using variable speed drive and soft starter in a hot strip...
TRANSCRIPT
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Using Variable Speed Drive and Soft Starter
in a Hot Strip Mill Direct Cooling Cycle
Presented by:
Mr.Supached Pandee
Department Manager of Energy Technology Development, and
Senior Expert of High Voltage, Low Voltage, and Motor
Authors:
Nupakon Kotcharak, Witthaya Paenthai,
Jakkit Thippayarat, Supached Pandee and
Somsak Pikkanesuan*
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OUTLINE
2
INTRODUCTION
SYSTEM DESCRIPTION
RESULTS and DISCUSSION
CONCLUSION and FUTURE WORK
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INTRODUCTION
Sahaviriya Steel Industries Public Company Limited (SSI),
a Hot-rolled Steel Sheet producer in Thailand, consuming large
amounts of electrical energy due to using large power of pumps
in processes3
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INTRODUCTION
3
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INTRODUCTION
3
Furnace Cooling Cycle
Direct Cooling Cycle Indirect Cooling
Cycle
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INTRODUCTION
4
Fig.1 Schematic diagram of Direct Cooling Cycle (DCC)
Direct cooling tower
Pressure sand filter
VEB002 A,B,C,D
VEB003 A,B,C CP004 A,B,C,D
4 bar system12 bar system
Scale pit system
Finishing millRoughing mill
Back-up roll coolingWork roll cooling
From furnace
Descaling Descaling
Coil Box
Descaling
Scale pit
Previous :
• When there is the plant breakdown,
the DCC still supply water without
stop any pumps because of affecting
to motor insulation.
4 bar
12 bar
Scale Pit
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INTRODUCTION
5
Manipulation High capacity pumps have chosen to review operation
characteristics.
West Coast Engineering Company Limited (WCE), an
affiliate of SSI group, investigated energy saving
opportunities by focusing on Direct Cooling Cycle (DCC).
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INTRODUCTION
6
Process Operation Characteristic
► Work rolls were cooled directly by water at normally 13.2 bar
supplied by the 1450-rpm fixed-speed pump during the process of
milling
► Meanwhile, backup rolls were also cooled directly by 4 bar
pressure water. When the production rates were low, gap time or
delay time occur, or rolls had to change. Discharge valves are
thus closed.
► Nevertheless, the relating pumps continue to work and water is
bypassed to the Scale Pit. Energy is wasted.??
► It was researched that pressure of cooling water can be reduced
from 13.2 bar to 11 bar when product thickness is more than 2
mm.
► The systems inside DCC are interrelated. Therefore, the study
and improvement for each system have to be taken place
simultaneously.
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INTRODUCTION
Objective:
To present the possible energy saving for the
systems of direct cooling cycle retrofitted by soft
starter and variable speed drive.
To consider reduction of Carbon Dioxide (CO2)
emission.
8
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SYSTEM DESCRIPTION (Direct Cooling Cycle)
Fig.2 Schematic diagram of DCC retrofitted with
Soft Starter and VSD.9
Level II
Condition 1
During Operation :
Level II will send
pressure reference to
PLCs
Condition 2
Breakdown or delay
time:
Some pumps will be
stopped by PLC
command.
4 bar :
1 VSD
1 Soft Start12 bar :
2 VSDs
1 Soft Start
Scale Pit :
1 VSDs
1 Soft Start
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SYSTEM DESCRIPTION (Control System)
Fig.3 Direct cooling controller system
10
12 bar
4 bar
Scale Pit
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Condition Parameter Unit
System
12-bar 4-bar Scale-pit
P I P I P I
Rolling
13 Bar
VFR m3/h 4600 4600 3500 3500 8100 8100
Operation
control13.2 bar 12 bar 6 bar 5.3 bar 4500 mm 4500 mm
Rolling
11 Bar
VFR m3/h 4600 4300 3500 3500 8100 7800
Operation
control13.2 bar 11 bar 6 bar 5.3 bar 4500 mm 4500 mm
Delay/
WR Change
VFR m3/h 0 0 3500 2500 3500 2500
Operation
control0 0 6 bar 5.3 bar 4500 mm 4500 mm
SYSTEM DESCRIPTION (Conditions of Operation)
Table 1 Operation pressure and volumetric flow rate for each system in DCC
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P = Previous System
I = Improved System
- The conditions are changed depended on product group
(thickness more than or less than or equal 2 mm)
- After process characteristics were investigated
1. Operation pressure for 12-bar and 4-bar system,
2. Average volumetric flow rate (VFR) of operation and
delay in each system,
3. Operation control are also shown in the table
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RESULTS & DISCUSSION
12
This figure implies that
- The previous system consumed energy at 918 kW constantly when
there are operation characteristic changings at constant pressure 13.2
bars
- After improvement, power consumption is reduced (Y-axis) depended
on pressure reduction (X-axis).
Fig.4 Illustrated power versus pressure reduction control of pump 12-bar system
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Topic System
Rolling Delay
Time
(h)
Power
(kW)
Energy
(GWh)
Time
(h)
Power
(kW)
Energy
(GWh)
Before improvement
12-bar
7,001
2,754 19.3 0 0 0
1,258 8.8 1,235
1,258 1.6 4-bar
SP 813 5.7 813 1.0
After improvement
12-bar
7,001
2,205 15.4 0 0 0
4-bar 1,210 8.5 1,235
629 0.8
792 5.5 SP 271 0.3
Energy Saving (GWh)
12-bar 3.84 0
4-bar 0.34 0.78
SP 0.15 0.67
Total Energy
Saving 3 System (GWh)5.77
RESULTS & DISCUSSION
12
Table 2 Summary of energy consumption and energy saving
This paper aims to discover energy saving benefit of project after
improvement,
Assumptions:
• Production rate is 2.0 Mtons/year
• Calendar Time (Tc) at 365 days/year
• Operation Time (Io) at 94% of Tc or 8,236 h
• Annual and regular shut down represented by delay time is
15% of Io or 1,235
• Working time (the difference between operation time and
delay time) is 7,001 h.
• Electricity price at 0.12 USD/kWh
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RESULTS & DISCUSSION
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Energy Saving
Pressure regulation by VSD is possible to decrease DCC energy
consumption totally about 5.77 GWh/year or 16%
Annual cost saving at 692,568.2 USD/year approximately
Overall investment can be estimated at 1.13 million USD
Payback period is 1.63 years according to SSI investment criteria
Carbon Dioxide Emission
Carbon dioxide emission factor for converting electricity reduction to
the emission is 0.561 kgCO2e/kWh[4].
► This project can reduce CO2 emission by 3,237 tCO2e or
► 0.75% compared to SSI Carbon dioxide emission in 2013
at 430,808 tCO2e
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CONCLUSION & FUTURE WORK
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Conclusion
■ A hot strip mill direct cooling cycle was picked up to reduce energy composed 3
systems; 12-bar, 4-bar, and Scale-Pit
■ Operation characteristics were studied to apply Soft Starter and Variable Speed
Drive technologies with pumps
■ Soft Starter has potential to expand pump lifespan and VSD can be decrease
pump power consumption
■ After improvement, it is possible to save energy by 5.77 GWh/year or 16% and
payback period is about 1.63 years when production rate is 2.0 Mton/year
■ This project can reduce CO2 emission by 3,237 tCO2e
Future Work
Product group should be classified specifically to utilize with proper operation
pressure less than 11 bar. The results from this study are assumptions to
manipulate the future work.
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References
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[1] J. Tolvanen: “Saving Energy with Variable Speed Drives”, World Pumps,
501(2008), pp. 32-33.
[2] W. J. Lukitsch, G. Waltersdorf, J. Theisen, and J. Streicher: “AC Drives and Soft
Starter Application Guide”, NETA WORLD Winter 2008-2009.
[3] JG Roos: “DSM Energy Efficiency Improvement Opportunities in a Hot Strip Mill
by Using Variable Speed Drives”, (2006).
[4] Thailand Greenhouse Gas Management Organization (Public Organization):
“Evaluation of the Carbon Footprint for Organization Guideline”, (2011),
pp.64- 65.
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Thank you
Q & A