direct fired oxy-fuel combustor for sco2 power cycles...governed by the timescale of chemical...

Direct Fired Oxy-Fuel Combustor for sCO2 Power Cycles

Jacob Delimont, Ph.D.Aaron McClung, Ph.D.

Southwest Research Institute

Marc PortnoffLalit Chordia, Ph.D.Thar Energy L.L.C.

Work supported by US DOE under DE-FE002401

11/10/2016 2016 University Turbine Systems Research Workshop 1

HEAT SOURCE

PRECOOLER

LOW TEMP RECUPERATOR

HIGH TEMPRECUPERATOR

EXPANDER

COMPRESSOR

RE-COMPRESSOR

P6 P7a P8

P1

P2

P3

P5

P7b

P7

P4

P4b

COOLING OUT COOLING IN

P4a

Outline

• Phase I Overview– Background– Project Objectives– Phase I Progress

• Cycle Modeling• Chemical Kinetics• Preliminary Combustor Design• Bench-top Combustor Test

• Phase II Project Plan

11/3/2015 2015 University Turbine Systems Research Workshop 2

What is a sCO2 cycle?

• Closed Cycle– Working fluid is CO2

• Cycle Type– Vapor phase– Transcritical– Supercritical

• Supercritical CO2 has:– High fluid density– High heat capacity– Low viscosity

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HEATSOURCE

PRECOOLER

RECUPERATOR

EXPANDERCOMPRESSOR

P5 P6

P1

P2

P4

COOLING OUTCOOLING IN

P3

Recuperated ClosedBrayton Power Cycle

Why sCO2 Power Cycles?

• Offer +3 to +5 percentage points over supercritical steam for indirect coal fired applications

• High fluid densities lead to compact turbomachinery

• Efficient cycles require significant recuperation

11/3/2015 2015 University Turbine Systems Research Workshop 4

Third Generation 300 MWe S-CO2 Layout from Gibba, Hejzlar, and Driscoll, MIT-GFR-037, 2006

Why Oxy-Fuel Combustion?

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HEAT SOURCE

PRECOOLER

LOW TEMP RECUPERATOR

HIGH TEMPRECUPERATOR

EXPANDER

COMPRESSOR

RE-COMPRESSOR

P6 P7a P8

P1

P2

P3

P5

P7b

P7

P4

P4b

COOLING OUT COOLING IN

P4a

• Capture 99% of carbon dioxide• Higher turbine inlet temperatures

possible

CO2

Project Objectives

• Optimize the supercritical CO2 power cycle for direct fired oxy-combustion– Target plant conversion efficiency is 52% (LHV)

• Technology gap assessment for direct fired plant configurations

• Develop a high inlet temperature oxy-combustor suitable for the optimized cycle– Target fuels are Natural Gas and Syngas

11/3/2015 2015 University Turbine Systems Research Workshop 6

Outline

• Phase I Overview– Background– Project Objectives– Phase I Progress

• Cycle Modeling• Chemical Kinetics• Preliminary Combustor Design• Bench-top Combustor Test

• Phase II Project Plan

11/3/2015 2015 University Turbine Systems Research Workshop 7

DESIGN -SPECCOMPMAT C

DESIGN -SPECFUELFLOW

DESIGN -SPECFUELPRES

DESIGN -SPECO2PRES

DESIGN -SPECPINLET

DESIGN -SPECT INLET

DESIGN -SPECT MIXBAL

CALCU LATORCOOLT OWR

CALCU LATOREFFICIEN

CALCU LATORO2CALC

PIPELCMP

PIPLNCO2

H2OSEPER FUELCOM

W

MIXER

FUELWORK

O2PUMP

COMBUST

W

MIXER

WMIXER

COOLER

FMIX

REJ ECT HX

FSPLIT

HXLOWHXHIGH

MAINCOMP

RECOMP

EXPANDER

CO2

S15

WPIPELIN

T AKEOFF

H20

S21

S3

CH4IN

CH4PRE

FUELCW

ASUPOWW

O2PWORK

WFUELSYS

O2IN

O2PRE

INLET

S14

WMAINCOM

WRECOMP

WT URBINE

WCOOLW

WNETW

S7

S10

QRECOMPC

Q

S9

S11

MAIN

S6

QREJECT

Q

RECOMPRE

S2

S8

S1

OUT LET

De-watering and Cleanup

Fuel, Oxidizer, and Combustion

Oxy-Combustion Plant Model

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Condensation and Recompression Cycles

ThermalInput

Cooler

Low TemperatureRecuperater

High TemperatureRecuperater

Turbine

Compressor

Recompressor

ThermalInput

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ThermalInput

CoolerRecuperater

Turbine

Compressor

Pump

ThermalInput

Cycle Analysis Results

• Recompression cycle has highest efficiency – 53.4% at 200 bar, 56.7% at 300 bar

• Condensation cycle – 51.6% at 200 bar, 54.0% at 300 bar– Superior in all other metrics – Reduced recuperation (~ 50%)– Lower combustor inlet temperature– Higher power density (power output / flow rate)

• Both cycle configurations are compatible with an auto-ignition style combustor for 1200 C Turbine inlet temperatures.

11/3/2015 2015 University Turbine Systems Research Workshop 10

Outline

• Phase I Overview– Background– Project Objectives– Phase I Progress

• Cycle Modeling• Chemical Kinetics• Preliminary Combustor Design• Bench-top Combustor Test

• Phase II Project Plan

11/3/2015 2015 University Turbine Systems Research Workshop 11

Kinetic Model: Motivation

• The fundamental size of the combustor is governed by the timescale of chemical reactions

• The chemical reaction kinetics determine how fast fuel oxidation occurs– A detailed chemical kinetic model is required to

size the combustor – A reduced chemical kinetic model is required for

detailed flow-field design in CFD

11/3/2015 2015 University Turbine Systems Research Workshop 12

Kinetics Knowledge Base

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CO2 concentration

PressureCurrent Application

P up to 200 barxCO2 up to 0.96 (mostly as diluent)

Well-Developed MechanismsP up to 20 bar

xCO2 < 0.10 (mostly as product)Sparse data at low pressure, high CO2

Sparse data at high pressure, low CO2

Knowledge front

No data available at conditions relevant to this application.

Mechanism Selection• Primary selection criterion is accurate prediction of the

overall reaction time scales– Drives the combustor design– More important than other details such as peak

concentration values• USC-II is the clear choice based on this criterion

– Most accurate in highest pressure flamespeed and autoignition validation comparisons

• USC-II also had good to adequate performance in low pressure CO2 studies

• USC-II predictions should carry +/- 50% uncertainty in this application

11/3/2015 2015 University Turbine Systems Research Workshop 14

Reduced Order Model

• For incorporation into a CFD model a reduced order model was developed

• Equations based on Arrhenius rate equation were tuned to match USC-II model predictions– Match autoignition delay– Match residual CO levels– Overall time to complete reaction

11/3/2015 2015 University Turbine Systems Research Workshop 15

Outline

• Phase I Overview– Background– Project Objectives– Phase I Progress

• Cycle Modeling• Chemical Kinetics• Preliminary Combustor Design• Bench-top Combustor Test

• Phase II Project Plan

11/3/2015 2015 University Turbine Systems Research Workshop 16

Mixing vs. Kinetics Time Scales

• Time scale of reaction kinetics is much smaller than physical mixing time scales

• Combustion size and length governed by physical mixing

• Use of CFD with finite rate chemistry to model this

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Time (ms)

Tem

pera

ture

(K)

Kinetics Models

Initial Combustor Concept

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CFD Model Setup

• ANSYS CFX 16.2• Unstructured mesh

– Boundary layer and injection region refinement

– 4 million elements– Mesh sizes from 2 to 17

million elements for independence study

• Finite rate chemistry– Extrapolated reduced order

equations

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Temperature in 45° Clocked Case

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1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

2000

0.00 0.20 0.40 0.60 0.80 1.00

Tem

pera

ture

(K)

Axial Distance (m)

Ave Temperature (K)

Max Temperature (K)

Change Injection Spacing

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4 Hole 45°Clocked

4 Hole 11.25°Clocked

4 Hole Aligned

• Injection oxygen and fuel need not be at same location

• Auto-ignition allows even small concentrations of fuel+oxidizer to react

Final Design: Fuel Injection 24in Upstream

• Fuel well mixed throughout combustor before oxygen• Allows hydrocarbon “cracking” before oxygen injection• Cooler max temperatures• Very good mixing at outlet• Very low unburnt fuel percentage

11/10/2016 2016 University Turbine Systems Research Workshop 22

1000

1100

1200

1300

1400

1500

1600

0.00 0.50 1.00 1.50 2.00

Tem

pera

ture

(K)

Distance (m)

Ave Temperature (K)

Max Temperature (K)

Preliminary Mechanical Design

• Thermal design– Thermal

containment using refractory insulating layer

– Cooling CO2

• Mechanical design– Utilizes stainless

steel ANSI pipe and flanges

11/10/2016 2016 University Turbine Systems Research Workshop 23

Hot Inlet Air

Combustion Processes

Cooling CO2

Outline

• Phase I Overview– Background– Project Objectives– Phase I Progress

• Cycle Modeling• Chemical Kinetics• Preliminary Combustor Design• Bench-top Combustor Test

• Phase II Project Plan

11/3/2015 2015 University Turbine Systems Research Workshop 24

Bench-top Combustor Test

• Small bench top test to study proof of concept, autoignition delay, and chemical kinetics

• Once through type system– 200 bar pressure

• Electric heaters used to set inlet temperature• Jet in cross flow type fuel and oxidizer

injection

11/10/2016 2016 University Turbine Systems Research Workshop 25

Test Stand Loop Design

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Oxy-fuel Test Reactor

• Machined from Haynes 230 bar stock

• Instrumentation standoff tubes welded to main combustor

• Two stage pre-heater to achieve 925°C combustor inlet

11/10/2016 2016 University Turbine Systems Research Workshop 27

Gas Sampling Cooling Jacket

WeldFitting

Green: 1.25” O.D. Reactor Body – 12” longOrange: Dynamic pressure sensorYellow: ThermocoupleRed: Gas SamplingPurple: Oxygen & Methane/Ethane injectionGray: Reactor inlet and outlet (1/2”)

Haynes 2301.25” O.D.0.188” I.D.

Inconel 625¼” O.D.

0.120” I.D.

CO2Flow

750°C1020°C

10”20”

3” O.D. Tool SteelHeated via 4 knuckle

band heaters (not shown)

Haynes 230½” O.D. x 0.093” I.D.

Heated via ceramic furnace heaters (not

shown)

To Reactor

Inlet

• Water jacketed gas sampling

Fuel and Oxygen Injector Design

• Precise sapphire orifice set into stainless steel mount

• Orifice constriction placed close to the combustor

• Mounted inside welded in place standoff

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OrificeBody

Orifice Guide316 Stainless Tube

1/8” x 0.035”

Standoff 0.5” OD x 0.135” ID

0.020” Support

Lip

Combustor Test Stand

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Test Stand Assembly

• Testing at Thar’s facility in Pittsburg, PA

• Outdoors with remote operation

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Instrumentation

• Thermocouples in combustion zone

• Dynamic pressure transducers

• Three gas sampling ports– Optical emission

spectroscopy (OES) to analysis chemical makeup

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OES• Optical emission

spectroscopy (OES)• Utilizes a plasma

generator to identify chemical species

• Requires rapid thermal quenching of sample to halt chemical reactions

• SwRI has experience using OES for gas species analysis

11/10/2016 2016 University Turbine Systems Research Workshop 32

Test Stand Operation

• Shake down tests– Observed auto-ignition

combustion during shakedowns at full pressure and 80% temperature

• Component failures– Backpressure control valve– Mass flow controllers

• Viton rubber does not mix with sCO2

11/10/2016 2016 University Turbine Systems Research Workshop 33

Outline

• Phase I Overview– Background– Project Objectives– Phase I Progress

• Cycle Modeling• Chemical Kinetics• Preliminary Combustor Design• Bench-top Combustor Test

• Phase II Project Plan

11/3/2015 2015 University Turbine Systems Research Workshop 34

Phase II

• Complete detailed design• Fabricate combustor and test loop• Shake down and commission • Test combustor• Phase II duration: 3.5 years• Partnered with Thar Energy, Georgia Tech, UCF

and GE Global Research

11/10/2016 2016 University Turbine Systems Research Workshop 35

Detailed Combustor Design

• Develop more detailed and accurate combustion kinetic mechanisms

• Utilize CFD to study combustion flow field

• Detailed thermal and mechanical design

• Final design for manufacturing

11/10/2016 2016 University Turbine Systems Research Workshop 36

Hot Inlet Air

Combustion Processes

Cooling CO2

Combustor Integration withSunshot Test Hardware

11/10/2016 2016 University Turbine Systems Research Workshop 37

Combustor Integration• Utilize existing Sunshot

hardware• Install oxy-fuel combustor

– Demonstrate a direct fired oxy-combustor in a closed Brayton cycle

– Evaluate combustor performance

– Evaluate flue gas cleanup– Indirect heater allows for

various combustor inlet conditions to be studied

11/10/2016 2016 University Turbine Systems Research Workshop

Oxy-Combustor added downstream of indirect heater

Add flue gas cleanup and water separation

38

Planned Test Measurements

• Multiple OES sample locations• Temperature measurements• High speed pressure measurement for acoustic

phenomena• Study water dropout and separation• Possible measurements

– Optical access for advanced diagnostics– Materials sample testing

11/10/2016 2016 University Turbine Systems Research Workshop 39

QUESTIONS?

11/10/2016 2016 University Turbine Systems Research Workshop 40

ThermalInput