Ansaldo Caldaie Experience in HRSG Design Developments

Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
Author: Giovanni Mainini
Co-authors: G. Guelfi – M. Penati – R. Piasente – L. Rusconi – A. Saponaro
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
General Overview
 The drive for reduction of CO2 emissions pushes both power generation sector and
boiler manufacturers towards the use of renewable energy sources
 Ansaldo Caldaie, a global supplier of Utility Boilers and Heat Recovery Steam
Generators, in cooperation with Tirreno Power, one of the primary Italian Power
Generation companies, has developed an experimental and engineering activity for
the co-firing of biomasses with coal
 This presentation highlights
•
the recent experimental activities for the direct co-firing of pulverised coal
with pulverised Wood Pellets (WP) and other potential biomass fuels in TEA-C /
TEA-C EFS Low-NOx Burner
•
the basic design features of major biomass feeding components required for
the implementation of the co-firing technology in a large scale boiler
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
Objectives of the testing activity
 To verify the firing performance in “nominal” co-firing conditions (20-30% heat
input) and with increased amounts of bio-fuel up to “full biomass firing”
 To investigate on the role played by pulverised fuel fineness (for both coal and
biomass)
 validation of “commercially achievable” levels
 To investigate and validate the biomass dosing and transport technologies within a
wide range of air / biomass ratios (dense vs. semi-dense options)
•
Dense option:
< 0.25 kg air / kg biomass
•
Semi-dense option: 0.5÷1 kg air / kg biomass
 optimised engineering from the cost-benefit point of view
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
Basic design criteria
 Direct injection of pulverised biomasses into the main pulverised coal piping
upstream the coal burner  no dedicated burners, no impact on coal grinding
 Separate biomass handling and pulverisation
 Pneumatic
transport
of
pulverised
biomasses

small
pipes,
segregated
environment
 Dense or semi-dense transport solutions  minimum impact on plant lay-out and
on burner fluid-dynamics
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
The firing equipment
Standard design of AC Low-NOx burner (TEA-C)
 Optimised axial staging effect for the clean
combustion of medium-high CV coals typically
available on the international market
Special design of AC Low-NOx burner (TEA-C EFS)
 Enhanced Flame Stability nozzle, optimised
for the clean combustion of low CV, high ash,
high moisture coals typically fired in India
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
The test facility
 Located in the Ansaldo Caldaie owned Combustion
& Environmental Research Centre (CCA)
 Designed to operate in full scale a boiler burner up
to 40 MWth fuel heat input, with gaseous, liquid
and solid fuels
 Equipped to manage 2 different solid fuel streams
in parallel:
• A coal stream (silo, feeder, ball mill + RC,
primary air system to burner)
• A biomass stream (pulverised fuel silo, dosing
system, pneumatic transport system to burner)
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
The Fuels
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
Wood Pellets Co-firing test results (TEA-C existing Burner, 35 MWth)
800
STD Nox-100% coal
750
STD CO-100% coal
700
STD Nox-90%coal+10%bio
 Appreciable NOx reduction with
increasing amounts of biomass
NOx, CO @ 6% O2 dry (mg/Nmc)
650
STD CO-90%coal+10%bio
600
STD Nox 85% coal+15%bio
550
STD CO 85%coal+15%bio
500
STD Nox 80%coal+20%bio
450
STD CO 80%coal+20%bio
400
350
300
250
200
co-firing
 Moderate increase of operating
150
100
50
0
0,00
0,50
1,00
1,50
2,00
2,50
3,00
3,50
4,00
4,50
5,00
5,50
6,00
6,50
7,00
O2 DRY (%)
excess air
700
28
NOx
CO
 Minor increase in UBC
% bio
O2
600
24
UBC
500
20
16
NOx, CO
400
15
300
12
10
200
8
100
4
0
0
1
2
3
4
% BIO, O2, UBC
20
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
Wood Pellets Co-firing test results (TEA-C EFS Burner, 35 MWth)
800
Nox-100% carbone
CO-100% carbone
700
Nox-80%carbone+20%WP
CO-80%carbone+20%WP
600
NOx, CO @ 6% O2 (mg/Nmc)
Nox-75%carbone+25%WP
CO-75%carbone+25%WP
500
Nox-70%carbone+30%WP
CO-70%carbone+30%WP
400
300
200
 Use
of
enhanced
flame stability nozzle
100
0
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
O2 dry (%)
 Similar NOx reduction with increasing biomass heat input
 Better CO control
 Satisfactory operating excess air
5,0
5,5
6,0
6,5
7,0
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
Palm Kernel Shells Co-firing test results (TEA-C EFS Burner, 35 MWth)
800
Nox-100% carbone
CO-100% carbone
700
Nox-80%carbone+20%PKS
CO-80%carbone+20%PKS
NOx, CO @ 6% O2 (mg/Nmc)
600
Nox-75%carbone+25%PKS
CO-75%carbone+25%PKS
500
400
300
200
100
0
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
5,0
O2 dry (%)
 Nitrogen content in bio-fuel determines a NOx increase trend
 CO is very well controlled
 Significantly lower operating excess air can be achieved
5,5
6,0
6,5
7,0
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
Wood Pellets full firing test results (TEA-C EFS Burner, 35 MWth)
 Warm-up with Natural Gas, load ramp with
increasing amounts of bio-fuel, no flame
support above 70÷80% MCR
 Very low NOx emission (approx. 150 mg/Nm3
@ 6% O2 dry), with good CO control and
“typical” operating O2 (approx 4% vol)
 UBC values corresponding to about 0.3%
Unburnt Efficiency Loss
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
Co-firing test results - Conclusions
 Burner co-firing capacities up to 20÷30% heat input have been
confirmed, according to initial targets
 Properly shaped and stable flames have been achieved in a wide range of
operating conditions
 Good combustion parameters (excess air, NOx, CO) have been verified
 Significant benefits have been achieved by using EFS coal nozzle, also
verifying the capability to accept full biomass firing on individual burners
of a coal-biomass co-fired boiler
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
The reference basic design for the pulverised biomass handling
 Various arrangements have been evaluated, among direct / indirect systems and
different bio-fuel grinding alternatives (direct grinding in coal mills, separate
pulverisation with various transport options)
 Safety issues and capital costs have been also taken into account
TRANSPORT SYSTEM
- Air –biomass ratio
DENSE OPTION
~ 0.25 : 1
SEMI-DENSE OPTION
CASE A
CASE B
~1:1
~ 0.5 : 1
- Dedicated line for each burner
- Transport air supply
Yes
Compressors
Medium
(moderate density variations)
Yes
One blower for each line to burner
Flow
Pressure (design / operating)
- Power consumption
4 x 3000 Nm3/h
4 / 2.5 bar
High
Small silos
Loading valves
(4 cycles/hour)
Barrels (sealing)
with load cells
Rotary valves
3÷4"
Gravimetric
24 x 2000 Nm3/h
24 x 900 Nm3/h
0.6 / 0.4 bar
0.6 / 0.5 bar
High
Medium-Low
Small silos
Screw feeders
Loading valves
Continuous feed
(2 cycles/hour)
Small hopper
with load cells
Rotary valves (sealing)
5÷6"
4"
Volumetric
Gravimetric
- Transport “flexibility” with different type of biomass
- Transport system components
- Transport line diameter
- Dosing system
High
for each line
(2% accuracy)
for each group of lines
(~ 5% accur.)
(~ 5% accur.)
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
AC guidelines for the reference design
 Direct injection of pulverised biomass into the p.c. piping upstream the burners
 Direct feeding system, with pneumatic transport
 Semi-dense phase with air blowers, small dosing bin with screw feeders and
properly selected rotary valves
 Use of Class A biomass according to CEN/TS 14961 and EU Bionorm, with the
following characteristics
•
LHV
> 3400 kcal/kg
•
Moisture
< 20% wt, a.r. basis
•
Pulv. Fuel fineness 100%
< 1.5 mm
 Basic engineering study, developed in cooperation with Tirreno Power, for the
potential retrofit of 320 MWe class coal fired units (applicable to TP Vado Ligure
Power Plant and ready for the detailed engineering & supply phases of the project)
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
AC guidelines for the reference design
Lay-out study and process flow diagram of a biomass co-firing fuel supply system
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
AC guidelines for the reference design
Burner logic groups
equipped for coal-biomass
co-firing (Vado Ligure # 3)
Ansaldo Caldaie Coal Biomass Co-firing Testing Experience
General Conclusions

Ansaldo Caldaie product development for coal biomass co-firing has achieved significant results

Full scale testing at Ansaldo Caldaie Combustion Centre demonstrated the satisfactory
performance of Ansaldo Caldaie TEA-C Low-NOx burner, equipped with enhanced coal nozzle
(EFS), in a 20÷30% co-firing configuration of bituminous coal and biomass

Good and stable combustion parameters, proper emission levels, wide operating load range
and performance flexibility for various
biomass types and for different kinds of biomass
transport configurations (dense or semi-dense solutions) have been confirmed

The capability of TEA-C EFS burner design to accept full biomass firing on individual burner has
been verified positively

A pre-engineered reference design suitable to the retrofit of large utility boilers has been
developed and is ready to be implemented

From the experience, Ansaldo Caldaie is ready for the development of a wide range of cofiring projects, to satisfy state of the art industry needs