Process Analysers For Gas and Liquid Phasedownload.caltech.se/download/web/nyheter/michell2014_massa/Proce… · If infrared energy passes through gas some energy gets absorbed ...

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Process Analysers

For

Gas and Liquid Phase

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Moisture technologies and their ranges

No single technology can cover the entire range All have limitations

Dew Point oC -110 -100 -80 -60 -40 -20 0 +20 +40 +60 +80 +100

Impedance

Dew-Point Sensors

Chilled Mirror

Hygrometer

10ppbV 10ppmV 1000pp

mV

23000ppmV 20 % V/V >50 % V/V

RH Sensors

Quartz Sensors

TDL

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Control Unit Sensor Assemblies

Promet I.S.

User interface

Safe area Hazardous area

Optional pressure transmitter

Sensor block

Dew-point transmitter

Electrical connections

Power port and

switch

Built-in I.S. barriers

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Promet IS Process analysers and sample systems

Promet Sampling

System

Easidew II IS

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A real example of diurnal heating

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Promet EExd: Flameproof Certified

• Purpose designed flameproof EExd process moisture analyser • Totally hazardous area installed analyser • ATEX certified • IEC Zone 1 & 2 • NEC Class 1, Div 1 & 2

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Promet EExd Measurement capabilities

• Single- or dual-channel • Comprehensive moisture content units: ppmV/ppbV, mg/Nm3 and LB/MMSCF, for ideal and natural gas • Pressure compensated automatic unit-to- unit conversions for both moisture content and dew point • Natural gas data using IGT#8 or ISO18453

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Conversion from measured dew point to moisture content

Mois

ture

Conte

nt,

mg/m

3

Temperature, oC

0

20

40

60

80

100

120

140

160

180

200

-35 -30 -25 -20 -15 -10 -5 0 5 10

Moisture content in gases @ 7MPa pressure

Natural Gas

n Ideal Gas Air

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Quartz Crystal

Quartz Disk Diameter: 15,5mm

Quartz Disk Thickness: 0,1665mm

• Moisture adsorbs or desorbs on polymer layer • Causes a change in mass of the vibrating crystal • Increase in mass reduces frequency, a decrease has opposite effect • Sorption process fully reversible • No long term drift • Reliable and repeatable performance

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Calibration curve for QMA

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Internal Sampling System Mechanical Assembly

Internal sampling system is self-contained in the oven:

•Fan

• Heater (11W)

• T probe (±0.1°C stability)

• Flow meter (sensor cell outlet)

• Sensor block

Note: Internal drier is external to the oven to retain full efficiency

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Measurement Circuit

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Intuitive touch screen Easy access to functional parameters

Front Screen

Secondary Screen

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QMA2020 Typical Response

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Michell’s Quartz Crystal QMA 2020 Series

• Eexd Zone 1

• 0.1 – 500 ppmV, trend to 1000ppmV • On line verification • ± 10% reading accuracy • -20 to +60°C ambient conditions • Selectable 0-1v, 4-20mA (2of), RS485 serial communications

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Works in NIR region Gas molecules vibrate at specific frequencies If infrared energy passes through gas some energy gets absorbed Water has two different atoms so resonant IR absorption will happen N2 has two identical atoms it is not IR active

Water in complex and non linear Has 3 modes of vibration Locations of peaks unique to water Allows water to be detected avoiding interference from other gases

TDL 600 Basic Theory

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To avoid just being a molecule counter gas is passed into a sample cell with mirrors to increase the path length.

TDL Basic Theory

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Basic Theory Direct Absorption Spectroscopy

Wavelength Modulation Spectroscopy

• Direct absorption: simpler but least sensitive • WMS sharper and less temperature dependant

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TDL600 Highlights • 1-5000ppmV range • ± 1% reading of 1 ppmV • Local display • EExd rated IEC and ATEX rated • ppmV, lb/MMscf, mg/m3, °C dp • 4-20mA (x3) and MODBUS RTU outputs • 5000 point data logger • Fast response to both increase & decrease in moisture • Active Background Compensation • Long term calibration free operation

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LIQUIDEW IS & EExd Moisture in Liquid Analyzer

Complete moisture measurement packages for critical petrochemical liquid applications

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Moisture Measurement in Liquids

• Liquids consisting of non polar molecules such as hydrocarbon

chain or hydrocarbon rings do not mix with water (immiscible).

• Liquid Hydrocarbons can absorb a certain amount of water

vapour (dissolved moisture) and thus have a limited saturation

concentration.

• Dissolved moisture acts as a gas, exerting a partial pressure

with corresponding dew point temperature.

• Saturation concentration is specific to the liquid and highly

dependant on temperature.

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Henry’s Law

In chemistry, Henry's law is one of the gas laws. It was formulated by William Henry (1774-1836) of Manchester, England in 1803.

Henry’s Law states that: At a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.

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Henry’s Law is used for determining Weight Portion of moisture in total Liquid.

Moisture content in ppmW = K X Pw

where K is Henry’s constant of particular solute liquid at measured temperature,

PW is Partial water vapour pressure, measured by our ceramic moisture sensor.

K = CS/PS

where CS = Saturation Concentration in ppmW

and PS = Saturation vapour pressure at temperature of measurement.

Henry’s Law

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Solubility data

Saturation concentration of propane and butane

0

100

200

300

400

500

600

700

0 10 20 30 40 50

Temperature of liquid, deg. C

Cs,

pp

mW

Propane

Butane

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Solubility data for mixtures

Calculated saturation concentration of

typical LPG propane and butane mixtures

0

100

200

300

400

500

600

700

0 10 20 30 40 50

Temperature of liquid, deg. C

Cs,

pp

mW

Propane

Butane

70%C3-30%C4

80%C3-20%C4

90%C3-10%C4

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Liquidew IS

Moisture in liquid analyzer with remote intrinsically safe measurement transmitters

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Liquidew IS Sampling Systems

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Liquidew EExd: Flameproof certified

• Purpose designed flameproof EExd process moisture analyser

• Totally hazardous area installed analyser

• ATEX & CSA(US) certified

• IEC Zone 1 & 2

• NEC Class 1, Div 1 & 2

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Liquidew EExd Measurement capabilities

• Single- or dual-channel

• Automatic real-time Henry’s Law calculation of moisture content

• Factory programmed saturation concentration values for 6 common solutes

• Custom Cs data entry for other solutes and mixtures

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Standard sample systems

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CONDUMAX II Hydrocarbon Dew Point Measurement

The latest generation Hydrocarbon dew point analyser from Michell

Instruments offers a major step forward in the precise measurement and control of a vital natural gas quality parameter.

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H2O Dewpoint

HC Dewpoint

-40 -30 -20 -10 0 +100

1

2

3

4

5

6

7

8

Wholly gaseousHC liquids

present in

gas

Water and

HC liquids

preset in

gas

Temperature, °C

Pressure

MPaTypical Phase Envelope for Northern Europe natural gas

WHAT IS HYDROCARBON DEW POINT? THEORECTICAL DEFINITION: ISO 14532:2005 (Natural gas – Vocabulary)

defines hydrocarbon dew point as “The temperature above which no

detectable condensation of hydrocarbons occurs at a specified pressure.”

APPLIED DEFINITION: Hydrocarbon Dew Point is the temperature at which the first visible film of hydrocarbon condensates are observed when natural gas is cooled, at constant pressure.

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1/10/2010 0.700 0.555 m 3 /m 3 d

1/10/2006 - 2 - o C at 1 – 70 bar (a) HC DP

- 8 - o C at 70 bar (a) H 2 O DP

1/10/2006 2.5 - mol % CO 2

1/10/2010 [0.01]* - mol % O 2

1/10/2006 6 - mg/m 3 RSH (as S)

1/10/2006 5 - mg/m 3 H 2 S + COS (as S)

1/10/2006 30 - mg/m 3 Total S

1/10/2010 15.81 [13.60] kWh/m 3 WI

Recommended

implementation date Max Min Unit Parameter

1/10/2010 0.700 0.555 m 3 /m 3 d

1/10/2006 - 2 - o C at 1 – 70 bar (a) HC DP

1/10/2006–Some exceptions - 8 - o C at 70 bar (a) H 2 O DP

1/10/2006 2.5 - mol % CO 2

1/10/2010 [0.01]* - mol % O 2

1/10/2006 6 - mg/m 3 RSH (as S)

1/10/2006 5 - mg/m 3 H 2 S + COS (as S)

1/10/2006 30 - mg/m 3 Total S

1/10/2010 15.81 [13.60] kWh/m 3 WI

Recommended

implementation date Max Min Unit Parameter

EASEE-gas approved gas quality parameters and values

• EASEE-gas: European Association for the Streamlining of Energy Exchange

• Objectives to harmonise business practices across the industry

• 80 cross border points across Europe

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Hydrate formations

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Compressor damage

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HC Dew Point Applications

Hydrocarbon Dew Point Reduction Processing

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Hydrocarbon Dew point Reduction Plant

Compressor

Well Head NGL

Separator

Glycol Contactor

10-15MPa

J.T. Valve

P

= 3 to 5 MPa

L.T.S.

Condensate

Transmission

Pipeline

7 to 15 MPa

Water dew point

reduction

Hydrocarbon

Dewpoint reduction

After extraction from the gas field, natural gas is processed to remove water and heavy hydrocarbon components, before transmission through the pipeline network. This diagram shows a typical plant for the removal of both excess moisture and heavy hydrocarbons

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What the processing achieves

• Adds cost to the process in running equipment

• Loss of NGL’s = Loss of burn value

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HC Dew Point Applications

Gas quality measurement at custody transfer

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HC Dew Point Applications: Gas Turbine Electricity Generation

• Avoid liquids in hot gas path

• Avoid flashbacks

• Turbine manufacturers stipulate 20 to 30°C of superheat for fuel gas to low NOx plant

• Dew-point measurement enables control of fuel gas heaters

• Potential return on investment through reduced parasitic load

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How can hydrocarbon dew point be measured?

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Manual Visual Cooled-Mirror Dew-Point Checker

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Images courtesy Ametek®

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• Gas Chromatographs provide Heating/Calorific Value (BTU/CV)

• Fiscal metering is based on BTU/CV and thus there is a large installed base

• Field units are mainly C6+ with a few C9+

• Equations of State (EOS) can give a calculated HCDP

Equation of State Method Using GC Analysis

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ISO 23874 (2006) ‘Natural Gas – Gas Chromatographic

requirements for hydrocarbon dew point calculation’

• “be capable of measuring alkenes up to and including dodecane”,

•“be capable of measuring individual alkenes at a concentration of 0.000 000 1 (0.1 ppm)” • “be capable of measuring individual alkenes at a concentration of 0.000 000 1 (0.1 ppm)” •“measure all hydrocarbons in the range C5 to C12”

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Equation of state calculation from extended GC analysis: Sample, analyse, calculate

Mol% C1 Methane CH4 88 C2 Ethane C2H6 5 C3 Propane C3H8 2 C4 Butane C4H12 1 C5 Pentane C5H14 0.3 C6 Hexane C6H16 0.1 C7 Heptane C7H16 0.03 C8 Octane C8H18 0.01 C9 Nonane C9H20 0.001 C10 Decane C10H22 0.0003 C11 Undecane C11H24 0.0000 C12 Dodecane C12H26 0.0000 CO2 1.5 H2O 0.005 (50ppm) H2S 0.0001 N2 2.0 O2 0.08

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3 calculations 3 results

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Source: AN ANALYSIS AND PREDICTION OF HYDROCARBON DEW POINTS ANDLIQUIDS IN GAS TRANSMISSION LINES

-12ºC 45 B

10ºC 35 B

45ºC 38 B

76ºC 32 B

C6+ dew point behavior

If C9 changes by 1ppm HCDP would change by about 0.5ºC. However: If C7 changes by 8ppm HCDP would change by about 0.5ºC

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The DARK SPOT Technique

Wetted with Condensate

Light Source Detector

Dry

Light Source Detector

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The DARK SPOT Technique

The dark spot forming

- - - -

- - -

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CONDUMAX Hydrocarbon Dewpoint Analyser

Confronting the issues:

• High sensitivity - DARK SPOT Technique

• Facility to produce an ‘LGR plot’ - sensitivity calibration routine

• Decoupling the sample flow rate/cooling rate inter-relationship - fixed volume sample analysis

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

10 15 20 25 30 35 40 45 50

Optical Surface Temperature, deg.F

Sig

nal C

han

ge, m

V

Trip point setting at 275mV (Factory Default)

Optical Surface Temperature, °F

Sig

nal Change, m

V

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CONDUMAX II Hydrocarbon Dewpoint Analyser

• Automatic System

• Dark Spot HCDP measurement

• Optional Ceramic Moisture Sensor

• EEx d ATEX approval

• Automatic, low maintenance

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CONDUMAX II Hydrocarbon Dewpoint Analyser

Control Unit

Remote interface

Sampling System

Sensor Assembly

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Inside the optical sensor cell

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Condumax II

•Optional moisture measurement

• Displays in °C and mg/m3

•Michell Ceramic Moisture Sensor

•Line pressure transducer

•Accuracy +/- 1°C WDP

•300 barg rated

•Sour gas compatible

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Thanks for you attention and patience

Questions??