ACCURRA-S 4030 measures methane (0 to 100 %, minimum range 0 to 5 %) and 6030 measures CO2 (0 to 20 % or 0 to 100 %) by NDIR, separately or in one dual-channel analyser. Wet, H2S-bearing biogas needs a sample conditioning review first.
The measurement and why it matters
Raw biogas from a digester typically carries methane in the range of half to two-thirds, with carbon dioxide making up most of the rest, plus water vapour and traces of hydrogen sulphide. An upgrading unit removes carbon dioxide and impurities to make a gas rich in methane for compression as CBG. Methane content is both the quality figure and the basis of the product's value.
ACCURRA-S 4030 measures methane from 0 to 100 percent, with a minimum range of 0 to 5 percent, using NDIR. Model 6030 measures carbon dioxide from 0 to 20 or 0 to 100 percent. A dual-channel analyser houses both in one enclosure with independent electronics, outputs and Modbus addresses, so one sample point gives both readings.
Biogas is wet, flammable and may carry hydrogen sulphide, so it falls outside the standard ACCURRA-S sample specification, which asks for a non-corrosive, non-toxic, non-flammable, dry sample. We review the composition and area classification for each project and design the sample conditioning around it. Tell us the H2S level and the moisture first.
Models and ranges
| Model | Measures | Range | Sensor and notes |
|---|---|---|---|
| 4030 | Methane | 0 to 100 % (min 0 to 5 %) | NDIR |
| 6030 | Carbon dioxide | 0 to 20 % or 0 to 100 % | NDIR |
| 4030 + 6030 | CO2 and CH4 together | Dual channel | One enclosure, independent outputs and Modbus IDs |
Process notes
Digester monitoring
Methane and carbon dioxide trends show whether the biology is healthy. A falling methane share can indicate a stressed digester, and a steady figure confirms stable operation.
Upgrading and CBG quality
After upgrading, methane content is the product quality figure. An analyser on the product gas gives a continuous reading for dispatch and for the control of the upgrading unit, and an analyser on the off-gas shows methane slip.
Sampling and installation
- Biogas is wet and may carry hydrogen sulphide. Tell us the composition so we can specify the sample conditioning.
- Condition the sample before the analyser: remove condensate and particulates, and protect against H2S where it is present.
- Flammable biogas means the analyser location and area classification need review.
- i-Cons is not suitable for samples containing H2S, HCl or HF.
ACCURRA-S sample specification: non-corrosive, non-toxic, non-flammable, non-condensing and dry, free from entrained oil; sample pressure 2 to 10 psig, regulated externally; flow about 1 LPM; dust below 3 micron. Where your sample differs, we design conditioning around it.
Send us your process data
The same pre-order design inputs our engineers design from, online. Fill in what you know, leave the rest. Your draft saves as you go, and you can print or send it when ready.
What the data sheet asks for
Send what you have and we will ask for the rest.
- The gases to measure, the range, and the accuracy you need
- Background gases and their typical composition
- Sample temperature, pressure and dew point at the tapping point
- Dust level, and whether the gas carries tar, oil or condensable vapour
- Process connection and, for ducts, the duct diameter
- Where the sample vents to, and at what pressure
- Area classification of the tapping point and of the analyser location, and the IP protection needed
- Distance between the tapping point and the analyser
- Outputs you need: 4-20 mA, dual range, relays, Modbus RTU
- Calibration approach, calibration gas available, and whether blowback is required
- Utilities at site: power supply, instrument air, nitrogen, steam and cooling water, and the ambient temperature range
- H2S, moisture and the range of methane you expect
Recommended Sarvesh products
ACCURRA-S
4030 methane and 6030 CO2, dual-channel option.
View ACCURRA-SHeadline filters
Headline filters and scrubber elements for conditioning.
View Headline filtersFrequently asked questions
Can I measure methane and CO2 in one analyser?
Yes. The dual-channel ACCURRA-S measures CO2 and CH4 from one sample, with independent outputs.
Is ACCURRA-S suitable for biogas with H2S?
The standard sample specification excludes toxic and corrosive samples, so H2S needs a conditioning review. Send the composition.
What range for upgraded gas?
Upgraded gas is high in methane, so the 0 to 100 percent range of the 4030 is used. For raw biogas the CO2 range 0 to 100 percent or 0 to 20 percent suits.
Does it work as an NDIR analyser for CBG compression stations?
NDIR methane and CO2 measurement suits any stage where the gas is a methane-CO2 mix. Send the pressure and sample details.