French-Azerbaijani University (UFAZ)
Group Work
Course Title: Membrane Separation Processes
Topic: Oxygen Enriched Air (OEA)
Submitted by
Farid Mammadov
Toghrul Karimli
Department of Chemical Engineering and
Physical Chemistry
Submitted to
Eric Favre
Date of Submission: 17 December 2021
Contents
Introduction .................................................................................................................................... 3
Membranes performances for the application .............................................................................. 4
Commercial membranes for OEA ............................................................................................... 4
Novel Membranes and Processes for Oxygen Enrichment ........................................................ 4
Oxygen enriched air using membrane for palm oil wastewater treatment ............................... 4
Membrane Oxygen Enrichment for Efficient Combustion ......................................................... 5
Development of Nanofiller-Modulated Polymeric Oxygen Enrichment Membranes for
Reduction of Nitrogen Oxides in Coal Combustion .................................................................... 5
O2 / N2 separation membranes that are under laboratory scale development ......................... 6
Engineering framework for a single stage membrane separation process: input data, resolution
(systems of equations), output ....................................................................................................... 7
Membrane Module Design: Methodology ............................................................................... 17
Single module design: surface and energy requirements ........................................................ 17
Multistage processes ................................................................................................................ 18
Hybrid PSA-Membrane System for Separating Oxygen from air .............................................. 19
Membrane-based oxygen-enriched combustion ..................................................................... 20
Technologies for Oxygen Enrichment from Air .................................................................... 20
Conclusion ..................................................................................................................................... 21
List of symbols and units............................................................................................................... 21
Authors contribution .................................................................................................................... 22
References .................................................................................................................................... 24
2
Introduction
Nowadays, people of the world are trying to get some results like waste product
elimination, usage of energy, and one of the most important problems, air pollution and
utilization. which is so important for human life. Oxygen-enriched air (OEA) can help us to solve
the problems with is related to polluting emission and plant production. Scientists and
researchers are doing some tests and researches for knowing that how oxygen plays important
role in industrial reactions and what happens when oxygen percentage is increased. Due to
these experiments, we get some interesting results such as when we increase oxygen
concentration a little more than 21 percentage in OEA can cause great changes. If we check this
experiment in industrial refineries, we can see that refinery catalyst regeneration, fluid catalytic
cracking (FCC), sulfur oxidation in the Claus plants, and so on are main examples for the
advantage of more concentrated oxygen. For example, air that is enriched with 30 percent
oxygen is used for natural gas furnaces we can save nearly 25 percent of 1650 kelvin gas
temperature. However, if the oxygen concentration is increased, the number of rising profits
reduces. That’s why mainly used oxygen concentration is between 25 percentage and 35
percentage. Furthermore, oxygen-enriched air is applied for dwindling of applications for flue
gas amount and CO2 concentration increasing and it results with decreasing of cost of CO 2. The
usage of EA has different situations owing to optimization of plant and existing plant. For these
situations, usage of the EA will rise the plant capacity and it will help to utilize plant capacity
and revamp some operations. Nevertheless, oxygen with higher concentration for new plants
directly plays a huge role in the size of the plant, because of economic situations. It also gives
an advantage for heat exchangers and compressors.
The basic working principle of the membrane gas separation process is that it requires an
unbalanced state. When further developed, there is no separation effect in equilibrium, which
represents a major difference compared to processes based on phase equilibrium. From a
practical point of view, the difference in partial pressure (or leakage) of the penetrating species
between the upstream and downstream sides is a necessity. Such a pressure difference will
create a chemical potential driving force that allows the species to penetrate through the
membrane material. The pressure difference between the two sections separated by a
membrane is obtained in the module.
3
Membranes performances for the application
Commercial membranes for OEA
Now, commercial methods and membranes will be explained briefly and some of them
are used in the industrial park will be discussed.
There are three main methods for enriching the air with oxygen: distillation, adsorption,
and membranes. Distillation is the most widely used and developed method for this process, as
it has a large-scale production and historical basis. The second method is Pressure Swing
Adsorption (PSA) obtained by reducing the total pressure in the system. In the adsorption field,
which is mainly zeolites A and X, nitrogen is significantly more adsorbed than oxygen at high
pressure. The two methods discussed above are more energy-intensive processes than
membrane separation techniques. The high demand for a more useful method necessitates the
replacement of both distillation and PSA in OEA by membrane separation. Sustainable process
for membrane process, environmental condition, etc. There are several advantages such as.
This section of the report will discuss several industrial membranes to obtain detailed
information on the range of use of this method. In general, the main membranes for oxygen
enrichment on the conductive side are polymeric membranes, cross-linked polymeric
membranes, block co-polymer-based membranes, liquid membranes, carbon membranes, and
so on.
This section will discuss several industrial membranes used in various fields.
Novel Membranes and Processes for Oxygen Enrichment
The main goal of this project is to get air that enriched with 25 percent – 35 percentage
oxygen for replacing feed of furnaces from air-fueled ones to oxygen-enriched furnaces. It helps
to rising up purity and efficiency of energy at combustion process, in addition it will cause to
decreasing of CO cost and flue gases. Furthermore, perfluoropolymers (PFPs) is expected to be
useful for oxygen/nitrogen separation that is used to be made into thin film composite
membranes. For oxygen permeance and Oxygen/nitrogen selectivity are 1200 gpu and 3.0
accordingly which are quite reasonable values to use this material as membranes. PFP-based
membrane, using MTR’s commercial coater was tested within 60 day long, permeability and
selectivity stood stable during this time.
Oxygen enriched air using membrane for palm oil wastewater treatment
Now, we will talk about oxygen enriched air using membranes and reduction palm oil
wastewater. For that, asymmetric polysulfone hollow fiber membrane is made to increase
4
oxygen in air. Then, palm oil wastewater samples are taken and tested to check their
Biochemical oxygen demand (BOD) with two system. One system is oxygen enriched air;
another is diffused air system. Quality of wastewater have huge difference in OES when we
compare two results with diffused air system. Aeration using OES improve concentration in
wastewater and consequently improve the Biochemical oxygen demand reduction and
influence other physical characteristics of wastewater.
Membrane Oxygen Enrichment for Efficient Combustion
Oxygen combustion is filled to decreasing pollution and CO 2 capture. When we increase
oxygen enrichment it will cause to efficiency rising up. It means in oxygen combustion, fuel and
recycled flue gas are burned with the help of oxygen enriched air (OEA). It gives us some
advantages such as OEA main helper for rising up heat, and ignition development, also main
thing for decreasing flue gas. In addition, it is main reason for productivity climbing, and energy
efficiency. Some polymeric membranes have been tested for understanding parameters that
can affected to the system and permeability of polymers. Perflurodioxole polymeric
membranes, silicone-coated polymeric membranes, polyphenylene oxide (PPO) membranes are
examples for the investigated ones for the process.
Development of Nanofiller-Modulated Polymeric Oxygen Enrichment
Membranes for Reduction of Nitrogen Oxides in Coal Combustion
To get more information about nanofiller-modulated polymeric oxygen enrichment
membranes and providing high-grade oxygen-enriched streams for combustions and some gas
related applications have been done at North-Carolina A&T State University in Greensboro,
North Carolina. In final, experimental and theoretical thoughts were used to get answer, the
membranes evaluated thus far include single-walled carbon nano-tube, nano-fumed silica
polydimethylsiloxane (PDMS), and zeolite-modulated polyimide membranes. Molecular
dynamics simulations were performed to calculate the theoretical oxygen molecular diffusion
coefficient and nitrogen molecular coefficient in single-walled carbon nanotubes PDMS
membranes to document the nano-filled modular polymer. The team conducted conductivity
and diffusion experiments using polymers consisting of nano-silica particles, nanotubes, and
zeolites as fillers; studied the effects of nanofillers on self-diffusion, free volume, glass
permeability, oxygen diffusion and solubility, and perm selectivity of oxygen in polymer
membranes; developed molecular models of single-walled carbon nanotubes and nano-fumed
silica PDMS membranes and zeolite-modulated polyimide membranes.
5
O2 / N2 separation membranes that are under laboratory scale development
It is a fact that, separation process in inseparable part of industry. Membrane separation
is one of the most commonly used separation methods in engineering. It has reverse osmosis
water filtration, gas separation and other control applications, where gas separation is very
important. One of the gas extractors is O2 / N2, which is used in the production of oxygen or
nitrogen-supplied gas, which is used to burn oxygen, increase the recovery of wastewater
treatment plants or to repair food, and to regulate atmospheric conditions in laboratories, and
has many other special applications. Today, other ways of separating O2 / N2, both cryogenic
distillation or PSA adsorption, as well as traditional O2 / N2 separation membranes, are
polymer-based due to their selectivity and reproductive properties. However, the release of
oxygen or nitrogen from the air is still a difficult and difficult problem because the atomic sizes
are 2.89 and 3.04. For this reason, the application of molecular sieves is not valid for
experiments that can be used to obtain the important, porous properties of zeolites. Currently,
there are other Mixed Matrix Membranes that have been effectively calculated for O2 / N2
selectivity. In Samarasinghe and others in 2020, MMM design can be used to obtain a highperformance polyimide-based Matrimid 5218 polymer matrix, filler CoPCMPs (microparticles of
cobalt (II) phthalocyanine and high-quality oxalic acid with high quality % 34. The idea of using a
polyimide-based membrane has been proposed and used by Air Liquid and Praxair. But it is also
a fact that it is a membrane material, where oxygen has a higher quality conductivity. The use
of magnetic f is possible. The new composite matrix composite membrane has also been
developed with NaX nanocrystals of the membrane system. tested for oxygen and nitrogen
release from the air process. According to the results, only the matrix composite 16.7 w ST-NaXNCs in the membranes develop air separation properties, where the selectivity of the pure
membrane will increase by 204%. The use of the Lewis-Nielsen model in this study also
examines a study that includes non-ideal effects in MMMs. Another Iranian research team from
Khorramabad, Fatemeh Bagri, and Yaqoob Mansourpanah, annealed NH2-fungicides and
processed Zeolitic Imidazolate Frame ZIF-8 nanoparticles in a polydimethylsiloxane matrix
MMM and anchored 102 mm in size. According to the results, the nitrogen potential of oxygen
was obtained in excess of 5.5, which is much higher than with ordinary membranes. In a similar
study, ZIF-8 / CA (Cellulose Acetate) MMMs were used to increase oxygen for nitrogen energy
selectivity (Shakir Azam et al., 2020), where ZIF-8 / CA concentration results and pressure
analysis were performed on pure cellulose. made. The selectivity of O2 / N2 with acetate
membranes is 300%
As mentioned, the structure of an MOF metal organic framework for O2 / N2 separation
is slightly stronger in terms of tips to ensure that a computational screening method for atomic
dimensions and oxygen / nitrogen so it is advised to use MOF / Polymer MMMs. Designed for
5000 MOF membrane and 78,000 type MOF / Polymer MMM separation performance. The O2 /
6
N2 selectivity for the experiment was estimated to be 19.8, which is a better performance than
zeolite or filled MMMs.
A different process, proposed by Xiuling Chen and his friends 2020, is the idea of
improving gas separation by using cross-linking. This study also evaluated the performance of
internal micro-porosity features. The results of the study showed that methylated polymers
with an internal micro-porosity produced 5.6 O2 / N2 selectivity and this selectivity increased to
6.5 and were subjected to a cross-linking process for about 5 hours at 300 degrees Celsius. In
addition, the plasticization pressure of the cross-linked membrane by itself with pure PIM-BM
(Bromo alkylated polymers of intrinsic microporosity) increased by 400%.
Engineering framework for a single stage membrane separation
process: input data, resolution (systems of equations), output
The figure which is added below indicates a membrane module with a compressor for a
significant mixing case. The question is that, why compressor is needed? And what is advantage
of that? Answer is so simple; it is needed for increasing the pressure and get target oxygen
purity.
Figure 1. Process flow diagram for a perfect mixing case.
The next table shows us the input data and answers after calculations with necessary
assumptions.
7
Input parameter provided
Oxygen volume or mole fraction in feed, 𝒙𝒇
Value and unit
21 % or 0.21
Oxygen mole or volume fraction in permeate, 𝒚𝒑
40 % or 0.40
Oxygen permeance, 𝑶𝟐 (PPO)
Membrane selectivity (PPO), 𝑶𝟐 /𝑵𝟐 or 𝜶∗
Oxygen permeance, 𝑶𝟐 (PSf)
Membrane selectivity (PSf), 𝑶𝟐 /𝑵𝟐 or 𝜶∗
Table 1. The input data provided.
200 GPU
4.5
27 GPU
5.7
There is no special target for design, it means that oxygen volume or mole fraction can be
change due to objectives in most useful and optimal way. The first membrane has a higher
oxygen permeance than the second, however it has a lower selectivity, that’s why the choice
can be made after design is finished.
Input parameter assumed
Membrane thickness, t
Temperature, T
Pressure in feed stream before compressor, 𝑷𝒇𝟏
Value and unit
0.1 μm
20 ºC or 293 K
1.0 bar
Pressure in permeate stream, 𝑷𝒑
1.0 bar
Total feed flow rate, 𝑳𝒇
Input parameter calculated
Oxygen permeability, 𝑷′𝑶𝟐 (PPO)
1 𝑚3 /s or 86400 𝑚3 /day
Value and unit
20 Barrer
Oxygen permeability, 𝑷′𝑶𝟐 (PSf)
2.7 Barrer
Table 2: Input data and calculated result
Oxygen permeability (in Barrer) = oxygen permeance (in GPU) * membrane thickness (in
cm) (1)
𝑐𝑚3
∗𝑐𝑚
𝑆𝑇𝑃
1 GPU = 10−6 𝑐𝑚2 ∗𝑠∗𝑐𝑚𝐻𝑔
permeance corresponds to a membrane thickness of 1 μm and
𝑐𝑚3
∗𝑐𝑚
𝑆𝑇𝑃
1 Barrer = 10−10 𝑐𝑚2 ∗𝑠∗𝑐𝑚𝐻𝑔
permeability.
The equations used for the design are as follows:
1.
The overall balance:
𝐿𝑓 = 𝐿𝑜 + 𝑉𝑝
(2)
8
Where 𝐿𝑓 is total feed flow rate, in 𝑚3 /s, 𝐿𝑜 is outlet reject (retentate) flow rate, in 𝑚3 /s,
and 𝑉𝑝 is outlet permeate flow rate, in 𝑚3 /s.
2.
The overall balance on the target component oxygen:
𝐿𝑓 *𝒙𝒇 = 𝐿𝑜 ∗ 𝒙𝒐 + 𝑉𝑝 ∗ 𝒚𝒑
(3)
Where 𝑥𝑓 is oxygen volume fraction in feed, 𝒙𝒐 is oxygen volume fraction in outlet reject
(retentate), and 𝑦𝑝 is oxygen volume fraction in outlet permeate.
3.
The stage cut, which is the ratio of outlet permeate flow rate to total feed flow
rate:
𝑉𝑝
θ=𝐿
(4)
𝑓
By using equations (2) and (3), the equation for the stage cut in terms of oxygen volume
fractions can be derived:
θ=
𝑥𝑓 −𝑥𝑜
(5)
𝑦𝑝 −𝑥𝑜
It can be deduced from the equation that the oxygen volume fraction in outlet reject
(retentate) cannot be greater than oxygen volume fraction in feed, because the stage cut
cannot be negative.
4.
The rate of diffusion or permeation of oxygen:
𝑉𝑶𝟐
𝐴𝑚
=
𝑉𝒑 ∗ 𝑦𝑝
𝐴𝑚
=
𝑃𝑂′ 2
𝑡
*(𝑝ℎ ∗ 𝑥0 − 𝑝𝑙 ∗ 𝑦𝑝 ) (6)
Where 𝐴𝑚 is the membrane area, 𝑝ℎ and 𝑝𝑙 are the total pressures in the high-pressure
side and the low-pressure side, respectively. The similar equation for the rate of diffusion or
permeation of nitrogen can be written:
𝑉𝑵𝟐
𝐴𝑚
=
𝑉𝒑 ∗ (1−𝑦𝑝)
𝐴𝑚
=
′
𝑃𝑁
2
𝐴𝑚
*(𝑝ℎ ∗ (1 − 𝑥0 ) − 𝑝𝑙 ∗ (1 − 𝑦𝑝 ))
(7)
By dividing the equation (7) by the equation (6):
𝑦𝑝
(1−𝑦𝑝)
𝑃𝑂′
=
𝑝
𝛼 ∗ ∗( 𝑥0 −( 𝑙 )∗ 𝑦𝑝 )
𝑝ℎ
𝑝
(1−𝑥0 )−( 𝑙 )∗(1−𝑦𝑝 )
𝑝
Where 𝛼 ∗ = 𝑃′ 2 (9) is the membrane selectivity and 𝑝 𝑙 = r
𝑁2
(8)
𝑝ℎ
ℎ
(10) is the pressure ratio.
9
The equation (8) is a quadratic equation, and its solution is:
𝑦𝑝 =
1
Where a = 1 + 𝛼 ∗ , b = -1 + 𝛼 ∗ + 𝑟 +
−𝑏+ √𝑏2 −4∗𝑎∗𝑐
𝑥0
𝑟
2∗𝑎
(11)
* (𝛼 ∗ − 1), and c =
−𝛼 ∗ ∗ 𝑥0
𝑟
In the quadratic equation and its parameters depicted, the oxygen mole fraction in outlet
permeates 𝑦𝑝 and the membrane selectivity 𝛼 ∗ have been provided. Hence, series of solutions
will be obtained for the oxygen mole fraction in outlet reject (retentate) and the pressure ratio
r.
In order to have a positive battery cutoff value, the value of x_0 will be less than 0.2099,
and if the graph is adjusted, the value can be calculated more than one dose to increase the
value.
The following tables provides a series of calculated values of these three parameters for
both membranes. As the total feed flow rate has been assumed as 1, the outlet permeate flow
rate will be equal to the stage cut, while the outlet reject (retentate) flow rate will be (1 – stage
cut), as shown in the tables:
Oxygen volume
fraction in outlet reject
(retentate), 𝒙𝒐
Pressure
ratio, r
0.131694
0.01
0.13542
0.025
0.142512
0.05
0.149276
0.075
0.156045
0.1
0.16285
0.125
0.169592
0.15
0.17675
0.175
0.182902
0.2
0.18959
0.225
0.196818
0.25
0.203684
0.275
0.2099
0.297622
Table 3: The solutions for the membrane PPO.
Stage cut, θ (and
permeate flow
𝑽𝒑 , 𝒊𝒏 𝟏 𝒎𝟑 /𝐬)
0.291854
0.281881
0.262101
0.242195
0.221167
0.19882
0.175376
0.148936
0.124821
0.097003
0.064879
0.032175
0.000526
Reject
flow,
𝑳𝒐 , 𝒊𝒏 𝟏 𝒎𝟑 /𝐬)
0.708146
0.718119
0.737899
0.757805
0.778833
0.80118
0.824624
0.851064
0.875179
0.902997
0.935121
0.967825
0.999474
10
Oxygen volume fraction
in outlet reject (retentate), 𝒙𝒐
Pressure
ratio, r
0.107684
0.01
0.112107
0.025
0.119063
0.05
0.126562
0.075
0.134039
0.1
0.141496
0.125
0.14894
0.15
0.15636
0.175
0.163269
0.2
0.17073
0.225
0.178156
0.25
0.185592
0.275
0.193023
0.3
0.2099
0.35536
Table 4: The solutions for the membrane PSf.
Stage cut, θ (and
permeate flow
𝑽𝒑 , 𝒊𝒏 𝟏 𝒎𝟑 /𝐬)
0.350019
0.340033
0.323692
0.305144
0.28561
0.265002
0.243209
0.220162
0.197403
0.171284
0.143542
0.113838
0.082025
0.000526
Reject
flow,
𝑳𝒐 , 𝒊𝒏 𝟏 𝒎𝟑 /𝐬)
0.649981
0.659967
0.676308
0.694856
0.71439
0.734998
0.756791
0.779838
0.802597
0.828716
0.856458
0.886162
0.917975
0.999474
When we check tables, we can see that pressure ratio and oxygen volume fraction is
rising up, however the stage cut is going down. The counter relationship will play significant
role when we review membrane area, the place will begin to goes up, then reach the maximum
and finally it will decrease slightly. Due to the energy requirement of the compressor, it is
counter proportional to the pressure ratio. When we increase pressure ratio values, there will
be a decreasing energy needed.
Finishing stage cut calculations, it is needed to find outlet permeate flow rates and outlet
reject (retentate) flow rates with the help of equations (2) and (4)
11
Psf
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
Pressure ratio
Pressure ratio
PPO
0
0.1
0.2
0.3
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0
0.4
0
0.1
0.2
0.3
0.4
Stage cut
Stage cut
Graphs 1 and 2: Pressure ratios vs stage cuts for membranes PPO and PSf.
If we check the graph of relationship between the pressure ratio and stage cut, we can
see that at the same pressure ratio, the first membrane gets the same target with a lower stage
cut and vice versa. In addition, when we increase the pressure of feed by compressor, it is the
same situation with total pressure in high-pressure side, it needs energy, and operational cost.
The higher the pressure ratio the lower the total pressure in the high-pressure side, so the
objective must be to achieve the same target oxygen purity with the highest-pressure ratio
possible. That’s why any stage cut value, the membrane PSf should be ok for achieving oxygen
purity in permeate.
There are a lot of assumptions, one of them is the pressure of the permeate stream 𝑃𝑝 = 1
bar is equal to the total pressure in the low-pressure side 𝑃𝑙 , which was totally mixed. By using
the pressure ratios, the total pressures 𝑃ℎ in the high-pressure side can be calculated.
Moreover, the equation (6) can be rearranged to compute the membrane areas and 𝑉𝑝
will be replaced by 𝜃 ∗ 𝐿𝑓 :
𝐴𝑚 =
𝜃∗𝐿𝑓 ∗ 𝑦𝑝
𝑃𝑂′ 2 ∗(𝑝ℎ ∗ 𝑥0 − 𝑝𝑙 ∗ 𝑦𝑝 )
(12)
While we make calculations, we need to change some parameters due to the oxygen
permeability unit, 𝑃𝑂′ 2 has dimension in cm and cmHg
12
Parameter
Total feed flow rate, 𝑳𝒇
Oxygen permeability 𝑷′𝑶𝟐
(PPO)
Membrane thickness, t
Oxygen permeability 𝑷′𝑶𝟐
Value
1 000 000
Unit
𝑐𝑚3 /s
3
0.000000002 𝑐𝑚𝑆𝑇𝑃
∗ 𝑐𝑚/(𝑐𝑚2 ∗ 𝑠 ∗ 𝑐𝑚𝐻𝑔)
0.00001
2.7E-10
3
𝑐𝑚𝑆𝑇𝑃
cm
∗ 𝑐𝑚/(𝑐𝑚2 ∗ 𝑠 ∗ 𝑐𝑚𝐻𝑔)
(PPO)
Total pressures 𝑷𝒉 in the
(Tables 6
high-pressure side
and 7)
Table 5: Changed units and corresponding values.
cmHg
Due to the assumption that the total pressure 𝑃𝑙 in the low-pressure side is equal to 1 bar,
the energy requirement of the compressor can be estimated as: [12]
𝛾∗𝑅∗𝑇
1
E = 𝐿𝑓 ∗ 𝜂∗(𝛾−1) [(𝑟 )
(𝛾−1)
𝛾
− 1]
(13)
Where 𝛾 is the adiabatic gas expansion coefficient and is equal to approximately 1.4 for
air at T=293 K, R = 8.314 J/ (mol K), and 𝜂 is the compressor efficiency and the typical value of
compressor efficiency is 0.85. In addition, the unit of 𝐿𝑓 must be changed from 𝑚3 /s to mol/s
by using the mixture mass density at T=293 K (The calculated as: 𝐿𝑓 = 41.352 mol/s).
Another assumption made was that the total pressure 𝑃ℎ in the high-pressure side is the
same as the pressure 𝑃𝑓2 of the feed stream going out of compressor. Regarding the pressure
𝑃𝑜 of the retentate stream, it does not play any role in the design of a single-stage membrane
with feed compression. It will play a significant role in the design of a multistage membrane
process, for instance, the case of using retentate streams as recycle streams. Moreover, the
design of hybrid process may involve the use of retentate stream as the feed stream for the
process other than the membrane separation.
Capital cost or CAPEX is determined by the membrane area, it is calculated by $50 for per
square meter of membrane area. Compressor and its cost estimation is second consideration of
capital cost. Due to the operating cost or OPEX, energy needs of compressor for a hour and its
cost estimation is $0.08 per kWh.
The following tables indicate the total pressures in the high-pressure side, the
membrane areas, the compressor power, the compressor energy consumptions, the total
capital costs, the operating costs, and the total costs
The table which is attached below shows total pressure in high-pressure side, area of
membrane, power of compressor, energy consumptions, CAPEX, OPEX costs, finally, total cost.
13
𝑷𝒉 ,
cmHg
7500
𝑨𝒎 ,
E, kW
𝟐
𝒎
60.948
57
149.83
36
285.25
15
406.10
9
508.23
1131.3
57
3000
775.23
03
1500
561.42
71
1000
454.64
09
750
386.03
68
600
587.27
336.57
2
39
500
640.10
298.43
36
63
428.5
651.08
267.70
71
71
57
375
646.94
242.15
14
8
333.3
584.41
220.41
33
62
83
300
446.74
201.58
08
18
272.7
251.85
185.02
28
76
37
251.9
4.5953
171.62
97
81
79
Table 6: The solutions for the membrane PPO
CAPEX,
$
565983
4
388364
3
282139
8
229351
0
195559
6
171223
3
152418
7
137108
3
124313
7
113131
2
103024
6
937711
.6
858369
.4
OPEX, $
3964275.8
75
2716406.9
72
1967240.6
69
1593061.6
62
1352673.0
63
1179354.9
18
1045720.7
94
938040.71
68
848521.52
76
772345.62
8
706342.52
5
648323.18
95
601384.24
42
TOTAL
,$
96241
10
66000
50
47886
39
38865
72
33082
69
28915
88
25699
07
23091
23
20916
58
19036
58
17365
88
15860
35
14597
54
14
𝑷𝒉 ,
cmHg
7500
𝑨𝒎 ,
E, kW
𝒎𝟐
666.82
1131.3
98
57
3000
1644.5
775.23
24
03
1500
3227.1
561.42
98
71
1000
4681.6
454.64
15
09
750
5999.3
386.03
27
68
600
7151.4
336.57
49
39
500
8102.2
298.43
95
63
428.57
8812.6
267.70
14
35
57
375
9365.6
242.15
42
8
333.33
9429.7
220.41
33
54
83
300
9069.6
201.58
71
18
272.72
8180.4
185.02
73
69
37
250
6656.4
170.29
49
62
211.05
54.497
142.66
37
03
1
Table 6: The solutions for the membrane PSf
CAPEX
,$
56901
28
39583
78
29684
96
25072
85
22301
51
20404
42
18972
96
17791
60
16790
72
15735
79
14613
92
13341
42
11843
03
71602
9.7
OPEX, $
TOTAL, $
3964275
.87
2716406
.97
1967240
.67
1593061
.66
1352673
.06
1179354
.92
1045720
.79
938040.
717
848521.
528
772345.
628
706342.
525
648323.
19
596717.
729
499884.
035
9654403.
72
6674784.
682
4935736.
208
4100346.
861
3582823.
568
3219796.
843
2943017.
038
2717200.
878
2527593.
47
2345924.
692
2167734.
953
1982465.
35
1781020.
972
1215913.
731
15
COST (PPO)
12000000
10000000
8000000
6000000
4000000
2000000
0
0
0.05
0.1
0.15
0.2
0.25
0.3
Pressure ratio, r
CAPEX
OPEX
TOTAL
Graph 1: Cost for the membrane PPO.
COST (PSf)
12000000
10000000
8000000
6000000
4000000
2000000
0
0
0.05
0.1
0.15
0.2
0.25
0.3
Pressure ratio, r
CAPEX
OPEX
TOTAL
Graph 2: Cost for the membrane PSf.
When we look at the graph we can see that CAPEX, OPEX, and Total amount of price goes
down when we increase pressure ratio. Although when the pressure ratio was between 0.025
and 0.15 it shows different style, however after 0.15, all of the costs nearly reach peak. That’s
why optimal value for pressure ratio is between 0.15 and 0.25, due to these numbers stage cut
will change from 0.175376 to 0.064879, for membrane PPO, and from 0.243209 to0.143542 for
PSf membrane. For choosing we need to know oxygen fraction in the outlet reject, because if a
higher recovery is needed so, we need to choose maximum optimal value for pressure ratio.
As we know total cost of membrane PSf is higher than membrane PPO for all pressure
ratios considered, not only in peaks. Furthermore, pressure ratio goes up, the difference in the
16
total cost between the membranes also increases, starting with 1 % difference when r = 0.025
and ending with 25 % difference when r = 0.275.
If we need to know that usage of membranes, selectivity of PSf is nearly 26.67 percentage
more than membrane of PPO, but main difference is in oxygen permeance because percentage
is nearly 678% (6.78 times).
Membrane Module Design: Methodology
A general methodology is proposed to predict the performance of a membrane
separation module based on a simplified hypothesis. The main interest of this approach was to
offer the possibility of obtaining a simple, easy-to-manage analytical expression. However, the
solutions obtained with this simplified approach can be used as a rough answer and the
assumption should be considered in terms of better expectations that are more realistic than
the industrial module. An additional hypothesis is proposed to predict the conditions of
hydrodynamic conditions in separation performance, such as precise plugging energy, as
proposed in chemical reactors, heat exchangers or glass transfer processes. The use of these
small tools leads to the restoration of differential equations and, strictly speaking, no serious
analytical product can be obtained anymore. It has spurred many research efforts in recent
years by providing approximate analytical solutions to this problem. Basically, different
configurations are presented in figure, 4 describes the main case. Fifth, the so-called view on
the one hand (together according to which movements at the top and the end of the traffic jam
on the bottom side) is also examined. However, this is rarely achieved, and the performance of
small industrial modules usually works as well as the four cases shown in Figure. It is interesting
to note that despite the treatment of more complex situations where computing capabilities
have increased today, modular design methodologies in general are still used successfully to
achieve. More precisely, hollow fiber modules can be designed with reasonable accuracy if the
conductor is a source of electrical energy or for the cross-section model to predict the ideal
reverse current to reduce power consumption.
Single module design: surface and energy requirements
When we do multi variate and optimization analysis, firstly we are interested in to know
the set of solutions enabling a fixed y and R to be obtained. The energy requirement and the
membrane surface area needed can be estimated due to the following situations:
Energy requirement estimation for a single stage process is straightforward and mostly
restricted to the contribution of the compressor or vacuum pump. As we know the pressure
ratio has a influence only in analysis, it means we can feed compression or vacuum pump at the
permeate side and it can be fecklessly applied. Because of the flow rate differences between
17
feed and permeate we cannot say that it is the same case. For instance, for a feed compression
with atmospheric pressure at the permeate side (p0 ¼ 1), the energy requirement can be
estimated as:
𝛾𝑅𝑇
1
𝐸 = 𝑄𝑖𝑛 𝜂(𝛾−1) [(𝜓)
𝛾−1
𝛾
− 1]
(14)
𝛾 is the adiabatic expansion factor of the gas mixture (e.g 𝛾 = 1.4 J mol-1K-1 for
nitrogen),
𝜂 is the isentropic efficiency,
T the inlet temperature (K).
For permeate vacuum pumping the energy requirement is calculated like that
E′ = 𝑄𝑝
𝛾𝑅𝑇
𝜂′(𝛾−1)
1
[( )
𝜓
𝛾−1
𝛾
− 1] = 𝜃𝐸
(15)
Such a simplified analysis will suggest a systematic implementation of a vacuum pumping
strategy to minimize the energy requirement of the process. Industry reviews show that this
choice is very rare for a variety of reasons.
When choosing a feed or vacuum compression, the compression ratio can be easily
determined by selecting the appropriate module area s. The cost per unit area of the membrane is
known and the corresponding capital costs can be estimated. Regarding the latter, it should be
noted that there may be significant inconsistencies in the literature. Depending on whether pretreatment costs are included or not, very different numbers are chosen, taking into account the
well-known and currently available membrane material, as opposed to speculation.
Multistage processes
Besides hybrid processes of cryogenic distillation & membranes and PSA Adsorption
chamber & Membranes there is a possibility of multistage membrane configuration to get
higher purity of OEA. However, it is a multistage process, it is the fact that it will cost much
higher due to the material and process configuration and because of complexity. It is also fact
that if we use optimal conditions and different type of membrane materials, we can decrease
the cost and we can get 99.9 percent pure nitrogen which is main interest of industrial process.
For industrial processes of separation of nitrogen from air for getting oxygen enriched air is
main priority, and doing all of them with minimum cost. However, industrial applications have
some disadvantages like leakage and higher footprint. For solving this problem compression
feed is needed and to have balance is another main thing between energy consumption and
membrane surface area. In addition, membrane material, polyphenylene oxide- PPO offers
higher permeance of oxygen and it results with decreasing of cost. We can also get the
18
information that permeance and selectivity importance is different for multistage
configuration. Nitrogen separation and OEA production with multistage configuration have long
way to improve itself.
Hybrid PSA-Membrane System for Separating Oxygen from air
Figure 2. Hybrid PSA-Membrane System
Input air is compressed by compressor and goes to membrane separation module.
Oxygen purity is between 25 percentage and 40 percentage. Outlet gas is recompressed and
enters to PSA. After PSA steam has 98% oxygen. But this number can be increased up to 99.2%
by recycling/
Delivery target=15.0 L /min
Delivery pressure=1.0 atm
Membrane selectivity=2.0
N2/AR selectivity=2.0
Pressure for membrane target I=100.0psig
Pressure for PSA target II=30psig
Atmospheric pressure=14.69psi
Incoming O2 composition=0.21
Incoming N2 composition=0.78
Incoming Ar composition=0.01
Recycle ratio= N/A
19
Membrane efficiency (O2 recovery from air)=90
PSA system N2 removal efficiency=99.87%
Fraction of O2 for PSA regeneration step=60.0%
The calculated values
Required input to the system=3.72 moles O2/min
System O2 output=15 LPM
O2 recovery efficiency=36.0%
O2 purity=98.6%
Available pressure for turbine=37.55psig
Reduction in PSA bed mass-54.7%
Membrane-based oxygen-enriched combustion
Advantages of using oxygen-enriched air in certain industrial processes such as catalyst
recovery in catalytic cracking (FCC), partial oxidation of sulfur in Claus plants, wastewater
treatment for glass and foundry operations, and incineration applications has been accepted as
a substitute for ambient air. Oxygen-enriched air can reduce capital and operating costs, reduce
CO2 emissions, and increase process flexibility and reliability. If oxygen-enriched air could be
produced at a lower cost and more energy-efficiently, the use of oxygen-enriched air would be
more attractive over a wider range and scale of combustion processes.
Technologies for Oxygen Enrichment from Air
Most oxygen is produced at present by cryogenic air separation and vacuum swing
adsorption. However, for many combustion applications, the high cost of oxygen from either of
the detailed methods simply prohibits the use of oxygen-enriched air.
20
Figure 3.
For both designs operate with membrane modules in cross-flow mode and is not highly
recommended with conventional technologies.
Conclusion
The method stream chart of a single organizes layer plan for generation of oxygen enhanced
discuss has been drawn, which includes a compressor and a film module with idealize blending.
A arrangement of arrangements have been gotten for the weight proportion and the arrange
cut for the layers called PPO and PSf. In expansion, the corresponding oxygen volume divisions
in outlet dismiss (retentate), the outlet penetrate stream rates, and the outlet dismiss
(retentate) stream rates have been assessed. After finding the film zones and the vitality
prerequisites of the compressor, CAPEX, OPEX, and the entire fetched have been calculated.
The choice for the weight proportion ought to be made inside the run of 0.15 to 0.25. Besides,
for any chosen organize cut value, the film PSf is decided to be more appropriate to attain the
target oxygen virtue in saturate with a somewhat more weight proportion, hence diminishing
the operational taken a toll. With respect to the membranes, PPO is cheaper than PSF for all the
conceivable weight proportions due to the high membrane permeance for the oxygen.
Additionally, the distinction between the overall costs of the layers increments from 1 % to 25
% as the weight proportion increments. In this manner, the choice between the layers gets to
be less critical at the low values of the weight proportion.
List of symbols and units
Membrane thickness, t in μm
Oxygen permeance, in GPU
Oxygen permeability, PO′ 2 in Barrer
21
Total feed flow rate, Lf in m3 /s
Oxygen volume or mole fraction in feed, xf
Pressure in feed stream before compressor, 𝑃𝑓1 in bar
Pressure in feed stream after compressor, 𝑃𝑓2 in bar
Outlet permeate flow rate Vp in m3 /s
Oxygen volume or mole fraction in permeate, yp
Pressure in outlet permeate stream, 𝑃𝑝 in bar
Outlet reject (retentate) flow rate, Lo in m3 /s
Oxygen volume or mole fraction in permeate, xo
Pressure in outlet reject (retentate) stream, 𝑃𝑜 in bar
Total pressures in the high-pressure side, 𝑃ℎ in bar
Total pressure in the low-pressure side, 𝑃𝑙 in bar
Membrane selectivity, α∗
Pressure ratio, r
Stage cut, θ
Membrane area, Am in m2
Energy requirement, E in W
Adiabatic gas expansion coefficient, 𝛾
Ideal gas constant, R = 8.314 J/*(mol*K)
Temperature, T in K
Compressor efficiency, 𝜂
Authors contribution
Farid Mammadov-Methodology to assess membrane and energy solutions; Engineering
framework for a single stage membrane separation process; Membrane performances for the
application (under development at laboratory scale. Multistage membrane processes
Toghrul Karimli-Introduction. Hybrid processes (Membrane-Based Oxygen-Enriched
Combustion); Commercially available membranes. Hybrid processes (Hybrid PSA-Membrane
System for Separating Oxygen from air); Conclusion; List of Symbols.
22
23
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