Burners for Oxy Burners for Oxy-coal coal A review of Oxy A review of Oxy-coal Burner Research coal Burner Research G.Coraggio G.Coraggio and T. and T. Klajny Klajny IFRF Livorno, Italy IFRF Livorno, Italy
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Burners for OxyBurners for Oxy--coalcoalA review of OxyA review of Oxy--coal Burner Researchcoal Burner Research
G.CoraggioG.Coraggio and T. and T. KlajnyKlajnyIFRF Livorno, ItalyIFRF Livorno, Italy
The content
1. Past oxy-combustion projects in IFRF
2. Critical aspects in oxy-coal combustion
3. Burner examples• AE&E oxy-coal burner (Austrian Energy)
• TEA-C burner (ENEL)
2
Oxy-com. projects in IFRF in the past
• First document related to combustion with air enriched with oxygen:
Michaud M, Suggestions on the use of oxygen in the experimental furnace in IJmuiden,
C85/bc/1, 1955.
• IFRF document G24/y/1, 2006 - List of all the IFRF documents related to combustion
with oxygen-enrichment (88 documents, about 50 F and K document)
Main IFRF Projects on Oxy-combustion:
1. OXYFLAM project (1994-1998)Oxygen and natural gas combustionOxygen and natural gas combustion
2. Advanced Power Generation (APG) project (1993-1995)Oxygen and coal combustion
3. TEA-C burner (ENEL) (2009-2012)
4. AE&E burner (Austrian Energy) (2009-2012)
5. RELCOM project (2011-2015)
3
Oxy-fuel combustion
Oxy-fuel combustion regimes
oxygen mole fraction and the preheat temperature of the reactant stream
4
Oxy-fuel combustion
Oxy-fuel combustion regimes
oxygen mole fraction and the preheat temperature of the reactant stream
5
Relcom
Conventional combustion system:
Fosper ENEL facilities
6
Conventional combustion system
We want to modify it to oxy-coal combustion
7
1. Oxygen feeding line
2. Flue Gas Recycle line
Combustion system with FGR
Blue lines: oxygen injection
Pink lines: recycled flue gas
8
Combustion system with FGR
Blue lines: oxygen injection
Pink lines: recycled flue gas
N2 → CO2
9
Stabilisation of the flame
Matching mass ratio, momentum or velocities we face ignition delay problem
10
Stabilisation of the flame
11
Stabilisation of the flame
• …
12
• Increase oxygen concentration • Decrease primary stream velocity
Oxygen concentration for oxy-coal burners
Hjartstam et al. using German lignite at Chalmers 100kW unit
• The stable combustion could not be established with O2 mole fractions lower than 25% in the feed gas streams
• improved combustion stabilisation was achieved when maintaining a stoichiometric fuel-oxygen ratiowhen maintaining a stoichiometric fuel-oxygen ratioand increasing the oxygen concentrationin the staging streams from 25% to 29%
13
Air combustion Oxy-coal combustion Oxy-coal combustion
No stable combustion Stable combustion
21% O2 < 25% O2 25% to 29% O2
Oxygen concentration for oxy-coal burners
Liu at al:
• the O2 mole fraction in the mixture of O2/CO2 has to be raised to 30% or higher to match the gas temperature profile of oxy-coal combustion to that of air-coal combustion
Kimura at al:
• During their trials an unstable, dark combustion • During their trials an unstable, dark combustion zone with high unburned carbon (UBC) was reportedwhen the O2 concentration in the secondary streamwas lower than 30%
• However, when a central oxygen nozzle was usedto directly inject O2 in the centreline axial directionof the burner, the flame was stable
14
Injection of pure oxygen
Nozaki et al.:
• the direct O2 injection improved combustion stability and coal ignition comparing to the conditions with the same O2 content in the combustion gas but without O2 injection
15
Oxygen injection nozzles
Praxair reviewed various oxygen nozzle prototypes for flame stabilisation
16
Oxygen injection nozzles
Praxair reviewed various oxygen nozzle prototypes for flame stabilisation
Oxygen injection into primary air
on temperature profile of the flame
17
Tests at 1.2 MWth industrial scale burner facility of Alstom Power
O2 injection in various streams
Standoff distances of co-axial turbulent diffusion oxy-coal flames:
• attached stable flame for > 52% O2 in the secondary stream
• or shifting O2 injection from secondary stream to the primary stream(maintaining the overall oxygen concentration at 40%, a constant λ=1.15)
18Zhang et al.- Tests at 40 kW non-swirl burner at the University of Utah
O2 injection in various streams
Standoff distances of co-axial turbulent diffusion oxy-coal flames:
• attached stable flame for > 52% O2 in the secondary stream
• or shifting O2 injection from secondary stream to the primary stream(maintaining the overall oxygen concentration at 40%, a constant λ=1.15)
19Zhang et al.- Tests at 40 kW non-swirl burner at the University of Utah
However, preheating the secondary stream from 216°C to 271°C makes the flame more stable.
Burnout in oxy-coal combustion
Volatiles combustion Char particles
20
Summary
Retrofitting units to oxy-coal combustion we have to solve:
1. Increasing complexity of the system
2. stabilisation of the flame - Oxy-coal ignition delay problem
3. Overall oxygen concentration to match heat transfer
4. Which stream to inject pure oxygen to4. Which stream to inject pure oxygen to
5. Methods of injecting pure oxygen
6. Preheating the RFG streams
7. Different combustion characteristic of the fuels
21
Other areas in oxy-coal combustion
• Flame temperature to avoid high NOx emissions
• Scaling criteria for Oxy-coal burners
• Oxy-coal combustion and gas-side corrosion
(higher concentration of CO2, H2O, SO2/SO3, HCI)
• Ash deposition and slagging• Ash deposition and slagging
• Exhaust gas cleaning
• Safety issues with oxygen lines
• Flame monitoring and control system
22
Oxy-coal burners review
1. TEA-C burner (ENEL)
2. AE&E oxy-coal burner (Austrian Energy)
23
The furnace – FOSPER
• …
24
Test fuel – Sebuku coal
• Indonesian Sebuku coal was used during all tests
composition of the coal cumulative particle size distribution
25
TEA – C burner (Triflusso ENEL Ansaldo)
ENEL Oxy-coal burner tests
2.5MW conventional low NOx burner for coal, oil and gas combustion
Tested in oxy-coal condition
26
TEA-C burner in oxy-coal comb.
• …
27
Optimisation of recycle ratio (oxy comb.)
1. The higher recycle ratio the higher NOx emission
2. The higher O2 in flue gas the higher NOx emission
28
Temperature profiles
Recycle ration = 0,61 (oxy comb.)
Port 1 – 170 mm from the burner
Port 2 – 460 mm from the burner
29
NOx profiles (oxy comb.)
30
The emissions in oxy combustion are lower
than conventional combustion for R<0,64
AE&E burner
This burner was designed by AE&E and tested for Austrian Energy
2.5MW coal burner designed for oxy-fuel combustion
31
• Conventional air-NG firing
• Conventional air-coal firing
• Coal combustion with pure oxygen and recycled flue gas
Tests parameters
Flame was always stable during the tests both for:
• Air-coal combustion (baseline)
• Oxy-coal combustion
NOx emission was measured for operative parameters:
• Air-coal combustion:
• Swirler setting
• Thermal load
• Oxy-coal combustion:
• Swirler setting
• Thermal load
• Pure oxygen injection
32
NOx emission vs. swirler position
air combustion oxy-coal combustion
33
NOx emission vs. thermal load
air combustion oxy-coal combustion
34
Temperature profiles
A higher temperature in the centre of the flame in the air-combustion case
35
NOx profiles (oxy comb.)
the NO production via
thermal mechanism is
favoured
36
A peak of NO
concentration can be
spotted close to the high
temperature peak
The burner after tests
the burner throat and the gas lance after the trial
Despite the fact that the burner underwent very hard conditions because of the pulses in the coal feeding, no particular sign of damage were reported
37
Concluding remarks on tests
• AE&E and TEA C burners: good stable performances in oxy-RFG conditions, both with NG and coal
• AE&E burner was stable for all tested conditions
• Both burner show lower NOx emission with oxy-coal combustion
• Modified FOSPER plant is suitable for oxy-combustion studies
• Important air in-leakage is present at high R (Ljungstrom/dry mode-evaluated on the basis of mass balances)
• Air in-leakage is resulted the major cause of the level of the CO2 in the flue gases lower than expected.
38
• The in-flame data are to be used to develop a better understandingof the changes in the chemical and physical processes involved in oxy-coal combustion.
• Overall and In-flame measurements provide good sets of data for more fundamental analysis (flame structure, NOx, carbon in ash, etc.)
Concluding remarks on tests (2)
• They can also provide modelers with a starting hint for the development of oxy-combustion flame mathematical simulation.
39
Thank youThank you
Related Documents
