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Thermosyphon wort boiling – new plants
and their impact on flavour stability
Dr John Andrews and Paul Dowd
World Grains Summit
San Francisco, California
17th to 20th September 2006
The outputs of wort boiling
• The sterilisation of the wort
• The inactivation of the enzymes to ‘fix’ the sugar
spectrum
• The extraction and isomerisation of hop alpha acids
• The formation of flavours and colour compounds
• The stripping of undesirable volatiles such as Di Methyl
Sulphide
• The denaturation and coagulation of protein
• The formation of reducing agents
• The evaporation of water
whilst minimising the heat damage
done to the wort
Energy consumption - environmental
challenges
Beer production 139,000 Btu/US BBL
125,000 kJ/hl
Bottling T
20%
Heating & Other T
14%
Fridge E
10%
Mashing T
14%
Pumps E
8%
Lighting E
2%
Kettle boil T
20%
Kettle Raise T
12%
Nucleate boiling
Most commonly used mode for boiling wort.
Internal heater or
External thermosyphon
Vapour bubbles beneficial
1) protein denaturation &
. coagulation
2) volatile stripping
3) hop acid isomerisation
two phase flow
(liquid & vapour)
The difference in
density between
single phase & two
phase is the driving
force for the
thermosypon
intensity of boil
The more steam vapour
bubbles formed per unit
volume of wort the more
intense the boil
single phase
flow (liquid)
Wort heater surface area
Open tangential return
above wort surface
Wort kettle
Typical internal heater
heater surface area
0.73ft 2/ US Brl
2
0.08 M / HL
Wort kettle
Typical British External
Thermosyphon
1.83ft 2/ US Brl
2
0.2 M / HL
Wort heater surface area
SURFACE AREA
2
2
ft / US BBL
M / hl
TYPICAL INTERNAL HEATER
0.73
0.08
BRITISH EXTERNAL THERMOSYPHON
1.83
0.20
Temperature profile across
clean heater surface
Wort boundary layer
Steam boundary layer
WORT
Internal heater
Steam 34psi 2.3 Bar
279 °F 137 °C
External heater
Steam 10psi 0.7 Bar
239 °F 115 °C
Heater surface contact temperature
WORT
Heater surface contact temperature
Wort boiling point (212 °F 100 °C
Higher surface area lowers heater surface temperature in contact with wort.
This lower Delta T is considered beneficial for foam, flavour & flavour stability
Heater surface fouling - evaporation
consistency
steam pressure Increased
(to compensate for fouling)
clean heater surface
steam
boundary
layer
wort
boundary
layer
steam
boundary
layer
steam
fouling
wort
boundary
layer
22psi 1.5 Bar
262°F 126°C
steam
10psi 0.7 Bar
239°F 115°C
heater surface
Contact Temperature
wort boiling point (212 °F 100°C)
µ = 1.57
clean heater surface
evaporation rate
7 % Hr
heater surface
Contact Temperature
wort boiling point (212 F° 100 C)
µ = 0.85
steam pressure increased
evaporation rate
7 % Hr
Steam control - evaporation consistency
The weight of water evaporated is directly related to the mass of steam condensed in
the wort heater.
Flow control
Temp.
transmitter
Constant
steam set
at 3 bar
max.
Steam flow
control valve
Steam
meter
Condensate
Pump by-pass
(pre-heat only)
Fouling of the heater surface slows heat transfer which reduces the steam mass condensed and
therefore evaporation. The flow control valve automatically opens sufficiently to raise the steam
temperature (pressure) to restore the target rate of steam condensation.
Breweries surveyed
Brewery
Geographical
location
Brewlength
(hl)
Evaporation
rate (%vol
per hr)
Length of
boil
(minutes)
Heater
surface area
per unit
volume
(m2/hl)
A
Australasia
830
6.5
70
0.22
B
North America
1215
4.67
90
0.24
C
North America
1215
4.67
90
0.24
D
Great Britain
570
6.5
45
0.22
Brewery A – DMS reduction during the boil
300
total DMS
free DMS
250
ug/litre
200
150
100
50
0
Start Kettle Boil
End Kettle Boil
Wort Cool Middle
Brewery A – Increase in Anti Radical Potential
- DPPH
700
Old Brewhse
New Brewhse
600
500
400
300
200
100
0
Start Kettle Boil
End Kettle Boil
Wort Cool Start Wort Cool Middle Wort Cool End
Brewery A – Reduction in Furfural levels
1600
Old Brewhse
New Brewhse
1400
1200
1000
800
600
400
200
0
Start Kettle Boil
End Kettle Boil
Brewery A - ESR Lag Time
PBN (Lag Time - min)
100
Old Brewhouse
New Brewhouse
80
60
40
20
0
EOF
Early
Storage
Late
Storage
BBT
PACK
Brewery A - ESR T150
T150 (Intensity Level)
12.0
Old Brewhouse
New Brewhouse
10.0
8.0
6.0
4.0
2.0
0.0
EOF
Early Storage
Late Storage
BBT
PACK
Brewery B - ESR T150’s
140
Pre EWB installation
Post EWB installation
120
T150 (000's)
100
80
60
40
20
0
Copper 1 up
Copper 1 cast
Brewery B - ESR T150’s
120
Pre EWB installation
Post EWB installation
100
T150 (000's)
80
60
40
20
0
Copper 2 up
Copper 2 cast
Brewery C - ESR T150’s
120
Pre EWB installation
Post EWB installation
100
T150 (000's)
80
60
40
20
0
Copper up
Copper cast
Brewery D – TBA values
50.00
45.22
45.00
40.00
35.57
35.00
30.00
25.00
20.88
20.00
15.00
10.00
5.00
0.00
start boil
end boil
start cool
Brewery D – Reduction of DMS
800
DMS
700
DMS-p
600
DMS (ppb)
500
400
300
200
100
0
start boil
end boil