Solid-Liquid Separation Basant Ahmed Richard Rodriguez Jennifer Gilmer David Quiroz Steven Hering...
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Transcript of Solid-Liquid Separation Basant Ahmed Richard Rodriguez Jennifer Gilmer David Quiroz Steven Hering...
Solid-Liquid Solid-Liquid SeparationSeparation
Basant AhmedRichard Rodriguez
Jennifer GilmerDavid Quiroz
Steven Hering
China high speed decanter centrifuge. 2010. Photograph. GN Solid ControlsWeb. 24 Nov 2013. <http://oilfield.gnsolidscontrol.com/china-high-speed-decanter-centrifuge/>.
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IntroductionIntroduction Solid-liquid separation is
a necessary step in obtaining the desired product from a precipitation or crystallization reaction
Centrifugation is the way to achieve the required solid-liquid separation
There are two types of centrifugation Sedimenting Filtering
Most popular in chemical and pharmaceutical applications and the main focus of this selection process
Crystallization. 2013. Photograph. WikipediaWeb. 24 Nov 2013. <http://upload.wikimedia.org/wikipedia/commons/d/d3/Snow_crystallization_in_Akureyri_2005-02-26_19-03-37.jpeg>.
http://www.visualphotos.com/photo/1x6037988/precipitation_reaction_giving_iron_ii_hydroxide_a500337.jpg
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Steps to Centrifuge Steps to Centrifuge SelectionSelection
The best process for choosing the proper centrifuge is the following detailed three step process
1. Process and Application Determine sedimenting or filtering Based on reaction type and process specifications
i.e. crystallization vs. precipitation Temperature, pH, flow rate, batch size
2.Product Properties Determine required centrifuge properties based on the
product properties Filterability for filtering centrifuges based product
properties i.e. particle size, shape , rigidity
3. Centrifuge Design Chose specific centrifuge based on prior selection
criteria that is process and product requirements Choose vertical, horizontal, or inverted for filter Decanter is on option for sedimenting centrifuge
selection
Patnaik, Tom. Solid-liquid Separation: A guide to Centrifuge Selection. 2012. Graphic. www.aiche.org/cepPrint.
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Selection by Process & Selection by Process & ApplicationApplication
First step is to choose filtering or sedimenting centrifugation This will be chosen based particle size, washing required, concentration of solid in slurry,
and throughput Filtering – a batch-operated machine that uses a filter media to capture and
collect a filter cake inside a rotating basket. Suitable for slurries with large particles due ease of filtration of large particles Dry solid products require filtering due to extending spinning helping dry the product
which is not possible in continuous sedimentation Preferable when the solid(the cake) is the required product and it allows for a long wash
liquid residence time inside the solid cake Sedeminting – a machine that is continuous and uses high rotational velocities
to create high magnitude g-forces inside a solid bowl to separate the liquid from the solid Preferable for when solid particle size and concentration are small and the volume of the
liquid is low because the filter needed increases with liquid volume Usually preferred when the liquid the valuable and desired product of the specific
reaction and products being purified
Patnaik, Tom. Solid-liquid Separation: A guide to Centrifuge Selection. 2012. Graphic. www.aiche.org/cepPrint.
Clarke, Peter. Theory of sedimentation and centrifugation. 2009. Infographic. n.p. Web. 24 Nov 2013. <http://www.bbka.org.uk/local/iceni/bm~doc/pollensuspension-2.pdf>.4
Selection by Product Selection by Product PropertiesProperties
An analysis of the particle size, shape and distribution is the main determinant of filterability which is an important factor when dealing with filtering centrifuges.
Particle shape is the main factor that influences filterability Spherical particles are the ideal for filtration and are
easiest to filter followed by rounded Fibrous particles are the most difficult to filter due to
formation of dense cakes The shape factor determined to compare actual shape
to ideal sphere Normalized from 0 to 1
Particle size is the factor affecting cake porosity, residual cake moisture and throughput rates Bigger particles form cakes with large capillaries and
thus have a higher porosity and higher thought rate System pressure also effects filterability. At high
pressure cake compact causing filterability to decrease
Slurry filterability is expressed in flux fate gpm/ft^2 Function of particle size, shape and structure To filter slurry flux rate can be between 1gpm/ft^2 to
6gpm/ft^2 to filter well
Patnaik, Tom. Solid-liquid Separation: A guide to Centrifuge Selection. 2012. Graphic. www.aiche.org/cepPrint.
5
Selection By Centrifuge DesignSelection By Centrifuge Design
Selection of the specific centrifuge base on the preceding factors
Filtering centrifuge specifics Use a perforate bowl lined with a filter cloth to retain the desired
solid cake and the liquid passes through and is discarded Usually operated as batch
Three types of Filter centrifuges Vertical Basket Horizontal Peeler Inverting Filter
Decanters A type of sedimenting centrifuge which is used in bio-
pharmaceutical process that need high g forces Separate solid and liquid by the basic process of sedimentation
filtration lined out in previous and proceeding slides
Patnaik, Tom. Solid-liquid Separation: A guide to Centrifuge Selection. 2012. Graphic. www.aiche.org/cepPrint.
6
Types of Filtrating CentrifugesTypes of Filtrating Centrifuges Vertical Basket
Used for slow/medium filtering slurries. Even distribution of cake across vertical face is ideal and is the result in slow and medium filtering
Prone to high process vibration Three types
Vertical basket manual discharge – cake discharge is manual
Vertical basket peeler – automatic plow used to discharge cake to avoid safety risks for toxic cakes
Vertical basket cGPM – designed for sanitary operation and have a clean in place system
Horizontal Peeler Have a high volume capacity Process components can be
separated from mechanical components
Limitation could be formation of heel
Inverting Filter Useable on a vide range of filtering
systems from easy to poor Do not form a heel which is suitable
for a thin-cake operationPatnaik, Tom. Solid-liquid Separation: A guide to Centrifuge Selection. 2012. Graphic. www.aiche.org/cepPrint. 7
Centrifuge ExamplesCentrifuge Examples
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http://www.rousselet-robatel.com/images/products/rental-SLAB-540lg.jpg
Vertical Centrifuge Horizontal Centrifuge
http://img.directindustry.com/images_di/photo-g/horizontal-peeler-centrifuges-71914-2503229.jpghttp://img.direct
industry.com/images_di/photo-g/inverting-filter-centrifuges-21373-2367189.jpg
Inverting Filter Centrifuge http://www.flottweg.de/cms/upload/bildergalerie/Komponenten/Decanter/unter_Druck_engl.jpg
Centrifuge TheoryCentrifuge Theory
The separation of solids from liquids via settling and filtration rely on many factors:
1. Flow rates2. Particle size3. Particle geometry
http://techalive.mtu.edu/meec/module06/images/soil_000.JPG
http://homepage.usask.ca/~mjr347/prog/geoe118/images/shape1.gif
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Centrifuge TheoryCentrifuge Theory The driving forces for
settling and filtration is gravity and pressure gradients. These forces are usually not enough on there own to create rapid separation.
Rate = Driving Force / Resistance
This relationship shows that in order to increase the rate of separation via settling and filtration is to either:
1. Decrease resistance2. Increase driving force
Centrifuges perform #2
http://www.thenakedscientists.com/HTML/uploads/RTEmagicC_Centrifuge-wheel-cff.png.png
http://i01.i.aliimg.com/img/pb/387/707/567/567707387_658.jpg
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Centrifuge TheoryCentrifuge Theory
Centrifuges are able to speed up separation by dramatically increasing the force of gravity by several thousand times.
Centrifuges do this by spinning at very high angular velocities creating very strong centripetal and centrifugal forces which are the same in magnitude by differ in directio
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Centrifuge TheoryCentrifuge Theory
Centrifugal force varies from gravitational forces in terms of magnitude only
RCF : relative centrifugal force (g-force)ω: angular velocityg: gravitational force
http://upload.wikimedia.org/wikipedia/commons/9/97/Centripetal_force.PNG
http://content.answcdn.com/main/content/img/oxford/Oxford_Sports/0199210896.centrifugal-force.1.jpg
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Centrifugal SettlingCentrifugal Settling
When the density of particles suspended in a solution is greater than the density of the liquid then settling will occur.
This does not always happen in a practical length of time, making centrifuges necessary.
Several forces are important when settling occurs:
1. Gravitational forces2. Buoyancy3. Centrifugal force4. Particle drag
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Centrifugal SettlingCentrifugal Settling
All of these forces are important when determining the velocity at which the particle will settle:
μ: viscosity of liquidDp: particle diameterV: settling velocityρp: particle densityρ: liquid densityac: centrifugal acceleration
function [ v ] = settlingv( ac,Dp,pp,p,u )% function settlingv calculates settling velocity of particle in centrifuge%% input:% ac = centrifugal acceleration (m/s2) % Dp = particle diameter (m)% pp = particle density (kg/m3) % p = liquid density (kg/m3)% u = liquid viscosity (Pa s)%% output:% v = settling velocity (m/s) v = Dp.^2*(pp-p)/18/u*ac; end
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Centrifugal SettlingCentrifugal Settling
>> ac = 250;>> pp = 1250;>> p = 1000;>> u = 0.001002;>> Dp = linspace(0.00001,0.00010);>> v = settlingv(ac,Dp,pp,p,u);>> plot(Dp,v);>> xlabel('particle diameter (m)');>> ylabel('settling velocity (m/s)');>> title('v vs. Dp');
>> Dp = 0.00004;>> pp = 1250;>> p = 1000;>> u = 0.001002;>> ac = linspace(100,500);>> v = settlingv(ac,Dp,pp,p,u);>> plot(ac,v);>> xlabel('centrifugal acceleration (m/s2)');>> ylabel('settling velocity (m/s)'); >> title('v vs. ac');
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Centrifugal SettlingCentrifugal Settling For a continuous centrifuge, the flow rate that the solution
is moving through the bowl will determine whether a particle will be filtered or if it will flow out.
Qc: volumetric flow rate through bowlμ: viscosity of liquidDp: particle diameterρp: particle densityρ: liquid densityac: centrifugal accelerationV: volume of liquid held in the bowls: thickness of a thin liquid layer
function [ Qc ] = VflowBowl( ac,u,Dp,pp,p,V,s )% function VflowBowl calculates the volumetric flow through bowl in centrifuge%% input: % ac = centrifugal acceleration (m/s2) % u = liquid viscosity (Pa s)% Dp = particle diameter (m)% pp = particle density (kg/m3) % p = liquid density (kg/m3)% V = volume of liquid in bowl (m3), default = 0.001% s = thickness of thin layer liquid (m), default = 0.001%% output:% Qc = Volumetric flow through bowl (m3/s)
if nargin<7||isempty(s), s = 0.001; endif nargin<6||isempty(V), V = 0.001; end
Qc = Dp.^2*(pp-p)*V/9/u/s*ac;
end 16
Centrifugal SettingCentrifugal Setting>> u = 0.001002; >> Dp = 0.00004; >> pp = 1250; >> p = 1000; >> ac = linspace(100,500); >> Qc = VflowBowl(ac,u,Dp,pp,p); >> plot(ac,Qc); >> xlabel('centrifugal acceleration (m/s2)'); >> ylabel('volumetric flow (m3/s)'); >> title('Qc vs. ac');
>> u = 0.001002; >> pp = 1250; >> p = 1000; >> ac = 250; >> Dp = linspace(0.00001,0.00010); >> Qc = VflowBowl(ac,u,Dp,pp,p); >> plot(Dp,Qc); >> xlabel('particle diameter (m)'); >> ylabel('volumetric flow (m3/s)'); >> title('Qc vs. Dp');
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Centrifugal FiltrationCentrifugal Filtration Filtration is achieved by creating a pressure difference
across a filter cloth. The pressure difference forces the liquid through the
cloth while leaving behind a cake (the solid) behind. This force is usually done using gravity or a vacuum
on the other side of the cloth but centrifugal force can be used as an alternative to creating a pressure difference across the cloth.
http://www.rousselet-robatel.com/images/products/HP-centrif-filtrationlg.jpg
http://img.medicalexpo.com/images_me/photo-g/laboratory-filtration-centrifuges-84315-6088741.jpg 18
Centrifugal FiltrationCentrifugal Filtration Volumetric Flow rate through the
filter
Q: volumetric flow rate through filter
ρ: density of filtrate ω: angular velocity r1: distance from the center to the
cake surface r2: distance from the center to the
centrifuge wall μ: viscosity of the solution mc: mass of cake deposited on
filter α: specific cake resistance A: area of cake Rm: resistance of the filter
medium to filtrate flow
http://csmres.co.uk/cs.public.upd/article-images/Fig-9---belt_cake_discharge.JPG
http://www.bokela.de/typo3temp/pics/27735eca79.jpg19
Centrifugal FiltrationCentrifugal Filtration>> w = linspace(100,500);>> Q = VflowFilter(w);>> plot(w,Q);>> xlabel('angular velocity (m/s)');>> ylabel('volumetric flow (m3/s)');>> title('Q vs. w');
function [ Q ] = VflowFilter( w,p,r1,r2,u,mc,a,A,Rm )% function VflowBowl calculates the volumetric flow through bowl in% centrifuge%% input: % w = angular velocity (m/s) % p = filtrate density (kg/m3), default = 900% r1 = distance from center to cake surface (m), default = 0.05% r2 = distance from center to centrifuge wall (m), default = 0.1% u = solution viscosity (Pa s), default = 0.001% mc = mass of cake deposited on filter (kg), default = 0.01% a = specific cake resistance (m/kg), default = 100% A = area of cake (m2), default = 0.00001% Rm = resistance of filter medium to filtrate flow (1/m), default = 0.000001 %% output:% Q = Volumetric flow through filter (m3/s)
if nargin<9||isempty(Rm), Rm = 0.000001; endif nargin<8||isempty(A), A = 0.00001; endif nargin<7||isempty(a), a = 100; endif nargin<6||isempty(mc), mc = 0.01; endif nargin<5||isempty(u), u = 0.001; endif nargin<4||isempty(r2), r2 = 0.1; endif nargin<3||isempty(r1), r1 = 0.05; endif nargin<2||isempty(p), p = 900; end
Q = w.^2*p*(r2^2-r1^2)/2/u/(mc*a/(A^2)+Rm/A);
end 20
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Conclusion Conclusion Solid Liquid Separation by
centrifugation Two types: Sedimenting and
Filtering
Centrifuge Selection Three Steps: Process and
Application, Product Properties, and Centrifuge Design
Centrifuge Designs Thee Types: Vertical Basket,
Horizontal Peeler, and Inverting Filter
http://cmbe.engr.uga.edu/engr4520/Other/Ch%205%20Disc%20Centrifuge%20schematic.jpg
http://www.sswm.info/sites/default/files/toolbox/EPA%202000%20Centrifuge%20Thickening%20and
%20Dewatering.jpg
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Conclusion Conclusion
Centrifuge Theory Rate of Separation = Driving
Forces/Resitance Centrifuges simply increase
the rate by increasing the driving forces
MATlab Programs Calculate the settling velocity
(m/s), and Volumetric flow through bowl (m3/s) in settling
Calculate the Volumetric flow through filter (m3/s) in filtering
http://bgsctechclub.files.wordpress.com/2011/08/centrifugal-force-diagram.jpg?w=682
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Future Work and ResearchFuture Work and Research Further research on the shape and structure for
maximizing recovery Increased Efficiency of Centrifuges
Particularly vital in the area of nuclear energy. “America's only domestic supplier of nuclear fuel, the United States Enrichment
Corporation (USEC), has created an advanced centrifuge that officials say is the world's fastest and largest, able to produce enriched uranium using just 5 percent of the electricity required by the company's previous design”
http://www.popularmechanics.com/science/energy/nuclear/4257042
http://www.world-nuclear.org/uploadedImages/org/info/Nuclear_Fuel_Cycle/Enrichment_and_Conversion/
centrfge.jpg