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Energas successfully deploys turnkey SNG gas plant as seamless back-up for LNG plant.

Energas having significant experience in the pipeline gas market; leveraged that experience to deploy a turnkey synthetic natural gas plant (SNG) as critical back-up for a liquified natural gas (LNG) plant.

Alternative Energy Sources to Natural Gas: Compressed Natural Gas and Liquefied Natural Gas

With the rising cost of LPG gas and alternative energy sources like LNG and biomethane becoming more available, the industry is looking towards alternatives for their current energy fuels like LPG. Whilst the cost of LPG is quite expensive, LNG, CNG, biogas, and biomethane are becoming more available at competitive prices to LPG.

Energas, having vast experience in the gas market and with different energy fuels, is well aware that price isn’t always the determining factor when it comes to selecting the best solution. Gas availability plays as big a role in selecting the best long-term and reliable solutions. In the case of LPG, it is the most readily available bulk energy fuel available in the South African market.

LPG vapor and dry-compressed air are mixed together to create a gas known as synthetic natural gas (SNG). This mixture has the same Wobbe Index as natural gas (typically 94% methane). SNG proves to be an effective backup or even primary gas source where the plant piping and equipment have been designed for natural gas (NG).

Cost and Plant Availability Balance

“Many clients are dependent on NG, and some on LNG, as their primary energy source for their combustion operations. Combustion operations are often critical processes like burners, ovens, water heating, or steam. There can thus never be outages, as production interruptions are very costly to the client. This is especially true in 24/7 operations with high production output.”

“For client operations where NG-fuelled critical operations interruptions are detrimental, SNG becomes a viable and effective solution for a seamless gas backup system without changes to a client’s plant operations,” says Darius Booyens, Energy Manager at Energas.

The cost of production losses due to gas interruptions far outweighs the cost of an SNG system over its lifecycle and proves to provide a short-term ROI.

SNG and Its Role in NG Availability

With rising uncertainty in NG supply from major pipeline gas suppliers, SNG provides an effective backup or even primary gas source. An SNG plant is an effective asset in curbing any uncertainty where NG supply may be a concern. NG systems, such as an LNG regasification plant, may also experience outages from maintenance or breakdowns.

An Energas SNG plant provides a customer with peace of mind that a seamless interchange between NG is a certainty. Energas has successfully deployed and operated an SNG plant in parallel with an LNG plant where the LNG plant was taken offline for maintenance, and the SNG plant took over seamlessly.

More on SNG

SNG, made from mixing LPG vapor and dry compressed air at levels above UEL (upper explosive limit), provides an effective “look-alike,” as far as Wobbe Index is concerned, for NG. Comparing the Wobbe Index of certain gases allows Energas to effectively match the Wobbe index of a customer’s existing fuel source, typically NG. Wobbe index can be viewed as a type of normalised calorific value which takes into consideration the physical property, specific gravity, of a gas. Two gasses with different calorific values and specific gravity can thus be compared to one another and their interchangeability in a process.

“Whilst SNG is a fairly new concept to the South African market, it has been used in the European market for quite some time and is a common sight where there are LPG installations or even where natural gas needs to be mixed with SNG,” says Booyens.

Process flow diagram for the application of SNG in process conditions designed for natural gas.
Process flow diagram for the application of SNG in process conditions designed for natural gas.

SNG mixed from LPG and dry compressed air is approximately 55% LPG and 45% dry compressed air and has a Wobbe Index range of 11.8 – 12.0 kcal/Nm³ depending on the specific LPG composition. As a reference LPG has Wobbe Index 19.1 – 20.8 kcal/Nm³.

Natural gas has a Wobbe Index of 11.8 kcal/Nm³ at a 94% methane composition. SNG, from LPG and compressed air, and LNG thus have similar Wobbe Index and allow for little to no piping, regulator or burner changes in combustion processes in a plant when switching between the fuel sources.

SNG and the South African Market

There has been a steady rise in inquiries for alternative fuel sources to replace a client’s current piped NG or to act as a seamless backup where NG or LNG sources are used as primary fuels. In certain cases, clients have shown interest in having SNG as their primary energy fuel where natural gas is not a viable option.