Hello there, galaxy brainers!
I have a question for you guys-
Have you guys ever wonder how natural gas is separated to fit its range of purposes?
In this entry, let's take a venture to understand how natural gas is processed for various uses.
BUT, before that, let's take a tour to know more about natural gas.
What's natural gas?
Natural gas is a type of energy source (fossil energy) that is formed deep underneath the Earth's surface. Natural gas contains assorted compounds such as
Methane a.k.a hydrocarbon gas (highest percentage found in the compound)
Natural gas liquids (NGLs): ethane, propane, butane, pentane
Non-hydrocarbon gas: carbon dioxide, nitrogen, water vapors
Courtesy of: https://www.pngkit.com/downpic/u2r5r5i1w7a9a9r5_natural-gas-formation-petroleum-and-natural-gas-formation/
The video below explains the composition of natural gas, do check it out!
If you wish to know more about the formation of natural gas in Earth's crust, please click the link below:
Natural gas can be utilized in many sectors, for instance:
transport sector as fuel
power sector to supply energy
industries for heat generation
fertilizer industries to produce ammonia
Since natural gas is a promising resource to many industries, gas separation is needed to separate impurities from natural gas.
Why do we need to separate impurities from natural gas?
Well, good question. Impurities such as hydrogen sulfide and carbon dioxide may:
reduce the heating value of natural gas
cause corrosion to equipment and pipelines
contribute to environmental pollution
*heating value: the amount of heat released during gas combustion. The heat value is measured as the fuel's energy density.
Feel free to click the link below, if you are interested to learn more about the importance of natural gas in multiple sectors
So, how does the gas separation process can be accomplished?
Actually, there are two distinct technologies for gas separation
Conventional gas separation
Membrane technology gas separation
We'll explore the mentioned procedures together, to identify the advantages and limitations of each procedure as well as unraveling our curiosity to grasp more knowledge about these technologies.
CONVENTIONAL TECHNOLOGY FOR GAS SEPARATION
Cryogenic distillation
applies for the removal of acid gases such as carbon dioxide from natural gas
the process consists of 2, 3, or 4 fractionating columns -depends on the composition of carbon dioxide in natural gas
How does it operate?
Initially, the gas stream is dehydrated and then cooled with refrigerant or pressure reduction.
Requires gas-to-liquid phase change in gas separation
The change of phase will increase the energy cost in this process
The video below explains how the cryogenic distillation process to liquefy natural gas:
MEMBRANE TECHNOLOGY FOR GAS SEPARATION
Membrane technology
applies for the removal of impurities (such as carbon dioxide, hydrogen sulfide) in natural gas
does not require a change of phase (from gas-to-liquid) for gas separation
utilizes membrane with specific material for gas separation
How does it operate?
The operability is based on the selectivity and permeability of a membrane
As you can see in the diagram above, there are two different colors and sizes of molecules
Orange molecules cannot pass through the membrane; the molecules are rejected by the membrane (this stream is known as retentate)
Green molecules can pass through the membrane; the molecules are selected by the membrane (this stream is known as permeate)
In simpler words;
Selectivity means only the selected molecules are allowed to pass through the membrane
Permeability means the number of selected molecules that is can pass through the membrane
Membrane Materials for Gas Separation
There are 2 types of common membrane materials for gas separation:
Polymeric membranes: made up of natural resources
Inorganic membranes: made up of chemicals
Okay, now that we know that there are 2 kinds of membrane materials-
Polymeric Membrane
also known as Organic membrane
Eg: Cellulose acetate, Polysulfones, Polyimide
Glassy/Rubbery materials
Advantages of Polymeric Membrane
Low cost of fabrication
Good reproducibility for large scale production
Highly flexible
Limitations of Polymeric Membrane
Plasticization
Aging
Inorganic Membrane
Eg: Zeolites, Silica, Alumina
Can be fabricated into the dense or porous membrane
Advantages of Inorganic Membrane
High thermal resistance
High stability
Limitations of Inorganic Membrane
Difficult to fabricate
Extremely expensive
If you wish to read more about the membrane materials utilized in the gas separation process, do click on the link provided:
The attached video shows one of the technologies applied in the gas separation system:
Here's the video that I personally made to address my interest in gas separation technology in real-life applications: