Types of Natural Gas: CNG, LNG, PNG and Equipment Applications

Natural gas is an important energy source for power generation, industrial production, commercial facilities and residential gas supply. Depending on the gas source, transportation distance, infrastructure and end-user requirements, natural gas can be delivered through pipelines, stored under high pressure as compressed natural gas (CNG), or transported in liquid form as liquefied natural gas (LNG).

Although CNG, LNG and piped natural gas (PNG) are often discussed as different types of natural gas, they mainly describe different supply and delivery methods rather than different chemical categories.

Understanding these differences helps engineers and project owners select appropriate gas pressure regulating, metering, vaporization and auxiliary equipment.

1. How Is Natural Gas Classified?

Natural gas can be classified in several ways, depending on whether the discussion concerns its geological source, composition, physical state or supply method.

1.1 Classification by Source

Natural gas may be obtained from conventional gas reservoirs or unconventional resources, including shale formations, tight formations and coal seams.

These resources can have different production characteristics and gas compositions. Before entering a transmission or distribution network, the gas may require processing to satisfy the applicable gas quality specifications.

Biomethane produced by upgrading biogas can also be used in certain gas networks when it meets the relevant injection and quality requirements. However, biomethane is not fossil natural gas, even though methane is its principal combustible component.

1.2 Classification by Supply Method

For downstream gas infrastructure, a more practical distinction is how natural gas is stored, transported and delivered to users.

The three commonly discussed supply forms are:

• PNG (Piped Natural Gas): Natural gas delivered through a pipeline network.

• CNG (Compressed Natural Gas): Natural gas compressed to high pressure for storage or transportation.

• LNG (Liquefied Natural Gas): Natural gas cooled to cryogenic temperatures and stored as a liquid.

These supply methods may use gas from similar sources, but their storage conditions, transportation arrangements and downstream equipment requirements are significantly different.

2. Piped Natural Gas (PNG)

Piped natural gas refers to natural gas supplied through a network of transmission and distribution pipelines.

It is widely used for city gas distribution, industrial fuel supply, power generation and commercial applications where pipeline infrastructure is available.

2.1 How PNG Supply Systems Work

Natural gas is transported through transmission pipelines and delivered to downstream distribution networks or industrial consumers.

Depending on the project, a gas receiving or regulating station may perform filtration, pressure reduction, flow measurement, safety protection and other required functions before gas is supplied to users.

Pressure levels vary between transmission networks, regional distribution systems and end-user installations. Equipment must therefore be selected according to the actual inlet pressure, required outlet pressure and flow demand.

2.2 Typical Equipment for PNG Applications

• Gas pressure regulating skids and stations.

• Natural gas metering skids and instruments.

• Gas filters and gas-liquid separators where required.

• Safety shut-off valves, relief devices and monitoring instruments.

• Gas heating and odorization equipment where specified.

For example, an integrated pressure regulating and metering station can combine multiple functions in a skid-mounted package. A dedicated natural gas metering skid can be configured according to the required flow range, pressure, gas properties and measurement requirements.

3. Compressed Natural Gas (CNG)

Compressed natural gas is natural gas stored at elevated pressure to increase the amount of gas contained within a given storage volume.

CNG is commonly used for natural gas vehicles, mobile gas transportation and gas supply applications where a direct pipeline connection is unavailable or impractical.

3.1 CNG Storage and Transportation

In many vehicle-fueling applications, CNG storage pressures are commonly around 20–25 MPa, depending on the system and applicable standards. Other CNG storage and transportation systems may use different pressure ratings.

High-pressure cylinders, storage modules or transport trailers are used to contain the compressed gas.

Compared with gas at near-atmospheric pressure, compression significantly reduces the storage volume required for a given quantity of natural gas. However, CNG still requires specialized high-pressure equipment and suitable safety arrangements.

3.2 CNG Pressure Reduction and Gas Supply

When CNG is delivered to an industrial or commercial user, its pressure generally needs to be reduced to the level required by the downstream gas system.

A CNG pressure reducing station may incorporate:

• High-pressure inlet isolation and protection devices.

• Pressure reduction stages.

• Gas heating where required to manage temperature reduction.

• Filtration and gas metering equipment.

• Pressure and temperature monitoring instruments.

• Safety shut-off and control functions.

Pressure reduction can cause substantial gas cooling, depending on the inlet conditions and pressure drop. Engineering assessment is therefore important when determining whether heating or additional protective measures are required.

3.3 Typical CNG Applications

• Natural gas vehicle fueling infrastructure.

• Industrial facilities without direct pipeline access.

• Satellite gas supply stations.

• Temporary or supplementary natural gas supply.

• Mobile gas distribution systems.

4. Liquefied Natural Gas (LNG)

Liquefied natural gas is natural gas cooled to a cryogenic temperature so that it becomes a liquid.

At approximately atmospheric pressure, LNG is typically stored at around −162°C, although its actual boiling temperature depends on composition and pressure.

Liquefaction greatly reduces the volume occupied by natural gas, making LNG suitable for large-scale transportation and storage where pipeline delivery is not practical.

4.1 LNG Storage and Transportation

LNG is transported using specially designed cryogenic vessels, including LNG carriers and road tankers.

It is stored in insulated tanks designed for low-temperature service. The storage system must account for thermal insulation, pressure management, boil-off gas and applicable safety requirements.

4.2 LNG Regasification

Before LNG can be supplied to most conventional gas distribution networks or industrial consumers, it must be converted back into gaseous form.

This process is known as regasification or vaporization.

Depending on the application, an LNG regasification system may include:

• LNG storage and liquid transfer equipment.

• LNG vaporizers.

• Pressure regulating equipment.

• Gas metering instruments.

• Safety and monitoring devices.

• Associated piping, valves and control systems.

The vaporization technology and downstream gas conditioning arrangements depend on LNG flow rate, required gas delivery pressure, ambient conditions and project specifications.

HUAYI provides project-specific LNG regasification and pressure regulating skid solutions for applicable gas supply projects.

4.3 Typical LNG Applications

• LNG satellite stations.

• Industrial natural gas supply.

• Regional gas distribution projects.

• Remote facilities without pipeline connections.

• Peak-shaving and supplementary gas supply applications.

5. CNG vs. LNG vs. PNG: Key Differences

The following comparison summarizes the main differences between these natural gas supply methods.

No single supply method is best for every project. The preferred option depends on gas demand, distance from existing pipelines, available infrastructure, transportation costs, operating conditions and project economics.

6. How Supply Method Affects Gas Equipment Selection

Although PNG, CNG and LNG may ultimately supply similar end users, their upstream conditions can be very different.

6.1 Pressure Regulation

Pressure regulating equipment must be selected according to the maximum and minimum inlet pressures, required downstream pressure, flow range and safety requirements.

High-pressure CNG supply may require staged pressure reduction and careful temperature management. Pipeline gas stations may have different operating ranges and redundancy requirements.

6.2 Gas Metering

Gas metering equipment should be selected according to flow range, pressure, temperature, gas composition, measurement accuracy and applicable standards.

Different projects may use turbine, ultrasonic, orifice or other metering technologies.

For integrated gas supply projects, natural gas metering skid systems can be configured with the required instruments, valves, piping and control interfaces.

6.3 Filtration and Separation

Gas filters and separators may be needed to protect downstream valves, regulators and meters from solid contaminants or entrained liquids.

The required equipment depends on the actual gas quality and operating conditions rather than the supply method alone.

For further technical guidance, see our article on natural gas quality requirements for pipelines and gas equipment.

6.4 Temperature Management

Gas temperature can change significantly during pressure reduction or LNG vaporization.

Engineers should consider operating temperature limits, potential condensation, hydrate formation and the temperature requirements of downstream equipment.

Heating, vaporization or other temperature management measures should be selected according to the process conditions.

7. Choosing the Right Natural Gas Supply System

When evaluating a natural gas supply project, engineers and project owners should consider the following information:

• Gas demand: Minimum, normal and maximum gas consumption.

• Supply availability: Existing pipeline access, CNG transport options or LNG delivery infrastructure.

• Pressure requirements: Available inlet pressure and required delivery pressure.

• Gas quality: Composition, moisture, contaminants and applicable quality specifications.

• Operating environment: Ambient temperature, site conditions and installation limitations.

• Continuity of supply: Storage, redundancy, backup supply and maintenance requirements.

• Project economics: Capital investment, transportation, energy consumption and operating costs.

• Applicable standards: Local regulations, engineering codes and contractual technical specifications.

A complete technical evaluation should consider the entire gas supply system rather than selecting individual components in isolation.

8. HUAYI Gas Equipment Solutions

Tianjin Huayi Gas Equipment Co., Ltd. provides natural gas pressure regulating, metering and related equipment for gas transmission, distribution and industrial gas supply applications.

Depending on the project requirements, relevant equipment may include:

• Natural gas pressure regulating and metering skids.

• Natural gas metering systems.

• CNG pressure regulating equipment.

• LNG vaporization and pressure regulating skids.

• Gas filtration, separation and auxiliary equipment.

Equipment configurations are determined according to the actual gas composition, design flow rate, pressure and temperature conditions, required functions and applicable project specifications.

For technical discussions, customers can provide the gas supply method, gas analysis, required flow capacity, inlet and outlet pressures, operating temperature range and relevant project specifications.

Conclusion

PNG, CNG and LNG are different ways of supplying natural gas, each with distinct infrastructure and equipment requirements.

Pipeline gas systems typically focus on pressure regulation, metering and distribution. CNG systems require high-pressure storage and controlled pressure reduction, while LNG systems require cryogenic storage and vaporization before conventional gas delivery.

Understanding these differences helps engineers select suitable gas supply equipment and develop reliable, project-specific system configurations.

Contact HUAYI to discuss pressure regulating, metering, LNG regasification and associated gas equipment for your project.

Technical note: This article provides general engineering information. Final equipment selection, pressure ratings, operating limits and safety requirements must be confirmed against applicable standards and project-specific design conditions.