Adsorption Columns & Equipment - How do they Work? (Lec127)
Summary
TLDRThis 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
- π¬ **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.
- π§ͺ **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.
- π‘οΈ **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.
- β±οΈ **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.
- π **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.
- π **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.
- π₯ **Temperature Swing Adsorption (TSA)**: TSA uses temperature changes, typically an increase, to favor desorption by shifting the adsorption equilibrium.
- π‘οΈ **Effect of Temperature**: An increase in temperature generally leads to a decrease in the quantity of adsorbate being adsorbed, which is useful for desorption.
- π§ **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.
- βοΈ **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
π¬ 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.
π‘οΈ 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.
π 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.
Mindmap
Keywords
π‘Absorption
π‘Stirred Tank
π‘Fixed Bed
π‘Pressure Swing Adsorption (PSA)
π‘Temperature Swing Adsorption (TSA)
π‘Displacement Purge Adsorption (DBA)
π‘Mass Transfer Zone (MTZ)
π‘Adsorbent
π‘Batch Processing
π‘Regeneration
π‘Equilibrium
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
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