Energy audit of mine refrigeration water systems by means of simulation
description
Transcript of Energy audit of mine refrigeration water systems by means of simulation
Copyright © M-Tech Industrial, 2011
Energy audit of mine refrigeration water
systems by means of simulation
16 August 2012Dr. Herman van Antwerpen
Pr.EngM-Tech Industrial
Copyright © M-Tech Industrial, 2011
Introduction
Purpose of this paper:
• Demonstrate the benefits of integrated system simulation,
• Its use in energy assessment of a mine refrigeration system.
Type of simulation:
Conservation of mass, energy and momentum at system level,
i.e. flow rates, temperatures and pressures
Copyright © M-Tech Industrial, 2011
Motivations for simulating a system
On a new design:
• Do component sizing
• Verify component selection, control philosophies, etc.
On an existing plant:
• Compile the data set that describes system operation
• Develop good understanding of system operation
• Check instrumentation consistency / high-level fault finding
• Assess changes at a system-level
• Identify savings opportunities: survival of deep mines
Copyright © M-Tech Industrial, 2011
Classification of loads and savings
Time of day
Con
sum
ptio
n
Energy efficiency
“DSM valves”Baseload
Peak load
Copyright © M-Tech Industrial, 2011
Basic refrigeration loop
Refrigeration plant (pumps,
dams, etc.)
Dewatering pumps
Working levels
Clean makeup water Bleed waterSurface
-1800m
-2400m
1800m
600m
0
1000
2000
3000
40005000
6000
7000
8000
9000
0 3 6 9 12Month
Ave
rage
pow
er c
onsu
mpt
ion
[kW
]
Pumping Refrigeration Total
Copyright © M-Tech Industrial, 2011
Water distribution system
Fridge plants
Pipe column in shaft
PRVs on levels
Pipes in haulages
Cooling cars
Level of instrumentation and control
Ease of maintenance
Influence on total flow requirement
Refrigeration plant (pumps, dams, etc.)
Drilling, stoping
Pip
e co
lum
n in
sha
ft
PRV
PRV
Pipes in haulages
Drilling, stoping
Drilling, stoping
Manos Engineering, Welkom
Copyright © M-Tech Industrial, 2011
Network for levelNetwork for levelNetwork for levelNetwork for level
Copyright © M-Tech Industrial, 2011
Required phenomena
• Elevation differences• Cooling car characteristics• Heat pickup along pipes in haulages
Refrigeration plant (pumps, dams, etc.)
Drilling, stoping
Pip
e co
lum
n in
sha
ft
PRV
PRV
Pipes in haulages
Drilling, stoping
Drilling, stoping
Copyright © M-Tech Industrial, 2011
Chilled water heating along haulages
Journal of the SA Institute of Mining and Metallurgy:Rawlins, C.A. (2007) “Mine cooling and insulation of chilled water transport pipes”Jones, M.Q.W. (2003) “Thermal properties of stratified rocks from Witwatersrand
gold mining areas”
Virgin Rock Temperature
Haulage wall
Ventilation air
Chilled water
Distance from shaft, along haulage
Tem
pera
ture
Shaft Cooling car
Low flow rate
High flow rate
Conduction
Convection
Convection
Copyright © M-Tech Industrial, 2011
TT
PID
25ºC
0
65
130
195
260
0 2 4 6 8 10 12 14 16
T_chilled water [C]
Wat
er d
eman
d to
leve
ls [l
/s]
Reference data
With thermostatic control
Cooling car control
Copyright © M-Tech Industrial, 2011
Power consumption
0
500
1000
1500
2000
2500
3000
3500
4000
5 6 7 8 9 10 11 12 13 14 15
Chilled water temperature [C]
Ave
rage
d po
wer
req
uire
men
t
0
200
400
600
800
1000
1200
1400
1600
Pre
ssur
e at
coo
ling
car
inle
t [kP
a]
kW_Pump kW_Refrig_elec kW_Total Pressure
Copyright © M-Tech Industrial, 2011
Conclusions
Regarding mine refrigeration
• Opportunity: “Mine-proof” cooling car flow control.
• For some mine layouts:
• Minimum refrigeration cost: highest possible chilled water
temperature.
• Constraint: cooling car inlet pressure.
Regarding simulation
• Industrial Energy Efficiency projects or system-level optimisation
requires integrated simulation: flow rate, temperature and pressure.