sugar plant energy conservation

8/3/2019 Sugar Plant Energy Conservation

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LATESTTRENDINENERGYCONSERVATIONANDSUGARMANUFACTURING

SubmittedbyG.V. Raman

S. Ramesh

A. Muralee

SEPTEMBER2011

AVANT-GARDE ENGINEERS AND CONSULTANTS (P) LTD

(AN ISO 9001:2008 ORGANISATION)

No. 68A, Porur Kundrathur High Road, Porur

Chennai - 600 116, India

Tel: + 91 -44 -2482 8717/ 18/ 19/ 20

Fax: + 91 -44 -24828531

[email protected]

www.avantgarde-india.com


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AVANT-GARDEEngineers and Consultants (P) Ltd

CONTENTS

Synopsis 1

Introduction 1

Sugar Plant Electrical Energy Conservation 4

Sugar plant Thermal Energy conservation 14

Adoption of new Sugar plant machinery andprocess

19

Water conservation in Sugar Plants 21

Sugar Cane Water circuit 22

Conclusion 23


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3 AVANT-GARDEEngineers and Consultants (P) Ltd

Synopsis

Energy conservation will contribute to the better management of steam, power, fuel and

water management in the Sugar Industry. Sugar Industries use steam at low pressure for

sugar processing. Some of the Sugar plants still use medium pressure steam for sugar

processing. Process steam utilization is exceeding 50% on Cane for sugar manufacture insome of the sugar plants in India and there are possibilities of reducing the process steam

consumption to a level less than 35% steam on cane. The power utilized for the process

exceeds 32kW per ton of cane crushed in some of the sugar plants in India whereas it is

possible to reduce the power consumption to about 24kW per ton of cane crushed. Most of

the sugar plants in India are operating high pressure co-generation power plants to increase

their profitability and viability, which makes it necessary for these plants to optimize/reduce

the process steam and power consumption. Energy needs are increasing day by day in India

and this ever increasing demand can be meted out by means of energy saving as much as

possible. Energy Saved is energy generated. This paper presents the measures adopted in

the Indian Sugar Industries for reducing Auxiliary power consumption by effectively using

variable frequency drives for different applications. This paper also brings out the steamconsumption reduction possibility in the process area of the sugar industries. The steam and

power reduction measures that could be adopted in the sugar plants are factory specific and it

is necessary to have a detailed study of the sugar factory and come up with the possible steam

and power reduction areas for adoption. This paper also presents the possibilities of water

conservation in the sugar industry.

1.0 Introduction: Today the Sugar Industry is viewed as Energy Industry as all the

products and bye products are potential sources of energy. Sugar cane is a rich

source of energy and the energy ratio for input to output is very high for sugarcane

than for any other agricultural crop. Sugarcane, being a renewable crop gives a lot ofrenewable energy resulting in reduction of green house effect. Energy conservation in

the sugar industry will contribute to steam, power, fuel and water management.

Presently, lot of heat and energy are used during processing in heating and cooling,

evaporating and concentrating the juices and intermediate sugar products. Some

factories use medium pressure steam for sulphur burning, pan washing, sugar drying,

melting and molasses heating and centrifugal station. Many sugar factories use a

large quantity of power per ton of cane for sugar processing. The economic viability

of a sugar factory increases with the installation of high pressure co-generation plant

and export of surplus electric power to the grid thereby bringing an additional source

of revenue to the sugar plant. There is a need for the sugar factories to reduce their

steam and power consumption in order that the revenues by export of surplus power isincreased, thereby the sugar factory will be competitive in the market for the sugar

production. It is a well known fact that sugar cane contains about 70% of water and

still many sugar factories draw huge quantity of fresh water for processing. Such

sugar factories are saddled with large quantity of effluent. It is possible to effectively

utilize the water in a sugar factory. The following paragraphs highlight the latest

changes in machinery and equipment in the sugar industry that has led to saving of

power and steam required in sugar manufacture.


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2.0 Sugar Plant Electrical Energy Conservation

In Sugar Mills, Reduction in Specific Power consumption increases Power Revenue.

Electrical energy consumption can be reduced by installing Energy Efficient

Equipment, correct sizing of the equipment or reducing loss in the energy

transmission.

Some of the Energy Efficient Equipment suitable for Energy Efficiency in Sugar

Mills are discussed here.

2.1 Cane Diffuser

In general juice extraction in a sugar factory is carried out either utilizing Diffusion

technology or milling technology. The milling technology is more prevalent in India

compared to the Diffusion technology even though, of late, there are some plants

adopting diffuser system. The major electrical energy consumption section in sugar

mill is Juice Extraction Plant. In the standard 2500 TCD milling plant, the powerconsumption is 1705 kWH whereas in 2500 TCD Diffuser plant power consumption

in 1200 kWH. The reduction in power consumption is 505 kWH.

Diffusion technology is commonly used in Australia and African countries. The

diffusion technology is energy efficient comparing to the milling technology. But in

India, the technology did not gain greater acceptance during its introduction period

itself. This is because; diffusion technology depends upon better cane preparation and

the plant automation. In diffusion system cane preparative index should be 90+ for

juice leaching in the diffuser. At the time of introduction of diffuser in India (during

1980s), the cane preparation equipments could only give a lower preparatory indexand since automation was not well developed, most of the plants adopted only milling

system. However presently two factories have adopted Diffuser system for energy

conservation purposes.

There will be power consumption reduction in the diffuser plant compared to

conventional milling plants. Typically, for a 2500 TCD sugar plant it has been

observed that the diffuser system power is about 505kWH lower than a corresponding

milling plant system. It should also be noted that the RME will be higher in the

diffuser plant compared to the milling plant.

Advantages of Cane Diffuser

Increase in extraction

Reduction of re-shelling of rollers

Sanitation improvement (higher temperature maintained in diffuser reduces sugarloss due to bio chemical inversion)

Increase in available bagasse on cane since vacuum filters are not used for filtermud separation

Reduction of oil and grease in effluent

Reduction of electrical power consumption. Avoidance of a building for the juice extraction system


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Crystallizers drives,

Molasses and magma pumps,

Pug-mills and Magma Mixers, etc.

2.5 Cane Unloading

Harvested cane from the field is being fed to the cane carrier by EOT cranes and

feeder tables. Grab type un-loaders, which were used for feeding the cane to the

feeder table/carrier from the vehicles, lead to frequent kick loads. Nowadays

hydraulic grabs and sling system are being used in the sugar factories for unloading

the cane on to the feeder table/ carrier. Hydraulic tipplers have been introduced in thenorthern part of India for cane unloading on to the carrier which is giving trouble free

operation. The hydraulic tippler reduces the power requirement of the cane unloading

area. At present, the rotating table type hydraulic tipper is being used in sugar

factories which help unloading to be faster compared to conventional hydraulic tipper,

where the positioning of the vehicle and unloading takes time.

ROTATING TABLE HYDRAULIC TIPPLER HYDRAULIC TIPPLER

2.6 Feeder Tables

Feeder tables are used to store the cane and feed it on to the cane carrier continuously

and uniformly. These feeder tables were driven by constant speed induction motor

coupled with Eddy current coupling and conventional gear boxes with open gearing,

to vary the feeding surface speed, till recently. Nowadays Variable Frequency Drives

in combination with shaft mounted planetary gear system is used for energy

conservation. This system reduces the power consumption. Typically for a 6000 TCD

plant using 7m x 8m feeder table, the installed power reduces from 22kW to 15kW for

the feeder table drive.


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Feeder Table Drive Arrangement

2.7 Cane Carrier

Cane carriers in most of the sugar factories in India are driven by squirrel cage

induction motors with eddy current coupling for speed variation, with conventional

gearbox and open gears for speed reduction.

Nowadays conventional motor with eddy current coupling is replaced by ACVF

drives with planetary gears for speed reduction. By this arrangement one third

electrical power gets saved.

ACVFD Motor with Planetary Gearbox for Cane Carrier Drive


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2.8 Cane preparation

Many sugar plants in India are using kicker, leveler/chopper, cutter and

Fibrizer/shredder for cane preparation prior to milling. The average power

consumption with this system works out to about 65 kW to 70 kW per ton of fibre.

Presently, we have tried the installation of a single cane preparatory system in theform of inline Shredder which consumes less power compared to the other system.

The inline shredder which is located right on the cane carrier has a carding drum and a

feed drum located prior to the Shredder as a single unit. This system does not require

knives for the cane preparation. The carding drum and the feed drum level the cane

and feed it to the shredder and this system consumes only about 55kW to 60kW per

ton of fibre thereby there is power saving in the preparatory system. This system also

gives long fibres without fine preparation.

Inline Shredder with Carding Drum & Feed Drum

2.9 Milling Tandem with Two roller mills:

Various type of mills are used in the sugar plants in India as per the various designs

adopted by the manufacturers, like vertical head stack, inclined head stack, auto

setting, self setting mills etc. Normally conventional mills are having three rollers

with feed, top and discharge rollers along with an under feed roller. The conventional

mills are having trash plate to convey the bagasse from first compression to second

compression in the mills. Usually the static trash plate consumes about 15% to 20%

of the mill drive power. During the traveling of bagasse a lot of extracted juice in thecompressions zone will be reabsorbed by bagasse due to improper drainage in the

mills.

Top

Feed Discharge

Juice drainage

Trash Plate


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Feed

Presently, in India, the two roller mill system is becoming more acceptable in the

sugar factories. These mills are not like our olden days crusher the typical

arrangement of two roller mill is as shown below.

Re-absorption

Juice drainage Limiting Device

In earlier days mills were driven by steam engines (14% thermal efficiency), later by

steam turbine drives (35% thermal efficiency) drives, which are very low efficiencydrives. Nowadays these drives are gradually getting replaced by energy efficient (90%

and above) DC Drives/ACVFD Motors along with planetary gear boxes. ACVFD

motors are most suitable for mill drives because of their own advantages.

For steam turbines power transmission system for mills, three stage gearing systems

were used i.e., high speed reduction gearbox, slow speed reduction gearbox and

bigger size open gearing arrangements. Total gearing efficiency in this system was

around 80.0% only. After introduction of electrical drives the first stage high speed

gearbox is completely eliminated and two stage speed reduction efficiency of 82.0%

was achieved. At present planetary gearbox eliminates slow speed gearbox and opengearing arrangement and its efficiency is around 95%.

ACVFD Motor with Planetary Gearbox for 36 x 78 Two

Roller Mill

For a 3500 TCD plant, the milling tandem having four numbers of two roller millswith the installed power of 430 kW ACVFD motor with foot mounted planetary (four

TOP

Bottom


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stage) gearbox is sufficient, whereas the same capacity sugar plant having three roller

mills of 36 x 78 size with conventional gearing system will require 600kW motor.

In the two roller mill trash plate is eliminated and there will not be any hydraulic load

on mill roller journals. Hence the power consumption in the milling will get reduced

thereby saving energy in mill plant.

View of Two Roller Milling Tandem

The figure below shows the two roller milling tandem with driving arrangement of

ACVFD motor, foot mounted planetary gearbox with flexible rope coupling operating

in a 3500 TCD sugar plant.

2.10 Inter Rake Carrier:

The inter rake carrier in the milling tandem are driven by constant speed motor, speed

variation is effected through eddy current coupling and power transmission is by

single stage worm gearbox and open gearing. In India, this system is getting replaced

by ACVFD motor and planetary gearbox for power saving.


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oot Mounted Planetary Gearbox

With ACVFD Motor for Inter

Rake Carrier

Shaft Mounted Planetary Gearbox

with ACVFD Motor for Short

Distance Inter Rake Carrier

2.11 Crystallizers:

Massecuite dropped from the pans are stored and cooled in the crystallizer. Open type

horizontal air cooled crystallizers were used for high grade massecuite and open type

horizontal water cooled crystallizers were used for low grade massecuite in the past.

At present for the lower grade massecuite single mono vertical crystallizer is being

used which will save lot of energy and maintenance cost.

Very low efficient worm and worm wheel type gears for crystallizer drive are

gradually getting replaced with high efficiency planetary gearbox, which saves nearly50% of power consumed in this area. Also in the centrifugal area pug mill and magma

mixer drives are getting replaced with planetary gears. By this replacement 50%

electrical power will be saved in this area.

Shaft Mounted Planetary Gearboxes in Magma Mixer and Crystallizers


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2.12 Centrifugals:

For A Massecuite curing batch centrifugals are used which are being driven by

regenerative type ACVFD motors for power saving to reduce the power consumption

form 3.0 kW per cycle (conventional three speed motor) to 1.08 kW per cycle.

ACVFD Motor Mounted on the Batch Centrifugal Machines

2.13 Juice and Water Flow Meters:

In sugar mills, by replacing the weighing scale for juice and imbibition water with

online meters, power spent on pumping can be conserved. In the juice clarification

area juice flow measurement is carried out through mass flow meter replacing the

conventional mechanical tipper weighing scale. This totally eliminates the mechanical

weighing system and weighed raw juice pumps are dispensed with thereby, saving

energy in the sugar plant operation.


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Mass Flow Meter for juice measurement

2.14 Condensers & Cooling System

Specific Power consumption in the injection Pumps is about 1.89 kW per ton cane.

By installing energy efficient condensers, Specific Power consumption in injectionPump station can be reduced to 1.20 kW per ton cane. By installing Energy Efficient

cooling system power consumption can be reduced by 33%.

2.15 Condensers:

To create vacuum in evaporation and crystallization system, Barometric condensers

were used earlier in sugar factories in India. Later these were replaced by Double

Entry Multi Jet Condensers. Nowadays the double entry multi jet condensers are

getting replaced with single entry multi jet condensers. Single entry multi jet

condensers are highly efficient and hence the water requirement for the condensing

system is reduced by one third and also the operation can be easily automated toreduce energy consumption.

Latest development in the condensing system is a single common centralized

condenser for entire process. Such system is already in operation in some new

installations, which are quite successful for steam and energy saving.

Centralized Condenser in a 3500 TCD sugar plant


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2.16 Energy efficient Pumps and Motors

In Sugar Mills, there are about 150 centrifugal pumps and 250 motors. By installing

energy efficient motors and pumps, installed power consumption can be reduced.

2.17 Energy Conservation by Proper Sizing

In sugar mills, it is a usual practice to provide higher capacity margin to cope up with

the fluctuation in the crushing rate and higher rating motor to avoid tripping. By

proper sizing of the equipment and installing less number of higher capacity machines

instead of more number of small capacity machines, installed HP and power

consumption can be reduced.

3.0 Sugar plant Thermal Energy conservation

3.1 Processing Steam % Cane

The sugar industry has many processes and systems that use steam (live, medium

pressure and exhaust). Some of the systems that have been using the live steam have

been replaced with exhaust steam and the average process steam consumption is

getting reduced from 50% steam on cane to about 35% steam on cane in the modern

sugar factories in India. Power-Steam ratio can be increased if the quality of steam

going to condensing mode is increased by decreasing the Processing Steam. If

processing steam % cane is reduced by adopting the thermal energy conserving

measures to 35% steam on cane from 50%, specific power generation and power

export to the grid can be increased. Sugar plants which have installed high pressure

co-generation system will gain very much by the reduction of process steam by way

of additional revenue earning due to increased power export.

3.2 Bleeding System

Maximum Steam economy can be achieved by optimizing vapour bleeding to Juice

heaters and Pans. Vapour required for each Juice Heater is almost fixed in

conventional sugar mills. Differential Juice Heating System-heating in stages,

improves steam economy. In the diffuser plant, Diffuser juice heating can be done in

two stages to improve the later body bleeding. This reduces vapour going to the

condenser which reduces the Evaporator injection water power consumption also.

3.3 Juice Heaters:

Juice heating by the tubular heater is gradually being replaced by Direct Contact

Heaters and Wide Gap Plate Type Heat Exchangers. Because of this juice can be

heated by later effect evaporators vapour to reduce the steam consumption in the

process. The approach temperature for the new generation heaters is very low (10C).

De-scaling of juice heaters is completely eliminated in the Direct Contact Heaters. In

the plate type heat exchanger automated cleaning systems are introduced and de-

scaling down time is reduced considerably.


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Direct Contact Juice Heater DCH Installed for

Sulphited Juice & Clear Juice Heating

3.4 Number of Effect in Multiple Effect Evaporators

In earlier days in India, single vapor cell with quad and Double Effect Vapor Cell

with quad were used in the boiling house which are getting replaced by quintuple

effect evaporation with a common single condenser. Because the boiling house gets

the steam supply from TG extraction, the steam pressure available for the first effect

will be steadily maintained around 1.5 Kg/cm2 and 1300C. This eliminates the

thermal shocks in the evaporation system. The first effect Roberts bodies are being

slowly replaced by Semi Kestner and Falling Film Evaporators which are providing

lower T in the evaporation. Even fourth body vapours can be utilized for panboiling.

Quintuple Effect Falling Film EvaporatorSet


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The above figure shows the FFE evaporator set installed in the 3500 TCD sugar plant

in Tamil Nadu, India where fourth body vapor is used for entire pan boiling. The

steam% cane of this factory is 31%.

Automatic juice flow stabilization control in clarification and auto control in

evaporator operation ensures consistency of operation and efficiency of the systems

3.5 Pan Boiling:

Vacuum pans are important equipment used in the manufacture of sugar. The

concentrated syrup from the evaporator at around 60-65 Brix is further concentrated

in these pans. This is a critical process for the production of good quality sugar and

involves the removal of water and deposition of sugar molecules on the nuclei.

Massecuite boiling is conventionally carried out by batch process in the Indian sugar

industry. These pans are characterized by:

High hydrostatic head requirement

High massecuite boiler temperature which cause color formation

Loss of fluidity of massecuite, particularly towards the end of the batch cycle.

Higher boiling point elevation resulting in lower heat flux for a given steamcondition.

Very high steam consumption due to the non-uniform times of the loading,

unloading and pan washing cycles.

The need to overcome these shortcomings led to the development of continuous

vacuum pans (CVP), which have now been installed in many sugar plants. The

technological development of these pans dates back to the 1970s, beginning with

modifications in batch pans and adapting them to continuous operations. The design

of these continuous systems aims to obtain maximum overall efficiency with

complete automation. Experience with continuous pans has shown improved

performances compared to batch pans with greater heat and mass transfer rates along

with the possibility of using low-pressure vapors. CVP technology for continuous

massecuite boiling in the sugar process offer several advantages, the most important

being:

Very low hydrostatic loads.

Improved grain-size quality.

Wide circulation passages

Heat balance optimization

In the crystallization process, nowadays, continuous vacuum pans, both horizontal

and vertical type are being utilized. These pans can be operated with low temperature

vapor. Hence later effect evaporators vapour (third and even fourth effect) will be

sufficient for the pan boiling. In the batch pans mechanical circulators (either bottom

mounted or top mounted) increases the circulation of massecuite and hence vapour

consumption reduces. By the above total steam consumption for sugar boiling is


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reduced, by about 2%. Total automation of pan boiling controls results in consistency,

uniformity & efficiency.

Vertical Continuous Pan

3.6 Pan Boiling Scheme

Pans evaporation rate varies between 17kg per Sq.Mt to 85 kg per Sq.Mt. A FootingPan, 32 kg per Sq.Mt and 72 kg per Sq.Mt in A Massecuite Boiling Pan, 10.7 kg per

Sq.Mt to 45 kg per Sq.Mt in B Massecuite Boiling and 1.6 kg per Sq.Mt to 36 kg per

Sq.Mt in C Boiling. Care is to be taken to minimize the fluctuation in Pan Vapour

demand to achieve maximum steam economy.

3.7 Reducing Vapour and Exhaust Steam Venting

During Massecuite dropping, it is a usual practice to let off the heating vapour and

this causes loss of thermal energy. In order to minimize this loss, the other pans

heating vapour valves are opened a little more. But in the Diffuser Plant, that vapour

can be let into the diffuser to heat the circulating juice by which diffuser juice heatingvapour can be reduced and steam % cane be reduced indirectly.


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3.8 Recirculation of molasses and sugar

In order to manufacture the best quality sugar and reduce sugar loss in Final Molasses

Multi Crystallization is being followed. Sugar recirculation index varies between 3.5

to 3.9, Solid recirculation index varies between 3.2 to 3.6 and Non Sugar

Recirculation index varies between 4.0 to 6.0 Recirculation of Sugar and molasses areto be optimized to reduce Steam % Cane.

3.9 Pan Washing Steam

In a 2500 TCD plant, about two tonnes of steam per day is consumed in Pan washing.

Two decades back 7 ata steam were being used for Pan Washing. At present Exhaust

steam is used for pan washing. Co-generation sugar mills can use Quint-I Vapour

instead of Exhaust Steam for Pan Washings to reduce Steam % Cane.

3.10 Molasses Conditioner Steam

At present 3 ata steam is being used for Molasses conditioning. Approximate

consumption of steam is around one ton per hour. The purpose of molasses

conditioning is to dissolve the small grains by diluting and raising the temperature.

Quint-I vapour can be used instead of 3 ata steam after suitably modifying the

molasses conditioners to conserve thermal energy and thereby Specific Power

Generation can be enhanced.

3.11 Continuous Melter

About one ton 3 ata steam and 3 tons hot water are being used per hour in the

continuous melter in a 2500 TCD plant. Quint-I Vapour can be used in the melter

after suitably modifying the Continuous Melter to reduce water to be evaporated and

3 ata steam consumption.

3.12 Stoppages & Cleaning Days

Frequent mill stoppages increases steam % cane. During the stoppage the

temperature of juices, storage tank syrup and molasses, Massecuite in the Pans, heat

exchangers, other vessels etc., comes down. During the restarting extra heat energy is

required to heat the cooled mass. This increases the Average Steam % Cane. Sostoppages should be as minimum as possible to conserve thermal energy. In the

milling Plant, wear and tear due to erosion and corrosion is more because of high

pressure squeezing and low juice pH. The percentage crushing stoppage due to mills

is about 2%.

Generally immediate after cleaning, steam % on Cane is less and bagasse saving is

more. As cleaning days approaches, steam, % on cane increases and bagasse saving

gets reduced. In order to achieve consistent steam % cane two sets of evaporator or

spare III, IV and V body can be installed. Moreover as the cleaning days approaches,

exhaust steam pressure increases which decreases the specific power generation also.

Similarly Periodical cleaning of the Juice heaters at the regular interval reduces steam% Cane.


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3.13 Thermal Insulation

All the heat exchangers, pipes, vessels, receiving tanks, storage tanks etc., are to be

lagged with appropriate thickness lagging material. There will be loss of heat by

radiation and convection if the piping system tanks and vessels are not insulated

properly, thereby increasing the steam percent Cane. If the lagging gets wetted, theinsulation capacity of the lagging material gets reduced. So the chance of thermal

insulation getting wetted should be as minimum as possible.

3.14 Flash Vapor Circulation and U Column

Vapour condensate circulation system and the utilization of flash vapour conserve

electrical and thermal energy. Providing U column for condensate withdrawal and

transfer of juice from one body to other body arrests the escape of the Vapour.

3.15 Steam and Vapour leakage

Leakage in the steam and vapour pope lines and flange joints leakage increases the

Steam % on Cane. By-passing the Steam traps and excess venting of Ammonia gases

increase the loss of Steam and vapour.

3.16 Thermal Energy Conservation and Mill Steaming

In the milling system, circulating juice is at around 30 degree C which is vary

conducive for the growth of the micro-organism. Inter carriers, Mill Head stock sides,

Roller sides, etc., are streamed with 2.5 ata Steam at regular interval to curb thegrowth of micro-organism in some of the sugar factories. This is being replaced by

hot water cleaning around 800C to conserve steam.

4.0 Adoption of new Sugar plant machinery and process

4.1 Juice Clarifier:

The conventional 444 clarifier is slowly getting replaced by Short Retention Time

(SRT) Juice Clarifier. Normally juice retention in this SRT type of clarifier is 45 min

as against 180 min in the conventional clarifier. SRT Clarifier eliminates the

reduction of clear juice temperature at the outlet of the clarifier due to short retentiontime thereby saving in thermal energy in juice heating.


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SRT Juice Clarifier

4.2 Filtrate Juice Clarification:

Filtrate juice from the Vacuum Filter/ Decanter is treated in the filtrate juice

clarification system (either by flotation or sedimentation process), so that the clarified

juice can be directly taken into the evaporator for further processing, which eliminates

around 12% juice re-circulation in the clarification process.

4.3 Sugar Cane Juice Processing:

Sugar cane Juice Processing for the production of sugar depends upon the juice

clarification process; the following are the processes adopted to remove the impurities

and coloring mater from the sugar cane juice.

Defecation Process

Double Sulphitation/Carbonation Process and

Phosphatation Floatation Process

The defecation & Phosphatation process are used to make raw sugar with colour value

of about 800 ICUMCA. The double sulphitation/Carbonation Process are used to

make direct consumable plantation white sugar with the colour value of around 150

ICUMCA.

In India, traditionally double sulphitation process is adopted to make direct

consumable plantation white sugar. As per Indian Sugar Standard Sulphur content

allowed is 70 mg/kg (Max) for double sulphitation process and 15 mg/kg (Max) for

refined sugar process. Sulphur content of 70 mg/kg in the sugar is not acceptable in

the beverage industries and in some countries.

Operation & maintenance of sulphur burners and SO2 gas lines are expensive and also

the cost of sulphur is fluctuating. To avoid these difficulties, nowadays sugar


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factories are switching over to defecation process for raw sugar production followed

by melt clarification and modified refining process with R1 & R2 massecuite boiling,

to produce lustrous, sulphurless white sugar of less than 50 ICUMCA. Apart from

that they are having the refinery columns for refined sugar production. By refinery

process, sugar colour value comes down to 20 to 30 ICUMCA.

4.4 Muddy Juice Filtration:

Muddy juice is currently being de-sweetened using rotary vacuum drum filters in

most of the sugar factories in India. Vacuum filters work on the basis of vacuum

filtration and in case of vacuum problem, the efficiency gets affected. In addition,

higher sugar losses through filter cakes are experienced in vacuum filters. An

alternative system for de-sweetening the muddy juice by using solid bowl decanters

has been established with encouraging results. The decanters eliminate the bagacillo

requirement and reduces pol loss in the mud.

View of Decanter Machine

5.0 Water conservation in Sugar Plants

It is well known that sugar cane contains water to the extent of 70% to 72% of its

weight. This water comes to the sugar factory along with sugar cane but still manyfactories draw huge quantity of fresh water to meet their process and cooling water

requirements. Hence these factories are saddled with large quantity of effluent. The

term fresh water is used to describe the water inputs to the factory that is drawn

from river, local catchments and bore-wells. The factory prefers to use fresh water

because of its low solids content and low temp.

The term effluent is used to describe the factory liquid effluent discharged to surface

water. Its quantity and quality depends on the sugar manufacturing technology and the

cooling system deployed by the factory. A sugar factory requires process water as

well as cooling water. The water content of the cane is adequate for the manufacture

of cane sugar. By recycling and its reuse, the consumption of fresh water for thevarious cooling circuits can be minimized. Adoption of water conservation measures


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would further minimize the generation of effluent. A stand alone sugar mill after

meeting its in house process and cooling water requirement should generate surplus

water.

Depleting water resources and restriction on use of ground water in most parts of the

country for industrial use, has motivated technologists to develop less water intensivesystems for sugar complexes and adopt ways and means to utilize the surplus water

from the sugar mill, for meeting the makeup water requirement. Incidentally the

sugar mill effluent has low levels of COD and BOD contamination and hence can be

recycled after suitable treatment.

6.0 Sugar Cane Water circuit

It is estimated that each tonn of fresh, clean cane entering the sugar mill would

comprise of about 710 kgs. of water, 145kgs. of dissolved solids (sucrose, reducing

sugars, impurities etc) and 145 kgs. of insoluble matter (fiber, dirt etc). Part of the

water in cane is lost in the solid and liquid waste material leaving the premises of the

sugar mill i.e. as moisture in bagasse, as vapours to the condensers, as moisture in

filter cake, as moisture in lime grit and as moisture in final molasses. There would be

variations in the quantity of water through the cane water circuit depending on the

cane quality and the processing technology deployed. An estimate of the cane water

circuit for the sugar mill with a rated capacity of 160 TCH is furnished below:

S.No Particulars Unit Qty.

1. Sugar Cane input TCH 160.0

2. Water in Sugar Cane @ 71% t/hr 113.6

3. Water out through various waste material

3.1 through bagasse @ 15% cane t/hr 24.0

3.2 through lime grit @ 0.1% cane t/hr 0.2

3.3 through filter cake @ 3% cane t/hr 4.8

3.4 through final molasses @ 0.5% cane t/hr 0.8

3.5 through vapour lost to condensers @ 25% cane t/hr 40.0

3.6 through vents and evaporation loss @ 4.4% cane t/hr 7.0

3.7 Total water out in waste material @ 48% cane t/hr 76.8

4.0 Excess water @ 23% cane t/hr 36.8

5.0. Excess water per ton of cane lit/tc 230.0


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The surplus condensate of about 36.8 tonnes per hour will be at a higher temperature

and at a COD content of about 300 PPM and dissolved solid content of 100 PPM.

This water can be cooled and treated further for reuse in the factory.

7.0 Conclusion

By product Power project improves the profitability of the Sugar Industry. Energy

Efficient Equipment improves the profitability of the Sugar Mills. Specific Electrical

Energy consumption can be reduced by incorporating various Energy Efficient

Equipments like Diffuser, VFD, Energy Efficient Transmission gears, pumps and

motors, etc. and thereby power export to the grid can be increased. Reduction in

process steam consumption will indirectly increase the surplus power export to grid.

Energy Efficient Equipment increases the profitability of the sugar mills due to the

increased revenue earned from the power projects. In near future, Sugar Mills

without high pressure Co-Generation and energy efficiency will not be viable.

Reduced water usage in a factory will also reduce the pollution from the sugar plants.The profitability of the sugar factory will improve with the adoption of energy and

water conservation measures.


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