Integrated Flue Gas Purification and Latent Heat Recovery for Staged,

Pressurized Oxy-Combustion

PI: RICHARD AXELBAUM

ENERGY, ENVIRONMENTAL AND CHEMICAL ENGINEERINGWASHINGTON UNIVERSITY IN ST. LOUIS

2018 NETL CO2 CAPTURE TECHNOLOGY

PROJECT REVIEW MEETING

AUG 13TH-18TH, 2018

DE-FE0025193

Project OverviewProject Objectives◦ Develop an enabling technology for simultaneous

recovery of latent heat and removal of SOx and NOx from flue gas during pressurized oxy-coal combustion.

Funding◦ Total award: $1,291,964 � DOE share: $996,652

Cost share: $295,312

Project Performance Dates◦ 09/01/2015 - 08/31/2018 (extended)

Project Participants◦ Washington University in St. Louis

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TechnologyBACKGROUND

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15 bar, 550 MWe power plant with > 90% CO2 capture

4

• Surface-moisture free feeding.• Exhaust [O2] ≈ 3 % (d.b.) = 0.26 bar (partial pressure), compared to 0.03 bar for atm. pressure

SPOC Process Flow Diagram

Main Contributors to efficiency gain:

◦ Heat from flue gas moisture condensation (~ 1.5 %-pts.)

◦ Lower exergy loss due to reduced recycle & surface-dry feeding (up to 3.5 %-pts.)

◦ Aux. load reduction due to staging & pressurization

◦ Effective integration of waste heat from oxygen production & compression

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b ca

~29.5%

35.7%~38.3%

> 90% CO2 captured

V. H

igh

CO2

purit

y (<

10

ppm

O2)

Low

er p

urity

CO

2(<

3%

O2)

Efficiency Gains in SPOC

SOx and NOx Removal

6

NO NO2N2O4N2O3

SO2

HSO3HNO2

H2SO4

HNO3

GasPhase

LiquidPhase

Knowledge Gaps:There are discrepancies about the role of N2O3 and N2O4 in NOx dissolutionAqueous phase kinetics and mechanism remain unclear

HON(SO3)22- (HADS)

Project Objectives◦ Develop a predictive model for reactor design & operation.

◦ Experimentally determine critical reactions and rates.

◦ Conduct parametric study (T and pH) to optimize process.

◦ Design, build, test prototype for 100 kW pressurized DCC.

◦ Determine size of the DCC for a full-scale SPOC plant in order to estimate capital and operating costs.

7

Project Organization

8

Project ManagementRichard Axelbaum

Ben Kumfer

ModelingLead:

Gregory Yablonsky

Oleg TemkinPiyush Verma

Prototype DCCLead:

Ben Kumfer

David Stokie

Chemical Mechanisms and Kinetics

ExperimentLead:

Young-Shin Jun

Yujia MinDavid Stokie

Process Modeling

Lead:Richard Axelbaum

Piyush VermaAkshay Gopan

Technical ApproachPROJECT SCOPE

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Technical Approach

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Continuously stirred tank reactor - CSTR(bench-scale)

Experiment

Modeling

Prototype DCC(100 kW)

Kinetic model &reduced

mechanismdevelopment

Scale

DCC model w/chemistry & transport

SPOC process & econ. model (550 MWe)

kineticdata

results

design

Coal Feeders

Coal Milling

Coal

ASU Cold Box

O2 Compressor

Main Air Compressor

Moist N2

BFW

N2 O2

Air

Dry N2 to Cooling Tower

Air

Steam Cycle

BFW BFW BFW BFW

Bottom Ash

Bottom Ash

Bottom Ash

Bottom Ash

Steam Cycle

Steam Cycle

Steam Cycle

Steam Cycle

BFW

Fly Ash

Direct Contact CoolerSulfur Scrubber

BFW

Steam Cycle

pH Control

Cooling Water

Cooling Tower

CO2 Boost Compressor

CO2 Purification

Unit

Vent Gas

CO2 Pipeline Compressor

CO2 to Pipeline

Particulate Filter

Steam Cycle

Progress and Current Status

MECHANISM AND KINETICS

BENCH-SCALE EXPERIMENTS

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Objectives of Bench Scale Experiments

◦ Experimentally validate the gas to liquid chemical mechanism

◦ Identify and determine the key reactions, reaction pathways and rates of the liquid chemistry

◦ Develop a robust kinetic model capable of accurately predicting the removal efficiency of a direct contact column

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Proposed mechanism

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NOx ReactionsGas Phase

1. 2NO (g) + O2(g) 2NO2 (g)2. 2NO2(g) ↔N2O4(g)3. NO(g) + NO2(g) →N2O3(g)

Gas + Liquid Phase4. 2 NO2 (g) + H2O (g, aq) HNO2 (aq) + HNO3 (aq)5. N2O4(g)+ H2O (g, aq) HNO2 (aq) + HNO3 (aq)6. N2O3(g) + 2H2O (g, aq) 2 HNO2 (aq)7. 3 HNO2 (aq)HNO3 (aq)+ 2 NO (g, aq)+ H2O (g, aq)

SOx Reactions8. SO2 (g) + H2O (g, aq) ↔ HSO3

- (aq) + H+ (aq)

SOx + NOx Reactions9. HNO2 (aq) + HSO3

- (aq) + H+ (aq)→ H2SO4 (aq)+ ½ N2O (g) + ½ H2O (aq)10. 2 HNO2 (aq) + HSO3

- (aq) + H+ (aq) → 2NO (g) + H2SO4 (aq) + H2O (aq)11. HNO2(aq) + 2HSO3

-(aq) → HON(SO3)22-(aq) + H2O(l)

Experiment to Obtain Kinetic Data

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Gas C

ylinderG

as Cylinder

Gas C

ylinderG

as Cylinder

O2, SO2, NO, NO2, and N2

Gas Mixer

High PressurePump

Gas inlet Gas outlet

pH probe

Liquid outlet

Gas analyzer

Ionic chromatographystirrer

The reactor design is optimized for conducting experiments under high pressure and temperature and highly acidic conditions

In situ pH measurements under high pressure/temperature conditions

• Pressure of 15 bar, 900 ppm NOx, NOx/SOx ratio of 2

Reduced mechanism

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NOx ReactionsGas Phase

1. 2NO (g) + O2(g) 2NO2 (g)2. 2NO2(g) ↔N2O4(g) Equilibrium3. NO(g) + NO2(g) →N2O3(g)

Gas + Liquid Phase4. 2 NO2 (g) + H2O (g, aq) HNO2 (aq) + HNO3 (aq)5. N2O4(g)+ H2O (g, aq) HNO2 (aq) + HNO3 (aq)6. N2O3(g) + 2H2O (g, aq) 2 HNO2 (aq)7. 3 HNO2 (aq)HNO3 (aq)+ 2 NO (g, aq)+ H2O (g, aq)

SOx Reactions8. SO2 (g) + H2O (g, aq) HSO3

- (aq) + H+ (aq)

SOx + NOx Reactions9. HNO2 (aq) + HSO3

- (aq) + H+ (aq)→ H2SO4 (aq)+ ½ N2O (g) + ½ H2O (aq)10. 2 HNO2 (aq) + HSO3

- (aq) + H+ (aq) → 2NO (g) + H2SO4 (aq) + H2O (aq)11. HNO2(aq) + 2HSO3

-(aq) → HON(SO3)22-(aq) + H2O(l)

SOx and NOx Removal

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NO NO2N2O4

SO2

HSO3HNO2

H2SO4

HNO3

GasPhase

LiquidPhase

HON(SO3)22- (HADS)

Knowledge Gaps:There are discrepancies about the role of N2O3 and N2O4 in NOx dissolutionAqueous phase kinetics and mechanism remain unclear

Liquid Chemistry

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When compared to previous models, the overall trends are the same however our model fits better to the experimental data

0.0E+00

2.0E-04

4.0E-04

6.0E-04

8.0E-04

1.0E-03

1.2E-03

1.4E-03

0 100 200 300 400 500 600

[HAD

S] (m

ol/L

)

Time (s)

[HADS] Model Comparison

Experimental Data Our Model Petrissans

Petrissans et. al. (2001)

The effect of temperature and pH

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0.0E+00

5.0E-04

1.0E-03

1.5E-03

2.0E-03

2.5E-03

3.0E-03

0 50 100 150 200 250 300

HSO

3-Co

ncen

trat

ion

(mol

/L)

Time (s)

72 C48 C22 C

Increase in temperature results in an increased rate of HSO3

-

consumption, however the proportionality of H2SO4 to [HADS] is similar

Decrease in pH results in an increase H2SO4 formed

Addition of 0.03 M of HCO3-

/CO32- results in no observable

change in reaction rates or concentrations

At 72 C additional reactions are observed

Increasing Temperature

Decreasing pH

0.0E+00

5.0E-04

1.0E-03

1.5E-03

2.0E-03

2.5E-03

3.0E-03

3.5E-03

0 50 100 150 200 250 300

HSO

3-Co

ncen

trat

ion

(mol

/L)

Time (s)

4

3.6

3

2.5

PROTOTYPE DIRECT CONTACT COOLER (DCC)

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Progress and Current Status

DCC Prototype

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Features:

•100 kWth SPOC facility integration

•Simulated flue gas capability

•Liquid recycle and pH control

Parameters:

•Vapor residence time: < 120 seconds

•pH range: 2 – 7

•L/G ratio: 3 – 80 (L/m3)

•1 -30 bar maximum operating pressure

•Flue Gas Temperatures: < 350 °C

DCC Test Facility

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CO2 CO2 + NO + SO2

NO and SO2

Cylinders

Gas Heater

O2

CO2 + O2 + NO + SO2

Exhaust Gas

Heat Exchanger

DCC Column

Mains Water

Effluent Water to Neutralization

Water Recycle

Scrubbing Water

The effect of O2 concentration on NOx conversion

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Conditions:

Pressure : 13.5 bar (abs)

Temperature : 24 °C

L:G Ratio : 1 kg:kg

Residence Time : 120 seconds

Inlet SO2 ppm : 421 ppm

Inlet NOx ppm : 550 ppm

L:G Ratio based on water flow for heat transfer requirementsO2 concentration range similar to oxyfuel outlet conditionsSO2 and NOx ppm similar to oxyfuel outlet conditions

0

100

200

300

400

500

600

700

0 1 2 3 4

NO

x (p

pm)

Oxygen Concentration (%)

Reducing OxygenConcentration

Increasing OxygvenConcentration

NO to NO2 Conversion

Full SOx conversion

FULL-SCALE DCC MODELING USING

IMPROVED MODEL OF CHEMISTRY

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Progress and Current Status

DCC Full Scale Modeling.Objectives:

1. Capturing latent heat from the flue gas2. Removal of SOx

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Inlet Flue Gas193.31 kg/s200 °C

Outlet Flue Gas152.84 kg/s55 °C

Inlet Cooling water223 kg/s42 °C

Water Outlet263.42 kg/s161 °C

Process Flow Diagram of system

Modeling Parameters

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Assumption for Modelling: Packed Column is used with Raschig metal rings. Cooling water flow rate was determined based on the flue gas outlet

temperature Height is calculated based on an outlet SOx concentration of less than 15 ppm.

Option A : Single DCC Option B: Two DCCs in parallel

Diameter is sized based on total gas flow rate with an approach to flooding velocity of 80%.

Diameter was fixed at 4 m because of ease of transportation. The total gas flow rate is split in two parts.

Approach to flooding velocity is 80% Approach to flooding velocity is 71%

Two configurations were studied for the process:

DCC Full-scale ModelingInlet Flue gas Composition

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O2 H2O NO NO2 SO2 SO3

Mole Fraction

3% 39% 700(ppm)

250(ppm)

700(ppm)

250(ppm)

H2O concentration SOx Removal NOx Removal

Single Column < 1.5% v/v > 99% 75.8%

Two Columns < 1.5% v/v > 99% 71.8%

Diameter Length Residence time

Single Column 5 m 60 m 80.4 s

Two Columns 4 m 45 m 77.1 s

Outlet Gas Results

Column Design Specification

Future Work

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◦ Operate lab-scale DCC at elevated flue gas temperature, up to 200 ˚C. Validate model under these conditions.

◦ Optimize the design of a full-scale DCC and feed this information into the techno-economic model being developed by EPRI, Doosan Babcock and Air Liquide (next talk).

AcknowledgementsU.S. Department of Energy:

Award #s DE-FE0025193

Consortium for Clean Coal Utilization:

Sponsors: Arch Coal, Peabody, Ameren

U.S. DOE DisclaimerThis report was prepared as an account of work sponsored by an agency of the United States Government.Neither the United States Government nor any agency thereof, nor any of their employees, makes anywarranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, orusefulness of any information, apparatus, product, or process disclosed, or represents that its use would notinfringe privately owned rights. Reference herein to any specific commercial product, process, or service bytrade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement,recommendation, or favoring by the United States Government or any agency thereof. The views and opinionsof the authors expressed herein do not necessarily state or reflect those of the United States Government orany agency thereof

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