TABLE OF CONTENTS

NO CONTENTS PAGE

1 Abstract

2 Introduction

3 Literature Review

4 Experiment Objective

5 Methodology

6 Results

7 Discussions

8 Conclusion & Recommendations

9 References

10 Appendices

ABSTRACT

Abstract contains references to all major aspects of laboratory report i.e. main purpose of the experiment, its importance, methodology/ approach, most significant results or findings, main conclusions and/or recommendation.

Gas absorption-adsorption experiment was conducted to demonstrate the basic principles of the

absorption and adsorption processes. The gas and liquid normally flow counter currently among some

packing which serve to provide the contacting of interfacial surface through which mass transfer take

place. Meanwhile, adsorptions involve the binding of molecules from their liquid or gaseous

environment onto the surface of solids. It is a separation process for the selective removal small

quantities of components from a fluid mixture or solution.

There are two objectives that should be achieved by students at the end of the experiment which

are to absorp and adsorp gas through a packed column in a batch process, which we have to absorp

Carbon Dioxide, CO2 into water and to adsorp of CO2 into activated carbon and to observe the effect of

liquid flow rate on the absorption-adsorption process.

Two packed columns filled with ceramic berl saddles mixed with activated carbon granules are

provided for absorption-adsorption experiments. Each column are to be run individually. Air and

carbon dioxide (CO2) are fed into the bottom of a packed column. Water is transferred to the top of the

column either from feed vessel B1 using a centrifugal pump P1, or entered directly from the laboratory

supply. Counter current flow among the carbon bed will cause the transfer of CO 2 from the air mixture

into the water and subsequently onto the activated carbon. The lean air mixture will exit at the top

whereas the spent water will accumulate at the bottom of the column and overflow out into either the

feed vessel B1 or receiving vessel B2. Some CO2 will present in the water can be stripped or desorbed in

the feed vessel B1. The spent water is heated in feed vessel B1 to decrease the solubility of CO2 in

water. Circulation of the hot liquid around the feed vessel through pump P1 will release the dissolved

CO2 into vent. To remove adsorbed CO2 from the activated carbon, hot air can be passed through the

column while the vacuum pump is in switched on.

Result n discussion

Conclusion recommendation

INTRODUCTION

Introduction is complete and well written; provides all necessary background principles and theory for the experiment. Present a concise lead-in to the laboratory experiment.

LITERATURE REVIEW

Gas absorption (also known as scrubbing) is an operation in which a gas mixture is

contacted with a liquid for the purpose of preferentially dissolving one or more components of

the gas mixture and to provide a solution of them in the liquid. Therefore we can see that there is

a mass transfer of the component of the gas from the gas phase to the liquid phase. The solute so

transferred is said to be absorbed by the liquid. In gas desorption (or stripping), the mass transfer

is in the opposite direction, i.e. from the liquid phase to the gas phase. The principles for both

systems are the same. (http://www.separationprocesses.com)

There are 2 types of absorption processes: physical absorption and chemical absorption,

depending on whether there is any chemical reaction between the solute and the solvent

(absorbent). When water and hydrocarbon oils are used as absorbents, no significant chemical

reactions occur between the absorbent and the solute, and the process is commonly referred to

as physical absorption. When aqueous sodium hydroxide (a strong base) is used as the absorbent

to dissolve an acid gas, absorption is accompanied by a rapid and irreversible neutralization

reaction in the liquid phase and the process is referred to as chemical absorption or reactive

absorption. (http://www.separationprocesses.com)

When a gas or vapor is brought into contact with a solid, part of it is taken up by the

solid. The molecules that disappear from the gas either enter the inside of the solid, or remain on

the outside attached to the surface. The former phenomenon is termed absorption (or dissolution)

and the latter adsorption. When the phenomena occur simultaneously, the process is

termed sorption. The solid that takes up the gas is called the adsorbent, and the gas or vapor

taken up on the surface is called the adsorbate. It is not always easy to tell whether the gas is

inside the solid or merely at the surface because most practical' absorbents are very porous

bodies with large internal' surfaces. It is not possible to determine the surface areas of such

materials by optical or electron microscopy because of the size and complexity of the pores and

channels of the material. The gas adsorption itself, however, can be used to determine the

accesible surface area of most absorbents. (http://www.chem.ufl.edu)

Activated carbon is a highly porous, amorphous solid consisting of microcrystallites with

a graphite lattice, usually prepared in small pellets or a powder. It is non-polar and cheap. One of

its main drawbacks is that it is combustible. Activated carbon can be manufactured from

carbonaceous material, including coal (bituminous, subbituminous, and lignite), peat, wood, or

nutshells (e.g., coconut). The carbonized particles are "activated" by exposing them to an

oxidizing agent, usually steam or carbon dioxide at high temperature. This agent burns off the

pore blocking structures created during the carbonization phase and so, they develop a porous,

three-dimensional graphite lattice structure. The size of the pores developed during activation is

a function of the time that they spend in this stage. Longer exposure times result in larger pore

sizes. (http://en.wikipedia.org, Activated carbon)

EXPERIMENT OBJECTIVES

The objectives of this experiments were to absorp and adsorp gas through a packed

column in a batch process (absorption of CO2 into water and adsorption of CO2 into activated

carbon) and to observe the effect of liquid flow rate on the absorption-adsorption process.

METHODOLOGY

Materials and methodology are complete and adequately detailed. Logical and easily followed. Description of procedure is complete, ensuring that it can be replicated.

RESULTS

Results I:

1. Setting Parameter

Parameter Setting 1 Setting 2

Air flowrate, m3/hr 2.0

CO2 flow rate, m3/hr 100

Water flowrate, L/hr 50

2. Result Table

Time (min)

Volume NaOH (titration), mL

Mol CO2 CO2 Composition, vol %

Inlet Outlet Inlet Outlet Inlet Outlet

0 0 0

5 1.2 2.4

10 1.2 2.5

15 1.4 2.6

20 1.6 2.8

25 2.0 2.8

30 2.0 3.0

Results II

1. Setting Parameter

Parameter Setting 1 Setting 2

Air flowrate, m3/hr 2.0

CO2 flow rate, m3/hr 100

Water flowrate, L/hr 130

2. Result Table

Time (min)

Volume NaOH (titration), mL

Mol CO2

CO2 Composition,

vol%

Inlet Outlet Inlet Outlet Inlet Outlet

0 0 0

5 2.4 3.8

10 2.0 3.4

15 2.0 3.2

20 2.0 3.8

25 2.0 4.0

30 2.0 4.0

Calculations:

CO2 (g) + H2O (l) → H+ (aq) + HCO3- (aq) ……..Equation 1

H+ (aq) + HCO3- (aq) + NaOH → NaHCO3 (aq) + H2O (l) ……. Equation 2

From equation 2, we assume that the amount of NaOH needed is equal to the amount of CO2

dissolved in the water. Calculating the number of mol and composition of CO2 in water for inlet

and outlet stream, we get:

M1.V1 = M2.V2 ……. Equation 3

Where,

M1 = Molar of CO2 (mol/L)

V1 = Volume of sample (L) = 0.01 L

M2 = Molar of NaOH (mol/L) = 0.05 mol/L

V2 = Volume of NaOH (L)

Substituting the value into equation 3 gives:

0.01 M1 = 0.05 V2 …….. Equation 4

Using the inlet and outlet value of NaOH recorded in tables, we can calculate the number of mol

of CO2.

To calculate the CO2 composition,

Vol% = [ (volume of solute (CO2) / volume of solution (sample) ] × 100%

DISCUSSIONS

At 50L/hr of water flow rate flowed into the gas absorption-adsorption unit, the CO2

composition was low, about volume%. When the flow rate increased, the CO2

composition increased to larger value which was At different setting parameters which

the flow rate of water flow into the gas absorption-adsorption unit increased from 50 L/hr to

130L/hr, the composition of Carbon Dioxide at the outlet water flow increased over time.

Gas absorption unit installation to prevent chlorine emission is one of the applications

that applied these concepts in petrochemical industry nowadays.

Description

The purpose of the chlorine destruction unit is to avoid large emissions of chlorine gas to the

environment during irregular plant operation and/or emergencies, and to take care of all chlorine-

containing waste gases during normal operation. The most common way to destroy the chlorine

is to absorb it in weak caustic soda to produce sodium hypochlorite. The absorption system can

make use of packed towers or venturi ejectors. However, packed columns, even though more

complex, are better in case of emergency if electricity supply fails. They can continue to absorb

chlorine from a pressure relief system using caustic soda stored in a gravity-fed head tank. The

concentration of caustic soda should not exceed 22% NaOH because of the risk of salt

deposition, causing blockages in the absorption plant, and freezing.

The design of an absorption system requires clear specifications of:

the maximum quantity of chlorine

the composition of the gas stream

the maximum instantaneous flow

It is very important to ensure that in case of a major accident, a massive release of chlorine could

be absorbed. The size of the unit is of great importance and should be calculated to cope with

emergency conditions. Caustic soda supply and the storage capacity for caustic soda and

hypochlorite solution should be correctly sized as well. It is essential that faults are detected

quickly and adequate instrumentation with alarms should be applied at the vent absorption plant

to ensure that warning is given if equipment fails. In particular, temperature control of the

absorption solution is essential, as is measurement to prevent over-chlorination. The emergency

power supply should be tested periodically.

If the sodium hypochlorite cannot be sold, it has to be treated before it is discharged. Several

technologies are available to destroy sodium hypochlorite without generating significant cross-

media effects, in particular catalytic processes.

 Main achieved emission levels

Absorption units are generally designed to limit the chlorine content to below 5-10 mg/m3 in the

emitted gas in the worst case scenario. Under normal operation the concentration of chlorine is

less than 1-3 mg/m3 in the case of partial liquefaction and less than 3-6 mg/m3 in the case of total

liquefaction.

 Cross-media effects

When the sodium hypochlorite (bleach) produced can be sold, no cross-media effects occur,

although it should be noted that the consumer might discharge free oxidants from the bleach.

When there is no demand for bleach, the bleach has to be destroyed before it can be discharged.

The effluent from the bleach destruction may have an adverse effect on the recipient water,

depending on the technology used.

(References: [Dutch report, 1998], [Gest 76/52, 1986], [Gest 87/130, 1996], [Gest 92/169, 1994],

[Le Chlore, 1996], [Schubert], [Wunderlich])

The second application is the extraction of impurities on valuable chemicals by Novasep.

Novasep has been supplying the food and bio-industries with adsorption units for many years.

Adsorption is a key process for the extraction of impurities on valuable chemicals. The

adsorbents can be from various origins (synthetic polymers or carbonaceous material). Novasep

has solid experience in adsorption processes and supplies the food and bio-

industrieswith adsorption units for applications such as:  decolorization of cane sugar juices;

polishing units of liquid sugar, sweeteners and polyols; recovery of plant extracts and colorants;

as well as recovery of antibiotics.

Adsorption Mechanism

There are several mechanisms which cause adsorption: we can list Van der Waals forces, steric

interaction, hydrogen bonds, hydrophobicity and polarity. Since the solution to be treated

contains a mixture of organics with different properties, the adsorption process is a combination

of these mechanisms. Color removal with ion exchange resins is also a combination of ion

exchange and adsorption. In fact, the main mechanism is adsorption rather ion exchange.

Regeneration of Adsorbents

There are two recognized methods for the reactivation of GAC:  volatilization of adsorbed

contaminants with steam or hot inert gas; or polymeric adsorbents which are usually regenerated

with a combination of chemicals (NaOH, HCl or solvents). Spent activated carbon rejuvenation

is incomplete and losses are faced. Sometimes the spent activated carbon is disposed of.

Example of an UPFLOW decolorization process (Production & regeneration)

Adsorption Applications

Novasep has been using adsorbent media in numerous applications sometimes combining both

activated carbon and polymeric adsorbents in order to meet the most stringent customer

specifications.

The main driver of this technology is the production of a final product with very stable

organoleptic properties in terms of color, taste and odor.

Novasep has supplied the industry with complete units, designing the whole process for

theindustrial biotech, pharmaceutical and nutraceutical industries.

Typical applications are:

decolorization of cane refinery syrups,

polishing of sweeteners and polyols juices,

production of liquid sugar,

recovery of flavonoids, plant extracts, colorants, aroma,

recovery of antibiotics,

recovery of proteins,

fruit juice debittering

(References: http://www.novasep.com)

Absorption occurred when two contacting phases are a gas and a liquid. A solute A or

several solutes are absorbed from the gas phase into the liquid phase in absorption. This process

involves molecular and turbulent diffusion or mass transfer of solute A through stagnant,

nondiffusing gas B into a stagnant liquid C. An example of absorption is the absorption of

ammonia from air by the liquid water.

However, stripping in the other hand is the reverse process of absorption that applied the

same theories and basic principles hold. Stripping is a physical separation process where one or

more components are removed from a liquid stream by a vapor stream. An example is the steam

stripping of nonvolatile oils, in which the steam contacts the oil and small amount of volatile

components of the oil pass out with the steam.

The calculation principal of adsorption is usually described through isotherms, that is, the

amount of adsorbate on the adsorbent as a function of its pressure (if gas) or concentration (if

liquid) at constant temperature. The quantity adsorbed is nearly always normalized by the mass

of the adsorbent to allow comparison of different materials.

Absorption calculation principal is based on the ratio of concentrations of some solute

species in two bulk phases in contact is constant for a given solute and bulk phases. In the case of

gas absorption, one may calculate its concentration by using e.g. the Ideal gas law, c = p/RT.

Alternatively, one may use partial pressures instead of concentrations.

CONCLUSION & RECOMMENDATIONS

As a conclusion, the objectives of the experiment were achieved. We had absorbed and

adsorbed gas through a packed column in a batch process in absorption of Carbon Dioxide and

adsorption of Carbon dioxide into activated carbon and we also observed the effect of liquid flow

rate on the absorption-adsorption process. As the flow rate of Carbon Dioxide increased, the

absorption-adsorption process also increased as the composition of the outlet volume of Carbon

Dioxide increased over time.

Recommendations have been made to contribute to the experiment’s improvement.

Firstly, make sure to understand the procedure for the gas absorption-adsorption unit before

running the experiment by referring to the Work Instruction. Secondly, collect the samples

simultaneously from both inlet and outlet of the packed column. Thirdly, to stop collecting the

samples, one of the three main conditions should be achieved. Finally, it is better for preparing a

colour comparison standard in order to analyzing dissolved CO2 in the water composition.

REFERENCES

Websites:

1. http://www.chem.ufl.edu/

2. http://www.separationprocesses.com/

3. http://en.wikipedia.org/

Books:

1. Transport Process And Separation Process Principles (Includes Unit Operations) 4th Edition, Christie John Geankoplis, Pearson Education Inc.