PSA Nitrogen Generator
Pressure Swing Adsorption (PSA) systems are one of the most common systems to produce high purity nitrogen (99.9995%). This system relies on the concept of selective adsorption, which is a gas’ tendency to stick to a solid surface under high pressure. The adsorber is the solid surface that adsorbs the gas. In the case of PSA nitrogen generators, carbon molecular sieves are used to adsorb oxygen from dry air, leaving high purity nitrogen.
PSA systems operate at ambient conditions and therefore do not require the air to be heated up. Air enters one of the pressure vessels at high pressure, where gas separation takes place. Oxygen is adsorbed onto the surface of the vessel while high purity nitrogen exits for use. When the adsorbent becomes saturated and not able to adsorb any more oxygen, the process “swings” to the other vessel and is blocked off from the inlet air entrance. The saturated vessel is depressurized to vent the oxygen out to the atmosphere while inlet air now enters the other vessel for separation. This system swings back and forth to continuously produce Nitrogen, with one vessel depressurizing and the other adsorbing.
Published August, 2017
What is a Membrane?
What is a membrane? A membrane is a permeable barrier that selectively permits entities to pass through it. Gas Land utilizes membrane technology to separate air (composed of 20.8% Oxygen , 78% Nitrogen, and 1.2% other gases) to produce a Nitrogen rich gas product. Gas Land's membrane separator modules consist of a cylindrical housing with densely packed hollow fibers. Pressurized, dried, and filtered air enters the membrane module and fast gases such as Oxygen permeate through the fibers leaving behind Nitrogen rich gas. The separation process depends on several factors such as the size of the molecules, speed of the molecules, and chemical interactions with the fibers. Typical Gas Land Nitrogen Generation Systems are designed to deliver between 96% and 98.5% Nitrogen purity depending on the customer’s needs. The primary advantage of membrane gas separation is that the process does not require any moving parts. This reduces maintenance and repair costs and ensures the system continues to perform for years to come.
Published August, 2017
FLNG: Floating Liquefied Natural Gas
Liquefaction of natural gas begins with natural gas being pumped into the LNG plant via pipelines. If the source for the feed gas is an offshore field the length of these pipelines would vary depending on how far the offshore drilling rig is set up. As one can imagine, some natural gas reserves are very far off-shore, making pipelines as a mode of transport unviable. Another option is through carrier ships, but due to the large volume of natural gas, transporting it to the LNG plant is not feasible.
These problems can be solved with a Floating Liquefied Natural Gas plant, a mobile LNG plant designed to extract, process, and liquefy natural gas right above the natural gas field. Once the natural gas is liquefied, it is stored in a hull and carrier ships can pick it up and deliver it to customers around the world. With a FLNG plant, onshore pipelines are not needed to transport the gas to a plant for liquefaction, saving time and money.
A floating plant of this scale comes with challenges that onshore LNG plants do not have. Since it is not on land, the size needs to be reduced as much as possible but also have enough space to fit all the elements that are necessary to process, liquefy, and store natural gas.
Published July, 2017
Typical Nitrogen Generation Plant
Nitrogen forms a critical component of the utility system as it is used for various applications in a LNG Plant. Nitrogen is mainly used for purging, blanketing, and as a seal gas for various compressors and pumps. The above figure depicts a typical Nitrogen Plant set up upstream and downstream of the Nitrogen Generator. The Nitrogen is distributed to various trains, or users via the Nitrogen Distribution Header. A secondary Nitrogen Generation system such as the Liquid Nitrogen Storage & Vaporization package or another Membrane Nitrogen Generator is generally used as a backup system.
Published June, 2017
Designing a Nitrogen Generator
There are many factors that one must consider while designing a Nitrogen Generation System.
1) Nitrogen Flow Required
2) Purity of Nitrogen
3) Inlet Air Pressure
4) Inlet Air Availability
5) Utilities Available
6) Nitrogen Discharge Temperature
7) Turndown Capability
These parameters form the basis of the design for the System. Higher inlet air pressure results in better separation of Nitrogen from Air. Additionally, one must also ensure that the compressors are sized sufficiently; so, they can provide the necessary feed air required for the Nitrogen Generator. Electrical utilities play a role in sizing of the Heater and related controls. Some applications may have a constraint on the discharge temperature of Nitrogen, which is a key parameter in establishing the process temperature for the separation to take place. It is also important to understand the turndown capability of the System as during startup downstream requirement may be much lesser than the intended design.
Published, May 2017
Gas Land Inc STARRT Card
During commissioning activities it is very critical that one has a strong strategy to implement decisions and to make sure that everything is covered before making those decisions.
The STARRT Card approach (Safety Task Analysis Risk Reduction Talk) enables the operator to take a step back and re-evaluate the task and the steps that would be required to accomplish it.
Gas Land's STARRT Card attempts to capture all the critical stages of any task and measures different levels of risks involved in performing those tasks.
A typical STARRT Card would have the following sections.
- Hazard Identification
- Hazard Control Measures
- Pre-Work Considerations
- Impacting Factors
- List of Tasks to be performed
- Steps required to perform the task
Published, April 2017
Nitrogen Usage in LNG Plants
Nitrogen is used for a wide variety of applications in the oil and gas industry. In LNG plants Nitrogen forms a critical part of the utility system without which operations would come to a standstill. Some of the main uses of Nitrogen in LNG plant are as follows:
- Blanketing of Tanks
- Purging of Cold Boxes
- Back-up purge for Flare Systems
- Refrigeration Compressor Seal Gas
- Boil off Gas Compressor Seal Gas
- Process Pump Seal Gas
- Loading Arms Purging and Draining
Published, March 2017
LNG Process Chain
Natural Gas consists entirely of methane, typically LNG is 85 to 95 plus percent methane along with a few percent ethane, and even less propane and butane with traces of Nitrogen. This exact composition varies according to the source of feed gas and the processing technology applied. To obtain LNG and delivering it to the end user consists of a series of steps as listed below.
Exploration & Production
Typically, when oil is produced you also produce some gas. Depending on the type of reservoirs the amount of gas produced can vary drastically. Also, the use of smart engineering techniques such as hydraulic fracturing and horizontal drilling can be crucial especially when it comes to producing from complex shale plays such as in the US.
Once this Natural Gas is produced through Exploration it becomes the feed gas to the Liquefaction or LNG Plant. In this facility, the feed gas is treated and processed to form Liquefied Natural Gas. The facility can almost be thought of as a big refrigeration unit where the entering feed gas is processed and condensed to its liquid form. This enables storage and transportation of the chilled fuel more viable.
Once LNG is produced and stored at the facility. LNG carriers or vessels are loaded with LNG to carry it to its destination.
Storage and Regasification
At the destination, the LNG carrier would transfer LNG at the receiving terminal where it would be transformed to its gaseous state and delivered to users.
Published, February 2017
Membrane Nitrogen Generators
In Oil and gas facilities the operation of the system may vary from the intended design due to the following reasons.
1. Change in Operation Philosophy
2. Startup or Commissioning Phase
3. Underestimation or Overestimation of required Nitrogen
This is crucial to be aware of as each project and client, depending on the application can have different requirements at different phases of the project.
Membrane Nitrogen Generators use membrane separators to produce Nitrogen from Air. A typical membrane separator contains thousands of fibers that are bundled and encased at both ends. The fiber selectively permeates Oxygen, Water vapor and other impurities while allowing Nitrogen to flow through.Like any other process there are governing principles from which you could maximize the most from these systems.
For instance, there are three key parameters to consider in order to understand the Nitrogen flow that can be produced from the System, these are Pressure, Temperature and Purity. These variables will dictate the Nitrogen that can be produced. Additionally, sizing of the package will be based on the flow rate of Nitrogen required, Operating Conditions and various other customers requirements.
Membrane Nitrogen Generators are highly reliable, flexible in their operation, require minimal maintenance and have no moving parts.
Published, January 2017
Gas Land Inc Highlights
Gas Land supplied Three (3) Nitrogen Generation Systems for Sabine Pass LNG – which was the only operational LNG Plant for export in the lower 48 states as of 2016. The facility started exporting the chilled fuel in February 2016. Since then it has shipped 40 cargoes produced from Two Liquefaction Trains with most of them landing in Latin America followed by Africa, Asia, and Europe. Gas Land's Systems are also used in major LNG Plants in Australia. The table below provides a list of our Australian installations.
Gas Land is proud that our systems are an essential component to the LNG Industry, which are part of the biggest LNG Plants in the world. By end of 2017, the total LNG produced by these Plants would be 37.9 MTPA, which accounts for 47% of the LNG produced from Australia.
Published, December 2016
Gas Land successfully commissioned the Nitrogen Generator System for Wheatstone LNG on 31st October 2016. Gas Land is proud to be an integral component of such a massive project which is set to redefine Australia's reputation as a LNG superpower.
The produced Nitrogen will be used for various applications such as blanketing of tanks, purging of cold boxes, compressor seal gas, and more importantly, purging of loading arms during shipping.
In addition to the Nitrogen Generator, Gas Land supplied the Liquid Nitrogen Back Up System for this project. The Liquid Nitrogen System consists of two Liquid Nitrogen Tanks, Pressure Building Coils, Ambient Air Vaporizers and an Economizer Circuit. Each tank can hold up to 94,000 US gallons of Liquid Nitrogen. These are the biggest tanks that Gas Land has ever built to date.
Published, November 2016
LNG Plants & The Optimized Cascade Process
The Optimized Cascade Process is one of the most extensively used process in major Liquefaction plants worldwide. From Sabine Pass Louisiana to Queensland's LNG plants in Australia, the Optimized Cascade Process has been used for over four decades. This technology is based on three multi staged , cascading circuits using pure refrigerants (Propane, Ethylene and Methane). Other key features include use of Brazed Aluminium Heat Exchangers and insulated Cold Box Modules. Heat Integration in the process has been modified such that it approaches Natural gas and Refrigerant cooling curves which results in high efficiency. The use of Brazed Aluminium Heat Exchangers and Cold Box Modules allows for efficient heat transfer which can serve a wide range of LNG plant sizes. Depending on the Feed Gas characteristics a HRU and NRU option can be integrated in the process to further optimize the plant performance. The table below shows a list of current and under construction LNG plants that would be using the Optimized Cascade Process for liquefaction of natural gas.
Published, October 2016
Australia Pacific LNG
Australia’s LNG boom can be attributed to the three simultaneous construction programs: Queensland Curtis LNG, Santos GLNG, and Australia Pacific LNG - which are part of the largest concentration of private capital investment in its history. When in operation of Q4 2016, the three plants would have a combined capacity of 25 million tons of LNG per annum. Out of the three, Australia Pacific LNG was the largest LNG plant to commence construction. It consists of a two train LNG facility with the potential for additional two trains. The plant is capable of producing a staggering nine million tons of LNG per annum.
The coal seam gas for Australis Pacific LNG is sourced from fields in the Surant and Bowen basins in South West and Central Queensland. The gas then enters a 329 mile gas transmission pipeline to reach the Curtis LNG facility where it is liquefied. When the gas is cooled to liquid, the volume of the gas is reduced by 600 times, this liquefaction allows the gas to be shipped and stored safely.
Australia Pacific LNG is a joint venture between Origin (37.5%), ConocoPhillips (37.5%) and Sinopec (25%). This facility uses the ConocoPhillips Optimized Cascade Technology to process coal seam gas into Liquefied Natural gas. Bechtel was awarded the EPC contract for the two train LNG facility.
Each train is made up of Prefabricated Modules, Structural Steel, Piping Systems, CO2 Absorber, Refrigerant Cold boxes and Gas Land’s very own Nitrogen Generation Systems with Liquid Nitrogen Systems as a backup. Recently, Gas Land successfully commissioned Train 2 in July 2016. The system was performing to design delivering better than the promised flow and purity.
Published, September 2016
LNG Chain – The Optimized Cascade Process
Making LNG involves liquefying natural gas for storage. To achieve this, first the feed gas must be treated to remove impurities such as CO2 and Water. The goal of the process is to increase methane concentration and to remove all impurities before liquefaction.
Let’s study the main equipment utilized in this process.
1. Auxiliary Oil Heater – This is an important component for the LNG process which provides the initial heat to the gas exchangers.
2. Acid Gas Removal Unit (AGRU): It removes sour gas from the feed gas before it enters the cooling phase.
3. Dehydration: From the AGRU the gas now moves to the dehydration unit where any remaining water is removed so it does not form ice when liquefied.
4. Mercury removal units: It is crucial to remove mercury primarily because of its corrosive nature on aluminum before it enters the cooling stage.
5. Compression: Gas is progressively compressed through the ConocoPhillips Optimized Cascade process. The gas is forced through by one of two independent compressors.
6. Cold Boxes: Propane, Ethylene, Methane are used as the three refrigerants to liquefy the natural gas to liquid. The cooling process takes place in the Cold Box’s within each train. It contains a cryogenic brazed aluminum heat exchanger.
7. Inlet Air Chilling: All the three Curtis Island projects have inlet air chilling on each gas turbine to boost compressor driver power in order to maximize LNG production.
The main highlights of the Optimized Cascade Process can be summarized as follows
- Two trains in one configuration yields higher plant efficiency
- Can handle a broad range of plant ambient temperatures and feed compositions
- Flexible operations which enable easy start up, shutdown and maintenance
- Use of Brazed Aluminum Heat Exchangers, Aeroderivative Gas Turbines with Waste Heat Integration leading to higher thermal efficiency.
Published, August 2016
Coal Seam Gas vs Shale Gas
Coal Seam Gas is primarily methane, which is colorless and odorless found in coal deposits. Natural gas collects in underground coal seams at depths of 300m to 1000m underground. It is sometimes referred to as coal bed methane (CBM) and would be classified under the umbrella of Unconventional Resources. The difference between conventional and unconventional gas is the geology of the reservoirs from which they are extracted and which therefore require different extraction techniques. With coal seam gas comprising mostly of methane, it has a much more simplified approach in drilling, production, storage and separation techniques when compared to producing shale gas in the US. Natural gas can get collected underground in coal seam beds by bonding to the surface of coal particles. These coal seams are generally filled with water. Interestingly, it is the pressure of the water that keeps the gas attached as a thin film to the surface of coal particles.
Like any other formation, a well is drilled to the required depth to access the coal seam gas, Origin, which is the upstream operator in Australia, uses hybrid drill rigs to obtain efficiency. The completion of the well enables some water to be pumped to the surface. Since the water is pumped to the surface the pressure within the formation is reduced which helps the gas to flow to the surface.
What’s intriguing is that hydraulic fracturing is not always required. Undoubtedly, this depends a lot on the formation itself but most of the current coal seam gas production serving Australia Pacific LNG is coming from high flowing wells, which are not hydraulically fractured. In comparison to US shale, to produce from shale plays such as Texas or North Dakota, hydraulic fracturing is a must because the formation is so tight. Without hydraulic fracturing of these shale plays production is not economical. Another key characteristic of hydraulically fractured wells in the US is that production is high for the first 6 months to a year and then drops rapidly. Many scholars have linked this decline to the closing of fractures and the natural decrease in the reservoir pressure of the formation due to production.
Published, July 2016
Sabine Pass Liquefaction & LNG Export
Sabine Pass is the first liquefied natural gas export terminal to be constructed in the lower 48 states. Owned and operated by Cheniere Energy, a Houston based company, is primarily engaged in LNG related businesses.
Located in Cameron Parish, Louisiana, Sabine Pass has completed construction of the first two of its six liquefaction trains. Each train has a capacity to liquefy 0.55 billion cubic feet per day (bcfd) of natural gas. Once all 6 trains are up and running, the plant would have a staggering capacity of 3.3 bcfd. In other words, each liquefaction train is expected to have nominal production capacity close to 4.5 million tons per annum (mtpa) of LNG. Three other trains at Sabine Pass are currently under construction, which are scheduled to come online in 2017-2019. Decision on financial investment on the sixth train is still awaiting approval. Through its owned subsidiary Cheniere Creole Trail Pipeline, Cheniere also owns a 94 mile pipeline that connects Sabine Pass LNG terminal with a number of large interstate pipelines.
Globally, six other liquefaction projects are scheduled to come online this year in Australia, Indonesia, and Malaysia. Together they would approximately add 8% to the global liquefaction capacity, while just the two trains at Sabine Pass would add 2% to the total.
The future of LNG production facility in the US looks extremely promising. Although one would argue that the current slump in oil price has stalled developing projects. LNG export facilities currently under construction in the US including Sabine Pass will have a total liquefaction capacity of 9.2 bcfd which is equivalent to 13% of current domestic natural gas production. Once all facilities under construction become operational, which is expected to happen somewhere around 2020, the US would possess the third largest liquefaction facility in the world after Australia and Qatar.
Published, June 2016
Declining Average Natural Gas Spot Prices
One of the biggest question in today’s market is when can we expect to see some sort of stability in oil and gas prices. The industry’s cyclical nature is a known fact but the phenomenal drop seen in the last 6 months is baffling to say the least. During 2008 – 2009, oil prices hit its prime at $140 per barrel; although that price was ephemeral in nature, we can see that from 2010 to October 2014, oil prices have been averaging between $80 – $100. One can expect that Natural Gas prices would follow a similar trend, but prices from 2010 to 2014 have averaged $3.5 – $4. Currently, Natural Gas prices are barely hovering above $2.
The Henry Hub is a distribution hub on the natural gas pipeline system located in Louisiana. Additionally, Henry Hub marks the pricing point for natural gas, which is traded on the New York Mercantile Exchange (NYMEX). In 2015, natural gas spot prices at the Henry Hub averaged $2.61 per million British thermal unit (MMBtu), which is the lowest average level since 1999. Henry Hub prices started low in the beginning of the year and fell continuously throughout 2015.
However, Henry Hub was not alone. Other key regional trading hubs ended the year lower than their starting point. In northeastern locations, prices spiked during the early months of 2015; normally, natural gas transmission infrastructure is often constrained. According to EIA, total natural gas production measured in terms of dry gas volume, averaged an estimated 74.9 billion cubic feet per day (Bcf/d) in 2015, 6.3% greater than in 2014. Surprisingly, this increase occurred as the number of natural gas drilling rigs decreased. As of December 18th, there were 168 natural gas drilling rigs in operation, which is about half the number of rigs at the beginning of 2015, according to data from Baker Hughes Inc. Nevertheless, these rigs have been very productive and producers have made huge gains in drilling efficiency.
The combination of low prices and strong production increased natural gas for electric power generation and surpassed coal as the leading source of electricity generation. Natural gas is primarily used for residential and commercial [heat]; in 2015, its consumption declined 6.7% and 4.4% - respectively, due to warmer weather.
Much of the growth in natural gas production can be attributed to Marcellus and Utica shale regions. This served as an incentive for several major pipeline projects that came online in 2015 to transport more natural gas from these plays to consumers. In August 2015, the Rockies Express Pipeline (REX) reversal was completed. The Rockies Express Pipeline is 1,679 mile long of high pressure natural gas pipeline system that connects Rocky Mountains of Colorado to eastern Ohio, which is one of the largest natural gas pipelines ever built in North America.
Published, May 2016
Gas Land, Inc.