Lab Reports

1
Lab Reports

• Rectifying Common Mistakes

2
Sections (Revised)

• Title Page (separate page)
• Abstract
• Background and Theory
• Materials and Methods
• Results and Discussion
• Conclusion
• Literature Cited (References)
• Appendix Sample Calculations

3
Title Page

• Title of lab
• Name
• Names of partners
• Date(s) performed
• Date submitted

4
Abstract

• Write the purpose of the experiment
• What effects and conclusions you observed
• Include some numerical data that you found (the
  variables that you observed)
• Note I always write the abstract LAST

5

• The purpose of this experiment is to
  observe pressure drops and determine flooding
  points of a packed column using various
  combinations of water and air flow rates. The
  effect of packing properties and liquid and gas
  velocities on the magnitude of the pressure drop
  in the column is investigated. For dry air runs,
  the experimental pressure drop across the column
  is compared to a theoretical value calculated by
  the Ergun equation. This equation depends on two
  packing characteristics fractional void volume
  and specific surface area, found to be 0.898 and
  240 ft-1, respectively. For liquid and gas
  counterflow runs, visual flooding points are
  observed and compared to a theoretical flooding
  line calculated by Wankats equation. The
  flooding line accounts for the packing
  characteristics by the packing factor, which is
  found to be 986. The pressure drop increases with
  high gas velocities, low fractional void volumes,
  and high packing factors.

6
Background and Theory

• Give background on the chemistry involved in the
  experiment
• Explain the topic. Give any definitions.
• Give chemical reactions and explain them
• Write equations used and explain them
• What are the chemicals used? What are their uses?
  Any distinctive properties?
• Any unique pieces of equipment used? Why? How do
  they work?
• Any applications in industry or everyday life?
• Do NOT give procedure here.

7
Background and Theory

• Pictures/Diagrams can and should be entered into
  background and theory
• Structural formulas of compounds used
• Pictures of actual samples of the compounds
• Pictures of equipment used
• Pictures of technology that use the theory
• Pictures should be pasted below the paragraph
  where they are mentioned (every picture should be
  mentioned).
• Pictures should be centered (one per line) with a
  title under or above the picture

Methylene chloride
8

• This experiment involves the use of a
  packed tower, which is a vertical column filled
  with selected packing material. A liquid stream
  is fed to the top of the column, where it is
  evenly distributed over the packing material by
  nozzles or distributor plates. A gas stream is
  fed to the bottom of the column and travels
  upward, where it meets the downward-flowing
  liquid, as illustrated in Figure 1. The gas runs
  in the void space between pieces of packing while
  the liquid flows over the packing surface 1.
  Hence, the packing in the tower provides a
  surface for vapor-liquid contact.

FIGURE 1 General Schematic of a Packed Tower 2
9
Background and TheoryEntering Equations

• Dont write equations in the body of a paragraph
• Each equation gets its own line and its own
  number
• Use an equation editor or write them in
• They should most likely be entered in background
  and theory
• Specify what each symbol means and its units
• Through measuring the mass and volume of the
  metals, the density can be experimentally
  determined
• (1)
• Where d density, g/mL v volume, mL
• m mass, g

10

• The pressure drop of a single-phase
  fluid flowing through a packed column can be
  calculated by the Ergun equation
• (1)
•  
• Where ?P Pressure drop across the
  column, lbf / ft2
• Z Packed bed height, ft
• µg Absolute fluid (air)
  viscosity, lb/ft-s
• e Fractional void volume,
  dimensionless
• gc Newtons law
  proportionality factor, 32.174 ft-lbm / lbm-s2
• ?g fluid (air) density
  lbm/ft3
• fsDp Effective particle
  diameter for the packing, ft
• vo Superficial air
  volumetric velocity, ft/s
• This equation can be used to determine
  the expected pressure drop per unit height of
  packing for the dry air run. The first term on
  the right hand side of the equation accounts for
  viscous losses in laminar flow, while the second
  term accounts for kinetic losses in turbulent
  flow. Therefore, the flooding curves in Figure 3
  should be curved lines with a slope approaching
  1.0 for laminar flow and a slope approaching 2.0
  for turbulent flow.

11
Materials and Methods

• If you were to create your own procedure, you
  would write your step-by-step recipe-type
  procedure
• Be specific about what equipment is used
• Ex 10 mL graduated cylinder
• Look at the procedures of other labs to see the
  level of detail needed

12
Materials and Methods

• When given the procedure, describe any changes
  from the procedure

Some changes made to the experiment include
changing the solvents used for the separation of
carotenoids in the annatto extract. The solvents
used in the experiment were methylene chloride,
acetone, 1 ethanol in methylene chloride, 2
ethanol in methylene chloride, and 4 ethanol in
methylene chloride. In addition, less than 15
fractions were collected, and the column was
stopped running after the orange bixin had
eluted. Finally, the weight of the bixin isolated
was not measured in the lab. No other deviations
from procedure were undertaken.
13
Results and Discussion

• This is where you will tabulate or graph your
  data and FULLY DISCUSS it
• The WHY (in terms of chemistry)
• Interpret your results. What do they mean? Do
  they make sense? Whats the chemistry reason for
  it?
• Compare your results to literature values.
• Include percent error/ percent discrepancy.
  Explain possible reasons for error.
• Include yield if possible
• Explain ways to eliminate error in the future or
  things you could have done differently.
• The answers to all prelab/postlab questions
  should be found here in paragraph form

14
Tables and Figures

• Give a bold title and number either above or
  below the table/figure
• Include units and symbols

TABLE 1. Physical Properties for PRO-PAK
Protruded Packing
Physical Properties Values Calculated from Data Values Found in Literature 6
Bulk Density, ?B lbm/ft3 16.2 21.0
Fractional Void Volume, e 0.898 0.96
Specific Surface Area, aP ft2/ft3 240 372
Packing Factor, Fp 331 420
15
Tables and Figures

• Place the table or figure centered below the
  first paragraph that you discuss it
• After showing the table or figure, you may
  continue to discuss it in following paragraphs.
• Always keep a chart together on one page

16

• The physical properties for the
  protruded PRO-PAK packing used in the column is
  shown in Table 1. The second column of the table
  lists the values that were calculated from
  measurements taken during the lab. The third
  column shows values for the same physical
  properties that are found in literature. The
  calculated bulk density of 16.2 lbm/ft3 is 22.8
  less than the expected value of 21.0 lbm/ft3.
  This discrepancy may be due to human error when
  measuring the total volume occupied by the
  packing. Another reason may be that since the
  packing is randomly dumped into the column, the
  bulk density can vary each time according to the
  random arrangement into which the packing falls.
  In a large column, the arrangement of packing has
  a negligible effect on the calculated value.
  However, with a smaller control volume such as
  the graduated cylinder, the arrangement will have
  a greater effect on the calculation and can
  foster greater deviation from the expected value.
  The calculated void fraction of 0.898 is only
  6.5 less than the expected value of 0.96, and
  its discrepancy may be due to the same reasons as
  the bulk density.

TABLE 1. Physical Properties for PRO-PAK
Protruded Packing
Physical Properties Values Calculated from Data Values Found in Literature 6
Bulk Density, ?B lbm/ft3 16.2 21.0
Fractional Void Volume, e 0.898 0.96
Specific Surface Area, aP ft2/ft3 240 372
Packing Factor, Fp 331 420
17
Literature Cited

• P.C. Wankat, Equilibrium Staged Separations,
  Elsevier Science
• Publishing Co., New York, NY, 1988, Chapter 13
• W.L. McCabe, J.C. Smith, and P. Harriott, Unit
  Operations of Chemical Engineering, 7th ed.,
  McGraw-Hill, New York, 2005, Chapter 7, Chapter
  18
• C.J. King, Separation Processes, Chemical
  Engineering Series, 2nd ed., McGraw Hill, New
  York, 1980, Chapter 4
• Fractional Distillation, Wikipedia, 2006, lt
  http//en.wikipedia.org/wiki/
• Fractional_distillationgt
• P.A. Schweitzer, Handbook of Separation
  Techniques for Chemical Engineers, 2nd edition,
  McGraw Hill, NewYork, 1988, Section 1.7
• PRO-PACK Protruded Metal Packing, Bulletin No.
  23, Scientific Development Co., State College,
  PA.

18
How to use your references

• The packed column is an apparatus that is
  commonly utilized in gas absorption, an operation
  in which one or more components of a gas stream
  are removed or absorbed by a liquid solvent.
  There are several industrial applications of
  packed columns for the purpose of gas absorption.
  One such application is the removal of CO2 and
  H2S from natural gas or synthesis gas by
  absorption in solutions of amines or alkaline
  salts 2. Another application includes the
  washing of ammonia from a mixture of ammonia and
  air by means of liquid water 2.

19
Sample Calculations

• In this section, you are to show all calculations
  (except error) done in the experiment.
• If there are several trials, you only have to
  show your work for one trial
• Explain what you are doing.
• Show the formula, then numbers plugged into the
  formula, and then your final answer.
• Carry correct units throughout the calculation
• Define any variables

20
Sample Calculations
Convert Inlet Temperature and Pressure to
Absolute English Units For the experimental data,
inlet temperature must be converted from F to
R, and inlet pressure must be converted from
psig to psia. These values are to be used in
subsequent equations. Using data from Run 6,
where Po 55 psig and To 73 F Po psia
Po psig 14.7 lb/in2 (2.1) Po 55
psig 14.7 lb/in2 69.7 psia To R
To F 460 (2.2) To
73 F 460 533 R
21

• Calculate the Air Density, ?g.
• The air density any at any point in the column
  for a given run, i, can be found by the ideal gas
  law
• (2.11)
• Where Ti Temperature in R at point
  for given run
• Pi Pressure in lbf/ft2 Pressure in lbf/in2
  
• multiplied by 144
  in2/ft2
• R Universal Gas constant in English Units
  1545.4 ft-lbf / lbmol-R
• Mair Molecular Weight of Air 29.0
  lbm / lbmol
• Take Dry Air Run 6 data and calculate the air
  density at the top of the column
• 0.0745 lbm/ft3

22
NOTE

•