TECHNICAL WRITING GUIDELINES CHE 334 (where appropriate), CHE 415, and CBEE 416 Unacceptable basic mistakes: · Misspelled words · Lack of introduction for a figure/table/equation in the preceding text · Lack of title and/or detailed caption on a figure or table · Unreasonable number of significant figures reported in Abstract/Conclusions · Decimal written without leading zero · Incomplete web site reference (site, date accessed, comments if appropriate) Writing · PROOFREAD YOUR WORK BEFORE YOU SUBMIT IT. · Don’t write in the first person. · Avoid starting sentences with prepositions, thereby being more direct and avoiding commas. · No figures, tables, equations, or footnotes in the abstract. · Introduce figures, tables, equation, etc., in the preceding text. · All figures need a title below, e.g. "Figure 1", and caption that explains the figure.  Make the caption summarize the relevance to somebody who has not read the report, i.e. it can stand alone. · Titles for figures, tables, equations, etc., should be capitalized in the text, e.q. “Equation 1”. · Don’t regurgitate/retype detailed information that is provided in a cited reference, e.g. a standard operating procedure (SOP). Provide sufficient details, but use a proper citation. · Spell names correctly. If unsure, find out. · Spell correctly and use the correct word: spellcheck may indicate a word is correctly spelled even if it is the wrong word. Some examples from previous years: “Miss counting”, “out liar”, “descent data”, “asses”, “ingrate”, “verse”. Calculations and Technical Stuff · Do not use unusual terms without introducing them first. · Abbreviations and acronyms need be defined either at first use, or in an appendix with reference. · Use good judgment in deciding how many significant figures to report, e.g. if you’re using a rotometer to measure flow, don’t report 5 significant figures. · Embrace terms like "prototype", "testbed" and "benchtop system".  For example, you might use a prototype gas absorption column to assess mass transfer properties, then "scale up" to an actual system design. Formatting · Never write a decimal without a leading zero to ensure it's not mistaken as an integer: 0.62, not .62. · Never start a sentence with a number, instead use “Thirty mL were delivered using a pipette.” · Always put a space between a number and its units.  It's easier to read and avoids alphanumeric confusion, e.g. If I write 6 liters as 6l, it sure looks like the number 61. · Indent titles and captions on tables and figures and consider using smaller font, e.g. 10 pt, to make them stand out from the surrounding text. Some even use italics. · Figures and tables should be centered on the page. · Use "Ca2+", "Na+", etc. to represent ions.  Elemental sodium (not ionic) would be "Na", and explosive when added to water! · One often sees "Enclosure" at the bottom of the page.  Is that not from the old days, when you "enclosed" something in the envelope?  · Many st ...

1. TECHNICAL WRITING GUIDELINES
CHE 334 (where appropriate), CHE 415, and CBEE 416
Unacceptable basic mistakes:
· Misspelled words
· Lack of introduction for a figure/table/equation in the
preceding text
· Lack of title and/or detailed caption on a figure or table
· Unreasonable number of significant figures reported in
Abstract/Conclusions
· Decimal written without leading zero
· Incomplete web site reference (site, date accessed, comments
if appropriate)
Writing
· PROOFREAD YOUR WORK BEFORE YOU SUBMIT IT.
· Don’t write in the first person.
· Avoid starting sentences with prepositions, thereby being
more direct and avoiding commas.
· No figures, tables, equations, or footnotes in the abstract.
· Introduce figures, tables, equation, etc., in the preceding text.
· All figures need a title below, e.g. "Figure 1", and caption that
explains the figure. Make the caption summarize the relevance

2. to somebody who has not read the report, i.e. it can stand alone.
· Titles for figures, tables, equations, etc., should be capitalized
in the text, e.q. “Equation 1”.
· Don’t regurgitate/retype detailed information that is provided
in a cited reference, e.g. a standard operating procedure (SOP).
Provide sufficient details, but use a proper citation.
· Spell names correctly. If unsure, find out.
· Spell correctly and use the correct word: spellcheck may
indicate a word is correctly spelled even if it is the wrong word.
Some examples from previous years: “Miss counting”, “out
liar”, “descent data”, “asses”, “ingrate”, “verse”.
Calculations and Technical Stuff
· Do not use unusual terms without introducing them first.
· Abbreviations and acronyms need be defined either at first
use, or in an appendix with reference.
· Use good judgment in deciding how many significant figures
to report, e.g. if you’re using a rotometer to measure flow, don’t
report 5 significant figures.
· Embrace terms like "prototype", "testbed" and "benchtop
system". For example, you might use a prototype gas
absorption column to assess mass transfer properties, then
"scale up" to an actual system design.
Formatting
· Never write a decimal without a leading zero to ensure it's not
mistaken as an integer: 0.62, not .62.
· Never start a sentence with a number, instead use “Thirty mL
were delivered using a pipette.”
· Always put a space between a number and its units. It's easier
to read and avoids alphanumeric confusion, e.g. If I write 6
liters as 6l, it sure looks like the number 61.

3. · Indent titles and captions on tables and figures and consider
using smaller font, e.g. 10 pt, to make them stand out from the
surrounding text. Some even use italics.
· Figures and tables should be centered on the page.
· Use "Ca2+", "Na+", etc. to represent ions. Elemental sodium
(not ionic) would be "Na", and explosive when added to water!
· One often sees "Enclosure" at the bottom of the page. Is that
not from the old days, when you "enclosed" something in the
envelope?
· Many struggle in Equation Editor without the ability to put in
spaces between numbers and units, etc. Try hitting Ctrl+space
bar to put in spaces, or convert the entire equation to text style,
which allows spaces.
· Italicize variables, e.g. tb. It makes them stand out better to
the reader. Do not italicize numbers.
Technical Report Guidelines
· Abstract
· Background
· Materials and Methods
· Results and Discussion
· Acknowledgements
· Appendices
Some guidance about what these sections look like:
· No Cover Page.
· Abstract is a high-level summary and includes (1) objectives,
(2) methods, and (3) results. The goal is 4-6 sentences.
Emphasize content: settings, ranges, numbers, units. No
references, equations, etc.
· Background should be shorter for CBEE 414 lab reports, with
brief theoretical background, then broaden as you move to more
open-ended labs and senior projects. Look for previous work on
the subject, e.g. have others measured that mass transfer

4. coefficient? How? What did they find? Use footnote
references liberally.
· Materials and Methods provides details about what you did. It
is written in past tense, a story of what was done, not in first
person, not as instructions, and not as bullets. The level of
detail should be sufficient to allow another worker to repeat
your work without having you physically there. Include
equipment, manufacturer, model, equipment
schematics/pictures.1 Cite provided documents/SOP.
· Results and Discussion is the section in which you present
data, calculations performed, error analysis performed, and
what you observe and conclude (trends, issues, etc.). It is
where you compare experimental results with theory (or
manufacturer-supplied) information. Most plots will be in this
section. If there is a design component to your lab, include it in
this section.
· Acknowledgements1are included to (1) thank those that helped
you setup equipment, explained equipment, etc., but also to (2)
provide a record of who helped you so that your readers might
use that information, e.g. Jill knows how to run the gas
chromatograph. Be succinct.
· Appendices1 are a location for supporting details. Sample
calculations are required and must include assumptions, unit,
etc., so the reader can follow and check your computations.
They can be hand-written if legible. A spreadsheet printout is
not enough. Other content might include copies of raw data,
equipment calibration data, non-critical charts, etc.
� Not necessary for CHE 334 reports.
Harding
2018
Oregon State University

5. Strong Foundations Engineering, Inc.
| T 541-737-4791 | http://cbee.oregonstate.edu |
SUBJECT:
Removal of CO2 from Air in a Packed Tower
A local landfill is planning to install a new packed tower to
process a 250 SCFM landfill gas stream that contains about
1.0% hydrogen sulfide. The hydrogen sulfide needs to be
scrubbed from the gas stream to allow its use in a solid-oxide
fuel cell. They are considering 0.05N aqueous NaOH as their
scrubbing solution and have requested our assistance to perform
empirical and predictive analyses using a 0.5% CO2 in air
mixture to model the proposed system. Your assignment is to
use the pilot-scale gas absorption unit in the Unit Operations
Laboratory to investigate the influence of solution and gas flow
rates on column performance and use that information to inform
a scale-up design. The packed tower has a 4-ft packed section
with ½-inch Raschig rings.
The pilot column has CO2 probes that measure the inlet and
outlet concentrations. Historically, they have had reliability
issues, so be sure to study the relevant documentation to
understand their operation. The SOP includes gas and liquid
rotometer calibrations. Planning, preparation, and
understanding theoretical underpinnings are critical.
Your team is asked to provide:
1. Theoretical and literature analysis to predict results when
using a NaOH scrubbing solution at the pilot scale, e.g. mass
transfer area, mass transfer coefficients, flux, etc. (be sure to
consider equilibrium conditions, e.g. y* and rate limiting
diffusion steps for the case of reaction in the liquid phase)
2. The dependence of the overall mass transfer coefficient for

6. CO2 on the liquid and gas superficial molar velocities
3. The dependence of outlet gas composition on the liquid and
gas superficial molar velocities
4. Limited investigation of the role of NaOH on resistance to
mass transfer, e.g. process performance using only water. We
suggest that you make one or two runs with water and compare
and briefly report on percent removal at the same liquid and gas
flowrates.
5. Proposed design parameters for a packed column capable of
treating the landfill gas stream described above using an NaOH
scrubbing solution, with predicted contaminant gas
concentrations at the outlet, and definition of the adequate
operational envelope to ensure safe operation of the column,
including a prediction of flooding point flow rates at extremes
of gas/solvent flows
CHE 415
School of CBEE
Oregon State University
CHE 415: Chemical Engineering Laboratory
Winter 2018
GAS ABSORPTION
Equipment Description
A packed tower for gas absorption experiments is located on the
east wall of Johnson 214. The tower is packed to a height of 4
feet with ½” Raschig rings and has an inner diameter of 4
inches. Pure carbon dioxide gas is supplied from a gas cylinder
and regulator. The carbon dioxide is mixed with utility air and
fed to the bottom of the column. NaOH solution is pumped to
the top of the tower from a Nalgene feed tank. Rotometers,
mounted on a control panel to the right of the tower measure

7. carbon dioxide, air, and liquid flow rates entering the column.
The valves for controlling each flow rate are located directly
below their respective rotometers. Calibration data for each
flowmeter are provided in Table 1. A manometer with taps at
the top and bottom of the column measures the pressure drop
across the column.
Two types of continuous-flow gas absorption experiments can
be performed with the packed tower. First, the gas flow rate is
kept constant while the liquid flow rate is varied. Second, the
liquid flow rate is kept constant while the gas flow rate is
varied. For both experiments, the gas mixture entering the
column is fixed at 0.5 mole % carbon dioxide.
Figure 1. Gas absorption pilot plant in JOHN 214. The 180 L
reservoir at left feed a pump that both recycles fluid back to the
tank and delivers it through a rotameter and to the 4 ft packed
section. Air (from house air) and CO2 (from the cylinder at
left) flow through rotameters, then combine and feed the column
bottom. CO2 sensor are positioned at both column feed and
outlet. A gas sample port is located on the inlet.
Equipment Operation
Note: Personal protective equipment is of paramount importance
in this lab. In addition to the lab minimum of protective
eyewear and a lab coat, you will wear an apron and face shield
during concentrated solution preparation (see below) and nitrile
gloves if operating or working around the batch reactor or PFR.
Be sure to identify roles so that the dry working lab space and
computer are not exposed to gloves of chemicals.
Your lab group will develop detailed procedures for operating
the equipment and acquiring the data. Therefore, you should
study the equipment carefully before performing any
experiments.

8. The sodium hydroxide scrubbing solution should be prepared at
the start of the lab session across from the fume hood in the
chem prep room (JOHN 210D). The feed reservoir volume is
180 liters. Determine in advance the mass of sodium hydroxide
pellets required, mass the pellets on the top-loading balance,
and then dissolve using the provide stir plate and 2 L beaker.
Make sure the pellets have completely dissolved, then transfer
the solution carefully to the provided Nalgene bottle(s). This
concentrate will be diluted in the feed reservoir.
CAUTION! Significant heat evolves when NaOH dissolves in
water! Start with cold water and continuously stir while slowly
adding pellets to the water to dissipate the heat of solution. The
resulting concentrated NaOH solution is also extremely caustic
– wear appropriate PPE (double gloves, goggles, face shield,
and lab coat) at all times when mixing and handling the
solution. Transport the solution in capped 1 L bottles.
Fill the feed reservoir approximately half-full with process
water and turn on the recirculation pump. Carefully pour the
concentrated sodium hydroxide solution into the tank while
continuing to fill the tank with water from hose (wear your PPE
and pour along the side of the tank to prevent splashing).
NOTE: Do not walk away from a reservoir as you fill it with a
hose. Fill the tank to 180 liters. Continue mixing the solution
using the pump and the column bypass line. Determine when
you think it’s sufficiently well-mixed. If desired, liquid
samples leaving the packed tower can be removed through the
sampling line at the bottom of the tower.
Figure 2. Chemical preparation area for concentrated NaOH
solutions. Be extra careful and communicative while working
in close quarters with others. Leave the workspace as you
found it, with stir plate, stir bar, graduated cylinders, etc.
IMPORTANT: Gas composition is assessed using Vernier
LabQuest® units with CO2 sensors. The power requirements of
the CO2 sensors allow only one CO2 probe per LabQuest®, so

9. two are provided. During column operation, water can collect
near the sensors, potentially damaging them or leading to
measurement error. Make sure that any time water is flowing
through the column, the gas is flowing as well. If you have
trouble with the CO2 probe readings:
1. Verify that all inlet gas plumbing is connected and leak free
2. Verify that there is not liquid near the inlet and outlet CO2
probes
3. Double-check your calcs for total flow and %CO2
4. Pull probe and check for 400 ppm
5. Contact instructor if problems persist
Shut Down
Turn off the carbon dioxide gas cylinder and bleed the pressure
in the carbon dioxide delivery line. Pump out the NaOH
solution to the drain using the bypass valve behind the panel.
Add fresh water to the feed tank until the tank is one-third full.
Pump water though the system to flush sodium hydroxide
solution from the pump, column packing, and tubing.
Appendix I. Rotameter Calibration
Do not attempt to calibrate the rotameters and assume the data
below is sound.
Table 1. Rotameter calibration data at 21 oC for the packed gas
absorption tower.
Flow (mL/s)
MeterAir**CO
2
*MeterWater
5976.21511.0
1019316.02017.2
1528626.42520.3

10. 2037636.73026.3
2546249.13532.3
407034037.4
508484540.0
7011015044.0
901303
*CO
2
measured at middle of the ball
**Air measured from bottom disc
Flow (mL/s)
Note:
The calibration data does not cover the full range of the
rotometers. Plot out this data before the first laboratory
session, fit flow rate vs. scale reading data for each rotometer to
determine the linear range of each. Decide on the range of gas
and liquid molar flowrates you expect to use in the pilot-scale
absorption tower before you begin the experiments.
� Performed by Dusty Berggren, March 2009
CHE 415: Chemical Engineering Laboratory
Winter 2018
GAS ABSORPTION
Equipment Description
A packed tower for gas absorption experiments is located on the
east wall of Johnson 214. The tower is packed to a height of 4

11. feet with ½” Raschig rings and has an inner diameter of 4
inches. Pure carbon dioxide gas is supplied from a gas cylinder
and regulator. The carbon dioxide is mixed with utility air and
fed to the bottom of the column. NaOH solution is pumped to
the top of the tower from a Nalgene feed tank. Rotometers,
mounted on a control panel to the right of the tower measure
carbon dioxide, air, and liquid flow rates entering the column.
The valves for controlling each flow rate are located directly
below their respective rotometers. Calibration data for each
flowmeter are provided in Table 1. A manometer with taps at
the top and bottom of the column measures the pressure drop
across the column.
Two types of continuous-flow gas absorption experiments can
be performed with the packed tower. First, the gas flow rate is
kept constant while the liquid flow rate is varied. Second, the
liquid flow rate is kept constant while the gas flow rate is
varied. For both experiments, the gas mixture entering the
column is fixed at 0.5 mole % carbon dioxide.
Figure 1. Gas absorption pilot plant in JOHN 214. The 180 L
reservoir at left feed a pump that both recycles fluid back to the
tank and delivers it through a rotameter and to the 4 ft packed
section. Air (from house air) and CO2 (from the cylinder at
left) flow through rotameters, then combine and feed the column
bottom. CO2 sensor are positioned at both column feed and
outlet. A gas sample port is located on the inlet.
Equipment Operation
Note: Personal protective equipment is of paramount importance
in this lab. In addition to the lab minimum of protective
eyewear and a lab coat, you will wear an apron and face shield
during concentrated solution preparation (see below) and nitrile
gloves if operating or working around the batch reactor or PFR.
Be sure to identify roles so that the dry working lab space and
computer are not exposed to gloves of chemicals.

12. Your lab group will develop detailed procedures for operating
the equipment and acquiring the data. Therefore, you should
study the equipment carefully before performing any
experiments.
The sodium hydroxide scrubbing solution should be prepared at
the start of the lab session across from the fume hood in the
chem prep room (JOHN 210D). The feed reservoir volume is
180 liters. Determine in advance the mass of sodium hydroxide
pellets required, mass the pellets on the top-loading balance,
and then dissolve using the provide stir plate and 2 L beaker.
Make sure the pellets have completely dissolved, then transfer
the solution carefully to the provided Nalgene bottle(s). This
concentrate will be diluted in the feed reservoir.
CAUTION! Significant heat evolves when NaOH dissolves in
water! Start with cold water and continuously stir while slowly
adding pellets to the water to dissipate the heat of solution. The
resulting concentrated NaOH solution is also extremely caustic
– wear appropriate PPE (double gloves, goggles, face shield,
and lab coat) at all times when mixing and handling the
solution. Transport the solution in capped 1 L bottles.
Fill the feed reservoir approximately half-full with process
water and turn on the recirculation pump. Carefully pour the
concentrated sodium hydroxide solution into the tank while
continuing to fill the tank with water from hose (wear your PPE
and pour along the side of the tank to prevent splashing).
NOTE: Do not walk away from a reservoir as you fill it with a
hose. Fill the tank to 180 liters. Continue mixing the solution
using the pump and the column bypass line. Determine when
you think it’s sufficiently well-mixed. If desired, liquid
samples leaving the packed tower can be removed through the
sampling line at the bottom of the tower.
Figure 2. Chemical preparation area for concentrated NaOH

13. solutions. Be extra careful and communicative while working
in close quarters with others. Leave the workspace as you
found it, with stir plate, stir bar, graduated cylinders, etc.
IMPORTANT: Gas composition is assessed using Vernier
LabQuest® units with CO2 sensors. The power requirements of
the CO2 sensors allow only one CO2 probe per LabQuest®, so
two are provided. During column operation, water can collect
near the sensors, potentially damaging them or leading to
measurement error. Make sure that any time water is flowing
through the column, the gas is flowing as well. If you have
trouble with the CO2 probe readings:
1. Verify that all inlet gas plumbing is connected and leak free
2. Verify that there is not liquid near the inlet and outlet CO2
probes
3. Double-check your calcs for total flow and %CO2
4. Pull probe and check for 400 ppm
5. Contact instructor if problems persist
Shut Down
Turn off the carbon dioxide gas cylinder and bleed the pressure
in the carbon dioxide delivery line. Pump out the NaOH
solution to the drain using the bypass valve behind the panel.
Add fresh water to the feed tank until the tank is one-third full.
Pump water though the system to flush sodium hydroxide
solution from the pump, column packing, and tubing.
Appendix I. Rotameter Calibration
Do not attempt to calibrate the rotameters and assume the data
below is sound.
Table 1. Rotameter calibration data at 21 oC for the packed gas
absorption tower.
Flow (mL/s)

14. MeterAir**CO
2
*MeterWater
5976.21511.0
1019316.02017.2
1528626.42520.3
2037636.73026.3
2546249.13532.3
407034037.4
508484540.0
7011015044.0
901303
*CO
2
measured at middle of the ball
**Air measured from bottom disc
Flow (mL/s)
Note:
The calibration data does not cover the full range of the
rotometers. Plot out this data before the first laboratory
session, fit flow rate vs. scale reading data for each rotometer to
determine the linear range of each. Decide on the range of gas
and liquid molar flowrates you expect to use in the pilot-scale
absorption tower before you begin the experiments.
� Performed by Dusty Berggren, March 2009
Abstract

15. The objective of this project is to analyze the removal of H2S
from a gas stream by a NaOH solution using a pilot-scale gas
absorption column separating CO2 from air using a 0.05N
aqueous NaOH solution. The pilot-scale gas absorption column
is packed with ½-inch Raschig rings to a height of 4 feet with a
5.5 inch diameter. The effects of inlet gas and liquid flow rates
on the gas absorption was investigated to find the parameters
that help scrub the highest amount of H2S from a landfill gas
stream. NaOH is used for the solution, as it is a strong base that
will react with CO2 and H2S irreversibly to produce a solid.
CO2 was used in place of H2S since they are similar in size,
and they react with NaOH in a similar manner, in addition to
CO2 being much safer. At a constant gas flow rate, Kya
increased with the increase of liquid flow rate. In addition, at a
constant liquid flow rate, Kya also increased with the increase
of gas flow rate. As the flow rate is increased, the trend of Kya
reaches equilibrium. Similarly, using H2O to absorb CO2 had
the same trend as the NaOH solution. However, the removed
CO2 concentration from H2O was less than NaOH solution. The
NaOH solution removed twice as much CO2 than H2O.
Background:
Many researches have been done on removing CO2 due to its
role in climate change[footnoteRef:1]. As CO2 is very similar
to H2S in terms of size and reaction to NaOH, it works as an
approximate substitute. In an experiment by Yazdanbaksh, et
al., an absorber column was used with 1.2 m of packing height
filled with 1 cm Raschig rings, and a column diameter of 10 cm,
was used to remove CO2 from industrial gas streams by an
NaOH solution[footnoteRef:2]. A counter-current flow rate
configuration was used, and the flux was calculated using the
equation: [1: "Overview of Greenhouse Gases." EPA.
Environmental Protection Agency, 20 Jan. 2017. Web. 01 Feb.
2017.] [2: Yazdanbakhsh, F., Soltani, A., and Hashemipour,
H.. "Investigating effects of gas flow rate and carbon dioxide

16. composition in chemical absorption of carbon dioxide in a
packed bed using sodium hydroxide." Proc. of 10th
International Conference on Environmental Science and
Technology, Kos island, Greece. N.p., n.d. Web. 22 Jan. 2017.]
(Eq. 1)
G is superficial molar velocity of gas, NCO2 is mass transfer
flux of CO2 – amount of CO2 transferred per area and time, Z is
a packed bed height, and a is the specific surface area of the
packing - the surface area of the packing per volume of packing.
From their research, they found out the liquid flow rate has no
effect on the concentration of CO2 at the outlet gas stream.
However, the gas flow rate affected the concentration of CO2.
As the gas flow rate increased the concentration of CO2 in the
outlet gas stream also increased.
In another experiment by Yaminah Jackson, recording data for a
COMSOL simulation of CO2
removal from air stream using water, using (Eq. 2) as a basis for
results.[footnoteRef:3] [3: Jackson, Yaminah Z. Modeling Gas
Absorption. Worcester Polytechnic Institute, 24 Apr. 2008.
Web. 24 Jan. 2017.]
(Eq. 2)
is the overall mass transfer coefficient based on the gas phase
driving force (mol/m3·hr), V is the average vapor molar flow
rate through the column, S is the cross-sectional area of the
column, and HOG is the height of a transfer unit.
According to the article by Yadolla and Hosseini, they used an
NaOH solution in order to remove the CO2 from
air.[footnoteRef:4] [4: Tavan, Yadollah, and Seyyed Hossein
Hosseini. "A novel rate of the reaction between NaOH with CO2

17. at low temperature in spray dryer." Petroleum (2016): n. pag.
Web. 3 Feb. 2017.]
CO2 (l) + 2NaOH (l) Na2CO3(s) + H2O (l) (Eq. 3)
From the equation 3, when CO2 reacts with NaOH, it makes
Na2CO3, which is a salt, and H2O. As it produces a salt in the
reaction, the y* value is 0. Furthermore, increasing the NaOH
concentration leads to a high CO2 removal efficiency.
Materials and Methods:
A 180 L tank was filled with a 0.05N aqueous NaOH solution.
The NaOH solution was created by combining 360 g of NaOH in
two liters of water as a concentration. The solution was
transferred to the tank where it was mixed thoroughly while
adding 178 L of water. The solution was pumped through the
packed bed column at a variety gas flow rates with constant
liquid flow rate and vice versa.
First, a gas (air and CO2) flow rate was chosen and was kept
constant while the liquid flow rate was varied. Measurements of
the entering and leaving gas concentrations were taken in CO2
ppm using LabQuest probes. The concentration measurements
were taken constantly and recorded when steady state was
reached. Steady state was considered reached when the
concentration had not changed in 20 seconds. Secondly, a liquid
flow rate was chosen and was kept constant, while varying the
gas flow rates. As before, CO2 concentration measurements
were taken using the probes when steady state was reached.
Steady state was reached in around 200 s. After measurements
were taken using the NaOH solution, the solution was drained
from the tank, and the column by flowing water through the
system. Measurements were taken using water as the liquid in
the column.

18. Results and Discussion:
The overall mass transfer coefficient, Kya was calculated using
equation (7) after rearranging equations (4-6). The detailed
calculations are in Appendix IV.
(Eq. 4)
(Eq. 5)
for very dilute systems (Eq. 6)
(Eq. 7)
where is the height of the column, HOG is the height of a
transfer unit, NOG is the number of transfer units, is the
average molar flow rate of the gas through the column, and S is
the cross-sectional area of the column.
NaOH reacts with CO2 irreversibly to produce Na2CO3, thus y*
is 0, which means CO2 is diluted.
For a constant gas flow rate, Kya increased as the NaOH
solution flow rate increased (Figure 1). At constant gas flow
rate of 6.2 mL/s, and a 26.3 mL/s liquid flow rate, which are the
smallest flow rates tested, Kya was found to be 23 mol/m3s. At
60 mL/s liquid flow rate, which is the highest flow rate tested,
Kya was found to be25 mol/m3s. The slope between 26.3 mL/s
and 44 mL/s is 0.072 mol/m3-mL, and the slope between 44
mL/s and 60 mL/s is 0.042 mol/m3-mL. The slope decreases
with increasing liquid flow rate. If there is more liquid flow
rate, there is more NaOH, thus there is more chance to transfer
CO2 concentration from gas to liquid in the column. If there is
more CO2 coming from the gas, then Kya increases more.
However, when there is more CO2 than NaOH can hold, then
Kya will reach equilibrium.
Figure 1: Kya of CO2 removal from air using a 0.05N aqueous
NaOH solution at different flow rates with constant gas flow
rate at 6.2mL/s.

19. For a constant liquid flow rate, Kya increased as the gas flow
rate increased (Figure 2). At 26.3 mL/s liquid flow rate, Kya
increased by 19 mol/m3s when the gas flow rate was increased
from 1.3 mL/s to 6.2 mL/s. When the liquid flow rate was
constant at 60 mL/s, Kya increased by 19 mol/m3s when the gas
flow rate was increased from 1.3 mL/s to 6.2 mL/s. The
increased value of Kya is similar, which is 19 mol/m3s even
though constant liquid was increased from 26.3 mL/s to 60
mL/s. When there is more gas flow rate, there is more chance to
transfer CO2 concentration from gas to liquid. However, if there
are no more spaces for the CO2 concentration transfer, then Kya
will reach equilibrium.
Figure 2: Kya of CO2 removal from air using a 0.05N aqueous
NaOH solution when holding the liquid flow rate constant while
varying the gas flow rate.
At the smaller gas flow rates, there is less Kya change (Figure
3). At 1.3mL/s of constant gas flow rate, the difference of Kya
with varied liquid flow rate was 1.27 x10-2 mol/m3s. However,
at 6.2 mL/s of constant gas flow rate, the difference was 2.08
mol/m3s. Therefore, the gas flow rate is more effective to
remove CO2 compared to liquid flow rates.
Figure 3: Kya of CO2 removal from air using an NaOH solution
at different liquid flow rates with constant gas flow rate.
The H2O solution had a similar trend as the NaOH solution at
constant gas flow rates (Figure 4, Appendix II). At constant gas
flow rate, Kya increased with the liquid flow rate. The trend of
Kya was same at constant liquid flow rates (Figure 5, Appendix
II). However, the value of Kya was less than the NaOH solution
value. At the same liquid flow rate of 60 mL/s and a gas flow
rate of 6.2 mL/s, the NaOH solution had a Kya value of 26
mol/m3s, while H2O had 17.8 mol/m3s. This means that there

20. was less transfer of concentration CO2 in H2O liquid compared
to NaOH solution. In addition, the NaOH solution removed
twice as much CO2 from air than the H2O solution (Figure 6,
Appendix II).
When 10000 ppm of CO2 gas inlet was used, Kya almost
doubled in comparison to 5000 ppm inlet (Figure 7, Appendix
II)
To calculate the flooding velocity, Eq (8) was used.
From this equation, the flooding velocity was found to be
0.0184 m/s. The detailed sample calculation is in Appendix V.
Appendix I.
PFD
Appendix II.
Figure 4: Kya of CO2 removal from air using water at different
liquid flow rates with constant gas flow rates.

21. Figure 5: Kya of CO2 removal from air using water at different
liquid flow rates with a constant gas flow rate of 1.3 mL/s
Figure 6: Comparison of the CO2 concentration at the gas outlet
for the NaOH solution and water
Figure 7: Kya of CO2 removal using a concentration of 10000
ppm as desired for H2S removal concentration, compared to a
concentration of 5000 ppm.
Appendix III.
Table 1 Raw data for the gas flow rate held constant (at two
different rates) with varying NaOH solution flow rates.
Includes the resulting CO2 concentrations in ppm, height of the
column and cross-sectional area of column.
L (mL/s)
CO2 (mL/s)
air (mL/s)
CO2 out (ppm)
CO2 in (ppm)
Z (m)
S (m2 )
26.3
6.2
1233.8
1590
5000
1.2
0.008
44.0
6.2

22. 1233.8
1370
5000
1.2
0.008
60.0
6.2
1233.8
1300
5000
1.2
0.008
26.3
6.2
1233.8
1580
5000
1.2
0.008
37.4
6.2
1233.8
1500
5000
1.2
0.008
44.0
6.2
1233.8
1400
5000
1.2
0.008
60.0
6.2
1233.8

23. 1300
5000
1.2
0.008
60.0
1.3
258.7
15
5000
1.2
0.008
60.0
6.2
1233.8
998
4953
1.2
0.008
60.0
6.2
1233.8
992
4904
1.2
0.008
26.3
1.3
258.7
6

24. 5000
1.2
0.008
26.3
6.2
1233.8
1280
4940
1.2
0.008
26.3
6.2
1233.8
1282
4928
1.2
0.008
44.0
6.2
1233.8
1087
4941
1.2
0.008
44.0
1.3
258.7
6
5000
1.2
0.008
44.0
6.2
1233.8
1074
4960

25. 1.2
0.008
Table 2 Kya results from the measured data of liquid flow rate,
CO2 flow rate, air flow rate and molar fraction change for CO2
in aqueous NaOH solution.
L (mL/s)
CO2 (mL/s)
air (mL/s)
yin - yout
Kya (mol/m3·s)
26.3
6.2
1233.8
0.00224
22.94
44.0
6.2
1233.8
0.00238
24.42
60.0
6.2
1233.8
0.00243
24.89
26.3
6.2
1233.8
0.00224
23.00
37.4
6.2
1233.8
0.00230
23.54

26. 44.0
6.2
1233.8
0.00236
24.22
60.0
6.2
1233.8
0.00243
24.89
60.0
1.3
258.7
0.00327
7.03
60.0
6.2
1233.8
0.00260
26.61
60.0
6.2
1233.8
0.00257
26.32
26.3
1.3
258.7
0.00328
7.05
26.3

27. 6.2
1233.8
0.00240
24.62
26.3
6.2
1233.8
0.00239
24.53
44.0
6.2
1233.8
0.00253
25.93
44.0
1.3
258.7
0.00328
7.05
44.0
6.2
1233.8
0.00255
26.14
Table 3 Raw data for the gas flow rate held constant (at two
different rates) with varying water flow rates. Includes the
resulting CO2 concentrations in ppm, height of the column and
cross-sectional area of column.
L (mL/s)
CO2 (mL/s)
air (mL/s)
CO2 out (ppm)
CO2 in (ppm)
Z (m)
S (m2)

28. 26.3
6.2
1233.8
2537
4983
1.22
0.008
44.0
6.2
1233.8
2380
4959
1.22
0.008
60.0
6.2
1233.8
2338
4983
1.22
0.008
26.3
1.3
258.7
2340
5032
1.22
0.008
44.0
1.3
258.7
2210
5026
1.22
0.008
60.0

29. 1.3
258.7
2134
5026
1.22
0.008
26.3
1.3
258.7
2390
5038
1.22
0.008
44.0
1.3
258.7
2231
5026
1.22
0.008
60.0
1.3
258.7
2137
5026
1.22
0.008
Table 4 Kya results from the measured data of liquid flow rate,
CO2 flow rate, air flow rate and molar fraction change for CO2
in water.
L (mL/s)
G (mL/s)
A (mL/s)
yin-yout
Kya (mol/m3· s)

30. 26.3
6.2
1233.8
0.00160
16.45
44.0
6.2
1233.8
0.00169
17.34
60.0
6.2
1233.8
0.00173
17.79
26.3
1.3
258.7
0.00177
3.80
44.0
1.3
258.7
0.00185
3.97
60.0
1.3
258.7
0.00190
4.08
26.3
1.3
258.7
0.00174
3.73
44.0

31. 1.3
258.7
0.00183
3.94
60.0
1.3
258.7
0.00190
4.07
Appendix IV.
Converting ppm to mole fractions:
NOG was found from the change in mole fraction between the
top and bottom of the column:
Finding the molar flow rates of the vapor, CO2 + air:
For the incoming stream:
Calculating overall mass transfer coefficient:

32. Appendix V.
Flooding velocity
The superficial gas velocity at flood is correlated by
= superficial gas velocity at flood, m/s
= total surface area packing, bed
= fractional voids in dry packing
g = gravitational constant, 9.8067
= liquid and has densities,
L/ G = liquid and gas flow ratio
= liquid viscosity, mPa*s (or cP)
= 1.225 kg/m3, = 1.98 kg/m3.There is 0.05% of CO2 is in the
mixed air, so the density can be assumed as air. Therefore, the
density of gas is 1.225kg/m3.
The density of liquid can be assumed as water density because
in aqueous NaOH solution, there is 0.2% of NaOH and 99.8% of
water. Therefore, the density of liquid is 1 kg/m3.
In trial 1, the liquid volumetric flow rate was 26.3mL/s and the
gas volumetric flow rate was 103.2 mL/s.
From the generalized correlation of flood points, packed
columns graph[footnoteRef:5], the x-axis is 0.282, therefore the
y-axis is 0.06. [5: Generalized correlation of flood points,
packed columns, Sherwood et al., Ind. Eng. Chem. 30, 768
(1938).]
From the characteristics of dumped tower packing chart, = 370,
= 0.64. The density of has is calculated in Eq. 6. = 1.225kg/m3,
g = 9.8067m/s, = 1kg/m3, and =1cP.

33. = 3.403 x 10-4 m2/s2
= 0.0184 m/s
Gas 6.2mL/s 26.3 44.0 60.0 16.44723466160312
17.34285121757167 17.78650305955781 Gas-1 1.3mL/s
26.3 44.0 60.0 3.795511958310095 3.970535838768211
4.077797265394337 Gas-2 1.3mL/s 26.3 44.0 60.0
3.733391817376836 3.940898760780612
4.073563159807454
H2O flowrate (mL/s)
Kya (mol/m3·s)
Trial 1 26.3 44.0 60.0 3.7955119583101
3.970535838768209 4.077797265394341 Trial 2 26.3
44.0 60.0 3.73339181737684 3.940898760780611
4.07356315980745
Liquid flowrate (mL/s)
Kya (mol/m3·s)
H2O 2537.0 2380.0 2338.0 26.3 44.0 60.0 NAOH
998.0 1282.0 1074.0 60.0 26.3 44.0
Concentration of CO2 in outlet (ppm)
Liquid flowrate (mL/s)
10000 ppm model 30.0 50.0 70.0 0.0281211215530425
0.028829813515346 0.0290998429631448 5000 ppm
model 30.0 50.0 70.0 0.0114808947401888
0.0122233681595977 0.0124596548178303
NaOH flow rate (mL/s)
Kya (mol/m3·s)
Trial 1 26.3 44.0 60.0 22.93607092378319
24.41758796794011 24.88902487041074 Trial 2 26.3
37.4 44.0 60.0 23.00340794132821 23.54212007899421
24.215550249345 24.88902487041074 Trial 3 30.0

34. 50.0 70.0 0.00704679667033133 0.00704679667033133
0.00703407630039255 Trial 4 30.0 50.0 70.0
0.0246215717661307 0.0259282738709048
0.0266082305416003 Trial 5 30.0 50.0 70.0
0.0245276646452005 0.0261431807186952
0.0263202599197678
Liquid flow rate (mL/s)
Kya (mol/m3 · s)
Liquid 60 mL/s1.3 6.2 6.2 7.03407630039255
26.6082305416003 26.3202599197678 Liquid 26.3 mL/s
1.3 6.2 6.2 7.04679667033133 24.6215717661307
24.5276646452005 Liquid 44 mL/s6.2 1.3 6.2
25.92827387090472 7.04679667033133
26.1431807186952
Gas flowrate (mL/s)
Kya (mol/m3 ·s)
Gas 1.3mL/s 60.0 26.3 44.0 7.03407630039255
7.04679667033133 7.04679667033133 Gas 6.2mL/s
60.0 60.0 26.3 26.3 44.0 44.0 26.6082305416003
26.3202599197678 24.6215717661307
24.5276646452005 25.92827387090472
26.1431807186952
Liquid flowrate (mL/s)
Kya (mol/m3 ·s)