GTG Webinar #3: Public Release and Knowledge Sharing Session on Minimum Load/Ramp Test Procedures for Coal Based Thermal Power Plants (TPPs) ...
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GTG Webinar #3: Public Release and Knowledge Sharing
Session on Minimum Load/Ramp Test Procedures
for Coal Based Thermal Power Plants (TPPs)
Renewable Integration and Sustainable Energy (RISE) Initiative
Greening the Grid (GTG) Program
A Joint Initiative by USAID and Ministry of Power
April 27, 2020 (Monday)
1
7 PM IST / 9:30 AM EDT
2
Coal Based Flexible Power Generation with NTPC and
GSECL
2
Scope & Expected Outcomes
Pilot Scope
• Examine techno economic feasibility of faster ramp rates and
lower technical minimum in two (2) units each at NTPC (Jhajjar
& Ramagundam TPS) & GSECL (Ukai TPS)
• Support implementation of recommended measures by NTPC &
GSECL for achieving flexible operations of the units
Expected Outcomes
• Specific recommendations for changes to O&M procedures/standards
and required design modifications based on Indian grid conditions
• Optimize plant availability and efficiency (including part load
efficiencies)
• Evaluation of incremental cost of generation due to cyclic operation
• Regulatory/policy advocacy & implementation strategy for identified
3
interventions 3
Pilot supports technical interventions and operational changes at NTPC’s Ramagundam (200 MW unit), Jhajjar (500
MW unit) and GSECL Ukai TPS (200MW & 500 MW unit)
Stage 1:Techno Stage 2: Regulatory Stage 3: Pilot Stage 4: Scale up
Economic Assessment Pathway and Fleet Implementation
& Roadmap Level Strategies • Assist in fleet-wide
• Technical Assistance in
• Technical due diligence • Assistance in framing pilot / fleet level implementation and
and detailed feasibility Regulatory Mechanisms implementation to national scale up
assessment for Flexibility NTPC
• Capacity building of
• Establishing reliable costs • Assistance in building • Leverage private operators –
of flexibilisation – capex fleet level strategies for partnerships and Procedures and
as well as opex NTPC / GSECL contribution in Operational Toolkits
investments
2017 2018 2019 2020
• Pilot Conceptualization • Technical Assessment • Regulatory Frameworks for • Facilitate fleet-wide
reports completed for flexibilization to CERC & GERC adoption and
• On Boarding of Technical
Assistance (TA) Firm NTPC and GSECL units • Pilot Test Runs & Fleet Wide Strategies National scale up
• Stakeholder Discussions & • Executive Exchanges to US • Changes to Operating Procedures • Knowledge
Data Collection • Knowledge Dissemination Dissemination
• Executive Exchanges & Knowledge Workshops
• TA Implementation Plan Workshops Dissemination Workshops 4
Glimpses from the field
Gujarat’s Low Load Test Runs
GSCEL, UKAI unit
March 2-4, 2020
NTPC Mauda Low Load Test
Runs
February 15-17, 2019 (Run
#1)
May 28-29, 2019 (Run #2)
5
6
Public Release and Knowledge Sharing Session
on Minimum Load/Ramp Test Procedures for Coal
Based Thermal Power Plants (TPPs)
Shri Prakash Tiwari Michael Satin
Director Operations Director - CLEEO
NTPC Ltd. USAID/India
7
8
Content
• Why do you need a test run ?
• Emerging Scenarios and Flexibility requirements
• Options vs Costs for Coal Flexing in India
• Harsh Realities of Cyclic Operation
• Criteria and Selection of units for Flexibilization
• Test run Procedures
• Key Takeaways from the field Tests
• Combustion Optimization
• Recommendations
• Best Practices
• Conclusion
9
Why do you need a test run & till what level?
• What happened during the 9 minutes/9pm on 5th
April? Do you see a relevance of coal units?
• Act now. Coal Units have to prove the reasons for
their existence for a greener role.Questions from Participants
- What is the future of coal based thermal power plants.
- Whether coal based thermal power plants are viable.
- At what minimum load a 660MW super critical thermal unit can be run
without oil support.
- How long it can be run at that minimum load?
- What should be the maximum limit for ramping up & down to meet
the
grid requirement
- How frequently the load change will occur during the day (tentative
forecast).
- Weather this load change will be based on merit order or some other
methodology will be applied.
- At Minimum load unit heat rate & APC will be effected, weather this
will be considered in calculating target Heat rate for those units which
are operating under PAT cycle.
- What will be the impact on boiler life cycle?
11Is this an economic despatch as claimed under SCED ?
Scheduling Effect on running of ISGS Stations –One example(April 20th)
Safety Issues
O&M cost – under
recovery
Ramp@2% Ramp@2% Need for investments in
30% down 43% down retrofits
Would the dispatcher
15% down schedule this way if
there were provisions
for additional O&M
cost recovery?
There is a clear
misalignment in the
understanding amongst
Generator, Despatcher
and Regulator
If we consider a significant load following of ramp size>15%,then we have at least 7 significant load
12c
followings
Each of this event costing >2lakhs for the generator, which the generator has no way to recover from
the present regulatory mechanism.
Is it still better than shutting down and starting the unit repeatedly?Emerging Scenario & Need for Flexibility
With SCED mechanism in
place-already, the low merit
order Stations have started
facing the heat of frequent With 175 GW RE …… Falling PLF for coal stations
changes in schedule
Units are typically facing
around 15 or more significant
load-followingg in a day.
Units which are unable to
reduce their minimum load
are asked to start-stop
There is no compensation for
recovery of O&M costs
incurred due to increased
cycling on the units
It is important for the station
to know what value of
flexibilization it can best
deliver
Coal units will have to compete with other resources for delivery of balancing power
13cHarsh Realities of Cyclic Operation
• Flexible operation is a difficult mode of operation
and even the most conservative approach will • Flexing with lack of awareness,
increase plant O&M costs along with per MW can be disastrous
variable costs
• Well known that cycling causes
• However those plants that can operate flexibly to damage and when equipment
meet market conditions while minimizing the degrades, performance
financial impact of operating in this environment,
degrades.
will continue to be dispatched, at least for the near
future.
• Damage not immediate but
• Investments in retrofits can enhance the flexibility to accumulated and not easy to
a large extent quantify
• Revisiting the operational procedures, Training of • By the time symptoms of
O&M manpower can enhance flexibilization damage is visible it may have
become very costly to Correct
• Proactive participation of stakeholders in enhancing
latent system flexibility can be driven by Policy and
regulatory interventions
14Harsh Realities of Cyclic Operation
• The limitations of a particular mode of operation are often not known. Sometimes they are due to faulty
operational practices .
• Subsequent flexibility in the units can be unlocked by procedural changes and upgrade of C&I systems.
• Proper operational strategies and procedures can minimise the damages and costs.
• There is no “one-fit-for all’ solution for flexibilization. Units need to identify what is best and cost effective
intervention required on individual level through test runs
15Options vs Costs for Coal Flexing in India
Does It Matter How Unit Flexibility is achieved?
Trade-off between Investment and Return
No required to be done
Intervention
(Business as
Usual)
Operational
Alterations
Operational
Alterations
Operational Cost
and
Cost of Flexible Control & Operational Alterations
Operations Instrumentation + C&I+ Digitalisation/Fleet wide
Monitoring Operational
Alteration +
Cold Start C&I +
Digitalisatio
Warm Start n/Fleet wide
monitoring+
Hot Start
Technologic
High Turn al
Down/MTL Intervention
Fast Ramp
Load Following
Increasing Investment
Operational
Control & Fleet
Changes / Technological
Instrumentatio Monitoring/Maintenance Digitalisation
Training Interventions
n (C&I) Practices
Coal
Blending ▪ Modify
▪ Upgrade
Technical Interventions for Flexible Operations
16Identification of Units for different modes of operation
Category Metrics
ECRRs.2.5/KWH)
Load GCV >2800,VM > 15%
Units>25 Years
Flex with
Unit size-200 and above
Efficiency HR> 2500
Retrofit
Flexible Daily ECR>> State M.O.
(unlikely to get schedule in 2022)
Start HR>2500, GCV>3400
Retire/replace >25Years
HR>2600
Unit sizesTest Run Procedures
18Gujarat’s Low Load Test Runs
GSCEL, UKAI unit
March 4th, 2020
NTPC Mauda Low Load Test Runs
NTPC, Mauda Unit
February 15 – 17, 2020
19Test Run Procedures
Objectives Testing Approach
• Evaluate the Unit’s response to: • Gradual load reduction until a
challenge/ obstacle occurs. (All loops in
– Ramp up/ Ramp down characteristics
between new/ old minimum load and
auto)
base load evaluation. • Define an approach to overcome any
– Response to minimum stable load such obstacle/s.
(Target: 40% minimum load without any
changes in plant configuration) – Manual intervention
• Identifying of the process limitations/ – Changing operation regime (e.g.
restrictions (thermal, mechanical,
changing combination of mills,
aerodynamically, operation) during the
new/ old minimum load changing main steam pressure)
• Check of control system and evaluation – Implementation of supplementary logic
of aging of equipment in the DCS
• Identification of Operational procedures
– Changes in set points of control loops
• Identification of retrofits for this plant -
Required and Possible – Revising the sliding pressure curves/PA
flow curves..
20Expected Issues during the Tests
• Poor combustion/poor flame
• Drum level control/TDBFPs
• Hot reheat steam temperature
• Main steam temperature
• Flame scanners
• Primary Air Fan Stalling
• Coal Pipes choking and improper
balancing between different coal
pipes
• Flue gas exit temperature
approaching acid dew point
• Turbine vibrations
21Description: 500 MW Unit
• Boiler: Drum type subcritical design,
Two pass boiler, Tilting tangential
fired, Controlled circulation with
rifled tubing, Balanced draft furnace
with fusion welded water walls,
Radiant reheat type
• Turbine: 3 cylinders turbine
consisting of HP, IP and LP module,
Single flow HP Turbine with 17
reaction stages, Double flow IP
Turbine with 12 reaction stages per
flow, Double flow LP Turbine, with 6
reaction stages per flow, • Coal Quality during the test:
Conventional governing system, 2- – GCV in the range of 2700-3930
pass double flow condenser Kcal/Kg
– VM-19-22%
– Ash-40-47%
22Field Tests done
Low Load
From 500MW to 198MW & BACK with hold points Ramp Rate
▪ 500-360 MW- 5mills
▪ 360MW-300MW- 4mills ▪ Ramp up/down of 1%, & 3% were
▪ 300MW-275MW-4mills checked at different load range
▪ 275-198MW-3 mills(C,D,E) ▪ CMC on except during ramp up @3%
from 360-500MW when CMC
response was very fast (CMC made off)
▪ There was a difference in CMC
Turndown of Mills response and actual ramp achieved at
Loading of mills were reduced till 50% load lower loads (for 3% ramp)
If any mill was required to be loaded below 50%,it was ▪ Unacceptable deviation in parameter
withdrawn and other mills loaded (SHTemp, RH, excessive SH spray)
▪ Due to thermal shock, falling of big
sized clinker which dislocated the SC
chain
Review of sliding pressure curve and PA flow ▪ Sliding pressure needed to be
curve modified
Conclusion: Upgrade of C&I system
needed changes in operational procedures
(eg- Soot blowing, Burner tilt operation,
Unit assessment with HP heaters bypass air flow, mills turndown)
23Issues faced during the test runs
• In all the test runs conducted, it was • Steam coil APH was not available/not used
observed that control loops were not tuned regularly
for low loads
• Burner tilts were on manual- key variable • Sliding pressure was in service
having significant influence on steam • The partial steaming of ECO occurred at low
temperature parameter control
load. Which can be allowed only for a short
• More number of mills than required were time.
kept in service to take care of the exigencies
of mill tripping. • Increase in SH temperature during load
ramping
• Primary air flow maintained higher than
anticipated values as mills were operated at • High SH spray
full mill air flow irrespective of the mill
loading • Jerky operation of feed water flow on
opening of the recirculation valves at low
• Secondary air flow is very much less than load.
the desired level resulting in no or low
windbox dP at part loads • The analysis of Dirty air flow results reveals
• WB pressure was improved by closing the that there is a good degree of imbalance in
secondary air dampers of the mills that were coal flow across the pipes at low load.
not in service and optimising the primary air flow
24Key Takeaways from the field Tests
25COMBUSTION OPTIMISATION
Improving Mill Turndown
Combustion
must be
completed
here
Residence
Time
Optimisati
on
Auto Coal Sampler
Fuel Firing System Optimization Package
for low load oprn:
• Air/Fuel ratio
Flame scanners modifications • Coal pipes dynamic balancing
Burner modification • Auto mill start
• Coal analyser
26Combustion Optimization to attain Minimum load reduction potential
• Compliance to the NFPA (National Fire Protection Association) guidelines.
• Balancing of Coal flow across the coal pipes • The standards of NFPA 8502 which requires that the airflow is maintained
at or above the purge rate (not less than 25% of the full load mass airflow)
• Fuel/Air ratio, Combustion air
during all operations must never be violated.
• Never add air to a dark smoky furnace. It is advisable to trip the unit &
• Furnace exit gas temperature
remove all ignition sources, then purge thoroughly before restarting.
• Improve Mill turndown- Minimum load on a mill – 50%
• Bottom Ash & Fly Ash Unburnt
• Flue gas temperature and excess air stratification
• Flue gas oxygen /Excess air level
• Temperature in the range of 70-930C with low VM coal (15-30%)
• Coal mill inlet/outlet temperature
and a range of 60-800C. Maintaining a slightly higher mill outlet
temperature at low loads will help faster stabilization of the
flame.
• Primary Air header pressure
• The primary air flow in mills to be as per air/fuel ratio
• Pulverized coal flow velocity /Temperature of coal
pipes
• Optimization of secondary air flow. Tertiary vanes of elevations that are
• Windbox pressure not in service to be reduced, ensuring just adequate flow for burners
cooling. Measurement of secondary air flow at individual burners to be
• Burner Tilt provided. This will help in further optimization of the process.
• Flame scanners
• Coal fineness
• Selection of burner
27Key Takeaways from the field Tests
• Measurement of excess air for
• Sliding pressure induces a combustion /Flue gas O2
sluggish load response for drum measurement may be validated
boilers. But the advantages are with CO measurement as CO is
unaffected by air in leakages.
far more. Modification of sliding
pressure curve (increased • Traditionally, C&I specs aimed at
automatic operation in the range
slightly) in small steps is to be of 60% to 100% MCR. The
done to ensure that there is no automatic control at lower loads
steaming in economizer and no becomes poor and sluggish mainly
DNB. due to changing unit response
characteristics.
• BFP recirculation valves must be • Another limitation with low load
able to operate at intermediate operation in the improper sizing
positions (inching type). of many control valves for low
load or low flows operation,
causing poor control response and
sometimes hunting of valves.
28Key Recommendations • Modified Procedures for low load, start-
• C&I System is crucial: up and lay-ups
• Fine tuning of Existing CMC Logic • Replacement of R/C valves for BFPs
• MS ,RH , Flue Gas Temperature Control
• Modification of sliding pressure curve
• Unit Control and Automatic Mill Operation (Mill
Scheduler) • Modification of PA fan curve
• Boiler lifetime monitoring
• Including operator’s view of the process
– Some available solutions for lifetime
monitoring (displayed on LVS or other screen) to
• COSTCOM(Intertek) include the actions that may be needed
• EPRI (BLESS) during the particular operating regime.
• PowerGEN Creep Fatigue Monitoring Eg Start-up/ Shutdown/Minimum Load
• ODAS(Australia) • Installation of Steam coil air pre-heater
• ERA Plus System • Replacement of actuators: to improve
• PADO(STEAG) fast load ramping and to meet the
• SIEMENS requirements of low load operation
• Flexsuite (GE)
• Automatic Plant Start-up
• Modifications for hot filling of boiler from
a running unit
• Combustion Optimization using an Online Coal Flow
Measurement
29Best Practices
• Increased ramp rate with Rapid response for • N2 blanketing of all DM storage tanks
frequency control
• Exploiting the storage capabilities of mills
• The Condensate Throttling
• Advanced process control • Automatic plant startup and guide
• Plasma Ignition System • Digital Boiler Plus (DB+) Low Load Advisor
• Automatic Mill Scheduler
• Heating blankets used to keep turbine warm
• Fully automatic operation of all burners/mills during stand-stills by balancing the upper and
without manual intervention between a load lower casing and thus avoiding the bending of
of 0 and 100 % the shell
• Automatic switching of burners/mills on/off
• On burner failure automatic selection of the
best alternative burner
• Automatic adaptation to changed load
requirements
• Plant operators can remove individual burners
from the regime of the burner and mill
• scheduler while the remaining burners
continue to be controlled optimally
30In Summary…. • For supporting 175 + GW of RE integration, coal units are required to run on increased cyclic mode. • Units will be required to identify the best value they can provide to the power system. • There is no “one-fit-for all’ solution for flexibilization. Units need to identify what is best and cost effective intervention required on individual level through test runs • Preparation for flexibilization will need the identification of limitations and the specific interventions required to be carried out on units. • In most of the cases, modification of Operational procedures and upgrades of C&I system can unlock substantial flexibility in the units.
Thank You for Your Time
Stay Safe. Maintain social distancing
We will deliver any information you require at your digital doorstep• RISE Contracting Officer
Representative: Monali Zeya
Anjan Kumar Sinha Hazra, USAID India,
Senior Advisor mhazra@usaid.gov
USAID GTG-RISE Initiative • Chief of Party:Tushar Sud RISE,
tsud@deloitte.com
sinha.anjan@gmail.com | Mob:+91 9650992971
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