Filter Press Q&A

Filter Press Q&A

Here are some links to YouTube videos that better explain how a filter press works:

Basic video of a drying press:

About filter cakes:

Recessed Plate Filter Press:

470mm Press in Operation:

Andritz Filter Press:


Filter Press for Dewaxing:

Q: What size presses do you sell and what size should I buy?
A:  We sell presses with plate dimensions of 470mm x 470mm, as well as 630mm, 800mm and larger.  A 470mm plate press can be made from 0.5 cubic feet to 4.0 cubic feet simply by adding more filter plates.  A 630mm press can be made from 2.0 to 8.0 cubic feet.  Testing should always be done on your feed material, to determine the necessary filtration area necessary to accomplish the necessary filtration.  Just because you have a 2 foot press does not mean you will be able to get 2 cubic feet of wax filtered out.  This is because the cloth may bind (clog) before the plates are actually full.  Most customers are unable to send samples to a testing lab, and waxes will change their shape once they melt.  This makes testing difficult and sometimes unreliable results are given.  We recommend getting a bigger press than needed and err on the side of caution.

Q: How much wax can your press hold?
A: A 2 cubic foot press has an internal cavity of about 56 liters.  This means you could potentially hold 56 liters of wax.  In reality that doesn't quite work out that way as it would tend to clog up before you reached that point.  For better filtration a filter aide is recommended as a precoat.  As each application is different and all waxes, fats, and lipid ratios are different its difficult to exactly know how much to precoat.  But if we were to do a 50% volume precoat and say we introduced 25 liters of filter aid into the system, we could easily remove 25 liters of wax in one cycle.  If your crude has 15% wax, this means you can clean 165 liters of crude per cycle (1-2 hours) or 1,650 liters of 10:1 crude:solvent mix.

Q: What percentage of wax will this machine remove?
A: It will remove 98-99% of the suspended solids you run through it.  So if 98% of waxes have dropped out of suspension, then you would remove 99% of those.  In practice that doesn't happen since many fats and lipids remain dissolved and you need to do 2 or 3 filtrations to remove all your lipids, fats and oils.  This has nothing to do with the function of the machine, its more about how these molecules behave and at what temperatures and rates they precipitate at.

Q: So you are saying you need to filter 3 times?
A: Yes and No.  If you can remove 98% of waxes, etc... with one pass and are happy with those results then congratulations, you are done.  If, because of the properties of you material, you are only able to remove 50% of the waxes in one pass, we recommend you winterize and filter again.

Q: Is the press capable of polishing? 
A: Yes.  Using the right filter aide, fantastic results can be achieved with a press.  A press is not like using filter paper so the results will never be as good or go down to sub micron sizes.  If you need a fantastic polishing machine, get a filter trolley.

Q: What is polishing anyways?
A: Filtration is accomplished in three steps.  The first step, or roughing step is where we remove the larger and heavier particles like waxes.  In a second step we remove lighter particles like fats and lipids.  Finally we remove very fine oils in a third pass called polishing.  As a reference roughing would be for +20 micron sizes, followed by -20 to +5 micron, finishing with a polish of -5 microns.

Q: Do you use filter paper on your press?
A: No.  Some presses do, but not this one.

Q: Does this press leak some solvent?
A: No.  Some presses do, this one does not.  This recessed plate has gaskets in every plate that ensure leak-proof operation.

Q: Hey my press is leaking, you said presses don't leak.
A: Our presses don't leak.  Looks like you bought your press from someone who has no clue about filtration.

Q: How long do the gaskets and filter cloth last?
A: 3-6 months depending on care.

Q: Is the filter press cloth expensive?
A: It isn't cheap, but far less expensive that using filter paper.

Q: Can I change the filter cloth every time I use the press?
A: No.  Cloth is meant to be changed once or twice a year.

Q: Do you use filter aides on this press?
A: Yes.  We have several grades and types of filter aides including food and lab grade diatomaceous earth and perlite.

Q: What is pre-coat?
A: Precoat is when you pump filter aid into the press before you begin to use it.  This protects the cloth from binding (clogging).  Its much like when you place a bed of DE over filter paper.

Q: This press sucks, the fluid is coming out dirty as if it isn't working!
A:  The first few minutes of filtration need to be sent back to the beginning of the process.  The filter cake is what actually does the filtration on a press, not the filter cloth.  As the press fills up it filters better and removes smaller particles.

Q: How much filter surface area does your press have?
A: A 2 cubic foot press has 37.4 cubic feet of filtration surface area.  It has 10 plates that are 470mm x 470mm filtering on both sides of each plate.

Q: Does each plate filter finer particles as the liquid moves through the press?
A: No.  All plates filter together at the same time and filter out the same particle size, pretty much...

Q: Is this system vacuum based like a Buchner?
A: No.  It is a pressurized positive pressure system and operates at 100 PSI.  Filtration at these pressures are faster, something that cannot happen on a vacuum based system.

Q: Will my solvent boil at 100 PSI?
A: Your solvent will boil at room temperature under vacuum.  This is not a vacuum based system so your solvent will never boil.

Q: How large a system can I purchase?
A: We have units that can handle multiple tons of solids.

Q: What size system should I purchase?
A: How many liters/gallons of crude do you process per batch?  What percentage of wax is in your crude?  Typically a batch is 1-2 hours.

Q: My lab does 500 liters of crude a day.  We run BHO that is 15% wax.  Our lab runs 24/7.
A: If my batch is 100 liters, I would run 5 batches per day and do so in about 8-9 hours.  Since my crude is 15% wax, I should be removing about 15 liters of wax per cycle.  If I intend to precoat, I should leave about 15 liters of space for that just in case I need that much space.  A 1 cubic foot press would hold 28 liters which seems pretty close to my needs.  To be safe I can get a 2 cubic foot press allowing for future growth.  I can always make a 2 cubic foot press into any size I want simply by adding an end plate between plates.

Q: How does a press compare in filter surface area to your filter trolleys?
A: An 800mm filter trolley has 5.41 square feet of surface are while a 2 cubic foot press has 37.4 cubic feet or 691% larger.  The trolley is 14.4% the size of a 2 cubic foot press.

Q: Will the pump melt my waxes?
A: The pump does not generate heat like a centrifugal pump.

Q: Will waxes get pushed through the filter cloth?
A: No.

Q: Is this machine insulated?
A: It is made with Polypropylene plates that have a high R value.  Your solvent will remain cold and waxes will stay solids.

Q: Is this machine food grade?
A: We can make a food grade version.

Q: Is this machine FDA Certified?
A: We can make an FDA version.

Q: Is this machine ASME certified?
A: Filter Presses, and for that matter all waste treatment equipment, does not get ASME certified, so there is no filter press that can get ASME certified.  We follow all guidelines with the piping, hydraulics, plates, etc... but the unit itself cannot be actually certified.  For example we have filter presses in many bottling, brewery, and liquor applications where all equipment must be FDA certified.  Each component on the filter press follows FDA guidelines, but the filter press itself cannot be FDA certified despite all components following the guidelines.

Q: Can these presses be used to remove carbon and clays?
A: Absolutely.  Since we filter at high pressures, removing these particles is easy with a press.

Q: How do I remove active compounds off my wax cake?
A: When you finish filtering, you can easily rinse your filter cake with cold solvent.  After the rinse, you can blow compressed air to remove solvent from the cake and clean out the press pipes.

Q: How much solvent is lost when operating this machine?
A: This is a closed system so the loss due to evaporation should be none.

Q: Do you offer automation options?
A: Yes.  We have options to close the press hydraulically on its own, and controls to do that automatically.  The press can open and close automatically, plates can open on their own and waxes get shaken off and fall on a dumpster.  We also have a machine that will wash your plates with hot water automatically, but its extremely expensive at over $100k just for that option.

Q: How much solvent will I lose on this machine?
A: None.  It is a sealed machine (closed loop) so no solvent will evaporate.  When you finish filtering, you blow compressed air through the press to remove solvent from your wax and from the pipes.

Q: In my buchner I wash my wax with solvent to remove remaining active compounds, can I do that with a press?
A: Yes.  Many customers wash their wax with cold solvent after they finish filtering and thus wash out the wax.

Filter Press for Drying Biomass:

Many of the answers of the normal press apply to the press made for solvent removal.

Q: How exactly does this work?
A: Biomass is pumped directly from your extraction vessel into a closed system that filters out solids.  After all solids are filtered out, two inflatable bags squeeze out all solvent from the biomass.  After that, compressed air is used to further dry the biomass and clear all solvent from pipes.  What is left is filtered solvent ready for solvent removal in ROTOVAP or FFE and a dry filter cake ready for disposal.

Q: Do I put brew bags with my plant material in the press?
A: No, biomass is pumped directly into the press.

Q: Does this system work on cold ethanol?
A: Yes it works on hot or cold solutions.

Q: What solvents can I use for this system?
A: Most organic solvents (ethanol, ISO, etc...) except Pentane.

Q: What pump do I use to move my biomass from my tank to the filter?
A: We supply the diaphragm pump needed.

Q: How long does the press take to dry my product?
A: Typical batch cycle times from start to finish are 1-2 hours be it for 50 pounds or 500 pounds. 

Q: How many employees does it take to operate this system?
A: One

Q: How difficult is it to operate this system?
A: Fairly straight forward.  1-2 hours of training will do.

Q: Can you send some over and help me install this and train me to use it?
A: Absolutely!

Q: How dry can this machine make the biomass.
A: It will not remove the moisture inside the cell structure.  If you start with material that will not adsorb moisture, exterior moisture can go down to 5-12% depending on how long you blow compressed air through it.

Q: I have a centrifugal dryer.  How does this compare?
A: For one, there is far less manipulation of the feed material as everything is pumped in.  The end product is far dryer than using a centrifugal dryer.  You will save money on labor, and you will recover more solvent and do it faster than on a centrifugal dryer. 

Q: Faster?  My centrifugal dryer does 10 pounds in 15 minutes, you must be joking to say your machine is faster.
A: Take into account the time you unload your extraction vessel, put your biomass in bags, load the bags to the centrifugal dryer, spin the dryer, offload the dryer and yes the overall process is faster on a press.  Remember you need to do this 5 times on a centrifugal dryer to get the same output of a press.  Also, you will recover more solvent and loose very little solvent to evaporation on a press.  You will save on labor as well. 

Q: How is this machine better than a Delta Separations CUP15?
A: It isn't.  The CUP is a complete system (chilling, extraction, filtration, etc...) that performs quite well.  Our press does not extract, only filters.  If comparing the filtration capabilities of both machines, the press is simply far larger; our smallest unit holds almost 200 pounds of biomass.  If you are using or plan to use a CUP15, most likely your scale is too small for a press.

Q: I need to process 100 tons a day, can you accommodate me?
A: Yes.  We can do 50 pounds per cycle, 500 pounds per cycle or 5 tons per cycle.  A 50 pound press can easily do 400 pounds in an 8 hour shift.

Q: Can I put whole plant in this system?
A: No.  We strongly recommend you debuck and grind your plant material for best results.

Q: How do I feed the plant matter into the pump?
A: The ground and debucked material is placed in an agitated extraction vessel to make a pulp of no more than 60% solids.  The more solvent used the better the results.  The more you grind the better the results.  The free flowing pulp drains into the pump which sucks at low pressure and pumps at high pressures into the press.

Q: What filter media is used, filter paper?
A: Filter cloth, which we provide the correct type for this application.

Q: How long does the cloth last?
A: 6 Months or so depending on care and maintenance.

Q: Do you need to use a filter aide?
A: You can but its not necessary.

Q: How does the equipment costs compare to competitors.
A: On a pound per pound basis, our smallest machine costs about $1,000 per pound compared to $4-5,000 per pound on our competitors.  500 pound machines cost about $400 per pound processed.

Q: Can I use this press to dewax?
A: Yes, but you shouldn't use the squeeze function as it won't help.  If you need to remove active ingredients from your wax you would do a solvent rinse, not a squeeze.  Also, if you only want to dewax, then we have a press that costs half as much as these machines.