pumps in this

industry, notably Gear Pumps, Sliding Vane Pumps and Progressing Cavity Pumps.

7.1.1 Gear PumpsThere are two main types of gear pump; internal gear and external gear. A comparison madebetween SSP rotary lobe pumps and gear pumps is as follows:

In a gear pump (internal or external), there is no external synchronisation, i.e. one geardrives the other gear. This means both gears are in constant contact with each other. Alubricant is required to ensure there is no excessive heat generation due to the constantcontact. The lubricant is always the pumped media, which means gear pumps cannot rundry, thus reducing process flexibility. Likewise pumped media with poor lubricationproperties also leads to overheating and wear problems. Both problems will lead to the

rapid destruction of gears which will in turn damage the pump head, leading to pumpbreakdown, with associated pump rebuild/replacement costs.Gear Rotary Lobe

Due to gear contact, component clearances within the pumphead are either very small ornon-existent. When the pumped media contains abrasive solids, such as magma,massecuite and molasses, depending upon the relative hardness of the pumpheadcomponent to media solid, there will be abrasion. This abrasion will apply to bothpumphead components, leading to performance loss resulting in increasedmaintenance/replacement cost, and to the pumped media with damage to the sugarcrystals, so reducing product yield and quality. The rates of abrasive wear and productdamage, due to the much smaller clearances, will be much higher than in a rotary lobe

pump.Gear Rotary Lobe

Due to gear contact, the pump may absorb more power during operation, to overcome theresultant frictional force. Any increase in absorbed power will lead to increased energyusage and therefore cost.Gear Rotary Lobe

Gear pumps typically have lower initial unit cost.Gear Rotary Lobe

7.1.2 Slid ing Vane Pumps

A sliding vane pump consists of a slotted rotor or impeller supported within a cycloidal cam orliner, which in turn is mounted within a housing. Two cover plates then seal the housing fromeach side. The rotor is located close to the wall of the cam so a crescent-shaped cavity isformed. As the rotor/impeller rotates and fluid enters the pump, vanes located within the slotsare pushed sequentially onto the walls of the liner, by a combination of centrifugal force,hydraulic pressure and push rods located in the slot behind the vane. This creates a distinctsuction/discharge region within the pump head.

As the pump continues to rotate, the housing and cam force fluid via holes in the cam into thepumping chamber, which then occupies the space created by the movement of vanes, rotor,cam relative to liner and cover plates. As the rotor continues around, the vanes sweep the fluid


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to the opposite side of the crescent where it is squeezed through discharge holes of the camas the vane approaches the point of the crescent. The fluid then exits the discharge port.

A comparison made between SSP rotary lobe pumps and sliding vane pumps is as follows:

Abrasive media will cause abrasion to the vanes and liner, resulting in higher maintenancerequirements and increased life cycle costs.Sliding Vane Rotary Lobe

The principle of operation means that vanes are in sequential constant contact with theliner. Dry running over an extended period of time is therefore not possible as the vanesneed lubrication. High friction area between vane and liner will result in wear. Frictionalforce resulting from constant contact will need to be overcome, leading to increase inabsorbed power requirement, therefore energy cost.Sliding Vane Rotary Lobe

Vanes are self compensating for wear due to the action of the push rod behind the vane.Should vane wear beyond the rotor groove, it will become lodged between the rotor andliner, leading to pump failure.Sliding Vane Rotary Lobe

Minimum rotational speed is required to provide enough centrifugal force to extend vanesto liner. This means slow speed start operation is not possible, sometimes being requiredparticularly on high viscosity applications (magma, massecuite, molasses), to overcomeproduct yield stress and allow product movement. To overcome this, product would needeither agitation/force feeding into the pump, or preheating or a combination of both, thusrequiring additional investment in equipment or increased operating costs.

Sliding Vane Rotary Lobe Potential of vane to stick inside rotor on high viscosity applications.

Sliding Vane Rotary Lobe Sliding Vane pumps are uni-directional, thereby loss of process/system flexibility.

Sliding Vane Rotary Lobe Sliding Vane pumps typically have lower initial unit cost.

Sliding Vane Rotary Lobe Sliding Vane pumps only have one shaft seal, compared to two on a rotary lobe pump.

Sliding Vane Rotary Lobe Self adjusting vanes keep volumetric efficiency approximately constant, even when wear

has taken place.Sliding Vane Rotary Lobe

Limited product slip within the sliding vane pumphead, due to operation principle, providesa better solution on clean low viscosity applications.Sliding Vane Rotary Lobe


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For increased pressures, a large increase in physical size is necessary for progressingcavity pumps due to additional stages required. This will also lead to large increase inpower required to overcome the increased friction from additional stage(s).

Progressing Cavity Rotary Lobe

Progressing Cavity pumps are uni-directional, thereby loss of process/system flexibility.Progressing Cavity Rotary Lobe

Progressing Cavity pumps typically have lower initial unit cost.Progressing Cavity Rotary Lobe

Progressing Cavity pumps only have one shaft seal, compared to two on a rotary lobepump.Progressing Cavity Rotary Lobe

Progressing Cavity pumps with zero clearances have better suction lift capability.Progressing Cavity Rotary Lobe

Rotary Lobe Pump

Up to 20 bar capability from thesame pump size.

Power increase only required toovercome pressure.

1 bar or 20 bar

1 bar

20 bar

Progressing Cavity Pump Large increase in physical size resulting from additional stages.

Large increase in pow er to overcome increased friction from additional stages required.


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Due to its compact design the rotary lobe pump occupies considerably less floor spacethan progressing cavity pumps, thereby providing potential for reduced costs.Progressing Cavity Rotary Lobe

Planning the space

Saving the space

Major savings in time and manpower to change majorpumping components resulting in reduced lifetime costs


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A summary comparison of Rotary Lobe, Progressing Cavity and Gear pump technologies strengthsand weaknesses is given in the table below:

Pump Technology

Lobe

ProgressingCavity

Gear

StrengthAbi li ty to pump abrasive media

Compact size

Easy maintenance Easy re-start Low capital investment Low energy consumption Low shear pumping Reduced lifecycle cost (versus others compared) Reduced lifecycle cost (versus Progessing Cavity) Single seal required Growing presence and acceptance High efficiency Large global presence Robust construction Suction capability

Traditional concept Wide current acceptance Wide range of displacements

WeaknessAbi li ty to pump abrasive media Capital cost Dry running capability High spares cost Large size (versus others compared) Material compatibility Pulsation Pumped media contamination Two seals required Whole life cost Limited presence Limited range of displacementsStill gaining acceptance Suction capability

Bold typeface shows attributes that are considered relevent in this industry.

Grey typeface shows attributes that are considered not relevent in this industry.


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8.0 Pump Selection and Application Summary

This section gives information as to pump selection for different pumped media found in the SugarIndustry.

It should be noted that the information given in this section is for gu idance purposes only -actual pump selection should be verified by our Technical Support after the provis ion of fullpumped media and duty details.


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Viscosity applicable in pump Pump Speed

low =350 - max rpm pump speed (system conditions permitting i.e. NPSHa etc)

Pumped Media Viscous Viscosity Speed Pump Series Sealing

Behaviour Type

CARBONATATION SLURRY Newtonian med med D, G Single Flu

GLUCOSE Newtonian high med S Single Flu

GOLDEN SYRUP Newtonian high med S Single Flu

HIGH GREEN SYRUP Newtonian high med S, D, G Single Flu

LOW GREEN SYRUP Newtonian med med S, D, G Single Flu

MAGMA Pseudoplastic high low D, G Single Flu

MASSECUITE Pseudoplastic high low D, G Single Flu

MOLASSES Newtonian high med D, G Single Flu

SUGAR PULP - BEET Pseudoplastic high low D, G Single Flu

SUGAR PULP - CANE Pseudoplastic high low D, G Single Flu

SUGAR SYRUP Newtonian med med S Single Flu

THICK JUICE Newtonian med med S, D, G Single Flu

TREACLE Newtonian high med S Single Flu

Sugar Applications Summary


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Alfa Laval Ltd

ssp pumps in sugar processing

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