Vibrating Element Technology for Gas Density, Specific Gravity, and Hydrogen Purity

| Vibrating Element Technology | 7-12-18 |
© Yokogawa Corporation of America
1
For Gas Density, Specific Gravity,
and Hydrogen Purity
Vibrating Element
Technology
Jared Hybart
Product Manager
Yokogawa Corporation of America

2
Host
Kristina Neahr
Marketing Specialist, Yokogawa
Kristina.neahr@us.yokogawa.com
678-423-2611

3
Housekeeping Items
n Connect to Audio: 1 877 668 4490
uMeeting Number: 715 581 383
n Questions/Technical Issues
uChat with Kristina Neahr
n Recorded Presentation
uLink to recording & presentation provided

4
Presenter
Jared Hybart
Product Manager, Process Gas Analyzers
Jared.hybart@us.yokogawa.com
770-254-0400 Ext. 5326

5
Agenda
• Vibrating Element System and how density is measured
• How % concentration is inferred from a density
measurement
• Specific Gravity and % concentration in refinery
applications
• Measuring BTU
• Other methods of measuring gas density and specific
gravity
• Q&A

6
The Vibrating Element System
n The Vibrating Element system measures
“Gas Density”
n From the primary density value, we can
calculate:
uMolecular Weight
uSpecific Gravity
uCaloric Value
u% Concentration
ØHydrogen Purity

7
The Vibrating Element System
Analyzer
Special Cable
Standard Twisted Pair
Detector
Pressure Transmitter

8
Measuring Density

9
Vibrating Element Technology
n The resonant frequency of a thin-walled cylinder
will vary according to the density of the gas
surrounding it
Protecting
cover
Gas flow
Multi-mode oscillation system
Piezoelectric actuatorDetector
Temperature Sensor ( PT
1000)
Resonator

10
Multi-Mode Oscillation

11
Advantage of Multi-Mode Oscillation
0
0.01
0.02
0.03
0 0.1 0.2 0.3
Dust accumulation (mg/cm3)
Densityerror(kg/m3)
Single-
m
ode
Multi-
mode

12
Temperature Compensation
n Pt1000 RTD contained in detector
Time (hours)
Density(kg/m3)
Temperature(ºC)
Density
Oven Temperature
60
40
20
0
-
20
1.300
1.296
1.290
1.285
1.280
1.275
10 ºC change
0 5 10 15 20 25 30 35 40 45 50
55 60
.001 kg/m3 / 10 C

13
Pressure Compensation
Raw Density
Compensated Density
Absolute Pressure Transmitter provides real-time values

14
Linearity

15
Calculating % Concentration
Power Plant Application

16
Why is Hydrogen used to cool generators?
n Very efficient at conducting heat (absorbs heat
from equipment readily)
n Very low viscosity = low windage (friction) for
rotating equipment = efficiency
n Abundance = low cost
n Why measure Hydrogen purity?
uSafety; Explosive range of H2 = 4%-75% in Air
uEfficiency; High Purity = Low Windage

17
Effects of Hydrogen Purity on Efficiency
0
1000
2000
3000
4000
5000
88 90 92 94 96 98 100 102
Hydrogen % Concentration
Dollarsperday
800 M W
400 M W

18
Calculating Percent Concentration
n Densities of Gasses in Generator applications
uHydrogen = 0.08988
uAir = 1.2928
uCarbon Dioxide = 1.9771
Values are kg/m3 @ STP

19
n Simple Calculation for binary gasses:
!" =
(%" − %')
(%)−%')
∗ !) − !' + !'
Co = Concentration of Measured Gas – Calculated
do = Density of Measured Gas – Measured
dz = Density of zero range – Known
ds = Density of span range – Known
Cz = Concentration of zero range – Known
Cs = Concentration of span range – Known

20
n Hydrogen Purity Example (85-100% H2):
u100% H2 = 0.08988 kg/m3
(Span)
u85% H2 / 15% Air = 0.27032 kg/m3 (Zero)
!" =
(%" − %')
(%)−%')
∗ !) − !' + !'
,-% =
(/01.3-435-)
(.367661.3-435-)
∗ 100 − 85 +85

21
Tri-Gas Analyzer
mA # 1 set for: Hydrogen
purity
H2 in AIR
Range : 85 - 100 % H2
mA # 2 set for replacement
gasses:
1. H2 in CO2 ; 0 – 100%
2. AIR in CO2 ; 0 – 100%
100
%
85%
HydrogenPurity
mA
4
20
CO2 100%
CO2
AIR
AIR 100%
H2 100%
CO2 100%
H2
CO2
mA
4
20
mA
4
20

22
Typical Configuration
Inlet Press. £ Max. 70
PSI Temp: -10 to 50 C
CO2
100% Outlet (Inlet-Outlet)
Diff. Press. ³ 0.071PSI
Sample Line Out
Vent or Generator
Flowmeter Setting
0.6 Liter/min.
H2
100%
C alibration G rade
G ases (99.99
Pure)
Generator Sample Line In
Pressure
Regulator
0- 100 PSIG
Non-Venting
Coalescing
Filter

23
Calibration
n We are calibrating “density”
u Zero Gas = 100% Hydrogen = 0.08988 kg/m3
u Span Gas = 100% Carbon Dioxide = 1.9771 kg/m3
n Use “calibration grade” or “instrument grade” gasses. Do
NOT use bulk gasses for calibration
H2
99.9%
CO
2
99.9%
Zero gas Span gas

24
Cleaning the Detector
n For oil contamination, clean
with detergent based solution
n Rinse with water, then pure
isopropyl alcohol
n Blow dry with clean, dry
instrument air

25
Refinery Applications
Specific Gravity / Hydrogen Purity

26
Hydrotreaters

27
Hydrotreaters
n Hydrotreaters or HDS (Hydrodesulfurization) units
remove sulfur from products of distillation like
Naphtha, Diesel, and Gas Oils
n This “sweetening” process protects the catalysts
used in down-stream units (Reformers) and
reduces SO2 emissions when the final product is
burned

28
Hydrotreaters
Liquid
Gas
= measuring point
Feed

29
Catalytic Reformers

30
Catalytic Reformers
n Catalytic Reformers convert sweetened Naphtha
with low octane ratings into high octane rating
Reformate
n This is done by “reforming” the straight chain feed
molecules into branched and cyclic molecules
CH3-CH2-CH2-CH2-CH2-CH2-CH3

31
Catalytic Reformers
n The process…
uThe feedstock is mixed with Hydrogen, then pressurized
and heated.
uThis mixture is sent to a series of reactors containing a
catalyst (usually platinum), where the reforming takes
place.
uThe products of this process is high-octane Reformate
and Hydrogen-rich gas (due to dehydrogenation of
straight-chain molecules).

32
Catalytic Reformers
= measuring point

33
Hydrocrackers

34
n Hydrocrackers break heavy, long chain gas oil molecules
into shorter, lighter, more valuable molecules
n Carbon bonds are broken, followed by Hydrogen saturation
n Typical feedstock is Coker gas oil and gas oils from crude
oil distillation

35
Hydrocrackers
n The process…
uFeed stock is mixed with Hydrogen, pressurized (2000
psi), and heated (425 C)
uThis mixture is sent to a reactor containing a catalyst
(typically platinum) where the cracking takes place
uThe hydrogen rich gas is then separated from the
cracked product, which is further fractionated

36
Hydrocrackers
= measuring point

37
Calibration for Density / Specific Gravity
n Choose calibration gasses (Zero and Span) that bracket
your normal measuring density
n Two point calibration (Zero and Span) is preferred
n If the density of the process does not vary widely, a single
point calibration is acceptable
n Linearity of density measurement allows for safe,
inexpensive calibration gasses

38
Calculating Caloric Value
BTU

39
Calculating BTU of Propane / Air Mixture
Propane /Air M ixture

40
n100% Propane = 2500 BTU = 2.012 Kg/m3
n50% Propane 50% Air = 1250 BTU = 1.6515
Kg/m3
n100% Air = 0 BTU = 1.2928 Kg/m3

41
Other Methods
Specific Gravity / Hydrogen Purity

42
Other Methods: Fan Differential

43
Other Methods: Thermal Conductivity

44
Vibrating Element Technology- Summarized
n Reliable, stable, accurate measurement
n Linear over wide range
n No warm-up time; no isothermal oven
n No reference gas required
n Calibration in a few minutes
n Standard calibration gasses (not custom)
n Withstands dust and oil in sample gas
n Virtually maintenance free
n Easily cleaned on site
n Tri-Gas analyzer (one unit for H2, Air, CO2)

45
Questions?

46Co-innovatingtomorrowis aregisteredtrademark of YokogawaElectric Corporation.
Thank you!

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