Here is typical Larox filter press sizing report.

The Kemess mine used pressure filters to dewater concentrate, but the moisture content was too high, and a subsequent dryer stage was added. Modification: The concentrate feed to the concentrate thickener was flocculated and the thickener underflow pressure filtered effectively to the necessary moisture content for trucking the concentrate off site. The dryer was then no longer required.

The optimum flocculant dosage for settling (in the concentrate thickener) coincides with the optimum flocculant dosage for maximum filtration rate. The flocculant selected would be the one that provides best filtration rates, but the flocculant testing (as a filter aid) can be initially performed via settling tests if this is more convenient. Then some laboratory filtration tests to confirm.

The earlier researches on flocculants (Kitchener et al and La Mer and Healy) preferred to use re-filtration rate in the lab because it was way more reproducible than settling rate or once through-filtration rate. As I recall, you can perform the settling rate in a one litre cylinder with added flocculant, then transfer the cylinder contents into the lab filtration device, filter, and take the filtrate and add back into the filtration device. Armed with the filtration rates for your concentrates, the manufacturer should be in a better position to advise on the size of the filtration equipment. When a flocculant aid is used, belt filters may be an alternative.

It is important to perform thickening and filtration tests to get reliable information on the settling rate and filtration rate. If you don't want to invest some money in a dewatering testing program, you could use a estimated filtration rate from filters manufacturers or any technical article on this matter.

By performing a thickening testing program you can evaluate the effect of particle size and mineralogical composition on the settling rate, also, it is possible to evaluate several flocculants and dosages to select the right one. At the end of the thickening testing program, you will know the optimum underflow density (e.g.65% w/w) and the settling rate.

Once you know the optimum underflow density, it is recommendable to perform filtration test. This time, you can evaluate several parameters such the different filter cloths, particle size, vacuum, pressure, time, filtrate quality, cake moisture. Results will indicate the optimum filtration rate and cake moisture. If you want to perform filtration tests try to contact filters manufacturers, they can perform the test. 

If you assume information, the filter size could be small o very big. This kind of decision has a cost. You should think about it.