Adsorption Columns & Equipment - How do they Work? (Lec127)

Summary

This lecture delves into various absorption equipment types, including stirred tanks, fixed beds, and pressure and temperature swing adsorption. It explains how these methods operate, their applications, and the factors influencing their efficiency. Stirred tanks are ideal for batch processes, while fixed beds, also known as percolation columns, are commonly used for gas and liquid separation. Pressure swing adsorption (PSA) and temperature swing adsorption (TSA) are highlighted for their effectiveness in regenerating adsorbents by manipulating pressure and temperature, respectively. The lecture also touches on displacement purge adsorption, which uses a preferential adsorbate to displace contaminants from the adsorbent surface.

Takeaways

• 🔬 **Absorption Equipment Types**: The lecture discusses various types of equipment used in absorption processes including stirred tanks, fixed beds, pressure swing adsorption, temperature swing adsorption, and displacement purge adsorption.
• 🧪 **Stirred Tank Operation**: Stirred tanks operate in batch mode where a slurry is formed for mass transfer, and the residence time is determined by the approach to equilibrium.
• 🌡️ **Fixed Bed Adsorption**: Fixed beds, also known as percolation columns, are used for gas and liquid phase separation and operate in a cyclic batch mode with at least two types of beds for absorption and reverse sorption.
• ⏱️ **Mass Transfer Zone (MTZ)**: In fixed bed adsorption, mass transfer occurs in a specific region known as the MTZ, which moves through the bed as the adsorbent becomes saturated.
• 🔄 **Bed Configuration**: The number and arrangement of fixed beds depend on factors like feed flow rate, pressure drops, energy requirements, and the method of adsorbent regeneration.
• 🌀 **Pressure Swing Adsorption (PSA)**: PSA involves reducing the partial pressure of the adsorbate to regenerate the adsorbent, which can be achieved by decreasing the system's total pressure or adding inert gas.
• 🔥 **Temperature Swing Adsorption (TSA)**: TSA uses temperature changes, typically an increase, to favor desorption by shifting the adsorption equilibrium.
• 🌡️ **Effect of Temperature**: An increase in temperature generally leads to a decrease in the quantity of adsorbate being adsorbed, which is useful for desorption.
• 💧 **Displacement Purge Adsorption (DBA)**: DBA removes adsorbate from the adsorbent surface by displacement with a more preferential adsorbate species, which can lead to product contamination.
• ⚖️ **Heat Considerations**: In DBA, the net heat generated or consumed is typically zero due to the similarity in the heat of adsorption between the displacement fluid and the original adsorbate.

Q & A

What are the main types of equipment used in absorption processes?

The main types of equipment used in absorption processes include stirred tanks, fixed beds, pressure swing adsorption, temperature swing adsorption, and displacement purge adsorption.

How does a stirred tank operate in the context of absorption?

A stirred tank operates at batch conditions where the adsorbent is added as a powder, and the liquid via a solvent is added to remove. The mixture is stirred to form a slurry in which mass transfer occurs.

What determines the required residence time in a stirred tank absorption process?

The required residence time in a stirred tank absorption process is mainly determined by how fast the adsorbent approaches equilibrium.

What is a fixed bed adsorption process, and what is its common application?

A fixed bed adsorption process, also known as a percolation column, involves a stationary bed of adsorbent through which the fluid flows. It is commonly used for gas and liquid phase separation.

How does the rate of interaction change in a fixed bed adsorption process over time?

In a fixed bed adsorption process, the rate of interaction typically increases initially but decreases over time as the adsorbent becomes saturated.

What are the factors that determine the number and arrangement of fixed beds in an adsorption process?

The factors that determine the number and arrangement of fixed beds in an adsorption process include feed flow rate, pressure drops, energy requirements, length of the mass transfer zone, method of adsorbent regeneration, and capital investment.

What is pressure swing adsorption, and how is regeneration achieved in this process?

Pressure swing adsorption is a process where adsorption and desorption are favored by changing the pressure conditions. Regeneration is achieved by reducing the partial pressure of the adsorbate, either by reducing the system's total pressure or by adding an inert gas.

How does temperature swing adsorption differ from pressure swing adsorption?

Temperature swing adsorption differs from pressure swing adsorption in that it uses changes in temperature, typically an increase, to favor desorption of the adsorbate from the adsorbent.

What is the effect of temperature on the adsorption equilibrium in temperature swing adsorption?

In temperature swing adsorption, an increase in temperature leads to a decrease in the quantity of adsorbate being adsorbed, favoring desorption.

What is displacement purge adsorption, and how does it work?

Displacement purge adsorption is a process where adsorbed species are removed from the adsorbent surface by replacing them with a more preferential adsorbate species, which can be a gas, liquid, or vapor.

What is a potential drawback of using displacement purge adsorption?

A potential drawback of displacement purge adsorption is that the displacement fluid can contaminate the product stream, as the displaced adsorbate is released back into the fluid.

Outlines

00:00

🔬 Absorption Equipment Overview

This paragraph introduces various types of equipment used in absorption processes, including stirred tanks, fixed beds, pressure swing adsorption (PSA), temperature swing adsorption (TSA), and displacement purge adsorption. The lecture emphasizes the importance of understanding the main types of equipment and their applications in separation processes. Stirred tanks operate in batch or continuous mode, mixing adsorbent and liquid to facilitate mass transfer. Fixed beds, also known as percolation columns, are used for gas and liquid separation and operate in a cyclic batch mode. The paragraph also touches on the factors determining the design and operation of these systems, such as residence time, adsorbent saturation, and the mass transfer zone.

05:03

🌡️ Temperature and Pressure Swing Adsorption

This section delves into the principles and applications of pressure swing adsorption (PSA) and temperature swing adsorption (TSA). PSA involves reducing the partial pressure of the adsorbate to facilitate desorption, which can be achieved by decreasing the total system pressure or by adding an inert gas. The benefits of PSA include the ability to control the adsorption process through pressure changes. TSA, on the other hand, uses temperature changes to regenerate the adsorbent. An increase in temperature favors desorption, making it possible to remove adsorbed materials. The paragraph discusses the effects of pressure and temperature on adsorption equilibrium, highlighting the importance of choosing appropriate operating conditions to optimize the separation process.

10:03

🌟 Displacement Purge Adsorption (DBA)

The final paragraph discusses displacement purge adsorption (DBA), a method where the adsorbate is removed from the adsorbent surface by displacing it with a more preferential adsorbate species. This displacement can be done using a gas, liquid, or vapor, and the process involves competition between the adsorbate species. The paragraph explains that the displacement fluid must be stronger than the original adsorbate to effectively displace it. However, this method can lead to contamination of the product stream if the displacement fluid is not carefully chosen. One advantage of DBA is that the net heat exchange is typically zero, as the heat of adsorption of the displacement fluid is similar to that of the original adsorbate, leading to a relatively constant temperature of the adsorbent.

Keywords

💡Absorption

Absorption is a process where a substance (the absorbate) is taken up by another substance (the absorbent). In the context of the video, absorption is a key mechanism in separation processes, where certain materials are preferentially adsorbed onto a surface. The video discusses various equipment types used in absorption, such as stirred tanks and fixed beds, to facilitate this process.

💡Stirred Tank

A stirred tank is a type of equipment used for mixing substances in batch operations. In the video, stirred tanks are mentioned as one of the main types of equipment used in absorption processes. They operate by continuously mixing the adsorbent with the liquid to be treated, creating a slurry where mass transfer occurs.

💡Fixed Bed

A fixed bed, also known as a percolation column, is a type of equipment where the adsorbent is held stationary and the fluid to be treated is passed through it. The video explains that fixed beds are widely used for gas and liquid phase separations, and they operate in a cyclic batch mode, with the adsorbent eventually becoming saturated and requiring regeneration.

💡Pressure Swing Adsorption (PSA)

Pressure Swing Adsorption is a process where the adsorption-desorption cycle is controlled by changing the pressure. The video describes PSA as a method where regeneration of the adsorbent is achieved by reducing the partial pressure of the adsorbate, either by decreasing the total system pressure or by adding an inert gas.

💡Temperature Swing Adsorption (TSA)

Temperature Swing Adsorption is a process that uses temperature changes to control the adsorption-desorption cycle. The video explains that in TSA, the adsorbent is regenerated by increasing the temperature, which favors the desorption of the adsorbate. This is because adsorption is typically an exothermic process.

💡Displacement Purge Adsorption (DBA)

Displacement Purge Adsorption is a method where adsorbed material is removed from the adsorbent surface by displacing it with a more preferential adsorbate species. The video mentions that this displacement can be done by a gas, liquid, or vapor, and it can lead to contamination of the product stream if not managed properly.

💡Mass Transfer Zone (MTZ)

The Mass Transfer Zone is a region within a fixed bed where adsorption and desorption occur. The video describes how the MTZ moves through the bed as the adsorbent becomes saturated, and it is a critical factor in determining the efficiency of the fixed bed process.

💡Adsorbent

An adsorbent is a material that has the ability to adsorb other substances onto its surface. In the video, the choice and management of adsorbents are crucial for the efficiency of absorption processes, with considerations for their regeneration and the avoidance of product contamination.

💡Batch Processing

Batch processing refers to a mode of operation where materials are processed in discrete batches rather than continuously. The video mentions that batch processing can be used in absorption processes, with the possibility of using multiple steps to reduce the amount of adsorbent required.

💡Regeneration

Regeneration in the context of adsorption processes refers to the steps taken to restore the adsorbent's capacity to adsorb after it has become saturated. The video discusses various methods of regeneration, including pressure and temperature swings, which are crucial for the continuous operation of adsorption equipment.

💡Equilibrium

Equilibrium in adsorption processes refers to the state where the rate of adsorption equals the rate of desorption, and no net transfer of material occurs. The video explains how the operation conditions, such as pressure and temperature, can affect the equilibrium and thus the efficiency of the adsorption process.

Highlights

Introduction to the main types of equipment used in absorption processes.

Description of stirred tanks used in batch conditions for absorption.

Explanation of fixed bed adsorption, also known as percolation columns.

Discussion on the cyclic batch operating mode using fixed beds for gas and liquid separation.

Insight into how the rate of interaction increases with the rate in fixed bed adsorption.

The concept of mass transfer zone (MTZ) and its movement through the bed.

Application of fixed bed adsorption in removing organic compounds and particulates from water.

Factors determining the number and arrangement of fixed beds in adsorption processes.

Advantages of using multiple beds in parallel for high flow rates and short MTZ.

Use of pressure swing adsorption (PSA) for regeneration by reducing the partial pressure of the adsorbate.

Mechanisms of pressure swing adsorption including system pressure reduction and inert gas addition.

Impact of partial pressure on equilibrium loading in PSA processes.

Introduction to temperature swing adsorption (TSA) for regeneration by changing temperature.

Effect of temperature on adsorption equilibrium and the desorption process.

Considerations for regeneration temperature to avoid degradation of adsorbents.

Explanation of displacement purge adsorption (DBA) and its mechanism.

Advantage of DBA where the net heat generated or consumed in the adsorbent is typically zero.

Discussion on the potential contamination of the product stream in DBA due to displacement fluid.

Transcripts

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this lecture is going to be long so bear

with me we're going to see the main type

of equipments used in absorption we

either have a stirred tank slowly at

cirsium tank we have a fixed bit at

certian it's very common and then we get

pressure swing adsorption which is also

very common temperature swing insertion

and displacement purge adsorption number

one will be the steered tanks the

reassertion as you can imagine this is a

tank this operates at batch conditions

you add the add servant be a powder you

add the liquid via a solvent to leave it

to remove and what you're going to do is

to mix it and working patch or this

continuously you're going to be forming

the slurry in which the mass transfer is

going to occur that is that certian is

going to curve here the required

residence time of the operation is

mainly determined by how fast it is

approach meaning that actually if you

have any material which is low in

equilibrium you're going to take a

longer than some material that might get

into the actual exertion very soon

typically you will either recover or

throw away this lorry or the adsorbent

we add the filtration of this lorry that

that's interesting and also very

important you can either discard it

throw it away or keep it one way of

reducing the total amount of adsorbent

required is to carry out the batch

processing in two steps

the field is first contacted with a

fresh batch of the adsorbent after

separation of the fluid from that

servant the fluid is then contacted with

a further fresh batch so you can see

here guys what we're doing is in

contouring or favoring the equilibrium

conditions second equipment will be the

fixed bed at certian which can also be

called percolation column and typically

you will have at least two types of bed

wine which is being absorbed and the

other one in the reverse

sorption and this is essentially a cycle

the cyclic batch operating mode using

fixed path fix med meaning that we have

the catalyst fixed or settle they don't

move they are not flowing around or

floating anything it is widely used with

both the gas and liquid feet separation

in a fixed bed is typically an unsteady

state but rate control process meaning

that if you add or increase the rate

typically you will increase the rate of

interaction but as time passes by the

adsorbent is going to be saturated this

means that the conditions at any

particular point within the fixed bed

part wait time meaning that if we were

to analyze the concentration of certain

material here and here at time 0 will be

different at time F a torsion only

occurs in a particular region of the bed

known as the mass transfer zone mtz

which moves through the bed now please

hopefully make sense for you guys so

imagine this is a 100% clean or not

saturated at servant the first

interactions are going to be stronger

initially until they start getting

saturated then you're going to have

interactions maybe at 1/2 point then

after the half point and eventually all

get saturated you are going to end up

working here application of fixed bed at

certian also called percolation include

the removal of the sole organic

compounds from water any kind of

particulate in water can also be

considered the cleaning of gases it is

air or anything like that anything

regarding a fluid which can pass through

can be in theory observed the factors

which determine the number and

arrangement of fixed beds will include

feed flow rate pressure drops energy

requirements length of the mass transfer

zone or the size of the catalyst bed

sorry not catalyst at serpent Bell

method of at servant regeneration

and of course capital investment how

much are you willing to invest in order

to achieve a steady flow of products

most applications typically include two

beds at a table before one will work in

a certain process and the other in the

reverse process we do these inert avoid

the well this rate for WordPress will be

we work then it gets saturated then we

get a material which they saturates of

disturbs the material and then we work

again this takes time and not only that

we are going to be working very batch

mode we want to work the most

continuously way as possible and this

fixes our problem multiple bed in

parallel will be used with a relatively

high flow rate and a short MTC length

while multiple beds in series will be

used if the MTC were along well this is

straightforward if you have longer MTC

then you will have more mass transfer

for high flow rates and large MTC length

the choice is likely to be multiple beds

in series and parallels of course

because you don't want to have a huge

very tall column rather you will prefer

to have lots of columns much safer but

it cost more more capital cost anyways

we then change to pressure swing at

certian which is also a very important

column to analyze that you can imagine

pressure will swing or will favor the

assertion or desertion depending on the

conditions regeneration in a PSA which

is pressuring at certian process is

achieved by reducing the partial

pressure of the add surveyed meaning we

are decreasing the pressure overall

typically when we decrease pressure at

servant is going to leave the active

sites or as a whole or the so-called

holes there are two ways in which this

can be achieved either a reduction in

the system total pressure or you can add

inert gas so the partial pressure

changes

in the merit of pressuring separations a

combination of these two methods is

going to be employed either we change

the pressure of the system or we change

the partial pressure by addition of a

inert gas use of a port fluid alone is

not likely to occur but it still can

happen this will be mostly favored when

you're working with a inert gas and then

you want to decrease the pressure so you

let the purge gas go away here the

effect of partial pressure on

equilibrium loading will have the

following curve as you can see here let

it be T 1 you have this Q 1 Q 2 versus P

2 P 1 the meaning of Q is essentially

the let it be the percentage or the

amount of the material being saturating

or saturating the adsorbent surface and

as you can imagine is here the

temperature was fixed because we are

changing pressure so we go from maybe

initial conditions very high saturation

let it be 90 percent saturation and this

is an anomaly it 30% pressure one very

high pressure what happens when we

decrease pressure well we're going to

decrease the observant but the observant

material in the observant now the

problem with this power here is that you

can change pressure but this will remain

and this remains because this is a

isotherm curve now what happens if we

want to change the temperature on our

system then we're going to be using

temperature swing adsorption

regeneration of adsorbent in a TSA or

temperature swing insertion process is

achieved by a change in temperature

typically an increase in temperature

remember that ad certian is a exothermic

process meaning that if we cool down or

decrease the temperature we're going to

favor the shift towards products which

is assertion of the material but we want

to do the reverse if we increase the

temperature we're going to favor the

reverse so the material which is already

observed it's going to go back into the

shrim this is what happens temperature 2

is larger than tomorrow greater than

temperature 1 so you're going to shift

the curve and now let it be this is

operating at 1 atmosphere let it be and

what's happening here will change the

temperature and remember previously we

stayed at q1 is 90% and q2 is 30%

we are still achieving the change in

saturation but now we're going or we're

doing this by changing the temperature

technically increasing the temperature

the effect of temperature on the

absorption equilibrium which is type 1

isotherm is going to be the following

for any given partial pressure of the

adsorbate in the gas phase or

concentration in the liquid phase an

increase in temperature will lead to a

decrease in the quantity being at zorb

and this is generally steady for some

cases might be reversed but overall this

is true let me check oh yeah

if the partial pressure remains constant

at pretty 1 which we already stated this

is one atmosphere increasing the

temperature from t1 to t2 let it be

hundred Celsius to 200 Celsius a

clearing going to change from Q to Q to

the saturation a relatively modest

increase in temperature can affect the

relatively large decrease in loadings it

is therefore generally possible to

desorb any components provided that the

temperature is higher however it is

important to ensure that the

regeneration temperature does not houses

any kind of degradation to the add

servants so this is the problem with

these type of operations it's very easy

to tell us to change temperatures in art

increase operation but then you're going

to encounter other type of processes

especially in the regulation and lastly

I think this is yeah this is the last

equipment I want to show you

displacement of purge absorption DBA I'm

sure rate can be removed from the

absorbent surface by replacing them with

a more preferential at servant species

essentially you're going to displace it

the displacement can either be done by a

gas liquid or vapor in theory you can

also

this by a using solid in polar but now

we're going to stick to fluids if you'll

absorb about as strong as the components

which are going to be disturbed

meaning that of course if you using

material X yet at certain rate gotta be

stronger than the material a while which

is already observed the mechanisms for

the sorption of the original adsorbate

involves two aspects one partial

pressure or concentration of our unit

original at serve it in the gas phase

and second there is competition of

insertion so what's going to end up is

displacement of the fluid from the

surface and this will present or sorry

the displacement fluid is present on the

at servant and thus will contaminate the

product well this is obvious you're

gonna if something is absurd and you're

using a materiality VA and beam let it

be this is the surface if you have a and

a is going to take the place of P then P

is going to go to the stream and of

course it means a unwanted material then

by definition you're going to be

polluting or contaminating the stream

remember this is actually a solvent

which contains a solid solid a one of

the main advantages of this placement

fluid method is that the net heat

generated or consumed in the adsorbent

will be typically zero this is

essentially to the heat of adsorption of

the displacement fluid likely to be

similar than the reverse so essentially

the plus and negative signs are similar

in magnitude so the net sum or in

network as well Network the net heat is

zero

thus the temperature of the adsorbent

shall remain more or less constant so

that's also a key advantage

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you