HYDROCYCLONE  By  Muhammad  Zulqayyim  Bin  Noor  Azizul  

School  of  Material  and  Mineral  Resources  Engineering,  Universiti  Sains  Malaysia    ABSTRACT  

Hydrocyclone  is  a  device  to  classify,  separate  or  sort  particles  in  a  liquid  suspension  based  on  ratio  of  their  centrifugal   force  to  fluid  resistance.  Hydrocyclone   is  simple  and  high  capacity  equipment   relative   to   its   size.   Hydrocyclone   is   suitable   for   particles   in   very   fine   size  separation,  normally  below  75  micron  size.  This  experiment  shows  a  sample  of  slurry  is  feed  into  a  hydrocyclone  and  the  slurry  will  create  a  swilling  motion  inside  the  hydrocyclone  and  eventually   divided   the   slurry   into   overflow   and   underflow.   Corse   particle   will   be   in   the  underflow  while  fine  particle  in  the  overflow  product.  This  experiment  is  conducted  at  two  different  pressures  which  are  5  psi  and  10  psi  to  compare  the  efficiency  of  the  hydrocyclone  according  to  pressure  given  at  the  feed.  The  experiment  shows  that  the  50%  size  distribution  of  particle  in  overflow  of  10  psi  sample  is  higher  than  5  psi.  So,  the  experiment  is  in  line  with  the  theory  which  says  that  separation  at  higher  pressure  will  be  more  effective.      INTRODUCTION  

A  hydrocyclone  is  a  static  device  that  applies  centrifugal  force  to  a  liquid  mixture  so  as   to   promote   the   separation   of   heavy   and   light   components.   Analytical   hydrocyclone  consist   of   a   conically   shaped   vessel,   open   at   its   apex,   or   underflow   joined   to   a   cylindrical  section,  which  has   tangential   feed   inlet.   The   top  of   the   cylindrical   section   is   closed  with   a  plate  though  which  passes  an  axially  mounted  overflow  pipe.  This  pipe  is  extended  into  the  body  of   the   cyclone  by   a   short,   removable   section   known  as   vortex   finder,  which  prevent  short  circulating  of  feed  directly  into  the  overflow.    

 Figure:  Hydrocyclone  

The  hydrocyclone  is  a  closed  vessel  designed  to  convert  incoming  liquid  velocity  into  rotary  motion.  It  does  this  by  directing  inflow  tangentially  near  the  top  of  a  vertical  cylinder.  This   spins   the   entire   contents   of   the   cylinder,   creating   centrifugal   force   in   the   liquid.   The  feed  flow,  which  is  a  slurry  of  small  particles,  into  liquid  enters  tangentially  into  the  cyclone  and  is  divided  into  underflow,  which  carries  most  of  the  solids,  and  overflow,  which  contacts  most   of   the   Liquid.   The   separation   of   solid   from   liquid   depends   on   the   particle   size   and  particle   density.   Centrifugal   force   throws   the   particles   out   against   the   wall   and   they  subsequently  drop  into  the  outlet  hopper.  Cyclone  consists  of  vertical  cylinder  with  conical  bottom.  The  inlet  point  is  near  the  top  of  the  cylindrical  portion.  The  particles  separated  are  collected  at  the  bottom.    

In   the  operation  of  hydrocyclones,  slurry   is   feed   into  a  hydrocyclone  under  certain  pressure  through  the  inlet.  Mineral  particles  that  entering  the  hydrocyclone  will  be  acted  by  two  different  forces  acting  on  the  contrary  which  are  the  centrifugal  force  and  drag  force:  

a.  Centrifugal   force   will   act   inwards.   According   to   Stokes   Law,   the   action   of  centrifugal   force  on   the  particles  accelerates   the   rate  of   sedimentation  of  mineral  particles.  Therefore,  the  particles  are  being  separated  by  the  difference  in  size  and  gravity.  Usually,  coarse  particles  that  settled  quickly  will  move  to  the  cyclone  wall,  where  the  velocity  is  low,  and  goes  out  through  the  opening  under  the  apex  of  the  flow.  This  particle  is  known  as  underflow  sample.  

b. By  the  action  of  drag  force,  the  particles  that  have  a  low  sedimentation  rate,  usually  the  fine  size,  will  move  to  low  pressure  zone  along  the  axis  of  the  cyclone  and  will  move  up  through  the  vortex  finder.  This  particle  is  known  as  overflow  sample.    Hydrocyclones  are  also  related  to  centrifuges  in  that  both  are  intended  to  separate  

heavies   and   lights   by   application   of   centrifugal   force   to   liquids.   The   key   difference   is   that  hydrocyclones   are   passive   separators   capable   of   applying   modest   amounts   of   centrifugal  force,   whereas   centrifuges   are   dynamic   separators   that   are   generally   able   to   apply  much  more  centrifugal   force  than  hydrocyclones.  Another  key  difference  between  hydrocyclones  and   centrifuges   is   cost.   Centrifuges   are   expensive   precision   rotating   machines   that   often  need   sophisticated   control,   whereas   hydrocyclones   have   no  moving   parts   and   usually   no  controls  at  all  so  they  are  lower  cost  devices.    OBJECTIVE  

This  experiment  is  conducted  to  exposed  student  to:  1. Introducing  the  hydrocyclone  as  one  of  the  important  tools  in  the  classification  process  

of  mineral  processing  industry.  2. Learn  the  operation  of  the  hydrocyclone  in  lab  scale  and  see  the  components  involved  

that  affects  the  efficiency  of  the  hydrocyclone.  3. Determine   the   operational   parameters   and   geometry   that   affect   the   performance   of  

hydrocyclone  efficiency.  4. Studies   about   the   particle   size   distribution   on   the   sample   of   feed,   overflow   and  

underflow.    

PROCEDURE  

1. 1  kg  of  sample  was  given  by  lab  assistant.  2. Hydrocyclone  was  clean  by  rinse  with  clean  water  and  let  to  flow  in  close  circuit.  3. Water  was  added  into  hydrocyclone  rig  until  20  mL  to  get  5%  solid.  4. Water  was  let  too  flow  in  close  circuit  for  a  few  minutes  to  get  a  consistent  flow  before  

the  test.      5. Sample  was  added  into  the  rig  thoroughly.  6. Pressure  gauge  was  adjusted  to  5  psi  and  let  to  flow  for  a  few  minutes.  7.  Overflow  and  underflow  rate  was  determined  by  using  clock  timer  and  flask  stinging.  8. Pulp  feed  density,  underflow  and  overflow  sample  was  taken  by  using  a  basin  in  2.8-­‐2.9  

seconds  for  particle  size  distribution  analysis.  9. Step  6-­‐8  was  repeated  by  using  pressure  of  10  psi.  10. All   samples  were  dried   in  oven  and  particle  size  distribution  was  determined  by  using  

particle  size  analyzer.    RESULT  

 

𝑃𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒  𝑆𝑜𝑙𝑖𝑑 =𝑊𝑒𝑖𝑔ℎ𝑡  𝑜𝑓  𝑠𝑜𝑙𝑖𝑑

𝑉𝑜𝑙𝑢𝑚𝑒  𝑜𝑓  𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛  ×  100%  

                                                                                                                                             = !  !"!"  !

 ×  100%  

                                 = 5  %  𝑠𝑜𝑙𝑖𝑑    

Table:  Operation  setting  of  hydrocyclone  

           

   

Pressure  (psi)   Sample    Time  to  Fill  Container  (s)  

Mass    (kg)  

Flow  Rate  (t/h)  

Pulp  Density  (kg/m3)  

5  

Feed   3.24   1.18   1.31   1180  

Overflow   4.02   1.12   1.00   1120  

Underflow   20.17   1.44   0.26   1440  

10  

Feed   7.90   1.14   0.52   1140  

Overflow   3.57   1.06   1.06   1060  

Underflow   17.85   1.20   0.24   1200  

𝐹𝑙𝑜𝑤  𝑅𝑎𝑡𝑒 =𝑀𝑎𝑠𝑠  𝑜𝑓  𝑓𝑖𝑙𝑙𝑒𝑑  𝑓𝑙𝑎𝑠𝑘  𝑠𝑡𝑖𝑛𝑔𝑖𝑛𝑔𝑇𝑖𝑚𝑒  𝑡𝑜  𝑓𝑖𝑙𝑙𝑒𝑑  𝑓𝑙𝑎𝑠𝑘  𝑠𝑡𝑖𝑛𝑔𝑖𝑛𝑔  

 

𝑃𝑢𝑙𝑝  𝐷𝑒𝑛𝑠𝑖𝑡𝑦 =𝑀𝑎𝑠𝑠  𝑜𝑓  𝑓𝑖𝑙𝑙𝑒𝑑  𝑓𝑙𝑎𝑠𝑘  𝑠𝑡𝑖𝑛𝑖𝑛𝑔𝑉𝑜𝑙𝑢𝑚𝑒  𝑜𝑓  𝑓𝑙𝑎𝑠𝑘  𝑠𝑡𝑖𝑛𝑔𝑖𝑛𝑔  

At  pressure  5  psi;         Feed  

𝐹𝑙𝑜𝑤  𝑅𝑎𝑡𝑒 =1.18  𝑘𝑔3.24  𝑠

 ×3600  𝑠1  ℎ

×1  𝑡

1000  𝑘𝑔  

                                                                                                                       = 𝟏.𝟑𝟏  𝒕/𝒉    

𝑃𝑢𝑙𝑝  𝐷𝑒𝑛𝑠𝑖𝑡𝑦 =1.18  𝑘𝑔1  𝐿

×  1000  𝐿1  𝑚!  

 = 𝟏𝟏𝟖𝟎  𝒌𝒈/𝒎𝟑  Overflow  

𝐹𝑙𝑜𝑤  𝑅𝑎𝑡𝑒 =1.12  𝑘𝑔4.02  𝑠

 ×3600  𝑠1  ℎ

×1  𝑡

1000  𝑘𝑔  

                                                                                                                       = 𝟏.𝟎𝟎  𝒕/𝒉    

𝑃𝑢𝑙𝑝  𝐷𝑒𝑛𝑠𝑖𝑡𝑦 =1.12  𝑘𝑔1  𝐿

×  1000  𝐿1  𝑚!  

 = 𝟏𝟏𝟐𝟎  𝒌𝒈/𝒎𝟑  Underflow  

𝐹𝑙𝑜𝑤  𝑅𝑎𝑡𝑒 =1.44  𝑘𝑔20.17  𝑠

 ×3600  𝑠1  ℎ

×1  𝑡

1000  𝑘𝑔  

                                                                                                                       = 𝟎.𝟐𝟔  𝒕/𝒉    

𝑃𝑢𝑙𝑝  𝐷𝑒𝑛𝑠𝑖𝑡𝑦 =1.44  𝑘𝑔1  𝐿

×  1000  𝐿1  𝑚!  

 = 𝟏𝟒𝟒𝟎  𝒌𝒈/𝒎𝟑    

At  pressure  10  psi;         Feed  

𝐹𝑙𝑜𝑤  𝑅𝑎𝑡𝑒 =1.14  𝑘𝑔7.90  𝑠

 ×3600  𝑠1  ℎ

×1  𝑡

1000  𝑘𝑔  

                                                                                                                       = 𝟎.𝟓𝟐  𝒕/𝒉    

𝑃𝑢𝑙𝑝  𝐷𝑒𝑛𝑠𝑖𝑡𝑦 =1.14  𝑘𝑔1  𝐿

×  1000  𝐿1  𝑚!  

 = 𝟏𝟏𝟒𝟎  𝒌𝒈/𝒎𝟑  Overflow  

𝐹𝑙𝑜𝑤  𝑅𝑎𝑡𝑒 =1.06  𝑘𝑔3.57  𝑠

 ×3600  𝑠1  ℎ

×1  𝑡

1000  𝑘𝑔  

                                                                                                                       = 𝟏.𝟎𝟔  𝒕/𝒉    

𝑃𝑢𝑙𝑝  𝐷𝑒𝑛𝑠𝑖𝑡𝑦 =1.06  𝑘𝑔1  𝐿

×  1000  𝐿1  𝑚!  

 = 𝟏𝟎𝟔𝟎  𝒌𝒈/𝒎𝟑      

Underflow  

𝐹𝑙𝑜𝑤  𝑅𝑎𝑡𝑒 =1.20  𝑘𝑔17.85  𝑠

 ×3600  𝑠1  ℎ

×1  𝑡

1000  𝑘𝑔  

                                                                                                                       = 𝟎.𝟐𝟒  𝒕/𝒉    

𝑃𝑢𝑙𝑝  𝐷𝑒𝑛𝑠𝑖𝑡𝑦 =1.20  𝑘𝑔1  𝐿

×  1000  𝐿1  𝑚!  

 = 𝟏𝟐𝟎𝟎  𝒌𝒈/𝒎𝟑      

Table:  Cumulative  Distribution  of  Particle  Size  

 Size  (micron)  

Cumulative  Distribution  (%)  5  psi   10  psi  

Feed   Overflow   Underflow   Feed   Overflow   Underflow  0.18   1.97   2.27   0.95   1.39   1.82   0.98  0.22   2.72   3.22   1.32   1.92   2.52   1.36  0.26   3.37   4.10   1.65   2.38   3.14   1.69  0.30   3.94   4.92   1.95   2.79   3.69   1.98  0.36   4.74   6.03   2.37   3.35   4.46   2.39  0.44   5.74   7.36   2.90   4.07   5.44   2.90  0.52   6.73   8.54   3.42   4.81   6.41   3.40  0.62   8.04   9.86   4.08   5.80   7.70   4.06  0.74   9.75   11.33   4.90   7.13   9.37   4.92  0.86   11.59   12.79   5.75   8.60   11.18   5.84  1.00   13.81   14.57   6.74   10.41   13.39   6.95  1.20   16.94   17.31   8.06   13.01   16.56   8.50  1.50   21.42   21.64   9.84   16.77   21.17   10.66  1.80   25.71   25.93   11.38   20.30   25.60   12.65  2.10   29.98   30.11   12.80   23.68   29.99   14.52  2.50   35.64   35.79   14.61   27.97   35.80   16.93  3.00   42.34   43.18   16.71   32.92   42.78   19.74  3.60   49.49   51.79   18.96   38.14   50.34   22.79  4.20   55.49   59.09   20.89   42.58   56.69   25.45  5.00   62.10   66.44   23.12   47.56   63.54   28.57  6.00   68.77   72.70   25.62   52.70   70.24   32.03  7.20   75.26   78.02   28.48   57.82   76.61   35.87  8.60   81.33   83.12   31.66   62.82   82.58   40.09  10.20   86.75   88.18   34.68   67.34   87.96   44.32  12.20   91.75   93.19   37.08   71.27   92.96   48.40  14.60   95.76   97.18   38.61   74.10   96.92   51.90  17.40   98.49   99.46   41.20   76.49   99.29   55.90  20.60   99.79   100.00   48.69   80.10   100.00   62.82  24.60   100.00   100.00   64.96   86.67   100.00   75.30  29.40   100.00   100.00   85.28   94.46   100.00   89.84  35.00   100.00   100.00   100.00   100.00   100.00   100.00  

 Graph  of  Cumulative  Distribution  against  Particle  Size  Distribution  

   

Table:  Size  for  which  50%  of  particle  reported  for  each  sample  Size  

Sample  D50  (𝜇𝑚)  

5  psi   10  psi  Feed   3.65   5.47  

Overflow   3.47   3.57  Underflow   20.92   13.30  

 DISCUSSION  

  Based  on  results  that  have  been  calculated,  it  can  be  show  that  the  pulp  density  of  underflow  sample  is  decrease  with  the  increase  in  pressure  form  5  to  10  psi.  This  mean  the  amount  of  solid  or  %  solid   in  sample   is  decrease  as  the  pressure   increase.  Higher  pressure  will  produce  better  efficiency  as  the  larger  centrifugal  force  created  in  the  hydrocyclone.  The  centrifugal  force  created  in  the  hydrocyclone  is  one  of  the  parameter  needed  to  control  the  efficiency  of  separation.  Therefore,  with  higher  pressure  contribute  to  the  feed  will  produce  better  separation.    

In  additional,  by   increasing  the  pressure  supply,   the  efficiency  of  hydrocyclone  can  be   increased   too   as  proved  by  particle   size  distribution   analysis   on   the   samples.   It   can  be  concluded  that  the  higher  the  pressure,  the  higher  the  efficiency  of  the  hydrocyclone  where  more  fine  particle  sample  can  be  separated  to  vortex  as  overflow.  Particle  size  distribution  test   show   that   the   size   for  which  50%  of  particle   reported   in  overflow   for  10  psi   is  higher  than  5psi.  This  means,  the  separation  at  higher  pressure  is  more  effective  compared  to  low  pressure.      

Theoretically,   in  the  operation  of  hydrocyclones,  there  are  several  parameters  that  influence   the   performance   or   efficiency   of   the   hydrocyclone.   These   parameters   can   be  divided  into  two  parts  which  are;  1-­‐  Operating  parameters  2-­‐  Geometrical  parameters.  

0

10

20

30

40

50

60

70

80

90

100

Y1 / %

0.10.1 0.5 1 5 10X / µm

5  psi  •    Feed  •    Overflow  •    Underflow    10  psi  •    Feed  •    Overflow  •    Underflow            

Operating  parameters  a. Feed  pulp  density  or  viscosity  b. Shape  of  particles  c. Feed  rate  d. Pressure  

Geometrical  parameters  a. Diameter  of  vortex  finder  b. Apex  diameter  c. Area  of  feed  inlet  d. The  cone  angle  e. The  cylinder  diameter  f. The  cylinder  length  

 Another  factor  that  distribute  to  some  error  of  hydrocyclone   is  due  to  the  random  

error  while  taking  the  reading  will  disturb  the  accuracy  of  the  result.  The  mass  of  the  sample  is  taken  by  using  pulp  density  scale  meter  is  not  accurate  as  the  horizontal  horizon  cannot  be  detected  on  the  scale.  Other  than  that,  errors  might  have  happen  when  calculating  the  time  to  fill  up  the  flask  stinging.  Some  errors  can  be  avoided  to  acquire  better  result  but  some  can  be  ignored  and  average  reading  will  be  taken.  Besides  that,  error  might  also  come  from  the  uncovered  rig.  This  cause   the  sample  spilt   from  the  rig  where   the  overflow  and  underflow  pulp  are  supposed  to  flow  directly  back  to  the  rig  as  the  circuit  is  closed  circuit.      CONCLUSION  

From   this   experiment,   it   shows   that   hydrocyclone   is   efficient   to   operate   at   high   pressure  because   the   separation  will  be  more  effective.   From   the   result,  we  can   see   that  at  5  psi  pressure,   hydrocyclone   can   produce   finer   particle   size   distribution   compared   to   10   psi  pressure.   Therefore,   the   increase   in   pressure   will   also   increase   the   efficiency   of  hydrocyclone.   But   this   result  might   be   different   from   the   theory   due   to   some   errors   that  cannot  be  neglected  while  doing  the  experiment.    In  overall,  the  classification  or  separation  of  mineral  particles  in  the  hydrocyclone  is  due  to:  a. The  nature  of  these  particles  such  as  size,  shape  and  specific  gravity.  b. The  physical  properties  of  liquid  such  as  density,  percent  solids  and  viscosity.  c. The  design  parameters  and  operating  parameters  of  the  hydrocyclone  itself.    REFERENCE  

§ B.A  Wills,  Mineral  Processing  Technology,  6th  edition.  An  Introduction  to  the  Practical  Aspects  of  Ore  Treatment  and  Mineral  Recovery,  England  1997.  

§ Richard   Holdich,   Fundamentals   of   Particle   Technology,   Loughborough,   United  Kingdom,  2002.  

§ Ph.  Hasler,   Th.  Nussbaumer,  Particle   Size   Distribution   Of   The   Fly   Ash   From   Biomass  Combustion,  Verenum  Research,  Langmauerstrasse  109,  Ch  -­‐  8006  Zurich,  Switzerland,  June  8–11  1998