los angeles november 10, 2008 api 73 rd fall refining and equipment standards meeting

Los Angeles November 10, 2008

API 73rd Fall Refining and Equipment Standards Meeting

Combustion Analysis Options for Process Heaters

David Fahle – VP of Marketing Hydrocarbon Processing

ENABLE YOU TO GO FURTHER

precision and expertise

• Industrial Gas

• Hydrocarbon Processing

• OEM Transducers

• Product Support

• Committed to your Success

• Quality Focus

• Process Oxygen

• Photometric

• Combustion

• Laser

• OEM transducers

• Analytical Systems

Experts in Gas Analysis

• Paramagnetic

• Zirconia

• Photometric

• Thick Film

• Tuneable Diode Laser

Markets Products Technology Support

Gas Analysis is what we do - And we do it best

Servomex Proud 50 Year History

• Servomex Controls Limited formed 1952• First paramagnetic cells made based on licence from

Distillers 1961• Bought by Sybron Corporation and integrated into Taylor

Instruments Group 1971 • MBO from Sybron Corporation 1987• Stock market flotation (London Stock Exchange) 1989• Acquired by The Fairey Group 1999• The Fairey Group renamed as Spectris plc 2001

Global PresenceGlobal Presence

Combustion Applications

Index of Applications

Thermal power generation

Incineration

Hydrocarbon Processing

Industrial Gases

Specialty Chemicals and Pharmaceuticals

Cement

Iron and steel

Hydrocarbon Processing

Process HeatersDirect-fired heat exchanger that usesthe hot gases of combustion to raise the temperature of afeed flowing through coils of tubes aligned throughout theheater. Typical temperatures 400°C-550°C (800-1000°F)

Thermal Crackers Heat exchanger where reactions take place while the feedtravels through the tubes, i.e. Ethylene cracking furnace. Typical temperatures 980°C-1200°C (1800-2200°F)

On-site IncineratorsDesigned to combust both solid and liquid chemical waste. The type depends upon the type of waste being disposedand include fluidized bed, multiple hearth and rotating kiln incinerators.Typical temperatures 1100°C (2000°F) or greater.

Application Types Hydrocarbon Processing

Application Types Hydrocarbon Processing

Process Heaters and Thermal Crackers -pipes run inside heating chamber to transfer heat

•Why measure gases during combustion?

•Detecting oxygen rich conditions: O2 measurement

•Detecting fuel rich conditions: CO measurement

•Combustion Analyzer Types

Complete Combustion

CxHy + (x+(y/4))O2 xCO2 + (y/2)H2O + HEAT

FUEL + OXYGEN CARBON DIOXIDE + WATER + HEAT

Combustion:Why measure gases?

0 10 20-10-20

Ideal

CO

O2

FUEL RICH

incomplete combustion

Too little oxygen = some fuel not burnt:

2000ppm excess CO above ideal means 1% extra

fuel cost

%

Combustion Efficiency

% Excess Air

% Excess Air0 10 20-10-20

Ideal

CO

O2

AIR RICH

complete combustion

Too much air

= cooling effect:

1.5% excess oxygen above

ideal means 1% extra fuel cost

FUEL RICH

incomplete combustion

Too little oxygen = some fuel not burnt:

2000ppm excess CO above ideal means 1% extra

fuel cost

%


NOx

-20 -10 0 10 20

20

16

FUEL RICH AIR RICH

IDEAL

EFFICIENCY

O2

12

8

4

CO


% Excess Air

Review - Breakthrough Concept

Example 1: Coal data, 10h sample

Typical COe 'Breakthrough' Event - 10 hour data period

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

0 1 2 3 4 5 6 7 8 9 10

Time (hours)

CO

e r

ea

din

g (

pp

m)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

O2

Re

ad

ing

(%

)

COe Reading (ppm) O2 Reading (%)

See Detail Zoom


Example 1: Coal data, 1h

Typical COe 'Breakthrough' Event - 1 hour data period

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 7.0

Time (hours)

CO

e R

ead

ing

(p

pm

)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

O2

Rea

din

g (

%)


2. COe 'breakthrough' event. Oxygen level

drops 2% COe level increases

3. Oxygen level returns to 'excess air'. COe reading drops quickly to base level

1. Process stable. Oxygen level controlled at approx 5%. COe at low background levels.


Example 1: Coal data, 5mins

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

384 385 386 387 388 389 390 391 392 393 394

Time (mins)

CO

e R

ead

ing

(p

pm

)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

O2

Rea

din

g (

%)



Example 2: Gas data, 3 week sample

0

5

10

15

20

25

0 50 100 150 200 250 300 350 400 450 500

TIME (hours)

Oxy

gen

(%

)

-100

0

100

200

300

400

500

CO

e (p

pm

)

Oxygen (%) AI05005.PV COeq (ppm) AI05041.PV


Example 2: Gas data, 10h sample

0

5

10

15

20

25

420 421 422 423 424 425 426 427 428 429 430

TIME (Hours)

OX

YG

EN

(%

)

-100

0

100

200

300

400

500

CO

e (

pp

m)

Oxygen (%) AI05005.PV COeq (ppm) AI05041.PV

NOx

-20 -10 0 10 20

20

16

FUEL RICH AIR RICH

IDEAL

EFFICIENCY

O2

12

8

4

CO


% Excess Air

How can oxygen be measured?

Paramagnetic• High accuracy• Need extractive sample system with moisture removed

“Zirconia” (zirconium oxide, ZrO2) based analysers

• Suitable accuracy, measure hot and wet• Fast analysis, low maintenance and low cost

Tuneable Diode Laser• In-situ analysis• Hot, corrosive, particulate latent samples

Combustion Control: O2 Measurement Detecting air rich conditions

Paramagnetic Paramagnetic TechnologyTechnology


Oxygen is unique.

It is strongly attracted

into a magnetic field.

It is described as being “ paramagnetic ”

O2

O2

O2

O2

O2

O2

O2

O2

O2

O2

O2

O2O2

O2

O2

O2

CO

COCO2 CO2

SO2 HCl HCl

N2

NO NO

N2

O2

O2

COCOCO2 CO2

SO2 SO2

HCl N2

NO2 NO2 NO2

O2

O2

O2

COCO

CO2 CO2

SO2 SO2

HCl N2

Paramagnetic Cell

Magnet pole pieces

Nitrogen filled spheres

Feed back coil

Suspension & mirror

LED source

Photocell sensor

Paramagnetic Technology Provides:Performance

• Fast response

• Exceptional linearity and repeatability

• High stability & accuracy

Economics• Long operational life

• Extractive sample system required

• Simple validation / calibration


Zirconia Oxide Zirconia Oxide TechnologyTechnology


At high temperatures, zirconia conducts electricity through the movement of oxygen ions.

Heated Chamber

Zirconium oxide (zirconia) based techniques

Zirconia disk

Electrodes


0 100

ReferenceSample

7000C

When the oxygen concentration

on each side is different,

an emf related to oxygen

concentration is generated.

Nernst Equation

Cell output, E = K x Ln ( Pr/ Ps) mV

assuming a constant cell temperature

Zirconium oxide (zirconia) based techniques


Zirconia Oxide Technology Provides:Performance

• Fast response

• Unaffected by background gases

• Sample at hot / wet conditions

Economics• Very acceptable operational life

• Low maintenance requirements

• Simple validation / calibration


TDLTDLTechnologyTechnology


Optical Absorption Spectroscopy

• Based on Beer-Lambert law• Used both in UV and IR• Typical wideband techniques have low spectral resolution and

sensitivity is limited by cross-interference• The alternative is single line spectroscopy using tuneable

diode lasers (TDL)• TDL are available for a range of gases of interest

Optical Absorption Spectroscopy

• Beer Lambert law: T = exp(-Sg(f)NL)– T is transmission– S is the absorption strength– g(f) is the line shape function– N is the concentration of absorbing molecules– L is the optical path length

• Measuring T and knowing S, g(f) and L, N can be found• Use single absorption lines in the NIR

Single Line Spectroscopy

Gas under test, typical absorption linewidth 0.05 nm

Absorption lines from other (background) gases

Laser scan range, typically 0.2 - 0.3 nm, note Laser spectral line width is ca. 0.0001 nm

UV / IR absorption spectroscopy linewidth > 2 nm


• Choose a single absorption line from available databases• Ensure no cross interference from other gases

Typical Gas Mix for Waste Incinerator– 10 mg/m3 HCl– 15% H2O

– 6% O2

– 500 mg/m3 SO2

– 350 mg/m3 NOx

– 100 mg/m3 CH4

– 150 mg/m3 CO– 10% CO2

0.9986

0.9988

0.9990

0.9992

0.9994

0.9996

0.9998

1.0000

5700 5720 5740 5760 5780 5800

Wavenumber (cm^-1)

Tra

nsm

issi

on

H2O

CH4

HCl


0.9986

0.9988

0.9990

0.9992

0.9994

0.9996

0.9998

1.0000

5737 5738 5739 5740 5741 5742

Wavenumber (cm^-1)

Tra

nsm

issi

on

H2O

CH4

HClLaser scan range

A single HCl line

Absorption spectrum for offgas from waste incinerator

Measurement influences

• Measurement influenced by:– Pressure– Temperature– Background gas composition

• Just like conventional IR measurements!

• Due to inter-molecular collisions, which strongly affect the absorption line:

– its amplitude– Its width– Its shape (asymmetry)

• Note: 2f WMS signal is just filtered version of line shape, so all information above is still available (non-linear relations however)

4

3

2

1

0

-2 -1 0 1 2

amplitude

width

asymmetry

• Pressure influence– Frequency of collisions increases with gas density i.e. total pressure– Causes line broadening, hence the term “pressure broadening”– Line amplitude (per molecule) is unchanged– Small line centre shift occurs also– Maximum measurement pressure limited by pressure broadening smearing the

line so as to overlap an adjacent line

8

6

4

2

0

-2

lock

-in a

mpl

ifier

out

put (

V)

-0.015 -0.010 -0.005 0.000 0.005 0.010 0.015wavelength scan (nm)

background 1.25 bar 1.0 bar 1.5 bar 2.0 bar 2.5 bar 3.0 bar 4.0 bar 5.0 bar

0.014

0.012

0.010

0.008

0.006lin

e w

idth

(nm

)

3.02.52.01.51.0abs. pressure (bar)

Pressure broadening measured for 2f WMS spectroscopy of O2 in N2

• Temperature influence– Changes gas density and molecular velocity distribution, hence collision

frequency and line width– Temperature also changes thermal excitation of molecular vibrations, hence the

line amplitude (per molecule)– Can be exploited to distinguish hot gas from cold gas e.g. 2900 (NEO) oxygen

analyser

8x10-24

6

4

2

0

line

inte

nsity

/(cm

/mol

)

775770765760wavelength/nm

800K 300K 1300K

Oxygen lines at high temperature

From HITRAN database

TDL (Tuneable Diode Laser) Provides:Performance

• Fast response

• In-situ measurement at process conditions

• Temperature and moisture measurement possible

Economics• Long operational life

• Low maintenance requirements

• Inferred validation


How can CO be measured?

Thick film• High accuracy at process conditions• Cost effective measurement in combination with O2

Tuneable Diode Laser• In-situ analysis• Hot, corrosive, particulate latent samples

Combustion Control: CO Measurement Detecting breakthrough and flooding

Very thin platinum tracks are printed onto a ceramic disk.

Combustion Control: CO via Thick Film Sensor



These form resistors in a “Wheatstone bridge”, an arrangement that allows small changes in resistance to be accurately detected.

Each quadrant is thermally isolated from next by slots.



These form resistors in a “Wheatstone bridge”, an arrangement that allows small changes in resistance to be accurately detected.

A special catalyst that is selective to CO is then

printed over two quadrants


Any CO in the sample will burn on the surface of the catalytic material, creating a change in temperature.

CO

CO

CO

COCO

CO

CO

COCO

COCO

COCO


CO

CO

CO

COCO

CO

CO

COCO

COCO

COCOThe change in temperature is detected by the platinum tracks

underneath, changing their resistance, which can be detected.


ServoTOUGH Fluegas

Servomex Combustion Analyzer History

700 B / N

700 Ex

2700

Model 700 Combustion Analyzer

• Model 700 was introduced circa 1987• Two Models 700B & 700EX• Key Features:

– Separate sensor head and remote control unit– Oxygen only or with combustibles option– Rugged design (IP55)/wide range of applications– Comprehensive range of probes and filters– Fast dynamic response– Low flow (300 ml) extractive design

• 700B was discontinued in 1998• 700EX was discontinued in 2003

700 B / N

700 Ex

Model 2700 Combustion Analyzer

• The 2700 was Introduced 1998• Three Models 2700, 2700B & 2700C• The 2700C was introduced in 2006• Key Features:

– Same basic principal of operation– Standard flame traps– Simple Intuitive User Interface– Auto Calibration and assignable alarm relays– Integral auxiliary air supply– Introduced the TFx combustible sensor for COe– Easy access to servable parts

Sensor Head and Remote Controller

Auxiliary Air

Aspirator Air

AutoCal &BlowBack

SampleInlet

Aspirator& Sample

Outlet

HeatedEnclosure

Flame Trap

InternalFilter

O2 Cell

COeSensor Breather

Low Flow Extractive

Aspirator

Flame Trap

Solenoid Valve

Principal of Operation 2700B

Aux Air

Rest.

Aspirator Air

AutoCal &BlowBack

SampleInlet

200ml/min

Aspirator& Sample

Outlet

HeatedEnclosure

Flame Trap

InternalFilter

O2 Cell

COe Cell

Breather

Aspirator

Flame Trap

Solenoid Valve

Probe

100 ml/min

Principal of Operation 2700C

Servomex Zirconia Cell

mV

Sample in

Servomex 2700 ZrO2 Zirconia Sensor

Heater

Reference Air In

Platinum Electrodes Zirconia Crucible

Diaphragm Springs

Servomex Thick Film Sensor

Sample enters and is heated by sensor body

Hot sample reaches sensor and CO combusts - calibrated as CO equivalents (COe)

Heater

Heater

Heater band

PRT

Headerassembly

Sensor housingOutlet

Inlet

Sensor disc

Thick Film Sensor Structure

CombustiblesSensor

OxygenCell

Internalfilter

FlameTrap

Aspirator

Heater

Thick Film Sensor Location

Thick Film Sensor Location

ZirconiaSensor

Thick FilmSensor

Insulatedcover keeps wetted components above

210°C

Keep it hot =Increase performance.

Stop condensation.Stop blockage.Stop corrosion.

Increase life.

InternalSample

Filter(5 micron)

FlameArrestor(tested by

external agency)

2700 Flame Traps and Filter

Flame traps prevent risk of sensors igniting unburnt fuel at start up and causing an explosion

Modular Design• Open, standard filter or large filter• Variable lengths, with or without probe retention• Wide range of temperatures: <700°C to 1750°C (<1300°F to 3182°F) • Special materials eg ceramics or alloys• 4” ANSI Standard, 3” ANSI, JIS, DIN, 700B or Thermox flanges

2700 Probes

Sample Tube

½” NPT Probe Fitting

Filter Element

InternalFilter &

Flame TrapAssembly

°F

Stainless Steel 316 Probe can be used up to 1292F at any probe length

Haynes Alloy 556 Probe used for temperatures < 1832F Max temp will be dependent upon probe length

High Temperature Ceramic Probe for temperatures < 3182F

°C

0

500

1000

1500

32

932

1832

2732

3182 1750

1292 700

Cer

amic

Hay

nes

All

oy

556

S.S

316

2700 Probes

Questions on Analyzer Operation

• How does the analyzer respond in a low oxygen and /or high combustible conditions?– The analyzer will continue to measure what it sees. The combustible measurement is

maintained by the auxiliary air. The oxygen reading is maintained but will be reduced from the true reading by an amount which is dependent on the combustible gas species and concentration. The sensors will not be adversely affected.

• What are the analyzer/sensor response times?– When installed with a typical probe for heater applications and unfiltered software the T90

response time for oxygen is 10 seconds and 20 seconds for combustibles at 300 ml/min sample rate.

• Is output signal damping available?– The software allows dampening of both the oxygen and combustible outputs and displays. It

can be applied by differing amounts and can be switch out if required.• How does the analyzer measure combustibles?

– The combustibles analysis is wet and is optimized and calibrated for carbon monoxide to enhance its use for combustion control. The combustibles sensor will respond to most flammable gases apart from methane. Its response to hydrogen is twice that of carbon monoxide.


• What is the recommended testing frequency?– The initial calibration intervals are 3 months for oxygen and 1 month for combustibles but

after operational experience this may typically be extended to 12 months and 2 months• What are the known failure modes for the analyzer?

– Internal failures• Temperature control oxygen• Temperature control combustibles• Sensor heads• Wiring faults• Block heater

– External failures• Aspirator air supply• Restricted probe• Sensor head temperature

– External issues• Mounting flange temperature• Radiated heat from process• Ambient temperature hot and cold


• What are the common known failure modes for the analyzer?– Loss of sample flow due to probe blockage– Loss of air pressure for aspiration, purging, etc.– Controller power– Sensor head power– Sensor head block heater

Best Practice for Installation

• Serviceable location• Ensure ambient temperature is within specifications• Protect from wind chill• Protect from radiant heat• Minimize flange distance from wall to insulation• Use correct cable• Minimize distance between sensor head and controller• Insure proper wiring termination• Use probe retention flange when temperature is above 700C• Locate utilities in a stable ambient environment• Consider blowback for high sulfur high particulate samples• Leave sensor head off process until ready to power up

ServoTOUGH Laser

ServoTOUGH Laser Gas II

Dual Modulation Technique

• Laser wavelength chosen to match absorption line, fine tuning with temperature and current

• Tune diode laser by temperature to pin-point the centre wavelength of a single absorption line (+/-5mK)

• Laser wavelength scanned by applying ramp current• High frequency modulation added for 2nd harmonic detection• 2nd harmonic signal extracted by use of mixer• CPU computes gas concentration

Dual Modulation Technique

Diodecurrent

Diodelaserpower

Rampcurrent

High freq.modulation

() (2)

DetectorProcess

gas Signalprocessing

Temp. contr.Diode laser

Det. current

Mixer

Filter

Second harm.

Direct signal

Differences from conventional IR spectroscopy

• Laser radiation is monochromatic i.e. a specific wavelength, whereas conventional IR source is “multi-chromatic”

• Allows TLDS to measure a single absorption line by scanning across it• Signal is the line shape or a filtered version of it (2f WMS)• Free of cross interfering absorptions if suitable line is chosen i.e. no other lines nearby.

3

2

1

0

-1

lock

-in s

igna

l (V

)

0.0100.000-0.010wavelength scan (nm)

Second harmonic WMS,2nd derivative of line shape

Direct absorption scan

Process gas

Flanges Transmitter

Diode Laser

Purg e gas inlet

Receiver Purge gas

inlet Detector Focusing lens

Instrument window

Process gas

Flanges Flanges Flanges Transmitter

Diode Laser

Purg e gas inlet

Receiver Purge gas

inlet Detector Focusing lens

Instrument window

Loop cable

Collimating lens

Set-up for a in-situ cross stack TDLAS system

HARNESS THE POWER OF

expertise

SERVOTOUGH Combustion Solutions

los angeles november 10, 2008 api 73 rd fall refining and equipment standards meeting

Documents

excess oxygen aboveideal

ppm excess

combustion efficiencynox

excess air01020

oxygen rich conditions

typical temperatures

ideal means

heatwhy measure gases