Design Concepts to Improve Energy Efficiency in a Petroleum Refinery
1
Design Concepts to Improve Energy Efficiency in a Petroleum Refinery Group 10: Kamal Brahmbhatt, Gurpreet Chahal, Garima Dua, Fariha Siddiqui Advisors: Ali Elkamel, Ushnik Mukherjee, Yusuf Ali (Imperial Oil) INTRODUCTION OPTIMIZATION ALTERNATIVES METHODOLOGY BASE CASE PFD PROCESS RESULTS ECONOMIC FEASIBILITY ENVIRONMENTAL IMPACT CONCLUSIONS & RECOMMENDATIONS HEALTH & SAFETY REFERENCES AKNOWLEDGEMENTS Problem Inefficient use of energy in refineries results in high OPEX and loss of valuable energy Opportunity Steam distribution losses represent 18% of total energy losses Objective Improve energy management system in steam distribution network to: • Minimize energy losses • Maximize cost savings • Reduce global CO 2 emissions Case #1 Optimize the steam distribution network by replacing PRVs with back-pressure turbines (BPTs) to produce electricity and minimize energy losses (MILP Problem) Case #2 Redesign the steam distribution network system by determining the optimal configuration of steam turbines so that energy losses through the PRVs are minimized (MINLP Problem) Case 1A Case 1B Objective Function Min Cost = [Capital Cost of BPTs + O&M costs – Electricity cost] Min Energy Loss = ∑ Energy loss through PRVs Constraints • Constant steam header pressure • Constant flowrate through steam headers • Constant steam output from boilers Same as Case 1A Case 2A Case 2B Objective Function Max Power Out = ∑ Power output from each steam turbine Max Power Out = Case 2A Results + ∑ Power output from BPTs Constraints • Constant steam output from boilers • Energy balance between headers is constant • Each turbine & PRV can only be selected once • Capacities of turbines and PRVs are constant Same as Case 2A Literature Review & PFD Selection Base Case Energy/Power Output Optimization Techniques Selection (Case 1A, 1B, 2A, 2B) Decision Variables Specification Constraints Definition Economic Feasibility Environmental Impact Optimum Case Selection No Yes Are the results optimum? Objective Function Definition Engineering Tools • GAMS Software for optimization • Microsoft Excel for data analysis 375 psig steam users Deaerators T11 T12 T13 T14 T15 T16 T32 Desuperheater Water T31 600 psig steam 375 psig steam 150 psig steam 75 psig steam 50 psig steam Condensate Vent 4 10 68 4 9 48 0 42 378 843 130 82 1 14 5 5 20 20 255 255 178 52 124 330 173 98 98 173 0.3 0.3 5 330 1136 392 53 95 50 1608 145 32 T21 2 2 3 119 213 36 11 486 285 0 136 145 21 289 36 4 263 250 To Boilers 13 2 Losses 8 Losses 5 Losses 600 psig steam users 375 psig steam users Waste Heat Boilers Utility Boilers CHP Boilers 150 psig Boilers 75 psig Boilers 75 psig steam users 50 psig steam users 150 psig Boilers 50 psig Boilers Condensate users Demin. Water make-up Flash Steam from B/D Flash Steam from B/D PRV 1 PRV 2 PRV 3 PRV 5 PRV 4 PRV 6 375 psig steam users Deaerators T11 T12 T13 T14 T16 T32 Desuperheater Water T31 600 psig steam 375 psig steam 150 psig steam 75 psig steam 50 psig steam Condensate Vent 4 0 0 9 0 0 42 378 843 130 82 1 14 5 5 20 20 255 255 17 8 52 124 33 0 98 98 0.3 0.3 5 330 1136 392 53 95 50 1608 14 5 32 T21 2 2 3 119 213 36 11 48 6 285 0 136 145 2 1 289 36 4 263 250 To Boilers 13 2 Losses 8 Losses 5 Losses 600 psig steam users 375 psig steam users Waste Heat Boilers Utility Boilers CHP Boilers 150 psig Boilers 75 psig Boilers 75 psig steam users 50 psig steam users 150 psig Boilers 50 psig Boilers Condensate users Demin. Water make-up Flash Steam from B/D Flash Steam from B/D T15 173 17 3 0 BPT 2 68 68 BPT 5 48 48 BPT 1 10 10 4 4 BPT 3 BPT 4 9 0 0 5 10 15 20 25 30 Case 1A Case 1B Case 2A Case 2B 8.48 11.44 24.89 25.97 Total Energy Savings (million kwh/yr) Potential Energy Savings Case 1A Redirect flows from PRVs 2 & 5 to BPTs installed in parallel Case 1B Redirect flows from PRVs 1 to 5 to BPTs installed in parallel Case 2A Reconfigure the steam network system subjected to the constraints defined (refer to PFD for optimized case #2) Case 2B Redirect flow from PRV 3 to BPT installed in parallel. Steam flow through PRV 2 is insignificant, hence infeasible to install a BPT 0 20 40 60 80 Case 1A Case 1B Case 2A Case 2B CO 2 savings (million lbs/year) Potential CO 2 Savings Natural Gas Coal Case 1A Case 1B Case 2A Case 2B NG Coal NG Coal NG Coal NG Coal No. of Cars 730 2,148 985 2,897 2,143 6,304 2,237 6,580 No. of Households 477 1,403 643 1,893 1,400 4,119 1,461 4,299 • CO 2 emissions savings can be translated into everyday terms such as annual emissions from cars and number of households 375 psig steam users Deaerators T11 T12 T13 T14 T15 T16 T32 Desuperheater Water T31 600 psig steam 375 psig steam 150 psig steam 75 psig steam 50 psig steam Condensate Vent 4 0 0 0 42 378 843 130 82 1 14 7.5 7.5 4 4 379.5 33.5 124 495 179.7 27 0.45 0.45 5 495 1136 392 53 95 50 1608 145 32 T21 3 3 3 119 213 36 11 486 285 0 136 145 21 289 36 4 263 250 To Boilers 13 2 Losses 8 Losses 5 Losses 600 psig steam users 375 psig steam users Waste Heat Boilers Utility Boilers CHP Boilers 150 psig Boilers 75 psig Boilers 75 psig steam users 50 psig steam users 150 psig Boilers 50 psig Boilers Condensate users Demin. Water make-up Flash Steam from B/D Flash Steam from B/D BPT 69 69 379.5 179.7 27 2.5 CASE 1 CASE 2 Case 1A Case 1B Case 2A Case 2B • Potential CO 2 savings from selling additional electricity to a natural gas (NG) or coal fired power plant $0 $200,000 $400,000 $600,000 $800,000 Case 1A Case 1B Case 2A Case 2B $117,569 $77,244 $631,464 $617,096 Total Cost Savings ($/yr) Potential Yearly Cost Savings 0 2 4 6 8 10 Case 1A Case 1B Case 2A Case 2B Payback Period (Years) Payback Period & Capital Investment Payback Period (yrs) 4.2 9.2 0 1.5 665,385 1,223,833 0 192,500 Capital Investment ($) Optimal Solution Case 2A Reconfigure the steam network system subjected to the constraints defined • 22M lbs in CO 2 savings (NG basis) • 66M lbs in CO 2 savings (Coal basis) 25M kWh/yr in energy savings ~ $630,000 in net profit/yr $0 in capital investment • We would like to express our gratitude and appreciation to Ushnik Mukherjee for providing assistance with GAMS programming • We would also like to thank Prof. Ali Elkamel and Yusuf Ali for providing valuable advice regarding the project • Venkatesan, V., & Lordanova, N. (2003). Proceedings from the Twenty-Fifth Industrial Energy Technology A case study of Steam System Evaluation in a Petroleum Refinery. Houston: Armstrong Service. • OSHA. (2015). Section IV: Chapter 2 - Petroleum Refining Process. From U.S. Department of Labor | Occupational Safety & Health Administration: https://www.osha.gov/dts/osta/otm/otm_iv/otm_iv_2.html#3 • Constantine, S., & Phillips, K. (2003). Steam System Efficiency Improvements in Refineries in Fushun, China. Beijing: Beijing Tuofeng Armstrong Steam System Energy Conservation Technologies. • Magalhães, E., Wada, K., & Secchi, A. (2005). Steam production optimization in a petrochemical industry. Mercosur Congress on Process Systems Engineering. HAZARDS CONSEQUENCES MITIGATION STEPS High pressure steam build-up • Pipe rupture • Explosions which can lead to fatalities • Installation of pressure relief valves (PRVs) Steam Leaks (distribution) • Health risks associated with severe steam burns • Steam can displace O 2 in an enclosed area resulting in an asphyxiation hazard • Ensure proper insulation of pipes • Perform walk down surveys on routine basis to detect steam leaks or "out-of-tolerance" conditions • Use of piping material suitable for HP steam Inadequate amount of feedwater to the boilers • Risk of running boilers dry leading to extreme temperatures • Explosions which can lead to fatalities • Usage of suitable process control measures to supply fuel in accordance with boiler feedwater flow Metal corrosion • Can lead to wall thinning and catastrophic failures of equipment • Usage of high-grade material • Application of coatings • Change in procedures to minimize corrosion possibilities • Regular corrosion monitoring and maintenance Noise resulting from high steam velocities • Can lead to hearing loss • Use of double hearing protection S E V E R I T Y L E V E L Table 2: Health & Safety Analysis Table 1: Translation of CO 2 emissions into everyday terms Note: All numbers in 1000 lbs/hr Note: All numbers in 1000 lbs/hr Note: All numbers in 1000 lbs/hr
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Transcript of Design Concepts to Improve Energy Efficiency in a Petroleum Refinery
Design Concepts to Improve Energy Efficiency in a Petroleum Refinery
Group 10: Kamal Brahmbhatt, Gurpreet Chahal, Garima Dua, Fariha Siddiqui
Advisors: Ali Elkamel, Ushnik Mukherjee, Yusuf Ali (Imperial Oil)
INTRODUCTION
OPTIMIZATION ALTERNATIVES
METHODOLOGY
BASE CASE PFD
PROCESS RESULTS
ECONOMIC FEASIBILITY
ENVIRONMENTAL IMPACT
CONCLUSIONS & RECOMMENDATIONS
HEALTH & SAFETY
REFERENCES
AKNOWLEDGEMENTS
ProblemInefficient use of energy in refineries results in high OPEX and loss of valuable energy
OpportunitySteam distribution losses represent 18% of total energy losses
ObjectiveImprove energy management system in steam distribution network to:
• Minimize energy losses • Maximize cost savings• Reduce global CO2 emissions
Case #1Optimize the steam distribution network by replacing PRVs with back-pressure turbines (BPTs) to produce electricity and minimize energy losses (MILP Problem)
Case #2Redesign the steam distribution network system by determining the optimal configuration of steam turbines so that energy losses through the PRVs are minimized (MINLP Problem)
Case 1A Case 1B
Objective Function
Min Cost = [Capital Cost of BPTs + O&M costs – Electricity cost]
Min Energy Loss = ∑ Energy loss through PRVs
Constraints• Constant steam header pressure• Constant flowrate through steam headers• Constant steam output from boilers
Same as Case 1A
Case 2A Case 2B
Objective Function
Max Power Out = ∑ Power output from each steam turbine
Max Power Out = Case 2A Results + ∑ Power output from BPTs
Constraints
• Constant steam output from boilers• Energy balance between headers is constant• Each turbine & PRV can only be selected once• Capacities of turbines and PRVs are constant
Same as Case 2A
Literature Review &
PFD Selection
Base Case Energy/Power
Output
Optimization Techniques Selection(Case 1A, 1B, 2A, 2B)
Decision Variables
Specification
Constraints Definition
Economic Feasibility
Environmental Impact
Optimum Case Selection
No
YesAre the results
optimum?
Objective Function
Definition
Engineering Tools• GAMS Software for optimization • Microsoft Excel for data analysis
375 psig steam users
Deaerators
T11 T12 T13 T14 T15 T16
T32
Desuperheater Water
T31
600 psig steam
375 psig steam
150 psig steam
75 psig steam
50 psig steam
Condensate
Vent4
10
68
4
948
0
42 378 843 130
82
1 14
5
5
20
20 255
255178
52
124
330 173 98
98
173
0.3
0.3
5
330
1136
392
53
95
50
1608
145
32
T21
2
2 3 119
213
36
11
486
285
0
136
145
21
289
36
4
263
250
To Boilers
13 2 Losses
8 Losses
5 Losses
600 psig steam users
375 psig steam users
Waste Heat Boilers
Utility Boilers
CHP Boilers
150 psig Boilers
75 psig Boilers
75 psig steam users
50 psig steam users
150 psig Boilers
50 psig Boilers
Condensate users
Demin. Water make-up
Flash Steam from B/D
Flash Steam from B/D
PRV 1
PRV 2
PRV 3
PRV 5 PRV 4
PRV 6
375 psig steam users
Deaerators
T11 T12 T13 T14 T16
T32
Desuperheater Water
T31
600 psig steam
375 psig steam
150 psig steam
75 psig steam
50 psig steam
Condensate
Vent4
0
0
9
0
0
42 378 843 130
82
1 14
5
5
20
20 255
255178
52
124
330
98
98
0.3
0.3
5
330
1136
392
53
95
50
1608
145
32
T21
2
23 119
213
36
11
486
285
0
136
145
21
289
36
4
263
250
To Boilers
13 2 Losses
8 Losses
5 Losses
600 psig steam users
375 psig steam users
Waste Heat Boilers
Utility Boilers
CHP Boilers
150 psig
Boilers
75 psig Boilers
75 psig steam users
50 psig steam users
150 psig
Boilers
50 psig Boilers
Condensate users
Demin. Water make-up
Flash Steam
from B/D
Flash Steam
from B/D
T15
173
173
0 BPT 2
68
68
BPT 5
48
48
BPT 1
10
10
4
4
BPT 3
BPT 4
9
0
0
5
10
15
20
25
30
Case 1A Case 1B Case 2A Case 2B
8.4811.44
24.89 25.97
Tota
l En
erg
y Sa
vin
gs
(mill
ion
kw
h/y
r)
Potential Energy SavingsCase 1ARedirect flows from PRVs 2 & 5 to BPTs installed in parallel
Case 1BRedirect flows from PRVs 1 to 5 to BPTs installed in parallel
Case 2AReconfigure the steam network system subjected to the constraints defined (refer to PFD for optimized case #2)
Case 2BRedirect flow from PRV 3 to BPT installed in parallel. Steam flow through PRV 2 is insignificant, hence infeasible to install a BPT
0
20
40
60
80
Case 1A Case 1B Case 2A Case 2BCO
2sa
vin
gs (
mill
ion
lbs/
year
)
Potential CO2 Savings
Natural Gas Coal
Case 1A Case 1B Case 2A Case 2B
NG Coal NG Coal NG Coal NG Coal
No. of Cars730 2,148 985 2,897 2,143 6,304 2,237 6,580
No. of Households
477 1,403 643 1,893 1,400 4,119 1,461 4,299
• CO2 emissions savings can be translated into everyday terms such as annual emissions from cars and number of households
375 psig steam users
Deaerators
T11
T12
T13 T14 T15 T16
T32
Desuperheater Water
T31
600 psig steam
375 psig steam
150 psig steam
75 psig steam
50 psig steam
Condensate
Vent4
0
0
0
42 378 843 130
82
114
7.5
7.5
4
4
379.533.5
124
495 179.7 27
0.45
0.45
5
495
1136
392
53
95
50
1608
145
32
T21
3
3 3 119
213
36
11
486
285
0
136
145
21
289
36
4
263
250
To Boilers
13 2 Losses
8 Losses
5 Losses
600 psig steam users
375 psig steam users
Waste Heat Boilers
Utility Boilers
CHP Boilers
150 psig
Boilers
75 psig Boilers
75 psig steam users
50 psig steam users
150 psig
Boilers
50 psig Boilers
Condensate users
Demin. Water make-up
Flash Steam
from B/D
Flash Steam
from B/D
BPT
69
69
379.5 179.7 27
2.5
CASE 1 CASE 2
Case 1A
Case 1B
Case 2A
Case 2B
• Potential CO2 savings from selling additional electricity to a natural gas (NG) or coal fired power plant
$0
$200,000
$400,000
$600,000
$800,000
Case 1A Case 1B Case 2A Case 2B
$117,569$77,244
$631,464 $617,096
Tota
l Co
st S
avin
gs (
$/y
r)
Potential Yearly Cost Savings
0
2
4
6
8
10
Case 1A Case 1B Case 2A Case 2B
Pay
bac
k P
eri
od
(Ye
ars)
Payback Period & Capital Investment
Payback Period (yrs) 4.2 9.2 0 1.5
665,385 1,223,833 0 192,500Capital Investment ($)
Optimal Solution
Case 2AReconfigure the steam network system subjected to the constraints defined
• 22M lbs in CO2
savings (NG basis)• 66M lbs in CO2
savings (Coal basis)
25M kWh/yr in energy savings
~ $630,000 in net profit/yr
$0 in capital investment
• We would like to express our gratitude and appreciation to Ushnik Mukherjee for providing assistance with GAMS programming
• We would also like to thank Prof. Ali Elkamel and Yusuf Ali for providing valuable advice regarding the project
• Venkatesan, V., & Lordanova, N. (2003). Proceedings from the Twenty-Fifth Industrial Energy Technology A case study of Steam System Evaluation in a Petroleum Refinery. Houston: Armstrong Service.
• OSHA. (2015). Section IV: Chapter 2 - Petroleum Refining Process. From U.S. Department of Labor | Occupational Safety & Health Administration: https://www.osha.gov/dts/osta/otm/otm_iv/otm_iv_2.html#3
• Constantine, S., & Phillips, K. (2003). Steam System Efficiency Improvements in Refineries in Fushun, China. Beijing: Beijing Tuofeng Armstrong Steam System Energy Conservation Technologies.
• Magalhães, E., Wada, K., & Secchi, A. (2005). Steam production optimization in a petrochemical industry. Mercosur Congress on Process Systems Engineering.
HAZARDS CONSEQUENCES MITIGATION STEPS
High pressure steam build-up
• Pipe rupture• Explosions which can
lead to fatalities
• Installation of pressure relief valves (PRVs)
Steam Leaks (distribution)
• Health risks associated with severe steam burns
• Steam can displace O2
in an enclosed area resulting in an asphyxiation hazard
• Ensure proper insulation of pipes• Perform walk down surveys on
routine basis to detect steam leaks or "out-of-tolerance" conditions
• Use of piping material suitable for HP steam
Inadequate amount of
feedwater to the boilers
• Risk of running boilers dry leading to extreme temperatures
• Explosions which can lead to fatalities
• Usage of suitable process control measures to supply fuel in accordance with boiler feedwaterflow
Metal corrosion
• Can lead to wall thinning and catastrophic failures of equipment
• Usage of high-grade material• Application of coatings• Change in procedures to minimize
corrosion possibilities• Regular corrosion monitoring and
maintenance
Noise resultingfrom high steam
velocities• Can lead to hearing loss • Use of double hearing protection
S
E
V
E
R
I
T
Y
L
E
V
E
L
Table 2: Health & Safety Analysis
Table 1: Translation of CO2 emissions into everyday terms
Note: All numbers in 1000 lbs/hr
Note: All numbers in 1000 lbs/hr Note: All numbers in 1000 lbs/hr
