Boiling Rate, Heat Transfer
And Viscosity of Cane Molasses
Audubon Sugar Institute
Michael Saska
2001
REPORTS FROM ONE MILL OF
INTERMITTENT PROBLEMS WITH
BOILING SUGAR
2002
REPEATED REPORTS FROM
SEVERAL MILLS OF SEVERE
PROBLEMS WITH BOILING SUGAR
LARGE SAMPLES TAKEN TO AND
STUDIED AT AUDUBON
FIELD OBSERVATIONS:
WET/RAIN
WARM
LACK OF SUN
COULD NOT BURN
LODGED CANE (MUSHROOM CANE)
“PUTRID SMELL IN THE FURROWS
ANAEROBIC CONDITIONS IN THE FIELD”
“ROTTING BROWN WET LEAVES ON CANE IN
WET & WARM WEATHER”
FACTORY OBSERVATIONS:
STARCH AND DEXTRAN NORMAL
MASSECUITE CONSISTENCY NORMAL
SYRUP pH > CLEAR JUICE pH (?)
FILM LEFT ON PAN TUBES – SOLUBLE IN
WATER
MEASURE
EVAPORATION
RATE
@ CONSTANT
BRIX (µWAVE)
ABS. PRESSURE
STEAM PRESSURE
LEVEL
STIRRER SPEED
CALCULATE
BOILING HEAT
TRANSFER
COEFFICIENT.
CHEMICAL CHARACTERIZATION
SUGARS, COLOR, pH, ANIONS, CATIONS,
AB AND HAZE DEXTRAN, STARCH, FAT,
FREE FATTY ACIDS,
PHYSICAL PROPERTIES
VISCOSITY, SURFACE TENSION,
CONTACT ANGLE
HEAT TRANSFER MEASUREMENTS
AFFECT OF BRIX
AFFECT OF ADDITIVES TO POOR
BOILING MOLASSES (ANTIFOAMS,
SURFACTANTS, SODA ASH, ACID)
POTENTIAL CULPRITS TO WELL
BOILING MOLASSES (DEXTRAN,
STARCH, CALCIUM ACETATE, ..)
AFFECT OF TREATING POOR
BOILING MOLASSES PRIOR TO
HEAT TRANSFER TEST WITH
ADSORBENT RESIN
GRANULAR ACTIVATED
CARBON
CLARIFICATION WITH
ETHANOL
4 Brix levels
0
30
60
2000
90 1201800
150 180 210 240 270 300 330 360
1600
1400Tim e, m in
1200
1000
800
600
400
200
0
0 30 60 90 120 150 180 210 240 270 300 330 360
Feed rate, m L/m in
RDS
Test “SM ‘A’”
Molasses
(1/17/03)
88
87
86
85
84
83
82
81
80
79
78
77
76
75
Time, m in
H eat tran sfer co efficien t,
W /m 2/C
Heat transfer properties of three
Louisiana 'A' molasses
St. Martin
10/28/02
1400
1200
St. James
2001
1000
800
600
Iberia
12/12/02
400
200
0
75 77 79 81 83 85 87 89 91 93
RDS
Austmeyer Low Grade
Beet
AFTER BOILING
COLLECT
& ANALYZE
MOLASSES AND
PAN WASHINGS
NO SIGNIFICANT
DIFFERENCE
FOUND
SUCROSE
GLUCOSE
FRUCTOSE
14 ANIONS
Na, K, Mg, Ca
CONCLUSIONS
HTB IS NOT DIRECTLY CAUSED BY DEXTRAN,
STARCH, CALCIUM IONS OR ORGANIC ACIDS,
IS UNRELATED TO FACTORS THAT AFFECT
MOLASSES VISCOSITY
HTB IS CAUSED BY PRECIPITATION ON
THE HEATING SURFACE OF A WATER
SOLUBLE LAYER OF UNKNOWN CHEMICAL
NATURE AT ABOUT 79-81 Bx
(SS ~ 0.9 - 1.1 FOR ‘A’ MOLASSES) -
CONCLUSIONS
SMALL IMPROVEMENT (~ 2x) IN BOILING
FROM ANTIFOAMS, ETHANOL
CLARIFICATION & POLYMERIC ADSORBENTS
SUBSTANTIAL IMPROVEMENT (~2-5x) FROM
GAC
CONCLUSIONS
DRASTIC IMPROVEMENT – HEAT
TRANSFER COEFFICIENT INCREASED
6-8 x - BY ACIDIFICATION WITH
HYDROCHLORIC ACID
87
Iberia 12/12/02
86
84
83
ACID ADDITIONS
82
81
80
0
30
60
90
120 150 180 210 240 270 300 330 360
2 levels of Bx
followed by
3 levels of acid
addition, 0.5 kg
each
Time, min
Feed rate, mL/min
RDS
85
2000
1800
1600
1400
1200
1000
800
600
400
200
0
AVERAGE WATER FEED RATE
82
231
592
584
147
0
30
60
90
120 150 180 210 240 270 300 330 360
Time, min
HTC, W/m2/K
Effect of Acidification on Heat Transfer
Properties of Iberia 12/12/02 'A' Molasses
800
6.5
600
6.0
400
5.5
200
5.0
0
4.5
0.0
0.5
1.0
Acid added, kg HCl/100 kg DS
1.5
HTC @
RDS
84.6%
HTC @
RDS
85.2%
pH @
65% RDS
2003 – 2004
DRY WEATHER IN 2003
NO INCIDENTS OF SEVERE SUGAR BOILING
PROBLEMS REPORTED
STUDY AT AUDUBON FACTORS THAT
AFFECT BOILING HEAT TRANSFER OF
FINAL MOLASSES
ARE RESPONSIBLE COMPONENTS ALWAYS
PRESENT IN CANE MOLASSES ALBEIT IN
LOWER AMOUNTS?
EXPERIMENTAL ADVANTAGES
OF WORKING WITH FINAL MOLASSES
- HIGHEST CONCENTRATION OF
IMPURITIES
- EASY STORAGE AND TRANSPORT
HTC, W/m2 /C
1200
Lafour
1000
Enterp
800
St.Mary
Cora
600
400
200
0
78
80
82
84
86
88
90
Viscosity (cP) @ 50C, 2sec-1
600000
R2 = 0.365
500000
86
88
400000
90
92
300000
R2 = 0.450
200000
R2 = 0.510
100000
R2 = 0.455
0
0.7
0.9
1.1
1.3
Calcium, % DS
1.5
1.7
CONCLUSIONS
THE INVERSE POWER AFFECT OF
VISCOSITY ON HTC
HTC (W/m2C) = 75,176 (µ-0.53)
INTERPRETATION OF DATA ON AFFECTS
OF CANE POLYSACCHARIDES ON
VISCOSITY IS COMPLICATED
BY USE OF ENZYMES AND NATURE OF
ANALYTICAL TECHNIQUES
CONCLUSIONS
POSSIBLE AFFECT OF CALCIUM ION ON
VISCOSITY - IMPLICATIONS FOR
SODA ASH CLARIFICATION OR IX
SOFTENING OF JUICE
APPARENT TOTAL ABSENCE OF THE
CULPRIT COMPOUNDS. THESE SEEM
TO BE TRIGGERED ONLY DURING
EXTREME CONDITIONS AS IN
2002
ACKNOWLEDGMENTS
AMERICAN SUGARCANE LEAGUE
DEDICATED RESEARCH FUNDING
COOPERATION AND SUPPORT OF
LOUISIANA SUGAR INDUSTRY