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Freeze concentration of sugarcane juice in a

jaggery making process

Milind V. Rane *, Siddharth K. Jabade

Mechanical Engineering Department, Heat Pump Laboratory, Indian Institute of Technology Bombay, Powai,

Mumbai 400 076, India

Abstract

A heat pump based Freeze Concentration System (FCS) is proposed to concentrate sugarcane juice from

20 to 40 Brix in a jaggery making process. Further concentration of the juice is carried out in a boiling pan.

Inclusion analysis is carried out to estimate sucrose loss in the ice formed in a layer freezing process. A

mathematical model is developed taking in to consideration effect of time varying ice thickness on evapo-rator temperature, compressor capacity, Coefficient of Performance (COP) of the heat pump. Data on

operating parameters for a jaggery unit located at Rahu Pimplgaon in Daund District, Maharashtra was

collected through field visits. Using this data, energy consumption of this conventional jaggery making pro-

cess is calculated. Energy balance has been carried out and Sankey diagram is drawn. Energy consumption

of the FCS is calculated using results of the mathematical model. Total energy consumption of the FCS

integrated jaggery making process is calculated. Comparison of the conventional process and FCS inte-

grated process is presented. Bagasse saving of about 1338 kg per day can be achieved using heat pump

based FCS along with bagasse fired pan boiling. Further, hot spots are eliminated thereby reducing cara-

melisation significantly resulting in improved jaggery color.

Keywords: Freeze concentration; Heat pump; Jaggery

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Nomenclature

Bx brix,CL concentration of liquid phase, Bx

CS concentration of solid phase, Bx

DL diffusion coefficient in the liquid phase, m2/s

Ds diffusion coefficient in the solid phase, m2/s

K distribution coefficient, DCS/DCLr radial distance, m

t time, s

T temperature, C

e position of solidliquid interface, m

m mass of melted ice water, kgqice density of pure ice, kg/m

3

xs,ice solute mass fraction of ice, w/w

A area covered by ice on the plate surface, m2

s run time, s

Bxice sucrose concentration in ice, Bx

Bxbulk sucrose concentration in bulk solution, Bxhl convective heat transfer coefficient from juice to growing ice body, W/m

2 K

ho convective heat transfer coefficient on the refrigerant side, W/m2 K

tl juice temperature, Cto refrigerant temperature, C

x ice thickness, mki thermal conductivity of ice, W/mKtfs thickness of the freezing surface material, m

hlat,ice latent heat of fusion, kJ/kgDtj time step, s

ljuice viscosity of sugarcane juice, kg/m smwater mass flow rate of water to be separated, kg/h

mjuice mass flow rate of sugarcane juice, kg/h

Bxj initial brix, Bx

Bxf final brix, Bx

c specific heat, kJ/kg K

Tjuice temperature of sugarcane juice, C

P purity of sugarcane juice

d film thickness, m

C mass flow rate per unit width of the surface, kg/m shjuice,20Bx,1 C enthalpy of juice at 1 C and 20 Brix, kJ/kg

hSyrup,40Bx,5 C enthalpy of syrup at 5 C and 40 Brix, kJ/kghfg enthalpy of evaporation, kJ/kg

CVbagasse calorific value of bagasse, kJ/kg

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1. Introduction

Heat pump based FCS is proposed to concentrate sugarcane juice from 20 to 40 Bx in jaggery

making process. The juice concentration in FCS is carried out up to 40 Bx because juice viscosity

increases considerably beyond 40 Bx, which has an adverse effect on heat transfer and sucrose

inclusion as well. Further concentration of the juice can be carried out in a boiling pan.

A unit at Rahu Pimpalgaon, Daund District in Maharashtra is considered for case study. Data

collected through the field visits is used as a basis for calculations in this paper. Following are the

details of the data:

COPnet net coefficient of performance

QR,ice heat rejected for ice melting, kW

QR,sink heat rejected to sink, kWPTotal total power input, kW

Pe,FCS electrical energy consumption of the FCS, kW h

QL,heat latent load for concentrated juice heating, kW

hfg latent heat of vaporization, kJ/kg

Qs, sensible load, kW

QT,heat total heat load, kW

Qin,con energy input in conventional process, kW

s sucrose content per unit bagassew moisture in bagasse relative to unity

mbagasse rate of bagasse consumption, kg/smbaggase.jag bagasse consumption per kg of jaggery, kg/kg of jaggerymjaggery rate of jaggery production, kg/s

c CO2 content per unit volume of flue gasm ratio of excess air weight to weight theoretical air

Tf temperature of flue gas, C

xs,1 mass fraction of the solute in the bulk solution, w/w

mice average ice growth rate in, lm/s

uS,1 solution velocity, m/s

a. Capacity 1000 kg jaggery per day

b. Working hours per day 10

c. Batches per day 4

d. Batch Duration 2.5 h

e. Sugarcane juice concentration rate 400 kg/h

f. Jaggery production rate 100 kg/h

g. Sucrose content per unit sugarcane 0.120.15

h. Initial juice concentration 2022 Bx

i. Juice purity 84

j. Weight of juice per batch 1000 kg

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2. Working principle of Freeze Concentration System (FCS)

The heat pump based FCS uses layer freezing process. The juice flows over the refrigerated sur-

face, called as freezing surface. This surface alternately performs function of a condenser or evapo-

rator. Layer freezing of water from the sugarcane juice and subsequent melting of ice takes placeon the freezing surface. Ice is melted using condenser heat. The ice in contact with the freezing

surface will melt using the heat of condensation of part of the vapours and the rest of the ice will

slide down the vertical freezing surface. The ice collected in the lower collection bin will melt using

the rest of the condensing vapours. Incoming juice is pre-cooled to 1 C using melted water and

concentrated juice leaving the FCS. The use of heat pump facilitates rejection of a major part of

the condenser heat at about 10 C while melting the ice. The temperature lift in this case is of the

order of 20 C.

3. Inclusion analysis of layer freezing process

Average Distribution Coefficient (ADC) for solute inclusion (solute mass fraction in ice), is de-

fined as ratio of the solute inclusion in ice to that in the bulk solution [1]. Experimental data on

the partitioning of solute between liquid phases is usually reported in terms of distribution coef-

ficient K.

3.1. Experimental apparatus

Test section is in the form of a C shaped stainless steel channel. It acts as a freezing surface for

layer freezing of water from the sugar solution. Refrigerant passage is provided at the bottom ofthe channel. The test section is insulated.

3.2. Experimental procedure

Sugar solution was prepared adding sucrose crystals in distilled water. Experiments were con-

ducted using 20 Bx concentration solution. It was confirmed that ice formation takes place over

the complete surface. The surface of the ice layer was washed with ice water immediately after the

solution flow was stopped. This helped in removing the thin dendritic layer of ice formed in which

sucrose is entrapped. Samples were collected for inclusion analysis.

k. Jaggery produced per batch 250 kg

l. Fuel Bagasse

m. Bagasse consumption per kg of jaggery 1.52 kg

n. Exhaust flue gas temperature 400 Co. Striking temperature of the juice 118 C

p. Moisture in bagasse relative to unity 0.50

q. Foot print of the unit along with chimney 7.5 m 7.5 m

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3.3. Measurements

The sucrose inclusion in ice and concentration of sucrose in bulk solution was measured using a

temperature controlled bench type Abbe Refractometer with a refractive index in the range of1.30001.7000 nD and accuracy of 0.0001 nD at room temperature. Temperature was measured

using thermocouples (K type) with accuracy 1 C and an indicator with accuracy 0.2 C, su-

crose and water weight was measured using weighing balance with accuracy 0.1 g.

3.4. Results and discussion

Figs. 1 and 2 indicate effect of operating parameters on ADC. It is a function of freezing surface

temperature, ice growth rate, solution velocity and bulk solution concentration. Chen has pro-

posed following correlation [2]

ADC 0:145 2:05xs;1 0:139 miceu0:5S;1

1

ADC, that is inclusion is more at a higher ice growth rate, because growth rate of the ice front can

become too high to overtake the solute outward movement. Increase in velocity increases mass

transfer coefficient. This helps solute at ice solution interface to be transported in to bulk flow

and reduces inclusion. At a lower freezing surface temperature, the driving force for ice growth is

larger, which results in increased inclusion [3]. The experimental results are in good agreement with

the Chens correlation. Fig. 2 indicates ADC value of 0.20 at 1 m/s velocity. Sucrose included in ice is

ADC Bxice

Bxbulk

0:20 Bxice

20

2

From Eqs. (2), sucrose in ice formed is 4 Bx. That is 4% sucrose is included in the ice. Thus, ice

purity is 96%.

-14 -12 -8 -6 -4 -2

Surface Temperature oC

0.0

0.1

0.2

0.3

0.4

0.5

0.6

AverageDistributio

nCoefficient

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Fig. 1. Effect of freezing surface temperature on average distribution coefficient.

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4. Method to calculate FCS energy consumption

Since juice is a binary mixture, its properties change with the concentration as it flows over the

freezing surface. Freezing surface is assumed to be divided in number of segments. Mass of ice

formed and corresponding concentration of the juice is calculated in each segment. Based on this

concentration, properties of the juice such as freezing point, density, viscosity, velocity and spe-

cific heat are calculated for the subsequent segment and are used for heat transfer calculations.

Fig. 3 shows flow chart of the method.

Fig. 4 shows idealized thermal circuit [4]. Initially, freezing surface is bare, that is there is no icebuilt up (Fig. 4a). The rate equation for this heat transfer qr is

qr tl to

1hl

tfsk

1ho

3

Ice thickness in ith segment and corresponding properties of the solution at the entry of the i+ 1th

segment are calculated as follows.

As shown in (Fig. 4b), equation for heat transfer q2 is

q2 tl

1

hl

4

The rate equation for heat transfer q1 is

q1 t0

xki

tfsk

1ho

5

From energy balance consideration, q1 is in excess ofq2 by the amount required for the rate of ice

formation dx/dt.

q1 q2 qicehlat;icedx=dt 6

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

Ice Growth Rate x 10-6 (m/s)

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

AverageDistributionCoefficient

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

Velocity 0.75m/s

Velocity 0.5m/s

Velocity 1m/s

Fig. 2. Effect of sucrose solution velocity and ice growth rate on average distribution coefficient.

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Start

Input initial juice and refrigerant temperature,freezing surface dimensions, total run time,time steps, number of segments, juiceproperties

Assume refrigerant temperature for firsttime step j

Calculate mass of ice formed in i th

segment

Calculate overall heat transfercoefficient in segment i

Calculate heat transfer in segment i

Summation of the individual heat transfers insegments 1 to i to calculate total heat transfer Qr

Calculate juice viscosity, density, specificheat, freezing temperature for the newconcentration of juice in i+1th segment

Calculate concentration of the juiceat the end of the ith segment

Calculate capacity of compressor Qccorresponding to assumed refrigerant temperature

Next time step j+1 and repeat calculationstaking into account ice thickness in the

previous time step

Is Qc=Qr

Calculate COP and energy consumption of

the compressor corresponding to therefrigerant temperature

No

Yes

Fig. 3. Flow chart of method of analysis for calculation of energy consumption of the Freeze Concentration System.

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Thermal energy abstraction in sub-cooling the ice is not considered. It is negligible relative to the

latent heat of freezing requirement [5].

Mass of ice is formed in the ith segment calculated as

Dmice;i q1 q2 Dtj

hlat;ice7

Concentration of the juice entering i+ 1 segment in terms of brix is calculated as

Bxi1 1 mjuice;i

100Bxi

100 mice;i

mjuice;i mice;i

24 35 8Mass flow rate of juice in the i+ 1 segment is calculated as

mjuice;i1 mjuice;i mice;i 9

The relation between concentration and freezing temperature is obtained from the sugarcane juice

phase diagram [6] using curve fitting as

Tsolution;i1 1 Bxi1 15 0:18 10

Sugarcane juice

h0

hl

Ro = 1/ ho

qr

t o

t l

Rh = t/k

Rl = 1/ h l

to

q r

t lRefrigerant

tfs

FreezingSurface

Sugarcane juice

Ice

h0

tfs

hl

x

q2

Rl = 1/ h l

t o

Ri = x/k

t =0

Ro = 1/ ho

q1

q1

q2

t o

t l

tl

Rh = t/k

Refrigerant

FreezingSurface

(a)

(b)

Fig. 4. Thermal circuit representations (a) bare freezing surface; (b) freezing surface with ice formation.

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The relation between viscosity and Bx in i+ 1 segment is obtained from a graph of temperature,

concentration and viscosity [7] as

ljuice;i1

a

a b Bxi1 c Bxi1 2

11

where a = 1.8214, b = 0.0337, c = 0.0002; Bx concentration of sugarcane juice (Bx).Specific heat of sugarcane juice varies with its concentration (Bx) and temperature, it is calcu-

lated as [7]

c 1 0:6 0:0018Tjuice 0:0008 100 P

Bx

100 4:19

& '12

Density of sugarcane juice in the i+ 1 segment is

qjuice;i1 1:59 Bxi1

100 100 Bxi1

100 !

100 13

Velocity of the sugarcane juice in i+ 1 segment is calculated by substituting the values from equa-

tions (11) and (13) in the following equations [8]:

Vgqd

2

3l14

where

d 3Cl

q2g

1=315

This equation assumes that there is no drag force at the gas liquid interface.

Initially, evaporator temperature is assumed. For the first time step, the heat transfer from juice

to refrigerant, that is qr is calculated for each of the segments taking in to consideration corre-

sponding properties of the juice in the respective segment. Compressor cooling capacity qc at

the assumed evaporator temperature and sum of the individual heat transfers in all the segments

are equated. If they do not converge, new evaporator temperature is assumed and above men-

tioned calculation is repeated to get evaporator temperature. Similar procedure is repeated for

the next time step. Resistance due to the ice formed in the previous time step in the corresponding

segments is taken in to consideration in the next time step. Compressor capacity and COP is cal-

culated for every time step using vapor compression cycle simulation program for R 22 refrigerant

with condenser temperature of 10 C and compressor isentropic efficiency: 0.8.

5. Electrical energy consumption of the FCS

Compressor of the FCS is selected based on the nominal capacity and evaporator temperature.

Nominal cooling capacity is calculated for the specifications of the unit at Rahu Pimpalgaon.

Water to be separated from the 400 kg/h juice to concentrate it from 20 to 40 Brix is

mwater mjuice1 Bxj=Bxf 200 kg=h 16

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Thus, concentrated juice (syrup) flow rate at the exit of the FCS is 200 kg/h. In FCS, juice is

cooled from 1 C at 20 Bx to 5 C corresponding to 40 Bx is. Total load is

Qtot; Qsensible;FCS Qlatent;FCS

mJuice;20Bx hJuice;20Bx;1 C mSyrup;40Bx hSyrup;40Bx;5 C

mwater hlat;ice

3 18:6 21:6 kW

Heat gain from ambient into the ice separated is, assumed to be 10% of the latent heat load, which

is 1.8 kW. Thus, nominal cooling capacity of the FCS is 23.4 kW. Assuming minimum approach

of 3 C, initial evaporator temperature is fixed at 8 C. Results were computed using the abovediscussed model.

5.1. Results and discussion

Results are shown in Fig. 5, the evaporator temperature decreases through out the ice building

process. As ice thickness on the freezing surface increases, overall heat transfer coefficient de-

creases because of increased ice resistance. This results in reduction of the evaporator temperature

and pressure leading to reduced cooling effect and power consumption. However, reduction in

cooling effect is much more than the reduction in power consumption leading to reduction in

the COP.

It can be seen that at 7 mm ice thickness, COP of the system is around 8. This COP value does

not take into account effect of mismatch of condenser and evaporator duties. The COP is based on

the assumption that the total heat in the condenser is rejected for melting ice only. In practice,

condenser can reject a part of the total heat (equivalent to the latent load) at 10 C for ice melting.

0 15 30 45 60 75 90 105 125 135

Time (minutes)

-15

-14

-13

-12

-11

-10

-9

-8

-7

Evaporator

TemperatureoC

7.

.

5

8.

.

0

8..

5

9.. 0

9..

5

10.

.

0

10.

.

5

Coefficient

ofPerformance

0

1

2

3

4

5

6

7

8

IceThic

kness(mm)

20

21

22

23

24

25

26

27

28

CompressorCapacity(kW)

Evaporator Temperature

Coefficient of Performance

Compressor Capacity

Ice Thickness

Fig. 5. Effect of time varying ice thickness on the compressor performance.

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Excess heat, contributed by compressor power input and leakages has to be rejected to heat sink

at ambient temperature. Effect of this heat rejection on the COP is analyzed in the following

section.

Fig. 6 illustrates the cooling loads and effect of delivery of excess heat to the sink at ambienttemperature on net COP. Thus, 23.4 kW heat has to be pumped to a higher temperature. Out

of this, part of the heat (16.5 kW) is pumped at 10 C for ice melting. Since cooling COP of

the FCS is 8, power input for pumping 16.5 kW heat is 16.5/8 = 2.1 kWe. Thus, total heat deliv-

ered for ice melting is 16.5 + 2.1 = 18.6 kW which is equal to the latent load.

Excess heat (6.9 kW) is pumped to 36 C in the water cooled condenser. Cooling COP of 3.7 is

calculated for this condensing temperature using vapor cycle simulation program. Power input for

pumping 6.9 kW heat to 36 C sink is 6.9/3.7 = 1.9 kWe. Thus, total heat delivered at 36 C is

6.9 + 1.9 = 8.8 kW.

The net COP is calculated as

COPnet QR;ice QR;sink

PTotal 18:6 8:8

1:9 2:1 6:8 17

Electrical energy consumption is

Pe;FCS Qcooling

COPnet

23:4

6:8 3:44 kW h 18

Since unit works for 10 h in a day, total electrical energy consumption of the FCS to concentrate

juice from 20 to 40 Bx for the day is 34.4 kW h.

Sensible heat load3 kWc

Latent heat load18.6 kWc at -10

oC

Total cooling load

23.4 kW

Freeze Concentration System

Heat rejection to heat sink

Heat leakage1.8 kW

Heat rejection for ice melting

COPc = 8Power Input

2.1 kWe

18.6 kWat 10 oC

16.5 kW

8.8 kW

at 36oC

COPc = 3.7

6.9 kW

Power Input

1.9 kWe

Net COP = (8.8 + 18.6)/(1.9 + 2.1)

= 6.85

Fig. 6. Effect of excess heat rejection on COP.

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6. Bagasse consumption for the concentrated juice boiling

It is required to evaporate 100 kg/h water at a striking temperature of 118 C from (200 kg/h)

concentrated juice coming from the FCS. Vapor generated in the boiling pan at 118 C is used toheat the concentrated juice at the exit of the FCS. With an approach of 6 C, the concentrated

juice is heated from 112 C before entering the boiling pan.The juice is heated from 112 to

118 C in the boiling pan. Total heat load in the boiling pan is

QT;heat mw hfg mSyrup c Tf Ti

100=3600 kg=s 2300 kJ=kg 200=3600 kg=s 3 kJ=kg K118 112

64:8 kW 19

Calorific value of bagasse with 50% moisture and 12% sucrose content is calculated as [7]:

Gross Calorific Value 4600 1 w 1200 s 4:187 9027 kJ=kg 20

Bagasse consumption is

mbagasse QT;heat

CVbagasse 25:8 kg=h 21

Assuming combustion efficiency to be 60%, actual bagasse consumption is 41.2 kg/h. Thus, total

bagasse consumption for producing 1000 kg jaggery in 10 h using FCS is 412 kg.

The total energy consumption for producing 1000 kg jaggery in 10 h constitutes the following:

a. Electrical energy consumption for concentration of the juice from 20 to 40 Bx using FCS is34.4 kW h.

b. Bagasse consumption in the boiling pan for further concentration is 412 kg.

7. Case study: Energy consumption of the conventional jaggery making process

Details of the energy consumption are:

Energy supplied by combustion of bagasse is calculated as

Qin;con mbagasseCVbagasse 22

The bagasse consumption per kg of jaggery produced is in the range of 1.52 kg. An average value

of 1.75 kg is considered for the analysis. The jaggery production rate is 100 kg/h, that is 0.03 kg/s.

Bagasse consumption rate is

mbagasse;con mbaggase;jagmjaggery 1:75 0:03 0:05 kg=s 23

From Eqs. (20), (22) and (23)

Qin;con 415:3 kW

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As indicated by Tiwari [9], natural convection boiling of sugarcane juice is up to 90 C and pool/

nucleate boiling starts at 9095 C. Fig. 7 shows the temperature ranges with corresponding sen-

sible and latent heat loads. It may be noted that in practice, sugarcane juice is heated in pan from

about 27 to 118 C in a single stage. Three stages and corresponding temperature ranges consid-ered in Fig. 7 are assumed for calculation of sensible and latent loads.

Total heat load is summation of latent and sensible heats in three stages. Thus

Qtot Qs;I Qs;II Qs;III QL;II QL;III

mjuice cavg 90 27 mjuice cavg 109 90 mjuice cavg 118 109

mw;ehfg@ 99:5 C mw;ehfg@ 113:5 C 216:6 kW 24

7.1. Sensible heat loss in flue gas

Ratio excess air weight to weight of air theoretically necessary is calculated as [7]:

c 0:871 w

4:451 wm 0:0561 w25

Assuming CO2 content per unit volume of flue gas to be 0.13, from Eq. (25)

m 1:52

Suarcane Juice at 20Bx,400 kg/h, 30oC

Vapor100oC,150kg/h

Syrup90 oC,400kg/h , 20 Bx

Syrup109 oC,250kg/h , 32 Bx

Vapor113.5oC,150kg/h

Jaggery paste

118 oC,100kg/h , 80 Bx

Stage I

Stage II

Stage III

Sensible heat

Sensible heat + Latent Heat

Sensible heat + Latent Heat

Fig. 7. Temperature ranges for heat load calculations.

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Heat loss is

Qf 1 w 1:4m 0:13 0:5 T 4:18 mbagasse;con 125:5 kW 26

Other losses include unburnt and radiation loss. Unburnt loss is assumed to be 10% of the totalheat input. The result of the energy balance is indicated in Fig. 8(a).

8. Comparison of the FCS integrated jaggery making with the conventional process

Fig. 8 shows that, bagasse consumption in FCS integrated process is 41.2 kg/h as against

175 kg/h in conventional process. Saving in bagasse is

175 41:2 133:8 kg=h

Energy Input 415.3 kWhBagasse Consumption 175 kg/h

Loss in Flue Gas125.5 kW

Juice Evaporation216.6 kW

Other Loss73.2 kW

(a)

Freeze ConcentrationSystem (FCS)

Sugarcane Juice400 kg/h27oC20 Bx

Ice Water200 kg/h0oC

Electrical Energy Input 34.4 kWe

Loss in Flue Gas28.7 kW

Other Loss9.5 kW

Energy Input 103 kWhBagasse Consumption 41.2 kg/h

Boiling Pan

112oC

Concentrated Juice200 kg/h1oC40 Bx

64.8 kW

Jaggery Paste100 kg/h

Water Vapor100 kg/h118oC

Condensate100 kg/h118 oC,

(b)

Fig. 8. Comparison of energy consumption of the Freeze Concentration System integrated jaggery making and

conventional process.

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Thus, bagasse saving for 1000 kg jaggery production in 10 h is 1338 kg.

8.1. Initial cost

The FCS consists of two latent heat exchangers, a sensible heat exchanger, multi way valve and

controls. A boiling pan of juice holding capacity 500 kg is used to further concentrate the juice

from the FCS. The initial cost of FCS and boiling pan is about Rs. 2 Lakh. Conventional jaggery

making unit essentially consists of a furnace, chimney and a boiling pan of juice holding capacity

1000 kg. Cost of the complete unit including construction of the chimney and furnace is about 2

Lakh.

8.2. Jaggery quality

The boiling pan in the proposed unit is half the capacity of the conventional jaggery makingunit. Reduced size of the boiling pan facilitates proper stirring of the juice. This reduces localized

hot spots. Further, time for which juice is exposed to high temperature reduces because 50% of the

concentration is carried out in the FCS. This reduces caramelisation and improves jaggery color

and quality.

9. Techno economics

As indicated in the results of the experiments, loss of sucrose is 4%. During 10 h working,

2000 kg ice is separated. Loss of sucrose in this ice is (2000 0.04) 80 kg. It is assumed that80 kg jaggery forms out of 80 kg sucrose loss in ice. Considering rate of jaggery as Rs. 3 per

kg realized by the farmer [10], Rs. 240 is the loss due to sucrose inclusion.

9.1. Net savings

Saved bagasse can be sold to various industries like sugar factory, paper and pulp industry at

the rate in the range of Rs. 0.60 to Rs. 1.2 per kg [10]. Considering an average value of Rs. 0.9 per

kg, revenue generated per day by sell of the 1338 kg saved bagasse is Rs. 1204.2.

Electrical energy consumption of the FCS for 1000 kg jaggery production is 34.4 kW h. Con-

sidering electricity rate of Rs. 5/kW h (in Maharashtra), electricity cost is Rs. 172.

Net saving per day is Revenue generated by the sell of bagasse

Electricity cost of the FCS

cost of the sucrose lost in inclusion

Rs: 1204 Rs: 172 Rs: 240 Rs: 792 per day

Simple pay back period of the system is about 252 days.

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10. Conclusion

A heat pump based Freeze Concentration System is proposed to concentrate sugarcane juice

from 20 to 40 Brix in a jaggery making process to save bagasse and enhance jaggery quality. Effectof operating parameters on ADC is studied through experiments. Use of heat pump facilitates

rejection of a major part of the condenser heat at about 10 C while melting the ice. COP of

the FCS is estimated as 6.8 using mathematical model and considering heat losses and mismatch

of evaporator and condenser duty. Comparison of the conventional and FCS integrated jaggery

making process is presented. FCS integrated process results in better quality jaggery by reducing

hot spots and caramelisation due to reduced size of the boiling pan. Bagasse saving of 1338 kg per

day or for 1000 kg jaggery can be achieved.

Acknowledgements

The authors would like to acknowledge the help and support offered by Dr. J.P. Patil, Director,

Regional Sugarcane and Jaggery Research Station, Kolhapur, Dr. B.S. Patil (Kolhapur) and Mr.

Hanumant Shinde from Rahu Pimpalgaon.

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formed from falling film flows on a sub-cooled surface, Journal of Food Engineering 39 (1999) 101105.

[4] A.L. London, R.A. Seban, Rate of ice formation, ASME Transactions 65 (1016) (1943) 771778.

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[6] A.G. Patil, Freeze concentration: an attractive alternative, International Sugar Journal 95 (1993) 349355.

[7] E. Hugot, Hand Book of Cane Sugar Engineering, Elsevier Science Publishers, Amsterdam, The Netherlands,

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[8] R.H. Perry, Perrys Chemical Engineers Handbook, seventh ed., McGraw-Hill, New York, 1997, pp. 642.

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[10] Personal communication with Mr Hanumant Shinde, jaggery unit owner at Rahu Pimpalgaon.

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