What is a process analyzer?
A process analyzer is an online instrument that automatically measures the chemical composition or properties of a gas or liquid stream while the process runs. It sends results to the control system in seconds or minutes, rather than hours later from a lab. Analyzers are used for control, product quality, safety and environmental compliance.
Every installation has three parts: a sample tap or in-situ probe, a sample conditioning system that delivers a representative sample, and the analyzer itself. Analyzer engineers often say the sample system decides success, because the most accurate detector cannot correct a sample that has condensed, lagged or been contaminated on its way in.
How process analyzer technologies work
No single technology covers every stream. The measurement principle is chosen for the analytes, required speed and background matrix:
| Technology | How it measures | Best suited to |
|---|---|---|
| Gas chromatography (GC) | Separates components on a column, then detects each peak | Full composition, heating value, natural gas and RNG |
| GC-IMS | GC separation followed by ion mobility detection | ppb-level siloxanes, odorants, volatiles |
| FTIR | Infrared spectrum of the whole sample | Many IR-active gases at once, including HCl and NH3 |
| NDIR | Absorption at a fixed infrared band | CO, CO2, SO2, moisture in solvents |
| Flame ionization (FID) | Ions formed when hydrocarbons burn in a hydrogen flame | Total hydrocarbons, VOC |
| Paramagnetic and zirconia | Oxygen’s magnetic properties or ion conduction | O2 in process and combustion gas |
| Zeeman atomic absorption | Mercury absorption with magnetic background correction | Mercury in natural gas, LNG, hydrogen |
| Optical luminescence | Luminescent dyes respond to oxygen or pH | Dissolved O2 and pH in bioprocess |
Speed and selectivity trade off against each other. A GC gives complete speciation but reports on a cycle time. Spectroscopic analyzers respond almost continuously but can be affected by overlapping absorbers. Many plants use both: a fast optical analyzer for control and a GC for verification.
Common applications
- Gulf Coast refining and chemical plants: hydrocarbon and VOC monitoring, solvent recovery, thermal oxidizer performance and mercury removal verification for gas processing.
- Renewable natural gas: landfill and farm digester projects across the Southeast measure methane, CO2, oxygen and siloxanes to meet pipeline interconnect specifications.
- Natural gas and LNG: mercury-in-gas monitoring upstream of cryogenic heat exchangers.
- Sulfuric acid and power plants: acid dew point monitoring for corrosion control.
- Research and life sciences: optical oxygen and pH sensing in bioreactors and university labs.
Choosing the right process analyzer
Begin with what the measurement must accomplish and how fast. A safety interlock on oxygen in a hydrocarbon header has very different needs from a daily heating value report. Next, document the stream completely, including the components you do not care about, because they cause interference and fouling.
Then size the sample system: tap location, transport time, heat tracing, filtration, fast loop and calibration injection. Finally, look at ownership. Carrier gases, calibration standards and consumables accumulate over time, and an analyzer that operators trust gets used, while one that drifts gets bypassed.
Manufacturers we represent for process analyzers
ENVEA brings decades of gas analysis experience from its emissions monitoring work, with FTIR, heated FID, NDIR, chemiluminescence and paramagnetic analyzers, mercury monitors for natural gas, and engineered sample conditioning. Its US line was expanded by the 2023 acquisition of California Analytical Instruments.
Ohio Lumex builds its Elemental Instruments line of process GCs, RNG and siloxane monitoring systems, mercury-in-gas analyzers and the Ei4200 acid dew point monitor. It backs them with an ISO/IEC 17025-accredited laboratory, onsite gas-quality sampling and, since 2026, an automation division for PLC and SCADA integration.
Get local application support
Our analyzer specialists can review stream data, sample tap locations and hazardous-area requirements, then coordinate a recommendation and quote with the factory. Visit engineering support, request a quote, or find your area manager on the territories page.
