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eurammon Symposium 2016
Requirements of compressors in CO2 plants
of the latest generation in the retail industry
Manuel Fröschle (GEA Bock)
Schaffhausen, 23rd/24th June, 2016
Schaffhausen, 23rd / 24th June, 2016 Page 2
F-Gas regulation – Europe
Phase down
21% CO2 eq. (2030)
High reduction in 2018
low GWP refrigerants
Refrigerant costs
Availability
Quota Leakage
Qualification
Prohibitions
GWP ≥2500 (2020)
GWP ≥150 (2015, 2020, 2022)
GWP ≥ 750 (2025)
Service (2020)
Service stop (2030)
R404A, R507
R404A, R507
Schaffhausen, 23rd / 24th June, 2016 Page 3
Solutions with low/medium GWP refrigerants
HFO blends GWP >750
Already known technologies but further developments for various applications
necessary
Qualification is essential
Proper handling of flammability at hydrocarbon and additional toxicity at
ammonia have to be considered
The advantage of CO2 results in high potential of the refrigerant at different
applications and also in warm climate zones
Flammability has to be considered
and further investigated
Solution for small capacities
Often only mid term solutions (too high GWP)
Further environmental influences
have to be considered
and further investigated
Natural refrigerants
Often only mid term solutions (still too high GWP)
Long term solutions
HFO refrigerants and further
refrigerant blends with medium
and low GWP < 750 or < 150
Schaffhausen, 23rd / 24th June, 2016 Page 4
System development with CO2 as refrigerant
VSD VSD
CO2 Booster Systems:
• Cooling: Only LT or MT & LT
• Heat recovery (hot water & heating)
+ Evaporator (outside) as heat pump function
• Air conditioning evaporator (AC)
Options to increase efficiency of the system:
• Adiabatic cooling of the gas cooler (spray system)
• Sub-cooler (separated system after gas cooler)
• Parallel compression
• Ejectors (vapor/liquid) + parallel compression
Heat recovery
LT evaporator
MT evaporator
LT evaporator
Main compressors Parallel compressor
Flash gas bypass
AC evaporator
Schaffhausen, 23rd / 24th June, 2016 Page 5
Key features of CO2 compressors
Designed for CO2 pressure requirements Stand still & operating pressures
Wide operating conditions
Wear resistance of the drive gear
for highest requirements High refrigerant solubility in the oil
Capacity control & part load requirements
(changing operating conditions)
Low oil carry over
Minimum pulsations & vibrations
Highest efficiency
Schaffhausen, 23rd / 24th June, 2016 Page 6
CO2 booster system with parallel compression
flash gas
x = 14 %
40°C
15°C
COP comp.
@ 40°C → 2,31
@ 15°C → 11,0
COP comp.
@ 40°C → 1,57
@ 15°C → 5,37
flash gas
x = 46 %
to_LT = -35°C (12,0 bar)
to_MT = -10°C (26,5 bar)
tm = 3°C (37,7 bar)
main compressor
parallel
compressor
Schaffhausen, 23rd / 24th June, 2016 Page 7
Comparison main compressor (to = -10°C) with
parallel compressor (to = +3°C)
@ 35°C (90 bar)/ 10 K/ Compressor: HGX34/210-4 S CO2 T
Power consumption at same mass flow
Compressor efficiency at parallel compression
Schaffhausen, 23rd / 24th June, 2016 Page 8
Compressor efficiency at parallel compression
0,4
0,5
0,6
0,7
0,8
0,9
1
1 2 3 4 5 6
Vo
lum
etr
ic &
is
en
tro
pic
eff
icie
ncy
[-]
Pressure ratio [-]
3°C/40°C (101 bar) (Parallel C.)
-10°C/40°C (101 bar)
3°C/15°C (50,9 bar) (Parallel C.)
-10°C/15°C (50,9 bar)
Average volumetric & isentropic efficiency
@ tga = 40°C
@ tc =15°C
volumetric
• Factor for refrigerant
mass flow
volumetric efficiency
isentropic
• Factor for compressor
power consumption
isentropic efficiency
Schaffhausen, 23rd / 24th June, 2016 Page 9
Compressor efficiency at parallel compression
40°C
35°C
30°C
25°C
20°C
15°C
COP within operating limits of
compressor:
HGX34/210-4 S CO2 T (18,2 m3/h @ 50 Hz)
5,4
4,2
3,3
2,5
1,9
1,6
COP main compressor
2,3
3,0
3,9
5,7
7,8
11,0
COP parallel compressor
www.asercom.org
2,9
12,1
tg_out
tc
to
Performance data proofed by
ASERCOM
Schaffhausen, 23rd / 24th June, 2016 Page 10
Efficiency increase due to new CO2 system technologies
Current feedback from field applications regarding seasonal performance factor :
Standard CO2 booster system +10% +10-20% + parallel compression + Ejectors
Depend on operating conditions and requirements.
Advansor
Schaffhausen, 23rd / 24th June, 2016 Page 11
CO2 booster system with parallel compression
Advantages
Retention of the established CO2 Booster
system with medium pressure separator
Compressor swept volume in the system
can be significantly reduced
Efficient compression of the flash gas from
higher suction pressure
Clear increase of efficiency of system
can be reached
Different technologies for further increase
of efficiency can be combined (air
conditioning evaporator (AC),
several MT levels, ejector…)
Oil management in the system
Capacity control & part load
requirements
Increasing requirements for system control
Increasing system complexity
Challenges
Schaffhausen, 23rd / 24th June, 2016 Page 12
Capacity control at parallel compression with VSD
High pressure stage:
Low temperature stage:
(to = -35°C)
(25)30-70 Hz 50 Hz 50 Hz
Pc_sub.
Qo_LT
Qc_LT
20-70 Hz 20-70 Hz 50 Hz
Pc_trans.
Qo_MT + Qc_LT
main compressor (to = -10°C)
50 Hz
parallel compressor
(to = +3°C)
Pc_trans.
Qc_all
Schaffhausen, 23rd / 24th June, 2016 Page 13
Compressor Requirements – Capacity Control with VSD
1
start / stop
%
140
120
100
80
60
40
0
Hz
70
60
50
40
30
20
compressor 1 with
frequency converter 20-70 Hz
Frequency controlled compressor
Co
ntr
ol ra
ng
Min. 20 Hz is possible as a result
using an oil pump
and optimized compressor design
Schaffhausen, 23rd / 24th June, 2016 Page 14
Compressor requirements – capacity control with VSD
compressor 1 with frequency
converter 20-70 Hz
compressor 2-4 without frequency
converter (50 Hz)
Schaffhausen, 23rd / 24th June, 2016 Page 15
Compressor requirements – oil carry over
• General high solubility of CO2 in the oil
• Optimized oil management in compressor necessary to reduce high oil carry over, particular under
following conditions:
• High evaporating temperature with high mass flow (e.g. parallel compression, heat pump applications…)
• High compressor frequency (capacity control with VSD > 50 Hz)
Optimized oil management system in
transcritical GEA Bock CO2 compressors:
• Separation of oil and refrigerant
• Oil return via suction gas to the compressor
oil sump is ensured
Reduction:
Oil carry over at to = 3°C (37,7 bar (abs.)) @ 50 Hz
Schaffhausen, 23rd / 24th June, 2016 Page 16
Food cold chain with refrigerant CO2
Supermarkets, Hypermarkets &
Convenience stores
Food production Freezer Cold storage
Schaffhausen, 23rd / 24th June, 2016 Page 17
Food production
MT: 550 kW (-5° C)
6 x HGX46 CO2 T (transcritical compressors)
LT: 12 kW (-30° C)
2 x HGX12e CO2 (subcritical compressors)
+ Heat recovery (350 kW)
Information regarding CO2 booster
Rack system: SCM Frigo
Installer: Van Cleven
End-user: Rabbit (Convenience Food)
Application: Food processing (production)
Schaffhausen, 23rd / 24th June, 2016 Page 18
Food production – fishing (Freezer)
LT ref. capacity: 240 kW (-50° C)
1-stage: 5 x HGX46 CO2 T (transcritical compressors)
2-stage: 6 x HGX46 CO2 T (transcritical compressors)
Information regarding CO2 booster
Rack system: Kuldeteknisk AS
End-user: Nordic wildfish AS (Boat: Roaldnes)
Application: Fisher boat with CO2 freezer
36 t fish per day (@ 25°C water temperature)
Higher freezing capacity of around 25 %
with higher freezer speed with CO2 compared to R22
→ higher product quality
+ 20 % less volume of the refrigeration system
Schaffhausen, 23rd / 24th June, 2016 Page 19
Cold storage
LT: 60 kW (-32° C)
1 stage: 3 x HGX22e CO2 (subcritical comp.)
2 stage: 3 x HG34 CO2 T (transcritical comp.)
+ Heat recovery
Information regarding CO2 booster
Rack system: Christof Fischer
Installer: Wallburg Kältetechnik GmbH
End-user: Aldinger GmbH + Co. KG
Application: Frozen convenience food
Schaffhausen, 23rd / 24th June, 2016 Page 20
Hypermarket – Cash and Carry
MT1 (+ AC, + flash gas): 85 kW (+2° C)
2 x HGX34 CO2 T (transcritical comp.)
MT2: 245 kW (-8° C)
4 x HGX46 CO2 T (transcritical comp.)
LT: 128 kW (-32° C)
3 x HGX34e CO2 (subcritical comp.)
+ Heat recovery 65 kW (+20/+60°C)
Information regarding CO2 booster
Rack system: Advansor
Installer: kke GmbH
End-user: Metro
Schaffhausen, 23rd / 24th June, 2016 Page 21
Convenience store (Japan)
MT: 30 kW (-10° C)
2 x HGX34 CO2 T (transcritical comp.)
LT: 7 kW (-40° C)
2 x HGX12e CO2 (subcritical comp.)
+ Heat recovery
Information regarding CO2 booster
Rack system: Nihon Netsugen
Installer: Fukushima Industry
End-user: Aeon
Contact eurammon:
Dr. Karin Jahn | Managing Director
Lyoner Strasse 18
D-60528 Frankfurt
Germany
Phone: +49 (0)69 6603 1277
E-mail: [email protected]