Biogas Thermal Mass Flow Meter
Biogas / Digester TMF
Accuracy of ±1.5% of rate
Temperature service −10 to +80 °C
Turndown ratio of 1:1200
- Line sizes DN25 to DN300
- Working pressure ≤ 1.6 MPa standard
- Sensor wetted parts Hastelloy C-276 standard for H₂S
The Biogas Thermal Mass Flow Meter measures raw digester gas on WWTP, landfill, agricultural digester, and CHP-feed lines. Hastelloy C-276 probe handles H₂S to 5,000 ppm without bearing failure.
Outputs Nm³/h directly on the 4-20 mA loop with on-board CH₄ correction option. The 0.2 Nm/s low-flow detection catches idle-leak drift on stand-by digester headers.
Benefits
- Direct mass flow: thermal-dispersion outputs Nm³/h or kg/h directly; one instrument replaces ultrasonic + flow-computer + analyzer-loop stack.
- ±1.5 % of rate: standard build on variable composition; tightens to ±1.0 % with the 4–20 mA composition-analyzer input.
- Hastelloy C-276 probe: 0–5,000 ppm H₂S continuous on WWTP/AD/LFG service; no bearing failure that retires ultrasonic and turbine alternatives.
- 0.2 Nm/s low-flow detection: resolves overnight digester idle and AD trickle that ultrasonic drops below 1–2 m/s, exposing 12–18 % under-reporting on legacy installs.
- 1:1200 velocity turndown: one model covers the 30× daily swing between overnight trough and CHP peak; no parallel-meter bypass piping.
- Hazardous-area: CNEX Ex d IIC T6 Gb (flameproof, Zone 1) standard; IP65/66/67 and EMC 2014/30/EU.
- Lead time: 5–7 business days from the factory.
Configure your build.
Select your specs; we’ll generate a TMF 12-position model code and ballpark price. Submit to engineering for verified sizing against your digester or landfill output profile, CH₄ composition range, H₂S level, and CHP or upgrader destination within 4 business hours.
Your Configuration
TMF-150-U-A-EX-4-H-M4-2-1-Q-S
Pipe sizeDN150
TransmitterIntegral
Accuracy±1.5 % of rate
CH₄ composition60 % (WWTP digester)
ConnectionFlanged PN16 / ANSI 150
Material / H₂SHastelloy C-276 · 5,000 ppm
ReferenceIUPAC STP (0 °C)
Output4-20 mA + HART
EnclosureCNEX Ex d (flameproof, Zone 1)
Estimated unit price
Verified after engineer review
$3,850
Subtotal (× 1)$3,850
🛒 Add to Cart
📩 Request Detailed Quote
✓ Hastelloy C-276 material certificate + H₂S tolerance report
✓ CNEX Ex d (flameproof, Zone 1) certificate + Zone 1 declaration
✓ EN 16723 biomethane-ready compliance letter
✓ Reply within 4 business hours
✓ CNEX Ex d (flameproof, Zone 1) certificate + Zone 1 declaration
✓ EN 16723 biomethane-ready compliance letter
✓ Reply within 4 business hours
Applications
WWTP Anaerobic Digester Output
Mesophilic/thermophilic sludge-digester output ahead of holders or CHP. Typical DN150 at 0.03 MPa, 60 % CH₄, 500 ppm H₂S logs Nm³/h to SCADA.
Agricultural & Food-Waste AD
Substrate-cycling AD on pig slurry, manure, energy crops, food-waste; CH₄ 55–68 %, H₂S to 3,000 ppm. Composition input required for feed-in-tariff reporting.
Landfill Gas (LFG) Collection
Newer cells with H₂S < 5,000 ppm on DN150–DN300 wellfield and flare. Aged cells with 15,000 ppm spikes use TMF-LFG.
CHP Feed & Biomethane Upgrader
Gas-engine fuel metering for Jenbacher/MAN/Caterpillar kWh reconciliation. Upstream of water-scrubber and PSA biomethane plants; EN 16723 reference setup.
Specifications
Performance
| Accuracy | ±1.5 % of rate standard across 50–65 % CH₄ · ±1.0 % of rate with composition-analyzer input locked · ±0.5 % repeatability |
|---|---|
| Velocity range | 0.2 to 120 Nm/s (1:600 practical, 1:1200 across product line) |
| Low-flow detection | 0.2 Nm/s; resolves 3 a.m. idle digester output, small AD plant trickle, LFG well-head low-yield periods |
| Temperature measurement | Pt1000 reference RTD, integrated · ±0.3 °C |
| Response time | 1 second; fast enough to log CH₄ spikes during digester feeding cycles |
| Pressure loss | Negligible > DN80 (< 1 kPa at rated flow) · wall-mounted probe, no bluff body, no bearing to seize |
| Power supply | 24 V DC or 220 V AC · ≤ 18 W maximum |
Process & Environment
| Medium | Raw biogas · WWTP digester gas · agricultural / food-waste AD plant gas · landfill gas (LFG) · CHP engine fuel · upgrader upstream biomethane |
|---|---|
| Composition range | 50–65 % CH₄ / 35–50 % CO₂ / 0–5,000 ppm H₂S / water-saturated · trace NH₃, siloxanes, VOCs acceptable |
| Pressure range | 0.01 – 0.6 MPa standard (raw biogas is low-pressure) · 1.6 MPa on request for compressed biomethane |
| Medium temperature | -10 to +80 °C (mesophilic 35 °C · thermophilic 55 °C · LFG and CHP ambient) |
| Ambient temperature | -20 to +65 °C · 5 % to 100 % RH (outdoor digester service) · 86 to 106 kPa atmospheric |
| Enclosure rating | CNEX Ex d (flameproof, Zone 1) standard (Zone 1) · dual-compartment with barrier seal for CHP engine-room · IP66 non-Ex for post-upgrader biomethane only |
| Signal distance | Sensor to remote display: up to 1000 m |
H₂S-Tolerant Probe Package
| Standard probe | Hastelloy C-276 wetted probe · 0–5,000 ppm H₂S continuous · 10-year design life verified by H₂S exposure tests |
|---|---|
| LFG option | Hastelloy + PTFE protective coating · 10,000 ppm H₂S continuous · 15,000 ppm spike tolerance with ±2 % accuracy impact during spike |
| Economy option | SS316L · ≤ 200 ppm H₂S only · suitable for desulfurized biomethane, upgrader-outlet polishing, pipeline-grade service |
| Compatibility testing | Sour-gas qualification · 720 h accelerated H₂S exposure at 5,000 ppm with mass-loss < 0.05 mg/cm² |
| Siloxane tolerance | No transducer face, no orifice edge; siloxane mist cannot concentrate on a flow-disturbing surface; periodic probe inspection recommended for LFG service |
| Water-vapor handling | thermal-dispersion physics insensitive to water-vapor fraction within ±1-2 % range · top-mount probe option rejects liquid slugs · knock-out pot recommended upstream on LFG |
Materials & Approvals
| Sensor wetted parts | Hastelloy C-276 standard · Hastelloy + PTFE coating option · SS316L economy (desulfurized service only) |
|---|---|
| Body material | SS304 standard · SS316L for brackish / coastal WWTP · aluminium-bronze for aggressive LFG leachate vapor |
| Sensor pair | Two Pt-class RTDs: one temperature reference, one heated at fixed ΔT |
| Elastomers | FKM (Viton) standard · HNBR for H₂S-rich service |
| Housing | CNEX Ex d (flameproof, Zone 1) flameproof aluminium · Zone 1 · dual-compartment with barrier seal for CHP vibration |
| Approvals | CE · UKCA · CNEX Ex d (flameproof, Zone 1) · ISO 9001 |
| Net weight (DN150) | 11.8 kg integral, PN16 flange · 14.4 kg dual-compartment · 7.2 kg DN50 threaded |
Flow range by pipe size.
Biogas flow range in Nm³/h referenced to IUPAC STP (0 °C, 101.325 kPa); the EN 16723 grid-injection default, typical 60 % CH₄ / 40 % CO₂ composition. The engineering team validates each sizing against the digester profile and downstream demand.
| Pipe size | Minimum (Nm³/h) | Typical range (Nm³/h) | Maximum (Nm³/h) | kg/h typical |
|---|---|---|---|---|
| DN25 (1″) | 1 | 15 – 110 | 160 | 18 – 133 |
| DN40 (1½″) | 2 | 36 – 290 | 420 | 44 – 351 |
| DN50 (2″) | 3 | 55 – 380 | 550 | 67 – 460 |
| DN80 (3″) | 6 | 140 – 950 | 1,360 | 169 – 1,150 |
| DN100 (4″) | 10 | 210 – 1,460 | 2,100 | 254 – 1,767 |
| DN150 (6″) | 20 | 470 – 3,300 | 4,720 | 569 – 3,993 |
| DN200 (8″) | 36 | 820 – 5,720 | 8,180 | 992 – 6,921 |
| DN250 (10″) | 56 | 1,320 – 9,220 | 13,180 | 1,597 – 11,156 |
| DN300 (12″) | 80 | 1,900 – 13,280 | 18,980 | 2,299 – 16,069 |
| DN300 HV (12″) | 108 | 2,560 – 17,920 | 25,610 | 3,098 – 21,683 |
Installation
Five rules separate a 10-year trouble-free biogas install from a probe lost in 12 months.
- Match probe to H₂S log; Hastelloy C-276 to 5,000 ppm; PTFE-coated above; SS316L pits in 3–6 months.
- Horizontal, ≥ 2 % slope; RH 100 % gas condenses over 10–30 m. Upstream KO-pot or top-mount probe.
- Spec CH₄ nominal at order; curve locks 50/55/60/65 % CH₄ at ±1.5 %; analyzer input gives ±1.0 % beyond ±3 %.
- Match CNEX to drawing; Ex d IIC T6 Gb covers Zone 1 digester rooms, wellheads, CHP skids; dual-compartment near engines.
- Match reference to invoice; EN 16723 uses 0 °C; CHP runs 15 °C; China 20 °C. Delta is 7.3 %.
Frequently asked questions
Why specify a thermal mass meter for biogas instead of an ultrasonic meter or a turbine meter?
Both are real alternatives with a structural weakness. Ultrasonic (Sick FLOWSIC100-PA, Emerson Rosemount 3800) is reference-grade when clean, but DN100–DN200 biogas builds list at $18,000–$40,000 plus flow-computer integration, and transducer faces foul from siloxane and fatty-acid mist. Turbine ($2,000–$6,000) seizes from H₂S corrosion; a 200–500 ppm WWTP trunk eats bearings inside 12 months, failing silent over-read first. TMF-BG threads both: Hastelloy C-276 probe tolerates 0–5,000 ppm H₂S, no bearing, no transducer face, $1,600–$6,200 price range. The 0.2 Nm/s low-flow detection sees the 3 a.m. digester idle that ultrasonic drops below 1–2 m/s, and composition input tracks CH₄ in real time. 10-year TCO is ~40 % of ultrasonic and ~60 % of turbine-with-replacements.
How does the composition-analyzer input work, and when do I need it?
A 4–20 mA loop carries live CH₄ % (0–100 % = 4–20 mA) from your existing IR sensor, analyzer cabinet, or upgrader GC. The meter rolling-corrects density and thermal-conductivity, holding ±1.0 % of rate across 50–65 % CH₄. Without it, the curve is locked to the specified nominal (e.g. “60 % CH₄ / 38 % CO₂ / 2 % other”) and accuracy relaxes to ±1.5 % of rate as CH₄ drifts ±3 %. Spec the input if feedstock varies (food-waste AD swings 55–68 %), you report to a carbon-credit scheme or feed-in tariff, or CHP engines need real-time calorific feedback. Skip it on stable mesophilic WWTP digesters where CH₄ rarely drifts more than ±1 %. Firmware accepts the input at any time; retrofit without factory intervention.
What H₂S level can the meter tolerate; and does it matter if my raw biogas swings?
Standard Hastelloy C-276 is rated 0–5,000 ppm H₂S continuous over a 10-year design life; covering WWTP digesters (100–800 ppm typical), agricultural AD (300–2,000 ppm, pig slurry being the high end), and food-waste digesters (500–3,000 ppm). For landfill service with 8,000 ppm H₂S spikes or aged cells, step up to the TMF-LFG PTFE-Hastelloy build (10,000 ppm continuous, 15,000 ppm spikes). SS316L economy is only suitable for desulfurized biomethane or pipeline-grade; ≤ 200 ppm H₂S; never specify it on a raw digester. If your H₂S profile is uncertain, send a 30-day log from any handheld or online meter and we’ll recommend the probe per header. The wrong call is typically a 6–12 month premature replacement.
Is CNEX certification required for biogas, and what zone does TMF-BG cover?
Yes; biogas is flammable above ~5 % CH₄ in air. TMF-BG ships CNEX Ex d (flameproof, Zone 1, gas group IIB covers CH₄ and biogas minor components). Adequate for indoor digester rooms and WWTP sludge buildings, outdoor CHP skids, upgrader plants, and LFG collection wellheads. For North American sites specifying NEC Class I Div 1 Group D, spec the NEC option. Dual-compartment build (flameproof terminal + barrier seal) is mandatory within 3 m of a running CHP engine because of vibration.
How does TMF-BG compare to TMF-NG (natural gas); can I use one model for both?
Same chassis, three physics-driven differences. (1) Composition: TMF-NG is calibrated 90–95 % CH₄ with AGA 8 / ISO 20765 Z-factor support; TMF-BG runs 50–65 % CH₄ / 35–50 % CO₂ with composition-analyzer input. The thermal-conductivity curves differ; not interchangeable without a factory profile swap (~5 working days). (2) H₂S: TMF-NG ships SS316L for desulfurized pipeline gas (< 4 ppm); TMF-BG ships Hastelloy C-276 for 0–5,000 ppm. Using TMF-NG on raw biogas pits the probe in 3–6 months. (3) Ex rating: TMF-NG is Ex d IIA T3 (natural gas); TMF-BG is Ex d (CNEX flameproof) (broader gas-group for unpredictable minor components). For an upgrader facility, spec both; the $500–800 probe delta is cheaper than a premature replacement.
Need help sizing the digester-gas build?
Send pipe size, CH₄ range, H₂S range, pressure, destination. Engineer replies with Nm³/h, model code, ballpark price in 4 business hours.