Glossary of LPG and SNG

Liquefied Petroleum Gas (LPG)
Liquefied petroleum gas, also known as LPG or LP gas, is a fuel gas consisting of a flammable mixture of hydrocarbons, mainly propane, n-butane, and isobutane. It can sometimes also contain other compounds, such as propylene, butylene, and isobutylene. LPG is used as a fuel gas for heating appliances, cooking equipment, and vehicles. Increasingly, it is used as an aerosol propellant and refrigerant, replacing chlorofluorocarbons to reduce damage to the ozone layer. LPG is also utilized as a transportation fuel, where it is often called autogas or simply gas. The varieties of LPG that are bought and sold include mixes that are mainly propane (C3H8), mainly butane (C4H10), and most commonly, mixes containing both propane and butane. In the northern hemisphere's winter, these mixes contain more propane, while in the summer, they contain more butane.

LPG-Air, Propane-Air, and SNG Systems
System LPG-Air, Propane-Air, also known as the SNG (Synthetic Natural Gas) system, is an installation that produces gas with almost identical properties to natural gas, making it an ideal alternative to NG. Liquid LPG or propane is converted into gas and mixed with air in specific proportions. The resulting mixture is fully compatible with natural gas and can replace it in nearly all applications without the need for modifications or changes to existing equipment. Such systems can also be directly connected to the natural gas network.

SNG systems are used in four main areas:
1) Primary Fuel Source – In locations where natural gas (NG) is not available or its supply is planned.
2) Backup System – During scheduled interruptions in natural gas supply related to technical, maintenance, and modernization work
3) Emergency (Backup) System – In case of failures in natural gas supply, such as due to natural disasters, network damage, or drops in pressure and heating value of the gas.
4) Peak Shaving System – In situations where restrictions on natural gas consumption create a need for additional energy sources or lead to increased costs.

What is the purpose of the Peak Shaving System?
The Peak Shaving System is a device that ensures the automatic dosing of synthetic gas (SNG) into the natural gas (NG) pipeline in the event of a lack or drop in natural gas pressure. Equipped with a control valve and an automatic monitoring system, it enables the mixing of SNG with natural gas.

An efficient solution is also the Auto Actuation System, which automatically switches to SNG supply when there is no natural gas pressure, utilizing an ON-OFF valve, but without the gas mixing function.

Does mixing air with gas in pipelines pose a danger?
Mixing LPG with air is completely safe. This process occurs in a specially designed section of pipe with a larger diameter within the SNG blender. The mixing does not take place in the direct flow; inside the mixer, there are special baffles with specific dimensions and angles that eliminate vibrations and ensure proper mixing.

Regarding explosive concentrations, this is relevant in the case of gas leaks in enclosed spaces. The explosive concentration of SNG gas ranges from 5 to 15% of the air volume in a given room. When the concentration of gas in the air is below 5% or above 15%, ignition may occur.

How are gas mixers utilized in the case of biomethane and biogas?
According to the standard EN 16723:2017 "Natural Gas and Biomethane for Use in Transport and Biomethane for Injection into the Natural Gas Network" in the European Union, it is necessary to monitor the heating value and Wobbe index every 30 minutes before injecting biomethane into the natural gas network. Biomethane obtained during the biogas purification process does not always meet the minimum required heating value of 34.0 MJ/m³ (8,120 kcal/m³).

To adapt biomethane to the requirements of the gas network, biomixers are used to enrich the biomethane by adding 2-10% LPG. This allows for achieving the required heating value before injecting the biomethane into the gas network. These mixers are particularly well-regarded in Germany and France, especially in biomethane applications.

What is the price of SNG and where can the price dynamics be analyzed?
To accurately calculate the cost of synthetic natural gas (SNG) for a company, the wholesale prices of LPG converted to 1 kWh must be added to the operating costs of the equipment, including.
1) Total cost of obtaining the vapor phase of LPG – costs associated with heating the gas in LPG vaporizers.
2) Electricity consumption costs – related to the operation of compressors and pumps.
In general, total operating costs typically amount to approximately 3% of the wholesale price of LPG
Price Dynamics Analysis?
The price dynamics of LPG and natural gas can be monitored on the websites of suppliers, exchanges, and other relevant platforms. In September 2022, natural gas was five times more expensive than LPG. However, the latest pricing indicators at the beginning of 2024 show that LPG is now 5-10% more expensive than natural gas.

It is important to note that the instability of natural gas prices may recur. During periods of rising natural gas prices, the profitability of SNG systems will be evaluated over months and sometimes even weeks of a company's operations.

Specific Requirements for the Installation and Connection of SNG Systems?
There are no specific requirements for the installation of SNG systems; the placement of the main components of the installation is carried out in accordance with regional regulations concerning the installation of LPG equipment, including LPG tanks, pumps, vaporizers, SNG blenders, pipelines, and so on.

Purpose of the Air Compressor in an SNG Blender System
The air compressor with an air tank is essential for the proper functioning of a high-pressure automatic SNG blender. The capacity of the compressor should be tailored to the specifications of the SNG system. Venturi-type SNG blenders can operate without a compressor at pressures up to 0.5 bar. During operation, the Venturi tubes produce a distinct loud sound as they draw air from the surroundings.

Purpose of the Venturi Propane-Air Mixer (LPG/Air Mixers)
The Venturi propane-air mixer (LPG/air mixers) is a device that combines propane or LPG to produce a synthetic natural gas (SNG) mixture by drawing in atmospheric air through the Venturi tube and diffuser. The maximum output pressure of this mixer is 0.5 bar (7.2 psi). However, achieving precise mixing and stable heating value of the gas at the output can be challenging.

Purpose of the Wobbe Index
In the context of synthetic natural gas, a key concept is the stability of the heat flow obtained during the combustion of the gas, which is characterized by the Wobbe Index. The Wobbe Index (both upper and lower values) is a parameter that defines a gas or gas fuel, determining its ability to generate thermal energy during combustion. It is the ratio of the calorific value to the square root of the relative pressure and density under the same reference conditions.

The Wobbe Index is significant because it affects the combustion process of the gas in devices such as burners, furnaces, and gas turbines. In practice, both the lower and upper values of the Wobbe Index are used, depending on the specific application.