1. To: Dr. Douglas Price
From: Name
Date: 2/2/2020
Nitrogen Production process using Membrane Technology
Introduction
As the global demand for energy grows, the need for natural gas also grows, the current
challenge is how to remove N2 from the air and many technologies have been forwarded to help
with the same. N2 is a gas with no heating value, it is inert, therefore the gas is separated from
the air to make its transportation and storage more efficient. Many methods have been used in
separating N2 from the air and the document studies the Membrane method of separation. There
are other methods such as adsorption, but the process is selected based on energy efficiency,
scalability, and safety (Singh & Koros, 2016). The method needs to be energy efficient since the
natural gas pumped at high pressure then processed further into methane (CH4) and then to
liquefied gas. The method needs to be nitrogen selective and this means that additional energy is
required to pressurize and depressurize the methane gas. Scalability is necessary so that the
process can serve cubic millions of demands. The process must also operate under moderate
temperature and pressure (Ning, 2014).
Polymorphic Membrane
During the separation process, the membranes serve as the semi-permeable barriers that
are applied to separate the gas stream and enriched retentate stream (Al-Rabiah & Ajbar, 2018).
The separation process is driven by the difference in partial pressure between the permeate side
2. and the gas feed side. The first commercialized membrane was done on the separation of
Hydrogen (H2) and its application has been expanded since. The technology is widely adopted
because it has no phase change, meaning that removal of Nitrogen can be done under moderate
temperatures, the process is also simple and has a simple flow scheme (Kim, Koros, Husk &
O'Brien, 2017). The process is also highly adaptable and can be applied to offshore applications
with low costs and easy operations.
The Membrane technology uses three types of membrane, Organic Polymer membrane,
Mixed matrix membrane, and Inorganic molecular sieve membrane. The mix matrix and the
inorganic can be used in the selection of both Nitrogen (N) and Methane (NH4). The polymer
membrane applies both a single stage of multistage temperature conditions, that rejects the flow
rates for Nitrogen (N2) from 0.004 to 25 MMscf. There is research that has shown that the
natural gas streams that have Nitrogen concentration that is lower than 12%, this could help to
sieve 93% of Methane recovery.
In case of higher concentrations of Nitrogen say 30%, the process becomes
uneconomically viable. At the same concentration, the membrane method becomes energy
inefficient as the pressure must be sacrificed (Jariwala & Lokhandwala, 2015). At these
concentrations, the additional energy and costs are required to compress the enriched methane
stream to reduce the gas pressure. This means that the high head pressure must be maintained
throughout the process (Robeson, 2011).
Separating Nitrogen
This method separates Nitrogen using a sieve. The technology used non-cryogenic
Nitrogen on-site. A polymeric fiber selectively permeates O2, H2O, and many other impurities
3. and allows Nitrogen to flow through the center of the membrane thus emerging as a product of
the process. The process uses thousands of hollow fibers that are bundled forming high
performance and high volume gas separation modules. One or more modules are mounted to
operate in parallel thus supplying over 200,000 SCfh of the continuous Nitrogen product. Figure
1 below shows an overview of the Polymer Membrane Technology.
Figure 1: Overview of Membrane Technology (Ning, 2014)
The technology works as shown in Figure 2 below.
Figure 2: TheMembrane Separation Process (Ning, 2014)
4. The membrane, therefore, separated N2 from O2, the process is not a chemical process,
therefore, has no chemical formulae.
Economics
The technology is the cheapest N2 production method in the market
The method produces high N2 volumes at low purity ratios.
The air designs ensure high reliability of the method
The method delivers lower delivery and operating pressures.
The gas generator technology flow diagram is as shown in Figure 3 below;
Figure 3: TheWorking Flow Diagram of thePolymer Membrane Technology (Ning, 2014)
The membrane Process
1. The first step is drawing air from the atmosphere
5. 2. The air is then compressed through the high-efficiency filter that removes particulate
matter and water vapor (Ning, 2014).
3. The clean air is then passed through an activated carbon scrubber that removes
hydrocarbons before the air enters the separation module.
4. The air is then passed through the hollow fiber membranes that are responsible for
separating O2 and H2O from the remaining gas (Baker, Lokhandwala, Wijmans & Da
Costa, 2013).
5. The final filter has activated carbon that ensures the production of high-quality Nitrogen.
6. Purified Nitrogen is then passed to an outlet that is connected to an application.
Advantages
The filter is inexpensive
The method does not suffer clogging
It can also filter large volumes of air and also introduce
Disadvantages
The method may absorb large volumes of filtrate
There a possibility of introducing metallic ions to the produced Nitrogen
Conclusion
The method provides an alternative separation technique, it is a safe and scalable method
that also brags of being energy efficient. There is also research on the other types of membranes
with satisfactory morphology before the membrane technology can compete with other
6. technologies such as cryogenic distillation, then be used as the main technology to be used in
purifying N2 from the natural air (Ning, 2014).
Works Cited
Baker, R. W., Lokhandwala, K. A., Pinnau, I., & Segelke, S. (2017). Methane/nitrogen
separation process (No. US 5,669,958/A/). Membrane Technology and Research, Inc.
Baker, R. W., Lokhandwala, K. A., Wijmans, J. G., & Da Costa, A. R. (2013). Nitrogen removal
from natural gas using two types of membranes (No. 6,630,011). Membrane Technology
and Research, Inc., Menlo Park, CA (United States).
Jariwala, A., & Lokhandwala, K. A. (2015). Nitrogen-rejecting membranes to increase gas
heating value and recover pipeline natural gas: A simple wellhead process approach. In
the 12th Annual International Petroleum Environmental Conference. Houston, TX2005.
Al-Rabiah, A. A., & Ajbar, A. (2018). Dusty Gas Model for Nanoporous Carbon Membrane
Used for Nitrogen Removal from Natural Gas.
Kim, T. H., Koros, W. J., Husk, G. R., & O'Brien, K. C. (2017). “Reverse permselectivity” of N2
over CH4 in aromatic polyimides. Journal of applied polymer science, 34(4), 1767-1771.
Robeson, L. M. (2011). Correlation of separation factor versus permeability for polymeric
membranes. Journal of membrane science, 62(2), 165-185.
7. Singh, A., & Koros, W. J. (2016). Significance of entropic selectivity for advanced gas
separation membranes. Industrial & engineering chemistry research, 35(4), 1231-1234.
Ning, X. (2014). Carbon molecular sieve membranes for nitrogen/methane separation (Doctoral
dissertation, Georgia Institute of Technology).
Koros, W. J., & Zhang, C. (2017). Materials for next-generation molecularly selective synthetic
membranes. Nature Materials, 16(3), 289-297.
