Gas Technology Glossary — SNG, LPG, CO₂, Argon, Biomethane & Industrial Gas Terms

GasGenix — Key Definitions & Technical Reference

www.gasgenix.com  |  office@gasgenix.com

This glossary defines key technical terms in gas technology. Topics covered include gas mixing systems, synthetic natural gas (SNG) production, biomethane conditioning, LPG vaporization, and CO₂ and argon supply systems. Definitions are based on applicable EN and ISO standards.
GasGenix applies these definitions across all stages of project delivery — from system concept and engineering design through to commissioning, service, and energy performance analysis.

1. Gas Types & Fuels

LPG — Liquefied Petroleum Gas

LPG is a mixture of liquefied hydrocarbon gases. It consists primarily of propane (C₃H₈) and butane (C₄H₁₀), in variable proportions. Additionally, it may contain isobutane and n-butane. The mixture is derived from petroleum refining. At ambient temperature and pressure, LPG exists as a gas. However, under moderate pressure it liquefies, enabling efficient storage and transport.

Propane (Technical Grade)

Technical propane contains approximately 95% (v/v) propane (C₃H₈). The remaining 5% (v/v) is n-butane (n-C₄H₁₀). In addition, trace quantities of other hydrocarbons may be present. All composition data are specified in the supplier’s quality documentation. As a result of its high propane content, technical propane is the primary fuel used in SNG production and LPG enrichment systems.

bioLPG — Renewable Liquefied Petroleum Gas

bioLPG is chemically identical to conventional LPG in composition and properties. However, it is produced from renewable biomass sources. These sources include vegetable oils, animal fats, glycerol, sugars, and organic waste streams. Furthermore, bioLPG is a direct drop-in replacement for fossil LPG. Therefore, it can be used in all LPG applications — including SNG production and backup gas systems — without system modifications. As a result, it significantly reduces lifecycle CO₂ emissions.

SNG — Synthetic Natural Gas

SNG is produced on-site by blending LPG with compressed air. The mixing ratio is precisely controlled in a gas mixer. Specifically, the ratio is calibrated to achieve a Wobbe Index equivalent to natural gas. The key engineering principle is: NG = SNG (LPG + AIR). As a result, SNG can replace natural gas in industrial burners without burner modification or reconfiguration. Moreover, the switchover is seamless and does not interrupt production.

bioSNG — Bio Synthetic Natural Gas

bioSNG is produced from biopropane (bioLPG) and air. It is the renewable equivalent of conventional SNG. Therefore, it delivers the same combustion performance as natural gas. In addition, bioSNG enables progressive decarbonisation of industrial gas supply. Specifically, it replaces fossil LPG with a renewable fuel — without requiring burner replacement or process reconfiguration.

2. Combustion & Energy Parameters

Gross Calorific Value (GCV) — Heat of Combustion

The Gross Calorific Value (GCV) is the heat released by complete combustion of a specified gas quantity. The combustion occurs at constant pressure. All products are returned to the initial temperature. Water condenses to liquid state. Furthermore, GCV is the primary parameter for energy billing and gas quality certification. It is expressed in MJ/Nm³ at standard reference conditions (0°C / 101.325 kPa).
Source: EN ISO 6976:2016 — Natural gas — Calculation of calorific values, density, relative density and Wobbe indices from composition.

Superior Wobbe Index (Ws) — Upper Wobbe Index

The Superior Wobbe Index (Ws) is the gross calorific value per unit volume. It is divided by the square root of the relative density. Both values are measured at the same reference conditions. In particular, the Wobbe Index is the fundamental parameter for combustion interchangeability. Two gases with the same Wobbe Index produce the same heat output through the same orifice at the same pressure. Therefore, it is the key parameter in gas mixing system design.
Typical values: Natural Gas (H-gas): 48–52 MJ/Nm³ | SNG (LPG+AIR, 60% LPG): ≈ 52 MJ/Nm³.
Source: ISO 6976:2016 — Natural gas — Calculation of calorific values, density, relative density and Wobbe indices from composition. 

3. Gas Mixing Systems & Components

Reference Gas (Base Gas)

The reference gas is the primary fuel of the process gas supply. All mixing system parameters are referenced to it. Specifically, the Wobbe Index (Ws) of the reference gas defines the target values for the mixed gas output. Furthermore, the reference gas determines the selection and control settings of the mixing system. As a result, the blended output delivered to end-use appliances is always calibrated to match the reference gas quality.

Corrective Gas

The corrective gas is dosed into the reference gas within the mixing system. Its purpose is to condition and stabilise fuel parameters at the outlet. Specifically, it regulates gross calorific value (Hs), Wobbe Index (Ws), and methane number. Furthermore, the corrective gas may be enriching or diluting. For example, propane/LPG/bioLPG increases calorific value. In contrast, air or nitrogen reduces it. Therefore, the choice of corrective gas depends on the target gas quality specification.

Gas Mixer

A gas mixer combines two or more gas streams into a homogeneous mixture. It provides controlled dosing of all components. Additionally, it ensures uniform concentration distribution across the flow cross-section. Moreover, the mixer maintains stability of mixture parameters over time. These include gross calorific value and Wobbe Index. Furthermore, all GasGenix gas mixers comply with ATEX and PED requirements for use in potentially explosive atmospheres.

Static Mixer

A static mixer has no moving parts. Mixing is achieved solely through the flow geometry. Specifically, baffles and mixing inserts force repeated stream separation and recombination. As a result, turbulence and dispersion increase significantly. Therefore, a static mixer achieves uniform concentration distribution across the flow cross-section. Additionally, it minimises fluctuations in mixture parameters at the outlet. However, the design must maintain an acceptable pressure drop.

4. Measurement Conditions & Standards

Normal Conditions (Nm³)

Normal conditions are the standard reference conditions used in the gas industry. Gas volume and flow are expressed as Nm³. Energy quantities are expressed as MJ/Nm³. Specifically, the reference conditions are: absolute pressure 101.325 kPa and temperature 273.15 K (0°C). Therefore, all GasGenix system flow data are expressed in Nm³/h at these standard conditions.

Combustion Reference Conditions

Combustion reference conditions define the temperature and pressure at which fuel is assumed to be burned. In Poland, these conditions are 25°C and 101.325 kPa. Furthermore, these values are mandatory for correct energy billing and gas quality certification.
Source: ISO 6976:2016 — Natural gas — Calculation of calorific values, density, relative density and Wobbe indices from composition. 

Working (Operating) Conditions

Working conditions describe the actual state of gas at a measurement point. They are defined by at least pressure (absolute) and temperature. Additionally, gas composition and compressibility factor may be required. As a result, conversion between working conditions and normal conditions requires PTZ calculation.

PTZ Conversion (Pressure-Temperature-Compressibility)

PTZ conversion calculates gas volume as a function of pressure, temperature, and compressibility factor. Therefore, it converts measurements from working conditions to Nm³. Moreover, PTZ conversion is essential for accurate energy metering and billing in gas mixing systems.

Source: EN 12405-1:2022, clause 1

5. GasGenix Core Services

Backup Gas System

A backup gas system maintains gas supply continuity during NG network interruptions. GasGenix backup systems use SNG (propane-air or LPG-air) mixing technology. As a result, they ensure Wobbe Index compatibility with the reference gas and seamless process switchover.

Biomethane Enrichment System

A biomethane enrichment system conditions raw biomethane by injecting propane or LPG. This increases calorific value and Wobbe Index to natural gas grid levels. Furthermore, GasGenix systems include precision flow control and real-time Wobbe Index monitoring. All components are ATEX-compliant and designed to EN 16723:2017.

CO₂ Vaporization System

A CO₂ vaporization system converts liquid carbon dioxide into gas for industrial applications. GasGenix systems use water bath vaporizers. Additionally, they include an integrated gas-fired boiler heating circuit, remote monitoring, and pressure safety systems. Specifically, the safety system prevents dry ice formation below the CO₂ triple point (5.18 bar / −78.5°C). Therefore, the system operates safely even at ambient temperatures as low as −20°C.

OPEX Analysis — Gas Energy Analytics

OPEX analysis is a comprehensive assessment of the ongoing costs of running a gas system. It covers fuel consumption, energy yield, maintenance, and service. Furthermore, GasGenix provides OPEX analysis to quantify the financial benefits of each system for the client’s specific process parameters. As a result, clients receive a clear, data-driven business case before committing to investment.

6. GasGenix System Types — Technical Descriptions

The following descriptions cover the principal gas system types engineered by GasGenix. Each system is defined by its process principle, technical parameters, and typical industrial applications. Furthermore, all systems comply with EN ATEX, PED, and GasGenix internal specifications.

6.1 Gas Backup System / SNG (LPG + Air) Blending System

Process principle: NG = SNG (LPG + AIR) — Wobbe Index (MJ/Nm³)
This system produces SNG on-site from LPG and compressed air. The blending ratio is precisely controlled to match the Wobbe Index of natural gas. As a result, the SNG output is fully combustion-interchangeable with NG. Therefore, no burner modification is required during switchover.

Key technical parameters (SNG Blender):

  • Output capacity: 100 to 10,000 Nm³/h (3,8–380 MMBTU/h)
  • Mixing precision: up to ±1.00% accuracy
  • Operating temperature: −20°C to +60°C
  • Operating pressure (inlet): 1 to 11 bar | Outlet (SNG): 1 to 10 bar
  • Connections: DN 25–150 (inlet) / DN 50–300 (SNG outlet)

Compliance: EN ATEX, PED | Fuels: propane, butane, bioLPG, DME

Main equipment: LPG tank → pump → containerised vaporization station → SNG blender → buffer tanks (optional) → peak shaving → process supply.
Applications: Glass factories, power plants, CHP units, metallurgical plants, food manufacturing, gas operators, biomethane plants, and district heating — wherever NG pipeline connection is uneconomical or impossible.

6.2 Methane Number Stabilization System (Syngas + CH₄)

Process principle: Syngas + NG (or Biomethane) = Stable Methane Number (MN).
The methane number (MN) quantifies knock resistance of gaseous fuels in gas engines. It is analogous to the octane number for liquid fuels. Pure methane has MN = 100; hydrogen has MN = 0. Furthermore, a low or unstable MN causes engine knock, increased wear, and unplanned shutdowns.
Real-world MN values:

  • Pyrolysis gas A: MN = 35 => CH₄ 9.69%, H₂ 60.42%, CO 17.8%
  • Pyrolysis gas B: MN = 47 => CH₄ 13.38%, H₂ 36.2%, CO 23.66%
  • Syngas: MN = 23 => CH₄ 18.95%, C₂H₆ 13.52%, C₃H₈ 21.18%
  • Target after NG stabilization: MN 40–50 — safe range for gas engines

Applications: Industrial CHP plants, biomass gasification, waste-to-energy, pyrolysis gas utilisation.

Therefore, the GasGenix stabilization system injects NG or biomethane as a corrective stream. The control system adjusts the blending ratio in real time. As a result, the MN remains stable within the engine’s operating range.

6.3 Heating Value Stabilization / Enrichment System (NG + LPG)

Process principle: NG + LPG → Heating Value ↑ (MJ/Nm³).

This system doses LPG (propane or propane/butane) into a natural gas stream. The purpose is to increase or stabilise the gross calorific value (GCV) and Wobbe Index. As a result, the enriched gas meets the quality requirements of industrial end-use appliances.

Verified calculation example:

  • Reference gas (NG Lw): 35.87 MJ/Nm³ | Blended with 9.48% propane (100.53 MJ/Nm³)
  • Target mixture: 42.00 MJ/Nm³ | Wobbe Index: 50.58 MJ/Nm³ (within H-gas spec)
  • Total flow: 3,314 Nm³/h (3,000 Nm³/h NG + 314 Nm³/h LPG)

Applications: Gas distribution operators, glass and metallurgical industry, biomethane injection, peakshaving installations.

Furthermore, this system is widely used for biomethane grid injection, where raw biomethane GCV must be uplifted to H-gas network specification.

6.4 Energy Flow Control Gas Blending System (SNG + NG)

Process principle: NG (limited) + SNG = defined energy output (kWh).
This system supplements a capacity-limited NG connection with SNG. The purpose is to achieve a defined energy flow rate (kWh/h) at the process inlet. Therefore, it is used where the NG network connection is insufficient for peak demand.

Verified calculation example:

  • NG (Group E, 41 MJ/Nm³): 1,000 Nm³/h available → supplemented with 797.79 Nm³/h SNG
  • Target energy output: 25,000 kWh | Wobbe Index of mixture: 53.22 MJ/Nm³
  • Blending ratio: 55.62% NG + 44.38% SNG.
Applications: Industrial heating, glass furnaces, drying lines, food processing, and any facility with insufficient NG connection capacity.

Furthermore, the system enables precise energy accounting and OPEX optimisation. As a result, clients achieve a lower blended gas cost compared to 100% SNG supply.

6.5 CO₂ Reduction (Decarbonization) Fuel Blending System

Process principle:

  1. BioSNG + NG = CO₂ reduction;
  1. BioSNG + SNG = CO₂ reduction.

  • Natural gas (NG): 55.73 kgCO₂/GJ — 39.00 MJ/Nm³.
  • LPG (95% propane): 63.10 kgCO₂/GJ — 100.53 MJ/Nm³.
  • bioLPG: 9.20 kgCO₂/GJ — identical energy content to LPG, renewable origin.
  • Verified result — BioSNG 34.31% + NG 65.69%: CO₂ reduction 30.00% vs 100% NG.

CO₂ emission reference data (KOBIZE): 

  1. Configuration A — Biomethane + SNG: Biomethane (from biogas upgrading) is injected into the SNG stream. This reduces the fossil carbon fraction of the backup gas supply.
  1. Configuration B — BioPropane + AIR = BioSNG + NG: Renewable biopropane is blended with air to produce BioSNG. It is then injected into the NG stream. Therefore, this configuration enables renewable backup supply without a biomethane grid connection.

Source: EU RED III 2023/2413; KOBIZE.

This system injects renewable gaseous fuels into the fossil gas stream. Specifically, it blends biomethane or bioSNG into natural gas or SNG. As a result, the carbon intensity of the fuel decreases proportionally to the renewable fuel blending ratio.

Furthermore, two system configurations are available:

Additionally, the system provides full data logging for EU ETS, CBAM, ESG/CSRD-ESRS, and RED III compliance reporting.