Firing Systems in the Focus of Energy Conversion · Hitachi Power Europe GmbH 1 Firing Systems in...
Transcript of Firing Systems in the Focus of Energy Conversion · Hitachi Power Europe GmbH 1 Firing Systems in...
Hitachi Power Europe GmbH 1
Firing Systems in the Focus of
Energy Conversion
Alfons Leisse
Hitachi Power Europe
26.02.2013
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What are the expectations on Firing Systems as state-of-the-art?
Reliability
Maintainability
Availability
Functionality
Flexibility
Effectivity
• Minimized Heat Losses (Unburned Carbon)
• Low Emission Values
• High Degree of Fuel Flexibility
Expectations on Firing Systems
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0
10
20
30
40
50
60
70
80
0 10 20 30 40
Net Calorific Value MJ/kg
Vo
lati
le M
att
er
(daf)
%
Lignite
Low Volatile
Coals
Low BTU
Lignite
Hard Coals
Sub-Bit.
PRB Coal
SA Coals
Indian Coals
Fuels
Wide Range of Coal Qualities
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Characterization of Solid Fuels
0
0.5
1.0
1.5
0 0.1 0.2 0.3 0.4 0.5
O/C
H/C
Anthracite
Bituminous
Coal
Lignite
Peat
Sub-bituminous Coal
Hard Lignite
Fuels
Biomass
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Coal Properties and their Influence on Design of Combustion System:
Ash, Moisture, Grindability Mill Size / Fuel Capacity
Ash Content Size of De-Ashing System
Heating Value Combustion Air Amount (Fan / Duct) /
Stoichiometric Figure
Volatile Matter Ignition Behaviour / NOx Emission
Nitrogen, Sulphur Emission Values
Sulphur, Chlorine Flue Gas Atmosphere / Corrosion Risk
Swelling Index Pyrolysis /
Unburned Carbon of the First Kind
Ash Properties Furnace Size /
Furnace Exit Gas Temperature /
Slagging / Fouling
Fuels
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Furnace Design
The term Combustion Facility describes the process and
location where the proper events and reactions for the transfer of
energy by oxidation of fuel products are initiated and executed.
This location is also known as the Furnace.
Aggregates and components such as Burners, Igniters, Coal
Bunkers, Feeders and Mills, De-Ashing Facilities, Fans, Air-Heaters
as well as Fuel Lines and Air and Flue Gas Ducts are sub-systems
that are built up, together with the Furnace, to the Combustion
System.
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Tangential
Bituminous Coal Lignite
Front Corner Down Shot Slag-Tap / U-Type
All-Wall Double Front / Opposed
All-Wall
Furnace Design
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A well balanced Furnace Design has to consider the Fuel Properties
in respect of the thermal requirements of the steam generator.
Therefor the Heat Release related to
- the Furnace Cross Section,
- the Heating Surface in the Burner Belt Area and
- the Furnace Volume
have to meet with the demand of highly efficient combustion system having
regard to complete combustion and low emission values.
Important Design Tools used by HPE
- PreFanal First Combustion Calculation and Furnace Layout
- FANAL Combustion Behaviour Furnace Temperatures / Emission
Values / Burnout Characteristics
- DAMAUS Thermal Boiler Calculation
- CFD Layout – Check and Optimization
Furnace Design
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Components of Coal Firing System
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Development of Low NOx Burners
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The development of high efficient combustion systems was
significantly affected by the processing of Low NOx
Combustion in the past three decades.
Learning from chemical processes, Low NOx Burners of
today are focused on ignition of fuel products and the
localisation and timely definition of the ignition point.
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NOx Sources
1500
1000
500
0
NOx
mg/m³
1000 1400 1800
Furnace Temperature °C
Thermal NOx
Fuel NOx
Prompt NOx
NOx Emission
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Burner Design
DS® Burner
Ignition
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Everything that is supposed to be burned must be ignited.
Ignition is the Initiation of all combustion processes.
DS® Burner Development
That’s why Initiation and the Course of Ignition is in the
Focus of Combustion Technology.
The First Theorem of Combustion:
The Second Theorem of Combustion: The Definition of Ignition
Ignition = Pyrolysis + Oxidation
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The younger the respective coal quality, the lower the rate of
carbonisation. That leads to higher amount of volatiles available
and better conditions for accelerated de-volatilization.
The release of volatiles mainly depends on coal type, particle
size, temperature, time for reaction and heat-up range.
DS® Burner Development / Pyrolysis
Pyrolysis starts at particle temperatures between 250°C and
400°C depending on coal quality.
The changing of coal happens under influence of heat without
any additional oxygen supply.
Pyrolysis describes the thermo-chemical split of organic
compounds by means of which high temperature forces the
breaking of bigger molecules into smaller ones.
Beside the coking coal production, tar and combustible gases,
namely the volatiles, are the main products of the pyrolysis
process.
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Conditions of Oxidation:
- Primary Oxygen Content
- Oxygen Quotient w
Conditions of Pyrolysis:
- Fuel Concentration
- Heat Transfer
- Time for Reaction
Ignition = Pyrolysis + Oxidation
DS® Burner Development
O2 primary (actual value)
O2 Demand of Volatiles w =
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Nitrogen Distribution during Pyrolysis
During coal pyrolysis, the fuel nitrogen is split into the portions of the char and volatiles.
Thus, it is also determined whether the HCN or NH3 branch of NO formation becomes relevant or
influences the decomposition reaction
Objective of the optimized pyrolysis: Release of the maximum possible
amount of volatiles and nitrogen in volatiles to accelerate the mechanisms
of reduction.
Raw Coal
Volatile
Matter
Char
Char Burnout
N
N
N
Fuel
Nitrogen
NOx Emission / Burner Pyrolysis Model
Fuel Nozzle Furnace
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Proceedings during Pyrolysis and Oxidation
Course of Oxidation
0
0,5
1
1,5
2
2,5
3
Sto
ich
iom
etr
y
Slow
Release
Fast
Release
0
20
40
60
80
100
Rele
ase
of
Vo
lati
les %
Fast
Release
Slow
Release
Course of Pyrolysis
NOx Emission / Burner Pyrolysis Model
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Stable Ignition at the Burner Tip
High Turn-down Rate
Low NOx-Emission
Operational Independence at Varying Coal Properties
Expectations and Requirements on Coal Burners
Homogeneous PC Distribution at the Fuel Nozzle
Definition of Ignition Conditions at the Fuel Nozzle
Intensive Swirl on the PC and Combustion Air Side
Residence Time High Enough at High Temperature and Low Oxygen Content
Delayed Oxygen Mixing Towards the Initial Flame during Pyrolysis
What’s of Importance…
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DS® Burner Today
Oil Gun
Core Air
Pulverized Coal Secondary Air Tertiary Air
Adjustable Swirl Sets
Fuel Nozzle
Due to centrifugal
forces the coal
particles are
concentrated at the
inner circumference
of the PC tube
The coal particles
hit towards a
resistance, loose
their flow velocity
for the time
necessary to start
pyrolysis
The secondary air is
deflected to prevent
early oxygen
admixture during
pyrolysis
The shape of the PC
bend enables an
homogeneous inflow
of the swirl insert
Heat transfer to the
PC particles due to
gas circulation
downstream Fuel
Nozzle
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DS® Burner Development, CFD Calculation
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0,7 0,8 0,9 1 1,1 1,2 1,3 1,4
0
200
400
600
800
1000
1200
1400
Burner air ratio
Vortex-Burner
DS-Burner
WS-Burner
DS® Burner / NOx Characteristic
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What makes the Burner being a functional unit?
Results of DS® Burner Testing
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Influence of Burner Swirl Settings on the Flame Shape
Burner Swirl: PA 25°/ SA 25°/ TA 30° Burner Swirl: PA 0°/ SA 25°/ TA 30° Burner Swirl: PA 35°/ SA 35°/ TA 30° Burner Swirl: PA 35°/ SA 25°/ TA 30° Burner Swirl: PA 35°/ SA 45°/ TA 60° Burner Swirl: PA 35°/ SA 45°/ TA 45°
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Different
Swirl Settings
Different
Burner Capacities
Influence on the Flame Shape
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DS® Burner, KK Coal, 100% load / DS® Burner, KK Coal, part load
DS® Burner, Flame Pattern
DS® Burner, KK Coal (60%) + Sawdust (40%), 100% load DS® Burner, Sawdust (91%) + NG (9%), 100% load
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DS® - Burner, Flame Pattern
DS® Burners were introduced early in the 1990th and
continuously developed over the years by:
Research and development using a Test Furnace in the US.
CFD Calculations under respect of Burner proximate area and
furnace configuration.
Operating Experience from more than 1500 applications in about 50
boilers.
Further development with test series at CCA test rig (Italy) for the use
of alternative fuels (biomass), high ash bit. coal as well as lignite and
pre-dried lignite.
With respect to the Origin of NOx
production DS® Burners are designed and
developed to prevent the relevant reactions.
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DS®- Burners are used for Direct Firing Systems
DS® The Burner System for all Kind of Solid Fuels
and even Blended Coal Qualities
High Level Flame Stability within the Burner Control
Range of 1 / 3.5
Exactly Defined Burner Air Ratios
Ultra Low NOx Characteristic within the Whole Load
Range
DS®- Burner Features
Thanks for Attention