1. Notes on Involved Energy in Cane Sugar Processing
Dr Carlos de Armas
Dr Oscar Almazan

2. Cane Sugar Processing Extraction Separation of the sugared juice
from the bagasse (fiber+water+ )
Purification Separation of non desirable
substances from juice; colloidal +
Evaporation Separation of most of the water
Cristallization Separation of sucrose from
different classes of molasses
Centrifugation Separation of sugar crystals
Steam and Power Generation

3. EXTRACTION (MILLING) bagasse purification Cane Pre- paration Mill No 1
No. N
Exhaust Section
Counter-current
Extraction
3 to 5 Mills
Mixing
Mixed juice to
purification
First extraction juice
water
Juice
Mixed juice
Brix to15
Purity 80 to 90

7. CANE SUGAR; AN ENERGY INTENSIVE INDUSTRY
Cane sugar industry is an insdustry with strong involvements with energy.
~The raw material, sugar cane, bring its own fuel for processing, and even more.
~It shows high thermal (steam) demand for processing , while its demand of mechanical energy is low, allowing high cogeneration.

8. SUGAR AND ETHANOL PRODUCTION
9 ton of cane ton sugar
2.5 ton bagasse
2.0 ton cane wastes
300 kg final molasses
15 ton of cane m3 ethanol
4.0 ton bagasse
15 m3 liquid wastes

9. Energy in Processing (Main Elements)
~Steam generation efficiency
~Efficient use of steam
~Efficiency in the conversion of
thermal energy into mechanical

10. Bagasse
It is the natural fuel in processes of production of sugar and etha-nol. Enough for fulfilling whole demands. Reaching in practice, in addition, a balance between produced and burned bagasse, through control of boilers effi-ciency. Surplus bagasse without a goal, is as bad as not enough bagasse.

11. Bagasse
In Cuba, when producing in a campaign, 6 million ton of sugar, there are ground 50 mil-lion ton of cane, with a bagasse production of 15 million ton, out of which, 95 % is burned, going the difference to derivatives. This 15 million ton bagasse, are equivalent to 3 million ton fuel oil.

12. Bagasse ..and the most interesting fact ..!!
While in producing cane sugar, it is spent the whole energy freed by the 2.5 kg of bagasse coming along with 1.0 kg of sugar , i.e kcal , in beet sugar proces-sing, there are spent per kg produ-ced not more than 2000, that is, potentially, there exists about 50 % surplus bagasse.
Why it is not so in practice?

13. ~ Up to the seventies there were
no possibilities, 1.0 bb of “fuel”
costed less than US $ 400
~Current policy ; to avoid surplus
without goal. They cost money.
~Seasonal fashion of sugar pro-
duction
~Different kinds of bussiness,
laws and regulations.
Bagasse

14. Generation and use of energy Sales to the grid
32-36 kW-h /tc for fulfilling
whole demand of the factory. For tc per day, 150 (ton/hour), power generation is of the order of 5000 kw (inclu-ding the mills). Energy reser-ves due to co-generation plus surplus bagasse may grow up to kw (70 kw-h/tc) as per Mauritius Island experience
Generation and use of energy Sales to the grid

15. Generation and Use of Energy Sales to the Grid
Through changes in steam generation parameters, and with efficient use of steam in process, which in general mean investments, there are reached surplus of the order of kw-h per ton of cane, i.e. for a factory grinding 150 ton per hour, it is not impossible to deliver to the grid kw with proved technologies (Mauricio Island and Hawaii).
Generation and Use of Energy Sales to the Grid

16. Generation and Use of Energy Different Approaches In Operation Today
1) BackPressure Turbines
To the Grid 10/15 kw/tc-h
2) Cond.-Extr. Turbines -
Mauricius Island 70 kw/tc-h
In development at present 3)
Combined Cycle, GT +
gasifying kw/tc-h

17. Extraction- Condensing Turbines A main drawback is the sea-
sonal character of cane sugar
processing all over the world
and the scale economy of Ran-
kine cycle. Possible sizes are
not enough efficient, and very
expensive per kw to operate 60
to 70 per cent time with fossil
fuels. It is possible only in very
small countries and where very
efficient cane harvest wastes use
are reached or with energy canes

18. Combined Cycle Present status -Following bagasse gasification;
It is almost ripe the technology.
After this, semi or commercial
tests. It will be ready in a few
years.
Through bagasse hydrolysis, the
fuel can be fed directly to the
combustor. It is now at bench
scale level, then semi or com
mertial tests. May be ready in
ten years.

19. Combined Cycle Economy Operation plus maintennance cost
of a hydroelectric plant in Brazil
is of the order of US $0.001/kw-h,
while capital cost US$ 0.06/kw-h
In a conventional fossil fuel plant
these costs are and 0.025
respectively and that of fuel 0.02
for a total of US $ 0.05 per kw-h

20. Combined Cycle Economy Gasification; operation plus
maintennance costs 0.005,
capital cost 0.025, fuel 0.02
for a total of US $ 0.05 per
kw-h.

21. SUMMARISING

22. STEAM AND POWER GENERATION Base: 1000 kg of cane Sugar; to 140 kg Bagasse; to 320 kg and 4.0 kg/kg sugar Steam; kg to 600 kg to 7.0 kg/kg sugar Energy; to 7400 kcal/kg sugar to 31.0 MJ /kg sugar common value 4500 kcal/kg sugar MJ/kg sugar

23. MAIN ASPECTS IN THE EFFICIENT USE OF ENERGY IN CANE SUGAR PROCESSING
Steam Generation Configuration
Engineering Design of Process Steam Layout
Engineering Design in the Transformation of Thermal Energy into Mechanical Energy

24. STEAM GENERATION
Characterizing SG Efficiency, specification
of Gross Calorific Value, or Nett Calorific Value
as a function of % moisture(W) .
metric units
NCV = *W/100 kcal/kg (Hugot)
english units *(kcal/kg) = Btu/lb
NCV = *W/100 Btu/lb (Hugot)
1.0 kW-h = 3.6*106 watt-seg (joule) = 860 kcal;
1.0 kcal = kj

25. BOILER EFFICIENCY FOR GCV AND NCV
Bagasse with 50 % moisture
NCV = 1825 kcal/kg GCV = 2300 kcal/kg
Eff. defined as the % of freed heat from the bagas-se, leaving with the steam (enthalpy of steam less enthalpy of fed water, times steam rate, divided by the Caloric Value of one mass unit of bagasse.
GCV Efficiency of best bagasse boilers %
NCV Efficiency of these units,
(2300/1825)* = 85 %

26. GENERAL BOILER CONFIGURATION
Furnace
Water walls
Screen
Superheater
Water Evaporation Bundle
Economizer
Air Pre-heater

27. MAIN ENERGY LOSSES IN STEAM GENERATION
Sensible heat carried by gases leaving, %
Non complete combustion, %
Excess air over the minimum necessary,
including air infiltration
Conduction and convection through walls 2%
Water Extractions

28. FURNACES; DIFFERENT TYPES
Burning in pile; Horse shoe
Cell
Spreader stoker (grate) oscillating
travelling
Suspension firing

29. COMBUSTION / STOICHIOMETRY
Bagasse (dry) analysis, changed to ashes free
Carbon /0.975 = 48.2 %
Hydrogen /0.975 = 6.7
Oxygen /0.975 = 45.1
Ashes
Dividing by the MW of each element it is reached a pseudo-
structural formula, with which it is easier to do the combustion calculations using the moles approach.
C4.02 H 6.7 O 2.82

30. Stoichiometry Equations
(/100)C4.02H6.7O2.82 ; Excess air %
bagasse ; Base of Calc. +
4.285(1.0 + /100)*(/100) O2
oxygen in air
16.12 (1.0 + /100)*(/100)  N2
nitrógen coming with air

31. Carbon anhydride + water from water due to
COMBUSTION PRODUCTS
4.02*(/100) CO2  + (3.35*( /100)+ BC*(hum/100)/18)H2O
Carbon anhydride + water from water due to
combustion moisture of fuel.
(/100)*(/100)O2
non-used oxygen in gases
(1.0 +  /100)*( /100)  N2
nitrogen in gases

32. ……..LAST COMMENTARIES AFTER STOICHIOMETRY, IT IS POSSIBLE TO BUILD MOLAR AND ENERGY BALANCES, AND AFTR THIS , ADDING DETAILS OF CONFIGURATION, TO BUILD THE WHOLE MODEL OF STEAM GENERATION AFTER THE ADDEQUATE PROCEDURES THE REST OF THE WHOLE PROCESS ENGINEERING MAY BE MODELED, REACHING THE WHOLE PROFILE OF ENERGY TRANSFORMATIONS.

33. Liquids transportation in the factory;
mixed and clarified juice to their tanks,
syrup and molasses to their tanks,
injection water to condensers and from
batches (barometric leg seal) to spray
pond. General purpose water from source
to tank. Imbibition and recirculation of
juices in mill, etc.

34. Mixed juice to tank; head 15 m, flow, one ton
of juice (1000 kg), 100 % mixed juice extract.
1000(2.204 lb/kg))15 (3.28 ft /m) =
= ft-lb / ton/hour, for 300 ton / hour
= *300 = ft-lb /hour
= /3600 = ft-lb / sec
as one hp = 550 ft-lb/sec, power for pumping
/550 = 16.4 hp, i e 12.3 kW

35. Another example; pumping cooling water to vacuum pans condensers
Another example; pumping cooling water to vacuum pans condensers. Evaporation in pans 18% cane = 180 kg / ton cane, need of cooling water 60 times, head 20 m, taking to English system
=180*60 *20 *2.204 *3.28 *300/3600/550 =
237 hp or 176 kW /300 = 0.6 kW-h/tc
Efficiencies has not been taken in consideration nor densities in pumping of
fluids other than water

36. Total Mechanical Energy Demand (different of installed power) is of the order of 32 to 36 kW-h( 115 to 130 mJ)
per ton (metric) of cane
Irrelevant of type of prime mover; steam or electric, it is a number slightly different
Note: metric ton may be identified also by
Tonne.

37. With a total, general distribution, just for
giving an approximate idea as follows
Cutting knives, including leveling blades
1.3 – 1.7 kW-h per ton cane (one machine)
Shredders 1.5 – 2.5 kW-h per ton cane,
depending on design

38. Milling, (only for energy demands
estimations, Hugot )
For three roller mills ; T= 0.134PnD / tc
T; kW- h per ton cane for each mill
P; total hydraulic load, tons, n; speed,
rpm, D; diameter of rollers, m
tc; ton cane coming in per hour.

39. Change coefficient by 0.1 for crusher (two rolls) For mills with pressure feeders (Walker), multiply power demand by 1.1 For losses in gearing use 2.0 % in closed reducers with oil bath, and 8 % in open gearing. In combined gearing
eff. in transmision=(1-0.02)*(0.92)=0.90
Energy demand at exit prime movers =
= energy demand at exit of speed red./ eff.

40. Energy demand in reception-transportation and elevation of cane
0.19 kW- h per ton cane
Energy demand in intermediate carriers
0.12 times number of intermediate
carriers kW- h per ton cane
Energy demand in carrier to steam boilers
0.03 kW-h for each 50 m length, / ton cane