Zeeco Power Hour · 2020. 9. 28. · • Ammonia (NH 3) Injection Grid (AIG) • SCR catalyst • Injected ammonia acts as a chemical reagent –SCR chemical reaction (exothermic:

Bob Langstine

Regional Sales Manager, Eastern US & Canada

Zeeco, Inc.

Zeeco Power Hour

Overview of Emissions Reduction Challenges & Techniques

First, a Safety Moment Equation

Be sure to shift your weight to match the activities, even in your personal activities.

+ =

Emissions Toolbox (Agenda)

Burner solutions

Flue Gas Recirculation (FGR)

Inert injection

Overfire Air/Staging (OFA)

Managing Combustion Air temperature vs unit efficiency

Selective Non-Catalytic Reduction (SNCR)

Selective Catalytic Reduction (SCR) (also CO Catalyst)

Electrostatic Precipitator (ESP)

Fabric Filters (Baghouse)

Scrubbers

Summary

Emission Limitations

NOx▪ O2, Excess Air

▪ Combustion Temperature

▪ Reaction with Nitrogen

▪ Lowering CO

CO▪ O2, Excess Air

▪ Combustion Efficiency

▪ Low NOx and FGR


▪ Air in-leakage

VOC▪ Combustion Efficiency


What factors determine achievable emissions?

▪ SOx▪ Fuel Dependent (Sulfur Content)

▪ Particulates▪ Fuel

▪ Combustion efficiency

▪ Fuel availability

▪ Technology Choices

▪ Cost

▪ Politics

Emissions – NOx

Fuel NOx Fuel Bound Nitrogen (FBN)

• Highly dependent on the concentration of fuel bound nitrogen

• Virtually all becomes NOx

Prompt NOx• Formed in the very early portion of the flame zone where air and fuel

first mix or react. The reaction occurs in a part of the flame where little, if any, Thermal NOx is formed.

Nothing can be done to prevent either of these, except changing fuel.

Emissions – NOx

Thermal NOx• For most gaseous fuels, the major concern is Thermal NOx.

• Thermal NOx formation rates are highly sensitive to peak flame temperatures.

• Thermal NOx begins to form at 2800°F (1538°C)

• Above 3200°F (1760°C), the NOx formation rate doubles for every 190°F (88°C) increase in flame temperature.

Thermal NOx is the prime target of Low NOx burners

• Burners

• Flares

• Incinerators

• Combustion Systems

TO CONVERT To:

Multiply by

From NOx SOx CO lb/MMBtu g/GJ

mg/Nm3

ppm ppm ppm COALa OILb GASc COALa OILb GASc

mg/Nm3

1 0.487 0.350 0.800 6.65E-04 6.25E-04 5.92E-04 0.286 0.269 0.255

NOx ppm 2.053 1 1.36E-03 1.28E-03 1.21E-03 0.587 0.552 0.523

SOx ppm 2.858 1 1.90E-03 1.78E-03 1.69E-03 0.818 0.768 0.728

CO ppm 1.250 1 8.30E-04 7.80E-04 7.39E-04 0.358 0.336 0.318

COALa 1503 734 527 1205 1 429.95

lb/MMBtu OILb 1600 781 561 1283 1 429.95

GASc 1689 824 592 1353 1 429.95

COALa 3.495 1.702 1.223 2.797 2.33E-03 1

g/GJ OILb 3.721 1.813 1.302 2.978 2.33E-03 1

GASc 3.928 1.913 1.374 3.143 2.33E-03 1

Notes:

a: COAL: Flue Gas dry 3% excess O2; Assumes 263 dsm3/GJ - 9780 dscf/MMBtu - Reference EPA 40CFR pt. 60, App. A, Meth. 19

b: OIL: Flue Gas dry 3% excess O2; Assumes 247 dsm3/GJ - 9190 dscf/MMBtu - Reference EPA 40CFR pt. 60, App. A, Meth. 19

c: GAS: Flue Gas dry 3% excess O2; Assumes 234 dsm3/GJ - 8710 dscf/MMBtu - Reference EPA 40CFR pt. 60, App. A, Meth. 19

STANDARD CONDITIONS (IMPERIAL); 68oF, 1 atm.

NORMAL CONDITIONS (SI); 32oF, 1 atm.

COMMON EMISSION

CONVERSION CHART

Emission Conversion Chart

Burner Zone Heat Release - BZHR

What do we mean by Burner Zone

Heat Release (BZHR)?

Available heating surface area

compared to the heat input.

NOx Correlation – The ‘Battle’ of Parameters

Proper Combustion Air Flow

95% OF MASS FLOW IN THE COMBUSTION PROCESS IS AIR, NOT FUEL

THREE FUNDEMENTAL ASSUMPTIONS OF BURNER DESIGN

1. Balanced airflow to all burners +/-2%

2. Even peripheral distribution around each

burner entrance +/-15%

3. No swirl entering the burner, other than

what’s imparted by the burner itself

Getting this right pays dividends for the life of the system.

Airflow Imbalance = Flame Imbalance = Emissions

BURNER #1 - PERIPHERAL VELOCITY DISTRIBUTION

0

1000

2000

3000

4000

5000

6000

7000

8000

12:00

1:30

3:00

4:30

6:00

7:30

9:00

10:30

Before Correction

After Correction

Physical Flow and CFD Modeling

▪ Burner-to-burner balance for multi-burner

installations

▪ Lowers excess air requirements

▪ Used on all burners* / OFA / FGR systems

▪ Required for all fuels and unit types

▪ Lowers CO2 footprint

▪ Minimizes startup and commissioning times

▪ Can Eliminate Combustion Vibration

* Except burners with E-style Windboxes

Dual Register Burner

• A portion of the exhaust gas is directed back to dilute the air/fuel stream of the burner in order to:• Absorb some of the heat of combustion

• Reduce adiabatic flame temperature, and thereby reducing Thermal NOx

• FGR is most often expressed as a percent and refers to the mass percent of the flue gas exiting the stack that is being directed back to the burner

Flue Gas Recirculation

Flue Gas Recirculation (FGR) - Lower Thermal NOx

Applied to Field-erected and Package boilers alike

Forced FGR Fan and Duct requirements▪ Higher capital and maintenance▪ Added controls▪ Less efficient system

External FGR will impact balance of heat transfer ▪ Lower radiant furnace heat transfer and higher convective heat transfer▪ Lower FEGT out of furnace ▪ More mass flow through convective bank▪ When adding more than 10% FGR, a boiler impact study should be

performed

Flue Gas Recirculation Rates

Flue Gas Recirculation Systems

• Induced Flue Gas Recirculation – IFGR• Uses the FD Fan Inlet to draw flue gas from the boiler outlet • Fan sizing could be influenced• System design and flow control can be difficult• Great mixing of inert flue gas with combustion air

• Forced Flue Gas Recirculation – FGR• Includes a dedicated FGR Fan to push flue gas into the burner• FGR Fan increases capital cost• There’s a Lifetime O&M Cost too

Induced FGR System

Flue Gas Recirculating to FD Fan

FD Fan with FGR Mixing Box

FGR-CombustionAir Mixture

15%-85% Typical

FGR Manual Damper

Flue Gas Outlet

Comb Air Inlet

Boiler Gas Out

Forced FGR System

Flue Gas Recirculating Fan

FD Fan

FGR Sparger Pipes (4)

Windbox

Boiler Outlet

Low NOx Burner

Low NOx Design:

▪ 50-80ppm w/no FGR

▪ 30ppm with 15% FGR

▪ 100ppm CO

Staged Gas within throat for NOx Reduction

Steam Injection for NOx ‘polishing’

Axial Flow Register

Dual Register Burner

Burner Stabilization

• Swirling air produces a vortex at the burner outlet which induces hot furnace gases to flow back towards the burner

• This is referred to as the Internal Recirculation Zone (IRZ)

• The IRZ creates burner stability

Airflow Dynamics

• Burner Swirl Number (Sn) represents the ratio of tangential momentum to axial momentum

• Sn = Tangential Momentum• Axial Momentum

• A ratio of 0.6 is required to form an IRZ

GB Low NOx Burner Technology

Capacity: 15 – 430+ MMBtu/hr (single burner)

Emissions:

▪ NOx:

▪ CO: 100 ppm

Excess Air: 10%

RDL: 5-12 in. w.c.

Turndown:

▪ 10:1 gas; 8:1 oil (operation)

▪ 4:1 (emissions)

No FGR 15% FGR

Nat. Gas 50 25

#2 Oil 80 50

#6 Oil 250 125

PPM

Firing example – ~100% load

Fuel Oil firing

• Avoid unnecessary airflow disruptions

Airflow Dynamics

Defining Ultra-low NOxFrom a combustion point of view

ULTRA-LOW NOx = CONTROLLED INSTABILITY

A very important point to be aware of and take into consideration. The significance of significant digits

▪ EPA MACT Requirement is 0.01 lb./MMBtu

▪ 0.01 does not necessary equal 0.010

▪ 9 ppm equals 0.011 (9 ppm NOx = 23.22 mg/Nm3)

▪ 0.010 equals 8 ppm

▪ 0.01 technically equals anything up to 0.0149 (12 ppm) (12 ppm or 24mg/Nm3)

▪DON’T PAINT YOURSELF INTO A BOX WHEN APPLYING FOR PERMITS!

Ultra-low NOx Burner

• Center Fired Gas (CFG) for Stability

• Staged outer gas for NOx Reduction

• Stages fuel and air, and local combustion

gases to dilute fuel

• Fuel gas is mixed with inert products of

combustion before combustion occurs, thus

“reconditioning the fuel gas”

Ultra-low NOx Burner Technology

Applicable to virtually any boiler type, industrial and power applications

Lowest NOx / 10-15% Excess Air

▪ 9 ppm NOx with 12-18% external FGR

▪ 30 ppm NOx with no external FGR

▪ 50 to 100 ppm CO

▪ Up to 360 MMBtu/hr in a single burner

Can use Internal and External FGR

Multi-fuel Capability

Turndown: 4 to1 on emissions, 10 to 1 on operation

Ultra-Low NOx Burner Technology

FREE-JET Ultra-Low NOx Burner Technology

Capacity: 15 – 440+ MMBtu/hr (single burner)

Emissions:▪ NOx:

▪ CO: 100 ppm

Excess air: 18%

RDL: 5-12 in. w.c.

Turndown:▪ 20:1 gas; 8:1 oil (operation)

▪ 4:1 (emissions)

No FGR 15% FGR

Nat. Gas 30 9

#2 Oil 80 50

#6 Oil 250 125

PPM

Different NOx Reduction Methods – OFA

Applied to Field Erected Boilers w/ “headroom”

Not applicable to package style / horizontal gas path boilers

Generally want 1-2 burner pitch (~6-16’) from top row of burners to

OFA ports

Minimum of 2 burner pitch (12-16’) from OFA port to nose

BOOS (Burners Out Of Service)

Typically designed for 15-30% of total Combustion Air

Can achieve 10-50% NOx reduction – depending on boiler

Tubular Type Air Preheater

Regenerative Type Air Heater

Combustion Air Heaters

• Replace Air Preheater with Economizer• Recommended when converting from coal to all gas• Improves unit efficiency; reduces combustion air temp• Allows use of existing fans, even when adding FGR• Reduces Register Draft Loss (RDL)

• Eliminate Steam / Hot water coil heaters• Unless needed for cold ambient conditions

• Heat Exchanger

• Increases boiler efficiency• 1% for every 10⁰ increase in feedwater

temperature

Economizer

Different NOx Reduction Methods

FUEL/ TECHNOLOGYGASEOUS LIQUID/ SOLID

STEAM INJECTIONEXCELLENT

MODERATE (LFO)/

POOR (OTHERS)

COMBUSTION AIR

TEMP REDUCTION EXCELLENT POOR-NONE

OFA

FGR

MODERATE EXCELLENT

EXCELLENT

MODERATE (LFO)/

POOR (OTHERS)

Burner & Boiler Room Capabilities

Low/ultra-low NOx burners

Duct burners

Ignition & pilot systems

Physical airflow modeling and CFD

Flame scanners

Fuel train systems

Ancillary burner and combustion equipment

Aftermarket & service

Products ApplicationsIndustrial water tube boilers

Field erected & utility boilers

HRSG’s & OTSG’s

Fluidized bed & circulating fluidized bed boilers

CO boilers

Oil/coal to gas burner retrofits

Start-up burners & ignitors for solid fuel boilers

Recovery boilers

Marine boilers

Stoker boilers (bark, hog fuel, garbage, bagasse)

Turn-key installed projects

What We Don’t Do

Burners for firetube boilers

Residential/commercial package burners

Solid fuel and coal burners

▪ But we can do Ignitors & Scanners

Burners for gas turbines

▪ But we do the HRSG Duct Burners

SNCR / SCR

▪ But we collaborate for best results

Baghouses / ESP

Scrubbers

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Beyond Burners and NOx

NOT a nuclear Power Plant.Hyperbolic Cooling Tower.

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Beyond Burners and NOx

≠

Yes, this was bad.

This is not bad. It’s steam.

NOx Reduction Strategies – SNCR

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SNCR Components

Photo courtesy of FuelTech

Main Components:

• Urea Distribution System• Urea Delivery/Storage

• Urea Mix station and tank

• Urea Control Flow Unit

• Urea Injectors

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SNCR Components

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SNCR Components

Optimum reaction between 1517°F – 1922°F

Selective Catalytic Reduction - SCR

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Applications

• Boiler

• Incinerator

• GT

• HRSG

• Heater

Courtesy of Nationwide/Catastack

NOX

NOX

NOX

NOX

NOX

NOX

SCR

CATALYST

N2 + H2O

+ NH3

+ NH3

+ NH3

SCR Technology - Principles

Ammonia

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• Ammonia (NH3) Injection Grid (AIG)

• SCR catalyst

• Injected ammonia acts as a chemical reagent

– SCR chemical reaction (exothermic: 1oC for each 100 ppm reduced)

– H2O and N2 are released to the atmosphere


Reagent:

• Ammonia– Historically used reagent

– Aqueous – safer than anhydrous but more costly

– Anhydrous – simple system. If small enough, bottle system is very convenient

• Urea– Safest reagent

– Requires higher temperature or longer residence time for direct injection

– Multi step conversion to NH3

– Easily transportable and simple to store

– Readily available

– Cost of use is similar to aqueous ammonia


SCR Technology - Principles

• Exhaust Gas Flow Profile – Velocity distribution

– Temperature distribution

– NOx distribution

– Allowable pressure drop

• Fuel– Natural Gas – lower sulfur, no

particulate, good NO/NO2 ratio

– Other fuels may have poisons,

particulate, temp limits due to SO3

• Physical Constraints– Vertical / Horizontal – Horizontal

configuration adds a complexity to the

sealing design

– Retrofit / New Build – How to add the tail end

system within an existing process

• Reagent– Ammonia – Anhydrous

– Ammonia - Aqueous

– Urea – Diesel Exhaust Fluid (DEF)

SCR Design Considerations


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SCR Design Considerations

Distribution of reagent is critical to performance and Reduction efficiency


Main Components:

• Ammonia Distribution System

• Ammonia Control Flow Unit

• AIG (Ammonia Injection Grid)

• Reactor Housing

• De-NOx Catalyst

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SCR Components


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SCR Catalyst

Catalyst is generally Corrugated plate, Bent Plate or Honeycomb construction, depending on SCR Supplier and application

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Electrostatic Precipitators

Electrically charged particles attach to the plate and get mechanically knocked off by a rapper at the top and collect I the bottom hoppers

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Fabric Filters / Baghouses

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Fabric Filters / Baghouses

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Fabric Bags with Support Cages

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Dry Scrubber

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Scrubbers - Wet

Zeeco Power Hour – June 11, 2020

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Comprehensive Emissions Control

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Clean Skies!

Thank you!

Bob Langstine

Regional Sales Manager, Eastern US & Canada

Zeeco Inc. - Boiler Burner Division

[email protected]

Cell: 470-345-7032

Documents

Zeeco Power Hour · 2020. 9. 28. · • Ammonia (NH 3) Injection Grid (AIG) • SCR catalyst • Injected ammonia acts as a chemical reagent –SCR chemical reaction (exothermic: