Water conservation in distilleries

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Water conservation in distilleries
D. A. Patil , K. A. Gaikwad and S. V.
Patil Vasantdada Sugar Institute e-mail
sv.patil_at_vsisugar.org.in
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• Indian distillery industry is on fast-track
• Number of sugar mills 620
• Number of molasses based distillery units 350
• Molasses based installed capacity 4.29 bln
  lit.
• Gain based distillery units 100
• Grain based installed capacity 1.8 bln lit.
• Future Molasses alcohol for Industrial and
  fuel purpose
• Grain alcohol for liquor purpose.
• Lignocellulosic ethanol is also expected to come
  (for fuel purpose).

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• Demand and Supply of Alcohol (2010-11)
• Maharashtra (mln lit.) India
• RS for CL 150-160 400
  -500
• ENA for IMFL 50-60
  1000-1100
• Export of ENA 40-50 --------
• Fuel Ethanol 140 1050
• Industrial use 200-350 650-1350
• Ethanol in
• neighboring states 160 ----------
• Total demand 740 to 920 3100-4000
• Production (Molasses) 550 - 650 2300-2600
• Production (Grain) 60-65 600-700
  
• Production (Total) 610-715
  2900-3300

DRIVER
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Three-fourths of earth is water Rivers,
groundwater, snow and ice 2.5 , Rest being
sea/salt water. Estimates by the Ministry of
Water Resources (MoWR) indicate that water used
for industry in India is around 7-8 per cent of
the total freshwater withdrawal in the country.
In the next two decades water consumption will
triple current levels.
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The industrial sector is the second highest user
of water after agriculture. According to CPCB
in 2000, Indias annual fresh water withdrawals
were about 500 billion cubic meters and the
Indian industry consumed about 10 billion cubic
meter of water as process water and 30 billion
cubic meters as cooling water.
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As per the World Bank studies, the water demand
for industrial uses and energy production will
grow at a rate of 4.2 percent /year, rising from
67 billion cubic meter in 1999 to 228 billion
cubic meter by 2025. Therefore, according to
World Bank the current industrial water use in
India is about 13 per cent of the total fresh
water withdrawal in the country.
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Cost of water supply varies widely and can be in
the range of Rs. 0.09 to 50.0 per cubic meter
It can be assumed that at about 2500 million
liters of alcohol production per annum in the
country, the consumption of fresh water by
distilleries alone could be 37,500 million liters
per annum or 125.0 million liters per day and
spent wash generation could be 25.0 to 30.0
billion liters per annum. This is an alarming
situation. Therefore, it is necessary to take
immediate steps to minimize the consumption of
water in distilleries. This can finally result
in reduction in spent wash generation and avoid
further complications.
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Make-up soft water 96.46 m3/d
CO2
Cooling Tower
6.1 m3/d
CO2 Scrubber
Process Water 493.2 m3/d
E 20.40 m3/d
FERMENTATION
410 m3/hr
D 68.87 m3/d
Molasses 180 m3/d
B/D 7.2 m3/d
(Overflow)
Nutrient dil. 0.1 m3/d
Spent wash Recycle 39.6 m3/d
F.W. 704.62 m3/d
Sludge 14.38 m3/d
Steam 252 MT/d
DISTILLATION
ENA 60 KLPD
176 .62 m3/d spent lees for R. S. dil. during
ENA production
340 m3 /hr
Spent wash 600 m3/d
Spent lees recycle 120 m3/d (as a make-up water)
Cooling Tower
560.4 m3/d For Biogas
E 92.01 m3/d
Composting OTCLA
D 57.11 m3/d
B/D 2.88 m3/d
Typical water consumption in a molasses based
distillery
(Overflow)
Fresh make-up soft water 32 m3/d
Total make-up water 152 m3/d (12032 m3/d)
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Table 1 Fresh water consumption for process
non-process
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Contd
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Table 2 Recycled streams for process
non-process
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Contd
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Table 3 Periodical fresh water required for
starting of distillery
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Table 4 Continuous polluted waste water
generation
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Table 5 Continuous non-polluted waste water
generation
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Table 6 Periodical waste water generation
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1) Water required for molasses dilution
High alcohol conc., yeast strain used, molasses
quality etc. 1) Biostil 12.50 to
13.00 2) Cascade 13.00 to 13.50 3)
Fed-batch 13.50 to 14.00 4) Batch
14.00 to 14.50 SW/RO permeate/process
condensate recycle Vs FE and alcohol quality

• Process water consumption in molasses based
• distilleries (How we can reduce the
  consumption?)

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2) Water required for sludge washing During
alcoholic fermentation some salts can precipitate
out of the solution and yeast suspended solids
settle down forming sludge. This sludge can
create operational or process problems if carried
to distillation columns/reboilers or to
biomethanation plant. Sludge has to be
properly removed from fermented wash. While
removing the sludge, it is necessary to wash it
with water to recover alcohol and avoid losses.
Sludge content of molasses also varies (8-25
v/v) depending on sugar processing operations.
(Indian molasses is unique and most inferior in
the world)
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3) Water required for CO2 scrubbing   CO2
evolved during fermentation carries some of the
alcohol formed during fermentation. To recover
the alcohol, it is necessary to wash CO2 with
process water. The CO2 scrubbed water containing
alcohol can be easily used for molasses dilution.
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 4) Water required for Nutrient dilution For
yeast cell growth and yeast fermentation
activity, usually nutrients such as urea, DAP,
MgSO4 etc. are used. These nutrients are diluted
with water to the required concentrations and
pumped to the fermenter. It is possible to
minimize water consumption for nutrient dilution.
5) DM water for RS dilution during ENA
production To enhance the quality of final
product (EQRS or ENA) rectified spirit is diluted
with DM water in specific ratio and distilled
again. It is possible to recycle spent lees
generated during distillation process to some
extent for RS dilution in place of fresh DM water
depending on the final alcohol quality required.
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B) Non-process water consumption in molasses
based distilleries 1) Water requirement
for cooling towers (2nd major use) Fermentation
is an exothermic reaction and normally,
fermentation temperatures are maintained at
32-330C. During distillation the enriched
alcohol vapours are also required to be condensed
using cooling water. Cooling towers are
necessary in distillery plants. To avoid scaling
in condensers, cooling towers are run using soft
water. Because of losses of water due to
evaporation and drift losses, the hardness of
soft water goes on increasing and it becomes
necessary to take water blow-down. After
blow-down, it is necessary to make-up the lost
water by adding fresh soft water.
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Contd.
In a distillery unit, two to three cooling
towers may be required depending on final
products to be produced. Proper check on
hardness built-up and minimizing leakages
losses can result in minimizing make-up soft
water requirement. 2) Water requirement for
laboratory use, floor washing, rinsing washing
of softener/DM plant, domestic use etc. For
maintaining cleanliness and hygienic conditions
in day to day process operations, floor washing
is necessary. For routine analysis and for
washing of various equipments in laboratory,
fresh water is required. Similarly, fresh water
is also required for periodic rinsing washing
of softener/DM water plant as well as for
domestic purpose. Use of water for such
applications can be rationed and minimized.
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3) PRDS de-superheating, Air CO2 blowers,
vacuum pump and pumps gland cooling water etc.
Fresh water is also required for uses such as
PRDS de-superheating, Air CO2 (water ring
type) blowers, vacuum pumps and pumps gland
cooling etc. Use of water for such applications
should be minimized by employing recycle/reuse
principle. Mechanical seal for pumps can be used
to minimize contamination of water streams.4)
Periodical fresh water requirement Fresh water
is also required periodically for cleaning of
Plate Heat Exchangers (PHEs), distillation
plant, yeast separators. RO plant rinsing and
evaporation calendria cleaning also requires
fresh water periodically. Use of water for such
applications should be minimized by employing
recycle/reuse principle.
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• Capacities and configurations
• Distillery A 80 KLPD, Batch fermentation system
  (9-Fermenters) conventional atmospheric
  distillation without reboilers.
• Distillery B 30 KLPD, Cascade continuous
  fermentation system (4-Fermenters)
  without yeast and spent wash recycle MPR
  distillation with reboilers.
• Distillery C 60 KLPD, Cascade Continuous
  Fermentation system with spent wash
  recycle 60 KLPD RS atmospheric distillation
  without reboilers and 55 KLPD RS to ENA
  atmospheric distillation system without
  reboilers.

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4) Distillery D 425 KLPD, Batch fermentation
system (285 KLPD, 14 batch Fermenters) with 205
KLPD conventional atmospheric distillation system
with reboilers to produce R.S. and 80 KLPD MPR
distillation system to produce ENA and Cascade
continuous fermentation system (6-Fermenters, 140
KLPD) with spent wash recycle system, atmospheric
distillation (140 KLPD) and reboilers. 5)
Distillery E 120 KLPD, Biostill Continuous
Fermentation system (2-Fermenters)
with MPR distillation, reboilers integrated
evaporation system. 6) Distillery F 25 KLPD,
Batch Fermentation System (6 Fermenters)
conventional atmospheric distillation without
reboilers.
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Results and Discussion
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(SWSL)
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Table 7 Average fresh water requirement in
molasses based distilleries for different
fermentation technologies.
Other than cooling tower
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Table 8 Average waste water generation in
molasses based distilleries for different
fermentation technologies.
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Water requirement of a modern grain based
distillery1. Grain Cleaning storage section
consisting of grain silos. 2. Grain handling
milling section consisting of pre-cleaner, de-
stoner, magnetic separator, hammer mills, bag
filters etc.3. Flour handling, slurry
preparation pre-liquefaction.4. Jet cooking,
post liquefaction pre-saccharification. 5.
Simultaneous saccharification fermentation.6.
Distillation to produce Rectified Spirit or Extra
Neutral Alcohol or Dehydration section to
produce fuel ethanol. 7. Decantation section to
separate whole stillage into wet cake thin
stillage.
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8. Multiple-effect evaporators for
concentration of thin stillage to syrup.
       9. Mingler section for mixing of wet
cake syrup to produce distillers wet
grains with solubles (DWGS).10. Drying of DWGS
in a dryer to produce distillers dried grains
with soluble (DDGS).11. Segregation of
various non-process waste water streams for
reuse.12. Effluent treatment system for
treatment of non-process final combined
effluent.
Contd.
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Table 9 Fresh water requirement for grain based
distillery
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Table 10 Recycle streams (Grain distillery)
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Table 11 Net water requirement (Grain
distillery)
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• Conclusion
• In the last few years, spent wash recycle has
  emerged as one of the measures to reduce fresh
  water consumption. Existing distilleries new
  coming distilleries should consider the spent
  wash recycling system.(FE Spirit Quality)
• Instead of direct steam sparging, where ever
  possible, reboilers should be fitted to
  distillation columns, to reduce the quantity of
  spent wash generation.
• Spent lees can be recycled in process or
  non-process after correcting the pH.
• Higher alcohol concentration in fermented wash
  can substantially reduces the fresh water
  requirement in the process as well as steam
  requirement for distillation. However, this would
  depend on the quality of molasses available with
  the distillery.

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• 5. The CO2 scrubbing water can be used for
  molasses dilution.
• 6. The non-process wastewater generated from pump
  glands, air and CO2 blowers and vacuum pumps can
  be recycled back to the fermentation process.
• For avoiding scaling in condensers and coolers
  and for proper maintenance of the plant, it is
  advisable to use soft water as make up water for
  cooling tower.
• 8. The evaporation plant steam condensate can
  be recycled back as boiler feed water and
  evaporation plant process condensate can be
  recycled back as process water after pH
  correction and polishing treatment.

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9. To reduce leakages from process pumps it
is advisable to install mechanical
seal. 10. The fresh water requirement in
molasses and grain based distilleries is
found out to be average 15.0 and 16.0 liters per
liter of alcohol produced,
respectively.
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THANK YOU
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