New Tunable Diode Laser Analyser for Gas Measurement in Harsh Environments

The new Yokogawa (The Netherlands) TruePeak tunable diode laser (TDL) analyser is designed to make fast, accurate measurements on near-infrared absorbing gases in harsh process environments. It is ideally suited to in situ analysis, particularly for measurements in environments involving changing pressure or temperature. It can operate with process pressures up to 20 bar absolute and process temperature up to 1500°C, has a fast response (from 1 to 20 seconds), and is interference-free for most applications.
The TruePeak analyser operates by measuring the amount of a laser light that is absorbed as it travels through the gas being measured. Involving no sensor contact with the process and no moving parts, it leads to a high MTBF and hence a low cost of ownership. It offers a range of flexible installation options, and features on-board diagnostics. Using a tunable diode laser as amonochromatic light source offers the benefits of sensitivity, selectivity to resolve single absorption lines, and power – to overcome the effects of optically thick environments with high particulate loading.
The new instrument is one of the most robust process analysers available. In addition to operating in conditions of high temperature or pressure, it can be used under difficult conditions including environments involving corrosive, aggressive and high particulate content materials.
The TruePeak TDL analyser forms a complementary solution to Yokogawa’s ZR Zirconia oxygen analyser, and measures oxygen (O2) with process temperatures as high as 1500°C and pressures as high as 20 bar absolute. Measurement span is typically between 1% and 100% oxygen.
Carbon monoxide (CO), from low ppm detection limits to percentage levels, and carbon dioxide (CO2) can also be measured at process temperatures of up to 1500°C. The analyser can also be used for measuring parts per million moisture content in corrosive and aggressive process streams including chlorine and hydrocarbons.
The ability of the new instrument to carry out accurate online process measurements makes it ideally suited to applications such as combustion control, where it can be used to optimise the combustion process bymeasuring excess oxygen and carbonmonoxide on a precise and continuous basis. It also allows carbon monoxide to be accurately measured on a continuous basis at low ppm levels so that air fuel ratios can be precisely and continually optimised.
Other potential applications include themonitoring of carbonmonoxide,methane andmoisture to enable burner flame-out and process tube leaks to be identified; the measurement of oxygen on flare lines, alkylation units and gas plants; the monitoring of carbon monoxide and oxygen on fluid catalytic cracking units for safety and catalyst regeneration; or the detection of low ppm concentrations of water in hydrocarbons in catalytic reforming processes.
The TruePeak analyser is a compact stand-alone unit with a built-in 4 × 20 vacuum fluorescent display for scrolling information and a 7-inch colour screen with keypad. The instrument offers a range of interfaces including Ethernet, USB and wired or wireless PDA communication for safe or hazardous areas. The instrument includes three configurable 4-20 mA outputs, two 4-20 mA in case of temperature and pressure compensation, and relay outputs including warning/fault relays and valve control.
The analyser is CE marked and ATEX approved for Zone 1 or 2 installations with purge system. The new TruePeak tunable diode laser (TDL) analyser is manufactured by Analytical Specialties Inc, and has been tested in harsh conditions by Dow Chemicals.