Biogas Turbine Flow Meter (LWGQ Series)

A biogas turbine flow meter is a velocity-type gas turbine sized and built for post-upgrade biomethane; the renewable-natural-gas stream that exits a biogas upgrading plant after H₂S scrubbing, CO₂ separation, and glycol drying. At that point the gas is ≥95 % CH₄, ≤10 ppm H₂S, ≤4 ppm H₂O, and single-phase dry. The LWGQ rotor reads volumetric flow through a calibrated K-factor; built-in T+P compensation outputs corrected volume at reference conditions on the 4-20 mA loop. The meter sits at the grid-injection skid or the off-taker delivery point as the fiscal-revenue basis for RNG settlement.

No. Raw biogas at the digester outlet is water-saturated, carries 30–45 % CO₂ and 100–10 000 ppm H₂S, and is often pulsating; out of the LWGQ medium binding (clean dry gas only). For raw biogas at the digester / CHP feed, use the biogas-swirl-flow-meter (LUXB Series) which tolerates wet gas, low pressure, and digester pulsation. The biogas-turbine page covers only the post-upgrade biomethane stream after the upgrading skid; that is where custody-grade ±0.5 % of rate billing happens.

The factory ships each meter with an ISO 9001 calibration certificate listing the K-factor, calibrated DN, and tested flow range. Hazardous-area cert is Ex d II CT6 Gb (flameproof) plus Ex ia II CT6 Ga (intrinsically safe); EMC compliance is to EU Directive 2014/30/EU. EN 16723 biomethane quality and OIML R 137 fiscal approval are buyer-arranged with a notified body in the deployment country; the meter is a candidate instrument that the buyer’s metrology consultant submits to a witnessed type-test if the local tariff regime requires it. Engineering will share build documentation and calibration traceability records to support that submission.

Titanium alloy is the standard biogas-turbine body for residual H₂S tolerance after the upgrade module. Even on a well-tuned amine + polishing train, H₂S in delivered biomethane runs 4–20 ppm with humidity excursions during column upsets; 316L corrodes under that exposure while titanium does not. The 316L body option is acceptable when (a) the upstream upgrading skid has a final activated-carbon polishing bed holding H₂S below 4 ppm and (b) glycol dryer dew-point margin is >15 K. Aluminium body is not offered on this build; the trace H₂S risk for aluminium is unacceptable on RNG fiscal service.

Same site; different points in the process. Biogas-swirl (LUXB) covers raw and partially-conditioned biogas at the digester outlet and pre-upgrading buffer: wet, low-pressure (2 kPa to 1.6 MPa), variable composition, sometimes pulsating from digester gas-pressure swings. Biogas-turbine (LWGQ) covers post-upgrade biomethane at the grid-injection skid or off-taker delivery point: dry, ≥95 % CH₄, pressurised (1.6 to 10 MPa), fiscal-billing basis. A typical RNG plant runs one swirl on the raw-biogas inlet to the upgrader and one turbine on the biomethane outlet to the grid. Don’t substitute; out-of-binding service voids the K-factor.

Biogas-thermal-mass (TMF) is the right pick for internal process metering on conditioned biogas where the buyer needs direct mass-flow output and the application is sub-billing (energy-balance, CHP fuel input, environmental reporting), not fiscal sale. TMF tolerates lower flow velocities and outputs Nm³/h directly with no T+P correction loop. Biogas-turbine takes over when the application crosses into fiscal custody; grid-injection billing, RNG off-taker invoice, premium-feedstock CHP-bonus reporting under REDII or comparable regime; where ±0.5 % of rate accuracy and audit-trail logging are required.

Standard lead time is 5 to 7 business days from order confirmation, factory direct. Each meter ships with an ISO 9001 calibration certificate listing the K-factor, calibrated DN, and tested flow range; a mill cert for the titanium body material; the build-coded serial plate with model string; and a daily-and-interval logger file pre-formatted for audit retrieval. Hazardous-area cert options are Ex d II CT6 Gb (flameproof, Zone 1) for general RNG-skid service plus Ex ia II CT6 Ga (intrinsically safe) for classified-area delivery points. EMC compliance to EU Directive 2014/30/EU ships standard, with IP65 and IP66 ingress ratings selectable at order.