By:R.Mazahernasab

Feb2013

PILOT-PLANT TESTWORKS FOR HYDROCYCLONE CIRCUIT DESIGN

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IntroductionDesign variablesHydrocyclone effi ciencyHydrocyclone designTestworks

CONTENT

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A hydrocyclone is a size classifier used to process slurries.

The separation mechanism is based on enhanced gravity and takes advantage of particle size and density.[5]

INTRODUCTION

Recovery of water to overflow is generally high (around 90%). It follows that the coarser particles exit through the underflow as a dense slurry.[5]

INTRODUCTION

Slurry is injected into the cylindrical zone

Cycloning starts to take place in the feed chamber.

Heavier particles move to the outer walls by centrifugal forces and move toward the apex.

Lighter particles stay near the center of the cone and are carried away by the vortex finder.

[1,7]

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Classification does not take-place throughout the whole body of the cyclone.

INTRODUCTION

Region A: unclassified feed Region B: fully classified coarse materialRegion C : fully classified fine materialRegion D: classification takes place. Across this region, decreasing sizes show maxima at decreasing radial distances from the axis.[1]

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Hydrocyclone design objectives:Maximum effi ciencyMaximum capacityLower operating costs

The process design criteria will be based on an interpretation of testwork carried out on the particular ore.

As more test work result are available and the ore characteristics and process become better defi ned a continuous updating of the design criteria is under taken.

Pilot scale testing is regerded as the most reliable method of selecting fl owsheets and generating design criteria for equipment sizing and selection.[4]

INTRODUCTION

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Cyclone geometry

Area of the inlet nozzle

Cyclone diameter

Cylindrical and conical sectionVortex finder

and apex orifice

Feed featuresSolids concentration

and Size distribution

Specific gravity of solid and liquid

Slurry and liquid viscosity

Initial pressure of feed

DESIGN VARIABLES

Cyclone performance

0.05 times the cyclone diameter squared

−Retention time−Length equal to cyclone diameter

−Angle:10°- 20°

[1],[2]

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The sharpness of the cut depends on the slope of the central section of the partition curve; the closer to vertical is the slope, the higher is the effi ciency.[1]

HYDROCYCLONE EFFICIENCY

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Small cyclone diameters give greater effi ciency.Effi ciency and P increase with height; normally

height is between 2 and 6 diameters.Smaller cone angle gives better effi ciency.Pressure drop is related to effi ciency, It increases

with effi ciency. In practice the effi ciency is limited because at high

P, velocities become high, and turbulence causes re entrainment and loss of particles.

Effi ciency increases with mass which increases with particle size.[1,6]

HYDROCYCLONE EFFICIENCY

EFFICIENCY, FLOWRATE AND P

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0water Flowrate, Q

0

ΔP,

m o

f w

ate

r co

lum

n

Effi

cien

cy

A

B

OptimumOperation

Eff

P

Theory

Practice

40

100

[6]

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You should start with calculating cyclone diameter:

Step1: Calculate required D50 using mass balance equations from known information.

Step2: Calculate D50(base) with multiplying times a series of correction factors designated by C1, C2, and C3:

D50C(application) = D50C(base)xC1xC2xC3 o C1: influence of the concentration of solids

HYDROCYCLONE DESIGN

[2],[3].[4]

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Larger amount of fines

coarser separation

Absence of fines

finer separation

HYDROCYCLONE DESIGN

this is aff ected by particle size and shape and liquid viscosity.

higher concentration results coarser separation. [2]

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o C2: influence of pressure drop

• Pressure drop is a measure of the energy being utilized in the cyclone to achieve the separation.

• It is recommended that pressure drops, be designed in the 40 to 70 kPa range to minimize energy requirements. [2]

C2 = 3.27 x ∆P -0.28

HYDROCYCLONE DESIGN

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HYDROCYCLONE DESIGN

Higher pressure drop finer separation [2]

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o C3: Infl uence of specifi c gravity of the solids and liquid

GS = Specifi c gravity of solids GL = Specifi c gravity of liquid

[2]

HYDROCYCLONE DESIGN

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D = 0.204 x (D50(base)) 1 .67 5

[2]

HYDROCYCLONE DESIGN

D50(base) = D50C(application)/C1xC2xc3

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Then determine cyclone capacity and number of cyclones:

The volume of feed slurry that a given cyclone can handle is proportional to the pressure drop.

Number of cyclone= total slurry fl ow rate /cyclone capacity.

Approximately 20% to 25% standby cyclones are recommended for operational as well as maintenance flexibility. [2],[3]

HYDROCYCLONE DESIGN

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HYDROCYCLONE DESIGN

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Determine apex diameter: [2]

HYDROCYCLONE DESIGN

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Vortex finder diameter:

where Dv is the vortex diameter and Dc is cyclone diameter

Inlet nozzle diameter:

[3]

HYDROCYCLONE DESIGN

Di = 0.05 × (Dc)2

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Sizing Measurement TestsSizing analyses provide useful information on the size

distribution of a sample of ore or other material, using a comprehensive set of screens and all screening done under standard and unvarying conditions to ensure self-consistency and reproducibility of the results.[8]

TESTWORKS

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X-ray Diff raction (XRD): Qualitative Identification - mineral present Semi-Quantitative analysis - identification and

estimation of major/minor/trace componentsQuantification of mineral species present -

Rietveld quantification[8]

The solids Specific gravity of the equivalent Mineral is:[9]

TESTWORKS

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Testwork 1: To collect the data on the operational performance of hydrocyclone, a series of pilot scale tests was conducted.

These experiments were carried out using feed slurry consisting of quartz

particles with a density of 2650 kg/m3. The feed size distribution is shown in Table 1.

TESTWORKS

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The liquid phase was water. A hydrocyclone of 100 mm diameter and 435 mm

total length, at a constant inlet pressure of 10 psi was used.

The variable parameters were; the overflow opening diameter in the range of 14–50 mm, the middling flow opening diameter in the range of 4–12 mm, and the underflow opening diameter in the range of 10–24 mm.

The inlet opening diameter was kept constant at 14 mm with all other conditions.[10]

TESTWORKS

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Test rigFig. 11 shows a schematic diagram of the test rig

used in the experimental work. It comprises a 100 hydrocyclone, a variable speed

slurry pump and 80 l baffl ed sump. The pressure drop across the cyclone was measured

with a pressure gauge using a diaphragm mounted on the feed inlet pipe.

Stirring of slurry in the sump was achieved by a mechanical agitator in conjunction with the turbulence created by the returning flows and baffl es which ensured a complete suspension of solids in the sump.[10]

TESTWORKS

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TESTWORKS

Fig. 11. A schematic diagram of the test rig constructed at the Mineral ProcessingLaboratory, Faculty of Engineering, Assiut University.[10]

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Test procedure, sampling and data analysis In each test, the appropriate components are

selected to obtain the desired hydrocyclone configuration.

Feed slurry containing approximately 4.8% solids was prepared in the sump. After attaining steady state condition, the overflow, middling flow and underflow streams were sampled simultaneously for a certain time.

This is immediately followed by sampling of the feed stream. The slurry samples are weighed, fi ltered, dried and reweighed to calculate the flow rates and solids percent in the diff erent products.

The obtained results were mass balanced and used for subsequent calculations and interpretations.[10]

TESTWORKS

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Testwork 2: Particle size distribution of the dispersed phase

A proper amount of tracer particles as the dispersion phase and the continuous phase was mixed in the feed tank and pumped into the pipe line with a centrifugal pump.

A return line was set near the inlet of the pump to manipulate the feed rate and to avoid the strong impact to the hydrocyclone by the inlet flow.

The light dispersion was separated and went back to the tank with the overflow, while the continuous phase went back to the tank directly with the underflow.

The position of the orifices in the hydrocyclone was determined by the research purpose. [11]

TESTWORKS

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For the study of the influence of the vortex finder’s structure parameter on the flow distribution, some representative and uniformly distributed axial cross-section should be chosen to set the orifices.

The weighting method was used to test the separation effi ciency under the same material system.[11]

TESTWORKS

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The results give a coordinated relationship of vortex finder parameters and performance of hydrocyclones for separating light dispersed phase.

The size of vortex finder has great influence on the distribution of the centrifugal separation factor, but the diff erent depth of vortex finder has little influence on the centrifugal separation factor.

With the reduction of the vortex finder diameter, the size of the dispersed particles gets smaller and the separation of the hydrocyclone gets better. [11]

TESTWORKS

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Testwork3: Eff ect of particle size and shape on hydrocyclone classifi cation

The hydrocyclone tests were carried out as follows: 30 L of the slurry, in the slurry tank was circulated by the circulation pump through the circulation line to agitate and disperse the particles in the slurry.

After the slurry fl ow through the hydrocyclone reached a steady-state, the overfl ow product (hereafter referred to as OP) from the vortex fi nder and the underfl ow product (UP) from the apex of the cyclone were sampled in plastic bottles.

the fl ow rates of the overfl ow and underfl ow were measured using measuring cylinders and a stopwatch.

Both the overfl ow and underfl ow products were dried, and the solids were weighed for calculations of the solid concentrations of the OP and UP as the solid mass per unit volume of the samples.[12]

TESTWORKS

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TESTWORKS

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Size distributions of particles contained in the OP and UP samples were measured using a laser-diff raction-dispersion-type particle size distribution analyzer, Microtrac MT3300SX (Microtrac Inc.), with the measurement condition:wavelength of light source, 780 nm;measured range of particle size, 0.021–1408 μm; measuring time, 30 s; refractive index, 1.55 for PTFE, 1.51 for glass flake, 1.33 for water; measure mode, transparent and nonspherical.

The results in the table suggest that the settling velocity of large particles is smaller than that of small particles when the particle Reynolds number is large.

In the hydrocyclone tests of PTFE and glass flake, recovery of coarser particles as underflow product decreased at high inlet velocities.[12]

TESTWORKS

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TESTWORKS

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[1] wil l ’s mineral processing technology, eddition7 [2] THE SIZING AND SELECTION OF HYDROCYCLONES, Richard A.

Arterburn [3] mineral processing, Dr. Nematollahi [4] mineral processing plant design practice and control,I [5] Fundamental understanding of swirl ing fl ow pattern in

hydrocyclones, Aurélien Davail les a,b,⇑, Eric Climent a,b, Florent Bourgeois c

[6] apresentation: Powder Technology – Part I I , DT275 Masters in Pharmaceutical and Chemical Process Technology, Gavin Duff y, School of Electrical Engineering Systems, DIT

[7] a presentation: An Introduction to Basic Hydrocyclone Operation [8] JK hydrocyclone test [9] DESIGNING AND TESTING THE REPRESENTATIVE SAMPLERS FOR

SAMPLING A MILLING CIRCUIT AT NKANA COPPER/COBALT CONCENTRATORChibwe, P.1, Simukanga, S.1, Witika, L.K.1,Chisanga, P.2 and Powell, M. 2005

REFERENCES

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[10] Performance of a three-product hydrocyclone Mahmoud M. Ahmed a,, Galal A. Ibrahim a, Mohamed G. Farghaly b, 2008

[11] The coordinated relationship between vortex fi nder parameters and performance of hydrocyclones for separating light dispersed phase Qiang Yang, Hua-lin Wang∗, Jian-gang Wang, Zhi-ming Li, Yi Liu, 2011

[12] Eff ect of particle shape on hydrocyclone classifi cation Kouki Kashiwaya , Takahiko Noumachi 1, Naoki Hiroyoshi, Mayumi Ito, Masami Tsunekawa, 2012

REFERENCES