As South Africa prepares for a transition from declining Mozambican natural gas to a proposed methane rich gas (MRG) bridge, with liquefied natural gas (LNG) potentially following, industrial users require fast, plant-level gas-data that can support approved burner and engine settings to mitigate equipment risk, says engineered solutions provider Energas Technologies.

South Africa’s inland gas market has been built around natural gas produced from the onshore Pande-Temane fields in Mozambique. The gas is processed and compressed at the Central Processing Facility and transported through the Republic of Mozambique Pipeline Investments Company pipeline to chemicals and energy company Sasol’s Secunda operations, where it enters the network serving industrial customers.

This relatively consistent supply has allowed burners, boilers and gas engines to be commissioned based on a familiar gas-quality envelope, says Energas.

However, Sasol is exploring alternative solutions to bridge the anticipated supply gap. Aligned with this, in November 2025, Sasol confirmed the technical feasibility of supplying MRG from its Secunda operations to external customers for a limited bridging period from July 2028 to June 2030.

The proposal remains subject to regulatory approval and the investment decisions needed for implementation.

LNG is being developed in parallel as a longer-term option. Biomethane and other renewable or synthetic gases may also become part of the Southern African gas market, however their injection into the Sasol network is not confirmed.

While this would address the supply gap, Energas points out that gas from different sources can have different calorific values, Wobbe index values, relative densities and constituent profiles.

Given this, measurement at the industrial user’s point of use is required, particularly during a transition or blending period.

Full Picture
While calorific value measures the heat released by a defined quantity of gas, the Wobbe index is a more useful metric for burner interchangeability.

For a fixed burner nozzle and an unchanged gas-pressure differential, thermal input is about proportional to Wobbe index.

A lower Wobbe gas can under-fire the process, resulting in the gas valve reaching its limit, furnace temperature or steam output falling, excess oxygen rising and flame stability deteriorating. Whereas a higher Wobbe gas can over-fire it, resulting in a rich air-fuel ratio, increased carbon monoxide or nitrogen oxides, overheating and flame impingement.

To mitigate this and restore proper heat input, end-users need to adjust gas pressure, valve or actuator maps, air-fuel ratio, oxygen trim, nozzle size or the burner itself.

Energas notes that final settings should always be confirmed through burner original-equipment manufacturer (OEM) review and site recommissioning.

Further, while the Wobbe index is essential, it is not a complete gas-engine compatibility test. 

Consequently, a change that appears acceptable on Wobbe index alone may still require a different fuel-valve map, lambda target, ignition timing, knock-control strategy or output derating.

This is particularly relevant with engine-generators above about 500 kW, where fuel flow, lost production and equipment risk become material. Smaller units must also remain within their approved fuel envelope to mitigate potential risks.

Compact Solution
Energas offers measurement specialist RMG’s RGQ 5 as a compact correlative gas-quality analyser for continuous measurement of combustible gases, using a correlation model built from a database of gas compositions to calculate combustion properties in line with recognised industry methods.

The unit enables burner and engine adjustments based on the gas in use, thereby protecting performance, efficiency and process safety.

It combines patented dynamic-viscosity measurement with micro-electromechanical system-based thermal conductivity, gas pressure and temperature measurement as well as optional infrared sensing.

The instrument continuously updates Wobbe index, calorific value, density, relative density, compressibility, stoichiometric air-fuel ratio and methane number.

Owing to the unit’s small footprint, minimal sample demand and lack of moving parts in the sensor, it is suitable for distributed plant monitoring where a full analyser shelter may be difficult to justify.

Explosion-protected, ATEX/IEC Ex-approved configurations are also available where required.

The RGQ 5 is offered in variants for conventional natural gas, renewable gas and hydrogen- containing mixtures, while proposed gas composition must be checked against RMG’s published concentration range.

To navigate the gas transition, industrial users should request the guaranteed gas-quality envelope and expected transition rate, obtain equipment-OEM approval and define the commissioning and fallback plan before the first fuel change arrives.