Union_CWD_English_Layout 1 23.09.13 18:51 Seite 1
®
UNION
Instruments
CWD
Calorimetry Measuring Devices
• MeasurementofWobbeindex
andspecificgravity
• Directdeterminationofthe
heatofreaction
• Calculationofnetandgross
calorificvalue/heatingvalue
• Useinpotentiallyexplosive
atmospheres
• Approvalforcalibration
measurements
• Integratedcomputerfor
controlandevaluation
Union_CWD_English_Layout 1 23.09.13 18:51 Seite 2
Gas composition and CWD product series
Gas composition, Wobbe index
CWD calorimeter series
Naturalgasandothercombustiblegaseshavegained
high importance as fuels for industrial processes.
Dependingontheirorigin,theydiffersignificantlyin
theirchemicalcompositionandcombustionbehaviour.
The technical terms are "gas composition" or "gas
properties" which desrcibe characteristics such as
heating value, calorific value and Wobbe index (see
textboxbelow).
Asuitablegasmeasurementtechnologyisrequiredto
master the variations in the gas composition while
supplyingheattoprocesses-UNIONInstrumentshas
beenofferingthistechnologywithitsextensiveCWD
deviceseriesformanydecades.
Inviewoftheincreasingdiversificationofnaturalgas
sources, consumers are increasingly supplied with
naturalgaswithvaryinggascompositionandthusdifferentcombustionbehaviour.Ifthegasconsumerisa
thermallysensitiveprocessorburner,thecomposition
ofthegassuppliedmustbemonitoredand,ifnecessary,
adjustedtotherequiredvaluebyconditioning.Otherwisethefunctionofaburnerandofthedownstream
processandhencealsotheproductqualityarejeopardised.Typicalexamplesareprocessesintheglassindustryandinmetallurgy.Asimilareffectiscreatedby
theincreasinguseofbiogasandbio-methaneorprocess
gases(blastfurnacegases)ascombustiongases.
Application segment
CWD
Device series
Low gas
Furnace gas
Coke gas
Mixed gases
High gas
Refineries
Mixed gases
CWD 2005
X
X
X
CWD 2005-CT
X
CWD 2005-DP
X
X
CWD 2005-PLUS
X
X
CT: Custody Transfer
X
Figure1givesanoverviewofthedifferentCWDvariantswiththeirmanifoldrangesofapplication,including custody transfer measurements (CT) and the
determinedparameters.Parametersmeasuredarethe
Wobbeindexandspecificgasdensity,fromwhichthe
heatingvalueandcalorificvaluearecalculated.
Fordetailsonthedevicedesignrefertopage4,for
technicaldatatopage6.
Special feature
Natural gas
Biomethane
Liquid gas
W 2005
CWDisamnemonicofthetermsCalorimetry,Wobbe
indexandspecificDensityanddesignatesamodular
productseriesfordeterminingcalorimetricvaluesin
gasesaccordingtotheDVGWcodesofpracticeG260
andG262(seepage7),
Hazardous
areas
Class I
Div. II
Custody
transfer
measur.
X
X
X
X
Measured values
Measured
values
Calculated values
Wobbe Index
Specific
density
Heating value
Calorific value
Wobbe Index
Heating value
Calorific value
(at constant
density)
DP: Direct Purge
Figure 1
Net calorific value
Maximumusableheatuponcombustionofagaswithoutcondensationofthewatervapourintheexhaust
gas.
Gross calorific value
Maximumusableheatuponcombustionofagaswith
condensationofthewatervapourintheexhaustgas.
Wobbe Index (Wobbe number, kWh/m3)
Indicator of the interchangeability of combustion
gaseswithrespecttothethermalloadontheburners.
Importantwhenusingcombustiongasesofchanging
compositioninoneburner.Ifcombustiongasesofdifferent composition have the same Wobbe index and
thesameflowpressureattheburner,theyhaveapproximatelythesameheatcapacity.
Union_CWD_English_Layout 1 23.09.13 18:51 Seite 3
Wobbe index - Direct or indirect determination
Wobbe index
Indirect determination
TheWobbeindexofagasisacorrectedheatingvalue
(seeequation1)andservesasanindexfortheinterchangeabilityofcombustiongasesatburners.Gases
ofdifferentchemicalcompositionbutwiththesame
Wobbeindexareequivalentintermsofburnerload
andcanbeinterchangedwithoutjeopardisingtheburners.Forsafeandefficientoperationofacombustion
system,theWobbeindexmustthereforebecontinuously determined before the combustion gas enters
theburner.Forthispurpose,directandindirectdeterminationmethodsareinuse.
ManyWobbedevicesdonotdeterminetheWobbeindex
directly;theydeterminetheresidualoxygenremaining
inthegasafteraleaner-than-stoichometric,catalytic
combustionofthegas.Oncethisindirectvalueisdeterminedbymeansofgasanalysis,theairrequirementis
calculatedandthen,afteritscorrection,thecharacteristic CARI (Combustion Air Requirement Index) for
combustion.Finally,theWobbeindexisdeterminedfrom
CARI(seeequation2)viaacorrelationfunction.
Direct determination
(principle of the CWD)
Theprecisionthatcanbeachievedwiththismethoddependsonhowthecatalystinfluencesthecompleteness
ofthecombustionandontheprecisionwithwhichthe
used correlation function represents the respective
application(i.e.thecurrentgasmix).Studiesinthesteel
industryhaveshownthatwhenusing"substitutegases",
faultscannotberuledoutasfrequentlyusedgasmixturesarepositionedoutsidethetypicalcorrelationcurves. Figure 2 shows this situation: There is a by no
meansclearcorrelationbetweentheWobbeindexand
CARIforgasestypicallyusedinthesteelindustry.The
followinggases(andtheirmixtures)areplotted:
AlldevicesoftheCWDseriesusethedirectmeasurementmethodtodeterminetheWobbeindex:Continuous measurement of the energy generated by the
combustion of a defined gas flow determines the
Wobbeindexdirectly.Inaddition,thespecificgravity
ismeasuredwhichcanservetocalculatetheheating
value. A correlation function is not required at any
point.
Evenunknownandunexpectedcomponentsinthegas
aredeterminedduringcombustionandtakenintoconsiderationinthemeasurement.Thatisofgreatimportancewithrapidlychanginggascompositionsofe.g.
residualgasesfromchemicalprocessesorsubstitute
gasesinthesteelindustry.
NG
BFG
BOFG
LPG
LDG
COG
C
CARI
ARI [Nm
[Nm3 fuel / Nm3 Ai
Air]
r]
3,50
N
NG
G-N
N2
2
3,00
CO
2,50
N
NG
G-A
Air
ir
BFG
BF
G - NG
NG
2,00
BFG
BF
G -C
-COG
COG
NaturalGas
BlastFurnaceGas
BasicOxygenFurnaceGas
LiquifiedPetroleumGas
LinzDonawitzGas
CokeOvenGas
BO
BOFG
FG (L
(LDG)
DG)
1,50
LPG
Air
L
PG - Air
1,00
BFG
0,50
0,00
0
2000
4000
6000
8000
10000
12000
14000
Wobbe-Index
W
obbe-Index [[kJ/Nm
kJ/Nm3]
Figure 2: Non-linear correlation between CARI and Wobbe index (steel industry)
Wobbe index
CARI
Specific gravity
*At the same conditions
Heating value
Specific gravity
Air demand
Specific gravity
Density fuel gas*
Density air*
(1)
(2)
(3)
Union_CWD_English_Layout 1 23.09.13 18:51 Seite 4
Device structure and device function
Figure 3: Device layout CWD
Thesamplegasiscombustedinthemeasuringcellwith
burner(1).Theflameisdetectedviatheenergyrelease
onsuccessfulignition.Todeterminetheenergyquantity,
thetemperatureincreaseisdetermineddirectlyinthe
exhaustgasflowusingveryruggedthermocouples.This
allowsforparticularlyfastmeasurementofheatingvalue
variationsofthesamplegas.
Thelow-pressuregassupply(2)offerstheuseranumberofadvantages:
•Theinletpressureofonly25-35mbarallowstheuse
ofapressureboosterpumptobeeliminatedinmany
cases.Thisalsoeliminatesapossiblesourceoferrors
becausethecompressionofvapour-saturatedgases
(e.g. boiler gases) generates condensation which
impairsthesubsequentmeasurement.Thisinfluence
isdeliberatelyminimisedintheCWDbythelowinlet
pressure.
•ThemeteringtechnologyoftheCWDenablesmeasurementswithsmallgasflowsfrom10l/h.Thisallows
theentiresamplegastobecombusted.Thiseliminates
theproblemsotherwiseencounteredbytheuserofthe
gasdisposal.
•ForprecisemeasurementoftheWobbeindex,thegas
mustbemeteredwithhighprecision.IntheCWD,this
is ensured by a system of pressure controller and
nozzle:TheprecisionpressurereducerfromUNIONInstrumentsistemperatureindependentandcancontrol
pressuredifferentialsof4mbarinconstantoperation.
Themeasuringrangeisdeterminedbyagasnozzle
withadiameterof0.4-1.5mm.
Theacousticdensitymeasurement(3)isperformedin
thebypasstothemainsamplegasflow.Ifoffersawide
measuringrangefrom0.2to2.2relativedensity.
Theairmeasurement(4)isperformedviaameasuring
orificeandaprecisiondifferentialpressuresensor.
Thegasissupplied(6)viaavalveblockwhichcontrols
thesupplyofsamplegasandcalibrationgastotheanalyser.Indevicevariantsapprovedforcustodytransfer,a
"blockandbleed"circuitwithincreasedsecurityisused.
Theother modules inFigure3are
(5) Automaticignitiondevice
(7) Datalogger
(8)
I/Osection
(9)
Powersupply
(10)
Fan
(11)
Electronics/powersupplyunit
Acoustic density measurement of gases
Thepiezoelectriceffectconvertsmechanicaldeformationsintoelectricsignalsandviceversa.
Oneofthemanyapplicationsistheacousticdensitymeasurementofgaseswithparticularlyhighlinearmeasuring
range(0.0-2.0relativedensity).The piezoceramics used for this in the CWD aregold-platedandtherefore
extremelycorrosion-resistant.Themeasurementisperformedinthebypasswithaverysmallgasthroughput
(1-4 l/h) and hence very low risk of soiling. The high measurement precision allows the Wobbe index to be
convertedintocalorificvalueevenforcustodytransfermeasurementsfornaturalgas.
Union_CWD_English_Layout 1 23.09.13 18:51 Seite 5
Control system (hardware and software)
Control and operation
The operating unit HMI (Human Machine Interface)
comprisesthecomponentscentralcontrolunit,display
and keyboard and is linked to two modules via the
device bus (Figure 4): The measurement technology
modulecollectsthemeasurementdata,theI/Omodule
controlstheexternalcommunication.Thedetailsofthe
userinterfaceareshowninFigure5.
HMI
Fieldbus,
e.g. Profibus
- CPU
- Display
- Keyboard
Temperature 1
Temperature 2
Pressure
Measurement
technology
module
Device
bus
Density
The software
isbasedonareal-timeoperatingsystem.Itisstructured
invariousmenulevelswhicharereachedviasoftkeys.
RS232
Digit. Input
I/O module
8x relays
20 mA galv.
Figure 4: CWD function flowchart
Figure 5: Operation and display panel CWD (Human Machine Interface)
1: Menukeys(softkeys)
2: Currentmeasurementdata(graphicdisplay)
3: Currentmeasurementdata(numerical,withdimension)
4: Infofield(date,time,internaloperatingdata,..)
5: Trenddisplays
6: Positionkeys
7: Inputkeys
8: Start/Stop
9: Burnerwindow(forobservingtheflame)
10: LEDstatusdisplays
Fieldbus
Termforserialcommunicationbussystemsinproductionandprocessautomationinwhichfielddevicessuch
as sensors, measurement devices and actuators (slaves) are connected to control systems (masters). The
bus enables bidirectional communication among the bus participants for digital data exchange. The most
successful field bus worldwide is Profibus. Fieldbuses are increasingly replacing the conventional 4-20 mA
technology.
Union_CWD_English_Layout 1 23.09.13 18:51 Seite 6
CWD - Technical data
Weight [kg]
CWD2005
CWD2005-CT
CWD2005-DP
CWD2005-PLUS
W2005
54
54
54
54
54
Dimensions (WxHxD) [cm]
72 x 102 x 33.7
IP degree of protection
Ex-proof classification
Setup site
IP 50
none
none
Class I, Div, 2
none
none
safe zone
safe zone
Zone 2
safe zone
safe zone
5° - 40° C
Operating temperature
Inputs of process gas
max. 2
1
1
max. 2
max. 2
Inputs of calibration gas
max. 2
1
1
max. 2
max. 2
Tests (optional)
SGS (NRTL-accredited)
Mains supply
240 VAC 50 Hz / 240 VAC 60 Hz / 110 VAC 60 Hz
Max. power consumption
200 VA
0° - 60° C
Storage temperature
CSA approval (optional)
( )
4-20mA, RS232, relay contacts, Ethernet (TCP/IP),
Profibus-DP, Modbus-TCP, Modbus-RTU, Profinet IO
Interfaces
Measuring ranges / precision / gas quantity
Range
Precision Wobbe index [ ±% MBE] / gas quantity [l/h]
Gas type
MJ / m3
3.0 / 40
1.5 / 25
–
–
–
–
–
–
–
Natural gas
1.5 / 25
LPG
1.5 / 15
0 - 15
Flare gas
3.0 / 40
3.5 - 6
Blast furnace gas
3.0 / 170
4.5 - 9
Converter gas
1.5 / 140
5 - 10
Mixed gas
2.0 / 140
15 - 30
Coke-oven gas
1.5 / 60
25 - 35
Biogas
1.5 / 70
25 - 50
Refinery gas
30 - 48
40 - 90
–
–
–
–
–
–
–
1.5 / 60
1.5 / 60
1.5 / 60
1.5 / 70
1.5 / 70
1.5 / 70
1.5 / 25
1.5 / 25
1.5 / 25
1.0 / 25
1.0 / 25
1.0 / 25
1.5 / 25
–
1.5 / 15
1.5 / 15
1.5 / 15
3.0 / 40
3.0 / 170
1.5 / 140
2.0 / 140
Figure 6: Technical data of the CWD devices
Ethernet
Termforacommunicationtechnologyfordataexchangeamongdevicesinanetworkwithespeciallyhightransfer
rates.Initsvariant"IndustrialEthernet",Ethernetistheacceptedindustrystandardonthelevelofinterlacing
controlsystemsandimplementingcontroltechnologytohigherlevels.Particularlyincombinationwithotherprotocols,EthernetiswidelyusedintheformofEthernet-basedsolutionssuchasPROFINETorModbusTCP.PROFINET
inparticularisbothIndustrialEthernetand100%Ethernetandisthereforesuitableforallindustrialapplications
andalsofortheuseofallweb-basedservicesandtools.
Union_CWD_English_Layout 1 23.09.13 18:52 Seite 7
CWD – Applications
There are many applications for CWD devices, both
withregardtothegasestobemeasuredandtothe
process-engineeringaspects(industries)andapplicationsintheproductionlines.Figure7providesanoverview.SpecialCWDdevicevariantsallowuseincustody
transfertrafficandoperationinpotentiallyexplosive
areas.
Use in custody transfer
Calibrationlawsrequirethatmeasuringdevicesused
incommercialbusiness(purchaseandsaleofmeasurablegoods)mustbecalibrated.Thisisreferredtoas
custodytransfer.
Thisisofspecialimportanceintheoilandgasindustry
because of the immense volume and energy flow
movedinthatfieldanddeliverdbetweendifferentsupplieresortoconsumers.Thisobligatorycalibrationalso
appliestocalorimetersforthecalorificvalueofgases.
therange8.4-13.1kWh/Nm³.Applicableforcalibrationisthemeasurementofprocessedbiogas,including
gasaswhichareconditionedbyusingairandliquified
gas.
Use in potentially explosive areas
Whencalorimetersareusedintheoilandgasindustry,
they are frequently installed in potentially explosive
areas.Thisrequiresspecialprotectivemeasuresinthe
devicetechnologyandcorrespondingapprovalbythe
authorities.
The version CWD2500-DP (Direct Purge) isdesignedaccordinglyandapprovedasClass1,Div.2accordingtoNEC500(USA).Thehousinghascompressed
airpurging(TypeZ)andasafetyshutdown.
ThecalorimeterCWD2005-CTfromUNIONInstruments
wasapprovedin2009asacalorificvaluemeasuring
deviceforcustodytransfer.Itcanbeusedforallgases
accordingtoCodeofPracticeG260/262oftheDVGW
(Deutscher Verband der Gas- und Wasserwirtschaft,
GermanAssociationofGasandWaterManagement)for
officiallyverifieddeterminationofthecalorificvaluein
Figure 8: CWD for potentially explosive areas
CWD Wobbe Measuring Device Series
Typical fields of application
Gas type
Industry
Biogas
Biomethane
Biogas processing
Biogas conditioning
Natural gas
Natural gas extraction
Natural gas distribution
Natural gas usage
Blast furnace
gases
Process gases
Steel industry
Refineries
Application
Measurement of raw biogas
Processing into biomethane
Conditioning of biomethane
Conditioning
Energy measurement (calibratable)
Quality measurement
Calorific value measurement
Combined systems natural gas/liquefied gas/air
Measurements at burners: glass industry
Measurements at burners: steel industry
Measurements at gas turbines
Roller mills
Sintering plants
Hot blast stoves
Power plants
Lime kilns
Flares
Figure 7: Fields of application
CWD in use in the production of float glass
Theproductionoffloatglassisacontinuousprocess.At1100°C,theglassmeltisguidedintoabathofliquidtin
onwhichthelighterglassfloats.Optimalcombustionconditionsandaconstanttemperatureofthisbathare
crucialforaconsistentlyhighglassquality.Theenergycontentofthecombustiongas,preferablynaturalgas,
varieshoweverovertime.ByhavingtheCWDpermanentlydeterminetheenergycontentandbycorresponding
compensation with suitable additions, constant flame temperature and stable combustion conditions can be
achieved.
Union_CWD_English_Layout 1 23.09.13 18:52 Seite 8
UNION Instruments
Company,marketpresence,support
UNIONInstrumentsisaGermancompanyfoundedin
1919 with headquarters in Karlsruhe and another
locationinLübeck.Theiractivitiesarecharacterised
byafastpaceofinnovationsandconcentrateongas
measurementtechnologyinprocessindustrywiththe
fieldscalorimetry(energycontentofgases)andgas
analysis(compositionofgases).
Withsalesactivitiesin20countries,UNIONInstruments demonstrates a wide and ever increasing
marketpresence.ApartfromtheEuropeancountries,
China and the US are in our focus where we
have a high market share in the pertinent market
segments. Sales is primarily done via distributors.
Withmodernmeansofcommunicationandthereadiness for intensive travel, our German specialists'
knowledge is available world-wide to all interested
customers.
Figure 9: UNION Instruments, device calibration
Advice before procurement
ThemodulardesignoftheUNIONdevicesallowscustomer-specificconfiguration.Tousethispotentialto
the full, we recommend clarifying the future tasks
beforeprocurement:Forthispurpose,UNIONInstrumentshasqualifiedspecialistswithyearsofexperienceintheapplicationsatyourdisposal.
Support after procurement
Eventhebestdevicetechnologywillnotdowithout
qualified service over its long service life. UNION
Instrumentsoffersatieredconceptforthis:
•Service on the spot by well-trained regionally
organised technicians. The number of countries
withthatserviceiscontinuouslybeingexpanded.
•ServicefromtheGermanlocationsbytechnicians
readyforworldwidetravel.Suchassignmentsare
at the same time used to support and train the
regionaltechnicians.
•Remote maintenance from German with modern
toolspermobiletelephoneand/orinternet.
Evenadeviceequippedtotheoptimumcanonlybe
useful if handled properly. Corresponding training
coursesaredesignedtosupplementthedocumentationsuppliedandtodaybelongtothescopeofsupply
ofsophisticatedmeasurementtechnology.
A spare parts service optimised for rapid dispatch
andarangeofsparepartkitsandservicecontracts
completetheservicerangeofferedbyUNIONInstruments.
UNION Instruments offers direct training sessions
duringtheinitialstartupandadditionallyoralternatively central training courses for different specific
topics.
®
UNION
Instruments
Figure 10: UNION Instruments, customer support
UNION Instruments GmbH
Zeppelinstraße 42
76185 Karlsruhe
Germany
Alfstraße 28-30
23552 Lübeck
Germany
Phone +49 (0) 721 680381 0
Fax
+49 (0) 451 7078063
info@union-instruments.com
www.union-instruments.com
02607099987V1.0009.13
Training during commissioning and
in central courses