TDLAS In-Situ Gas Analyzer

What is the TDLAS In-Situ Gas Analyzer?

A laser spectrometer that measures specific gases across the stack without extracting a sample. It is the right choice for fast, low-interference measurement of ammonia, hydrogen chloride, moisture and oxygen in difficult flue gas.

Overview

The TDLAS analyzer projects a near-infrared laser beam across the duct to a detector on the opposite side, scanning the wavelength across a single absorption line of the target gas. Because the measurement is made in situ over the full duct width, it gives a path-averaged concentration that represents the whole cross-section and responds in about one second. The narrow linewidth avoids the interference that broad-band methods suffer from, so ammonia, hydrogen chloride, moisture and oxygen can be measured in hot, wet, dusty gas with minimal conditioning. Wavelength modulation and second-harmonic detection improve the signal-to-noise ratio and allow low detection limits. Alignment, window cleanliness and temperature and pressure compensation are the main operating requirements, and an in-situ probe or a cross-stack pair can be used. The technique supports ammonia slip control in DeNOx systems and moisture correction for other analyzers.

How does it work?

Stack gas analyzers combine gas extraction or in-situ probes with one or more detection techniques. Electrochemical cells and zirconia sensors measure oxygen and select gases in portable instruments, while non-dispersive infrared detectors quantify carbon monoxide, carbon dioxide and sulfur dioxide by absorption at characteristic wavelengths. Chemiluminescence or ultraviolet absorption is used for nitrogen oxides. Fourier transform infrared analyzers resolve many gases at once from a single spectrum, including hydrogen chloride, ammonia and moisture. Tunable diode laser analyzers scan a narrow absorption line in situ and give fast, interference-resistant readings of species such as ammonia or hydrogen chloride. A heated sample line and conditioning system remove water and dust so the composition reaching the detector represents the stack. Flow monitors, temperature probes and data acquisition complete a continuous emission monitoring system.

What are the key features?

• In-situ cross-stack measurement gives one-second, path-averaged results.
• Narrow laser line avoids interference from overlapping gas absorptions.
• Measures NH3, HCl, H2O and O2 in hot, wet, dusty gas.
• Wavelength modulation detects low concentrations with high signal-to-noise.
• No sample extraction means no heated line or conditioning losses.
• Supports ammonia slip control and moisture correction.

What are the technical specifications?

A typical tdlas in-situ gas analyzer configuration offers measurement principle of Tunable diode laser absorption spectroscopy, target gases of NH3, HCl, H2O, O2, CO, optional others, lower detection limit of < 0.5 ppm (NH3, HCl), response time of 1–2 s, path length of 0.5–10 m (stack width) and maximum gas temperature of Up to 800 °C (probe dependent). 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 TDLAS In-Situ Gas Analyzer is used in deNOx ammonia slip monitoring, waste incineration HCl control, moisture measurement for CEMS correction and cement and glass kiln gas analysis. Across the wider Stack Gas Analyzers class, laboratories also deploy it for power plant continuous emission monitoring, cement and steel plant flue gas analysis and waste incineration emission control.

Which standards and certifications apply?

Relevant standards and methods include EN 14181, ISO 16911-1, ISO 12039, US EPA 40 CFR Part 60 Appendix B, HJ 75 and GB 13223. Certification candidates for this model are CE, China environmental monitoring instrument certification and ISO 9001 manufacturing; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Locate the sampling point where the gas is well mixed and within the acceptable temperature range, and keep the heated line above the acid dew point to prevent sulfur trioxide and water condensation. Calibrate with certified standards and check linearity, and run zero and span checks on the schedule required by the quality assurance standard. For continuous systems, annual surveillance audits and periodic reference method comparisons are commonly required. Replace filters, dryer components and pump parts regularly, and verify flow and temperature sensors. Protect optics and sensors from dust and corrosion, and record all calibration and maintenance events. Document the measurement uncertainty and apply the applicable quality assurance levels for reporting.

How do I select the right TDLAS In-Situ Gas Analyzer?

Select TDLAS for fast, low-interference measurement of specific gases, particularly ammonia and hydrogen chloride, in difficult flue gas. For a broad multi-gas suite, FTIR or NDIR is more economical. In an RFQ, specify the gas, detection limit, stack width and temperature and the window purge arrangements.

How does it compare with other Stack Gas Analyzers variants?

Choose by purpose: portable analyzers for combustion tuning and periodic checks, fixed systems for continuous emission compliance. Define the gas list and the ranges: oxygen typically 0 to 25 percent, carbon monoxide 0 to 1000 ppm, sulfur dioxide 0 to 500 ppm and nitrogen oxides 0 to 500 ppm for many combustion sources, with wider ranges for waste incineration and cement kilns. Select the extraction or in-situ format according to the need for fast response, the corrosiveness of the gas and the number of components. For multi-component compliance, NDIR plus chemiluminescence or FTIR systems are standard; for specific acidic or reactive species, TDLAS offers low interference. Confirm heated sampling, dust and moisture removal, calibration gas arrangements and conformity with the applicable method.