TDLAS measurement with a 0.5 mg/m³ detection limit and one-second response, used for reagent dosing control.
Ammonia slip is the unreacted reagent leaving an SCR or SNCR reactor. It wastes reagent, forms ammonium bisulphate (NH₄HSO₄) with SO₃, and blocks air preheaters and catalyst layers.
LD500 scans a single absorption line of NH₃ with a narrow-linewidth tunable diode laser. Because the line is resolved individually, SO₂, H₂O and CO₂ do not interfere. The analyser is mounted away from the duct and connected by optical fibre, with the measurement path across the duct.
HJ 2053-2018 (technical specification for ultra-low emission flue gas treatment in coal-fired power plants) requires ammonia slip at the SCR outlet to stay at or below 2.5 mg/m³. Fast response allows the measurement to be used directly in closed-loop reagent dosing.
| Measurement principle | TDLAS (tunable diode laser absorption spectroscopy) |
| Measured gas | NH₃; extendable to HCl / HF / CO / CO₂ / CH₄ / O₂ |
| Measuring range | 0–20 mg/m³ (adjustable) |
| Detection limit | 0.5 mg/m³ (1 m path, 30 s) |
| Response time | From 1 s |
| Installation | Cross-stack or reflective |
| Certification | TÜV · MCERTS |
Typical data from OPSIS product documentation; specifications depend on the application and are confirmed at quotation stage.
What is the ammonia slip limit?
HJ 2053-2018 requires ammonia slip at the SCR outlet to be no higher than 2.5 mg/m³.
What detection limit does LD500 achieve?
0.5 mg/m³ at a 1 m measurement path and 30 s measurement time. Range is 0–20 mg/m³ and can be adjusted.
Can it be used for closed-loop control?
Yes. Response time is as short as one second, which allows the measurement to drive ammonia dosing directly.
Send the gases, ranges, duct or path dimensions and required certification — we will respond with a technical proposal.