Overview of Typical Filter Press Testing Program

3.1        Introduction

This section provides an overview of the tests and their typical order.

3.2       Outline

3.2.1    Slurry Characterization  Mandatory Tests on All Slurries

Slurry Total Solids

Slurry Density Optional Tests

Other tests that are required to understand the specific process.  These tests will vary for each project.  Common tests are pH, temperature, and conductivity.

3.2.2   Screening Test

Buchner Funnel

3.2.3   Filtration Tests Slurry Samples

If the slurry is different from the previous sample, i.e. a fresh batch, a new slurry sample is required and at a minimum the mandatory slurry tests must be run on it.  Chemical Conditioning

Accurate data on the all the volumes and concentrations used must be kept.  This includes the slurry volume.  Filtration Data

Accurate data of each part the test include time, pressure, temperature, and volumes collected are required.  Filtrate

Visual description is the minimum.  Other data is by customer request.  Cake

Cake Solids

Cake Density

Cake Thickness

Cake Release

Visual Description


Slurry characterization is necessary for press sizing and process design.  Mandatory tests must be always done.  Other characterization tests are done only when needed to understand the process better.  Additional characterization tests are most commonly done when cake washing is required.


Screening tests are done to determine the slurry filterability and any required chemical conditioning.  Many times the slurry characterization data is not immediately available, but accurate notes of what was done will allow one to proceed. The type of chemical conditioning that may be used determines whether the Baroid or CST is used.  The Baroid is used for all except polymer and the CST is used only with polymers.


For the filtration tests a fresh sample of the slurry may used.  One can not assume that this sample is identical to any previous sample.  Each fresh sample must be tested to verify its characteristics.


During the filtration tests, accurate recording of the data is essential, including chemical conditioning volumes and concentrations.  It is not unusual for the slurry characterization not to be finished while running a filtration test.


Filtrate data is used to determine the solids capture and the variation of various process parameters during each step of the test.  If the behavior is expected to vary significantly with time or total flow, a grab sample is taken at specific intervals.  Otherwise, a composite sample is taken.  If quantitative analysis is to be done, a visual description is still required.


Cake characterization is required for sizing the filter press (solids, density, and thickness) and documenting other important behavior (release and description) that impacts the overall process.  The importance of the quantitative is easier to understand.  While the importance of the quantitative data is easier to grasp, the qualitative data is just as important.  A very important issue for a filter press is how easy the cake discharges from it and a description of the cake release is important to understand this.  Depending how the cake is being handled, a description of the cake is important because it may highlight potential handling problems down stream of the filter press.