THERMAL SUPPLY AT THE FILTER MEDIUM LEVEL : A SOLUTION TO ENHANCEDEXPRESSION PROCESS

摘要

This work deals with liquid solid separation processes and specially with a technique of mechanicalrndehydration : filtration/expression. The aim of this work is to study the effects of a local thermalrnsupply on the filtration expression process. The Thermal supply is performed at the filter mediumrnlevel, where the more resistive part of the process is located.rnA significant part of this work concerns the design of an experimental rig which allows to performrnfiltration/expression tests with a local thermal supply at filter medium and/or at cake surface level.rnThe design step consisted in developing a classical filtration expression cell (defined as an Europeanrnstandard) by adding a circular piece ahead of the piston (called pseudo piston) which protects thernpressure sensor placed at the piston surface and receives a heat component.rnMinerals suspensions were used for the experimental study. Results obtained showed a greatrnefficacy of a heat supply at filter medium level to enhance the separation kinetic. During expression, arnmodification of the cake structure (cake collapse) occurs when temperature of filter medium reachesrntemperature of liquid boiling. This cake collapse is quick at the expression scale and depends onrnexperimental conditions and cake compressibility. Moreover, this phenomena enables to reach highrndry matter content (> 90 %) what indicates that drying step is not necessary in a production process.