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API 73 rd Fall Refining and Equipment Standards Meeting. Los Angeles November 10, 2008. Combustion Analysis Options for Process Heaters. David Fahle – VP of Marketing Hydrocarbon Processing. precision and expertise. ENABLE YOU TO GO FURTHER. Experts in Gas Analysis. Markets. Products.

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Los angeles november 10 2008

API 73rd Fall Refining and Equipment

Standards Meeting

Los Angeles November 10, 2008


Combustion analysis options for process heaters

Combustion Analysis Options for Process Heaters

David Fahle – VP of Marketing Hydrocarbon Processing


Los angeles november 10 2008

precision and expertise

ENABLE YOU TO GO FURTHER


Los angeles november 10 2008

Experts in Gas Analysis

Markets

Products

Technology

Support

  • Process Oxygen

  • Photometric

  • Combustion

  • Laser

  • OEM transducers

  • Analytical Systems

  • Industrial Gas

  • Hydrocarbon Processing

  • OEM Transducers

  • Paramagnetic

  • Zirconia

  • Photometric

  • Thick Film

  • Tuneable Diode Laser

  • Product Support

  • Committed to your Success

  • Quality Focus

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


Los angeles november 10 2008

Servomex Controls Limited formed1952

First paramagnetic cells made based on licence from

Distillers1961

Bought by Sybron Corporation and integrated into Taylor

Instruments Group1971

MBO from Sybron Corporation1987

Stock market flotation (London Stock Exchange)1989

Acquired by The Fairey Group1999

The Fairey Group renamed as Spectris plc2001

Servomex Proud 50 Year History


Los angeles november 10 2008

Global Presence

Global Presence


Los angeles november 10 2008

Combustion Applications


Los angeles november 10 2008

Index of Applications

  • Thermal power generation

  • Incineration

  • HydrocarbonProcessing

  • Industrial Gases

  • Specialty Chemicals and Pharmaceuticals

  • Cement

  • Iron and steel


Los angeles november 10 2008

HydrocarbonProcessing


Los angeles november 10 2008

Application Types

Process Heaters

Direct-fired heat exchanger that uses

the hot gases of combustion to raise the temperature of a

feed flowing through coils of tubes aligned throughout the

heater. Typical temperatures 400°C-550°C (800-1000°F)

Thermal Crackers

Heat exchanger where reactions take place while the feed

travels through the tubes, i.e. Ethylene cracking furnace.

Typical temperatures 980°C-1200°C (1800-2200°F)

On-site Incinerators

Designed to combust both solid and liquid chemical waste.

The type depends upon the type of waste being disposed

and include fluidized bed, multiple hearth and rotating kiln incinerators.

Typical temperatures 1100°C (2000°F) or greater.

HydrocarbonProcessing


Los angeles november 10 2008

Process Heaters and Thermal Crackers -

pipes run inside heating chamber to transfer heat

Application Types

HydrocarbonProcessing


Los angeles november 10 2008

  • Why measure gases during combustion?

  • Detecting oxygen rich conditions: O2 measurement

  • Detecting fuel rich conditions: CO measurement

  • Combustion Analyzer Types


Complete combustion

Combustion:Why measure gases?

Complete Combustion

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

FUEL + OXYGEN  CARBON DIOXIDE + WATER + HEAT


Los angeles november 10 2008

Combustion Efficiency

Ideal

FUEL RICH

incomplete combustion

%

CO

Too little oxygen = some fuel not burnt:

2000ppm excess CO above ideal means 1% extra fuel cost

O2

-20

-10

0

10

20

% Excess Air


Los angeles november 10 2008

Combustion Efficiency

Ideal

FUEL RICH

incomplete combustion

AIR RICH

complete combustion

%

CO

Too much air

= cooling effect:

1.5% excess oxygen above

ideal means 1% extra fuel cost

Too little oxygen = some fuel not burnt:

2000ppm excess CO above ideal means 1% extra fuel cost

O2

-20

-10

0

10

20

% Excess Air


Los angeles november 10 2008

Combustion Efficiency

FUEL RICH

20

AIR RICH

16

NOx

CO

12

EFFICIENCY

8

4

IDEAL

O2

0

10

20

-20

-10

% Excess Air


Los angeles november 10 2008

Review - Breakthrough Concept

Example 1: Coal data, 10h sample


Los angeles november 10 2008

Review - Breakthrough Concept

Example 1: Coal data, 1h


Los angeles november 10 2008

Review - Breakthrough Concept

Example 1: Coal data, 5mins


Los angeles november 10 2008

Review - Breakthrough Concept

Example 2: Gas data, 3 week sample


Los angeles november 10 2008

Review - Breakthrough Concept

Example 2: Gas data, 10h sample


Los angeles november 10 2008

Combustion Efficiency

FUEL RICH

20

AIR RICH

16

NOx

CO

12

EFFICIENCY

8

4

IDEAL

O2

0

10

20

-20

-10

% Excess Air


Los angeles november 10 2008

Combustion Control: O2 Measurement Detecting air rich conditions

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


Los angeles november 10 2008

Combustion Control: O2 Measurement Detecting air rich conditions

Paramagnetic

Technology


Los angeles november 10 2008

SO2

O2

CO2

O2

SO2

CO2

CO

HCl

N2

CO

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

O2

NO

NO

O2

O2

O2

O2

O2

O2

NO2

NO2

NO2

O2

SO2

HCl

CO2

CO

SO2

SO2

CO2

HCl

CO

CO2

CO2

N2

CO

HCl

N2

N2

CO


Los angeles november 10 2008

Paramagnetic Cell

Magnet pole pieces

Nitrogen filled spheres

Feed back coil

Suspension & mirror

LED source

Photocell sensor


Los angeles november 10 2008

Combustion Control: O2 Measurement Detecting air rich conditions

Paramagnetic Technology Provides:

Performance

  • Fast response

  • Exceptional linearity and repeatability

  • High stability & accuracy

    Economics

  • Long operational life

  • Extractive sample system required

  • Simple validation / calibration


Los angeles november 10 2008

Combustion Control: O2 Measurement Detecting air rich conditions

Zirconia Oxide

Technology


Los angeles november 10 2008

Zirconia disk

Electrodes

Combustion Control: O2 Measurement Detecting air rich conditions

Zirconium oxide (zirconia) based techniques

Heated Chamber

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


Los angeles november 10 2008

0

100

Combustion Control: O2 Measurement Detecting air rich conditions

Zirconium oxide (zirconia) based techniques

When the oxygen concentration on each side is different,

an emf related to oxygen concentration is generated.

Sample

Reference

Nernst Equation

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

assuming a constant cell temperature

7000C


Los angeles november 10 2008

Combustion Control: O2 Measurement Detecting air rich conditions

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


Los angeles november 10 2008

Combustion Control: O2 Measurement Detecting air rich conditions

TDL

Technology


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


Optical absorption spectroscopy1

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

Optical Absorption Spectroscopy


Single line spectroscopy

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


Single line spectroscopy1

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

Single Line Spectroscopy


Single line spectroscopy2

A single HCl line

Laser scan range

Single Line Spectroscopy

Absorption spectrum for offgas from waste incinerator


Measurement influences

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)


Los angeles november 10 2008

  • 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

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


Los angeles november 10 2008

  • 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

From HITRAN database


Los angeles november 10 2008

Combustion Control: O2 Measurement Detecting air rich conditions

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


Los angeles november 10 2008

Combustion Control: CO Measurement Detecting breakthrough and flooding

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


Los angeles november 10 2008

Combustion Control: CO via Thick Film Sensor

Very thin platinum tracks are printed onto a ceramic disk.


Los angeles november 10 2008

Combustion Control: CO via Thick Film Sensor

Very thin platinum tracks are printed onto a ceramic disk.

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


Los angeles november 10 2008

Combustion Control: CO via Thick Film Sensor

Very thin platinum tracks are printed onto a ceramic disk.

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.


Los angeles november 10 2008

Combustion Control: CO via Thick Film Sensor

A special catalyst that is selective to CO is then printed over two quadrants


Los angeles november 10 2008

Combustion Control: CO via Thick Film Sensor

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

CO

CO

CO

CO

CO

CO

CO

CO

CO

CO

CO

CO

CO


Los angeles november 10 2008

Combustion Control: CO via Thick Film Sensor

CO

CO

CO

CO

CO

CO

CO

CO

CO

CO

CO

The change in temperature is detected by the platinum tracks underneath, changing their resistance, which can be detected.

CO

CO


Servotough fluegas

ServoTOUGH Fluegas


Servomex combustion analyzer history

700 B / N

700 Ex

Servomex Combustion Analyzer History

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 700 Combustion Analyzer


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

Model 2700 Combustion Analyzer


Los angeles november 10 2008

Sensor Head and Remote Controller


Principal of operation 2700b

Principal of Operation 2700B

Solenoid

Valve

Aspirator Air

O2 Cell

Auxiliary Air

COe

Sensor

Breather

Heated

Enclosure

Flame

Trap

Flame

Trap

Aspirator

Internal

Filter

AutoCal &

BlowBack

Sample

Inlet

Low Flow Extractive

Aspirator

& Sample

Outlet


Principal of operation 2700c

Solenoid Valve

Aspirator Air

Heated

Enclosure

Aspirator

Aspirator

& Sample

Outlet

COe Cell

Aux

Air

Rest.

Flame

Trap

Internal

Filter

100 ml/min

Sample

Inlet

200ml/min

Probe

Flame

Trap

O2 Cell

AutoCal &

BlowBack

Breather

Principal of Operation 2700C


Los angeles november 10 2008

Servomex Zirconia Cell


Servomex 2700 zro2 zirconia sensor

Diaphragm Springs

Heater

Reference Air In

Sample in

Platinum Electrodes

Zirconia Crucible

mV

Servomex 2700 ZrO2 Zirconia Sensor


Los angeles november 10 2008

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


Los angeles november 10 2008

Thick Film Sensor Structure

Sensor disc

Heater band

Outlet

Sensor housing

PRT

Inlet

Header

assembly


Los angeles november 10 2008

Thick Film Sensor Location

Heater

Combustibles

Sensor

Flame

Trap

Oxygen

Cell

Aspirator

Internal

filter


Los angeles november 10 2008

Thick Film Sensor Location

Insulated

cover keeps wetted components above 210°C

Keep it hot =

Increase performance.

Stop condensation.

Stop blockage.

Stop corrosion.

Increase life.

Thick Film

Sensor

Zirconia

Sensor


Los angeles november 10 2008

2700 Flame Traps and Filter

Internal

Sample

Filter

(5 micron)

Flame

Arrestor

(tested by

external agency)

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


Los angeles november 10 2008

2700 Probes

Internal

Filter &

Flame Trap

Assembly

Sample Tube

Filter Element

½” NPT Probe Fitting

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


Los angeles november 10 2008

2700 Probes

3182

1750

High Temperature Ceramic Probe for temperatures < 3182F

2732

1500

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

1000

1832

Ceramic

1292

700

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

932

500

Haynes Alloy 556

S.S 316

°F

°C

0

32


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.

Questions on Analyzer Operation


Questions on analyzer operation1

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

Questions on Analyzer Operation


Questions on analyzer operation2

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

Questions on Analyzer Operation


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

Best Practice for Installation


Servotough laser

ServoTOUGH Laser


Servotough laser gas ii

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


Dual modulation technique1

Dual Modulation Technique

Diodecurrent

Diode

laser

power

Ramp

current

High freq.

modulation

()

(2)

Process

gas

Second harm.

Temp. contr.

Diode laser

Signal

processing

Mixer

Detector

Filter

Direct signal

Det. current


Differences from conventional ir spectroscopy

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.

Second harmonic WMS,

2nd derivative of line shape

Direct absorption scan


Los angeles november 10 2008

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


Los angeles november 10 2008

HARNESS THE POWER OF

expertise

SERVOTOUGH Combustion Solutions


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