Pivotal LNG and Tulane Energy Institute

We exited the freeway just outside of Birmingham, Alabama and made our way through the wooded back roads of Trussville. Pivotal LNG owns and operates a natural gas liquefaction plant located on their 40-acre property. Meeting and learning from industry professionals in person gives us a complete understanding of how different cost drivers effect our current research project.

The Energy Projects class in the MME program provides students with unique industry experiences. Our group consists of four graduate students and we are studying the development of using LNG as fuel for long haul trucking. This past week, the LNG –Trucking Group went on another field trip to understand how natural gas is liquefied. The plant we toured has a liquefaction capacity of 60,000 gallons per day, which is a relatively small facility and falls under the category of a micro plant. Still, the liquefaction procedure is the same across the industry.

Pivotal owns and operates five LNG facilities, including plants in Trussville, Chattanooga, Cherokee, Riverdale and Macon. The one we visited in Trussville is their first facility that has been placed in service over 40 years ago. The plant manager of the Trussville LNG facility, Ed Davis, gave us a very informative tour. The Trussville plant runs on natural gas with a Btu content of 1,000-1,010. The gas is ordered by a company called CGAS which measures the quality, quantity and other features of the source.

At the beginning, Ed Davis showed us around the control room. He is very experienced and has been working in this LNG plant since 1978. He pointed out that the hardest period of time for him is training the new employees. It often takes a year and a half for a new hire to really get to know the plant. Currently, the plant is staffed with five operators, three maintenance people, and one plant manager.

Safety and security are highly regulated by sophisticated computer software in the control room. The software will show the state of the plant, the liquefaction, storage and composer status, as well as the information about the other equipment in the plant. In addition, the same information is accessible from the other plants owned by AGL Resources. The facilities are always open so in the event there is a staff member working alone at one site, someone will still be able to check in on them from another location to verify there are no problems.

After learning about the control room, Ed Davis gave us an overview of the liquefaction process then walked us towards the equipment in the facility. He explained to us the key elements of the LNG plant as well as how LNG is dispensed. The main equipment in the plant includes the turbine, the heat exchanger, the LNG storage tank, the CO2 removal unit, and the compressor.

We passed the Hortonsphere which is a spherical pressure vessel used to storage compressed gases in liquid and gas stage. It is able to store large volumes of liquids and gases economically and reliably under a wide range of pressure and temperature conditions. The spherical shape provides uniform stress resistance, and requires less land area with more capacity than other pressure storage vessels.

We were also able to see the compressors in the facility, which is a machine driven by an internal combustion engine or turbine that creates pressure to “push” the gas through the lines. There are four compressors in the Trussville LNG plant. The facility separates natural gas into different components. Three compressors are used to deal with the mainstream while an additional compressor is used to handle the extra portion of isolates. The compressors, which have 400 horsepower motors inside, run constantly. They are the source of power used in the liquefaction process.

Since CB&I originally built the facility as a peak shaving plant, there is plenty of storage for excess LNG. Now the plant is used mostly for distributing LNG to Pivotal LNG’s markets (trucking, marine, and rail). Although the liquefaction process may seem complex at first, the method is fairly simple. Natural gas arrives though a pipeline from Texas, passes through a Cryex process removing carbon dioxide, then it is refrigerated and distilled into methane, ethane, propane and butane. Once the gas is fully liquefied, it is either placed in storage or pumped into a tanker truck.

The LNG pipelines are heavily insulated containing a space between the inner and outer pipes to keep stability of the pressure and ambient temperature. There are three main directional flows for the pipelines: gas to heat exchanger, LNG to storage tank, LNG to tanker loading.

Before we left, we got to see the tanker loading facility that was serving a LNG trailer truck. We learned that it usually takes an hour for the truck to get filled by LNG. Normally the trailers that depart from the plant have a one-way travel time of about 600-700 hours. This means that the trailers carrying LNG can be parked for up to a month before the LNG content starts to vaporize back into natural gas.

When the tour was complete, we had an exclusive presentation on the fundamentals of the trucking industry from David Jaskolski. He has over 30 years of experience in the trucking industry and he was able to answer all of the questions we had in full detail. Our weekend trip to Alabama was a great way to reinforce our knowledge of the project as well as to bond with our corporate sponsor.

Stuart Kenney, Tyler Goldich, and Xiaogeng “Arebise” Deng

Master of Management in Energy Candidates 2015