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Solid-Liquid Separation

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Solid-Liquid Separation. Basant Ahmed Richard Rodriguez Jennifer Gilmer David Quiroz Steven Hering. China high speed decanter centrifuge. 2010. Photograph. GN Solid ControlsWeb. 24 Nov 2013. . Introduction. - PowerPoint PPT Presentation
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Solid-Liquid Solid-Liquid Separation Separation Basant Ahmed Richard Rodriguez Jennifer Gilmer David 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/>. 1
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Page 1: Solid-Liquid Separation

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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Page 2: Solid-Liquid Separation

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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Page 3: Solid-Liquid Separation

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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Page 4: Solid-Liquid Separation

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

Page 5: Solid-Liquid Separation

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.

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Page 6: Solid-Liquid Separation

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.

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Page 7: Solid-Liquid Separation

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

Page 9: Solid-Liquid Separation

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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Page 10: Solid-Liquid Separation

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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Page 11: Solid-Liquid Separation

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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Page 12: Solid-Liquid Separation

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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Page 13: Solid-Liquid Separation

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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Page 14: Solid-Liquid Separation

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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Page 15: Solid-Liquid Separation

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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Page 16: Solid-Liquid Separation

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

Page 17: Solid-Liquid Separation

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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Page 18: Solid-Liquid Separation

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

Page 19: Solid-Liquid Separation

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

Page 20: Solid-Liquid Separation

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

Page 21: Solid-Liquid Separation

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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

Page 22: Solid-Liquid Separation

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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

Page 23: Solid-Liquid Separation

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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


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