COSA/Xentaur - Continuous Hydrogen Analyzer (CHA) Brochure

INTRODUCTIONThe 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, petrochemi-cal 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 hydro-gen 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-conduct-ing properties, the CHA sensor detects hydrogen con-centrations ranging from 400 ppm to 100% by volume in discrete ranges with ±1% accuracy or better (depen-dent upon sample concentration and reference gas compo-sition). A. The sensor’s proton-conducting 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. C. By quantifying these electrons as voltage across the electrodes, hydrogen concentration in the sample is then determined.APPLICATIONSHydrogen concentration is critical in many different refining, petrochemical, and electric power generation 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 isomeriza-tion process. Examples include: optimizing the hydro-gen/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 detect-ing 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 concentra-tion 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 wind-age losses and unsafe hydrogen-air mixtures.• Hydrotreating – Continuously monitoring the hydro-gen 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.CHA with optional enclosurePlatinumElectrodes Sample StreamProton Conducting MembraneReference GasH2H2H2H2H2H2H+ H+H+H+e-e-e- e-VCONTINUOUSHYDROGEN ANALYZERwww.cosaxentaur.com© 2004 UOP LLC. All rights reserved.The information in this document should not be construed as a representation for which UOP and COSA/Xentaur assumes legal responsibility, or an authorization or recommendation to practice a patented invention without a license.© 2004 COSA Instrument CorporationINSTALLATION, CALIBRATION, AND MAINTENANCEDepending on the application, a sample gas stream is typically diverted to the CHA from the makeup gas line, reactor outlet, stabilizer offgas, or power generator cas-ing. As it exits the analyzer, the sample stream can either be vented or returned to the process. Installation is eas-ily completed by plant personnel. Qualified field service engineers are available to inspect and commission the installation.Upon installation, the analyzer is calibrated for measur-ing hydrogen concentration within a discrete, specified range. Using two calibration gases of known concentra-tion and a specific, continuous flowing reference gas, a simple two-point calibration is completed in less than 30 minutes. Thereafter, calibration checks are recommended every three months, or when the reference gas cylinder is changed.With no moving parts and extremely high stability, the CHA requires very little maintenance. Commercial uptime is reported to exceed 99%. AVAILABLE EXCLUSIVELY THROUGHCOSA Xentaur125 North Loop East Houston, Texas 77028Phone: 713.947.9591Fax: 713.947.7549Email: sales@cosaxentaur.comwww.cosaxentaur.comProcess LineVentReferenceGasSampleCOSAHydrogenAnalyzer4-20 mAOutputSignalTypical InstallationCONTINUOUS HYDROGEN ANALYZER SPECIFICATIONSPerformance SpecificationsDisplay Range .............................................0.0 to 100% Hydrogen by volume (.1% H2 display resolution).Measurement Range .................................04 to 100% Hydrogen by volume.Output Signal ..............................................4-20 mA current loop, software configurable, fail signal also software configurable.Response Time ............................................2 minutes for 10-90% of 1 to 100% H2 step change at analyzer inlet.Rpeatability ..................................................Within 0.6% of original Hydrogen value with up to 99% H2 step change, in 5 minutes at typical flow rates. Noise band is less than 0.6% H2.Temperature Drift .......................................025% H2/C.Calibration Accuracy ................................±.1% H2 in 1-100% H2 two-point calibration range, accuracy no better than combined Calibration and Reference Gas Cylinder accuracy.Measurement Accuracy ..........................±.1% H2 anywhere in 1-100% H2 two-point calibration range, accuracy no better than combined Calibration and Reference Gas cylinder accuracy.Physical SpecificationsDetector Type ..............................................Potentiometric Proton Conducting Membrane Hydrogen Sensor.Sample Flow Rate ......................................5 L/min (5000 cc/minute) (10.6 cubic ft/hr) fast loop, vent to flare. 0.5 L/min (500cc/minute)(1.1 cubic ft/hr) @20 psi across sensor cell slow loop to analyzer, atmospheric vent or vent to flare.Sample Pressure .........................................35 bar (500 psig) maximum to sample system fast loop, 30 psig maximum upstream regulator set point limit by gauge.Sample Temperature ................................Sample line must be between 0-50°C (122°F), non condensing.Material of Construction .........................All wetted parts are 300 series stainless stell, Teflon, Viton.Ambient Temperature Range ...............0 to 50°C (32 to 122°F) limited by hydrogen sensor exposure.Calibration ....................................................2-point manual calibration done periodically as needed or with a reference gas cylinder change.Analyzer Dimensions ( WxHxD) ...........20” Wide x 24” High x 12” Deep (50.8cm x 61cm x 30.5cm).Net Weight ...................................................approximately 26 kg (50 lbs).Piping Connection ....................................¼” Swagelok Tube fittings with sensor/sample system.Enclosure Certfication .............................NEMA 4X suitable for Class I Division 1 Group B installations per US National Electrical Code (NEC) and Zone 0, EEx ia IIC T4 per CENELEC; Sensor and Transmitter is CENELEC KEMA (No. Ex-00.E.1033) approved.UtilitiesOptional Heater ..........................................220.120 VAC, 500 Watts.Reference Hydrogen Consumption ...50% H2 remainder N2 @ 20 psig across sensor cell: 25 cc/min. typical. 100% H2 remainder N2 @ 20 psig across sensor cell: 30 cc/min typical.Cal Gas Hydrogen Consumption ........1% H2 remainder N2 @ 20 psig across sensor cell: 175 cc/min typical. 100% H2 reaminder N2 @ 20 psig across sensor cell: 500 cc/min typical.Contaminant LimitsHydrogen Chloride HCL ..........................150 ppm(v) maximum in 500 ppm moisture maximum.Represented by:CHA.D.BR.0001_A