Continuous Hyrdrogen Analyzer Brochure0 pages

CONTINUOUS
HYDROGEN ANALYZER
INTRODUCTION
The COSA/Xentaur Continuous Hydrogen Analyzer
(CHA), used in countless UOP Schedule A applications
for many years, is built under a license to a patented
UOP design. It provides petroleum refiners, petrochemical producers, and electric power generators a means
to continuously and accurately monitor hydrogen
concentration in gaseous streams. Utilizing a unique,
patented electrochemical sensor, the CHA outputs a
continuous signal corresponding directly to the hydrogen concentration. Used in conjunction with real-time
controls, alarms, and shut-off mechanisms, the CHA
responds immediately to changing hydrogen levels for
improved operations and safety.

A UNIQUE, HYDROGEN-SPECIFIC SENSOR
Unlike thermal conductivity-based hydrogen analyzers,
the CHA measures hydrogen directly and specifically.
Built around a polymer membrane with proton-conducting properties, the CHA sensor detects hydrogen concentrations ranging from 400 ppm to 100% by volume
in discrete ranges with ±1% accuracy or better (dependent upon sample
concentration and
Platinum
reference gas compoSample Stream
Electrodes
sition).
Proton Conducting Membrane

A. The sensor’s protonconducting membrane is
platinum-coated on both sides,
creating two electrodes. One
electrode is in contact with the
sample gas stream, the other with
a reference gas stream of known
hydrogen concentration.
B. As hydrogen molecules
dissociate, the resulting protons
are conducted from the stream
with higher hydrogen partial
pressure through the membrane
to the stream with lower hydrogen
partial pressure. The resulting
electrons do not pass through
the membrane, creating a charge
imbalance across the sensor.

Reference Gas
H2

H2
H+

H2

e- e-

H+

H2

e-

H2

V
H+ H+

e-

H2

C. By quantifying these electrons as voltage across the electrodes, hydrogen
concentration in the sample is then determined.

APPLICATIONS
Hydrogen concentration is critical in many different
refining, petrochemical, and electric power generation

CHA with
optional
enclosure

applications whether being monitored as a reactant,
product, process “health” indicator, or coolant. COSA/
Xentaur configures the CHA to match each installation’s
unique sample conditioning and operational needs.
• Catalytic reforming – By enabling on-line control of the
hydrogen/hydrocarbon ratio, the CHA allows optimization
of catalyst life and minimizes utility consumption.
• Isomerization – Determining hydrogen concentration
is valuable at several different points in the isomerization process. Examples include: optimizing the hydrogen/hydrocarbon ratio to assure stoichiometric balance;
detecting processing upsets as they begin to occur;
determining purity of recycled gas to reduce compressor
utilities; monitoring makeup hydrogen purity; and detecting hydrogen-consuming side reactions caused by feed
impurities, e.g., benzene saturation, which reduces the
hydrogen in the offgas.
• Polyolefin production – The concentration of hydrogen
in the reactor dictates the molecular weight, and thus
the physical and chemical properties, of the polymer.
Continuous measurement of the hydrogen concentration allows for rapid changes from one polymer grade to
another with minimal off-spec material.
• Hydrogen production – By continuously monitoring
hydrogen purity, the CHA immediately detects process
upsets, bed poisoning, or processing deviations that lead
to decreased yield and/or low product purity.
• Hydrogen-cooled power generation – Efficient and safe
operation of hydrogen-cooled generators depends upon
high hydrogen purity within the generator casing. The CHA
enables power generation facilities to immediately detect
casing air leaks which, if not corrected, can lead to windage losses and unsafe hydrogen-air mixtures.

• Hydrotreating – Continuously monitoring the hydrogen concentration of the gas stream to the reactor
enables the operator to satisfy the chemical demands
and control the coke rate, without causing excessive
utility usage.

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