Selection of feed pumps for lter press Sai Durga Prasad V V.S., .S., Sasikumar D., Sriram Subramanian, & Sangeetha Subramanian
Introduction Pump can be defned as a device used or transerring uid or as eeders or unit processes. When using pumps as eeders or equipments such as fters that deveop head oss, positive dispacement pumps are a better choice compared to centriuga pumps. !uid contro equipments are eading manuacturers o ftration s"stems or more than # decades and share their e$perience in pump seection or fter presses in this artice. !iter press is a pressure ftration device that has ound a niche pace in various industries. %ommon" used appications incude iquid soid phase separation in chemica and pharma industries, podered activated carbon ftration rom sugar s"rup, ceramic industr", Surace treatment and phosphating industr", Water, e'uent and seage sudge deatering etc. Depending on the appication some customers require ftrate, hie others require the separated cake as their end product. !or customers ho need the ftrate as their product, throughput ftrate o rate rom the fter press is dependent on three basic actors ( ). !itrat itration ion area area provi provided ded *. !eed pump pump o o rat rate e and and #. +a$imum +a$imum perating perating pressur pressure e possibe possibe b" eed pump. pump. !or those ho need the deatered cake as their end product, cake compression compression is an important perormance eature o fter press hich i depend on the tota pressure head capacit" o the eed pump. Whatever be the si-e o the fter press, the throughput o ftrate obtained depends on the eed pump. atch atch requenc" and operation and maintenance constraints decide to choose the si-e o the fter press. /his artice ocuses on the seection o appropriate eed pumps or pressure ftration in fter press.
Typical lter press operation !iters are batch operations oper ations b" nature. /he" accumuate unanted partices on one side o the membrane, aoing remaining uid to pass through. 0s this process happens over a period o time, tim e, head oss 1back pressure registered on pressure gage2 deveops across the fter, resuting in decreasing o rate. When the o rate as beo required or permissibe range, the fter is shut don and the accumuated soids are removed rom the fter and the process is restarted. /he beo graph shos t"pica ftrate ftrate o rate versus head oss in a fter press. /he data as coected during ftration o anaerobic anaerobic digested sudge.
!igure )3 /hroughput and head oss progression over time in fter press /"pica head oss permitted or fter press is about #.4 to 5.6 kg7 sq cm. !eed pump shoud be capabe o deveoping at east ) kg7sq cm higher pressure than the ma$imum permissibe head oss. n" then, the fter press i be abe to unction at optima throughput rates.
Pump selection for lter press Pump seection is based on a number o criteria and is critica to ensure optima unctioning o the machine. !or a given pressure o ftration, ftrate through put rate i var" depending on sudge properties such as soids concentration, viscosit", temperature as e as pump capacit" and ftration area being provided b" the ftration equipment. /he actors to be considered hie choosing a pump are
Flow rate /he pump o rate seected has to take into consideration the ftrate throughput rate required, b"pass or return o i an", and optima ftration rate or avaiabe ftration area. /abe beo ists t"pica thumb rues or seecting pump o rates or some industries. S.8o . ). *. #. 5.
9ndustr" Sugar s"rup ftration
Pump capacit". 1$ e$pected orate2 ).*4 to ).4 $
0ctivated carbon ftration :/P7 S/P
).*4 to ).4 $
nine ftration in eectropating and
*.6 to *.4 $
*.6 to *.4 $
4.
phosphating /e$ties and d"estu;
*.6 to *.4 $
<.
Pup and paper industries
*.6 to *.4 $
=.
i, resins, pasticisers
*.4 to #.6 $
>.
iotech and pharma
*.6 to *.4 $
?.
+achiner" fters 1%8% cutting machines, :D+ etc2 )6. ther industries
).4 to *.6 $
).*4 to #.6 $
9t shoud be noted that the h"drauic u$ rate through the fter shoud not be e$ceeded. Pump o rate shoud be seected proportiona to the !itration area aso. 9 ftration rate has to increase, si-e o the fter press i aso increase ater a given range. !u$ rates or ftration using fter press range beteen )46 ph7 m* to <66 ph7 m* depending on sudge viscosit", soids percentage, temperature o ftration, fter medium being used, eve o carit" required and pumping rates. !or better estimation o ftration and pumping rates or a particuar surr", piot trias can be conducted.
Selecting type of pump and MOC /he most common" encountered pump in the market is the centriuga pump. @oever, these are not the best suited pumps or couping ith the fter press. /he impeer o a centriuga pump rotates to move iquid through the pump. /he impeerAs veocit" imparts energ" on the uid. /he resuting rise in pressure, or head, is proportiona to the veocit" o the iquid. 9n contrast, a positive dispacement pump moves a set voume o iquid. /he deivered capacit" is near" constant throughout the discharge pressure range. Positive dispacement pumps are capabe o pumping at the same rate against an" obstruction or raise in pressure in the s"stem. !or seecting a eed pump or fter press, it is preerred to use a positive dispacement pumpB it can be cassifed into to t"pes, i. ii.
Cotar" t"pe pumps such as Scre Pumps, ear Pumps, Vane Pumps and Ceciprocating t"pe such as 0ir perated Diaphragm Pump and Piston Pumps
!igure *3 !iter press couped ith scre pumpB mounted on troe" or mutipe ocation usage
!igure #3 !iter press couped ith 0ir perated Doube Diaphragm pump
!igure 53 !iter press couped ith centriuga h"gienic pump. Depending on the t"pe o industr", the pump is seected. /abe beo ists common appications and the t"pe o pump chosen. S.No. Industry/ Process parameters Type of pump application taen into consideration ). i and resins @igh" viscous ( high @eica ear pumps temperature *. Sugar s"rup Eo viscosit" ( high %entriuga h"gienic temperatureF o soids pumps content #. S/P7 :/P Eo viscosit" ( ambient Scre pumps7 muti temperature ( good stage centriuga pump soids compacting required 5. :ectropating @igh temperature, easi" 0DD pump and phosphating precipitated, setting surr" F high soids content 4. /e$tie and @igh temperature, easi" 0DD pump7 centriuga
d"estu; <.
Pup and Paper
=.
iotech and pharma
>.
+achiner" fters
precipitated, setting surr" 0mbient temperature, high voume /emperature, presence o sovents, cean room operation 0mbient temperature
surr" pump %entriuga surr" pump7 0DD pump Sanitar" pump7 0DD pump Scre pump7 muti stage centriuga pump
%entriuga pumps are genera" not couped ith fter presses due to the head oss generated across the equipment. 9 the pump has to be seected such that a reasonabe o is obtained ti cake compression is achieved, the pump i be ver" oversi-ed in terms o poer and initia throughput rate. So, in order to avoid this, on" P.D. pumps are suggested to be couped ith fter press. 9n certain e$treme or critica p@7 temperature appications ike hot dip -inc gavani-ing, here acid baths are set up, it is easier to adopt e$isting pumping practices instead o tr"ing to introduce a ne pump aong ith the fter press. 9 centriuga pump chosen is oversi-ed in such situations, it is suggested to ao a bigger b"pass ine, as compared to the inet ine. Gsing singe inet and mutipe outet confgurations aong ith suitabe b"pass i hep to reguate o ithout damage to the fter media.
Conclusion When using pumps as eeders or equipments that deveop head oss, positive dispacement pumps can serve as e;ective soutions. Proper precautions in the orm o pressure reie vave7 pressure sitches shoud be incorporated into the ine in order to prevent e$treme buidFup o pressure in the process ine. ?6H o fter press operationa diIcuties arise on" due to eed pump aiure. !iter presses can be operated to their ma$imum potentia on" hen couped ith suitabe eed pump. 0 suitabe trade o; beteen poer consumed, t"pe o pump, capita investment has to be made and pump seected according".
!eferences ). %haracteristics o Scre pumps ( C.J.0nnis hio state engineer *. %onsider positive dispacement pumps ( +c%andess and Cichard +eighann, %hemica processing, Ku" *6)*.
Contact +s. Sangeetha Subramanian @ead F technoog" !uid contro equipments 0F4, nathanAs compe$,
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