How Is Natural Gas Transported?

How Is Natural Gas Transported?

Natural gas is an increasingly vital part of our global energy landscape currently accounting for about 25% of energy consumption worldwide and growing. Natural gas powers everything from home heating and cooking to electricity generation and industrial manufacturing processes.

To meet this growing demand, immense quantities of natural gas must be efficiently transported over long distances–often thousands of miles–from production sites to end users. This is where the importance of natural gas pipeline transmission comes in. In this article, we’ll look at various modes of transportation of natural gas and some of their inherent advantages and disadvantages.

Pipeline Transportation

Natural gas transmission pipelines are complex, highly engineered systems designed to transport gas safely and efficiently. Natural gas is transported using compressors which help propel gas flow up to 100 feet per second at pressures between 200 to 1500 pounds per square inch (psi) down the network of pipelines.

Transmission mainline pipelines themselves are constructed from large diameter steel pipe most often ranging from 12 inches to 48 inches in diameter. The pipeline steel typically used is high-strength, corrosion-resistant, and coated externally to provide protection from corrosion when buried under the ground.  The pipe is also tested before being used and periodically throughout its lifetime, to pressures well above normal operating pressures, as part of a pipeline operator’s Integrity Management Program.

To maintain desired pressures and throughput, compressor stations are placed every 40 to 100 miles along the pipeline route. These stations house powerful centrifugal, reciprocating, or gas turbine natural gas compressors, to re-pressurize the flowing gas at each station.

Pipeline Advantages

Pipeline transmission offers advantages over other transportation methods. Compared to shipping liquefied natural gas (“LNG”) across the country via trucking, rail, or ship, pipelines have lower capital costs, and lower operating costs, resulting in lower fees to customers. Transporting natural gas by pipeline networks also minimizes public safety concerns, improves reliability, and helps address environmental goals which are lacking in trucking or rail transport, which are susceptible to accidents, weather conditions, and other external disruptions. Pipelines also facilitate a continuous supply of natural gas, which is crucial for meeting energy demands of urban centers, power generators, and industrial complexes. These factors make pipeline transmission an economic and indispensable link in the natural gas supply chain.

Liquefied Natural Gas Pipeline Transportation

While pipelines are well-suited for overland and some offshore transportation, natural gas can also be transported long distances overseas in liquefied form. This involves cooling natural gas to ultra-low temperatures to convert it to a liquid state. Liquefied natural gas takes up 1/600^th the volume of gaseous natural gas allowing large quantities to be transported efficiently in specially designed LNG carriers.

The liquefaction process involves progressively cooling the gas in stages, ultimately to around  -260°F. This condenses the gas into a liquid which is about 97% methane. LNG is finally stored in double-walled, vacuum-insulated tanks on ships.

Massive LNG carrier ships transport LNG around the world. These vessels contain insulated tanks able to hold over 267,000 cubic meters of LNG in many cases. Regassification facilities are required at the destination sites as well as distribution pipelines from those regassification processing plants to industries and the public. Economies of scale make LNG transport affordable over very long intercontinental distances.

Advantages and Disadvantages

Shipping natural gas as LNG provides access to overseas natural gas reserves not reachable by pipeline. LNG can also be stored for months and transported to meet seasonal demand spikes. It also provides a flexible supply option, enabling countries to source natural gas from different suppliers across the globe, which can be critical in times of supply disruptions.

However, liquefaction facilities, LNG tankers, and re-gasification terminals require major capital investment. Safety is a top concern when handling ultra-chilled (cryogenic)LNG. Strict procedures help prevent accidents resulting in leaks and spills. Additionally, the energy required for the liquefaction and regasification processes is significant.

However, LNG transport provides a flexible way to diversify global natural gas supply options for nations without an adequate internal supply. Both LNG carriers and transmission pipelines will continue to serve a growing international natural gas market for many years to come.

Road and Rail Transport

Transporting natural gas via road or rail, or alternatively using natural gas to power vehicles provide additional transportation options for natural gas, typically for shorter distances.

Compressed Natural Gas (CNG) for Vehicles

Compressed natural gas (CNG) can be used to fuel natural gas vehicles like buses, trucks, and cars. CNG as a vehicular fuel has been gaining traction due to its lower emissions compared to traditional fuels. The gas is compressed to pressures up to 3,600 psi in on-board fuel cylinders in place of fuel tanks for gasoline or diesel fuel.

When transported, CNG can be dispensed at dedicated fueling stations, much like gasoline and diesel, for use in vehicles. Converting vehicles to CNG can cost thousands of dollars. However, many modern vehicles are also available with factory-fitted CNG fuel systems. On the disadvantage side, slow refueling of CNG tanks on vehicles, and reduced driving range are challenges. Still, CNG can displace high-carbon-intensity oil-based fuels for certain transportation applications.

Challenges in Road and Rail Transport

Natural gas can be transported as CNG in specialized pressurized tank rail cars. Rail provides more delivery options and flexibility than pipelines do, but is better suited for small gas volumes. Also, loading and unloading CNG railcars is time-consuming.

Safety and cost-effectiveness are also concerns with transporting CNG by truck or rail. Road and rail are also weather-dependent. For these reasons, these modes of transportation tend to serve shorter-haul transportation, rather than long distances covered more efficiently via transmission pipelines or LNG tankers.

Despite these challenges, road and rail transport of CNG do provide a valuable solution for delivering natural gas to areas not serviced by pipelines or waterways. This mode of transportation complements other forms of natural gas transportation, ensuring a more diversified and resilient supply chain, capable of meeting the diverse energy needs across diverse regions.

Safety and Environmental Considerations

The transportation of natural gas, be it through pipelines, LNG carriers, or road and rail, each requires stringent safety measures in their design and operation, in order to mitigate potential risks in the delivery of this low-carbon fuel that helps us reduce our carbon footprint.

Protocols and Technologies Ensuring Safety

For gas pipeline networks, integrity management programs are among the many programs incorporated by pipeline companies to ensure pipeline mechanical integrity and safety over the long term. Also, automated shut-off valves are strategically placed along the route of pipeline systems to automatically halt the flow of gas in certain events, minimizing the risk of leaks or accidents.

Advanced monitoring systems equipped with sensors are incorporated within pipeline operations and on LNG carriers to detect anomalies such as leaks or pressure drops in real time, enabling prompt response to prevent impacts. Additionally, the utilization of cutting-edge leak detection technologies such as infrared cameras and laser-based systems contributes to the early detection and remediation of leaks.

Both transmission pipelines and LNG carriers will continue to grow as clean natural gas displaces higher-polluting energy sources worldwide. Their strategic expansion promises a bright future built on this vital and low-carbon bridge fuel.