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
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 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/>.
1
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>.
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.
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
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.
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
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”