In-Situ Laser Gas Analyzer for Stack and Duct

What is the In-Situ Laser Gas Analyzer for Stack and Duct?

A cross-duct tunable diode laser analyzer that measures gases such as HCl, NH3, O2, CO and H2O directly in the flue gas without extraction. It is the right choice for fast response process control, ammonia slip monitoring and stacks where sample conditioning is difficult.

Overview

A tunable diode laser analyzer sends a narrow laser beam across the duct to a receiver and scans across a single absorption line of the target gas, such as NH3 near 1512 nm or HCl near 1742 nm. Absorption is calculated using the Beer–Lambert law, with temperature and pressure compensation, giving concentration averaged over the optical path in about one second. No sample transport is required, so there is no loss of reactive gases and maintenance is limited to window purging and periodic alignment. Purge air protects optics from dust and heat. Because the signal averages across the duct, path length and stratification influence accuracy. Units are well suited to DeNOx ammonia slip control, combustion optimization with O2 and CO, and high-temperature processes up to 1400 °C.

How does it work?

Emission monitors determine pollutants in hot, wet and dusty flue gas. Extractive systems withdraw a sample through a heated probe and line at 180 °C, remove particles with a filter, and either keep the gas hot for analysis or dry it in a chiller before measurement. Analyzers use non-dispersive infrared for CO, CO2 and SO2, chemiluminescence or UV for NOx, paramagnetic or zirconia cells for O2, and FTIR for multi-component measurement. In-situ systems measure across the stack using tunable diode laser absorption or UV. Particulate monitors use light scattering, transmissometry for opacity, or triboelectric signals, and flow is measured by differential pressure pitot tubes or ultrasonic transit time. A data acquisition system normalizes values to reference oxygen, dry basis and standard conditions, applies calibration and reports averages.

What are the key features?

• Cross-duct measurement responds in about one second for process control loops.
• No sample extraction avoids loss of reactive gases such as NH3 and HCl.
• Single-line laser spectroscopy gives high selectivity with minimal cross-interference.
• Automatic transmission and temperature compensation maintain accuracy in dusty gas.
• Purge air protects optical windows and reduces maintenance frequency.
• Reference cell option provides continuous wavelength lock and self-check.

What are the technical specifications?

A typical in-situ laser gas analyzer for stack and duct configuration offers measured gases of NH3, HCl, O2, CO, H2O (single or dual), NH3 range of 0–10 / 0–50 ppm, NH3 detection limit of 0.1 ppm·m, HCl range of 0–50 / 0–500 mg/m³, optical path length of 0.5–20 m and response time of ≤ 2 s. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The In-Situ Laser Gas Analyzer for Stack and Duct is used in SCR ammonia slip control, waste-to-energy HCl monitoring, combustion optimization with O2 and CO and process gas safety monitoring. Across the wider Emission Monitoring class, laboratories also deploy it for coal and gas power plant stacks, cement and lime kiln emissions and waste incineration monitoring.

Which standards and certifications apply?

Relevant standards and methods include EN 14181, EN 15267-3, EN 15259, ISO 12039, US EPA 40 CFR Part 60, US EPA 40 CFR Part 75, HJ 75 and HJ 76. Certification candidates for this model are CE, ATEX or IECEx for hazardous areas and IEC 60825-1 laser safety; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Choose sampling locations that meet EN 15259 or HJ/T 397 requirements for straight duct length and port access, because flow profile affects representativeness. Keep heated lines above the acid dew point to prevent condensation and corrosion, and replace probe filters and pump heads regularly. Perform daily automatic zero and span checks, quarterly or annual linearity checks, and an annual surveillance test against a standard reference method under EN 14181 QAL3 and AST. Protect cabinets from dust and temperature extremes, and provide calibration gas cylinders with certified uncertainties. Keep records of maintenance, calibration and data substitution, since regulators audit these, and train operators in safe work on platforms.

How do I select the right In-Situ Laser Gas Analyzer for Stack and Duct?

Select the in-situ laser analyzer for fast single-gas measurement where extraction is difficult or reactive species must not be lost. It is less flexible for multi-component compliance than extractive systems. In an RFQ, specify gas, range, duct diameter, temperature, dust level, purge air supply and compliance status needed.

How does it compare with other Emission Monitoring variants?

Start with the regulated pollutants, emission limits and the standard your permit cites, such as EN 14181 or HJ 75. Decide between extractive and in-situ systems according to stack temperature, moisture, acid gas content and the number of species: extractive suits multi-component and low-level measurements, while in-situ suits single gases and fast response. Check that measurement ranges are suitable for the limits, with limits in the lower third of the range where possible. Consider reporting requirements for averaging, data validation and certified instrument status under schemes such as EN 15267 or China CEMS certification. Include sample conditioning maintenance, calibration gas logistics, shelter size and the ability to cope with wet scrubber stacks.